Apparent diffusion coefficient correlation with oesophageal tumour stroma and angiogenesis
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Aoyagi, Tomoyoshi; Shuto, Kiyohiko; Okazumi, Shinichi; Hayano, Kohichi; Satoh, Asami; Saitoh, Hiroshige; Shimada, Hideaki; Nabeya, Yoshihiro; Matsubara, Hisahiro [Chiba University, Department of Frontier Surgery, Graduate School of Medicine, Chiba (Japan); Kazama, Toshiki [Chiba University, Department of Radiology, Graduate School of Medicine, Chiba (Japan)
2012-06-15
Because diffusion-weighted imaging (DWI) can predict the prognosis of patients with oesophageal squamous cell carcinoma (ESCC), we hypothesised that apparent diffusion coefficient (ADC) values might be correlated with the collagen content and tumour angiogenesis. The purpose of this study was to determine the correlation between ADC values of ESCC before treatment and oesophageal tumour stroma and angiogenesis. Seventeen patients with ESCC were enrolled. The ADC values were calculated from the DWI score. Seventeen patients who had undergone oesophagectomy were analysed for tumour stroma, vascular endothelial growth factor (VEGF) and CD34. Tissue collagen was stained with azocarmine and aniline blue to quantitatively analyse the extracellular matrix in cancer stroma. Tissues were stained with VEGF and CD34 to analyse the angiogenesis. The ADC values decreased with stromal collagen growth. We found a negative correlation between the tumour ADC and the amount of stromal collagen (r = -0.729, P = 0.001), i.e. the ADC values decreased with growth of VEGF. We also found a negative correlation between the ADC of the tumours and the amount of VEGF (r = 0.538, P = 0.026). Our results indicated that the ADC value may be a novel prognostic factor and contribute to the treatment of oesophageal cancer. circle Magnetic resonance apparent diffusion coefficient values inversely indicate tumour stromal collagen circle There is also negative correlation between ADCs and vascular endothelial growth factor circle ADC values may contribute to the treatment of oesophageal cancer. (orig.)
Apparent diffusion coefficient correlation with oesophageal tumour stroma and angiogenesis
International Nuclear Information System (INIS)
Because diffusion-weighted imaging (DWI) can predict the prognosis of patients with oesophageal squamous cell carcinoma (ESCC), we hypothesised that apparent diffusion coefficient (ADC) values might be correlated with the collagen content and tumour angiogenesis. The purpose of this study was to determine the correlation between ADC values of ESCC before treatment and oesophageal tumour stroma and angiogenesis. Seventeen patients with ESCC were enrolled. The ADC values were calculated from the DWI score. Seventeen patients who had undergone oesophagectomy were analysed for tumour stroma, vascular endothelial growth factor (VEGF) and CD34. Tissue collagen was stained with azocarmine and aniline blue to quantitatively analyse the extracellular matrix in cancer stroma. Tissues were stained with VEGF and CD34 to analyse the angiogenesis. The ADC values decreased with stromal collagen growth. We found a negative correlation between the tumour ADC and the amount of stromal collagen (r = -0.729, P = 0.001), i.e. the ADC values decreased with growth of VEGF. We also found a negative correlation between the ADC of the tumours and the amount of VEGF (r = 0.538, P = 0.026). Our results indicated that the ADC value may be a novel prognostic factor and contribute to the treatment of oesophageal cancer. circle Magnetic resonance apparent diffusion coefficient values inversely indicate tumour stromal collagen circle There is also negative correlation between ADCs and vascular endothelial growth factor circle ADC values may contribute to the treatment of oesophageal cancer. (orig.)
Time course of the apparent diffusion coefficient after cerebral infarction
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Ahlhelm, F.; Backens, M.; Reith, W.; Hagen, T. [Department of Neuroradiology, University of Saarland, 66424 Homburg/Saar (Germany); Schneider, G. [Department of Radiology, University of Saarland, 66424 Homburg/Saar (Germany)
2002-09-01
The purpose of this study was to evaluate quantitative apparent diffusion changes in the center of infarction by measurement of the apparent diffusion coefficient (ADC), and to investigate the influence of ischemia on the contralateral hemisphere. By diffusion echo-planar imaging (EPI) 52 patients showing cerebral infarction were studied within 5 h to >12 months after onset of clinical symptoms. Using three diffusion gradient strengths (b1=30 s/mm{sup 2}; b2=300 s/mm{sup 2}, b3=1100 s/mm{sup 2}) ADC maps were generated. After onset of ischemia, ADC in the center of infarction was lower than in the contralateral regions of human brain. At first ADC declined for approximately 28 h to a minimum of approximately 150 x 10{sup -8} cm{sup 2}/s. Then the ADC reincreased and reached a ''pseudonormalization'' after approximately 5 days. Chronic infarctions did show much higher ADC values (2000 x 10{sup -8} cm{sup 2}/s) than unaffected areas. Neither localization nor size of infarctions showed a significant influence on this time course. In the center of infarction diffusion is isotropic. Even brain regions of the contralateral hemisphere are influenced by cerebral ischemia. In these regions ADC is higher than for physiological conditions. The ADC also declines especially for the first 2-3 days after onset of symptoms, also followed by reincrease. The ADC calculation enables determination of the onset of infarction more exactly than is possible using only diffusion-weighted imaging. Diffusion in the center of infarction is isotropic; hence, orientation of the diffusion gradients has no significant influence on sensitivity of measurements. The calculation of the ADC ratio based on data derived from the center of infarction and the contralateral hemisphere seems to be critical because the ADC in the unaffected contralateral hemisphere also changes. (orig.)
Time course of the apparent diffusion coefficient after cerebral infarction
International Nuclear Information System (INIS)
The purpose of this study was to evaluate quantitative apparent diffusion changes in the center of infarction by measurement of the apparent diffusion coefficient (ADC), and to investigate the influence of ischemia on the contralateral hemisphere. By diffusion echo-planar imaging (EPI) 52 patients showing cerebral infarction were studied within 5 h to >12 months after onset of clinical symptoms. Using three diffusion gradient strengths (b1=30 s/mm2; b2=300 s/mm2, b3=1100 s/mm2) ADC maps were generated. After onset of ischemia, ADC in the center of infarction was lower than in the contralateral regions of human brain. At first ADC declined for approximately 28 h to a minimum of approximately 150 x 10-8 cm2/s. Then the ADC reincreased and reached a ''pseudonormalization'' after approximately 5 days. Chronic infarctions did show much higher ADC values (2000 x 10-8 cm2/s) than unaffected areas. Neither localization nor size of infarctions showed a significant influence on this time course. In the center of infarction diffusion is isotropic. Even brain regions of the contralateral hemisphere are influenced by cerebral ischemia. In these regions ADC is higher than for physiological conditions. The ADC also declines especially for the first 2-3 days after onset of symptoms, also followed by reincrease. The ADC calculation enables determination of the onset of infarction more exactly than is possible using only diffusion-weighted imaging. Diffusion in the center of infarction is isotropic; hence, orientation of the diffusion gradients has no significant influence on sensitivity of measurements. The calculation of the ADC ratio based on data derived from the center of infarction and the contralateral hemisphere seems to be critical because the ADC in the unaffected contralateral hemisphere also changes. (orig.)
Apparent diffusion coefficient measurements in progressive supranuclear palsy
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Ohshita, T.; Oka, M.; Imon, Y.; Yamaguchi, S.; Mimori, Y.; Nakamura, S. [Hiroshima Univ. (Japan). School of Medicine
2000-09-01
We measured the apparent diffusion coefficient (ADC), using diffusion-weighted imaging (DWI) and signal intensity on T2-weighted MRI in the cerebral white matter of patients with progressive supranuclear palsy (PSP) and age-matched normal subjects. In PSP, ADC in the prefrontal and precentral white matter was significantly higher than in controls. There was no significant difference in signal intensity on T2-weighted images. The ADC did correlate with signal intensity. The distribution of the elevation of ADC may be the consequence of underlying pathological changes, such as neurofibrillary tangles or glial fibrillary tangles in the cortex. Our findings suggest that ADC measurement might be useful for demonstrating subtle neuropathological changes. (orig.)
Apparent diffusion coefficient measurements in progressive supranuclear palsy
International Nuclear Information System (INIS)
We measured the apparent diffusion coefficient (ADC), using diffusion-weighted imaging (DWI) and signal intensity on T2-weighted MRI in the cerebral white matter of patients with progressive supranuclear palsy (PSP) and age-matched normal subjects. In PSP, ADC in the prefrontal and precentral white matter was significantly higher than in controls. There was no significant difference in signal intensity on T2-weighted images. The ADC did correlate with signal intensity. The distribution of the elevation of ADC may be the consequence of underlying pathological changes, such as neurofibrillary tangles or glial fibrillary tangles in the cortex. Our findings suggest that ADC measurement might be useful for demonstrating subtle neuropathological changes. (orig.)
Isotropic apparent diffusion coefficient mapping of postnatal cerebral development
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Diffusion-weighted imaging (DWI) allows us to image the motion of tissue water. This has been used to demonstrate acute ischaemia. Diffusion imaging is also sensitive to water movement along neuronal tracts. Our objective was to map brain maturation in vivo using maps of apparent diffusion coefficient (ADC). We studied 22 children without neurological disease aged between 2 and 720 days. MRI was performed at 1.5 tesla. Multislice single-shot echoplanar DWI was performed at b 0 and 1000 s/mm2. ADC maps were generated automatically and measurements were performed in the basal ganglia, frontal and temporal white matter and the pons. There was a decrease over time in water diffusion in the areas examined, most marked in the frontal (0.887-1.898 x 10-3 mm2/s) and temporal (1.077-1.748 x 10-3 mm2/s)lobes. There was little change, after an initial decrease, in the basal ganglia (0.690-1.336 x 10-3 mm2/s). There was a difference in water diffusion between the anterior (0.687-1.581 x 10-3 mm2/s) and posterior (0.533-1.393 x 10-3 mm2/s) pons. These changes correlate well with those observed in progressive myelination: the increased water content probably reflects incomplete myelination and the decrease with time in water motion reflects the increase in myelinated brain. (orig.)
Age dependence of the renal apparent diffusion coefficient in children
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Diffusion imaging has proved to be a powerful tool for diagnosing ischemic lesions in the brain, and the technique is now being applied to other organs, including the kidneys. For quantitative studies it is important to define the normal values of the apparent diffusion coefficient (ADC), given the important physiological changes that occur in the kidney during early childhood it is likely that the ADC changes markedly during this period. To evaluate the age dependent changes in the ADC of normal kidneys in the pediatric population. The whole kidney ADC was calculated for 62 pediatric patients on a 1.5-T system using a respiratory-triggered, single-shot diffusion tensor imaging sequence with b values of 50, 200, and 350 mm2/s. The ADC was found to increase with age with the largest increase being in the first year of life, the rate of change being described by a constant plus a power function, specifically 1349+{358.5*{age0.34}}, (P < 0.001). The renal ADC changes significantly during childhood. (orig.)
Apparent diffusion coefficients of breast tumors. Clinical application
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The purpose of this study was to evaluate the usefulness of apparent diffusion coefficient (ADC) for the differential diagnosis of breast tumors and to determine the relation between ADC and tumor cellularity. One hundred and thirty-six female patients (age range, 17-83 years; average age, 51.7 years) with 140 histologically proven breast tumors underwent diffusion-weighted magnetic resonance (MR) imaging (DWI) using the spin-echo echo-planar technique, and the ADCs of the tumors were calculated using 3 different b values, 0, 500, and 1000 s/mm2. The diagnoses consisted of fibroadenoma (FA, n=16), invasive ductal carcinoma, not otherwise specified (IDC, n=117), medullary carcinoma (ME, n=3) and mucinous carcinoma (MU, n=4). Tumor cellularity was calculated from surgical specimens. The ADCs of breast tumors and cellularity were compared between different histological types by analysis of variance and Scheffe's post hoc test. The correlation between tumor cellularity and ADC was analyzed by Pearson correlation test. Significant differences were observed in ADCs between FA and all types of cancers (P2=0.451). The ADC may potentially help in differentiating benign and malignant breast tumors. Tumor ADC correlates inversely with tumor cellularity. (author)
Discrimination of paediatric brain tumours using apparent diffusion coefficient histograms
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Bull, Jonathan G.; Clark, Christopher A. [UCL Institute of Child Health, Imaging and Biophysics Unit, London (United Kingdom); Saunders, Dawn E. [Great Ormond Street Hospital for Children NHS Trust, Department of Radiology, London (United Kingdom)
2012-02-15
To determine if histograms of apparent diffusion coefficients (ADC) can be used to differentiate paediatric brain tumours. Imaging of histologically confirmed tumours with pre-operative ADC maps were reviewed (54 cases, 32 male, mean age 6.1 years; range 0.1-15.8 years) comprising 6 groups. Whole tumour ADC histograms were calculated; normalised for volume. Stepwise logistic regression analysis was used to differentiate tumour types using histogram metrics, initially for all groups and then for specific subsets. All 6 groups (5 dysembryoplastic neuroectodermal tumours, 22 primitive neuroectodermal tumours (PNET), 5 ependymomas, 7 choroid plexus papillomas, 4 atypical teratoid rhabdoid tumours (ATRT) and 9 juvenile pilocytic astrocytomas (JPA)) were compared. 74% (40/54) were correctly classified using logistic regression of ADC histogram parameters. In the analysis of posterior fossa tumours, 80% of ependymomas, 100% of astrocytomas and 94% of PNET-medulloblastoma were classified correctly. All PNETs were discriminated from ATRTs (22 PNET and 4 supratentorial ATRTs) (100%). ADC histograms are useful in differentiating paediatric brain tumours, in particular, the common posterior fossa tumours of childhood. PNETs were differentiated from supratentorial ATRTs, in all cases, which has important implications in terms of clinical management. (orig.)
Solid focal liver lesion characterisation with apparent diffusion coefficient ratios
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Non-invasive characterisation of focal liver lesions using diffusion-weighted imaging (DWI) has been heavily investigated and has shown substantial overlap between benign and malignant lesions. We have calculated a ratio of lesion to normal liver to determine if it improves accuracy for correct categorisation. All hepatic MRI studies performed between 1st April 2009 and 26th September 2011 were retrospectively reviewed. Patients with solid focal liver lesions in whom a diagnosis could be established and had lesions over 10mm were included. Haemangiomas, cysts and patients with chronic liver disease were excluded. Apparent diffusion coefficient (ADC) values were calculated for each lesion and adjacent normal liver on breath hold DWI. Two hundred fifty-eight studies were performed and 206 were excluded leaving 52 scans and 58 lesions of which 47 were benign and 11 were malignant. The mean ADC value for benign lesions was 1196.6 (two standard deviations (2SD)=±399.9) and of benign liver 1101.5 (2SD=±329.8) with a ratio of benign lesion to benign liver of 1.1005 (2SD=±0.3783). The mean ADC of malignant lesions was 1153.0 (2SD=±604.9) and malignant liver of 1080.7 (2SD=±533.4) giving a malignant lesion to malignant liver ratio of 1.0890 (2SD=±0.4975). None of these results were statistically significant (all P>0.5). DWI is unable to reliably differentiate solid benign lesions from solid malignant lesions.
Somford, DM; Marks, MP; Thijs, VN; Tong, DC
2004-01-01
BACKGROUND AND PURPOSE: Diffusion-weighted (DW) imaging is more sensitive for early ischemia than CT, and apparent diffusion coefficient (ADC) mapping permits quantification of the severity of cytotoxic edema. We examined the relationship between early CT findings, ischemic lesion volume on DW image
In vivo measurement of apparent diffusion coefficients of hyperpolarized 13C‐labeled metabolites
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Søgaard, Lise Vejby; Schilling, Franz; Janich, Martin A.; Menzel, Marion I.; Ardenkjær-Larsen, Jan Henrik
2014-01-01
The combination of hyperpolarized MRS with diffusion weighting (dw) allows for determination of the apparent diffusion coefficient (ADC), which is indicative of the intra‐ or extracellular localization of the metabolite. Here, a slice‐selective pulsed‐gradient spin echo sequence was implemented t...
Diffusion-weighted MR and apparent diffusion coefficient in the evaluation of severe brain injury
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Purpose: To study apparent diffusion coefficient (ADC) maps in severely brain-injured patients. Material and Methods: Four deeply comatose patients with severe brain injury were investigated with single-shot, diffusion-weighted, spin-echo echo planar imaging. The tetrahedral diffusion gradient configuration and four iterations of a set of b-values (one time of 0 mm2/s, and four times of 1000 mm2/s) were used to create isotropic ADC maps with high signal-to-noise ratio. ADC values of gray and white matter were compared among patients and 4 reference subjects. Results: one patient was diagnosed as clinically brain dead after the MR examination. The patient's ADC values of gray and white matter were significantly lower than those of 3 other brain-injured patients. In addition the ADC value of white matter was significantly lower than that of gray matter. Conclusion: The patient with fatal outcome shortly after MR examination differed significantly from other patients with severe brain injury but non-fatal outcome, with regard to ADC values in gray and white matter. This might indicate a prognostic value of ADC maps in the evaluation of traumatic brain injury
Chen, Lihua; Liu, Min; Bao, Jing; XIA, YUNBAO; Zhang, Jiuquan; Zhang, Lin; Huang, Xuequan; Jian WANG
2013-01-01
Objective To perform a meta-analysis exploring the correlation between the apparent diffusion coefficient (ADC) and tumor cellularity in patients. Materials and Methods We searched medical and scientific literature databases for studies discussing the correlation between the ADC and tumor cellularity in patients. Only studies that were published in English or Chinese prior to November 2012 were considered for inclusion. Summary correlation coefficient (r) values were extracted from each study...
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To evaluate the usefulness of apparent diffusion coefficient (ADC) values using diffusion-weighted magnetic resonance imaging (DWI) in patients with ovarian cystic tumors. During past 12 months, we studied 30 patients who were clinically suspected of having ovarian cystic tumors and who underwent DWI using a 1.5 T MR unit, Eight patients with small cystic ovarian lesions of less than 3 cm in diameter and insufficient DWI were excluded from the calculation of the ADC values. The remaining twenty-six cystic ovarian lesions in 22 patients were classified into four groups; ovarian cysts, cystadenomas, other benign tumors, and malignant tumors. DWI was obtained using single-shot spin echo planar imaging and two gradient steps (b values of 0, 800 sec/mm2). The ADC values were measured using regions-of-interest (ROI) in the cystic components of the DWI located in the same section as the T2-weighted image and away from the septation and solid components. The mean ADC values were 0.196 ± 0.105 x 10-3 mm2/sec in the ovarian cysts, 1.312 ± 1.064 x 10-3 mm2/sec in the cystadenomas, 0.274 ± 0.124 x 10-3 mm2/sec in the other benign tumors, and 1.011 ± 0.080 x 10-3 mm2/sec in the malignant tumors. The differences in the ADC values between the ovarian cysts and cystadenomas, the ovarian cysts and malignant tumors, the cystadenomas and other benign tumors, and the other benign tumors and mailgnant tumors were statistically significant (ρ 0.05). The calculated ADC values using DWI should be helpful in the differential diagnosis of cystic ovarian tumors
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Objective: To evaluate the relationship between apparent diffusion coefficient (ADC) value and the local invasiveness of endometrial carcinoma. Methods and materials: The MR imaging of seventy-three patients with endometrial carcinoma proved by post-operative pathology and sixty-four patients with healthy uteri were retrospectively reviewed. All MR examinations included axial T2WI and T1WI, sagittal T2WI and diffusion-weighted sequences (b = 0 and b = 1000 s/mm2). Tumor size, mean ADC value (ADCm) and quartile ADC (ADCq) were acquired on post-processing workstation using voxel-analysis software. Differences between the ADC values among three layers of normal uterine body and endometrial carcinomas were compared by ANOVA test. Groups were divided according to pathologic type, histologic grade, depth of myometrial infiltration, presence of cervical invasion and lymphovascular space invasion, and lymph node metastasis. Tumor size and ADC values were compared and analyzed. Results: ADC values were different in three zones of uterine body (P −3 mm2/s] and highest in outer myometrium [(1.496 ± 0.196) × 10−3 mm2/s]. Mean ADC value of endometrial carcinomas [(1.011 ± 0.121) × 10−3 mm2/s] was lower than the normal uterine body. Quartile ADC and tumor size were greater in groups with more invasive pathologic factors (P < 0.05). Deep myometrial infiltration, cervical invasion, lymphovascular space invasion and lymph node metastasis were more common as quartile ADC values and tumor sizes increased. Conclusion: Mean ADC value was lower in endometrial carcinoma was lower than the normal uterus. Quartile ADC, representing the intra-tumor heterogeneity of water movement, had a profound relationship with invasiveness of endometrial carcinomas, while mean ADC value did not. ADC values may serve as a quantitative indicator to complement routine sequences.
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Costantini, M.; Belli, P.; Rinaldi, P. [Department of Bio-Sciences and Radiological Imaging, Catholic University, Rome (Italy); Bufi, E., E-mail: reagandus@alice.i [Department of Bio-Sciences and Radiological Imaging, Catholic University, Rome (Italy); Giardina, G. [Department of Bio-Sciences and Radiological Imaging, Catholic University, Rome (Italy); Franceschini, G. [Department of Surgery, Catholic University, Rome (Italy); Petrone, G. [Department of Pathology, Catholic University, Rome (Italy); Bonomo, L. [Department of Bio-Sciences and Radiological Imaging, Catholic University, Rome (Italy)
2010-12-15
Aim: To assess the utility of diffusion-weighted imaging in diagnosing and characterizing breast malignancy. Materials and methods: From April 2006 to April 2009, all consecutive patients with breast cancer undergoing breast magnetic resonance imaging (MRI) and subsequent surgery in our hospital were enrolled in this study. MRI was performed using a 1.5 T MRI unit using a dedicated, bilateral, four-channel breast coil. The MRI protocol included a diffusion sequence acquired using b values of 0 and 1000 s/mm{sup 2}. For each malignant lesion the relationships between tumour grade and histology and the relative value of the apparent diffusion coefficient (ADC) were analysed. Results: There were 136 female patients with 162 lesions. Histology revealed 149 invasive carcinomas and 13 ductal carcinomas in situ. There were 34 grade 1, 61 grade 2, and 67 grade 3 lesions. The mean ADC value of all malignant lesions was 1.03 x 10{sup -3} mm{sup 2}/s. The mean ADC values for invasive and in situ carcinomas were 1.03 x 10{sup -3} mm{sup 2}/s and 1.05 x 10{sup -3} mm{sup 2}/s, respectively. The mean ADC values for grade 1, 2, and 3 tumours were 1.25 x 10{sup -3} mm{sup 2}/s, 1.02 x 10{sup -3} mm{sup 2}/s, and 0.92 x 10{sup -3} mm{sup 2}/s, respectively. A statistically significant (p < 0.001) inverse correlation was disclosed between the ADC value and the tumour grading. The mean ADC value of the 'less aggressive' group of disease (G1 and in situ lesions) was 1.19 x 10{sup -3} mm{sup 2}/s, whereas the mean ADC value of the 'more aggressive' group (G2-G3 invasive carcinomas) was 0.96 x 10{sup -3} mm{sup 2}/s (p < 0.001). Conclusion: The study confirms the usefulness of diffusion imaging in assessing the aggressiveness of breast tumours. ADC appears to be a promising parameter in the evaluation of the degree of malignancy of breast cancer tissue.
Lu, Hong; Lei, Xiaoyan
2014-01-01
After traumatic brain injury, vasogenic and cytotoxic edema appear sequentially on the involved side. Neuroimaging investigations of edema on the injured side have employed apparent diffusion coefficient measurements in diffusion tensor imaging. We investigated the changes occurring on the injured and uninjured sides using diffusion tensor imaging/apparent diffusion coefficient and histological samples in rats. We found that, on the injured side, that vasogenic edema appeared at 1 hour and in...
Apparent diffusion coefficient parametric response mapping MRI for follow-up of glioblastoma
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Yoon, Ra Gyoung [Catholic Kwandong University International St. Mary' s Hospital, Catholic Kwandong University College of Medicine, Department of Radiology, Seo-gu, Incheon (Korea, Republic of); Kim, Ho Sung; Hong, Gil Sun; Kim, Sang Joon [Asan Medical Center, University of Ulsan College of Medicine, Department of Radiology and Research Institute of Radiology, Songpa-Gu, Seoul (Korea, Republic of); Kim, Dae Yoon [Bundang Jesaeng Hospital, Department of Radiology, Seongnam-si, Gyeonggi-do (Korea, Republic of)
2016-04-15
To determine the diagnostic superiority of parametric response mapping of apparent diffusion coefficient (ADCPR) for predicting glioblastoma treatment response, compared to single time point measurement. Fifty post-treatment glioblastoma patients were enrolled. ADCPR was calculated from serial apparent diffusion coefficient (ADC) maps acquired before and at the time of first detection of an enlarged contrast-enhancing lesion on voxel-by-voxel basis. The percentage-decrease in ADCPR and tenth percentile histogram cutoff value of ADC (ADC10) were compared at subsequent 3-month and 1-year follow-ups. The percentage-decrease in ADCPR was significantly higher in the progression group (mean = 33.2-38.3 %) than in the stable-response group (mean = 9.7 %) at 3 months follow-up (corrected p < 0.001 for both readers). ADCPR significantly improved area under the receiver operating characteristic curve from 0.67 to 0.88 (corrected p = 0.037) and from 0.70 to 0.92 (corrected p = 0.020) for both readers, respectively, compared to ADC10 at 3-month follow-up, but did not significantly improve at 1-year follow-up. The inter-reader agreement was higher for ADCPR than ADC10 (intraclass correlation coefficient, 0.93 versus 0.86). Voxel-based ADCPR appears to be a superior imaging biomarker than ADC, particularly for predicting early tumour progression in patients with glioblastoma. (orig.)
Apparent diffusion coefficient parametric response mapping MRI for follow-up of glioblastoma
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To determine the diagnostic superiority of parametric response mapping of apparent diffusion coefficient (ADCPR) for predicting glioblastoma treatment response, compared to single time point measurement. Fifty post-treatment glioblastoma patients were enrolled. ADCPR was calculated from serial apparent diffusion coefficient (ADC) maps acquired before and at the time of first detection of an enlarged contrast-enhancing lesion on voxel-by-voxel basis. The percentage-decrease in ADCPR and tenth percentile histogram cutoff value of ADC (ADC10) were compared at subsequent 3-month and 1-year follow-ups. The percentage-decrease in ADCPR was significantly higher in the progression group (mean = 33.2-38.3 %) than in the stable-response group (mean = 9.7 %) at 3 months follow-up (corrected p < 0.001 for both readers). ADCPR significantly improved area under the receiver operating characteristic curve from 0.67 to 0.88 (corrected p = 0.037) and from 0.70 to 0.92 (corrected p = 0.020) for both readers, respectively, compared to ADC10 at 3-month follow-up, but did not significantly improve at 1-year follow-up. The inter-reader agreement was higher for ADCPR than ADC10 (intraclass correlation coefficient, 0.93 versus 0.86). Voxel-based ADCPR appears to be a superior imaging biomarker than ADC, particularly for predicting early tumour progression in patients with glioblastoma. (orig.)
A new in-situ method to determine the apparent gas diffusion coefficient of soils
Laemmel, Thomas; Paulus, Sinikka; Schack-Kirchner, Helmer; Maier, Martin
2015-04-01
Soil aeration is an important factor for the biological activity in the soil and soil respiration. Generally, gas exchange between soil and atmosphere is assumed to be governed by diffusion and Fick's Law is used to describe the fluxes in the soil. The "apparent soil gas diffusion coefficient" represents the proportional factor between the flux and the gas concentration gradient in the soil and reflects the ability of the soil to "transport passively" gases through the soil. One common way to determine this coefficient is to take core samples in the field and determine it in the lab. Unfortunately this method is destructive and needs laborious field work and can only reflect a small fraction of the whole soil. As a consequence insecurity about the resulting effective diffusivity on the profile scale must remain. We developed a new in-situ method using new gas sampling device, tracer gas and inverse soil gas modelling. The gas sampling device contains several sampling depths and can be easily installed into vertical holes of an auger, which allows for fast installation of the system. At the lower end of the device inert tracer gas is injected continuously. The tracer gas diffuses into the surrounding soil. The resulting distribution of the tracer gas concentrations is used to deduce the diffusivity profile of the soil. For Finite Element Modeling of the gas sampling device/soil system the program COMSOL is used. We will present the results of a field campaign comparing the new in-situ method with lab measurements on soil cores. The new sampling pole has several interesting advantages: it can be used in-situ and over a long time; so it allows following modifications of diffusion coefficients in interaction with rain but also vegetation cycle and wind.
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In summary, cellular components are greatly responsible for the reduced diffusion coefficient in biologic tissues, and there is growing evidence that membranes, even if they are permeable, are likely the main actor that 'hinders' the water diffusion process. Even if one reduces the diffusion process to membrane interactions, the ADC is expected to depend on both the membrane permeability and its geometry within the tissue, which could have conflicting results on the overall diffusion MR imaging signal. Such considerations have led to some speculations on how the ADC is modulated by cell size (decrease in ADC associated with cell swelling and membrane surface increase, as observed in stroke or neuronal activation), cell density (decrease in ADC associated with the increased membrane content), or cell or membrane orientation (diffusion anisotropy in white matter fibers). But those 'explanations' have remained desperately qualitative. Clearly one would like to know much more: amount of cell swelling, or cell density, and so on. To understand better, some physical modeling comes in as a necessity. Simulation work shows that the ADC which is obtained at low b values (typically a few hundred up to 1000 sec/mm2) mostly reflects the extracellular space unless cells or some cellular elements are strongly elongated along the diffusion measurement direction. The intracellular space remains invisible (and variations of intracellular diffusion cannot be seen), as long as membrane permeability remains normal (that is not particularly high). The variations in ADC according to physiologic or pathologic conditions that have been observed, thus, result from the negative indirect imprint of the cells on the topology of the extracellular space: Cell swelling and cell proliferation tend to 'squeeze' the extracellular space, resulting in an increase in tortuosity and a decrease in ADC. However, specificity remains low. For instance, in the presence of two
The effect of age on apparent diffusion coefficient values in normal spleen: A preliminary study
International Nuclear Information System (INIS)
Aim: To investigate and characterize the effect of age on apparent diffusion coefficient (ADC) values in normal spleen. Materials and methods: A population of 127 patients (age range 10–79 years, mean age 44.4 years) without magnetic resonance imaging findings in abdominal scans, was selected over a 5-year period. The ADC values of the spleen were analysed in all ages, and dependency of ADC values on age was characterized using Spearman's correlation coefficient test. Results: A reduction of ADC values with ageing was found in the spleen (r = −0.702, p < 0.001). Conclusions: The ADC values of the spleen decline with age. This should be taken into consideration when disease is diagnosed
Apparent diffusion coefficients of normal uterus in premenopausal women with 3 T MRI
International Nuclear Information System (INIS)
Aim: To investigate the apparent diffusion coefficient (ADC) values of the normal uterine cervical zonal structures (cervical epithelium, the junctional zone, and myometrium) during different phases of the menstrual cycle among premenopausal women in different age groups. Materials and methods: Seventy healthy women, who were divided into three age groups (group A, 24 women in their twenties; group B, 23 women in their thirties; group C, 23 women in their forties), underwent 3 T magnetic resonance imaging (MRI) with T2-weighted and diffusion-weighted imaging (DWI) during the mid-proliferative and the mid-secretory phases. Results: The ADC values of each cervical zonal structure were significantly different from one another (p 0.05). Conclusion: ADC values of normal cervical epithelium and the junctional zone change with different phases of the menstrual cycle, which should be taken into consideration when early cervical disease is detected, when monitoring treatment response, and differentiating early tumour recurrence
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Highlights: • Apparent diffusion coefficient is a quantitative parameter which reflects molecular water movement. • Grading is an independent prognostic factor which correlates with other histopathological features. • Apparent diffusion coefficient values were significantly different between G1 and G3 classes. - Abstract: Purpose: The aim of this study was to evaluate whether the apparent diffusion coefficient (ADC) provided by 3.0 T (3 T) magnetic resonance diffusion-weighted imaging (DWI) varied according to the grading of invasive breast carcinoma. Materials and methods: A total of 92 patients with 96 invasive breast cancer lesions were enrolled; all had undergone 3 T magnetic resonance imaging (MRI) for local staging. All lesions were confirmed by histological analysis, and tumor grade was established according to the Nottingham Grading System (NGS). MRI included both dynamic contrast-enhanced and DWI sequences, and ADC value was calculated for each lesion. ADC values were compared with NGS classification using the Mann–Whitney U and the Kruskal–Wallis H tests. Grading was considered as a comprehensive prognostic factor, and Rho Spearman test was performed to determine correlation between grading and tumor size, hormonal receptor status, HER2 expression and Ki67 index. Pearson's Chi square test was carried out to compare grading with the other prognostic factors. Results: ADC values were significantly higher in G1 than in G3 tumors. No significant difference was observed when G1 and G3 were compared with G2. Tumor size, hormonal receptor status, HER2 expression and Ki67 index correlated significantly with grading but there was a significant difference only between G1 and G3 related to the ER and PR status, HER2 expression and Ki67 index. There was no statistically significant difference in lesion size between the two groups. Conclusion: ADC values obtained on 3 T DWI correlated with low-grade (G1) and high-grade (G3) invasive breast carcinoma. 3
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Cipolla, Valentina, E-mail: valentina.cipolla@yahoo.it [Department of Radiological Sciences, University of Rome “Sapienza”, Viale del Policlinico 155, 00161 Rome (Italy); Santucci, Domiziana; Guerrieri, Daniele; Drudi, Francesco Maria [Department of Radiological Sciences, University of Rome “Sapienza”, Viale del Policlinico 155, 00161 Rome (Italy); Meggiorini, Maria Letizia [Department of Gynaecological Sciences, University of Rome “Sapienza”, Viale del Policlinico 155, 00161 Rome (Italy); Felice, Carlo de [Department of Radiological Sciences, University of Rome “Sapienza”, Viale del Policlinico 155, 00161 Rome (Italy)
2014-12-15
Highlights: • Apparent diffusion coefficient is a quantitative parameter which reflects molecular water movement. • Grading is an independent prognostic factor which correlates with other histopathological features. • Apparent diffusion coefficient values were significantly different between G1 and G3 classes. - Abstract: Purpose: The aim of this study was to evaluate whether the apparent diffusion coefficient (ADC) provided by 3.0 T (3 T) magnetic resonance diffusion-weighted imaging (DWI) varied according to the grading of invasive breast carcinoma. Materials and methods: A total of 92 patients with 96 invasive breast cancer lesions were enrolled; all had undergone 3 T magnetic resonance imaging (MRI) for local staging. All lesions were confirmed by histological analysis, and tumor grade was established according to the Nottingham Grading System (NGS). MRI included both dynamic contrast-enhanced and DWI sequences, and ADC value was calculated for each lesion. ADC values were compared with NGS classification using the Mann–Whitney U and the Kruskal–Wallis H tests. Grading was considered as a comprehensive prognostic factor, and Rho Spearman test was performed to determine correlation between grading and tumor size, hormonal receptor status, HER2 expression and Ki67 index. Pearson's Chi square test was carried out to compare grading with the other prognostic factors. Results: ADC values were significantly higher in G1 than in G3 tumors. No significant difference was observed when G1 and G3 were compared with G2. Tumor size, hormonal receptor status, HER2 expression and Ki67 index correlated significantly with grading but there was a significant difference only between G1 and G3 related to the ER and PR status, HER2 expression and Ki67 index. There was no statistically significant difference in lesion size between the two groups. Conclusion: ADC values obtained on 3 T DWI correlated with low-grade (G1) and high-grade (G3) invasive breast carcinoma. 3
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To define a range of apparent diffusion coefficient values in spinal tuberculosis and to evaluate the sensitivity of diffusion-weighted magnetic resonance imaging (DW-MRI) and apparent diffusion coefficient values in patients of spinal tuberculosis. This study was conducted over a period of 20 months and included 110 patients with a total of 230 vertebral bodies. The study was performed in two parts. The first part included all patients of known tuberculosis and patients with classical features of tuberculosis. The second part included patients with spinal pathology of indeterminate etiology. All the patients underwent a routine MRI examination along with diffusion sequences. The apparent diffusion coefficient (ADC) values were calculated from all the involved vertebral bodies. The mean ADC value of affected vertebrae in first part of the study was found to be 1.4 ± 0.20 × 10−3 mm2/s. This ADC value was then applied to patients in the second part of study in order to determine its ability in predicting tuberculosis. This range of ADC values was significantly different from the mean ADC values of normal vertebrae and those with metastatic involvement. However, there was an overlap of ADC values in a few tuberculous vertebrae with the ADC values in metastatic vertebrae. We found that DW-MRI and ADC values may help in the differentiation of spinal tuberculosis from other lesions of similar appearance. However, an overlap of ADC values was noted with those of metastatic vertebrae. Therefore diffusion imaging and ADC values must always be interpreted in association with clinical history and routine MRI findings and not in isolation
Apparent diffusion coefficient and fractional anisotropy of newly diagnosed grade II gliomas.
Khayal, Inas S; McKnight, Tracy R; McGue, Colleen; Vandenberg, Scott; Lamborn, Kathleen R; Chang, Susan M; Cha, Soonmee; Nelson, Sarah J
2009-05-01
Distinguishing between low-grade oligodendrogliomas (ODs) and astrocytomas (AC) is of interest for defining prognosis and stratifying patients to specific treatment regimens. The purpose of this study was to determine if the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) from diffusion imaging can help to differentiate between newly diagnosed grade II OD and AC subtypes and to evaluate the ADC and FA values for the mixed population of oligoastrocytomas (OA). Fifty-three patients with newly diagnosed grade II gliomas were studied using a 1.5T whole body scanner (23 ODs, 16 ACs, and 14 OAs). The imaging protocol included post-gadolinium T1-weighted images, T2-weighted images, and either three and/or six directional diffusion imaging sequence with b = 1000 s/mm(2). Diffusion-weighted images were analyzed using in-house software to calculate maps of ADC and for six directional acquisitions, FA. The intensity values were normalized by values from normal appearing white matter (NAWM) to generate maps of normalized apparent diffusion coefficient (nADC) and normalized fractional anisotropy (nFA). The hyperintense region in the T2 weighted image was defined as the T2All region. A Mann-Whitney rank-sum test was performed on the 25th, median, and 75th nADC and nFA among the three subtypes. Logistic regression was performed to determine how well the nADC and nFA predict subtype. Lesions diagnosed as being OD had significantly lower nADC and significantly higher nFA, compared to AC. The nADC and nFA values individually classified the data with an accuracy of 87%. Combining the two did not enhance the classification. The patients with OA had nADC and nFA values between those of OD and AC. This suggests that ADC and FA may be helpful in directing tissue sampling to the most appropriate regions for taking biopsies in order to make a definitive diagnosis. PMID:19125391
Apparent diffusion coefficient and fractional anisotropy of newly diagnosed grade II gliomas†
Khayal, Inas S.; McKnight, Tracy R.; McGue, Colleen; Vandenberg, Scott; Lamborn, Kathleen R.; Chang, Susan M.; Cha, Soonmee; Nelson, Sarah J.
2013-01-01
Distinguishing between low-grade oligodendrogliomas (ODs) and astrocytomas (AC) is of interest for defining prognosis and stratifying patients to specific treatment regimens. The purpose of this study was to determine if the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) from diffusion imaging can help to differentiate between newly diagnosed grade II OD and AC subtypes and to evaluate the ADC and FA values for the mixed population of oligoastrocytomas (OA). Fifty-three patients with newly diagnosed grade II gliomas were studied using a 1.5T whole body scanner (23 ODs, 16 ACs, and 14 OAs). The imaging protocol included post-gadolinium T1-weighted images, T2-weighted images, and either three and/or six directional diffusion imaging sequence with b = 1000 s/mm2. Diffusion-weighted images were analyzed using in-house software to calculate maps of ADC and for six directional acquisitions, FA. The intensity values were normalized by values from normal appearing white matter (NAWM) to generate maps of normalized apparent diffusion coefficient (nADC) and normalized fractional anisotropy (nFA). The hyperintense region in the T2 weighted image was defined as the T2All region. A Mann–Whitney rank-sum test was performed on the 25th, median, and 75th nADC and nFA among the three subtypes. Logistic regression was performed to determine how well the nADC and nFA predict subtype. Lesions diagnosed as being OD had significantly lower nADC and significantly higher nFA, compared to AC. The nADC and nFA values individually classified the data with an accuracy of 87%. Combining the two did not enhance the classification. The patients with OA had nADC and nFA values between those of OD and AC. This suggests that ADC and FA may be helpful in directing tissue sampling to the most appropriate regions for taking biopsies in order to make a definitive diagnosis. PMID:19125391
DEFF Research Database (Denmark)
Boesen, Lars; Chabanova, Elizaveta; Løgager, Vibeke; Balslev, Ingegerd; Thomsen, Henrik S
2015-01-01
PURPOSE: To evaluate the correlation between apparent diffusion coefficient measurements (ADCtumor and ADCratio ) and the Gleason score from radical prostatectomy specimens. MATERIALS AND METHODS: Seventy-one patients with clinically localized prostate cancer scheduled for radical prostatectomy...... correlated with the Gleason score from the prostatectomy specimens. RESULTS: The association between ADC measurements and Gleason score showed a significant negative correlation (P < 0.001) with Spearman's rho for ADCtumor (-0.421) and ADCratio (-0.649). There was a statistically significant difference...... ) and 0.90 (ADCratio ) when discriminating Gleason score ≤7(3+4) from Gleason score ≥7(4+3). CONCLUSION: ADC measurements showed a significant correlation with tumor Gleason score at final pathology. The ADCratio demonstrated the best correlation compared to the ADCtumor value and radically improved...
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Hong Lu; Xiaoyan Lei
2014-01-01
After traumatic brain injury, vasogenic and cytotoxic edema appear sequentially on the in-volved side. Neuroimaging investigations of edema on the injured side have employed apparent diffusion coefficient measurements in diffusion tensor imaging. We investigated the changes occurring on the injured and uninjured sides using diffusion tensor imaging/apparent diffusion coefficient and histological samples in rats. We found that, on the injured side, that vasogen-ic edema appeared at 1 hour and intracellular edema appeared at 3 hours. Mixed edema was observed at 6 hours, worsening until 12-24 hours post-injury. Simultaneously, microglial cells proliferated at the trauma site. Apparent diffusion coefficient values increased at 1 hour, decreased at 6 hours, and increased at 12 hours. The uninjured side showed no significant pathological change at 1 hour after injury. Cytotoxic edema appeared at 3 hours, and vasogen-ic edema was visible at 6 hours. Cytotoxic edema persisted, but vasogenic edema tended to decrease after 12-24 hours. Despite this complex edema pattern on the uninjured side with associated pathologic changes, no significant change in apparent diffusion coefficient values was detected over the first 24 hours. Apparent diffusion coefficient values accurately detected the changes on the injured side, but did not detect the changes on the uninjured side, giving a false-negative result.
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Diffusion-weighted imaging (DWI) along with the calculation of apparent diffusion coefficient (ADC), is a novel, non-invasive, and reliable technique of choice for accurate assessment and for the treatment planning of different types of brain tumors. It is more advantageous in the distinction and differentiation of benign from malignant meningiomas on the basis of ADC values. To investigate the utility of DW magnetic resonance imaging (MRI), and to compare the apparent diffusion coefficient (ADC) obtained at two b-values for an authentic and preoperative characterization of meningiomas. Twenty-six patients with clinically diagnosed or histologically verified meningioma (18 benign and 8 malignant) underwent imaging including DWI at 1.5 T. DW images were obtained at b = 1000 s/mm2 and b = 2000 s/mm2, ADC maps were generated at both the b-values. Signal intensities (SIs) and ADCs for solid tumorous tissues, contralateral normal tissues, and peritumoral edema were calculated and normalized ADC (NADC) ratio were determined for tumorous tissues. SI scores, ADC maps, and ADC values were analyzed visually and quantitatively, and were compared at both the b-values. DW images at b = 2000 s/mm2 were more conspicuity (either hyperintense or hypointense) with improved contrast. The mean ADC of malignant meningiomas (0.64 ± 0.05 and 0.42 ± 0.03) was significantly lower (P < 0.05) as compared with benign meningiomas (1.04 ± 0.12 and 0.80 ± 0.07) at both the b-values. Mean NADC ratio in the malignant type was also significantly lower (P < 0.05) than the benign type at both the b-values. Mean ADC values for peritumoral edema do not differ between benign and malignant meningiomas. 1.5-T DWI using high b-values improved our ability to differentiate benign from malignant meningiomas. DWI may play an important role in the preoperative radiological evaluation and the recognition of these types for proper surgical treatment
The use of MRI apparent diffusion coefficient (ADC in monitoring the development of brain infarction
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Yuan Jian-Jun
2011-01-01
Full Text Available Abstract Background To study the rules that apparent diffusion coefficient (ADC changes with time and space in cerebral infarction, and to provide the evidence in defining the infarction stages. Methods 117 work-ups in 98 patients with cerebral infarction (12 hyperacute, 43 acute, 29 subacute, 10 steady, and 23 chronic infarctions were imaged with both conventional MRI and diffusion weighted imaging. The average ADC values, the relative ADC (rADC values, and the ADC values or rADC values from the center to the periphery of the lesion were calculated. Results The average ADC values and the rADC values of hyperacute and acute infarction lesion depressed obviously. rADC values in hyperacute and acute stage was minimized, and increased progressively as time passed and appeared as "pseudonormal" values in approximately 8 to 14 days. Thereafter, rADC values became greater than normal in chronic stage. There was positive correlation between rADC values and time (P Conclusion The ADC values of infarction lesions have evolution rules with time and space. The evolution rules with time and those in space can be helpful to decide the clinical stage, and to provide the evidence in guiding the treatment or judging the prognosis in infarction.
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Naganawa, Shinji; Sato, Chiho; Ishigaki, Takeo [Nagoya University School of Medicine, Department of Radiology, Nagoya (Japan); Kumada, Hisashi; Miura, Shunichi [Toyohashi Municipal hospital, Department of Radiology, Toyohashi, Aich (Japan); Takizawa, Osamu [Siemens-Asahi Medical Technologies Ltd, Tokyo (Japan)
2005-01-01
A relation between apparent diffusion coefficient (ADC) values and tumor cellular density has been reported. The purpose of this study was to measure the ADC values of cervical cancers in the uterus and compare them with those of normal cervical tissues, and to test whether ADC could differentiate between normal and malignant cervical tissues in the uterus. Twelve consecutive female patients with cervical cancer of the uterus and ten female patients with other pelvic abnormalities were included in this study. ADC was measured at 1.5 T with b-factors of 0, 300 and 600 s/mm{sup 2} using single-shot echo-planar diffusion-weighted imaging and a parallel imaging technique. The mean ADC value of cervical cancer lesions was 1.09{+-}0.20 x 10{sup -3} mm{sup 2}/s, and that of normal cervix tissue was 1.79{+-}0.24 x 10{sup -3} mm{sup 2}/s (P<0.0001). In nine patients treated by chemotherapy and/or radiation therapy, the mean ADC value of the cervical cancer lesion increased significantly after therapy (P<0.001). The present study showed, with a small number of patients, that ADC measurement has a potential ability to differentiate between normal and cancerous tissue in the uterine cervix. Further study is necessary to determine the accuracy of ADC measurement in monitoring the treatment response. (orig.)
Regional apparent diffusion coefficient values in 3rd trimester fetal brain
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Hoffmann, Chen [Tel Aviv University, Department of Radiology, Sheba Medical Center, Tel Hashomer (affiliated to the Sackler School of Medicine), Tel Aviv (Israel); Sheba Medical Center, Diagnostic Imaging, 52621, Tel Hashomer (Israel); Weisz, Boaz; Lipitz, Shlomo; Katorza, Eldad [Tel Aviv University, Department of Obstetrics and Gynecology, Sheba Medical Center, Tel Hashomer (affiliated to the Sackler School of Medicine), Tel Aviv (Israel); Yaniv, Gal; Bergman, Dafi [Tel Aviv University, Department of Radiology, Sheba Medical Center, Tel Hashomer (affiliated to the Sackler School of Medicine), Tel Aviv (Israel); Biegon, Anat [Stony Brook University School of Medicine, Department of Neurology, Stony Brook, NY (United States)
2014-07-15
Apparent diffusion coefficient (ADC) values in the developing fetus can be used in the diagnosis and prognosis of prenatal brain pathologies. To this end, we measured regional ADC in a relatively large cohort of normal fetal brains in utero. Diffusion-weighted imaging (DWI) was performed in 48 non-sedated 3rd trimester fetuses with normal structural MR imaging results. ADC was measured in white matter (frontal, parietal, temporal, and occipital lobes), basal ganglia, thalamus, pons, and cerebellum. Regional ADC values were compared by one-way ANOVA with gestational age as covariate. Regression analysis was used to examine gestational age-related changes in regional ADC. Four other cases of CMV infection were also examined. Median gestational age was 32 weeks (range, 26-33 weeks). There was a highly significant effect of region on ADC, whereby ADC values were highest in white matter, with significantly lower values in basal ganglia and cerebellum and the lowest values in thalamus and pons. ADC did not significantly change with gestational age in any of the regions tested. In the four cases with fetal CMV infection, ADC value was associated with a global decrease. ADC values in normal fetal brain are relatively stable during the third trimester, show consistent regional variation, and can make an important contribution to the early diagnosis and possibly prognosis of fetal brain pathologies. (orig.)
Apparent diffusion coefficient histogram analysis of neonatal hypoxic-ischemic encephalopathy
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Cauley, Keith A. [University of Massachusetts Medical School, Department of Radiology, Worcester, MA (United States); New York Presbyterian Hospital, Columbia University Medical Center, Department of Radiology, New York, NY (United States); Filippi, Christopher G. [New York Presbyterian Hospital, Columbia University Medical Center, Department of Radiology, New York, NY (United States)
2014-06-15
Diffusion-weighted imaging is a valuable tool in the assessment of the neonatal brain, and changes in diffusion are seen in normal development as well as in pathological states such as hypoxic-ischemic encephalopathy (HIE). Various methods of quantitative assessment of diffusion values have been reported. Global ischemic injury occurring during the time of rapid developmental changes in brain myelination can complicate the imaging diagnosis of neonatal HIE. To compare a quantitative method of histographic analysis of brain apparent coefficient (ADC) maps to the qualitative interpretation of routine brain MR imaging studies. We correlate changes in diffusion values with gestational age in radiographically normal neonates, and we investigate the sensitivity of the method as a quantitative measure of hypoxic-ischemic encephalopathy. We reviewed all brain MRI studies from the neonatal intensive care unit (NICU) at our university medical center over a 4-year period to identify cases that were radiographically normal (23 cases) and those with diffuse, global hypoxic-ischemic encephalopathy (12 cases). We histographically displayed ADC values of a single brain slice at the level of the basal ganglia and correlated peak (s-sD{sub av}) and lowest histogram values (s-sD{sub lowest}) with gestational age. Normative s-sD{sub av} values correlated significantly with gestational age and declined linearly through the neonatal period (r {sup 2} = 0.477, P < 0.01). Six of 12 cases of known HIE demonstrated significantly lower s-sD{sub av} and s-sD{sub lowest} ADC values than were reflected in the normative distribution; several cases of HIE fell within a 95% confidence interval for normative studies, and one case demonstrated higher-than-normal s-sD{sub av}. Single-slice histographic display of ADC values is a rapid and clinically feasible method of quantitative analysis of diffusion. In this study normative values derived from consecutive neonates without radiographic evidence of
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Balliu, E. [Department of Magnetic Resonance, IDI Girona, Hospital Universitari de Girona Dr Josep Trueta, Girona (Spain)], E-mail: eballiu@gmail.com; Vilanova, J.C. [Department of Magnetic Resonance, Clinica Girona, Girona (Spain)], E-mail: Kvilanova@comg.es; Pelaez, I. [Department of Magnetic Resonance, IDI Girona, Hospital Universitari de Girona Dr Josep Trueta, Girona (Spain)], E-mail: isapelaezrx@yahoo.es; Puig, J. [Department of Magnetic Resonance, IDI Girona, Hospital Universitari de Girona Dr Josep Trueta, Girona (Spain)], E-mail: jpuigalcantara@yahoo.es; Remollo, S. [Department of Magnetic Resonance, IDI Girona, Hospital Universitari de Girona Dr Josep Trueta, Girona (Spain)], E-mail: sremollo@gmail.com; Barcelo, C. [Department of Computer Science and Applied Mathematics, University of Girona (Spain)], E-mail: carles.barcelo@udg.es; Barcelo, J. [Department of Magnetic Resonance, Clinica Girona, Girona (Spain)], E-mail: rmgirona@comg.es; Pedraza, S. [Department of Magnetic Resonance, IDI Girona, Hospital Universitari de Girona Dr Josep Trueta, Girona (Spain)], E-mail: sapedraza@gmail.com
2009-03-15
Aim: The aim of this study is to evaluate the value of the apparent diffusion coefficient (ADC) obtained in diffusion-weighted (DW) MR sequences for the differentiation between malignant and benign bone marrow lesions. Method: Forty-five patients with altered signal intensity vertebral bodies on conventional MR sequences were included. The cause of altered signal intensity was benign osteoporotic collapse in 16, acute neoplastic infiltration in 15, and infectious processes in 14; based on plain-film, CT, bone scintigraphy, conventional MR studies, biopsy or follow-up. All patients underwent isotropic DW MR images (multi-shot EPI, b values of 0 and 500 s/mm{sup 2}). Signal intensity at DW MR images was evaluated and ADC values were calculated and compared between malignancy, benign edema and infectious spondylitis. Results: Acute malignant fractures were hyperintense compared to normal vertebral bodies on the diffusion-weighted sequence, except in one patient with sclerotic metastases. Mean ADC value from benign edema (1.9 {+-} 0.39 x 10{sup -3} mm{sup 2}/s) was significantly (p < 0.0001) higher than untreated metastasic lesions (0.9 {+-} 1.3 x 10{sup -3} mm{sup 2}/s). Mean ADC value of infectious spondilytis (0.96 {+-} 0.49 x 10{sup -3} mm{sup 2}/s) was not statistically (p > 0.05) different from untreated metastasic lesions. ADC value was low (0.75 x 10{sup -3} mm{sup 2}/s) in one case of subacute benign fracture. Conclusions: ADC values are a useful complementary tool to characterize bone marrow lesions, in order to distinguish acute benign fractures from malignant or infectious bone lesions. However, ADC values are not valuable in order to differentiate malignancy from infection.
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Adachi, Yuko; Sato, Noriko; Yamashita, Fumio; Kida, Jiro; Takahashi, Tomoyuki [National Center Hospital of Neurology and Psychiatry, Department of Radiology, Kodaira, Tokyo (Japan); Okamoto, Tomoko [National Center Hospital of Neurology and Psychiatry, Department of Neurology, Kodaira, Tokyo (Japan); Sasaki, Masayuki; Komaki, Hirofumi [National Center Hospital of Neurology and Psychiatry, Department of Child Neurology, Kodaira, Tokyo (Japan); Matsuda, Hiroshi [Saitama Medial University Hospital, Department of Nuclear Medicine, Iruma-gun, Saitama (Japan)
2011-01-15
Our purpose was to clarify the magnetic resonance (MR) imaging characteristics of the brachial and lumbar plexuses in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) using various kinds of sequences, including diffusion-weighted images (DWI). We evaluated the MR imaging findings for lumbar and/or brachial nerve plexuses in 13 CIDP patients and 11 normal volunteers. The nerve swelling was evaluated in comparison with normal controls by coronal short tau inversion recovery (STIR), and signal abnormalities were evaluated by coronal STIR, T1-weighted images, and DWIs. The degrees of contrast enhancement and apparent diffusion coefficient (ADC) values of the plexus were also assessed. In the patient group, diffuse enlargement and abnormally high signals were detected in 16 out of 24 plexuses (66.7%) on STIR, a slightly high signal was detected in 12 of 24 plexuses (50%) on T1-weighted images, and a high-intensity signal was detected in 10 of 18 plexuses (55.6%) on DWIs with high ADC values. Contrast enhancement of the plexuses was revealed in 6 of 19 plexuses (31.6%) and was mild in all cases. There were statistically significant differences between the ADC values of patients with either swelling or abnormal signals and those of both normal volunteers and patients without neither swelling nor abnormal signals. There were no relationships between MR imaging and any clinical findings. STIR is sufficient to assist clinicians in diagnosing CIDP. T1-weighted images and DWIs seemed useful for speculating about the pathological changes in swollen plexuses in CIDP patients. (orig.)
Apparent diffusion coefficient values of normal testis and variations with age
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Athina C Tsili
2014-06-01
Full Text Available The usefulness of diffusion-weighted magnetic resonance imaging (DWI in the evaluation of scrotal pathology has recently been reported. A standard reference of normal testicular apparent diffusion coefficient (ADC values and their variations with age is necessary when interpreting normal testicular anatomy and pathology. We evaluated 147 normal testes using DWI, including 71 testes from 53 men aged 20-39 years (group 1, 67 testes from 42 men aged 40-69 years (group 2 and nine testes from six men older than 70 years (group 3. DWI was performed along the axial plane, using a single shot, multislice spin-echo planar diffusion pulse sequence and b-values of 0 and 900 s mm−2 . The mean and standard deviation of the ADC values of normal testicular parenchyma were calculated for each age group separately. Analysis of variance (ANOVA followed by post hoc analysis (Dunnett T3 was used for statistical purposes. The ADC values (× 10−3 mm 2 s−1 of normal testicular tissue were different among age groups (group 1: 1.08 ± 0.13; group 2: 1.15 ± 0.15 and group 3: 1.31 ± 0.22. ANOVA revealed differences in mean ADC among age groups (F = 11.391, P < 0.001. Post hoc analysis showed differences between groups 1 and 2 (P = 0.008 and between groups 1 and 3 (P = 0.043, but not between groups 2 and 3 (P = 0.197. Our findings suggest that ADC values of normal testicular tissue increase with advancing age.
International Nuclear Information System (INIS)
Objectives: to evaluate the prognostic value of apparent diffusion coefficient (ADC) values from MR diffusion-weighted imaging of unresectable hepatocellular carcinoma after chemoembolization. Methods: our study was proved by our institute and informed consent was obtained from all patients before commencement of the study. Twenty-three patients with unresectable hepatocellular carcinoma were scanned immediately before and after chemoembolization within 24 h using conventional anatomical MR imaging and diffusion-weighted imaging, from which ADC values in the lesions were measured. The changes in ADC values after chemoembolization were calculated. The relationship between the lesion ADC and the survival time was analyzed by correlation analysis. The overall cumulative survival was analyzed by the Kaplan–Meier method, and survival curves were compared by the log-rank test. Results: the mean overall survival period was (25.0 ± 8.7) months. The pre-chemoembolization lesion ADC value was (1.36 ± 0.249) ×10−3 mm2/s; the change in ADC values post-chemoembolization was (0.377 ± 0.332) ×10−3 mm2/s. There were significant linear regression relation between the survival time and pre-chemoembolization lesion ADC values (r = −0.698, P 2 = 7.339, P = 0.007) or the changes in ADC value post-chemoembolization (χ2 = 9.820, P = 0.002) significantly influenced the overall cumulative survival. Conclusion: Pre-treatment ADC values as well as changes in ADC values after treatment may provide useful information for predicting survival for patients with unresectable hepatocellular carcinoma.
Serial analysis of the apparent diffusion coefficient time course in human stroke
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Acute cerebral ischemic injury can be rapidly detected on diffusion-weighted images. The apparent diffusion coefficient (ADC) depends on the stage of cytotoxic edema and water content in the infarcted parenchyma. The purpose of this study is to determine the time course of ADC during the first days of ischemic stroke. These data should make it possible to distinguish between multiple stroke and a single progressive infarction. Eight patients with clinically diagnosed acute cerebral ischemia were examined by diffusion-weighted MRI from 2 to 20 h after onset of symptoms. Daily control scans were performed for up to 10 days. ADC values were analyzed from 55 MRI studies. Furthermore, ADC was measured in the tissue which showed a hyperintense signal at the first examination and in the contralateral tissue. White and gray matter were analyzed separately. Data were expressed as the ratio ADC (rADC) of lesion to control region of interest. All patients showed a uniform reduction in rADC from the first hours of stroke and decreasing to the 3rd day. The rADC increased again from the 4th day up to the point of pseudo-normalization on day 9. The gray matter showed a slightly faster increase than the white matter. rADC shows significant changes in the first days after stroke, following a rather uniform time course. Together with T2-weighted MRI this makes it possible to differentiate between hyperacute, acute, and chronic stroke. Furthermore, the age of an ischemia can be determined and multiple strokes can be distinguished from a single progressive stroke. (orig.)
Study of the apparent diffusion coefficient values in the grading of cerebral astrocytic tumors
International Nuclear Information System (INIS)
Objective: To investigate the diagnostic value of the apparent diffusion coefficient (ADC) values in the grading of cerebral astrocytic tumors. Methods: Diffusion weighted MR imaging (DWI) was performed for 56 cases of cerebral astrocytic tumors proved pathologically. The ADC and the exponential diffusion coefficient (EDC) values were measured at the tumoral core, per/tumoral edematous region, peritumoral normal-appearance white matter and the contralateral white matter. The rADC and rEDC values of the tumoral core, peritumoral edematous region and peritumoral normal-appearance white matter were calculated. The relationship between the various diffusion coefficient values and tumor grading was analyzed. Results: Fifty six cases of cerebral astrocytic tumors included 2 pilocytic astrocytoma (grade I), 33 astrocytoma (grade II), 8 anaplastic astrocytoma (grade III), 13 glioblastoma multiforme (grade IV). The ADC values of the tumor core of low grade astrocytoma, anaplastic astrocytoma and glioblastoma multiforme were (1.44 ± 0.26) x 10-3, (0.98 ± 0.22) x 10-3 and (0.83 ± 0.15) x 10-3 mm2/s respectively, and the rADC values were (1.91±0.39)%, (1.34±0.33)% and (1.06± 0.20)% respectively. The EDC values were 0.26±0.11, 0.39±0.09 and 0.44±0.07 respectively, and the rEDC values were (0.55±0.20)%, (0.81±0.19)% and (0.98±0.16)% respectively. Significant differences of these values at the tumoral core were seen between different pathological grades of the astrocytic tumors (F=36.189, 31.756, 19.623 and 24.760, P=0.000). The ADC and rADC values of high-grade astrocytic tumors were (0.89 ± 0.19) x 10-3 mm2/s and (1.17±0.28)% respectively, which were lower than those of low-grade astrocytic tumors (t=8.332 and 7.620, P=0.000), while the EDC and rEDC values of high-grade tumors were 0.42±0.08 and (0.91±0.18)% respectively, being higher than those of low-grade turnors (t=-6.082 and -6.776, P=0.000). The accuracy was 89.3% when rADC of 1.52% was set as the
Yang, Yunjun; Gao, Lingyun; Fu, Jun; Zhang, Jun; Li, Yuxin; Yin, Bo; Chen, Weijian; Geng, Daoying
2013-11-01
Supratentorial cerebral infarction can cause functional inhibition of remote regions such as the cerebellum, which may be relevant to diaschisis. This phenomenon is often analyzed using positron emission tomography and single photon emission CT. However, these methods are expensive and radioactive. Thus, the present study quantified the changes of infarction core and remote regions after unilateral middle cerebral artery occlusion using apparent diffusion coefficient values. Diffusion-weighted imaging showed that the area of infarction core gradually increased to involve the cerebral cortex with increasing infarction time. Diffusion weighted imaging signals were initially increased and then stabilized by 24 hours. With increasing infarction time, the apparent diffusion coefficient value in the infarction core and remote bilateral cerebellum both gradually decreased, and then slightly increased 3-24 hours after infarction. Apparent diffusion coefficient values at remote regions (cerebellum) varied along with the change of supratentorial infarction core, suggesting that the phenomenon of diaschisis existed at the remote regions. Thus, apparent diffusion coefficient values and diffusion weighted imaging can be used to detect early diaschisis. PMID:25206615
A preliminary study of apparent diffusion coefficient in chemotherapy-induced liver damage
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Objectives: To investigate changes in the hepatic apparent diffusion coefficient (ADC) in patients undergoing chemotherapy. Methods: We enrolled 54 patients (25 women; mean age 57.0 ± 13.1 years, range 29–89 years) undergoing chemotherapy for tumor and 10 controls (7 women; mean age 55.1 ± 17.5 years, range 23–81 years). The patients were tested for serum alanine aminotransferase (ALT) activity (abnormal, normal) and fatty liver. Hepatic ADC values were compared among controls, patients and subgroups. Pearson correlation coefficient was used to assess the correlation between ADC and ALT activity. Results: Hepatic ADC0,850 (×10−3 mm2/s) was lower for patients than controls (1.14 ± 0.18 vs. 1.28 ± 0.12, P = 0.02) and was lower for patients with than without fatty liver and controls (1.01 ± 0.06 vs. 1.18 ± 0.18 and 1.28 ± 0.12, respectively, all P < 0.01), with no significant difference between patients without fatty liver and controls (P = 0.07). ADC0,850 was lower for patients with abnormal ALT than normal ALT activity and controls (0.99 ± 0.06 vs. 1.17 ± 0.18 and 1.28 ± 0.12, respectively, all P < 0.05), with a significant difference also being seen between patients with normal ALT activity and controls (P = 0.04). Hepatic ADC0,850 was not correlated with ALT activity in patients (r = -0.24, P = 0.08). Conclusions: Although ADC did not correlate with ALT values, it did distinguish patient likely to have chemotherapy-induced liver damage as indicated by abnormal ALT values or fatty liver. These mechanisms need to be disentangled.
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Tsili, Athina C., E-mail: a_tsili@yahoo.gr [Department of Radiology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Ntorkou, Alexandra, E-mail: alexdorkou@yahoo.com [Department of Radiology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Baltogiannis, Dimitrios, E-mail: Greece.dbaltog@cc.uoi.gr [Department of Urology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Goussia, Anna, E-mail: agoussia@uoi.gr [Department of Pathology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Astrakas, Loukas G., E-mail: astrakas@uoi.gr [Department of Medical Physics, Medical School, University of Ioannina, 45110 Ioannina (Greece); Malamou-Mitsi, Vasiliki, E-mail: vmalamou@cc.uoi.gr [Department of Pathology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Sofikitis, Nikolaos, E-mail: akrosnin@hotmail.com [Department of Urology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Argyropoulou, Maria I., E-mail: margyrop@cc.uoi.gr [Department of Radiology, Medical School, University of Ioannina, 45110 Ioannina (Greece)
2015-05-15
Highlights: • ADC values proved useful in the discrimination between TGCNs and normal testis. • Testicular intraepithelial neoplasia represents the precursor of most TGCNs. • ADC values cannot be used to detect testicular intraepithelial neoplasia. - Abstract: Introduction: The aim of this study is to improve detection of testicular intraepithelial neoplasia (TIN) by measurement of apparent diffusion coefficient (ADC) values. Materials and methods: Fifty-six MRI examinations of the scrotum, including 26 histologically proven testicular germ cell neoplasms were retrospectively evaluated. DWI was performed using a single shot, multi-slice spin-echo planar diffusion pulse sequence and b-values of 0 and 900 s mm{sup −2}. ADC measurements were classified into three groups according to their location: group 1 (n = 19), non-tumoral part, adjacent to testicular carcinoma, where the possible location of TIN was; group 2 (n = 26), testicular carcinoma; and group 3 (n = 60), normal testicular parenchyma. Analysis of variance (ANOVA) followed by post hoc analysis (Dunnett T3) was used for statistical purposes. Results: The mean ± s.d. of ADC values (×10{sup −3} mm{sup 2}/s) of different groups were: group 1, 1.08 ± 0.20; group 2, 0.72 ± 0.27; and group 3, 1.11 ± 0.14. ANOVA revealed differences of mean ADC between groups (F = 38.859, P < 0.001). Post hoc analysis showed differences between groups 2 and 3 (P < 0.001), groups 2 and 1 (P < 0.001), but not between groups 3 and 1 (P = 0.87). Conclusions: Based on our preliminary results, ADC values do not provide a reliable differentiation between TIN and testicular carcinoma or normal testicular parenchyma.
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To study the rules that apparent diffusion coefficient (ADC) changes with time and space in cerebral infarction, and to provide the evidence in defining the infarction stages. 117 work-ups in 98 patients with cerebral infarction (12 hyperacute, 43 acute, 29 subacute, 10 steady, and 23 chronic infarctions) were imaged with both conventional MRI and diffusion weighted imaging. The average ADC values, the relative ADC (rADC) values, and the ADC values or rADC values from the center to the periphery of the lesion were calculated. The average ADC values and the rADC values of hyperacute and acute infarction lesion depressed obviously. rADC values in hyperacute and acute stage was minimized, and increased progressively as time passed and appeared as 'pseudonormal' values in approximately 8 to 14 days. Thereafter, rADC values became greater than normal in chronic stage. There was positive correlation between rADC values and time (P < 0.01). The ADC values and the rADC values in hyperacute and acute lesions had gradient signs that these lesions increased from the center to the periphery. The ADC values and the rADC values in subacute lesions had adverse gradient signs that these lesions decreased from the center to the periphery. The ADC values of infarction lesions have evolution rules with time and space. The evolution rules with time and those in space can be helpful to decide the clinical stage, and to provide the evidence in guiding the treatment or judging the prognosis in infarction
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Highlights: • ADC values proved useful in the discrimination between TGCNs and normal testis. • Testicular intraepithelial neoplasia represents the precursor of most TGCNs. • ADC values cannot be used to detect testicular intraepithelial neoplasia. - Abstract: Introduction: The aim of this study is to improve detection of testicular intraepithelial neoplasia (TIN) by measurement of apparent diffusion coefficient (ADC) values. Materials and methods: Fifty-six MRI examinations of the scrotum, including 26 histologically proven testicular germ cell neoplasms were retrospectively evaluated. DWI was performed using a single shot, multi-slice spin-echo planar diffusion pulse sequence and b-values of 0 and 900 s mm−2. ADC measurements were classified into three groups according to their location: group 1 (n = 19), non-tumoral part, adjacent to testicular carcinoma, where the possible location of TIN was; group 2 (n = 26), testicular carcinoma; and group 3 (n = 60), normal testicular parenchyma. Analysis of variance (ANOVA) followed by post hoc analysis (Dunnett T3) was used for statistical purposes. Results: The mean ± s.d. of ADC values (×10−3 mm2/s) of different groups were: group 1, 1.08 ± 0.20; group 2, 0.72 ± 0.27; and group 3, 1.11 ± 0.14. ANOVA revealed differences of mean ADC between groups (F = 38.859, P < 0.001). Post hoc analysis showed differences between groups 2 and 3 (P < 0.001), groups 2 and 1 (P < 0.001), but not between groups 3 and 1 (P = 0.87). Conclusions: Based on our preliminary results, ADC values do not provide a reliable differentiation between TIN and testicular carcinoma or normal testicular parenchyma
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Highlights: • Functional MRI in the characterization of testicular germ cell tumors was assessed. • ADC values proved useful in the characterization of testicular germ cell tumors. • Testicular germ cell tumors had similar enhancement patterns of dynamic MRI. - Abstract: Introduction: The aim of this study is to investigate the role of apparent diffusion coefficient (ADC) values and dynamic contrast enhancement (DCE) patterns in differentiating seminomas from nonseminomatous germ cell tumors (NSGCTs). Materials and methods: The MRI examinations of the scrotum of 26 men with histologically proven testicular GCTs were reviewed. DWI was performed in all patients, using a single shot, multi-slice spin-echo planar diffusion pulse sequence and b-values of 0 and 900 s/mm2. Subtraction DCE-MRI was performed in 20 cases using a 3D fast-field echo sequence after gadolinium administration. Time-signal intensity curves were created and semi-quantitative parameters (peak enhancement, time to peak, wash-in and wash-out rate) were calculated. The Student's t-test was used to compare the mean values of ADC, peak enhancement, time to peak, wash-in and wash-out rate between seminomas and NSGCTs. ROC analysis was also performed. Results: Histopathology disclosed the presence of 15 seminomas and 11 NSGCTs. The mean ± s.d. of ADC values (× 10−3 mm2/s) of seminomas (0.59 ± 0.009) were significantly lower than those of NSGCTs (0.90 ± 0.33) (P = 0.01). The optimal ADC cut-off value was 0.68 × 10−3 mm2/s. No differences between the two groups were observed for peak enhancement (P = 0.18), time to peak (P = 0.63) wash-in rate (P = 0.32) and wash-out rate (P = 0.18). Conclusions: ADC values may be used to preoperatively differentiate seminomas from NSGCTs
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Aim: To identify retrospectively potential associations between apparent diffusion coefficient (ADC) values of pancreatic adenocarcinoma and tumour grade as well as other pathological features, using histopathological assessment from the Whipple procedure as the reference standard. Materials and methods: Thirty patients with pancreatic adenocarcinoma underwent magnetic resonance imaging (MRI) including diffusion-weighted imaging with b-values of 0 and 500 s/mm2 before the Whipple procedure. Two radiologists independently recorded the ADC values of the tumour and benign pancreas for all cases. ADC values were compared with histopathological findings following the Whipple procedure. Results: The intra-class correlation coefficient was 0.689 for benign pancreas and 0.695 for tumours, indicating good inter-reader agreement for ADC values. The mean ADC value was significantly lower in tumours than in benign pancreas for both readers (reader 1: 1.74 ± 0.34 × 10−3 mm2/s versus 2.08 ± 0.48 × 10−3 mm2/s, respectively, p = 0.006; reader 2: 1.69 ± 0.41 × 10−3 mm2/s versus 2.11 ± 0.54 × 10−3 mm2/s, respectively, p −3 mm2/s versus 1.78 ± 0.33 × 10−3 mm2/s, respectively, p = 0.491; reader 2: 1.62 ± 0.33 × 10−3 mm2/s versus 1.75 ± 0.49 × 10−3 mm2/s, respectively, p = 0.405). The area under the curve (AUC) for differentiation of poorly and well/moderately differentiated tumours was 0.611 and 0.596 for readers 1 and 2, respectively, and was not significantly better than an AUC of 0.500 for either reader (p ≥ 0.306). In addition, ADC was not significantly different for either reader between tumours with stage T3 versus stage T1/T2, between tumours with and without metastatic peri-pancreatic lymph nodes, or between tumours located in the pancreatic head versus other pancreatic regions (p ≥ 0.413). Conclusion: No associations between ADC values of pancreatic adenocarcinoma and tumour grade or other adverse pathological features were observed
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Objectives: To reveal the contribution of MRI and diffusion-weighted imaging (DWI) to the diagnosis of mitochondrial encephalopathy (ME) and to evaluate the parenchymal changes associated with this disease in the involved parenchymal areas using the apparent diffusion coefficient (ADC) parameter. Methods: Ten patients who had undergone MRI and DWI analysis with a pre-diagnosis of neurometabolic disease, and who were subsequently diagnosed with ME in laboratory and/or genetic studies, were included in our study. ADC values were compared with a control group composed of 20 patients of similar age with normal brains. Evaluations involved measurements made in 20 different areas determined on the ADC map. The dominance or contribution of ADC coefficient measurements to the conventional sequences was compared with the controls. Results: In the first examination, an increase in both diffusion and ADC values was detected in six cases and diffusion restriction and a decrease in ADC values in three patients. While an increase in both diffusion and ADC values was demonstrated in four cases, there was diffusion restriction and a decrease in ADC values in three cases in the control examinations. Conclusions: DWI provides information that complements conventional MRI sequences in the diagnosis of ME
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Uysal, Fatma, E-mail: afatmauysal@gmail.com [Dokuz Eylül University, Department of Pediatric Radiology, Izmir (Turkey); Çakmakçı, Handan, E-mail: handan.cakmakci@deu.edu.tr [Dokuz Eylül University, Department of Pediatric Radiology, Izmir (Turkey); Yiş, Uluç, E-mail: ulucyis@deu.edu.tr [Dokuz Eylül University, Department of Pediatric Neurology, Izmir (Turkey); Ellidokuz, Hülya, E-mail: hulyaellidokuz@deu.edu.tr [Dokuz Eylül University, Department of Medical Statistics, Izmir (Turkey); Hız, Ayşe Semra, E-mail: aysesemrahiz@deu.edu.tr [Dokuz Eylül University, Department of Pediatric Neurology, Izmir (Turkey)
2014-01-15
Objectives: To reveal the contribution of MRI and diffusion-weighted imaging (DWI) to the diagnosis of mitochondrial encephalopathy (ME) and to evaluate the parenchymal changes associated with this disease in the involved parenchymal areas using the apparent diffusion coefficient (ADC) parameter. Methods: Ten patients who had undergone MRI and DWI analysis with a pre-diagnosis of neurometabolic disease, and who were subsequently diagnosed with ME in laboratory and/or genetic studies, were included in our study. ADC values were compared with a control group composed of 20 patients of similar age with normal brains. Evaluations involved measurements made in 20 different areas determined on the ADC map. The dominance or contribution of ADC coefficient measurements to the conventional sequences was compared with the controls. Results: In the first examination, an increase in both diffusion and ADC values was detected in six cases and diffusion restriction and a decrease in ADC values in three patients. While an increase in both diffusion and ADC values was demonstrated in four cases, there was diffusion restriction and a decrease in ADC values in three cases in the control examinations. Conclusions: DWI provides information that complements conventional MRI sequences in the diagnosis of ME.
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Objective: To study the roles of isotropic diffusion weighted imaging and apparent diffusion coefficients (ADC) mapping in diagnosing cerebral infarction, monitoring the development of cerebral infarction and defining the infarction stages. Methods: 86 work-ups in 70 patients with cerebral infarction (8 hyperacute, 13 acute, 32 subacute, 11 steady, and 22 chronic) were imaged with both conventional MRI and single-shot echo-planar isotropic diffusion weighted imaging. The change of the infarct lesion in DWI and T2WI was also analyzed. The average ADC, relative ADC (rADC), and the ADC from center to periphery of the lesion were calculated. Results: 8 hyperacute cerebral ischemic regions were revealed at DWI and ADC mapping. Hyperacute and acute infarcts appeared as areas of hyperintensity on DWI, and their average ADC was significantly depressed compared with that of homologous contralateral tissue [(0.698±0.104) x 10-3 mm2/s versus (0.990±0.161) x 10-3 mm2/s; t=-14.372, P2WI, ADC values can differentiate different stages of infarction and may portend the time when stroke may be treated more effectively and with individually tailored therapy, and may be used to define the core and penumbra of ischemic lesions, and to evaluate the efficacy of treatments by dynamic observation
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Tsili, Athina C., E-mail: a_tsili@yahoo.gr [Department of Radiology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Sylakos, Anastasios, E-mail: anasylakos@yahoo.gr [Department of Urology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Ntorkou, Alexandra, E-mail: alexdorkou@yahoo.com [Department of Radiology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Stavrou, Sotirios, E-mail: s.sotiris@yahoo.gr [Department of Urology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Astrakas, Loukas G., E-mail: astrakas@uoi.gr [Department of Medical Physics, Medical School, University of Ioannina, 45110 Ioannina (Greece); Sofikitis, Nikolaos, E-mail: akrosnin@hotmail.com [Department of Urology, Medical School, University of Ioannina, 45110 Ioannina (Greece); Argyropoulou, Maria I., E-mail: margyrop@cc.uoi.gr [Department of Radiology, Medical School, University of Ioannina, 45110 Ioannina (Greece)
2015-07-15
Highlights: • Functional MRI in the characterization of testicular germ cell tumors was assessed. • ADC values proved useful in the characterization of testicular germ cell tumors. • Testicular germ cell tumors had similar enhancement patterns of dynamic MRI. - Abstract: Introduction: The aim of this study is to investigate the role of apparent diffusion coefficient (ADC) values and dynamic contrast enhancement (DCE) patterns in differentiating seminomas from nonseminomatous germ cell tumors (NSGCTs). Materials and methods: The MRI examinations of the scrotum of 26 men with histologically proven testicular GCTs were reviewed. DWI was performed in all patients, using a single shot, multi-slice spin-echo planar diffusion pulse sequence and b-values of 0 and 900 s/mm{sup 2}. Subtraction DCE-MRI was performed in 20 cases using a 3D fast-field echo sequence after gadolinium administration. Time-signal intensity curves were created and semi-quantitative parameters (peak enhancement, time to peak, wash-in and wash-out rate) were calculated. The Student's t-test was used to compare the mean values of ADC, peak enhancement, time to peak, wash-in and wash-out rate between seminomas and NSGCTs. ROC analysis was also performed. Results: Histopathology disclosed the presence of 15 seminomas and 11 NSGCTs. The mean ± s.d. of ADC values (× 10{sup −3} mm{sup 2}/s) of seminomas (0.59 ± 0.009) were significantly lower than those of NSGCTs (0.90 ± 0.33) (P = 0.01). The optimal ADC cut-off value was 0.68 × 10{sup −3} mm{sup 2}/s. No differences between the two groups were observed for peak enhancement (P = 0.18), time to peak (P = 0.63) wash-in rate (P = 0.32) and wash-out rate (P = 0.18). Conclusions: ADC values may be used to preoperatively differentiate seminomas from NSGCTs.
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Aim: To compare the efficacy of apparent diffusion coefficient (ADC) and normalized ADC (nADC) for estimating the histological grade of vesical urothelial carcinoma and to identify an optimal reference for nADC calculation. Materials and methods: Thirty patients with histologically confirmed vesical urothelial carcinomas underwent preoperative diffusion-weighted magnetic resonance imaging (DW-MRI) of the pelvis. nADC of the tumour was calculated as ADC (tumour)/ADC (reference) using urine in the bladder lumen, and the obturator internus and gluteus maximus muscles as reference. Receiver operating characteristic (ROC) curves were constructed and compared to identify an optimal reference for nADC calculation. Results: Both ADC and nADC of low-grade tumours (1.112 ± 0.159 × 10−3 mm2/s, 0.403 ± 0.047 × 10−3 mm2/s) were significantly (p < 0.001) higher than those of high-grade tumours (0.772 ± 0.091 × 10−3 mm2/s, 0.276 ± 0.033 × 10−3 mm2/s). The area under the nADC ROC curve using urine as reference was significantly (p = 0.000) larger (0.995) than those using obturator internus (0.960) and gluteus maximus (0.945). Conclusions: nADC is superior to ADC for estimating the histological grade of bladder carcinoma using urine in the bladder lumen as an optimal reference for nADC calculation. - Highlights: • We use a new non-invasive method in bladder cancer preoperative pathological grade evaluation. • We first use the normalized ADC value in bladder cancer. • Normalized ADC value was confirmed to be more reliable than ADC value
Arlinghaus, Lori R.; Xia LI; Rahman, A. Ridwan; Welch, E. Brian; Xu, Lei; Gore, John C.; Yankeelov, Thomas E.
2011-01-01
MRI techniques have been developed that can noninvasively probe the apparent diffusion coefficient (ADC) of water via diffusion weighted MRI (DW-MRI). These methods have found much application in cancer where it is often found that the ADC within tumors is inversely correlated with tumor cell density, so that an increase in ADC in response to therapy can be interpreted as an imaging biomarker of positive treatment response. Dynamic contrast enhanced MRI (DCE-MRI) methods have also been develo...
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Purpose: To test the reproducibility of apparent diffusion coefficients (ADC) measurements of the normal liver, kidney and spleen parenchyma with different b values. Materials and methods: Eleven healthy volunteers were imaged twice with use of the same protocol. Each DWI was performed with b-factors of 0, 100 and 500 s/mm2. The ADCs were organized according to session (1 or 2), anatomic location and repetition (twice with two different b value per session). The ADC data were analyzed with repeated-measures analysis of variance to demonstrate the influence of anatomic location, session and different b values. The coefficient of variation was calculated for each subject, b value and anatomic location, then analyzed by using repeated-measures analysis of variance. Results: There were significant differences in mean ADCs among the three anatomic locations and with different b values (P .05). The CV values range between 7.3% and 14.7%. There were no significant differences in CV values neither between the two b values nor for the various organ locations (P > .05). Conclusion: Using the same technical parameters, patients and the same observer, CV values range between 7.3% and 14.7%. And we recommend to be careful in examination and comparison of the measured ADC values, below these limits, without knowledge technical parameters that has been used, otherwise differences that are merely because of changes in the measurement technique could be interpreted as differences because of progression of disease or therapy
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Purpose: To investigate the feasibility of diffusion-weighted MRI (DWI) as an early and reproducible change indicator in patients receiving radiotherapy for prostate cancer (PC). Methods and Materials: Eight consecutive patients with biopsy-proven PC underwent DWI at 3T. All patients who received external-beam radiotherapy had four serial MR scans, as follows: before therapy (PreTx); after 1 week of therapy (PostT1); after 3 weeks of therapy (PostT2); and 1 month after the completion of therapy (PostT3). At each time, the apparent diffusion coefficient (ADC) was measured in tumors and normal tissues. For reproducibility of the ADC measurement, five patients also had two separate pretreatment DWI scans at an interval of −3 mm2/s in sequence, respectively. Compared with PreTx, PostT1 (p = 0.005), PostT2 (p = 0.003), and PostT3 (p −3 mm2/s in sequence, respectively. Reproducibility of ADC measurements was confirmed with a mean difference in ADC of –0.04 in peripheral zone and –0.017 in transition zone between two separate pretreatment MR scans. The mean PSA levels from PreTx to PostT3 were 9.05, 9.18, 9.25, and 4.11 ng/mL in sequence, respectively. Conclusions: DWI, as a reproducible biomarker, has the potential to evaluate the early therapeutic changes of PC to radiotherapy.
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Aim: To investigate and characterize the effect of age on apparent diffusion coefficient (ADC) values in the normal adult pancreas using diffusion-weighted magnetic resonance imaging (DWI). Materials and methods: Five hundred and fifty-nine adult patients without pancreatic disease, ranging from 20–81 years of age (mean 50.9 years; 436 men, 123 women), were included in this study. Breath-hold single-shot echo-planar DWI (b-values = 0, 500 s/mm2) was employed to determine the ADCs across all patients. Dependency of ADCs on age was characterized using a Spearman rank-order correlation test. Results: Across the age spectrum, there was no significant correlation between ADC and age (p = 0.409). Conclusion: The findings of the present study suggest that the effect of age on ADCs can be excluded from the diagnosis of pancreatic diseases and design of future studies using breath-hold single-shot DWI and ADCs (as calculated with b-values of 0 and 500 s/mm2)
Metin, Melike R.; Aydın, Hasan; Çetin, Hüseyin; Özmen, Evrim; Kayaçetin, Serra
2016-01-01
Objectives: To establish retrospectively the relation between the histopathologic grade of colorectal liver metastasis and apparent diffusion coefficient (ADC) values of hepatic metastases of colorectal adenocarcinomas. Methods: The diagnoses of liver metastases were confirmed with biopsy, surgery, and follow-up imaging findings. Twenty-six patients with 94 liver metastasis were included in the study. Of 94 masses, 59 were poorly-differentiated adenocarcinoma, 18 were moderately-differentiated adenocarcinoma, and 17 were well-differentiated regarding the diameters, ADC values, and ratio index (RI) values. Kolmogorov-smirnov normality test, Kruskal-wallis analysis of variance, Mann-Whitney U test with Bonferroni correction, Spearman correlation analysis, and receiver operating characteristics curve methods were applied to evaluate the statistical relations. Results: There was a statistically significant difference in terms of ADC values and RI between poorly-differentiated adenocarcinoma and moderately-differentiated adenocarcinoma plus well-differentiated adenocarcinomas. Poorly-differentiated adenocarcinomas have the lowest ADC values and highest RI values among other groups. Conclusion: Use of ADC values alone can be executed for the diagnosis of focal hepatic masses and also can aid in the differentiation of benign and malignant hepatic lesions. PMID:27052280
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Liu, Song, E-mail: songliu532909756@gmail.com [Department of Radiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Guan, Wenxian, E-mail: wenxianguan123@126.com [Department of Gastrointestinal Surgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Wang, Hao, E-mail: wanghao20140525@126.com [Department of Gastrointestinal Surgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Pan, Liang, E-mail: panliang2014@126.com [Department of Radiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Zhou, Zhuping, E-mail: zhupingzhou@126.com [Department of Radiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Yu, Haiping, E-mail: haipingyu2012@126.com [Department of Radiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Liu, Tian, E-mail: tianliu2014@126.com [Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, GA 30322 (United States); Yang, Xiaofeng, E-mail: xiaofengyang2014@126.com [Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, GA 30322 (United States); He, Jian, E-mail: hjxueren@126.com [Department of Radiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China); Zhou, Zhengyang, E-mail: zyzhou@nju.edu.cn [Department of Radiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing 210008 (China)
2014-12-15
Highlights: • Gastric cancers’ ADC values were significantly lower than normal gastric wall. • Gastric adenocarcinomas with different differentiation had different ADC values. • Gastric adenocarcinomas’ ADC values correlated with histologic differentiations. • Gastric cancers’ ADC values correlated with Lauren classifications. • Mean ADC value was better than min ADC value in characterizing gastric cancers. - Abstract: Objective: The purpose of this study was to evaluate the correlations between histological differentiation and Lauren classification of gastric cancer and the apparent diffusion coefficient (ADC) value of diffusion weighted imaging (DWI). Materials and methods: Sixty-nine patients with gastric cancer lesions underwent preoperative magnetic resonance imaging (MRI) (3.0T) and surgical resection. DWI was obtained with a single-shot, echo-planar imaging sequence in the axial plane (b values: 0 and 1000 s/mm{sup 2}). Mean and minimum ADC values were obtained for each gastric cancer and normal gastric walls by two radiologists, who were blinded to the histological findings. Histological type, degree of differentiation and Lauren classification of each resected specimen were determined by one pathologist. Mean and minimum ADC values of gastric cancers with different histological types, degrees of differentiation and Lauren classifications were compared. Correlations between ADC values and histological differentiation and Lauren classification were analyzed. Results: The mean and minimum ADC values of gastric cancers, as a whole and separately, were significantly lower than those of normal gastric walls (all p values <0.001). There were significant differences in the mean and minimum ADC values among gastric cancers with different histological types, degrees of differentiation and Lauren classifications (p < 0.05). Mean and minimum ADC values correlated significantly (all p < 0.001) with histological differentiation (r = 0.564, 0.578) and
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Highlights: • Gastric cancers’ ADC values were significantly lower than normal gastric wall. • Gastric adenocarcinomas with different differentiation had different ADC values. • Gastric adenocarcinomas’ ADC values correlated with histologic differentiations. • Gastric cancers’ ADC values correlated with Lauren classifications. • Mean ADC value was better than min ADC value in characterizing gastric cancers. - Abstract: Objective: The purpose of this study was to evaluate the correlations between histological differentiation and Lauren classification of gastric cancer and the apparent diffusion coefficient (ADC) value of diffusion weighted imaging (DWI). Materials and methods: Sixty-nine patients with gastric cancer lesions underwent preoperative magnetic resonance imaging (MRI) (3.0T) and surgical resection. DWI was obtained with a single-shot, echo-planar imaging sequence in the axial plane (b values: 0 and 1000 s/mm2). Mean and minimum ADC values were obtained for each gastric cancer and normal gastric walls by two radiologists, who were blinded to the histological findings. Histological type, degree of differentiation and Lauren classification of each resected specimen were determined by one pathologist. Mean and minimum ADC values of gastric cancers with different histological types, degrees of differentiation and Lauren classifications were compared. Correlations between ADC values and histological differentiation and Lauren classification were analyzed. Results: The mean and minimum ADC values of gastric cancers, as a whole and separately, were significantly lower than those of normal gastric walls (all p values <0.001). There were significant differences in the mean and minimum ADC values among gastric cancers with different histological types, degrees of differentiation and Lauren classifications (p < 0.05). Mean and minimum ADC values correlated significantly (all p < 0.001) with histological differentiation (r = 0.564, 0.578) and Lauren
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Mahmoud, Omar M., E-mail: omarmostafa2008@yahoo.co [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Department of Radiology, South Egypt Cancer Institute, Assiut University, Assiut 71515 (Egypt); Tominaga, Atsushi, E-mail: atom@hiroshima-u.ac.j [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Amatya, Vishwa Jeet, E-mail: amatya@hiroshima-u.ac.j [Department of Pathology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551 (Japan); Ohtaki, Megu, E-mail: ohtaki@hiroshima-u.ac.j [Department of Environmetrics and Biometrics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8551 (Japan); Sugiyama, Kazuhiko, E-mail: brain@hiroshima-u.ac.j [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Saito, Taiichi, E-mail: taiichi@hiroshima-u.ac.j [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Sakoguchi, Tetsuhiko, E-mail: sakog@hiroshima-u.ac.j [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Kinoshita, Yasuyuki, E-mail: d055634@hiroshima-u.ac.j [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Shrestha, Prabin, E-mail: prabinshrestha@hotmail.co [Department of Neurosurgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Abe, Nobukazu, E-mail: abebe@hiroshima-u.ac.j [Dept. of Clinical Radiology, Graduate School of Biomedical Sciences, Hiroshima Univ., Hiroshima 734-8551 (Japan)
2010-06-15
Objective: To evaluate the role of the apparent diffusion coefficient (ADC) using periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion weighted imaging (DWI) in the differentiation between sellar and parasellar mass lesions. Materials and methods: The study protocol was approved by our institutional review board. We retrospectively studied 60 patients with sellar and parasellar lesions who had undergone PROPELLER DWI on a 3-T MR imager. Conventional MRI findings were expressed as the ratio of signal intensity (SI) in the lesions to the normal white matter and the degree of contrast enhancement. ADC values were calculated as the minimum (ADC-MIN), mean (ADC-MEAN), and maximum (ADC-MAX). All patients underwent surgery and all specimens were examined histologically. Logistic discriminant analysis was performed by using the SI ratios on T1- and T2-weighted images (T1-WI, T2-WI), the degree of enhancement, and absolute ADC values as independent variables. Results: ADC-MIN of hemorrhagic pituitary adenomas was lower than of the other lesions with similar appearance on conventional MRI (non-hemorrhagic pituitary adenomas, craniopharyngiomas, Rathke's cleft cysts; accuracy 100%); the useful cut-off value was 0.700 x 10{sup -3} mm{sup 2}/s. ADC-MAX of meningiomas was lower than of non-hemorrhagic pituitary adenomas (accuracy 90.3%; p < 0.01). ADC-MIN of craniopharyngiomas was lower than of Rathke's cleft cysts (accuracy 100%; p < 0.05). Conclusion: As PROPELLER DWI is less sensitive to susceptibility artifacts than single-shot echoplanar DWI, it is more useful in the examination of sellar and parasellar lesions. Calculation of the ADC values helps to differentiate between various sellar and parasellar lesions.
International Nuclear Information System (INIS)
Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8 x 8 x 2 cm3 containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm3 were compared. The water content was increased in patients compared with controls (GM: 244±21 vs. 194±10 a.u.; WM: 245±32 vs. 190±11 a.u.), FA decreased (GM: 0.226±0.038 vs. 0.270±0.020; WM: 0.337±0.044 vs. 0.402±0.011) and ADC increased [GM: 1134±203 vs. 899±28 (x 10-6 mm2/s); WM: 901±138 vs. 751±17 (x 10-6 mm2/s)]. Correlations of water content with FA and ADC in WM were strong (r=-0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=-0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=-0.88; P<0.00001) than in GM (r=-0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue. (orig.)
Macarini, Luca; Stoppino, Luca Pio; Milillo, Paola; Ciuffreda, Pierpaolo; Fortunato, Francesca; Vinci, Roberta
2010-01-01
The purpose of the study was to assess the capability and the reliability of apparent diffusion coefficient (ADC) measurements in the evaluation of different benign renal abnormalities. Twenty-five healthy volunteers and 31 patients, divided into seven different groups (A-G) according to pathology, underwent diffusion-weighted magnetic resonance imaging (DW MRI) of the kidneys using 1.5-T system. DW images were obtained in the axial plane with a spin-echo echo planar imaging single-shot sequence with three b values (0, 300, and 600 s/mm²). Before acquisition of DW sequences, we performed in each patient a morphological study of the kidneys. ADC was 2.40±0.20×10⁻³ mm² s⁻¹ in volunteers. A significant difference was found between Groups A (cysts=3.39±0.51×10⁻³ mm² s⁻¹) and B (acute/chronic renal failure=1.38±0.40×10⁻³ mm² s⁻¹) and between Groups A and C (chronic pyelonephritis=1.53±0.21×10⁻³ mm² s⁻¹) (P.05). A considerable correlation between glomerular filtration rate and ADC was found (P=.04). In conclusion, significant differences were detected among different patient groups, and this suggests that ADC measurements can be useful in differentiating normal renal parenchyma from most commonly encountered nonmalignant renal lesions. PMID:21092872
K. Coenegrachts; J. Delanote; L. ter Beek; M. Haspeslagh; S. Bipat; J. Stoker; L. Steyaert; H. Rigauts
2009-01-01
PURPOSE: To assess the added value of true diffusion (D), perfusion factor (f) and apparent diffusion coefficient at low b-values (ADC(low)) for differentiation between liver metastases and hemangiomas based on respiratory-triggered high-resolution Black-Blood Single-Shot SpinEcho Echo Planar Imagin
Rosenkrantz, A.B.; Oei, M.T.H.; Babb, J.S.; Niver, B.E.; Taouli, B.
2011-01-01
PURPOSE: To compare single-shot echo-planar imaging (SS EPI) diffusion-weighted MRI (DWI) of abdominal organs between 1.5 Tesla (T) and 3.0T in healthy volunteers in terms of image quality, apparent diffusion coefficient (ADC) values, and ADC reproducibility. MATERIALS AND METHODS: Eight healthy vol
DEFF Research Database (Denmark)
Kallehauge, Jesper Folsted; Tanderup, Kari; Haack, Søren;
2010-01-01
Diffusion weighted imaging (DWI) has gained interest as an imaging modality for assessment of tumor extension and response to cancer treatment. The purpose of this study is to assess the impact of the choice of b-values on the calculation of the Apparent Diffusion Coefficient (ADC) for locally ad...
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When studying diffusion weighted imaging (DWI), it is important to create a phantom that has a reliably controlled diffusion coefficient. In this study, we investigated phantoms to control both the diffusion coefficient and the T2-value by changing the concentration of gelatin or sucrose and MnCl2, respectively. The results showed that the diffusion coefficient decreased linearly with increases in the gelatin or sucrose concentration, and decreasing of their relaxation times was observed. By properly adjusting the MnCl2 concentrations, we were able to equalize the T2-values between phantoms having different gelatin or sucrose concentrations. Temperature dependence of the diffusion coefficient was also revealed. This phantom can be made stable for a few months by adding a small amount of NaN3 as an antiseptic agent, has a diffusion coefficient similar to that of neural tissue or clinical tumor, and is able to control the T2-value properly. We consider this phantom suitable for studying SE-type DWI and contributes to elucidation of this technique. (author)
Yu, Jiangsheng; Law, Michelle; Kadlecek, Stephen; Emami, Kiarash; Ishii, Masaru; Stephen, Michael; Woodburn, John M.; Vahdat, Vahid; Rizi, Rahim R.
2009-01-01
Hyperpolarized 3He (HP 3He) MRI shows promise to assess structural and functional pulmonary parameters in a sensitive, regional and non-invasive way. Structural HP 3He MRI has applied the apparent diffusion coefficient (ADC) for the detection of disease-induced lung microstructure changes at the alveolar level, and HP 3He pulmonary partial pressure of oxygen (pO2) imaging measures the oxygen transfer efficiency between the lung and blood stream. Although both parameters are affected in chroni...
DEFF Research Database (Denmark)
Diaz, Sandra; Casselbrant, Ingrid; Piitulainen, Eeva;
2008-01-01
PURPOSE: To compare apparent diffusion coefficient (ADC) measurements from hyperpolarized (HP) helium ((3)He)-magnetic resonance imaging (MRI) with quantitative data from multislice Computed Tomography (CT) (MSCT) of the whole lungs and pulmonary function tests (PFT). MATERIALS AND METHODS: Twenty...... from MSCT. Both mean ADC and MSCT data were compared to PFT, especially percent of predicted diffusing capacity of carbon monoxide (%predicted DLCO), using Pearson's correlation test. RESULTS: Mean ADC and standard deviation values were 0.392+/-0.119 cm(2)/s for the established emphysema group and 0...
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Objective: The goal of this study was to evaluate whether the values of ADC in spondylarthritis axial active inflammatory lesions are different from ADC values in type 1 Modic changes. Subjects and methods: 95 patients with recent lumbar pain, including 46 patients with diagnosed or suspected spondylarthritis and 49 patients with purely degenerative history, underwent spine MRI. T1w, STIR, and diffusion-weighted images (DWI) were obtained. Two musculoskeletal radiologists interpreted the images. Axial active inflammatory lesions from the SpA group and type 1 Modic changes from the degenerative group were identified on T1w and STIR sequences. ADC values from these lesions and from healthy subchondral bone were compared. Results: All axial active inflammatory lesions (n = 27) and type 1 Modic changes (n = 22) identified in T1w and STIR images were visible on DWI. ADC values were significantly higher (p < 0.05) for axial active inflammatory lesions (median = 0.788 × 10−3 mm2/s, IQR 25–75 [0.7 × 10−3 mm2/s; 0.9 × 10−3 mm2/s]) than for type 1 Modic changes (median = 0.585 × 10−3 mm2/s, IQR 25–75 [0.55 × 10−3 mm2/s; 0.60 × 10−3 mm2/s]) and normal subchondral bone (median = 0.443 × 10−3 mm2/s, IQR 25–75 [0.40 × 10−3 mm2/s; 0.50 × 10−3 mm2/s]). Intra-class correlation coefficients for intra- and inter-reader ADC values comparison were excellent (0.89 and 0.98 respectively). Conclusion: DWI is a sensitive and fast sequence that offer the possibility of quantifying diffusion coefficients of the lesions, which could help to discriminate between spondylarthritis axial active inflammatory and type 1 Modic changes
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Objective: The relationship between tumor consistency and apparent diffusion coefficient (ADC) values is controversial. We evaluated the role of the ADC using an advanced diffusion-weighted imaging (DWI) technique. We employed periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) DWI acquired on a 3-T magnetic resonance imaging (MRI) scanner to assess the consistency of pituitary adenomas and examined the relationship between the ADC and the hormone secretion status of the tumors and their MIB-1 labeling index (MIB-1 LI). Materials and methods: The study protocol was approved by our institutional review board. We retrospectively studied 24 operated patients with pituitary adenomas who had undergone PROPELLER DWI on a 3-T MRI scanner. Conventional MRI findings were expressed as the ratio of the signal intensity (SI) in the lesions to the SI of the normal white matter and the degree of contrast enhancement. Minimum-, mean-, and maximum ADC (ADCmin, ADCmean, ADCmax) values were calculated. The consistency of the tumors was determined by neurosurgeons. All surgical specimens were submitted for histological study to calculate the MIB-1 LI and the percent collagen content. Preoperative MRI-, intraoperative-, and histological findings were analyzed by a statistician. Results: Our study included 15 soft-, 5 fibrous-, and 4 hard tumors. Tumor consistency was strongly associated with the percent collagen content. However, neither the tumor consistency nor the percent collagen content was correlated with MRI findings or ADC values. The SI of growth hormone-producing adenomas on T2-WI was lower than of the other pituitary adenomas studied (p < 0.01); no other significant difference was found in the ADC or on conventional MRI between pituitary adenomas with different secretory functions. The MIB-1 LI of pituitary adenomas was not correlated with their appearance on conventional MRI or their ADC values. Conclusion: Using the PROPELLER DWI
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Highlights: •The solid component of all invasive epithelial cancers showed high b1000 signal intensity. •ADCs can predict the histologic grade of epithelial ovarian cancer. •ADCs correlate negatively to the surgical stage of epithelial ovarian cancer. •ADCs may be useful imaging biomarkers to assess epithelial ovarian cancer. -- Abstract: Objective: The purpose of this article is to correlate the apparent diffusion coefficient (ADC) values of epithelial ovarian cancers with histologic grade and surgical stage. Materials and methods: We enrolled 43 patients with pathologically proven epithelial ovarian cancers for this retrospective study. All patients underwent preoperative pelvic magnetic resonance imaging (MRI) including diffusion-weighted images with b value of 0 and 1000 s/mm2 at 3.0-T unit. The mean ADC values of the solid portion of the tumor were measured and compared among different histologic grades and surgical stages. Results: The mean ADC values of epithelial ovarian cancers differed significantly between grade 1 (well-differentiated) and grade 2 (moderately-differentiated) (P = 0.013) as well as between grade 1 and grade 3 (poorly-differentiated) (P = 0.01); however, no statistically significant difference existed between grade 2 and grade 3 (P = 0.737). The receiver-operating characteristic analysis indicated that a cutoff ADC value of less than or equal to 1.09 × 10−3 mm2/s was associated with 94.4% sensitivity and 85.7% specificity in distinguishing grade 1 and grade 2/3 cancer. The difference in mean ADC values was statistically significant for early stage (FIGO stage I) and advanced stage (FIGO stage II-IV) cancer (P = 0.011). The interobserver agreement for the mean ADC values of epithelial ovarian cancers was excellent. Conclusion: The mean ADC values of the solid portion of epithelial ovarian cancers negatively correlated to histologic grade and surgical stage. The mean ADC values may be useful imaging biomarkers for assessment of
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Oh, Ji-Won, E-mail: fromentin@naver.com [Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701 (Korea, Republic of); Rha, Sung Eun, E-mail: serha@catholic.ac.kr [Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701 (Korea, Republic of); Oh, Soon Nam, E-mail: hiohsn@catholic.ac.kr [Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701 (Korea, Republic of); Park, Michael Yong, E-mail: digirave@kmle.com [Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701 (Korea, Republic of); Byun, Jae Young, E-mail: jybyun@catholic.ac.kr [Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701 (Korea, Republic of); Lee, Ahwon, E-mail: klee@catholic.ac.kr [Department of Hospital Pathology, Seoul St. Mary' s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 137-701 (Korea, Republic of)
2015-04-15
Highlights: •The solid component of all invasive epithelial cancers showed high b{sub 1000} signal intensity. •ADCs can predict the histologic grade of epithelial ovarian cancer. •ADCs correlate negatively to the surgical stage of epithelial ovarian cancer. •ADCs may be useful imaging biomarkers to assess epithelial ovarian cancer. -- Abstract: Objective: The purpose of this article is to correlate the apparent diffusion coefficient (ADC) values of epithelial ovarian cancers with histologic grade and surgical stage. Materials and methods: We enrolled 43 patients with pathologically proven epithelial ovarian cancers for this retrospective study. All patients underwent preoperative pelvic magnetic resonance imaging (MRI) including diffusion-weighted images with b value of 0 and 1000 s/mm{sup 2} at 3.0-T unit. The mean ADC values of the solid portion of the tumor were measured and compared among different histologic grades and surgical stages. Results: The mean ADC values of epithelial ovarian cancers differed significantly between grade 1 (well-differentiated) and grade 2 (moderately-differentiated) (P = 0.013) as well as between grade 1 and grade 3 (poorly-differentiated) (P = 0.01); however, no statistically significant difference existed between grade 2 and grade 3 (P = 0.737). The receiver-operating characteristic analysis indicated that a cutoff ADC value of less than or equal to 1.09 × 10{sup −3} mm{sup 2}/s was associated with 94.4% sensitivity and 85.7% specificity in distinguishing grade 1 and grade 2/3 cancer. The difference in mean ADC values was statistically significant for early stage (FIGO stage I) and advanced stage (FIGO stage II-IV) cancer (P = 0.011). The interobserver agreement for the mean ADC values of epithelial ovarian cancers was excellent. Conclusion: The mean ADC values of the solid portion of epithelial ovarian cancers negatively correlated to histologic grade and surgical stage. The mean ADC values may be useful imaging
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Mahmoud, Omar M. [Department of Neurosurgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Department of Radiology, South Egypt Cancer Institute, Assiut University, Assiut 71515 (Egypt); Tominaga, Atsushi [Department of Neurosurgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Amatya, Vishwa Jeet [Department of Pathology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551 (Japan); Ohtaki, Megu [Department of Environmetrics and Biometrics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8551 (Japan); Sugiyama, Kazuhiko; Sakoguchi, Tetsuhiko; Kinoshita, Yasuyuki [Department of Neurosurgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Takeshima, Yukio [Department of Pathology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551 (Japan); Abe, Nobukazu; Akiyama, Yuji [Department of Clinical Radiology, Hiroshima University Hospital, Hiroshima 734-8551 (Japan); El-Ghoriany, Ahmad I. [Department of Neurosurgery, Faculty of Medicine, Assiut University, Assiut 71515 (Egypt); Alla, Abdel Karim H. Abd; El-Sharkawy, Mostafa A.M. [Department of Radiology, Faculty of Medicine, Assiut University, Assiut 71515 (Egypt); Arita, Kazunori [Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima (Japan); Kurisu, Kaoru [Department of Neurosurgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan); Yamasaki, Fumiyuki, E-mail: fyama@hiroshima-u.ac.jp [Department of Neurosurgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan)
2011-11-15
Objective: The relationship between tumor consistency and apparent diffusion coefficient (ADC) values is controversial. We evaluated the role of the ADC using an advanced diffusion-weighted imaging (DWI) technique. We employed periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) DWI acquired on a 3-T magnetic resonance imaging (MRI) scanner to assess the consistency of pituitary adenomas and examined the relationship between the ADC and the hormone secretion status of the tumors and their MIB-1 labeling index (MIB-1 LI). Materials and methods: The study protocol was approved by our institutional review board. We retrospectively studied 24 operated patients with pituitary adenomas who had undergone PROPELLER DWI on a 3-T MRI scanner. Conventional MRI findings were expressed as the ratio of the signal intensity (SI) in the lesions to the SI of the normal white matter and the degree of contrast enhancement. Minimum-, mean-, and maximum ADC (ADC{sub min}, ADC{sub mean}, ADC{sub max}) values were calculated. The consistency of the tumors was determined by neurosurgeons. All surgical specimens were submitted for histological study to calculate the MIB-1 LI and the percent collagen content. Preoperative MRI-, intraoperative-, and histological findings were analyzed by a statistician. Results: Our study included 15 soft-, 5 fibrous-, and 4 hard tumors. Tumor consistency was strongly associated with the percent collagen content. However, neither the tumor consistency nor the percent collagen content was correlated with MRI findings or ADC values. The SI of growth hormone-producing adenomas on T2-WI was lower than of the other pituitary adenomas studied (p < 0.01); no other significant difference was found in the ADC or on conventional MRI between pituitary adenomas with different secretory functions. The MIB-1 LI of pituitary adenomas was not correlated with their appearance on conventional MRI or their ADC values. Conclusion: Using the
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Kim, Sang Joon; Choi, Choong Gon; Kim, Jeong Kon [Dept. of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Yun, Sung Cheol [Dept. of Biostatistics, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Jeong, Ha Kyu [Dept. of Radiology, East-West Neomedical Center, Kyung Hee University College of Medicine, Seoul (Korea, Republic of); Kim, Eun Ju [Clinical Scientist, MR, Philips Healthcare, Seoul (Korea, Republic of)
2015-04-15
To validate the usefulness of a diffusional anisotropic capillary array phantom and to investigate the effects of diffusion tensor imaging (DTI) parameter changes on diffusion fractional anisotropy (FA) and apparent diffusion coefficient (ADC) using the phantom. Diffusion tensor imaging of a capillary array phantom was performed with imaging parameter changes, including voxel size, number of sensitivity encoding (SENSE) factor, echo time (TE), number of signal acquisitions, b-value, and number of diffusion gradient directions (NDGD), one-at-a-time in a stepwise-incremental fashion. We repeated the entire series of DTI scans thrice. The coefficients of variation (CoV) were evaluated for FA and ADC, and the correlation between each MR imaging parameter and the corresponding FA and ADC was evaluated using Spearman's correlation analysis. The capillary array phantom CoVs of FA and ADC were 7.1% and 2.4%, respectively. There were significant correlations between FA and SENSE factor, TE, b-value, and NDGD, as well as significant correlations between ADC and SENSE factor, TE, and b-value. A capillary array phantom enables repeated measurements of FA and ADC. Both FA and ADC can vary when certain parameters are changed during diffusion experiments. We suggest that the capillary array phantom can be used for quality control in longitudinal or multicenter clinical studies.
International Nuclear Information System (INIS)
To validate the usefulness of a diffusional anisotropic capillary array phantom and to investigate the effects of diffusion tensor imaging (DTI) parameter changes on diffusion fractional anisotropy (FA) and apparent diffusion coefficient (ADC) using the phantom. Diffusion tensor imaging of a capillary array phantom was performed with imaging parameter changes, including voxel size, number of sensitivity encoding (SENSE) factor, echo time (TE), number of signal acquisitions, b-value, and number of diffusion gradient directions (NDGD), one-at-a-time in a stepwise-incremental fashion. We repeated the entire series of DTI scans thrice. The coefficients of variation (CoV) were evaluated for FA and ADC, and the correlation between each MR imaging parameter and the corresponding FA and ADC was evaluated using Spearman's correlation analysis. The capillary array phantom CoVs of FA and ADC were 7.1% and 2.4%, respectively. There were significant correlations between FA and SENSE factor, TE, b-value, and NDGD, as well as significant correlations between ADC and SENSE factor, TE, and b-value. A capillary array phantom enables repeated measurements of FA and ADC. Both FA and ADC can vary when certain parameters are changed during diffusion experiments. We suggest that the capillary array phantom can be used for quality control in longitudinal or multicenter clinical studies.
Institute of Scientific and Technical Information of China (English)
Yuelang Zhang; Xingwang Sun; Guangnan Quan; Yongqian Qiang; Chenxia Li
2008-01-01
Objective:To find the value of the apparent diffusion coefficient (ADC) of diffusion weighted magnetic resonance imaging of common renal diseases. Methods: There were 30 healthy subjects and 81 patients with renal lesions (56 cases of renal carcinoma, 18 lesions of 12 cases of renal angiomyolipoma, and 21 lesions of 13 cases of renal cysts). Conventional magnetic resonance imaging and diffusion weighted magnetic resonance imaging were carded out. We measured the average ADC value of the renal lesions and normal kidneys. ADC maps from different b values were generated by a statistical package. Results: The ADC values of normal kidneys with three different motion-probing gradients(b=500, 800, 1000 sec/mm2) were 2.78±0.14×10-3mm2s-1,2.45±0.13×10-3mm2s-1, 2.13±0.14×10-3mm2s-1, respectively. The ADC values of renal cell carcinoma with three different motion-probing gradients(b=500, 800, 1008 sec/mm2) were 1.63±0.14×10-3mm2s-1, 1.31±0.18×10-3mm2s-1, 1.07±0.15-310-3mm2s-1, respectively. Among the renal cell carcinoma, the ADC value of clear cell type were 1.67±0.09×10-3mm2s-1, 1.36±0.13×10-3mm2s-1, 1.15±0.14×10-3mm2s-1,respectively; the ADC values of granular cell type were 1.59±0.19×10-3mm2s-1, 1.25±0.22×10-3mm2s-1, 0.97±0.12×10-3mm2s-1, respectively. The ADC values of renal angiomyolipoma with three different motion-probing gradients(b=500, 800, 1008 sec/mm2) were 0.88±0.08×10-3mm2s-1, 0.63±0.07×10-3mm2s-1, 0.43±0.04×10-3mm2s-1, respectively. The ADC values of renal cystic lesions with three different motion-probing gradients(b=500, 800, 1000 sec/mm2) were 3.73±0.18×10-3mm2s-1, 3.44±0.13×10-3mm2s-1, 3.09±0.21×10-3mm2s-1, respectively. Statistically significant differences exists between the ADC values of normal kidney, renal carcinomas, renal angiomyolipomas and renal cysts when the b value is the same. Among the different cell types of renal carcinomas, the ADC value of granular cell carcinoma is lower than that of clear cell
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Giannotti, E., E-mail: ytteb84@hotmail.com [Breast Imaging Department, Ninewells Hospital and Medical School, Dundee DD1 9SY (United Kingdom); Waugh, S., E-mail: shelley.waugh@nhs.net [Department of Medical Physics, Ninewells Hospital and Medical School, Dundee DD1 9SY (United Kingdom); Department of Clinical Radiology, Ninewells Hospital and Medical School, Dundee DD1 9SY (United Kingdom); Priba, L., E-mail: lpriba@nhs.net [Department of Medical Physics, Ninewells Hospital and Medical School, Dundee DD1 9SY (United Kingdom); Davis, Z., E-mail: zoedavis@doctors.org.uk [Breast Imaging Department, Ninewells Hospital and Medical School, Dundee DD1 9SY (United Kingdom); Crowe, E., E-mail: e.crowe@nhs.net [Department of Clinical Radiology, Ninewells Hospital and Medical School, Dundee DD1 9SY (United Kingdom); Vinnicombe, S., E-mail: s.vinnicombe@dundee.ac.uk [Division of Imaging and Technology, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY (United Kingdom)
2015-09-15
Highlights: • Inter-scan errors have minimal contribution to ADC measurement variability. • Intra-observer measures of ADC values in breast cancer are excellent. • ADC measures in whole tumour are more reproducible than minimum ADC measures. • ADC measurement error is most influenced by multiple readers. - Abstract: Purpose: Apparent Diffusion Coefficient (ADC) measurements are increasingly used for assessing breast cancer response to neoadjuvant chemotherapy although little data exists on ADC measurement reproducibility. The purpose of this work was to investigate and characterise the magnitude of errors in ADC measures that may be encountered in such follow-up studies- namely scanner stability, scan–scan reproducibility, inter- and intra- observer measures and the most reproducible measurement of ADC. Methods: Institutional Review Board approval was obtained for the prospective study of healthy volunteers and written consent acquired for the retrospective study of patient images. All scanning was performed on a 3.0-T MRI scanner. Scanner stability was assessed using an ice-water phantom weekly for 12 weeks. Inter-scan repeatability was assessed across two scans of 10 healthy volunteers (26–61 years; mean: 44.7 years). Inter- and intra-reader analysis repeatability was measured in 52 carcinomas from clinical patients (29–70 years; mean: 50.0 years) by measuring the whole tumor ADC value on a single slice with maximum tumor diameter (ADC{sub S}) and the ADC value of a small region of interest (ROI) on the same slice (ADC{sub min}). Repeatability was assessed using intraclass correlation coefficients (ICC) and coefficients of repeatability (CoR). Results: Scanner stability contributed 6% error to phantom ADC measurements (0.071 × 10{sup −3} mm{sup 2}/s; mean ADC = 1.089 × 10{sup −3} mm{sup 2}/s). The measured scan-scan CoR in the volunteers was 0.122 × 10{sup −3} mm{sup 2}/s, contributing an error of 8% to the mean measured values (ADC
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Highlights: • Inter-scan errors have minimal contribution to ADC measurement variability. • Intra-observer measures of ADC values in breast cancer are excellent. • ADC measures in whole tumour are more reproducible than minimum ADC measures. • ADC measurement error is most influenced by multiple readers. - Abstract: Purpose: Apparent Diffusion Coefficient (ADC) measurements are increasingly used for assessing breast cancer response to neoadjuvant chemotherapy although little data exists on ADC measurement reproducibility. The purpose of this work was to investigate and characterise the magnitude of errors in ADC measures that may be encountered in such follow-up studies- namely scanner stability, scan–scan reproducibility, inter- and intra- observer measures and the most reproducible measurement of ADC. Methods: Institutional Review Board approval was obtained for the prospective study of healthy volunteers and written consent acquired for the retrospective study of patient images. All scanning was performed on a 3.0-T MRI scanner. Scanner stability was assessed using an ice-water phantom weekly for 12 weeks. Inter-scan repeatability was assessed across two scans of 10 healthy volunteers (26–61 years; mean: 44.7 years). Inter- and intra-reader analysis repeatability was measured in 52 carcinomas from clinical patients (29–70 years; mean: 50.0 years) by measuring the whole tumor ADC value on a single slice with maximum tumor diameter (ADCS) and the ADC value of a small region of interest (ROI) on the same slice (ADCmin). Repeatability was assessed using intraclass correlation coefficients (ICC) and coefficients of repeatability (CoR). Results: Scanner stability contributed 6% error to phantom ADC measurements (0.071 × 10−3 mm2/s; mean ADC = 1.089 × 10−3 mm2/s). The measured scan-scan CoR in the volunteers was 0.122 × 10−3 mm2/s, contributing an error of 8% to the mean measured values (ADCscan1 = 1.529 × 10−3 mm2/s; ADCscan2 = 1.507 × 10
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Objective: To investigate the diagnostic value of apparent diffusion coefficient in the evaluation of sinonasal masses. Methods: Sixty-seven sinonasal solid masses over 1 cm in diameter confirmed by pathology were retrospectively analyzed, all patients underwent preoperative routine MRI with DWI, the ADC values were measured in ROI within the solid mass. The patients were divided into benign and malignant groups by the histopathology, according to pathological findings, the patients were further divided into the hematolymphoid tumors, the malignancy of epithelium and mesenchymal tissue, the benign tumors of epithelial and mesenchymal tissue, and vasogenic masses. ANOVA test and t test were used to compare the ADC values of different groups. The receiver operating characteristic curve (ROC) was constructed using various cut points of ADC for different parameters to confirm the diagnostic threshold value and evaluate the diagnostic efficacy. Results: All lesions were solitary. There were 22 malignant tumors, of which 6 lesions were hematolymphoid tumors and 16 lesions malignancy from epithelium and mesenchymal tissue. There were 45 benign tumors, of which 22 lesions were benign tumors from epithelium and mesenchymal tissue and 23 lesions vasogenic masses. The mean ADC value of malignant and benign masses was (0.88 ± 0.26) × 10-3 mm2/s and (1.54 ± 0.41) × 10-3 mm2/s respectively. There was statistically significant differences between them (t=6.897, P <0.01). The mean ADC value was(0.63 ± 0.10) × 10-3 mm2/s in hematolymphoid tumors,(0.97 ±0.24) × 10-3 mm2/s in malignancy from epithelium and mesenchymal tissue, (1.38 ± 0.23) × 10-3 mm2/s in benign tumors from epithelium and mesenchymal tissue,(1.68 ± 0.49) × 10-3 mm2/s in vasogenic masses respectively. There was statistically significant difference among all 4 groups(F=22.788, P<0.01), and the differences between any 2 groups were still statistically significant (P <0.05). The area under the ROC calculated
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Haack, Soeren (Dept. of Clinical Engineering, Aarhus Univ. Hospital (Denmark)), E-mail: Soeren.haack@stab.rm.dk; Morre Pedersen, Erik (Dept. of Radiology, Aarhus Sygehus, Aarhus Univ. Hospital (Denmark)); Jespersen, Sune N. (Center of Functionally Integrative Neuroscience, Aarhus Univ. Hospital (Denmark)); Kallehauge, Jesper F. (Dept. of Medical Physics, Aarhus Univ. Hospital (Denmark)); Lindegaard, Jacob Christian; Tanderup, Kari (Dept. of Oncology Aarhus Univ. Hospital (Denmark))
2010-10-15
Background and purpose. T2 weighted MRI is recommended for image guided adaptive brachytherapy (IGABT) in cervical cancer. Diffusion weighted imaging (DWI) and the derived apparent diffusion coefficient (ADC) may add additional biological information on tumour cell density. The purpose of this study was to evaluate the distribution of the ADC within target volumes as recommended by GEC-ESTRO: Gross Tumour Volume at BT (GTVBT), High-Risk Clinical Tumour Volume (HR-CTV) and Intermediate-Risk Clinical Target Volume (IR-CTV) and to evaluate the change of diffusion between fractions of IGABT. Material and methods. Fifteen patients with locally advanced cervical cancer were examined by MRI before their first (BT1) and second (BT2) fraction of IGABT, resulting in a total of 30 MR examinations including both T2 weighted and DWI sequences. The Apparent Diffusion Coefficient (ADC) was calculated by use of three levels of b-values (0, 600, 1000 s/mm2). ADC maps were constructed and fused with the GEC ESTRO target contours. The mean ADC value within each target volume was calculated. Furthermore, volumes of low diffusion (ADClow) were defined based on an ADC threshold of 1.2 x 10-3 mm2/s, and overlap with target volumes was evaluated. Change of ADC level in target volumes and change of ADClow volume from BT1 to BT2 was also evaluated. Results. The mean ADC was significantly lower in GTVBT than in HR-CTV (p<0.001) which again was significantly lower than in IR-CTV (p<0.001). There was no significant change of the ADClow volume or ADC level within each target structure between BT1 and BT2 (p=0.242). All three GEC-ESTRO volumes contained volumes with low diffusion. The GTVBT contained 37.2% volume of low diffusion, HR-CTV 20.3% and IR-CTV 10.8%. Conclusion. With DWI we were able to find a significant difference in ADC-values for the three different GEC ESTRO targets. This supports the assumption that the target volumes used for dose prescription in IGABT contain tissues with
The apparent diffusion coefficient of water in gray and white matter of the infant brain
DEFF Research Database (Denmark)
Toft, P B; Leth, H; Peitersen, Birgit;
1996-01-01
at the basal ganglia level was investigated with the diffusion-encoding gradients in the slice-selection direction. RESULTS: On ADC maps, the corpus callosum and the optic radiations appeared dark before the onset of myelination, and the crus posterior of the internal capsule could be visualized...
Institute of Scientific and Technical Information of China (English)
Hui Hu; Hong Lu; Zhanping He; Xiangjun Han; Jing Chen; Rong Tu
2012-01-01
To investigate the effects of mRNA interference on aquaporin-4 expression in swollen tissue of rats with ischemic cerebral edema, and diagnose the significance of diffusion-weighted MRI, we injected 5 μL shRNA- aquaporin-4 (control group) or siRNA- aquaporin-4 solution (1:800) (RNA interference group) into the rat right basal ganglia immediately before occlusion of the middle cerebral artery. At 0.25 hours after occlusion of the middle cerebral artery, diffusion-weighted MRI displayed a high signal; within 2 hours, the relative apparent diffusion coefficient decreased markedly, aquaporin-4 expression increased rapidly, and intracellular edema was obviously aggravated; at 4 and 6 hours, the relative apparent diffusion coefficient slowly returned to control levels, aquaporin-4 expression slightly increased, and angioedema was observed. In the RNA interference group, during 0.25- 6 hours after injection of siRNA- aquaporin-4 solution, the relative apparent diffusion coefficient slightly fluctuated and aquaporin-4 expression was upregulated; during 0.5-4 hours, the relative apparent diffusion coefficient was significantly higher, while aquaporin-4 expression was significantly lower when compared with the control group, and intracellular edema was markedly reduced; at 0.25 and 6 hours, the relative apparent diffusion coefficient and aquaporin-4 expression were similar when compared with the control group; obvious angioedema remained at 6 hours. Pearson's correlation test results showed that aquaporin-4 expression was negatively correlated with the apparent diffusion coefficient (r = -0.806, P < 0.01). These findings suggest that upregulated aquaporin-4 expression is likely to be the main molecular mechanism of intracellular edema and may be the molecular basis for decreased relative apparent diffusion coefficient. Aquaporin-4 gene interference can effectively inhibit the upregulation of aquaporin-4 expression during the stage of intracellular edema with time
Carrero-González, L; Kaulisch, T; Ruiz-Cabello, J; Pérez-Sánchez, J M; Peces-Barba, G; Stiller, D; Rodríguez, I
2012-09-01
The apparent diffusion coefficient (ADC) of hyperpolarized (HP) gases is a parameter that reflects changes in lung microstructure. However, ADC is dependent on many physiological and experimental variables that need to be controlled or specified in order to ensure the reliability and reproducibility of this parameter. A single breath-hold experiment is desirable in order to reduce the amount of consumed HP gas. The application of a positive end-expiratory pressure (PEEP) causes an increase in the residual gas volume. Depending on the applied PEEP, the ratio between the incoming and residual gas volumes will change and the ADC will vary, as long as both gases do not have the same diffusion coefficient. The most standard method for human applications uses air for breathing and a bolus of pure HP (3)He for MRI data acquisition. By applying this method in rats, we have demonstrated that ADC values are strongly dependent on the applied PEEP, and therefore on the residual gas volume in the lung. This outcome will play an important role in studies concerning certain diseases, such as emphysema, which is characterized by an increase in the residual volume. Ventilation with an oxygen-helium mixture (VOHeM) is a proposed single breath-hold method that uses two different gas mixtures (O(2)-(4)He for ventilation and HP (3)He-N(2) for imaging). The concentration of each gas in its respective mixture was calculated in order to obtain the same diffusion coefficient in both mixtures. ADCs obtained from VOHeM are independent of PEEP, thus minimizing the effect of the different residual volumes. PMID:22275333
Reversal of apparent diffusion coefficient (ADC) following transient focal cerebral ischemia in cats
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To determine the minimal threshold ADC ratio suggesting reversible ischemia in a temporary model of MCAO. Seven Korean cats weighing 3-3.5 kg were used as a temporary model of MCAO. The MCA was occluded for 1 hour, and diffusion-weighted images (DWI), and ADC and regional cerebral blood volume (rCBV) maps, were obtained at 1, 3, 6 and 24 hours after reperfusion using a 1.5T MR unit. The Cats were sacrificed 24 hours after imaging. Triphenyl tetrazolium chloride (TTC) staining of brain slices was performed, and DWI images and TTC-stained brain slices were compared with the naked eye. Reversible ischemia was defined as the area of high signal intensity at 1-hour DWI that normalized at follow-up DWI and in which TTC staining was normal. Using the ADC image obtained at 1 hour after reperfusion, 60 ADC ratios were obtained in the periphery of the infarct and reversible ischemia. Tissue survival showing normal TTC staining was used for final determination. The sensitivity and specificity of each ADC ratio was obtained and an ROC curve was plotted. Five of seven cats showed the reversible ischemia. An area of high signal intensity was seen on DWI images obtained 1 hours after reperfusion, and this improved at follow-up imaging. The distribution of the ADC ratio in the periphery of the infarct core was 0.71-0.81, and in the periphery of reversible ischemia it was 0.79-0.93. The ADC ratio of 0.80 obtained 1 hr after reperfusion predicted the survival of the ischemic tissure with 93% sensitivity and 90% specificity. The ADC ratio of the reversible ischemia was 0.82 ±0.03 at 1 hour after reperfusion, and this was higher than that of the infarct, which was 0.74±0.03. The minimal threshold ADC ratio suggesting reversible ischemia in this temporary model of MCAO was 0.80
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John N Morelli
Full Text Available Hepatic lesions often present diagnostic connundrums with conventional MR techniques. Hepatobiliary phase contrast-enhanced imaging with gadoxetic acid can aid in the characterization of such lesions. However, quantitative measures describing late-phase enhancement must be assessed relative to their accuracy of hepatic lesion classification.To compare quantitative parameters in gadoxetic acid contrast-enhanced dynamic and hepatobiliary phase imaging versus apparent diffusion coefficients in hepatic lesion characterization.57 patients with focal hepatic lesions on gadoxetic acid MR were included. Lesion enhancement at standard post-contrast time points and in the hepatobiliary phase (HB; 15 and 25 minutes post-contrast was assessed via calculation of contrast (CR and enhancement ratios (ER. Apparent diffusion coefficient (ADC values were also obtained. Values for these parameters were compared among lesions and ROC analyses performed.HB enhancement was greatest with FNH and adenomas. HB ER parameters but not HB CR could distinguish HCC from benign entities (0.9 ER ROC AUC versus 0.5 CR ROC AUC. There was no statistically significant difference found between the 15 and 25 minutes HB time points in detection of any lesion (p>0.4. ADC values were statistically significantly higher with hemangiomas (p<0.05 without greater accuracy in lesion detection relative to HB phase parameters.Hepatobiliary phase gadoxetic acid contrast-enhanced MR characterizes focal hepatic lesions more accurately than ADC and conventional dynamic post-contrast time point enhancement parameters. ER values are generally superior to CR. No discernible benefit of 25 minute versus 15 minute delayed imaging is demonstrated.
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Purpose. To determine association between apparent diffusion coefficient value on diffusion-weighted imaging and Gleason score in patients with prostate cancer. Methods. This retrospective case series was conducted at Radiology Department of Aga Khan University between June 2009 and June 2011. 28 patients with biopsy-proven prostate cancer were included who underwent ultrasound guided sextant prostate biopsy and MRI. MRI images were analyzed on diagnostic console and regions of interest were drawn. Data were entered and analyzed on SPSS 20.0. ADC values were compared with Gleason score using one-way ANOVA test. Results. In 28 patients, 168 quadrants were biopsied and 106 quadrants were positive for malignancy. 89 lesions with proven malignancy showed diffusion restriction. The mean ADC value for disease with a Gleason score of 6 was 935 mm2/s (SD = 248.4 mm2/s); Gleason score of 7 was 837 mm2/s (SD = 208.5 mm2/s); Gleason score of 8 was 614 mm2/s (SD = 108 mm2/s); and Gleason score of 9 was 571 mm2/s (SD = 82 mm2/s). Inverse relationship was observed between Gleason score and mean ADC values. Conclusion. DWI and specifically quantitative ADC values may help differentiate between low-risk (Gleason score, 6), intermediate-risk (Gleason score, 7), and high-risk (Gleason score 8 and 9) prostate cancers, indirectly determining the aggressiveness of the disease
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Diffusion anisotropy index, diffusion trace and eigenvalues of the pyramidal tracts were measured in 19 patients with supratentorial brain tumor using diffusion tensor MR imaging. These indices reflected condition of pyramidal tract, being compressed and/or being T2-high. Estimation of eigenvalues, in addition to diffusion anisotropy and the trace, should provide more detailed information about the pyramidal tract in brain tumor cases. (author)
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Nural, Mehmet Selim, E-mail: msnural@omu.edu.tr [Department of Radiology, Medical Faculty, Ondokuz Mayis University, 55139 Samsun (Turkey); Danaci, Murat, E-mail: danacim55@yahoo.com [Department of Radiology, Medical Faculty, Ondokuz Mayis University, 55139 Samsun (Turkey); Soyucok, Ahmet, E-mail: soyucokac@hotmail.com [Department of Radiology, Medical Faculty, Ondokuz Mayis University, 55139 Samsun (Turkey); Okumus, Nilgun Ozbek, E-mail: 2121@omu.edu.tr [Department of Radiation Oncology, Medical Faculty, Ondokuz Mayis University, 55139 Samsun (Turkey)
2013-10-01
Objective: To evaluate effectiveness of apparent diffusion coefficient (ADC) values measured by diffusion-weighted magnetic resonance imaging (DW-MRI) in differentiation of colorectal tumor recurrences and posttherapeutical soft tissue changes. Methods: For this prospective study, 30 patients (22 males, 8 females; age range 30–81 years; mean age 61 ± 12 years) who underwent surgery for colorectal tumors and had a mass detected by computed tomography (CT) and/or MRI during follow-up examinations were divided into 2 groups [17 patients (Group 1) with recurrence and 13 patients (Group 2) with benign fibrosis/granulation tissue]. Final diagnoses were based on histopathological examination in 14 patients and clinical follow-up at least 6 months in the remaining 16. In the latter, the diagnosis of recurrence was made in cases in which the lesion was larger on follow-up CT and MRI; recurrence was ruled out in cases of stable or shrinking lesions without any increase in tumor markers. DW-MRI was performed in the axial plane, for two different b values (b = 0 and 800 s/mm{sup 2}). The mean apparent diffusion coefficient (ADC) values were measured by manual delineation of regions of interest on ADC maps. Results: The median ADC values were 1.07 × 10{sup −3} mm/s{sup 2} (min: 0.82, max: 2.05) and 1.91 × 10{sup −3} mm/s{sup 2} (min: 1.51, max: 2.22) in Groups 1 and 2, respectively. A statistically significant difference was detected between the two groups (P < 0.001). When the threshold value used to determine whether the lesions recurred was 1.48 × 10{sup −3} mm/s{sup 2} based on ROC analysis, the sensitivity was 82% and the specificity was 100%. There were three patients with a false-negative diagnosis, and the primary histopathological diagnosis of all was mucinous adenocarcinoma. Conclusions: Because recurrences in mucinous adenocarcinomas have high ADC values, they may show overlap with benign lesions. In the detection of the local recurrence of colorectal
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Park, Yaewon; Kim, Man Deuk; Jung, Dae Chul; Lee, Shin Jae; Kim, Gyoungmin; Park, Sung Il; Won, Jong Yun; Lee, Do Yun [Yonsei University College of Medicine, Department of Radiology, Severance Hospital, Seoul (Korea, Republic of)
2015-05-01
To determine the usefulness of the apparent diffusion coefficient (ADC) in predicting response to uterine artery embolization (UAE) for symptomatic adenomyosis. A prospective study was performed on 25 patients who underwent diffusion-weighted (DW) magnetic resonance imaging (MRI) before UAE between June 2011 and December 2012. All patients underwent 3-month follow-up MRI after UAE using non-spherical polyvinyl alcohol (PVA) particles ranging from 150 to 500 μm. Quantitative measurement of the ADC was performed for each adenomyosis. Complete response and incomplete response were defined as ≥90 % or <90 %, respectively, of the non-perfusion area with adenomyosis at the follow-up MRI. The ADC values were compared between patients who achieved complete or incomplete response which was assessed according to the MRI findings after UAE. Nineteen patients showed complete response, and six showed incomplete response. The ADC value ranged from 0.842 to 1.346 x 10{sup -3} mm{sup 2}/s (mean 1.075 ± 0.117). The mean ADC was 1.043 ± 0.237 in the complete response group and 1.176 ± 0.429 in the incomplete response group (0.012). Using a threshold of <1.147 x 10{sup -3} mm{sup 2}/s, the sensitivity and specificity of the ADC to predict success after UAE were 83.3 % and 84.2 %. The ADC of adenomyosis may potentially predict a successful response to UAE for adenomyosis. (orig.)
International Nuclear Information System (INIS)
To determine the usefulness of the apparent diffusion coefficient (ADC) in predicting response to uterine artery embolization (UAE) for symptomatic adenomyosis. A prospective study was performed on 25 patients who underwent diffusion-weighted (DW) magnetic resonance imaging (MRI) before UAE between June 2011 and December 2012. All patients underwent 3-month follow-up MRI after UAE using non-spherical polyvinyl alcohol (PVA) particles ranging from 150 to 500 μm. Quantitative measurement of the ADC was performed for each adenomyosis. Complete response and incomplete response were defined as ≥90 % or <90 %, respectively, of the non-perfusion area with adenomyosis at the follow-up MRI. The ADC values were compared between patients who achieved complete or incomplete response which was assessed according to the MRI findings after UAE. Nineteen patients showed complete response, and six showed incomplete response. The ADC value ranged from 0.842 to 1.346 x 10-3 mm2/s (mean 1.075 ± 0.117). The mean ADC was 1.043 ± 0.237 in the complete response group and 1.176 ± 0.429 in the incomplete response group (0.012). Using a threshold of <1.147 x 10-3 mm2/s, the sensitivity and specificity of the ADC to predict success after UAE were 83.3 % and 84.2 %. The ADC of adenomyosis may potentially predict a successful response to UAE for adenomyosis. (orig.)
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Littooij, Annemieke S. [University Medical Centre Utrecht, Department of Radiology, Utrecht (Netherlands); Humphries, Paul D. [Great Ormond Street Hospital for Children, Department of Radiology, London (United Kingdom); University College London Hospital, Department of Radiology, London (United Kingdom); Olsen, Oeystein E. [Great Ormond Street Hospital for Children, Department of Radiology, London (United Kingdom)
2015-10-15
The apparent diffusion coefficient (ADC) is potentially useful for assessing treatment response in nephroblastoma (Wilms tumour). However the precision of ADC measurements in these heterogeneous lesions is unknown. To assess intra- and interobserver variability of whole-tumour ADC measurements in viable parts of nephroblastomas at diagnosis and after preoperative chemotherapy. We included children with histopathologically proven nephroblastoma who had undergone MRI with diffusion-weighted imaging before and after preoperative chemotherapy. Three independent observers performed whole-tumour ADC measurements of all lesions, excluding non-enhancing areas. One observer evaluated all lesions on two occasions. We performed analyses using Bland-Altman plots and concordance correlation coefficient (CCC) calculations with 95% limits of agreement for median ADC, difference between pre- and post-chemotherapy median ADC (ADC shift) and percentage of pixels with ADC values <1.0 x 10{sup -3} mm{sup 2}/s. In 22 lesions (13 pretreatment and 9 post-treatment) in 10 children the interobserver variability in median ADC and ADC shift were within the interval of approximately ±0.1 x 10{sup -3} mm{sup 2}/s (limits of agreement for median ADC ranged -0.08-0.11 x 10{sup -3} mm{sup 2}/s and for ADC-shift -0.11-0.09 x 10{sup -3} mm{sup 2}/s). The interobserver variability for percentage of low-ADC pixels was larger and also biased. The calculated CCC confirmed good intra- and interobserver agreement (ρ-c ranging from 0.968 to 0.996). Measurements of whole-tumour ADC values excluding necrotic areas seem to be sufficiently precise for detection of chemotherapy-related change. (orig.)
Diffusion coefficient in photon diffusion theory
Graaff, R; Ten Bosch, JJ
2000-01-01
The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to
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Background: With the increased clinical use of 3-Tesla (3T) magnets, it becomes important to identify the potential applications of advanced magnetic resonance (MR) imaging techniques such as diffusion-weighted imaging in head and neck pathologies. Purpose: To establish the 3T apparent diffusion coefficient (ADC) values for normal neck structures, and to examine the utility of ADC values in distinguishing head and neck squamous cell carcinomas (HNSCC) from normal neck anatomy. Material and Methods: 3T diffusion-weighted imaging was performed on 10 normal volunteers and 10 patients with known HNSCC. In the volunteers, mean ADC was calculated in the parotid gland, submandibular gland, base of the tongue, pterygoid muscle, masseter muscle, paraspinal muscles, true vocal cord, thyroid gland, thyroid cartilage, cricoid cartilage, and lymph nodes. The mean tumor ADC value was calculated from the 10 patients with HNSCC and compared with the normal ADC values from various neck structures. Results: The mean ADC value measured in the HNSCC was 1.101 (±0.214)x10-3mm2/s. This was significantly lower than ADC values of paraspinal muscles, pterygoid muscle, masseter muscle, thyroid gland, and base of the tongue (P=0.0006, 0.0002, 0.0001, 0.001, and 0.002, respectively). The tumor ADC values were not significantly different from ADC values of parotid and submandibular glands (P=0.057 and 0.14, respectively). Conclusion: 3T ADC values show potential for distinguishing HNSCC from normal extracranial head and neck structures
Directory of Open Access Journals (Sweden)
Vijayakumar Chinnadurai
2010-05-01
Full Text Available A novel Neuro – level set algorithm is proposed and evaluated for simultaneous segmentation and grading of brain tumors. The algorithm utilizes vascular and cellular information provided by the reconstructed images of dynamic contrast susceptibility magnetic resonance images and apparent diffusion coefficient images. The reconstructed images are relative cerebral blood volume (rCBV image, time to peak (TTP image and percentage of base at peak (PBP image along with apparent diffusion coefficient (ADC maps. The proposed neural - levelset algorithm utilizes a neural block to provide the speed image for the levelset methods. In this study, two different architectures of levelset method have been implemented and their results are compared. The results show that the proposed Neuro- Levelset method performs better in differentiating the tumor, edema,necrosis in reconstructed images of dynamic contrast susceptibility magnetic resonance images and apparent diffusion coefficient MR images.
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Sasaki,Takanori
2012-06-01
Full Text Available The roles of cell density, extracellular space, intracellular factors, and apoptosis induced by the molecularly targeted drug rituximab on the apparent diffusion coefficient (ADC values were investigated using bio-phantoms. In these bio-phantoms, Ramos cells (a human Burkittｾs lymphoma cell line were encapsulated in gellan gum. The ADC values decreased linearly with the increase in cell density, and declined steeply when the extracellular space became less than 4 μm. The analysis of ADC values after destruction of the cellular membrane by sonication indicated that approximately 65% of the ADC values of normal cells originate from the cell structures made of membranes and that the remaining 35% originate from intracellular components. Microparticles, defined as particles smaller than the normal cells, increased in number after rituximab treatments, migrated to the extracellular space and significantly decreased the ADC values of bio-phantoms during apoptosis. An in vitro study using bio-phantoms was conducted to quantitatively clarify the roles of cellular factors and of extracellular space in determining the ADC values yielded by tumor cells and the mechanism by which apoptosis changes those values.
Zolal, Amir; Juratli, Tareq A; Linn, Jennifer; Podlesek, Dino; Sitoci Ficici, Kerim Hakan; Kitzler, Hagen H; Schackert, Gabriele; Sobottka, Stephan B; Rieger, Bernhard; Krex, Dietmar
2016-05-01
Objective To determine the value of apparent diffusion coefficient (ADC) histogram parameters for the prediction of individual survival in patients undergoing surgery for recurrent glioblastoma (GBM) in a retrospective cohort study. Methods Thirty-one patients who underwent surgery for first recurrence of a known GBM between 2008 and 2012 were included. The following parameters were collected: age, sex, enhancing tumor size, mean ADC, median ADC, ADC skewness, ADC kurtosis and fifth percentile of the ADC histogram, initial progression free survival (PFS), extent of second resection and further adjuvant treatment. The association of these parameters with survival and PFS after second surgery was analyzed using log-rank test and Cox regression. Results Using log-rank test, ADC histogram skewness of the enhancing tumor was significantly associated with both survival (p = 0.001) and PFS after second surgery (p = 0.005). Further parameters associated with prolonged survival after second surgery were: gross total resection at second surgery (p = 0.026), tumor size (0.040) and third surgery (p = 0.003). In the multivariate Cox analysis, ADC histogram skewness was shown to be an independent prognostic factor for survival after second surgery. Conclusion ADC histogram skewness of the enhancing lesion, enhancing lesion size, third surgery, as well as gross total resection have been shown to be associated with survival following the second surgery. ADC histogram skewness was an independent prognostic factor for survival in the multivariate analysis. PMID:26830088
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Hai-Yi Wang; Jia Wang; Ye-Huan Tang; Hui-Yi Ye; Lin Ma
2015-01-01
Background:Coronal diffusion-weighted magnetic resonance imaging (DW-MRI) and apparent diffusion coefficient (ADC) values have gradually become applied (following conventional axial DW-MRI) in the renal analysis.To explore whether data obtained using coronal DW-MRI are comparable with those derived using axial DW-MRI,this preliminary study sought to assess the agreement in renal ADC values between coronal DW-MRI and axial DW-MRI.Methods:Thirty-four healthy volunteers were enrolled in the study; written consents were obtained.All subjects underwent respiratory-triggered axial and coronal DW-MRI using a 1.5-MR system with b values of 0 and 800 s/mm2.The signal-to-noise ratios (SNRs) of the two DW-MRI sequences were measured and statistically compared using the paired t-test.The extent of agreement of ADC values of the upper pole,mid-pole,and lower pole of the kidney; the mean ADC values of the left kidney and right kidney; and the mean ADC values of the bilateral kidneys were evaluated via calculation of intraclass correlation coefficients (ICCs) or Bland-Altman method between the two DW-MRI sequences.Results:The SNR of coronal DW-MR images was statistically inferior to that of axial DW-MR images (P ＜ 0.001).The ICCs of the ADC values of each region of interest,and the mean ADC values of bilateral kidneys,between the two sequences,were greater than 0.5,and the mean ADCs of the bilateral kidneys demonstrated the highest ICC (0.869; 95％ confidence interval:0.739-0.935).In addition,94.1％ (32/34),94.1％ (32/34),and 97.1％ (31/34) of the ADC bias was inside the limits of agreement in terms of the mean ADC values of the left kidneys,right kidneys,and bilateral kidneys when coronal and axial DWI-MRI were compared.Conclusions:ADC values derived using coronal DW-MRI exhibited moderate-to-good agreement to those of axial DW-MRI,rendering the former an additional useful DW-MRI method,and causing the ADC values derived using the two types of DW-MRI to be comparable.
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Background and purpose: The application of a fluid-attenuated inversion-recovery pulse with a conventional diffusion-weighted MRI sequence (FLAIR DWI) decreases the partial volume effects from cerebrospinal fluid on apparent diffusion coefficient (ADC) measurements. For this reason, FLAIR DWI may be more useful in the evaluation of ischemic stroke, but few studies have looked at the effect of FLAIR on ADC measurements in this setting. This study quantitatively compares FLAIR DWI and conventional DWI in ischemic stroke of varying ages to assess the potential advantages of this technique. Methods: We respectively analyzed 139 DWI studies in patients with ischemic stroke with and without FLAIR at varying time points ranging from hyperacute to chronic. ADC values were measured in each lesion, as well as in the contralateral normal side. Comparisons were made between the ADC values obtained from the DWI sequences with and without FLAIR for both the lesion and the normal contralateral side. Results: The ADC measurements within the ischemic lesion were very similar on FLAIR DWI and conventional DWI for lesions less than 14 days old (p > 0.05), but were significantly decreased on FLAIR DWI for lesions between 15 and 30 days old and in lesions >31 days old (chronic stage) (p < 0.01). The contralateral ADC values were all significantly decreased on the FLAIR DWI sequence compared with conventional DWI (p < 0.01). Conclusions: The application of an inversion pulse does not significantly affect the ADC values for early stage ischemic stroke (less than 14 days from symptom onset), but results in a more accurate relative ADC measurement by reducing the cerebrospinal fluid partial volume effects of the normal contralateral side. In addition, combined with the conventional DWI, FLAIR DWI may be helpful in determining the age of ischemic lesions.
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Yiqun Sun
Full Text Available OBJECTIVE: We elected to analyze the correlation between the pre-treatment apparent diffusion coefficient (ADC and the clinical, histological, and immunohistochemical status of rectal cancers. MATERIALS AND METHODS: Forty-nine rectal cancer patients who received surgical resection without neoadjuvant therapy were selected that underwent primary MRI and diffusion-weighted imaging (DWI. Tumor ADC values were determined and analyzed to identify any correlations between these values and pre-treatment CEA or CA19-9 levels, and/or the histological and immunohistochemical properties of the tumor. RESULTS: Inter-observer agreement of confidence levels from two separate observers was suitable for ADC measurement (k = 0.775. The pre-treatment ADC values of different T stage tumors were not equal (p = 0.003. The overall trend was that higher T stage values correlated with lower ADC values. ADC values were also significantly lower for the following conditions: tumors with the presence of extranodal tumor deposits (p = 0.006 and tumors with CA19-9 levels ≥ 35 g/ml (p = 0.006. There was a negative correlation between Ki-67 LI and the ADC value (r = -0.318, p = 0.026 and between the AgNOR count and the ADC value (r = -0.310, p = 0.030. CONCLUSION: Significant correlations were found between the pre-treatment ADC values and T stage, extranodal tumor deposits, CA19-9 levels, Ki-67 LI, and AgNOR counts in our study. Lower ADC values were associated with more aggressive tumor behavior. Therefore, the ADC value may represent a useful biomarker for assessing the biological features and possible relationship to the status of identified rectal cancers.
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Purpose: To compare apparent diffusion coefficient (ADC) measurements from hyperpolarized (HP) helium (3He)-magnetic resonance imaging (MRI) with quantitative data from multislice Computed Tomography (CT) (MSCT) of the whole lungs and pulmonary function tests (PFT). Materials and methods: Twenty-seven subjects, 22 with established emphysema and 5 with preclinical emphysema defined by PFT criteria, were examined with HP 3He-MRI and MSCT. Mean age was 55 (±12) years, 18 female and 9 male. Mean ADC from 3He-MRI was compared with emphysema index (EI), 15th percentile and mean lung density (MLD) values from MSCT. Both mean ADC and MSCT data were compared to PFT, especially percent of predicted diffusing capacity of carbon monoxide (%predicted DLCO), using Pearson's correlation test. Results: Mean ADC and standard deviation values were 0.392 ± 0.119 cm2/s for the established emphysema group and 0.216 ± 0.046 for the pre-clinical emphysema group. MSCT values for the established emphysema group and pre-clinical emphysema group were: EI (%) 11 ± 12 and 0.4 ± 0.6, respectively; 15th percentile (Hounsfield Units (HU)), -956 ± 25 and -933 ± 13, respectively and MLD (HU) -877 ± 20 and -863 ± 15, respectively. Correlations between mean ADC and EI and 15th percentile were both r = 0.90 and for MLD r = 0.59. There was higher correlation between mean ADC and %predicted DLCO (r = 0.90) than between EI and %predicted DLCO (r = 0.76). Conclusion: HP 3He-MRI correlates well with density measurements from MSCT and agrees better than MSCT with %predicted DLCO which is the PFT most related to emphysema.
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Rundle-Thiele, Dayle [Centre for Clinical Research, University of Queensland, Brisbane, Queensland (Australia); Day, Bryan; Stringer, Brett [Brain Cancer Research Unit, Queensland Institute of Medical Research, Brisbane, Queensland (Australia); Fay, Michael [Department of Radiation Oncology, Royal Brisbane and Women' s Hospital, Brisbane, Queensland (Australia); Martin, Jennifer [Discipline of Clinical Pharmacology, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales (Australia); Jeffree, Rosalind L [Department of Neurosurgery, Royal Brisbane and Women' s Hospital, Brisbane, Queensland (Australia); Thomas, Paul [Queensland PET Service, Royal Brisbane and Women' s Hospital, Brisbane, Queensland (Australia); Bell, Christopher [Centre for Clinical Research, University of Queensland, Brisbane, Queensland (Australia); Salvado, Olivier [CSIRO Digital Productivity Flagship, CSIRO, Herston, Queensland (Australia); Gal, Yaniv [Centre for Medical Diagnostic Technologies in Queensland, University of Queensland, Brisbane, Queensland (Australia); Coulthard, Alan [Discipline of Medical Imaging, University of Queensland, St Lucia, Queensland (Australia); Department of Medical Imaging, Royal Brisbane and Women' s Hospital, Brisbane, Queensland (Australia); Crozier, Stuart [Centre for Medical Diagnostic Technologies in Queensland, University of Queensland, Brisbane, Queensland (Australia); Rose, Stephen, E-mail: stephen.rose@csiro.au [CSIRO Digital Productivity Flagship, CSIRO, Herston, Queensland (Australia); Centre for Clinical Research, University of Queensland, Brisbane, Queensland (Australia)
2015-06-15
Accurate knowledge of O{sup 6}-methylguanine methyltransferase (MGMT) gene promoter subtype in patients with glioblastoma (GBM) is important for treatment. However, this test is not always available. Pre-operative diffusion MRI (dMRI) can be used to probe tumour biology using the apparent diffusion coefficient (ADC); however, its ability to act as a surrogate to predict MGMT status has shown mixed results. We investigated whether this was due to variations in the method used to analyse ADC. We undertook a retrospective study of 32 patients with GBM who had MGMT status measured. Matching pre-operative MRI data were used to calculate the ADC within contrast enhancing regions of tumour. The relationship between ADC and MGMT was examined using two published ADC methods. A strong trend between a measure of ‘minimum ADC’ and methylation status was seen. An elevated minimum ADC was more likely in the methylated compared to the unmethylated MGMT group (U = 56, P = 0.0561). In contrast, utilising a two-mixture model histogram approach, a significant reduction in mean measure of the ‘low ADC’ component within the histogram was associated with an MGMT promoter methylation subtype (P < 0.0246). This study shows that within the same patient cohort, the method selected to analyse ADC measures has a significant bearing on the use of that metric as a surrogate marker of MGMT status. Thus for dMRI data to be clinically useful, consistent methods of data analysis need to be established prior to establishing any relationship with genetic or epigenetic profiling.
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Accurate knowledge of O6-methylguanine methyltransferase (MGMT) gene promoter subtype in patients with glioblastoma (GBM) is important for treatment. However, this test is not always available. Pre-operative diffusion MRI (dMRI) can be used to probe tumour biology using the apparent diffusion coefficient (ADC); however, its ability to act as a surrogate to predict MGMT status has shown mixed results. We investigated whether this was due to variations in the method used to analyse ADC. We undertook a retrospective study of 32 patients with GBM who had MGMT status measured. Matching pre-operative MRI data were used to calculate the ADC within contrast enhancing regions of tumour. The relationship between ADC and MGMT was examined using two published ADC methods. A strong trend between a measure of ‘minimum ADC’ and methylation status was seen. An elevated minimum ADC was more likely in the methylated compared to the unmethylated MGMT group (U = 56, P = 0.0561). In contrast, utilising a two-mixture model histogram approach, a significant reduction in mean measure of the ‘low ADC’ component within the histogram was associated with an MGMT promoter methylation subtype (P < 0.0246). This study shows that within the same patient cohort, the method selected to analyse ADC measures has a significant bearing on the use of that metric as a surrogate marker of MGMT status. Thus for dMRI data to be clinically useful, consistent methods of data analysis need to be established prior to establishing any relationship with genetic or epigenetic profiling
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Daniel Paech
Full Text Available To explore the correlation between Nuclear Overhauser Enhancement (NOE-mediated signals and tumor cellularity in glioblastoma utilizing the apparent diffusion coefficient (ADC and cell density from histologic specimens. NOE is one type of chemical exchange saturation transfer (CEST that originates from mobile macromolecules such as proteins and might be associated with tumor cellularity via altered protein synthesis in proliferating cells.For 15 patients with newly diagnosed glioblastoma, NOE-mediated CEST-contrast was acquired at 7 Tesla (asymmetric magnetization transfer ratio (MTRasym at 3.3ppm, B1 = 0.7 μT. Contrast enhanced T1 (CE-T1, T2 and diffusion-weighted MRI (DWI were acquired at 3 Tesla and coregistered. The T2 edema and the CE-T1 tumor were segmented. ADC and MTRasym values within both regions of interest were correlated voxelwise yielding the correlation coefficient rSpearman (rSp. In three patients who underwent stereotactic biopsy, cell density of 12 specimens per patient was correlated with corresponding MTRasym and ADC values of the biopsy site.Eight of 15 patients showed a weak or moderate positive correlation of MTRasym and ADC within the T2 edema (0.16≤rSp≤0.53, p0.05, n = 4 or yielded rSp≈0 (p0.05, n = 6. The biopsy-analysis within CE-T1 tumor revealed a strong positive correlation between tumor cellularity and MTRasym values in two of the three patients (rSppatient3 = 0.69 and rSppatient15 = 0.87, p<0.05, while the correlation of ADC and cellularity was heterogeneous (rSppatient3 = 0.545 (p = 0.067, rSppatient4 = -0.021 (p = 0.948, rSppatient15 = -0.755 (p = 0.005.NOE-imaging is a new contrast promising insight into pathophysiologic processes in glioblastoma regarding cell density and protein content, setting itself apart from DWI. Future studies might be based on the assumption that NOE-mediated CEST visualizes cellularity more accurately than ADC, especially in the CE-T1 tumor region.
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Jang-Zern Tsai
2014-01-01
Full Text Available Determination of the volumes of acute cerebral infarct in the magnetic resonance imaging harbors prognostic values. However, semiautomatic method of segmentation is time-consuming and with high interrater variability. Using diffusion weighted imaging and apparent diffusion coefficient map from patients with acute infarction in 10 days, we aimed to develop a fully automatic algorithm to measure infarct volume. It includes an unsupervised classification with fuzzy C-means clustering determination of the histographic distribution, defining self-adjusted intensity thresholds. The proposed method attained high agreement with the semiautomatic method, with similarity index 89.9 ± 6.5%, in detecting cerebral infarct lesions from 22 acute stroke patients. We demonstrated the accuracy of the proposed computer-assisted prompt segmentation method, which appeared promising to replace the laborious, time-consuming, and operator-dependent semiautomatic segmentation.
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Schroeder, Paul C.; Donovan Post, M. Judith; Bruce-Gregorios, Jocelyn [University of Miami, Jackson Memorial Hospital, Miami, FL (United States); Oschatz, Elizabeth; Stadler, Alfred; Thurnher, Majda M. [Medical University of Vienna, Department of Radiology Neuroradiology Section, Vienna (Austria)
2006-10-15
Toxoplasmosis and lymphoma are common lesions of the central nervous system in patients with AIDS. It is often difficult to distinguish between these lesions both clinically and radiographically. Previous research has demonstrated restricted diffusion within cerebral lymphomas and bacterial abscesses. However, little work has been done to evaluate the diffusion characteristics of toxoplasmosis lesions. This study was designed to explore further the utility of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps and values in making the distinction between toxoplasmosis and lymphoma. The magnetic resonance imaging (MRI) studies of 36 patients, including 22 with toxoplasmosis (all of whom had AIDS) and 14 with lymphoma (8 of whom had AIDS), at two institutions were reviewed retrospectively. The characteristics of the lesions on DWI were evaluated, and the ADC ratios of the lesions were calculated and compared. There was significant overlap of the ADC ratios of toxoplasma and lymphoma, most notably in the intermediate (1.0-1.6) range. There was variability in ADC ratios even among different lesions in the same patient. In only a minority of the lymphoma patients were the ADC ratios low enough to suggest the correct diagnosis. Our study showed that toxoplasmosis exhibits a wide spectrum of diffusion characteristics with ADC ratios which have significant overlap with those of lymphoma. Therefore, in the majority of patients, ADC ratios are not definitive in making the distinction between toxoplasmosis and lymphoma. (orig.)
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Background. Diffusion weighted imaging (DWI) has gained interest as an imaging modality for assessment of tumor extension and response to cancer treatment. The purpose of this study is to assess the impact of the choice of b-values on the calculation of the Apparent Diffusion Coefficient (ADC) for locally advanced gynecological cancer and to estimate a stable interval of diffusion gradients that allows for best comparison of the ADC between patients and institutions. Material and methods. Six patients underwent a high resolution single shot EPI based DWI scan with 16 different diffusion gradients on a 3 Tesla Philips Achieva MR-scanner. Data analysis was performed by applying a monoexponential and a biexponential model to the acquired data. The biexponential function models the effect of both perfusion and diffusion. Results and conclusion. ADC changes of up to 40% were seen with the use of different b-values. Using a lower b-value = 150 s/mm2 and an upper b-value = 700 s/mm2 limited the variation to less that 10% from the reference ADC value. By eliminating the contribution of perfusion the uncertainty of quantitative ADC values were significantly reduced.
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Toxoplasmosis and lymphoma are common lesions of the central nervous system in patients with AIDS. It is often difficult to distinguish between these lesions both clinically and radiographically. Previous research has demonstrated restricted diffusion within cerebral lymphomas and bacterial abscesses. However, little work has been done to evaluate the diffusion characteristics of toxoplasmosis lesions. This study was designed to explore further the utility of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps and values in making the distinction between toxoplasmosis and lymphoma. The magnetic resonance imaging (MRI) studies of 36 patients, including 22 with toxoplasmosis (all of whom had AIDS) and 14 with lymphoma (8 of whom had AIDS), at two institutions were reviewed retrospectively. The characteristics of the lesions on DWI were evaluated, and the ADC ratios of the lesions were calculated and compared. There was significant overlap of the ADC ratios of toxoplasma and lymphoma, most notably in the intermediate (1.0-1.6) range. There was variability in ADC ratios even among different lesions in the same patient. In only a minority of the lymphoma patients were the ADC ratios low enough to suggest the correct diagnosis. Our study showed that toxoplasmosis exhibits a wide spectrum of diffusion characteristics with ADC ratios which have significant overlap with those of lymphoma. Therefore, in the majority of patients, ADC ratios are not definitive in making the distinction between toxoplasmosis and lymphoma. (orig.)
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Atsushi Umemura
Full Text Available BACKGROUND: It is often hard to differentiate Parkinson's disease (PD and parkinsonian variant of multiple system atrophy (MSA-P, especially in the early stages. Cardiac sympathetic denervation and putaminal rarefaction are specific findings for PD and MSA-P, respectively. PURPOSE: We investigated diagnostic accuracy of putaminal apparent diffusion coefficient (ADC test for MSA-P and (123I-metaiodobenzylguanidine (MIBG scintigram for PD, especially in early-stage patients. METHODS: The referral standard diagnosis of PD and MSA-P were the diagnostic criteria of the United Kingdom Parkinson's Disease Society Brain Bank Criteria and the second consensus criteria, respectively. Based on the referral standard criteria, diagnostic accuracy [area under the receiver-operator characteristic curve (AUC, sensitivity and specificity] of the ADC and MIBG tests was estimated retrospectively. Diagnostic accuracy of these tests performed within 3 years of symptom onset was also investigated. RESULTS: ADC and MIBG tests were performed on 138 patients (20 MSA and 118 PD. AUC was 0.95 and 0.83 for the ADC and MIBG tests, respectively. Sensitivity and specificity were 85.0% and 89.0% for MSA-P diagnosis by ADC test and 67.0% and 80.0% for PD diagnosis by MIBG test. When these tests were restricted to patients with disease duration ≤ 3 years, the sensitivity and specificity were 75.0% and 91.4% for the ADC test (MSA-P diagnosis and 47.7% and 92.3% for the MIBG test (PD diagnosis. CONCLUSIONS: Both tests were useful in differentiating between PD and MSA-P, even in the early stages. In early-stage patients, elevated putaminal ADC was a diagnostic marker for MSA-P. Despite high specificity of the MIBG test, careful neurological history and examinations were required for PD diagnosis because of possible false-negative results.
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Mori, Naoko; Mugikura, Shunji; Takasawa, Chiaki; Shimauchi, Akiko; Ota, Hideki; Takase, Kei; Takahashi, Shoki [Tohoku University Graduate School of Medicine, Department of Diagnostic Radiology, Sendai (Japan); Miyashita, Minoru; Ishida, Takanori [Tohoku University Graduate School of Medicine, Department of Surgical Oncology, Sendai (Japan); Kasajima, Atsuko [Tohoku University Graduate School of Medicine, Department of Pathology, Sendai (Japan); Kodama, Tetsuya [Tohoku University Graduate School of Medicine, Department of Biomedical Engineering, Sendai (Japan)
2016-02-15
To evaluate whether visual assessment of T2-weighted imaging (T2WI) or an apparent diffusion coefficient (ADC) could predict lymphovascular invasion (LVI) status in cases with clinically node-negative invasive breast cancer. One hundred and thirty-six patients with 136 lesions underwent MRI. Visual assessment of T2WI, tumour-ADC, peritumoral maximum-ADC and the peritumour-tumour ADC ratio (the ratio between them) were compared with LVI status of surgical specimens. No significant relationship was found between LVI and T2WI. Tumour-ADC was significantly lower in the LVI-positive (n = 77, 896 ± 148 x 10{sup -6} mm{sup 2}/s) than the LVI-negative group (n = 59, 1002 ± 163 x 10{sup -6} mm{sup 2}/s; p < 0.0001). Peritumoral maximum-ADC was significantly higher in the LVI-positive (1805 ± 355 x 10{sup -6} mm{sup 2}/s) than the LVI-negative group (1625 ± 346 x 10{sup -6} mm{sup 2}/s; p = 0.0003). Peritumour-tumour ADC ratio was significantly higher in the LVI-positive (2.05 ± 0.46) than the LVI-negative group (1.65 ± 0.40; p < 0.0001). Receiver operating characteristic curve analysis revealed that the area under the curve (AUC) of the peritumour-tumour ADC ratio was the highest (0.81). The most effective threshold for the peritumour-tumour ADC ratio was 1.84, and the sensitivity, specificity, positive predictive value and negative predictive value were 77 % (59/77), 76 % (45/59), 81 % (59/73) and 71 % (45/63), respectively. We suggest that the peritumour-tumour ADC ratio can assist in predicting LVI status on preoperative imaging. (orig.)
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To evaluate whether visual assessment of T2-weighted imaging (T2WI) or an apparent diffusion coefficient (ADC) could predict lymphovascular invasion (LVI) status in cases with clinically node-negative invasive breast cancer. One hundred and thirty-six patients with 136 lesions underwent MRI. Visual assessment of T2WI, tumour-ADC, peritumoral maximum-ADC and the peritumour-tumour ADC ratio (the ratio between them) were compared with LVI status of surgical specimens. No significant relationship was found between LVI and T2WI. Tumour-ADC was significantly lower in the LVI-positive (n = 77, 896 ± 148 x 10-6 mm2/s) than the LVI-negative group (n = 59, 1002 ± 163 x 10-6 mm2/s; p < 0.0001). Peritumoral maximum-ADC was significantly higher in the LVI-positive (1805 ± 355 x 10-6 mm2/s) than the LVI-negative group (1625 ± 346 x 10-6 mm2/s; p = 0.0003). Peritumour-tumour ADC ratio was significantly higher in the LVI-positive (2.05 ± 0.46) than the LVI-negative group (1.65 ± 0.40; p < 0.0001). Receiver operating characteristic curve analysis revealed that the area under the curve (AUC) of the peritumour-tumour ADC ratio was the highest (0.81). The most effective threshold for the peritumour-tumour ADC ratio was 1.84, and the sensitivity, specificity, positive predictive value and negative predictive value were 77 % (59/77), 76 % (45/59), 81 % (59/73) and 71 % (45/63), respectively. We suggest that the peritumour-tumour ADC ratio can assist in predicting LVI status on preoperative imaging. (orig.)
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We tested the feasibility of a simple method for assessment of prostate cancer (PCa) aggressiveness using diffusion-weighted magnetic resonance imaging (MRI) to calculate apparent diffusion coefficient (ADC) ratios between prostate cancer and healthy prostatic tissue. The requirement for institutional review board approval was waived. A set of 20 standardized core transperineal saturation biopsy specimens served as the reference standard for placement of regions of interest on ADC maps in tumorous and normal prostatic tissue of 22 men with PCa (median Gleason score: 7; range, 6–9). A total of 128 positive sectors were included for evaluation. Two diagnostic ratios were computed between tumor ADCs and normal sector ADCs: the ADC peripheral ratio (the ratio between tumor ADC and normal peripheral zone tissue, ADC-PR), and the ADC central ratio (the ratio between tumor ADC and normal central zone tissue, ADC-CR). The performance of the two ratios in detecting high-risk tumor foci (Gleason 8 and 9) was assessed using the area under the receiver operating characteristic curve (AUC). Both ADC ratios presented significantly lower values in high-risk tumors (0.48 ± 0.13 for ADC-CR and 0.40 ± 0.09 for ADC-PR) compared with low-risk tumors (0.66 ± 0.17 for ADC-CR and 0.54 ± 0.09 for ADC-PR) (p < 0.001) and had better diagnostic performance (ADC-CR AUC = 0.77, sensitivity = 82.2%, specificity = 66.7% and ADC-PR AUC = 0.90, sensitivity = 93.7%, specificity = 80%) than stand-alone tumor ADCs (AUC of 0.75, sensitivity = 72.7%, specificity = 70.6%) for identifying high-risk lesions. The ADC ratio as an intrapatient-normalized diagnostic tool may be better in detecting high-grade lesions compared with analysis based on tumor ADCs alone, and may reduce the rate of biopsies
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Aim: To assess how the joint use of apparent diffusion coefficient (ADC) and kinetic parameters (uptake phase and delayed enhancement characteristics) from dynamic contrast-enhanced (DCE) can boost the ability to predict breast lesion malignancy. Materials and methods: Breast magnetic resonance examinations including DCE and diffusion-weighted imaging (DWI) were performed on 51 women. The association between kinetic parameters and ADC were evaluated and compared between lesion types. Models with binary outcome of malignancy were studied using generalized estimating equations (GEE), (GEE), and using kinetic parameters and ADC values as malignancy predictors. Model accuracy was assessed using the corrected maximum quasi-likelihood under the independence confidence criterion (QICC). Predicted probability of malignancy was estimated for the best model. Results: ADC values were significantly associated with kinetic parameters: medium and rapid uptake phase (p<0.001) and plateau and washout curve types (p=0.004). Comparison between lesion type showed significant differences for ADC (p=0.001), early phase (p<0.001), and curve type (p<0.001). The predicted probabilities of malignancy for the first ADC quartile (≤1.17×10−3 mm2/s) and persistent, plateau and washout curves, were 54.6%, 86.9%, and 97.8%, respectively, and for the third ADC quartile (≥1.51×10−3 mm2/s) were 3.2%, 15.5%, and 54.8%, respectively. The predicted probability of malignancy was less than 5% for 18.8% of the lesions and greater than 33% for 50.7% of the lesions (24/35 lesions, corresponding to a malignancy rate of 68.6%). Conclusion: The best malignancy predictors were low ADCs and washout curves. ADC and kinetic parameters provide differentiated information on the microenvironment of the lesion, with joint models displaying improved predictive performance. -- Highlights: •ADC and kinetic parameters provide diverse information regarding lesion environment. •The best predictors of
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Purpose: To assess the added value of true diffusion (D), perfusion factor (f) and apparent diffusion coefficient at low b-values (ADClow) for differentiation between liver metastases and hemangiomas based on respiratory-triggered high-resolution Black-Blood Single-Shot SpinEcho Echo Planar Imaging (BB SS SE-EPI). Materials and methods: Twenty-five patients suspected for malignant colorectal liver lesions were included in this study. A total of 106 lesions were examined. Different b-value images were compared for lesion conspicuity, image quality and artifacts using rank order statistic (RIDIT) and Student's t-test. D, f, and ADClow values were calculated. Pearson correlation coefficient is used for comparison of interobserver variability. Results: Best lesion conspicuity (p 2); best image quality (p 2. Image artifacts were lowest (p 2. Over the whole sample, D in metastases (Dmet) was significantly (p hem); f and ADClow of metastases (fmet, respectively, ADClowmet) were significantly (p low of hemangiomas (fhem, respectively, ADClowhem). All Pearson correlations were statistically significant at a 0.01 level. Conclusions: This preliminary study shows the potential of BB SS SE-EPI as a useful technique to aid in differentiating between liver metastasis and hemangioma. The calculation of D, f and ADClow provides useful additional information for differentiating metastases from hemangiomas
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Objective: To compare the apparent diffusion coefficients (ADC), proton MR spectroscopy (1H-MRS) and pathologic changes in young pigs subjected to acute hypoxic-ischemic brain damage (HIBD). Methods: Thirty 7-day-old neonatal pigs were divided into sham-operation group (n=5) and hypoxic-ischemic group (n=25). HI group was divided into five small groups. ADC value, NAA/Cho, NAA/Cr, Lac/NAA, Lac/Cho and Lac/Cr were calculated on cessation of the insult, 3, 6, 12 and 24 h after resuscitation in subcortical white matter, periventricular white matter and basal ganglia. Immediately after MR examinations, injury of the brains was evaluated by hematoxylin-eosin-stained and histopathologic study. Results: The hypoxic-ischemic piglets showed ADC (3.69±1.45) reduction, NAA/Cho (0.712± 0.080) and NAA/Cr(1.040±0.137) decrease, Lac/NAA(1.798±0.139), Lac/Cho(1.280±0.167) and Lac/Cr(1.876±0.357)increase on cessation of the insult; transient ADC, Lac/NAA, Lac/Cho and Lac/Cr recovery, NAA/Cho progressive decrease (P0.05) flora 3 h to 12 h after resuscitation; secondary ADC (4.06±1.25)reduction, Lac/NAA (1.221±0.128), Lac/Cho (0.716±0.088) and Lac/Cr (1.212±0.177) increase 24 hours after resuscitation. Corresponding pathologic study revealed astrocytes gradually swelled and collapsed after resuscitation, while neurons changed mildly. The control piglets showed normal ADC, H-MRS and pathologic investigations. Conclusions: ADC value and 1H-MRS can sensitively detect lesions of early HIBD. NAA/Cho has the highest correlation with the pathological changes of early HIBD and is superior to ADC value and the other metabolite ratios in evaluating early HIBD. (authors)
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O' Flynn, Elizabeth A.M.; Morgan, Veronica A.; Giles, Sharon L. [Cancer Research UK and ESPSRC Cancer Imaging Centre, Clinical Magnetic Resonance Group, Surrey (United Kingdom); deSouza, Nandita M. [Royal Marsden NHS Foundation Trust, Clinical Magnetic Resonance Group, Institute of Cancer Research, Surrey (United Kingdom)
2012-07-15
To establish the reproducibility of apparent diffusion coefficient (ADC) measurements in normal fibroglandular breast tissue and to assess variation in ADC values with phase of the menstrual cycle and menopausal status. Thirty-one volunteers (13 premenopausal, 18 postmenopausal) underwent magnetic resonance twice (interval 11-22 days) using diffusion-weighted MRI. ADC{sub total} and a perfusion-insensitive ADC{sub high} (omitting b = 0) were calculated. Reproducibility and inter-observer variability of mean ADC values were assessed. The difference in mean ADC values between the two phases of the menstrual cycle and the postmenopausal breast were evaluated. ADC{sub total} and ADC{sub high} showed good reproducibility (r% = 17.6, 22.4). ADC{sub high} showed very good inter-observer agreement (kappa = 0.83). The intraclass correlation coefficients (ICC) were 0.93 and 0.91. Mean ADC values were significantly lower in the postmenopausal breast (ADC{sub total} 1.46 {+-} 0.3 x 10{sup -3} mm{sup 2}/s, ADC{sub high} 1.33 {+-} 0.3 x 10{sup -3} mm{sup 2}/s) compared with the premenopausal breast (ADC{sub total} 1.84 {+-} 0.26 x 10{sup -3} mm{sup 2}/s, ADC{sub high} 1.77 {+-} 0.26 x 10{sup -3} mm{sup 2}/s; both P < 0.001). No significant difference was seen in ADC values in relation to menstrual cycle (ADC{sub total} P = 0.2, ADC{sub high} P = 0.24) or between postmenopausal women taking or not taking oestrogen supplements (ADC{sub total} P = 0.6, ADC{sub high} P = 0.46). ADC values in fibroglandular breast tissue are reproducible. Lower ADC values within the postmenopausal breast may reduce diffusion-weighted contrast and have implications for accurately detecting tumours. (orig.)
Directory of Open Access Journals (Sweden)
Matthew D Blackledge
Full Text Available We describe our semi-automatic segmentation of whole-body diffusion-weighted MRI (WBDWI using a Markov random field (MRF model to derive tumor total diffusion volume (tDV and associated global apparent diffusion coefficient (gADC; and demonstrate the feasibility of using these indices for assessing tumor burden and response to treatment in patients with bone metastases. WBDWI was performed on eleven patients diagnosed with bone metastases from breast and prostate cancers before and after anti-cancer therapies. Semi-automatic segmentation incorporating a MRF model was performed in all patients below the C4 vertebra by an experienced radiologist with over eight years of clinical experience in body DWI. Changes in tDV and gADC distributions were compared with overall response determined by all imaging, tumor markers and clinical findings at serial follow up. The segmentation technique was possible in all patients although erroneous volumes of interest were generated in one patient because of poor fat suppression in the pelvis, requiring manual correction. Responding patients showed a larger increase in gADC (median change = +0.18, range = -0.07 to +0.78 × 10(-3 mm2/s after treatment compared to non-responding patients (median change = -0.02, range = -0.10 to +0.05 × 10(-3 mm2/s, p = 0.05, Mann-Whitney test, whereas non-responding patients showed a significantly larger increase in tDV (median change = +26%, range = +3 to +284% compared to responding patients (median change = -50%, range = -85 to +27%, p = 0.02, Mann-Whitney test. Semi-automatic segmentation of WBDWI is feasible for metastatic bone disease in this pilot cohort of 11 patients, and could be used to quantify tumor total diffusion volume and median global ADC for assessing response to treatment.
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To investigate the utility of diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) and the correlation with hepatobiliary phase (delayed phase imaging, DPI) findings in the differentiation of cirrhotic hepatocellular nodules. Forty-three patients with 53 pathology-proven nodules (29 hepatocellular carcinomas (HCCs), 13 high-grade (HGDNs) and 11 low-grade dysplastic nodules (LGDNs); mean size 2.17 cm, range 1-4 cm), who underwent liver MRI with DWI and DPI sequences, were retrospectively reviewed. Lesions were classified as hypointense, isointense, or hyperintense relative to the adjacent liver parenchyma. ADC of each nodule, of the surrounding parenchyma, and lesion-to-liver ratio were calculated. Hyperintensity versus iso/hypointensity on DWI, hypointensity versus iso/hyperintensity on DPI, and the mean lesion-to-liver ratio showed a statistically significant difference both between HCCs versus DNs and between ''HCCs + HGDNs'' versus LGDNs (p < 0.05); sensitivity, specificity, and accuracy for the diagnosis of ''HCCs + HGDNs'' were 96.8 %, 100 %, 97.4 % respectively when combining hyperintensity on DWI and hypointensity on DPI, and 90.9 %, 81.0 %, 83.6 % respectively when lesion-to-liver ratio was <0.95. Hyperintensity on DWI, especially in association with hypointensity on DPI, and low lesion-to-liver ratios should raise the suspicion of HCC, or at least of HGDN, thus helping the characterization of atypically enhancing lesions. (orig.)
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Shen, Guohua; Jia, Zhiyun; Deng, Houfu [Sichuan University, Department of Nuclear Medicine, West China Hospital, Chengdu, Sichuan (China)
2016-02-15
The potential performance of apparent diffusion coefficient (ADC) values for distinguishing malignant and benign pulmonary lesions, further characterizing the subtype of lung cancer was assessed. PubMed, EMBASE, Cochrane Library, EBSCO, and three Chinese databases were searched to identify eligible studies on diffusion-weighted imaging (DWI) of focal pulmonary lesions. ADC values of malignant and benign lesions were extracted by lesion type and statistically pooled based on a linear mixed model. Further analysis for subtype of lung cancer was also performed. The methodological quality was assessed using the quality assessment of diagnostic accuracy studies tool. Thirty-four articles involving 2086 patients were included. Malignant pulmonary lesions have significantly lower ADC values than benign lesions [1.21 (95 % CI, 1.19-1.22) mm{sup 2}/s vs. 1.76 (95 % CI, 1.72-1.80) mm{sup 2}/s; P < 0.05]. There is a significant difference between ADC values of small cell lung cancer and non-small cell lung cancer (P < 0.05), while the differences were not significant among histological subtypes of lung cancer. The methodological quality was relatively high, and the data points from Begg's test indicated that there was probably no obvious publication bias. The ADC value is helpful for distinguishing malignant and benign pulmonary lesions and provides a promising method for differentiation of SCLC from NSCLC. (orig.)
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Aim: To determine what disease entities show accentuated grey-white differentiation of the cerebral hemisphere on diffusion-weighted images (DWI) or apparent diffusion coefficient (ADC) maps, and whether there is a correlation between the different patterns and the cause of the brain injury. Methods and materials: The DWI and ADC maps of 19 patients with global brain injury were reviewed and evaluated to investigate whether there was a correlation between the different patterns seen on the DWI and ADC maps and the cause of global brain injury. The ADC values were measured for quantitative analysis. Results: There were three different patterns of ADC decrease: a predominant ADC decrease in only the cerebral cortex (n = 8; pattern I); an ADC decrease in both the cerebral cortex and white matter (WM) and a predominant decrease in the WM (n = 9; pattern II); and a predominant ADC decrease in only the WM (n = 3; pattern III). Conclusion: Pattern I is cerebral cortical injury, suggesting cortical laminar necrosis in hypoxic brain injury. Pattern II is cerebral cortical and WM injury, frequently seen in brain death, while pattern 3 is mainly WM injury, especially found in hypoglycaemic brain injury. It is likely that pattern I is decorticate injury and pattern II is decerebrate injury in hypoxic ischaemic encephalopathy.Patterns I and II are found in severe hypoxic brain injury, and pattern II is frequently shown in brain death, whereas pattern III was found in severe hypoglycaemic injury.
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The potential performance of apparent diffusion coefficient (ADC) values for distinguishing malignant and benign pulmonary lesions, further characterizing the subtype of lung cancer was assessed. PubMed, EMBASE, Cochrane Library, EBSCO, and three Chinese databases were searched to identify eligible studies on diffusion-weighted imaging (DWI) of focal pulmonary lesions. ADC values of malignant and benign lesions were extracted by lesion type and statistically pooled based on a linear mixed model. Further analysis for subtype of lung cancer was also performed. The methodological quality was assessed using the quality assessment of diagnostic accuracy studies tool. Thirty-four articles involving 2086 patients were included. Malignant pulmonary lesions have significantly lower ADC values than benign lesions [1.21 (95 % CI, 1.19-1.22) mm2/s vs. 1.76 (95 % CI, 1.72-1.80) mm2/s; P < 0.05]. There is a significant difference between ADC values of small cell lung cancer and non-small cell lung cancer (P < 0.05), while the differences were not significant among histological subtypes of lung cancer. The methodological quality was relatively high, and the data points from Begg's test indicated that there was probably no obvious publication bias. The ADC value is helpful for distinguishing malignant and benign pulmonary lesions and provides a promising method for differentiation of SCLC from NSCLC. (orig.)
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Inchingolo, Riccardo; De Gaetano, Anna Maria; Curione, Davide; Ciresa, Marzia; Bonomo, Lorenzo [Catholic University of the Sacred Heart, Department of Bioimaging and Radiological Sciences, Institute of Radiology, ' ' Agostino Gemelli' ' Hospital, Rome (Italy); Miele, Luca; Pompili, Maurizio [Catholic University of the Sacred Heart, Department of Internal Medicine, ' ' Agostino Gemelli' ' Hospital, Rome (Italy); Vecchio, Fabio Maria [Catholic University of the Sacred Heart, Department of Anatomo-Pathology, ' ' Agostino Gemelli' ' Hospital, Rome (Italy); Giuliante, Felice [Catholic University of the Sacred Heart, Department of Surgery, ' ' Agostino Gemelli' ' Hospital, Rome (Italy)
2015-04-01
To investigate the utility of diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) and the correlation with hepatobiliary phase (delayed phase imaging, DPI) findings in the differentiation of cirrhotic hepatocellular nodules. Forty-three patients with 53 pathology-proven nodules (29 hepatocellular carcinomas (HCCs), 13 high-grade (HGDNs) and 11 low-grade dysplastic nodules (LGDNs); mean size 2.17 cm, range 1-4 cm), who underwent liver MRI with DWI and DPI sequences, were retrospectively reviewed. Lesions were classified as hypointense, isointense, or hyperintense relative to the adjacent liver parenchyma. ADC of each nodule, of the surrounding parenchyma, and lesion-to-liver ratio were calculated. Hyperintensity versus iso/hypointensity on DWI, hypointensity versus iso/hyperintensity on DPI, and the mean lesion-to-liver ratio showed a statistically significant difference both between HCCs versus DNs and between ''HCCs + HGDNs'' versus LGDNs (p < 0.05); sensitivity, specificity, and accuracy for the diagnosis of ''HCCs + HGDNs'' were 96.8 %, 100 %, 97.4 % respectively when combining hyperintensity on DWI and hypointensity on DPI, and 90.9 %, 81.0 %, 83.6 % respectively when lesion-to-liver ratio was <0.95. Hyperintensity on DWI, especially in association with hypointensity on DPI, and low lesion-to-liver ratios should raise the suspicion of HCC, or at least of HGDN, thus helping the characterization of atypically enhancing lesions. (orig.)
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Diffusion-weighted imaging (DWI) has been demonstrated to be a practical method for the diagnosis of various brain diseases such as acute infarction, brain tumor, and white matter disease. In this study, we used two techniques to examine the average signal intensity (SI) and apparent diffusion coefficient (ADC) of the brains of patients who ranged in age from 10 to 60 years. Our results indicated that the average SI was the highest in amygdala (as derived from DWI), whereas that in the cerebrospinal fluid was the lowest. The average ADC was the highest in the cerebrospinal fluid, whereas the lowest measurement was derived from the pons. The average SI and ADC were higher in T2-DW-EPI than in FLAIR-DW-EPI. The higher the b-value, the smaller the average difference in both imaging techniques; the lower the b-value, the greater the average difference. Also, comparative analysis of the brains of patients who had experienced cerebral infarction showed no distinct lesion in the general MR image over time. However, there was a high SI in apparent weighted images. Analysis of other brain diseases (e.g., bleeding, acute, subacute, chronic infarction) indicated SI variance in accordance with characteristics of the two techniques. The higher the SI, the lower the ADC. Taken together, the value of SI and ADC in accordance with frequently occurring areas and various brain disease varies based on the b-value and imaging technique. Because they provide additional useful information in the diagnosis and treatment of patients with various brain diseases through signal recognition, the proper imaging technique and b-value are important for the detection and interpretation of subacute stroke and other brain diseases.
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Full text of publication follows: The study of the dispersion of radioactive materials in soils and in engineering barriers plays an important role in the safety analysis of nuclear waste repositories. In order to proceed with such kind of study the involved physical properties must be determined with precision, including the apparent mass diffusion coefficient, which is defined as the ratio between the effective mass diffusion coefficient and the retardation factor. Many different experimental and estimation techniques are available on the literature for the identification of the diffusion coefficient and this work describes the implementation of that developed by Pereira et al [1]. This technique is based on non-intrusive radiation measurements and the experimental setup consists of a cylindrical column filled with compacted media saturated with water. A radioactive contaminant is mixed with a portion of the media and then placed in the bottom of the column. Therefore, the contaminant will diffuse through the uncontaminated media due to the concentration gradient. A radiation detector is used to measure the number of counts, which is associated to the contaminant concentration, at several positions along the column during the experiment. Such measurements are then used to estimate the apparent diffusion coefficient of the contaminant in the porous media by inverse analysis. The inverse problem of parameter estimation is solved with the Levenberg-Marquart Method of minimization of the least-square norm. The experiment was optimized with respect to the number of measurement locations, frequency of measurements and duration of the experiment through the analysis of the sensitivity coefficients and by using a D-optimum approach. This setup is suitable for studying a great number of combinations of diverse contaminants and porous media varying in composition and compacting, with considerable easiness and reliable results, and it was chosen because that is the
Pope, WB; Qiao, XJ; Kim, HJ; Lai, A.; Nghiemphu, P; Xue, X.; Ellingson, BM; Schiff, D.; Aregawi, D; Cha, S; Puduvalli, VK; Wu, J.; Yung, WKA; Young, GS; Vredenburgh, J
2012-01-01
We have tested the predictive value of apparent diffusion coefficient (ADC) histogram analysis in stratifying progression-free survival (PFS) and overall survival (OS) in bevacizumab-treated patients with recurrent glioblastoma multiforme (GBM) from the multi-center BRAIN study. Available MRI's from patients enrolled in the BRAIN study (n = 97) were examined by generating ADC histograms from areas of enhancing tumor on T1 weighted post-contrast images fitted to a two normal distribution mixtu...
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We wanted to evaluate the ability of the apparent diffusion coefficient (ADC) values to differentiate between benign and malignant breast lesions and the normal breast parenchyma. We used breast MRI, including DWI, to obtain images of 167 breast lesions (18 benign lesions and 149 malignant lesions) of 152 women (mean age: 48.6 years, range: 24-80 years). The mean ADC values of the malignant lesions were compared to those of the benign lesions and the normal parenchyma. We compared the ADC values of IDC, DCIS and other types of breast cancer and we also compared the ADC values with the nuclear grade of IDC. The mean ADC values of the malignant lesions were lower than those of the benign lesions and the normal parenchyma (p-3 mm2/s for discriminating between malignant and benign lesion showed a specificity of 53% and a sensitivity of 100%, and the ADC threshold value of 1.33 X 10-3 mm2/s showed a specificity of 93% and a sensitivity of 94% for discriminating between malignant and benign lesion.
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The aim of this study was to investigate the diagnostic role of the apparent diffusion coefficient (ADC) measurement in the diagnosis of focal parenchymal lesions and to understand the discriminating role of the ADC value for differentiating Fasciola lesions from other focal liver lesions. We measured ADC values of parenchymal lesions and liver parenchyma in 18 patients with Fasciola hepatica infestation at b 100, b 600, and b 1000 s/mm2 gradients. We further measured average ADC values of hepatic metastases (n=21), hepatocellular carcinomas (n=21), cholangiocarcinomas (n=7), hydatid cysts (n=12), and focal nodular hyperplasia (FNH) (n=12) and compared them with average ADC values for Fasciola hepatica. The differences between average ADC values of lesions (2.16±0.36 x 10-3 mm2/s) and parenchyma (1.64±0.2 x 10-3 mm2/s) at three gradients were statistically significant (P<0.05). Mean ADC values of Fasciola hepatica lesions were significantly different from most of the other focal hepatic lesions, except FNH at all gradients and hydatid cyst at only the b 100 gradient. ADC measurement may be a complementary method in the diagnosis of Fasciola hepatica, and it may be used to differentiate these lesions from other focal liver lesions. (author)
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Nakajo, Masatoyo [Nanpuh Hospital, Department of Radiology, Kagoshima (Japan); Kagoshima University, Department of Radiology, Graduate School of Medical and Dental Sciences, Kagoshima (Japan); Kajiya, Yoriko; Tani, Atsushi; Ueno, Masako [Nanpuh Hospital, Department of Radiology, Kagoshima (Japan); Kaneko, Tomoyo; Kaneko, Youichi [Kaneko Clinic, Department of Breast Surgery, Kagoshima (Japan); Takasaki, Takashi [Department of Pathology, Clinical Pathology Laboratory, Kagoshima (Japan); Koriyama, Chihaya [Kagoshima University, Department of Epidemiology and Preventive Medicine, Graduate School of Medical and Dental Sciences, Kagoshima (Japan); Nakajo, Masayuki [Kagoshima University, Department of Radiology, Graduate School of Medical and Dental Sciences, Kagoshima (Japan)
2010-11-15
To correlate both primary lesion {sup 18}F-fluorodeoxyglucose (FDG) maximum standardized uptake value (SUVmax) and diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC) with clinicopathological prognostic factors and compare the prognostic value of these indexes in breast cancer. The study population consisted of 44 patients with 44 breast cancers visible on both preoperative FDG PET/CT and DWI images. The breast cancers included 9 ductal carcinoma in situ (DCIS) and 35 invasive ductal carcinomas (IDC). The relationships between both SUVmax and ADC and clinicopathological prognostic factors were evaluated by univariate and multivariate regression analysis and the degree of correlation was determined by Spearman's rank test. The patients were divided into a better prognosis group (n = 24) and a worse prognosis group (n = 20) based upon invasiveness (DCIS or IDC) and upon their prognostic group (good, moderate or poor) determined from the modified Nottingham prognostic index. Their prognostic values were examined by receiver operating characteristic analysis. Both SUVmax and ADC were significantly associated (p<0.05) with histological grade (independently), nodal status and vascular invasion. Significant associations were also noted between SUVmax and tumour size (independently), oestrogen receptor status and human epidermal growth factor receptor-2 status, and between ADC and invasiveness. SUVmax and ADC were negatively correlated ({rho}=-0.486, p = 0.001) and positively and negatively associated with increasing of histological grade, respectively. The threshold values for predicting a worse prognosis were {>=}4.2 for SUVmax (with a sensitivity, specificity and accuracy of 80%, 75% and 77%, respectively) and {<=}0.98 for ADC (with a sensitivity, specificity and accuracy of 90%, 67% and 77%, respectively). SUVmax and ADC correlated with several of pathological prognostic factors and both indexes may have the same potential for predicting the
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Purpose: Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) enhanced liver MRI is widely used for detection and differentiation of focal liver lesions. Diffusion weighted imaging (DWI) including apparent diffusion coefficient (ADC) measurements is increasingly utilised as a fast and, with limitations, quantitative method for liver lesion detection and characterisation. Herein we investigate whether the administration of Gd-EOB-DTPA affects DWI. Materials and methods: 31 consecutive patients referred to standardised liver MRI (1.5 T, Gd-EOB-DTPA, 0.025 mmol/kg) were retrospectively reviewed. All underwent a breathhold DWI sequence before and after contrast agent administration (EPI-DWI, TR/TE (effective): 2100/62 ms, b-values: 0 and 800 s/mm2). Patients with previously treated liver lesions were excluded. Signal intensity of lesion, parenchyma and noise on DWI images as well as the ADC value were measured after identification by two observers in consensus using manually placed regions of interest. The reference standard was imaging follow-up determined separately by two radiologists. Data analysis included signal-to-noise (SNR) ratio and contrast-to-noise ratio (CNR) calculations, comparisons were drawn by employing multiple Bonferroni corrected Wilcoxon signed-rank tests. Results: 50 malignant and 39 benign lesions were identified. Neither SNR, CNR nor ADC values showed significant differences between pre- and postcontrast DWI. Both pre- and postcontrast ADC values differed significantly between benign and malignant lesions (P < 0.001). Conclusion: We did not identify a significant influence of Gd-EOB-DTPA on DWI of liver lesions. This allows for individual tailoring of imaging protocols according to clinical needs.
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Cavalleri, Francesca; Todeschini, Alessandra [Azienda Unita Sanitaria Locale di Modena, Neuroradiology Unit, Department of Neuroscience, Nuovo Ospedale Civile S. Agostino Estense di Modena, Modena (Italy); Lugli, Licia; Pugliese, Marisa; Della Casa, Elisa; Gallo, Claudio; Frassoldati, Rossella; Ferrari, Fabrizio [Modena University Hospital, Institute of Pediatrics and Neonatal Medicine and NICU, Modena (Italy); D' Amico, Roberto [University of Modena and Reggio Emilia, Department of Clinical and Diagnostic Medicine and Public Health, Modena (Italy)
2014-09-15
The diagnostic and prognostic assessment of newborn infants with hypoxic-ischemic encephalopathy (HIE) comprises, among other tools, diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps. To compare the ability of DWI and ADC maps in newborns with HIE to predict the neurodevelopmental outcome at 2 years of age. Thirty-four term newborns with HIE admitted to the Neonatal Intensive Care Unit of Modena University Hospital from 2004 to 2008 were consecutively enrolled in the study. All newborns received EEG, conventional MRI and DWI within the first week of life. DWI was analyzed by means of summation (S) score and regional ADC measurements. Neurodevelopmental outcome was assessed with a standard 1-4 scale and the Griffiths Mental Developmental Scales - Revised (GMDS-R). When the outcome was evaluated with a standard 1-4 scale, the DWI S scores showed very high area under the curve (AUC) (0.89) whereas regional ADC measurements in specific subregions had relatively modest predictive value. The lentiform nucleus was the region with the highest AUC (0.78). When GMDS-R were considered, DWI S scores were good to excellent predictors for some GMDS-R subscales. The predictive value of ADC measurements was both region- and subscale-specific. In particular, ADC measurements in some regions (basal ganglia, white matter or rolandic cortex) were excellent predictors for specific GMDS-R with AUCs up to 0.93. DWI S scores showed the highest prognostic value for the neurological outcome at 2 years of age. Regional ADC measurements in specific subregions proved to be highly prognostic for specific neurodevelopmental outcomes. (orig.)
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The diagnostic and prognostic assessment of newborn infants with hypoxic-ischemic encephalopathy (HIE) comprises, among other tools, diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps. To compare the ability of DWI and ADC maps in newborns with HIE to predict the neurodevelopmental outcome at 2 years of age. Thirty-four term newborns with HIE admitted to the Neonatal Intensive Care Unit of Modena University Hospital from 2004 to 2008 were consecutively enrolled in the study. All newborns received EEG, conventional MRI and DWI within the first week of life. DWI was analyzed by means of summation (S) score and regional ADC measurements. Neurodevelopmental outcome was assessed with a standard 1-4 scale and the Griffiths Mental Developmental Scales - Revised (GMDS-R). When the outcome was evaluated with a standard 1-4 scale, the DWI S scores showed very high area under the curve (AUC) (0.89) whereas regional ADC measurements in specific subregions had relatively modest predictive value. The lentiform nucleus was the region with the highest AUC (0.78). When GMDS-R were considered, DWI S scores were good to excellent predictors for some GMDS-R subscales. The predictive value of ADC measurements was both region- and subscale-specific. In particular, ADC measurements in some regions (basal ganglia, white matter or rolandic cortex) were excellent predictors for specific GMDS-R with AUCs up to 0.93. DWI S scores showed the highest prognostic value for the neurological outcome at 2 years of age. Regional ADC measurements in specific subregions proved to be highly prognostic for specific neurodevelopmental outcomes. (orig.)
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We have developed a magnetic resonance (MR) spin echo method to obtain diffusion weighted imaging using motion probing gradient (MPG) pulses in orthogonal direction before and after a 180 degree pulse. Phantom models containing water, acetone, cupric sulfate and agar, and normal brains of Wistar rats and puppies were examined. MRI was performed using a SISCO SIS 200/400 MRI/MRS experimental system for small animals (4.7 tesla, 400 mm bore). The apparent diffusion coefficient (ADC) values, given in mm2/sec, were 2.19±0.02 x 10-3 in water, 4.51±0. 18 x 10-3 in acetone, and the ADC of water was independent on longitudinal (T1) or transverse (T2) relaxation time. Time-dependent ADC changes were not demonstrated, however position-dependent ADC changes were significant. It is therefore important to set the sample at the same position for repeated MRI studies and for the evaluation of the time course of experimental studies. Mean ADC values of rat brains were 0.65 x 10-3 for cortex, 0.69 x 10-3 for caudate-putamen, 0.69 x 10-3 (perpendicular to axon) for corpus callosum, 1.11 x 10-3 (parallel to axon) for optic nerve, and 1.38 x 10-3 (parallel to axon) for trigeminal nerve. Those of puppies were 1.14- 1.42 x 10-3 for gray matter, 1.17 (parallel to axon) and 0.89 (perpendicular to axon) x 10-3 for white matter, 1.66 (parallel to axon) and 0.57 (perpendicular to axon) x 10-3 for internal capsule, and 0.91-0.95 x 10-3 for thalamus. On the in vivo ADC maps, white matter tracts successfully showed anisotropic diffusion. This technique has promising implications for the evaluation of the time course of cerebral damage and degenerative changes. (author)
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Ahn, Hye Shin; Chang, Yun Woo; Choi, Kyung Hee; Kim, Hyun Joo; Hong, Seong Suk; Hwang, Jung Hwa; Kwon, Kui Hyang [Dept.of Radiology, Soonchunhyang University Hospital, Seoul (Korea, Republic of); Kim, Yong Bae [Dept. of Preventive Medicine, Soonchunhyang University Hospital, Seoul (Korea, Republic of)
2011-04-15
We wanted to evaluate the ability of the apparent diffusion coefficient (ADC) values to differentiate between benign and malignant breast lesions and the normal breast parenchyma. We used breast MRI, including DWI, to obtain images of 167 breast lesions (18 benign lesions and 149 malignant lesions) of 152 women (mean age: 48.6 years, range: 24-80 years). The mean ADC values of the malignant lesions were compared to those of the benign lesions and the normal parenchyma. We compared the ADC values of IDC, DCIS and other types of breast cancer and we also compared the ADC values with the nuclear grade of IDC. The mean ADC values of the malignant lesions were lower than those of the benign lesions and the normal parenchyma (p<0.001, respectively). The mean ADC value of IDC was lower than those of DCIS and other breast cancers (p<0.001, respectively). The mean ADC value of mucinous carcinoma among the other breast cancer was characteristic high compared with that of the normal parenchyma. There was no significant differentiation of the ADC values between the nuclear grades of IDC (p<0.828). The ADC threshold value of 0.98 X 10{sup -3} mm{sup 2}/s for discriminating between malignant and benign lesion showed a specificity of 53% and a sensitivity of 100%, and the ADC threshold value of 1.33 X 10{sup -3} mm{sup 2}/s showed a specificity of 93% and a sensitivity of 94% for discriminating between malignant and benign lesion.
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The goal of our study was to evaluate the diagnostic efficacy of diffusion-weighted imaging (DWI) in the differentiation of benign and malignant breast lesions. Between June 2012 and March 2013, 60 patients with 63 lesions (age range 29-70 years, mean age 48.6 years) were included in our study. All lesions, except complicated cysts and intra-mammary lymph nodes, were confirmed histopathologically. The patients were evaluated with a 1.5 Tesla MR scanner using dedicated bilateral breast coil. DWI images were obtained by echo planar imaging sequence and 'b' values were selected as 200, 600 and 1000 s/mm2. Apparent diffusion coefficient (ADC) values of both breast lesions and the normal fibroglandular tissue of the contralateral breast were calculated and statistically compared using Shapiro-Wilk test, Student's t-test, Mann-Whitney U test, chi-square test and the receiver operating curve. Of 63 lesions, 22 were malignant and 41 were benign. In malignant lesions, the mean ADC values were 1.40 ± 0.41 × 10−3mm2/s for b = 200, 1.05 ± 0.28 × 10−3mm2/s for b = 600 and 0.91 ± 0.20 × 10−3mm2/s for b = 1000 and in benign lesions, the mean ADC values were 2.13 ± 0.85 × 10−3mm2/s for b = 200, 1.64 ± 0.47 × 10−3mm2/s for b = 600 and 1.40 ± 0.43 × 10−3mm2/s for b = 1000. The success of ADC values in differentiation of benign and malignant lesions was statistically significant (P = 0.0001). The threshold values were determined to be 1.50 × 10−3mm2/s for b = 200, 1.22 × 10−3mm2/s for b = 600 and 0.98 × 10−3mm2/s for b = 1000 (P < 0.05). DWI can be an effective radiological method in the differentiation of benign and malignant breast lesions.
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MacKenzie, John D. [Children' s Hospital of Philadelphia, Department of Pediatric Radiology, Philadelphia, PA (United States); UCSF Benioff Children' s Hospital, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Hernandez, Andrea; Pena, Andres; Khrichenko, Dmitry; Gonzalez, Leonardo; Jaramillo, Diego [Children' s Hospital of Philadelphia, Department of Pediatric Radiology, Philadelphia, PA (United States); Ruppert, Kai [Children' s Hospital of Philadelphia, Department of Pediatric Radiology, Philadelphia, PA (United States); University of Virginia, Department of Radiology, Charlottesville, VA (United States); Jawad, Abbas F. [Children' s Hospital of Philadelphia, Department of Pediatrics, Philadelphia, PA (United States); Wells, Lawrence [Children' s Hospital of Philadelphia, Department of Orthopedics, Philadelphia, PA (United States); Smith-Whitley, Kim [Children' s Hospital of Philadelphia, Department of Hematology, Philadelphia, PA (United States)
2012-06-15
Avascular necrosis (AVN) is a common morbidity in children with sickle cell disease (SCD) that leads to pain and joint immobility. However, the diagnosis is often uncertain or delayed. To examine the ability of apparent diffusion coefficient (ADC) measurements on diffusion-weighted imaging to detect AVN in children with SCD. ADC values were calculated at the hips of normal children (n = 19) and children with SCD who were either asymptomatic with no known previous hip disease (n = 13) or presented for the first time with clinical symptoms of hip pathology (n = 12). ADC values were compared for differences among groups with and without AVN using non-parametric statistical methods. The ADC values were elevated in the hips of children with AVN (median ADC = 1.57 x 10{sup -3} mm{sup 2}/s [95% confidence interval = 0.86-2.10]) and differed significantly in pairwise comparisons (all P < 0.05) from normal children (0.74 [0.46-0.98]), asymptomatic children with SCD (0.55 [0.25-0.85]), and SCD children who had symptoms referable to their hips but did not show findings of hip AVN on conventional MRI or radiographs (0.46 [0.18-0.72]). Children with sickle cell disease have elevated apparent diffusion coefficient values in their affected hips on initial diagnosis of avascular necrosis. (orig.)
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Avascular necrosis (AVN) is a common morbidity in children with sickle cell disease (SCD) that leads to pain and joint immobility. However, the diagnosis is often uncertain or delayed. To examine the ability of apparent diffusion coefficient (ADC) measurements on diffusion-weighted imaging to detect AVN in children with SCD. ADC values were calculated at the hips of normal children (n = 19) and children with SCD who were either asymptomatic with no known previous hip disease (n = 13) or presented for the first time with clinical symptoms of hip pathology (n = 12). ADC values were compared for differences among groups with and without AVN using non-parametric statistical methods. The ADC values were elevated in the hips of children with AVN (median ADC = 1.57 x 10-3 mm2/s [95% confidence interval = 0.86-2.10]) and differed significantly in pairwise comparisons (all P < 0.05) from normal children (0.74 [0.46-0.98]), asymptomatic children with SCD (0.55 [0.25-0.85]), and SCD children who had symptoms referable to their hips but did not show findings of hip AVN on conventional MRI or radiographs (0.46 [0.18-0.72]). Children with sickle cell disease have elevated apparent diffusion coefficient values in their affected hips on initial diagnosis of avascular necrosis. (orig.)
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Aim: To investigate the effects of age and gender on apparent diffusion coefficient (ADC) measurements of bilateral kidneys at 3 T MRI, and compare the ADC values of left and right kidneys. Materials and methods: In all, 137 healthy participants (mean age 42.8 ± 14.7 years; age range 16–75 years) comprising 68 male and 69 female participants were enrolled. Three Tesla echo-planar diffusion-weighted imaging (DWI) of bilateral kidneys was performed and ADC values were measured in the cortex, medulla, and whole parenchyma. Pearson correlation analysis and linear regression were performed to determine the associations between the ADC values in each region and age. Effects of age and gender on ADC values were analysed using two-factor analysis of variance (ANOVA). The paired-samples t-test was established to compare the ADC values between left and right kidneys. Results: ADC values were significantly higher in the young group (≤50 years) than in the old group (>50 years), and correlated inversely with the age in all regions. Male participants had higher ADC values than female participants in all regions except left medulla. Two-factor ANOVA of age × gender showed no significant interactions between the variables age and gender were found. No significant differences in ADC values between left and right kidneys were observed. Conclusion: Renal ADC values are age- and gender-dependent, and show no significant difference between left and right kidneys. Age- and gender-related effects should be taken into consideration in future renal DWI studies when using normal ADC values from health controls. - Highlights: • Renal apparent diffusion coefficient (ADC) values decrease with ageing. • Men tend to have higher renal ADC values than women. • Bilateral kidneys seem to have no significantly different ADC values
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Diaz, Sandra; Casselbrant, Ingrid; Piitulainen, Eeva;
2008-01-01
-seven subjects, 22 with established emphysema and 5 with preclinical emphysema defined by PFT criteria, were examined with HP (3)He-MRI and MSCT. Mean age was 55 (+/-12) years, 18 female and 9 male. Mean ADC from (3)He-MRI was compared with emphysema index (EI), 15th percentile and mean lung density (MLD) values...... from MSCT. Both mean ADC and MSCT data were compared to PFT, especially percent of predicted diffusing capacity of carbon monoxide (%predicted DLCO), using Pearson's correlation test. RESULTS: Mean ADC and standard deviation values were 0.392+/-0.119 cm(2)/s for the established emphysema group and 0....... Correlations between mean ADC and EI and 15th percentile were both r=0.90 and for MLD r=0.59. There was higher correlation between mean ADC and %predicted DLCO (r=0.90) than between EI and %predicted DLCO (r=0.76). CONCLUSION: HP (3)He-MRI correlates well with density measurements from MSCT and agrees better...
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The purpose was to determine the reproducibility of apparent diffusion coefficient (ADC) measurements in a two-centre phase I clinical trial; and to track ADC changes in response to the sequential administration of the vascular disrupting agent, combretastatin A4 phosphate (CA4P), and the anti-angiogenic drug, bevacizumab. Sixteen patients with solid tumours received CA4P and bevacizumab treatment. Echo-planar diffusion-weighted MRI was performed using six b values (b = 0-750 s/mm2) before (x 2), and at 3 and 72 h after a first dose of CA4P. Bevacizumab was given 4 h after a second dose of CA4P, and imaging performed 3 h post CA4P and 72 h after bevacizumab treatment. The coefficient of repeatability (r) of ADC total (all b values), ADC high (b = 100-750) and ADC low (b = 0-100) was calculated by Bland-Altman analysis. The ADC total and ADC high showed good measurement reproducibility (r% = 13.3, 14.1). There was poor reproducibility of the perfusion-sensitive ADC low (r% = 62.5). Significant increases in the median ADC total and ADC high occurred at 3 h after the second dose of CA4P (p < 0.05). ADC measurements were highly reproducible in a two-centre clinical trial setting and appear promising for evaluating the effects of drugs that target tumour vasculature. (orig.)
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), (181±34), (413±62), (474±83), (424±41), (332±341) and (302±39) U/L for the levels of ALT, and (79±10), (454±55), (547±72), (607± 31), (649±79), (785±49) and (1526±167) U/L for the AST respectively. The levels of AST and ALT in IRI groups were significantly higher than those in the Sham group (P<0.01). Histological findings showed diffuse hepatocytes swelling and erythrocytes depositing in the hepatic sinusoids, portal area, central venous and arterials at the initial phase. With the injury aggravated, inflammatory cell infiltration, hepatocyte nuclear condensation of apoptosis, sinusoidal dissociation and coagulation necrosis developed eventually. Conclusion: 3.0 T DWI can monitor the pathological process of rabbit liver ischemia reperfusion injury dynamically, and provides a feasible imaging modality for clinical diagnosis and treatment. (authors)
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To establish standard apparent diffusion coefficient (ADC) and the fat content as a function of age, gender and body mass index (BMI) in healthy parotid glands, and to address the influences of fat suppression on ADC measurements. A total of 100 healthy adults (gender and age evenly distributed) were prospectively recruited, with parotid fat content measured from gradient-echo images with fat-water separated using iterative decomposition with echo asymmetry and least squares (IDEAL). The ADCs were estimated using both fat-saturated and non-fat-saturated diffusion-weighted imaging via a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technique. Parotid fat content was larger in men than in women by about 10 percentage points (P < 0.005), and positively associated with BMI and age for both genders (mostly with P < 0.001). ADCs estimated with non-fat-saturated PROPELLER were significantly lower in men than in women (P < 0.005), but showed no gender difference if measured using fat-saturated PROPELLER (P = 0.840). The negative association between parotid ADC and age/BMI/fat (P < 0.001) showed greater regression slopes in non-fat-saturated PROPELLER than in fat-saturated data. Parotid fat content in healthy adults correlates positively with both age and BMI; the correlation with age is gender-dependent. Parotid ADC measurements are strongly influenced by fat saturation. (orig.)
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The objective of this study was to investigate the correlation of pretreatment and posttreatment measurements as the mean apparent diffusion coefficient (ADCmean) by diffusion-weighted magnetic resonance imaging (DWI) findings with prognostic factors in patients with squamous cell carcinoma (SCC) of primary cervical cancer. The pretreatment and posttreatment ADCmean of the primary tumor were examined for their correlations with the prognosis in 69 patients with SCC of primary cervical cancer by radiotherapy (RT) with or without concurrent chemotherapy (CCRT). The median disease-free survival (DFS) and overall survival (OS) times of patients were 20.97 and 23.47 months (follow-up periods for DFS and OS: 1–72 and 1–72 months). The DFS and OS rates of patients with low pretreatment and posttreatment ADCmean of the primary tumor were also significantly worse than those of patients exhibiting high pretreatment and posttreatment ADCmean of the primary tumor (DFS; P = 0.0130 and P < 0.0001, OS; P = 0.0010 and P < 0.0001). Multivariate analyses showed that low posttreatment ADCmean of the primary tumor was an independent prognostic factor for DFS and OS (P < 0.0001 and P < 0.0001). The low posttreatment ADCmean of the primary tumor is a useful clinical prognostic biomarker for recurrence and survival in patients with cervical cancer. The low posttreatment ADCmean of the primary tumor is a useful clinical prognostic biomarker for recurrence and survival in patients with cervical cancer
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Chang, Hing-Chiu [National Taiwan University, Graduate Institute of Biomedical Electronics and Bioinformatics, Taipei (China); Duke University Medical Center, Brain Imaging and Analysis Center, Durham, NC (United States); GE Healthcare, Applied Science Laboratory, Taipei (China); Juan, Chun-Jung; Hsu, Hsian-He [National Defense Medical Center, Department of Radiology, Taipei (China); Tri-Service General Hospital, Department of Radiology, Taipei (China); Chiu, Hui-Chu [Tatung University, Graduate Institute of Design Science, Taipei (China); Cheng, Cheng-Chieh; Chiu, Su-Chin [National Taiwan University, Graduate Institute of Biomedical Electronics and Bioinformatics, Taipei (China); Liu, Yi-Jui [Feng Chia University, Department of Automatic Control Engineering, Taichung (China); Chung, Hsiao-Wen [National Taiwan University, Graduate Institute of Biomedical Electronics and Bioinformatics, Taipei (China); Tri-Service General Hospital, Department of Radiology, Taipei (China); National Taiwan University, MD.624, Department of Electrical Engineering, Taipei (China)
2014-09-15
To establish standard apparent diffusion coefficient (ADC) and the fat content as a function of age, gender and body mass index (BMI) in healthy parotid glands, and to address the influences of fat suppression on ADC measurements. A total of 100 healthy adults (gender and age evenly distributed) were prospectively recruited, with parotid fat content measured from gradient-echo images with fat-water separated using iterative decomposition with echo asymmetry and least squares (IDEAL). The ADCs were estimated using both fat-saturated and non-fat-saturated diffusion-weighted imaging via a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technique. Parotid fat content was larger in men than in women by about 10 percentage points (P < 0.005), and positively associated with BMI and age for both genders (mostly with P < 0.001). ADCs estimated with non-fat-saturated PROPELLER were significantly lower in men than in women (P < 0.005), but showed no gender difference if measured using fat-saturated PROPELLER (P = 0.840). The negative association between parotid ADC and age/BMI/fat (P < 0.001) showed greater regression slopes in non-fat-saturated PROPELLER than in fat-saturated data. Parotid fat content in healthy adults correlates positively with both age and BMI; the correlation with age is gender-dependent. Parotid ADC measurements are strongly influenced by fat saturation. (orig.)
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Aim: To explore possible correlations between tumour apparent diffusion coefficient (ADC), morphological tumour volume, and clinical and histological characteristics in endometrial carcinomas and to evaluate interobserver agreement for preoperative staging by MRI and for ADC measurements. Materials and methods: Preoperative conventional MRI including diffusion-weighted imaging (DWI) was performed in 105 endometrial carcinoma patients. Three radiologists independently reviewed the images for the presence of deep myometrial invasion, cervical stromal invasion, and lymph node metastases, and measured tumour ADC in regions of interest (ROIs). ADC values were analysed in relation to histomorphological characteristics and tumour volume. Kappa coefficients (κ) and intraclass correlation coefficients (ICC) for interobserver agreement for MRI staging results and ADC measurements, respectively, were calculated, and receiver operating characteristic (ROC) curves for identification of deep of myometrial invasion were generated. Results: Mean tumour ADC was significantly lower in tumours with deep myometrial invasion (ADC = 0.75 × 10−3 mm2/s) compared to tumours with superficial or no myometrial invasion (ADC = 0.85 × 10−3 mm2/s; p < 0.001). ADC was negatively correlated to tumour size (p = 0.007). The interobserver agreement was fair (κ = 0.32) for depth of myometrial invasion, good for cervical stromal invasion (κ = 0.66), and moderate for lymph node metastases (κ = 0.54), and the interobserver variability for ADC value measurements was low (ICC = 0.60). Conclusion: Tumour ADC measurements may in the future provide an adjunct tool, aiding in the preoperative identification of high-risk patients with deep myometrial infiltration. - Highlights: • Low tumour ADC is associated with deep myometrial invasion in endometrial carcinomas. • Tumour ADC value is negatively correlated to tumour size. • Preoperative staging by MRI is prone to
Knight, Michael J; McGarry, Bryony L; Rogers, Harriet J; Jokivarsi, Kimmo T; Gröhn, Olli Hj; Kauppinen, Risto A
2016-07-01
The objective of this study is to present a mathematical model which can describe the spatiotemporal progression of cerebral ischaemia and predict magnetic resonance observables including the apparent diffusion coefficient (ADC) of water and transverse relaxation time T2 This is motivated by the sensitivity of the ADC to the location of cerebral ischaemia and T2 to its time-course, and that it has thus far proven challenging to relate observations of changes in these MR parameters to stroke timing, which is of considerable importance in making treatment choices in clinics. Our mathematical model, called the cytotoxic oedema/dissociation (CED) model, is based on the transit of water from the extra- to the intra-cellular environment (cytotoxic oedema) and concomitant degradation of supramacromolecular and macromolecular structures (such as microtubules and the cytoskeleton). It explains experimental observations of ADC and T2, as well as identifying the rate of spread of effects of ischaemia through a tissue as a dominant system parameter. The model brings the direct extraction of the timing of ischaemic stroke from quantitative MRI closer to reality, as well as providing insight on ischaemia pathology by imaging in general. We anticipate that this may improve patient access to thrombolytic treatment as a future application. PMID:26661188
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We prospectively investigated whether the value of the apparent diffusion coefficient (ADC) of a primary lesion prior to treatment correlated with local failure of head and neck squamous cell carcinoma (HNSCC) following radiotherapy. In 17 patients who underwent radiotherapy for primary HNSCC, we compared variables considered to affect local failure, including parameters related to magnetic resonance (MR) imaging, such as ADC and its alteration ratio, between cases of local failure and controls and analyzed survival among those patients in whom the variables differed or demonstrated association with local failure. We also retrospectively analyzed variables in a validation study of 40 patients. In the prospective study, pretreatment values of ADChigh (calculated with b-values of 300, 500, 750, and 1000 s/mm2) alone showed significant association with local failure (P=0.0186). In the validation study, pretreatment values of tumor volume (P=0.0217) and ADChigh (P=0.0001) were significantly associated with local failure. Pretreatment ADChigh was superior to pretreatment tumor volume regarding association with local failure. These results suggest that pretreatment values of both ADC obtained using high b-values and tumor volume correlate with local failure of HNSCC treated with radiotherapy. (author)
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The clinical differentiation of Parkinson's disease (PD) from multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) may be challenging, especially in their early stages. The aim of this study was to evaluate the utility of apparent diffusion coefficient (ADC) measurement to distinguish among these degenerative disorders. Twenty-five MSA, 20 PSP, and 17 PD patients and 18 healthy controls were retrospectively studied. Axial diffusion-weighted and T2-weighted images were obtained using a 3-T MR system. Regions of interest (ROIs) were precisely placed in the midbrain, pons, putamen, globus pallidus, caudate nucleus, thalamus, superior cerebellar peduncle, middle cerebellar peduncle, cerebellar white matter, and cerebellar dentate nucleus, and the regional ADC (rADC) value was calculated in each ROI. In MSA, rADC values in the pons, middle cerebellar peduncle, cerebellar white matter, and cerebellar dentate nucleus were significantly higher than in PSP, PD, and controls. Furthermore, rADC values in the posterior putamen were significantly higher in MSA than in PSP and controls. In PSP, rADC values were significantly higher in the globus pallidus and midbrain than in MSA, PD, and controls. Furthermore, rADC values in the caudate nucleus and superior cerebellar peduncle were significantly higher in PSP than in MSA and controls. In PD, there were no significant differences in the rADC values compared to in MSA, PSP, and controls in all regions. Evaluation of rADC values in characteristic lesions in MSA, PSP, and PD by placing ROIs using 3-T systems can provide useful additional information for differentiating these disorders. (orig.)
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Purpose: This study was performed to evaluate whether the apparent diffusion coefficient (ADC) of a primary lesion correlates with local failure in primary head-and-neck squamous cell carcinoma (HNSCC) treated with chemoradiotherapy or radiotherapy. Methods and Materials: We retrospectively studied 38 patients with primary HNSCC (12 oropharynx, 20 hypopharynx, 4 larynx, 2 oral cavity) treated with chemoradiotherapy or radiotherapy with radiation dose to gross tumor volume equal to or over 60 Gy and who underwent pretreatment magnetic resonance imaging, including diffusion-weighted imaging. Ten patients developed local failure during follow-up periods of 2.0 to 9.3 months, and the remaining 28 showed local control during follow-up periods of 10.5 to 31.7 months. The variables that could affect local failure (age, tumor volume, ADC, T stage, N stage, dose, treatment method, tumor location, and overall treatment time) were analyzed using logistic regression analyses for all 38 patients and for 17 patients with Stage T3 or T4 disease. Results: In univariate logistic analysis for all 38 cases, tumor volume, ADC, T stage, and treatment method showed significant (p < 0.05) associations with local failure. In multivariate analysis, ADC and T stage revealed significance (p < 0.01). In univariate logistic analysis for the 17 patients with Stage T3 or T4 disease, ADC and dose showed significant (p < 0.01) associations with local failure. In multivariate analysis, ADC alone showed significance (p < 0.05). Conclusions: The results suggest that pretreatment ADC, along with T stage, is a potential indicator of local failure in HNSCC treated with chemoradiotherapy or radiotherapy.
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Objective: to assess the repeatability and consistency of magnetic resonance apparent diffusion coefficient (MR ADC) values of the completely remitted lesions of primary hepatocellular carcinoma (HCC) after TACE in order to provide a reference for clinical application. Methods: The MR ADC values of 21 completely remitted lesions were measured at 1, 3 and 6 months after TACE by the same radiologist (radiologist A) using the same sequence, which were measured again by another radiologist (radiologist B) one week later. By calculating the intra-class correlation coefficient (ICC) value and drawing Bland-Altman graph, the respectability and consistency of the ADC value measurement were evaluated. ICC values > 0.75 indicated good reliability and high repeatability. The consistency was considered to be enough high when 75% of the sites were located in the 95% confidence interval within the reference line on the Bland-Altman graph. Results: The ICC values measured by radiologist A 1, 3 and 6 months after TACE were 0.928, 0.878 and 0.934 respectively, which were 0.873, 0.940 and 0.871 respectively measured by radiologist B. The ICC values measured by radiologist A and radiologist B at different time one week before 1, 3 and 6 months after TACE were 0.854, 0.940 and 0.960 respectively, while the values were 0.788, 0.945 and 0.858 respectively one week after 1, 3 and 6 months after TACE. All the above values were greater than 0.75, indicating that the reliability was high. As 90% of the sites were located in the 95% confidence interval within the reference line on the Bland-Altman graph, the repeatability was regarded to be very high. Conclusion: The ADC values of the completely remitted lesions of HCC after TACE are quite stable. The measurements of ADC values for these lesions carry high degree of repeatability and consistency. With the help of ADC values, the stability of HCC lesions after TACE can be dynamically assessed and the therapeutic effectiveness can be promptly
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Aim: To evaluate the performance of normalised apparent diffusion coefficient (ADC) values for prostate cancer assessment when performed by independent observers blinded to histopathology findings. Materials and methods: Fifty-eight patients undergoing 3 T phased-array coil magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm2) before prostatectomy were included. Two radiologists independently evaluated the images, unaware of the histopathology findings. Regions of interest (ROIs) were drawn within areas showing visually low ADC within the peripheral zone (PZ) and transition zone (TZ) bilaterally. ROIs were also placed within regions in both lobes not suspicious for tumour, allowing computation of normalised ADC (nADC) ratios between suspicious and non-suspicious regions. The diagnostic performance of ADC and nADC were compared. Results: For PZ tumour detection, ADC achieved significantly higher area under the receiver operating characteristic curve (AUC; p=0.026) and specificity (p=0.021) than nADC for reader 1, and significantly higher AUC (p=0.025) than nADC for reader 2. For TZ tumour detection, nADC achieved significantly higher specificity (p=0.003) and accuracy (p=0.004) than ADC for reader 2. For PZ Gleason score >3+3 tumour detection, ADC achieved significantly higher AUC (p=0.003) and specificity (p=0.005) than nADC for reader 1, and significantly higher AUC (p=0.023) than nADC for reader 2. For TZ Gleason score >3+3 tumour detection, ADC achieved significantly higher specificity (p=0.019) than nADC for reader 1. Conclusion: In contrast to prior studies performing unblinded evaluations, ADC was observed to outperform nADC overall for two independent observers blinded to the histopathology findings. Therefore, although strategies to improve the utility of ADC measurements in prostate cancer assessment merit continued investigation, caution is warranted when applying normalisation to improve diagnostic
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Ishihara, Makiko; Hayashi, Hiromitsu; Amano, Yasuo; Takagi, Ryo; Nakahara, Madoka; Kumazaki, Tatsuo [Nippon Medical School, Tokyo (Japan); Cho, Keiichi; Okada, Susumu
1998-06-01
The purpose of the present study is to evaluate diffusional anisotropy of white matter in patients with multiple lacunar infarcts using diffusion-weighted echo-planar imaging (DW-EPI), and to examine the relationship between diffusional anisotropy and global cognitive ability as assessed by the mini-mental status examination (MMSE). In particular, we focused on the parameter changes for the corpus callosum as a marker for disconnection of the associative cortices. Twenty-nine patients divided into 2 cognitive level groups (low MMSE, n=16; high MMSE, n=13) and 8 normal controls were examined with a GE 1.5 T Horizon system. Three series of DW-EPI images were obtained using the following epidw{sub g}{center_dot}psd{sup TM} sequence: TR/TE=6500/120 ms, single shot, 6.5 mm slice thickness and 1.5 mm gap transaxial sections of the whole brain, with b-factors of 0 and 710 along each x- and y-axial direction. The parametric maps for apparent diffusion coefficient (ADC) in each direction, ADC(x) and ADC(y), and their rate map (ADC rate=ADC(x)/ADC(y)) were created on a pixel-by-pixel basis. ROI data were extracted from images of the corpus callosum and bilateral optic radiata. As a result, the ADC(x) was markedly larger for corpus callosum than that for optic radiata, whereas the ADC(y) showed an inverse trend, attributable to regional differences of diffusional anisotropy. In corpus callosum, however, the ADC(y) values were observed to increase with the level of disease severity, resulting in a decrease of the ADC rate. Notably, there was a significant difference between the three groups for callosal genu, with a slight positive correlation between the ADC rate and the MMSE scores. Our study suggests that a relationship exists between the reduction of diffusional anisotropy in callosal genu and the global cognitive impairment seen in patients with multiple lacunar infarcts. (K.H.)
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The purpose of the present study is to evaluate diffusional anisotropy of white matter in patients with multiple lacunar infarcts using diffusion-weighted echo-planar imaging (DW-EPI), and to examine the relationship between diffusional anisotropy and global cognitive ability as assessed by the mini-mental status examination (MMSE). In particular, we focused on the parameter changes for the corpus callosum as a marker for disconnection of the associative cortices. Twenty-nine patients divided into 2 cognitive level groups (low MMSE, n=16; high MMSE, n=13) and 8 normal controls were examined with a GE 1.5 T Horizon system. Three series of DW-EPI images were obtained using the following epidwg·psdTM sequence: TR/TE=6500/120 ms, single shot, 6.5 mm slice thickness and 1.5 mm gap transaxial sections of the whole brain, with b-factors of 0 and 710 along each x- and y-axial direction. The parametric maps for apparent diffusion coefficient (ADC) in each direction, ADC(x) and ADC(y), and their rate map (ADC rate=ADC(x)/ADC(y)) were created on a pixel-by-pixel basis. ROI data were extracted from images of the corpus callosum and bilateral optic radiata. As a result, the ADC(x) was markedly larger for corpus callosum than that for optic radiata, whereas the ADC(y) showed an inverse trend, attributable to regional differences of diffusional anisotropy. In corpus callosum, however, the ADC(y) values were observed to increase with the level of disease severity, resulting in a decrease of the ADC rate. Notably, there was a significant difference between the three groups for callosal genu, with a slight positive correlation between the ADC rate and the MMSE scores. Our study suggests that a relationship exists between the reduction of diffusional anisotropy in callosal genu and the global cognitive impairment seen in patients with multiple lacunar infarcts. (K.H.)
Karki, Kishor; Hugo, Geoffrey D.; Ford, John C.; Olsen, Kathryn M.; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth
2015-10-01
The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in non-small cell lung cancer. Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5 T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with \\text{TR}≈ 4500 ms, TE = 74 ms, eight b-values of 0-1000 μs μm-2, pixel size = 1.98× 1.98 mm2, slice thickness = 6 mm, interslice gap = 1.2 mm, 7 axial slices and total acquisition time ≈6 min. One or more DW-MRI scans together covered the whole tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0-2000 μs μm-2 from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the tumour volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250-1000 μs μm-2 were not significantly different from ADCIVIM values (p>0.05 , paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets—0-1000 50-1000 100-1000 500-1000 and 250 and 800 μs μm-2 were significantly different from the ADCIVIM values. From Rician noise simulation
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Objective: The purpose of this study is to discuss the diagnostic accuracy of normalized liver ADC using the spleen and renal cortex as reference organs for the diagnosis of liver fibrosis. Methods: Forty three patients with liver disease (chronic liver disease group) at compensated stage and 10 healthy volunteers (control group) were retrospectively assessed with diffusion-weighted imaging at a 3.0 T MR unit. Liver ADC, spleen ADC, renal ADC and normalized ADC (defined as the ratio of liver ADC to spleen ADC or renal cortex ADC, S-ADC and R-ADC for short) were measured in patients stratified by fibrosis stage. Spearman analysis was used to see the correlation between fibrosis stages and ADC, one-way ANOVA was used to compare the ADCs in different fibrosis stages. Logistic regression analysis was used to determine the performance of ADC for prediction of liver fibrosis, and show the area under the curve (AUC), sensitivity and specificity choosing the optimal cutoff value that maximized the Youden index. Results: Ten volunteers belonged to S0 stage. From S0 to S4 stage, there were 2, 5, 9, 12 and 15 patients, correspondingly, liver ADC were (1.37±0.13) ×10-3, (1.33±0.16) ×10-3, (1.17±0.16) ×10-3, (1.23±0.14) ×10-3 and (1.12 ±0.11) × 10-3 mm2/s, S-ADC were 1.86 ±0.18, 1.68 ±0.12, 1.34 ±0.14, 1.48 ±0.15 and 1.34±0.10, R-ADC were 0.71 ±0.08, 0.68 ±0.12, 0.61 ±0.09, 0.64 ±0.11 and 0.60 ±0.08 respectively, and the differences among them were significant (F=6.48, 18.70 and 3.04, P<0.05). The correlation between fibrosis stage and S-ADC was stronger than between fibrosis stage and liver ADC, R-ADC (r=-0.71, -0.51, -0.41; P<0.01). S-ADC was superior to liver ADC and R-ADC for detection of S2, S3 and S4 fibrosis stage (Youden index: 0.91, 0.58, and 0.59). Conclusion: Spleen normalized liver ADC improves diagnostic accuracy for detection of liver fibrosis than liver ADC and renal normalized liver ADC. (authors)
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Purpose: Tumor grading is very important both in treatment decision and evaluation of prognosis. While tissue samples are obtained as part of most therapeutic approaches, factors that may result in inaccurate grading due to sampling error (namely, heterogeneity in tissue sampling, as well as tumor-grade heterogeneity within the same tumor specimen), have led to a desire to use imaging better to ascertain tumor grade. The purpose in our study was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), area under the curve (AUC), and accuracy of diffusion-weighted MR imaging (DWI), proton MR spectroscopic imaging (MRSI) or both in grading primary cerebral gliomas. Materials and methods: We performed conventional MR imaging (MR), DWI, and MRSI in 74 patients with newly diagnosed brain gliomas: 59 patients had histologically verified high-grade gliomas: 37 glioblastomas multiform (GBM) and 22 anaplastic astrocytomas (AA), and 15 patients had low-grade gliomas. Apparent diffusion coefficient (ADC) values of tumor and peritumoral edema, and ADC ratios (ADC in tumor or peritumoral edema to ADC of contralateral white matter, as well as ADC in tumor to ADC in peritumoral edema) were determined from three regions of interest. The average of the mean, maximum, and minimum for ADC variables was calculated for each patient. The metabolite ratios of Cho/Cr and Cho/NAA at intermediate TE were assessed from spectral maps in the solid portion of tumor, peritumoral edema and contralateral normal-appearing white matter. Tumor grade determined with the two methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic (ROC) curve analysis were performed to determine optimum thresholds for tumor grading. Measures of diagnostic examination performance, such as sensitivity, specificity, PPV, NPV, AUC, and accuracy for identifying high-grade gliomas were also calculated
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Server, Andres, E-mail: a.s.alonso@medisin.uio.no [Section of Neuroradiology, Department of Radiology and Nuclear Medicine, Oslo University Hospital-Ullevaal and University of Oslo, Kirkeveien 166, NO-0407 Oslo (Norway); Kulle, Bettina, E-mail: b.k.andreassen@medisin.uio.no [Department of Biostatistics, University of Oslo, Oslo (Norway); Gadmar, Oystein B., E-mail: gays@uus.no [Interventional Centre, Oslo University Hospital and Institute for Hospital Medicine, University of Oslo, Oslo (Norway); Josefsen, Roger, E-mail: roos@uus.no [Department of Neurosurgery, Oslo University Hospital-Ullevaal, Oslo (Norway); Kumar, Theresa, E-mail: thku@uus.no [Department of Pathology, Oslo University Hospital-Ullevaal, Oslo (Norway); Nakstad, Per H., E-mail: pena@uus.no [Section of Neuroradiology, Department of Radiology and Nuclear Medicine, Oslo University Hospital-Ullevaal and University of Oslo, Kirkeveien 166, NO-0407 Oslo (Norway)
2011-11-15
Purpose: Tumor grading is very important both in treatment decision and evaluation of prognosis. While tissue samples are obtained as part of most therapeutic approaches, factors that may result in inaccurate grading due to sampling error (namely, heterogeneity in tissue sampling, as well as tumor-grade heterogeneity within the same tumor specimen), have led to a desire to use imaging better to ascertain tumor grade. The purpose in our study was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), area under the curve (AUC), and accuracy of diffusion-weighted MR imaging (DWI), proton MR spectroscopic imaging (MRSI) or both in grading primary cerebral gliomas. Materials and methods: We performed conventional MR imaging (MR), DWI, and MRSI in 74 patients with newly diagnosed brain gliomas: 59 patients had histologically verified high-grade gliomas: 37 glioblastomas multiform (GBM) and 22 anaplastic astrocytomas (AA), and 15 patients had low-grade gliomas. Apparent diffusion coefficient (ADC) values of tumor and peritumoral edema, and ADC ratios (ADC in tumor or peritumoral edema to ADC of contralateral white matter, as well as ADC in tumor to ADC in peritumoral edema) were determined from three regions of interest. The average of the mean, maximum, and minimum for ADC variables was calculated for each patient. The metabolite ratios of Cho/Cr and Cho/NAA at intermediate TE were assessed from spectral maps in the solid portion of tumor, peritumoral edema and contralateral normal-appearing white matter. Tumor grade determined with the two methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic (ROC) curve analysis were performed to determine optimum thresholds for tumor grading. Measures of diagnostic examination performance, such as sensitivity, specificity, PPV, NPV, AUC, and accuracy for identifying high-grade gliomas were also calculated
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Objective: To evaluate the apparant diffusion coefficient (ADC) values of cerebellar and the middle cerebellar peduncles in the differential diagnosis of multiple system atrophy (MSA) and Parkinson disease (PD). Methods: Conventional MRI and DWI were performed in 18 clinically proved MSA patients with 7 cases of early cases (early-stage MSA group), 19 PD patients (PD group) and 18 age- matched normal controls (the control group). DWI was performed using a single shot-spin echo-echo planar imaging sequences, and ADC values were measured in the ROIs (0.16 cm2) of the bilateral cerebellum, the middle cerebellar peduncles and cerebral white matter. Then one way ANOVA test was used for statistical analysis. Results: Of the 18 MSA patients, 11 had MR abnormalities, 8 had hot-cross bun sign in the pons on T2-weighted images, 11 patients had pontine, cerebellar and medulla oblongata atrophy, 10 patients had atrophy of the middle cerebellar peduncles, 2 patients had hyperintense rim of the putamen and putaminal atrophy on T2-weighted images. The ADC values in the middle cerebellar peduncles were significantly increased in the MSA group [(0.98±0.07)×103 mm2/s] and early-stage MSA group [(0.95±0.05) × 103 mm2/s] as compared to PD group [(0.77±0.04) × 103 mm2/s] and control group [(0.78±0.04) × 103 mm2/s]. There was statistical significant difference among them (F=91.049, 55.301, P3 mm2/s], early-stage MSA group [(0.86-1.02) × 103 mm2/s] and PD group [(0.68-0.84) × 103 mm2/s] and the control group [(0.69-0.82) × 103 mm2/s]. The ADC values in the cerebellum were significantly increased in the MSA group [(0.95±0.09) × 103 mm2/s] and early-stage MSA group [(0.92±0.07) × 103 mm2/s] as compared to PD group [(0.78±0.05) × 103 mm2/s] and control group [(0.79±0.05) × 103 mm2/s]. Statistically significant difference was found among them (F= 39.274, 18.623, P3 mm2/s, early stage MSA group (0.80-0.99) × 103 mm2/s, PD group (0.72- 0.90) × 103 mm2/s, control group (0
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Oh, Jong Kap [Dept. of Radiology, Cheomdan Medical Center, Gwangju (Korea, Republic of); Im, Jung Yeol [Dept. of Digital Management Information Graduate School of Nambu Univesity, Gwangju (Korea, Republic of)
2009-09-15
Diffusion-weighted imaging (DWI) has been demonstrated to be a practical method for the diagnosis of various brain diseases such as acute infarction, brain tumor, and white matter disease. In this study, we used two techniques to examine the average signal intensity (SI) and apparent diffusion coefficient (ADC) of the brains of patients who ranged in age from 10 to 60 years. Our results indicated that the average SI was the highest in amygdala (as derived from DWI), whereas that in the cerebrospinal fluid was the lowest. The average ADC was the highest in the cerebrospinal fluid, whereas the lowest measurement was derived from the pons. The average SI and ADC were higher in T{sub 2}-DW-EPI than in FLAIR-DW-EPI. The higher the b-value, the smaller the average difference in both imaging techniques; the lower the b-value, the greater the average difference. Also, comparative analysis of the brains of patients who had experienced cerebral infarction showed no distinct lesion in the general MR image over time. However, there was a high SI in apparent weighted images. Analysis of other brain diseases (e.g., bleeding, acute, subacute, chronic infarction) indicated SI variance in accordance with characteristics of the two techniques. The higher the SI, the lower the ADC. Taken together, the value of SI and ADC in accordance with frequently occurring areas and various brain disease varies based on the b-value and imaging technique. Because they provide additional useful information in the diagnosis and treatment of patients with various brain diseases through signal recognition, the proper imaging technique and b-value are important for the detection and interpretation of subacute stroke and other brain diseases.
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Lim, Seong Joo; Kim, Keum Won; Jang, Hye Young; Hwang, Cheol Mog; Kim, Dae Ho; Sohn, Jang Sihn; Kim, Jin Suk; Lee, Jin Yong [Konyang Univ. College of Medicine, Daejeon (Korea, Republic of)
2012-09-15
To correlate the apparent diffusion coefficient (ADC) value and peak standardized uptake value (pSUV) with histologic grade and clinical prognostic factors of breast ductal carcinoma. Fifty breast cancers of 49 patients (age range: 37-83 years, mean: 53 years) were studied retrospectively. The breast cancers included 4 ductal carcinoma in situ (DCIS) and 46 invasive ductal carcinomas (IDC). The relationships for both pSUV and ADC values with clinicopathological prognostic factors (age, tumor size, histologic grade, nodal metastasis, hormone receptor and HER-2 neu status) were statistically evaluated. The histologic type of ductal carcinoma include DCIS (n = 4) and IDC (n = 46, grade 1 = 10, grade 2 = 13, and grade 3 = 23). pSUV was associated with histologic grade and tumor size and the ADC value was associated with histologic grade (p < 0.05). As the histologic grade becomes higher, the ADC values decrease, while pSUV and pSUV/ADC increase (p < 0.05). The characterization accuracy of pSUV/ADC (90.2%) was higher than pSUV (86.7%) and ADC values (25.4%) alone for the diagnosis of breast cancer (p < 0.05). pSUV and ADC values correlated with histologic grade, and tumor size. The pSUV/ADC value had a high accuracy for the diagnosis of breast cancer. Therefore, pSUV and ADC values provided additional information for predicting histologic grade and prognosis of breast cancer.
International Nuclear Information System (INIS)
To correlate the apparent diffusion coefficient (ADC) value and peak standardized uptake value (pSUV) with histologic grade and clinical prognostic factors of breast ductal carcinoma. Fifty breast cancers of 49 patients (age range: 37-83 years, mean: 53 years) were studied retrospectively. The breast cancers included 4 ductal carcinoma in situ (DCIS) and 46 invasive ductal carcinomas (IDC). The relationships for both pSUV and ADC values with clinicopathological prognostic factors (age, tumor size, histologic grade, nodal metastasis, hormone receptor and HER-2 neu status) were statistically evaluated. The histologic type of ductal carcinoma include DCIS (n = 4) and IDC (n = 46, grade 1 = 10, grade 2 = 13, and grade 3 = 23). pSUV was associated with histologic grade and tumor size and the ADC value was associated with histologic grade (p < 0.05). As the histologic grade becomes higher, the ADC values decrease, while pSUV and pSUV/ADC increase (p < 0.05). The characterization accuracy of pSUV/ADC (90.2%) was higher than pSUV (86.7%) and ADC values (25.4%) alone for the diagnosis of breast cancer (p < 0.05). pSUV and ADC values correlated with histologic grade, and tumor size. The pSUV/ADC value had a high accuracy for the diagnosis of breast cancer. Therefore, pSUV and ADC values provided additional information for predicting histologic grade and prognosis of breast cancer
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Aim: To evaluate whether the apparent diffusion coefficient (ADC) of metastatic bone tumours on diffusion-weighted magnetic resonance imaging (MRI) images differs according to the type of primary cancer, the affected bone, and clinical factors. Materials and methods: For this retrospective study, two radiologists reviewed MRI images, including ADC maps, of 67 patients (M:F=38:29; median age, 48 years) who were diagnosed with bone metastasis by means of histological or clinical confirmation. The primary tumours included 29 lung adenocarcinomas, 15 invasive ductal adenocarcinomas of the breast, 13 hepatocellular carcinomas, six prostatic carcinomas, and four renal cell carcinomas. ADC values of the metastatic tumour were compared according to the type of primary malignancy, the affected bone, and the age and sex of the patient using Kruskal–Wallis and Mann–Whitney U-tests with Bonferroni correction. In addition, pre-contrast CT images were available in 38 of 67 patients; a subanalysis of the CT radiodensity and ADC values were performed with Spearman correlation. Results: The mean, standard deviation, and minimum and maximum values of the ADC of metastatic bone tumours did not differ significantly according to type of primary malignancy, the affected bone, or clinical variables (p>0.1). The ADC value was not significantly correlated with CT radiodensity (p=0.24). Intra- and interobserver agreements for the mean ADC values were excellent (intra-observer: p=0.98; interobserver: p=0.98). Conclusions: Assessment of the ADC value of metastatic bone tumours is not reliable for differentiation of the type of primary cancer. -- Highlights: •ADC of bone metastasis is not reliable for separation of the type of primary cancer. •ADC of bone metastasis does not differ according to the affected bone. •There is no significant correlation between ADC value and CT density
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Regier, M., E-mail: mregier@uke.uni-hamburg.de [Center for Radiology and Endoscopy, Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg (Germany); Derlin, T. [Center for Radiology and Endoscopy, Department of Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg (Germany); Schwarz, D.; Laqmani, A.; Henes, F.O.; Groth, M.; Buhk, J.-H. [Center for Radiology and Endoscopy, Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg (Germany); Kooijman, H. [Philips Healthcare, Clinical Application, Luebeckertordamm 5, 20099 Hamburg (Germany); Adam, G. [Center for Radiology and Endoscopy, Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg (Germany)
2012-10-15
Introduction: To investigate the potential correlation of the apparent diffusion coefficient assessed by diffusion-weighted MRI (DWI) and glucose metabolism determined by the standardized uptake value (SUV) at 18F-FDG PET/CT in non-small cell lung cancer (NSCLC). Materials and methods: 18F-FDG PET/CT and DWI (TR/TE, 2000/66 ms; b-values, 0 and 500 s/mm{sup 2}) were performed in 41 consecutive patients with histologically verified NSCLC. Analysing the PET-CT data calculation of the mean (SUV{sub mean}) and maximum (SUV{sub max}) SUV was performed. By placing a region-of-interest (ROI) encovering the entire tumor mean (ADC{sub mean}) and minimum ADC (ADC{sub min}) were determined by two independent radiologists. Results of 18F-FDG PET-CT and DWI were compared on a per-patient basis. For statistical analysis Pearson's correlation coefficient, Bland–Altman and regression analysis were assessed. Results: Data analysis revealed a significant inverse correlation of the ADC{sub min} and SUV{sub max} (r = −0.46; p = 0.032). Testing the correlation of the ADC{sub min} and SUV{sub max} for each histological subtype separately revealed that the inverse correlation was good for both adenocarcinomas (r = −0.47; p = 0.03) and squamouscell carcinomas (r = −0.71; p = 0.002), respectively. No significant correlation was found for the comparison of ADC{sub min} and SUV{sub mean} (r = −0.29; p = 0.27), ADC{sub mean} vs. SUV{sub mean} (r = −0.28; p = 0.31) or ADC{sub mean} vs. SUV{sub max} (r = −0.33; p = 0.23). The κ-value of 0.88 indicated a good agreement between both observers. Conclusion: This preliminary study is the first to verify the relation between the SUV and the ADC in NSCLC. The significant inverse correlation of these two quantitative imaging approaches points out the association of metabolic activity and tumor cellularity. Therefore, DWI with ADC measurement might represent a new prognostic marker in NSCLC.
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Introduction: To investigate the potential correlation of the apparent diffusion coefficient assessed by diffusion-weighted MRI (DWI) and glucose metabolism determined by the standardized uptake value (SUV) at 18F-FDG PET/CT in non-small cell lung cancer (NSCLC). Materials and methods: 18F-FDG PET/CT and DWI (TR/TE, 2000/66 ms; b-values, 0 and 500 s/mm2) were performed in 41 consecutive patients with histologically verified NSCLC. Analysing the PET-CT data calculation of the mean (SUVmean) and maximum (SUVmax) SUV was performed. By placing a region-of-interest (ROI) encovering the entire tumor mean (ADCmean) and minimum ADC (ADCmin) were determined by two independent radiologists. Results of 18F-FDG PET-CT and DWI were compared on a per-patient basis. For statistical analysis Pearson's correlation coefficient, Bland–Altman and regression analysis were assessed. Results: Data analysis revealed a significant inverse correlation of the ADCmin and SUVmax (r = −0.46; p = 0.032). Testing the correlation of the ADCmin and SUVmax for each histological subtype separately revealed that the inverse correlation was good for both adenocarcinomas (r = −0.47; p = 0.03) and squamouscell carcinomas (r = −0.71; p = 0.002), respectively. No significant correlation was found for the comparison of ADCmin and SUVmean (r = −0.29; p = 0.27), ADCmean vs. SUVmean (r = −0.28; p = 0.31) or ADCmean vs. SUVmax (r = −0.33; p = 0.23). The κ-value of 0.88 indicated a good agreement between both observers. Conclusion: This preliminary study is the first to verify the relation between the SUV and the ADC in NSCLC. The significant inverse correlation of these two quantitative imaging approaches points out the association of metabolic activity and tumor cellularity. Therefore, DWI with ADC measurement might represent a new prognostic marker in NSCLC
DEFF Research Database (Denmark)
Mahmood, Faisal; Johannesen, Helle H; Geertsen, Poul; Fiskarbekk Opheim, Giske; Hansen, Rasmus H
2015-01-01
coefficients (ADC) in patients receiving palliative RT to brain metastases. MATERIAL AND METHODS: Twenty-two metastases from nine patients, treated with whole-brain irradiation (30 Gy in 10 fractions) were analyzed. Patients were scanned with a 1T MR system to acquire DW- (eight b-values), T2*W-, T2W- and T1W...
Investigating Diffusion Coefficient Using Dynamic Light Scattering Technique
Sun, Yong
2006-01-01
In this work, the Z-average, effective, apparent diffusion coefficients and their poly-dispersity indexes were investigated for dilute poly-disperse homogeneous spherical particles in dispersion where the Rayleigh-Gans-Debye approximation is valid. The results reveal that the values of the apparent and effective diffusion coefficients at a scattering angle investigated are consistent and the difference between the effective and Z-average diffusion coefficients is a function of the mean partic...
Asteggiano, F.; VELLA A; Scola, E; E. Pirola; Minichiello, M.; Miozzo, M; Caroli, M.; Bergamasco, L.; Rampini, P; Triulzi, F
2014-01-01
INTRODUCTION: Glioblastoma (GBM) is the most aggressive type of primary brain tumour. O6-methylguanine-DNA-methytransferase (MGMT) gene promoter methylation status has proven to be a predictive prognostic marker for longer survival in patients with newly diagnosed GBM treated with surgery, radiotherapy and chemotherapy. Patients showing a methylation of the MGMT promoter have a longer overall survival. We used Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) to obtain data about brain t...
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This meta-analysis evaluates the diagnostic accuracy of diffusion-weighted MR imaging with ADC values for differentiation between malignant and benign hepatic focal lesions. From retrieved articles, we selected 7 sets of data in 6 articles, which met all the included criteria, for meta-analysis. The pooled sensitivity and specificity were 86% (95% CI, 0.83–0.90) and 84% (95% CI, 0.78–0.88), respectively. However, notable heterogeneity between studies was noted and no covariate evaluated can explain the cause. Only b factor correlated with the mean ADC values of malignant and benign hepatic tumors. In conclusion, ADC value was useful for differentiation between malignant and benign hepatic focal lesions. But, significant heterogeneity between studies underlines the need for further efforts to optimize standardization and reproducibility of the utilized techniques and methods.
Portable vapor diffusion coefficient meter
Ho, Clifford K.
2007-06-12
An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.
Diffusion coefficients for absorbing materials
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A method to improve the diffusion results for systems containing strong absorbers is described. Each absorbing material is transformed into an equivalent rectangle. Transport and diffusion calculations in slab geometry are performed for both directions of the rectangle, and group-dependent diffusion coefficients are determined by matching the outgoing currents. Test problems comprise a critical slab, a compact PWR fuel element storage pool and two BWR fuel elements with a control rod and a poison cell. The multiplication factors of these systems are calculated with an accuracy of 1 to 2%. (Auth.)
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Purpose: To compare the apparent diffusion coefficient (ADC) in non-small cell lung cancer lesions with standardized uptake values (SUV) derived from combined 18F-fluoro-deoxy-glucose-positron emission tomography/magnetic resonance imaging (FDG-PET/MRI) and those derived from FDG-PET/CT. Materials and Methods: In 18 consecutive patients with histologically proven NSCLC (17 men, 1 woman; mean age, 61 ± 12 years), whole-body FDG-PET/MRI was performed after whole-body FDG-PET/CT. Regions of interest (ROI) encompassing the entire primary tumor were drawn into FDG-PET/CT and FDG-PET/MR images to determine the maximum and mean standardized uptake value (SUVmax; SUVmean) and into ADC parameter maps to assess mean ADC values. Pearson's correlation coefficients were calculated to compare SUV and ADC values. Results: The SUVmax of NSCLC was 12.3 ± 4.8 [mean ± SD], and the SUVmean was 7.2 ± 2.8 as assessed by FDG-PET/MRI. The SUVmax and SUVmean derived from FDG-PET/CT and FDG-PET/MRI correlated well (R = 0.93; p mean of the pulmonary tumors was 187.9 ± 88.8 x 10-5mm2/s [mean ± SD]. The ADCmean exhibited a significant inverse correlation with the SUVmax (R = -0.72; p < 0.001) as well as with the SUVmean assessed by FDG-PET/MRI (R = -0.71; p < 0.001). Conclusion: This simultaneous PET/MRI study corroborates the assumed significant inverse correlation between increased metabolic activity on FDG-PET and restricted diffusion on DWI in NSCLC. (orig.)
Directory of Open Access Journals (Sweden)
Benedikt Michael Schaarschmidt
Full Text Available To compare the apparent diffusion coefficient (ADC in lymph node metastases of non-small cell lung cancer (NSCLC patients with standardized uptake values (SUV derived from combined 18F-fluoro-deoxy-glucose-positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI.38 patients with histopathologically proven NSCLC (mean age 60.1 ± 9.5 y received whole-body PET/CT (Siemens mCT™ 60 min after injection of a mean dose of 280 ± 50 MBq 18F-FDG and subsequent PET/MRI (mean time after tracer injection: 139 ± 26 min, Siemens Biograph mMR. During PET acquisition, simultaneous diffusion-weighted imaging (DWI, b values: 0, 500, 1000 s/mm² was performed. A maximum of 10 lymph nodes per patient suspicious for malignancy were analyzed. Regions of interest (ROI were drawn covering the entire lymph node on the attenuation-corrected PET-image and the monoexponential ADC-map. According to histopathology or radiological follow-up, lymph nodes were classified as benign or malignant. Pearson's correlation coefficients were calculated for all lymph node metastases correlating SUVmax and SUVmean with ADCmean.A total of 146 suspicious lymph nodes were found in 25 patients. One hundred lymph nodes were eligible for final analysis. Ninety-one lymph nodes were classified as malignant and 9 as benign according to the reference standard. In malignant lesions, mean SUVmax was 9.1 ± 3.8 and mean SUVmean was 6.0 ± 2.5 while mean ADCmean was 877.0 ± 128.6 x10(-5 mm²/s in PET/MRI. For all malignant lymph nodes, a weak, inverse correlation between SUVmax and ADCmean as well as SUVmean and ADCmean (r = -0.30, p<0.05 and r = -0.36, p<0.05 existed.The present data show a weak inverse correlation between increased glucose-metabolism and cellularity in lymph node metastases of NSCLC patients. 18F-FDG-PET and DWI thus may offer complementary information for the evaluation of treatment response in lymph node metastases of NSCLC.
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Metastatic colorectal cancer (mCRC) may present various behaviours that define different courses of tumor evolution. There is presently no available tool designed to assess tumor aggressiveness, despite the fact that this is considered to have a major impact on patient outcome. CORIOLAN is a single-arm prospective interventional non-therapeutic study aiming mainly to assess the natural tumor metabolic progression index (TMPI) measured by serial FDG PET-CT without any intercurrent antitumor therapy as a prognostic factor for overall survival (OS) in patients with mCRC. Secondary objectives of the study aim to test the TMPI as a prognostic marker for progression-free survival (PFS), to assess the prognostic value of baseline tumor FDG uptake on PFS and OS, to compare TMPI to classical clinico-biological assessment of prognosis, and to test the prognostic value on OS and PFS of MRI-based apparent diffusion coefficient (ADC) and variation of vADC using voxel-based diffusion maps. Additionally, this study intends to identify genomic and epigenetic factors that correlate with progression of tumors and the OS of patients with mCRC. Consequently, this analysis will provide information about the signaling pathways that determine the natural and therapy-free course of the disease. Finally, it would be of great interest to investigate whether in a population of patients with mCRC, for which at present no known effective therapy is available, tumor aggressiveness is related to elevated levels of circulating tumor cells (CTCs) and to patient outcome. Tumor aggressiveness is one of the major determinants of patient outcome in advanced disease. Despite its importance, supported by findings reported in the literature of extreme outcomes for patients with mCRC treated with chemotherapy, no objective tool allows clinicians to base treatment decisions on this factor. The CORIOLAN study will characterize TMPI using FDG-PET-based metabolic imaging of patients with chemorefractory m
Imaging and assessment of diffusion coefficients by magnetic resonance
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The problem of assessment of molecular diffusion by magnetic resonance is highlighted and some typical applications of diffusion imaging in the diagnosis, e.g., of cerebral ischemia, changes in patients with phenylketonuria or multiple sclerosis are discussed. The images were obtained by using diffusion weighted spin echo Echo-Planar Imaging sequence with subsequent correction of the geometrical distortion of the images and calculation of the Apparent Diffusion Coefficient map
On diffusion approximation with discontinuous coefficients
Krylov, N. V.; Liptser, R.
2002-01-01
Convergence of stochastic processes with jumps to diffusion processes is investigated in the case when the limit process has discontinuous coefficients. An example is given in which the diffusion approximation of a queueing model yields a diffusion process with discontinuous diffusion and drift coefficients.
Institute of Scientific and Technical Information of China (English)
陈利华; 陈永峰; 张久权; 王文伟; 夏云宝; 王健
2012-01-01
目的 探讨DWI表观扩散系数(ADC)值鉴别肺癌组织学类型的价值.方法 对58例高度怀疑肺癌患者(男39例,女19例)行胸部DWI检查,b值选择为50和1000 s/mm2,计算ADC值.采用单因素方差分析方法检测不同组织学类型肺癌ADC值的差异,并应用ROC曲线评价ADC值鉴别肺癌组织学类型的能力.结果 小细胞肺癌的平均ADC值为(1.02±0.24)×10-3 mm2/s;非小细胞肺癌的平均ADC值为(1.03±0.24)×10-3 mm2/s,其中腺癌、鳞癌的平均ADC值分别为(1.10±0.14)×10-3 mm2/s、(0.89±0.09)×10-3 mm2/s.腺癌的平均ADC值显著高于鳞癌(P＜0.001).在非小细胞肺癌中,腺癌的ROC曲线下面积为0.91±0.04.结论 腺癌的平均ADC值显著高于鳞癌；ADC值有助于鉴别肺腺癌和鳞癌.%Objective To investigate the possibility of using the apparent diffusion coefficient (ADC) value to differentiate histological subtypes of lung cancers. Methods Fifty-eight patients with suspected lung cancer (39 men, 19 women) underwent magnetic resonance diffusion-weighted imaging (DWI)of the chest with b factor of 50 and 1000 s/mm2. ADC values were calculated and correlated with histological subtypes of lung cancers. ROC analysis of ADC value was used to predict histological subtypes. Results The mean ADC value of small and non-small cell lung cancer was (1. 02±0. 24) X 10-3 mm2/s and (1. 03 ± 0. 24) X 10-3 mm2/s, respectively, while of squamous cell carcinoma and adenocarcinoma was (0. 89±0. 09)X10-3 mm2/s and (1. 10±0. 14)X10-3 mm2/s, respectively. ADC value of adenocarcinoma was significantly higher than that of squamous cell carcinoma (P<0. 001). The area under ROC curve was 0. 91±0. 04 for adenocarcinoma of non-small cell lung cancer. Conclusion The mean ADC value of lung adenocarcinoma is significantly higher than that of squamous cell carcinoma. ADC value may help to differentiate the histological subtypes of lung cancers.
Institute of Scientific and Technical Information of China (English)
卜春晓; 张勇; 程敬亮; 李颜良
2015-01-01
Objective To investigate the assessment value of diffusion-weighted magnetic resonance imaging (DWI)and apparent diffusion coefficient (ADC)in the differential diagnosis of common cerebellar tumors of children.Methods 45 patients with cerebel-lar tumors were retrospectively analyzed,including 23 medulloblastomas,14 astrocytomas,and 8 ependymomas .The ADCmin of parenchyma of different tumors were measured and Receiver operating characteristic (ROC)curve were delineated.The optimum ADC value for differential diagnosis of common cerebellar tumors of children was analyzed and determined.Results The mean ADC-min of medulloblastoma (0.497 ± 0.023 )× 10 -3 mm2/s was lowest,the mean ADCmin of astrocytoma (1.572 ± 0.145 )× 10 -3 mm2/s was highest,while that of ependymoma was (0.784 ± 0.037 )× 10 -3 mm2/s.The optimum ADC to distinguish ependymomas from medulloblastomas was 0.61 1 × 10 -3 mm2/s (100% sensitivity and 95.7% specificity).The optimum ADC to distinguish low-grade astrocytomas from ependymomas was 1.064×10 -3 mm2/s (92.9% sensitivity and 100% specificity).Conclu-sion ADC is very helpful with differential diagnosis of common cerebellar tumors of children.%目的：探讨扩散加权成像(DWI)和表观扩散系数(ADC)值在鉴别儿童小脑常见肿瘤中的价值。方法回顾性分析本院经手术病理证实的45例儿童小脑肿瘤患者,其中髓母细胞瘤23例,星形细胞瘤14例,室管膜瘤8例。测量不同肿瘤的实质部分的最小 ADC 值,绘制 ROC 曲线,预测儿童常见小脑肿瘤鉴别诊断的最佳 ADC 值。结果髓母细胞瘤的平均最小 ADC 值最低,为(0.497±0.023)×10-3 mm2/s；低级星形细胞瘤的平均最小 ADC 值最高,为(1.572±0.145)×10-3 mm2/s；室管膜瘤的平均最小ADC 值为(0.784±0.037)×10-3 mm2/s。髓母细胞瘤鉴别室管膜瘤的最佳 ADC 值为0.611×10-3 mm2/s,敏感度100%,特异性95.7%；室管膜瘤鉴别低级星形细胞瘤的最佳 ADC 值为1.064×10-3 mm2/s,敏感度92
Apparent distribution coefficients of transuranium elements in UK coastal waters
International Nuclear Information System (INIS)
The authorized inputs of low-level radioactive waste into the Irish Sea from the British Nuclear Fuels plc reprocessing plant at Sellafield may be used to advantage to study the distribution and behaviour of artificial radionuclides in the marine environment. Apparent distribution coefficients (Ksub(d)) for the transuranium elements Np, Pu, Am and Cm have been determined by the analysis of environmental samples collected from UK coastal waters. The sampling methodology for obtaining suspended sediment-seawater Ksub(d)s by filtration is described and critically evaluated. Artefacts may be introduced in the sample collection stage. Ksub(d) values have also been determined for seabed sediment-interstitial waters and the precautions taken to preserve in-situ chemical conditions are described. Variations in Ksub(d) values are discussed in relation to distance from Sellafield, suspended load, redox conditions and oxidation state changes. (author)
Diffusion coefficients of paracetamol in aqueous solutions
International Nuclear Information System (INIS)
Highlights: ► Mutual diffusion coefficients of paracetamol in aqueous dilute solutions. ► Influence of the thermodynamic factors on the variation of their mutual diffusion coefficients. ► Estimation of the mutual limiting diffusion coefficients of the molecular, Dm0, and ionized forms, D±0, of this drug. - Abstract: Binary mutual diffusion coefficients measured by the Taylor dispersion method, for aqueous solutions of paracetamol (PA) at concentrations from (0.001 to 0.050) mol·dm−3 at T = 298.15 K, are reported. From the Nernst–Hartley equation and our experimental results, the limiting diffusion coefficient of this drug and its thermodynamic factors are estimated, thereby contributing in this way to a better understanding of the structure of such systems and of their thermodynamic behaviour in aqueous solution at different concentrations.
Photon diffusion coefficient in an absorbing medium
Aronson, Raphael; Corngold, Noel
1999-01-01
A number of investigators have recently claimed, based on both analysis from transport theory and transport theory-based Monte Carlo calculations, that the diffusion coefficient for photon migration should be taken to be independent of absorption. We show that these analyses are flawed and that the correct way of extracting diffusion theory from transport theory gives an absorption-dependent diffusion coefficient. Experiments by two different sets of investigators give conflicting results con...
Institute of Scientific and Technical Information of China (English)
季学满; 张宗军; 卢光明; 毕俊; 袁彩云; 王俊鹏; 贾传海
2011-01-01
Objective To assess the utility of apparent diffusion coefficient ADC) for differential diagnosis of common pediatric posterior possa tumors. Materials and Methods In 43 pediatric patients with surgically and pathologically confirmed posterior possa tumors, there were 24 medulloblastomas,10 pilocytic astrocytomas,and 9 ependymomas. All pediatric patients recevied conventional MRI,DWI and contrast enhanced MRI examination, the signal intensity of tumor parenchyma was compared with that of normal cerebellar parenchymas. ADC values of tumor parenchyma were measured quantitatively. ADC values of medullohlastomas, pilocytic a8trocytomas,and ependymomas were compared by Wilcoxon rank sum test. Results On ADC map,In 24 patients with medulloblastomas, the tumors showed hypointense in 9 patients, slightly hypointense in 12 patients, and isointense in 3 patients; the average ADC value of tumor parenchymas was (0.70 ±0. II) x 10-3 mm2/s. All tumors showed hyperintense in 10 patients with pilocytic astrocytoma, the average ADC value of tumor parenchymas was (1.80 ±0.30) ×10-3 mm2/s. In 9 patients with ependymomas, the tumors showed slightly hyperintense in 5 patients, hyperintense in 4 patients; the average ADC value of tumor parenchymas was ( 1. 16 ±0.18) ×10-3 mm2/s. The ADC value of medulloblastoma was lower than that of pilocytic astrocytoma, which was statistically significant ( Z = -4. 54, P < 0.01). The ADC value of medulloblastoma was lower than that of ependymoma, which was statistically significant (Z= -4.29,P < 0.01), The ADC value of pilocytic astrocytoma was higher than that of ependymoma,which was statistically significant (Z= -3. 27,P < 0. 05). Conclusion Measurement of ADC value of cerebral tumor parenchyma is a simple and available method, which is useful for preoperative differentiation of pediatric posterior possa tumors, especially in differential diagnosis of medulloblastoma and pilocytic astrocytoma.%目的 评价MRI表观扩散系数(ADC)值在儿
Problems with Discontinuous Diffusion/Dispersion Coefficients
Directory of Open Access Journals (Sweden)
Stefano Ferraris
2012-01-01
accurate on smooth solutions and based on a special numerical treatment of the diffusion/dispersion coefficients that makes its application possible also when such coefficients are discontinuous. Numerical experiments confirm the convergence of the numerical approximation and show a good behavior on a set of benchmark problems in two space dimensions.
Improved Diffusion Coefficients for Stellar Plasmas
Brassard, P.; Fontaine, G.
2014-04-01
We are currently working on the fourth generation of our codes for building evolutionary and static models of hot subdwarf and white dwarf stars. One of the improvements of these codes consists in an update of all the microphysics involved in the computations. As part of our efforts, we have taken a look at possible improvements for the diffusion coefficients. Since the publication of the widely used diffusion coefficients of Paquette et al. (1986), the number-crunching power of computers has immensely increased, allowing more accurate computations of the triple collision integrals. We have thus produced new tables of diffusion coefficients with higher accuracy and higher resolution than before, of general use in stellar astrophysics.
Correlation and prediction of gaseous diffusion coefficients.
Marrero, T. R.; Mason, E. A.
1973-01-01
A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.
Apparent linear attenuation coefficients in phase contrast X-ray tomography
International Nuclear Information System (INIS)
In the inline phase contrast X-ray tomography the reconstructed apparent linear attenuation coefficient values may be greatly larger than sample's linear attenuation coefficients or even be negative. In this work we present a general formula to quantitatively relate the apparent linear attenuation coefficient values in cone-beam phase contrast tomography to sample's linear attenuation coefficients and refractive indices. This formula overcomes the gross inaccuracy of the existing formula in the literature in analyzing high-resolution phase contrast tomography, and it will be useful for correctly interpreting and quantifying the apparent linear attenuation coefficients in cone-beam X-ray phase contrast tomography.
Apparent Linear Attenuation Coefficients in Phase Contrast X-Ray Tomography
Yan, Aimin; Wu, Xizeng
2011-01-01
In the inline phase contrast x-ray tomography the reconstructed apparent linear attenuation coefficient values may be greatly larger than sample’s linear attenuation coefficients or even be negative. In this work we present a general formula to quantitatively relate the apparent linear attenuation coefficient values in cone-beam phase contrast tomography to sample’s linear attenuation coefficients and refractive indices. This formula overcomes the gross inaccuracy of the existing formula in t...
Diffusion Coefficient Measurements: Sulphuric Acid – Air
Czech Academy of Sciences Publication Activity Database
Brus, David; Neitola, K.; Petäjä, T.; Lihavainen, H.
Helsinki : -, 2010, P2L7. ISBN N. [International Aerosol Conference IAC 2010. Helsinki (FI), 29.08.2010-03.09.2010] Institutional research plan: CEZ:AV0Z40720504 Keywords : diffusion coefficient * sulphuric acid * flow tube Subject RIV: CF - Physical ; Theoretical Chemistry www.iac2010.fi
DEFF Research Database (Denmark)
Haack, Søren; Pedersen, Erik Morre; Vinding, Mads Sloth;
Diffusion weighted MRI has shown great potential in diagnostic cancer imaging and may also have value for monitoring tumor response during radiotherapy. Uncertainties due to geometric distortions caused by B0-inhomogeneity and tumor delineation are major obstacles for implementing DWI for use in ...
Effective Diffusion Coefficients in Coal Chars
DEFF Research Database (Denmark)
Johnsson, Jan Erik; Jensen, Anker
2001-01-01
Knowledge of effective diffusion coefficients in char particles is important when interpreting experimental reactivity measurements and modeling char combustion or NO and N2O reduction. In this work, NO and N2O reaction with a bituminous coal char was studied in a fixed-bed quartz glass reactor....... In the case of strong pore diffusion limitations, the error in the interpretation of experimental results using the mean pore radius could be a factor of 5 on the intrinsic rate constant. For an average coal char reacting with oxygen at 1300 K, this would be the case for particle sizes larger than...
Institute of Scientific and Technical Information of China (English)
何为; 周延; 刘剑羽; 周振宇
2016-01-01
Objective To evaluate the diagnostic performance of multi ⁃ b value DWI to differentiate pancreatic adenocarcinoma from healthy pancreas using the apparent diffusion coefficient (ADC) and parameters derived from the intravoxel incoherent motion (IVIM) theory. Methods Forty⁃eight patients with histopathologically proven pancreatic adenocarcinoma and fifty patients with healthy pancreas were examined at 3.0 Tesla using a single⁃shot echo⁃planar imaging DWI pulse sequence. Eight b⁃values ranging from 0 to 1 000 s/mm2 were used. ADC, diffusion coefficient (D), perfusion⁃related diffusion (D*) and perfusion fraction (f) were compared between pancreatic adenocarcinoma and healthy pancreas, t test or Mann⁃Whitney U test was used to compare the MRI parameters, ROC was used to evaluate the diagnostic efficiency. Results In comparison to healthy pancreatic tissue, a significant reduction of the ADC, D*and f was found in pancreatic adenocarcinoma [healthy pancreatic tissue:(1.68±0.31)×10-3mm2/s, 27.10×10-3mm2/s, (36.92±12.47)%;pancreatic adenocarcinoma:(1.51±0.37)×10-3mm2/s, 13.90×10-3mm2/s, (30.06±19.84)%] (P0.05). In the ROC⁃analyses, the area under curve for D* was the largest (0.727), followed by f and ADC in order (0.680 and 0.669). Conclusion Using the IVIM DWI approach, the D*, f and ADC value are useful for differentiating pancreatic adenocarcinoma from healthy pancreatic tissue.%目的：探讨DWI单指数模型及体素内不相干运动（IVIM）模型参数诊断胰腺癌的价值。方法回顾性分析经手术病理证实为胰腺癌，且在术前1个月内行胰腺MRI检查的48例患者作为胰腺癌组；搜集同期MRI检查胰腺未见异常的50例患者作为对照组。所有受试者均行胰腺常规MRI和IVIM序列检查。对图像进行后处理，得到单指数模型参数ADC值和IVIM模型参数[包括真实扩散系数（D值）、灌注相关扩散系数（D*值）和灌注分数（f
Institute of Scientific and Technical Information of China (English)
王海屹; 王佳; 叶慧义; 张旭; 王殿军; 郭爱桃; 钟燕; 王鑫坤
2011-01-01
目的 比较肾脏病变自由呼吸扩散加权成像与屏气扩散加权成像在表观弥散系数(ADC)值及图像质量方面的异同.资料与方法 本研究纳入41例经病理结果或临床随访证实患有肾脏疾病的患者.所有患者均在1.5T磁共振扫描仪上进行自由呼吸扩散加权成像及屏气扩散加权成像.两种成像序列方面的参数除激励次数(NEX)之外均相同.两组图像的信噪比(SNR)、对比噪声比(CNR)及相对病变对比度的比较通过Wilcoxon检验进行统计学分析.两组肾实质ADC值及病变ADC值的一致性通过Pearson相关分析及信度分析方法进行分析.结果 自由呼吸扩散加权成像图像的SNR及CNR都显著高于屏气扩散加权成像图像(P＜0.01).但两组图像的病变相对对比度差异无统计学意义(P=0.459).两种扩散加权成像方法计算出的肾脏病变ADC值表现出良好的一致性(Pearson相关系数为0.888;信度分析中校正的a系数为0.949,组内相关系数为0.901).两组肾实质ADC值之间亦表现出良好的一致性(Pearson相关系数为0.871;信度分析中校正的a系数为0.931,组内相关系数为0.931).结论 自由呼吸扩散加权成像适用于肾脏病变的评价,特别适用于屏气困难的患者,而且ADC值与屏气扩散加权成像一致性良好.%Purpose To compare free-breathing and breath-hold diffusion-weighted MRI of renal lesions and to assess the coincidence of the apparent diffusion coefficient (ADC) values between the two sequences. Materials and Methods 41 patients were enrolled into this study with 41 renal masses (median diameter, 4.0cm) confirmed by pathology results or follow-up. All patients underwent both free-breathing and breath-hold diffusion-weighted MR imaging (DWI) at a 1.5 T MR system. Both sequences had identical imaging parameters except for signal averages, which were 8 in free-breathing and 2 in breath-hold sequences. Signal-to-noise ratio (SNR) of the kidney
International Nuclear Information System (INIS)
Recently, a bentonite sorption data base, comprising values taken from batch sorption data, was developed for a performance assessment study for high-level waste and spent fuel (Entsorgungsnachweis). Thus distribution coefficients (Kd) determined on dispersed systems were used to calculate apparent diffusion coefficients (Da) subsequently applied in diffusive transport calculations for the highly compacted system. Whenever such a procedure is adopted, questions invariably arise as to whether this is conservative or not. On the occasions when Kd values have been extracted from (mainly) indiffusion experiments and compared with those obtained from batch tests, apparent discrepancies have been found. In the majority of cases the batch values are larger, sometimes significantly. Hypotheses from 'surface diffusion' to 'double layer pore constrictivity effects' have been proposed to explain the inconsistencies. However, although such discrepancies have been reported periodically over the past twenty years or so, and have become generally accepted facts of life, there are surprisingly few quantitative studies directly dealing with this issue. Further, two other points are worthy of mention. The first is that a diffusion model (including the associated assumptions) is needed in order to deduce Kd values from diffusion measurements. Thus the sorption values calculated are model dependent. The second is that too little attention has been paid to the potential effects of water chemistry, i.e. a comparison between sorption values is only valid when the water chemistry in the batch tests is the same as, or very close to, the porewater chemistry in the intact material. In practice, this condition is difficult to achieve because of the uncertainties concerning the latter. This report describes a study in which Kd values for Cs(I), Ni(II), Sm(III), Am(III), Zr(IV) and Np(V) were calculated from in-diffusion data published in the open literature for a Na-bentonite (Kunigel V1) at
Oxygen transport in waterlogged soils, Part II. Diffusion coefficients
International Nuclear Information System (INIS)
Several equations are available for Oxygen Transport in Waterlogged Soils and have been used for soils and plants. All of them are some form of first Fick's law as given by dQ = - DA(dc/dx)/dt. This equation illustrates some important aspects of aeration in waterlogged soils; first, D is a property of the medium and the gas, and is affected by temperature T. Likewise, the amount of diffusing substance dQ in dt is a direct function of the cross sectional area A and inversely proportional to the distance x. In fact, increasing the water content of air-dry soil, drastically decreases A and creates a further resistance for the flow of oxygen through water films around root plants, soil micro organisms and soil aggregates. The solid phase is also limiting the cross-section of surface of the free gaseous diffusion and the length and tortuosity of diffusion path in soil. In most of cases, soil gas porosity and tortuosity of soil voids are expressed in the equations of diffusion as a broad 'diffusion coefficient' (apparent coefficient diffusion). The process of soil respiration is complicated, involves many parameters, and is difficult to realistically quantify. With regard to the oxygen supply, it is convenient to distinguish macro and micro models, and hence, the flux of oxygen is assumed to have two steps. The first step is related to oxygen diffusion from the atmosphere and the air-filled porosity. The second step is related to the oxygen diffusion through water-films in and around plant roots, soil micro organisms and aggregates. Because of these models we obtain coefficients of macro or micro diffusion, rates of macro or micro diffusion, etc. In the macro diffusion process oxygen is transferred in the soil profile, mainly from the soil surface to a certain depth of the root zone, while micro diffusion deals with the flux over very short distances. Both processes, macro and micro diffusion are highly influenced by soil water content. Of course, if water is added to
Measurements of Xe diffusion coefficient of UN
International Nuclear Information System (INIS)
Post irradiation annealing (PIA) tests were performed to obtain the Xe-133 diffusion coefficients of uranium nitride (UN). UN powder was obtained from the mixed powder of UO2 and carbon under the H2-N2 gas mixture. Porous discs (45%TD) of UN were made and used for the specimens for the PIA tests. For comparison purposes, porous discs of UO2 (47%TD) were also made. Each 300mg specimen was irradiated to a burnup of 0.1 MWd/t-U. PIA tests were performed at 1200degC, 1300degC and 1400degC for UN, and 1400degC, 1500degC and 1600degC for UO2, continuously. The oxygen potential during the annealing tests was about 440 ± 20 kJ/mol. The disc specimens of UN and UO2 were found to be cracked or broken in pieces after annealing tests. The xenon diffusion coefficient for the near stoichiometric UN turned out to be about 1,000 times higher than that of UO2 at 1400degC. And, the activation energy of diffusion in UN is about 230 kJ/mol, while that of UO2 measured to be about 393 kJ/mol. (author)
Local diffusion coefficient determination: Mediterranean Sea experiments
International Nuclear Information System (INIS)
The Mediterranean is a semi/enclosed basin characterized by the presence of channels and straits influencing the circulation, temperature and salinity fields. The tides generally have amplitudes of the order of 10 cm and velocities of few cm/s. Conversely, the wind forced circulation is very strong and can assume velocity values of 1 m/s at the sea surface. The temperature and salinity fields have a high temporal and spatial variability, because of many mixing processes existing in the sea. For example, the waters coming from the Provencal basin meet those waters coming from the Tyrrhenian Sea in the eastern Ligurian Sea, creating meanders and eddies. Local runoff influences significantly the coastal circulation. This paper describes diffusion experiments carried out in this complex environment. The experimental apparatus for the detection of the fluorescine released at sea was composed by two Turner mod. 450 fluorometres. During the experiments, temperature and salinity vertical profiles were measured by using a CTD; meteorological data were acquired on a dinghy. The positioning was obtained by means of a Motorola system, having a precision of about 1 meter. The experiments were carried out under different stratification and wind conditions. From data analysis it was found that the horizontal diffusion coefficient does not depend on time or boundary conditions. The role of stratification is important with regard to vertical displacement of the dye. However, its role with regard to vertical diffusion cannot be assessed with the actual experimental apparatus
Study of the measurement about the apparent heat transfer coefficient of solid uranium hexafluoride
International Nuclear Information System (INIS)
In order to provide the conditions for designing the congealed accept container of uranium hexafluoride, a set of experiment system of measuring apparent heat transfer coefficient in which the small-sized congealed accept container was considered as main equipment was set up. Then the experiments of loading and unloading uranium hexafluoride were carried out. The process of loading and unloading uranium hexafluoride in small-sized congealed accept container were simulated by the barrel model of steady heat transfer in this paper, and the apparent heat transfer coefficient of solid uranium hexafluoride was obtained. (authors)
Verifying reciprocal relations for experimental diffusion coefficients in multicomponent mixtures
DEFF Research Database (Denmark)
Medvedev, Oleg; Shapiro, Alexander
2003-01-01
coefficients for a three-component mixture consists of four Fickian diffusion coefficients, each being reported separately. However, the Onsager theory predicts the existence of only three independent coefficients, as one of them disappears due to the symmetry requirement. Re-calculation of the Fickian......The goal of the present study is to verify the agreement of the available data on diffusion in ternary mixtures with the theoretical requirement of linear non-equilibrium thermodynamics consisting in symmetry of the matrix of the phenomenological coefficients. A common set of measured diffusion...... diffusion coefficients into Onsager coefficients for a non-ideal mixture involves derivatives of the chemical potentials and, thus, should be based on a certain thermodynamic model (cubic equation of state (EoS), an activity coefficient model, etc.). Transformation of the Fickian diffusion coefficients into...
Stochastic Modelling of the Diffusion Coefficient for Concrete
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
In the paper, a new stochastic modelling of the diffusion coefficient D is presented. The modelling is based on physical understanding of the diffusion process and on some recent experimental results. The diffusion coefficients D is strongly dependent on the w/c ratio and the temperature....
Digital speckle pattern interferometric measurement of diffusion coefficients in hydrogels
Institute of Scientific and Technical Information of China (English)
周金芳; 韩雁; 章献民; 徐坚
2003-01-01
The technique of real-time digital speckle pattern interferometry is proposed to study diffusion of surfactants in hydrogel. The diffusion coefficient is simply and directly determined from the interferograms. An example of diffusion coefficient measurement of surfactant in agarose gel demonstrates the usefulness of the method. The results obtained are compared with the theoretical simulating values.
International Nuclear Information System (INIS)
Highlights: • Physical and osmotic properties of [HMim][TfO] in alcohols are reported. • Apparent molar properties and osmotic coefficients were obtained. • Apparent molar volumes were fitted using a Redlich–Meyer type equation. • The osmotic coefficients were modeled with the Extended Pitzer and the MNRTL models. -- Abstract: In this work, density for the binary mixtures of 1-hexyl-3-methylimidazolium trifluoromethanesulfonate in alcohols (1-propanol, or 2-propanol, or 1-butanol, or 2-butanol, or 1-pentanol) was measured at T = 323.15 K and atmospheric pressure. From this property, the corresponding apparent molar volumes were calculated and fitted to a Redlich–Meyer type equation. For these mixtures, the osmotic and activity coefficients, and vapor pressures of these binary systems were also determined at the same temperature using the vapor pressure osmometry technique. The experimental osmotic coefficients were modeled by the Extended Pitzer model of Archer. The parameters obtained in this correlation were used to calculate the mean molal activity coefficients and the excess Gibbs free energy for the studied mixtures
Diffusion coefficient adaptive correction in Lagrangian puff model
International Nuclear Information System (INIS)
Lagrangian puff model is widely used in the decision support system for nuclear emergency management. The diffusion coefficient is one of the key parameters impacting puff model. An adaptive method was proposed in this paper, which could correct the diffusion coefficient in Lagrangian puff model, and it aimed to improve the accuracy of calculating the nuclide concentration distribution. This method used detected concentration data, meteorological data and source release data to estimate the actual diffusion coefficient with least square method. The diffusion coefficient adaptive correction method was evaluated by Kincaid data in MVK, and was compared with traditional Pasquill-Gifford (P-G) diffusion scheme method. The results indicate that this diffusion coefficient adaptive correction method can improve the accuracy of Lagrangian puff model. (authors)
Apparent digestibility coefficients and consumption of corn silage with and without Bt gene in sheep
Camila Memari Trava; Mauro Sartori Bueno; Geraldo Balieiro
2012-01-01
Corn silage is the most important preserved food for ruminants. The transgenic corn was inserted into the genetic code Bt gene (Bacillus thuringiensis) that expresses a toxic protein to caterpillars pests of maize, reducing production costs. To evaluate the varieties of plant corn silage DKB and AG with or without the Bt gene on the voluntary intake of DM (g/day) and apparent digestibility coefficients (CDA) of nutrients in sheep, the experiment was conducted at the Institute of Animal Scienc...
Zhang, Yingqi; Liu, Hui-Hai; Zhou, Quanlin; Finsterle, Stefan
2005-01-01
Heterogeneities of diffusion properties are likely to influence the effective matrix diffusion coefficient determined from tracer breakthrough curves. The objectives of this study are (1) to examine if it is appropriate to use a single, effective matrix diffusion coefficient to predict breakthrough curves in a fractured formation, (2) to examine if a postulated scale dependence of the effective matrix diffusion coefficient is caused by heterogeneity in diffusion properties, and (3) to ex...
Heavy Quark Momentum Diffusion Coefficient from Lattice QCD
Banerjee, Debasish; Datta, Saumen; Gavai, Rajiv; Majumdar, Pushan
2011-01-01
The momentum diffusion coefficient for heavy quarks is studied in a deconfined gluon plasma in the static approximation by investigating a correlation function of the color electric field using Monte Carlo techniques. The diffusion coefficient is extracted from the long distance behavior of such a correlator. For temperatures Tc < T
Invariant coefficients of diffusion in iron-chromium-nickel system
Energy Technology Data Exchange (ETDEWEB)
Mokrov, A.P.; Akimov, V.K.; Golubev, V.G.
1984-02-01
The temperature and concentration dependences of the Dsub(c) coefficients in the ..gamma..-phase of iron-chromium-nickel system are determined. It is proposed to described mutual diffusion in multicomponent systems using invariant, i.e. independent of the choice of solvent, coefficients of diffusion. The assumption that their temperature dependence follows the Arrhenius law is confirmed by the experiment.
Invariant coefficients of diffusion in iron-chromium-nickel system
International Nuclear Information System (INIS)
The temperature and concentration dependences of the Dsub(c) coefficients in the γ-phase of iron-chromium-nickel system are determined. It is proposed to described mutual diffusion in mul-- ticomponent systems using invariant, i. e. independent of the choice of solvent, coefficients of diffusion. The assumption that their temperature dependence follows the Arrhenius law is confirmed by the experiment
Calculation of self-diffusion coefficients in iron
Baohua Zhang
2014-01-01
On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and ɛ phases) have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature r...
Measurement of carbon dioxide diffusion coefficient of concrete
Villain, G.; PAVOINE, A; Thiery, M.
2006-01-01
The carbonation of concrete is a chemical reaction, which can be at the origin of the premature degradation of reinforced concrete structures. In order to predict service life of reinforced concrete structures, many models based on gas diffusion were developed. The carbon dioxide diffusion coefficient of concrete is thus a significant input datum for these models. The objective of this article is to present a simple reliable testing method to quantify the carbon dioxide diffusion coefficient ...
Determination of mutual diffusion coefficients in quaternary alloy systems
International Nuclear Information System (INIS)
Procedures of experimental study of mutual diffusion in four-component system are developed, limit ratios for diffusion coefficients are found at the transition from four component system to three-component one and experimental check of some of these ratios is carried out. Concentrational dependence of complete matrix of outer diffusion coefficients in Fe-Cr-Ni-Co system is determined. Limit correlations for this system are checked up at cobalt concentration yielding to zero
Evaluation of satellite derived spectral diffuse attenuation coefficients
Digital Repository Service at National Institute of Oceanography (India)
Suresh, T.; Talaulikar, M.; Desa, E.; Mascarenhas, A.A.M.Q.; Matondkar, S.G.P.
Spectral diffuse attenuation K sub(d)(lambda) is an important apparent optical property that provide information about the attenuation of the spectral downwelling solar irradiance with depth in water. The spectral K sub(d)(lambda) at lambda = 412...
Diffusion Coefficients of Fluorinated Surfactants in Water:
Pereira, Luís A.M.; Martins, Luís F. G.; Ascenso, José R.; Morgado, Pedro; Ramalho, João P. P.; Filipe, Eduardo J. M.
2014-01-01
Intradiffusion coefficients of 2,2,2-trifluoroethanol in water have been measured by the pulsed field gradient (PFG)-NMR spin−echo technique as a function of temperature and composition on the dilute alcohol region. The measurements extend the range of compositions already studied in the literature and, for the first time, include the study of the temperature dependence. At the same time, intradiffusion coefficients of 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoropropan-1-ol, ...
Mutual diffusion coefficients of L-lysine in aqueous solutions
International Nuclear Information System (INIS)
Highlights: • Mutual diffusion coefficients of L-lysine in aqueous solutions. • Influence of the thermodynamic factors on the variation of their mutual diffusion coefficients. • Estimation of the hydrodynamic radius of L-lysine. - Abstract: Mutual diffusion coefficients, D, were determined for aqueous solutions of L-lysine at T = 298.15 K at concentrations from (0.001 to 0.100) mol · dm−3. From these experimental results, the hydrodynamic radius Rh, diffusion coefficients at infinite dilution D0, the thermodynamic factors and activity coefficients γ, by using the Hartley equation, have been estimated, permitting us to have a better understanding of the thermodynamic of these systems of L-lysine in aqueous solutions
International Nuclear Information System (INIS)
Diffusion-weighted imaging (DWI) is important in the assessment of fetal brain development. However, it is clinically challenging and time-consuming to prepare neuromorphological examinations to assess real brain age and to detect abnormalities. To demonstrate that the Gini coefficient can be a simple, intuitive parameter for modelling fetal brain development. Postmortem fetal specimens(n = 28) were evaluated by diffusion-weighted imaging (DWI) on a 3-T MRI scanner using 60 directions, 0.7-mm isotropic voxels and b-values of 0, 150, 1,600 s/mm2. Constrained spherical deconvolution (CSD) was used as the local diffusion model. Fractional anisotropy (FA), apparent diffusion coefficient (ADC) and complexity (CX) maps were generated. CX was defined as a novel diffusion metric. On the basis of those three parameters, the Gini coefficient was calculated. Study of fetal brain development in postmortem specimens was feasible using DWI. The Gini coefficient could be calculated for the combination of the three diffusion parameters. This multidimensional Gini coefficient correlated well with age (Adjusted R2 = 0.59) between the ages of 17 and 26 gestational weeks. We propose a new method that uses an economics concept, the Gini coefficient, to describe the whole brain with one simple and intuitive measure, which can be used to assess the brain's developmental state. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Viehweger, Adrian; Sorge, Ina; Hirsch, Wolfgang [University Hospital Leipzig, Department of Pediatric Radiology, Leipzig (Germany); Riffert, Till; Dhital, Bibek; Knoesche, Thomas R.; Anwander, Alfred [Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig (Germany); Stepan, Holger [University Leipzig, Department of Obstetrics, Leipzig (Germany)
2014-10-15
Diffusion-weighted imaging (DWI) is important in the assessment of fetal brain development. However, it is clinically challenging and time-consuming to prepare neuromorphological examinations to assess real brain age and to detect abnormalities. To demonstrate that the Gini coefficient can be a simple, intuitive parameter for modelling fetal brain development. Postmortem fetal specimens(n = 28) were evaluated by diffusion-weighted imaging (DWI) on a 3-T MRI scanner using 60 directions, 0.7-mm isotropic voxels and b-values of 0, 150, 1,600 s/mm{sup 2}. Constrained spherical deconvolution (CSD) was used as the local diffusion model. Fractional anisotropy (FA), apparent diffusion coefficient (ADC) and complexity (CX) maps were generated. CX was defined as a novel diffusion metric. On the basis of those three parameters, the Gini coefficient was calculated. Study of fetal brain development in postmortem specimens was feasible using DWI. The Gini coefficient could be calculated for the combination of the three diffusion parameters. This multidimensional Gini coefficient correlated well with age (Adjusted R{sup 2} = 0.59) between the ages of 17 and 26 gestational weeks. We propose a new method that uses an economics concept, the Gini coefficient, to describe the whole brain with one simple and intuitive measure, which can be used to assess the brain's developmental state. (orig.)
Propagators and Time-Dependent Diffusion Coefficients for Anomalous Diffusion
Wu, Jianrong; Berland, Keith M.
2008-01-01
Complex diffusive dynamics are often observed when one is investigating the mobility of macromolecules in living cells and other complex environments, yet the underlying physical or chemical causes of anomalous diffusion are often not fully understood and are thus a topic of ongoing research interest. Theoretical models capturing anomalous dynamics are widely used to analyze mobility data from fluorescence correlation spectroscopy and other experimental measurements, yet there is significant ...
International Nuclear Information System (INIS)
By using polarizable molecular dynamics (MD) simulations of lanthanoid(III) and actinoid(III) ions in water, we obtained ionic diffusion coefficients and hydration enthalpies for both series. These values are in good agreement with experiments. Simulations thus allow us to relate them to microscopic structure. In particular, across the series the diffusion coefficients decrease, reflecting the increase of ion-water interaction. Hydration enthalpies also show that interactions increase from light to heavy ions in agreement with experiment. The apparent contradictory result of the decrease of the diffusion coefficient with decreasing ionic radius is tentatively explained in terms of dielectric friction predominance on Stokes' diffusive regime. (authors)
Methods for measuring diffusion coefficients of radon in building materials
Cozmuta, [No Value; van der Graaf, ER
2001-01-01
Two methods for determining the Rn-222 diffusion coefficient in concrete are presented. Experimentally, the flush and adsorption technique to measure radon release rates underlines both methods. Theoretically, the first method was developed fur samples of cubical geometry. The radon diffusion equati
Stationary space-periodic structures with equal diffusion coefficients
DEFF Research Database (Denmark)
Andresen, Peter Ragnar; Bache, Morten; Mosekilde, Erik;
1999-01-01
The paper investigates a chemical reaction-diffusion model in an open flow system. It is shown that such a system may, with particular boundary conditions, exhibit stationary space-periodic structures even in the case of equal diffusion coefficients. This is confirmed through numerical simulations....
Measurement and Modeling of Solute Diffusion Coefficients in Unsaturated Soils
Chou, Hsin-Yi
2010-01-01
Solute diffusion in unsaturated soils refers to the transport of dissolved constituents in liquid phase from a higher to a lower concentration point. Several empirical and conceptual models were proposed to predict the solute diffusion coefficients in unsaturated soils, but they were not systematically tested and evaluated under the same conditions using soils of different textures. Our experimental data showed that there is no perfect model that can depict the behavior of solute diffusion co...
Exploring non-linear cosmological matter diffusion coefficients
Velten, Hermano
2014-01-01
Since microscopic velocity diffusion can be incorporated into general relativity in a consistent way, we study cosmological background solutions when the diffusion phenomena takes place in an expanding universe. Our focus here relies on the nature of the diffusion coefficient $\\sigma$ which measures the magnitude of such transport phenomena. We test dynamics where $\\sigma$ has a phenomenological dependence on the scale factor, the matter density, the dark energy and the expansion rate.
Calculation of self-diffusion coefficients in iron
Energy Technology Data Exchange (ETDEWEB)
Zhang, Baohua, E-mail: zhangbh148@qq.com [Laboratory for High Temperature and High Pressure Study of the Earth' s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550002, China and Institute for Study of the Earth' s Interior, Okayama University, Misasa, Tottori-ken 682-0193 (Japan)
2014-01-15
On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and ε phases) have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K) and pressure range (0-100 GPa), compare favorably well with experimental or theoretical ones when the uncertainties are considered.
Calculation of self-diffusion coefficients in iron
Directory of Open Access Journals (Sweden)
Baohua Zhang
2014-01-01
Full Text Available On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and ɛ phases have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K and pressure range (0-100 GPa, compare favorably well with experimental or theoretical ones when the uncertainties are considered.
Diffusion coefficient of the decay products of krypton and xenon
International Nuclear Information System (INIS)
Measurement of diffusion coefficient of the decay products of krypton and xenon e.g. sup(88,89)Rb and 138Cs is useful for evaluating the inhalation dose and also for the measurement of the concentration of noble gases by double filter method. A diffusion sampler developed by Kotrappa et al., based on Mercer's theory of diffusional deposition between the concentric circular plates was used. The deposition of decay products of krypton and xenon on the circular plates was measured using a multichannel analyser available in this division of BARC (HPGe 4K MCA). Experiments were conducted at 15 and 140 air changes per hour and at different humidities (50-100%). The diffusion coefficient for 88Rb, 89Rb, 138Cs were found to be 0.050±0.008, 0.047±0.008 and 0.047±0.006 respectively at 15 air changes per hour. The diffusion coefficients for these radionuclides were observed to be 0.061±0.005, 0.059±0.006 and 0.058±0.005 at high ventilation rate (140 air changes per hour). This study demonstrates that the diffusion coefficients increase with increasing ventilation rates. The effect of relative humidity on diffusion coefficient is less pronounced at high ventilation rate. (author). 8 refs., 1 fig., 2 tabs
Calculation of diffusion coefficients in air-metal thermal plasmas
Energy Technology Data Exchange (ETDEWEB)
Cressault, Y; Gleizes, A [Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France)
2010-11-03
This paper presents the combined diffusion coefficients of metal vapours (silver, copper and iron) in air thermal plasmas for temperatures ranging from 300 to 30 000 K. The theory used to calculate these coefficients is remembered and validated by comparison with the literature values in several cases such as Ar-He, Ar-Cu and N{sub 2}-O{sub 2} mixtures. The results are discussed showing the influences of the metal concentration, of the vapour nature and of the pressure. The results show rather similar behaviour for the three metals. The maximum values of the combined ordinary diffusion coefficient in the evolution with temperature are obtained for temperature around 10 000 K but this peak is shifted to the highest temperatures when the metal proportion increases. Another result shows that the diffusion coefficient decreases when pressure increases.
Numerical study of the Transverse Diffusion coefficient for a one component model of a plasma
Valvo, Lorenzo
2016-01-01
We report the results of MD numerical simulations for a one component model of a plasma in the weakly coupled regime, at different values of temperature $T$ and applied magnetic field $\\vec B$, in which the diffusion coefficient $D_{\\perp}$ transverse to the field is estimated. We find that there exists a threshold in temperature, at which an inversion occurs, namely, for $T$ above the threshold the diffusion coefficient $D_{\\perp}$ starts decreasing as $T$ increases. This is at variance with the behavior predicted by the Bohm law $D_{\\perp}\\sim T/B$, which actually holds below the threshold. In addition we find that, for temperatures above such a threshold, another transition occurs, now with respect to the values of the magnetic field: for weak magnetic fields the diffusion coefficients scales as $1/B^2$, in agreement with the predictions of the standard kinetics theory, while it apparently saturates when the field strength is sufficiently increased.
Institute of Scientific and Technical Information of China (English)
张泉; 张云亭; 冯凯琳; 张敬; 张权
2011-01-01
Objective To investigate the correlation of apparent diffusion coefficient (ADC) value of hippocampus with the volume and magnetic resonance spectroscopy (MRS) of hippocampus in patients with hippocampal sclerosis (HS), and to evaluate the diagnostic value of ADC value. Methods Thirteen HS patients (HS group) of unilateral temporal lobe epilepsy (TLE) and 20 age-matched healthy subjects (control group) were studied with hippocampal ADC maps, volume measurement of hippocampus and N-acetylaspartate to choline and creatine ratios [NAA/(Cho+Cr)]. The ADC values of bilateral hippocampi and asymmetry index (AI, including AIADC, AIVOLUME and AIMRS) were measured respectively, and the correlations of ADC value with other quantitative MR measurements, age at onset and duration of epilepsy were evaluated.Results The ADC value in ipsilateral hippocampus was higher than that in contralateral side and the control group (both P ＜0. 001 ), and AIADC in patients with HS was also higher than that in the control group (P＜0. 001). Significant correlations were found between ADC value and the volume of ipsilateral hippocampus (r=-0.854, P＜0. 001), also between AIADC and AIVPLUME (r=0. 611, P＜0. 05). AIADC showed positive correlation with the duration of epilepsy in HS patients (r=0. 676, P＜0. 05). Conclusion The ADC value of hippocampus is helpful for the preoperative diagnosis of HS and has certain correlation with volume measurement and duration of epilepsy.%目的 探讨海马硬化(HS)患者的海马表观扩散系数(ADC)值与海马体积及磁共振波谱的相关性,并评价ADC值在HS诊断中的价值.方法 对13例单侧颞叶癫痫HS患者(HS组)和20名健康志愿者(正常对照组)行常规MR及磁共振扩散加权成像(DWI)检查,并对HS患者进行海马体积测量和磁共振波谱(MRS)检查,计算双侧海马的ADC值、标准化体积、N-乙酰天门冬氨酸/(胆碱+肌酸)[NAA/(Cho+Cr)]及不对称指数(AI,包括AIADC、AIVOLUME及AIMRS),评
Institute of Scientific and Technical Information of China (English)
杨晶; 敦旺欢; 马雪英; 麻少辉; 张宇辰; 刘继新; 张明
2016-01-01
目的：研究青年女性正常子宫体各结构表观扩散系数（ADC ）值在不同月经周期的变化规律，并探讨其生理机制及临床意义。方法19例健康青年女性分别于围排卵期、分泌晚期及月经期接受3次子宫体扩散加权成像（DWI）（b＝0，1000 s／mm2）扫描，后分别测量子宫内膜、结合带及子宫肌层的ADC值并分析各结构ADC值的差异及其在不同月经周期的变化规律。结果特定月经周期不同子宫结构ADC值之间均有显著统计学差异（P＜0．05），其中子宫肌层ADC值最高，子宫内膜居中，结合带最低；特定子宫结构在不同月经周期下ADC值存在显著统计学差异（F＝55．674，P＜0．05）；月经周期与子宫结构之间存在交互效应（F＝12．501，P＜0．05）。结论不同结构区及月经周期会对子宫ADC值产生影响，采用ADC值分析子宫病变时，应考虑到子宫不同结构区、不同月经周期对子宫ADC值的影响。%Objective To investigate the cyclical changes of the apparent diffusion coefficient (ADC) values of the normal uterine zonal structures and explore physiological mechanism and clinical significance of the changes .Methods Nineteen healthy young fe‐male volunteers were selected to receive DWI (b=0 and 1 000 s/mm2 ) scan during periovulatory ,late secretory and menstrual pha‐ses .The ADC values of endometrium ,junctional zone and myometrium were measured and the differences of the ADC values were analyzed .Results The ADC values among three structures were significantly different in three phases (P< 0 .05) .The ADC value of myometrium was highest and the second was endometrium and the last was junctional zone .The differences of specific uterine zonal structures in different phases were statistically significant (F=55 .674 ,P<0 .05) .There was a interaction effect between menstrual cycle and uterine structures .Conclusion The effect of zones and different phases of
Mutual diffusion coefficients in systems containing the nickel ion
Ribeiro, Ana C. F.; Veríssimo, Luis V. M. M.; Gomes, Joselaine C. S.; Santos, Cecilia I. A. V.; Barros, Marisa C. F.; Lobo, Victor M. M.; Sobral, Abílio J. F. N.; Esteso, Miguel A.; Leaist, Derek G.
2013-04-01
Mutual diffusion coefficients of nickel chloride in water have been measured at 293.15 K and 303.15 K and at concentrations between 0.020 mol dm-3 and 0.100 mol dm-3, using a conductimetric cell. The experimental mutual diffusion coefficients are discussed on the basis of the Onsager-Fuoss model. The equivalent conductances at infinitesimal concentration of the nickel ion in these solutions at those temperatures have been estimated using these results. In addition, from these data, we have estimated some transport and structural parameters, such as limiting diffusion coefficient, ionic conductance at infinitesimal concentration, hydrodynamic radii and activation energy, contributing this way to a better understanding of the structure of these systems and of their thermodynamic behavior in aqueous solution at different concentrations.
Continuum estimate of the heavy quark momentum diffusion coefficient $\\kappa$
Kaczmarek, Olaf
2014-01-01
Among quantities playing a central role in the theoretical interpretation of heavy ion collision experiments at RHIC and LHC are so-called transport coefficients. Out of those heavy quark diffusion coefficients play an important role e.g. for the analysis of the quenching of jets containing c or b quarks (D or B mesons) as observed at RHIC and LHC. We report on a lattice investigation of heavy quark momentum diffusion within pure SU(3) plasma above the deconfinement transition with the quarks...
Wavelet estimation of the diffusion coefficient in time dependent diffusion models
Institute of Scientific and Technical Information of China (English)
Ping; CHEN; Jin-de; WANG
2007-01-01
The estimation problem for diffusion coefficients in diffusion processes has been studied in many papers,where the diffusion coefficient function is assumed to be a 1-dimensional bounded Lipschitzian function of the state or the time only.There is no previous work for the nonparametric estimation of time-dependent diffusion models where the diffusion coefficient depends on both the state and the time.This paper introduces and studies a wavelet estimation of the time-dependent diffusion coefficient under a more general assumption that the diffusion coefficient is a linear growth Lipschitz function.Using the properties of martingale,we translate the problems in diffusion into the nonparametric regression setting and give the Lr convergence rate.A strong consistency of the estimate is established.With this result one can estimate the time-dependent diffusion coefficient using the same structure of the wavelet estimators under any equivalent probability measure.For example,in finance,the wavelet estimator is strongly consistent under the market probability measure as well as the risk neutral probability measure.
Institute of Scientific and Technical Information of China (English)
杜鲲; 管生; 胡小波; 刘朝; 李明省; 陈振; 彭强
2011-01-01
目的 评估原发性肝癌介入术后完全缓解病灶磁共振表观扩散系数(ADC)值测量的可重复性和一致性,为临床应用提供参考.方法 对21个完全缓解病灶在术后第1、3、6个月时由同一名医师同一序列测量ADC值、不同医师间隔1周测量病灶的ADC 值,通过计算组内相关系数(ICC)值及绘制Bland-Altman图表确定ADC值测量的可重复性及一致性.ICC值大于0.75表示信度良好,可重复性高,75%的位点位于Bland-Altman图95%的置信区间的参考线内,其一致性高.结果 A医师术后1、3、6个月测量ICC值分别为0.928、0.878、0.934;B医师术后1、3、6个月测量ICC值分别为0.873、0.940、0.871,1周前不同时间A、B医师1、3、6个月测量ICC值分别为0.854、0.940、0.960;1周后不同时间A、B医师术后1、3、6个月测量ICC值分别为:0.788、0.945、0.858,均大于0.75,提示可信度较高,可重复性强.90%的位点Bland-Altman图95%的置信区间的参考线内,数值测量的可重复性高.结论 HCC完全缓解病灶的ADC值稳定,测量具有较高的一致性和可重复性,可以动态观察原发性肝癌介入治疗后病灶的稳定程度,可及时有效的评估巩固治疗时机.%Objective To assess the repeatability and consistency of magnetic resonance apparent diffusion coefficient (MR ADC) values of the completely remitted lesions of primary hepatocellular carcinoma (HCC) after TACE in order to provide a reference for clinical application. Methods The MR ADC values of 21 completely remitted lesions were measured at 1, 3 and 6 months after TACE by the same radiologist (radiologist A) using the same sequence, which were measured again by another radiologist (radiologist B) one week later. By calculating the intra-class correlation coefficient (ICC) value and drawing Bland-Altman graph, the repeatability and consistency of the ADC value measurement were evaluated. ICC values > 0.75 indicated good reliability and high repeatability
Diffusion Coefficient Measurements of Sulphuric Acid in Air
Czech Academy of Sciences Publication Activity Database
Brus, David; Neitola, K.; Petäjä, T.; Lihavainen, H.
-, 2011, 456 /4P54/. ISBN N. [European Aerosol Conference EAC 2011. Manchester (GB), 04.09.2011-09.09.2011] Institutional research plan: CEZ:AV0Z40720504 Keywords : diffusion coefficient * sulphuric acid * flow tube Subject RIV: CF - Physical ; Theoretical Chemistry
Raman spectroscopic determination of concentration dependent diffusion coefficients
International Nuclear Information System (INIS)
The determination of concentration dependent diffusion coefficients D(c) is possible, if two concentration profiles in a solution at short time distances are recorded by means of the Raman spectroscopic method. D(c) is elegantly obtained by application of the Boltzmann transformation in connection with Fick's second law. (author)
Temperature Dependence of the Particle Diffusion Coefficient in Dust Grains
Pechal, Radim; Richterova, Ivana; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek
2014-05-01
During the interaction of ions/neutrals with dust grains, some of the particles are implanted into the grain and, as a consequence, the density gradient induces their diffusion toward the grain surface. Their release can cause a transport of these particles over large distances in space. In our laboratory experiment, measurements of the diffusion coefficient of the particles implanted into the dust grain are carried out in an electrodynamic quadrupole trap. Although experimental setup does not allow an assessment of the dust grain temperature, it can be modified (e.g., by changing thermal radiation from the surrounding walls, laser irradiation, etc.). We present an upgraded laboratory set-up and the resulting temperature dependence of diffusion coefficient estimations and discuss implications for the space dust.
International Nuclear Information System (INIS)
Diffusion coefficients of metal ions and metal-ligand complexes in hydrogels were measured at ionic strengths of 0.1-100 mmol L-1 using a diffusion cell. The three different types of hydrogel were all based on polyacrylamide and have been commonly used in the technique of diffusive gradients in thin films (DGT), where accurate diffusion coefficients are essential for the assessment of the concentrations of labile metal in solution. There was little difference in the diffusion coefficients of either Cu and Cd measured in gels with thicknesses of 0.4, 0.8 and 1.6 mm, showing that any diffusion boundary layer in solution was negligibly small. The diffusion coefficients of Pb, Ni, Cu and Cd in simple inorganic solutions was independent of ionic strength (1-100 mmol L-1), except at very low ionic strengths (0.1 mmol L-1) where the value of D was 50% lower. This observation is consistent with the gel having a positive charge that creates a Donnan partitioning of cations at the gel surface. Diffusion coefficient of Pb complexes decreased with increasing size of the ligand, in the order of diglycolic acid (DGA), nitrilotriacetic acid (NTA), fulvic acid and humic acid. In freshwaters the contribution of fulvic acid species to measured DGT mass should be considered. No significant difference was found between the rate of diffusion of Cu and Cd through the mostly commonly used gel and the filter membrane at the face of the DGT device. Diffusion coefficients obtained using a gel with small pore size (restricted gel) plus filter membrane were higher than those obtained using the restricted gel alone. It may be necessary to modify the standard DGT equation for restricted gel deployments, to take into account the difference in diffusion between the gel and the filter membrane
Determination of thermal diffusion coefficient of nanofluid: Fullerene-toluene
Martin, Alain; Bou-Ali, M. Mounir
2011-05-01
Thermodiffusion coefficient at fullerene mass concentrations of 0.05%, 0.1%, 0.15%, and 0.2% was established for pure fullerene (C 60) diluted in toluene solutions. For this, the thermogravitational technique has been used in planar configuration with 4 extraction points. The determination of the concentration distribution along the column in steady state is determined by the method of analysis based on density measurements. In order to determine the thermal diffusion coefficient all thermophysical properties such as density, viscosity, thermal expansion coefficient and mass expansion coefficients were determined. All these studies coincide with the importance of the knowledge of the thermophysics and transport properties of the nanofluids to develop new applications and to optimize the existing ones.
Determination of diffusion coefficient in disordered organic semiconductors
Rani, Varsha; Sharma, Akanksha; Ghosh, Subhasis
2016-05-01
Charge carrier transport in organic semiconductors is dominated by positional and energetic disorder in Gaussian density of states (GDOS) and is characterized by hopping through localized states. Due to the immobilization of charge carriers in these localized states, significant non-uniform carrier distribution exists, resulting diffusive transport. A simple, nevertheless powerful technique to determine diffusion coefficient D in disordered organic semiconductors has been presented. Diffusion coefficients of charge carriers in two technologically important organic molecular semiconductors, Pentacene and copper phthalocyanine (CuPc) have been measured from current-voltage (J-V) characteristics of Al/Pentacene/Au and Al/CuPc/Au based Schottky diodes. Ideality factor g and carrier mobility μ have been calculated from the exponential and space charge limited region respectively of J-V characteristics. Classical Einstein relation is not valid in organic semiconductors due to energetic disorders in DOS. Using generalized Einstein relation, diffusion coefficients have been obtained to be 1.31×10-6 and 1.73×10-7 cm2/s for Pentacene and CuPc respectively.
International Nuclear Information System (INIS)
Diffusion is a dominant mechanism regulating the transport of released nuclides. The through-diffusion method is typically applied to determine the diffusion coefficients (D). Depending on the design of the experiment, the concentrations in the source term [i.e., inlet reservoir (IR)] or the end term [i.e., outlet reservoir (OR)] can be fixed or vary. The combinations involve four distinct models (i.e., the CC-CC model, CC-VC model, VC-CC model, and the VC-VC model). Studies discussing the VC-CC model are scant. An analytical method considering the decay effect is required to accurately interpret the radioactive nuclide diffusion experiment results. Therefore, we developed a CC-CC model and a CC-VC model with a decay effect and the simplified formulas of these two models to determine the diffusion coefficient (i.e., the CC-CC method and CC-VC method). We also proposed two simplified methods using the VC-VC model to determine the diffusion coefficient straightforwardly based upon the concentration variation in IR and OR. More importantly, the best advantage of proposed method over others is that one can derive three diffusion coefficients based on one run of experiment. In addition, applying our CC-VC method to those data reported from Radiochemica Acta 96:111-117, 2008; and J Contam Hydrol 35:55-65, 1998, derived comparable diffusion coefficient lying in the identical order of magnitude. Furthermore, we proposed a formula to determine the conceptual critical time (Tc), which is particularly beneficial for the selection of using CC-VC or VC-VC method. Based on our proposed method, it becomes possible to calculate diffusion coefficient from a through-diffusion experiment in a shorter period of time. (author)
Measurement of the diffusion coefficient of sulfur hexafluoride in water
King, D. B.; Saltzman, E. S.
1995-01-01
Sulfur hexafluoride has been widely used in field studies and laboratory experiments to develop a relationship between gas transfer and wind speed. The interpretation of the data from such studies requires the diffusion coefficient of SF6 (D SF6), which has not previously been measured. In this study, D SF6 has been determined in pure water and in 35‰ NaCl over a temperature range of 5–25°C. The measurements were made using a continuous-flow diffusion cell where SF6 fl...
Continuum estimate of the heavy quark momentum diffusion coefficient $\\kappa$
Kaczmarek, Olaf
2014-01-01
Among quantities playing a central role in the theoretical interpretation of heavy ion collision experiments at RHIC and LHC are so-called transport coefficients. Out of those heavy quark diffusion coefficients play an important role e.g. for the analysis of the quenching of jets containing c or b quarks (D or B mesons) as observed at RHIC and LHC. We report on a lattice investigation of heavy quark momentum diffusion within pure SU(3) plasma above the deconfinement transition with the quarks treated to leading order in the heavy mass expansion. We measure the relevant colour-electric Euclidean correlator and based on several lattice spacings perform the continuum extrapolation. This extends our previous studies progressing towards a removal of lattice artifacts and a physical interpretation of the results. We find that the correlation function clearly exceeds its perturbative counterpart which suggests that at temperatures just above the critical one, non-perturbative interactions felt by the heavy quarks ar...
Continuum estimate of the heavy quark momentum diffusion coefficient κ
International Nuclear Information System (INIS)
Among quantities playing a central role in the theoretical interpretation of heavy ion collision experiments at RHIC and LHC are so-called transport coefficients. Out of those heavy quark diffusion coefficients play an important role e.g. for the analysis of the quenching of jets containing c or b quarks (D or B mesons) as observed at RHIC and LHC [1]. We report on a lattice investigation of heavy quark momentum diffusion within pure SU(3) plasma above the deconfinement transition with the quarks treated to leading order in the heavy mass expansion. We measure the relevant “colour-electric” Euclidean correlator and based on several lattice spacings perform the continuum extrapolation. This extends our previous studies [2,3] progressing towards a removal of lattice artifacts and a physical interpretation of the results. We find that the correlation function clearly exceeds its perturbative counterpart which suggests that at temperatures just above the critical one, non-perturbative interactions felt by the heavy quarks are stronger than within the weak-coupling expansion. Using an Ansatz for the spectral function which includes NNLO perturbative contributions we were able to determine, for the first time, a continuum estimate for the heavy quark momentum diffusion coefficient
Energy Technology Data Exchange (ETDEWEB)
Takeda, M.; Hiratsuka, T.; Ito, K.; Finsterle, S.
2011-02-01
Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an
Rafelski, Susanne M.; Keller, Lani C.; Alberts, Jonathan B.; Marshall, Wallace F.
2011-04-01
The degree to which diffusion contributes to positioning cellular structures is an open question. Here we investigate the question of whether diffusive motion of centrin granules would allow them to interact with the mother centriole. The role of centrin granules in centriole duplication remains unclear, but some proposed functions of these granules, for example, in providing pre-assembled centriole subunits, or by acting as unstable 'pre-centrioles' that need to be captured by the mother centriole (La Terra et al 2005 J. Cell Biol. 168 713-22), require the centrin foci to reach the mother. To test whether diffusive motion could permit such interactions in the necessary time scale, we measured the motion of centrin-containing foci in living human U2OS cells. We found that these centrin foci display apparently diffusive undirected motion. Using the apparent diffusion constant obtained from these measurements, we calculated the time scale required for diffusion to capture by the mother centrioles and found that it would greatly exceed the time available in the cell cycle. We conclude that mechanisms invoking centrin foci capture by the mother, whether as a pre-centriole or as a source of components to support later assembly, would require a form of directed motility of centrin foci that has not yet been observed.
International Nuclear Information System (INIS)
The degree to which diffusion contributes to positioning cellular structures is an open question. Here we investigate the question of whether diffusive motion of centrin granules would allow them to interact with the mother centriole. The role of centrin granules in centriole duplication remains unclear, but some proposed functions of these granules, for example, in providing pre-assembled centriole subunits, or by acting as unstable 'pre-centrioles' that need to be captured by the mother centriole (La Terra et al 2005 J. Cell Biol. 168 713–22), require the centrin foci to reach the mother. To test whether diffusive motion could permit such interactions in the necessary time scale, we measured the motion of centrin-containing foci in living human U2OS cells. We found that these centrin foci display apparently diffusive undirected motion. Using the apparent diffusion constant obtained from these measurements, we calculated the time scale required for diffusion to capture by the mother centrioles and found that it would greatly exceed the time available in the cell cycle. We conclude that mechanisms invoking centrin foci capture by the mother, whether as a pre-centriole or as a source of components to support later assembly, would require a form of directed motility of centrin foci that has not yet been observed
Apparent digestibility coefficients and consumption of corn silage with and without Bt gene in sheep
Directory of Open Access Journals (Sweden)
Camila Memari Trava
2012-12-01
Full Text Available Corn silage is the most important preserved food for ruminants. The transgenic corn was inserted into the genetic code Bt gene (Bacillus thuringiensis that expresses a toxic protein to caterpillars pests of maize, reducing production costs. To evaluate the varieties of plant corn silage DKB and AG with or without the Bt gene on the voluntary intake of DM (g/day and apparent digestibility coefficients (CDA of nutrients in sheep, the experiment was conducted at the Institute of Animal Science Nova Odessa-SP. Were used 20 sheep and the experimental design was randomized blocks in scheme factorial type 2x2 (two varieties of plant corn to silage, with the presence or absence of Bt gene, with five animals per treatment. These animals were housed in metabolism cages, with collector and separator feces and urine for 21 days, comprising 8 days for diet adaptation and 7 days for determination of intake, followed by 6 days of collection of feces, to measure DMI (g/day, CDA DM, CP and NDF. Samples of feed offered, leftovers and feces were identified and placed in a circulating air oven maintained at 55°C to constant weight. The analyses were performed in Bromatological Analysis Laboratory of the Institute of Animal Science. To CTMS (g/day was interaction effect (p<0.05 than in the variety AG (779.36 was greater than DKB (637.52, because the DM content of the sheet AG (31.09 was superior to DKB (29.17. The AG (779.36 was higher than your counterpart isogenic without the gene (575.15 p<0.05. The DKB without the gene (637.52 did not differ (p>0.05 from your counterpart DKBBt with the gene (590.78. The lowest total DM intake in g/day was observed for varieties with Bt gene insertion (genetically modified organism - GMO and a possible explanation is the higher value of NDF in the silages of variety with the Bt gene in relation to their isogenic counterparts without the gene. The CDA, DM and NDF no had interaction effect between varieties factors and GMO (p>0
Radon diffusion coefficients in soils of varying moisture content
Papachristodoulou, C.; Ioannides, K.; Pavlides, S.
2009-04-01
Radon is a naturally occurring radioactive gas that is generated in the Earth's crust and is free to migrate through soil and be released to the atmosphere. Due to its unique properties, soil gas radon has been established as a powerful tracer used for a variety of purposes, such as exploring uranium ores, locating geothermal resources and hydrocarbon deposits, mapping geological faults, predicting seismic activity or volcanic eruptions and testing atmospheric transport models. Much attention has also been given to the radiological health hazard posed by increased radon concentrations in the living and working environment. In order to exploit radon profiles for geophysical purposes and also to predict its entry indoors, it is necessary to study its transport through soils. Among other factors, the importance of soil moisture in such studies has been largely highlighted and it is widely accepted that any measurement of radon transport parameters should be accompanied by a measurement of the soil moisture content. In principle, validation of transport models in the field is encountered by a large number of uncontrollable and varying parameters; laboratory methods are therefore preferred, allowing for experiments to be conducted under well-specified and uniform conditions. In this work, a laboratory technique has been applied for studying the effect of soil moisture content on radon diffusion. A vertical diffusion chamber was employed, in which radon was produced from a 226Ra source, was allowed to diffuse through a soil column and was finally monitored using a silicon surface barrier detector. By solving the steady-state radon diffusion equation, diffusion coefficients (D) were determined for soil samples of varying moisture content (m), from null (m=0) to saturation (m=1). For dry soil, a D value of 4.1×10-7 m2s-1 was determined, which increased moderately by a factor of ~3 for soil with low moisture content, i.e. up to m ~0.2. At higher water fractions, a decrease
Density dependence of the diffusion coefficient of alkali metals
International Nuclear Information System (INIS)
The effect of density on transport coefficients of liquid Li, Na and K at high temperatures using the method of Molecular Dynamics simulation has been studied. Simulation of these liquid alkali metals were carried out with 800 particles in simulation boxes with periodic boundary conditions imposed. In order to test the reliability of the interatomic potential used in the calculations, experimental data on the structural properties were compared with calculated results. The calculations showed a linear relationship between the density and the diffusion coefficient in all the systems investigated except in lithium, where, due to the small size of the atom, standard molecular dynamics simulation method may not be appropriate for calculating the properties of interest. (author)
Diffusion coefficient of metal vapours into rare gases. Mercury - argon
International Nuclear Information System (INIS)
The source information is present as well as the results of analysis and integration of data on mutual diffusion coefficient (MDC) of mercury - argon mixture at Hg concentration → 0 in 300-2500 K temperature range. Reference data on MDC for metal - inert gas binary mixtures obtained on the base of complex analysis of various information, as it exemplified by Hg-Ar pair, can be used as a part of metrological support at calibration of devices for determination MDC of gas - metal vapors
Signal Processing in MR Measurement of Diffusion Coefficients
Czech Academy of Sciences Publication Activity Database
Bartušek, Karel; Smékal, Z.; Liberda, O.
Žilina: University of Žilina, 2007 - (Mikolaj, J.; Bujňák, J.), s. 179-182 ISBN 978-80-8070-694-4. [European Conference of Young Research and Scientific Workers /7./ - TRANSCOM 2007. Žilina (SK), 25.06.2007-27.06.2007] R&D Projects: GA ČR(CZ) GA102/07/1086 Institutional research plan: CEZ:AV0Z20650511 Keywords : signal processing * MR measurement * diffusion coefficients Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Sorption and Diffusion Coefficients of Single Enantiomers in Chiral Membranes
Czech Academy of Sciences Publication Activity Database
Izák, Pavel; Sysel, P.; Hovorka, Š.; Randová, A.; Vychodilová, Hana; Červenková Šťastná, Lucie; Brožová, Libuše; Žitka, Jan
Praha : Česká společnost průmyslové chemie, 2015, s. 27 /p50./. ISBN 978-80-86238-73-9. [mezinárodní chemicko-technologická konference (ICCT 2015) /3./. Mikulov (CZ), 13.04.2015-15.04.2015] R&D Projects: GA ČR(CZ) GAP106/12/0569 Institutional support: RVO:67985858 ; RVO:61389013 Keywords : polymeric membranes * hyperbranched polyimide membranes * diffusion coefficients Subject RIV: CI - Industrial Chemistry, Chemical Engineering
Evaluation of downwelling diffuse attenuation coefficient algorithms in the Red Sea
Tiwari, Surya Prakash
2016-05-07
Despite the importance of the optical properties such as the downwelling diffuse attenuation coefficient for characterizing the upper water column, until recently no in situ optical measurements were published for the Red Sea. Kirby et al. used observations from the Coastal Zone Color Scanner to characterize the spatial and temporal variability of the diffuse attenuation coefficient (Kd(490)) in the Red Sea. To better understand optical variability and its utility in the Red Sea, it is imperative to comprehend the diffuse attenuation coefficient and its relationship with in situ properties. Two apparent optical properties, spectral remote sensing reflectance (Rrs) and the downwelling diffuse attenuation coefficient (Kd), are calculated from vertical profile measurements of downwelling irradiance (Ed) and upwelling radiance (Lu). Kd characterizes light penetration into water column that is important for understanding both the physical and biogeochemical environment, including water quality and the health of ocean environment. Our study tests the performance of the existing Kd(490) algorithms in the Red Sea and compares them against direct in situ measurements within various subdivisions of the Red Sea. Most standard algorithms either overestimated or underestimated with the measured in situ values of Kd. Consequently, these algorithms provided poor retrieval of Kd(490) for the Red Sea. Random errors were high for all algorithms and the correlation coefficients (r2) with in situ measurements were quite low. Hence, these algorithms may not be suitable for the Red Sea. Overall, statistical analyses of the various algorithms indicated that the existing algorithms are inadequate for the Red Sea. The present study suggests that reparameterizing existing algorithms or developing new regional algorithms is required to improve retrieval of Kd(490) for the Red Sea. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is
Araruna, F. D.; Braz e Silva, P.; Carvalho, R. R.; Rojas-Medar, M. A.
2015-06-01
We consider the motion of a viscous incompressible fluid consisting of two components with a diffusion effect obeying Fick's law in ℝ3. We prove that there exists a small time interval where the fluid variables converge uniformly as the viscosity and the diffusion coefficient tend to zero. In the limit, we find a non-homogeneous, non-viscous, incompressible fluid governed by an Euler-like system.
El-Shafai, S.A.A.M.; El-Gohary, F.; Verreth, J.A.J.; Schrama, J.W.; Gijzen, H.J.
2004-01-01
Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso-N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35%), corn (29%), wheat (20%), wheat bran (10%),
Garzó, Vicente; Murray, J. Aaron; Vega Reyes, Francisco
2013-04-01
The mass flux of a low-density granular binary mixture obtained previously by solving the Boltzmann equation by means of the Chapman-Enskog method is considered further. As in the elastic case, the associated transport coefficients D, Dp, and D' are given in terms of the solutions of a set of coupled linear integral equations which are approximately solved by considering the first and second Sonine approximations. The diffusion coefficients are explicitly obtained as functions of the coefficients of restitution and the parameters of the mixture (masses, diameters, and concentration) and their expressions hold for an arbitrary number of dimensions. In order to check the accuracy of the second Sonine correction for highly inelastic collisions, the Boltzmann equation is also numerically solved by means of the direct simulation Monte Carlo (DSMC) method to determine the mutual diffusion coefficient D in some special situations (self-diffusion problem and tracer limit). The comparison with DSMC results reveals that the second Sonine approximation to D improves the predictions made from the first Sonine approximation. We also study the granular segregation driven by a uni-directional thermal gradient. The segregation criterion is obtained from the so-called thermal diffusion factor Λ, which measures the amount of segregation parallel to the temperature gradient. The factor Λ is determined here by considering the second-order Sonine forms of the diffusion coefficients and its dependence on the coefficients of restitution is widely analyzed across the parameter space of the system. The results obtained in this paper extend previous works carried out in the tracer limit (vanishing mole fraction of one of the species) by some of the authors of the present paper.
Institute of Scientific and Technical Information of China (English)
肖吉; 陆九芳; 陈健; 李以圭
2001-01-01
Molecular dynamics simulation has been performed to determine the infinite-dilution diffusion coefficients of oxygen and nitrogen, and the diffusion coefficients of NaCl in supercritical water from 703.2- 763.2 K and 30-45 MPa.The results obtained show that the diffusion coefficients in supercritical water increase with temperature, while decreasing with pressure. Nevertheless, the diffusion coefficients in supercritical water are much larger than those in normal water.
High silicon self-diffusion coefficient in dry forsterite
Katsura, T.; Fei, H.; Hegoda, C.; Yamazaki, D.; Wiedenbeck, M.; Yurimoto, H.; Shcheka, S.
2012-12-01
Plastic deformation of mantle minerals is believed to be controlled by self-diffusion of the slowest species, which is silicon in silicate minerals. Olivine is the main constituent of upper mantle. Therefore, silicon self-diffusion coefficient (DSi) in olivine provides the basic information of upper mantle rheology. Dohmen et al. [1] and Jaoul et al. [2] measured the DSi at ambient pressure under dry conditions in natural olivine and iron-free forsterite, respectively. However, their results were ~2-3 orders of magnitude lower than that estimated from deformation experiments [3]. In this study, we revisited DSi in forsterite and resolved this discrepancy [4]. Forsterite single crystals were polished in colloidal silica solution, deposited with 300-500 nm of 29Si enriched Mg2SiO4 films, covered by 100 nm of ZrO2 films, and annealed at 1600-1800 K from ambient pressure up to 13 GPa using an ambient pressure furnace and multi-anvil apparatus. The surface roughness after diffusion were reduced to Geodyn. 4, 95-100. [3] Goetze and Kohlstedt (1973), JGR 78 (26), 5961-5971. [4] Fei et al. (2012), EPSL 345-348, 95-103. [5] Shimojuku et al. (2009), EPSL 284, 103-112.
Measurement of diffusion coefficient of propylene glycol in skin tissue
Genin, Vadim D.; Bashkatov, Alexey N.; Genina, Elina A.; Tuchin, Valery V.
2015-03-01
Optical clearing of the rat skin under the action of propylene glycol was studied ex vivo. It was found that collimated transmittance of skin samples increased, whereas weight and thickness of the samples decreased during propylene glycol penetration in skin tissue. A mechanism of the optical clearing under the action of propylene glycol is discussed. Diffusion coefficient of propylene glycol in skin tissue ex vivo has been estimated as (1.35±0.95)×10-7 cm2/s with the taking into account of kinetics of both weight and thickness of skin samples. The presented results can be useful for enhancement of many methods of laser therapy and optical diagnostics of skin diseases and localization of subcutaneous neoplasms.
Directory of Open Access Journals (Sweden)
Lorena Sigaut
2014-06-01
Full Text Available The gradient of Bicoid (Bcd is key for the establishment of the anterior-posterior axis in Drosophila embryos. The gradient properties are compatible with the SDD model in which Bcd is synthesized at the anterior pole and then diffuses into the embryo and is degraded with a characteristic time. Within this model, the Bcd diffusion coefficient is critical to set the timescale of gradient formation. This coefficient has been measured using two optical techniques, Fluorescence Recovery After Photobleaching (FRAP and Fluorescence Correlation Spectroscopy (FCS, obtaining estimates in which the FCS value is an order of magnitude larger than the FRAP one. This discrepancy raises the following questions: which estimate is "correct''; what is the reason for the disparity; and can the SDD model explain Bcd gradient formation within the experimentally observed times? In this paper, we use a simple biophysical model in which Bcd diffuses and interacts with binding sites to show that both the FRAP and the FCS estimates may be correct and compatible with the observed timescale of gradient formation. The discrepancy arises from the fact that FCS and FRAP report on different effective (concentration dependent diffusion coefficients, one of which describes the spreading rate of the individual Bcd molecules (the messengers and the other one that of their concentration (the message. The latter is the one that is more relevant for the gradient establishment and is compatible with its formation within the experimentally observed times.
On applicability of permanent coefficient model to diffusion description in solid state
International Nuclear Information System (INIS)
A mathematical method is assessed using the model of the constant diffusion coefficients for the solution of diffusion equations in bynary and multicomponent systems. Consideration is given to the solution of a direct problem, viz., determination of element concentration from available diffusion coefficients, and a inverse problem, viz., determination of the diffusion coefficients from known concentration curves. Errors due to using this method are estimated (particularly, in the case of the Fe-Cr-Ni ternary system)
Optimal estimation of the diffusion coefficient from non-averaged and averaged noisy magnitude data
Kristoffersen, Anders
2007-08-01
The magnitude operation changes the signal distribution in MRI images from Gaussian to Rician. This introduces a bias that must be taken into account when estimating the apparent diffusion coefficient. Several estimators are known in the literature. In the present paper, two novel schemes are proposed. Both are based on simple least squares fitting of the measured signal, either to the median (MD) or to the maximum probability (MP) value of the Probability Density Function (PDF). Fitting to the mean (MN) or a high signal-to-noise ratio approximation to the mean (HS) is also possible. Special attention is paid to the case of averaged magnitude images. The PDF, which cannot be expressed in closed form, is analyzed numerically. A scheme for performing maximum likelihood (ML) estimation from averaged magnitude images is proposed. The performance of several estimators is evaluated by Monte Carlo (MC) simulations. We focus on typical clinical situations, where the number of acquisitions is limited. For non-averaged data the optimal choice is found to be MP or HS, whereas uncorrected schemes and the power image (PI) method should be avoided. For averaged data MD and ML perform equally well, whereas uncorrected schemes and HS are inadequate. MD provides easier implementation and higher computational efficiency than ML. Unbiased estimation of the diffusion coefficient allows high resolution diffusion tensor imaging (DTI) and may therefore help solving the problem of crossing fibers encountered in white matter tractography.
International Nuclear Information System (INIS)
The diffusion coefficients of hydrogen gas dissolved in water-saturated, compacted montmorillonite are required to estimate the performance of bentonite buffer materials for geological disposal of nuclear waste. As part of the effort to determine the diffusion coefficients, the diffusion coefficients of helium in water-saturated, compacted calcium montmorillonite (Ca-montmorillonite) were determined as a function of dry density, 0.78 to 1.37x103kg m-3, by a transient diffusion method. The diffusion coefficients were from 8.3x10-10m2s-1 at 0.78x103kgm-3 to 2.8x10-10m2s-1 at 1.37x103kgm-3. The data obtained by this diffusion experiment of helium were highly reproducible. The diffusion coefficients of helium in Ca-montmorillonite were somewhat larger than those previously obtained for helium in sodium montmorillonite (Na-montmorillonite). The diffusion coefficients of hydrogen gas in the montmorillonites were roughly estimated using the diffusion coefficients of helium. These estimates were based on assumptions that both helium and hydrogen molecules are non-adsorptive and that the geometric factors in the compacted montmorillonites are approximately the same for diffusion of helium and diffusion of hydrogen. (author)
Inner zone electron radial diffusion coefficients - An update with Van Allen Probes MagEIS data
O'Brien, Paul; Fennell, Joseph; Guild, Timothy; Mazur, Joseph; Claudepierre, Seth; Clemmons, James; Turner, Drew; Blake, Bernard; Roeder, James
2016-07-01
Using MagEIS data from NASA's recent Van Allen Probes mission, we estimate the quiet-time radial diffusion coefficients for electrons in the inner radiation belt and slot, for energies up to ~700 keV. We provide observational evidence that energy diffusion is negligible. The main dynamic processes, then, are radial diffusion and elastic pitch angle scattering. We use a coordinate system in which these two modes of diffusion are separable. Then we integrate over pitch angle to obtain a field line content whose dynamics consist of radial diffusion and loss to the atmosphere. We estimate the loss timescale from periods of exponential decay in the time series. We then estimate the radial diffusion coefficient from the temporal and radial variation of the field line content. We show that our diffusion coefficients agree well with previously determined values. Our coefficients are consistent with diffusion by electrostatic impulses, whereas outer zone radial diffusion is thought to be dominated by electromagnetic fluctuations.
Impact of Hygrothermal and Loading Conditions on Apparent Diffusivity of GFRP Composites
Directory of Open Access Journals (Sweden)
Sushma SINGH
2014-02-01
Full Text Available Glass fibre-reinforced polymer (GFRP has been used as an alternative to steel in concrete due to high strength-to-weight ratio, high stiffness-to-weight ratio, and corrosion and fatigue resistance. The main environmental factors for the deterioration of GFRP sandwich composites are temperature, sunshine, water/moisture, alkalinity and load. Most of the early durability tests were carried out with reference to application of FRP (Fibre Reinforced Polymer in aerospace industries. Hygrothermal behaviour of preloaded sandwich structure immersed in water is examined herein. Moisture uptake was monitored for 50 days yielding percentage weight gain curves for samples of matrix (epoxy and sandwich structure with different core thickness. The apparent diffusivity values extracted from the weight gain are significantly greater for initial days for greater core thickness sandwich structures.
Delgado, J. M. P. Q.; Ramos, N. M. M.; de Freitas, V. P.
2011-11-01
This work proposes two simple dynamic methods that provide an accurate method for measurement of diffusion coefficients in building materials. Experimental measurements of moisture diffusion coefficients covered three commonly used building materials and they were carried out for a range of the relevant parameters, as temperature and relative humidity. The diffusion coefficients obtained by the two dynamic methods show a deviation comparatively to the steady-sate cup method; however, this variance is in accordance with the results presented in literature.
Prediction of diffusion coefficients of chlorophenols in water by computer simulation
Martins, Luís F. G.; Parreira, M. Cristina B.; Prates Ramalho, João P.; Morgado, Pedro; Filipe, Eduardo. J. M.
2015-01-01
Intra-diffusion coefficients of seven chlorophenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,6-dichlorophenol and pentachlorophenol) in water were determined by computer simulation (molecular dynamics) for dilute solutions at three different temperatures and the corresponding mutual diffusion coefficients estimated. The mutual diffusion coefficients of 2-chlorophenol in water agree with the available experimental results from the...
Buffie, Kaitlynn; Heesen, Volker; Shalchi, Andreas
2012-01-01
Diffusion coefficients are usually used to describe the propagation of Cosmic Rays through the Universe. Whereas such transport parameters can be obtained from experiments in the Solar System, it is difficult to determine diffusion coefficients in the Milky Way or in external galaxies. Recently a value for the perpendicular diffusion coefficient in the nearby starburst halaxy NGC 253 has been proposed. In the present paper we reproduce this value theoretically by using an advanced analytical ...
van Beijeren, H.; Kehr, K. W.
1986-01-01
The correlation factor, defined as the ratio between the tracer diffusion coefficient in lattice gases and the diffusion coefficient for a corresponding uncorrelated random walk, is known to assume a very simple form under certain conditions. A simple derivation of this is given with the aid of the Green-Kubo formula for the tracer diffusion coefficient and it is generalised to a frequency-dependent correlation factor. The application to lattice gases with nearly vanishing vacancy concentrati...
LUNG DIFFUSION CAPACITY CAN PREDICT MAXIMAL EXERCISE IN APPARENTLY HEALTHY HEAVY SMOKERS
Directory of Open Access Journals (Sweden)
Alfredo Chetta
2008-06-01
Full Text Available Chronic exposure to tobacco smoking may damage lung and heart function. The aim of this study was to assess maximal exercise capacity and its relationship with lung function in apparently healthy smokers. We recruited 15 heavy smokers (age 47 years ± 7, BMI 25 kg/m2 ± 3, pack/years 32 ± 9 without any cardiovascular or pulmonary signs and symptoms. Fifteen healthy non smoking subjects were enrolled as a control group. All subjects underwent pulmonary function tests, electrocardiograms at rest and graded cycle exercise tests. In smokers and controls, resting lung and cardiac function parameters were in the normal range, apart from diffusing lung capacity (TLCO values which were significantly lower in smokers (p < 0.05. As compared to controls, smokers presented lower maximal exercise capacity with lower values at peak of exercise of oxygen uptake (peak VO2, workload, oxygen uptake/watt ratio and oxygen pulse (p < 0.05 and higher dyspnoea perception (p < 0.05. Moreover, peak VO2, maximal workload and oxygen pulse at peak exercise were related to and predicted by TLCO (p < 0. 05. Our study confirms that maximal exercise capacity is reduced in apparently healthy heavy smokers, and shows that TLCO explains some of the variance in maximal exercise
Method for quantitative determination of a small difference between diffusion coefficients
International Nuclear Information System (INIS)
Small differences between diffusion coefficients are determined by separative diffusion in the transient state. The method compares experimental results for cylindrical diffusion with computer results. As an example the isotope effect in the diffusion of uranyl nitrate in agar gel was investigated. (U.S.)
Estimation of diffusion coefficient of lanthanum ions from one-dimensional Liesegang farmation
International Nuclear Information System (INIS)
Experimental conditions for obtaining Liesegang rings in the growth of lanthanum molybdate crystals in silica gel by single diffusion technique have been discussed. The time law, spacing law and the law relating diffusion depth and width are verified. Making use of Fick's law of diffusion, a method has been devised to estimate the diffusion coefficient of lanthanum ions in silica gel and the various parameters under which the coefficient varies are investigated. (author)
Institute of Scientific and Technical Information of China (English)
郭成伟; 梁长虹; 张水兴; 沈三弟; 刘再毅; 贾乾君
2011-01-01
.0 h and 48. 0 h IRI groups, they were (80±8), (181 ±34), (413 ±62), (474 ±83), (424 ±41 ),(332 ±41 )and(302 ±39) U/L for the levels of ALT,and (79 ± 10), (454 ±55), (547 ±72), (607±31 ), (649 ±79), (785 ±49) and ( 1526 ± 167) U/L for the AST respectively. The levels of AST and ALT in IRI groups were significantly higher than those in the Sham group ( P ＜ 0. 01 ). Histological findings showed diffuse hepatocytes swelling and erythrocytes depositing in the hepatic sinusoids, portal area, central venous and arterials at the initial phase. With the injury aggravated, inflammatory cell infiltration,hepatocyte nuclear condensation of apoptosis, sinusoidal dissociation and coagulation necrosis developed eventually. Conclusion 3.0 T DWI can monitor the pathological process of rabbit liver ischemia reperfusion injury dynamically, and provides a feasible imaging modality for clinical diagnosis and treatment.%目的 探讨DWI及ADC值对兔肝缺血再灌注损伤（IRI）的诊断价值及通过与肝酶、病理对照研究探讨其病理生理机制。方法 新西兰大白兔42只，用数字表法随机分成7组，每组6只。按照IRI后行MR扫描时间分为0.5、2.0、6.0、12.0、24.0和48.0 h IRI组及假手术（Sham）组。IRI组阻断肝左叶血供60 min后，恢复血供。Sham组未作缺血处理。采用3.0 T DWI，梯度因子(b)＝20、50、100、200、300、400、500、600 s/mm2，同时行T2WI、T1WI和T1WI增强扫描，并行组织病理学和肝酶学丙氨酸转氨酶(ALT)和天冬氨酸转氨酶(AST)检查。不同b值下多组ADC值、各IRI与Sham组的AST、ALT值的比较采用单因素方差分析，组间均数差异的比较采用LSD-t法。结果 ADC值的总体变化趋势是在复氧后0.5h明显下降，然后在2.0h组急剧上升，经过6.0～12.0h缓慢上升后，24.0h组再次下降，于48.0 h组ADC明显升高。B值分别为20、50、100、200、300 s/mm2时，Sham组ADC值分别为(3.47±0.53)×10-3、(3.11±0
Energy Technology Data Exchange (ETDEWEB)
Tringe, J.W., E-mail: tringe2@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA (United States); Ileri, N. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA (United States); Department of Chemical Engineering & Materials Science, University of California, Davis, CA (United States); Levie, H.W. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA (United States); Stroeve, P.; Ustach, V.; Faller, R. [Department of Chemical Engineering & Materials Science, University of California, Davis, CA (United States); Renaud, P. [Swiss Federal Institute of Technology, Lausanne, (EPFL) (Switzerland)
2015-08-18
Highlights: • WGA proteins in nanochannels modeled by Molecular Dynamics and Monte Carlo. • Protein surface coverage characterized by atomic force microscopy. • Models indicate transport characteristics depend strongly on surface coverage. • Results resolve of a four orders of magnitude difference in diffusion coefficient values. - Abstract: We use Molecular Dynamics and Monte Carlo simulations to examine molecular transport phenomena in nanochannels, explaining four orders of magnitude difference in wheat germ agglutinin (WGA) protein diffusion rates observed by fluorescence correlation spectroscopy (FCS) and by direct imaging of fluorescently-labeled proteins. We first use the ESPResSo Molecular Dynamics code to estimate the surface transport distance for neutral and charged proteins. We then employ a Monte Carlo model to calculate the paths of protein molecules on surfaces and in the bulk liquid transport medium. Our results show that the transport characteristics depend strongly on the degree of molecular surface coverage. Atomic force microscope characterization of surfaces exposed to WGA proteins for 1000 s show large protein aggregates consistent with the predicted coverage. These calculations and experiments provide useful insight into the details of molecular motion in confined geometries.
International Nuclear Information System (INIS)
Highlights: • WGA proteins in nanochannels modeled by Molecular Dynamics and Monte Carlo. • Protein surface coverage characterized by atomic force microscopy. • Models indicate transport characteristics depend strongly on surface coverage. • Results resolve of a four orders of magnitude difference in diffusion coefficient values. - Abstract: We use Molecular Dynamics and Monte Carlo simulations to examine molecular transport phenomena in nanochannels, explaining four orders of magnitude difference in wheat germ agglutinin (WGA) protein diffusion rates observed by fluorescence correlation spectroscopy (FCS) and by direct imaging of fluorescently-labeled proteins. We first use the ESPResSo Molecular Dynamics code to estimate the surface transport distance for neutral and charged proteins. We then employ a Monte Carlo model to calculate the paths of protein molecules on surfaces and in the bulk liquid transport medium. Our results show that the transport characteristics depend strongly on the degree of molecular surface coverage. Atomic force microscope characterization of surfaces exposed to WGA proteins for 1000 s show large protein aggregates consistent with the predicted coverage. These calculations and experiments provide useful insight into the details of molecular motion in confined geometries
Zhigao Liao; Jiuping Xu; Liming Yao
2013-01-01
This paper studies the innovation diffusion problem with the affection of urbanization, proposing a dynamical innovation diffusion model with fuzzy coefficient, and uses the shifting rate of people from rural areas stepping into urban areas to show the process of urbanization. The numerical simulation shows the diffusion process for telephones in China with Genetic Algorithms and this model is effective to show the process of innovation diffusion with the condition of urbanization process.
Asymptotic Behavior of a Competition-Diffusion System with Variable Coefficients and Time Delays
Miguel Uh Zapata; Eric Avila Vales; Angel G. Estrella
2008-01-01
A class of time-delay reaction-diffusion systems with variable coefficients which arise from the model of two competing ecological species is discussed. An asymptotic global attractor is established in terms of the variable coefficients, independent of the time delays and the effect of diffusion by the upper-lower solutions and iteration method.
The apparent diffusion coefficient of water in gray and white matter of the infant brain
DEFF Research Database (Denmark)
Toft, P B; Leth, H; Peitersen, Birgit; Lou, H C; Thomsen, C
1996-01-01
before it appeared on T1- or T2-weighted images. In gray and white matter, the mean ADC ranged from 0.95 x 10(-9) to 1.76 x 10(-9) m2/s. In the frontal and occipital white matter, in the genu corporis callosi, and in the lentiform nucleus, the ADC decreased with increasing age. The cortex/white matter...... ratio of the ADC increased with age and approached 1 at the age of 30 weeks. CONCLUSION: ADC maps add information to the T1 and T2 images about the size and course of unmyelinated as well as myelinated tracts in the immature brain....
International Nuclear Information System (INIS)
Objective: To investigate the predictive value of ADC value in grading of neuroepithelial tumors. Methods: The clinical data and images of 70 patients with neuroepithelial tumors pathologically proven were collected and analyzed retrospectively. All the patients were classified into low (WHO I or II) and high (WHO III or IV) grade groups which included 40 and 30 cases respectively according to the 2007 WHO classification of tumours of the central nervous system. All the patients underwent plain and contrast-enhanced MR scan and DWI before surgery. The minimum ADC (MinADC) value was measured postoperatively on ADC maps. The Ki-67 labeling index (Ki-67 LI) of tumor tissue was determined by immunohistochemistry. MinADC values for two groups were analyzed using student t test, while the age and Ki-67 LI for the two groups was analyzed using Mann-Whitney test (P-3 mm2/s] of the low grade group was significantly higher than that [(0.74±0.18) x 10-3 mm2/s] of the high grade group (t=5.42, P-3 mm2/s for the differentiation between high and low grade neuroepithelial tumors provided the best combination of sensitivity (90.0%) and specificity (77.5%) (receiver operating characteristic analysis). Conclusion: MinADC value is helpful for prediction of neuroepithelial tumor grade.. (authors)
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Objective: To analyze the differences of ADC values in breasts of women of different ages and different menstrual phases, so as to direct the choice of the examination time of MR DWI. Methods: The breasts of 65 healthy volunteers were scanned with the routine MRI plain scan and DWI in the menstrual, proliferative and secretary phases. DWI was conducted with single shot echo planar imaging technique and b value were 0, 1000 s/mm2. The women were divided into three groups: Group 1 (aged 20 to 29 years, 21 cases), Group 2 (aged 30 to 39, 21 cases), and Group 3 (aged 40 to 49, 23 cases). The ADC values of all 130 breasts at nipple level in the different phases were measured. The ADC values in the three age groups and in the different menstrual phases were compared using ANOVA. Results: The mean ADC values of Group 1 were (2.14±0.14) × 10-3, (2.03±0.18) × 10-3 and (2.10±0.19) × 10-3 mm2/s for left breast, and (2.08±0.17) × 10-3. (2.02±0.16) × 10-3 and (2.09±0.17) × 10-3 mm2/s for right breast in the menstrual, proliferative and secretary phases. They were slightly higher than Group 3, which were (2.02±0.27) × 10-3 (1.97±0.25) × 10-3 and (2.03±0.22) × 10-3 mm2/s for left breast and (1.99±0.29) × 10-3, (1.93±0.26) × 10-3 and (2.03±0.28) × 10-3 mm2/s for right breast. The mean ADC values of Group 2 [left breast: ( 1.94 + 0. 25) × 10-3, (1.91±0.21) × 10-3 and (1.97±0.21) × 10-3 mm2/s; right breast: (1.97±0.26) × 10-3, (1.89± 0.25) × 10-3 and (1.96±0.22) × 10-3 mm2/s] were the lowest among the three age groups. There were significant differences in different menstrual phases (F=23.600, P 0.05). Conclusions: The mean ADC values of breasts decrease markedly in the proliferative phase. The effects of the menstrual cycle on the breast ADC values should be considered in the evaluation of breast diseases with DWI. (authors)
Electrophoretic method for the determination of diffusion coefficients of ions in aqueous solutions
International Nuclear Information System (INIS)
The electrophoretic method was recently developed for the determination of diffusion coefficients of ions in aqueous solution. By solving the Fick's second law in the presence of unlimited media and constant quantity of diffusing species we obtain a relationship between the diffusion coefficient and the standard deviation of the distribution profile. The diffusion coefficients of Cd(II), In(III), Zr(IV), Hf(IV), Pu(VI) and [InDTPA]2- in nitric acid solution were determined as well as the effective charge of In-DTPA complex at pH 4.50. (author)
Data set for diffusion coefficients of alloying elements in dilute Mg alloys from first-principles
Directory of Open Access Journals (Sweden)
Bi-Cheng Zhou
2015-12-01
Full Text Available Diffusion coefficients of alloying elements in Mg are critical for the development of new Mg alloys for lightweight applications. Here we present the data set of the temperature-dependent dilute tracer diffusion coefficients for 47 substitutional alloying elements in hexagonal closed packed (hcp Mg calculated from first-principles calculations based on density functional theory (DFT by combining transition state theory and an 8-frequency model. Benchmark for the DFT calculations and systematic comparison with experimental diffusion data are also presented. The data set refers to “Diffusion coefficients of alloying elements in dilute Mg alloys: A comprehensive first-principles study” by Zhou et al. [1].
International Nuclear Information System (INIS)
6-gingerol and 6-shogaol are the main constituents as anti-inflammatory or bioactive compounds from zingiber officinale Roscoe. These bioactive compounds have been proven for inflammatory disease, antioxidatives and anticancer. The effect of temperature on diffusion coefficient for 6-gingerol and 6-shogaol were studied in subcritical water extraction. The diffusion coefficient was determined by Fick's second law. By neglecting external mass transfer and solid particle in spherical form, a linear portion of Ln (1-(Ct/Co)) versus time was plotted in determining the diffusion coefficient. 6-gingerol obtained the higher yield at 130°C with diffusion coefficient of 8.582x10−11 m2/s whilst for 6-shogaol, the higher yield and diffusion coefficient at 170°C and 19.417 × 10−11 m2/s.
Molecular Dynamics Simulations of Self-diffusion Coefficients ofExponential-six Fluids
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Self-diffusion coefficients of exponential-six fluids are studied using equilibrium moleculardynamics simulation technique. Mean-square displacements and velocity autocorrelationfunctions are used to calculate self-diffusion coefficients through Einstein equation and Green-Kuboformula. It has been found that simulation results are in good agreement with experimental data for liquidargon which is taken as exponential-six fluid. The effects of density, temperature and steepness factor forrepulsive part of exponential-six potential on self-diffusion coefficients are also investigated. Thesimulation results indicate that the self-diffusion coefficient of exponential-six fluid increases astemperature increases and density decreases. In addition, the larger self-diffusion coefficients are obtainedas the steepness factor increases at the same temperature and density condition.
Ilia Anisa, Nor; Azian, Noor; Sharizan, Mohd; Iwai, Yoshio
2014-04-01
6-gingerol and 6-shogaol are the main constituents as anti-inflammatory or bioactive compounds from zingiber officinale Roscoe. These bioactive compounds have been proven for inflammatory disease, antioxidatives and anticancer. The effect of temperature on diffusion coefficient for 6-gingerol and 6-shogaol were studied in subcritical water extraction. The diffusion coefficient was determined by Fick's second law. By neglecting external mass transfer and solid particle in spherical form, a linear portion of Ln (1-(Ct/Co)) versus time was plotted in determining the diffusion coefficient. 6-gingerol obtained the higher yield at 130°C with diffusion coefficient of 8.582x10-11 m2/s whilst for 6-shogaol, the higher yield and diffusion coefficient at 170°C and 19.417 × 10-11 m2/s.
International Nuclear Information System (INIS)
Procedure of calculating the parameters of continuous Markov diffusion process (drift and diffusion coefficients) during its application for approximating the ageing processes for separate NPP equipment is presented, taking into account the latter's specific peculiarities. Question, related to the accuracy of mch an approximation is discussed. It is shown, that coefficients of Markov process drift and diffusion may be calculated through the first derivatives by the time of mathematical expectation and dispersion process. To determine time dependences of mathematical expectation and dispersion process it is proposed to use regression analysis methods. Obtaining the interval estimations of continuous Markov diffusion process parameters mentioned is considered
On the Diffusion Coefficient of Water in Polymer Electrolyte Membranes
DEFF Research Database (Denmark)
Olesen, Anders Christian; Berning, Torsten; Kær, Søren Knudsen
2012-01-01
The Fickian diffusivity of water in Nafion has been shown to exhibit a local maximum. In the present research effort it is shown that this spike vanishes if the equilibrium water content and chemical diffusivity are modeled carefully. Further, it is shown that permeation experiments falsely can g...
Institute of Scientific and Technical Information of China (English)
张连顺; 张春平; 王新宇; 祁胜文; 许棠; 田建国; 张光寅
2002-01-01
The applicability of diffusion theory for the determination of tissue optical properties from steady-state diffuse reflectance is investigated. Analytical expressions from diffusion theory using the two most commonly assumed boundary conditions at the air-tissue interface and the two definitions of the diffusion coefficient are compared with Monte Carlo simulations. The effects of the choice of the boundary conditions and diffusion coefficients on the accuracy of the findings for the optical parameters are quantified, and criteria for accurate curve-fitting algorithms are developed. It is shown that the error in deriving the optical coefficients is considerably smaller for the solution which uses the extrapolated boundary condition and the diffusion coefficient independence of absorption coefficient, compared to the other three solutions.
International Nuclear Information System (INIS)
Experimental determination of diffusion invariant coefficients in a four-component Fe-Cr-Ni-Co system is conducted for alloys with 16 mas.% of Cr, 13 mas.% of Ni, 2-14 mas.% of Co. Activation energies, corresponding to diffusion invariant coefficients are calculated by the least squares technique. The analysis of concentrational dependences of these coefficients has shown that under a low cobalt content the system can be characterized by the unique activation energy value
Mass-dependence of self-diffusion coefficients in disparate-mass binary fluid mixtures
I. Binas; I.Mryglod
2009-01-01
Self-diffusion coefficients of a binary fluid mixture with components differing only in their particle masses are studied, in particular the case when mass ratio μ of light and heavy particles tends to zero. These coefficients were calculated within the memory function formalism, using the systematic subsequence of approximations for the relaxation times of velocity autocorrelation function. We obtained a general relation for the self-diffusion coefficients which show polynomial dependence on...
Response-matrix directional diffusion coefficients for application within large cavities
International Nuclear Information System (INIS)
A deterministic definition of the directional diffusion coefficient is proposed which allows diffusion theory codes to adequately reproduce the transport effects within a large cavity. The methodology has been tested satisfactorily upon the TREAT Upgrade hodoscope slot. This preliminary testing illustrates that the directional diffusion coefficients were applicable to a wide range of perturbations of the original model, thus exhibiting a high degree of versatility
NMR measurements of solvent self-diffusion coefficients in polymer solutions
Blum, Frank D.; Pickup, Stephen; Waggoner, R. Allen
1989-11-01
The transport of solvents and other small molecules in polymer solutions is important in many areas such as reaction rates, drying of coatings, plasticizer loss, curing of resins, elimination of residual monomer, and controlled drug release. Some of the work done in our laboratory on the diffusion of small molecules in polymer solutions and dispersions is reviewed. The diffusion data was used to test the Vrentas and Duda's free-volume theory for self-diffusion coefficients; test the independence of the normalized solvent self-diffusion for several polymer-solvent systems; and predict the solvent loss curves for drying of coatings based on solvent self-diffusion coefficients.
The diffusion coefficient of water in biobased hydrogels were measured utilizing a simple NMR method. This method tracks the migration of deuterium oxide through imaging data that is fit to a diffusion equation. The results show that a 5 wt% soybean oil based hydrogel gives aqueous diffusion of 1.37...
Radioisotope spectrometric method to determine diffusion coefficients in metals and alloys
International Nuclear Information System (INIS)
A brief description of the spectrometric installation to study diffusion in metals using #betta#-decay radio-isotopes is presented. Diffusion coefficients of nickel in 70% Co-5% Fe-15% Si-10% B amorphous alloy are determined according to #betta#-radiation absorption in diffusion zone. Plate samples of 10x10 mm size and about 300 μm in thickness are used. Diffusion annealing is conducted during 100 hrs. The calculation of the diffusion coefficients has been carried out by the formula I/I0= esup(μsup(2)Dtau)erfc μ √ Dtau, where I0, I is an initial and a final radiation intensity; μ- an absorption coefficient of 63Ni #betta#-ray in the given material (at calculation μ=1.3x106 m-1 was taken); tau- duration of diffusion annealing; D- diffusion coefficient at the designed temperature. The value of the diffusion coefficient of nickel in 70% Co-5% Fe-15% S-10% B amorphous alloy at the temperature of 200 deg C is turned out to be equal to 4x10-21 m2/s. It should be noted that the self-diffusion coefficient of cobalt in Co-Fe alloy, found by extrapolation from high-temperature region, is equal to 10-35 m2/s, i.e. in 14 orders lower than that of the same basis in amorphous alloy
Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples
Energy Technology Data Exchange (ETDEWEB)
Kammerer, Catherine [University of Central Florida, Orlando; Kulkarni, Nagraj S [ORNL; Warmack, Robert J Bruce [ORNL; Perry, Kelly A [ORNL; Belova, Irina [University of Newcastle, NSW, Australia; Murch, Prof. Graeme [University of Newcastle, NSW, Australia; Sohn, Yong Ho [University of Central Florida
2013-08-01
Increasing use and development of lightweight Mgalloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.
Directory of Open Access Journals (Sweden)
Zhouhu Wu
2011-06-01
Full Text Available In the calculation of mixed-transport capacity of pollutants which were discharged from bank outfall of wide straight rivers or reservoirs, the lateral diffusion coefficient can better demonstrate the mixed-diffusion characteristics near the bank than the transverse diffusion coefficient. For deep rivers and reservoirs, the vertical diffusion coefficient is one of the important water quality parameters. Based on the theoretical calculation method of pollutant mixing zone, the unified equations of the standard curve and curved surface outside the borders of pollutant mixing zone were deduced, including the characteristic parameters of maximum length Ls, maximum width bs and maximum depth ds et al. The shape of curve is akin to semi-elliptic, and the shape of curved surface is akin to part ellipsoid, which is similar to the pollution of the mixing zone. The calculation equation of lateral diffusion coefficient or vertical diffusion coefficient which was determined by the maximum length and maximum width or maximum depth of the outer boundary of pollutant mixing zone near the discharge outfall and the mean velocity were put forward in this paper. The calculation method of the lateral diffusion coefficient or vertical diffusion coefficient which was overall controlled by the area or volume of pollutant mixing zone and the practical method of vertical diffusion coefficient which was determined by the concentration of surface transverse integration was proposed in the paper. The lateral diffusion coefficient of the downstream of Guangfu River in low water season was given, which was 0.27 m2/s by analyzing the data from field observation.
International Nuclear Information System (INIS)
Full text of publication follows: The long-term quantitative analysis of the migration behaviour of the relevant radionuclides (RN) within the geological barrier of a radioactive waste repository requires, amongst other data, the introduction of reliable transport parameters, as diffusion coefficients. Since the determination of diffusion coefficients within crystalline rocks is complex and requires long experimental times even for non-sorbing radionuclides, the data available in the literature are very scarce. The nuclear ion beam technique RBS (Rutherford Backscattering Spectrometry) that is successfully used to determine diffusion profiles in thin film science is here examined as possible suitable technique to determine the diffusion coefficients of different RN within granite. As first step, the technique sensitivity and limitations to analyse diffusion coefficients in granite samples is evaluated, considering that the technique is especially sensitive to heavy elements. The required experimental conditions in terms of experimental times, concentration and methodology of analysis are discussed. The diffusants were selected accounting the RBS sensitivity but also trying to cover different behaviours of critical RN and a wide range of possible oxidation states. In particular, Cs(I) was chosen as representative fission product, while as relevant actinides or homologues, the diffusion of Th(IV), U(IV) and Eu (III) was studied. The diffusion of these above-mentioned cations is compared to the diffusion of Re, and I as representative of anionic species. The methodology allowed evaluating diffusion coefficients in the granite samples and, for most of the elements, the values obtained are in agreement with the values found in the literature. The diffusion coefficients calculated ranged from 10-13 to 10-16 m2/s. It is remarkable that the RBS technique is especially promising to determine diffusion coefficients of high-sorbing RN and it is applicable to a wide range of
Seasonal changes of apparent thermal diffusivity of different kinds of soils
Dedecek, Petr; Safanda, Jan; Correia, Antonio; Rajver, Dusan; Cermak, Vladimir; Kresl, Milan
2013-04-01
The paper addresses the problem of seasonal changes of apparent thermal diffusivity (ATD) in different types of soils in different climatic conditions. The long-term (several years) temperature series recorded at observatories in Czechia, Slovenia and Portugal were processed using a program based on the error function solution of the heat conduction equation for a semi-infinite solid. The program simulates penetration of temperature changes represented by the observed time-temperature series in differently wide time floating intervals, and in different depth levels of the soil profile. Synthetic temperature series for different values of thermal diffusivity (with a step of 1E-8 m2/s) are automatically compared with measured temperature time series in a given depth. The ATD value minimizing the standard deviation of difference between the measured and computed temperature series is considered as the best approximation of reality. The method has been applied to the temperature series from (i) observatory in Prague, where the temperature monitoring in different kinds of soil (sand, bare clayey soil, grassy soil) and asphalt is running from 2002, (ii) Evora - Portugal (gravelly sand, running from 2005), and finally (iii) Malence - Slovenia (grassy clayey soil, running from 2003). The soil temperature is measured at the depths of 2, 5, 10, 20 and 50 cm at each of the observatories. Results have shown a gradual increase of the ATD with depth caused by the soil density gradient in case of Malence and Prague (excluding asphalt). The ATD of the upper part of sand (2 - 5 cm), contrary to grassy surface, is quite sensitive to weather pattern (e.g. periods of rain or drought), when the strong convective heat transport in soil can occur. The ATD values in Evora show an annual run connected with a long dry summer season. The seasonal pattern is characterized, especially in the upper part of soil, by a rapid decrease from 7*E-7 to 4*E-7 m2/s in June and a return to higher values
Velocity-Space Diffusion Coefficients Due to Full-Wave ICRF Fields in Toroidal Geometry
International Nuclear Information System (INIS)
Jaeger et al. have calculated bounce-averaged QL diffusion coefficients from AORSA full-wave fields, based on non-Maxwellian distributions from CQL3D Fokker-Planck code. A zero banana-width approximation is employed. Complementing this calculation, a fully numerical calculation of ion velocity diffusion coefficients using the full-wave fields in numerical tokamak equilibria has been implemented to determine the finite orbit width effects. The un-approximated Lorentz equation of motion is integrated to obtain the change in velocity after one complete poloidal transit of the tokamak. Averaging velocity changes over initial starting gyro-phase and toroidal angle gives bounce-averaged diffusion coefficients. The coefficients from the full-wave and Lorentz orbit methods are compared for an ITER DT second harmonic tritium ICRF heating case: the diffusion coefficients are similar in magnitude but reveal substantial finite orbit effects
Directory of Open Access Journals (Sweden)
Salem Abdelmalek
2014-11-01
Full Text Available In this article we construct the invariant regions for m-component reaction-diffusion systems with a tridiagonal symmetric Toeplitz matrix of diffusion coefficients and with nonhomogeneous boundary conditions. We establish the existence of global solutions, and use Lyapunov functional methods. The nonlinear reaction term is assumed to be of polynomial growth.
Measurement of effective air diffusion coefficients for trichloroethene in undisturbed soil cores
Bartelt-Hunt, Shannon L.; Smith, James A.
2002-06-01
In this study, we measure effective diffusion coefficients for trichloroethene in undisturbed soil samples taken from Picatinny Arsenal, New Jersey. The measured effective diffusion coefficients ranged from 0.0053 to 0.0609 cm 2/s over a range of air-filled porosity of 0.23-0.49. The experimental data were compared to several previously published relations that predict diffusion coefficients as a function of air-filled porosity and porosity. A multiple linear regression analysis was developed to determine if a modification of the exponents in Millington's [Science 130 (1959) 100] relation would better fit the experimental data. The literature relations appeared to generally underpredict the effective diffusion coefficient for the soil cores studied in this work. Inclusion of a particle-size distribution parameter, d10, did not significantly improve the fit of the linear regression equation. The effective diffusion coefficient and porosity data were used to recalculate estimates of diffusive flux through the subsurface made in a previous study performed at the field site. It was determined that the method of calculation used in the previous study resulted in an underprediction of diffusive flux from the subsurface. We conclude that although Millington's [Science 130 (1959) 100] relation works well to predict effective diffusion coefficients in homogeneous soils with relatively uniform particle-size distributions, it may be inaccurate for many natural soils with heterogeneous structure and/or non-uniform particle-size distributions.
Experimental setup for evaluation of radon effective diffusion coefficient in soil
International Nuclear Information System (INIS)
Full text: It has been well recognized that radon and its decay products inhalation significantly contributes to the exposure of public. Radon is mainly generated from soil, building material and ground water. The infiltration of radon gas from soil has been identified as one of the main mechanisms influencing indoor radon levels. Therefore, radon exhalation rate from soil is one of the most important factors for the evaluation of environmental radon levels. In order to estimate the radon exhalation rate, several parameters related to soil characteristic have to be determined (i.e. effective diffusion coefficient, porosity and moisture content). In this study, an optimum experimental set-up to evaluate the radon effective diffusion coefficient was examined. This experimental setup consists of radon source (radon chamber), measuring device (scintillation cell) and diffusion column. The radon chamber calibrated by PTB (Physikalisch-Technischen Bundesanstalt, Germany) was applied as the radon source system. Also the measuring device was calibrated by the same facilities. The diffusion column was filled with glass beads instead of soil. As radon does not generate from the glass beads, therefore, it was possible to evaluate the effective diffusion coefficient precisely. Considering quality assurance of this experimental set-up, preliminary experiments as checking leakage and evaluating the radon effective diffusion coefficient in gas phase were performed. And an analytical method which evaluates the effective diffusion coefficient in a short time was discussed in this study. In general, experimental method for evaluating the effective diffusion coefficient is classified in a steady state method and a transient method. The transient method can evaluate the effective diffusion coefficient in a short time, however, it is very difficult to reach the analytical solution because two independent variables (time and position) have to be treated at the same time. In this study
Model calculations for evaluation of bulk- and grain boundary diffusion coefficients
International Nuclear Information System (INIS)
Model calculations are developed for evaluation of bulk- and grain boundary diffusion coefficients in polycrystalline media in the case of a semi-infinite diffusion source. The Matrix is assumed to be either quasi-homogeneous or to be composed of grain material and ''grain boundary-material''. Using Whipple's solution of the diffusion equation the flux of material from the grain boundaries into the grain is considered additionally. Examples are given to show the possibility to classify experimentally found diffusion profiles. (author)
Optimal estimation of diffusion coefficients from single-particle trajectories
DEFF Research Database (Denmark)
Vestergaard, Christian L.; Blainey, Paul C.; Flyvbjerg, Henrik
2014-01-01
substrate, the CVE is biased by substrate motion. However, given some long time series and a substrate under some tension, an extended MLE can separate particle diffusion on the substrate from substrate motion in the laboratory frame. This provides benchmarks that allow removal of bias caused by substrate...
Diffusion coefficient of aqueous sulfur dioxide at 25/sup 0/C
Energy Technology Data Exchange (ETDEWEB)
Leaist, D.G.
1984-07-01
The diffusion coefficient of aqueous sulfur dioxide has been measured at 25/sup 0/C over the concentration range 0.003-0.1 mol dm/sup -3/ by the Harned conductimetric technique. At concentrations less than about 0.02 mol dm/sup -3/, extensive hydrolysis to bisulfite and hydrogen ions produces a sharp increase in the rate of diffusion of the sulfur dioxide component. The observed concentration dependence of the diffusion coefficient is consistent with theory for diffusion with simultaneous hydrolysis.
EFFECTIVE DIFFUSION AND EFFECTIVE DRAG COEFFICIENT OF A BROWNIAN PARTICLE IN A PERIODIC POTENTIAL
Institute of Scientific and Technical Information of China (English)
Hongyun Wang
2011-01-01
We study the stochastic motion of a Brownian particle driven by a constant force over a static periodic potential.We show that both the effective diffusion and the effective drag coefficient are mathematically well-defined and we derive analytic expressions for these two quantities.We then investigate the asymptotic behaviors of the effective diffusion and the effective drag coefficient,respectively,for small driving force and for large driving force.In the case of small driving force,the effective diffusion is reduced from its Brownian value by a factor that increases exponentially with the amplitude of the potential.The effective drag coefficient is increased by approximately the same factor.As a result,the Einstein relation between the diffusion coefficient and the drag coefficient is approximately valid when the driving force is small.For moderately large driving force,both the effective diffusion and the effective drag coefficient are increased from their Brownian values,and the Einstein relation breaks down. In the limit of very large driving force,both the effective diffusion and the effective drag coefficient converge to their Brownian values and the Einstein relation is once again valid.
International Nuclear Information System (INIS)
This document corresponds to the deliverable D2 of the Work Package 1 of the 'Spent Fuel Stability under repository conditions' (SFS) European project. It constitutes a synthesis report on relevant diffusion coefficients of fission products and helium in spent nuclear fuels at high and low temperatures. Coefficients corresponding to thermally activated diffusion were reviewed from literature data for O, U (self-diffusion coefficients), fission gases and other fission products. Data showed that thermal diffusion was irrelevant at temperatures expected in repository conditions. The occurrence of diffusion enhanced by alpha self-irradiation was studied through different theoretical approaches. A 'best estimate' value of the alpha self-irradiation diffusion coefficient, D (m2.s-1), is proposed. It is extrapolated from enhanced diffusion under irradiation observed in reactor and would be proportional to the volume alpha activity in the spent nuclear fuel, Av (Bq.m-3) as: D/Av ≅ 2.10-41 (m5)The migration of stable Pb in Oklo's uraninites was studied in order to validate the proposed diffusion coefficient. The obtained value is one order of magnitude higher than the theoretical proposed value. As for He behaviour in spent nuclear fuel, a few data are today available in open literature. The document will be completed as soon as new experimental results are available. (authors)
An atmospheric electrical method to determine the eddy diffusion coefficient
Indian Academy of Sciences (India)
M N Kulkarni; A K Kamra
2010-02-01
The ion–aerosol balance equations are solved to get the profiles of atmospheric electric parameters over the ground surface in an aerosol-rich environment under the conditions of surface radioactivity. Combining the earlier results for low aerosol concentrations and the present results for high aerosol concentrations, a relation is obtained between the average value of atmospheric electric space charge in the lowest ∼2m, the surface electric field and eddy diffusivity/aerosol concentration. The values of eddy diffusivity estimated from this method using some earlier measurements of space charge and surface electric field are in reasonably good agreement with those calculated from other standard methods using meteorological or electrical variables.
Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite
DEFF Research Database (Denmark)
Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.
2008-01-01
Abstract. In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated...
Evaluation of diffusion coefficients in multicomponent mixtures by means of the fluctuation theory
DEFF Research Database (Denmark)
Shapiro, Alexander
2003-01-01
We derive general expressions for diffusion coefficients in multicomponent non-ideal gas or liquid mixtures. The derivation is based on the general statistical theory of fluctuations around an equilibrium state. The matrix of diffusion coefficients is expressed in terms of the equilibrium...... characteristics. We demonstrate on several examples that the developed theory is in agreement with the established experimental facts and dependencies for the diffusion coefficients. (C) 2002 Elsevier Science B.V. All rights reserved....... thermodynamic characteristics of the mixture (such as molar densities and internal energy), as well as in terms of the newly introduced parameters, the penetration lengths. This result serves to reduce the problem of determining the diffusion coefficients to a smaller number of physically meaningful...
Leahy-Dios, Alana; Zhuo, Lin; Firoozabadi, Abbas
2008-05-22
New thermal diffusion coefficients of binary mixtures are measured for n-decane-n-alkanes and 1-methylnaphthalene-n-alkanes with 25 and 75 wt % at 25 degrees C and 1 atm using the thermogravitational column technique. The alkanes range from n-pentane to n-eicosane. The new results confirm the recently observed nonmonotonic behavior of thermal diffusion coefficients with molecular weight for binary mixtures of n-decane- n-alkanes at the compositions studied. In this work, the mobility and disparity effects on thermal diffusion coefficients are quantified for binary mixtures. We also show for the binary mixtures studied that the thermal diffusion coefficients and mixture viscosity, both nonequilibrium properties, are closely related. PMID:18438988
Diffusion Coefficient when fine Aerosol Media Propagate in a Confined Volume
Korovina N.V.; Zharova I.K.; Kudryashova O.B.; Titov S.S.
2016-01-01
An experimental estimation is reported of the value of the effective diffusion coefficient during aerosol deposition in a confined volume. Aerosol propagation regularities have experimentally been studied in a chamber of a complex configuration with different placement of aerosol generators.
Akimoto, Takuma
2016-01-01
Local diffusion coefficients in living cells are highly heterogeneous and may change over time. Such a time-dependent and spatially heterogeneous environment results in irreproducibility of single-particle-tracking measurements. Here, we provide rigorous descriptions of equilibrium and non-equilibrium diffusion processes for a heterogeneous diffusion model in living cells. We give exact solutions for the mean square displacement (MSD) and the relative standard deviation of the time-averaged MSD for equilibrium and non-equilibrium situations. We find that the time-averaged MSD grows linearly with time and that the diffusion coefficients are intrinsically random in non-equilibrium situations. Our findings pave the way for a theoretical understanding of irreproducible diffusion coefficients in cell biology.
International Nuclear Information System (INIS)
The apparent diffusivity of strontium-85 in the compacted MX-80 bentonite under different salinity conditions and dry densities was conducted were studied from the viewpoint of activation energy. Through in-diffusions experiments the effect of salinity on diffusion behavior of Sr-85 ions can also can be explained. As we know, Sr-90 is by product of the fission materials of nuclear wastes and should be manage properly. Sr-85 is radioactive isotope with the same chemical properties of Sr-90. Adsorption affects only non-steady-state diffusion while at the steady state (e.g., a constant concentration gradient between a constant source and a constant sink), there is no net uptake or release by adsorption, so adsorption has no effect on diffusion (Drever, James I., 1997). The changes in the basal spacing of bentonite as a function of salinity are needed to be observed by the X-ray diffraction method to understand the microstructure changes in diffusion pathways for Sr-85 in MX-80 bentonite. As we know, there could be three potential pathways for radionuclide diffusion in solution-saturated, compacted montmorillonite, i.e., pore water, external surfaces and the internal surface (interlayer spaces) of montmorillonite aggregates (Kozaki et al., 2008). So, it is important to understand the diffusion processes in term of apparent diffusivity of Sr-85 ions in different salinity concentration at low dry density of MX-80. Several parameters are needed in explaining the process such as dry density, activation energy, temperature dependence and concentration of the salinity solutions. (author)
The use of CACTUS to generate modified diffusion coefficients in LWRWIMS
International Nuclear Information System (INIS)
A new method has been devised in the lattice code, LWRWIMS, for modifying diffusion coefficients for poison pins. The method is based on an earlier one which used a one dimensional transport calculation of flux gradient and leakage to determine the effective diffusion coefficient. The improvement is to use a two dimensional characteristics transport calculation to overcome the approximations in geometry made previously. The report explains the theory of the method, describes its use within LWRWIMS, and gives some results obtained. (author)
FITTING OF THE DATA FOR DIFFUSION COEFFICIENTS IN UNSATURATED POROUS MEDIA
Energy Technology Data Exchange (ETDEWEB)
B. Bullard
1999-05-01
The purpose of this calculation is to evaluate diffusion coefficients in unsaturated porous media for use in the TSPA-VA analyses. Using experimental data, regression techniques were used to curve fit the diffusion coefficient in unsaturated porous media as a function of volumetric water content. This calculation substantiates the model fit used in Total System Performance Assessment-1995 An Evaluation of the Potential Yucca Mountain Repository (TSPA-1995), Section 6.5.4.
Diffusion Decay Coefficient for Chloride Ions of Concrete Containing Mineral Admixtures
Jae-Im Park; Kwang-Myong Lee; Soon-Oh Kwon; Su-Ho Bae; Sang-Hwa Jung; Sung-Won Yoo
2016-01-01
The diffusion coefficient for chloride ions and the diffusion decay coefficient for chloride ions are essential variables for a service life evaluation of concrete structures. They are influenced by water-binder ratio, exposure condition, curing temperature, cement type, and the type and use of mineral admixture. Mineral admixtures such as ground granulated blast furnace slag, fly ash, and silica fume have been increasingly used to improve resistance against chloride ions penetration in concr...
Diffusion Decay Coefficient for Chloride Ions of Concrete Containing Mineral Admixtures
Directory of Open Access Journals (Sweden)
Jae-Im Park
2016-01-01
Full Text Available The diffusion coefficient for chloride ions and the diffusion decay coefficient for chloride ions are essential variables for a service life evaluation of concrete structures. They are influenced by water-binder ratio, exposure condition, curing temperature, cement type, and the type and use of mineral admixture. Mineral admixtures such as ground granulated blast furnace slag, fly ash, and silica fume have been increasingly used to improve resistance against chloride ions penetration in concrete structures built in an offshore environment. However, there is not enough measured data to identify the statistical properties of diffusion decay coefficient for chloride ions in concrete using mineral admixtures. This paper is aimed at evaluating the diffusion decay coefficient for chloride ions of concrete using ordinary Portland cement or blended cement. NT BUILD 492 method, an electrophoresis experiment, was used to measure the diffusion coefficient for chloride ions with ages. It was revealed from the test results that the diffusion decay coefficient for chloride ions was significantly influenced by W/B and the replacement ratio of mineral admixtures.
Institute of Scientific and Technical Information of China (English)
LI Pengping; SU Dagen; WANG Shengnian; FAN Zhihong
2011-01-01
The influence of binder composition and pore structure of concrete on chloride diffusion coefficient in concrete were investigated by the natural immersion test, MIP test, SEM and EDS test, respectively. The experimental results showed that the effect of binder composition on chloride diffusion coefficient was the comprehensive result of concrete pore structure and binder hydration products, and the porosity and pore size distribution were the main factors that influence the changes of diffusion coefficient. The chloride diffusion coefficient decreased with increasing the curing temperature and the relative humidity. The hydration degree were promoted by improving curing temperatures, and then the porosity of concrete decreased and the proportion of gel pore and transitional pore increased, respectively. But the water evaporation decreased with increasing the relative humidity and then decreased porosity and increased the proportion of gel pore and transitional pore. Additionally, The chloride diffusion coefficient of concrete got the lower value when the appropriate replacement of fly ash in the ranges of 10%-20%, when the double-adding fly ash and slag content was 50%. The porosity increased and the ratio of C/S in C-S-H decreased with further increasing the fly ash content, which led to increase the chloride diffusion coefficient in concrete.
Diffusion Coefficient of Iodide ions in Aqueous Medium and in Vacuum: An Appraisal
International Nuclear Information System (INIS)
Diffusion Coefficient of iodide ion was determined through cyclic voltammetric technique and compared with the values in literature. The contribution of (a) the fractal surface of the electrode, and (b) possible involvement of subsequent chemical reaction (EC) to the peak current affecting the diffusion coefficient were analyzed. It was concluded that the diffusion coefficient obtained via peak current of the cyclic voltammogram corrected for sweep dependence could be relied upon. The diffusion coefficient, D, of ion in aqueous media is deduced to be 1.95 (± 0.05) *10 /sup -5/ cm /sup 2/ s /sup -1/. Fractal analysis showed there is very negligible effect of fractal surface of the electrode. Diffusion coefficient of iodide ion in vacuum was calculated from equation , where h is Planck constant and mI-, is the mass of iodide ion. D of in vacuum came out to be much smaller, 2.5 *10 /sup -6/ cm /sup 2/ s /sup -1/, as compared to the one in aqueous solution. This D may be considered as the lower limit of the diffusion coefficient of a species, here. (author)
L. W. Somathilake; Peiris, J. M. J. J.
2005-01-01
We deal with a mathematical model for a four-component chemical reaction-diffusion process. The model is described by a system of strongly coupled reaction-diffusion equations with different diffusion rates. The existence of the global solution of this reaction-diffusion system in unbounded domain is proved by using semigroup theory and estimates on the growth of solutions.
Imel, Adam; Miller, Brad; Holley, Wade; Baskaran, Durairaj; Mays, Jimmy; Dadmun, Mark
2015-03-01
The diffusion properties of nanoparticles in polymer nanocomposites are largely unknown and depend intimately on the dispersion of the nanoparticles. We examine the diffusion of soft, organic nanoparticles, which disperse in a polymer matrix due to the interpenetration of polymer chains and particles and the reduction in the depletion of entropy in the system. The impact of the presence of soft nanoparticles on the diffusion coefficient of polystyrene chains has recently been determined with neutron reflectivity. This was completed by monitoring the interdiffusion of deuterated and protonated polystyrene nanocomposite bilayers with and without the soft nanoparticles dispersed throughout both layers and extracting the diffusion coefficient from the one-dimensional solution to Fick's second law of diffusion. In this work, we extend this method to bilayer systems with only the soft nanoparticles as one of the layers and a linear deuterated polystyrene as an adjacent layer. The development of this method allows us to determine the tracer diffusion coefficient of the soft polystyrene nanoparticles for the first time by analyzing the mutual diffusion coefficient from Fick's second law and the fast and slow modes theories for diffusion.
International Nuclear Information System (INIS)
We discuss the role of the dynamic Oseen tensor in setting the time scales involved in the scaling of the time-dependent self-diffusion coefficient measured by diffusing wave spectroscopy. We elucidate the paradoxical short time behavior for which scaling is observed and clarify the possible discrepancies between theory and experiments
Layta Dinira; Barlah Rumhayati; Rachmat Triandi Tjahjanto
2013-01-01
Excess phosphate in natural water can cause algae grow rapidly, to the extent causing many fish deaths that led to the extinction of certain species. Therefore, an analysis or periodic observations of phosphate levels in the water is needed. The commonly used method is diffusive gradient in thin films (DGT) technique. The DGT technique is based on the ability of analyte to diffuse through a gel, which have a value named diffusion coefficient. This research was conducted in order to study the ...
Rengel Estévez, Raúl; Martín Martínez, María Jesús
2013-01-01
In this paper, the diffusivity in suspended monolayer graphene at low and high electric fields is investigated. The knowledge of this quantity and its dependence on the electric field is of primary importance not only for the investigation of the electronic transport properties of this material, but also for the development of accurate drift-diffusion models. The results have been obtained by means of an ensemble Monte Carlo simulation. For the calculation of the diffusion coefficient, two di...
Institute of Scientific and Technical Information of China (English)
Xin-yu Lai; Nan-rong Zhao
2013-01-01
Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts.A generalized Langevin equation is adopted to describe the diffusion dynamics.Mode-coupling theory is employed to calculate the memory kernel of friction.For simplicity,only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism.The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure.The effect of nanoparticle size and that of the polymer size are clarified explicitly.The structural functions,the friction kernel,as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length.We find that for small nanoparticles or short chain polymers,the characteristic short time non-Markov diffusion dynamics becomes more prominent,and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant.This constant due to the microscopic contributions will decrease with the increase of nanoparticle size,while increase with polymer size.Furthermore,our result of diffusion constant from modecoupling theory is compared with the value predicted from the Stokes-Einstein relation.It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers.Inversely,when nanonparticle is big,or polymer chain is short,the hydrodynamic contribution might play a significant role.
Modeling diffusion coefficients in binary mixtures of polar and non-polar compounds
DEFF Research Database (Denmark)
Medvedev, Oleg; Shapiro, Alexander
2005-01-01
The theory of transport coefficients in liquids, developed previously, is tested on a description of the diffusion coefficients in binary polar/non-polar mixtures, by applying advanced thermodynamic models. Comparison to a large set of experimental data shows good performance of the model. Only...... four temperature-independent parameters are required in order to describe the behavior of diffusion coefficients at different temperatures. The physical meaning of the parameters is analyzed. This makes it possible to reduce further their number to just two parameters for described mixtures with polar...
Energy Technology Data Exchange (ETDEWEB)
Maes, N.; Moors, H.; De Canniere, P.; Aertsens, M.; Put, M.
1997-03-01
Classical diffusion experiments for strongly retarded radionuclides take a very long time. The migration can be accelerated considerably by applying an electrical field across a saturated porous medium (electromigration). Under the influence of the electric field, the ions will attain a constant velocity which is related to the diffusion coefficient by the law of Einstein (V=zeED/KT). The displacement of the concentration profile is a direct measure for the diffusion coefficient. A description of the problems of pH-disturbances, electro-osmosis and dispersion is given and an the feasibility of the electromigration method is evaluated.
Calculation of the coefficient and dynamics of water diffusion in graphite joints
Institute of Scientific and Technical Information of China (English)
WANG Jun; LIU Wen-bin
2006-01-01
The coefficient and dynamics of water diffusion in adhesive-graphite joints were calculated insitu with energy dispersive X-ray (EDX) analysis, a method that is significantly simpler than elemental analysis. Water diffusion coefficient and dynamics of adhesive-graphite joints treated by different surface treatment methods were also investigated. Calculation results indicated that the water diffusion rate in adhesive-graphite joints treated by sandpaper was higher than that treated by chemical oxidation or by silane couple agent. Also the durability of graphite joints treated by coupling agent is superior to that treated by chemical oxidation or sandpaper burnishing.
The method of calculation of radiation stimulated diffusion coefficients of impurities in silicon
International Nuclear Information System (INIS)
The simplified method of calculation of radiation stimulated diffusion coefficients of impurities in semiconductors like calculation method of 'dilution' of lithium diffusion profile in silicon because of drift at 400 K is proposed. The diffusion coefficients of lithium and zinc in silicon under the action of cobalt-60 gamma-rays and gamma-neutron irradiation were determined. The method developed can be applied also in the case of electron and proton irradiation. With the use of this method the change of p-n junction level because of irradiation and correspondingly the degradation of main characteristics of photoelectrical converters can be calculated. (A.D. Avezov). 7 refs.; 2 figs.; 1 tab
Binary diffusion coefficients of L-histidine methyl ester dihydrochloride in aqueous solutions
International Nuclear Information System (INIS)
Highlights: • Mutual diffusion coefficients of L-histidine methyl ester dihydrochloride in aqueous solutions. • Influence of the thermodynamic and kinetic factors on the variation of the mutual diffusion coefficients. • Estimation of the hydrodynamic radius of L-histidine methyl ester dihydrochloride. - Abstract: The Taylor dispersion technique has been used for measuring mutual diffusion coefficients of L-histidine methyl ester as its dihydrochloride at T = 298.15 K and finite concentrations from (0.001 to 0.100) mol · dm−3. On the basis of experimental mutual diffusion coefficients, the hydrodynamic radii, Rh, the diffusion coefficient at infinite dilution D0 and the dependence of thermodynamic factors, FT, on the concentration, have been estimated using the Onsager–Fuoss equation. Further insight on the diffusion has been obtained from 1H and 13C NMR spectroscopy and DFT calculations, which suggest that the L-histidine methyl ester is present as its dication in acidic solution in a fully extended conformation, with considerable charge delocalization over the imidazolium ring. These experimental and computational results allow us to have a better understanding of the thermodynamic and kinetic behavior of this amino acid derivative in aqueous solutions
Entropy-scaling laws for diffusion coefficients in liquid metals under high pressures
International Nuclear Information System (INIS)
Molecular dynamic simulations on the liquid copper and tungsten are used to investigate the empirical entropy-scaling laws D*=A exp(BSex), proposed independently by Rosenfeld and Dzugutov for diffusion coefficient, under high pressure conditions. We show that the scaling laws hold rather well for them under high pressure conditions. Furthermore, both the original diffusion coefficients and the reduced diffusion coefficients exhibit an Arrhenius relationship DM=DM0 exp(−EM/KBT), (M=un,R,D) and the activation energy EM increases with increasing pressure, the diffusion pre-exponential factors (DR0 and DD0) are nearly independent of the pressure and element. The pair correlation entropy, S2, depends linearly on the reciprocal temperature S2=−ES/T, and the activation energy, ES, increases with increasing pressure. In particular, the ratios of the activation energies (Eun, ER, and ED) obtained from diffusion coefficients to the activation energy, ES, obtained from the entropy keep constants in the whole pressure range. Therefore, the entropy-scaling laws for the diffusion coefficients and the Arrhenius law are linked via the temperature dependence of entropy
Directory of Open Access Journals (Sweden)
Franco Marinozzi
2014-01-01
Full Text Available We firstly measured the swelling of single trabeculae from human femur heads during water imbibition. Since the swelling is caused by water diffusing from external surfaces to the core of the sample, by measuring the sample swelling over time, we obtained direct information about the transport of fluids through the intimate constituents of bone, where the mineralization process takes place. We developed an apparatus to measure the free expansion of the tissue during the imbibition. In particular, we measured the swelling along three natural axes (length L, width W, and thickness T of plate-like trabeculae. For this aim, we developed a 3D analytical model of the water uptake by the sample that was performed according to Fickian transport mechanism. The results were then utilized to predict the swelling over time along the three sample directions (L, W, T and the apparent diffusion coefficients DT, DW, and DL.
Dorval, Eric
2016-01-01
Neutron transport calculations by Monte Carlo methods are finding increased application in nuclear reactor simulations. In particular, a versatile approach entails the use of a 2-step pro-cedure, with Monte Carlo as a few-group cross section data generator at lattice level, followed by deterministic multi-group diffusion calculations at core level. In this thesis, the Serpent 2 Monte Carlo reactor physics burnup calculation code is used in order to test a set of diffusion coefficient model...
Mass-dependence of self-diffusion coefficients in disparate-mass binary fluid mixtures
Directory of Open Access Journals (Sweden)
I. Binas
2009-01-01
Full Text Available Self-diffusion coefficients of a binary fluid mixture with components differing only in their particle masses are studied, in particular the case when mass ratio μ of light and heavy particles tends to zero. These coefficients were calculated within the memory function formalism, using the systematic subsequence of approximations for the relaxation times of velocity autocorrelation function. We obtained a general relation for the self-diffusion coefficients which show polynomial dependence on the mass ratio μ. The obtained expression has a correct Brownian limit. We developed the hierarchy of approximations for the self-diffusion coefficients that tends to an exact result from above and below when the order of approximations increases.
Dense fluid self-diffusion coefficient calculations using perturbation theory and molecular dynamics
Directory of Open Access Journals (Sweden)
COELHO L. A. F.
1999-01-01
Full Text Available A procedure to correlate self-diffusion coefficients in dense fluids by using the perturbation theory (WCA coupled with the smooth-hard-sphere theory is presented and tested against molecular simulations and experimental data. This simple algebraic expression correlates well the self-diffusion coefficients of carbon dioxide, ethane, propane, ethylene, and sulfur hexafluoride. We have also performed canonical ensemble molecular dynamics simulations by using the Hoover-Nosé thermostat and the mean-square displacement formula to compute self-diffusion coefficients for the reference WCA intermolecular potential. The good agreement obtained from both methods, when compared with experimental data, suggests that the smooth-effective-sphere theory is a useful procedure to correlate diffusivity of pure substances.
An improved method for measuring the surface sound energy diffusion coefficient in a room
Institute of Scientific and Technical Information of China (English)
ZHANG Jiping; WU Shuoxian; LI Ningrong
2003-01-01
The partly specular reflection and partly diffusion reflection model is a convenientway to express the phenomena of surface sound energy scattering in room acoustics. Soundenergy diffusion coefficient becomes a key factor to study surface scattering. But there havebeen very few methods for determining the average sound energy diffusion coefficient. Vorlanderproposed such an easy one based on the correlation principle. However, his method ignoredthe correlation from direct sound, in which defect is present. A new approximate method forcalculating sound energy diffusion coefficient, including direct sound and first strong reflectionsis presented. Therefore, Vorlander's defect is overcome. In addition, with the aid of digitalmeasuring technology, a relevant measuring system was developed. The experiment resultshows that the method is improved than Vorlander's.
Directory of Open Access Journals (Sweden)
L. W. Somathilake
2005-01-01
Full Text Available We deal with a mathematical model for a four-component chemical reaction-diffusion process. The model is described by a system of strongly coupled reaction-diffusion equations with different diffusion rates. The existence of the global solution of this reaction-diffusion system in unbounded domain is proved by using semigroup theory and estimates on the growth of solutions.
Rafelski, Susanne M.; Keller, Lani C.; Alberts, Jonathan B.; Marshall, Wallace F
2011-01-01
The degree to which diffusion contributes to positioning cellular structures is an open question. Here we investigate the question of whether diffusive motion of centrin granules would allow them to interact with the mother centriole. The role of centrin granules in centriole duplication remains unclear, but some proposed functions of these granules, for example in providing pre-assembled centriole subunits, or by acting as unstable “pre-centrioles” that need to be captured by the mother cent...
DEFF Research Database (Denmark)
Jespersen, Sune Nørhøj; Lundell, Henrik; Sønderby, Casper Kaae;
2013-01-01
orientation dispersion when applied to macroscopically anisotropic systems. Here we propose a new framework, the d-PFG 5-design, to enable rotationally invariant estimation of double wave vector diffusion metrics (d-PFG). The method is based on the idea that an appropriate orientational average of the signal...... pairs of diffusion wave vectors (the d-PFG 5-design) facilitating a theoretically exact determination of the fourth order Taylor or cumulant expansion of the orientationally averaged signal. The d-PFG 5-design is evaluated with numerical simulations and ex vivo high field diffusion MRI experiments in a...... nonhuman primate brain. Specifically, we demonstrate rotational invariance when estimating compartment eccentricity, which we show offers new microstructural information, complementary to that of fractional anisotropy (FA) from diffusion tensor imaging (DTI). The imaging observations are supported by a new...
Determination of diffusion coefficients by quantitative evaluation of X-ray fluorescence
International Nuclear Information System (INIS)
A nondestructive method has been developed to follow changes of concentration caused by diffusion in small samples, using a micro-beam analyser. An advanced mathematical procedure was applied to evaluate directly curves of changing intensity of fluorescent radiation along the diffusion path. Experimental results of diffusion of sulphur in liquid iron served as an example. It has been proved that the experimental curves follow the shape of theoretical Gaussian curve with probabilities far exceeding the usually considered level of 0.05. The length of diffusion paths has been determined with highest possible accuracy by minimizing differences of measured and theoretical values with X2 function. Thus it was possible to apply second Fick's law for determination of diffusion coefficients of sulphur in liquid iron at temperatures from 1773 to 19230K. The proposed method can be generally applied to any diffusion systems suitable for examination under the electron beam microanalyser. The mathematical procedure given, enables to determine diffusion coefficients on very small samples and there is no need to know the absolute values of concentrations of the diffusing element along the diffusion path. The only results needed are the relative changes of concentration along the diffusion path. (author)
International Nuclear Information System (INIS)
Highlights: ► Diffusion coefficients of aqueous systems containing lactose and cadmium chloride. ► Influence of the lactose on the diffusion of cadmium chloride. ► Interactions between Cd2+ and lactose. -- Abstract: Diffusion coefficients of an aqueous system containing cadmium chloride 0.100 mol · dm−3 and lactose at different concentrations at 25 °C have been measured, using a conductimetric cell and an automatic apparatus to follow diffusion. The cell relies on an open-ended capillary method and a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries, at recorded times. From these results and by ab initio calculations, it was possible to obtain a better understanding of the effect of lactose on transport of cadmium chloride in aqueous solutions
Albedo-adjusted fast-neutron diffusion coefficients in reactor reflectors
International Nuclear Information System (INIS)
In the newer, larger pressurized-water reactor cores, the calculated power distributions are fairly sensitive to the number of neutron groups used and to the treatment of the reflector cross sections. Comparisons between transport and diffusion calculations show that the latter substantially underpredict the reflector albedos in the fast (top) group and that the power distribution is shifted toward the core center when compared to 4-group transport theory results. When the fast-neutron diffusion coefficients are altered to make the transport- and diffusion-theory albedos agree, the power distributions are also brought into agreement. An expression for the fast-neutron diffusion coefficients in reflector regions has been derived such that the diffusion calculation reproduces the albedo obtained from a transport solution. In addition, a correction factor for mesh effects applicable to coarse mesh problems is presented. The use of the formalism gives the correct albedos and improved power distributions. (U.S.)
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
4 new model, phase equilibrium-kinetics model (PEKM), for estimation of diffusioncoefficient was proposed in this paper. Kinetic experiments of phenol desorption on NKAII resin inthe presence and the absence of ultrasound were separately conducted, and diffusion coefficients ofphenol within an adsorbent particle were estimated by means of proposed PEKM and classicsimplified model. Results show that the use of ultrasound not only changes the phase equilibriumstate of NKAll resin/phenol/water system which had been equilibrium at normal condition, but alsoenhances diffusion of phenol within the resin. The diffusion coefficient of phenol in the resin in thefield of ultrasound increases in an order of magnitude in comparison with the diffusion coefficientdetermined under no ultrasound Experimental results also indicated that the diffusion coefficientsestimated by PEKM were more accurate than that estimated by the classic simplified model.
International Nuclear Information System (INIS)
Simple diffusion theory cannot be used to evaluate control rod worths in thermal neutron reactors because of the strongly absorbing character of the control material. However, reliable control rod worths can be obtained within the framework of diffusion theory if the control material is characterized by a set of mesh-dependent effective diffusion parameters. For thin slab absorbers the effective diffusion parameters can be expressed as functions of a suitably-defined pair of 'blackness coefficients'. Methods for calculating these blackness coefficients in the P1, P3, and P5 approximations, with and without scattering, are presented. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method, based on reaction rate ratios, is discussed. (author)
Annunziata, Onofrio; Vergara, Alessandro; Paduano, Luigi; Sartorio, Roberto; Miller, Donald G; Albright, John G
2009-10-01
We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, D(ij), for the lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 degrees C using precision Rayleigh interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that the protein diffusion coefficient, D(11), decreases as polymer concentration increases at a given salt concentration. This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion from high to low protein concentration. This effect increases in the presence of poly(ethylene glycol). Finally, we have evaluated systematic errors associated with measurements of protein diffusion coefficients by dynamic light scattering. This work overall helps characterize protein diffusion in crowded environments and may provide guidance for further theoretical developments in the field of protein crystallization and protein diffusion in such crowded systems, such as the cytoplasm of living cells. PMID:19746957
International Nuclear Information System (INIS)
A numerical study of the dynamics of pattern evolution in reaction-diffusion systems is performed, although limited to one spatial dimension. The diffusion coefficients are nonlinear, based on powers of the scalar variables. The system keeps the dynamics of previous studies in the literature, but the presence of nonlinear diffusion generates a field of strong nonlinear interactions due to the presence of receding travelling waves. This field is limited by the plane of symmetry of the space domain and the last born outgoing travelling wave. These effects are discussed. (author). 10 refs., 7 figs
Institute of Scientific and Technical Information of China (English)
宋鲁光; 孙伟; 高建明
2015-01-01
The chloride apparent diffusion coefficients at different immersion time in slag with differ-ent curing ages were studied through natural immersion tests.The influence of the curing age on chlo-ride apparent diffusion coefficients was analyzed.And the apparent diffusion coefficient was consid-ered as the integral mean of the instantaneous diffusion coefficients during the testing period,and the obtained apparent diffusion coefficient was transferred to the instantaneous diffusion coefficients.The relationship between the curing age and the constant of time dependence of the instantaneous diffusion coefficient was derived.The experimental results show that the chloride apparent diffusion coefficient decreases with the increase of the curing age and the decrease rate slows down gradually.There is a power function relationship between the apparent diffusion coefficient and the curing age.The constant of time dependency of the instantaneous diffusion coefficient increases with the increase of the curing age and the increase rate slows down gradually.There is a square root relationship between the con-stant of time dependency of the instantaneous diffusion coefficient and the curing age.%利用自然浸泡试验，研究了不同养护龄期的矿渣混凝土在不同暴露时间下的氯离子表观扩散系数，分析了养护龄期对氯离子表观扩散系数的影响。将表观扩散系数看作暴露时间内即时扩散系数的积分平均值，将得到的表观扩散系数转换为即时扩散系数，推导出养护龄期与即时扩散系数时间依赖性常数的关系。结果表明，混凝土中氯离子表观扩散系数随着养护龄期的增加而减小，且减小幅度逐渐减缓；养护龄期与表观扩散系数成幂函数关系。即时扩散系数的时间依赖性常数随着养护龄期的增加而增加，且增加幅度逐渐减小；即时扩散系数时间依赖性常数与养护龄期符合平方根关系。
Diffusion of Nd in hcp Mg and interdiffusion coefficients in Mg–Nd system
International Nuclear Information System (INIS)
Diffusion couple experiments for Mg–Nd system were performed to investigate the Nd diffusion in Mg solid solution and the interdiffusivities of intermediate phases. Experiments were conducted at 460, 480 and 500 °C for 3, 4 and 3 days respectively. Phase diagram data obtained from the diffusion couple experiments are consistent with previous experimental data and thermodynamic modeling. Impurity diffusion coefficient of Nd in Mg solid solution is almost three times of Gd and Y but lower than that of Al and Zn
On the Diffusion Coefficient of Two-step Method for LWR analysis
Energy Technology Data Exchange (ETDEWEB)
Lee, Deokjung; Choi, Sooyoung [UNIST, Ulsan (Korea, Republic of); Smith, Kord S. [Massachusetts Institute of Technology, Cambridge (United States)
2015-10-15
The few-group constants including diffusion coefficients are generated from the assembly calculation results. Once the assembly calculation is done, the cross sections (XSs) are spatially homogenized, and a critical spectrum calculation is performed in order to take into account the neutron leakages of the lattice. The diffusion coefficient is also generated through the critical spectrum calculation. Three different methods of the critical spectrum calculation such as B1 method, P1 method, and fundamental mode (FM) calculation method are considered in this paper. The diffusion coefficients can also be affected by transport approximations for the transport XS calculation which is used in the assembly transport lattice calculation in order to account for the anisotropic scattering effects. The outflow transport approximation and the inflow transport approximation are investigated in this paper. The accuracy of the few group data especially the diffusion coefficients has been studied to optimize the combination of the transport correction methods and the critical spectrum calculation methods using the UNIST lattice physics code STREAM. The combination of the inflow transport approximation and the FM method is shown to provide the highest accuracy in the LWR core calculations. The methodologies to calculate the diffusion coefficients have been reviewed, and the performances of them have been investigated with a LWR core problem. The combination of the inflow transport approximation and the fundamental mode critical spectrum calculation shows the smallest errors in terms of assembly power distribution.
Czech Academy of Sciences Publication Activity Database
Hovorka, Š.; Randová, A.; Borbášová, T.; Sysel, P.; Vychodilová, Hana; Červenková Šťastná, Lucie; Brožová, Libuše; Žitka, Jan; Storch, Jan; Kačírková, Marie; Drašar, P.; Izák, Pavel
2016-01-01
Roč. 158, JAN 28 (2016), s. 322-332. ISSN 1383-5866 R&D Projects: GA ČR(CZ) GAP106/12/0569 Institutional support: RVO:67985858 ; RVO:61389013 Keywords : diffusion coefficient measurement * permeability * nafion * cellophane * chirality of polymer membrane Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.091, year: 2014
Energy Technology Data Exchange (ETDEWEB)
Liu, Fei; Kolesov, Grigory; Parkinson, Bruce A.
2014-09-26
A simple and straightforward method for measuring diffusion coefficients using interdigitated array (IDA) electrodes is reported. The method does not require that the exact electrode area be known but depends only the size of the gap between the IDA electrode pairs. Electroactive molecules produced at the generator electrode of the IDA by a voltage step or scan can diffuse to the collector electrode and the time delay before the current for the reverse electrochemical reaction is detected at the collector is used to calculate the diffusion coefficient. The measurement of the diffusion rate of Ru(NH3)6+2 in aqueous solution has been used as an example measuring diffusion coefficients using this method. Additionally, a digital simulation of the electrochemical response of the IDA electrodes was used to simulate the entire current/voltage/time behavior of the system and verify the experimentally measured diffusion coefficients. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences.
International Nuclear Information System (INIS)
In this paper, the estimation of the thermal diffusivity from perturbative experiments in fusion plasmas is discussed. The measurements used to estimate the thermal diffusivity suffer from stochastic noise. Accurate estimation of the thermal diffusivity should take this into account. It will be shown that formulas found in the literature often result in a thermal diffusivity that has a bias (a difference between the estimated value and the actual value that remains even if more measurements are added) or have an unnecessarily large uncertainty. This will be shown by modeling a plasma using only diffusion as heat transport mechanism and measurement noise based on ASDEX Upgrade measurements. The Fourier coefficients of a temperature perturbation will exhibit noise from the circular complex normal distribution (CCND). Based on Fourier coefficients distributed according to a CCND, it is shown that the resulting probability density function of the thermal diffusivity is an inverse non-central chi-squared distribution. The thermal diffusivity that is found by sampling this distribution will always be biased, and averaging of multiple estimated diffusivities will not necessarily improve the estimation. Confidence bounds are constructed to illustrate the uncertainty in the diffusivity using several formulas that are equivalent in the noiseless case. Finally, a different method of averaging, that reduces the uncertainty significantly, is suggested. The methodology is also extended to the case where damping is included, and it is explained how to include the cylindrical geometry. (paper)
Directory of Open Access Journals (Sweden)
Aleš Mráček
2010-02-01
Full Text Available The amorphous polymer film swelling in a liquid solvent below the glass transition temperature was characterized by a few kinetic parameters (especially the mutual diffusion coefficient of swelling and its mean value obtained by interference of monochromatic light in the wedge arrangement. This interferometric method allows one to determine the concentration field in the swollen surface layer and consequently to compute the concentration-dependent diffusion coefficient. A software system developed at the Department of Physics and Material Engineering at TBU in Zlin has been used for the evaluation of the main kinetic parameters of the swelling process. The software can be used for the on-line analyses of interferograms during the swelling process. The main application outputs are the computation of the concentration profile, the concentration gradient, the mutual diffusion coefficient of the swelling by the solvent and its mean value.
Field-Scale Effective Matrix Diffusion Coefficient for FracturedRock: Results From Literature Survey
Energy Technology Data Exchange (ETDEWEB)
Zhou, Quanlin; Liu, Hui Hai; Molz, Fred J.; Zhang, Yingqi; Bodvarsson, Gudmundur S.
2005-03-28
Matrix diffusion is an important mechanism for solutetransport in fractured rock. We recently conducted a literature survey onthe effective matrix diffusion coefficient, Dem, a key parameter fordescribing matrix diffusion processes at the field scale. Forty fieldtracer tests at 15 fractured geologic sites were surveyed and selectedfor study, based on data availability and quality. Field-scale Dem valueswere calculated, either directly using data reported in the literature orby reanalyzing the corresponding field tracer tests. Surveyed dataindicate that the effective-matrix-diffusion-coefficient factor FD(defined as the ratio of Dem to the lab-scale matrix diffusioncoefficient [Dem]of the same tracer) is generally larger than one,indicating that the effective matrix diffusion coefficient in the fieldis comparatively larger than the matrix diffusion coefficient at therock-core scale. This larger value could be attributed to the manymass-transfer processes at different scales in naturally heterogeneous,fractured rock systems. Furthermore, we observed a moderate trend towardsystematic increase in the emDFmDDF value with observation scale,indicating that the effective matrix diffusion coefficient is likely tobe statistically scale dependent. The FD value ranges from 1 to 10,000for observation scales from 5 to 2,000 m. At a given scale, the FD valuevaries by two orders of magnitude, reflecting the influence of differingdegrees of fractured rock heterogeneity at different sites. In addition,the surveyed data indicate that field-scale longitudinal dispersivitygenerally increases with observation scale, which is consistent withprevious studies. The scale-dependent field-scale matrix diffusioncoefficient (and dispersivity) may have significant implications forassessing long-term, large-scale radionuclide and contaminant transportevents in fractured rock, both for nuclear waste disposal and contaminantremediation.
Salazar, Agustín; Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Celorrio, R.
2011-08-01
The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.
A new method for the calculation of diffusion coefficients with Monte Carlo
International Nuclear Information System (INIS)
This paper presents a new Monte Carlo-based method for the calculation of diffusion coefficients. One distinctive feature of this method is that it does not resort to the computation of transport cross sections directly, although their functional form is retained. Instead, a special type of tally derived from a deterministic estimate of Fick's Law is used for tallying the total cross section, which is then combined with a set of other standard Monte Carlo tallies. Some properties of this method are presented by means of numerical examples for a multi-group 1-D implementation. Calculated diffusion coefficients are in general good agreement with values obtained by other methods. (author)
Vaneeva, O O; Sophocleous, C
2011-01-01
The group classification of a class of variable coefficient reaction-diffusion equations with exponential nonlinearities is carried out up to both the equivalence generated by the corresponding generalized equivalence group and the general point equivalence. The set of admissible transformations of this class is exhaustively described via finding the complete family of maximal normalized subclasses and associated conditional equivalence groups. Limit processes between variable coefficient reaction-diffusion equations with power nonlinearities and those with exponential nonlinearities are simultaneously studied with limit processes between objects related to these equations (including Lie symmetries, exact solutions and conservation laws).
DEFF Research Database (Denmark)
Shojaee Nasirabadi, Parizad; Jabbaribehnam, Mirmasoud; Hattel, Jesper Henri
2016-01-01
Nowadays, many electronic systems are exposed to harsh conditions of relative humidity and temperature. Masstransport properties of electronic packaging materials are needed in order to investigate the influence of moisture andtemperature on reliability of electronic devices. Polycarbonate (PC) is...... widely used in the electronics industry. Thus, in this work the water diffusion coefficient into PC is investigated. Furthermore, numerical methods used for estimation of the diffusion coefficient and their assumptions are discussed. 1D and 3D numerical solutions are compared and based on this, itis...
International Nuclear Information System (INIS)
Using a numerical library for arbitrary precision arithmetic I study the irregular dependence of the diffusion coefficient on the slope of a piecewise linear map defining a dynamical system. I find that the graph of the diffusion coefficient as a function of the slope has the fractal dimension 1, but the convergence to this limit is slowed down by logarithmic corrections. The exponent controlling this correction depends on the slope and is either 1 or 2 depending on existence and properties of a Markov partition. (author)
Fluorinated surfactants in solution: Diffusion coefficients of fluorinated alcohols in water
Martins, Luís F. G.; Pereira, Luís A.M.; Silva, Gonçalo M.C.; Ascenso, José R.; Morgado, Pedro; Ramalho, João P. Prates; Filipe, Eduardo J. M.
2016-01-01
Intra-diffusion coefficients of three fluorinated alcohols, 2,2,3,3,3-pentafluoropropan-1-ol (PFP), 2,2,3,3,4,4,4-heptafluorobutan-1-ol (HFB) and 2,2,3,3,4,4,5,5,5-nonafluoropentan-1-ol (NFP) in water have been measured by the PFG–NMR spin-echo technique as a function of temperature and composition, focusing on the alcohol dilute region. For comparison, intra-diffusion coefficients of 2,2,2- trifluoroethanol (TFE) and HFB have also been measured in heavy water using the same me...
A New Method for the Calculation of Diffusion Coefficients with Monte Carlo
Dorval, Eric
2014-06-01
This paper presents a new Monte Carlo-based method for the calculation of diffusion coefficients. One distinctive feature of this method is that it does not resort to the computation of transport cross sections directly, although their functional form is retained. Instead, a special type of tally derived from a deterministic estimate of Fick's Law is used for tallying the total cross section, which is then combined with a set of other standard Monte Carlo tallies. Some properties of this method are presented by means of numerical examples for a multi-group 1-D implementation. Calculated diffusion coefficients are in general good agreement with values obtained by other methods.
Self-diffusion coefficient of Na+ ions in Nafion-117 from radioactive tracer measurements
International Nuclear Information System (INIS)
The tracer self-diffusion coefficient of Na+ in Nafion-117 was measured using two different methodologies. The method based on the two parameters non-linear fit of experimental data with an analytical solution of Fick's second law was found to be simple and reliable. The value of tracer self-diffusion coefficient of Na+ in Nafion-117, obtained by this method (1.03 ± 0.07) x 10-6 cm2/sec, was in good agreement with other method based on Fick's first law. (author)
Quantum statistics of classical particles derived from the condition of free diffusion coefficient
Hoyuelos, Miguel
2016-01-01
We derive an equation for the current of particles in energy space; particles are subject to a mean field effective potential that may represent quantum effects. From the assumption that non-interacting particles imply a free diffusion coefficient in energy space we derive Maxwell-Boltzmann, Fermi-Dirac and Bose-Einstein statistics. Other new statistics are associated to a free diffusion coefficient; their thermodynamic properties are analyzed using the grand partition function. A negative relation between pressure and energy density for low temperatures can be derived, suggesting a possible connection with cosmological dark energy models.
Direct evaluation of the radial diffusion coefficient near L=6 due to electric field fluctuations
International Nuclear Information System (INIS)
The radial diffusion coefficient for radiation belt particles near L=6 has been calculated from the measured electric field fluctuations. Simultaneous balloon flights in August 1974 from six auroral zone sites ranging 1800 in magnetic longitude produced the electric field data. The large scale slowly varying ionospheric electric fields from these flights have been mapped to the equator during the quiet magnetic conditions of this campaign. These mapped equatorial electric fields were then Fourier transformed in space and time to produce power spectra of the first two terms of the global azimuthal electric field. From these power spectra the radial diffusion coefficient has been calculated
International Nuclear Information System (INIS)
Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220–258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243–318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258–323 K). The dispersion of 1H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz–20 MHz, and the studies are complemented by 19F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the 1H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the 1H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the 19F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids
FIELD-SCALE EFFECTIVE MATRIX DIFFUSION COEFFICIENT FOR FRACTURED ROCK:RESULTS FROM LITERATURE SURVEY
Energy Technology Data Exchange (ETDEWEB)
Q. Zhou; Hui-Hai Liu; F.J. Molz; Y. Zhang; G.S. Bodvarsson
2005-04-08
Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, D{sub m}{sup e}, a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D{sub m}{sup e} values were calculated, either directly using data reported in the literature or by reanalyzing the corresponding field tracer tests. Surveyed data indicate that the effective-matrix-diffusion-coefficient factor F{sub D} (defined as the ratio of D{sub m}{sup e} to the lab-scale matrix diffusion coefficient [D{sub m}] of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate trend toward systematic increase in the F{sub D} value with observation scale, indicating that the effective matrix diffusion coefficient is likely to be statistically scale dependent. The F{sub D} value ranges from 1 to 10,000 for observation scales from 5 to 2,000 m. At a given scale, the F{sub D} value varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scale-dependent field-scale matrix diffusion coefficient (and dispersivity) may have significant implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal
Conservation Laws and Exact Solutions for a Reaction-Diffusion Equation with a Variable Coefficient
Directory of Open Access Journals (Sweden)
Zhijie Cao
2014-01-01
Full Text Available In this paper a variable-coefficient reaction-diffusion equation is studied. We classify the equation into three kinds by different restraints imposed on the variable coefficient b(x in the process of solving the determining equations of Lie groups. Then, for each kind, the conservation laws corresponding to the symmetries obtained are considered. Finally, some exact solutions are constructed.
Directory of Open Access Journals (Sweden)
Shumanova M.V.
2015-03-01
Full Text Available The process fish salting has been studied by the method of photon correlation spectroscopy; the distribution of salt concentration in the solution and herring flesh with skin has been found, diffusion coefficients and salt concentrations used for creating a mathematical model of the salting technology have been worked out; the possibility of determination by this method the coefficient of dynamic viscosity of solutions and different media (minced meat etc. has been considered
Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites
Wei, Chenyu; Srivastava, Deepak; Cho, Kyeongjae
2002-01-01
Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and Van der Waals forces for polymer-nanotube interfaces are used to invetigate the thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Additions of carbon nanotubes to polymer matrix are found to increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. These findings could have implic...
Group Analysis of Variable Coefficient Diffusion-Convection Equations. IV. Potential Symmetries
Ivanova, N M; Sophocleous, C
2007-01-01
This paper completes investigation of symmetry properties of nonlinear variable coefficient diffusion-convection equations of the form $f(x)u_t=(g(x)A(u)u_x)_x+h(x)B(u)u_x$. Potential symmetries of equations from the considered class are found and the connection of them with Lie symmetries of diffusion-type equations is shown. Exact solutions of the Fujita--Storm equation $u_t=(u^{-2}u_x)_x$ are constructed.
Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite
DEFF Research Database (Denmark)
Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.
Abstract. In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated...... composition dependent diffusivity of carbon derived from the simulated experiments was compared with the input data. The most promising procedure for an accurate determination is shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the stepsize, the more accurate the...
Application of the Clustering Method in Molecular Dynamics Simulation of the Diffusion Coefficient
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Using molecular dynamics (MD) simulation, the diffusion of oxygen, methane, ammonia and carbon dioxide in water was simulated in the canonical NVT ensemble, and the diffusion coefficient was analyzed by the clustering method. By comparing to the conventional method (using the Einstein model) and the differentiation-interval variation method, we found that the results obtained by the clustering method used in this study are more close to the experimental values. This method proved to be more reasonable than the other two methods.
Calculation of the effective diffusion coefficient during the drying of clay samples
Vasić Miloš; Radojević Zagorka; Grbavčić Željko
2012-01-01
The aim of this study was to calculate the effective diffusion coefficient based on experimentally recorded drying curves for two masonry clays obtained from different localities. The calculation method and two computer programs based on the mathematical calculation of the second Fick’s law and Cranck diffusion equation were developed. Masonry product shrinkage during drying was taken into consideration for the first time and the appropriate correction was entered into the calculation. ...
Energy Technology Data Exchange (ETDEWEB)
Ikonomov, Julian; Schmitz, Christoph H.; Sokolowski, Moritz [Institut fuer Physikalische und Theoretische Chemie, Universitaet Bonn, Wegelerstr. 12, 53115 Bonn (Germany)
2009-07-01
The diffusion of organic molecules on surfaces has so far been mostly investigated by molecule tracking using the video STM technique. This method requires small molecule coverages and small diffusion coefficients. Here we present a new technique suitable for higher temperatures and arbitrarily coverages based on the temporal increase in the tunneling current that occurs when a molecule diffuses under the STM tip. For our measurements, we have chosen the model system perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) on Ag(100). The PTCDA molecules form highly ordered two-dimensional islands surrounded by gas-like phase. In order to determine the diffusion coefficients, we used a continuum model to describe the diffusion of the molecules under the tip. Due to the finite size of the molecule it is even possible to obtain the spatial anisotropy of the diffusion coefficient. From the density of the peaks in the current-time spectra, one may in addition quantitatively estimate the tip-molecule interaction and the mean local coverage.
International Nuclear Information System (INIS)
The radon diffusion coefficient and the free radon production rate are important parameters for describing radon migration in the fragmented uranium ore. In order to determine the two parameters, the pure diffusion migration equation for radon was firstly established and its analytic solution with the two parameters to be determined was derived. Then, a self manufactured experimental column was used to simulate the pure diffusion of the radon, the improved scintillation cell method was used to measure the pore radon concentrations at different depths of the column loaded with the fragmented uranium ore, and the nonlinear least square algorithm was used to inversely determine the radon diffusion coefficient and the free radon production rate. Finally, the solution with the two inversely determined parameters was used to predict the pore radon concentrations at some depths of the column, and the predicted results were compared with the measured results. The results show that the predicted results are in good agreement with the measured results and the numerical inverse method is applicable to the determination of the radon diffusion coefficient and the free radon production rate for the fragmented uranium ore. - Highlights: • Inverse method for determining two transport parameters of radon is proposed. • A self-made experimental apparatus is used to simulate radon diffusion process. • Sampling volume and position for measuring radon concentration are optimized. • The inverse results of an experimental sample are verified
Variation of diffuse attenuation coefficient of downwelling irradiance in the Arctic Ocean
Institute of Scientific and Technical Information of China (English)
WANG Weibo; ZHAO Jinping
2014-01-01
The diffuse attenuation coefficient (Kd) for downwelling irradiance is calculated from solar irradiance data measured in the Arctic Ocean during 3rd and 4th Chinese National Arctic Research Expedition (CHINARE), including 18 stations and nine stations selected for irradiance profiles in sea water respectively. In this study, the variation of attenuation coefficient in the Arctic Ocean was studied, and the following results were ob-tained. First, the relationship between attenuation coefficient and chlorophyll concentration in the Arctic Ocean has the form of a power function. The best fit is at 443 nm, and its determination coefficient is more than 0.7. With increasing wavelength, the determination coefficient decreases abruptly. At 550 nm, it even reaches a value lower than 0.2. However, the exponent fitted is only half of that adapted in low-latitude ocean because of the lower chlorophyll-specific absorption in the Arctic Ocean. The upshot was that, in the case of the same chlorophyll concentration, the attenuation caused by phytoplankton chlorophyll in the Arctic Ocean is lower than in low-latitude ocean. Second, the spectral model, which exhibits the relationship of attenuation coefficients between 490 nm and other wavelength, was built and provided a new method to estimate the attenuation coefficient at other wavelength, if the attenuation coefficient at 490 nm was known. Third, the impact factors on attenuation coefficient, including sea ice and sea water mass, were discussed. The influence of sea ice on attenuation coefficient is indirect and is determined through the control of enter-ing solar radiation. The linear relationship between averaging sea ice concentration (ASIC, from 158 Julian day to observation day) and the depth of maximum chlorophyll is fitted by a simple linear equation. In addition, the sea water mass, such as the ACW (Alaskan Coastal Water), directly affects the amount of chlo-rophyll through taking more nutrient, and results in the
International Nuclear Information System (INIS)
The change in slope of the Arrhenius curve for the diffusion coefficient as a function of temperature is discussed and its occurance is explained by vacancies concentration dependence of the formation energy. It is shown that a sign of the mixing energy parameter of the regular solid solution of vacancies in pure metals is closely connected with the sign of the curvature of the diffusion plot. For the analysis of this plot as well as for the estimation of other parameters of self diffusion of bcc Cs we used the total energy calculations based on the Full Potential LMTO method. (orig.)
Measurement and modeling of CO2 diffusion coefficient in Saline Aquifer at reservoir conditions
Azin, Reza; Mahmoudy, Mohamad; Raad, Seyed; Osfouri, Shahriar
2013-12-01
Storage of CO2 in deep saline aquifers is a promising techniques to mitigate global warming and reduce greenhouse gases (GHG). Correct measurement of diffusivity is essential for predicting rate of transfer and cumulative amount of trapped gas. Little information is available on diffusion of GHG in saline aquifers. In this study, diffusivity of CO2 into a saline aquifer taken from oil field was measured and modeled. Equilibrium concentration of CO2 at gas-liquid interface was determined using Henry's law. Experimental measurements were reported at temperature and pressure ranges of 32-50°C and 5900-6900 kPa, respectively. Results show that diffusivity of CO2 varies between 3.52-5.98×10-9 m2/s for 5900 kPa and 5.33-6.16×10-9 m2/s for 6900 kPa initial pressure. Also, it was found that both pressure and temperature have a positive impact on the measures of diffusion coefficient. Liquid swelling due to gas dissolution and variations in gas compressibility factor as a result of pressure decay was found negligible. Measured diffusivities were used model the physical model and develop concentration profile of dissolved gas in the liquid phase. Results of this study provide unique measures of CO2 diffusion coefficient in saline aquifer at high pressure and temperature conditions, which can be applied in full-field studies of carbon capture and sequestration projects.
Diffusion Coefficient of H2SO4 in Air Laboratory Measurements Using Laminar Flow Technique
Czech Academy of Sciences Publication Activity Database
Škrabalová, Lenka; Brus, D.; Ždímal, Vladimír; Hermann, E.
Prague: Czech Aerosol Society, 2014 - (Kubelová, L.), s. 59-62 ISBN 978-80-86186-64-1. [Annual Conference of the Czech Aerosol Society /15./. Valtice (CZ), 30.10.2014-31.10.2014] Institutional support: RVO:67985858 Keywords : sulphuric acid * diffusion coefficient * modelling Subject RIV: CF - Physical ; Theoretical Chemistry http://cas.icpf.cas.cz/download/Sbornik_VKCAS_2014.pdf
International Nuclear Information System (INIS)
The mathematical apparatus and the experimental installation for the rapid determination of radon diffusion coefficient in various materials are developed. The single test lasts not longer than 18 h and allows testing numerous materials, such as gaseous and liquid media, as well as soil, concrete and radon-proof membranes, in which diffusion coefficient of radon may vary in an extremely wide range, from 1·10−12 to 5·10−5 m2/s. The uncertainty of radon diffusion coefficient estimation depends on the permeability of the sample and varies from about 5% (for the most permeable materials) to 40% (for less permeable materials, such as radon-proof membranes). - Highlights: • The new method and installation for determination of radon diffusion coefficient D are developed. • The measured D-values vary in an extremely wide range, from 5×10-5 to 1×10-12 m2/s. • The materials include water, air, soil, building materials and radon-proof membranes. • The duration of the single test does not exceed 18 hours. • The measurement uncertainty varies from 5% (in permeable materials) to 40% (in radon gas barriers)
A unified derivation of the various definitions of lattice cell diffusion coefficient
International Nuclear Information System (INIS)
The various definitions of lattice cell diffusion coefficients are discussed within the context of a one-dimensional slab lattice in one energy group. It is shown how each definition, although originally derived in its own particular way, can be derived from a single approach. This makes clear the differences between, and the advantages of, the various definitions. (author)
De Mezquia, D Alonso; Bou-Ali, M Mounir; Larrañaga, M; Madariaga, J A; Santamaría, C
2012-03-01
In this work we have measured the molecular diffusion coefficient of the n-alkane binary series nC(i)-nC(6), nC(i)-nC(10), and nC(i)-nC(12) at 298 K and 1 atm and a mass fraction of 0.5 by using the so-called sliding symmetric tubes technique. The results show that the diffusion coefficient at this concentration is proportional to the inverse viscosity of the mixture. In addition, we have also measured the diffusion coefficient of the systems nC(12)-nC(6), nC(12)-nC(7), and nC(12)-nC(8) as a function of concentration. From the data obtained, it is shown that the diffusion coefficient of the n-alkane binary mixtures at any concentration can be calculated from the molecular weight of the components and the dynamic viscosity of the corresponding mixture at 50% mass fraction. PMID:22263833
Determination of the concentration dependent diffusion coefficient of nitrogen in expanded austenite
DEFF Research Database (Denmark)
Christiansen, Thomas; Somers, Marcel A. J.
2008-01-01
The concentration dependent diffusion coefficient of nitrogen in expanded austenite was determined from of the rate of retracting nitrogen from thin initially N-saturated coupons. Nitrogen saturated homogeneous foils of expanded austenite were obtained by nitriding AISI 304 and AISI 316 in pure...
Novel Technique for Direct Measurement of the Plasma Diffusion Coefficient in Magnetized Plasma
Czech Academy of Sciences Publication Activity Database
Brotánková, Jana; Martines, E.; Adámek, Jiří; Stöckel, Jan; Popa, G.; Costin, C.; Ionita, G.; Schrittwieser, R.; Van Oost, G.
2008-01-01
Roč. 48, 5-7 (2008), s. 418-423. ISSN 0863-1042. [International Workshop on Electrical Probes in Magnetized Plasmas/7th./. Praha, 22.07.2007-25.07.2007] Institutional research plan: CEZ:AV0Z20430508 Keywords : Tokamak * probe diagnostics * diffusion coefficient Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.250, year: 2008
International Nuclear Information System (INIS)
The paper discusses a numerical method of calculating the diffusion coefficient β of the radioactive elements for the case when diffusion occurs from an instantaneous source into a semi-infinite medium. A computer program has been compiled, using which the dependence has been tabulated of the quantity (Dxt) on the ratio of the values of the integrated activity J(xsub(n), t) J(o, t)=0.95 - 0.05 with a step of 0.02 and on the value xsub(n)=0.0005=0.0500 cm with a step of 0.0005 cm for the β-radioactive elements with the radiation absorption coefficient μ=100 1/cm
Poirier, David R.
2014-08-01
This article is a review of empirical and calculated data on density, viscosity, and diffusion coefficients in hypereutectic Al-Si liquid alloys. Many regressions of the data were effected in order to consolidate the data as functions, which can be used to calculate each property as a function of temperature and concentration of Si. The chemical diffusion coefficient in the alloys was derived based on the Sutherland model, which relates the diffusion coefficient to viscosity.
Ionization dynamics in ionic liquids probed via self-diffusion coefficient measurements
International Nuclear Information System (INIS)
Graphical abstract: - Highlights: • Exploiting non-Arrhenius nature of physiochemical properties of ionic liquids to understand ion dynamics. • Estimation of ion concentration in ionic liquids via self-diffusion coefficient measurements. • Thermodynamics of the ionization process in ionic liquids. • Thermodynamics of the self-diffusion of cations and anions through Arrhenius and Eyring equations. - Abstract: Ionic liquids contain ions and ion pairs with fast exchange between them. We propose a novel process to deduce the fraction of ions present in an ionic liquid and the equilibrium constants of ionization processes from measured ion self-diffusion coefficients using Pulsed Field Gradient (PFG) NMR. The enthalpy and entropy changes of ionization and ion self-diffusion processes are obtained for a series of ionic liquids using this method. These data were used to explain the interactions between cations and anions of ionic liquids. The interactions are also interpreted by the delocalization of the ion’s charge densities. The self-diffusion coefficients of cations and anions for measured ionic liquids are discussed
Ionization dynamics in ionic liquids probed via self-diffusion coefficient measurements
Energy Technology Data Exchange (ETDEWEB)
Mao, Yougang; Damodaran, Krishnan, E-mail: damodak@pitt.edu
2014-08-31
Graphical abstract: - Highlights: • Exploiting non-Arrhenius nature of physiochemical properties of ionic liquids to understand ion dynamics. • Estimation of ion concentration in ionic liquids via self-diffusion coefficient measurements. • Thermodynamics of the ionization process in ionic liquids. • Thermodynamics of the self-diffusion of cations and anions through Arrhenius and Eyring equations. - Abstract: Ionic liquids contain ions and ion pairs with fast exchange between them. We propose a novel process to deduce the fraction of ions present in an ionic liquid and the equilibrium constants of ionization processes from measured ion self-diffusion coefficients using Pulsed Field Gradient (PFG) NMR. The enthalpy and entropy changes of ionization and ion self-diffusion processes are obtained for a series of ionic liquids using this method. These data were used to explain the interactions between cations and anions of ionic liquids. The interactions are also interpreted by the delocalization of the ion’s charge densities. The self-diffusion coefficients of cations and anions for measured ionic liquids are discussed.
Mueller, R; Zhang, S; Klink, M; Bäumer, M; Vasenkov, S
2015-11-01
Pulsed field gradient (PFG) NMR was applied to measure tortuosity factors for carbon dioxide diffusion in the Knudsen and gas regimes inside monoliths of a samaria-alumina aerogel catalyst, a high porosity material containing micropores in addition to meso- and macropores. The apparent tortuosity factor obtained from PFG NMR measurements for the Knudsen diffusion in the meso- and macropores of the catalyst has an unexpectedly large value of approximately 6 if carbon dioxide adsorption in the micropores and other types of surface adsorption sites of the catalyst is ignored. At the same time, the corresponding apparent tortuosity factor in the gas regime was found to be around 2. Application of a proposed model which describes fast molecular exchange between the surface adsorption sites and the main pore volume of the catalyst yields corrected tortuosity factors which depend only on the pore system geometry. Using this model, the corrected tortuosity factors were found to be around 2 for both diffusion regimes, in agreement with the expectations based on a high porosity of the studied catalyst. PMID:26426141
International Nuclear Information System (INIS)
The diffusion coefficient is one of the parameters necessary for the obtention of the extraction exponential coefficients, that are contained within the H.T.U. (height of transfer unity) calculation expression, when operating with continuous organic phase. The organic phase used was tri-n-butyl-phosphate (TBP) and varsol in the 35% and 65% proportions respectively. After each experiment, the uranium content present in each compartment was spectrophotometrically determined and the quantities contained in the aqueous phases were determined by means of volumetric titration. It was found out that the uranyl ion diffusion coefficient is two and one half times less in organic phase, this just being attributed to the greater interactions of the uranyl ions in organic than in aqueous medium
International Nuclear Information System (INIS)
Graphical abstract: -- Highlights: •Former random walk approach for FIA simulations has been improved. •Random walk and uniform dispersion models have been used for FIA simulations. •Diffusivities have been optimized by genetic and the Levenberg–Marquardt methods. •Both approaches have given similar results in agreement with experimental ones. -- Abstract: Stochastic and deterministic simulations of dispersion in cylindrical channels on the Poiseuille flow have been presented. The random walk (stochastic) and the uniform dispersion (deterministic) models have been used for computations of flow injection analysis responses. These methods coupled with the genetic algorithm and the Levenberg–Marquardt optimization methods, respectively, have been applied for determination of diffusion coefficients. The diffusion coefficients of fluorescein sodium, potassium hexacyanoferrate and potassium dichromate have been determined by means of the presented methods and FIA responses that are available in literature. The best-fit results agree with each other and with experimental data thus validating both presented approaches
Spin--echo diffusion coefficients of water to 2380 bar and -20degreeC
International Nuclear Information System (INIS)
The self-diffusion coefficient of water has been measured by the steady-gradient spin-echo method at pressures up to 2380 bar and temperatures between 2 and -200C in the stable liquid range using both strengthened glass and beryllium--copper pressure vessels. At low temperatures and high pressures the diffusion coefficient becomes almost independent of pressure. However, a rapid increase in D/sub H/2/sub O/ with the first kilobar of applied pressure is inferred for the supercooled liquid from the relation of the new data to the 1 atm pressure diffusivity of supercooled water. The observations may be correlated with the high pressure low temperature thermodynamic properties of water in a manner consistent with the Adam--Gibbs entropy theory of liquid transport processes
Measuring the effective diffusion coefficient of dissolved hydrogen in saturated Boom Clay
International Nuclear Information System (INIS)
Highlights: • Experiments with H2 are often disturbed by micro organisms. • A complex sterilisation procedure was developed. • Heat sterilisation, gamma irradiation and the use of a microbial inhibitor were combined. • 3 reliable H2 diffusion coefficients were obtained. - Abstract: Boom Clay is studied as a potential host formation for the disposal of high-and intermediate level long-lived radioactive waste in Belgium. In such a geological repository, generation of gases (mainly H2 from anaerobic corrosion) will be unavoidable. In order to make a good evaluation of the balance between gas generation vs. gas dissipation for a particular waste form and/or disposal concept, good estimates for gas diffusion coefficients of dissolved gases are essential. In order to obtain an accurate diffusion coefficient for dissolved hydrogen in saturated Boom Clay, diffusion experiments were performed with a recently developed through-diffusion set-up for dissolved gases. Due to microbial activity in the test set-up, conversion of hydrogen into methane was observed within several experiments. A complex sterilisation procedure was therefore developed in order to eliminate microbiological disturbances. Only by a combination of heat sterilisation, gamma irradiation and the use of a microbial inhibitor, reliable, reproducible and accurate H2(g) diffusion coefficients (measured at 21 °C) for samples oriented parallel (Deff = 7.25 × 10−10 m2/s and Deff = 5.51 × 10−10 m2/s) and perpendicular (Deff = 2.64 × 10−10 m2/s) to the bedding plane were obtained
Hermes, Helen E; Sitta, Christoph E; Schillinger, Burkhard; Löwen, Hartmut; Egelhaaf, Stefan U
2015-06-28
The dissolution of polyethylene oxide (PEO) tablets in water has been followed in situ by neutron radiography. When in contact with water, the crystalline phase of semi-crystalline PEO melts once a certain water content is attained. Polymer concentration profiles obtained from the neutron transmission images exhibited a pronounced kink which corresponds to a sharp front in the images and which is related to the melting transition. Sharp diffusion fronts and phase transitions are often linked to non-Fickian behaviour. However, by considering the time evolution of the complete concentration profiles in detail it is shown that the dissolution process can be explained using Fickian diffusion equations with a concentration-dependent diffusion coefficient. PMID:26018995
Energy Technology Data Exchange (ETDEWEB)
Berne, P.; Brouard, C.; Pocachard, J. [CEA, FrancCEA/LITEN/LCSN, F-38054 Grenoble cedex 9 (France); Duhart-Barone, A.; Grec, D.; Le Cocguen, A. [CEA/DSN/LECD, F-13108 Cadarache (France)
2009-07-01
In water-saturated media the main mode for contaminant transport is liquid transfer, and the confinement capacity of the materials is notably characterized by the effective diffusion coefficient (EDC) of tritiated water. The major problem lies in the duration of experiments, that can exceed several years, so two methods have been explored for the development of accelerated ones. The first consists in a variation of the through-diffusion technique: a given tracer concentration, C{sub 0}, is applied on one face of the sample that has been previously impregnated with a C{sub 0/2} concentration. The duration of the essay can then be divided by 3. The second method involves accelerated migration under the influence of an electric field and direct measurement of the current density. The results are in the same range as the classical through-diffusion experiments, and obtained in about one month. In non water-saturated media, the diffusing fluid of interest is generally the gaseous phase. Two applications at various steps of the nuclear fuel cycle are presented: characterization of the migration of hydrogen in the host rock formation of a geological waste storage, and of the diffusion of tritium gas in the concrete containment structure of decommissioned UNGG nuclear power plants. In both cases the media are close to saturation and the pore water content must be precisely controlled. This paper presents a method which allows to determine the intrinsic permeability and gas diffusion coefficients of the materials. (authors)
Energy Technology Data Exchange (ETDEWEB)
Benoist, P. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1964-01-15
In an previous publication, a simple and general formulation of the diffusion coefficient, which defines the mode of weighting of the mean free paths of the various media, in introducing the collision probabilities in each medium, was established. This expression is demonstrated again here through a more direct method, and the velocity is introduced; new terms are emphasised, the existence of which implies that the representation of the diffusion area as the mean square of the straight line distance from source to absorption is not correct in a lattice. However these terms are of small enough an order of magnitude to he treated as a correction. The general expression also shows the existence, for the radial coefficient, of the series of angular correlation terms, which is seen to converge very slowly for large channels. The term by term computation which was initiated in the first work was then interrupted and a global formulation, which emphasize a resemblance with the problem of the thermal utilisation factor, was adopted. An integral method, analogous to that use for the computation of this factor, gives the possibility to establish new and simple practical formulae, which require the use of a few basic functions only. These formulae are very accurate, as seen from the results of a variational method which was studied as a reference. Various correction effects are reviewed. Expressions which allow the exact treatment of fuel rod clusters are presented. The theory is confronted with various experimental results, and a new method of measuring the radial coefficient is proposed. (author) [French] Dans une publication anterieure, on a etablie une formulation simple et generale du coefficient de diffusion, qui definit le mode de ponderation des libres parcours des differents milieux constituants en faisant apparaitre les probabilites de collision dans chaque milieu. On redemontre ici cette expression d'une maniere plus directe, tout en introduisant la variable
Worth, H; Nüsse, W; Piiper, J
1978-01-01
In order to provide data required for quantitative analysis of gas diffusion in lung airways, diffusion of He, CO, O2, CO2 and SF6 in various gases used in respiratory physiology was studied in vitro at 37 degrees C and 25 degrees C. The gases were allowed to mix by diffusion in a closed cylindrical tube (length 2 m, internal diameter 1 cm), one half of which was initially filled with 1% test gas in a second gas and the other half of which was filled with the second gas only. Kinetics of diffusional equilibration was determined by withdrawal of spot samples analyzed by gas chromatography. The binary (mutual) diffusion coefficients (D) computed there from were in most cases in good agreement with values calculated on the basis of the Chapman-Enskog theory. PMID:625611
Petruk, V. G.; Ivanov, A. P.; Kvaternyuk, S. M.; Barun, V. V.
2016-03-01
We have designed an experimental setup, based on two integrating spheres, that lets us measure the optical diffuse reflectance spectra (diffuse reflection coefficient vs. wavelength) of human skin quickly under clinical conditions in vivo. For the wavelength interval 520-1100 nm, we give the values of the diffuse reflection coefficient for healthy tissue, skin with a benign nevus, and skin with a malignant melanoma for a large group of test subjects. We experimentally established a number of wavelengths in the red-near IR region of the spectrum which can be used for early differential diagnosis of nevi and melanoma in patient cancer screening. According to the Kramer-Welch test, the probability of the diffuse reflection coefficient for skin with melanoma and a nevus having different distributions is >0.94, and at many wavelengths it is >0.999. By solving the inverse problem, we estimated the changes in a number of structural and biophysical parameters of the tissue on going from healthy skin to nevus and melanoma. The results obtained can provide a basis for developing a clinical approach to identifying the risk of malignant transformation of the skin before surgery and histological analysis of the tissue.
Diffusion coefficients of β-cyclodextrin sulfated sodium salt in aqueous solutions
International Nuclear Information System (INIS)
Graphical abstract: Structure of β-cyclodextrin sulfated sodium salt. - Highlights: • Mutual diffusion coefficients of β-cyclodextrin sulfated sodium salt (NaSO3βCD) in aqueous solutions were measured. • Influence of the viscosity, thermodynamic and temperature factors on the variation of diffusion was analysed. • Estimation of the hydrodynamic radius of NaSO3βCD was obtained. - Abstract: The Taylor dispersion technique has been used for measuring mutual diffusion coefficients of β-cyclodextrin sulfated sodium salt (NaSO3βCD) at temperatures (298.15 and 310.15) K and at finite concentrations. These studies have been complemented by density and viscosity measurements. From these experimental results, the hydrodynamic radius Rh, and its dependence on the viscosity, diffusion coefficient at infinitesimal concentration, D0, ion conductivity of NaSO3βCD and the thermodynamic factor, FT, have been estimated, permitting us to have a better understanding of the structure of the aqueous system containing NaSO3βCD
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Kruk, D. [Faculty of Mathematics and Computer Science, University of Warmia and Mazury in Olsztyn, Słoneczna 54, PL-10710 Olsztyn (Poland); Universität Bayreuth, Experimentalphysik II, 95440 Bayreuth (Germany); Meier, R.; Rössler, E. A. [Universität Bayreuth, Experimentalphysik II, 95440 Bayreuth (Germany); Rachocki, A. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań (Poland); Korpała, A. [Department of Biophysics, Jagiellonian University Medical College, Łazarza 16, 31-530 Kraków, Poland and Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków (Poland); Singh, R. K. [Ionic Liquid and Solid State Ionics Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221 005 (India)
2014-06-28
Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220–258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF{sub 4}, 243–318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF{sub 6}, 258–323 K). The dispersion of {sup 1}H spin-lattice relaxation rate R{sub 1}(ω) is measured in the frequency range of 10 kHz–20 MHz, and the studies are complemented by {sup 19}F spin-lattice relaxation measurements on BMIM-PF{sub 6} in the corresponding frequency range. From the {sup 1}H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF{sub 4}, and BMIM-PF{sub 6} are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the {sup 1}H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R{sub 1} on square root of frequency. From the {sup 19}F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF{sub 6}. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.
Estimation of the eddy diffusivity coefficient in a warm monomictic tropical Lake
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David A. Salas de León
2016-03-01
Full Text Available We used a two-year dataset (1998-1999 of monthly temperature profiles from Lake Alchichica, Mexico to estimate values of the vertical coefficient of eddy diffusivity. This lake is located in a tropical region at high altitude and shows considerable seasonal variations (i.e., rainy and dry seasons. It has an area of 2.3 km2 and a mean depth of 40.9 m. Alchichica is a warm monomictic lake, which annually becomes isothermal near the end of December or early January at the onset of the dry season and remains stratified for the rest of the year (from late March or early April to early December during the warm-rainy season. Mathematical models of the spatial and temporal variation of passive substances in lakes and oceans require a quantitative formulation of the vertical transport. Vertical mixing is generally a function of the density profile, which, in lakes, can be directly related to the temperature profile. A widely used method to estimate the vertical diffusion coefficients in lakes from temperature data is the flux-gradient method. In the present study, we applied a simple approach to calculate the eddy diffusivity coefficient (Kz based on the solution of the vertical component of the modeled temperature equation. We characterized the eddy diffusivity coefficient (Kz in Lake Alchichica as a dynamic coefficient that changes during the year, between years, and with depth, ranging from 10-10 to 10-6 m2 s-1, whereas typical values of Kz in thermally stratified lakes range from 10-9 to 10-2 m2 s-1. As expected, we found the lowest values in the deeper regions of the lake, and that the temporal variation of temperature with depth showed a quasi-bimodal shape from one year to the next. We also found a structure of alternating peaks and troughs in the vertical Kz, which indicates a response to oscillating vertical mixing. We concluded that the solution of the vertical component of the temperature equation could be a useful tool to estimate the eddy
Suzuki, S.; Itoh, H.
2016-05-01
The diffusion coefficient of the metastable excited Ne(3P2) atom in neon, the reflection coefficient of Ne(3P2) at the surface of an electrode and the rate coefficient of Ne(3P2) for collisional quenching by Ne(1S0) were determined from the gas pressure dependence of the effective lifetime of Ne(3P2). The effective lifetime of Ne(3P2) was measured from the transient current after turning off the Ultraviolet (UV) light in a Townsend discharge. The observed transient current waveform was analysed by solving the diffusion equation for the metastable excited Ne(3P2) atom using the third kind of boundary condition. The rate coefficient of Ne(3P2) for collisional quenching by Ne(1S0) and the reflection coefficient were determined by a nonspectroscopic method for the first time in neon to the best of our knowledge and were (3.2 ± 0.4) × 10‑16 cm3 s‑1 and 0.10 ± 0.04, respectively. The obtained diffusion coefficient at 1 Torr was 177 ± 17 cm2 s‑1, which is consistent with the value reported by Dixon and Grant. Moreover, the present results are compared with the results of Phelps and were found to be in good agreement. We also discuss the deexcitation rate of Ne(3P2) at pressures of up to 60 Torr in comparison with previously reported values.
International Nuclear Information System (INIS)
A systematic comparison of the diffusion coefficients of cations (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) and oxyanions (Al, As, Mo, Sb, V, W) in open (ODL) and restricted (RDL) diffusive layers used by the DGT technique was undertaken. Diffusion coefficients were measured using both the diffusion cell (Dcell) method at pH 4.00 and the DGT time-series (DDGT) method at pH 4.01 and 7.04 (pH 8.30 was used instead of 7.04 for Al) using the Chelex-Metsorb mixed binding layer. The performance of Chelex-Metsorb as a new DGT binding layer for Al uptake was also evaluated for the first time. Reasonable agreement was observed between Dcell and DDGT measurements for both ODL and RDL, except for V and W. The ratios of Dcell/DDGT for V of 0.44 and 0.39, and for W of 0.66 and 0.63 with ODL and RDL respectively, were much lower due to the formation of a high proportion of polyoxometalate species at the higher concentrations required with the Dcell measurements. This is the first time that D values have been reported for several oxyanions using RDL. Except for Al at pH 8.30 with ODL, all DDGT measurements were retarded relative to diffusion coefficients in water (DW) for both diffusive hydrogels. Diffusion in RDL was further retarded compared with ODL, for all elements (0.66–0.78) with both methods. However, the degree of retardation observed changed for cations and anions at each pH. At pH 7.04 cations had a slightly higher DDGT and oxyanions had a slightly lower DDGT than at pH 4.01 for both ODL and RDL. It is proposed that this is due to partial formation of acrylic acid functional groups (pKa ≈4.5), which would be fully deprotonated at pH 7.04 (negative) and mostly protonated at pH 4.01 (neutral). As Al changes from being cationic at pH 4.01 to anionic at pH 8.30 the results were more complex. - Highlights: • Determining elemental diffusion coefficients in open and restricted diffusive gels. • The DGT times-series method was preferred over the diffusion cell method.
International Nuclear Information System (INIS)
A Devanathan-Stachurski type diffusion cell made from a fuel cell assembly is designed to evaluate the gas transport properties of a proton exchange membrane as a function of cell temperature and gas pressure. Data obtained on this cell using the electrochemical monitoring technique (EMT) is used to estimate solubility and diffusion coefficient of oxygen (O2), carbon monoxide (CO) and hydrogen sulfide (H2S) in Nafion membranes. Membrane swelling and reverse-gas diffusion due to water flux are accounted for in the parameter estimation procedure. Permeability of all three gases was found to increase with temperature. The estimated activation energies for O2, CO and H2S diffusion in Nafion 112 are 12.58, 20 and 8.85 kJ mol-1, respectively. The estimated enthalpies of mixing for O2, CO and H2S in Nafion 112 are 5.88, 3.74 and 7.61 kJ mol-1, respectively. An extensive comparison of transport properties estimated in this study to those reported in the literature suggests good agreement. Oxygen permeability in Nafion 117 was measured as a function of gas pressures between 1 and 3 atm. Oxygen diffusion coefficient in Nafion 117 is invariant with pressure and the solubility increases with pressure and obeys Henry's law. The estimated Henry's constant is 3.5 x 103 atm.
Buzatu, D; Buzatu, F D; Albright, J G
2004-01-01
This paper presents a diffusion experimental study for ternary lysozyme-Na$_2$SO$_4$-water system, from moderate precipitant concentrations into the supersaturated region and provides a complete set of four diffusion coefficients. These data are important in order to provide accurate models of protein diffusion with applications in growth of protein crystals for X-ray diffraction studies. All three-component mutual-diffusion experiments reported here were performed by Rayleigh interferometry at pH$=4.5$, T$=25^o$ C and at a mean lysozyme concentration (average of top and bottom solution concentrations) of 0.6 mM (8.6 mg/mL). Four experiments, with different combinations of protein and Na$_2$SO$_4$ concentration differences, were performed at each of five mean Na$_2$SO$_4$ concentrations (0.1, 0.25, 0.5, 0.65 and 0.8 M), for a total of 20 experiments. In addition, we have measured dynamic light-scattering diffusion coefficients of the ternary system lysozyme chloride-Na$_2$SO$_4$-water.
Diffusion coefficients of Fokker-Planck equation for rotating dust grains in a fusion plasma
Energy Technology Data Exchange (ETDEWEB)
Bakhtiyari-Ramezani, M., E-mail: mahdiyeh.bakhtiyari@gmail.com; Alinejad, N., E-mail: nalinezhad@aeoi.org.ir [Plasma Physics and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute (NSTRI), 14395-836 Tehran (Iran, Islamic Republic of); Mahmoodi, J., E-mail: mahmoodi@qom.ac.ir [Department of Physics, Faculty of Science, University of Qom, Qom (Iran, Islamic Republic of)
2015-11-15
In the fusion devices, ions, H atoms, and H{sub 2} molecules collide with dust grains and exert stochastic torques which lead to small variations in angular momentum of the grain. By considering adsorption of the colliding particles, thermal desorption of H atoms and normal H{sub 2} molecules, and desorption of the recombined H{sub 2} molecules from the surface of an oblate spheroidal grain, we obtain diffusion coefficients of the Fokker-Planck equation for the distribution function of fluctuating angular momentum. Torque coefficients corresponding to the recombination mechanism show that the nonspherical dust grains may rotate with a suprathermal angular velocity.
Diffusion coefficients of Fokker-Planck equation for rotating dust grains in a fusion plasma
International Nuclear Information System (INIS)
In the fusion devices, ions, H atoms, and H2 molecules collide with dust grains and exert stochastic torques which lead to small variations in angular momentum of the grain. By considering adsorption of the colliding particles, thermal desorption of H atoms and normal H2 molecules, and desorption of the recombined H2 molecules from the surface of an oblate spheroidal grain, we obtain diffusion coefficients of the Fokker-Planck equation for the distribution function of fluctuating angular momentum. Torque coefficients corresponding to the recombination mechanism show that the nonspherical dust grains may rotate with a suprathermal angular velocity
Maryshev, Boris; Latrille, Christelle; Néel, Marie-Christine
2016-01-01
Tracer tests in natural porous media sometimes show abnormalities that suggest considering a fractional variant of the Advection Diffusion Equation supplemented by a time derivative of non-integer order. We are describing an inverse method for this equation: it finds the order of the fractional derivative and the coefficients that achieve minimum discrepancy between solution and tracer data. Using an adjoint equation divides the computational effort by an amount proportional to the number of freedom degrees, which becomes large when some coefficients depend on space. Method accuracy is checked on synthetical data, and applicability to actual tracer test is demonstrated.
Towards an intrinsic relationship between diffusion coefficients and microscopic feature of cements?
International Nuclear Information System (INIS)
Long-term behavior of cemented waste packages requires the knowledge of water diffusion coefficients (water is supposed to be the main degradation agent, by solubilization of some chemical compounds). A simple modeling, based on the use of hydration code CEMHYD3D is proposed and validated for pure OPC pastes (sound or degraded) at mass ratio water / cement lying between 0.25 and 0.65. The nature of the porosity available for diffusion and the role of residual anhydrous compounds are discussed. Copyright (2001) Material Research Society
Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites
Wei, Chengyu; Srivastava, Deepak; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)
2001-01-01
Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and van der Waals forces for polymer-nanotube interface have been used to investigate thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Addition of carbon nanotubes to polymer matrix is found to significantly increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. The increase has been attributed to the temperature dependent increase of the excluded volume for the polymer chains, and the findings could have implications in the composite processing, coating and painting applications.
Kernel-based regression of drift and diffusion coefficients of stochastic processes
Energy Technology Data Exchange (ETDEWEB)
Lamouroux, David [Department of Epileptology, University of Bonn (Germany)] [Helmholtz-Institute for Radiation and Nuclear Physics, University of Bonn (Germany); Lehnertz, Klaus, E-mail: klaus.lehnertz@ukb.uni-bonn.d [Department of Epileptology, University of Bonn (Germany)] [Helmholtz-Institute for Radiation and Nuclear Physics, University of Bonn (Germany)] [Interdisciplinary Center for Complex Systems, University of Bonn (Germany)
2009-09-21
To improve the estimation of drift and diffusion coefficients of stochastic processes in case of a limited amount of usable data due to e.g. non-stationarity of natural systems we suggest to use kernel-based instead of histogram-based regression. We propose a method for bandwidth selection and compare it to a widely used cross-validation method. Kernel-based regression reveals an enhanced ability to estimate drift and diffusion especially for a small amount of data. This allows one to improve resolvability of changes in complex dynamical systems as evidenced by an exemplary analysis of electroencephalographic data recorded from a human epileptic brain.
Integral formula for the effective diffusion coefficient in two-dimensional channels
Kalinay, Pavol
2016-07-01
The effective one-dimensional description of diffusion in two-dimensional channels of varying cross section is revisited. The effective diffusion coefficient D (x ) , extending Fick-Jacobs equation, depending on the longitudinal coordinate x , is derived here without use of scaling of the transverse coordinates. The result of the presented method is an integral formula for D (x ) , calculating its value at x as an integral of contributions from the neighboring positions x' depending on h (x') , a function shaping the channel. Unlike the standard formulas based on the scaling, the new proposed formula also describes D (x ) correctly near the cusps, or in wider channels.
Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas
DEFF Research Database (Denmark)
Bruun, Georg
2012-01-01
Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components. It is demonstr......Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components. It is...... demonstrated that the minimum value of the viscosity decreases with the mass ratio, since Fermi blocking becomes less efficient. We furthermore analyze recent experimental results for the quadrupole mode of a two-dimensional gas in terms of viscous damping, obtaining a qualitative agreement using no fitting...
Diffusion-Coefficients of Sulfate and Methane in Marine-Sediments - Influence of Porosity
DEFF Research Database (Denmark)
IVERSEN, N.; JØRGENSEN, BB
1993-01-01
Tracer diffusion coefficients of sulfate and methane were determined in seawater (D(o)) and in sediments (D(s)). The diffusion coefficients in seawater (20 parts per thousand S) at 4-degrees-C were 0.56 +/- 0.04*10(-5) cm2 s-1 for sulfate and 0.87 +/- 0.10*10(-5) cm2 s-1 for methane. The sediment...... our data, it was possible to deduce the empirical equation theta2 = 1 + n(1 - phi), which was used to calculate D(s) from D(o):D(s) = D(o)/1 + n(1 - phi), using n = 3 for clay-silt sediments and n = 2 for sandy sediments....
Thermal diffusivity coefficient of glycerin determined on an acoustically levitated drop.
Ohsaka, K; Rednikov, A; Sadhal, S S
2002-10-01
We present a technique that can be used to determine the thermal diffusivity coefficient of undercooled liquids that exist at temperatures below their freezing points. The technique involves levitation of a small amount of liquid in the shape of a flattened drop using an acoustic levitator and heating it with a CO2 laser. The heated drop is then allowed to cool naturally by heat loss from the surface. Due to acoustic streaming, heat loss is highly non-uniform and appears to mainly occur at the drop circumference (equatorial region). This fact allows us to relate the heat loss rate with a heat transfer model to determine the thermal diffusion coefficient. We demonstrate the feasibility of the technique using glycerin drops as a model liquid. PMID:12446319
Determination of the Solute Diffusion Coefficient by the Droplet Migration Method
Energy Technology Data Exchange (ETDEWEB)
Shan Liu; Jing Teng; Jeongyun Choi
2007-07-01
Further analysis of droplet migration in a temperature gradient field indicates that different terms can be used to evaluate the solute diffusion coefficient in liquid (D{sub L}) and that there exists a characteristic curve that can describe the motion of all the droplets for a given composition and temperature gradient. Critical experiments are subsequently conducted in succinonitrile (SCN)-salol and SCN-camphor transparent alloys in order to observe dynamic migration processes of a number of droplets. The derived diffusion coefficients from different terms are the same within experimental error. For SCN-salol alloys, D{sub L} = (0.69 {+-} 0.05) x 10{sup -3} mm{sup 2}/s, and for SCN-camphor alloys, D{sub L} = (0.24 {+-} 0.02) x 10{sup -3} mm{sup 2}/s.
A Monte Carlo model for determination of binary diffusion coefficients in gases
Panarese, A.; Bruno, D.; Colonna, G.; Diomede, P.; Laricchiuta, A.; Longo, S.; Capitelli, M.
2011-06-01
A Monte Carlo method has been developed for the calculation of binary diffusion coefficients in gas mixtures. The method is based on the stochastic solution of the linear Boltzmann equation obtained for the transport of one component in a thermal bath of the second one. Anisotropic scattering is included by calculating the classical deflection angle in binary collisions under isotropic potential. Model results are compared to accurate solutions of the Chapman-Enskog equation in the first and higher orders. We have selected two different cases, H 2 in H 2 and O in O 2, assuming rigid spheres or using a model phenomenological potential. Diffusion coefficients, calculated in the proposed approach, are found in close agreement with Chapman-Enskog results in all the cases considered, the deviations being reduced using higher order approximations.
Diffusion coefficients of sodium fluoride in aqueous solutions at 298.15 k and 310.15 k.
Ribeiro, Ana C F; Lobo, Victor M M; Sobral, Abilio J F N; Soares, Helder T F C; Esteso, Ana R J; Esteso, Miguel A
2010-06-01
Mutual diffusion coefficients (interdiffusion coefficients) have been measured for sodium fluoride in water at 298.15 K and 310.15 K at concentrations between 0.003 mol dm-3 and 0.05 mol dm-3. The diffusion coefficients were measured using a conductimetric cell. The experimental mutual diffusion coefficients are discussed on the basis of the Onsager-Fuoss model. The limiting molar conductivity of the fluoride ion in these solutions at 310.15 K has been estimated using these results. PMID:24061738
DEFF Research Database (Denmark)
Christensen, Eva Arnspang; Koffman, Jennifer Skaarup; Marlar, Saw; Weissman, Paul; Nejsum, Lene Niemann
2014-01-01
available code to measure diffusion coefficients of proteins. kICS calculates a time correlation function from a fluorescence microscopy image stack after Fourier transformation of each image to reciprocal (k-) space. Subsequently, circular averaging, natural logarithm transform and linear fits to the...... correlation function yields the diffusion coefficient. This paper provides a step-by-step guide to the image analysis and measurement of diffusion coefficients via kICS. First, a high frame rate image sequence of a fluorescently labeled plasma membrane protein is acquired using a fluorescence microscope Then...... slopes" plot from the k-space time correlation functions, and the diffusion coefficient is calculated from the slope of the plot. Below is a step-by-step kICS procedure to measure the diffusion coefficient of a membrane protein using the renal water channel aquaporin-3 tagged with EGFP as a canonical...
Enhanced Group Analysis of Variable Coefficient Semilinear Diffusion Equations with a Power Source
Vaneeva, O O; Sophocleous, C
2007-01-01
A new approach to group classification problems and more general investigations on transformational properties of classes of differential equations are proposed. It is based on mappings between classes of differential equations, generated by families of point transformations. A class of variable coefficient (1+1)-dimensional semilinear reaction--diffusion equations of the general form $f(x)u_t=(g(x)u_x)_x+h(x)u^m$ ($m\
Liu, M. K.; Li, P.; Giddings, J. C.
1993-01-01
In this study three flow field-flow fractionation (flow FFF) channels are utilized for the separation of proteins and for the simultaneous measurement of their translational diffusion coefficients, D. One channel has a traditional sample inlet, whereas the other two incorporate a frit inlet design that permits more convenient and rapid sample introduction. The dependence of retention time on D, which leads to differential elution and the opportunity to measure D for protein peaks purified by ...
A new approach to the calculation of axial and radial neutron diffusion coefficients
International Nuclear Information System (INIS)
A new approach to the calculation of axial and radial diffusion coefficients is developed that introduces a new angle dependent 'transport cross-section'. Calculations are carried out using the programme WDSN(ST) for both AGR-type and SGHWR lattices. The results are compared with the standard method due to Benoist embodied in WIMS and, in the AGR case, with Monte Carlo results. The comparisons suggest major errors in the WIMS results for SGHWR clusters in the axial direction. (author)
Determination of the diffusion coefficient of new insulators composed of vegetable fibers
Boulaoued I.; Mhimid A.
2012-01-01
The knowledge of the moisture transport of building materials is necessary for the performance of building structures. The control of moisture transport is essential to describe the moisture migration process through the building walls. The present work’s aim is to determine through experiment the water diffusion coefficient of different insulators in unsteady-state based on the Fick’s second law equation. This equation was solved analytically by the separation of variables method (MOD1...
Diffusion coefficients-surface and interfacial tensions - Particular study of some lauryl compounds
International Nuclear Information System (INIS)
Two important results of the double lipophilic and hydrophilic character of some heavy organic compounds with a polar group at the end of the chain, were studied: - In a first part, molecular diffusion coefficients were measured in order to prove the micellar aggregation of tri-laurylammonium nitrate in some organic solutions; - In a second part, the tensioactivity of some lauryl compounds (lauric acid, lauric alcohol, mono-laurylamine, etc.), was studied. (author)
Mukherjee, Arnab; Bhattacharyya, Sarika; Bagchi, Biman
2002-01-01
Extensive isothermal-isobaric (NPT) molecular dynamics simulations at many different temperatures and pressures have been carried out in the well-known Kob-Andersen binary mixture model to monitor the effect of pressure (P) and temperature (T) on the dynamic properties such as the viscosity (\\eta) and the self-diffusion (Di) coefficients of the binary system. The following results have been obtained: (i) Compared to temperature, pressure is found to have a weaker effect on the dynamical prope...
Scaling Limits of a Tagged Particle in the Exclusion Process with Variable Diffusion Coefficient
Gonçalves, Patrícia; Jara, Milton
2008-09-01
We prove a law of large numbers and a central limit theorem for a tagged particle in a symmetric simple exclusion process in ℤ with variable diffusion coefficient. The scaling limits are obtained from a similar result for the current through -1/2 for a zero-range process with bond disorder. For the CLT, we prove convergence to a fractional Brownian motion of Hurst exponent 1/4.
NOVEL TECHNIQUE FOR DIRECT MEASUREMENT OF THE PLASMA DIFFUSION COEFFICIENT IN MAGNETISED PLASMA
Czech Academy of Sciences Publication Activity Database
Brotánková, Jana; Martines, E.; Adámek, Jiří; Stöckel, Jan; Popa, G.; Costin, C.; Schrittwieser, R.; Ionita, C.; Van Oost, G.
Praha, 2007. s. 40. [International Workshop on Electric Probes in Magnetized Plasmas/7th./. 22.7.2007-25.7.2007, Praha] R&D Projects: GA AV ČR(CZ) KJB100430601 Institutional research plan: CEZ:AV0Z20430508 Keywords : Probes * ball-pen probe * katsumata * edge * tokamak * probe diagnostics * diffusion coefficient Subject RIV: BL - Plasma and Gas Discharge Physics http://iwep2007.mff.cuni.cz/book_of_abstracts.pdf
International Nuclear Information System (INIS)
Diffusion coefficients of trace-level cesium in un-irradiated IG-110 graphite were determined by thin-source annealing experiments. Thus obtained values of the diffusion coefficients were larger by 3-4 orders of magnitude than in-pile values for the same brand graphite. Activation energies of the diffusion coefficients for the un-irradiated graphite were 112 and 95 kJ/mol for two series of the laboratory experiments, which are considerably lower than the in-pile value of 157 kJ/mol. An extended diffusion-trap model is proposed to explain the decreased diffusion coefficient and the increased activation energy for the in-pile diffusion, by considering the trapping effect of irradiation-induced lattice defects. (orig.)
Comparative analyses of diffusion coefficients for different extraction processes from thyme
Directory of Open Access Journals (Sweden)
Petrovic Slobodan S.
2012-01-01
Full Text Available This work was aimed to analyze kinetics and mass transfer phenomena for different extraction processes from thyme (Thymus vulgaris L. leaves. Different extraction processes with ethanol were studied: Soxhlet extraction and ultrasound-assisted batch extraction on the laboratory scale as well as pilot plant batch extraction with mixing. The extraction processes with ethanol were compared to the process of supercritical carbon dioxide extraction performed at 10 MPa and 40°C. Experimental data were analyzed by mathematical model derived from the Fick’s second law to determine and compare diffusion coefficients in the periods of constant and decreasing extraction rate. In the fast extraction period, values of diffusion coefficients were one to three orders of magnitude higher compared to those determined for the period of slow extraction. The highest diffusion coefficient was reported for the fast extraction period of supercritical fluid extraction. In the case of extraction processes with ethanol, ultrasound, stirring and extraction temperature increase enhanced mass transfer rate in the washing phase. On the other hand, ultrasound contributed the most to the increase of mass transfer rate in the period of slow extraction.
Institute of Scientific and Technical Information of China (English)
WANG Chao; WANG Zhi; WANG Jing; SU Tao
2007-01-01
To determinate the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis(EDX) is used to establish the content change of oxygen in the adhesive in adhesive/carbon fiber reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analysis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of both energy dispersive X-ray spectroscopy and elemental analysis. The determined results with EDX analysis are almost the same as those determined with elemental analysis and the results also show that the durability of the adhesive/carbon fiber reinforced epoxy resin composite joints subjected to silane coupling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treatment.
International Nuclear Information System (INIS)
The diffusion coefficients of sodium iodide vapor in the rare gases, argon, krypton and xenon, are determined by a method combining the analysis of measured diffusing mass with continuous monitoring of the sodium iodide vapor concentration in a flowing stream of sodium iodide-rare gas mixture. The flowing sodium iodide vapor is ionized upon its passage over a heated filament, and the generated ions are collected by a negatively-charged arched plate saddling the filament. The resulting ion current, measured by digital current meter, is integrated in time to obtain cumulative values from outset of run. The curve of the integrated values plotted against time approaches linearity with progress of run. The asymptote of the curve intersects the time axis at a point whose position serves to determine the diffusion coefficient, by applying an equation derived from the formula given by Carslaw and Jaeger. The coefficients thus determined for the three rare gases in runs at temperatures between 660degC and 710degC have proved to agree well with the values estimated using the semi-empirical correlation presented by Wilke and Lee. (author)
International Nuclear Information System (INIS)
A novel method to obtain the full neoclassical transport matrix for general toroidal plasmas by using the solution of the linearized drift kinetic equation with the pitch-angle-scattering collision operator is shown. In this method, the neoclassical coefficients for both poloidal and toroidal viscosities in toroidal helical systems can be obtained, and the neoclassical transport coefficients for the radial particle and heat fluxes and the bootstrap current with the nondiagonal coupling between unlike-species particles are derived from combining the viscosity-flow relations, the friction-flow relations, and the parallel momentum balance equations. Since the collisional momentum conservation is properly retained, the well-known intrinsic ambipolar condition of the neoclassical particle fluxes in symmetric systems is recovered. Thus, these resultant neoclassical diffusion and viscosity coefficients are applicable to evaluating accurately how the neoclassical transport in quasi-symmetric toroidal systems deviates from that in exactly symmetric systems
Analysis of Diffusion Coefficient using Reversed-Flow Gas Chromatography-A Review
Directory of Open Access Journals (Sweden)
Khalisanni Khalid
2011-01-01
Full Text Available Problem statement: Since the earliest publication on the technique, Reversed-Flow Gas Chromatography (RF-GC has been used to determine physicochemical properties by measuring the value of one in the presence of another. The method is precise, accurate and simple compared to other conventional techniques. Approach: The experimental setup consists of a small modification of a commercial gas chromatograph, so that it includes a four- or six-port gas sampling valve and a simple cell placed inside the chromatographic oven. Results: This cell suppresses the effects of the carrier gas flow on the physicochemical occurrence taking place in the stationary phase. These phenomena pertain to rate coefficients and diffusion coefficients. Conclusion: The RF-GC methodologies can be considered as a wise instrumental approach to study the physicochemical phenomenon of liquid pollutants. It can be used to determine the rate coefficients and diffusion coefficients values of samples at various temperatures for the studies of environmental science and physical chemistry research areas. However, the methodologies are not restricted to the current fields of research. It is also relevant in the area of food chemistry, geochemistry, material science, nanotechnology, biological science and chemical technology.
Molecular dynamics calculation of rotational diffusion coefficient of a carbon nanotube in fluid
Cao, Bing-Yang; Dong, Ruo-Yu
2014-01-01
Rotational diffusion processes are correlated with nanoparticle visualization and manipulation techniques, widely used in nanocomposites, nanofluids, bioscience, and so on. However, a systematical methodology of deriving this diffusivity is still lacking. In the current work, three molecular dynamics (MD) schemes, including equilibrium (Green-Kubo formula and Einstein relation) and nonequilibrium (Einstein-Smoluchowski relation) methods, are developed to calculate the rotational diffusion coefficient, taking a single rigid carbon nanotube in fluid argon as a case. We can conclude that the three methods produce same results on the basis of plenty of data with variation of the calculation parameters (tube length, diameter, fluid temperature, density, and viscosity), indicative of the validity and accuracy of the MD simulations. However, these results have a non-negligible deviation from the theoretical predictions of Tirado et al. [J. Chem. Phys. 81, 2047 (1984)], which may come from several unrevealed factors of the theory. The three MD methods proposed in this paper can also be applied to other situations of calculating rotational diffusion coefficient.
Kim, Changho; Borodin, Oleg; Karniadakis, George Em
2015-12-01
We analyze two standard methods to compute the diffusion coefficient of a tracer particle in a medium from molecular dynamics (MD) simulation, the velocity autocorrelation function (VACF) method, and the mean-squared displacement (MSD) method. We show that they are equivalent in the sense that they provide the same mean values with the same level of statistical errors. We obtain analytic expressions for the level of the statistical errors present in the time-dependent diffusion coefficient as well as the VACF and the MSD. Under the assumption that the velocity of the tracer particle is a Gaussian process, all results are expressed in terms of the VACF. Hence, the standard errors of all relevant quantities are computable once the VACF is obtained from MD simulation. By using analytic models described by the Langevin equations driven by Gaussian white noise and Poissonian white shot noise, we verify our theoretical error estimates and discuss the non-Gaussianity effect in the error estimates when the Gaussian process approximation does not hold exactly. For validation, we perform MD simulations for the self-diffusion of a Lennard-Jones fluid and the diffusion of a large and massive colloid particle suspended in the fluid. Our theoretical framework is also applicable to mesoscopic simulations, e.g., Langevin dynamics and dissipative particle dynamics.
Mutual diffusion coefficient models for polymer-solvent systems based on the Chapman-Enskog theory
Directory of Open Access Journals (Sweden)
R. A. Reis
2004-12-01
Full Text Available There are numerous examples of the importance of small molecule migration in polymeric materials, such as in drying polymeric packing, controlled drug delivery, formation of films, and membrane separation, etc. The Chapman-Enskog kinetic theory of hard-sphere fluids with the Weeks-Chandler-Andersen effective hard-sphere diameter (Enskog-WCA has been the most fruitful in diffusion studies of simple fluids and mixtures. In this work, the ability of the Enskog-WCA model to describe the temperature and concentration dependence of the mutual diffusion coefficient, D, for a polystyrene-toluene system was evaluated. Using experimental diffusion data, two polymer model approaches and three mixing rules for the effective hard-sphere diameter were tested. Some procedures tested resulted in models that are capable of correlating the experimental data with the refereed system well for a solvent mass fraction greater than 0.3.
DIFFUSION COEFFICIENTS IN POLYMER-SOLVENT SYSTEMS FOR HIGHLY CONCENTRATED POLYMER SOLUTIONS
Directory of Open Access Journals (Sweden)
R.A. Reis
2001-12-01
Full Text Available The Vrentas/Duda proposal for the diffusion of polymer-solvent systems, which is based on the free-volume theory, was employed in correlating and predicting mutual diffusion coefficients in highly concentrated polymer solutions. It has been observed that the predictive version of the model is capable of qualitatively representing the experimental data, while the use of an adjustable parameter greatly improves the performance of the model. The systems studied were poly(vinyl acetate-toluene and Neoprene-acetone, and a comparison between experimental data and calculated values from the Vrentas/Duda model is reported. A new experimental apparatus based on the sorption technique was built to provide reliable diffusivity data on the Neoprene-acetone system.
Coefficient of Thermal Diffusivity of Insulation Brick Developed from Sawdust and Clays
Directory of Open Access Journals (Sweden)
E. Bwayo
2014-01-01
Full Text Available This paper presents an experimental result on the effect of particle size of a mixture of ball clay, kaolin, and sawdust on thermal diffusivity of ceramic bricks. A mixture of dry powders of ball clay, kaolin of the same particle size, and sawdust of different particle sizes was mixed in different proportions and then compacted to high pressures before being fired to 950°C. The thermal diffusivity was then determined by an indirect method involving measurement of thermal conductivity, density, and specific heat capacity. The study reveals that coefficient of thermal diffusivity increases with decrease in particle size of kaolin and ball clay but decreases with increase in particle size of sawdust.
Mialdun, A; Shevtsova, V
2015-12-14
We report on the measurement of diffusion (D), Soret (S(T)), and thermodiffusion (D(T)) coefficients in toluene-cyclohexane mixture with mass fraction of toluene 0.40 onboard of the International Space Station. The coefficients were measured in the range of the mean temperatures between 20 °C and 34 °C. The Soret coefficient is negative within the investigated temperature range and its absolute value |S(T)| decreases with increasing temperature. The diffusion coefficient for this system increases with temperature rising. For comparison, the temperature dependence of diffusion coefficient was measured in ground laboratory using counter-flow cell technique and revealed a good agreement with microgravity results. A non-direct comparison of the measured onboard Soret coefficients with different systems indicated a similar trend for the temperature dependent behavior. Unexpected experimental finding is that for this system the thermodiffusion coefficient D(T) does not depend on temperature. PMID:26671399
Sokoletsky, Leonid; Yang, Xianping; Shen, Fang
2014-11-01
Radiative transfer modelling in atmosphere, water, and on the air-water surface was used to create an algorithm and computer code for satellite monitoring Chinese estuarine and coastal waters. The atmospheric part of the algorithm is based on the Reference Evaluation of Solar Transmittance (REST) model for calculation of optical properties of the atmosphere from the top of the atmosphere to the target; for modelling optical properties from target towards satellite's sensor, an optical reciprocity principle has been used. An algorithm uses estimates derived from three different sources: 1) the MODIS-based software; 2) radiative transfer equations, and 3) well-known empirical relationships between measured parameters and optical depths and transmittances for such atmospheric components as molecules, aerosols, ozone, nitrogen dioxide, precipitable water vapor and uniformly mixed gases. Using this model allowed us to derive a reliable relationship relating an important parameter, the diffuse-to-global solar incoming irradiance ratio, to the aerosol optical thickness, solar zenith angle and wavelength. The surface and underwater parts of the algorithm contained theoretical and semi-empirical relationships between inherent (such as absorption, scattering and backscattering coefficients) and apparent (remote-sensing reflectance and diffuse attenuation coefficient, Kd) optical properties, and suspended sediment concentration (SSC) measured in the Yangtze River Estuary and its adjacent coastal area. The first false colour maps of SSC and Kd demonstrated a well accordance with the multi-year field observations in the region, and suggest promise for use of this algorithm for the regular monitoring of Chinese and worldwide natural waters.
The role of diffusion coefficients in the dynamics of nuclear processes
International Nuclear Information System (INIS)
The dissipation process in open quantum systems at initial time before the setting of the equilibrium state plays a key role in such physical processes, as quantum-optical processes, nuclear fission and fusion and deep inelastic collisions of heavy ions. The goal of a given work is to demonstrate the advanced method for the calculation of non-stationary diffusion coefficients of the collective system, in case when the collective subsystem and thermostat are linearly coupled in the coordinate and momentum. As a result of the interaction between the degrees of freedom of collective and intrinsic subsystems, the transport and diffusion coefficients on coordinate, momentum and coordinate-momentum appear in the system. The Langevin formalism which is effective in description of fluctuation and dissipative processes in macroscopic systems has been introduced in derivation of equations of motion. In the kinetic theory the Leaving's method significantly simplifies a procedure of calculation of non-stationary quantum and thermal fluctuations and provides a clear picture of the dynamics of the process. The microscopic Hamiltonian of the system (thermostat plus collective system) is given. For example, while describing the interaction of nuclei at low energies, the coupling in the coordinate responses for the influence of the mean field of each nucleus on the single-particle motion in other nucleus whereas the last term describes the relation between the currents of intrinsic and collective motion. In the procedure of solving the second order Heisenberg equations, the integro-differential quantum stochastic Langevin Equations are obtained directly. Knowing its solution we may write the equations for the first and second moments which provide us the expressions for the transport and diffusion coefficients. In the figure the time dependencies of diffusion coefficients at the temperature T=0.1 MeV are given. In our calculations we consider the case of a large mass μ=448m0 (m0
Diffusion Coefficients and Activation Energies for Ag Transport through SiC
International Nuclear Information System (INIS)
One of the desired functions of TRISO coating is to prevent the release of fission products from inside the particle into the coolant. Among these layers, the retention of fission products is accomplished primarily by the SiC layer of the coating. These processes include oxide fuel kernel migration (via the transport of carbon from the cool to hot side); intra-layer crack formation, noble gas (Kr, Xe), Ba, Ag, Sr, Cs diffusion out of the kernel; pressure build-up due to noble gas release from the kernel and CO from released oxygen in ungettered oxide kernel; a Pd attack on SiC and noble gas, Pd, Ba, Sr, Cs, Ag, transport via bulk diffusion, grain boundaries, and cracks through the coating layers. In this paper, the measured and estimated diffusion coefficients of Ag in and/or through SiC are compared based on the following experimental methods: 1) measuring Ag diffusion through ion-implanted cubic (3C) SiC and 6H-SiC samples and annealing, 2) measuring Ag diffusion through a diffusion couple and annealing, and 3) fitting the overall integrated/fractional Ag release from a batch of TRISO fuel particle during heating after irradiation and irradiation testing. The causes of uprising Ag transport through SiC, the coating layer of TRISO fuel are complex depending on the temperature during operation or irradiation testing. Although Ag transport depends on the microstructure of SiC (such as grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, etc.), neutron irradiation, irradiation temperature, Pd attack, thermal decomposition, transmutation products, layer thinning and coated particle shape, etc., Ag diffusion along the grain boundary of SiC plays a major role. Considering that the current Ag diffusion coefficient is summarized and compared from previous studies, it might also be possible that, considering the irradiation effects of SiC, the Ag retention ability of a TRISO particle somehow improves during the TRISO
International Nuclear Information System (INIS)
The calculation of diffusion coefficients in a lattice necessitates the knowledge of a correct method of weighting the free paths of the different constituents. An unambiguous definition of this weighting method is given here, based on the calculation of leakages from a zone of a reactor. The formulation obtained, which is both simple and general, reduces the calculation of diffusion coefficients to that of collision probabilities in the different media; it reveals in the expression for the radial coefficient the series of the terms of angular correlation (cross terms) recently shown by several authors. This formulation is then used to calculate the practical case of a classical type of lattice composed of a moderator and a fuel element surrounded by an empty space. Analytical and numerical comparison of the expressions obtained with those inferred from the theory of BEHRENS shows up the importance of several new terms some of which are linked with the transparency of the fuel element. Cross terms up to the second order are evaluated. A practical formulary is given at the end of the paper. (author)
Measuring diffusion coefficients via two-photon fluorescence recovery after photobleaching.
Sullivan, Kelley D; Brown, Edward B
2010-01-01
Multi-fluorescence recovery after photobleaching is a microscopy technique used to measure the diffusion coefficient (or analogous transport parameters) of macromolecules, and can be applied to both in vitro and in vivo biological systems. Multi-fluorescence recovery after photobleaching is performed by photobleaching a region of interest within a fluorescent sample using an intense laser flash, then attenuating the beam and monitoring the fluorescence as still-fluorescent molecules from outside the region of interest diffuse in to replace the photobleached molecules. We will begin our demonstration by aligning the laser beam through the Pockels Cell (laser modulator) and along the optical path through the laser scan box and objective lens to the sample. For simplicity, we will use a sample of aqueous fluorescent dye. We will then determine the proper experimental parameters for our sample including, monitor and bleaching powers, bleach duration, bin widths (for photon counting), and fluorescence recovery time. Next, we will describe the procedure for taking recovery curves, a process that can be largely automated via LabVIEW (National Instruments, Austin, TX) for enhanced throughput. Finally, the diffusion coefficient is determined by fitting the recovery data to the appropriate mathematical model using a least-squares fitting algorithm, readily programmable using software such as MATLAB (The Mathworks, Natick, MA). PMID:20190730
Measuring partition and diffusion coefficients for volatile organic compounds in vinyl flooring
Cox, Steven S.; Zhao, Dongye; Little, John C.
Interactions between volatile organic compounds (VOCs) and vinyl flooring (VF), a relatively homogenous, diffusion-controlled building material, were characterized. The sorption/desorption behavior of VF was investigated using single-component and binary systems of seven common VOCs ranging in molecular weight from n-butanol to n-pentadecane. The simultaneous sorption of VOCs and water vapor by VF was also investigated. Rapid determination of the material/air partition coefficient ( K) and the material-phase diffusion coefficient ( D) for each VOC was achieved by placing thin VF slabs in a dynamic microbalance and subjecting them to controlled sorption/desorption cycles. K and D are shown to be independent of concentration for all of the VOCs and water vapor. For the four alkane VOCs studied, K correlates well with vapor pressure and D correlates well with molecular weight, providing a means to estimate these parameters for other alkane VOCs. While the simultaneous sorption of a binary mixture of VOCs is non-competitive, the presence of water vapor increases the uptake of VOCs by VF. This approach can be applied to other diffusion-controlled materials and should facilitate the prediction of their source/sink behavior using physically-based models.
International Nuclear Information System (INIS)
We have fabricated parallel stripes of nanostructures in an n-type Si substrate by implanting 30 keV Ga+ ions from a focused ion beam (FIB) source. Two sets of implantation were carried out. In one case, during implantation the substrate was held at room temperature and in the other case at 400 deg. C. Photoemission electron microscopy (PEEM) was carried out on these samples. The implanted parallel stripes, each with a nominal dimension of 4000 nm x 100 nm, appear as bright regions in the PEEM image. Line scans of the intensities from the PEEM image were recorded along and across these stripes. The intensity profile at the edges of a line scan is broader for the implantation carried out at 400 deg. C compared to room temperature. From the analysis of this intensity profile, the lateral diffusion coefficient of Ga in silicon was estimated assuming that the PEEM intensity is proportional to Ga concentration. The diffusion coefficient at 400 deg. C has been estimated to be ∼1.3 x 10-15 m2/s. Across the stripes an asymmetric diffusion profile has been observed, which has been related to the sequence of implantation of these stripes and the associated defect distribution due to lateral straggling of the implanted ions.
The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering
Directory of Open Access Journals (Sweden)
Meyer Andreas
2015-01-01
Full Text Available Quasielastic incoherent neutron scattering (QENS has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to undercoolings of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and 73germanium isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points.
The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering
International Nuclear Information System (INIS)
Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to an under-cooling of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and 73Ge isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points. (author)
Evolution of the Magnetic Field Line Diffusion Coefficient and Non-Gaussian Statistics
Snodin, A. P.; Ruffolo, D.; Matthaeus, W. H.
2016-08-01
The magnetic field line random walk (FLRW) plays an important role in the transport of energy and particles in turbulent plasmas. For magnetic fluctuations that are transverse or almost transverse to a large-scale mean magnetic field, theories describing the FLRW usually predict asymptotic diffusion of magnetic field lines perpendicular to the mean field. Such theories often depend on the assumption that one can relate the Lagrangian and Eulerian statistics of the magnetic field via Corrsin’s hypothesis, and additionally take the distribution of magnetic field line displacements to be Gaussian. Here we take an ordinary differential equation (ODE) model with these underlying assumptions and test how well it describes the evolution of the magnetic field line diffusion coefficient in 2D+slab magnetic turbulence, by comparisons to computer simulations that do not involve such assumptions. In addition, we directly test the accuracy of the Corrsin approximation to the Lagrangian correlation. Over much of the studied parameter space we find that the ODE model is in fairly good agreement with computer simulations, in terms of both the evolution and asymptotic values of the diffusion coefficient. When there is poor agreement, we show that this can be largely attributed to the failure of Corrsin’s hypothesis rather than the assumption of Gaussian statistics of field line displacements. The degree of non-Gaussianity, which we measure in terms of the kurtosis, appears to be an indicator of how well Corrsin’s approximation works.
Measurement of Retinalamin diffusion coefficient in human sclera by optical spectroscopy
Genina, Elina A.; Bashkatov, Alexey N.; Zubkova, Elena A.; Kamenskikh, Tatiana G.; Tuchin, Valery V.
2008-12-01
The use of cytomedines (such as Retinalamin) in clinical practice has shown high effectiveness of the medicaments in ophthalmology. The study of diffusion of Retinalamin in scleral tissue is important for estimation of a drug dose delivered into inner tissue of eye, time of drug action, etc. In vitro measurements of spectral reflectance of sclera interacting with aqueous solution of Retinalamin have been carried out. Ten human sclera samples were included in the study. The results of the experiments have shown that penetration of Retinalamin into scleral tissue leads to the decrease of scleral reflectance due to optical immersion. Estimation of diffusion coefficient of studied solution has been made on the basis of analysis of optical reflectance dynamics of the sclera samples. The diffusion coefficient of Retinalamin in human scleral tissue was evaluated as (1.82±0.14)×10 -6 cm 2/s. The results are important for treatment of partial optic atrophy observed at primary open-angle glaucoma and others eye diseases.
Directory of Open Access Journals (Sweden)
Edgar de Alencar Teixeira
2010-06-01
Full Text Available Neste trabalho, determinou-se o valor nutritivo de quatro alimentos energéticos (fubá de milho, sorgo, farelo de arroz integral e quirera de arroz para juvenis de surubim. Os coeficientes de digestibilidade aparente da matéria seca (MS, proteína bruta (PB e energia bruta (EB foram avaliados pela metodologia de substituição do alimento numa ração-referência usando-se 0,1% de óxido crômico como indicador externo. Utilizaram-se 240 alevinos com 30 g de peso médio distribuídos em tanques apropriados para coleta de fezes. O delineamento foi inteiramente casualizado com quatro dietas, cada uma com quatro repetições. O coeficiente de digestibilidade aparente da matéria seca do fubá de milho foi de 62,3%; do farelo de arroz, 59,7%; da quirera de arroz, 40,4%; e do sorgo, 38%. Os coeficientes de digestibilidade da proteína bruta, nesta ordem, foram 87,4; 83,8; 85,3; e 81,1%; e os da energia bruta, 62,4; 66,4; 46,9 e 47,8%. Entre os alimentos avaliados, o que possui maior digestibilidade da matéria seca, proteína bruta e energia bruta é o farelo de arroz e o de menor digestibilidade, o sorgo.It was determined, in this work, the nutritional value of four energetic feeds (corn meal, sorghum, whole rice bran, and ground rice for surubim juveniles. Apparent digestibility coefficients of dry matter (DM, crude protein (CP, and gross energy (GE were evaluated by food replacement methodology in a reference-feeding using 0.1% of chromic oxide as an external marker. It was used 240 fingerlings with an average weight of 30 g distributed in tanks fitted for faeces collection. A complete random design with four diets, each one with four replicates, was used. Apparent digestibility coefficient of dry matter for corn meal was 62.3%; for rice bran, 59.7%; for ground rice, 40.4%, and for sorghum, 38%. Digestibility coefficients for crude protein were, in this order, the following: 87.4, 83.8, 85.3 and 81.1% and digestibility coefficient for gross
Energy Technology Data Exchange (ETDEWEB)
Lovera, P.; Ferry, C.; Poinssot, Ch. [CEA Saclay, Dept. de Physico-Chimie (DPC), 91 - Gif sur Yvette (France); Johnson, L. [Nagra, Baden (Switzerland)
2003-07-01
This document corresponds to the deliverable D2 of the Work Package 1 of the 'Spent Fuel Stability under repository conditions' (SFS) European project. It constitutes a synthesis report on relevant diffusion coefficients of fission products and helium in spent nuclear fuels at high and low temperatures. Coefficients corresponding to thermally activated diffusion were reviewed from literature data for O, U (self-diffusion coefficients), fission gases and other fission products. Data showed that thermal diffusion was irrelevant at temperatures expected in repository conditions. The occurrence of diffusion enhanced by alpha self-irradiation was studied through different theoretical approaches. A 'best estimate' value of the alpha self-irradiation diffusion coefficient, D (m{sup 2}.s{sup -1}), is proposed. It is extrapolated from enhanced diffusion under irradiation observed in reactor and would be proportional to the volume alpha activity in the spent nuclear fuel, A{sub v} (Bq.m{sup -3}) as: D/A{sub v} {approx_equal} 2.10{sup -41} (m{sup 5})The migration of stable Pb in Oklo's uraninites was studied in order to validate the proposed diffusion coefficient. The obtained value is one order of magnitude higher than the theoretical proposed value. As for He behaviour in spent nuclear fuel, a few data are today available in open literature. The document will be completed as soon as new experimental results are available. (authors)
International Nuclear Information System (INIS)
Based on a mechanistic understanding of solute migration in pure clay at nano-metric scale, a model has been developed to evaluate the effective diffusion coefficient De in clay-rocks at the centimeter scale from the description of the mineralogy (and its heterogeneity) of the rock at the micrometer scale. Given a DeCHTO in the clay matrix an effective diffusion coefficient can be calculated for the rock taking into account the mineralogical microstructure of the sample. The diffusion properties of the clay matrix govern the diffusion behaviour of chloride. (authors)
Energy Technology Data Exchange (ETDEWEB)
Diaz, N.; Goutelard, F. [CEA Saclay, Dept. de Physico-Chimie (DEN/DPC/SECR/L3MR), 91 - Gif sur Yvette (France); Turq, P. [Universite Pierre et Marie Curie, LI2C, 75 - Paris (France)
2007-07-01
Based on a mechanistic understanding of solute migration in pure clay at nano-metric scale, a model has been developed to evaluate the effective diffusion coefficient De in clay-rocks at the centimeter scale from the description of the mineralogy (and its heterogeneity) of the rock at the micrometer scale. Given a De{sub C}{sup HTO} in the clay matrix an effective diffusion coefficient can be calculated for the rock taking into account the mineralogical microstructure of the sample. The diffusion properties of the clay matrix govern the diffusion behaviour of chloride. (authors)
Energy Technology Data Exchange (ETDEWEB)
Milgram, M
1999-07-01
Collision probability theory has been used to calculate neutronics parameters in nuclear reactors for many years, although it has long been suspected that this technique breaks down in the presence of material voids. In this work, the circumstances under which the breakdown of the probability theory occurs is first carefully determined, to be followed by an excruciatingly detailed explanation showing how to cure the problem mathematically, and how to verify that the remedy is operating properly. Once cured, it becomes possible to more accurately calculate parameters, such as directed diffusion coefficients, that are important to reactor analysis, particularly in the estimation of reactivity coefficients. Such calculations are performed here as a demonstration of the significance of the old and new mathematical methods to problems of practical interest. The most significant parameter investigated is a comparison of void reactivity in the presence of leakage by an experimental version of the lattice cell code WIMS-AECL using the old and new methods.
DEFF Research Database (Denmark)
Galliero, Guillaume; Medvedev, Oleg; Shapiro, Alexander
2005-01-01
different binary liquid mixtures of non-polar components that computed penetration lengths, for various temperatures and compositions, are consistent with those deduced from experiments in the framework of the formalism of the fluctuation theory. Moreover, the mutual diffusion coefficients obtained from a......Mutual diffusion in condensed phases is a theoretically and practically important subject of active research. One of the most rigorous and theoretically advanced approaches to the problem is a recently developed approach based on the concept of penetration lengths (Physica A 320 (2003) 211; Physica...... coupled fluctuation theory and molecular dynamics scheme exhibit consistent trends and average deviations from experimental data around 10-20%. (c) 2004 Elsevier B.V. All rights reserved....
Ivanova, N M; Sophocleous, C
2007-01-01
This is the second part of the series of papers on symmetry properties of a class of variable coefficient (1+1)-dimensional nonlinear diffusion-convection equations of general form $f(x)u_t=(g(x)A(u)u_x)_x+h(x)B(u)u_x$. At first, we review the results of Part 1 of the series on equivalence transformations and group classification of the class under consideration. Investigation of non-trivial limits of parameterized subclasses of equations from the given class, which generate contractions of the corresponding maximal Lie invariance algebras, leads to the natural notion of contractions of systems of differential equations. After a brief discussion on contractions of symmetries, equations and solutions in general case, such types of contractions are studied for diffusion--convection equations. A detailed symmetry analysis of an interesting equation from the class under consideration is performed. Exact solutions of some subclasses of the considered class are also given.
Integral formula for the effective diffusion coefficient in two-dimensional channels.
Kalinay, Pavol
2016-07-01
The effective one-dimensional description of diffusion in two-dimensional channels of varying cross section is revisited. The effective diffusion coefficient D(x), extending Fick-Jacobs equation, depending on the longitudinal coordinate x, is derived here without use of scaling of the transverse coordinates. The result of the presented method is an integral formula for D(x), calculating its value at x as an integral of contributions from the neighboring positions x^{'} depending on h(x^{'}), a function shaping the channel. Unlike the standard formulas based on the scaling, the new proposed formula also describes D(x) correctly near the cusps, or in wider channels. PMID:27575072
SEYHAN-GÜRTAŞ, Ferda; AK, M. Mehmet; Evranuz, E. Özgül
2001-01-01
The kinetics of water absorption by chickpeas (Koçbaşı, Kuşbaşı), lentils (green Pul) and beans (Battal, Dermason, Horoz, Şeker) grown in Turkey were studied by a gravimetric method during soaking at 15, 25 and 40ºC to determine moisture diffusivity of these selected legumes. The water diffusion coefficients of the legumes were in the range 9.71x10-11 - 5.98x10-10 m2/s for the chickpeas, 3.53x10-10 - 1.33x10-9 m2/s for the lentils and 4.35x10-11 - 3.79x10-9 m2/s for the beans. An Arrhenius-t...
Wu, Yan; Duan, Guosheng; Zhao, Xiang
2015-03-01
Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ-Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ-Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.
Sanford, R.F.
1982-01-01
Geological examples of binary diffusion are numerous. They are potential indicators of the duration and rates of geological processes. Analytical solutions to the diffusion equations generally do not allow for variable diffusion coefficients, changing boundary conditions, and impingement of diffusion fields. The three programs presented here are based on Crank-Nicholson finite-difference approximations, which can take into account these complicating factors. Program 1 describes the diffusion of a component into an initially homogeneous phase that has a constant surface composition. Specifically it is written for Fe-Mg exchange in olivine at oxygen fugacities appropriate for the lunar crust, but other components, phases, or fugacities may be substituted by changing the values of the diffusion coefficient. Program 2 simulates the growth of exsolution lamellae. Program 3 describes the growth of reaction rims. These two programs are written for pseudobinary Ca-(Mg, Fe) exchange in pyroxenes. In all three programs, the diffusion coefficients and boundary conditions can be varied systematically with time. To enable users to employ widely different numerical values for diffusion coefficients and diffusion distance, the grid spacing in the space dimension and the increment by which the grid spacing in the time dimension is increased at each time step are input constants that can be varied each time the programs are run to yield a solution of the desired accuracy. ?? 1982.
International Nuclear Information System (INIS)
This paper presents the experimental determination of the diffusion coefficient of borohydride anion and solution kinematic viscosity for a large panel of NaOH + NaBH4 electrolytic solutions relevant for use as anolyte in Direct Borohydride Fuel Cells (DBFC). The diffusion coefficients have been measured by the transit-time technique on gold rotating ring-disk electrodes, and verified using other classical techniques reported in the literature, namely the Levich method and Electrochemical Impedance Spectroscopy on a gold RDE, or chronoamperometry at a gold microdisk. The agreement between these methods is generally good. The diffusion coefficients measured from the RRDE technique are however ca. twice larger than those previously reported in the literature (e.g. ca. 3 x 10-5 cm2 s-1 in 1 M NaOH + 0.01 M NaBH4 at 25 deg. C in the present study vs. ca. 1.6 x 10-5 cm2 s-1 in 1 M NaOH + 0.02 M NaBH4 at 30 deg. C in the literature, as measured by chronoamperometry at a gold microsphere), which is thoroughly discussed. Our measurements using chronoamperometry at a gold microdisk showed that such technique can yield diffusion coefficient values below what expected. The origin of such finding is explained in the frame of the formation of both a film of boron-oxide(s) at the surface of the (static) gold microdisk and the generation of H2 bubbles at the electrode surface (as a result of the heterogeneous hydrolysis at Au), which alter the access to the electrode surface and thus prevents efficient measurements. Such film formation and H2 bubbles generation is not so much of an issue for rotating electrodes thanks to the convection of electrolyte which sweeps the electrode surface. In addition, should such film be present, the transit-time determination technique on a RRDE displays the advantage of not being very sensible to its presence: the parameter measured is the time taken by a perturbation generated the disk to reach the ring trough a distance several orders of
Energy Technology Data Exchange (ETDEWEB)
Chatenet, M. [Laboratoire d' Electrochimie et de Physico-chimie des Materiaux et des Interfaces, LEPMI, UMR 5631 CNRS/Grenoble-INP/UJF, 1130 rue de la piscine, BP75, 38402 Saint Martin d' Heres Cedex (France)], E-mail: Marian.Chatenet@phelma.grenoble-inp.fr; Molina-Concha, M.B. [Laboratoire d' Electrochimie et de Physico-chimie des Materiaux et des Interfaces, LEPMI, UMR 5631 CNRS/Grenoble-INP/UJF, 1130 rue de la piscine, BP75, 38402 Saint Martin d' Heres Cedex (France); El-Kissi, N. [Laboratoire de Rheologie, UMR 5520 CNRS/Grenoble-INP/UJF, 1301 rue de la piscine, 38041 Grenoble Cedex 9 (France); Parrour, G.; Diard, J.-P. [Laboratoire d' Electrochimie et de Physico-chimie des Materiaux et des Interfaces, LEPMI, UMR 5631 CNRS/Grenoble-INP/UJF, 1130 rue de la piscine, BP75, 38402 Saint Martin d' Heres Cedex (France)
2009-07-15
This paper presents the experimental determination of the diffusion coefficient of borohydride anion and solution kinematic viscosity for a large panel of NaOH + NaBH{sub 4} electrolytic solutions relevant for use as anolyte in Direct Borohydride Fuel Cells (DBFC). The diffusion coefficients have been measured by the transit-time technique on gold rotating ring-disk electrodes, and verified using other classical techniques reported in the literature, namely the Levich method and Electrochemical Impedance Spectroscopy on a gold RDE, or chronoamperometry at a gold microdisk. The agreement between these methods is generally good. The diffusion coefficients measured from the RRDE technique are however ca. twice larger than those previously reported in the literature (e.g. ca. 3 x 10{sup -5} cm{sup 2} s{sup -1} in 1 M NaOH + 0.01 M NaBH{sub 4} at 25 deg. C in the present study vs. ca. 1.6 x 10{sup -5} cm{sup 2} s{sup -1} in 1 M NaOH + 0.02 M NaBH{sub 4} at 30 deg. C in the literature, as measured by chronoamperometry at a gold microsphere), which is thoroughly discussed. Our measurements using chronoamperometry at a gold microdisk showed that such technique can yield diffusion coefficient values below what expected. The origin of such finding is explained in the frame of the formation of both a film of boron-oxide(s) at the surface of the (static) gold microdisk and the generation of H{sub 2} bubbles at the electrode surface (as a result of the heterogeneous hydrolysis at Au), which alter the access to the electrode surface and thus prevents efficient measurements. Such film formation and H{sub 2} bubbles generation is not so much of an issue for rotating electrodes thanks to the convection of electrolyte which sweeps the electrode surface. In addition, should such film be present, the transit-time determination technique on a RRDE displays the advantage of not being very sensible to its presence: the parameter measured is the time taken by a perturbation generated the
Vaneeva, O O; Sophocleous, C
2010-01-01
Reduction operators (called also nonclassical or $Q$-conditional symmetries) of variable coefficient semilinear reaction-diffusion equations with exponential source $f(x)u_t=(g(x)u_x)_x+h(x)e^{mu}$ are investigated using the algorithm involving a mapping between classes of differential equations, which is generated by a family of point transformations. A special attention is paid for checking whether reduction operators are inequivalent to Lie symmetry operators. The derived reduction operators are applied to construction of exact solutions.
International Nuclear Information System (INIS)
A number of new methods are discussed for determining the electron heat conduction coefficient chisub(e) in a tokamak from the experimental observation of the space-time evolution of the temperature perturbations induced by internal disruptions. In the Oak Ridge Tokamak (ORMAK) the various average values of chisub(e) and the radial dependence of chisub(e) are found to be consistent with and more precise than the chisub(e)(r) determined by conventionally analysing the electron power balance equation. The net result of these measurements is to conclusively prove that the dominant radial electron heat transport mechanism in tokamaks is a microscopic, diffusive process. (author)
Energy Technology Data Exchange (ETDEWEB)
Shiva, Amir Houshang; Teasdale, Peter R., E-mail: p.teasdale@griffith.edu.au; Bennett, William W.; Welsh, David T.
2015-08-12
A systematic comparison of the diffusion coefficients of cations (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) and oxyanions (Al, As, Mo, Sb, V, W) in open (ODL) and restricted (RDL) diffusive layers used by the DGT technique was undertaken. Diffusion coefficients were measured using both the diffusion cell (D{sub cell}) method at pH 4.00 and the DGT time-series (D{sub DGT}) method at pH 4.01 and 7.04 (pH 8.30 was used instead of 7.04 for Al) using the Chelex-Metsorb mixed binding layer. The performance of Chelex-Metsorb as a new DGT binding layer for Al uptake was also evaluated for the first time. Reasonable agreement was observed between D{sub cell} and D{sub DGT} measurements for both ODL and RDL, except for V and W. The ratios of D{sub cell}/D{sub DGT} for V of 0.44 and 0.39, and for W of 0.66 and 0.63 with ODL and RDL respectively, were much lower due to the formation of a high proportion of polyoxometalate species at the higher concentrations required with the D{sub cell} measurements. This is the first time that D values have been reported for several oxyanions using RDL. Except for Al at pH 8.30 with ODL, all D{sub DGT} measurements were retarded relative to diffusion coefficients in water (D{sub W}) for both diffusive hydrogels. Diffusion in RDL was further retarded compared with ODL, for all elements (0.66–0.78) with both methods. However, the degree of retardation observed changed for cations and anions at each pH. At pH 7.04 cations had a slightly higher D{sub DGT} and oxyanions had a slightly lower D{sub DGT} than at pH 4.01 for both ODL and RDL. It is proposed that this is due to partial formation of acrylic acid functional groups (pK{sub a} ≈4.5), which would be fully deprotonated at pH 7.04 (negative) and mostly protonated at pH 4.01 (neutral). As Al changes from being cationic at pH 4.01 to anionic at pH 8.30 the results were more complex. - Highlights: • Determining elemental diffusion coefficients in open and restricted diffusive gels. • The DGT
Lateral diffusivity coefficients from the dynamics of a SF6 patch in a coastal environment
Kersalé, M.; Petrenko, A. A.; Doglioli, A. M.; Nencioli, F.; Bouffard, J.; Blain, S.; Diaz, F.; Labasque, T.; Quéguiner, B.; Dekeyser, I.
2016-01-01
The dispersion of a patch of the tracer sulfur hexafluoride (SF6) is used to assess the lateral diffusivity in the coastal waters of the western part of the Gulf of Lion (GoL), northwestern Mediterranean Sea, during the Latex10 experiment (September 2010). Immediately after the release, the spreading of the patch is associated with a strong decrease of the SF6 concentrations due to the gas exchange from the ocean to the atmosphere. This has been accurately quantified, evidencing the impact of the strong wind conditions during the first days of this campaign. Few days after the release, as the atmospheric loss of SF6 decreased, lateral diffusivity coefficient at spatial scales of 10 km has been computed using two approaches. First, the evolution of the patch with time was combined with a diffusion-strain model to obtain estimates of the strain rate (γ = 2.5 10- 6 s- 1) and of the lateral diffusivity coefficient (Kh = 23.2 m2 s- 1). Second, a steady state model was applied, showing Kh values similar to the previous method after a period of adjustment between 2 and 4.5 days. This implies that after such period, our computation of Kh becomes insensitive to the inclusion of further straining of the patch. Analysis of sea surface temperature satellite imagery shows the presence of a strong front in the study area. The front clearly affected the dynamics within the region and thus the temporal evolution of the patch. Our results are consistent with previous studies in open ocean and demonstrate the success and feasibility of those methods also under small-scale, rapidly-evolving dynamics typical of coastal environments.
International Nuclear Information System (INIS)
Apparent molar volumes φV and viscosity B-coefficients for caffeine in (0.00, 0.03, 0.05, and 0.07) mol . dm-3 aqueous thorium nitrate, Th(NO3)4, solutions were determined from solution density and viscosity measurements over the temperature range (298.15 to 318.15) K as function of concentration of caffeine and the relation: φV0=a0+a1T+a2T2, have been used to describe the temperature dependence of the standard partial molar volumes φV0. These results have been used to deduce the standard volumes of transfer ΔφV0 and viscosity B-coefficients of transfer ΔB for caffeine from water to aqueous Th(NO3)4 solutions for rationalizing various interactions in the ternary solutions. The structure-making or breaking ability of caffeine has been discussed in terms of the sign of (δ2φV0/δT2)P. The Friedman-Krishnan co-sphere model was used to explain the transfer volume of caffeine with increasing Th(NO3)4 molarity. The activation parameters of viscous flow for the ternary solutions were also discussed in terms of transition state theory.
Energy Technology Data Exchange (ETDEWEB)
Sinha, Biswajit, E-mail: biswachem@gmail.co [Department of Chemistry, University of North Bengal, Darjeeling 734013 (India); Roy, Pran Kumar; Sarkar, Bipul Kumar; Brahman, Dhiraj [Department of Chemistry, University of North Bengal, Darjeeling 734013 (India); Roy, Mahendra Nath, E-mail: mahendraroy2002@yahoo.co.i [Department of Chemistry, University of North Bengal, Darjeeling 734013 (India)
2010-03-15
Apparent molar volumes phi{sub V} and viscosity B-coefficients for caffeine in (0.00, 0.03, 0.05, and 0.07) mol . dm{sup -3} aqueous thorium nitrate, Th(NO{sub 3}){sub 4}, solutions were determined from solution density and viscosity measurements over the temperature range (298.15 to 318.15) K as function of concentration of caffeine and the relation: phi{sub V}{sup 0}=a{sub 0}+a{sub 1}T+a{sub 2}T{sup 2}, have been used to describe the temperature dependence of the standard partial molar volumes phi{sub V}{sup 0}. These results have been used to deduce the standard volumes of transfer DELTAphi{sub V}{sup 0} and viscosity B-coefficients of transfer DELTAB for caffeine from water to aqueous Th(NO{sub 3}){sub 4} solutions for rationalizing various interactions in the ternary solutions. The structure-making or breaking ability of caffeine has been discussed in terms of the sign of (delta{sup 2}phi{sub V}{sup 0}/deltaT{sup 2}){sub P}. The Friedman-Krishnan co-sphere model was used to explain the transfer volume of caffeine with increasing Th(NO{sub 3}){sub 4} molarity. The activation parameters of viscous flow for the ternary solutions were also discussed in terms of transition state theory.
Shiva, Amir Houshang; Teasdale, Peter R; Bennett, William W; Welsh, David T
2015-08-12
A systematic comparison of the diffusion coefficients of cations (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) and oxyanions (Al, As, Mo, Sb, V, W) in open (ODL) and restricted (RDL) diffusive layers used by the DGT technique was undertaken. Diffusion coefficients were measured using both the diffusion cell (Dcell) method at pH 4.00 and the DGT time-series (D(DGT)) method at pH 4.01 and 7.04 (pH 8.30 was used instead of 7.04 for Al) using the Chelex-Metsorb mixed binding layer. The performance of Chelex-Metsorb as a new DGT binding layer for Al uptake was also evaluated for the first time. Reasonable agreement was observed between D(cell) and D(DGT) measurements for both ODL and RDL, except for V and W. The ratios of D(cell)/D(DGT) for V of 0.44 and 0.39, and for W of 0.66 and 0.63 with ODL and RDL respectively, were much lower due to the formation of a high proportion of polyoxometalate species at the higher concentrations required with the D(cell) measurements. This is the first time that D values have been reported for several oxyanions using RDL. Except for Al at pH 8.30 with ODL, all D(DGT) measurements were retarded relative to diffusion coefficients in water (DW) for both diffusive hydrogels. Diffusion in RDL was further retarded compared with ODL, for all elements (0.66-0.78) with both methods. However, the degree of retardation observed changed for cations and anions at each pH. At pH 7.04 cations had a slightly higher D(DGT) and oxyanions had a slightly lower D(DGT) than at pH 4.01 for both ODL and RDL. It is proposed that this is due to partial formation of acrylic acid functional groups (pKa ≈4.5), which would be fully deprotonated at pH 7.04 (negative) and mostly protonated at pH 4.01 (neutral). As Al changes from being cationic at pH 4.01 to anionic at pH 8.30 the results were more complex. PMID:26320970
Alonso de Mezquia, David; Wang, Zilin; Lapeira, Estela; Klein, Michael; Wiegand, Simone; Mounir Bou-Ali, M
2014-11-01
In this study, the thermodiffusion, molecular diffusion, and Soret coefficients of 12 binary mixtures composed of toluene, n-hexane and n-dodecane in the whole range of concentrations at atmospheric pressure and temperatures of 298.15 K and 308.15 K have been determined. The experimental measurements have been carried out using the Thermogravitational Column, the Sliding Symmetric Tubes and the Thermal Diffusion Forced Rayleigh Scattering techniques. The results obtained using the different techniques show a maximum deviation of 9% for the thermodiffusion coefficient, 8% for the molecular diffusion coefficient and 2% for the Soret coefficient. For the first time we report a decrease of the thermodiffusion coefficient with increasing ratio of the thermal expansion coefficient and viscosity for a binary mixture of an organic ring compound with a short n-alkane. This observation is discussed in terms of interactions between the different components. Additionally, the thermogravitational technique has been used to measure the thermodiffusion coefficients of four ternary mixtures consisting of toluene, n-hexane and n-dodecane at 298.15 K. In order to complete the study, the values obtained for the molecular diffusion coefficient in binary mixtures, and the thermodiffusion coefficient of binary and ternary mixtures have been compared with recently derived correlations. PMID:25376978
DEFF Research Database (Denmark)
Zhelezny, Petr; Shapiro, Alexander
2006-01-01
The present work describes a new experimental method that makes it possible to investigate diffusion coefficients in a porous medium. The method is based on application of X-ray computed tomography (CT). The general applicability of this method for the determination of diffusion coefficients is...... demonstrated. A series of such experiments was carried out. Several samples of carbonaceous and sandstone rock were investigated. The diffusion coefficients in porous media were determined by measuring the concentration of salt in different slices of a sample as a function of time. In cases where stable values...... of diffusion coefficients were obtained (all samples except for one highly heterogeneous sample), these values served for the determination of the tortuosity-porosity factors for a given type of porous medium....
Wu, Dan; Lu, Wanjun
2015-04-01
Injecting CO2 into lean-oil reservoirs is not only a way to geological storage but also enhanced oil recovery. In the secondary displacements of oil reservoir by CO2-injection, diffusion coefficients and solubility of CO2 are key parameters to calculate the volume of CO2 injected and the time to achieve the desired viscosity in the numerical simulation. Unfortunately, the experimental data on the CO2 diffusion coefficient and solubility in liquid hydrocarbons under high pressure conditions are scarce. Hexadecane has properties similar to the average properties of Brazilian heavy oil. Experimental data on the diffusion coefficients and solubility of CO2 in hexadecane were reviewed by Nieuwoudt and Rand (2002), Rincon and Trejo (2001) and Breman et al (1994), indicating that the data in the literature were limited at relatively low temperatures and/or low pressures. In this paper, the diffusion coefficients of carbon dioxide in hexadecane at different temperature and pressure were determined with in situ Raman spectroscopy. A model was established to describe relationship among diffusion coefficients, temperature, and pressure. The solubility of CO2 in hexadecane was obtained from 298.15 to 473.15 K and 10 to 45 MPa. The experimental results show that:(1) Solubility of CO2 decreases with increasing temperature.(2) Increasing pressure increases the CO2 solubility. in terms of the degree of influence,100K is similar with 10MPa.(3) Diffusion coefficients of CO2 increases with increasing temperature. (4) Increasing pressure decreases the CO2 diffusion coefficients, whereas the pressure effect on CO2 diffusion coefficients is very weak. Compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for solubility measurements eliminates possible uncertainty caused by sampling and ex situ analysis. (2) it is simple and efficient, and (3) high-pressure data can be obtained safely.
Indian Academy of Sciences (India)
BHARDWAJ S B; SINGH RAM MEHAR; SHARMA KUSHAL; MISHRA S C
2016-06-01
Attempts have been made to explore the exact periodic and solitary wave solutions of nonlinear reaction diffusion (RD) equation involving cubic–quintic nonlinearity along with timedependent convection coefficients. Effect of varying model coefficients on the physical parameters of solitary wave solutions is demonstrated. Depending upon the parametric condition, the periodic,double-kink, bell and antikink-type solutions for cubic–quintic nonlinear reaction-diffusion equation are extracted. Such solutions can be used to explain various biological and physical phenomena.
A study of quasilinear diffusion coefficient of the fokker-planck equation based on full wave method
International Nuclear Information System (INIS)
Based on the wave fields evaluated by full wave method, the various components of quasilinear diffusion coefficient in spherical velocity coordinates are obtained by numerically resolving. The quasilinear diffusion coefficient of Fokker-planck equation is presented for investigating fast wave current drive in the ion cyclotron range of frequencies, and the results will be used to solve bounce-averaged quasilinear Fokker-Planck equation for further study of fast wave current drive. (authors)
Diffusion-Exchange Weighted Imaging
Saadallah Ramadan
2009-01-01
A method has been developed whereby diffusion and exchange in micro cellular structures in the human brain are correlated to produce a new type of image contrast leading to determination of water exchange rates in vivo. The diffusion method relies on differential apparent diffusion coefficients as detectable nuclei exchange between adjacent compartments marked with different apparent diffusion coefficient values (e.g. intra- and extra-cellular compartments). A new pulse sequence was developed...
Group Analysis of Variable Coefficient Diffusion--Convection Equations. III. Conservation Laws
Ivanova, N M; Sophocleous, C
2007-01-01
The notions of generating sets of conservation laws of systems of differential equations with respect to symmetry groups and equivalence groups are introduced and applied. This allows us to generalize essentially the procedure of finding potential symmetries for the systems with multidimensional spaces of conservation laws. A class of variable coefficient (1+1)-dimensional nonlinear diffusion-convection equations of general form $f(x)u_t=(g(x)A(u)u_x)_x+h(x)B(u)u_x$ is investigated. Using the most direct method, we carry out two classifications of local conservation laws up to equivalence relations generated by both usual and enhanced equivalence groups. Equivalence with respect to $\\hat G^{\\sim}$ and correct choice of gauge coefficients of equations play the major role for simple and clear formulation of the final results. The notion of contractions of conservation laws and one of characteristics of conservation laws are introduced and contractions of conservation laws of diffusion-convection equations are f...
Computing the blood brain barrier (BBB) diffusion coefficient: A molecular dynamics approach
Shamloo, Amir; Pedram, Maysam Z.; Heidari, Hossein; Alasty, Aria
2016-07-01
Various physical and biological aspects of the Blood Brain Barrier (BBB) structure still remain unfolded. Therefore, among the several mechanisms of drug delivery, only a few have succeeded in breaching this barrier, one of which is the use of Magnetic Nanoparticles (MNPs). However, a quantitative characterization of the BBB permeability is desirable to find an optimal magnetic force-field. In the present study, a molecular model of the BBB is introduced that precisely represents the interactions between MNPs and the membranes of Endothelial Cells (ECs) that form the BBB. Steered Molecular Dynamics (SMD) simulations of the BBB crossing phenomenon have been carried out. Mathematical modeling of the BBB as an input-output system has been considered from a system dynamics modeling viewpoint, enabling us to analyze the BBB behavior based on a robust model. From this model, the force profile required to overcome the barrier has been extracted for a single NP from the SMD simulations at a range of velocities. Using this data a transfer function model has been obtained and the diffusion coefficient is evaluated. This study is a novel approach to bridge the gap between nanoscale models and microscale models of the BBB. The characteristic diffusion coefficient has the nano-scale molecular effects inherent, furthermore reducing the computational costs of a nano-scale simulation model and enabling much more complex studies to be conducted.
Kubo number and magnetic field line diffusion coefficient for anisotropic magnetic turbulence
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The magnetic field line diffusion coefficients Dx and Dy are obtained by numerical simulations in the case that all the magnetic turbulence correlation lengths lx, ly, and lz are different. We find that the variety of numerical results can be organized in terms of the Kubo number, the definition of which is extended from R=(δB/B0)(l#parallel#/l#perpendicular#) to R=(δB/B0)(lz/lx), for lx≥ly. Here, l#parallel# (l#perpendicular#) is the correlation length along (perpendicular to) the average field B0=B0{cflx e}z. We have anomalous, non-Gaussian transport for R{approx-lt}0.1, in which case the mean square deviation scales nonlinearly with time. For R{approx-gt}1 we have several Gaussian regimes: an almost quasilinear regime for 0.1{approx-lt}R{approx-lt}1, an intermediate, transition regime for 1{approx-lt}R{approx-lt}10, and a percolative regime for R{approx-gt}10. An analytical form of the diffusion coefficient is proposed, Di=D(δBlz/B0lx)μ(li/lx)νlx2/lz, which well describes the numerical simulation results in the quasilinear, intermediate, and percolative regimes
Double obstacle phase field approach to an inverse problem for a discontinuous diffusion coefficient
Deckelnick, Klaus; Elliott, Charles M.; Styles, Vanessa
2016-04-01
We propose a double obstacle phase field approach to the recovery of piece-wise constant diffusion coefficients for elliptic partial differential equations. The approach to this inverse problem is that of optimal control in which we have a quadratic fidelity term to which we add a perimeter regularization weighted by a parameter σ. This yields a functional which is optimized over a set of diffusion coefficients subject to a state equation which is the underlying elliptic PDE. In order to derive a problem which is amenable to computation the perimeter functional is relaxed using a gradient energy functional together with an obstacle potential in which there is an interface parameter ɛ. This phase field approach is justified by proving {{Γ }}- convergence to the functional with perimeter regularization as ε \\to 0. The computational approach is based on a finite element approximation. This discretization is shown to converge in an appropriate way to the solution of the phase field problem. We derive an iterative method which is shown to yield an energy decreasing sequence converging to a discrete critical point. The efficacy of the approach is illustrated with numerical experiments.
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Objective: To investigate the diagnostic value of ADC on delayed encephalopathy after acute carbon monoxide poisoning (DEACMP). Methods: Forty healthy subjects with normal head MRI appearance and 32 cases with DEACMP were recruited and scanned using MRI. ADC values in bilateral globus pallidus, cerebral white matter (peri-ventricle, centrum semioval) and cortex were measured respectively. According to conventional MRI, 32 DEACMP patients were divided into abnormal and normal signal intensity groups, and followed up more than one year. Thirteen cases without evident symptoms and 3 cases with little headache and dizziness were good prognosis group. Fifteen cases with disturbance of intelligence and mental anomaly and one case with manifested unresponsive, inability in life self-care, urinary and fecal incontinence were poor prognosis group. Independent samples t-test was used to compared all parts of brain ADC values between DEACMP group and normal control, abnormal and normal signal intensity groups, normal signal intensity group and normal control, good and poor prognosis groups. Results: According to MRI findings, DEACMP were classified into three types: type 1: showing white matter involvement; type 2: showing neural nuclei involvement and type 3: showing brain cortex involvement. The ADC values [peri-ventricle white matter (0.62±0.06) x 10-3 mm2/s, the globus pallidus (0.67± 0.05) x 10-3 mm2/s, centrum semioval(0.57±0.07) x 10-3 mm2/s] in DEACMP group were statistically different with those [(0.74±0.03) x 10-3, (0.74±0.04) x 10-3, (0.73±0.05) x 10-3 mm2/s] in normal people (t=2.82,2.89,2.98, P-3 mm2/s, centrum semioval(0.52±0.09) x 10-3 mm2/s] in 20 cases with abnormal signal on routine MRI were statistically different with the ADC values [(0.66±0.05) x 10-3, (0.62±0.06) x 10-3 mm2/s] in 12 cases without abnormal signal (t=4.45,3.98, P-3 mm2/s, centrum semioval (0.58±0.05) x 10-3 mm2/s] in good prognosis group, the ADC value of 16 cases [(0.56±0.02) x 10-3, (0.50±0.06) x 10-3 mm2/s] in poor group decreased significantly (t=6.19,4.12,P<0.01). Conclusions: The decreased ADC values of white matter (centrum semioval particularly) is of the important in diagnosing of the DEACMP. For cases with abnormal signal on routine MRI,the ADC values can be used to evaluate the degree of poisoning, to be used as the reference of occurrence, development and to be used to evaluate the prognosis of the diseases. For the other cases with clinical symptoms but without abnormal signal on routine MRI, ADC value is a very sensitive index. (authors)
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Objective: To evaluate the correlation of ADC values on 3.0 T MR with the pathological grades in pT1b clear cell renal cell carcinoma (CCRCC). Methods: Conventional MR images, ADC values and Fuhrman pathological grading of pT1b CCRCC were performed in 30 patients. Grade Ⅰ and Ⅱ were defined as low-grade group; grade Ⅲ and Ⅳ were defined as high-grade group. The differences of ADC values among four different pathologic grades were compared with a one-way analysis of variance. The comparison of ADC values of two different grade groups was performed with t test, and the ROC curve was performed to evaluate the diagnostic efficacy of ADC value. Correlation between pathological grading and ADC values was assessed with Spearman rank correlation analysis. Results: (1) The mean ADC value of grading Ⅰ (10 patients), Ⅱ (8 patients), Ⅲ (7 patients), Ⅳ (5 patients) was (0.94 ± 0.11) ×10-3 mm2/s, (0.82 ±0.13) × 10-3 mm2/s,(0.68 ±0.09) × 10-3 mm2/s, (0.59 ±0.03) × 10-3 mm2/s, respectively. Significant differences of ADC values among the four grades were present (F=16.422, P=0.000). (2) The mean ADC value of the low-grade group was significantly higher than that of the high-grade group (t=5.738, P=0.000). Sensitivity and specificity of diagnosing the low-grade group was 88.9% and 83.3% respectively. There was a negative correlation between pathological grading and ADC value (r=-0.807, P<0.05). Conclusions: The ADC values of pT1b CCRCC have close correlation with pathological grading. They can be used to predict the degree of tumor malignancy preoperatively and guide surgical planning. (authors)
In-situ estimate of submesoscale horizontal eddy diffusion coefficients across a front
Nencioli, Francesco; d'Ovidio, Francesco; Doglioli, Andrea; Petrenko, Anne
2013-04-01
Fronts, jets and eddies are ubiquitous features of the world oceans, and play a key role in regulating energy budget, heat transfer, horizontal and vertical transport, and biogeochemical processes. Although recent advances in computational power have favored the analysis of mesoscale and submesoscale dynamics from high-resolution numerical simulations, studies from in-situ observations are still relatively scarce. The small dimensions and short duration of such structures still pose major challenges for fine-scale dedicated field experiments. As a consequence, in-situ quantitative estimates of key physical parameters for high-resolution numerical models, such as horizontal eddy diffusion coefficients, are still lacking. The Latex10 campaign (September 1-24, 2010), within the LAgrangian Transport EXperiment (LATEX), adopted an adaptive sampling strategy that included satellite data, ship-based current measurements, and iterative Lagrangian drifter releases to successfully map coherent transport structures in the western Gulf of Lion. Comparisons with AVHRR imagery evidenced that the detected structures were associated with an intense frontal feature, originated by the convergence and subsequent stirring of colder coastal waters with warmer open-sea waters. We present a method for computing horizontal eddy diffusion coefficients by combining the stirring rates estimated from the Lagrangian drifter trajectories with the shapes of the surface temperature and salinity gradient (assumed to be at the equilibrium) from the ship thermosalinograph. The average value we obtained from various sections across the front is 2.5 m2s-1, with horizontal scales (width of the front) ranging between 0.5 and 2.5 km. This is in line with the values commonly used for high-resolution numerical simulations. Further field experiment will be required to extend the results to different ocean regions and regimes, and to thoroughly test the robustness of the equilibrium hypothesis. Remote sensed
Theory of the diffusion coefficient of neutrons in a lattice containing cavities
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In an previous publication, a simple and general formulation of the diffusion coefficient, which defines the mode of weighting of the mean free paths of the various media, in introducing the collision probabilities in each medium, was established. This expression is demonstrated again here through a more direct method, and the velocity is introduced; new terms are emphasised, the existence of which implies that the representation of the diffusion area as the mean square of the straight line distance from source to absorption is not correct in a lattice. However these terms are of small enough an order of magnitude to he treated as a correction. The general expression also shows the existence, for the radial coefficient, of the series of angular correlation terms, which is seen to converge very slowly for large channels. The term by term computation which was initiated in the first work was then interrupted and a global formulation, which emphasize a resemblance with the problem of the thermal utilisation factor, was adopted. An integral method, analogous to that use for the computation of this factor, gives the possibility to establish new and simple practical formulae, which require the use of a few basic functions only. These formulae are very accurate, as seen from the results of a variational method which was studied as a reference. Various correction effects are reviewed. Expressions which allow the exact treatment of fuel rod clusters are presented. The theory is confronted with various experimental results, and a new method of measuring the radial coefficient is proposed. (author)
Yoshida, Ken; Matubayasi, Nobuyuki; Nakahara, Masaru
2008-12-01
The self-diffusion coefficients D for water, benzene, and cyclohexane are determined by using the pulsed-field-gradient spin echo method in high-temperature conditions along the liquid branch of the coexistence curve: 30-350 °C (1.0-0.58 g cm-3), 30-250 °C (0.87-0.56 g cm-3), and 30-250 °C (0.77-0.48 g cm-3) for water, benzene, and cyclohexane, respectively. The temperature and density effects are separated and their origins are discussed by examining the diffusion data over a wide range of thermodynamic states. The temperature dependence of the self-diffusion coefficient for water is larger than that for organic solvents due to the large contribution of the attractive hydrogen-bonding interaction in water. The density dependence is larger for organic solvents than for water. The difference is explained in terms of the van der Waals picture that the structure of nonpolar organic solvents is determined by the packing effect due to the repulsion or exclusion volumes. The dynamic solvation shell scheme [K. Yoshida et al., J. Chem. Phys. 127, 174509 (2007)] is applied for the molecular interpretation of the translational dynamics with the aid of molecular dynamics simulation. In water at high temperatures, the velocity relaxation is not completed before the relaxation of the solvation shell (mobile-shell type) as a result of the breakdown of the hydrogen-bonding network. In contrast, the velocity relaxation of benzene is rather confined within the solvation shell (in-shell type).
A non-perturbative estimate of the heavy quark momentum diffusion coefficient
Francis, A; Laine, M; Neuhaus, T; Ohno, H
2015-01-01
We estimate the momentum diffusion coefficient of a heavy quark within a pure SU(3) plasma at a temperature of about 1.5Tc. Large-scale Monte Carlo simulations on a series of lattices extending up to 192^3*48 permit us to carry out a continuum extrapolation of the so-called colour-electric imaginary-time correlator. The extrapolated correlator is analyzed with the help of theoretically motivated models for the corresponding spectral function. Evidence for a non-zero transport coefficient is found and, incorporating systematic uncertainties reflecting model assumptions, we obtain kappa = (1.8 - 3.4)T^3. This implies that the "drag coefficient", characterizing the time scale at which heavy quarks adjust to hydrodynamic flow, is (1.8 - 3.4) (Tc/T)^2 (M/1.5GeV) fm/c, where M is the heavy quark kinetic mass. The results apply to bottom and, with somewhat larger systematic uncertainties, to charm quarks.
Drag and diffusion coefficient of a spherical particle attached to a fluid interface
Hardt, Steffen; Doerr, Aaron; Masoud, Hassan; Stone, Howard
2015-11-01
We consider a spherical particle attached to the interface between two immiscible fluids of large viscosity contrast. The degree of immersion in the two fluids is determined by the contact angle. For small enough particles and significant contact-angle hysteresis, it can be assumed that the three-phase contact line is pinned at the particle surface. We study the movement of such particles along the fluid interface for the case of small Reynolds and capillary numbers. We solve the Stokes equation based on two geometric perturbation expansions around contact angles of 90 degrees and 180 degrees, the latter corresponding to a particle completely immersed in the less viscous phase. Based on the Lorentz Reciprocity Theorem we obtain expressions for the drag coefficient of an interfacial particle which are analogs of the well-known Stokes drag coefficient for a particle moving in an unbounded medium. Interpolation of the two results gives a relationship which approximates the drag coefficient quite accurately over the entire range of contact angles. A comparison with previously published numerical results for contact angles below 90 degrees shows good agreement. Using the fluctuation-dissipation theorem, we also obtain expressions for the diffusion constant of a small particle attached to a fluid interface.
Blackness coefficients, effective diffusion parameters, and control rod worths for thermal reactors
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Simple diffusion theory cannot be used to evaluate control rod worths in thermal reactors because of the strongly absorbing character of the control material. However, good results can be obtained from a diffusion calculation by representing the absorber slab by means of a suitable pair of internal boundary conditions, α and β, which are ratios of neutron flux to neutron current. Methods for calculating α and β in the P1, P3, and P5 approximations, with and without scattering, are presented. By appropriately weighting the fine-group blackness coefficients, broad group values, and , are obtained. The technique is applied to the calculation of control rod worths of Cd, Ag-In-Cd, and Hf control elements. Results are found to compare very favorably with detailed Monte Carlo calculations. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method is briefly discussed and applied to the calculation of control rod worths in the Ford Nuclear Reactor at the University of Michigan. Calculated and measured worths are found to be in good agreement
Kikugawa, Gota; Ando, Shotaro; Suzuki, Jo; Naruke, Yoichi; Nakano, Takeo; Ohara, Taku
2015-01-01
In the present study, molecular dynamics (MD) simulations on the monatomic Lennard-Jones liquid in a periodic boundary system were performed in order to elucidate the effect of the computational domain size and shape on the self-diffusion coefficient measured by the system. So far, the system size dependence in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient depends linearly on the inverse of the system size, which is theoretically predicted based on the hydrodynamic interaction. We examined the system size effect not only in the cubic cell systems but also in rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. As a result, the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly with the side length. On the other hand, the diffusion coefficient in the direction along the long side is almost constant or slightly decreases. Consequently, anisotropy of the diffusion coefficient emerges in a rectangular cell with periodic boundary conditions even in a bulk liquid simulation. This unexpected result is of critical importance because rectangular fluid systems confined in nanospace, which are present in realistic nanoscale technologies, have been widely studied in recent MD simulations. In order to elucidate the underlying mechanism for this serious system shape effect on the diffusion property, the correlation structures of particle velocities were examined.
Drabik, Dominik; Przybyło, Magda; Sikorski, Aleksander; Langner, Marek
2016-03-01
Fluorescence Correlation Spectroscopy (FCS) is a technique, which allows determination of the diffusion coefficient and concentration of fluorescent objects suspended in the solution. The measured parameter is the fluctuation of the fluorescence signal emitted by diffusing molecules. When 100 nm DOPC vesicles labeled with various fluorescent dyes (Fluorescein-PE, NBD-PE, Atto488 DOPE or βBodipy FL) were measured, different values of diffusion coefficients have been obtained. These diffusion coefficients were different from the expected values measured using the dynamic light scattering method (DLS). The FCS was initially developed for solutions containing small fluorescent molecules therefore the observed inconsistency may result from the nature of vesicle suspension itself. The duration of the fluorescence signal may depend on the following factors: the exposure time of the labeled object to the excitation beam, the photo-physical properties (e.g., stability) of a fluorophore, the theoretical model used for the calculations of the diffusion coefficient and optical properties of the vesicle suspension. The diffusion coefficients determined for differently labeled liposomes show that its dependence on vesicle size and quantity of fluorescent probed used for labeling was significant demonstrating that the fluorescence properties of the fluorophore itself (bleaching and/or blinking) were critical factors for a correct outcome of FCS experiment. The new, based on combined FCS and DLS measurements, method for the determination of the focal volume prove itself to be useful for the evaluation of a fluorescence dye with respect to its applicability for FCS experiment. PMID:26695945
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Highlights: • Atomic mobilities of bcc-A2 and bcc-B2 Al–Ni–Fe phases were determined. • Experimental interdiffusivities and tracer diffusivities were critically evaluated. • Main diffusivities show minimum around section x(Al) = 50 at.%. • Cross diffusivities show different features for negative and positive values. • The results reveal the importance of full diffusion-distance measurement. - Abstract: The influence of composition and temperature on the atomic mobilities of Al, Ni and Fe in the bcc-A2 and bcc-B2 Al–Ni–Fe phases was investigated based on a recently developed phenomenological model, together with the newly published thermodynamic description. The experimental interdiffusivities and tracer diffusivities of Ni and Fe in various Al–Ni–Fe alloys available in the literature were critically evaluated. The calculated diffusivities can reasonably reproduce the experimental ones. The calculated iso-diffusivity lines in the B2 phase show a minimum around the quasi-binary section at 50 at.% Al for the main diffusivities of both Al and Ni, while for the cross diffusivities of Al and Ni, they show significantly different characteristics when changing from negative to positive values. The obtained atomic mobilities were further used to predict the concentration profiles and diffusion paths in a variety of B2 Al–Ni–Fe diffusion couples. The comparison reveals the importance of full diffusion-distance measurement for the accurate determination of diffusion coefficients
Ivanova, N M; Sophocleous, C
2007-01-01
After discussing the classical statement of group classification problem and some its extensions in the general case, we carry out the complete extended group classification for a class of (1+1)-dimensional nonlinear diffusion-convection equations with coefficients depending on the space variable. At first, we construct the usual equivalence group and the extended one including transformations which are nonlocal with respect to arbitrary elements. The extended equivalence group has interesting structure since it contains a non-trivial subgroup of non-local gauge equivalence transformations. The complete group classification of the class under consideration is performed with respect to the extended equivalence group and with respect to the set of all local transformations. Usage of extended equivalence and correct choice of gauges of arbitrary elements play the major role for simple and clear formulation of the final results. The set of admissible transformations of this class is preliminary investigated.
Varga, Agnes; Gyetvai, Gergely; Nagy, Lívia; Nagy, Géza
2009-08-01
The diffusion coefficient of glucose in different media is an important parameter in life sciences, as well as in biotechnology and microbiology. In this work a simple, fast method is proposed that is based on the electrochemical time of flight principle. In most of the earlier time of flight experiments performed, a constant flight distance was applied. In the present work a scanning electrochemical microscope (SECM) was applied as a measuring tool. With use of the SECM, the flying distance could be changed with high precision, making measurements with several flight distances more accurate and reliable values could be obtained for solutions as well as for gels. The conventional voltammetric methods are not applicable for glucose detection. In our work electrocatalytic copper oxide coated copper microelectrodes and micro-sized amperometric enzyme sensors were used as detectors, while microdroplet-ejecting pneumatically driven micropipettes were used as a source. PMID:19517100
Remote sensing of the diffuse attenuation coefficient of ocean water. [coastal zone color scanner
Austin, R. W.
1981-01-01
A technique was devised which uses remotely sensed spectral radiances from the sea to assess the optical diffuse attenuation coefficient, K (lambda) of near-surface ocean water. With spectral image data from a sensor such as the coastal zone color scanner (CZCS) carried on NIMBUS-7, it is possible to rapidly compute the K (lambda) fields for large ocean areas and obtain K "images" which show synoptic, spatial distribution of this attenuation coefficient. The technique utilizes a relationship that has been determined between the value of K and the ratio of the upwelling radiances leaving the sea surface at two wavelengths. The relationship was developed to provide an algorithm for inferring K from the radiance images obtained by the CZCS, thus the wavelengths were selected from those used by this sensor, viz., 443, 520, 550 and 670 nm. The majority of the radiance arriving at the spacecraft is the result of scattering in the atmospheric and is unrelated to the radiance signal generated by the water. A necessary step in the processing of the data received by the sensor is, therefore, the effective removal of these atmospheric path radiance signals before the K algorithm is applied. Examples of the efficacy of these removal techniques are given together with examples of the spatial distributions of K in several ocean areas.
On the parametrization of the energetic-particle pitch-angle diffusion coefficient
Directory of Open Access Journals (Sweden)
Vainio Rami
2013-03-01
Full Text Available Context: Solar energetic particle (SEP events are one of the key ingredients of the near-Earth radiation environment. Pitch-angle scattering by fluctuations imposed on the large-scale magnetic field is assumed to be t