Impact of blood flow on diffusion coefficients of the human kidney: A time‐resolved ECG‐triggered diffusion‐tensor imaging (DTI) study at 3T

Purpose:

To evaluate the impact of renal blood flow on apparent diffusion coefficients (ADC) and fractional anisotropy (FA) using time‐resolved electrocardiogram (ECG)‐triggered diffusion‐tensor imaging (DTI) of the human kidneys.

Materials and Methods:

DTI was performed in eight healthy volunteers (mean age 29.1 ± 3.2) using a single slice coronal echoplanar imaging (EPI) sequence (3 b‐values: 0, 50, and 300 s/mm²) at the timepoint of minimum (20 msec after R wave) and maximum renal blood flow (200 msec after R wave) at 3T. Following 2D motion correction, region of interest (ROI)‐based analysis of cortical and medullary ADC‐ and FA‐values was performed.

Results:

ADC‐values of the renal cortex at maximum blood flow (2.6 ± 0.19 × 10^?3 mm²/s) were significantly higher than at minimum blood flow (2.2 ± 0.11 × 10^?3 mm²/s) (P < 0.001), while medullary ADC‐values did not differ significantly (maximum blood flow: 2.2 ± 0.18 × 10^?3 mm²/s; minimum blood flow: 2.15 ± 0.14 × 10^?3 mm²/s). FA‐values of the renal medulla were significantly greater at maximal blood (0.53 ± 0.05) than at minimal blood flow (0.47 ± 0.05) (P < 0.01). In contrast, cortical FA‐values were comparable at different timepoints of the cardiac cycle.

Conclusion:

ADC‐values in the renal cortex as well as FA‐values in the renal medulla are influenced by renal blood flow. This impact has to be considered when interpreting renal ADC‐ and FA‐values. J. Magn. Reson. Imaging 2013;37:233–236. © 2012 Wiley Periodicals, Inc.

     

Repeatability of quantitative parameters derived from diffusion tensor imaging in patients with glioblastoma multiforme

Purpose

To quantify the repeatability of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in patients with glioblastoma multiforme.

Materials and Methods

IRB approval and informed consent were obtained for this Health Insurance Portability and Accountability Act‐compliant study. Sixteen patients with glioblastoma multiforme underwent MR imaging at two time points without interval intervention. ADC and FA maps were registered to the contrast‐enhanced and fluid‐attenuated inversion recovery (FLAIR) image volumes. Volumes of tumor‐related enhancement (TRE) and FLAIR signal abnormality (FSA) were defined using a semiautomated segmentation technique.

Results

Repeated observations of mean ADC and mean FA were highly consistent within both TRE (ADC: r = 0.947,P < 0.0001; FA: r = 0.947, P < 0.0001) and FSA (ADC: r = 0.979, P < 0.0001; FA: r = 0.972, P < 0.0001). Within TRE, repeatability coefficients and 95% confidence intervals (CIs) for change measured 0.104 × 10^?3 mm²S^?1 and 7.4% (ADC) and 0.0196 and 13.9% (FA), respectively. Within FSA, repeatability coefficients and 95% CI for change measured 0.071 × 10^?3 mm²S^?1 and 5.2% (ADC) and 0.0159 and 8.7% (FA), respectively. To detect 10% changes in mean ADC, sample sizes of nine (TRE) and six (FSA) patients would be required. The same change in mean FA would require sample sizes of 21 (TRE) and 10 (FSA) patients, respectively.

Conclusion

Changes after therapy greater than the repeatability coefficient or 95% CI for change are unlikely to be related to variability in the measurement of ADC and FA. J. Magn. Reson. Imaging 2009;29:1199–1205. © 2009 Wiley‐Liss, Inc.

     

Diffusion tensor imaging of the anal canal at 3 tesla: feasibility and reproducibility of anisotropy measures

Purpose:

To assess the feasibility and reproducibility of 3‐tesla diffusion tensor imaging (DTI) of the anal canal.

Materials and Methods:

DTI was performed in 25 men with no clinical history of anal canal disease undergoing MRI for prostate cancer. Analysis of fractional anisotropy (FA), relative anisotropy (RA), and apparent diffusion coefficient (ADC) were determined for the epithelial/subepithelial layer, internal sphincter, external sphincter, and puborectalis. The directionality of diffusion was recorded from color‐coded tractography maps. Obturator internus and gluteus maximus served as reference muscles. Mean (SD) of values for FA, RA, and ADC were compared using analysis of variance. Intra and inter‐rater agreement and test reproducibility (n = 5) was assessed by Bland‐Altman statistics.

Results:

Mean (SD) for the epithelial/subepithelial layer, internal, external sphincter, and puborectalis were as follows: FA: 0.283 (0.099); 0.337 (0.049); 0.415 (0.072); and 0.407 (0.062), respectively. RA: 0.241 (0.094); 0.292 (0.050); 0.371 (0.083); 0.361 (0.067), respectively; and ADC: 1.49 (0.23); 1.59 (0.19); 1.51 (0.28); and 1.54 (0.29) × 10^?3mm²/s, respectively. Good overall intra and inter‐rater agreement and test–retest reproducibility was noted (coefficient of variation of 4.8–19.4% and 5.9–12.9%, respectively).

Conclusion:

Anisotropy is evident in the anal canal with good inter‐rater agreement and test reproducibility. J. Magn. Reson. Imaging 2012;35:820–826. © 2011 Wiley Periodicals, Inc.

     

Multi‐system repeatability and reproducibility of apparent diffusion coefficient measurement using an ice‐water phantom

Purpose:

To determine quantitative quality control procedures to evaluate technical variability in multi‐center measurements of the diffusion coefficient of water as a prerequisite to use of the biomarker apparent diffusion coefficient (ADC) in multi‐center clinical trials.

Materials and Methods:

A uniform data acquisition protocol was developed and shared with 18 participating test sites along with a temperature‐controlled diffusion phantom delivered to each site. Usable diffusion weighted imaging data of ice water at five b‐values were collected on 35 clinical MRI systems from three vendors at two field strengths (1.5 and 3 Tesla [T]) and analyzed at a central processing site.

Results:

Standard deviation of bore‐center ADCs measured across 35 scanners was <2%; error range: ?2% to +5% from literature value. Day‐to‐day repeatability of the measurements was within 4.5%. Intra‐exam repeatability at the phantom center was within 1%. Excluding one outlier, inter‐site reproducibility of ADC at magnet isocenter was within 3%, although variability increased for off‐center measurements. Significant (>10%) vendor‐specific and system‐specific spatial nonuniformity ADC bias was detected for the off‐center measurement that was consistent with gradient nonlinearity.

Conclusion:

Standardization of DWI protocol has improved reproducibility of ADC measurements and allowed identifying spatial ADC nonuniformity as a source of error in multi‐site clinical studies. J. Magn. Reson. Imaging 2013;37:1238–1246. © 2012 Wiley Periodicals, Inc.

     

Transmural heterogeneity of left ventricular myocardium remodeling in postinfarct porcine model revealed by MR diffusion tensor imaging

Purpose:

To investigate the transmural heterogeneity of left ventricular myocardium structural remodeling.

Materials and Methods:

Ex vivo diffusion tensor imaging (DTI) was performed in six adult porcine heart samples with apical septum infarction collected 13 weeks after permanent left anterior descending coronary artery ligation and six age‐matched intact controls. Alterations in diffusion indices and myocardial fiber orientation, including fractional anisotropy (FA), mean apparent diffusion coefficient (mean ADC), axial diffusivity (λ_∥), radial diffusivity (λ_?), and fiber helix angle were investigated at five transmural zones across myocardium wall in regions adjacent and remote to the infarct.

Results:

In both adjacent and remote regions of infarcted hearts, FA showed no significant alteration across transmural zones compared to controls. However, mean ADC, λ_∥, and λ_? exhibited significant decreases at endocardium zones but not epicardium zones. Moreover, myocardial fiber helix angle shifted towards left‐handed orientation at all transmural zones, especially in regions adjacent to the infarct, becoming more aligned with the epicardium fiber orientation.

Conclusion:

These experimental DTI findings indicate that the endocardium was more vulnerable to infarction, leading to more pronounced microstructural changes during remodeling. The current DTI approach reveals additional information in delineating postinfarct remodeling process, which may provide insights into cardiac mechanics and clinical assessment of cardiac diseases. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Diffusion tensor imaging of the median nerve in healthy and carpal tunnel syndrome subjects

Purpose

To determine if diffusion tensor imaging (DTI) of the median nerve could allow identification of patients with carpal tunnel syndrome (CTS).

Materials and Methods

A total of 13 healthy subjects and 9 CTS patients were scanned on a 3T magnetic resonance imaging (MRI) scanner. The MRI protocol included a DTI sequence from which the fractional anisotropy (FA), apparent diffusion coefficient (ADC), and the parallel and radial diffusivities could be extracted. Those parameters were quantified at different locations along the median nerve (proximal to the carpal tunnel, within the carpal tunnel, and distal to the carpal tunnel).

Results

At the carpal tunnel, the FA, radial diffusivity, and ADC differed significantly between healthy subjects and CTS patients (P < 0.0002). This highly significant difference between the two groups was due to an opposite trend of changes in the DTI indices between the proximal to the carpal tunnel and within the carpal tunnel locations. In healthy subjects the FA increased (+20%, P < 0.001) and the radial diffusivity and ADC decreased (by ?15% and ?8%, respectively, P < 0.05) between the proximal to the carpal tunnel and within the carpal tunnel locations. In CTS subjects the FA decreased (by ?21%, P < 0.05) and the radial diffusivity increased (by +23%, P < 0.01) between the proximal to the carpal tunnel and within the carpal tunnel locations.

Conclusion

DTI enables visualization and characterization of the median nerve in healthy subjects and CTS patients. DTI indices show clear‐cut discrimination between the two groups and in fact enables the of use DTI in the diagnosis of CTS. J. Magn. Reson. Imaging 2009;29:657–662. © 2009 Wiley‐Liss, Inc.

     

Ability of diffusion-weighted imaging for the differential diagnosis between chronic expanding hematomas and malignant soft tissue tumors

Purpose

To evaluate the potential of diffusion‐weighted imaging (DWI) in distinguishing chronic expanding hematomas (CEHs) from malignant soft tissue tumors.

Materials and Methods

We performed conventional MRI and DWI of six CEHs and 31 malignant soft tissue tumors from 37 patients seen between May 2000 and November 2006. DWI was obtained with a single‐shot echo‐planar imaging (EPI) sequence using a 1.5T MR imager. The mean apparent diffusion coefficient (ADC) value was also calculated. We evaluated MRI findings of CEHs and compared ADC value of CEHs with malignant soft tissue tumors.

Results

On conventional MRI, two of six CEHs were difficult to differentiate from malignant soft tissue tumors based on imaging findings. The mean ADC value of CEHs and malignant soft tissue tumors was 1.55 ± 0.121 × 10^?3 mm²/sec and 0.92 ± 0.139 × 10^?3 mm²/sec (mean ± SD), respectively. The mean ADC value of CEHs was significantly higher than that of malignant soft tissue tumors (P < 0.01). There was no overlap in the minimum ADC values among CEHs and malignant soft tissue tumors.

Conclusion

DWI is useful for differentiating between CEHs and malignant soft tissue tumors. J. Magn. Reson. Imaging 2008;28:1195–1200. © 2008 Wiley‐Liss, Inc.

     

Predicting response to neoadjuvant chemoradiation therapy in locally advanced rectal cancer: diffusion-weighted 3 Tesla MR imaging

Purpose:

To evaluate the efficacy of diffusion‐weighted imaging (DWI) on 3 Tesla (T) MR imaging to predict the tumor response to neoadjuvant chemoradiation therapy (CRT) in patients with locally advanced rectal cancer.

Materials and Methods:

Thirty‐five patients who underwent neoadjuvant CRT and subsequent surgical resection were included. Tumor volume was measured on T2‐weighted MR images before and after neoadjuvant CRT and the percentage of tumor volume reduction was calculated. The apparent diffusion coefficient (ADC) value was measured on the DWI before and after neoadjuvant CRT, and the change of ADC (Δ ADC) was calculated. The histopathologic response was categorized either as a responder to CRT or as a nonresponder. The relationship between the ADC parameters and the percentage of tumor volume reduction or histopathologic response was then evaluated.

Results:

There was a significant correlation between tumor volume reduction and pre‐CRT ADC and Δ ADC, respectively (r = ?0.352, r = 0.615). Pre‐CRT ADC of the histopathologic responders was significantly lower than that of the histopathologic nonresponders (P = 0.034). Δ ADC of the histopathologic responders was significantly higher than that of the histopathologic nonresponders (P < 0.005).

Conclusion:

DWI on 3T MR imaging may be a promising technique for helping to predict and monitor the treatment response to neoadjuvant CRT in patients with locally advanced rectal cancer. J. Magn. Reson. Imaging 2012;35:110‐116. © 2011 Wiley Periodicals, Inc.

     

Navigator respiratory‐triggered diffusion‐weighted imaging in the follow‐up after hepatic radiofrequency ablation—initial results

Purpose

To evaluate diffusion alterations after hepatic radiofrequency (RF) ablation using a navigator respiratory‐triggered diffusion‐weighted imaging (NRT‐DWI) sequence with regard to potential diagnostic information for detection of local tumor progression (LTP).

Materials and Methods

One hundred forty‐eight consecutive follow‐up magnetic resonance (MR) examinations of 54 patients after hepatic RF ablation were reviewed. Apparent diffusion coefficient (ADC) values of ablation zones and liver parenchyma were assessed using a single‐shot echoplanar imaging sequence with the NRT technique. ADC values of ablation zones and adjacent signal alterations identified in NRT‐DWI were analyzed with regard to LTP.

Results

Mean ADC values of ablation zones (119.9 ± 30.5 × 10^?5 mm²/sec) and liver (106.3 ± 21.2 × 10^?5 mm²/sec) differed significantly (P = 0.0003). No evident changes in ablations' ADC values over time could be identified. ADC values obtained from the entire ablation zone did not significantly differ regarding the presence of LTP. In 58 examinations, hyperintense areas in the periphery of the ablation zone were detected on the NRT‐DWI. Corresponding ADC values were significantly lower in patients with LTP (102.1 ± 22.4 versus 130.8 ± 47.6 × 10^?5 mm²/sec; P = 0.0124).

Conclusion

NRT‐DWI is useful in the follow‐up imaging after RF ablation. ADC‐based evaluation of signal alterations adjacent to the ablation zone may contribute to the identification of LTP and nontumoral posttreatment tissue changes. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

Diffusion‐weighted imaging of breast cancer: Correlation of the apparent diffusion coefficient value with prognostic factors

Purpose

To evaluate the role of diffusion‐weighted imaging (DWI) in the detection of breast cancers, and to correlate the apparent diffusion coefficient (ADC) value with prognostic factors.

Materials and Methods

Sixty‐seven women with invasive cancer underwent breast MRI. Histological specimens were analyzed for tumor size and grade, and expression of estrogen receptors (ER), progesterone receptors, c‐erbB‐2, p53, Ki‐67, and epidermal growth factor receptors. The computed mean ADC values of breast cancer and normal breast parenchyma were compared. Relationships between the ADC values and prognostic factors were determined using Wilcoxon signed rank test and Kruskal‐Wallis test.

Results

DWI detected breast cancer as a hyperintense area in 62 patients (92.5 %). A statistically significant difference in the mean ADC values of breast cancer (1.09 ± 0.27 × 10^?5 mm²/s) and normal parenchyma (1.59 ± 0.27 × 10^?5 mm²/s) was detected (P < 0.0001). There were no correlations between the ADC value and prognostic factors. However, the median ADC value was lower in the ER‐positive group than the ER negative group, and this difference was marginally significant (1.09 × 10^?5 mm²/s versus 1.15 × 10^?5 mm²/s, P = 0.053).

Conclusion

The ADC value was a helpful parameter in detecting malignant breast tumors, but ADC value could not predict patient prognosis. J. Magn. Reson. Imaging 2009;30:615–620. © 2009 Wiley‐Liss, Inc.

     

Diffusion-weighted magnetic resonance imaging in the detection of testicular torsion: feasibility study

Purpose:

To investigate the feasibility and usefulness of diffusion‐weighted magnetic resonance imaging in the detection of testicular torsion.

Materials and Methods:

Institutional Review Board approval and informed consent from all participants were obtained. Consecutive 28 patients with acute scrotal symptoms were included in this study. Fat‐suppressed T2‐weighted, dynamic subtraction contrast‐enhanced, and diffusion‐weighted images were obtained in the coronal plane with a 1.5 T MR unit. An apparent diffusion coefficient (ADC) map was reconstructed from the diffusion‐weighted images obtained with b‐factor of 0 and 800 s/mm². Comparisons of ADC values between the affected and nonaffected testes were performed with Mann–Whitney's U‐test.

Results:

Diffusion‐weighted and ADC images with diagnostic quality were obtained in 23 out of the 28 patients (82%). In testicular torsion (n = 9), the mean ADC value of the twisted testes was significantly lower than that of the nonaffected testes (0.750 ± 0.297 vs. 1.017 ± 0.165 × 10^?3 mm²/sec, P < 0.05). In other scrotal disorders (n = 14), there was no significant difference in the mean ADC value of the testes between the affected and nonaffected side (P = 0.655). The affected‐to‐nonaffected ratio of ADC value was significantly lower in testicular torsion than that in other scrotal disorders (P < 0.05).

Conclusion:

Diffusion‐weighted imaging of the scrotum with testicular ADC measurement can allow for the detection of testicular torsion without any use of contrast media. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

     

Comparison of apparent diffusion coefficients and distributed diffusion coefficients in high‐grade gliomas

Purpose:

To compare apparent diffusion coefficients (ADCs) with distributed diffusion coefficients (DDCs) in high‐grade gliomas.

Materials and Methods:

Twenty patients with high‐grade gliomas prospectively underwent diffusion‐weighted MRI. Traditional ADC maps were created using b‐values of 0 and 1000 s/mm². In addition, DDC maps were created by applying the stretched‐exponential model using b‐values of 0, 1000, 2000, and 4000 s/mm². Whole‐tumor ADCs and DDCs (in 10^?3 mm²/s) were measured and analyzed with a paired t‐test, Pearson's correlation coefficient, and the Bland‐Altman method.

Results:

Tumor ADCs (1.14 ± 0.26) were significantly lower (P = 0.0001) than DDCs (1.64 ± 0.71). Tumor ADCs and DDCs were strongly correlated (R = 0.9716; P < 0.0001), but mean bias ± limits of agreement between tumor ADCs and DDCs was ?0.50 ± 0.90. There was a clear trend toward greater discordance between ADC and DDC at high ADC values.

Conclusion:

Under the assumption that the stretched‐exponential model provides a more accurate estimate of the average diffusion rate than the mono‐exponential model, our results suggest that for a little diffusion attenuation the mono‐exponential fit works rather well for quantifying diffusion in high‐grade gliomas, whereas it works less well for a greater degree of diffusion attenuation. J. Magn. Reson. Imaging 2010;31:531–537. © 2010 Wiley‐Liss, Inc.

     

Diffusion‐weighted imaging of human carotid artery using 2D single‐shot interleaved multislice inner volume diffusion‐weighted echo planar imaging (2D ss‐IMIV‐DWEPI) at 3T: Diffusion measurement in atherosclerotic plaque

Purpose:

To determine if 2D single‐shot interleaved multislice inner volume diffusion‐weighted echo planar imaging (ss‐IMIV‐DWEPI) can be used to obtain quantitative diffusion measurements that can assist in the identification of plaque components in the cervical carotid artery.

Materials and Methods:

The 2D ss‐DWEPI sequence was combined with interleaved multislice inner volume region localization to obtain diffusion weighted images with 1 mm in‐plane resolution and 2 mm slice thickness. Eleven subjects, six of whom have carotid plaque, were studied with this technique. The apparent diffusion coefficient (ADC) images were calculated using DW images with b = 10 s/mm² and b = 300 s/mm².

Results:

The mean ADC measurement in normal vessel wall of the 11 subjects was 1.28 ± 0.09 × 10^?3 mm²/s. Six of the 11 subjects had carotid plaque and ADC measurements in plaque ranged from 0.29 to 0.87 × 10^?3 mm²/s. Of the 11 common carotid artery walls studied (33 images), at least partial visualization of the wall was obtained in all ADC images, more than 50% visualization in 82% (27/33 images), and full visualization in 18% (6/33 images).

Conclusion:

2D ss‐IMIV‐DWEPI can perform diffusion‐weighted carotid magnetic resonance imaging (MRI) in vivo with reasonably high spatial resolution (1 × 1 × 2 mm³). ADC values of the carotid wall and plaque are consistent with similar values obtained from ex vivo endarterectomy specimens. The spread in ADC values obtained from plaque indicate that this technique could form a basis for plaque component identification in conjunction with other MRI/MRA techniques. J. Magn. Reson. Imaging 2009;30:1068–1077. © 2009 Wiley‐Liss, Inc.

     

Microperfusion‐induced elevation of ADC is suppressed after contrast in breast carcinoma

Purpose

To investigate the effect of gadolinium (Gd)‐DTPA on the apparent diffusion coefficient (ADC) of breast carcinoma and to analyze the relationship between pre/postcontrast ADC and the degree of contrast enhancement.

Materials and Methods

Nineteen histopathologically confirmed breast carcinomas (mean size = 22 mm) were analyzed. Their ADCs before and after contrast administration were measured. The contrast‐to‐noise ratios (CNRs) of the tumors were measured on fat‐suppressed 3D T1‐weighted images in precontrast, early, and late postcontrast phases. These results were correlated with the measured ADC values.

Results

A significant decrease in the measured ADC was noted after contrast administration (?23%, P = 0.01). Lesions with relatively high ADC before contrast (>1.3 × 10^?3 mm²/sec; n = 12) demonstrated a larger degree of ADC reduction (mean 34%) than lesions with low ADC (≤1.3 × 10^?3 mm²/sec; n = 7) (mean 4.5%). When an early postcontrast image was used as a surrogate marker of malignant potential, we found a significant inverse correlation with postcontrast ADC (γ = ?0.57, P = 0.02).

Conclusion

Postcontrast ADC exhibited lower values than precontrast ADC, which is thought to reflect suppression of the microperfusion‐induced effect on diffusion‐weighted imaging. Postcontrast ADC may be a better indicator than precontrast ADC to reflect malignant potential of tumors. J. Magn. Reson. Imaging 2009;29:1080–1084. © 2009 Wiley‐Liss, Inc.

     

Diffusion-weighted MRI of fatty liver

Purpose:

To investigate the effect of fat infiltration on the apparent diffusion coefficient (ADC) of liver, and assess the relationship between ADC and hepatic fat fraction (HFF).

Materials and Methods:

MRI scans of 120 consecutive patients were included in this retrospective study. Of these, 42 patients were included in the fatty liver group and 78 in the control group. ADC values were measured from a pair of diffusion‐weighted (DW) images (b = 0 mm²/s and 1000 mm²/s). HFFs were measured using T1W GRE dual‐echo images. The difference between the ADCs of the two groups was assessed with the t‐test. The relationship between HFF and ADC was determined using linear regression analysis and the Pearson correlation coefficient (r).

Results:

Mean HFFs were 0.85 ± 2.86 and 13.67 ± 8.62 in the control and fatty liver groups, respectively. The mean ADC of fatty liver group 1.20 ± 0.22 × 10^?3 mm²/s was significantly lower than that of the control group 1.32 ± 0.23 × 10^?3 mm²/s (P = 0.02). Linear regression analysis revealed an inverse relationship between ADC and HFF (r = ?0.39, P < 0.0001).

Conclusion:

ADC significantly decreases in patients with >5% HFF, and ADC and HFF exhibit an inverse relationship. J. Magn. Reson. Imaging 2012;35:1109‐1111. © 2011 Wiley Periodicals, Inc.

     

Diffusion-weighted imaging of the healthy pancreas: apparent diffusion coefficient values of the normal head, body, and tail calculated from different sets of b-values

Purpose:

To evaluate differences in apparent diffusion coefficient (ADC) values between head, body, and tail regions and the impact of sets of b‐values used in diffusion weighted imaging (DWI) of the normal pancreas.

Materials and Methods:

In 51 healthy volunteers echo‐planar DWI of the pancreas was prospectively performed with b‐values of 50, 400, and 800 s/mm². All four possible combinations of b‐values were used to calculate ADC values in a total of 587 regions in the pancreas head, body, and tail regions. Dependency of ADC values on the anatomical regions and on the applied sets of b‐values was calculated using multivariate analysis of variance (ANOVA).

Results:

Mean ADC values differed significantly between the anatomical regions with the lowest values measured in the pancreatic tail (head 1.13 ± 0.20, body 1.05 ± 0.20, and tail 0.94 ± 0.18 × 10^?3 mm²/s; P < 0.05). ANOVA showed no dependency of ADC values on the sets of b‐values used.

Conclusion:

ADC values differed significantly between the pancreatic head, body, and tail region, with decreasing ADC values toward the tail. Cautious interpretation of DWI results with adjusted, normalized values adapted to the anatomical region seems advisable. The knowledge of such differences may enhance the method's capability to differentiate between different pancreatic pathologies. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Is apparent diffusion coefficient reliable and accurate for monitoring effects of antiangiogenic treatment in a longitudinal study?

Purpose:

To evaluate the reliability and accuracy of the apparent diffusion coefficient (ADC) for monitoring antiangiogenic treatment in a longitudinal study.

Materials and Methods:

Tumor volume and ADC were monitored by T2‐weighted magnetic resonance imaging (MRI) and diffusion‐weighted MRI, respectively, in 18 mice with angiogenesis‐dependent tumors (U118MG) before (day 0) and after 2, 7, 14, and 21 days of administration of the antiangiogenic agent sunitinib maleate (n = 12) or vehicle (n = 6). Percent changes in tumor volume and ADC were calculated and correlations between tumor volume and ADC were evaluated.

Results:

Tumor volume and ADC showed a negative correlation at 69 of the 72 (96%) follow‐up measurements. In the 13 mice with tumor regrowth, ADC started to decrease before (27%) or at the same time (73%) as tumor regrowth. Pretreatment ADC and percent change in ADC change on days 0–2 were similar in mice with positive and negative responses to treatment (0.851 vs. 0.999, 24% vs. 16%). Percent change of ADC showed significant negative correlation with percent change in tumor volume in both the control (r = ?0.69) and treated (r = ?0.65) groups.

Conclusion:

Percent change in ADC is a reliable and accurate marker for monitoring the effects of antiangiogenic treatment, whereas pretreatment ADC and early changes in ADC (ie, days 0–2) are limited in predicting treatment outcome. J. Magn. Reson. Imaging 2012;35:1430–1436. © 2012 Wiley Periodicals, Inc.

     

In vivo and ex vivo measurements of the mean ADC values of lipid necrotic core and hemorrhage obtained from diffusion weighted imaging in human atherosclerotic plaques

Purpose:

To determine the apparent diffusion coefficient (ADC) values of lipid and hemorrhage in atherosclerotic plaque in human carotid arteries in vivo and compare the values obtained from ex vivo carotid endarterectomy specimens.

Materials and Methods:

In vivo diffusion‐weighted imaging (DWI) of carotid plaques was performed using a 2D single shot Interleaved Multislice Inner Volume Diffusion Weighted Echo Planar Imaging (2D ss‐IMIV DWEPI) on 8 subjects who subsequently underwent carotid endarterectomy. A total of 32 slices used to construct the ADC maps were reviewed for the measurement of the mean ADC values in vessel wall, hemorrhage, and lipid necrotic core. The 8 endarterectomy specimens were scanned using by three‐dimensional ms‐IV‐DWEPI. After the ADC maps were created, the mean ADC values in the same locations selected for in vivo values were calculated.

Results:

The mean ADC values obtained from in vivo DWI in normal vessel wall, lipid rich core, and hemorrhage were 1.27 ± 0.16, 0.38 ± 0.1, and 0.98 ± 0.25 × 10^?3 mm²/s, respectively. The mean ADC values in ex vivo lipid necrotic core, and hemorrhage were 0.33 ± 0.08, 1.28 ± 0.10 × 10^?3 mm²/s, respectively. These components mean ADC values obtained from in vivo and ex vivo ADC maps were compared.

Conclusion:

ADC values of the carotid plaque components in vivo are consistent with values obtained from ex vivo endarterectomy specimens. The ability to obtain consistent plaque ADC values in vivo indicates that this technique could be an integral part of the basis for plaque component identification in conjunction with other MRI techniques. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

     

Ex vivo water diffusion tensor properties of the fibroid uterus at 7 T and their relation to tissue morphology

Purpose:

To investigate the water diffusion tensor properties of ex vivo tissue in the fibroid uterus, including the influence of degeneration, and the relevance of the principal eigenvector orientation to the underlying tissue structure.

Materials and Methods:

Following hysterectomy, high‐resolution structural T₂‐weighted and diffusion tensor magnetic resonance imaging (DT‐MRI) were performed on nine uteri at 7 T. Mean diffusivity (MD), fractional anisotropy (FA), and principal eigenvector orientation were measured in myometrium and in myxoid and dense tissue in fibroids. Imaging data and measurements of water diffusion parameters were compared with histopathology findings.

Results:

The nine uteri yielded 23 fibroids. MD was 50% higher in regions of myxoid degeneration compared to dense fibroid tissue (P = 0.001), while myometrium was intermediate in value (dense fibroid tissue, P = 0.15; myxoid degeneration, P = 0.23). FA was lower in dense fibroid tissue than in myometrium (P = 3 × 10^?5), but higher than in myxoid tissue (P = 0.003). Principal eigenvector orientation corresponded qualitatively with that of uterine smooth muscle fibers.

Conclusion:

The water diffusion tensor measured ex vivo in the fibroid uterus is a sensitive probe of tissue type, myxoid degeneration, and morphology. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

     

Interobserver and intraobserver variability of the apparent diffusion coefficient in treated malignant hepatic lesions on a 3.0T machine: Measurements in the whole lesion versus in the area with the most restricted diffusion

Purpose:

To assess the inter/intraobserver variability of apparent diffusion coefficient (ADC) measurements in treated hepatic lesions and to compare ADC measurements in the whole lesion and in the area with the most restricted diffusion (MRDA).

Materials and Methods:

Twenty‐five patients with treated malignant liver lesions were examined on a 3.0T machine. After agreeing on the best ADC image, two readers independently measured the ADC values in the whole lesion and in the MRDA. These measurements were repeated 1 month later. The Bland–Altman method, Spearman correlation coefficients, and the Wilcoxon signed‐rank test were used to evaluate the measurements.

Results:

Interobserver variability for ADC measurements in the whole lesion and in the MRDA was 0.17 × 10^?3 mm²/s [?0.17, +0.17] and 0.43 × 10^?3 mm²/s [?0.45, +0.41], respectively. Intraobserver limits of agreement could be as low as [?0.10, +0.12] 10^?3 mm²/s and [?0.20, +0.33] 10^?3 mm²/s for measurements in the whole lesion and in the MRDA, respectively.

Conclusion:

A limited variability in ADC measurements does exist, and it should be considered when interpreting ADC values of hepatic malignancies. This is especially true for the measurements of the minimal ADC. J. Magn. Reson. Imaging 2010;32:647–653. © 2010 Wiley‐Liss, Inc.