Discrimination of metastatic lymph nodes in patients with gastric carcinoma using diffusion‐weighted imaging

Purpose:

To determine the accuracy of diffusion‐weighted imaging (DWI) in discrimination of metastatic lymph nodes (LNs) in gastric carcinoma with rigorous histopathological correlation.

Materials and Methods:

With Institutional Review Board (IRB) approval, 28 patients with gastric carcinoma underwent magnetic resonance imaging (MRI) and DWI before surgery. LNs were resected at surgery and thereafter submitted for histopathological analyses. All histopathologically identified LNs (≥5 mm) that exactly matched the location and size of nodes on MRI/DWI were submitted to lesion‐by‐lesion analyses. Short‐axis diameter, border irregularity, enhanced patterns, and apparent diffusion coefficient (ADC) values of each LN were recorded. Each measurement was compared between metastatic and benign LNs, confirmed by nodal histopathology. A receiver operating characteristic (ROC) curve was generated to evaluate the capability of morphological and ADC measurements in distinguishing metastatic lymph nodes.

Results:

The median ADC value of metastatic nodes was significantly lower (1.28 × 10^?3 mm²/sec; interquartile range, 1.20–1.31) than that of benign (1.55; 1.47–1.73) nodes (P < 0.001). DWI showed greater diagnostic accuracy in determining metastatic nodes (AUC = 0.857) than the combined morphological measurements of short‐axis, border irregularity, and enhanced patterns (AUC = 0.746, P = 0.03). Adding ADC values to the combined morphologic criteria demonstrated the greatest predictive power (AUC = 0.889).

Conclusion:

DWI may provide great potential in effective discrimination of metastatic LNs in gastric carcinoma. J. Magn. Reson. Imaging 2013;37:1436–1444. © 2012 Wiley Periodicals, Inc.

     

Impact of nonrigid motion correction technique on pixel-wise pharmacokinetic analysis of free-breathing pulmonary dynamic contrast-enhanced MR imaging

Purpose:

To investigates the impact of nonrigid motion correction on pixel‐wise pharmacokinetic analysis of free‐breathing DCE‐MRI in patients with solitary pulmonary nodules (SPNs). Misalignment of focal lesions due to respiratory motion in free‐breathing dynamic contrast‐enhanced MRI (DCE‐MRI) precludes obtaining reliable time–intensity curves, which are crucial for pharmacokinetic analysis for tissue characterization.

Materials and Methods:

Single‐slice 2D DCE‐MRI was obtained in 15 patients. Misalignments of SPNs were corrected using nonrigid B‐spline image registration. Pixel‐wise pharmacokinetic parameters K^trans, v_e, and k_ep were estimated from both original and motion‐corrected DCE‐MRI by fitting the two‐compartment pharmacokinetic model to the time–intensity curve obtained in each pixel. The “goodness‐of‐fit” was tested with χ²‐test in pixel‐by‐pixel basis to evaluate the reliability of the parameters. The percentages of reliable pixels within the SPNs were compared between the original and motion‐corrected DCE‐MRI. In addition, the parameters obtained from benign and malignant SPNs were compared.

Results:

The percentage of reliable pixels in the motion‐corrected DCE‐MRI was significantly larger than the original DCE‐MRI (P = 4 × 10^?7). Both K^trans and k_ep derived from the motion‐corrected DCE‐MRI showed significant differences between benign and malignant SPNs (P = 0.024, 0.015).

Conclusion:

The study demonstrated the impact of nonrigid motion correction technique on pixel‐wise pharmacokinetic analysis of free‐breathing DCE‐MRI in SPNs. J. Magn. Reson. Imaging 2011;33:968–973. © 2011 Wiley‐Liss, Inc.

     

A diffusion tensor imaging group study of the spinal cord in multiple sclerosis patients with and without T2 spinal cord lesions

Purpose

To examine the T₂‐normal appearing spinal cord of patients with multiple sclerosis (MS) using diffusion tensor imaging.

Materials and Methods

Diffusion tensor images of the spinal cord were acquired from 21 healthy subjects, 11 MS patients with spinal cord lesions, and 10 MS patients without spinal cord lesions on the T₂‐weighted MR images. Different diffusion measures were evaluated using both a region of interest (ROI) ‐based and a diffusion tensor tractography‐based segmentation approach.

Results

It was observed that the FA, the transverse diffusivity λ_?, and the ratio of the longitudinal and transverse diffusivities (λ_∥/λ _?) were significantly lower in the spinal cord of MS patients with spinal cord lesions compared with the control subjects using both the ROI method (P = 0.014, P = 0.028, and P = 0.039, respectively) and the tractography‐based approach (P = 0.006, P = 0.037, and P = 0.012, respectively). For both image analysis methods, the FA and the λ _∥/λ _? values were significantly different between the control group and the MS patient group without T₂ spinal cord lesions (P = 0.013).

Conclusion

Our results suggest that the spinal cord may still be affected by MS, even when lesions are not detected on a conventional MR scan. In addition, we demonstrated that diffusion tensor tractography is a robust tool to analyze the spinal cord of MS patients. J. Magn. Reson. Imaging 2009;30:25–34. © 2009 Wiley‐Liss, Inc.

     

Phase‐contrast magnetic resonance quantification of normal pulmonary venous return

Purpose

To assess the feasibility of phase‐contrast magnetic resonance (PCMR) in quantifying the pulmonary venous return in normal subjects.

Materials and Methods

PCMR was performed in 12 healthy adult volunteers (mean age 38 years, range 27–60 years; 9 men; body surface area 1.81 ± 0.15 m²) for the ascending and descending aorta, caval veins, main and branch pulmonary arteries, and pulmonary veins. Two readers independently quantified blood flow in all subjects.

Results

Intraobserver differences were ?2.0% (95% confidence interval [CI]: ?9.9% to 5.9%), ?4.5% (95% CI: ?15.6% to 6.5%), and ?0.7% (95% CI: ?4.5% to 3.0%) for all vessels, pulmonary veins, and other great vessels, respectively. Interobserver differences were ?2.0% (95% CI: ?10.6% to 6.6%), ?3.1% (95% CI: ?16.0% to 9.9%), and ?1.4% (95% CI: ?6.4% to 3.5%) for all vessels, pulmonary veins, and other great vessels, respectively. Pulmonary venous flow volume showed high correlations with the volumes of the pulmonary arterial flow, systemic arterial flow, and systemic venous flow (r = 0.76–0.92, P < 0.005).

Conclusion

Flow quantification of normal pulmonary venous return using PCMR is feasible with high reproducibility and accuracy. J. Magn. Reson. Imaging 2009;29:588–594. © 2009 Wiley‐Liss, Inc.

     

Feasibility of FAIR imaging for evaluating tumor perfusion

Purpose:

To evaluate the feasibility of flow‐sensitive alternating inversion recovery (FAIR) for measuring blood flow in tumor models.

Materials and Methods:

In eight mice tumor models, FAIR and dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) was performed. The reliability for measuring blood flow on FAIR was evaluated using the coefficient of variation of blood flow on psoas muscle. Three regions of interest (ROIs) were drawn in the peripheral, intermediate, and central portions within each tumor. The location of ROI was the same on FAIR and DCE‐MR images. The correlation between the blood flow on FAIR and perfusion‐related parameters on DCE‐MRI was evaluated using the Pearson correlation coefficient.

Results:

The coefficient of variation for measuring blood flow was 9.8%. Blood flow on FAIR showed a strong correlation with Kep (r = 0.77), percent relative enhancement (r = 0.73), and percent enhancement ratio (r = 0.81). The mean values of blood flow (mL/100 g/min) (358 vs. 207), Kep (sec^?1) (7.46 vs. 1.31), percent relative enhancement (179% vs. 134%), and percent enhancement ratio (42% vs. 26%) were greater in the peripheral portion than in the central portion (P < 0.01).

Conclusion:

As blood flow measurement on FAIR is reliable and closely related with that on DCE‐MR, FAIR is feasible for measuring tumor blood flow. J. Magn. Reson. Imaging 2010;32:738–744. © 2010 Wiley‐Liss, Inc.

     

Assessing liver function using dynamic Gd‐EOB‐DTPA‐enhanced MRI with a standard 5‐phase imaging protocol

Purpose:

To evaluate liver function obtained by tracer‐kinetic modeling of dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) data acquired with a routine gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd‐EOB‐DTPA)‐enhanced protocol.

Materials and Methods:

Data were acquired from 25 cases of nonchronic liver disease and 94 cases of cirrhosis. DCE‐MRI was performed with a dose of 0.025 mmol/kg Gd‐EOB‐DTPA injected at 2 mL/sec. A 3D breath‐hold sequence acquired 5 volumes of 72 slices each: precontrast, double arterial phase, portal phase, and 4‐minute postcontrast. Regions of interest (ROIs) were selected semiautomatically in the aorta, portal vein, and whole liver on a middle slice. A constrained dual‐inlet two‐compartment uptake model was fitted to the ROI curves, producing three parameters: intracellular uptake rate (UR), extracellular volume (Ve), and arterial flow fraction (AFF).

Results:

Median UR dropped from 4.46 10^?2 min^?1 in the noncirrhosis to 3.20 in Child–Pugh A (P = 0.001), and again to 1.92 in Child–Pugh B (P < 0.0001). Median Ve dropped from 6.64 mL 100 mL^?1 in the noncirrhosis to 5.80 in Child–Pugh A (P = 0.01). Other combinations of Ve and AFF changes were not significant for any group.

Conclusion:

UR obtained from tracer kinetic analysis of a routine DCE‐MRI has the potential to become a novel index of liver function. J. Magn. Reson. Imaging 2013;37:1109–1114. © 2012 Wiley Periodicals, Inc.

     

Monitoring of acute axonal injury in the swine spinal cord with EAE by diffusion tensor imaging

Purpose

To evaluate the ability of diffusion tensor imaging (DTI) to detect and monitor acute axonal injury in swine spinal cord with acute experimental allergic encephalomyelitis (EAE).

Materials and Methods

Magnetic resonance imaging of the cervical spinal cord was performed in vivo at different time points through the onset and progression of EAE using a 3 Tesla clinical scanner. The DTI parameters were calculated in four separate regions of interest at the C2/C3 level. The quantitative DTI‐pathology and DTI‐clinical correlations were verified.

Results

In the monophasic acute course of EAE onset and progression, axial diffusivity (AD) decrease correlates with acute axonal injury (r = ?0.84; P < 0.001). By contrast, radial diffusivity does not change and no demyelination in histopathology was detected. Moreover, a clear correlation between clinical disease and axial diffusivity was found in two swine EAE models (r = ?0.86; P < 0.001 and r = ?0.92; P < 0.001).

Conclusion

AD corresponds with axonal injury in the absence of demyelination and may be a useful noninvasive tool to investigate the underlying pathogenic processes of multiple sclerosis and to monitor the effects of experimental treatments for axonal injury. J. Magn. Reson. Imaging 2009;30:277–285. © 2009 Wiley‐Liss, Inc.

     

Inter- and intraobserver variability in the evaluation of dynamic breast cancer MRI

Purpose

To quantify variations within and between observers ascribable to manual region of interest (ROI) placement in patients with breast cancer undergoing dynamic MRI.

Materials and Methods

Expert and nonexpert observers independently outlined tumor ROIs on 30 dynamic T₁‐weighted (T₁W) MRI scans on five occasions over two months. Lesion size (number of pixels) and kinetic parameter estimates, including the transfer constant (K^trans), were calculated for each ROI placement. Inter‐ and intraobserver variability was assessed with respect to the interval between drawings, lesion morphology, and observer experience.

Results

For the nonexpert, the variability reduced with decreasing time intervals between ROI drawings (the coefficient of variance (wCV) values at two months, two weeks, one day, and same‐day time intervals were respectively 11.6%, 10.7%, 4.8%, and 2.6% for lesion size, and 8.9%, 9.7%, 6.7%, and 3.2% for K^trans). For the expert observer, the variability was smaller overall and more constant, but improved for same‐day ROI placements (region size wCV: 7.5%, 6.2%, 7.1%, and 3.7%; K^trans wCV: 5.4%, 5.3%, 5.6%, and 4.5%).

Conclusion

Significant observer variability in manual ROI placement occurs in dynamic MRI of breast cancer. For serial patient studies, ROI placements should be outlined at the same sitting to minimize observer error. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.

     

Morphological and hemodynamic magnetic resonance assessment of early neonatal brain injury in a piglet model

Purpose

To investigate the utility of functional and morphological magnetic resonance imaging (MRI) to assess the extent of brain injury in a hypoxia‐ischemia (HI) piglet model and further to validate that the desired ischemic injury was successfully induced.

Materials and Methods

MRI was performed at 1.5 T in anesthetized piglets (N = 10, age = 12‐36 hours). Relative cerebral blood flow (rCBF), time‐to‐peak (TTP) contrast, and apparent diffusion coefficient (ADC) were estimated at different time points pre‐, during, and post‐HI. The effect following bilateral clamping of the carotid arteries was assessed by contrast‐enhanced MR angiography (MRA) and phase contrast MR angiography (PCA) (N = 4).

Results

A linear correlation was observed between relative cerebral perfusion reduction and cerebral ADC during HI (r² = 0.85, P < 0.05). There was no correlation between rCBF reduction during 30 minutes of HI and cerebral ADC after 30 or 150 minutes of reperfusion/reoxygenation (RR).

Conclusion

The combination of morphological and functional (perfusion and diffusion) MRI enabled consistent assessment of both the presence and absence of complete occlusion as well as the functional significance of the occlusion. J. Magn. Reson. Imaging 2004;20:8–15. © 2004 Wiley‐Liss, Inc.

     

Cardiac MRI evaluation of hypertrophic cardiomyopathy: Left ventricular outflow tract/aortic valve diameter ratio predicts severity of LVOT obstruction

Purpose:

To evaluate if left ventricular outflow tract/aortic valve (LVOT/AO) diameter ratio measured by cardiac magnetic resonance (CMR) imaging is an accurate marker for LVOT obstruction in patients with hypertrophic cardiomyopathy (HCM) compared to Doppler echocardiography.

Materials and Methods:

In all, 92 patients with HCM were divided into three groups based on their resting echocardiographic LVOT pressure gradient (PG): <30 mmHg at rest (nonobstructive, n = 31), <30 mmHg at rest, >30 mmHg after provocation (latent, n = 29), and >30 mmHg at rest (obstructive, n = 32). The end‐systolic dimension of the LVOT on 3‐chamber steady‐state free precession (SSFP) CMR was divided by the end diastolic aortic valve diameter to calculate the LVOT/AO diameter ratio.

Results:

There were significant differences in the LVOT/AO diameter ratio among the three subgroups (nonobstructive 0.60 ± 0.13, latent 0.41 ± 0.16, obstructive 0.24 ± 0.09, P < 0.001). There was a strong linear inverse correlation between the LVOT/AO diameter ratio and the log of the LVOT pressure gradient (r = ?0.84, P < 0.001). For detection of a resting gradient >30 mmHg, the LVOT/AO diameter ratio the area under the receiver operating characteristic (ROC) curve was 0.91 (95% confidence interval [CI] 0.85–0.97). For detection of a resting and/or provoked gradient >30 mmHg, the LVOT/AO diameter ratio area under the ROC curve was 0.90 (95% CI 0.84–0.96).

Conclusion:

The LVOT/AO diameter ratio is an accurate, reproducible, noninvasive, and easy to use CMR marker to assess LVOT pressure gradients in patients with HCM. J. Magn. Reson. Imaging 2012;36:598–603. © 2012 Wiley Periodicals, Inc.

     

Evaluating the severity of nonalcoholic steatohepatitis with superparamagnetic iron oxide‐enhanced magnetic resonance imaging

Purpose

To evaluate the utility of noninvasive assessment of human nonalcoholic fatty liver disease (NAFLD) patients using superparamagnetic iron oxide (SPIO)‐enhanced MRI.

Materials and Methods

Nineteen NAFLD patients underwent SPIO‐enhanced MRI. The values of τ, a time constant for an exponential approximation, were calculated using gradient‐echo echo‐planar imaging, and the values of %T2, a marker of the T2 relaxation effect of SPIO, were calculated using T2‐weighted fast spin‐echo images. Correlations between these values and the histological NAFLD activity scores were evaluated. The study protocol was approved by our Institutional Review Board and all patients gave informed consent.

Results

There was a statistically significant relationship between the NAFLD activity scores and the τ values (r = 0.66, P = 0.002). The %T2 values were also significantly correlated with the NAFLD activity score (r = ?0.58, P = 0.009). A cutoff τ value of 42.8 predicted “definitive NASH” (NAFLD activity score ≥5) with a specificity of 66.7% and a sensitivity of 99.9%, whereas a cutoff %T2 value of 32.5 predicted “definitive NASH” with a specificity of 72.7% and a sensitivity of 87.5%.

Conclusion

Noninvasive SPIO‐enhanced MRI may be helpful for identifying NASH patients among patients suspected of having NAFLD. J. Magn. Reson. Imaging 2008;28:1444–1450. © 2008 Wiley‐Liss, Inc.

     

MR‐diffusion weighted imaging of healthy liver parenchyma: Repeatability and reproducibility of apparent diffusion coefficient measurement

Purpose:

To compare repeatability and reproducibility of four different methods of apparent diffusion coefficient (ADC) evaluation of liver parenchyma. In fact, repeatability and reproducibility assessment is mandatory in quantitative evaluations, however, these have not been accurately investigated in liver MR‐diffusion‐weighted studies.

Materials and Methods:

Diffusion‐weighted sequences, b‐value = 0–1000 s/mm², were acquired on 30 healthy volunteers by a 1.5T scanner whose reliability has been validated by a phantom study. Four sampling methods, evaluating various parenchyma percentages by different‐sized region‐of‐interests (ROIs), were compared by two observers: 70% and 30% of the volume, 4%‐one‐ROI‐per‐segment, and 4%‐one‐ROI‐per‐slice in the right‐lobe. Ninety‐five percent limits of agreement and intraclass correlation coefficient (ICC) were calculated.

Results:

Complete measurements on the left lobe could be obtained in less than half of patients. The 4%‐one‐ROI‐per‐slice and 4%‐one‐ROI‐per‐segment yielded lower mean values compared with 30–70% volume methods (1343–1373 versus 1463–1560·10^?6 mm²/s, respectively). Repeatability was acceptable (ICCs ～ 0.80) whereas reproducibility was low (ICCs ≤ 0.45) for all methods. Averaging at least 3 measurements in middle‐lower sections of the right lobe improved both repeatability (ICCs to ≥0.87) and reproducibility (ICCs to 0.82) for 30–70% V methods.

Conclusion:

ADC measurements were repeatable but not reproducible in our study. Reproducibility could be improved by taking averages on the right lobe with large ROI methods. Studies on procedures that standardize ADC measurements using more than two observers are needed. J. Magn. Reson. Imaging 2010;31:912–920. ©2010 Wiley‐Liss, Inc.

     

Pineal volume and circadian melatonin profile in healthy volunteers: An interdisciplinary approach

Purpose

To correlate pineal parenchyma volume (PP) to circadian melatonin profiles and to determine the 24‐hour melatonin per volume of pineal tissue (MLPV). Furthermore, we compared melatonin profiles of cystic and solid glands.

Methods

In 15 healthy male subjects (20–27 years) the PP was determined using high‐resolution magnetic resonance imaging (trueFISP, isotropic voxel: 0.8 mm³). Melatonin plasma concentrations (MC) were determined every 2 hours for 24 hours.

Results

Mean PP was 125 ± 54 mm³. PP correlated linearly to maximum MC and to 24‐hour melatonin (r = 0.61 and r = 0.64, P < 0.05) but not to minimum MC. The 24‐hour melatonin was 653 ± 242.6 pg/mL, MLPV was 5.8 ± 2.3 pg/mL*ml^?1. Nine pineal glands were solid and six were cystic. PP of solid glands showed higher linear correlations to maximum melatonin, to 24‐hour melatonin, and to the slope of the melatonin increase of the curve (P < 0.05).

Conclusion

PP correlates linearly to melatonin plasma concentrations in humans. MLPV displays similar interindividual differences as 24‐hour melatonin. PP of solid glands show better correlation to melatonin profiles than cystic. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

Effect of MRI strength and propofol sedation on pediatric core temperature change

Purpose:

To determine core body temperature variations in children undergoing MRI exams on 1.5 Tesla (T) and 3T magnetic field strengths and with and without propofol sedation.

Materials and Methods:

Temporal artery temperatures were prospectively collected on 400 consecutive patients undergoing 1.5 Tesla (T) or 3.0T MRI scans. A cumulative logistic regression model was created using age, weight, MRI protocol, sedation status, pre‐MRI temperature and MRI strength to assess risk of temperature change.

Results:

For patients with complete pre‐ and post‐MRI temperature data, mean temperatures did not significantly change (?0.0155°C, 95%CI, ?0.035, 0.064; n = 385). Temperature changes differed significantly between propofol‐sedated and nonsedated patients (?0.26°C ± .44 versus 0.24°C ± 0.42; P < 0.0001), as did temperature changes for patients on the 3T (0.076°C ± 0.52) versus 1.5T (?0.06°C ± 0.48; P = 0.011). Sedation status, age, MRI strength, and MRI protocol accounted for 44.17% of temperature variance. The temperatures of 15 patients' (3.9%) decreased >1°C; 12 were on the 1.5T. All 7 patients (1.8%) who increased >1°C were non‐sedates.

Conclusion:

Clinically significant core body temperature change is uncommon in children undergoing MRI with different magnetic field strengths, and with and without propofol sedation. J. Magn. Reson. Imaging 2011;33:950–956. © 2011 Wiley‐Liss, Inc.

     

Accuracy of MRI for predicting the circumferential resection margin,mesorectal fascia invasion,and tumor response to neoadjuvant chemoradiotherapy for locally advanced rectal cancer

Purpose

To evaluate the diagnostic accuracy of MRI for predicting the circumferential resection margin (CRM), mesorectal fascia (MRF) invasion, and the tumor response to neoadjuvant chemoradiotherapy (CRT) for locally advanced rectal cancer.

Materials and Methods

Sixty‐five consecutive patients with locally advanced rectal cancer (≥T3 or lymph node‐positive) who underwent neoadjuvant CRT and subsequent surgery were enrolled in this retrospective study. Two blinded radiologists independently reviewed both the pre‐ and post‐CRT rectal MR images and measured the post‐CRT CRM; they recorded their confidence level with respect to the MRF invasion and tumor response using a 5‐point scale. The diagnostic accuracy of each reviewer was calculated using receiver operating characteristic curve (ROC) analysis.

Results

The measured CRM was not significantly different from the reference standard (mean difference, ?1.4 mm; 95% limits of agreement, ?8.3–5.4 mm; interclass correlation coefficient, 0.82). The diagnostic accuracy (A_z) for determining MRF invasion was 0.890 for reviewer 1 (95% confidence interval [CI], 0.788–0.954) and 0.829 for reviewer 2 (95% CI, 0.715–0.911). The A_z for predicting complete or near‐complete regression was 0.791 for reviewer 1 (95% CI, 0.672–0.882) and 0.735 for reviewer 2 (95% CI, 0.611–0.837).

Conclusion

MRI provides accurate information regarding the CRM of locally advanced rectal cancer after neoadjuvant CRT; it also shows relatively high accuracy for predicting MRF invasion and moderate accuracy for assessing tumor response. J. Magn. Reson. Imaging 2009;29:1093–1101. © 2009 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.

     

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.

     

MR-guided radiofrequency ablation of hepatic malignancies at 1.5 T: initial results

Purpose

To assess the feasibility of magnetic resonance (MR)‐guided radiofrequency ablation (RFA) of hepatic malignancies using a high‐field MR scanner.

Materials and Methods

A total of 10 patients with 14 primary (N = 1) or secondary (N = 13) hepatic malignancies underwent MR‐guided RFA using a closed‐bore 1.5 T MR scanner. Lesion diameters ranged from 2.0 cm to 4.7 cm. RFA was performed using a 200‐W generator in combination with a 3.5‐cm LeVeen electrode applying a standardized energy protocol.

Results

RFA was technically feasible in all patients. Necrosis diameter ranged from 2.5 cm to 6.8 cm. The mean follow‐up period is 12.2 ( 1 - 18 ) months. In nine out of 10 patients, local tumor control was achieved. For this purpose, a second CT‐guided RFA was required in two patients. In four patients, multifocal hepatic tumor progression occurred, with the treated lesion remaining tumor‐free in three of these patients. Two patients showed extrahepatic tumor progression. Four patients remained tumor‐free. No major complications occurred.

Conclusion

MR‐guided RFA of hepatic malignancies in a closed‐bore high‐field MR scanner is technically feasible and safe. It can be advantageous in locations considered unfavorable for CT‐guided puncture or in patients in which iodinated contrast material is contraindicated. J. Magn. Reson. Imaging 2004;19:342–348. © 2004 Wiley‐Liss, Inc.

     

Imaging age‐related cognitive decline: A comparison of diffusion tensor and magnetization transfer MRI

Purpose

To determine which MR technique was the most sensitive to age‐related white matter damage. We compared both diffusion tensor imaging (DTI) and magnetization transfer (MT) maps to determine which technique correlated most strongly with cognitive function in a middle‐aged and elderly community population.

Materials and Methods

In all, 64 healthy subjects (aged 50–90) underwent MRI and neuropsychology. Histograms were generated for white matter mean diffusivity (MD), fractional anisotropy (FA), and MT ratio (MTR). White matter hyperintensity volume (WMH) and brain volume were also determined. Composite neuropsychological scores were derived for 4 cognitive domains (executive function, working memory, episodic memory, and information processing speed).

Results

All MRI parameters correlated with age (FA r = 0.726, P < 0.001; MD r = ?0.619 P < 0.001, MTR r = ?0.566, P < 0.001, WMH r = 0.511, P < 0.001). All MRI parameters correlated with cognition, but DTI, and particularly FA, correlated most strongly. Adding DTI parameters explained more variance in cognition than WMH alone; the increase was greatest with FA, which alone explained 45%, 33%, and 25% of the variance in cognition for information processing speed, episodic memory, and executive function, respectively.

Conclusion

DTI appears the most sensitive imaging parameter to determine age‐related white matter damage. The stronger relationship with FA suggests that axonal damage is important in age‐related cognitive decline. J. Magn. Reson. Imaging 2009;29:23–30. © 2008 Wiley‐Liss, Inc.

     

Magnetic resonance imaging findings of the mass-forming type of autoimmune pancreatitis: comparison with pancreatic adenocarcinoma

Purpose:

To determine the characteristic magnetic resonance imaging (MRI) features of mass‐forming autoimmune pancreatitis (AIP), which allow its differentiation from pancreatic adenocarcinoma (PAC).

Materials and Methods:

MR images of 37 patients with either pathologically proven, mass‐forming AIPs (n = 9) or PACs (n = 28) were retrospectively reviewed. The pancreatic MR protocol included unenhanced images, contrast‐enhanced dynamic images, diffusion‐weighted imaging (DWI), and MR‐cholangiopancreatography (MRCP). Two reviewers analyzed the MR images regarding the number, location, morphologic features, and enhancement degree and pattern of the lesions as well as secondary changes of the pancreatic parenchyma, the biliary and pancreatic ducts. The size and apparent diffusion coefficient (ADC) values of the lesions were measured.

Results:

Although sensitivities were low (28.6%–44.4%), specificities of multiplicity, capsule‐like rim enhancement, and skipped stricture of the biliary or pancreatic duct in mass‐forming AIP were high (100%). Sensitivities and specificities of irregular or geographic shape, delayed enhancement, and a low ADC value <1.26 × 10^?3 mm²/s in mass‐forming AIP were favorable (71.4%–83.3% and 78.5%–89.3%).

Conclusion:

Although to differentiate mass‐forming AIP from pancreatic cancer is difficult, the combination of MRI findings including contrast‐enhanced dynamic images, MRCP, and DWI can be a help. J. Magn. Reson. Imaging 2012;36:188–197. © 2012 Wiley Periodicals, Inc.