Gd‐EOB‐DTPA‐enhanced MR imaging: Prediction of hepatic fibrosis stages using liver contrast enhancement index and liver‐to‐spleen volumetric ratio

Purpose:

To develop and evaluate a quantitative parameter for staging hepatic fibrosis by contrast enhancement signal intensity and morphological measurements from gadoxetic acid (Gd‐EOB‐DTPA)‐enhanced MR imaging.

Materials and Methods:

MR images were obtained in 93 patients; 75 patients had histopathologically proven hepatic fibrosis and 18 patients who had healthy livers were evaluated. The liver‐to‐muscle signal intensity ratio (SI_post = SIliver/SImuscle), contrast enhancement index (CEI = SIpost/SIpre), and liver‐to‐spleen volumetric ratio (VR = Vliver/Vspleen) were evaluated for staging hepatic fibrosis.

Results:

VR was most strongly correlated with fibrosis stage (7.21; r = ?0.83; P < 0.001). Sensitivity, specificity, and area under the ROC curve demonstrated by linear regression formula generated by VR and CEI in predicting fibrous scores were 100%, 73%, and 0.91, respectively, for the detection of hepatic fibrosis F1 or greater (≥ F1),100%, 87%, and 0.96 for ≥ F2, 74%, 98%, and 0.93 for ≥ F3 and 91%, 100%, and 0.97 for F4.

Conclusion:

The liver‐to‐spleen volumetric ratio and contrast enhancement index were reliable biomarkers for the staging of hepatic fibrosis on Gd‐EOB‐DTPA‐enhanced MR imaging. J. Magn. Reson. Imaging 2012;36:1148–1153. © 2012 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.

     

Resovist enhanced MR imaging of the liver: Does quantitative assessment help in focal lesion classification and characterization?

Purpose:

To improve characterization of focal liver lesions by a prospective quantitative analysis of percentage signal intensity change, in dynamic and late phases after slow (0.5 mL/s) Resovist administration.

Materials and Methods:

Seventy‐three patients were submitted on clinical indication to MR examination with Resovist. Signal intensity of 92 detected focal lesions (5–80 mm) were measured with regions of interest and normalized to paravertebral muscle in arterial, portal, equilibrium and T1/T2 late phases, by two observers in conference. Five values of percentage variations per patient were obtained and statistically evaluated.

Results:

The enhancement obtained on dynamic study is more suitable in hemangiomas and focal nodular hyperplasias than in adenomas and hepatocellular carcinomas. To discriminate benign versus malignant lesions on late‐phase‐T2‐weighted images, a cutoff = ?26%, allowed sensitivity and specificity values of 97.4% and 97.7%, respectively. Area under the receiver operating characteristic (ROC) curve was 0.99. To differentiate hemangioma versus all other focal liver lesions, on late‐phase‐T1‐weighted images, a cutoff = +40% permitted sensitivity and specificity values of 90.5% and 98.0%, respectively. Area under the ROC curve was 0.98.

Conclusion:

Late phase quantitative evaluation after slow Resovist administration, allows to differentiate malignant from benign hepatic masses and hemangiomas from all the others focal liver lesions, on T2‐/T1‐weighted acquisitions, respectively. J. Magn. Reson. Imaging 2009;30:1012–1020. © 2009 Wiley‐Liss, Inc.

     

Semi-automatic deformable registration of prostate MR images to pathological slices

Purpose

To present a semi‐automatic deformable registration algorithm for co‐registering T2‐weighted (T2w) images of the prostate with whole‐mount pathological sections of prostatectomy specimens.

Materials and Methods

Twenty‐four patients underwent 1.5 Tesla (T) endorectal MR imaging before radical prostatectomy with whole‐mount step‐section pathologic analysis of surgical specimens. For each patient, the T2w imaging containing the largest area of tumor was manually matched with the corresponding pathologic slice. The prostate was co‐registered using a free‐form deformation (FFD) algorithm based on B‐splines. Registration quality was assessed through differences between prostate diameters measured in right–left (RL) and anteroposterior (AP) directions on T2w images and pathologic slices and calculation of the Dice similarity coefficient, D, for the whole prostate (WP), the peripheral zone (PZ) and the transition zone (TZ).

Results

The mean differences in diameters measured on pathology and MR imaging in the RL direction and the AP direction were 0.49 cm and ?0.63 cm, respectively, before registration and 0.10 cm and ?0.11 cm, respectively, after registration. The mean D values for the WP, PZ and TZ, were 0.76, 0.65, and 0.77, respectively, before registration and increased to 0.91, 0.76, and 0.85, respectively, after registration. The improvements in D were significant for all three tissues (P < 0.001 for all).

Conclusion

The proposed semi‐automatic method enabled successful co‐registration of anatomical prostate MR images to pathologic slices. J. Magn. Reson. Imaging 2010;32:1149–1157. © 2010 Wiley‐Liss, Inc.

     

Correction of arterial input function in dynamic contrast-enhanced MRI of the liver

Purpose:

To develop a postprocessing method to correct saturation of arterial input function (AIF) in T1‐weighted dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) for quantification of hepatic perfusion.

Materials and Methods:

The saturated AIF is corrected by parameterizing the first pass of the AIF as a smooth function with a single peak and minimizing a least‐squares error in fitting the liver DCE‐MRI data to a dual‐input single‐compartment model. Sensitivities of the method to the degree of saturation in the AIF first‐pass peak and the image contrast‐to‐noise ratio were assessed. The method was also evaluated by correlating portal venous perfusion with an independent overall liver function measurement.

Results:

The proposed method corrects the distorted AIF with a saturation ratio up to 0.45. The corrected AIF improved hepatic arterial perfusion by ?23.4% and portal venous perfusion by 26.9% in a study of 12 patients with liver cancers. The correlation between the mean voxelwise portal venous perfusion and overall liver function measurement was improved by using the corrected AIFs (R² = 0.67) compared with the saturated AIFs (R² = 0.39).

Conclusion:

The method is robust for correcting AIF distortion and has the potential to improve quantification of hepatic perfusion for assessment of liver tissue response to treatment in patients with hepatic cancers. J. Magn. Reson. Imaging 2012;36:411–421. © 2012 Wiley Periodicals, Inc.

     

Changes in hepatic venous morphology with cirrhosis on MRI

Purpose

To identify changes in vascular morphology on magnetic resonance imaging (MRI) in patients with cirrhosis and to compare these findings to liver donors.

Materials and Methods

Patients undergoing liver transplantation with biopsy‐proven cirrhosis (n = 74) and liver donor candidates (n = 85) underwent dynamic gadolinium‐enhanced 3D MR at 1.5T. Vessel diameters were measured independently by three radiologists and features of cirrhosis were identified and correlated with cirrhosis.

Results

Hepatic veins were smaller in patients with cirrhosis (4.9, 4.5, and 5.0 mm for right, middle, and left vs. 9.9, 7.6, and 8.9 mm in donors, P ? 0.001) and were negatively correlated with cirrhosis (P < 0.001). Right hepatic vein (RHV) <5 mm diagnosed cirrhosis with 59% sensitivity and 99% specificity; the sensitivity and specificity were 88% and 85% for RHV <7 mm. Main portal vein was minimally larger in cirrhosis, 14 versus 12 mm (P < 0.001) in donors. Right portal veins were smaller in cirrhotic patients, 6.5 and 6.2 mm compared to 8.4 and 7.6 mm (P ? 0.001), respectively, in donors.

Conclusion

Vascular features of cirrhosis include small hepatic veins, minimally enlarged main portal vein, and small intrahepatic portal veins; these features may facilitate identification of cirrhosis. J. Magn. Reson. Imaging 2009;29:1085–1092. © 2009 Wiley‐Liss, Inc.

     

T(1) independent, T(2) (*) corrected chemical shift based fat-water separation with multi-peak fat spectral modeling is an accurate and precise measure of hepatic steatosis

Purpose:

To determine the precision and accuracy of hepatic fat‐fraction measured with a chemical shift‐based MRI fat‐water separation method, using single‐voxel MR spectroscopy (MRS) as a reference standard.

Materials and Methods:

In 42 patients, two repeated measurements were made using a T₁‐independent, T‐corrected chemical shift‐based fat‐water separation method with multi‐peak spectral modeling of fat, and T₂‐corrected single voxel MR spectroscopy. Precision was assessed through calculation of Bland‐Altman plots and concordance correlation intervals. Accuracy was assessed through linear regression between MRI and MRS. Sensitivity and specificity of MRI fat‐fractions for diagnosis of steatosis using MRS as a reference standard were also calculated.

Results:

Statistical analysis demonstrated excellent precision of MRI and MRS fat‐fractions, indicated by 95% confidence intervals (units of absolute percent) of [?2.66%,2.64%] for single MRI ROI measurements, [?0.81%,0.80%] for averaged MRI ROI, and [?2.70%,2.87%] for single‐voxel MRS. Linear regression between MRI and MRS indicated that the MRI method is highly accurate. Sensitivity and specificity for detection of steatosis using averaged MRI ROI were 100% and 94%, respectively. The relationship between hepatic fat‐fraction and body mass index was examined.

Conclusion:

Fat‐fraction measured with T₁‐independent T‐corrected MRI and multi‐peak spectral modeling of fat is a highly precise and accurate method of quantifying hepatic steatosis. J. Magn. Reson. Imaging 2011;33:873–881. © 2011 Wiley‐Liss, Inc.

     

Hepatic enhancement during the hepatobiliary phase after gadoxetate disodium administration in patients with chronic liver disease: the role of laboratory factors

Purpose:

To identify factors influencing hepatobiliary phase (HBP) hepatic enhancement on gadoxetate disodium‐enhanced MRI in patients with chronic liver disease (CLD).

Materials and Methods:

We retrospectively reviewed abdominal gadoxetate disodium‐enhanced MRIs and medical records of patients with (n = 97) and without (n = 48) CLD. CLD subgroups were formed based on normal/abnormal components of liver function tests (LFTs). Hepatic enhancement coefficients (HEKs) were calculated on MRI, and compared with LFTs and Model for End‐stage Liver Disease (MELD) scores.

Results:

The mean HEK was significantly lower (P < 0.0008) in the CLD than control group. The mean HEK was similar to controls in the subgroup with all normal LFTs (P = 0.09) and subgroup with normal direct bilirubin (DB) (p = 0.09), while it was significantly reduced (P < 0.0001) in the subgroup with elevated DB. For all other LFT components, regardless of normal or abnormal values, there was a significant reduction in the mean HEKs versus controls (all P values <0.01). There was a highly negative correlation between the mean HEKs in CLD subgroups and number of abnormal LFTs (r = ?0.93) and MELD scores (r = ?0.89).

Conclusion:

HBP hepatic enhancement in CLD patients is similar to those with no CLD as long as direct bilirubin remains normal. Higher MELD scores and higher number of abnormal LFT components are associated with reduced hepatic enhancement. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Diffusion‐weighted MRI for monitoring tumor response to photodynamic therapy

Purpose:

To examine diffusion‐weighted MRI (DW‐MRI) for assessing the early tumor response to photodynamic therapy (PDT).

Materials and Methods:

Subcutaneous tumor xenografts of human prostate cancer cells (CWR22) were initiated in athymic nude mice. A second‐generation photosensitizer, Pc 4, was delivered to each animal by a tail vein injection 48 h before laser illumination. A dedicated high‐field (9.4 Tesla) small animal MR scanner was used to acquire diffusion‐weighted MR images pre‐PDT and 24 h after the treatment. DW‐MRI and apparent diffusion coefficients (ADC) were analyzed for 24 treated and 5 control mice with photosensitizer only or laser light only. Tumor size, prostate specific antigen (PSA) level, and tumor histology were obtained at different time points to examine the treatment effect.

Results:

Treated mice showed significant tumor size shrinkage and decrease of PSA level within 7 days after the treatment. The average ADC of the 24 treated tumors increased 24 h after PDT (P < 0.001) comparing with pre‐PDT. The average ADC was 0.511 ± 0.119 × 10^?3 mm²/s pre‐PDT and 0.754 ± 0.181 × 10^?3 mm²/s 24 h after the PDT. There is no significant difference in ADC values pre‐PDT and 24 h after PDT in the control tumors (P = 0.20).

Conclusion:

The change of tumor ADC values measured by DW‐MRI may provide a noninvasive imaging marker for monitoring tumor response to Pc 4‐PDT as early as 24 h. J. Magn. Reson. Imaging 2010;32:409–417. © 2010 Wiley‐Liss, Inc.

     

Weight-bearing MRI of patellofemoral joint cartilage contact area

Purpose

To measure contact area of cartilage in the patellofemoral joint during weight bearing using an open MRI scanner.

Materials and Methods

We developed an MR‐compatible back support that allows three‐dimensional imaging of the patellofemoral cartilage under physiologic weight‐bearing conditions with negligible motion artifact in an open MRI scanner. To measure contact areas, we trained observers using a phantom of known area and tested intra‐ and interobserver variability. We measured in vivo contact areas between the patella and femoral cartilage with the knee in 30 degrees of flexion, loaded and unloaded, in six volunteers.

Results

We were able to measure the contact area of the patellofemoral cartilage with small interobserver (CV 7.0%) and intraobserver (CV 3.0%) variation. At 30 degrees of knee flexion, mean contact area increased from 400 mm² (unloaded) to 522 mm² (loaded to 0.45 times body weight per leg).

Conclusion

Using an open magnet and specially designed apparatus, it is possible to image the patellar cartilage during physiologic loading. Knowledge of patellar cartilage contact area is needed to assess patellofemoral stress, which may be increased in patients with patellofemoral pain syndrome. J. Magn. Reson. Imaging 2004;20:526–530. Published 2004 Wiley‐Liss, Inc.

     

Amide proton transfer MR imaging of prostate cancer: a preliminary study

Purpose:

To evaluate the capability of amide proton transfer (APT) MR imaging for detection of prostate cancer that typically shows a higher tumor cell proliferation rate and cellular density leading to an MRI‐detectable overall elevated mobile protein level in higher grade tumors.

Materials and Methods:

Twelve patients with biopsy‐proven prostate cancer were imaged on a 3 Tesla MR imaging system before prostatectomy. APT‐MR images were acquired by means of a single‐slice single‐shot turbo spin echo sequence with a saturation prepulse preparation using 33 different frequency offsets (?8 to 8 ppm, interval 0.5 ppm). For quantification we used the APT ratio (APTR) based on the asymmetry of the magnetization transfer ratio at 3.5 ppm in respect to the water signal. Tumor and peripheral zone benign regions of interest (ROIs) were delineated based on whole mount pathology slides after prostatectomy.

Results:

APTR in prostate cancer ROIs was 5.8% ± 3.2%, significantly higher than that in the peripheral zone benign regions (0.3% ± 3.2%, P = 0.002).

Conclusion:

APT‐MR imaging is feasible in prostate cancer detection and has the potential to discriminate between cancer and noncancer tissues. J. Magn. Reson. Imaging 2011;33:647–654. © 2011 Wiley‐Liss, Inc.

     

Repeatability of magnetic resonance elastography for quantification of hepatic stiffness

Purpose:

To determine the sources of variability of MRE hepatic stiffness measurements using healthy volunteers and patients and to calculate the minimum change required for statistical significance. Hepatic stiffness measured with magnetic resonance elastography (MRE) has demonstrated tremendous potential as a noninvasive surrogate of hepatic fibrosis, although the underlying repeatability of MRE for longitudinal tracking of liver disease has not been documented.

Materials and Methods:

MRE stiffness measurements from 20 healthy volunteers and 10 patients were obtained twice on the same day, and repeated 2–4 weeks later for volunteers in this institutional review board‐approved study. A linear mixed effects model was used to estimate the component sources of variability in the data.

Results:

The standard deviation of MRE measurements of the same individual on different days is 11.9% (percent of the measured stiffness) using the same reader and 12.0% using different readers. The standard deviation of the difference between two measurements (i.e., longitudinal change in an individual) is 17.4%; the corresponding 95% confidence interval for zero change is (?27.0%, 37.0%).

Conclusion:

MRE is a repeatable method for quantifying liver stiffness. Using the described MRE technique, changes greater than 37.0% of the smaller measured stiffness value represent meaningful changes in longitudinal liver stiffness measurements. J. Magn. Reson. Imaging 2010;31:725–731. © 2010 Wiley‐Liss, 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.

     

Usefulness of Gd‐EOB‐DTPA‐enhanced MR imaging in the evaluation of simple steatosis and nonalcoholic steatohepatitis

Purpose:

To evaluate the usefulness of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd‐EOB‐DTPA)‐enhanced MR imaging (EOB‐MRI) in differentiating between simple steatosis and nonalcoholic steatohepatitis (NASH), as compared with MR in‐phase/out‐of‐phase imaging. The correlations between the MR features and histological characteristics were preliminarily investigated.

Materials and Methods:

From April 2008 to October 2011, 25 patients (13 simple steatosis and 12 NASH) who underwent both EOB‐MRI and in‐phase/out‐of‐phase imaging were analyzed. The hepatobiliary‐phase enhancement ratio and signal intensity loss on opposed‐phase T1‐weighted images (fat fraction) were compared between the simple steatosis and NASH groups. In the simple steatosis and NASH groups, the correlations between enhancement ratio and histological grade/stage were explored. In the NASH group, fat fraction was correlated with the steatosis score.

Results:

The enhancement ratio in NASH was significantly lower than that in simple steatosis (P = 0.03). In the simple steatosis and NASH groups, the enhancement ratio was significantly correlated with the fibrosis stage (r = ?0.469, P = 0.018). Fat fraction in NASH was strongly correlated with the steatosis score (r = 0.728, P = 0.007).

Conclusion:

In simple steatosis and NASH, the hepatobiliary‐phase enhancement ratio of EOB‐MRI showed significant association with fibrosis stage, and may be a useful discriminating parameter compared with the fat fraction measured by in‐phase/out‐of‐phase imaging. J. Magn. Reson. Imaging 2012;37:1137–1143. © 2012 Wiley Periodicals, 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.

     

3D-liver perfusion MRI with the MS-325 blood pool agent: a noninvasive protocol to asses liver fibrosis

Purpose:

To evaluate a 1.5T magnetic resonance imaging (MRI) protocol, including a dedicated acquisition sequence and a postprocessing tool for the quantitative analysis of hepatic tissue perfusion. Estimated perfusion parameters and histological results based on the METAVIR classification were prospectively compared for hepatic fibrosis assessment.

Materials and Methods:

The study protocol was approved by the experimentation Ethics Committee and informed consent was obtained. Sixteen patients (6 women, 10 men; average age, 52.4 ± 14.8 years) with chronic liver diseases were prospectively enrolled after a liver biopsy. MS‐325 (paramagnetic blood pool agent)‐enhanced MRI was performed using a free‐breath 3D‐VIBE T_1w sequence. Image volumes were registered by an automatic rigid method. Liver perfusion was modeled by a dual‐input‐one‐compartment model and quantitative perfusion parameters such as arterial, portal, and total perfusion mean transit time (MTT) and hepatic perfusion index (HPI) were obtained using in‐house developed software.

Results:

Arterial perfusion increased with METAVIR stage, whereas portal perfusion decreased leading to an HPI increase with fibrosis stage. MTT increased with F3, F4. A nonparametric Mann–Whitney test demonstrated that HPI and portal perfusion were relevant in discriminating between advanced and nonadvanced fibrosis, between fibrosis and cirrhosis, then between nonfibrosis and fibrosis (P < 0.01). A strong correlation was found between portal perfusion fall‐off and HPI increase (r = ?0.97; P < 0.001). HPI and portal perfusion were strongly correlated with fibrosis stage (r = 0.83 and ?0.88; P < 0.001, respectively).

Conclusion:

HPI and portal perfusion could be relevant indicators for the clinical follow‐up in patients with chronic liver diseases. J. Magn. Reson. Imaging 2012;35:1380–1387. © 2012 Wiley Periodicals, Inc.

     

Liver MRI and histological correlates in chronic liver disease on multiphase gadolinium-enhanced 3D gradient echo imaging

Purpose:

To evaluate intrinsic hepatic enhancement patterns on multiphase, gadolinium‐enhanced, fat‐suppressed, 3D T1‐weighted, gradient echo magnetic resonance imaging (MRI) as a quantitative correlate for severity of pathological changes in chronic liver disease (CLD).

Materials and Methods:

This study was HIPAA‐compliant and Institutional Review Board‐approved. In all, 75 patients were studied by contrast‐enhanced multiphase abdominal MRI. CLD patients had liver histology correlation derived from right lobe liver biopsies. Contrast‐enhanced arterial‐ and delayed‐phase 3D gradient recalled echo (GRE) liver MRI were scored using feature categorization templates to quantify enhancement patterns by three independent readers. Liver histopathology was staged/graded for fibrosis/inflammation using the Scheuer system. Statistical testing for MRI histology correlates used a Pearson's product moment correlation and a Wilcoxon–Mann–Whitney two‐sample rank‐sum test. Reader agreement was analyzed by a modified Fleiss' kappa test.

Results:

MRI histology correlation was high for delayed‐phase MRI versus fibrosis stage (95% confidence interval [CI] 0.941 < r < 0.976, P = 5 × 10^?7), but lower for all other comparisons (delayed‐phase vs. inflammation and arterial‐phase vs. inflammation or fibrosis all showed a CI no greater than 0.64). Paired testing between delayed‐phase MRI score and histology fibrosis staging incremental levels was significant (from P < 10^?2 to P < 10^?5).

Conclusion:

A standard gadolinium‐enhanced liver MRI may provide a correlate measure of hepatic fibrosis over a spectrum of severity. J. Magn. Reson. Imaging 2012;36:422–429. © 2012 Wiley Periodicals, Inc.

     

Slice offset frequency and shim adjustment for interactive steady‐state free‐precession (SSFP) imaging

Purpose

To devise a method allowing real‐time optimization of center frequency (CF) and shim for an interactive steady‐state free‐precession (SSFP) sequence by reformatting a previously acquired field map in the same orientation as the interactive acquisition.

Materials and Methods

Field maps were acquired in a rectangular parallel‐piped phantom and a normal volunteer. An SSFP sequence was modified to communicate the current slice offset and rotation to an external program that reformatted the field map into the same plane, calculated the CF and shim offsets, and passed them back to the sequence. CF offsets as a function of position for the phantom were compared with the scanner prescan‐determined offset.

Results

In the phantom, the CF measurements agreed with the scanner‐determined offsets. Bland‐Altman analysis showed a bias of ?14 Hz (field map – prescan) and limits of agreement of ?28 to 0 Hz. In the volunteer there was a qualitative improvement in image quality when using the optimized center frequencies and shims.

Conclusion

The proposed method demonstrates how CF and shim can be optimized for any interactively positioned slice, resulting in reduced off‐resonance artifacts. J. Magn. Reson. Imaging 2009;29:1230–1233. © 2009 Wiley‐Liss, Inc.

     

Reliability in detection of hemorrhage in acute stroke by a new three-dimensional gradient recalled echo susceptibility-weighted imaging technique compared to computed tomography: a retrospective study

Purpose

To compare the sensitivity of magnetic resonance (MR) susceptibility‐weighted imaging (SWI) with conventional MR sequences and computed tomography (CT) in the detection of hemorrhage in an acute infarct.

Materials and Methods

A series of 84 patients suspected of having acute strokes had both CT and MR imaging (MRI) scans with diffusion‐weighted imaging (DWI) and SWI. The SWI sequence is a new high‐resolution three‐dimensional (3D) imaging technique that amplifies phase to enhance the magnitude contrast.

Results

Thirty‐eight of 84 cases showed abnormal DWI consistent with acute infarct. Of the 38, SWI showed evidence of hemorrhage in 16 cases, compared to eight cases with spin echo (SE) T2, seven cases with fluid attentuated inversion recovery (FLAIR), and only five cases with CT. In a subset of 17 cases of acute infarct who had both two‐dimensional gradient recalled echo (2D‐GRE) T2*‐weighted imaging and SWI, in addition to conventional MRI, evidence of hemorrhage was seen in 10 cases using SWI, compared to seven cases with 2D‐GRE T2*.

Conclusion

SWI proved to be a powerful new approach for visualizing hemorrhage in acute stroke compared to CT and conventional MRI methods. J. Magn. Reson. Imaging 2004;20:372–377. © 2004 Wiley‐Liss, Inc.

     

Comparison of a 28-channel receive array coil and quadrature volume coil for morphologic imaging and T2 mapping of knee cartilage at 7T

Purpose:

To compare a new birdcage‐transmit, 28‐channel receive array (28‐Ch) coil and a quadrature volume coil for 7T morphologic MRI and T2 mapping of knee cartilage.

Materials and Methods:

The right knees of 10 healthy subjects were imaged on a 7T whole body magnetic resonance (MR) scanner using both coils. 3D fast low‐angle shot (3D‐FLASH) and multiecho spin‐echo (MESE) sequences were implemented. Cartilage signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), thickness, and T2 values were assessed.

Results:

SNR/CNR was 17%–400% greater for the 28‐Ch compared to the quadrature coil (P ≤ 0.005). Bland–Altman plots show mean differences between measurements of tibial/femoral cartilage thickness and T2 values obtained with each coil to be small (?0.002 ± 0.009 cm / 0.003 ± 0.011 cm) and large (?6.8 ± 6.7 msec/?8.2 ± 9.7 msec), respectively. For the 28‐Ch coil, when parallel imaging with acceleration factors (AF) 2, 3, and 4 was performed SNR retained was: 62%–69%, 51%–55%, and 39%–45%.

Conclusion:

A 28‐Ch knee coil provides increased SNR/CNR for 7T cartilage morphologic imaging and T2 mapping. Coils should be switched with caution during clinical studies because T2 values may differ. The greater SNR of the 28‐Ch coil could be used to perform parallel imaging with AF2 and obtain similar SNR as the quadrature coil. J. Magn. Reson. Imaging 2012;441‐448. © 2011 Wiley Periodicals, Inc.