Diffusion-weighted MRI of metastatic liver lesions: is there a difference between hypervascular and hypovascular metastases?

BACKGROUND: Different perfusion characteristics and histopathologic features of liver metastasis may potentially lead to different diffusion-weighted magnetic resonance imaging (DW-MRI) characteristics which can affect the performance of DW-MRI in their diagnosis. PURPOSE: To compare ADC values of hypervascular and hypovascular metastases and the added value of DW-MRI to T2-weighted (T2-w) images in their detection. MATERIAL AND METHODS: In this retrospective study, 46 patients (21 with hypervascular, 25 with hypovascular liver metastases) who had undergone abdominal MRI were included. Two independent observers first reviewed T2-w images only and then T2-w+DW-MR images and recorded number of metastases in each session. Lesion detection rate was compared using McNemar test. ADC of metastases in each patient was measured and compared between hypo- and hypervascular lesions using t-test. RESULTS: A total of 153 hypervascular and 187 hypovascular metastases were detected at consensus review. Two observers detected significantly more hypervascular metastases on T2-w+DW-MR image review session compared to T2-w image only review session (reader 1: 148 [96.7%] vs. 129 [84.3%], P=0.002; reader 2: 125 [81.9%] vs. 113 [73.8%], P=0.004). Detection rate of hypovascular metastases was similar between two sessions for both observers (reader 1: 180 [96.2%] vs. 184 [98.4%]; reader 2: 176 [94.1%] vs. 180 [96.2%], P>0.05). The mean ADC value of hypervascular metastases was significantly lower than mean ADC value of hypovascular metastases (1.23+/-0.31 × 10(-3)mm(2)/s vs. 1.49+/-0.19 × 10(-3)mm(2)/s) (P=0.001). CONCLUSION: Liver metastases are not a homogenous group of lesions with uniform DW-MRI features. Hypervascular metastases demonstrate significantly lower ADC values compared to hypovascular metastases. DW-MRI improved detection of hypervascular metastases compared to T2-w images alone and is a useful adjunct to T2-w images for their detection.

Diffusion-weighted MR imaging of focal liver lesions in the left and right lobes: is there a difference in ADC values?

RATIONALE AND OBJECTIVES: To determine possible differences between the left and right hepatic lobes in apparent diffusion coefficient (ADC) values of benign and malignant focal liver lesions (FLLs) and normal liver parenchyma. MATERIALS AND METHODS: Thirty-six patients (16 males, 20 females; mean age 56.8 years) with FLLs of the same etiology in both the left and right hepatic lobes (13 patients with 26 benign FLLs and 23 patients with 46 malignant FLLs) who underwent 1.5T magnetic resonance imaging (MRI) including diffusion-weighted MRI (b values: 0 and 800 seconds/mm) with respiratory gating and without cardiac gating were included in this Health Insurance Portability and Accountability Act-compliant and institutional review board-approved study. ADC values of normal liver parenchyma and FLLs in each hepatic lobe were calculated and compared by using Student's t-test and Wilcoxon signed-rank test, respectively. RESULTS: The mean ADC values of normal liver parenchyma, benign FLLs, and malignant FLLs were significantly higher (P < .001, P = .003, and P = .005, respectively) in the left hepatic lobe (1.74 × 10(-3), 1.81 × 10(-3), and 1.48 × 10(-3) mm²/second, respectively) than in the right hepatic lobe (1.48 × 10(-3), 1.54 × 10(-3), and 1.24 × 10(-3) mm²/second, respectively). CONCLUSION: ADC values of benign and malignant FLLs calculated from noncardiac-gated DW-MRI are significantly higher in the left hepatic lobe compared with the right hepatic lobe. This may be a limitation for characterization of FLLs based on ADC measurements.

Diffusion-weighted MRI: role in detecting abdominopelvic internal fistulas and sinus tracts.

PURPOSE: To retrospectively determine the incremental value of diffusion-weighted MR-imaging (DW-MRI) to T2-weighted (T2w) images in diagnosis of internal fistulas (IFs) and sinus tracts (STs). MATERIALS AND METHODS: Fourteen patients with 25 IFs and STs arising from the small bowel (20), colon (4) and biliary tract (1) were included. Two independent observers reviewed T2w images, T2w+DW-MRI images and T2w+contrast enhanced T1-weighted (CE T1w) images at three sessions to detect IF/ST based on a confidence scale of five. Sensitivity and confidence score of each session was compared. RESULTS: 10/25 (40%) and 9/25 (36%) IFs and STs were detected on T2w images by observer 1 and 2, respectively. Both observers detected 19/25 (76%) and 24/25(96%) IFs and STs on T2w+DW-MRI and T2w+CE T1w images, respectively. Detection rate and confidence score improved significantly by combining T2w images with DW-MRI or CE T1w images (reader 1 + 2: P ≤ 0.01). There was no significant difference between the IF/ST detection rate of T2w+DW-MRI and T2w+CE T1 image combinations. Confidence scores with T2w+CE T1w images were significantly greater than DW-MRI+T2w images (reader 1:P = 0.01; reader 2: P = 0.03). CONCLUSION: DW-MRI showed additional value to T2w imaging for diagnosis of IF and ST. DW-MRI can be a useful adjunct, especially for patients with renal failure.

Magnetic resonance enterography in Crohn's disease: Standard and advanced techniques.

Crohn's disease (CD) is a chronic autoimmune disorder that affects mainly young people. The clinical management is based on the Crohn's Disease Activity Index and especially on biologic parameters with or without additional endoscopic and imaging procedures, such as barium and computed tomography examinations. Recently, magnetic resonance (MR) imaging has been a promising diagnostic radiologic technique with lack of ionizing radiation, enabling superior tissue contrast resolution due to new pulse-sequence developments. Therefore, MR enterography has the potential to become the modality of choice for imaging the small bowel in CD patients.

Prostate cancer: differentiation of central gland cancer from benign prostatic hyperplasia by using diffusion-weighted and dynamic contrast-enhanced MR imaging.

PURPOSE: To analyze the diffusion and perfusion parameters of central gland (CG) prostate cancer, stromal hyperplasia (SH), and glandular hyperplasia (GH) and to determine the role of these parameters in the differentiation of CG cancer from benign CG hyperplasia. MATERIALS AND METHODS: In this institutional review board-approved (with waiver of informed consent), HIPAA-compliant study, 38 foci of carcinoma, 38 SH nodules, and 38 GH nodules in the CG were analyzed in 49 patients (26 with CG carcinoma) who underwent preoperative endorectal magnetic resonance (MR) imaging and radical prostatectomy. All carcinomas and hyperplastic foci on MR images were localized on the basis of histopathologic correlation. The apparent diffusion coefficient (ADC), the contrast agent transfer rate between blood and tissue (K(trans)), and extravascular extracellular fractional volume values for all carcinoma, SH, and GH foci were calculated. The mean, standard deviation, 95% confidence interval (CI), and range of each parameter were calculated. Receiver operating characteristic (ROC) and multivariate logistic regression analyses were performed for differentiation of CG cancer from SH and GH foci. RESULTS: The average ADCs (× 10(-3) mm(2)/sec) were 1.05 (95% CI: 0.97, 1.11), 1.27 (95% CI: 1.20, 1.33), and 1.73 (95% CI: 1.64, 1.83), respectively, in CG carcinoma, SH foci, and GH foci and differed significantly, yielding areas under the ROC curve (AUCs) of 0.99 and 0.78, respectively, for differentiation of carcinoma from GH and SH. Perfusion parameters were similar in CG carcinomas and SH foci, with K(trans) yielding the greatest AUCs (0.75 and 0.58, respectively). Adding K(trans) to ADC in ROC analysis to differentiate CG carcinoma from SH increased sensitivity from 38% to 57% at 90% specificity without noticeably increasing the AUC (0.79). CONCLUSION: ADCs differ significantly between CG carcinoma, SH, and GH, and the use of them can improve the differentiation of CG cancer from SH and GH. Combining K(trans) with ADC can potentially improve the detection of CG cancer. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100021/-/DC1.