Noncontrast-Enhanced MR-Based Conductivity Imaging for Breast Cancer Detection and Lesion Differentiation.

BACKGROUND: There is increasing interest in noncontrast-enhanced MRI due to safety concerns for gadolinium contrast agents. PURPOSE: To investigate the clinical feasibility of MR-based conductivity imaging for breast cancer detection and lesion differentiation. STUDY TYPE: Prospective. SUBJECTS: One hundred and ten women, with 112 known cancers and 17 benign lesions (biopsy-proven), scheduled for preoperative MRI. FIELD STRENGTH/SEQUENCE: Non-fat-suppressed T2-weighted turbo spin-echo sequence (T2WI), dynamic contrast-enhanced MRI and diffusion-weighted imaging (DWI) at 3T. ASSESSMENT: Cancer detectability on each imaging modality was qualitatively evaluated on a per-breast basis: the conductivity maps derived from T2WI were independently reviewed by three radiologists (R1-R3). T2WI, DWI, and pre-operative digital mammography were independently reviewed by three other radiologists (R4-R6). Conductivity and apparent diffusion coefficient (ADC) measurements (mean, minimum, and maximum) were performed for 112 cancers and 17 benign lesions independently by two radiologists (R1 and R2). Tumor size was measured from surgical specimens. STATISTICAL TESTS: Cancer detection rates were compared using generalized estimating equations. Multivariable logistic regression analysis was performed to identify factors associated with cancer detectability. Discriminating ability of conductivity and ADC was evaluated by using the areas under the receiver operating characteristic curve (AUC). RESULTS: Conductivity imaging showed lower cancer detection rates (20%-32%) compared to T2WI (62%-71%), DWI (85%-90%), and mammography (79%-88%) (all P < 0.05). Fatty breast on MRI (odds ratio = 11.8, P < 0.05) and invasive tumor size (odds ratio = 1.7, P < 0.05) were associated with cancer detectability of conductivity imaging. The maximum conductivity showed comparable ability to the mean ADC in discriminating between cancers and benign lesions (AUC = 0.67 [95% CI: 0.59, 0.75] vs. 0.84 [0.76, 0.90], P = 0.06 (R1); 0.65 [0.56, 0.73] vs. 0.82 [0.74, 0.88], P = 0.07 (R2)). DATA CONCLUSION: Although conductivity imaging showed suboptimal performance in breast cancer detection, the quantitative measurement of conductivity showed the potential for lesion differentiation. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Predicting Axillary Response to Neoadjuvant Chemotherapy: Breast MRI and US in Patients with Node-Positive Breast Cancer.

Background In patients who are expected to achieve axillary pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC), omission of axillary lymph node (LN) dissection could prevent morbidity and complications. Purpose To develop a clinical model to predict residual axillary LN metastasis in patients with clinically node-positive breast cancer after NAC by using MRI and US. Materials and Methods In this retrospective study, women with clinically node-positive breast cancer who were treated with NAC following surgery between January 2015 and September 2017 were included. The patients were randomly assigned to a test and validation set (7:3 ratio). Univariable and multivariable logistic regression analyses were performed to evaluate the independent predictors of residual axillary LN metastasis in the test set. A prediction risk score was developed based on the odds ratios from the multivariable analysis and validated in both sets. Results A total of 408 women were included (mean age ± standard deviation, 47.9 years ± 9.6). The axillary pCR rate was 56.6% (231 of 408). Independent predictors of residual axillary LN metastasis were clinical stage N2 or N3, presence of axillary lymphadenopathy at US after NAC, tumor size reduction less than 50% at MRI, Ki-67 negativity, hormone receptor positivity, and human epidermal growth factor receptor 2 negativity (all, P < .05). In a model using these predictors, the area under the receiver operating characteristic curve in the test and validation sets was 0.84 (95% confidence interval: 0.79, 0.88) and 0.78 (95% confidence interval: 0.70, 0.87), respectively. When the patients had a simplified risk score of 1, the false-negative rates ranged between 5%-10%. Conclusion A prediction model incorporating nodal status stage, US finding, MRI response, and molecular receptor status shows good diagnostic performance for residual axillary lymph node metastasis after neoadjuvant chemotherapy in patients with clinically node-positive breast cancer. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Whitman in this issue.

Prognosis prediction of non-enhancing T2 high signal intensity lesions in glioblastoma patients after standard treatment: application of dynamic contrast-enhanced MR imaging.

OBJECTIVES: To identify candidate imaging biomarkers for early disease progression in glioblastoma multiforme (GBM) patients by analysis of dynamic contrast-enhanced (DCE) MR parameters of non-enhancing T2 high signal intensity (SI) lesions. METHODS: Forty-nine GBM patients who had undergone preoperative DCE MR imaging and received standard treatment were retrospectively included. According to the Response Assessment in Neuro-Oncology criteria, patients were classified into progression (n = 21) or non-progression (n = 28) groups. We analysed the pharmacokinetic parameters of Ktrans, Ve and Vp within non-enhancing T2 high SI lesions of each tumour. The best percentiles of each parameter from cumulative histograms were identified by the area under the receiver operating characteristic curve (AUC) and were compared using multivariate stepwise logistic regression. RESULTS: For the differentiation of early disease progression, the highest AUC values were found in the 99th percentile of Ktrans (AUC 0.954), the 97th percentile of Ve (AUC 0.815) and the 94th percentile of Vp (AUC 0.786) (all p < 0.05). The 99th percentile of Ktrans was the only significant independent variable from the multivariate stepwise logistic regression (p = 0.002). CONCLUSIONS: We found that the Ktrans of non-enhancing T2 high SI lesions in GBM patients holds potential as a candidate prognostic marker in future prospective studies. KEY POINTS: • DCE MR imaging provides candidate prognostic marker of GBM after standard treatment. • Cumulative histogram was applied to include entire non-enhancing T2 high SI lesions. • The 99th percentile value of Ktrans was the most likely potential biomarker.

Anatomic variations of lower extremity venous system in varicose vein patients: demonstration by three-dimensional CT venography.

Background Understanding the anatomy of the lower extremity veins is essential for successful varicose vein treatment. Computed tomography (CT) venography may be used to obtain a comprehensive overview and detailed information regarding this. Purpose To describe anatomic variations of the lower extremity venous system in patients with varicose veins, using three-dimensional (3D) CT venography. Material and Methods A total of 810 limbs in 405 patients with suspected varicose veins were prospectively referred to undertake CT venography and included in our study population retrospectively. The CT venography images were evaluated by consensus of two cardiovascular radiologists. Anatomical variations of the lower extremity venous system and their incidence were analyzed. Specifically, the number of tributaries at saphenofemoral junction, relative location of the great saphenous vein (GSV) with respect to the common femoral artery bifurcation, pattern of saphenopopliteal junction, and end of thigh extension from the small saphenous vein (SSV) were assessed. Results The most frequent number of tributaries joining the GSV was four (44.4%, 360/810). Only 0.7% (6/810) of the limbs demonstrated unusual location of the GSV between the bifurcated superficial and deep femoral arteries. The most common pattern of veins at the saphenopopliteal junction was a larger caliber of saphenopopliteal junction than thigh extension from SSV (43.8%, 355/810), end of which joining the femoral vein directly (41.0%, 288/703). Conclusion CT venography with 3D reconstruction can be used to understand the anatomy of lower extremity veins and how their variations contribute to varicose veins.

Feasibility of 320-row area detector CT coronary angiography using 40 mL of contrast material: assessment of image quality and diagnostic accuracy.

OBJECTIVES: To assess the image quality and diagnostic accuracy of 320-row area detector CT (320-ADCT) coronary angiography using 40 mL of contrast material in comparison with 60-mL protocol. METHODS: This retrospective study included 183 patients who underwent 320-ADCT coronary angiography using 40 mL of contrast and additional 183 sex- and body mass index-matched patients using 60 mL of contrast constituting the control group. Both groups used the same 5-mL/sec injection rate. Quantitative image quality measurements and diagnostic accuracies were calculated and compared. RESULTS: Mean attenuation and contrast-to-noise ratio (CNR) at the aorta and all coronary arteries were lower in the 40-mL group than in the 60-mL group (all, p < 0.05), except for the CNR at proximal coronary arteries at 100 kVp (p = 0.073). However, the proportion of coronary segments with vessel attenuation >250 HU was not different between groups (all, p > 0.05), except for distal coronary arteries at 80 kVp (p = 0.001). Furthermore, there were no differences in per-patient and per-segment diagnostic accuracies between the groups (all, p > 0.05). CONCLUSIONS: 320-ADCT coronary angiography using 40 mL of contrast showed image quality and diagnostic accuracy comparable to the 60-mL protocol, demonstrating the clinical feasibility of lowering the risk of contrast-induced nephropathy through contrast volume reduction. KEY POINTS: • 320-ADCT might enable reduction of contrast material volume. • A 40-mL contrast protocol for 320-ADCT provided acceptable image quality. • A 40-mL contrast protocol for 320-ADCT demonstrated sufficient diagnostic accuracy.

Differentiation of intrahepatic mass-forming cholangiocarcinoma from hepatocellular carcinoma on gadoxetic acid-enhanced liver MR imaging.

OBJECTIVES: To determine the different imaging features of intrahepatic mass-forming cholangiocarcinoma (IMCC) from hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced magnetic resonance imaging (MRI). METHODS: This retrospective study was institutional review board approved and the requirement for informed consent was waived. Patients who underwent gadoxetic acid-enhanced MRI with histologically confirmed IMCCs (n = 46) or HCCs (n = 58) were included. Imaging features of IMCCs and HCCs on gadoxetic acid-enhanced MRI including T2- and T1-weighted, diffusion weighted images, dynamic study and hepatobiliary phase (HBP) images were analyzed. Univariate and multivariate logistic regression analyses were performed to identify relevant differentiating features between IMCCs and HCCs. RESULTS: Multivariate analysis revealed heterogeneous T2 signal intensity and a hypointense rim on the HBP as suggestive findings of IMCCs and the wash-in and "portal wash-out" enhancement pattern as well as focal T1 high signal intensity foci as indicative of HCCs (all, p < 0.05). When we combined any three of the above four imaging features, we were able to diagnose IMCCs with 94 % (43/46) sensitivity and 86 % (50/58) specificity. CONCLUSIONS: Combined interpretation of enhancement characteristics including HBP images, morphologic features, and strict application of the "portal wash-out" pattern helped more accurate discrimination of IMCCs from HCCs. KEY POINTS: • Analysis of enhancement characteristics helped accurate discrimination of IMCCs from HCCs. • Wash-out should be determined on the PVP of gadoxetic acid-enhanced MRI. • A hypointense rim on the HBP was a significant finding of IMCCs.

Differentiation of lipid poor angiomyolipoma from hepatocellular carcinoma on gadoxetic acid-enhanced liver MR imaging.

PURPOSE: To investigate magnetic resonance (MR) findings of angiomyolipoma (AML) on gadoxetic acid-enhanced MR imaging, and to identify features that differentiate AML from hepatocellular carcinoma (HCC) in patients with a low risk of HCC development. METHODS: This retrospective study was institutional review board approved, and the requirement for informed consent was waived. Twelve patients with hepatic AML who underwent gadoxetic acid-enhanced MRI with no risk factors for HCC development were recruited. Twenty-seven patients with HCC under the same inclusion criteria were recruited as control. Two radiologists analyzed the images in consensus for morphologic features, enhancement patterns, and hepatobiliary phase (HBP) findings. All results were analyzed using the Mann-Whitney test, two-tailed Fisher exact test, and chi-square test. RESULTS: Patients with AML were younger than those with HCC (48.8 ± 15 years for AML vs. 62.7 ± 14.2 years for HCC, p = 0.008) with female predominance, while most HCC patients were male (75% (9/12) vs. 15% (4/27), p < 0.001). The most prevalent enhancement pattern was arterial enhancement followed by hypointensity at portal or transitional phases for both AMLs (58% (7/12)) and HCCs (74% (20/27)) (p = 0.455). However, during the HBP, AMLs frequently showed more homogeneous hypointensity than HCCs (83% (10/12) vs. 41% (11/27), p = 0.018). When compared with the signal intensity of the spleen, the mean relative signal intensity of the AML was 91.2 ± 15.4%, while in HCCs, it was 128.7 ± 40% (p < 0.001). CONCLUSIONS: Although AMLs showed similar enhancement patterns to HCCs during the dynamic phases of gadoxetic acid-enhanced MRI, using characteristic MR features of AML during the HBP and demographic differences, one can better differentiate AML from HCC.