Description: ABSTRACT Purpose The aim of the study was to determine in patients undergoing gadoxetate disodium (Gx)-enhanced MR exams whether proton density fat fraction (PDFF) estimation accuracy of magnitude-based multi-gradient-echo MRI (MRI-M) could be improved by using high flip angle (FA) on post-contrast images. Materials and Methods Thirty-one adults with known or suspected hepatic steatosis undergoing 3T clinical Gx-enhanced liver MRI were enrolled prospectively. MR spectroscopy (MRS), the reference standard, was performed before Gx to measure MRS-PDFF. Low (10°)- and high (50°)-flip angle (FA) MRI-M sequences were acquired before and during the hepatobiliary phase after Gx administration; MRI-PDFF was estimated in the MRS-PDFF voxel location. Linear regression parameters (slope, intercept, average bias, R 2 ) were calculated for MRS-PDFF as a function of MRI-PDFF for each MRI-M sequence (pre-Gx low-FA, pre-Gx high-FA, post-Gx low-FA, post-Gx high-FA) for all patients and for patients with MRS-PDFF 〈10%. Regression parameters were compared (Bonferroni-adjusted bootstrap-based tests). Results Three of the four MRI-M sequences (pre-Gx low-FA, post-Gx low-FA, post-Gx high-FA) provided relatively unbiased PDFF estimates overall and in the low-PDFF range, with regression slopes close to 1 and intercepts and biases close to zero. Pre-Gx high-FA MRI overestimated PDFF in proportion to MRS-PDFF, with slopes of 0.72 (overall) and 0.63 (low-PDFF range). Based on regression bias closest to 0, the post-Gx high-FA sequence was the most accurate overall and in the low-PDFF range. This sequence provided statistically significant improvements in at least two regression parameters compared to every other sequence. Conclusion In patients undergoing Gx-enhanced MR exams, PDFF estimation accuracy of MRI-M can be improved by using high-FA on post-contrast images.

Description: Purpose The aim of this retrospective study was to evaluate the role of delayed images after forced diuresis coupled with oral hydration in abdominopelvic 18 F-FDG PET/CT. Materials and methods Forty-six patients consisting of 17 urological diseases, 9 gynecological tumors, 18 colorectal malignancies, and 2 cancers of unknown primary site were retrospectively analyzed. All patients who presented with indeterminate or equivocal abdominopelvic foci on standard 18 F-FDG PET/CT underwent a delayed abdominopelvic imaging after administration of 20 mg furosemide intravenously and extra water intake of 500 mL. PET/CT images before and after furosemide were compared with each other and their findings correlated with pathology or clinical follow-up (〉6 months). Results On initial PET/CT, the glucose metabolism characters of lesions were disguised by radioactive urine, or some undetermined 18 F-FDG accumulating foci near the urinary tract appeared. While postdiuretic PET/CT demonstrated an excellent urinary tracer washout, and hypermetabolic lesions could be clearly detected and precisely localized in all cases. On the other hand, the suspected active foci caused by potential stagnation of excreted 18 F-FDG in urinary tract were eliminated. The sensitivity, specificity, and accuracy were 94.4% (34/36), 8/10, 91.3% (42/46), respectively. Furthermore, the additional lesions with surrounding invasion or locoregional metastasis were discovered in 8 of 46 (17.4%) patients only by the delayed images, including 2 gynecological and 6 rectal malignancies. Conclusion Detection of abdominopelvic malignancies can be improved using delayed 18 F-FDG PET/CT images after a diuretic and oral hydration.

Description: Purpose The aim of this study was to assess the effect of denoising on objective heterogeneity scores and its diagnostic capability for the diagnosis of angiomyolipoma (AML) and renal cell carcinoma (RCC). Materials and Methods A total of 158 resected renal masses ≤4 cm [98 clear cell (cc) RCCs, 36 papillary (pap)-RCCs, and 24 AMLs] from 139 patients were evaluated. A representative contrast-enhanced computed tomography (CT) image for each mass was selected by a genitourinary radiologist. A largest possible region of interest was drawn on each mass by the radiologist, from which three objective heterogeneity indices were calculated: standard deviation (SD), entropy (Ent), and uniformity (Uni). Objective heterogeneity indices were also calculated after images were processed with a denoising algorithm (non-local means) at three strengths: weak, medium, and strong. Two genitourinary radiologists also subjectively scored each mass independently using a three-point scale (1–3; with 1 the least and 3 the most heterogeneous), which were added to represent the final subjective heterogeneity score of each mass. Heterogeneity scores were compared among mass types, and area under the ROC curve (AUC) was calculated. Results For all heterogeneity indices, cc-RCC was significantly more heterogeneous than pap-RCC and AML ( p  〈 0.001), but no significant difference was found between pap-RCC and AML ( p  〉 0.01). For cc-RCC and pap-RCC differentiation, AUCs were 0.91, 0.81, 0.78, and 0.78 for the subjective score, SD, Ent, and Uni, respectively, using original images. The corresponding AUC values were 0.84, 0.74, 0.79, and 0.80 for differentiation of AML and cc-RCC. Noise reduction at weak setting improves AUC values by 0.03, 0.05, and 0.05 for SD, entropy, and uniformity for differentiation of cc-RCC from pap-RCC. Further increase of filtering strength did not improve AUC values. For differentiation of AML vs. cc-RCC, the AUC values stayed relatively flat using the noise reduction technique at different strengths for all three indices. Conclusions Both subjective and objective heterogeneity indices can differentiate cc-RCC from pap-RCC and AML. Noise reduction improved differentiation of cc-RCC from pap-RCC, but not differentiation of AML from cc-RCC.

Description: Transarterial chemoembolization (TACE) is a proven catheter-based locoregional therapy for treatment of hepatocellular carcinoma (HCC). Drug-eluting bead TACE involves delivering micrometer-sized particles preloaded with doxorubicin directly to the tumor via its arterial blood supply and results in vascular embolization with intra-tumoral drug release. Effective therapy requires mapping of the tumor arterial supply, which in some cases cannot be accomplished with conventional angiographic techniques alone. Contrast-enhanced ultrasound (CEUS) is an imaging technique which utilizes microbubble contrast agents to demonstrate blood flow and tissue perfusion, enabling tumor visualization in real time. CEUS with intravenous contrast administration is well established for evaluation of HCC. Intra-arterial (IA) CEUS, on the other hand, is an emerging technique that allows more selective evaluation of the arterial supply to the tumor. The three cases in this report illustrate the utility of intra-procedural IA CEUS during TACE. Specifically, IA CEUS aided TACE in cases where the HCC showed poor arterial enhancement, an extrahepatic arterial supply, and a portal venous supply, respectively.

Description: Purpose To evaluate the capacity of perfusion CT imaging to distinguish between complete and incomplete responders after neoadjuvant chemoradiation therapy for rectal carcinoma, with particular attention to segmentation technique. Materials and methods 17 patients were evaluated in this prospective IRB-approved study. For each patient, a perfusion CT acquisition was obtained prior to the initiation of chemoradiation, at 1–2 weeks after the start of chemoradiation, and at 12 weeks after the start of chemoradiation therapy. From each dataset, three perfusion parameters were measured, each in two different ways: a region of interest incorporating only “hot spots” of greatest enhancement and whole-tumor measurements. Results In univariate analysis, blood volume and permeability differed significantly between responders and non-responders. In logistic regression analysis evaluating predictors of the “complete response” outcome, only two predictors were retained as statistically significant: peak hot spot blood volume 1–2 weeks into therapy (OR 10.25, p  = 0.0026) and hot spot permeability decline at 12 weeks after the initiation of therapy (OR 5.62, p  = 0.03). The overall likelihood ratio test for this model supported the conclusion that hot spot blood volume and hot spot permeability decline were significant predictors of the complete pathologic response outcome ( p  〈 0.0001). Conclusion In this pilot study, peak tumor blood volume and decline in tumor permeability, when measured in “hot spots” of greatest enhancement, were strong predictors of complete therapeutic response in rectal cancer after neoadjuvant therapy.

Description: Purpose To assess the utility of morphologic and quantitative CT features in differentiating abdominal wall endometriosis (AWE) from other masses of the abdominal wall. Methods Retrospective IRB-approved study of 105 consecutive women from two institutions who underwent CT and biopsy/resection of abdominal wall masses. CTs were independently reviewed by two radiologists blinded to final histopathologic diagnoses. Associations between CT features and pathology were tested using Fisher’s Exact Test. Sensitivity, specificity, positive, and negative predictive values were calculated. P values were adjusted for multiple variable testing. Results 24.8% (26/105) of patients had histologically proven abdominal wall endometriosis. The other most common diagnoses included adenocarcinoma NOS (21%; 22/105), desmoid (14.3%; 15/105), and leiomyosarcoma (8.6%; 9/105). CT features significantly associated with endometriosis for both readers were location below the umbilicus ( P  = 0.0188), homogeneous density ( P  = 0.0188), and presence of linear infiltration irradiating peripherally from a central soft tissue nodule (i.e., “gorgon” sign) ( P  〈 0.0001). The highest combined sensitivity (0.69, 95% CI: 0.48–0.86) and specificity (0.97, 95% CI: 0.91–1.00) for both readers occurred for patients having all three of these features present. Border type ( P  = 0.0199) was only significant for R 2, peritoneal extension ( P  = 0.0188) was only significantly for R 1, and the remainder of features were insignificant ( P  = 0.06–60). There was overlap in Hounsfield units on non-contrast CT ( N  = 26) between AWE (median: 45HU, range: 39–54) and other abdominal wall masses (median: 38.5HU, range: 15–58). Conclusion CT features are helpful in differentiating AWE from other abdominal wall soft tissue masses. Such differentiation may assist decisions regarding possible biopsy and treatment planning.

Description: Purpose To investigate the relationship of pre-treatment volumetric apparent diffusion coefficient (ADC) histogram parameters with post-operative histopathologic treatment response and clinical outcomes following pre-operative chemoradiation treatment (CRT) in rectal cancer. Materials and methods In a Health Insurance Portability and Accountability Act compliant retrospective study, 78 rectal cancer patients treated with pre-operative CRT and rectal MRI were included. MR imaging analysis was performed using OncoTREAT (software tool). Multiple volumetric ADC histogram parameters (voxel distribution across ADC ranges, kurtosis, and skewness) were assessed. Correlation was made to post-operative pathological complete response, clinical, or radiological evidence of disease progression using the Mann–Whitney test. Results Post CRT, 8 patients showed pathologic complete response and 13 patients showed distant disease progression. Pre-treatment mean ADC was 1.2 × 10 −3 mm 2 /s (range 0.3–1.99 × 10 −3 mm 2 /s). Mean kurtosis measured was 0.56 (range −1 to 6; SD 1.36). Mean skewness was 0.3 (range −1 to 2; SD 0.69). Skewness had significant correlation ( p value = 0.006) with disease progression. The mean rectal tumor volume was 24cc (range 1cc–134cc). Pre-treatment MRI tumor volume showed significant correlation ( p value = 0.013) with pathologic complete response. Mean ADC and percentage voxels distribution against ADC ranges had no significant correlation with treatment response or disease outcomes. Conclusion Volumetric ADC histogram analysis of pre-CRT rectal cancer MRI appears promising for prediction of post-CRT complete response and disease progression.

Description: Purpose To evaluate the correlation of CT perfusion parameters with the Fuhrman grade in pT1b (4–7 cm) renal cell carcinoma (RCC). Methods CT perfusion imaging and Fuhrman pathological grading of pT1b RCC were performed in 48 patients (10 grade 1, 27 grade 2, 9 grade 3, and 2 grade 4). Equivalent blood volume ( BV Equiv ), permeability surface area product (PS), and blood flow (BF) of tumors were measured. Grade 1 and 2 were defined as low-grade group ( n  = 37), meanwhile high-grade group ( n  = 11) included grade 3 and 4. Comparisons of CT perfusion parameters and tumor size of the two different groups were performed. Correlations between CT perfusion parameters, Fuhrman grade (grade 1, 2, 3, and 4), and tumor size were assessed. Results PS was significantly lower in high grade than in low-grade pT1b RCC ( P  = 0.004). However, no significant differences were found in BV Equiv and BF between the two groups ( P  〉 0.05 for both). The optimal threshold value, sensitivity, specificity, and the area under the ROC curve for distinguishing the two groups using PS were 68.8 mL/100 g/min, 0.7, 0.8, and 0.8, respectively. Negative significant correlation was observed between PS and Fuhrman grade ( r  = −0.338, P  = 0.019). Conclusions The PS of pT1b RCC had negative significant correlation with Fuhrman grade. CT perfusion appeared to be a non-invasive means to predict high Fuhrman grade of pT1b RCC preoperatively and guide the optimal treatment for the patient.

Description: Purpose The aim of this study was to evaluate the impact of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique on quantitative and qualitative image analysis in patients with gastrointestinal stromal tumors (GISTs) at dual-energy computed tomography (DECT) of the abdomen. Methods Forty-five DECT datasets of 21 patients (14 men; 63.7 ± 9.2 years) with GISTs were reconstructed with the standard linearly blended (M_0.6) and VMI+ and traditional virtual monoenergetic (VMI) algorithm in 10-keV increments from 40 to 100 keV. Attenuation measurements were performed in GIST lesions and abdominal metastases to calculate objective signal-to-noise (SNR) and contrast-to-noise ratios (CNR). Five-point scales were used to evaluate overall image quality, lesion delineation, image sharpness, and image noise. Results Quantitative image parameters peaked at 40-keV VMI+ series (SNR 27.8 ± 13.0; CNR 26.3 ± 12.7), significantly superior to linearly blended (SNR 16.8 ± 7.3; CNR 13.6 ± 6.9) and all VMI series (all P  〈 0.001). Qualitative image parameters were highest for 60-keV VMI+ reconstructions regarding overall image quality and image sharpness (median 5, respectively; P  ≤ 0.023). Qualitative assessment of lesion delineation peaked in 40 and 50-keV VMI+ series (median 5, respectively). Image noise was superior in 90 and 100-keV VMI and VMI+ reconstructions (all medians 5). Conclusions Low-keV VMI+ reconstructions significantly increase SNR and CNR of GISTs and improve quantitative and qualitative image quality of abdominal DECT datasets compared to traditional VMI and standard linearly blended image series.