Jee Hyun Baek

Hepatocellular Carcinoma: Imaging Patterns on Gadoxetic Acid–enhanced MR Images and Their Value as an Imaging Biomarker

PURPOSE To investigate the patterns of imaging appearance of hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced magnetic resonance (MR) images and to assess their potential value as prognostic markers of HCC associated with tumor recurrence after surgery. MATERIALS AND METHODS The institutional review board approved this retrospective study and informed consent was waived. A total of 216 patients with 304 pathologically proved HCCs underwent gadoxetic acid-enhanced MR imaging prior to surgery and were included in the study. Two reviewers, blinded to the clinical data, evaluated in consensus the imaging patterns of HCC according to enhancement patterns on dynamic phase images and signal intensity on hepatobiliary phase (HBP) images. The association of imaging features with clinical-pathologic findings was evaluated by using the Student t test, χ(2) test, Mann-Whitney U test, and linear-by-linear association. The dependence of time to tumor recurrence (TTR) after surgery was evaluated by using the Kaplan-Meier method, log-rank test, and Cox proportional hazard model. RESULTS HCCs with atypical enhancement pattern (P = .0167, P = .0450, P < .0001, respectively) and iso- to hyperintensity on HBP images (P = .0001, P = .0002, P < .0001, respectively) had smaller tumor size, lower histologic grade, and worse Child-Pugh class. The log-rank test (P = .0064) and Cox proportional hazards model (hazard ratio, 5.676; P = .0158) revealed that HCCs with iso- to hyperintensity on HBP images had significantly longer TTR than HCCs with hypointensity on HBP images. CONCLUSION HCCs can be classified into several imaging patterns on gadoxetic acid-enhanced MR images, which are associated with tumor aggressiveness and outcome. In addition, iso- to hyperintensity on HBP images may be a useful imaging biomarker to indicate longer TTR after surgery. .

Small (≤20 mm) Pancreatic Adenocarcinomas: Analysis of Enhancement Patterns and Secondary Signs with Multiphasic Multidetector CT

PURPOSE To evaluate the enhancement patterns, prevalence of secondary signs, and histopathologic features of 20-mm-diameter or smaller pancreatic cancers seen on multiphasic multidetector computed tomographic (CT) images. MATERIALS AND METHODS This retrospective study was approved by the institutional review board; the requirement for informed consent was waived. From January 2002 through September 2009, the authors reviewed the clinical and imaging data of 130 consecutive patients (76 men, 54 women; mean age, 64.1 years; age range, 28-82 years) who had surgically proven 30-mm-diameter or smaller pancreatic cancers and underwent preoperative multidetector CT and 33 consecutive patients (17 men, 16 women; mean age, 65.1 years; age range, 48-84 years) who had histopathologically proven pancreatic cancer and underwent incidental multidetector CT before the diagnosis was rendered. Only pancreatic phase CT was performed in two patients, and only hepatic venous phase CT was performed in nine patients. Two radiologists in consensus classified the tumor attenuation as hyper-, iso-, or hypoattenuation during the pancreatic and hepatic venous phases. Accompanying secondary signs, temporal changes in tumor attenuation, and histopathologic findings also were analyzed. The Fisher exact test, χ(2) test, generalized estimating equation, and Student t test were used to compare the variables. RESULTS Seventy tumors were 20 mm or smaller, and 93 were 21-30 mm. Isoattenuating pancreatic cancers were more commonly observed among the 20-mm or smaller tumors (16 of 59, 27%) than among the 21-30-mm tumors (12 of 93, 13%) (P = .033). They were also more common among well-differentiated tumors (seven of 12, 58%) than among moderately differentiated (20 of 124, 16%) and poorly differentiated (one of 10, 10%) tumors (P = .001). The prevalence of secondary signs differed significantly according to tumor size (53 [76%] of 70 ≤20-mm tumors vs 92 [99%] of 93 21-30-mm tumors) (P < .001). The prevalence of secondary signs was high among isoattenuating pancreatic cancers (14 [88%] of 16 ≤20-mm tumors vs all 12 [100%] 21-30-mm tumors). Most of the isoattenuating tumors seen at prediagnostic CT were hypoattenuating after 6 months (100% [four of four] during pancreatic phase, 71% [five of seven] during hepatic venous phase). CONCLUSION The prevalence of isoattenuating pancreatic cancers differed significantly according to tumor size and cellular differentiation. Most small isoattenuating pancreatic cancers showed secondary signs. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101133/-/DC1.

Attenuation-based Automatic Tube Voltage Selection and Tube Current Modulation for Dose Reduction at Contrast-enhanced Liver CT

PURPOSE To retrospectively determine whether the combined use of automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) can effectively reduce radiation dose at contrast material-enhanced liver computed tomography (CT) while maintaining acceptable image quality compared with the use of ATCM alone. MATERIALS AND METHODS This study was approved by an institutional review board, and informed consent was waived. Three hundred fourteen consecutive patients suspected of having liver disease were divided into three groups. In two groups, both ATVS and ATCM were used (group A1, n=97; group A2, n=101) but with different contrast gain settings; in one group, only ATCM with a fixed tube potential of 120 kV (group B, n=116) was used. Weighted volume CT dose index and dose-length product, contrast-to-noise ratios (CNRs), and mean image noise were assessed. Qualitative analysis was performed by two board-certified radiologists and one radiology resident. Statistical analysis was performed by using the one-way analysis of variance test, two-tailed paired t test, Kruskal-Wallis test, and noninferiority test. RESULTS In groups A1 and A2, a significant dose reduction was obtained compared with that in group B (P<.0001). The mean dose reduction was 20% in group A1 and 31% in group A2. Furthermore, CNRs were significantly higher in groups A1 and A2 than in group B (P<.0001). Despite the higher image noise in groups A1 and A2, the overall image quality was acceptable. CONCLUSION Compared with the use of ATCM alone, the combined use of ATVS and ATCM allowed reduction of radiation exposure while maintaining good image quality at contrast-enhanced liver CT.

Small (≤3 cm) Solid Pseudopapillary Tumors of the Pancreas at Multiphasic Multidetector CT

PURPOSE To analyze the imaging features of small (≤3 cm) solid pseudopapillary tumors (SPTs) seen at multiphasic multidetector computed tomography (CT) in comparison with those of larger SPTs. MATERIALS AND METHODS This retrospective study was approved by the institutional review board, and the requirement for informed consent was waived. CT images of 42 histopathologically proven SPTs in the pancreas were retrospectively reviewed. Two radiologists in consensus analyzed the CT findings for the shape, location, diameter, ratio of solid-to-cystic components, border and margin, enhancement pattern, and enhancement grade of the tumors, as well as the presence of calcification, dilatation of the pancreatic duct, and parenchymal atrophy. Then, according to the feature analysis results, the reviewers classified all SPTs as typical or atypical; they also subdivided all SPTs into small (≤3 cm) and large SPTs (>3 cm) depending on the tumor size. Differences in the morphologic features between small SPTs and large typical and atypical SPTs were statistically evaluated by using the Fisher exact test; differences in attenuation between the pre- and postcontrast images and in the dynamic enhancement pattern according to nodule size (≤3 cm versus >3 cm) were evaluated by using the χ(2) test or Fisher exact test for categorical variables. RESULTS There were 20 typical SPTs and 22 atypical SPTs. Of the 22 atypical SPTs, 12 (54%) were 3 cm or smaller in diameter and 10 (45%) were larger than 3 cm in diameter. Small atypical SPTs usually appeared as solid tumors with a sharp margin and without accompanying pancreatic duct dilatation or parenchymal atrophy. They also showed weak enhancement during the pancreatic phase and a gradually increasing enhancement pattern. All typical SPTs were larger than 3 cm and appeared as well-defined cystic and solid masses with heterogeneous enhancement, while all large atypical SPTs appeared as calcified solid masses or large cystic masses. CONCLUSION The imaging features of small SPTs are different from those of large SPTs, and small SPTs frequently appear as purely solid tumors with a sharp margin and gradual enhancement.

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

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

MR elastography for noninvasive assessment of hepatic fibrosis: reproducibility of the examination and reproducibility and repeatability of the liver stiffness value measurement.

To determine the reproducibility of MR elastography (MRE) and the reproducibility and repeatability of the stiffness measurement of MRE in the staging of liver fibrosis.

Evaluation of hepatic fibrosis using intravoxel incoherent motion in diffusion-weighted liver MRI.

Objectives To determine whether intravoxel incoherent motion (IVIM)–diffusion-weighted image (DWI)–derived parameters showed better diagnostic performance than the apparent diffusion coefficient (ADCtotal) for the evaluation of hepatic fibrosis (HF). Methods This retrospective study was approved by institutional review board, and informed consent was waived. Fifty-five patients with chronic liver disease who had undergone IVIM-DWI using 8 b-values at 3 T were included. True diffusion coefficient (Dt), pseudo-diffusion coefficient (Dp), perfusion fraction (f), and ADCtotal were calculated. Receiver operating characteristic analysis was performed for all parameters for the HF staging. Results All parameters showed a significant correlation with the HF stages (−0.31 to −0.72, P < 0.05). All parameters were significantly higher in F0 to F1 than in F4 (P < 0.05). The Dp showed better performance than the ADCtotal in differentiating significant HF (≥F2) from F0 to F1. Conclusions The IVIM-derived parameters and ADCtotal showed significant correlation with HF. The D p showed better diagnostic performance for differentiating significant HF than did ADCtotal.

Low Tube Voltage Intermediate Tube Current Liver MDCT: Sinogram-Affirmed Iterative Reconstruction Algorithm for Detection of Hypervascular Hepatocellular Carcinoma

OBJECTIVE The purpose of this study was to compare image quality and lesion detectability in the evaluation of hypervascular hepatocellular carcinoma (HCC) on low-tube-voltage half-dose liver CT scans subjected to sinogram-affirmed iterative reconstruction (SAFIRE) with the quality and detectability on full-dose scans reconstructed with filtered back projection (FBP). MATERIALS AND METHODS A total of 126 patients with suspected HCC who underwent liver CT including arterial phase scanning at 80 kVp in the dual-source mode (300 mAs for each tube) were included in the study. The half-dose arterial scans were reconstructed with FBP, iterative reconstruction in image space (IRIS), and five SAFIRE strengths (S1-S5) and were compared with full-dose virtual scans (600 mA) reconstructed with FBP. We assessed image noise, contrast-to-noise ratio (CNR) of the liver and blood vessels, and lesionto-liver CNR. Two radiologists evaluated image quality and lesion detectability attained with the different imaging sets. RESULTS Image noise on SAFIRE images was significantly lower than that on the other images, and the CNRs on SAFIRE images were higher than those on half-dose FBP images (p < 0.001). In addition, lesion-to-liver CNR on the half-dose S5 SAFIRE images was higher than on IRIS and full-dose FBP images (p < 0.05). Among the half-dose scans, SAFIRE images had significantly better image quality than FBP images (p < 0.05). Regarding lesion detection, half-dose SAFIRE images were better than half-dose FBP images and were comparable with full-dose FBP images (observer 1, 91.8% vs 96%; observer 2, 98% vs 98%; p > 0.05). CONCLUSION Performing half-dose 80-kVp liver CT with SAFIRE technique may increase image quality and afford comparable lesion detectability of hypervascular HCC at a reduced radiation dose compared with full-dose CT with FBP.

Added value of diffusion‐weighted imaging to MR cholangiopancreatography with unenhanced mr imaging for predicting malignancy or invasiveness of intraductal papillary mucinous neoplasm of the pancreas

To investigate the added value of diffusion‐weighted imaging (DWI) to magnetic resonance cholangiopancreatography (MRCP) with unenhanced MR imaging for predicting the malignancy or invasiveness of intraductal papillary mucinous neoplasms (IPMNs).

Differentiation of Intraductal Growing–type Cholangiocarcinomas from Nodular-type Cholangiocarcinomas at Biliary MR Imaging with MR Cholangiography

PURPOSE To describe the magnetic resonance (MR) findings of intraductal growing (IDG)-type cholangiocarcinoma (CC) and to identify the features that differentiate it from nodular-type CC. MATERIALS AND METHODS The institutional review board approved this retrospective study and waived the informed consent requirement. Thirty-nine patients with pathologically proved IDG-type (n = 19) or nodular-type (n = 20) CCs who had undergone preoperative gadolinium-enhanced MR imaging with MR cholangiography were included in this study. Analysis of MR findings included determination of the (a) shape, enhancement degree, and pattern of the tumor; (b) outer caliber of the tumor-bearing segment; and (c) presence of tumor multiplicity, upstream and downstream bile duct dilatation, bile duct wall thickening adjacent to the tumor, and adjacent organ invasion. The significance of these findings was determined with the χ² test. RESULTS Significant features in the differentiation of IDG-type CCs from nodular-type CCs included papillary or irregular polypoid shape, lack of constriction of the tumor-bearing segment, hypoenhancement of the tumor to the liver during the equilibrium phase, tumor multiplicity, upstream and downstream bile duct dilatation, and no bile duct wall thickening adjacent to the tumor (P < .05). When at least two of these six imaging features were used in combination, sensitivity and specificity in the diagnosis of IDG-type CCs were 95% and 70%, respectively. CONCLUSION By using characteristic MR features, one can differentiate IDG-type CC from nodular-type CC with a high degree of accuracy at biliary MR imaging with MR cholangiography.