Ijin Joo

Intravoxel Incoherent Motion Diffusion-weighted MR Imaging of Hepatocellular Carcinoma: Correlation with Enhancement Degree and Histologic Grade

PURPOSE To compare the association of intravoxel incoherent motion (IVIM)-derived parameters and apparent diffusion coefficient (ADC) with the histologic grade of hepatocellular carcinoma (HCC) and evaluate the relationship between IVIM-derived parameters and arterial enhancement degree. MATERIALS AND METHODS This retrospective study was institutional review board-approved, and informed consent was waived. Forty patients with 42 surgically confirmed HCCs underwent diffusion-weighted magnetic resonance (MR) imaging with eight b values (0-800 sec/mm(2)). ADC, diffusion coefficient (D), pseudodiffusion coefficient, and perfusion fraction (f) were calculated. Two radiologists determined the enhancement degree in consensus, as well as the percentage of arterial enhancement of HCC. The relationship between the parameters and histologic grade, as well as arterial enhancement, was assessed by using the Spearman or Pearson correlation test. Receiver operating characteristic (ROC) analysis of discrimination between low-grade (grades 1 and 2) and high-grade (grades 3 and 4) HCC was performed for D and ADC values. RESULTS D and ADC values were both significantly correlated with histologic grade: r = -0.604 (P < .0001) and r = -0.448 (P = .002), respectively. D and ADC values were both significantly lower in high-grade HCC (D = [0.99 ± 0.13] × 10(-3)mm(2)/sec, ADC = [1.13 ± 0.14] × 10(-3)mm(2)/sec) than in low-grade HCC (D = [1.18 ± 0.16] × 10(-3)mm(2)/sec, ADC = [1.25 ± 0.17] × 10-(3)mm(2)/sec) (P < .0001 and P = .029, respectively). However, ROC analysis demonstrated a higher area under the ROC curve value for D than for ADC for differentiating high-grade HCC from low-grade HCC (0.838 vs 0.728; P = .026). The percentage of arterial enhancement was correlated with f (r = 0.621, P < .0001). CONCLUSION IVIM-derived D values of HCC showed significantly better diagnostic performance than ADC values in differentiating high-grade HCC from low-grade HCC, and significant correlation was observed between f and the percentage of arterial enhancement.

Hepatic Fibrosis: Prospective Comparison of MR Elastography and US Shear-Wave Elastography for Evaluation

PURPOSE To compare magnetic resonance (MR) elastography and ultrasonographic shear-wave elastography ( SWE shear-wave elastography ) for the staging of hepatic fibrosis ( HF hepatic fibrosis ) in the same individuals. MATERIALS AND METHODS This prospective study was approved by the institutional review board, and informed consent was obtained from all patients. The technical success of and reliable liver stiffness ( LS liver stiffness ) measurement rates at MR elastography and SWE shear-wave elastography were compared in 129 patients who underwent both examinations. For mutual validation, LS liver stiffness values measured at both examinations were correlated by using Pearson correlation. The diagnostic performance of the two techniques for the assessment of substantial HF hepatic fibrosis (stage ≥ F2) was compared by using nonparametric receiver operating characteristic analysis. RESULTS The technical success rates of MR elastography and SWE shear-wave elastography were 95.35% (123 of 129) and 97.67% (126 of 129), respectively (P = .51). MR elastography provided significantly more reliable LS liver stiffness measurements than did SWE shear-wave elastography (95.35% [123 of 129] vs 75.2% [97 of 129], P < .001). The two examinations showed moderate correlation (r = 0.724). In patients with HF hepatic fibrosis stages of F3 or lower, the two examinations showed moderate-to-strong correlation (r = 0.683 in normal livers, 0.754 in livers with stage F0 or F1 HF hepatic fibrosis , and 0.90 in livers with stage F2 or F3 HF hepatic fibrosis ; P < .001); however, they did not show significant correlation for stage F4 HF hepatic fibrosis (r = 0.30, P = .31). MR elastography and SWE shear-wave elastography showed similar diagnostic capability in depicting HF hepatic fibrosis of stage F2 or greater (P = .98) when LS liver stiffness measurements were reliably performed. CONCLUSION MR elastography and SWE shear-wave elastography showed moderate correlation and similar diagnostic performance in the diagnosis of HF hepatic fibrosis of stage F2 or greater; however, MR elastography yielded more reliable LS liver stiffness measurements than did SWE shear-wave elastography .

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).

Intravoxel Incoherent Motion Diffusion-weighted MR Imaging for Monitoring the Therapeutic Efficacy of the Vascular Disrupting Agent CKD-516 in Rabbit VX2 Liver Tumors

PURPOSE To evaluate the diagnostic value of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance (MR) imaging in the quantitative assessment of the therapeutic efficacy of a vascular disrupting agent (VDA) (CKD-516) in rabbit VX2 liver tumors. MATERIALS AND METHODS The institutional animal care and use committee approved this study. In 21 VX2 liver tumor-bearing rabbits, IVIM DW imaging examinations were serially performed with a 3.0-T imaging unit by using 12 b values from 0 to 800 sec/mm(2). The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudodiffusion coefficient (D*), perfusion fraction (f), and blood flow-related parameter (fD*) of tumors at different time points (baseline, 4 hours, 24 hours, 3 days, and 7 days after CKD-516 administration) were compared within the treated group (n = 15) by using the Friedman test as well as between the control (n = 6) and treated groups by using the Mann-Whitney test. Correlation between the change in tumor size and IVIM DW imaging parameters was analyzed by using the Spearman rank test. RESULTS In the treated group, D* and f significantly decreased at 4 hours and then recovered to baseline at 24 hours, while D significantly increased at 24 hours (P < .005). All IVIM-derived parameters showed no significant differences between the control and treated groups at 3- and at 7-day follow-up. The greater decrease observed in f and fD* at 4 hours correlated with the smaller increase in tumor size during the 7 days of follow-up (ρ = 0.53 and 0.65, respectively; P < .05 for both). CONCLUSION The therapeutic effect induced by a VDA could be effectively evaluated by using IVIM DW imaging, and f and fD* may be early predictive indicators of tumor response.

Staging of hepatic fibrosis: comparison of magnetic resonance elastography and shear wave elastography in the same individuals.

Objective To cross-validate liver stiffness (LS) measured on shear wave elastography (SWE) and on magnetic resonance elastography (MRE) in the same individuals. Materials and Methods We included 94 liver transplantation (LT) recipients and 114 liver donors who underwent either MRE or SWE before surgery or biopsy. We determined the technical success rates and the incidence of unreliable LS measurements (LSM) of SWE and MRE. Among the 69 patients who underwent both MRE and SWE, the median and coefficient of variation (CV) of the LSM from each examination were compared and correlated. Areas under the receiver operating characteristic curve in both examinations were calculated in order to exclude the presence of hepatic fibrosis (HF). Results The technical success rates of MRE and SWE were 96.4% and 92.2%, respectively (p = 0.17), and all of the technical failures occurred in LT recipients. SWE showed 13.1% unreliable LSM, whereas MRE showed no such case (p < 0.05). There was moderate correlation in the LSM in both examinations (r = 0.67). SWE showed a significantly larger median LSM and CV than MRE. Both examinations showed similar diagnostic performance for excluding HF (Az; 0.989, 1.000, respectively). Conclusion MRE and SWE show moderate correlation in their LSMs, although SWE shows higher incidence of unreliable LSMs in cirrhotic liver.

Recent Advances in CT and MR Imaging for Evaluation of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Accurate diagnosis and assessment of disease extent are crucial for proper management of patients with HCC. Imaging plays a crucial role in early detection, accurate staging, and the planning of management strategies. A variety of imaging modalities are currently used in evaluating patients with suspected HCC; these include ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine, and angiography. Among these modalities, dynamic MRI and CT are regarded as the best imaging techniques available for the noninvasive diagnosis of HCC. Recent improvements in CT and MRI technology have made noninvasive and reliable diagnostic assessment of hepatocellular nodules possible in the cirrhotic liver, and biopsy is frequently not required prior to treatment. Until now, the major challenge for radiologists in imaging cirrhosis has been the characterization of small cirrhotic nodules smaller than 2 cm in diameter. Further technological advancement will undoubtedly have a major impact on liver tumor imaging. The increased speed of data acquisition in CT and MRI has allowed improvements in both spatial and temporal resolution, which have made possible a more precise evaluation of the hemodynamics of liver nodules. Furthermore, the development of new, tissue-specific contrast agents such as gadoxetic acid has improved HCC detection on MRI. In this review, we discuss the role of CT and MRI in the diagnosis and staging of HCC, recent technological advances, and the strengths and limitations of these imaging modalities.

Small- and Medium-sized Hepatocellular Carcinomas: Monopolar Radiofrequency Ablation with a Multiple-Electrode Switching System—Mid-term Results

PURPOSE To prospectively assess the safety and mid-term therapeutic effectiveness of monopolar radiofrequency (RF) ablation with a multiple-electrode switching system for treating small- and medium-sized (≤ 5 cm) hepatocellular carcinomas (HCCs). MATERIALS AND METHODS The institutional review board approved this prospective study, and all patients gave informed consent. From February 2009 to January 2010, 166 patients (110 men and 56 women; age range, 38-86 years; mean age, 62 years ± 10 [standard deviation]) with 166 HCCs less than or equal to 5 cm in diameter were treated with monopolar RF ablation with a multiple-electrode switching system. One of three experienced radiologists performed the RF ablation. Technique effectiveness, ablation volume and time, and major complications were evaluated by means of computed tomography (CT) immediately after RF ablation and at follow-up CT examinations at 1 month and then every 3 months after the procedure. The overall survival, disease-free survival, and local tumor progression-free survival rates were evaluated by using the Kaplan-Meier method. RESULTS The technique effectiveness rate determined 1 month after RF ablation was 99.4%. Mean ablation parameters were as follows: volume, 85 cm(3) ± 54; maximum diameter, 61 mm ± 13; and minimum diameter, 43 mm ± 11. The major complication rate was 4.8%. The 6-month and 1-, 2-, and 3-year local tumor progression rates were 2%, 6%, 10%, and 11%, respectively. The overall survival rates at 1, 2, and 3 years after RF ablation were 99%, 97%, and 96%, and corresponding local tumor progression-free survival rates were 94%, 90%, and 89%, respectively. The disease-free survival rates at 1, 2, and 3 years after RF ablation were 75%, 60%, and 54%, respectively. CONCLUSION Monopolar RF ablation with a multiple-electrode switching system in small- and medium-sized HCCs was safe and efficient, and it provided successful local tumor control and high local tumor progression-free survival rates because an adequate ablation volume was obtained.

New Paradigm for Management of Hepatocellular Carcinoma by Imaging

Based on recent clinical practice guidelines, imaging is largely replacing pathology as the preferred diagnostic method for determination of hepatocellular carcinoma (HCC). A variety of imaging modalities, including ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), nuclear medicine, and angiography, are currently used to examine patients with chronic liver disease and suspected HCC. Advancements in imaging techniques such as perfusion imaging, diffusion imaging, and elastography along with the development of new contrast media will further improve the ability to detect and characterize HCC. Early diagnosis of HCC is essential for prompt treatment, which may in turn improve prognosis. Considering the process of hepatocarcinogenesis, it is important to evaluate sequential changes via imaging which would help to differentiate HCC from premalignant or benign lesions. Recent innovations including multiphasic examinations, high-resolution imaging, and the increased functional capabilities available with contrast-enhanced US, multidetector row CT, and MRI have raised the standards for HCC diagnosis. Although hemodynamic features of nodules in the cirrhotic liver remain the main diagnostic criterion, newly developed cell-specific contrast agents have shown great possibilities for improved HCC diagnosis and may overcome the diagnostic dilemma associated with small or borderline hepatocellular lesions. In the 20th century paradigm of medical imaging, radiological diagnosis was based on morphological characteristics, but in the 21st century, a paradigm shift to include biomedical, physiological, functional, and genetic imaging is needed. A multidisciplinary team approach is necessary to foster an integrated approach to HCC imaging. By developing and combining new imaging modalities, all phases of HCC patient care, including screening, diagnosis, treatment, and therapy, can be dramatically improved.

Solid Pancreatic Lesions: Characterization by Using Timing Bolus Dynamic Contrast-enhanced MR Imaging Assessment—A Preliminary Study

PURPOSE To assess the feasibility of postprocessing dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging timing bolus data by using a three-dimensional radial gradient-echo technique with k-space-weighted image contrast (KWIC) for the characterization of solid pancreatic diseases. MATERIALS AND METHODS This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 45 patients suspected of having biliary or pancreatic disease underwent pancreatic MR examination with a 3.0-T imager with a low-dose (2 mL gadopentetate dimeglumine) timing bolus by using the radial KWIC technique. There were 24 patients with pancreatic cancers, eight with pancreatic neuroendocrine tumors (PNETs), three with chronic pancreatitis, and 10 with a normal pancreas. By using a dedicated postprocessing software program for DCE MR imaging, the following perfusion parameters were measured for tumor and nontumorous parenchyma: volume transfer coefficient (K(trans)) and extracellular extravascular volume fraction; the rate constant (k(ep)) and initial area under the concentration curve in 60 seconds (iAUC) were then generated. The perfusion parameters acquired on DCE MR images were compared among the groups by using the analysis of variance test. RESULTS K(trans), k(ep), and iAUC values in patients with pancreatic cancer (0.042 min(-1) ± 0.023 [standard deviation], 0.761 min(-1) ± 0.529, and 2.841 mmol/sec ± 1.811, respectively) were significantly lower than in patients with a normal pancreas (0.387 min(-1) ± 0.176, 6.376 min(-1) ± 2.529, and 7.156 mmol/sec ± 3.414, respectively) (P < .05 for all). In addition, k(ep) values of PNETs and normal pancreas also differed (P < .0001), and K(trans), k(ep), and iAUC values of pancreatic cancers and PNETs differed significantly (P < .0001, P = .038, and P < .0001, respectively). CONCLUSION Results of timing bolus DCE MR imaging with the radial KWIC sequence from routine examinations can be postprocessed to yield potentially useful perfusion parameters for the characterization of pancreatic diseases.

Nonalcoholic Fatty Liver Disease: Intravoxel Incoherent Motion Diffusion-weighted MR Imaging—An Experimental Study in a Rabbit Model

PURPOSE To evaluate the feasibility of using intravoxel incoherent motion (IVIM) diffusion-weighted imaging with multiple b values for the noninvasive diagnosis of nonalcoholic fatty liver disease (NAFLD). MATERIALS AND METHODS This study was approved by the institutional animal care and use committee. Twenty-seven 8-week-old rabbits were fed a variety of diets (from a standard diet to a high-fat, high-cholesterol diet) before IVIM diffusion-weighted imaging was performed with seven b values by using a 3-T magnetic resonance (MR) imaging unit. At histologic analysis of the animals, livers were categorized by NAFLD severity as normal, NAFLD, borderline nonalcoholic steatohepatitis (NASH), or NASH. The apparent diffusion coefficient and IVIM-derived parameters including true diffusion coefficient, pseudodiffusion coefficient, and perfusion fraction of the liver parenchyma were measured. Each parameter was correlated with NAFLD severity, and optimal cutoff values were determined by means of receiver operating characteristics analysis. RESULTS Perfusion fraction was significantly lower in rabbits with NAFLD than in those with a normal liver, and it decreased further as severity of NAFLD increased, with medians of 22.2%, 14.8%, 11.3%, and 9.5% in the rabbits in the normal, NAFLD, borderline, and NASH groups, respectively (ρ = -0.83, P < .001). Apparent diffusion coefficient, true diffusion coefficient, and pseudodiffusion coefficient were not significantly different between the NAFLD severity groups. In terms of the diagnostic performance of perfusion fraction, area under the curve values were 0.984 (normal vs NAFLD or more severe disease), 0.959 (NAFLD or less severe vs borderline or more severe disease), and 0.903 (borderline or less severe vs NASH) with optimal cutoff values of 15.2%, 13.2%, and 11.0%, respectively. CONCLUSION Perfusion fractions extracted from IVIM diffusion-weighted imaging may help in the differentiation of early stage NASH from simple steatosis.