Yuichi Kumagae

Pancreatic Adenocarcinoma: Variability of Diffusion-weighted MR Imaging Findings

PURPOSE To compare the apparent diffusion coefficients (ADCs) of pancreatic adenocarcinomas that appear hyperintense with clearly defined borders (clear hyperintense) with those that do not show clear hyperintense borders on diffusion-weighted magnetic resonance (MR) images. MATERIALS AND METHODS Institutional review board approval was obtained and informed consent was waived. Eighty patients with histologically confirmed pancreatic adenocarcinoma (mean tumor size, 32 mm) underwent fat-suppressed single-shot echo-planar 3.0-T diffusion-weighted MR imaging with diffusion gradients (b = 1000 sec/mm(2)). ADC values of the pancreatic adenocarcinomas (n = 80) and proximal (n = 51) and distal (n = 70) pancreas were compared by using the Friedman test, followed by the Wilcoxon signed-rank test, and the difference in serum amylase levels between pancreatic adenocarcinomas with and without clear hyperintensity was evaluated by using the x(2) test. RESULTS In 38 of 80 patients, pancreatic adenocarcinomas showed clear hyperintensity relative to the surrounding pancreas; 26 were hyperintense with unclear distal borders; 12, isointense; and four, hypointense. In all patients, the mean ADC (± standard deviation) of the tumors (1.16 × 10(-3) mm(2)/sec ± 0.22) was significantly lower than those of the proximal pancreas (1.33 × 10(-3) mm(2)/sec ± 0.16, P < .001) and the distal pancreatic parenchyma (1.24 × 10(-3) mm(2)/sec ± 0.23, P = .004). No significant difference in ADC was seen between the pancreatic adenocarcinomas without clear hyperintensity and the distal pancreas. The frequency of serum amylase levels greater than 120 U/L (2.00 μkat/L) was significantly higher than in those with clear hyperintense pancreatic adenocarcinomas (P < .001). CONCLUSION Diffusion-weighted MR imaging was not useful for delineating 47% of pancreatic adenocarcinomas, because of hyperintensity of the pancreatic parenchyma distal to the cancer.

Quantitative evaluation of liver function with T1 relaxation time index on Gd-EOB-DTPA-enhanced MRI: Comparison with signal intensity-based indices

To evaluate whether the reduction rate of T1 relaxation time of the liver (T1 relaxation time index) before and 20 minutes after gadolinium‐ethoxybenzyl‐diethylenetriaminepentaacetic acid (Gd‐EOB‐DTPA) injection has the potential to serve as an magnetic resonance imaging (MRI)‐based liver function test in comparison with signal intensity‐based indices.

Gd-EOB-DTPA-enhanced magnetic resonance imaging features of hepatic hemangioma compared with enhanced computed tomography.

AIM To clarify features of hepatic hemangiomas on gadolinium-ethoxybenzyl-diethylenetriaminpentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) compared with enhanced computed tomography (CT). METHODS Twenty-six patients with 61 hepatic hemangiomas who underwent both Gd-EOB-DTPA-enhanced MRI and enhanced CT were retrospectively reviewed. Hemangioma appearances (presence of peripheral nodular enhancement, central nodular enhancement, diffuse homogenous enhancement, and arterioportal shunt during the arterial phase, fill-in enhancement during the portal venous phase, and prolonged enhancement during the equilibrium phase) on Gd-EOB-DTPA-enhanced MRI and enhanced CT were evaluated. The degree of contrast enhancement at the enhancing portion within the hemangioma was visually assessed using a five-point scale during each phase. For quantitative analysis, the tumor-muscle signal intensity ratio (SIR), the liver-muscle SIR, and the attenuation value of the tumor and liver parenchyma were calculated. The McNemar test and the Wilcoxons signed rank test were used to assess the significance of differences in the appearances of hemangiomas and in the visual grade of tumor contrast enhancement between Gd-EOB-DTPA-enhanced MRI and enhanced CT. RESULTS There was no significant difference between Gd-EOB-DTPA-enhanced MRI and enhanced CT in the presence of peripheral nodular enhancement (85% vs 82%), central nodular enhancement (3% vs 3%), diffuse enhancement (11% vs 16%), or arterioportal shunt (23% vs 34%) during arterial phase, or fill-in enhancement (79% vs 80%) during portal venous phase. Prolonged enhancement during equilibrium phase was observed less frequently on Gd-EOB-DTPA-enhanced MRI than on enhanced CT (52% vs 100%, P < 0.001). On visual inspection, there was significantly less contrast enhancement of the enhancing portion on Gd-EOB-DTPA-enhanced MRI than on enhanced CT during the arterial (3.94 ± 0.98 vs 4.57 ± 0.64, respectively, P < 0.001), portal venous (3.72 ± 0.82 vs 4.36 ± 0.53, respectively, P < 0.001), and equilibrium phases (2.01 ± 0.95 vs 4.04 ± 0.51, respectively, P < 0.001). In the quantitative analysis, the tumor-muscle SIR and the liver-muscle SIR observed with Gd-EOB-DTPA-enhanced MRI were 0.80 ± 0.24 and 1.28 ± 0.33 precontrast, 1.92 ± 0.58 and 1.57 ± 0.55 during the arterial phase, 1.87 ± 0.44 and 1.73 ± 0.39 during the portal venous phase, 1.63 ± 0.41 and 1.78 ± 0.39 during the equilibrium phase, and 1.10 ± 0.43 and 1.92 ± 0.50 during the hepatobiliary phase, respectively. The attenuation values in the tumor and liver parenchyma observed with enhanced CT were 40.60 ± 8.78 and 53.78 ± 7.37 precontrast, 172.66 ± 73.89 and 92.76 ± 17.92 during the arterial phase, 152.76 ± 35.73 and 120.12 ± 18.02 during the portal venous phase, and 108.74 ± 18.70 and 89.04 ± 7.25 during the equilibrium phase, respectively. Hemangiomas demonstrated peak enhancement during the arterial phase, and both the SIR with Gd-EOB-DTPA-enhanced MRI and the attenuation value with enhanced CT decreased with time. The SIR of hemangiomas was lower than that of liver parenchyma during the equilibrium and hepatobiliary phases on Gd-EOB-DTPA-enhanced MRI. However, the attenuation of hemangiomas after contrast injection was higher than that of liver parenchyma during all phases of enhanced CT. CONCLUSION Prolonged enhancement during the equilibrium phase was observed less frequently on Gd-EOB-DTPA-enhanced MRI than enhanced CT, which may exacerbate differentiating between hemangiomas and malignant tumors.

Distinguishing adrenal adenomas from non-adenomas on dynamic enhanced CT: A comparison of 5 and 10 min delays after intravenous contrast medium injection

AIM To evaluate the usefulness of several parameters of 5 min compared to 10 min delayed contrast-enhanced CT in distinguishing adenomas from non-adenomas. MATERIALS AND METHODS The study population consisted of 94 patients (52 men and 42 women; mean age 62 years) with 103 adrenal lesions (75 adenomas and 28 non-adenomas). In each patient, unenhanced CT was followed by early, 5 and 10 min enhanced CT. Diagnostic parameters included delayed enhanced attenuation at 5 and 10 min, washout attenuation (WO) at 5 and 10 min, absolute percentage washout (APW) at 5 and 10 min, and relative percentage washout (RPW) at 5 and 10 min. The accuracy of each parameter for diagnosing adenomas from non-adenomas was calculated using receiver operating characteristic (ROC) analysis. RESULTS Upon comparison between 5 and 10 min delayed contrast-enhanced CT for differentiating total adenomas or lipid-poor adenomas from non-adenomas, there was no significant difference in the area under the binomial ROC curve (Az) values of delayed enhanced attenuation (total adenomas versus non-adenomas, p = 0.164; lipid-poor adenomas versus non-adenomas, p = 0.178), WO (total adenomas versus non-adenomas, p = 0.216; lipid-poor adenomas versus non-adenomas, p = 0.230), APW (total adenomas versus non-adenomas, p = 0.401; lipid-poor adenomas versus non-adenomas, p = 0.870), or RPW (total adenomas versus non-adenomas, p = 0.160; lipid-poor adenomas versus non-adenomas, p = 0.780). CONCLUSION Five minute contrast-enhanced CT was as useful as 10 min contrast-enhanced CT for differentiation of adrenal adenomas from non-adenomas.

ADC histogram analysis for adrenal tumor histogram analysis of apparent diffusion coefficient in differentiating adrenal adenoma from pheochromocytoma

To determine the diagnostic performance of apparent diffusion coefficient (ADC) histogram analysis in diffusion‐weighted (DW) magnetic resonance imaging (MRI) for differentiating adrenal adenoma from pheochromocytoma.

Value of diffusion tensor imaging in differentiating malignant from benign parotid gland tumors

PURPOSE To evaluate whether diffusion tensor imaging (DTI) can be used to differentiate malignant parotid gland tumors from the benign ones. MATERIALS AND METHODS The study population comprised 59 parotid gland tumors (24 Warthins tumors, 19 pleomorphic adenomas, seven other benign tumors, and nine malignant tumors). Single-shot echo-planar DTI was performed with motion-probing gradients along 30 noncollinear directions (b=1000s/mm2) at 3.0T. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values for benign and malignant tumors were compared using the Mann-Whitney U test. Receiver-operating characteristic (ROC) curve analysis was performed to assess the ability of the ADC and FA values to differentiate malignant tumors from the benign ones. RESULTS ADC values showed no significant difference between malignant (0.93±0.21×10-3mm2/s) and benign tumors (1.19±0.50×10-3mm2/s) (p=0.225). FA values of malignant tumors were significantly higher than those of benign tumors (0.26±0.06 vs. 0.17±0.05, p<0.001). The area under the ROC curve of FA was significantly greater than that under the curve of ADC (0.884 vs. 0.628, p=0.010). CONCLUSIONS DTI, particularly FA, can help differentiate malignant parotid gland tumors from the benign ones.

Hepatic Hemangiomas: Factors Associated with Pseudo Washout Sign on Gd-EOB-DTPA-enhanced MR Imaging

PURPOSE Our study aim was to clarify the characteristics of hemangiomas with pseudo washout sign (PWS) by comparing their features with those of hemangiomas without PWS on gadolinium-ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging. METHODS We evaluated the features of hemangiomas on Gd-EOB-DTPA-enhanced MR imaging of 70 hepatic hemangiomas in 31 patients, investigating the presence of peripheral or central nodular enhancement, diffuse enhancement, and arterioportal shunt during the arterial phase, fill-in enhancement during the portal venous phase, and PWS, which is low signal intensity during the late phase. We visually assessed the intensity of contrast enhancement of the lesion during the arterial, portal venous, late, and hepatobiliary phases using a 4-grade scale and used the Fisher exact and Mann-Whitney U tests to compare hemangiomas with and without PWS. RESULTS We observed PWS in 33 (47%) of 70 hemangiomas, which were significantly smaller than the hemangiomas without PWS (17.4 mm ± 20.3 versus 30.1 mm ± 28.5; P = 0.005); more frequent diffuse enhancement in hemangiomas with PWS than those without (21.2% versus 2.7%; P = 0.026); and no significant differences in nodular enhancement (P = 0.231), arterioportal shunt (P = 0.403), or fill-in enhancement (P = 0.357) between hemangiomas with and without PWS. Visually determined grades of tumor contrast enhancement were significantly lower in hemangiomas with PWS during the portal venous (P = 0.007) and late (P < 0.001) phases. CONCLUSIONS Small hemangiomas tend to decrease in signal intensity during the portal venous phase and show PWS during the late phase.

Prospective Study on the Incidence of Cerebrovascular Disease After Coronary Angiography

Aim: Previous studies have reported a 10.2%–22% rate of silent cerebral infarction and a 0.1% –1% rate of symptomatic cerebral infarction after coronary angiography (CAG). However, the risk factors of cerebral infarction after CAG have not been fully elucidated. For this reason, we investigated the incidence and risk factors of CVD complications within 48 h after CAG using magnetic resonance imaging (MRI) (Diffusion-weighted MRI) at Kagoshima University Hospital. Methods: From September 2013 to April 2015, we examined the incidence and risk factors, including procedural data and patients characteristics, of cerebrovascular disease after CAG in consecutive 61 patients who underwent CAG and MRI in our hospital. Results: Silent cerebral infarction after CAG was observed in 6 cases (9.8%), and they should not show any neurological symptoms of cerebral infarction. Only prior coronary artery bypass grafting (CABG) was more frequently found in the stroke group (n = 6) than that in the non-stroke group (n = 55); however, no significant difference was observed (P = 0.07). After adjusting for confounders, prior CABG was a significant independent risk factor for the incidence of stroke after CAG (odds ratio: 11.7, 95% confidence interval: 1.14–129.8, P = 0.04). Conclusions: We suggested that the incidence of cerebral infarction after CAG was not related to the catheterization procedure per se but may be caused by atherosclerosis with CABG.

Feasibility of a fixed scan delay technique using a previous bolus tracking technique data for dynamic hepatic CT.

OBJECTIVE To compare the quality of contrast enhancement and hepatic CT images acquired using bolus tracking technique at two different time points and those acquired with fixed scan delay technique using a previous bolus tracking data. MATERIALS AND METHODS Fifty patients who underwent 3 different hepatic CT exams (25-s fixed injection of 600 mg iodine (I)/kg or 100mL of 370 mg I/mL nonionic contrast medium) were enrolled. The first and second exams were performed with a bolus tracking technique. The third exam was performed with a fixed scan delay technique using the first exam data. Differences in attenuation values in the abdominal organs were examined and evaluated visually on hepatic arterial phase images. RESULTS There was no significant difference in the mean 50-HU threshold times between the first and second bolus tracking exams with intra-patient differences between them (1.3±0.9 s). No significant intra-patient differences were noted in organ attenuation and visual evaluation on hepatic arterial phase images between the 3 exams. CONCLUSION The fixed scan delay technique using a previous bolus tracking data is feasible for hepatic CT exams to follow up hepatocellular carcinoma.

Conspicuity of Malignant Liver Tumors on Diffusion-Weighted Imaging With Short tau Inversion Recovery After Gadolinium Ethoxybenzyl Diethylenetriaminepentaacetic Acid Administration: STIR-DWI After Gd-EOB-DTPA Injection

Diffusion‐weighted imaging (DWI) has been used for the detection and characterization of liver tumors because it has excellent contrast resolution. DWI using short tau inversion recovery (STIR) can improve tumor‐to‐liver contrast after gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd‐EOB‐DTPA) administration that shortens the T1 relaxation of liver parenchyma.