Katsuhiro Nasu

Diffusion-weighted imaging of surgically resected hepatocellular carcinoma: imaging characteristics and relationship among signal intensity, apparent diffusion coefficient, and histopathologic grade.

OBJECTIVE The objective of our study was to determine the relationship between the signal intensity of hepatocellular carcinoma (HCC) assessed with diffusion-weighted imaging (DWI) and T2-weighted imaging and the apparent diffusion coefficient (ADC) with the histopathologic grade of each nodule. MATERIALS AND METHODS MR examinations including DWI and T2-weighted imaging of 125 surgically resected hypervascular HCCs in 99 patients were retrospectively reviewed. Pathologic examinations revealed 25 well-, 61 moderately, and 39 poorly differentiated HCCs. Two radiologists reviewed the images and classified the signal intensity of each tumor on DWI and T2-weighted imaging by mutual agreement. The incidence of each signal intensity and the relationship between signal intensity and histopathologic grade were assessed for each sequence. The relationship between the ADC and histopathologic grade was also evaluated. RESULTS On DWI, 11 of 125 HCCs appeared hypo- to isointense, 27 tumors appeared slightly hyperintense, and the remaining 87 tumors appeared obviously hyperintense to the surrounding liver. Overall, 91.2% (114/125) of HCCs showed hyperintensity to the surrounding hepatic parenchyma. Statistical analysis showed that this rate on DWI was significantly higher than that on T2 turbo spin-echo (TSE) imaging (p < 0.001). On DWI, the tumors tended to show a brighter signal with rising histopathologic grade (p = 0.031), but this trend was not observed on T2-weighted imaging. ADC measurements revealed that the mean ADCs of well-, moderately, and poorly differentiated HCCs were approximately 1.45, 1.46, and 1.36 x 10(-3) mm(2)/s, respectively. There was no significant correlation between ADC and histopathologic grade. CONCLUSION The histopathologic grade of HCC had no correlation with the ADC, but HCC tumors tended to show a higher signal on DWI as the histopathologic grade rose. However, predicting the correct histopathologic grade of each HCC before surgery on the basis of DWI findings was difficult because of the large overlap among histopathologic grades.

Measurement of the apparent diffusion coefficient in the liver: is it a reliable index for hepatic disease diagnosis?

PurposeThe aim of this study was to determine the validity of the hepatic apparent diffusion coefficient (ADC) measurement. The influence of differences in measured location and administration of Buscopan (hyoscine butylbromide) for ADC were assessed.Materials and methodsSENSE-DWI (b = 0, 500) was obtained before and after Buscopan administration to 30 patients suspected of having a liver tumor. In this sequence, respiration gating was employed, but cardiac triggering was not. ADC measurement was performed in the hepatic parenchyma of both right and left lobes in selected slices. A statistical analysis was performed to estimate the correlation among ADC, measured location, Buscopan, and pulse rate. The images were visually evaluated to categorize the subcardiac signal loss in the left lobe.ResultsThe ADC showed higher values in the left lobe than in the right lobe in both pre- and postloaded studies (P < 0.001). In a comparison between ADCs in the pre- and postloaded studies, the differences were not significant in the left lobe (P = 0.93) or the right lobe (P = 0.41). No correlation was noted between ADCs and the pulse rate. Visual evaluation revealed that the subcardiac signal loss was more prominent in the postloaded study.ConclusionADC measurement of the left hepatic lobe was far more incorrect than that of the right lobe if cardiac gating was not employed. The administration of Buscopan worsened the image quality of the left lobe and made visual evaluation difficult.

Radiofrequency Ablation of the Liver: Determination of Ablative Margin at MR Imaging with Impaired Clearance of Ferucarbotran—Feasibility Study

Institutional review board approval and informed consent were obtained. The feasibility of magnetic resonance (MR) imaging with impaired clearance of ferucarbotran to visualize ablated liver parenchyma surrounding a tumor (ablative margin [AM]) was evaluated after radiofrequency (RF) ablation of the liver. Twenty-one patients with hepatocellular carcinomas underwent RF ablation 2-7 hours after ferucarbotran-enhanced MR imaging. On unenhanced T2*-weighted images acquired after 3-5 days, AMs appeared as hypointense rims. The AM status was related to incidence of residual or recurrent tumors. This technique is feasible for visualization of AM and prediction of residual or recurrent tumors after RF ablation of the liver.

Comparison of diffusion-weighted images using short inversion time inversion recovery or chemical shift selective pulse as fat suppression in patients with breast cancer

PurposeFat suppression is essential for diffusion-weighted imaging (DWI) in the body. However, the chemical shift selective (CHESS) pulse often fails to suppress fat signals in the breast. The purpose of this study was to compare DWI using CHESS and DWI using short inversion time inversion recovery (STIR) in terms of fat suppression and the apparent diffusion coefficient (ADC) value.Materials and methodsDWI using STIR, DWI using CHESS, and contrast-enhanced T1-weighted images were obtained in 32 patients with breast carcinoma. Uniformity of fat suppression, ADC, signal intensity, and visualization of the breast tumors were evaluated.ResultsIn 44% (14/32) of patients there was insufficient fat suppression in the breasts on DWI using CHESS, whereas 0% was observed on DWI using STIR (P < 0.0001). The ADCs obtained for DWI using STIR were 4.3% lower than those obtained for DWI using CHESS (P < 0.02); there was a strong correlation of the ADC measurement (r = 0.93, P < 0.001).ConclusionDWI using STIR may be excellent for fat suppression; and the ADC obtained in this sequence was well correlated with that obtained with DWI using CHESS. DWI using STIR may be useful when the fat suppression technique in DWI using CHESS does not work well.

A novel preoperative fusion analysis using three-dimensional MDCT combined with three-dimensional MRI for patients with hilar cholangiocarcinoma

The purpose of the present study was to evaluate the anatomical relationship between the tumor, portal veins, hepatic arteries, and hilar hepatic ducts at the hepatic hilum using a novel preoperative fusion analysis for patients with hilar cholangiocarcinoma. This involved combining three-dimensional multidetector-row computed tomography with three-dimensional magnetic resonance imaging. This novel fusion imaging technique can play an important clinical role for patients undergoing surgery for hilar cholangiocarcinoma.

Usefulness of MR imaging of the parotid glands in patients with secondary Sjögren's syndrome associated with rheumatoid arthritis

Abstract Objective. To assess the correlation between MR imaging (MRI) of parotid glands with X-ray sialography, histopathology of the labial salivary glands, and salivary secretion, in patients with secondary Sjögrens syndrome (SS) associated with rheumatoid arthritis (RA). Methods. Non-contrast MRI of the parotid glands was performed in 13 secondary SS patients associated with RA who satisfied the revised Japanese diagnostic criteria for SS (1999), and the ACR/EULAR classification criteria for RA (2010). The MRI findings were classified according to the degree of high-intensity signal on T1-weighted images (T1WI) and short inversion time inversion recovery (STIR) images into five grades (0–4), using the modified Nagasaki University grading method. The results of MRI grading were compared with the Rubin and Holt staging of X-ray sialography (0–4), the Greenspan grading of labial salivary gland histopathology (0–4), and salivary secretion by the gum test (ml/10 min). Results. All 13 patients were females, with a mean age of 50.2 ± 11.3 years. According to the MRI grading, 3 patients were Grade 1, 5 were Grade 2, 5 were Grade 3, and none was Grade 0 or Grade 4. The mean stage by X-ray sialography was 1.7 ± 1.0, the mean grade by histopathology was 2.4 ± 1.2, and the mean volume of salivary secretion was 9.7 ± 3.9 ml. The MRI grading correlated significantly with the Rubin and Holt staging and Greenspan grading (P < 0.01 each, Spearmans rank correlation), and significantly and inversely with the results of the gum test (P < 0.05). Conclusion. The results suggest that MRI of the parotid glands is a useful noninvasive tool for evaluating destruction and inflammation in the salivary glands.

Pancreatic cancer screening employing noncontrast magnetic resonance imaging combined with ultrasonography

PurposeWe have conducted an initial evaluation on the potential of combining noncontrast magnetic resonance imaging (MRI) and ultrasonography (US) to screen for pancreatic cancer.Materials and methodsAn independent ethics committee approved this study. A total of 2511 patients who underwent US were enrolled. Among them, noncontrast MRI was performed in patients in whom the entire pancreas was difficult to depict or in those with USsuspected pancreatic lesions. In total, using 1.5-T MRI, T1- and T2-weighted imaging, magnetic resonance cholangiopancreatography, and diffusion-weighted imaging, we acquired a variety of images. The efficacy of US and MRI in screening for pancreatic lesions, including pancreatic cancer, was evaluated.ResultsOf 2511 patients, 184 underwent MRI, and the pancreas was demonstrated in all of them. Among the 2511, five pancreatic cancers were detected by MRI combined with US (detection rate 0.20%). Of the five pancreatic cancers, three were detected by US (detection rate 0.12%) and two by MRI. Four of the five pancreatic cancers were resectable.ConclusionBy combining noncontrast MRI with US, pancreatic cancer can be detected with high accuracy. Other pancreatic lesions that require follow-up, including intraductal papillary mucinous neoplasms, can also be detected. Thus, pancreatic cancer screening with a combination of US and MRI is suggested.

Thymic MALT lymphoma MR imaging findings and their correlation with histopathological findings on four cases

There has been no report on the MRI findings of primary thymic MALT lymphoma. We report the correlation between MRI findings and histopathology in four cases of this entity. While primary thymic MALT lymphomas exhibited diverse characteristics, the cystic components inside, which were clearly depicted on T2-weighted images, were considered to be pathognomonic. Primary thymic MALT lymphoma should be considered as one of the differential diagnoses of anterior mediastinal tumors having multilocular cysts that arise in patients with immunological abnormalities.

Feasibility of diffusion-weighted imaging under split breath-hold acquisition and postprocessing (DWI-SBAP): an attempt to suppress hepatic pseudo-anisotropy

PurposeTo suppress hepatic pseudo-anisotropy, which is a specific artifact in diffusion-weighted imaging (DWI) of the liver obtained under respiratory triggering, the authors developed a novel acquisition technique for DWI that we termed “diffusion-weighted imaging under split breath-hold acquisition and postprocessing” (DWI-SBAP). We evaluated its feasibility in this study.Materials and methodsOf 113 patients whose hepatic DWI under respiratory triggering (RT-DWI) showed prominent hepatic pseudo-anisotropy, 35 were included in the study. DWI-SBAP was additionally performed in these patients. Two radiologists visually evaluated the RT-DWI and DWI-SBAP from the viewpoints of the degree of pseudo-anisotropy and the image quality of trace images of both sequences. During evaluation of the image quality of trace images, both pseudo-anisotropy and slice misregistration artifacts were taken into consideration.ResultsThe pseudo-anisotropy seen was significantly lower in DWI-SBAP than that in RT-DWI. Regarding visual evaluation of the trace images, the image quality of DWI-SBAP was superior to that of RT-DWI, although misregistration artifacts were observed in DWI-SBAP trace images of two patients.ConclusionDWI-SBAP is a feasible technique for obtaining fine abdominal DWI and is effective in suppressing hepatic pseudo-anisotropy. To use this sequence in the clinical scenario, we believe it is necessary to develop a method of generating apparent diffusion coefficient maps and simultaneous use of slice tracking techniques.

Organ Atrophy Induced by Sorafenib and Sunitinib - Quantitative Computed Tomography (CT) Evaluation of the Pancreas, Thyroid Gland and Spleen.

Summary Background To evaluate organ atrophy induced by sorafenib and sunitinib, we retrospectively reviewed the CT scans of renal cell carcinoma (RCC) patients receiving molecular targeted therapy (MTT) using sorafenib or sunitinib, and performed volumetric analysis of the pancreas, thyroid gland, and spleen. Material/Methods Thirteen RCC patients receiving MTT were assigned as the evaluation cases (MTT group), while thirteen additional RCC patients not receiving MTT were retrieved as the Control group. We evaluated the baseline and follow-up CT studies. The volume of the three organs estimated by CT volumetry was compared between the baseline and follow-up CTs. The atrophic ratio of the organ volume in the follow-up CT to that in the baseline CT was calculated, and compared between the MTT and Control groups. Results All measured organs in the MTT group showed statistically significant volume loss, while no significant change was observed in the Control group. Mean atrophic ratio in the MTT group was 0.74, 0.58, and 0.82 for the pancreas, thyroid and spleen, respectively. The differences in atrophic ratios between both groups were all statistically significant (P<0.05). Conclusions Single-agent sorafenib or sunitinib therapy induced statistically significant atrophy in the pancreas, thyroid, and spleen.