Biomedical subjects

Katsuhiro Nasu

Publications and source records attributed to Katsuhiro Nasu.

11 recordsLinked to original sources

PubMed2006

Hepatic metastases: diffusion-weighted sensitivity-encoding versus SPIO-enhanced MR imaging.

PURPOSE: To retrospectively compare accuracy of diffusion-weighted (DW) single-shot echo-planar imaging with sensitivity encoding (SENSE) with that of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging in the evaluation of hepatic metastases due to extrahepatic malignancies. MATERIALS AND METHODS: Patients provided informed consent; ethics committee approval was not required. The data of 24 patients (16 men, eight women; age range, 41-68 years; mean age, 61.9 years) with 40 resected hepatic metastases were retrospectively reviewed. Before SPIO administration, DW SENSE imaging and T2-weighted fast spin-echo (SE) and T1-weighted dual-echo fast field-echo (FFE) MR imaging were performed. After SPIO administration, T2-weighted fast SE, T1-weighted dual-echo, and T2*-weighted FFE MR examinations were performed. Images were divided into two sets: The SPIO-enhanced MR image set consisted of pre- and postcontrast T2-weighted fast SE and dual-echo T1-weighted FFE images and postcontrast T2*-weighted FFE images. The DW SENSE image set included DW SENSE images and precontrast T2-weighted fast SE and dual-echo T1-weighted FFE images. Three radiologists individually interpreted these images and sorted the confidence levels for presence of hepatic metastasis in each section into five grades. Area under the receiver operating characteristic (ROC) curve (A(z)) was calculated for each image set. RESULTS: Hepatic metastases showed higher signal intensity on DW SENSE images than on T2-weighted fast SE images. Conversely, signals from vessels and cysts were suppressed with DW SENSE imaging. ROC analysis showed higher A(z) values when the DW SENSE image set was interpreted (0.90) than when the SPIO-enhanced MR image set was interpreted (0.81). The sensitivity and specificity, respectively, of total cases were 0.66 and 0.90, for the SPIO-enhanced MR image set and 0.82 and 0.94 for the DW SENSE image set. During SPIO-enhanced MR image interpretation, lesions 1 cm in diameter or smaller showed significantly lower sensitivity than lesions larger than 1 cm in diameter. During both interpretation sessions, left lobe lesions showed significantly lower sensitivity than right lobe lesions. CONCLUSION: Combined reading of DW SENSE images and T2-weighted fast SE and dual-echo T1-weighted FFE MR images showed higher accuracy in the detection of hepatic metastases than did reading of SPIO-enhanced MR images.

Adult↗

PubMed2006

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

PURPOSE: The 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 METHODS: SENSE-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. RESULTS: The 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. CONCLUSION: ADC 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.

Adult↗

PubMed2006

The effect of simultaneous use of respiratory triggering in diffusion-weighted imaging of the liver.

OBJECTIVE: To determine the effect of simultaneous use of respiratory triggering in hepatic diffusion-weighted imaging (DWI), we compared DWI with respiratory triggering (RT-DWI) and DWI under free breathing (FB-DWI) in terms of relative contrast between hepatic tumor and surrounding liver parenchyma, apparent diffusion coefficient (ADC) measurement, and frequency of respiratory misregistration. MATERIALS AND METHODS: Thirty patients (21 men, 9 women, aged 25 to 80 years) with liver metastasis or hepatocellular carcinoma in the right hepatic lobe were examined with RT- and FB-DWI. In patients having multiple tumors, up to 3 lesions were selected by mutual agreement of 2 diagnostic radiologists. Finally, 59 nodules were selected for evaluation. Relative contrast ratio (RCR) between the lesions and surrounding parenchyma and ADC were measured in each hepatic lesion in each sequence. The differences in RCR and ADC between RT- and FB-DWI were statistically analyzed using Wilcoxon's signed rank test. The frequency of respiratory misregistration advents in each sequence was visually evaluated by the 2 diagnostic radiologists and assessed using McNemar's test. RESULTS: RCRs were significantly higher in RT- than in FB-DWI (P<0.001). The difference in ADC between the 2 sequences was not significant. However, ADCs tended to be more scattered in FB- than in RT-DWI. The frequency of respiratory misregistration advents was significantly higher in FB- than in RT-DWI. CONCLUSION: FB- was inferior to RT-DWI in both contrast between tumors and surrounding liver parenchyma and in accuracy of ADC measurement as far as the numbers of excitation in each sequence were the same. For preoperative examination of hepatic resection, RT- is more suitable than FB-DWI.

Adult↗

PubMed2004

Optimization of Gd-DTPA-enhanced balanced turbo field echo sequence in abdominal imaging: a basic study.

PURPOSE: To determine the optimum imaging conditions for the balanced turbo field echo (bTFE) sequence in abdominal imaging, we performed phantom experiments and scanning of a normal volunteer while noting the correlation among signal intensity, k-space ordering, flow velocity and Gd-DTPA concentration. MATERIALS AND METHODS: Initially, the abdomen of a healthy volunteer and some samples (water, blood and bovine albumin solutions with various Gd-DTPA concentrations, and olive oil) were examined with the bTFE sequence under various conditions to define the correlation among signal intensity, k-space ordering and Gd-DTPA concentration. Another experiment was performed to assess the correlation between the flow velocity and Gd-DTPA concentration. With the centric-bTFE sequence, we measured the signal intensity of water samples having various Gd-DTPA concentrations flowing in a long tube with an internal diameter of 4 mm. RESULTS: The experiments revealed the following issues: (i) The contrast of bTFE images was much influenced by k-space ordering; (ii) Gd-DTPA did not exhibit an overt enhancement effect in water and blood under stable conditions; (iii) The signal intensity of moving water decreased in centric-bTFE images, and this signal drop became more significant as the fluid speed increased; and (iv) Gd-DTPA decreased the range of signal loss in the moving fluid; however, this effect had no correlation with Gd-DTPA concentration. CONCLUSION: When the bTFE sequence was employed for abdominal imaging, centric view ordering, fat suppression and Gd-DTPA contrast enhancement were assumed to be necessary.

Abdomen↗

PubMed2004

Optimization of Gd-DTPA-enhanced balanced turbo field echo sequence in abdominal imaging: clinical application.

PURPOSE: We performed MRI examinations of patients in order to confirm the enhancement effect of the balanced turbo field echo (bTFE) sequence with centric view ordering and SPIR (SPIR-centric-bTFE) as mentioned in the prior paper, and to evaluate the actual image quality of this sequence. MATERIALS AND METHODS: The upper abdomens of 30 patients with various abdominal disorders were examined with the SPIR-centric-bTFE sequence before and after Gd-DTPA administration. To assess the enhancement effect of Gd-DTPA, ROI measurements were taken in the aorta, superior mesenteric artery, portal vein, liver and bile juice in the common bile duct in each patient both in pre- and postcontrast images. Visual evaluations were also carried out in order to depict the peripheral vessels in the peritoneal fat and the apparent brightness of the soft-tissue organs. RESULTS: In all patients, the signal of the arteries after Gd-DTPA administration increased by about 50% compared with precontrast images. On the other hand, the veins and the liver showed a signal gain of less than 20% in postcontrast images. Consequently, only the signal of the arteries appeared enhanced in the postcontrast images. The visual evaluation revealed that postcontrast SPIR-centric-bTFE acquisition can depict the thin vessels clearly and the abdominal soft-tissue organs brightly. CONCLUSION: The balanced turbo field echo sequence with centric view ordering and SPIR after Gd-DTPA injection was considered the most appropriate protocol when this sequence was employed for abdominal imaging.

Blood Flow Velocity↗

PubMed2004

Diffusion-weighted imaging of breast cancer with the sensitivity encoding technique: analysis of the apparent diffusion coefficient value.

PURPOSE: The usefulness of diffusion-weighted imaging (DWI) in the field of neuroradiology has been established. Despite its high contrast resolution, DWI has the disadvantages of susceptibility artifact and chemical shift artifact. We performed DWI of breast cancer with the sensitivity encoding (SENSE) technique. METHODS: The subjects were 60 female patients with breast mass. All patients underwent MRI including SENSE-DWI and were diagnosed histologically. Of these patients, 55 were diagnosed with breast cancer and the remaining five were diagnosed with benign mass. The histological diagnoses of breast cancer were as follows: 39 cases of invasive ductal carcinoma (IDC); 11 cases of IDC with a predominant intraductal component and non IDC (pure or predominant NIDC); and five cases of special types of cancer. The MR system used was a Gyroscan Intera 1.5T (Philips Medical Systems). In addition to routine MRI for breast cancer, including contrast-enhanced dynamic, SENSE-DWI was obtained. The accuracy of the positional information of SENSE-DWI was visually compared with that of conventional images. The apparent diffusion coefficient (ADC) values of breast mass were analyzed with SENSE-DWI. RESULTS: The accuracy of positional information was adequate for diagnosing of all patients. The mean ADC value of breast cancer was 1.021x10(-3) mm2/s and that of benign mass was 1.488x10(-3) mm2/s (p=0.0002). The mean ADC value of IDC was 0.968x10(-3) mm2/s and that of pure or predominant NIDC was 1.218x10(-3) mm2/s (p=0.0011). CONCLUSION: SENSE-DWI was of sufficient quality to support diagnosis of breast mass. SENSE-DWI may permit the acquisition of more detailed information about lesions, including tumor cellularity, that is difficult to obtain with conventional techniques.

Artifacts↗

PubMed2004

Diffusion-weighted single shot echo planar imaging of colorectal cancer using a sensitivity-encoding technique.

BACKGROUND: We wanted to determine the feasibility of diffusion-weighted single shot echo planar imaging using a sensitivity-encoding technique (SENSE-DWI) in depicting colorectal cancer. METHODS: Forty-two patients with sigmoid colon cancer and rectal cancer, all proven pathologically, were examined on T2-turbo spin echo (TSE) and SENSE-DWI. No bowel preparation was performed before examination. The b-factors used in SENSE-DWI were zero and 1000 s/mm(2). In 10 randomly selected cases, the images whose b-factors were 250 and 500 s/mm(2) were also obtained. The reduction factor of SENSE was 2.0 in all sequences. Two radiologists evaluated the obtained images from the viewpoints of tumor detectability, image distortion and misregistration of the tumors. The apparent diffusion coefficients (ADCs) of the tumors and urine in the urinary bladders in each patient were measured to evaluate the correlation between ADC and pathological classification of each tumor. RESULTS: All tumors were depicted hyperintensely on SENSE-DWI. Even though single shot echo planar imaging (EPI) was used, the image distortion and misregistration was quite pronounced because of simultaneous use of SENSE. On SENSE-DWI whose b-factor was 1000 s/mm(2), the normal colon wall and feces were always hypointense and easily differentiated from the tumors. The mean ADC value of each tumor was 1.02 +/- 0.1 (x 10(-3)) mm(2)/s. No overt correlation can be pointed out between ADC and pathological classification of each tumor. CONCLUSION: SENSE-DWI is a feasible method for depicting colorectal cancer. SENSE-DWI provides strong contrast among colorectal cancers, normal rectal wall and feces.

Adult↗

PubMed2004

[Evaluation of pancreatic cancer extent using balanced turbo field echo (bTFE)].

PURPOSE: Recent advances in MR system technology have allowed for the development of new imaging techniques. Balanced turbo field echo (bTFE) is one such example. The purpose of this study was to evaluate the usefulness of bTFE for evaluating pancreatic cancer extent. MATERIALS AND METHODS: 45 patients with pathologically proven pancreatic cancer were examined with bTFE. The images obtained were evaluated by the consensus of two radiologists, from the following viewpoints: tumor detection and vascular invasion, e.g., celiac axis (CA); superior mesenteric artery (SMA); portal vein (PV); and splenic artery (SA). The results of vascular evaluation were compared with those of dynamic CT. RESULTS: All tumors were demonstrated on bTFE images, however, tumors in the pancreatic head were less clear than those in the pancreatic body. Vascular evaluation on bTFE images was in good agreement with that on dynamic CT scan. CONCLUSION: bTFE is a useful method for evaluating pancreatic cancer extent. Because image quality does not show overt changes in this sequence as time passes, unlike so-called dynamic study, not only are divided scans or respiration-trigered scans available, but repeated scans and multi-directional image acquisition can be performed as well.

Adult↗

PubMed2002

Efficacy of MR mammography (MRM) in providing preoperative locoregional information on breast cancer: correlation between MRM and histological findings.

RATIONALE AND OBJECTIVES: To assess the efficacy of MRM in providing preoperative locoregional information on patients with breast cancer. METHODS: MRI was performed on 62 female breast cancer patients. A 1.5T MR-system was used to acquire fat-suppressed T(1)WI, T(2)WI and dynamic-contrast-enhanced images with an SPGR pulse sequence. The extent of the cancer measured with MRM was confirmed histologically in all patients. RESULTS: The size obtained from MRM correlated well with the size obtained histologically, including intraductal spread of cancer (R: 0.853). As for shape, the round/oval type evident from MRM correlated more accurately (R: 0.934) than the ill-defined type associated with a linear and/or clumped enhanced area (R: 0.744). The difference between the size obtained from MRM and the size obtained histologically, including IDS, was less than 15 mm in the majority of patients (93.5%). CONCLUSIONS: MRM accurately reveals the extent of cancer, including IDS, and is effective at providing preoperative locoregional information for breast-conserving therapy for breast cancer.

Adult↗

PubMedDate not supplied

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.

Adult↗

PubMedDate not supplied

Positron emission tomography with F-18 fluorodeoxyglucose in evaluating colorectal hepatic metastasis down-staged by chemotherapy.

BACKGROUND: The efficacy of positron emission tomography with 18F fluoro-2-deoxy-D-glucose (FDG-PET) is obscure in evaluating viability or the extent of colorectal hepatic metastasis (CHM), down-staged by chemotherapy. PATIENTS AND METHODS: A retrospective lesion-by-lesion analysis was performed for seven consecutive patients, who had received rescue hepatectomy for initially unresectable CHM, in order to evaluate the correlation between results of imaging modalities and the corresponding pathology. RESULTS: The sensitivity and positive predictive value of the conventional modalities (CT and MRI) were 92% and 42%, respectively, while the sensitivity, specificity, positive predictive value and negative predictive value of FDG-PET were 58%, 100%, 100% and 75% respectively. The sensitivity of FDG-PET was 100% in evaluating the viability of tumors >2 cm, however, this fell to 17% in tumors <2 cm. CONCLUSION: FDG-PET is effective in assessing the viability of tumors >2 cm, but not those <2 cm, in patients with CHM down-staged by chemotherapy.

Adult↗