[en] By the application of dynamic contrast enhanced MR imaging with use of a phased-array multicoil, excellent angiographic images can be obtained. With use of a phased-array coil, however, increased signal from subcutaneous fat may obscure the visualization of vessels. Subtraction is an effective method to suppress signals from background tissue. We evaluated the value of contrast enhanced three-dimensional high-speed gradient echo subtraction magnetic resonance angiographic imaging on a 1.5 T MR unit with evaluation of clinical data. The effect of image resolution on vessel visualization by phantoms was also evaluated. With the subtraction technique, smaller peripheral vessels were clearly visualized in comparison with the results of non-subtraction techniques. In order to obtain high resolution images, a higher signal-to-noise ratio was required. (author)

[en] Contrast agents have come increasingly into use for MR angiography for the purpose of improving flow contrast. Three-dimensional gradient echo imaging can be performed during or after administration of the contrast agent, Gd-DTPA. In this article, we review pertinent current imaging techniques from both a basic and a clinical point of view. The importance of hemodynamic considerations relevant to contrast-enhanced MR angiography is stressed. (author). 58 refs

[en] Dynamic MRI has been used to improve the detection of tumors and to make differential diagnosis. Most malignant lesions show early enhancement and early washout of contrast media on dynamic MRI, but the characterization of the tumor remains unclear. Pharmacokinetic analysis of dynamic MRI can provide information about the permeability of contrast media in the tumor that may reflect the oxygen concentration of the tumor. This information may be useful in the prediction of a tumor's response to radiation therapy. (author)

[en] T₁-weighted liver imaging using respiratory-triggered 3-dimensional Fourier transformation (3D-FT) fast gradient echo sequence at 1.5 T was compared with breath-hold gradient echo (GRE) and conventional spin echo (SE) sequences in 25 patients with focal liver lesions and 5 normal volunteers. Signal-to-noise ratio (SNR) of the liver, contrast-to-noise ratio (CNR) of the liver to spleen, and CNR of the lesion to liver were significantly higher with respiratory-triggered fast GRE than with breath-hold GRE and conventional SE. The degree of artifacts including respiratory motion and pulsation artifact was less severe on the respiratory-triggered fast GRE sequence. With this sequence, hepatic vascular anatomy was clearly visualized. We believe this new T₁-weighted imaging technique can replace previous T₁-weighted imaging sequences. (author)

[en] The staging of 15 renal pelvis and ureteral tumors were evaluated by MRI retrospectively. T2WI-HASTE and post-Gd. enhanced fast-suppressed T1WI-FLASH sequence were used. The accuracy was 80.0% in all. Each accuracy of renal pelvis carcinoma, ureteral carcinoma was 66.7%, 88.9%. MRI was valuable in diagnosis on ureteral carcinoma. MRI may be useful modality in staging of renal pelvis and ureteral carcinoma. (author)

[en] Magnetic resonance (MR) imaging was performed in 45 patients with 52 surgically proved ovarian teratomas. MR findings of these tumors were classified into three types depending on the degree of fatty proportions in the tumor. The majority of teratomas were filled with fatty tissue in the cystic cavity (n = 43, 82.7%). In 5 tumors (9.6%), fatty tissue was seen at the edge or within the cyst wall. Fatty tissue could not be seen in any part of the tumor in 4 cases (7.7%). The tumors without a fatty component on MR images tend to have fewer sebaceous glands and less fatty tissue within the cyst wall than tumors with an abundant fatty component. Demonstration of fatty tissue is pathognomonic for these tumors. However, tumors with a small amount of fatty tissue may be indistinguishable from cystic ovarian tumors on MR images. (author)

[en] A phased array multicoil represents an important technical development in MR imaging of the upper abdomen. With the use of the CP phased array coil for the reception of MR signals, a substantial improvement in signal-to-noise ratio (S/N) is achieved compared to the body coil. The S/N of the CP phased array coil in a phantom and upper abdominal studies were compared with that of the body coil. In a phantom study, S/Ns of the CP phased array multicoil were approximately 1.5 to 3.5 fold increase in comparison with the body coil. However, higher S/N was achieved at the cost of a reduced sensitive volume and with inhomogeneous sensitivity. (author)

[en] Transcatheter embolization of the hepatic artery for hepatomas was performed with the use of Gelfoam and Lipiodol-ADM in 98 patients (Gelfoam 63 patients; Lipiodol-ADM 35 patients). The cumulative one-year survival rate was 52.9 % for the Gelfoam group and 28 % for the Lipiodol-ADM group. Response to hepatic embolization was most remarkable in the nodular type; CR was obtained in five patients and PR in 31 patients (response rate: CR + PR = 57.1 %) in the Gelfoam group, with no CR and six PRs (response rate, 17.6 %) in the Lipiodol-ADM group. Alfa-feto protein (AFP) decrease of more than 50 % was observed in 78.1 % of the Gelfoam group and 40 % of the Lipiodol-ADM group. The side effects were transient and controlled with conservative treatment. Gelfoam seemed to be more effective in the treatment of hepatoma, but the damage to normal tissue was more severe with this embolic material. (author)

[en] To improve the local control of T2-stage glottic carcinomas, we performed concomitant chemoradiation therapy with UFT (uracil and tegafur) and low dose cisplatin (CDDP). The predictive value of MR findings was also evaluated. Thirty six patients with T2N0-stage glottic carcinomas were included in this study. Tumors adjacent to the thyroid cartilage on MRI were classified as adjacent'', and undetectable tumors or tumors separate from the cartilage were classified as ''intact''. Radiation therapy with 64 Gy/32 fractions was delivered by 4 MV linear accelerator. Intravenous infusion of CDDP (4 mg/m²) and oral administration of UFT (450 mg/body) were continued concomitantly from day one of irradiation for four weeks. Kaplan-Meier methods were used to estimate the time to local recurrence distribution. Differences were determined using log-rank tests for univariate analysis. No severe acute and late adverse effects (grade 3 or more) were observed. Two-year local control rate with chemoradiation therapy was 82%. According to MR findings, local control rates were 95% for intact lesions (n=20) and 68% for adjacent lesions (n=16) (p=0.0249). Concomitant chemoradiation therapy with UFT and low dose CDDP was considered to be effective for T2-stage glottic carcinomas. However, the results were not enough for tumors adjacent to the thyroid cartilage on MRI. (author)

[en] We have developed a phantom simulating various liver neoplasms for the evaluation of tissue contrast on T₂-weighted MR imaging. The phantom simulates normal liver tissue, hepatoma, hemangioma and cyst, and is composed from various amounts of agarose, copper sulfate and fat. The T₂ values of the phantom were similar to those with resected specimen and clinical studies. (author)