Biomedical subjects

Y Korogi

Publications and source records attributed to Y Korogi.

147 records · Page 9Linked to original sources

PubMedDate not supplied

Value of magnetization transfer contrast in intracranial enhancing and nonenhancing lesions with paramagnetic contrast agents.

PURPOSE: To evaluate normal brain structures and various brain lesions by magnetic resonance (MR) imaging with magnetization transfer (MT) under the use of paramagnetic contrast agents. METHODS: T1-weighted MR images were obtained before and after the administration of gadopentetate dimeglumine with and without MT in 125 lesions of 61 patients. Normal brain structures and various brain lesions were evaluated by means of MT ratios (MTR) and contrast-to-noise ratios (C/N). RESULTS: Among normal structures, the white matter had a larger MTR than the gray matter, and no significant difference in MTRs was noted between pre- and postcontrast T1-weighted images. The MTRs were smaller in both enhancing and nonenhancing lesions than in the white matter. For most enhancing lesions, the MT technique increased the C/N on postcontrast images, whereas it decreased them on precontrast images. Improvement in C/N was observed on precontrast images in some gliomas as well as white matter lesions such as tuberous sclerosis and multiple sclerosis. CONCLUSION: The MTC method improves conspicuity and detection of intracranial enhancing lesions with use of paramagnetic contrast agents. Although the MTC method does not replace the conventional method, it is useful for detecting small enhancing lesions and for evaluating some nonenhancing lesions.

Adolescent↗

PubMedDate not supplied

Determination of the optimal pulses in MR imaging with magnetization transfer contrast at 7 Tesla.

OBJECTIVE: The magnetization transfer contrast (MTC) effect depends on the shape, duration, amplitude, and offset frequency of the saturation pulse. In the present study, we investigated optimal combinations of these four parameters in vitro. METHODS: All experiments were performed with a 7.05 Tesla MR system, and the spin echo technique (TR 500/TE 30) was adopted. We used a simple phantom composed of 1% agar and water, representing restricted and free proton pools, respectively. Signal intensity changes were measured in the agar (Ma) and water (Mw), when the shape, duration, magnitude, and offset frequency of the saturation pulses were varied. The MTC effect was examined with the Mw/Ma ratio. RESULTS: The suppression of Mw was less with the gauss pulse than with the square and sinc pulses. The gauss pulse had the best MTC effect. The suppression of both Ma and Mw was greatest with a saturating duration of 60 msec. The MTC effect was greatest with a longer saturation pulse. The larger the amplitude, the stronger the MTC effect obtained. Mw was suppressed with an offset frequency of less than 3 kHz, and the MTC effect was greatest with an offset frequency closer to the spectrum of the free proton pool. CONCLUSION: In the present study the optimal MTC pulse at 7 Tesla is the gauss pulse with longer duration, maximal amplitude, and approximately 3 kHz off resonance.

Contrast Media↗

PubMedDate not supplied

Totally occluded iliac arteries: long-term results of percutaneous transluminal angioplasty.

PURPOSE: To evaluate the initial and long-term results of percutaneous transluminal angioplasty (PTA) for totally occluded iliac arteries. METHODS: Fifty-four occluded iliac arteries in 54 patients were treated by PTA. The mean length of the occlusions was 8.0 cm (range 0.5-24.0 cm). Patients were followed for a maximum of 124 months (mean, 56 months). RESULTS: The initial success rate was 57% (31 of 54). On follow-up study, two arteries were reoccluded, and six showed evidence of restenosis. These recurrences were observed within 20 months after PTA. The long-term results obtained by Kaplan-Meier life-table analysis revealed a 71% primary patency rate and 93% secondary patency rate for 124 months. Thirteen arteries were treated by surgical intervention, while the other arteries with unsuccessful PTA were followed conservatively because of a high risk for surgery or patients' refusal to have surgery. Major complications were recorded in 7% (4 of 54) of cases: thrombosis requiring emergent bypass surgery in one artery, and distal embolization requiring thromboembolectomy in three. CONCLUSION: Although the procedure is difficult, the long-term results suggest that PTA is an effective method and a treatment of choice for totally occluded iliac arteries.

Aged↗