Diagnosis of aortic diseases using multidetector computed tomography.
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Aortic Dissection↗
Biomedical subjects
Hiroya Rikimaru
Publications and source records attributed to Hiroya Rikimaru.
Time-related changes of radiofrequency ablation lesion in the normal rabbit liver: findings of magnetic resonance imaging and histopathology.
RATIONALE AND OBJECTIVES: To study time-related magnetic resonance imaging (MRI) and histopathological findings after radiofrequency ablation (RFA) in the normal liver. METHODS: Under ultrasound guidance, RFA was performed in 22 rabbits with a 15-gauge expandable probe inserted into the liver. The RF power was applied at 10 W initially with a 5-W increment every minute until RF power "roll-off" occurred. The rabbits subjected to postmortem MRI at 3 days (n = 6), 2 weeks (n = 6), 4 weeks (n = 6), and 12 weeks (n = 4) after RFA. Spin-echo (SE) T(1)-weighted image (WI) (TR/TE=500/12) and fast SE T2-WI (TR/TE= 3500/99) were obtained. The liver specimens were excised and processed for conventional histologic study. The MRI and pathologic findings were compared qualitatively and quantitatively. RESULTS: The lesion diameters measured with MRI and liver specimen were well correlated (P < 0.05). The coagulated regions presented 2 of 4 laminar patterns on T1/T2-WI 3 days after RFA, and 2 of 3 laminar patterns on T1/T2-WI 2 to 4 weeks after RFA. 12 weeks after RFA, the signal intensity in coagulated regions increased on T1-WI with a 2-laminar pattern still visible on T2-WI, the same as that of 2 to 4 weeks. The observed pathologic changes (enlarged sinusoids, marginal fibrous tissue and hepatocyte degeneration) could be responsible for the MRI laminar patterns and signal intensity changes. CONCLUSION: The time-related pathologic changes of RFA lesions in rabbit livers can be reflected as laminar patterns on MR images. Understanding of the zone structure of the lesions is useful for the evaluation of follow-up MRI.
Animals↗
Quantitative vascular measurements in arterial occlusive disease.
Accuracy in quantifying arterial occlusive disease requires an understanding of the relevant technical considerations and familiarity with the strengths and weaknesses of various imaging modalities in this setting. The degree of stenosis is evaluated in terms of diameter stenosis, which can be measured on either projection images or cross-sectional images, or area stenosis, which can be measured only on cross-sectional images. With projection images, the minimum luminal diameter should be sought on multiple images obtained at different angles. The reference site used for measurement should be noted and may be located at the level of the lesion or in a normal-looking portion of the stenotic vessel near the lesion. Multi-detector row computed tomographic (CT) angiography and magnetic resonance (MR) angiography are starting to replace digital subtraction angiography in quantifying arterial occlusive disease. CT angiography allows accurate evaluation without reducing in-plane resolution, although beam-hardening artifacts from high-attenuation structures can degrade image quality. MR angiography is useful even in cases of severe calcification but has a lower spatial resolution. Ultrasonography (US) may also be helpful in quantifying arterial occlusive disease; US analysis is almost always based on blood flow velocity measurement. Precise measurements of stenotic occlusion will help determine optimal therapy for affected patients.
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