[The improvement in the cerebral blood flow analysis software in case of CT-perfusion inspection and the examination of the scan protocol].

In our hospital, CT-perfusion was introduced in April, 2002. It is used to diagnose, to determine what treatment to use and to prognosticate cerebral blood flow after operation in super acute period brain infarct. At the beginning of the introduction, processing time and dosage for partial areas needed improvement. Therefore, we investigated the possibility of shorter processing time and lower dosage of radiation with the help of improvement in the analysis software as well as a different scan method. Two methods of reducing radiation dosage were examined. (1) The speed of X-ray rotation was slowed down; while photon per image was maintained, total mAs was lowered. (2) Continuation scan was replaced by intermission one. Analyzing time with older and newer version of analysis software was compared. The dosage was able to decrease by 25% as a result of the rotation speed slowed down; it became further less by 50% with the intermission scan. Processing such as the vein extraction was automated by using new analysis software and successfully shorten the analysing time without damaging the reliability of analyses. We forecast that more clinical research on further lowering dosage and stabilization of analyzing will enable us to provide better information.

[Visualization of coronary artery stents by MSCT at 0.5-mm slice thickness].

Coronary artery visualization by multi-slice CT and the evaluation of coronary stenosis were examined. Multi-slice CT could not be used for evaluation after the coronary artery stent custody method. We examined various coronary artery stent custody phantoms and stent visualization of clinical examples by using multi-slice CT with a slice thickness of 0.5 mm. ECG-gated scanning was done by inputting ECG using 4DAS (Data Acquisition System) multi-slice CT with a slice thickness of 0.5 mm. We carried out image reconstruction, measured the CT number, and examined the inside stent. The CT number of the inside stent rose in accordance with stent diameter. The inside stent was visualized clearly at 0.5 mm in comparison with 1.0 mm in slice thickness. Visualization of the lumen was influenced in the Stent Custody Phantom by the quality of the stent material, Strut form, and the size of the diameter. The inside stent could be evaluated with the S670 4 mmphi stent. Form evaluation of the inside stent was possible, although the cavity in the stent was influenced by the difference in distance between peaks.