Chulalongkorn Medical Journal


Background : The 320- detector row CT scanner with a larger z-coverage (16 cm) competently enables whole brain imaging that is need for patients who are been requested for comprehensive stroke imaging with axial volume mode which exposes the patient to a relatively high dose of radiation. Objective : The purpose of the study is to determine the radiation dose on whole brain computed tomography in comprehensive stroke imaging using Axial Volumetric 320-detector MDCT. Designs : Observational retrospective study. Setting : Advanced Diagnostic Imaging Center (AIMC), Ramathibodi Hospital, Bangkok. Material and Method : The collected data include scan parameters and radiation doses for CT perfusion of the brain examination in comprehensive stroke imaging using the combo protocol in axial volume mode. The effective dose, E, is determined and compared with other studies. Twenty-one patients, 11males and 10 females, with their age range of 6 - 77 years and mean age of 45.4 years were studied. Results : Range of cumulative radiation dose for CTDIvol, DLP and E were 142.9 - 313.4 mGy, 2286.6 - 5014.2 mGy.cm and 4.8 - 10.5 mSv respectively. The cumulative dose, average dose, and average dose per volume scan of CTDIvol, DLP and E were 200.5, 40.8 and 10.7 mGy; 3206.8, 652.6 and 171.3 mGy.cm and 6.7, 1.4, and 0.4 mSv consecutively. Conclusions : The high radiation dose in this study resulted from large z-coverage of axial volume mode, high tube current and large number of total volume scans. The data were compared with DRLs and other studies for the setup of the dose reduction protocols appropriate for various age and groups of the patients size in future study. Although the high radiation dose is one of the main concerns, this investigation resulted in the elimination of the brain coverage limitation. The lower settings on scan parameters can reduce the volume of the contrast media and the acquisition time.



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