Evaluation of skin exposure during cerebral CT perfusion studies on a phantom

ObjectivesTo evaluate the skin dose during cerebral CT perfusion on a phantom, and estimate the weighted CT dose index (CTDIw) to maximum skin dose conversion factors for four types of CT scanners.Study designWe evaluated the relationship between surface dose during cerebral CT perfusion and distance from the scan center in the x–y plane using a 64-multidetector row CT scanner. Skin doses were also assessed with 4 different 64-multidetector CT scanners.ResultsThe surface doses decreased with the distance from the scan center in the x–y plane. The surface doses at the points 6 cm and 10 cm from the scan center in the x–y plane were different from the dose at the point 8 cm by about 15%. CTDIw and skin doses differed among the CT scanners (CTDIw, 143–590 mGy; averaged temporal skin dose, 126–590 mGy). For all the four types of CT scanner, the doses increased in the following order: occipital point < frontal point < temporal points. The ratios of the maximum skin dose (averaged temporal skin dose) to CTDIw differed among the CT scanners (64–100%).ConclusionsThe maximum skin dose during cerebral CT perfusion and the dose to CTDIw ratios differs among CT scanners. The CTDIw is useful for estimation of the maximum skin dose during cerebral CT perfusion using a proper conversion factor specific to each type of CT scanner.