Abstract TP340: Imaging Related Radiation Dose and Cancer Risk Assessment of Brain in Acute Ischemic Stroke Patients

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Background and aims: Recently, safety concerns were raised about the radiation dose for acute ischemic stroke (AIS) patients undergoing computed tomography (CT), CT angiography (CTA) and CT perfusion (CTP). We evaluated precise radiation dose to the brain during various imaging studies in our AIS patients.

Methods: Brain imaging was performed with 64-detector row CT scanner (Phillips-iCT256) using standard protocols recommended by American Association of Physicist in Medicine. For each procedure, volume weighted CT dose index (CTDIvol, mGy) and dose-length product DLP (mGy.cm) were obtained from dose reports generated at the time of acquisition. Organ specific dose to brain, eye, bone marrow and thyroid were also obtained. The estimates of cancer risk were interpolated.

Results: In this prospective study, a total of 18 patients who underwent CT, CTA as well as CTP were included. Mean DLP for non-enhanced CT, CTA and CTP were 1068.25, 1150 and 1197 mGy.cm, respectively. Corresponding whole body effective dose for the CT, CTA and CTP were calculated as 2.57, 2.6, 2.4 mSv, respectively. Cumulative doses to the brain, eyes, bone marrow and thyroid gland were 33.81, 32.8, 1.21 and 1.31 mGy for the non-contrast brain CT. CTDIvol measurements for different protocols tested by the phantom were in agreement with values given in dose reports.

Conclusions: The effective radiation doses are less than previously reported and much below the radiation threshold level for deterministic effects for brain and optic lens (500-2000mGy). Estimated life-time attributable cancer risks are very low with the current radiation doses.

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