Abstract 688: Risk of Radiation Induced Cancer from Cardiac CT in a Real-Life Clinical Patient Population
Previous studies on lifetime cancer risks from radiation at cardiac CT are based on extrapolation of data unrelated to medical imaging and on presumptive scan protocols but not on actual patient cohorts. We aimed to determine the realistic risk of radiation induced cancer based on a real-life clinical patient population undergoing cardiac CT. We studied 104 consecutive patients undergoing 64-slice cardiac CT (Siemens). Data were obtained on patient demographics (sex, age, weight) as well as CT technique (kV, mAs, scan length, DLP) which were used to determine median values and the 10th and 90th percentiles. Organ dose estimates were obtained using the ImPACT dosimetry spreadsheet. Organ doses were converted into patient lifetime risk of developing radiation induced fatal and non-fatal cancer using the BEIR VII approach. Patient cancer risks were adjusted taking into account patient sex, age and weight, the latter being an often neglected factor influencing radiation risk. The majority of patients (62%) were males, with a median patient age of 59 years (41–72) and a median weight of 92 kg (69–116). All scans were performed at 120 kV, and the median DLP was 1124 mGy-cm (940–1500). In normal sized patients, the organs receiving the highest radiation doses were the lung (76 mGy) and the female breasts (92 mGy). The average patient lifetime risk for developing a radiation induced cancer was 0.12%, of which 90% would be fatal. Approximately 85% of the radiation risk arises from the irradiation of the lung. Patients with an age and weight at the 10th percentile, who receive a DLP at the 90th percentile would have a cancer risk double the average value. In a typical clinical population undergoing cardiac CT patients are predominantly male, heavier set, and in their 5th–7th decade of life. In such a patient population the realistic risk of radiation induced cancer from cardiac CT is 0.12%, with the risk to the most sensitive patients being about twice this value. Thus, in a real-life clinical patient cohort the realistic risk of radiation induced cancer from cardiac CT is substantially lower than previously reported for general populations. Appropriate patient selection and indication remain the most important means for radiation protection.