Radiation exposure associated with dedicated renal mass computed tomography protocol: impact of patient characteristics.

BACKGROUND AND PURPOSE: Renal mass protocol CT (RMP-CT) using multiphase abdomen and pelvis CT imaging is the mainstay for diagnosis, characterization, and follow-up for renal masses; however, it is associated with ionizing radiation to the patient. We sought to quantify the effective dose associated with RMP-CT and to determine how patient factors affect radiation exposure. MATERIAL AND METHODS: We retrospectively reviewed the records of 247 patients undergoing management of a small renal mass (cT1a) between 2005 and 2011 at our institution. Body mass index (BMI) was categorized as normal weight, overweight, obese, and morbidly obese (≤25, 25.1-30, 30.1-35 and >35, respectively). Effective dose of RMP-CT was calculated through the dose-length-product multiplied by a factor coefficient (0.015). Effective doses in milliSieverts (mSv) were correlated to patient characteristics. RESULTS: Patients' median age was 61 years, and median BMI was 28.7 kg/m(2); 72% were Caucasian and 56% were male. Median effective dose was 26.1 mSv (interquartile range 20.6-35.3). When stratified by BMI, the median effective doses were 18.9, 25.2, 27.7, and 36.2mSv for normal weight, overweight, obese, and morbidly obese patients, respectively. On multivariable analyses, BMI and male sex were significantly associated with increased radiation dose. CONCLUSIONS: In this series, the median effective dose for RMP-CT was 26.1 mSv. Obesity was independently associated with markedly increased radiation exposure, with morbidly obese patients being exposed to almost twice the amount of radiation compared with normal weight persons. These findings should be considered when devising management strategies in patients with a renal mass and strategies should be developed to reduce medical ionizing radiation exposure.

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