Maria Vittoria Spampinato MD, Abstract Co-Author: Nothing to Disclose

Walter Huda PhD, Presenter: Research support, Siemens AG

Dennise Magill BS, ARRT, Abstract Co-Author: Nothing to Disclose

To estimate thyroid doses, and corresponding cancer risks, to pediatric patients undergoing neck CT examinations.

Data was acquired on 78 consecutive patients undergoing neck CT examinations with ages ranging from newborns to 19 years. For each patient, we recorded demographic data (age and sex) as well as the average CTDIvol value (mGy) used to perform the CT examination. CTDIvol data were used to estimate the corresponding thyroid dose in the mathematical anthropomorphic phantom used in the ImPACT Patient CT Dosimetry Calculator. Patient doses were obtained by modeling the patient and phantom neck regions as mass equivalent water cylinders. A patient size dependent correction factor was obtained using published relative dose data as a function of water cylinder size.

The mean patient age was 8 ± 5 years. The mean water cylinder diameter that modeled the patient’s neck was 14 ± 4 cm. The mathematical anthropomorphic phantom has a neck that is 16.5 cm diameter, and for a constant CT exposure would have thyroid doses that are 17% lower than the average pediatric patient. CTDIvol were approximately independent of patient age and sex, with an average of 13 ± 7 mGy. Mean thyroid doses were 37 mGy for infants, and 30 mGy for teenagers. For infant females, thyroid cancer risk were approximately 0.4%, and fell to 0.05% for teenagers. Cancer risk for males were 0.03% for infants, and fell to 0.01% for teenagers.

The thyroid cancer risk is 7 times higher in females compared to males, and 4 to 8 times higher in one year olds than that in 16 year olds for males and females respectively.

Understanding pediatric thyroid organ dose in neck CT examinations and its relation to the incident thyroid cancer risk is vital to maximizing imaging benefits and minimizing radiation risk.

Spampinato, M, Huda, W, Magill, D, Thyroid Doses and Risks to Pediatric Patients Undergoing Neck CT Examinations.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9005764.html