Jenny K. Hoang MBBS, Presenter: Nothing to Disclose

Robert E. Reiman MD, Abstract Co-Author: Nothing to Disclose

Giang Huong Nguyen MD, PhD, Abstract Co-Author: Nothing to Disclose

Natalie Januzis, Abstract Co-Author: Nothing to Disclose

Carolyn R. Lowry BS, Abstract Co-Author: Nothing to Disclose

Bennett B. Chin MD, Abstract Co-Author: Nothing to Disclose

Terry T. Yoshizumi PhD, Abstract Co-Author: Nothing to Disclose

The aim of this study was to measure the effective dose and organ doses for parathyroid 4DCT and sestamibi scintigraphy, and to estimate the lifetime attributable risk (LAR) of cancer incidence based on the measured radiation doses.

We measured the organ radiation doses for 4DCT and sestamibi scintigraphy (with SPECT-CT) based on scanning with our institution’s protocols. An anthropomorphic phantom with MOSFET detectors was scanned to measure radiation dose from CT. Organ doses from the radionuclide for scintigraphy were based on NUREG/CR-6345. Effective dose was calculated for 4DCT and scintigraphy, and used to estimate the LAR of cancer incidence for patients differing in age and gender with the approach established by the Biologic Effects of Ionizing Radiation VII report. A 55-year-old female was selected as the standard patient based on demographics of patients with primary hyperparathyroidism.

The organs that received the highest radiation dose for 4DCT were the thyroid (150 mGy), salivary glands (137 mGy) and the esophagus (87 mGy). For sestamibi scintigraphy, the highest organ doses were to the colon (42 mGy), gall bladder (35 mGy) and the kidneys (32 mGy). The effective dose was 26 mSv for 4DCT compared to 12 mSv for sestamibi scintigraphy. The baseline lifetime incidence of any cancer in the unexposed standard patient.was 46438/100,000. In the exposed patient, the LAR for cancer incidence was 172/100,000 for 4DCT and 66/100,000 for sestamibi scintigraphy. This resulted in an increase in lifetime incidence of cancer over baseline risk of 0.46% for 4DCT and 0.18% for sestamibi scintigraphy. In a 25-year-old female (nonstandard) the increase in the lifetime incidence of cancer over baseline risk was higher at 0.94% for 4DCT and 0.36% for sestamibi scintigraphy.  

Effective dose from 4DCT is double that of sestamibi scintigraphy, but both studies cause negligible increases in lifetime risk of cancer. Clinicians should not allow concern for radiation-induced cancer influence decisions regarding workup in older patients with primary hyperparathyroidism. In younger women, 4DCT should not be the first-line imaging modality given a substantially higher LAR from 4DCT compared to scintigraphy.

Clinicians should not allow concern for radiation-induced cancer influence decisions regarding workup in older patients (≥ 55 years) with primary hyperparathyroidism.

Hoang, J, Reiman, R, Nguyen, G, Januzis, N, Lowry, C, Chin, B, Yoshizumi, T, Lifetime Attributable Risk of Cancer from Radiation Exposure during Parathyroid Imaging: Comparison of 4DCT and Sestamibi Scintigraphy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14009866.html