Comparison of Effective Dose and Lifetime Risk of Cancer Incidence of Computed Tomography Attenuation Correction Acquisitions and Radiopharmaceutical Administration for Myocardial Perfusion Imaging

Objectives: To measure the organ dose and calculate effective dose from CTAC acquisitions from four commonly used gamma camera SPECT/CT systems. Method: CTAC dosimetry data was collected using thermoluminescent dosimeters on GE's Infinia Hawkeye four and single slice systems, Siemen's Symbia T6 and the Philips Precedence. Organ and effective dose from the administration of 99m Tc-tetrofosmin and 99m Tc-sestamibi were calculated using ICRP reports 80 and 106. Using this data the lifetime biological risk was calculated. Results: The Siemens Symbia gave the lowest CTAC dose (1.8 mSv) followed by the GE Infinia Hawkeye single-slice (1.9 mSv), GE Infinia Hawkeye four-slice (2.5 mSv) and Philips Precedence (3.0). Doses were significantly lower than the calculated doses from radiopharmaceutical administration (11 mSv and 14 mSv for 99m Tc-Tetrofosmin and 99m Tc-Sestamibi respectively). Overall lifetime biological risks were lower suggesting that using CTAC data posed minimal to the risk to the patient. Comparison of data for breast tissue demonstrated a higher risk than that from the radiopharmaceutical. Conclusions: CTAC doses were confirmed to be much lower than from radiopharmaceutical administration. The localised nature of the CTAC exposure compared to the radiopharmaceutical biological distribution indicated dose and risk to the breast to be higher. Advances in knowledge: This research proved that CTAC is a comparatively low dose acquisition. However, it has been shown that there is increased risk to breast tissue especially in the younger patient. As per legislation justification is required and CTAC should only be used in situations that demonstrate sufficient net benefit.