Radiation exposure during simulated equine head and limb fan beam standing computed tomography appears safe for personnel using lead shielding

Objective: To evaluate the radiation dose to personnel locations during simulated head and limb scans with a novel equine standing CT (sCT) system.

Methods: Measurements were made with the use of a helical fan beam sCT system (Equina; Asto CT Inc). Scatter radiation was measured in different positions in the sCT room to mimic the location of the control operator, horse handler, and lead rope handler during simulated equine head and limb imaging. Operator/handler dose was quantified at each location using entrance air kerma measured with a spherical ionization chamber and electrometer.

Results: Radiation dose to the control operator, horse handler, and lead rope handler locations wearing a lead apron during simulated head imaging was 13.3, 3.5, and 6.8 µGy, respectively. Radiation dose to the control operator location wearing a lead apron was 1.3 µGy, and dose to the lead rope handler location wearing a lead apron was 0.2 and 5.4 µGy during simulated pelvic limb and thoracic limb imaging, respectively.

Conclusions: With the more widespread clinical use of equine sCT units in clinical practice, there is concern for increased risk of radiation exposure to personnel who stay in the sCT room during scanning. The control operator location had the highest dose during simulated head imaging, and the lead rope handler location in thoracic limb sCT had the highest dose during simulated limb imaging. Limiting the number of personnel in the sCT room, rotating personnel between handler positions, increasing operator distance from the scanner, and using lead shields and eyeglasses are recommended.

Clinical relevance: Our findings suggest that scanning large numbers of horses per year with the Asto CT Equina would not lead to occupational radiation exposure above the recommended safe threshold for handlers using lead shields and eyeglasses.