Quantification of Breast Dose From Thoracic Computed Tomography Examinations with Dose Reduction Methods
A Mench1*, L Sinclair1, T Griglock2, B Cormack1, S Bidari1, M Arreola1, (1) University of Florida, Gainesville, FL, (2) Oregon Health & Science Univ, Portland, ORMO-D-134-3 Monday 2:00PM - 3:50PM Room: 134
Purpose: To quantify the breast dose delivered to female patients undergoing routine thoracic Computed Tomography (CT) exams and assess the dose savings provided by the use of bismuth shielding as well as iterative image reconstruction algorithms.
Methods: Breast shields have been used at the University of Florida for three years with unanimous agreement by radiologists in terms of acceptable image quality and non-existent artifacts. To assess the dose savings provided by both bismuth shields and adaptive iterative reconstruction algorithms (AIDR 3D), breast doses were directly measured on cadaveric subjects using optically-stimulated luminescent dosimeters (OSLDs) implanted via tubes into the subjects. The cadavers were scanned with the clinically standardized Chest protocol on a Toshiba Aquilion One 320-slice CT scanner. Next, they were scanned again, with all other parameters unchanged, using the bismuth shield and finally using the AIDR 3D algorithm. Average breast doses were measured for four female cadaveric subjects of various Body Mass Indices (BMIs). Breast doses were measured with the bismuth shield in place for two cadavers, while the AIDR 3D algorithm was investigated using the second pair of subjects. Tube current modulation was activated for all scans.
Results:Average breast doses for all four cadaver subjects ranged from 7 to 24 mGy. Dose savings offered by the bismuth breast shield were 27% for the smaller cadaver and 18% for the larger cadaver. The set of subjects scanned with AIDR 3D turned on received an average breast dose savings of 26% and 21%, for the lower and higher BMI subjects, respectively.
Conclusion:This research reveals that both bismuth shielding and iterative reconstruction algorithms are effective methods of reducing radiation dose to highly radiosensitive breast tissue. Neither of these methods has impacted clinical image quality negatively. Employing dose savings methods, however trivial or complex, benefits patients tremendously.