Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT using radiochromic film

Jainil P. Shah; Steve D. Mann; Randolph L. McKinley; Martin P. Tornai

doi:10.1117/12.2082081

18 March 2015 Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT using radiochromic film

Jainil P. Shah, Steve D. Mann, Randolph L. McKinley, Martin P. Tornai

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Proceedings Volume 9412, Medical Imaging 2015: Physics of Medical Imaging; 94121K (2015) https://doi.org/10.1117/12.2082081
Event: SPIE Medical Imaging, 2015, Orlando, Florida, United States

Abstract

A novel breast CT system capable of traversing non-traditional 3D trajectories was developed to address cone beam sampling insufficiency for pendant breast imaging. The purpose of this study was to characterize differences in three dimensional x-ray dose distributions in a target volume due to the acquisition trajectory. Three cylindrical phantoms of different diameters and an anthropomorphic breast phantom were scanned in a pendant geometry with two orbits- azimuthal orbit with no polar tilt, and a saddle orbit with ±15° contiguous polar tilts. The phantoms were initially filled with water and then with a 75:25% water: methanol mixture, to simulate different density breast tissues. Fully-3D CT scans were performed using a tungsten anode x-ray source. Ionization chamber calibrated radiochromic film was used to determine average dose delivered to the central sagittal slice of a volume, as well as to visualize the 2D dose distribution across the slice. Results indicated that the mean glandular dose for normal imaging exposures, measured at the central slice across different diameters ranged from 3.93-5.28 mGy, with the lowest average dose measured on the largest diameter cylinder. In all cases, the dose delivered by the saddle was consistently 1-3% lower than the no-tilt scans. These results corroborate previous cylinder Monte Carlo studies which showed a 1% reduction in saddle dose. The average dose measured in the breast phantom filled with 75:25 mixture was slightly higher for saddle. Non-traditional 3D breast CT scans have slightly better dose performance for equal image noise compared with simple, under sampled circular orbits.

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Jainil P. Shah, Steve D. Mann, Randolph L. McKinley, and Martin P. Tornai "Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT using radiochromic film", Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94121K (18 March 2015); https://doi.org/10.1117/12.2082081

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KEYWORDS

Breast

Chest

Nipple

X-rays

3D acquisition

X-ray computed tomography

Calibration

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