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Validation of a Novel CT Breast Dosimetry Method in Post Mortem, Unembalmed Female Subjects


D Sandoval

D Sandoval1*, G Hatch2, C Gerrard2, P Heintz1, (1) Department of Radiology, University of New Mexico School of Medicine (2)Radiology-Pathology Center for Forensic Imaging, University of New Mexico School of Medicine

TU-G-103-3 Tuesday 4:30PM - 6:00PM Room: 103

Purpose:
Validate breast dose from CT in post mortem subjects, as measured by implanted dosimeters, for later comparison to currently accepted calculation methods.

Methods:
The study population consisted of 22 female decedents, referred to the New Mexico Office of the Medical Investigator and scheduled for autopsy. Exclusion criteria were: postmortem interval greater than 24hours, significant trauma to the thorax, large pleural or vascular gas collections and significant external or internal decomposition.
Under CT guidance, using a Philips large bore 16 slice CT scanner, a microMOSFET detector was implanted in the glandular tissue of the decedent's left breast using plastic flexi-needles under CT guidance. The implanted dosimeter was placed in the subaereolar breast, at a depth midway between nipple and the posterior margin of glandular tissue. An additional MOSFET and Unfors PSD detector (for cross comparison) were placed on the skin surface, over the nipple of the contralateral breast. Each decedent was scanned using our standard clinical chest and clinical CTA protocol.
Breast dose calculations were performed using ImpactCT dose calculator and PCXMCrotation software packages for comparison to measured data.

Results:
Results demonstrate good agreement between the implanted microMOSFET detector, PSD, and the surface microMOSFET detector. Additionally, there is poor agreement between measured doses and the Impact CT calculations, which are limited by the assumption of a single standard patient size. Calculations using PCXMCrotation, which allows for some patient size specifications, are in progress.

Conclusion:
The agreement between the implanted surface dosimeters suggests that 1) an accurate surface measurement may be sufficient to determine the breast dose, and 2) as employed, the method of measuring dose using an implanted microMOSFET is accurate. The postmortem microMOSFET model presented here may, in future, produce more meaningful dose estimates and patient specific dose models and be used for measuring dose in other radiosensitive organs.

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