Program Information
A Real-Time Skin-Dose Mapping System for Region-Of-Interest (ROI) Fluoroscopy
s vijayan*, V Rana , Z Xiong , S Setlur Nagesh , S Rudin , D Bednarek , Toshiba Stroke and Vascular Research Center, University at Buffalo, Buffalo, New York
Presentations
TH-AB-201-1 (Thursday, July 16, 2015) 7:30 AM - 9:30 AM Room: 201
Purpose:The real-time dose-tracking system (DTS) which we developed for fluoroscopically–guided procedures has been upgraded so that it can track the patient skin dose when using a region-of-interest (ROI) beam attenuator.
Methods:ROI fluoroscopy is a method for greatly reducing patient dose by inserting an attenuator with an aperture into the x-ray beam. The aperture defines an ROI with normal dose and image quality, while under the attenuator the dose and quality are reduced. A moveable copper ROI attenuator has been installed in the collimator assembly of a Toshiba Infinix system. The DTS provides a 3D-dose mapping on a patient graphic and, to track dose for ROI fluoroscopy, the software now models the attenuator shape and position. A calibration file provides values for the transmission of the attenuator as a function of kVp and beam filtration and dose corrections are performed if a ray to a given point on the patient graphic is determined to intersect the attenuator. Backscatter is included in the skin-dose determination and is dependent on the ROI beam size projected onto the patient. In the current version, a spatially invariant factor corrects for backscatter within the ROI and from the ROI region into the attenuated region. The agreement of the dose distribution calculated by the DTS with the actual distribution was verified by measurement with calibrated radiochromic film and a 20-cm PMMA phantom.
Results:The DTS is able to accurately model the size and position of the ROI attenuator as projected onto the patient graphic. Measurements with radiochromic film show the skin-dose estimation agreement to be within +/-12%, with most error arising from the spatial variation of backscatter.
Conclusion:The dose distribution on the patient can now be tracked in real-time with acceptable accuracy when the new dose-saving feature of ROI fluoroscopy is used.
Funding Support, Disclosures, and Conflict of Interest: This research was supported in part by Toshiba Medical Systems Corporation and NIH Grant R01EB002873.
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