Jun Deng PhD, Presenter: Nothing to Disclose

Yibao Zhang, Abstract Co-Author: Nothing to Disclose

Shanglian Bao, Abstract Co-Author: Nothing to Disclose

Ravinder Nath PhD, Abstract Co-Author: Nothing to Disclose

To develop an optimizer tool for optimal mAs and kVp settings in kVCBCT based on patient anatomy and user-defined priorities on normal tissue sparing and image quality.

A benchmarked EGS4 Monte Carlo code was employed to calculate kVCBCT-contributed mean organ doses in patients scanned at both half-fan and full-fan modes. The relationship between absorbed dose, mAs and kVp was investigated with phantom measurements and fit with analytical functions. An optimizer based on conjugated gradient searching algorithm in multi-dimensions was developed to generate optimal settings of mAs and kVp for individual patient based on mean organ doses of the patient, with consideration of user-defined priorities on normal tissue sparing and image quality. The effectiveness of the optimizer was tested on Catphan and various patient anatomies.

Our phantom study indicates that the dose depositions from Varian OBI CBCT depend linearly on mAs while exponentially on kVp settings for both half-fan and full-fan modes. Analytical functions in the form of lnf(mAs‚kVp)=a+b·ln(mAs)+c·kVp can be used to predict kVCBCT doses accurately at any given mAs and kVp. For kVCBCT scans of Catphan, the recommended mAs and kVp settings yield much reduced dose depositions (by 21% for head protocol and 60% for pelvis protocol) as compared to the default settings, while maintaining good image quality of kVCBCT scans. For patient anatomies, the optimized modes deposit much less doses to various organs in comparison to the default modes, with reduction of 61-66% to the adult and 45-68% to the children, respectively.

A novel kVCBCT scan protocol optimizer has been developed to help clinicians choose appropriate mAs and kVp settings for individual patient while maintaining a balance between normal tissue sparing and image quality. With optimal settings, the dose depositions to the patients could reduce by 45-68% compared to default settings without much loss of image quality. The proposed optimizer could significantly improve the radiation safety in medical imaging of all patients, which is highly aligned with the missions of recent campaigns of Image Gently for children and Image Wisely for adults.

A kVCBCT scan protocol optimizer can help clinicians choose optimal mAs and kVp settings for individual patient so that patient doses can be significantly reduced while maintaining good image quality.

Deng, J, Zhang, Y, Bao, S, Nath, R, A kVCBCT Scan Protocol Optimizer for Individual Patient Undergoing IGRT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11002894.html