Encrypted login | home

Program Information

A Preliminary Study On the Dosimetric Impact of Detector Based Spectral Ct On Proton Therapy Treatment Planning

C Cheng

C Cheng1*, S Lee1 , R Muzic2 , B Wessels1 , F Jesseph1 , R Ellis1 , D Mansur1 , A Dhanantwari3 , (1) University Hospitals Case Medical Center, Cleveland, OH, (2) Case Western Reserve University, Mentor, OH (3) Philips Healthcare, Solon, OH


SU-F-J-210 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare the difference in Hounsfield unit-relative stopping power and evaluate the dosimetric impact of spectral vs. conventional CT on proton therapy treatment plans.

Method: The Philips prototype (IQon), a detector-based, spectral CT system (spectral) was used to scan calibration and Rando phantoms. Data were reconstructed with and without energy decomposition to produce monoenergetic 70 keV, 140 keV, and the Zeff images. Relative stopping power (RSP) in the head and lung regions were evaluated as a function of HU in order to compare spectral and conventional CT. Treatment plans for the Rando phantom were also generated and used to produce DVHs of fictitious target volume and organ-at-risk contoured on the head and lung.

Results: Agreement of the Zeff of the tissue-substitute materials determined using spectral CT agrees to within 1 to 5% of the Zeff of the known phantom composition. The discrepancy is primarily attributed to non-uniformity in the phantom. Differences between the HU-RSP curves obtained using spectral and conventional CT were small except for in the lung curve at HU>1000. The large difference in planned doses using Spectral vs. conventional CT occurred in a low-dose brain region (1.7mm between the locations of the 100 cGy lines and 3 mm for 50 cGy lines).

Conclusion:Conventionally, a single HU-RSP from CT scanner is used in proton treatment planning. Spectral CT allows site-specific HU-RSP for each patient. Spectral and conventional HU-RSP may result in different distributions as shown here. Additional study is required to evaluate the impact of Spectral CT in proton treatment planning.

Funding Support, Disclosures, and Conflict of Interest: This study is part of a research agreement between Philips and University Hospitals/Case Medical Center.

Contact Email: