Program Information
Assessing Magnetic Resonance-Generated Synthetic-CT Images for Brain MR Guided Radiation Treatment Planning (MRgRTP): A Feasibility Study
B Morris*, C Yang , M Kanakamedala , H Bhat , S Vijayakumar , A Fatemi , University of Mississippi Med. Center, Jackson, MS
Presentations
WE-RAM3-GePD-J(B)-3 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Lounge - B
Purpose: Feasibility study investigated dosimetric accuracy of synthetic-CT images derived from MR images for stand-alone brain radiotherapy. Synthetic-CT images allow more accurate volume delineation for better tumor control probability and normal tissue sparing. Results were compared to conventional CT based and homogeneous density treatment plans.
Methods: MR and CT images acquired. Synthetic-CT images were generated from MR images using a syngo.via Frontier prototype software (Siemens Healthcare). The physician defined target and normal tissues on separate T1 MR image set, then both synthetic-CT and MR images with structures were rigidly aligned to the CT. A VMAT SRT plan (25Gy in 5 fractions) was designed on the CT set (with and without heterogeneity correction), and the plan was transferred exactly to the synthetic-CT images. PTV coverage and hot spot along with normal tissue doses were analyzed, as well as gradient metrics. Finally, 2-dimensional analyses of dose distributions were performed using 1%/1mm gamma criteria.
Results: PTV coverage (V100) for the CT, synthetic-CT, and homogeneous calculations was 95.7%, 97.1%, and 99.1%, respectively. Normal tissue doses were comparable. R50% (V50%/V100%) values were 4.59, 4.45, and 4.32. Max doses were 29.8Gy, 30.3Gy, and 30.8Gy. Gamma analysis showed passing agreement of 97.6% and 96.8% for comparisons of the synthetic-CT and homogeneous calculation relative to the CT dose distribution, respectively.
Conclusion: Synthetic-CT compared favorably to the homogeneous calculation when analyzed relative to the CT image set. These initial feasibility study results indicate that accurate dose calculation from a MR generated synthetic-CT may be advantageous with the benefit of MR accurate structure delineation and dose calculation accuracy exceeding that achieved with a homogeneous density calculation. In addition, this study indicated that ignoring heterogeneity corrections in brain region could give the clinician false target coverage.Acknowledgement: Siemens Healthcare for providing synthetic-CT prototype software. Acknowledgement: Siemens Healthcare for providing synthetic-CT prototype software
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