MENU

Click here to

×

Are you sure ?

Yes, do it No, cancel
  1. Home
  2. Meeting Program
  3. All Sessions
  4. All Joint Imaging-Therapy General ePoster Discussion
  5. Dosimetric Evaluation of MR-Derived Synthetic-CTs for MR-Only Proton Treatment Planning

Dosimetric Evaluation of MR-Derived Synthetic-CTs for MR-Only Proton Treatment Planning

D Aramburu Nunez1*, S Fontenla2 , L Rydquist3 , G Del Rosario4 , Z Han5 , C Chen6 , M Hunt7 , D Mah8 , N Tyagi9 , (1) Memorial Sloan Kettering Cancer Center, New York, NY, (2) Memorial Sloan Kettering Cancer Center, New York, NY, (3) ProCure Proton Therapy Center, Somerset, NJ, (4) ProCure Proton Therapy Center, Somerset, NJ, (5) ProCure Proton Therapy Center, Somerset, NJ, (6) Procure Treatment Center, Somerset, NJ, (7) Memorial Sloan Kettering Cancer Center, New York, NY, (8) ProCure Proton Therapy Center, Somerset, NJ, (9) Memorial Sloan Kettering Cancer Center, New York, NY

Presentations

(Tuesday, 7/31/2018) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 2

Purpose: To evaluate dose calculation accuracy of optimized pencil beam scanning (PBS) plans on MR-derived synthetic-CTs for prostate patients.

Methods: Ten patient datasets with both a CT and an MRI were planned with opposed lateral proton beams optimized to single field uniform dose under an IRB approved study. The plans were performed on datasets generated by a commercial synthetic CT-based software called MRCAT (MR for Calculating ATtenuation) routinely used in our clinic for photon-based planning. The CTV was expanded to 2 mm posteriorly, and 3 mm elsewhere to create the PTV. A PTVeval volume was created by expanding PTV laterally by 5mm to take into account proton range uncertainty. A standard prescription of 79.2 Gy (RBE) and 68.4 Gy (RBE) was used for intact prostate and prostate bed cases. Proton plans were then recalculated on a deformed-CT, deformed to match outer contour between MRCAT-CT and original CT. The same beam arrangement, total MUs, MUs/spot, spot positions were used to recalculate dose on deformed-CT without re-normalization. DVH analysis compared D98% for PTVeval, CTV, and V70Gy, V50Gy for OARs. Gamma analysis using (2%/2mm) was performed between the MRCAT-CT and deformed-CT.

Results: The percentage dose difference between MRCAT-CT and deformed-CT, were (1.14 ± 2.37 %) for PTVeval D98% and (0.04±0.06%) for CTV D98%. Rectum V70Gy, V50Gy, and Bladder V70Gy were (2.76±4.01 %), (11.6±11.2 %), and (3.41±2.86 %) respectively for the MRCAT CT, and (3.23±3.63 %), (11.3±8.18 %), and (3.29±2.76 %) respectively for the deformed-CT. The average gamma pass rate using (2%/2mm)10% between MRCAT-CT and deformed-CT were 99.3 ±1.1 %.

Conclusion: Dosimetric analysis shows that MR-only proton planning is feasible using MR-derived MRCAT synthetic-CT based on current clinical margins that account for a range uncertainty. With multi-spectral CT, the accuracy of synthetic-CT for PBS will need to be further evaluated.

Funding Support, Disclosures, and Conflict of Interest: Memorial Sloan Kettering Cancer Center has a master research agreement with Philips Healthcare.

Keywords

Protons, MRI, Treatment Planning

Taxonomy

TH- External Beam- Particle therapy: Proton therapy - treatment planning/virtual clinical studies

Contact Email

Additional Links