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Analysis of Spot Scanning Proton Verification Scan and Re-Plan Frequency

D Mundy1*, R Harper2 , N Deiter1 , (1) Mayo Clinic, Rochester, MN, (2) University of Minnesota, Minneapolis, MN


(Monday, 7/15/2019) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 7

Purpose: Due to the sensitivity of proton therapy to changes in patient anatomy, verification CT scans are acquired throughout the course of treatment to assess the stability of the treatment plan. If significant changes in the dose are observed, a new plan is created. The processing and evaluation of each verification scan requires significant resources. The purpose of this study was to determine, for all disease sites, how often a verification scan results in a re-plan with the intent of reducing the clinical burden of verification scans where possible.

Methods: For approximately 2 years, our practice has kept track of all verification scans, recording data that included the date of the scan, the results of the plan analysis, and reasons for re-planning. We recently began a retrospective review of the first ~700 patients. For each site, the number of patients, verifications scans, and resulting re-plans were of primary interest for this study. All treatment sites were included.

Results: Head and neck (H&N) patients account for the largest verification workload in our clinic, with 1033 verification scans acquired for 164 patients, resulting in 91 re-plans. 47.6% of H&N patients were re-planned at least once. For 138 prostate patients, a total of 259 verification scans were acquired and analyzed, resulting in 3 re-plans. Sites with the highest re-plan per verification scan rate were craniospinal, bone/spine/chordoma/sarcoma (combined group), pelvis, and lung/chest (14-17%). Those with the lowest were prostate and gyn (<2%).

Conclusion: Analysis of this data continues with the objective to inform and optimize clinical practice. Early results indicate a number of anatomic treatment sites where verification scans can be reduced or eliminated, suggest that treatment planning techniques could be reviewed for increased robustness, and illustrate a need for identification of optimal verification scan timing during the course of treatment.


Protons, Treatment Verification, Treatment Planning


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

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