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Dosimetry Analysis On Proton Treatment Plan Using CT Images with Automatic Metal Artifact Reduction

R Wu

R wu1*, R Hunter2 , A Liu3 , M Amin4 , P Blanchard5 , X Zhu6 , (1) ,,,(2) MD Anderson Cancer Ctr, Houston, texas, (3) MD Anderson Cancer Ctr, Houston, texas, (4) MD Anderson Cancer Ctr, Houston, texas, (5) UT MD Anderson Cancer Center, Houston, TX, (6) UT MD Anderson Cancer Center, Houston, TX


SU-K-108-7 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 108

Purpose: To illustrate the differences in dose to clinical target volume (CTV) and organs at risk (OARs) when automatic metal artifact reduction is used on proton head and neck treatment plans.

Methods: 10 oropharyngeal cancer patients who had dental filling/implants were retrospectively selected. Each patient used right/left anterior oblique and a posterior beams. The original treatment plans were created using the Eclipse treatment planning system with conventionally manual overwritten (MO) scan on dental artifacts and replaced with estimated CT# of tissue around. Verification plans were created with Metal Artifact Reduction for Orthopedic Implants (O-MAR, Phillips) applied on planning CT images. We compared doses to CTVs and OARs between the MO plan and O-MAR plan. Wilcoxon signed-rank test was used for the statistical analysis.

Results: Dosimetric results are displayed in the table. There is no significant difference in mean dose or D95 for CTV1-3 between MO and OMAR plan. There is no significant dose difference for parotid mean, mandible mean, brainstem max, spinal cord max and sub-mandible gland mean between MO and O-MAR plan. There is detectable difference (p<0.04) in CTV1 D5 dose between MO scan and O-MAR scan. For base of tongue (BOT) type of patient, the absolute dose difference in D5 was more pronounced than other type of patients, likely due to the proximity of the artifacts.

Conclusion: CT scans with O-MAR correction can be safely used for proton treatment planning. A larger cohort study should be performed to further investigate the effect of O-MAR scan for BOT type patient.

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