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Use and Validation of Contoured 3D-Printed Neck Compensators for Total Body Irradiation

G Baltz

G Baltz*, P Chi , D Craft , M Peters , J Pollard , R Howell , UT MD Anderson Cancer Center, Houston, TX


SU-I-GPD-T-513 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The goal of total body irradiation (TBI) is to deliver uniform dose (±10%) over the entire body. However, regions with reduced thickness, e.g., neck, are prone to hot spots. Current standard of care (SOC) uses rice bags as neck compensators to improve dose homogeneity. However, the positions and shapes of rice bags are difficult to reproduce on daily basis. Highly conformal patient-specific 3D-printed neck compensators could overcome this limitation. The purpose of this study was to demonstrate clinical feasibility of 3D-printed neck compensators for TBI.

Methods: An optical 3D scan of an anthropomorphic phantom was used to create a 3D model of anterior and posterior neck compensators. The compensators were printed on a 3D printer using a flexible material equivalent to soft tissue in physical/radiological properties. A CT scan of the phantom was acquired with neck compensators. Using a clinically commissioned treatment planning system (TPS), we created two TBI SOC treatment plans: one with compensators and one with the compensators’ density overridden to zero. The phantom was irradiated with and without the compensators and doses validated using thermoluminescent dosimeters (TLDs).

Results: The 3D-printed neck compensators had uniform tissue equivalent density; mean Hounsfield units were 107.9 ± 9.6. The compensators conformed well to the phantom’s neck and readily stayed in place. The treatment with the 3D compensators was more uniform, with lower homogeneity index (HI = 1.06) and less volume receiving ≥ 110% of the prescribed dose (3.4%) in the phantom’s neck, compared to the treatment without compensators (HI = 1.14, Volume ≥ 110% = 77.9%). TLD and TPS results were in good agreement (within 5%).

Conclusion: End-to-end testing of 3D-printed neck compensators for TBI demonstrated its clinical feasibility. The method is simple and does not require CT-based planning because the compensators can be accurately designed from an optical scan.

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