Total skin helical tomotherapy based on 3D printed total skin bolus

Abstract

Objective To investigate the effectiveness of the 3D printing total skin bolus which was first used to treat mycosis fungoides (MF) with total skin helical tomotherapy (TSHT). Materials and Methods A 65-year-old female MF patient with a 3-year medical history was studied, and an in-house desktop fused deposition modeling printer was used to make flexible material of 5 mm thickness for the total skin bolus to increase the skin dose through build-up. The patient was scanned in upper and lower segments while the position of 10cm above the patella was defined as the dividing line, the prescription was 24 Gy in 24 fractions, and 5 times per week. The plan parameters consisting of the FW of 5 cm, the pitch of 0.287 and the MF of 3. The complete block was 4 cm away from the planning target volume (PTV) to reduce the dose of the internal organ at risk (OAR) especially the total bone marrow. Cheese Phantom point dose, ArcCHECK 3D plane dose, and total body multi-point EBT3 film verification was performed to ensure dose delivery accuracy. Finally, MVCT guidance was used to ensure the accuracy of setup and treatment. Results A 5 mm thick 3D printing suit was used as the bolus to achieve target volume coverage with 95% of the prescribed dose. The lower target's conformity index (CI) and homogeneity index (HI) were slightly better than the upper target. The doses of bone marrow gradually decreased with increasing distance from the skin, and the doses of other OARs were within the clinical requirements. The deviation of point dose verification was less than 1%, the 3D plane dose verification was greater than 90%, and the film multi-point dose verification deviation was less than 3%, multiple verification methods have proved the accuracy of the actual dose. The total treatment time was about 1.5 hours (0.5 hour for wearing 3D printing suit and 1 hour for beam-on), and patients may only have slight fatigue, mild nausea or vomiting, low-grade fever, and grade Ⅲ bone marrow suppression. Conclusion The TSHT of 3D printing suit can produce a uniform dose distribution with a short treatment time, simple implementation process, good clinical effect, and low toxic effect, this study provides one more treatment method to reach a better clinical effect for the treatment of MF.