Modeling and Evaluation of Customizable Immobilization Masks for Precision Radiotherapy | JoVE Visualize

Area of Science:

Materials Science
Biomedical Engineering
Radiotherapy Physics

Background:

Accurate patient immobilization is crucial in head and neck (H&N) radiotherapy for precise dose delivery and minimizing healthy tissue irradiation.
Conventional thermoplastic masks have limitations including imperfect surface replication, mechanical weakness, patient discomfort, and workflow inefficiencies.
Personalized CT or MRI scans enable the creation of more accurate, patient-specific immobilization masks.

Purpose of the Study:

To design and evaluate customizable immobilization masks using acrylonitrile butadiene styrene (ABS)-based composites reinforced with bismuth oxide (Bi2O3).
To compare the mechanical performance of these novel ABS/Bi2O3 masks against commercially available thermoplastic masks.
To assess the potential for improved immobilization accuracy, patient comfort, and sustainability in radiotherapy.

Main Methods:

Fabrication and tensile testing of ABS and ABS/Bi2O3 composite filaments (5, 10, 20 wt%).
Finite Element Analysis (FEA) of patient-specific virtual masks under clinically relevant loading conditions (neck flexion, lateral bending).
Benchmarking of mechanical properties and displacement against two commercial thermoplastic masks.

Main Results:

ABS and ABS/Bi2O3 composites demonstrated significantly higher stiffness (1.7-2.5 GPa) and yield strength (20-25 MPa) than commercial thermoplastics (0.25-0.3 GPa, ~7 MPa).
FEA showed markedly reduced displacement in ABS masks (1-5 mm at 2 mm thickness; <1 mm at 4 mm thickness) compared to commercial masks (>20 mm under lateral load).
Hybrid mask designs with reinforced edges further improved rigidity while optimizing material use.

Conclusions:

Customizable ABS-based immobilization masks offer superior mechanical stability and displacement control over conventional thermoplastics.
These masks have the potential to reduce planning margins, enhance radiotherapy precision, and improve patient comfort.
The recyclability of ABS-based masks and Bi2O3 composites supports sustainable practices and waste reduction in radiotherapy device manufacturing.