A dynamic anthropomorphic phantom for end-to-end testing in image- and surface-guided adaptive radiotherapy

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Medical Imaging

Background:

• Respiratory and digestive motion significantly impacts radiotherapy accuracy, affecting tumor targeting and healthy tissue sparing.
• Existing phantoms struggle to replicate complex organ movements and lack compatibility with advanced imaging like MRI and 4DCT, hindering adaptive radiotherapy.
• The BRaVIDA phantom is developed to overcome these limitations by simulating realistic organ motion and supporting MRI-based adaptive radiotherapy workflows.

Purpose of the Study:

• Introduce the BRaVIDA (Breathing Radiotherapy Visual monitoring, Imaging, and Dosimetric Anthropomorphic) phantom, a novel anthropomorphic phantom.
• Enable realistic simulation of respiratory motion for comprehensive end-to-end testing in adaptive radiotherapy.
• Enhance motion management, imaging accuracy, and dosimetric validation for improved radiotherapy treatments.

Main Methods:

• Designed with realistic thoracic and abdominal anatomical structures, the BRaVIDA phantom utilizes a hydraulic system for simulating respiratory and digestive motion.
• The phantom was imaged using CT and MRI protocols (CT, MRI, 4DCT, 4DMRI) to assess image contrast and motion parameters.
• Dosimetric properties, including relative electron density (RED) and stopping power ratio (SPR) for ion beams, were measured and compared against treatment planning system (TPS) values.

Main Results:

• BRaVIDA exhibited realistic image contrast in CT and MRI, closely mimicking human tissue anthropomorphic characteristics.
• 4DCT and 4DMRI successfully captured motion amplitudes for various organs (pancreas, stomach, liver).
• Measured RED and SPR values aligned well with TPS reference data, with photon attenuation deviations below 1.5% for all materials.

Conclusions:

• BRaVIDA is a versatile, MRI-compatible phantom offering anthropomorphic image contrast, realistic motion simulation, and accurate radiation attenuation for photon therapy.
• The phantom facilitates end-to-end testing in adaptive image- and surface-guided photon radiotherapy workflows.
• For ion beam therapies, SPR values in the TPS require adaptation based on BRaVIDA's measured data for accurate range calculations, positioning it as a valuable tool for adaptive radiotherapy research and clinical practice.