A New Anthropomorphic Pediatric Spine Phantom for Proton Therapy Clinical Trial Credentialing

Abstract

Purpose: To design and evaluate an anthropomorphic spine phantom for use in credentialing proton therapy facilities for clinical trial participation by the Imaging and Radiation Oncology Core Houston QA Center. Materials and Methods: A phantom was designed to perform an end-to-end audit of the proton spine treatment process, including simulation, dose calculation, and proton treatment delivery. Because plastics that simulate bone in proton beams are unknown, 11 potential materials were tested to identify suitable phantom materials. Once built, preliminary testing using passive scattering and spot scanning treatment plans (including a field junction) were created in-house and delivered 3 times to test reproducibility. The following measured attributes were compared with the calculated values: absolute dose agreement using thermoluminescent dosimeters, planar gamma agreement, distal range, junction match, and right and left profile alignment using radiochromic film. Finally, credentialing results from 10 institutions were also assessed. Results: A suitable bone substitute was identified (Techtron HPV Bearing Grade), which had a measured relative stopping power that agreed within 1.1% of its value calculated by Eclipse. In-house passive scatter testing of the phantom demonstrated that the phantom was suitable for assessing craniospinal irradiation dose delivery. However, the in-house scanning beam results were more mixed, highlighting challenges in treatment delivery. Seven of ten institutions passed the proposed criteria for this phantom, a pass rate consistent with other Imaging and Radiation Oncology phantoms. Conclusions: An anthropomorphic proton spine phantom was developed to evaluate proton therapy delivery. This phantom provides a realistic challenge for centers wishing to participate in proton clinical trials and highlights the need for caution in applying advanced treatments.

Dosimetric impact of commercial CT metal artifact reduction algorithms and a novel in‐house algorithm for proton therapy of head and neck cancer

“…The lower jaw was cut to expose the top and bottom teeth, and holes were drilled in each of the eight molars (four superior and four inferior). We created capsules using bone‐equivalent material in proton beams 21 ; these were inserted into molars to simulate no fillings (Techton HPV Bearing Grade; Gammex). We used capsules made with metal amalgams (Dispersalloy; Milford, DE) to simulate fillings and introduce metal artifacts.…”

Development of a heterogeneous phantom to measure range in clinical proton therapy beams

“…To derive the range of the other configurations (Table, 1, configurations 2-7), firstly the solid water equivalent thickness of the material, m, was determined via equation (6).…”

“…For both proton reference dosimetry audits [5] and end-to-end based dosimetric audits [4,6], phantoms are used that vary in shape and are made from a range of materials [7]. For proton therapy, most audit phantoms are anthropomorphic in design; including Imaging and Radiation Oncology Core's (IROC) head, paediatric spine, liver, lung and prostate phantoms as well as the CIRS head phantom [4,8,9].…”

Advances in radiotherapy technology for pediatric cancer patients and roles of medical physicists: COG and SIOP Europe perspectives

“…Pediatric anthropomorphic phantoms are being increasingly used for end-to-end tests and credentialing. Examples include a pediatric TBI phantom 62 and a pediatric spine phantom, 63 along with a pediatric CT dose index and anthropomorphic phantoms for dosimetry verification. F I G U R E 3 An 11-year-old male with HL who underwent 4D MRI to define the ITV for consolidative RT to the spleen.…”

“…Pediatric anthropomorphic phantoms are being increasingly used for end-to-end tests and credentialing. Examples include a pediatric TBI phantom 62 and a pediatric spine phantom, 63 along with a pediatric CT dose index and anthropomorphic phantoms for dosimetry verification. RT but are commonly used for younger patients and for those with extremity or head and neck (including orbital) sarcomas or metastases and/or for those undergoing reirradiation.…”