It was necessary for MIDCO to develop a quality assurance device for the BodyLoc System™. To this end, MIDCO developed and manufactured an acrylic hexagonal shaped phantom called the HexaPhant™.
The HexaPhant™ is designed with a film cassette holder that has six brass pins and accommodates an 85 mm x 85 mm piece of film. An ion chamber holder can also be positioned in place of the film cassette.
The HexaPhant™ has two test probes that have 8mm MR compatible gelatin balls and two probes that contain five 2mm tungsten balls spaced 3mm apart that are radiologically identifiable. This can be used for quality assurance for inline CT imaging parameters.
HexaPhant™ shown with film cassette oriented in sagittal and coronal planes
The HexaPhant™ can be mounted to the BodyLoc frame (at any location) so that the film cassette or ion chamber can be oriented in either the sagittal or coronal plane (see image below). The location of the center pin within the film cassette is designed to coincide with the stereotactic target coordinate of a 5mm cylindrical irradiated volume. MD-55 Radiochromic film, or similar film, can then loaded into the HexaPhant™ film cassette and punctured with the six pins. The film can then be irradiated with a simulated treatment plan.
The HexaPhant™ can be used to quality assure the entire system including setup, treament planning, and imaging accuracy. See Reference Article. The Delivery Quality Assurance (DQA) module of the TomoTherapy Planning system was used to analyze the dose profiles on the exposed film. Profile analysis demonstrated the Hexaphant Accuracy Test (HAT) resulted in a vector displacement of 0.6mm which is within the ACR recommended values for either intracranial or extracranial applications.
The HexaPhant™ System can be used to quality assure virtually any radiosurgery sysystem by special adapters supplied by MIDCO.