Clinical Radiation Physics Service

Miller, Robert

Abstract

We have instituted routine dynamic Intensity Modulated Radiation Therapy (dIMRT). This is the most complex of IMRT treatments and requires considerable pre-treatment verification to ensure accurate execution. These treatments are delivered using our twin Clinac-21EX accelerators. A Hi-ART system (Tomotherapy Inc.) for delivering treatments via helical tomotherapy has been installed, accepted and is currently treating patients. This system provides ROB with cutting edge treatment technology to support future clinical trials. We have started a series of initiatives with our Nucletron High Dose-Rate Afterloader (HDR) using a small, high intensity 192Ir source for interstitial and intercavitary brachytherapy. The department now has two state-of-the-art Varian TrueBeam STX accelerators which are equipped with 120 leaf high definition multi-leaf collimators with leaf widths as thin as 2.5 mm. This renders them capable of performing frameless stereotactic radiosurgery (SRS), although a set of circular collimators with diameters ranging from 4mm to 25mm and an SRS planning module are included in the acquisition. The patient couches also provide for 6 Degrees-of-Freedom (6DOF) to greatly improve positional accuracy by permitting corrections for pitch, roll and yaw, in addition to the traditional longitudinal, lateral and vertical position adjustments. The treatment delivery parameters of these two accelerators are matched to within 0.5%, thus providing true redundancy, assuring that patients can continue to receive their treatments according to their fractionation schedule. These machines include the Edge Extracranial SABR Package that will permit them to deliver frameless stereotactic body radiation therapy (SBRT) using advanced motion management based on radiofrequency local positioning using implanted fiducial transponders and infrared cameras. The revised Edge package includes a Calypso radiofrequency positioning system, utilizing implantable fiducial transducers and real-time tracking capability. The real-time optical tracking utilizes an upgraded Optical Surface Monitoring System (OSMS) system to monitor the body surface and to interrupt the treatment if the surface distorts (due to motion) and the clinical implementation of a prostate radiotherapy protocol using Calypso RF transponders to monitor prostate position and correspondingly gate the treatment delivery. ROB has acquired a new Elekta Flexitron 40 channel High-Dose-Rate (HDR) remote brachytherapy afterloader to replace its previous unit. Additionally, ROB has acquired a new B-K ultrasound unit, which has vastly improved imaging capabilities relative to the previous unit. We have acquired a couch-mounted stepper-stabilizer to improve needle insertion methodology and are working on adapting a motorized scanning system for the probe to speed image acquisition. ROB has removed its Tomotherapy unit from B2-3643 and is set to begin construction to optimize the room for brachytherapy and other minor surgical procedures.