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 oldest Clinac-21EX accelerator has been replaced with a new machine is a state-of-the-art Varian TrueBeam STX. This accelerator will be equipped with the new high definition multi-leaf collimator with leaf widths as thin as 2.5 mm. This will render it 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 couch also provides 6 Degrees-of-Freedom (6DOF) to greatly improve positioning accuracy by permitting corrections for pitch, roll and yaw, in addition to the traditional longitudinal, lateral and vertical position adjustments. This machine includes the Edge Extracranial SABR Package that will permit the unit 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. ROB has acquired a second TrueBeam STX unit to replace its RapidArc Clinac-21EX. This machine provides treatment redundancy with the older unit, as well as having additional photon energies of 8 MV and 18 MV. Work is now progressing on upgrading the OSMS system on the older unit and the clinical implementation of a prostate radiotherapy protocol using Calypso RF transponders tomonitor 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 are currently acquiring a couch-mounted stepper-stabilizer to improve needle insertion methodology. As a next step, ROB is planning to remove its Tomotherapy unit from B2-3643 and to modify the room into a brachytherapy suite which is optimized for minor surgical procedures such as this. .