Image-guided stereotactic radiosurgery using a specially designed high-dose-rate linac.
Stereotactic radiosurgery and image-guided radiotherapy (IGRT) place enhanced demands on treatment delivery machines. In this study, we describe a high-dose-rate output accelerator as a part of our stereotactic IGRT delivery system. The linac is a Siemens Oncor without a flattening filter, and enables dose rates to reach 1000 monitor units (MUs) per minute. Even at this high-dose-rate, the linac dosimetry system remains robust; constancy, linearity, and beam energy remain within 1% for 3 to 1000 MU. Dose profiles for larger field sizes are not flat, but they are radially symmetric and, as such, able to be modeled by a treatment planning system. Target localization is performed via optical guidance utilizing a 3-dimensional (3D) ultrasound probe coupled to an array of 4 infrared light-emitting diodes. These diodes are identified by a fixed infrared camera system that determines diode position and, by extension, all objects imaged in the room coordinate system. This system provides sub-millimeter localization accuracy for cranial applications and better than 1.5 mm for extracranial applications. Because stereotactic IGRT can require significantly longer times for treatment delivery, the advantages of the high-dose-rate design and its direct impact on IGRT are discussed.
Bayouth
John E
JE
Department of Radiation Oncology, Holden Comprehensive Cancer Center, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA. john-bayouth@uiowa.edu
Kaiser
Heather S
HS
Smith
Mark C
MC
Pennington
Edward C
EC
Anderson
Kathleen M
KM
Ryken
Timothy C
TC
Buatti
John M
JM
D006801:Humans; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D010315:Particle Accelerators / Q000295:instrumentation*; D016634:Radiosurgery / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D014463:Ultrasonography / Q000295:instrumentation*