Radiation Physics

PV QA 3 - Poster Viewing Q&A 3

TU_5_3163 - Patient Motion Analysis of First 50 Frameless Fixation Cases with Leksell Gamma Knife ICON

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Patient Motion Analysis of First 50 Frameless Fixation Cases with Leksell Gamma Knife ICON
J. O. Kim1, K. Fallon1, G. Bednarz2, M. S. Huq1, J. C. Flickinger Sr1, E. Monaco3, A. Niranjan3, and L. D. Lunsford3; 1University of Pittsburgh Medical Center Hillman Cancer Center, Pittsburgh, PA, 2UPMC Hillman Cancer Center, Pittsburgh, PA, 3Center for Image-guided Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, PA

Purpose/Objective(s): A new generation of Gamma Knife®, ICON, provides either frame-based or frameless patient fixation for high accuracy radiation surgery treatment. With the frameless patient fixation, a High Definition Motion Management (HDMM) system monitors the patients motion and controls the Gamma Knife beam delivery with a user defined tolerance of acceptable motion. Patient motion is recorded into a logfile. This study analyzed the logfile to derive the extents of the patient motion in 3-dimensional space.

Materials/Methods: The infrared camera of the HDMM system tracks the relative position of the patient marker, attached to the patient’s nose, with respect to four reference markers fixed on the mask adapter that locks to the unit. The ICON produces several log files that record events and messages from the operations of Gamma Knife unit. The log files report the patient marker position when the motion deviated from a previous position by 0.2 mm. The log files were exported to a Universal Serial Bus (USB) memory stick and the patient motion was extracted with an in-house software that statistically analyzed the patient motion in terms of average positions and standard deviation over several “beam-on” times. First 50 treatments with the frameless patient fixation have been analyzed and presented.

Results: There were 50 treatments analyzed with the following sites; sizable brain metastasis targets were 27, meningioma were 21, and 2 GBM treatments were included. Overall treatment time was 37.6 ± 20.1 min (range, 10.4 to 107.7 min) and age of patients was 66.7 ± 10.4 years old. Net beam-on time was 20.8±10.2 min. Elapsed beam time including beam paused time due to motion out of the user defined tolerance was 27.3±18.7 min, and elapsed treatment time including patient loading and unloading time was 37.6±20.1 min. The total mean displacement in three dimensions and its standard deviation was 0.33±0.27, 0.25±0.19, and 0.43±0.35 mm in x, y, and z, respectively. The maximum patient motion was 3.95, 3.71, and 6.87 mm (1st generation ICON automatically removed patients when out of tolerance, it did not retract sources) and mean range was 1.19, 1.08, and 1.91 mm in x, y, and z, respectively. Patient recorded motion demonstrated motion in superior-inferior direction.

Conclusion: Patient motions with first 50 frameless fixation cases with Leksell Gamma Knife® ICON™ have been statistically analyzed using log files. Results of analysis confirms that the HDMM of the ICON successfully manage the patient motion within desired tolerance. It is expected that the results will be used to reproduce the dose delivery under consideration of patient motions.

Author Disclosure: J. Kim: None. K. Fallon: None. G. Bednarz: None. M. Huq: Honoraria; Varian Medical Systems. Chair, Therapy Physics Committee (TPC); AAPM. Vice chair, Science Council; American Association of Physicists in Medicine. J.C. Flickinger: None. E. Monaco: Wife; University of Pittsburgh Practice. A. Niranjan: None. L. Lunsford: DSMB; Insightec. Stock; Elekta.

Jong Oh Kim, PhD

Biography:
Jong Oh Kim, PhD, DABR, University of Pittsburgh Medical Center, Hillman Cancer Center
Dr. Kim received his Ph.D. in Nuclear Engineering in 1997 from the Hanyang University in Seoul Korea. Following his graduation, he became a postdoctoral researcher at the Korea Atomic Energy Research Institute in Taejon Korea. He joined the Laboratory for Threat-Material Detection of University of New Brunswick, Fredericton, New Brunswick, Canada in April 1998 where he was involved in research developing of a Non-Rotating X-Ray System for Composition and Density Imaging using Compton scattering imaging. In November 1999, Dr. Kim joined Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia as a postdoctoral fellow and became a faculty member as instructor in July 2002, where he was involved in Monte Carlo application projects for radiation leakage calculation from multi-leaf collimator and for portal image calculation of electronic portal imaging device. In parallel to his works, he developed an IMRT quality assurance procedure using film measurement and carried out the IMRT QA for over IMRT patients. Dr. Kim left VCU in September 2003 and joined the physics and research of the CMS, Inc. in St. Louis, Missouri as a research scientist. Dr. Kim returned to clinic and joined Department of Radiation Oncology, University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania in September 2007. He has served on medical physicist at UPMC Hillman Cancer Center and Center for Image-Guided Neurosurgery. His research interests include Monte Carlo application in medical physics and patient motion study in Gamma Knife treatment.

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