skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for microchamber and diode detectors

Abstract

Purpose: To measure the output factors (OFs) of the small fields formed by the variable aperture collimator system (iris) of a CyberKnife (CK) robotic radiosurgery system, and determine the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for a microchamber and four diode detectors. Methods: OF measurements were performed using a PTW PinPoint 31014 microchamber, four diode detectors (PTW-60017, -60012, -60008, and the SunNuclear EDGE detector), TLD-100 microcubes, alanine dosimeters, EBT films, and polymer gels for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators at 650 mm, 800 mm, and 1000 mm source to detector distance (SDD). The alanine OF measurements were corrected for volume averaging effects using the 3D dose distributions registered in polymer gel dosimeters. k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for the PinPoint microchamber and the diode dosimeters were calculated through comparison against corresponding polymer gel, EBT, alanine, and TLD results. Results: Experimental OF results are presented for the array of dosimetric systems used. The PinPoint microchamber was found to underestimate small field OFs, and a k{submore » Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factor ranging from 1.127 {+-} 0.022 (for the 5 mm iris collimator) to 1.004 {+-} 0.010 (for the 15 mm iris collimator) was determined at the reference SDD of 800 mm. The PinPoint k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factor was also found to increase with decreasing SDD; k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} values equal to 1.220 {+-} 0.028 and 1.077 {+-} 0.016 were obtained for the 5 mm iris collimator at 650 mm and 1000 mm SDD, respectively. On the contrary, diode detectors were found to overestimate small field OFs and a correction factor equal to 0.973 {+-} 0.006, 0.954 {+-} 0.006, 0.937 {+-} 0.007, and 0.964 {+-} 0.006 was measured for the PTW-60017, -60012, -60008 and the EDGE diode detectors, respectively, for the 5 mm iris collimator at 800 mm SDD. The corresponding correction factors for the 15 mm iris collimator were found equal to 0.997 {+-} 0.010, 0.994 {+-} 0.009, 0.988 {+-} 0.010, and 0.986 {+-} 0.010, respectively. No correlation of the diode k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors with SDD was observed. Conclusions: This work demonstrates an experimental procedure for the determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors required to obtain small field OF results of increased accuracy.« less

Authors:
; ; ; ; ; ; ; ; ; ;  [1]
  1. Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens (Greece) and CyberKnife Center, Iatropolis-MagnitikiTomografia, 54-56 Ethnikis-Antistaseos, 152 31 Athens (Greece)
Publication Date:
OSTI Identifier:
22098947
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 39; Journal Issue: 8; Other Information: (c) 2012 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; ALANINES; COLLIMATORS; FILMS; POLYMERS; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY; SURGERY; THERMOLUMINESCENT DOSEMETERS

Citation Formats

Pantelis, E., Moutsatsos, A., Zourari, K., Petrokokkinos, L., Sakelliou, L., Kilby, W., Antypas, C., Papagiannis, P., Karaiskos, P., Georgiou, E., Seimenis, I., Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athen, Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens, Accuray Incorporated, Sunnyvale, California 94089, 1st Department of Radiology, Aretaieion Hospital, Medical School, University of Athens, Vas. Sophias, 115 28 Athens, Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens, and Medical Physics Laboratory, Medical School, Democritus University of Thrace, 2nd Building of Preclinical Section, University Campus, 68100 Alexandroupolis. On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for microchamber and diode detectors. United States: N. p., 2012. Web. doi:10.1118/1.4736810.
Pantelis, E., Moutsatsos, A., Zourari, K., Petrokokkinos, L., Sakelliou, L., Kilby, W., Antypas, C., Papagiannis, P., Karaiskos, P., Georgiou, E., Seimenis, I., Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athen, Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens, Accuray Incorporated, Sunnyvale, California 94089, 1st Department of Radiology, Aretaieion Hospital, Medical School, University of Athens, Vas. Sophias, 115 28 Athens, Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens, & Medical Physics Laboratory, Medical School, Democritus University of Thrace, 2nd Building of Preclinical Section, University Campus, 68100 Alexandroupolis. On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for microchamber and diode detectors. United States. doi:10.1118/1.4736810.
Pantelis, E., Moutsatsos, A., Zourari, K., Petrokokkinos, L., Sakelliou, L., Kilby, W., Antypas, C., Papagiannis, P., Karaiskos, P., Georgiou, E., Seimenis, I., Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athen, Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens, Accuray Incorporated, Sunnyvale, California 94089, 1st Department of Radiology, Aretaieion Hospital, Medical School, University of Athens, Vas. Sophias, 115 28 Athens, Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens, and Medical Physics Laboratory, Medical School, Democritus University of Thrace, 2nd Building of Preclinical Section, University Campus, 68100 Alexandroupolis. Wed . "On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for microchamber and diode detectors". United States. doi:10.1118/1.4736810.
@article{osti_22098947,
title = {On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for microchamber and diode detectors},
author = {Pantelis, E. and Moutsatsos, A. and Zourari, K. and Petrokokkinos, L. and Sakelliou, L. and Kilby, W. and Antypas, C. and Papagiannis, P. and Karaiskos, P. and Georgiou, E. and Seimenis, I. and Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athen and Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens and Accuray Incorporated, Sunnyvale, California 94089 and 1st Department of Radiology, Aretaieion Hospital, Medical School, University of Athens, Vas. Sophias, 115 28 Athens and Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens and Medical Physics Laboratory, Medical School, Democritus University of Thrace, 2nd Building of Preclinical Section, University Campus, 68100 Alexandroupolis},
abstractNote = {Purpose: To measure the output factors (OFs) of the small fields formed by the variable aperture collimator system (iris) of a CyberKnife (CK) robotic radiosurgery system, and determine the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for a microchamber and four diode detectors. Methods: OF measurements were performed using a PTW PinPoint 31014 microchamber, four diode detectors (PTW-60017, -60012, -60008, and the SunNuclear EDGE detector), TLD-100 microcubes, alanine dosimeters, EBT films, and polymer gels for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators at 650 mm, 800 mm, and 1000 mm source to detector distance (SDD). The alanine OF measurements were corrected for volume averaging effects using the 3D dose distributions registered in polymer gel dosimeters. k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors for the PinPoint microchamber and the diode dosimeters were calculated through comparison against corresponding polymer gel, EBT, alanine, and TLD results. Results: Experimental OF results are presented for the array of dosimetric systems used. The PinPoint microchamber was found to underestimate small field OFs, and a k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factor ranging from 1.127 {+-} 0.022 (for the 5 mm iris collimator) to 1.004 {+-} 0.010 (for the 15 mm iris collimator) was determined at the reference SDD of 800 mm. The PinPoint k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factor was also found to increase with decreasing SDD; k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} values equal to 1.220 {+-} 0.028 and 1.077 {+-} 0.016 were obtained for the 5 mm iris collimator at 650 mm and 1000 mm SDD, respectively. On the contrary, diode detectors were found to overestimate small field OFs and a correction factor equal to 0.973 {+-} 0.006, 0.954 {+-} 0.006, 0.937 {+-} 0.007, and 0.964 {+-} 0.006 was measured for the PTW-60017, -60012, -60008 and the EDGE diode detectors, respectively, for the 5 mm iris collimator at 800 mm SDD. The corresponding correction factors for the 15 mm iris collimator were found equal to 0.997 {+-} 0.010, 0.994 {+-} 0.009, 0.988 {+-} 0.010, and 0.986 {+-} 0.010, respectively. No correlation of the diode k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors with SDD was observed. Conclusions: This work demonstrates an experimental procedure for the determination of the k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub m}{sub s}{sub r}}}}}}}}} correction factors required to obtain small field OF results of increased accuracy.},
doi = {10.1118/1.4736810},
journal = {Medical Physics},
issn = {0094-2405},
number = 8,
volume = 39,
place = {United States},
year = {2012},
month = {8}
}