Evaluation of a diode array for QA measurements on a helical tomotherapy unit
Abstract
A helical tomotherapy system is used in our clinic to deliver intensity-modulated radiation therapy (IMRT) treatments. Since this machine is designed to deliver IMRT treatments, the traditional field flatness requirements are no longer applicable. This allows the unit to operate without a field flatness filter and consequently the 400 mm wide fan beam is highly inhomogeneous in intensity. The shape of this beam profile is mapped during machine commissioning and for quality assurance purposes the shape of the beam profile needs to be monitored. The use of a commercial diode array for quality assurance measurements is investigated. Central axis beam profiles were acquired at different depths using solid water built-up material. These profiles were compared with ion chamber scans taken in a water tank to test the accuracy of the diode array measurements. The sensitivity of the diode array to variations in the beam profile was checked. Over a seven week period, beam profiles were repeatedly measured. The observed variations are compared with those observed with an on-board beam profile monitor. The diode measurements were in agreement with the ion chamber scans. In the high dose, low gradient region the average ratio between the diode and ion chamber readings wasmore »
- Authors:
- Department of Radiation Oncology, M.D. Anderson Cancer Center Orlando, Orlando, Florida (United States)
- (United States)
- Publication Date:
- OSTI Identifier:
- 20726906
- Resource Type:
- Journal Article
- Resource Relation:
- Journal Name: Medical Physics; Journal Volume: 32; Journal Issue: 11; Other Information: DOI: 10.1118/1.2089547; (c) 2005 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; BEAM PROFILES; CALIBRATION STANDARDS; COMMISSIONING; COMPUTERIZED TOMOGRAPHY; IONIZATION CHAMBERS; QUALITY ASSURANCE; RADIATION DOSES; RADIOTHERAPY; SENSITIVITY
Citation Formats
Langen, K.M., Meeks, S.L., Poole, D.O., Wagner, T.H., Willoughby, T.R., Zeidan, O.A., Kupelian, P.A., Ruchala, K.J., Olivera, G.H., and TomoTherapy Inc., Madison, Wisconsin. Evaluation of a diode array for QA measurements on a helical tomotherapy unit. United States: N. p., 2005.
Web. doi:10.1118/1.2089547.
Langen, K.M., Meeks, S.L., Poole, D.O., Wagner, T.H., Willoughby, T.R., Zeidan, O.A., Kupelian, P.A., Ruchala, K.J., Olivera, G.H., & TomoTherapy Inc., Madison, Wisconsin. Evaluation of a diode array for QA measurements on a helical tomotherapy unit. United States. doi:10.1118/1.2089547.
Langen, K.M., Meeks, S.L., Poole, D.O., Wagner, T.H., Willoughby, T.R., Zeidan, O.A., Kupelian, P.A., Ruchala, K.J., Olivera, G.H., and TomoTherapy Inc., Madison, Wisconsin. Tue .
"Evaluation of a diode array for QA measurements on a helical tomotherapy unit". United States.
doi:10.1118/1.2089547.
@article{osti_20726906,
title = {Evaluation of a diode array for QA measurements on a helical tomotherapy unit},
author = {Langen, K.M. and Meeks, S.L. and Poole, D.O. and Wagner, T.H. and Willoughby, T.R. and Zeidan, O.A. and Kupelian, P.A. and Ruchala, K.J. and Olivera, G.H. and TomoTherapy Inc., Madison, Wisconsin},
abstractNote = {A helical tomotherapy system is used in our clinic to deliver intensity-modulated radiation therapy (IMRT) treatments. Since this machine is designed to deliver IMRT treatments, the traditional field flatness requirements are no longer applicable. This allows the unit to operate without a field flatness filter and consequently the 400 mm wide fan beam is highly inhomogeneous in intensity. The shape of this beam profile is mapped during machine commissioning and for quality assurance purposes the shape of the beam profile needs to be monitored. The use of a commercial diode array for quality assurance measurements is investigated. Central axis beam profiles were acquired at different depths using solid water built-up material. These profiles were compared with ion chamber scans taken in a water tank to test the accuracy of the diode array measurements. The sensitivity of the diode array to variations in the beam profile was checked. Over a seven week period, beam profiles were repeatedly measured. The observed variations are compared with those observed with an on-board beam profile monitor. The diode measurements were in agreement with the ion chamber scans. In the high dose, low gradient region the average ratio between the diode and ion chamber readings was 1.000{+-}0.005 ({+-}1 standard deviation). In the penumbra region the agreement was poorer but all diodes passed the distance to agreement (DTA) requirement of 2 mm. The trend in the beam profile variations that was measured with the diode array device was in agreement with the on-board monitor. While the calculated amount of variation differs between the devices, both were sensitive to subtle variations in the beam profile. The diode array is a valuable tool to quickly and accurately monitor the beam profile on a helical tomotherapy unit.},
doi = {10.1118/1.2089547},
journal = {Medical Physics},
number = 11,
volume = 32,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
-
The Delta4 biplanar diode array dosimeter was validated for helical tomotherapy delivery QA. The basic detector characteristics were found to be satisfactory in terms of short-term reproducibility (0.1%), linearity (<0.1%), dose rate dependence (0.4%), and absolute calibration accuracy (0.4% in the center of the phantom compared with the independently calibrated diode). Relative calibration of the arrays was verified by comparison with film and by rotating the detector 180{sup o}. The dosimeter response to rotational irradiation changed by no more than 0.2% when one of the detector boards was replaced by the homogeneous phantom material. The daily output correction factor canmore »
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The use of a commercial QA device for daily output check of a helical tomotherapy unit
Helical tomotherapy radiation therapy units, due to their particular design and differences from a traditional linear accelerator, require different procedures by which to perform routine quality assurance (QA). One of the principal QA tasks that should be performed daily on any radiation therapy equipment is the output constancy check. The daily output check on a Hi-Art TomoTherapy unit is commonly performed utilizing ionization chambers placed inside a solid water phantom. This provides a good check of output at one point, but does not give any information on either energy or symmetry of the beam, unless more than one point ismore » -
SU-E-T-631: Commissioning and Comprehensive Evaluation of the ArcCHECK Cylindrical Diode Array for VMAT QA
Purpose: Commissioning and comprehensive evaluation of ArcCHECK phantom for dosimetry of VMAT QA, using 6MV photon beam with and without the flattening filter. Methods: ArcCHECK was evaluated for response dependency on linac dose rate, instantaneous dose rate, radiation field size, beam angle and couch insertion. Scatter dose characterization, consistency and symmetry of response, dosimetric accuracy of fixed aperture arcs and clinical VMAT plans were investigated. Measurements were done using TrueBeam™ STx accelerator (Console version 1.6) with a 6 MV beam with and without flattening filter. Reference dose-grids were calculated using Eclipse TPS Analytical Anisotropic Algorithm (AAA version 10.0.39). Planned dosesmore » -
QA for helical tomotherapy: Report of the AAPM Task Group 148
Helical tomotherapy is a relatively new modality with integrated treatment planning and delivery hardware for radiation therapy treatments. In view of the uniqueness of the hardware design of the helical tomotherapy unit and its implications in routine quality assurance, the Therapy Physics Committee of the American Association of Physicists in Medicine commissioned Task Group 148 to review this modality and make recommendations for quality assurance related methodologies. The specific objectives of this Task Group are: (a) To discuss quality assurance techniques, frequencies, and tolerances and (b) discuss dosimetric verification techniques applicable to this unit. This report summarizes the findings ofmore » -
SU-E-I-15: Quantitative Evaluation of Dose Distributions From Axial, Helical and Cone-Beam CT Imaging by Measurement Using a Two-Dimensional Diode-Array Detector
Purpose: To evaluate quantitatively dose distributions from helical, axial and cone-beam CT clinical imaging techniques by measurement using a two-dimensional (2D) diode-array detector. Methods: 2D-dose distributions from selected clinical protocols used for axial, helical and cone-beam CT imaging were measured using a diode-array detector (MapCheck2). The MapCheck2 is composed from solid state diode detectors that are arranged in horizontal and vertical lines with a spacing of 10 mm. A GE-Light-Speed CT-simulator was used to acquire axial and helical CT images and a kV on-board-imager integrated with a Varian TrueBeam-STx machine was used to acquire cone-beam CT (CBCT) images. Results: Themore »