Journal List > Prog Med Phys > v.29(4) > 1126763

Kim, Shin, Choi, Min, Kwon, Jung, and Kim: Guideline on Acceptance Test and Commissioning of High-Precision External Radiation Therapy Equipment

Abstract

The complex dose distribution and dose transfer characteristics of intensity-modulated radiotherapy increase the importance of precise beam data measurement and review in the acceptance inspection and preparation stages. In this study, we propose a process map for the introduction and installation of high-precision radiotherapy devices and present items and guidelines for risk management at the acceptance test procedure (ATP) and commissioning stages. Based on the ATP of the Varian and Elekta linear accelerators, the ATP items were checked step by step and compared with the quality assurance (QA) test items of the AAPM TG-142 described for the medical accelerator QA. Based on the commissioning procedure, dose quality control protocol, and mechanical quality control protocol presented at international conferences, step-by-step check items and commissioning guidelines were derived. The risk management items at each stage were (1) 21 ionization chamber performance test items and 9 electrometer, cable, and connector inspection items related to the dosimetry system; (2) 34 mechanical and dose-checking items during ATP, 22 multileaf collimator (MLC) items, and 36 imaging system items; and (3) 28 items in the measurement preparation stage and 32 items in the measurement stage after commissioning. Because the items presented in these guidelines are limited in terms of special treatment, items and practitioners can be modified to reflect the clinical needs of the institution. During the system installation, it is recommended that at least two clinically qualified medical physicists (CQMP) perform a double check in compliance with the two-person rule. We expect that this result will be useful as a radiation safety management tool that can prevent radiation accidents at each stage during the introduction of radiotherapy and the system installation process.

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Fig. 1
Ionization chamber performance test.
pmp-29-123f1.tif
Fig. 2
The risk management items for electrometer, cable and connector check.
pmp-29-123f2.tif
Fig. 3
The risk management items for acceptance test of external radiation therapy equipment: Mechanical and dosimetry test.
pmp-29-123f3.tif
Fig. 4
The risk management items for acceptance test of external radiation therapy equipment: MLC.
pmp-29-123f4.tif
Fig. 5
The risk management items for acceptance test of external radiation therapy equipment: Imaging system.
pmp-29-123f5.tif
Fig. 6
The risk management items for commissioning of external radiation therapy equipment: preparation of beam measurement.
pmp-29-123f6.tif
Fig. 7
The risk management items for commissioning of external radiation therapy equipment: beam measurement.
pmp-29-123f7.tif
Table 1.
The derived risk management items were compared for the correlation with TG-142 quality assurance items.
Step Mechanical and Dosimetry check
Sub-step Risk management items TG-142 Quality assurance items Period IMRT Tolerance Remark
Mechanical test Mechanical isocenter variation (with collimator, gantry, couch rotation) Gantry/collimator angle indicators (digital only) Monthly Cardinal angles
Treatment couch position indicator Monthly 2 mm/1°
Collimator rotation isocenter Annual ±1 mm Change from baseline
Gantry rotation isocenter Annual ±1 mm Change from baseline
Couch rotation isocenter Annual ±1 mm Change from baseline
Cross-hair check Cross-hair centering (walkout) Monthly 1 mm
Digital display indicator calibration Collimator size indicator Daily 2 mm
 (Jaw position, gantry, collimator rotation) Gantry/collimator angle indicators (digital only) Monthly Cardinal angles
Jaw position indicators (symmetry) Monthly 2 mm
Jaw position indicators (asymmetry) Monthly 1 mm
Couch movement (rotation, Treatment couch position indicator Monthly 2 mm/1°
longitudinal, lateral, vertical) Table top sag Annual 2 mm Change from baseline
Table angle Annual
Table travel maximum range movement Annual ±2 mm
in all directions
Optical distance indicator (ODI) Distance indicator (ODI) at isocenter Daily 2 mm
verification Distance check device for lasers Monthly 1 mm
compared with front pointer
Radiation isocenter Spoke shot (Gantry rotation) Coincidence of radiation and mechanical l Annual ±2 mm Change from baseline
check isocenter
Winston-Lutz test (with gantry/ Collimator rotation isocenter Annual ±1 mm Change from baseline
collimator/couch rotation) Gantry rotation isocenter Annual ±1 mm Change from baseline
Couch rotation isocenter Annual ±1 mm Change from baseline
Coincidence of light field and X-ray Light/radiation field coincidence Monthly 2 mm or 1%
field (symmetry)
Light/radiation field coincidence Monthly 1 mm or 1%
(asymmetry)
Laser guard collision Protection zone area verification Laser guard-interlock test Monthly Functional
protection system Protection zone tilt verification
Motion stop function verification
Power key switch and override function verification
Beam performance Photon PDD X-ray beam quality (PDD10 or TMR20,10) Annual ±1% Change from baseline
test Photon field flatness/symmetry Photon beam profile constancy Monthly 1%
X-ray flatness change from baseline Annual 1%
X-ray symmetry change from baseline Annual ±1%
Electron PDI Electron energy constancy Monthly 2%/2 mm
Electron beam quality (R50) Annual ±1 mm Change from baseline
Electron field flatness/symmetry Electron beam profile constancy Monthly 1%
Electron flatness change from baseline Annual 1%
Electron symmetry change from baseline Annual ±1%
Symmetry interlock check Follow manufacturer's test procedure Annual Functional
Beamstopper interlocked angles Follow manufacturer's test procedure Annual Functional
Dosimetry Dose reproducibility X-ray output constancy Daily 3% All energies
Monthly 2% All energies
Electron output constancy Daily 3%
Monthly 2%
Backup monitor chamber constancy Monthly 2%
X-ray/electron output calibration (TG-51) ) Annual ±1% Absolute dosimetry
Spot check of field size dependent output Annual 2% Two or more field size
factors for X-ray <4×4 cm2 check
1% ≥4×4 cm2
Output factors for electron applicators Annual ±2% - Change from baseline
- Spot check of on
applicator/energy
Dose linearity with MU X-ray monitor unit linearity output Annual ±2% ±5% (2-4 MU)
constancy (≥5 MU)
Electron monitor unit linearity output Annual ±2%
constancy (≥5 MU)
Dose linearity with dose rate Typical dose rate profile constancy Monthly 2%
X-ray output constancy vs. dose rate Annual ±2% Change from baseline
Dose reproducibility with gantry angle X-ray output constancy vs. gantry angle Annual ±1% Change from baseline
Electron output constancy vs. gantry angle Annual ±1%
Mechanical test Field light alignment Setting vs. radiation field for two patterns Monthly 2 mm
Coincidence of light field and X-ray field Monthly ±2 mm All energies
Cross-hair alignment Cross-hair centering (walkout) Monthly 1 mm
Gantry/collimator rotation isocenter Gantry/collimator angle indicators Monthly Cardinal angles
(digital only)
Collimator rotation isocenter Annual ±1 mm Change from baseline
Gantry rotation isocenter Annual ±1 mm Change from baseline
Optical distance indicator (ODI) Distance indicator (ODI) at isocenter Daily 2 mm
verification Distance check device for lasers Monthly 1 mm
compared with front pointer
Collimator rotation readout calibration Gantry/collimator angle indicators Monthly Cardinal angles
(digital only)
Accessory mount Accessory trays (i.e., port film graticle tray) Monthly 2 mm
Latching of wedges, block tray Monthly Functional
Static MLC Leaf position accuracy Qualitative test (i.e., matched segments, Weekly Visual inspection for
aka “Picket fence”) discernable deviations
such as an increase in
interleaf transmission
Leaf position accuracy Monthly 1 mm Four cardinal angles
Leaf position repeatability Leaf position repeatability Annual ±1 mm
Radiation test Collimator spoke shot Leaf spoke shot Annual ≤1.0 mm (radius)
Gantry spoke shot Leaf spoke shot Annual ≤1.0 mm (radius)
Coincidence of light field and X-ray field Coincidence of light field and X-ray field Monthly ±2 mm All energies
Dynamic MLC MLC transmission dose rates MLC transmission (average of leaf and Annual ±0.5% Change from baseline
interleaf transmission) All energies
AutoDynalogs for the Millennium MLC - - - Only Varian
Generate dynalogs for Mark series or - - - Only Varian
m3 MLC
RV modeup - - -
Arc dynamic leaf speed test Travel speed Monthly Loss of leaf speed>0.5
cm/s
Arc dynamic interlock trip test Arc mode (Expected MU, degrees) Annual ±1 mm Change from baseline
Arc dynamic typical plan test Arc mode (Expected MU, degrees) Annual ±1 mm Change from baseline
Segmental IMRT test (Step and shoot) Segmental IMRT (step and shoot) test Annual RMS maximum of
error<0.35 cm
Moving window IMRT test Moving window IMRT Annual RMS maximum of Four cardinal gantry
error<0.35 cm angles
Moving window IMRT typical plan test
OBI Safety test Door interlock - - -
Mechanical kV source positioning test Positioning/repositioning Daily ≤2 mm
position accuracy kV Imager positioning test Positioning/repositioning Daily ≤2 mm
verification
X-ray check Distance measurement demonstration Scaling Monthly Baseline
kV imager panel virtual alignment Imaging and treatment coordinate Daily ≤1 mm
demonstration coincidence
Optical isocenter demostration Imaging and treatment coordinate Daily ≤2 mm Single gantry angle
coincidence Monthly ≤2 mm Four cardinal angles
X-ray X-ray measurement-digital fluoroscopy, Imaging dose Annual Baseline
generator pulsed mode (kVp, mA, mS)
test Digital radiography-dual gain standard Imaging dose Annual Baseline
resolution (kVp, mA, mS)
HVL using Digital fluoroscopy pulsed Beam quality/energy Annual Baseline
mode
High contrast resolution Spatial resolution Monthly Baseline
Gray scale linearity Spatial resolution Monthly Baseline
Low contrast sensitivity Contrast Monthly Baseline
Cone beam CT number (Hounsfield unit) HU constancy Monthly Baseline
CT Spatial linearity measurement Geometric distortion Monthly Baseline
(distance)
Image uniformity measurements Uniformity and noise Monthly Baseline
High resolution Spatial resolution Monthly Baseline
Low contrast resolution Contrast Monthly Baseline
TOOLS
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