Prog Med Phys.  2013 Dec;24(4):315-322. 10.14316/pmp.2013.24.4.315.

Report on the External Audits Conducted by Korean Society of Medical Physics

• Huh HD
• Cho KH
• Cho SJ
• Choi SH
• Kim DW
• Hwang UJ
• Kim KH
• Min CK
• Choi TJ
• Oh YK
• Lee SJ
• Park D
• Park SK
• Ji YH

• KMID: 1910575
• DOI: http://doi.org/10.14316/pmp.2013.24.4.315

Abstract

The aim of this work is to verify the self-quality assurances in medical institutions in Korea through the external audits by the group of experts and have a mutual discussion of the systematic problems. In order to validate the external audits 30 of 80 medical institutions across the nation were picked out considering the regional distribution and the final 25 institutions applied voluntarily to take part in this work. The basic rules were setup that any information of the participants be kept secrete and the measurements be performed with the dosimetry system already verified through intercomparision. The outputs for 2 or more photon beams, the accuracy of gantry rotation and collimator rotation and the poistional accuracy of MLC movement were measured. The findings for the output measurement showed the differences of -0.8%~4.5%, -0.79%~3.01%, and -0.7%~0.07% with respect to that of the verified dosimetry system for the 6MV, 10MV, and 15MV, respectively. For the reference absorbed dose 8 (16%) of 50 photon beams in 25 medical institutions differed 2.0% or greater from the reference value. The coincidences of Field size with x-ray beam and radiation isocenters of Gantry roration and collimator rotation gave the results of within +/-2 mm for every institute except 2 institutions. The positional accuracy of MLC movement agreed to within +/-1 mm for every institute. For the beam qualities of 6 MV photon beams kQ values showed the distribution within 0.4% between maximum and minimum. For the protocols 21 institutions (84%) used absorbed dose to water based protocol while 4 insitutions (16%) used air kerma based one. 22 institutions employed the SSD technique while 3 institutions did the SAD one. External audit plays an important role in discovering the systematic problems of self-performing Quality Assurances and having in depth discussion for mutual complementation. Training experts of international level as well as national support system are required so that both the group of experts of medical physicists and government laboratory could perform together periodical and constant external audits.

Keyword

External audit; Linear accelerator; MLC; Gantry; Collimator; Output

MeSH Terms

Complement System Proteins
Korea
Particle Accelerators
Reference Values
Silver Sulfadiazine
Water
Complement System Proteins
Silver Sulfadiazine
Water

Figure

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  Fig. 1. Meeting for the precheck up of the preparation items for the external audit.

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  Fig. 2. Star patterns to determine radiation isocenter of (a) gantry rotation and (b) collimator rotation. These angles are 0o, 30o, 90o, 135o, 225o, 300o.

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  Fig. 3. Picket and fence test to determine the positional accuracy of MLC movement.

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  Fig. 4. Distribution of outputs for 6, 10, and 15 MV photon beams performed in 25 hospitals.

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  Fig. 5. Distribution of radiation isocenters of gantry rotation and collimator rotation in 25 hospitals.

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  Fig. 6. Distribution of MLC positional erors determined by the Picket and fence test.

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  Fig. 7. Distribution of TPR10/20 ratios for 6, 10, and 15 MV photon beams in 25 hospitals.

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