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1 The Comparison the Output dose of a Linear Accelerator Photon Beams by Using the Ionization Chamber IC-10 Series Through TG-21 Protocol to Postal Monitoring Output of MDACC for One and Half Decade Tae Jin Choi, Ph.D., Jin Hee Kim, M.D., Ok Bae Kim, M.D. Department of Medical Engineering and Physics 1, Radiation Oncology, Keimyung University School of Medicine, Daegu, Korea Abstract

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4 20 ADCL Exposure calibration factor Nx INSTITUTE Cavity-gas calibration factor Ngas Phantom, calibration depth Dose to water Dmed Fig. 1. Flow chart shows the determination of water absorbed dose from exposure calibration factor which can be obtained from an Accredited Dosimetry Calibration Laboratory (ADCL) at time of the 60 Co exposure calibration. gas ( ) wall gas ( ) wall air wall Dgas = Jgas (W/e) Ngas = Dgas A ion / M Ngas = Nx Ngas = Nx Nx = X/M ( ) bldcap gas

Flow chart shows the determination of water absorbed dose from exposure calibration factor which can be obtained from

5 21 ( ) bldcap air ) ND = D water /M Ngas = N D D med/dgas = ( ) med gas =

6 22 Fig. 2. Schematic diagram of IC-10 Ionization Chamber. Table 1. The composition of % weight for chamber wall material C-552 of IC-10 series % Element H C O F Si density atomic No.% % mass g/cc Table 2. The parameters of ionization chamber IC-10 and IC-15 are provided from the manufacture and NBS for the exposure calibration factor Nx of which Co-60 gamma ray Chamber type inner radius (cm) chamber wall material Wall thickness (g/cm 2 ) Buildup material/thick (g/cm 2 ) SN active volume length Nx R/nc To ( o C) Po (mmhg) IC C Acrylic IC C PMMA

7 23 A wall = 1 - t /100

8 24 ( ) med gas D med = M Ngas ( ) med gas P ion P repl P wall P wall =

9 25 Table 3. The parameter of ionization chamber IC-10 and IC-15 for getting the Ngas factor Nx from exposure calibration Chamber type SN Nx R/nc Aion Awall uen/ L/ L/ 1 uen/ Ngas IC x10 8 IC x10 8 Table 4. The parameters of ionization chambers IC-10 and IC-15 in pulsed radiation beam for water absorbed dose (Gy) Chamber type SN Ngas (Gy/C) Xray Energy (MV) IC x IC x Pion Prepl Pwall Monitoring the output dose by TG-21 using the IC 10 and IC 15 ionization chambers. Fig. 3. The dose evaluations of output dose of linear accelerator (Mevatron, Siemens) verified constancy for 15 years long term from 1989 to The constancy have shown the for 6 MV and for 23 MV X rays.

The parameters of ionization chambers IC-10 and IC-15 in pulsed radiation beam for water absorbed dose (Gy) Chamber type SN Ngas (Gy/C) Xray Energy (MV) IC-10 351 1.852x10 8 6 1.128 1.01 1.00 0.

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11 27 Table 5. Determination of Pwall of ionization chambers IC-10 and IC-15 for 6 MV X and 23 MV X rays, respectivelly Chamber E (MV) 1 Pwall IC-10 IC

rays, respectivelly Chamber E (MV) 1 Pwall IC-10 IC-15 6 0.25 1.128 1.111 1.000 1.

12 28 1. Burlin TE. Radiation Dosimetry. 2nd ed. New York: Academic press;1968, p Kase KR, Bjarngard BE, Attix FH. The dosimetry of inonizing radiation. Vol II. Orland: Academic press;1987, p A protocol for the determination of absorbed dose from high-energy photon and electron beams. Med Phys 1983;10(5): Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, et al. AAPM s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 1999;26(9): Kirby TH, Hanson WF, Gastorf RJ, Chu CH, Shalek RJ. Mailable TLD system for photon and electron therapy beams. Int J Radiation Oncol Biol Phys 1986:12(2) ICRU Report No.14. Radiation dosimetry: X-Rays and Gamma Rays with Maximum Photon Energies Between 0.6 and 50MeV. ICRU, Washington, D.C.1969, p White GA Hr, Gibbs GL. Comments on A protocol for the determination of absorbed dose from highenergy photon and electron beams. Med Phys 1985;12(1): Johns HE, Cunningham JR. The Physics of Radiology. 4th ed. Springfield, : Charles C Thomas; 1977, p Khan FM. The Physics of Radiation Therapy. 4th ed. Philadelphia. : Lippincott Williams & Wilkins; 2009, p Nahum A.E. Water/air mass stopping power ratios for megavoltage photon and electron beams. Phys Med Biol 1978;23(1): Tomé WA, Palta JR. On the calculation of mean restricted collision stopping powers. Med Phys 1998;25(5): Fletcher GH. Textbook of radiotherapy, 3rd ed. Philadelphia: Lea and Febiger; 1981, p ICRU Report No.24. Determination of Absorbed Dose in a Patient Irradiated by Beams of X or Gamma Rays in Radiotherapy Procedures. Washington, D.C: ICRU;1976, p Kutcher GJ, Coia L, Gillin M, Hanson WF, Leibel S, Morton RJ, et al. Comprehensive QA for radiation oncology: Report of AAPM Radiation Therapy Committee Task Group 40. Med Phys 1994;21(4): American Association of Physicists in Medicine. AAPM Report No.86. Quality assurance for clinical trials: A primer for physicists. Madison: Medical Physics Publishing;2004, p Klein EE, Hanley J, Bayouth J, Yin FF, Simon W, Dresser S, et al. Task Group 142, American Association of Physicists in Medicine. Task Group 142 report: quality assurance of medical accelerators. Med Phys 2009;36(9): Khan FM. The Physics of Radiation Therapy. 4th ed. Philadelphia. Lippincott Williams & Wilkins; Ding GX, Cygler JE, Kwok CB. Clinical reference dosimetry: Clinical reference dosimetry: comparison between AAPM TG-21 and TG-51 protocols. Med Phys 2000;27(6):

Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, et al. AAPM s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 1999;26(9):1847-70. 5.

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