Introduction: Irregular/blocked fields are routinely used in radiotherapy. The doses of these fields are usually calculated by means of equivalent square method that is inherently prone to uncertainty. On the other hand, Clarkson’s sector integration method is a dose calculation method which offers far better accuracy in dose calculation of irregular fields. The Scatter Air Ratio (SAR) of an individual sector, in which whole field has been divided, is calculated and averaged over all sectors to find total SAR for the whole field. Percentage depth dose (PDD) and tissue-maximum ratio (TMR) for irregularly shaped beams can be calculated by the SAR values using the standard relationships of these measurement quantities. Material and Methods: The present study was conducted on 40 actual patient treatment fields. The PDD values for depths up to 15 cm were calculated using both Clarkson’s sector integration method and conventional methods, and their results were compared with the measured PDDs for all patients. Results: Maximum deviation for Clarkson’s calculation was under 2.7% for any field size, shape, and depth. However for conventional methods, this value exceeded ±5.5% for some field shapes, specifically at larger depths. Conclusion: Better results of sector integration are more prominent for field shapes with a large field size and a shielded area of regular shape. For the treatment fields with a very large degree of approximation for assessing reduced field size, Clarkson’s method is the most accurate technique for the calculation of absorbed dose.
Cigna AA, Nassisi D, Masenga D, Raffo R, Rotta P. Dose due to scattered radiation in external radiotherapy: A prostate cancer case history. Radiation protection dosimetry. 2004 Jan 1;108(1):27-32.
ICRU.ICRU-24-Determination of Absorbed Dose in a Patient Irradiated by Beams of X or Gamma Rays in Radiotherapy.Washington D.C; 1976.
IAEA.IAEA Human Health Series 31 - Accuracy Requirements and Uncertainties in Radiotherapy. IAEA Hum. Heal. Ser.2016;31:297.
Pirotta M, Aquilina D, Bhikha T, Georg D. Comparison of the ESTRO Formalism for monitor unit calculation with a Clarkson based algorithm of a treatment planning system and a traditional „full-scatter” methodology. Zeitschrift fuer Medizinische Physik. 2005 Jan 1;15(4):235-46.
Khan FM. The Physics of Radiation Therapy, 5th ed. Wolters Kluwer; 2014.
Johns HE , Cunningham JR. Physics of Radiology, 4th ed. Charles C. Thomas; 1983.
Sibtain A, Morgan A, N. Macdougall N. Physics for Clinical Oncology; 2012.
Cunningham JR, Shrivastava PN, Wilkinson JM. Program IRREG—calculation of dose from irregularly shaped radiation beams. Computer Programs in Biomedicine. 1972 Apr 1;2(3):192-9.
Bentel GC, Nelson CE, Noell KT. Treatment planning and dose calculation in radiation oncology, 4th ed. Pergamon Press Inc; 1989.
IAEA.TRS-398 Absorbed Dose Determination in External Beam Radiotherapy. VIENNA; 2000.
Lewis V, Woods MJ, Burgess P, Green S, Simpson J, Wardle J. The assessment of uncertainty in radiological calibration and testing. National Physical Laboratory; 2005.
Mayles P, Nahum AE, Rosenwald JC. Handbook of radiotherapy physics: theory and practice. CRC Press; 2007 Jun 12.
Steidley KD, Gamper C, Greener A, Caggiano A. A Clarkson's sector integration routine for personal computers. Medical physics. 1994 Jan;21(1):61-4.
Cruzet RU. Comparison between clinically used irregular fields shaped by Cerrobend blocks and by multileaf collimator using a Clarkson sector integration computer program. InWorld Congress on Medical Physics and Biomedical Engineering, September 7-12, 2009, Munich, Germany 2009 (pp. 867-870). Springer, Berlin, Heidelberg.
Tatcher M, Bjärngard BE. Equivalent squares of irregular photon fields. Medical physics. 1993 Jul;20(4):1229-32.
Tajiri M, Maeda T, Koba Y, Isobe Y, Kuroiwa T, Fukuda S, Tanimoto K, Shibayama K. Calculation method using Clarkson integration for the physical dose at the center of the spread‐out Bragg peak in carbon‐ion radiotherapy. Medical physics. 2013 Jul 1;40(7).
[Tajiri M, Maeda T, Isobe Y, Tanimoto K, Shibayama K. Correction method for the physical dose calculated using Clarkson integration at the center of the spread-out Bragg peak for asymmetric field in carbon-ion radiotherapy. Physica Medica. 2014 Dec 1;30(8):985-8.
Shahban, M., Waqar, M., Soomro, Q., Qasim, M., & Ijaz, U. (2019). Absorbed Dose Calculation In Irregular Blocked Radiation Fields: Evaluation of Clarkson’s Sector Integration Method for Radiation Fields Commonly Used in Conventional Radiotherapy. Iranian Journal of Medical Physics, 16(1), 103-111. doi: 10.22038/ijmp.2018.27328.1285
Muhammad Shahban; Muhammad Waqar; Quratulain Soomro; Muhammad Qasim; Umar Ijaz. "Absorbed Dose Calculation In Irregular Blocked Radiation Fields: Evaluation of Clarkson’s Sector Integration Method for Radiation Fields Commonly Used in Conventional Radiotherapy". Iranian Journal of Medical Physics, 16, 1, 2019, 103-111. doi: 10.22038/ijmp.2018.27328.1285
Shahban, M., Waqar, M., Soomro, Q., Qasim, M., Ijaz, U. (2019). 'Absorbed Dose Calculation In Irregular Blocked Radiation Fields: Evaluation of Clarkson’s Sector Integration Method for Radiation Fields Commonly Used in Conventional Radiotherapy', Iranian Journal of Medical Physics, 16(1), pp. 103-111. doi: 10.22038/ijmp.2018.27328.1285
Shahban, M., Waqar, M., Soomro, Q., Qasim, M., Ijaz, U. Absorbed Dose Calculation In Irregular Blocked Radiation Fields: Evaluation of Clarkson’s Sector Integration Method for Radiation Fields Commonly Used in Conventional Radiotherapy. Iranian Journal of Medical Physics, 2019; 16(1): 103-111. doi: 10.22038/ijmp.2018.27328.1285