In Vivo Dosimetry Using a Flat Surface Sun Nuclear Corporation Diode in 60co Beams for Some Radiotherapy Treatments in Ghana

Document Type : Original Paper


1 Department of Oncology, Komfo Anokye Teaching Hospital, Kumasi, Ghana

2 Departments of Medical Physics, School of Nuclear and Allied Science, University of Ghana- Atomic Campus, Ghana

3 National Radiotherapy and Nuclear Medicine Centre, Korle-bu Teaching Hospital, Accra, Ghana


Introduction: One of the useful standard quality assurance techniques in radiation therapy is monitoring entrance doses in in-vivo dosimetry. An overall tolerance limit of 5% of the absorbed radiation dose has been recommended by the International Commission of Radiological Units. The implementation of an in vivo dosimetry still remains as a challenge to clinical medical physicists. As a result, the practice of constant monitoring of patients undergoing radiation therapy in most of the radiotherapy departments in Africa has not been given much attention. The study aimed at the evaluation of in-vivo entrance dosimetry using diodes to verify the accuracy of the radiation delivered to patients, compared to prescribed doses.
Material and Methods: In this paper, a protocol for in vivo dosimetry using a two flat surface Sun Nuclear Corporation diode in a radiotherapy department has been implemented in equinox Cobalt 60 beams. A water phantom calibrated was performed using the International Atomic Energy Agency standards (TRS 398). Calibration coefficients were determined with diodes using a Perspex phantom to derive correction factors. A total number of 137 patients’ doses were measured with the diodes during the treatment of 4 different sites.
Results: The average deviation between the measured and expected entrance dose performed by the phantom studies was 5% (0.34±1.8%) in almost all cases.
Conclusion: The developed protocol in this study indicates that in vivo dosimetry using silicon diodes is reliable, which can be adopted as a universal quality assurance tool in the radiotherapy departments. Moreover, measurements with diodes can be acquired online which produces an instant readout and is relatively cheaper as compared to the ion chamber. 


Main Subjects



    1. Huang, K., Bice Jr, W. S., & Hidalgo‐Salvatierra, O.  Characterization of an in vivo diode dosimetry system for clinical use. Journal of applied clinical medical physics, 2003; 4(2), 132-142.
    2. Feldman A, Edwards FM. The routine use of personal patient dosimeters is of little value in detecting therapeutic misadministrations; Point/Counterpoint. Med Phys. 2001;28:295–7.
    3. 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; 21:581–618.
    4. Vinall, A. J., A. J. Williams, V. E. Currie, A. Van Esch, and D. Huyskens. "Practical guidelines for routine intensity-modulated radiotherapy verification: pre-treatment verification with portal dosimetry and treatment verification with in vivo dosimetry." The British journal of radiology 83, no. 995 (2010): 949-957.
    5.  Meiler RJ , Podgorsak MB. Characterization of the response of commercial diode detectors used for in vivo dosimetry. Med Dosim. 1997; 22(6): 31–7.
    6. Gager LD, Wright AE, Almond PR. Silicon diode detectors used in radiological physics measurements, Part I: Development of an energy compensating shield.  Med Phys. 1997; 4: 494–8.
    7. Huyskens D, Bogaerts R, Verstraete J, Lööf M, Nyström H, Fiorino C, et al. Practical guidelines for the implementation of in vivo dosimetry with diodes in external radiotherapy with photon beams (entrance dose). ESTRO booklet. 2001; 5: 13-28.
    8. Essers M, Mijnheer BJ. In vivo dosimetry during external photon beam radiotherapy. Int J Radiat Oncol Biol Phys. 1999; 43:245-59.
    9. Jornet N, Ribas M, Eudaldo T. In vivo dosimetry: Intercomparison between p-type and n-type based diodes for the 16-25 MV range. Med Phys. 2000; 27:1287-93.
    10. Mrčela I, Bokulić T, Budanec M, Kusić Z. Calibration of p-type silicon diodes for dosimety in 60Co beams. Zbornikradova Šestogasimpozija Hrvatskogadru štvazazaštituodzra čenja. 2005;300-5.
    11. International Atomic Energy Agency. Absorbed dose determination in external beam radiotherapy: An international code of practice for dosimetry based on standards of absorbed dose to water; technical reports series, Vienna, Austria. 2000; 398.
    12. Huyskens D, Bogaerts R., Verstraete J, Lööf M, Nyström H, Fiorino C, et al. Practical Guidelines for the Implementation of in vivo Dosimetry with Diodes in External radiotherapy with Photon Beams (entrance dose). ESTRO Physics for Clinical Radiotherapy, Booklet No. 5. 2001.
    13. International Atomic Energy Agency. Development of Procedures for in Vivo Dosimetry in Radiotherapy. Human Health Reports, No. 8. 2013. Available from:
    14. Voordeckers M, Goossens H, Rutten J, Van den Bogaert W. The implementation of in vivo dosimetry in a small radiotherapy department. Radiotherapy and oncology. 1998;47(1): 45-8.
    15. Van Dam J, Marinello G. Methods for in vivo dosimetry in external radiotherapy. Physics for clinical radiotherapy. ESTRO Booklet No.l. 1994.