Diagnostic Reference Level of Computed Tomography Examinations and Need for Dose Optimization in Ondo State, Nigeria

Document Type : Original Paper


1 Department of Physics, Federal University of Technology Akure, Nigeria

2 Department of Physics, Federal University of Technology Akure, Ondo State, Nigeria and University of Medical Sciences, Ondo, Ondo State, Nigeria

3 Department of Radiology, University of Medical Sciences, Ondo, Ondo State, Nigeria

4 Department of Radiology, Federal Medical Center, Owo, Ondo State, Nigeria


Introduction: The present study was conducted to obtain State diagnostic reference levels (DRLs) of five routine computed tomography (CT) examinations from two CT centers in Ondo State and to identify factors responsible for dose variation and escalation in these CT centers.
Material and Methods: Acquisition parameters and CT dose indices were collected from the storage drives of the two CT centers namely Federal Medical Centre, Owo and Trauma Center, Ondo, Ondo State, Nigeria, for six months on electronic spreadsheets for cranial, sinus, chest, abdomen and pelvis examinations. In addition, dose indices for multiphase examinations were collected to analyze chest and abdominal doses. Wilcoxon rank-sum test was used to assess variations in dose distributions of the two health institutions.
Results: The following diagnostic reference levels (DRLs) were obtained at 91 mGy; 1943 mGy.cm, 69 mGy; 1159 mGy.cm, 45 mGy; 1064 mGy.cm, 50 mGy; 2545 mGy.cm and 26 mGy; 622 mGy.cm in cranial, sinus, chest, abdomen and pelvis examinations respectively.
Conclusion: Estimated State DRLs exceed national and other DRLs indicating that there is a need to improve the quality of CT-examination for a better benefit to risk ratio.However, benchmarking DRLs to median dose levels (Achievable dose levels) instead of the upper quartile will be a good starting point in achieving the optimal dose level. 


Main Subjects

  1. References


    1. International Commission on Radiological Protection. The 2007 recommendations of the International Commission on Radiological Protection. ICRP 103. Elsevier limited, annals of the ICRP. 2007.
    2. Hart D, Hillier MC Wall BF. Doses to patients from radiographic and fluoroscopic and fluoroscopic x-ray imaging procedures in the UK–2005 review, Report HPA-RTD-029. Health protection agency. 2007.
    3. Hart D, Hillier MC, Shrimpton PC. Doses to Patients from radiographic and fluoroscopic x-ray imaging procedures in the UK–2010 review, Report HPA-CRCE-034. Health protection agency. 2012.
    4. Menrel HG, Schibilla H, Teunen D. European guidelines on quality criteria for computed tomography. Luxembourg: European Commission. 2000; 16262.
    5. Shrimpton PC, Hillier MC, Lewis MA, Dunn M. National survey of doses from CT in the UK: 2003. The British journal of radiology. 2006; 79(948):968–80
    6. Australian Radiation Protection and Nuclear Safety Agency. National diagnostic reference level fact sheet. 2013.
    7. Japan Association on Radiological Protection in Medicine. Diagnostic reference levels based on latest surveys in Japan. Journal of medical imaging and radition sciences. 2015.
    8. Qurashi A, Rainford L, Foley S. Establishment of diagnostic reference levels for CT trunk examinations in Saudi Arabia. Radiation protection dosimetry. 2014; 167 (4): 569-75.
    9. Sadri L, Khosravi HR, Setayeshi S. Assessment and evaluation of patient doses in adult common CT examinations towards establishing national diagnostic reference levels. Int. J. of Radiat. Res. 2013 Oct 1:11(4):245-52.
    10. Brix G, Nagel HD, Stamm G, Veit R, Lechel U, Griebel J, et al. Radiation exposure in multi-slice versus single-slice Spiral CT : results of a nationwide survey. European radiology. 2003;13(8):1979–91.
    11. Löve A, Olsson ML, Siemund R, Stålhammar F, Björkman-Burtscher IM, Söderberg M. Six iterative reconstruction algorithms in brain CT: a phantom study on image quality at different radiation dose levels. The British journal of radiology. 2013;86(1031):20130388.
    12. Thomas P, Hayton A, Beveridge T, Marks P, Wallace A. Evidence of dose saving in routine CT practice using iterative reconstruction derived from a national diagnostic reference level survey. The British journal of radiology. 2015; 88(1053):20150380.
    13. Palorini F, Origgi D, Granata C, Matranga D, Salerno S. Adult exposures from MDCT including multiphase studies: first Italian nationwide survey. European radiology. 2014;24(2):469-83.
    14. Li J, Udayasankar UK, Toth TL, Seamans J, Small WC, Kalra MK. Automatic patient centering for MDCT: effect on radiation dose. American journal of roentgenology. 2007;188(2):547–52.
    15. Catuzzo P, Aimonetto S, Zenone F, Fanelli G, Marchisio P, Meloni T, et al. Population exposure to ionising radiation from CT examinations in Aosta Valley between 2001 and 2008.  British journal of radiology. 2010;83(996):1042–51.
    16. Korir GK, Wambani JS, Korir IK, Tries MA, Boen PK. National diagnostic reference level initiative for computed tomography examinations in Kenya. Radiation protection dosimetry. 2016; 168(2):242- 52.
    17. Foley SJ, McEntee MF, Rainford LA. Establishment of CT diagnostic reference levels in Ireland. British journal of radiology. 2012; 85(1018):1390–7.
    18. Abdulkadir MK, Schandorf C. Determination of computed tomography diagnostic reference levels in North-Central Nigeria. The pacific journal of science and technology. 2016; 17(2):341–9.
    19. Mundi A, Hammed S, Dlama J, Abdul-Jamiu A, Peter E, Itopa R, et al. Diagnostic reference level for adult brain computed tomography scans: a case study of a tertiary health care center in Nigeria. IOSR Journal of dental and medical sciences. 2015; 14(1):66–75.
    20. ImPACT. ImPACT’s CT dosimetry tool. CTDosimetry version 1.0.4. 2011. Available from: http//www.impactscan.org/ctdosimetry.htm.
    21. Origgi D, Vigorito S, Villa G, Bellomi M, Tosi G. Survey of computed tomography techniques and absorbed dose in Italian hospitals: a comparison between two methods to estimate the dose-length product and the effective dose and to verify fulfilment of the diagnostic reference levels.  European radiology. 2006; 16(1):227–37.
    22. Ataç GK, Parmaksız A, İnal T, Bulur E, Bulgurlu F, Öncü T, et al. Patient doses from CT examinations in Turkey. Diagnostic and Interventional Radiology. 2015;21(5):428.
    23. Fukushima Y, Tsushima Y, Takei H, Taketomi-Takashi A, Otake H, Endo K. Diagnostic reference level of computed tomography ( CT ) in Japan, Radiation protection dosimetry. 2012; 151(1):51–7.
    24. Treier R, Aroua A, Verdun FR, Samara E, Stuessi A, Trueb PR. Patient doses in CT examinations in Switzerland: implementation of national diagnostic reference levels. Radiation protection dosimetry. 2010; 142(2):244–54.
    25. Wambani JS, Korir GK, Onditi EG, Korir IK. A survey of computed tomography imaging techniques and patient dose in Kenya. East african medical journal. 2010; 87(10):400–07.
    26. Ekpo E, Adejoh T, Akwo JD, Emeka OC, Modu AA, Abba M, et al. Diagnostic reference levels for common computed tomography (CT) examinations: results from the first Nigerian nationwide dose survey. Journal of  radiological protection. 2018; 38(2):525-35.

    26.Santos J, Foley S, Paulo G, McEntee MF, Rainford L. The establishment of computed tomography diagnostic reference levels in Portugal. Radiation protection dosimetry. 2014; 158(3):307–17.

    1. Asadinezhad M, Bahreyni Toossi MT, Nouri M. Diagnostic reference levels for computed tomography examinations in Iran: a nationwide radiation dose survey. Iran J. Med. Phys. 2019; 16:19-26.