Document Type : Original Article


1 Radiography Unit, Department of Radiology, Federal University Teaching Hospital Owerri (Formerly, Federal Medical Center Owerri), Imo State Nigeria

2 Department of Physics, Federal University of Technology Owerri, Imo state, Nigeria

3 Department of Physics, Nigerian Army University, Biu, Borno State, Nigeria


The work aimed at establishing DRLs for adult CT examination of the head in Rivers State, Nigeria. The dose report and scan parameters for adult Head examination was retrospectively surveyed during the study period of four months in three CT center. Sixty-nine patient folders, comprising twenty-five subjects for center A, twenty-three subjects for center B, and twenty-one subjects for center C were included. Data on CT dose index (CTDIvol) and dose length product (DLP) displayed on CT scanner console from three (3) selected hospitals were recorded for each facility. The percentile (75th) was assessed for all centers to set up center-unique DRLs. Lastly, a summed percentile (75th) for mean of DLP and CTDIv in the entire centers was assessed to obtain DRLs in adult Head examinations across investigated area. Facts were analyzed with the aid of SPSS (version 25.0). The modern files (digital) of 24 female and 45 male patients with age bracket 16-100 years old were analyzed. Centre-unique percentile (75th) of mean DLP and CTDIv of three centers A, B, and C were 39 mGy and 820, 70.9 mGy, and 1330, 55 mGy, and 1158, respectively. The head CT examination DRLs for the area was 54.9 mGy and 1103 The Head CT examination’s DRLs for the state of Rivers has been obtained. Nonetheless, variation between CT scan center was noted, CTDIvol is lower than recommendations of European Commission (EC) of 60mGy. The DLP is slightly supper than EC value of 1000 Personnel training and more awareness on optimization of dosage may still aid to further guide down the dosage of radiation within the location compared to international values. Therefore, centers with fairly lower values than the state derived DRLs (LDRL) should retain their values, while those whose values are higher should implement dose optimization.

Graphical Abstract

Establishment of Diagnostic Reference Levels for Adult Head CT Examinations in Rivers State, South-South Nigeria


Main Subjects


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  1. Pearce MS, Salotti JA, Little MP, McHugh K, Lee C, Kim KP, Howe NL, Ronckers CM, Rajaraman P, Craft AW, Parker L. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study, The Lancet; 2012 Aug 4; 380(9840):499-505. [Crossref], [Google Scholar], [Publisher]
  2. Committee to assess health risks from exposure to low levels of ionising radiation NRC. Health risks from exposure to low levels of ionising radiation: BEIR VII phase 2. Washington, DC: National Academies Press: 2006. [Publisher]
  3. Hall EJ, Brenner DJ. Cancer risks from diagnostic radiology, The British Journal of Radiology; 2008 May; 81(965):362-78. [Crossref], [Google Scholar], [Publisher]
  4. De González AB, Mahesh M, Kim KP, Bhargavan M, Lewis R, Mettler F, Land C. Projected cancer risks from computed tomographic scans performed in the United States in 2007, Archives of Internal Medicine; 2009 Dec 14; 169(22):2071-2077. [Google Scholar], [Publisher]
  5. Radiological protection and safety in medicine. A report of the International Commission on Radiological Protection. Ann ICRP. 1996; 26(2):1-47. [Google Scholar]
  6. Institute of Physics and Engineering in Medicine. Guidance on the establishment and use of diagnostic reference levels for Medical X-ray examinations. IPEM report No. 88. York, UK: IPEM, 2004. [Publisher]
  7. Adejoh T, Nzotta CC, Aronu ME, Dambele MY. Diagnostic reference levels for computed tomography of the head in Anambra State of Nigeria, West African Journal of Radiology; 2017 Jul 1; 24(2):142-6. [Google Scholar], [Publisher]
  8. Garba I, Engel-Hills P, Davidson F, Tabari AM. Computed tomography dose index for head CT in northern Nigeria, Radiation protection dosimetry; 2015 Jul 1; 165(1-4):98-101. [Crossref], [Google Scholar], [Publisher]
  9. Abdulkadir MK, Schandorf C, Hasford F. Determination of computed tomography diagnostic reference levels in North-Central Nigeria, The pacific journal of science and technology; 2016; 17(2):341-9. [Google Scholar], [Publisher]
  10. Santos J, Foley S, Paulo G, McEntee MF, Rainford L. The establishment of computed tomography diagnostic reference levels in Portugal, Radiation protection dosimetry; 2014 Feb 1; 158(3):307-17. [Crossref], [Google Scholar], [Publisher]
  11. Lee KL, Beveridge T, Sanagou M, Thomas P. Updated Australian diagnostic reference levels for adult CT, Journal of medical radiation sciences; 2020 Mar; 67(1):5-15. [Crossref], [Google Scholar], [Publisher]
  12. 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 Dec 1; 142(2-4):244-54. [Crossref], [Google Scholar], [Publisher]
  13. Protection ER. 109: Guidance on Diagnostic Reference Levels (DRLs) for Medical Exposures, Directorate-General Environment, Nuclear Safety and Civil Protection; 1999. [Google Scholar]
  14. Shrimpton PC, Hillier MC, Lewis MA, Dunn M. National survey of doses from CT in the UK: 2003, The British journal of radiology; 2006 Dec; 79(948):968-80. [Crossref], [Google Scholar], [Publisher]
  15. Sistrom CL. The ACR appropriateness criteria: translation to practice and research, Journal of the American College of Radiology; 2005 Jan 1; 2(1):61-7. [Crossref], [Google Scholar], [Publisher]
  16. Wall BF, Shrimpton PC. The historical development of reference doses in diagnostic radiology, Radiation protection dosimetry; 1998 Nov 1; 80(1-3):15-9. [Crossref], [Google Scholar], [Publisher]
  17. Kumsa MJ, Nguse TM, Ambessa HB, Gele TT, Fantaye WG, Dellie ST. Establishment of local diagnostic reference levels for common adult CT examinations: a multicenter survey in Addis Ababa, BMC Medical Imaging; 2023 Jan 9; 23(1):6. [Crossref], [Google Scholar], [Publisher]
  18. McCollough CH, Leng S, Yu L, Cody DD, Boone JM, McNitt-Gray MF. CT dose index and patient dose: they are not the same thing, Radiology; 2011 May; 259(2):311-6. [Crossref], [Google Scholar], [Publisher]
  19. Bongartz G. European guidelines on quality criteria for computed tomography (Report EUR 16262, Brussels): Chapter 1, Quality criteria for computed tomography, Chest; 1998. [Google Scholar], [Publisher]
  20. European Commission European Guidelines on Quality Criteria for Diagnostic Radiographic images EUR 16260 EN. 1996. [Publisher]
  21. Tipnis S, Thampy R, Rumboldt Z, Spampinato M, Matheus G, Huda W. Radiation intensity () and visibility of anatomical structures in head CT examinations, Journal of Applied Clinical Medical Physics; 2016 Jan; 17(1):293-300. [Crossref], [Google Scholar], [Publisher]
  22. Goo HW, Suh DS. The influences of tube voltage and scan direction on combined tube current modulation: a phantom study, Pediatric radiology; 2006 Aug; 36:833-40. [Crossref], [Google Scholar], [Publisher]
  23. Aweda MA, Arogundade RA. Patient dose reduction methods in computerized tomography procedures: A review, Int J Phys Sci; 2007 Jan 1; 2(1):1-9. [Google Scholar], [Publisher]
  24. ICRP A. Radiological protection and safety in medicine, Ann. ICRP; 1996; 26(2):1-31. [Google Scholar]
  25. Wildberger JE, Mahnken AH, Schmitz-Rode T, Flohr T, Stargardt A, Haage P, Schaller S, GÜNTHER RW. Individually adapted examination protocols for reduction of radiation exposure in chest CT, Investigative radiology; 2001 Oct 1; 36(10):604-11. [Crossref], [Google Scholar], [Publisher]
  26. L.K. Sabiu, U. Rilwan, H.O. Aboh, I. Umar, H. A. Abdullahi, Assessment of Radiation Dose in Computed Tomography Examination of Adult Patient in Abuja and Keffi, Hospitals in Nigeria. Journal of Nuclear Medicine and Radiation Research; 2021 Aug 09; 12: 1-7. [Publisher], [PDF]
  27. Rilwan U, Onuchukwu GC, Sabiu LK, Abdullahi HA, Umar I. Abdominal CT Dose Examination for Adult Patient in Abuja and Keffi, Hospitals in Nigerian, Asian Journal of Advanced Research and Reports; 2020 Jan 24; 8(1):36-44. [Google Scholar]
  28. Rilwan U, C Onuchukwu G, Umar I, K Sabiu L, A Abdullahi H. Chest CT Dose Examination for Adult Patient in Abuja and Keffi, Hospitals in Nigerian, Asian Journal of Advanced Research and Reports; 2020 Jan 27; 8(2):1-9. [Google Scholar]
  29. Rilwan U, Onuchukwu GC, Abdullahi HA, Umar I, Sabiu LK. Head CT Dose Examination for Adult Patient in Abuja and Keffi, Hospitals in Nigerian, Asian Journal of Advanced Research and Reports; 2020 Mar 16; 9(1):8-13. [Google Scholar]
  30. Hassan AA, Ibrahim U, Ige TA, Zira JD, Aisha BA, Usman R. Assessment of Dose to Patients Undergoing Computed Tomography Procedures at Selected Diagnostic Centers in Kano, Nigeria. [Crossref], [Google Scholar]