Effective Dose Levels from Computed Tomography of the Head during Contrast Studies in Nigeria

Thomas Adejoh^1*, Nzotta Chukwuemeka Christian², Flavious Bobuin Nkubli³, Joseph Zira Dlama⁴

¹Radiology Department, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Nigeria.
²Department of Radiography and Radiological Sciences, College of Health Sciences, Nnamdi Azikiwe University, Nnewi Campus, Nnewi, Nigeria.
³Department of Medical Radiography, College of Medical Sciences, University of Maiduguri, Nigeria.
⁴Radiology Department, Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria.

DOI: 10.4236/health.2015.78108                

Abstract

Background: Diagnostic reference levels for a number of common diagnostic radiological examinations against which individual centres could compare their performance have been recommended by relevant international agencies. Due to variations in different populations globally, local and national diagnostic reference levels are more reliable. To the best of our knowledge, no centre-specific study has been carried out and national surveys are not available. Objective: To establish a preliminary local and national diagnostic reference level in Nigeria. Methods: A pro-spective and cross-sectional study involving 30 conscious paediatrics and adult patients referred for head computed tomography scan. They were positioned supine and scanned according to the standard protocol for head computed tomography with manual mA selection. The total dose-length products were recorded at the end of the pre-contrast and post-contrast sequences respectively. The pre-contrast dose was taken into cognizance in the determination of the post-contrast value. The effective dose was established by multiplying the dose-length product by 0.0023 mSv.mGy^-1.cm^-1, a conversion coefficient for brain tissue adopted from the European Commission. Statistical Package for Social Sciences version 17.0 was used to analyze the data. Results: 30 paediatrics and adult patients of mixed gender participated in the study. Their ages ranged from 1 to 74 years with a mean age of 41.47 ± 23.30 years. The pre-contrast effective dose ranged from 1.93 mSv to 3.32 mSv with mean of 2.56 ± 0.51 mSv and 75th percentile of 3.11 mSv while the post-contrast effective dose ranged from 4.06 mSv to 6.97 mSv with mean of 5.27 ± 0.97 mSv and 75th percentile of 6.13 mSv. The mean effective dose from this work and two other isolated studies was 3.0 mSv. Conclusion: Although our quantified doses are below threshold limits for occupational exposures they are higher than the recommended level for the public. A further optimization of scanning protocols by the radiographers could lower the effective dose for patients undergoing contrast head computed tomography in our centre and in the country.

Keywords

Effective Dose, Diagnostic Reference Level, Radiographer, Computed Tomography, Head

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Foley, S.J., McEntee, M.F. and Rainford, L.A. (2012) Establishment of CT Diagnostic Reference Levels in Ireland. British Journal of Radiology, 85, 1390-1397. http://dx.doi.org/10.1259/bjr/15839549
[2]	International Commission on Radi-ological Protection (1990) Recommendations of the International Commission on Radiological Protection (Report 60). Annals of the ICRP, 21.
[3]	Miller, D.L., Kwon, D. and Bonavia, G.H. (2009) Reference Levels for Patient Radiation Doses in Interventional Radiology: Proposed Initial Values for U.S. Practice. Radiology, 253, 753-764. http://dx.doi.org/10.1148/radiol.2533090354
[4]	(2007) Recommendations of the International Commission on Radi-ological Protection. ICRP Publication 103. Annals of ICRP, 37, 1-332.
[5]	European Commission (1999) European Guide-lines on Quality Criteria for Computed Tomography. Report EUR 16262 EN. Office for Official Publications of the European Commission, Luxembourg, 66-78.
[6]	Osei, E.K. and Darko, J.A. (2013) Survey of Organ Equivalent and Effective Doses from Diagnostic Radiology Procedures. ISRN Radiology, 2013, Article ID: 204346. http://dx.doi.org/10.5402/2013/204346
[7]	Abdullahi, M., Shittu, H., Joseph, D., Aribisala, A.-J., Eshiett, E.P., Richard, I. and Kpaku, G. (2015) 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, 14, 66-75.
[8]	Ogbole, G.I. and Obed, R. (2014) Radiation Doses in Computed Tomography: Need for Optimization and Application of Dose Reference Levels in Nigeria. West African Journal of Radiology, 21, 1-6.
[9]	Brix, G., Nagel, H.D., Stamm, G., Veit, R., Lechel, U., Griebel, J. and Galanski, M. (2003) Radiation Exposure in Multi-Slice versus Single-Slice Spiral CT: Results of a Nationwide Survey. European Radiology, 13, 1979-1991. http://dx.doi.org/10.1007/s00330-003-1883-y
[10]	Origgi, D., Vigorito, S., Villa, G., Bellomi, M. and Tosi, G. (2006) 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 Fulfillment of the Diagnostic Reference Levels. European Radiology, 16, 227-237. http://dx.doi.org/10.1007/s00330-005-2682-4
[11]	Heidi, R.C., Timothy, R.P.L., Ting-Yim, L. and William, D.P. (2002) Dynamic, Contrast-Enhanced CT of Human Brain Tumors: Quantitative Assessment of Blood Volume, Blood Flow, and Microvascular Permeability: Report of Two Cases. American Journal of Neuro-Radiology, 23, 828-832.
[12]	Yamauchi-Kawara, C., Fujii, K., Aoyama, T., Yamauchi, M. and Koyama, S. (2010) Radiation Dose Evaluation in Multidetector-Row CT Imaging for Acute Stroke with an Anthropomorphic Phantom. British Journal of Radiology, 83, 1029-1041. http://dx.doi.org/10.1259/bjr/52267127