Head computed tomography doses in four selected hospitals in Nigeria Tom Adejoh (M.Sc) *Mark C. Okeji (Ph.D) **Musa Y. Dambele (M.Sc) Radiology Department NAU Teaching Hospital, Nnewi, Nigeria *Department of Radiography & Radiological Sciences, University of Nigeria **Department of Medical Radiography Bayero University, Kano, Nigeria PACORI CONFERENCE, TANZANIA 16 - 19 FEBRUARY, 2017

BACKGROUND OF THE STUDY Stochastic effects are main concerns of patient dose in CT (Ionnis, 2010). Justification, limitations and optimization are relevant principles of CT radiation protection ( ICRP, 1996). Efficient optimization → high quality images with minimal radiation dose (saravanakumar, 2014). Regular dose audits will produce efficient optimization (Huda, 2008). In Africa there is a paucity of literature on CT dose (Ogbole, 2014)

Global range for head CT LITERATURE REVIEW CT Dosimetrics CTDIvol (mGy) DLP (mGy-cm) (Foley 2012; IEC 2002) Global range for head CT CTDIvol: 32 – 77 mGy DLP: 925 -1050 mGy-cm (Saravanakumar, 2014; McCollough, 2009; Brix 2003) LITERATURE REVIEW

STATEMENT OF THE PROBLEM The region selected had the highest number of CT scanners of different models and radiation outputs. A perusal of series ‘999’ showed consistent higher dose than the 1999 European Commission recommendations of 60 mGy (CTDIvol) and 1050 mGy.cm (DLP). There was no evidence of dose survey since the scanners were installed. To audit the CT dose from the subregion as a quality control measure SIGNIFICANCE OF THE STUDY Awareness on dose output for the CT community Practical actions on dose optimization as a result of findings. AIM OF THE STUDY

Method & MATERIAL * Design: retrospective study * Place of study: Three tertiary hospitals (centres A-C) & a private diagnostic centre in Anambra State of Nigeria * Duration of study: February – August, 2016 *Ethical Considerations: approval & confidentiality settled *Inclusion criteria →for centre:highest throughput, available CT dosimetrics →for subjects: ≥ 18 years, nil scalp pathology * Scanners :GE, 4-slice; Toshiba, 16-slice (2x); Philips, 16-slice * Data analysis: SPSS version 20.0

Methodology A retrospective analyses of archived CT images of subjects aged ≥ 18 years Confidentiality of digital information was maintained by the activation of image anonymity features on the console. All the images that met the inclusion criteria were included in the study. The exposure parameters extracted from the first axial series and the on-screen CTDIvol and DLP for the subjects were recorded. The mean and 75th percentile of the CTDIvol and DLP were then calculated for each centre as well as for the four centres combined. Data were subjected to descriptive statistics and analyzed using analysis of variance.

Table 1: Anthropotechnical parameters for head CT RESULTS Table 1: Anthropotechnical parameters for head CT Variables Range Centre A Centre B Centre C Centre D M:F ratio 104:96 24:26 25:25 30:20 Age range 18 - 93 19 - 73 20 - 82 18 - 75 kVp 80 - 140 120 140 mA 10 - 350 220 250 mA modulation Yes/No No Yes Gantry rot time (s) 0.48 - 4 1 2 Scan range (mm) 180 - 320 200 Pitch 0.75 – 1.5 1.5 0.7 0.75 Scan mode Helical/axial Axial Helical Azimuth 0 - 360 90/180 0/90

Table 2: DOSE OUTPUT FROM THE CENTRES Variables European Commission 75th percentile Centre A B C D All centres Mean CTDIvol (mGy) 60 58 57 73 44 55 75th percentile CTDIvol (mGy) 59 86 46 66 Mean DLP (mGy) 1050 891 1195 1612 734 1108 75th percentile DLP (mGy-cm) 945 1414 1785 794 1444

Discussion Remedy Peer review Initial protocol Radiographer: Programmer: Initial protocol Peer review Radiographer: Remedy

DISCUSSION CONTINUED Initial programme: Default protocols that are faulty often give high radiation dose (centres B and C from table 1 & 2). → appropriate ab initio programme is a great step in dose optimization Peer review of dose output places an obligation on radiographer to optimize: output from Nigeria were higher than recommended values by EC and from literature Radiographer: The remedy for acceptable dose output lies with the radiographer’s regular dose audit.

RECOMMENDATIONS LIMITATIONS CONCLUSION * Dose output from the four centres in Nigeria were higher (66 mGy/ 1444 mGy-cm) than the recommendations of the European Commission (60 mGy/ 1050 mGy-cm). LIMITATIONS Absence of dosimetrics on some scanners decreased our sample size * A more widespread dose audit is advised * Regular dose audit of CT scanners is recommeded * Default protocol audit and remediation is also advised * Radiologists should request for dose summary to place an obligation on CT radiographers to be dose conscious RECOMMENDATIONS

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