Analysis of Effective Dose at Computed Tomography in a Modern 64 slice Multidetector CT System in an Irish Tertiary Care Centre with Local and International Reference Standards

Background Computed tomography (CT), by its nature, imparts a high dose of ionising radiation to patients being imaged. Diagnostic Reference Levels (DRLs) are used extensively in research but are also used in practice to establish if local imaging protocols have been optimised. Aim To audit effective dose (ED) at CT for four commonly performed examinations performed with a modern multidectector 64 slice CT (MDCT) system at large tertiary care centre by comparison with current international reference standards Methods 800 consecutive studies of CT brain, cervical spine, thorax and abdomen-pelvis were examined. All patients were imaged on 64-slice MDCT with study-specific protocols. Dose descriptors were extracted from image dose reports. ED was calculated using dose-length product conversion coefficients for all patients. Data was collated with Irish national and local DRLs, and published international point values. Results ED range at CT abdomen-pelvis of 2.03-26.04 mSv (mean 8.041 mSv) was 28.5% above the national DRL (9 mSv) and 26% above the local DRL (9.75 mSv). ED at CT thorax of 2.46-10.09 mSv (5.061 mSv) was 3.5% greater than local DRL (8.4mSv) and 42.5% greater than the national DRL (5.46 mSv). ED at CT brain of 2.25-8.08 mSv (3.075 mSv) was 100% above both the local (1.98 mSv) and national (2.06 mSv) DRLs. CT cervical spine ED of 1.49-21.94 mSv (5.14 mSv) was 79% greater than the local (3.07 mSv) and 100% greater than the national DRL (1.42 mSv). Conclusions All studies exceed national DRLs. A significant optimisation potential is noted, in particular, for studies involving the head and cervical spine. A further review of study protocols is necessary to facilitate optimisation of total study radiation dose. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial Student Audit Project was not registered for trial ID ### Funding Statement No external funding. ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Dataset for the study is available on request. * ATCM : Automated tube current modulation ASIR : Adaptive statistical iterative reconstruction CT : Computed tomography CTDIvol : Computed tomography dose index (volume) CUH : Cork University Hospital DAP : Dose-area product DLP : Dose-length product DRL : Diagnostic Reference Level ED : Effective dose FBP : Filtered back projection GE : General Electrical HSE : Health Service Executive IRCP : International Commission on Radiological Protection MDCT : Multidetector Computed Tomography mGy : milliGrays MSCT : Multislice Computed Tomography mSv : milliSieverts NRF : Noise Reduction Filtration PACS : Picture archiving and communication system SSCT : Single slice computed tomography TSL : Total scan length US : United States