Computed Tomography
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Introduction

Research on multi-slice/detector computed tomography (MDCT) is being undertaken in the Radiology Group, NDS, University of Oxford. Work involves balancing image quality and radiation exposure for patients undergoing MDCT for medical purposes. Areas of particular interest for our group include cervical spine imaging, low contrast imaging of the abdomen and abdominal sepsis. Dose survey work in collaboration with HPA Medical Dosimetry Group was undertaken and an initial draft report completed. The clinical expansion of CT and radiation dose are also discussed in Chapter 2 of the updated Springer book “Radiation Dose from Adult and Pediatric Multidetector Computed Tomography” (abstract).

 

Safety and efficacy of MDCT - abdominal sepsis

Part of the research into radiation dose constraint was funded by the EC (framework 6). The EC research programme sought to establish clinical justification of MDCT by field studies of use, safety and dose levels used in MDCT. Meta-analysis of published literature showed that new clinical applications of MDCT had been the target of recent research, but established common applications of CT were underrepresented in the new technology. Consequently, prospective studies undertaken by the consortium were designed to explore important information and guidance on the justification and optimisation of use of CT. Our work supported this programme and concentrated on abdominal sepsis. An education exhibit poster paper was presented for the EC group at ECR 2007, entitled “Current practices of MSCT: a descriptive analysis”, based on data collected from six radiology departments in different European countries. This was followed-up by an oral presentation at ECR 2008 entitled “Practice in multi-slice computed tomography: How do we perform?” (B-292). The results of our meta-analysis and retrospective/prospective studies on abdominal sepsis have been published (abstract). A scientific e-Poster paper on the diagnostic accuracy study was presented at UKRC in Birmingham and the poster was awarded the IPEM Poster Prize for best electronic poster exhibition at the UKRC Congress 2008. The following year an e-Poster paper reporting on the relationship between patient cross-sectional area and volume CTDI in abdominal MDCT (with automatic exposure control) was presented at the UKRC in Manchester. A scientific paper covering the work on patient cross-sectional area has been published (abstract).

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Third UK national CT dose survey

Following the further development of CT technology, a reduction in scan times, and expansion of new clinical applications there was a need to review current practice. The third UK national CT dose survey (2010/11) was undertaken to update existing examination specific national reference doses and provide guidance for some new establishing examinations. These will also act as the baseline for follow-up optimisation studies. The survey covers a range of diagnostic examinations, including disorders of the head and neck, chest, vasculature, abdomen and pelvis, bowels, and urology.

CT dose survey invitation hosted by CT Users Group QR code - Survey files

The invitation to take part in the survey was hosted by the CT Users Group on their website. However the survey documents (guidance notes + spreadsheet) can still be accessed and downloaded. The guidance notes for both the Third UK National and the UK Paediatric CT dose surveys are also available below.

Guidance notes for National CT dose survey Guidance notes for Paediatric CT dose survey

An e-Poster paper (e1606) was presented at the UKRC congress in Birmingham in 2010. The paper focused on early work on the CT dose survey, presenting results from pilot studies. An oral presentation (pdf) at the recent CT Users Group meeting, in London, provided a concise “introduction to the Third UK national CT dose survey”. The electronic forms and guidance documents were demonstrated, highlighting key features and procedures. Early progress with the survey was presented as an e-Poster paper (e103) at the 10th UKRC congress in Manchester. An article about the poster later appeared on auntminnie.com.

An internal draft report on the Third UK national CT dose survey was completed at the end of my fixed-term secondment period in July 2012. However, I was forbidden further access to the data by HPA whose replacement, Public Health England, published a final report in 2014. (Regarding the UK paediatric CT dose survey (participation by invitation), valuable data from paediatric centres of excellence were also available but have not been reported on.)

3rd UK national CT dose survey report

PHE report PHE-CRCE-013 published September 2014.

Dose reduction - cervical spine

Feasibility studies were performed to evaluate the potential for dose reduction when investigating cervical spine trauma using MDCT, without reducing fracture detectability. The studies utilised both in vitro phantom work and low-dose clinical images from archive. An oral paper was presented at the UKRC congress in Birmingham covering the initial results from work investigating potential dose reductions for cervical spine examinations using MDCT without reducing fracture detectability. The first phase of the cervical spine study concentrated on in vitro phantom work to avoid unnecessary patient exposure. The presentation showed that there is clear latitude for reducing dose while preserving image quality. An electronic poster covering two studies was presented at ECR 2015 in Vienna (the single-page mini e-Poster will be available below soon). A scientific paper has been accepted for publication (abstract).

 

Test phantom for low contrast abdominal imaging

A custom built phantom for both CT and MR has been constructed and tested, with the aim of simulating low contrast features in the abdomen. Known feature locations can be randomised between exposures to avoid learning effects by radiologists. Two electronic posters were presented at ECR 2014 in Vienna. The single-page mini e-Poster will be available below soon. A scientific paper has been accepted for publication (abstract).

ECR 2014 mini e-Poster available soon
ECR 2015 mini e-Poster available soon

Local audit

The image quality afforded by newer CT equipment also offers the potential to reduce patient exposure. As technology advances it becomes important to ensure that the exposure limitation potential is realised in practice, and historical dose audit can offer guidance. A study over a four year period was undertaken to determine if dose length product reductions were achieved in practice when a general CT service went through successive equipment upgrades from the same manufacturer. Results showed that upgrading the technology in itself did not automatically reduce the DLP and further work was required to optimise examinations with the aim of further dose constraint.

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Radiation Exposure in CT: What Is the Professionally Responsible Approach?
Golding SJ. Radiology 2010;255:683-686.

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EC work was financially supported by the EC-EURATOM 6 Framework Programme (2002-2007) and forms part of the CT Safety & Efficacy (Safety and Efficacy of Computed Tomography (CT): A broad perspective) project, contract FP6/002388.

WP1 group at Leiden - 12 Dec 2007

Framework 6, WP1 Group at Leiden Meeting, Wednesday 12th December 2007

(Back row, left to right) Koos Geleijns, Stephen Golding, Henning Ritter von Maravic, Christopher Alvey, Kostas Chlapoutakis, Alex Meijer; (Middle row, left to right) Aart van der Molen, Tilo Niemann, Karl Schneider, Veronica Alonso Ferreira, Georg Bongartz, Cesar Cordeiro Alves; (Front row, left to right) Yiannis Damilakis, Ying-Lie O, me, Alfonso Calzado Cantera.

Photograph - LUMC Medical Photography

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CT Guidelines and History
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IPEM Press Briefings Project and Committee

I am a member of the new IPEM Press Briefings Project and committee. The project aims to promote the IPEM along with the work of medical physicists and engineers through the supply of brief summaries of research articles that will interest the media and general public. The summaries are written to appeal to laypeople. Examples will be included here shortly.

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Last modified 20th November 2017

Stuart Meeson

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