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Patient-dose audit and subsequent optimisation of CT aortic angiograms
Patient-dose audit and subsequent optimisation of CT aortic angiograms
Submitted on 09 Sep 2015

Mr David J Platten (1), Dr Davis V Thomas (2)
1. Medical Physics Department, 2. Department of Radiology, Northampton General Hospital, United Kingdom
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Poster Abstract
Audit showed that doses for CT Aortic Angiograms (CTAA) were above the recommended national reference dose (NRD). This group of patients was looked at in more detail, which showed the dose was within the NRD. Nevertheless, changes were made to reduce cumulative doses.

Study information was exported from OpenREM for adult studies carried out using a Siemens Definition AS scanner between June and August 2014. The mean DLP for CTAA was 1170 (n=45), exceeding the NRD (1040 A larger number of studies was analysed in more detail (n=70). Each was reviewed: scans that included the peripheral run-off or thoracic aorta were excluded. Patients with a diameter larger than 500 mm were also excluded.

The mean DLP of the filtered dataset was 1180 (n=64). However, due to the skewness of the dose distribution, the median (1030 was used. This is comparable with the NRD (1040 and therefore acceptable.

The CTAA scan protocol was examined with a view to optimise cumulative dose. The patient group is typically men between the ages of 60-80 with abdominal aortic aneurysms (AAA). AAA is usually treated using endovascular stent-graft insertion (EVAR), necessitating up to three follow-up CTA scans in the first year.

The existing scanning protocol involved pre- and post-contrast acquisitions from diaphragm to groins. We concluded that the pre-contrast acquisition was required on the initial study but not at follow-up, thereby reducing dose by 50% for each follow-up scan and the cumulative dose in the first year by up to 37%. A follow-up re-audit is planned after one year to confirm our estimates and re-evaluate practice.

1. “PHE-CRCE 013: Doses from computed tomography (CT) examinations in the UK (2011 review)”, Public Health England, September 2014.
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