National diagnostic reference levels for coronary CT angiography

On 15 November 2018, Public Health England published national diagnostic reference levels (NDRLs) for prospectively ECG-gated coronary CT angiography with and without tube current padding, and for retrospectively ECG-gated coronary CT angiography with tube current pulsing. The NDRLs are based on the BSCI radiation dose audit of coronary CT angiography carried out in 2014. The NDRLs can be found at

https://www.gov.uk/government/publications/diagnostic-radiology-national-diagnostic-reference-levels-ndrls/ndrl

For information:-

Coronary CT angiography (CTA)  Prospective, no padding 170
  Prospective, with padding 280
  Retrospective, with gating 380

 

BSCI/BSCCT coronary CT angiography radiation dose audit 2016

The BSCI/BSCCT has repeated the radiation dose survey of coronary CT angiography (CCTA) that was first carried out in 2014 in order to get an idea of how radiation doses have changed in the UK over the last two years.

Data was collected on 46 CT scanners during the period October 2016 – May 2017. Although the number of CT scanners in the sample was slightly smaller than in 2016 (50 CT scanners), the number of exams submitted per scanner was higher, with 78% of scanners providing 50 or more CCTAs as opposed to 56% of scanners providing 20 or more CCTAs in 2014.  

The median value across all participating centres of the centre median exam DLP was 170 mGycm (interquartile range 120-220 mGycm), approximately a 20% reduction compared to 2014. The median value of the centre median heart rate and BMI remained unchanged. Of note was a 30% reduction in the median exam DLP for prospective ECG-gated acquisitions with tube current padding, suggesting that padding is being used more sparingly. An increase in median exam DLP was observed as BMI and heart rate increased, but in the case of the latter the increase was not as marked as in 2014.

A report of the dose audit is available here.

 

BSCI radiation dose audit of computed tomography coronary angiography 2014

In 2014 the BSCI carried out an audit of the radiation dose of computed tomography coronary angiography, led by Dr Elly Castellano.

During March, 49 centres collected information on their cardiovascular CT work at the scanner side. Data included administration of beta-blockers, patient heart rate and BMI, and radiation dose descriptors for each series and for the total exam. The data at each centre was analysed to extract the median exam DLP, acquisition heart rate and patient BMI. If sufficient exams were available, further analysis was carried out to calculate the median exam DLP for prospective and retrospective acquisitions separately, and for the average patient with a heart rate of 60 bpm and a BMi of 28 kg/m2.

The median value across all participating centres of the median exam DLPs was 200 mGycm (inter-quartile range 130 to 320 mGycm). Using padding doubles the exam DLP from 120 to 250 mGycm for prospectively acquired exams, whereas retrospective gating with tube current pulsing increases the exam DLP by only a further 25% to 320 mGycm.

The audit has been published in the Journal of Cardiovascular Computed Tomography:-

A prospective national survey of coronary CT angiography radiation doses in the United Kingdom. Castellano IA, Nicol ED, Bull RK, Roobottom CA, Williams MC, Harden SP. J Cardiovasc Comput Tomogr. 2017 Jul - Aug;11(4):268-273. doi: 10.1016/j.jcct.2017.05.002.