Introduction Minimisation of radiation exposure during cardiac procedures is required by statute (IRMER 2000). During coronary angiography 26% of radiation dose is related to screening at standard frame rate (15 frames per second). Digital fluoroscopic technology has improved imaging making the use of lower frame rates feasible. This study assessed whether low frame rate screening (7.5 frames per second) was acceptable to operators and reduced radiation.
Method We collected prospective data from consecutive radial coronary angiographic procedures performed at reduced screening frame rate (7.5 frames/s). For inclusion angiograms had to be radial, diagnostic, non-training procedures. Graft cases and right heart catheters were excluded. Audit data from angiograms performed at standard frame rate with the same inclusion criteria were the control group. Phillips Allura flat plate XPER FD10 catheterisation equipment was used.
The frame rate could be increased to standard at the operator's request, and any safety concerns were reported immediately.
Data Collection Patient data:
Screening DAP (mGycm2)
Total DAP (mGycm2)
Total Fluoroscopy time (mm:ss)
Number of acquisition runs
Image quality: excellent, good, adequate, inadequate
Need to increase screening frame rate
Results Forty-one consecutive studies were examined at low-frame rate and compared with the audit control group (n=50). Image quality was reported as being adequate or better in all cases. Good or excellent quality reported in 67%. The patients in the low screening rate group were heavier (mean 83.5 kg) than the controls (79.5 kg), but of similar age. The screening times and number of acquisition runs were similar in each group.
Screening and Total DAPs (mean mGycm2) were 41% and 15% lower respectively in the low frame rate group. Statistical comparison was made with the Man–Whitney U test. This showed a significant reduction in the Screening DAP (p=<0.01) with low frame rate screening. See Abstract 53 Table 1 and Abstract 53 Figure 1.
Conclusions Low frame rate screening is a practical way of reducing radiation exposure in line with the ALARA “As Low as Reasonably Achievable” principle. We have shown that using low frame rate screening for diagnostic coronary angiography gives good imaging quality and is safe. Radiation exposure from screening is significantly reduced by 41% and total exposure is reduced by 15%.
Low frame rate screening should be standard practice where modern facilities allow. We suggest that centres currently using 15 frames per second screening should undertake a similar assessment in order to minimise radiation.
- frame rate
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