Diagnostic reference levels in interventional radiology

Abstract

Following the release of European Directive EU 97/43, radiodiagnostic facilities within the European Union are required to implement a system of patient dose reviews based on comparisons with European, national and local diagnostic reference levels (DRLs). Establishing these levels for typical interventional radiology examinations presents a problem as definition of 'typical' examinations can be difficult, patient numbers are limited and these procedures are often performed at a few specialist centres. This paper uses dose-area product (DAP) gathered over a period of 3 years from 40 fluoroscopy rooms to investigate potential difficulties when it comes to forming diagnostic reference levels for interventional radiology. Comparison of DAP distributions with standard complex (fluoroscopy based) examinations such as barium enema reveals considerably more variation for interventional procedures. Two methods of forming a DRL are compared: pooled patient DAP distributions versus a distribution of DAP per room. The bootstrap resampling method is then applied to DAP distributions to form a confidence interval for the chosen DRL statistic. Potential error on a DRL formed at a local level from a limited number of patient dose readings and x-ray rooms is significant. The results are reviewed in the wider context of DRLs in general radiology. For complex examinations, it is suggested that the function of the DRL is best served by setting DRLs based on pooled size-corrected patient DAP distributions rather than distributions of average DAP per room.

How to set up and apply reference levels in fluoroscopy at a national level

“…More and more effort is focused on dose-intensive fluoroscopy examinations. At the international level, the results of several investigations of patients' doses have been published in the recent literature [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Since the dose-intensive examinations involving fluoroscopy may result in a significant risk of deterministic effects, notably to the skin, it is recommended that the entrance surface doses be monitored for preventing skin injuries.…”

“…This is due to several factors, including the often loose definition of the examination, differences in the techniques and protocols used, the variability in the complexity of the cases and the experience of the radiologist. In 2000 already, Marshall et al [9] pointed out the difficulties encountered when establishing RLs for interventional radiology, such as the difficulty of defining a "typical" examination, the limited number of patients and the restriction to specialist centres. On the other hand, the large variability related to the procedures makes it meaningless in the application of RLs to compare a single interventional examination to the RL value.…”

“…As an alternative, the pooling of all the examinations registered regardless of their type is proposed to improve the accuracy of the RL values [9].…”

Radiation dose in vertebroplasty

“…The radiation risk to the radiologist is therefore high; the absorbed dose might cause deterministic dosedependent damage. There are reports on radiation exposure to the operator in neurodiagnostic and interventional procedures [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19], but to our knowledge none is available concerning vertebroplasty procedures. Our aim was therefore to measure the absorbed radiation dose during fluoroscopically controlled vertebroplasty and to evaluate the possibility of deterministic radiation effects to the operator.…”

A large-scale multicentre study of patient skin doses in interventional cardiology: dose–area product action levels and dose reference levels

“…Initial national DRL values can be derived from the 75th percentile of the overall DAP distribution of patients undergoing a particular procedure. This method of DRL calculation is indicated when a small number of catheterisation rooms contribute to the study [13]. Comparing the local mean values with proposed national DRLs gives an idea of how the current practice in a hospital ranks with respect to patient dose.…”