Radiation protection in interventional radiology.

Abstract

Introduction Furthermore, this information is usually displayed at the operator’s console where it cannot be seen In recent years there has been an increase in by the interventionalist undertaking the examinthe number, type and complexity of interventional ation. Unfortunately, total elapsed fluoroscopy radiology procedures. The impetus behind this time does not correlate very well with maximum rapid and continuing expansion has been the desire skin entrance dose. The latter quantity being for improved, more cost-effective medicine, in dependent on the automatic dose-rate control setwhich the patient can look forward to an improved ting selected, patient’s size, focus–skin distance and prognosis. Often patients having interventional the period of time that the area of skin was radiology procedures are treated as either outirradiated. Equipment developments are required patients or day cases, whereas the alternative surgito enable the interventionalist to be provided with cal technique would require hospitalization. This an on-line display which provides a better indiexpansion in interventional radiology has occurred cation of the potential onset of deterministic effects. in many countries worldwide, irrespective of the Extended fluoroscopy times, sometimes coupled type of system for health care delivery, because of with higher than average fluoroscopy currents can the many benefits. lead to an increased risk of non-deterministic In the main, interventional procedures are characeffects such as leukaemia in which the probability terized by having extended fluoroscopy times, and of the effect is proportional to the dose. The risk sometimes requiring many radiographic images to of inducing a hypothetical cancer at some time in be taken. As a consequence, developments in interthe future from interventional radiology correlates ventional radiology have a number of profound reasonably well with dose–area product. radiation protection implications for both patients Dose–area product is a quantity which may be and staff. In particular, the application of the conmeasured using a large area ionization chamber cept of justification to these procedures is different placed at the output port of the X-ray tube or than to other radiological examinations, as both inferred from a knowledge of X-ray technique deterministic and non-deterministic effects on the factors and the field size. Measurement of dose– patient have to be considered. area product is also recommended in the National Patient Dosimetry Protocol [1]. Patient dose The maximum skin entrance dose can be deduced from the dose–area product if the field For the patient, long fluoroscopy times lead to size and focus–skin distance are known. higher radiation doses, sometimes limited to a Instrumentation that is able to accomplish this is small area of the patient’s skin surface. This in in an early developmental stage. The display of turn leads to the potential for deterministic effects, total dose–area product and the estimated maxisuch as skin erythema, to be seen in patients who mum skin entrance dose on the interventionalist’s have had interventional radiology procedures. television monitor would provide information Physicians treating patients who have had an about the two types of radiation effect. interventional radiology procedure need to be It is also important to minimize patient doses aware of this possibility. whenever possible. One method of trying to achieve The potential induction of deterministic effects patient dose reductions would be to provide the in the skin is compounded by the lack of approinterventionalist with online dose rate information. priate patient dosimetry information available to The interventionalist could then select techniques the interventionalist during the procedure. At prewhich resulted in a lower patient dose, if desired. sent, fluoroscopy units used for interventional radiology are only required to be fitted with an Staff dose indication of total elapsed fluoroscopy time.