Radiation hazards for the patient in cardiological proceduresThe radiation dose to both staV and patients in interventional cardiology and radiology procedures is high compared to diagnostic procedures, particularly in the cardiological techniques of percutaneous coronary intervention (PCI) and radiofrequency ablation as well as developing techniques such as direct myocardial revascularisation.In considering the potential harmful eVects of radiation it is necessary to consider eVects on the patients themselves as well as the staV performing the procedure.There is considerable experience relating to the exposure of staV and increasing awareness of the importance of radiation protection for the staV and patients.Regulations covering both groups have been in place for 10-15 years.The aim of this article is to review the radiation hazards to the patient and the radiation protection measures taken to ensure that the risk to the patient is kept as low as reasonably practicable.In addition it will review the newly implemented Ionising Radiation Regulations. Radiation biologyThere are two main biological eVects of ionising radiation: deterministic and stochastic.Deterministic eVects are those in which the number of cells lost in an organ or tissue is so great that there is a loss of tissue function.The harm will not occur below a threshold and above this the severity of the eVect will increase with dose.Skin erythema and ulceration are examples of deterministic eVects.Stochastic eVects occur if an irradiated cell is modified rather than killed and then goes on to reproduce.The result may be the manifestation of a cancer after a prolonged and variable delay called the latent period.Stochastic eVects do not appear to have a threshold and the probability of the eVect occurring is related to the radiation dose.The International Commission for Radiation Protection (ICRP), an international professional body, produce recommendations which are the basis for the conceptual framework and key principles of radiation protection world wide.The current international recommendations 1 (ICRP 60) lay out the principles of justification, optimisation, and limitation of all radiation exposures.While there are no specified dose limits for patients, the main principle is that all deterministic eVects should be avoided while optimising radiation exposure to gain maximum diagnostic accuracy with minimum dose.In most interventional procedures the doses are such that only stochastic eVects need to be considered for radiation protection purposes, but recently a number of cases of skin erythema, necrosis and ulceration have been reported in the USA 2 3 and Europe. 4The case reports 5 published recently in this journal are two such examples.Unfortunately such problems generally come to light when reported by others and so there is usually little information about the procedure and radiation doses used to produce the damage as in the current reports.Nevertheless such cases serve as important examples of how things can go wrong.

The potential and problems of the superimposition of medical images from different techniques is addressed. Examples of current work and methods of combining images from nuclear medicine and radiology are presented, with discussion of their usefulness.

Digital images are produced by many medical imaging modalities. In general, imaging techniques have tended to compare rather than combine image information. Video and photographic methods have, however, been used to transfer image features from one modality to another (Higa et al, 1983; Morin & Sirr, 1984) and it has become practicable to transfer digital image data between devices. Hence it is now feasible to investigate the digital combination of images which display data in the same plane of interest. This should be particularly worthwhile if one modality provides complementary information, either by providing features which the other modality lacks or by confirming image features derived from a different physiological measurement. Transmission computed tomography (CT) and emission computed tomography (ECT) images are particularly suited for combination as the former provides anatomical detail whilst the latter provides functional information. The good edge features of the CT images should allow the correlation of images and improve the quantitation of the ECT studies. This paper describes the methods used and the problems found both in transferring digital image data between systems and in presenting the combined information on a single image data processor.

Summary. A radiolabelled monoclonal antibody (NDOG,) directed against placental alkaline phosphatase (PLAP) was used in the radio‐immunodetection of ovarian carcinoma. Tumour deposits were successfully visualized in 11 of 15 patients and the abnormalities demonstrated were classified as focal or diffuse. Of the 11 patients, eight showed focal abnormalities alone and three had a diffuse abnormality, of which two also showed a focal abnormality. False‐positive results may occur not only due to uptake of 123I by gut mucosa and an inadequately blocked thyroid gland but also from activity in an incompletely emptied bladder. A false‐negative result occurred due to high background activity in the liver masking a known, discrete tumour deposit.

Exposure to radiation by surgeon and patient was measured in ten cases during insertion of a dynamic hip screw, using image intensified screening. There were low levels of irradiation of the thyroid and eyes of the surgeon. However, the dominant hand of the surgeon was often exposed to higher levels. The use of a memory during screening significantly reduced the level of radiation measured (P < 0.05). Recommendations are made for reducing radiation exposure by the surgeon, and a method is described to measure the irradiation of surgeons' hands.