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Radiological Protection of Patients |
Interventional Cardiology |
Cardiologists are among the most intensive users of fluoroscopy in the medical profession, if not the most frequent. However, many of them are unaware that they may be exposing patients to relatively high levels of radiation during cardiac catheterization procedures - levels much higher than those handled by many radiologists. While staff protection is definitely important, there are bigger issues of patient protection in interventional procedures using X rays. For description of radiation units and dose quantities, please click here..
No. Radiation induced skin injuries happen very rarely and the rough estimate is around one in 10,000 interventions. This figure can vary by a large margin as many injuries go unreported. The skin injuries can vary from mild erythema to deep skin ulceration. Many interventionalists still do not acknowledge that skin injuries have or could occur. Such denial has lead, in many cases, to uncertain and ill-directed care for some patients. Injuries occur weeks or months after the interventional procedure was performed and could create problems in diagnosis. Most of these injuries can be avoided by using established radiation protection approaches.
Experience has shown that patients normally go to a physician or dermatologist when symptoms are detected. The delay between the interventional procedure and occurrence of symptoms coupled with the lack of instruction by the interventionalist to report back to him if there is any skin iritation on ports of entries of the X ray beam (typically patient's back), are responsible for misdiagnosis. There have been situations of misdiagnosis as insect bites, electrical burns, chemical burns or contact dermatitis. Typically in radiation induced injuries, normal methods of treatment with creams fail to give relief to the patient.
In most, if not all cases, the answer is ‘yes’, at least as far as the severe injuries are concerned. The experience from a centre where cardiologists were trained in radiological protection and the equipment was monitored and covered by a quality control programme indicates an absence of skin injuries in patients who underwent 5-7 PTCAs and 5-14 additional angiographies [VANO, E., et al., Skin radiation injuries in patients following repeated coronary angioplasty procedures, Br. J. Radiol. 74 887(2001) 1023-1031].
Entrance exposure to patients in diagnostic and therapeutic angiography might be a few hundreds to even a thousand times more than in a chest radiograph.
It must be emphasized that this way of comparing is an over-simplification as exposure situations are not similar.
There are patient, equipment and procedure dependent factors.
Patient factors include: body mass or body thickness in the beam, complexity of the lesion and anatomic target structure, radiosensitivity of some patients (ataxia telangiectasia); connective tissue disease and diabetes mellitus.
Equipment factors include: setting done by the manufacturer on fluoro- and cine mode, appropriate quality control, existence of cine loop, last image hold, pre-selectable number of radiographic frames per run and virtual collimation.
The main procedure related factors are: number of radiographic frames per run, collimation, the fluoroscopic and radiographic acquisition modes, fluoroscopy time, wedge filter, magnification, distance of patient to image receptor (image intensifier or flat panel detector), distance between X ray tube and patient and tube angulations. For further details please consult the references below.
Patient’s anatomic state, e.g. weight and the complexity of intervention are relevant and may be fixed, but a number of factors can help the interventionalist in patient exposure management. Collimation, a commonly neglected factor can prove to be the most efficient influencing factor. Restriction to the essential number of radiographic frames and to adequate (required image information) instead of best-possible image quality are more efficient than the potential of optimisation of fluoroscopy time. Further, adequately short radiographic runs, inspiration during radiography, avoid irradiating arms and breast, use means to monitor exposure, preference of less irradiating angulations, e.g. short skin-to-image-intensifier distance, use of the lowest image magnification compatible with the clinical objective [KUON, E., et al., Radiation-reducing planning of cardiac catheterization, Z. Kardiol. 94 10 (2005) 663-673].
Optimization of protection requires that exposure of patients be the minimum necessary to achieve the required diagnostic (BSS) and therapeutic objective of the intereventional procedure. By no means should dose reduction compromise clinical information and outcome. If overlooked, the adverse effects may be quality and extent of information.
The radiation exposure of the cardiologist is of significance principally for following three reasons:
Further factors to consider are:
Considering all these factors, the exposure to intervantionalists can be many times higher than a staff wo works only at the console located just outside the X ray room. [REHANI, M.M., ORTIZ-LOPEZ, P., Radiation effects in fluoroscopically guided cardiac interventions- keeping them under control, Int. J. Cardiol. 109 2 (2006) 147-151].
Proper use of radiation protection tools (most importantly the protective screens or lead glass barrier) and techniques can prevent deterministic effects such as cataracts for work in catheterization laboratory to cover full professional life.
There is a published report of radiation induced cataracts of one interventional radiologist and two nurses [VANO, E., et al., Lens injuries induced by occupational exposure in non-optimised interventional radiology laboratories, Br. J. Radiol. 71 847 (1998) 728-33]. Recent presentations in conference indicate early micro-lesions in a certain number of interventional radiologists [HASKAL,Z .J., Interventional radiology carries occupational risks for cataracts, RSNA News, June 2004, p 5].
At the moment, it is not clear if these early changes will lead to lens opacity. The subject of radiation induced cataract is under review by the International Commission on Radiological Protection (ICRP).
The interventional practice is increasing and some interventionalists perform many procedures (say 1000 procedures per year or more). Measurements and calculations indicate that if radiation protection devices and procedures are not used, the threshold for cataract can be exceeded with possibility of radiation induced lens injury. At the same time, it is clear that proper use of radiation protection can avoid lens injuries even with high workload.
Yes it is possible. Under optimized conditions when the equipment is periodically tested and it is operating properly, when personal protective devices (lead apron of suitable lead equivalence of 0.25 to 0.35 mm and wrap around type, protective eye wears or protective shields are used for head/face and leg region), when proper technique is employed, it is possible to achieve negligible probability of all known radiation effects during a full professional life. There are situations where patient protection poses a great challenge, not so much in staff protection where it can reasonable achieved.