3.79.
Image guided interventional procedures, performed either in fluoroscopy rooms or dedicated interventional rooms, tend to be complex and are performed on patients who can be very ill or have a life threatening condition. As a consequence, more staff will be needed in the room to attend to the patients’ individual medical needs (e.g. interventionists, anaesthetists, medical radiation technologists, nurses and other specialists). Not only will more staff be exposed during interventional procedures, but they may also be standing close to the patient, where dose rates from radiation scattered by the patient are high.
3.80.
Interventional procedures require specifically designed and dedicated equipment. The dose rate in the vicinity of the patient is lower on the beam exit side of the patient. For a vertical orientation, an under-couch X ray tube with an over-couch image receptor has lower levels of scatter radiation in the area of the operator’s trunk and head than an over-couch X ray tube with an under-couch image receptor. A similar situation exists with lateral projections, where the maximum scatter radiation is on the X ray tube side of the patient. Staff should, where practicable, always stand on the image receptor side of the patient during lateral or oblique projections.
3.81.
There are simple methods of reducing exposure of staff by means of operational factors, including choosing where to stand in the room. Since the patient is the main source of scatter radiation, staff members should remain as far away as practicable from the patient when exposures take place to reduce exposure of staff. For the interventionist, taking a step or even half a step back during image acquisition will result in a significant reduction in occupational dose. As stated in para. 3.80, the orientation and positioning of the X ray tube will determine where it is best to stand in order to be in an area subject to relatively low amounts of scatter radiation. Automatic contrast media injectors should be used when feasible to allow personnel to move away from the patient, ideally behind a shield.
3.82.
Staff should never be subject to direct beam exposure. This includes avoiding the placing of hands in the beam whenever possible. When the hands of the operator are close to the direct beam, an under-couch X ray tube with an over-couch image receptor should be used because the dose rate is lower on the beam exit side of the patient and the exposure of the operator’s hands is significantly reduced.
3.83.
There are many operational factors that affect patient dose during image guided interventional procedures, and these factors in turn affect staff dose because the dose to the patient determines the amount of scatter radiation being produced. Methods to reduce patient dose are described in paras 3.189–3.195, and should always be used to reduce both patient and staff doses.
3.84.
Medical radiological equipment specifically designed for image guided interventional procedures often incorporates protective devices, such as ceiling suspended, lead acrylic viewing screens, and under-table and lateral shielding attachments to the X ray couch, and personal mobile shields. Alternatively, such devices can be purchased separately. These devices can afford individuals significant degree of radiation protection, but they can sometimes be cumbersome to use. However, the appropriate use of these devices will result in a significant reduction in staff doses.
3.85.
A higher incidence of radiation injuries to the lens of the eye has been reported for interventionists and nurses performing image guided interventional procedures [117]. For this reason interventionists, and other staff who routinely work close to the patient, should always use ceiling mounted screens or protective eyewear. This is further reinforced by the relatively low dose limit (20 mSv per year) for the lens of the eye (see para. 2.22 and Box 1). It is quite likely that the dose limit would be exceeded for an interventionist performing several hundred image guided interventional procedures in a year if that person did not use any protection for the eyes. Protective shielding devices are effective only when they are interposed between the source of radiation and the eye. Care should be taken in the proper positioning of the imaging displays to ensure optimum benefit is derived from the use of screens and protective eyewear.
3.86.
Further specific guidance on interventional radiology and interventional cardiology, endorsed by several regional professional societies, can be found in Refs [117, 118].
3.87.
Some image guided interventional procedures are performed using CT, and the guidance given in para. 3.71 applies.
3.88.
For image guided interventional procedures involving intracoronary implantation of unsealed and sealed radiation sources, reference should be made to the guidance, where appropriate, in paras 4.75–4.89 and paras 5.117–5.145, respectively.