Question

33. Provide at least two examples where excellent projection and positioning in X-ray imaging can be used effectively to reduce patient exposure and provide radiation protection

Answer 1

The use of radiation in medical examinations and procedures is the largest man-made source of radiation exposure.

The challenging task is to translate, for both patients and professionally exposed staff, the generic population risk obtained from epidemiological age- and gender-based risk into a personalized risk. Several genetic, environmental, and dietary variables can affect the variability of damage observed to any given level of radiation. For instance, radiation-associated chromosomal damage in interventional cardiologists is amplified by smoking and by genetic polymorphism of the genes involved in DNA repair.It would lead us beyond the scope of this text, to delve into these personal risk factors.

During catheter ablation procedures, the left anterior oblique (LAO) (and in some studies also the posteroanterior imaging)36 leads to a 40–50% higher dose rate for the patients than the right anterior oblique (RAO) projection because the spinal column and more cardiac tissue increase the tube settings. Patient doses depend on many other geometry factors and patient size, in addition to the projection angle. For the operator, the effect of the projection angle is the most relevant. With an LAO projection, the beam entrance site, where most scatter originates, is much closer to the operator than the AP or the RAO projection. The patient also poorly ‘shields’ that entrance site from the operator. As a result, the radiation towards the operator can be six times higher with LAO than with RAO. Minimizing LAO use thus greatly reduces both the patient and the operator exposure. With left-sided device implantation, RAO causes a higher dose rate for the operator than LAO, but the latter still causes more radiation for the patient and the other personnel

Reduce the magnification to the lowest amount needed for accurate imaging

The X-ray tube output is proportional to the distance between the tube and the detector. The detector should therefore be lowered onto the patient throughout the procedure. If table adjustments are required, there should be attention to lower the detector again after the table adjustments. Additional hardware, such as electroanatomical mapping systems, may result in the need to increase the tube–detector distance to prevent electromagnetic interference.

Avoid screening the pelvic area during advancement of the catheters from the groin, especially in young women. With gentle rotation, aiming the catheter curve anteriorly, the catheter generally can be advanced without need for fluoroscopic guidance.