Preventing unnecessary exposure in fluoroscopy
» What are the two major concerns in radiation protection?
Because the X-ray beam is usually moved over different areas of the body during a procedure, there are two very different aspects to consider. One is the area most exposed by the beam, which results in the highest absorbed dose to that specific part of the skin and to specific organs. The other is the total radiation energy imparted to the patient’s body, which is related to the Kerma Area Product (KAP or PAK), a quantity that is easily measurable.
The absorbed dose to a specific part of the skin and other tissues is of concern in fluoroscopy for two reasons: one is the need for minimizing the dose to sensitive organs, such as the gonads and breast, by careful positioning of the X-ray beam and using shielding when appropriate. The second is the possible incidence of the radiation beam to an area of the skin for a long time that can result in radiation injuries in cases of very high exposure. On the other hand, the total radiation energy imparted to the patient’s body during a procedure is closely related to the effective dose and to the risk of radiation induced cancer.
In fluoroscopy, as in all types of X-ray imaging, the minimum exposure required to form an image depends on the specific image information requirements. An important characteristic of a fluoroscopic system is its sensitivity, i.e. the amount of exposure required to produce images. The use of intensifier tubes and more modern digital flat panel receptors make it possible to optimize the balance of patient exposure with image quality so as not to expose the patient to unnecessary radiation. Non-intensified fluoroscopy with just a fluorescent screen for a receptor should not be used because of the excessive exposure to the patient.
» What is the appropriate action that a medical facility can take to eliminate unnecessary patient exposure during fluoroscopy?
There are two general sources of unnecessary exposure. The first one is equipment deficiency and the second is operational deficiency. Physicists working in the context of radiation safety and quality assurance procedures can detect deficiencies in design and equipment performance. Physicians using fluoroscopic equipment can also have an effect on the radiation exposure of the patient, as there are many variables associated with the procedure that are controlled by the physician. These include selection of kV values, field of view, fluoroscopic time, use of beam limitation, and the use of specific imaging modes. Some modess uch as pulsed fluoroscopy can reduce exposure while the high-dose-rate mode contributes to increased exposure. A major factor is the use of appropriate fluoroscopic equipment. The use of non-intensified (dark room) fluoroscopy is not recommended both because of low image quality and excessive radiation exposure to patients and staff.
Table 1: Mean effective doses and DAP values from contrast procedures involving fluoroscopy
| Orthopaedic pinning (hip)[1] | 0.7 | 35 | |
| Pelvimetry[2] | 0.8 | 40 | |
| Micturating Cystourethrogram (MCU)[2] | 1.2 | 6.4 | 60 |
| Hysterosalpingogram (HSG)[2] | 1.2 | 4 | 60 |
| Discography[3] | 1.3 | 65 | |
| Barium Swallow[4] | 1.5 | 75 | |
| Fistulogram [2] | 1.7 | 6.4 | 85 |
| Cystography [2] | 1.8 | 10 | 90 |
| Myelography [2] | 2.46 | 12.3 | 123 |
| Barium meal [2] | 2.6 | 130 | |
| Barium meal follow through [4] | 3 | 150 | |
| Sinography [2] | 4.2 | 16 | 210 |
| Barium enema [2] | 7.2 | 360 | |
| Small bowel enema [2] | 7.8 | 30 | 390 |
[1] Crawley, M.T., Rogers, A.T., Dose area product measurements in a range of common orthopaedic procedures and their possible use in establishing local reference levels, Br. J. Radiol. 73 871 (2000) 740-744.
[2] Hart, A., Wall, B.F., Radiation exposure of the UK population from medical and dental x-ray examinations, NRPB-W4 (2002).
[3] Martin, C.J., Hunter, S., Analysis of patient doses from myelogram and discogram and their reduction trhugh changes in equipment set-up, Br J Radiol 68 809 (1995) 508-514.
[4] Wall, B.F., Hart, D., revised radiation doses for typical x-ray examinations, Br. J Radiol 70 833 (1997) 437-439.