Radiation protection for angiography procedure

Radiation protection for angiography procedure
1. Describe the practice of radiation protection for angiography procedure.

Fluoroscopic procedure produces the greatest patient radiation exposure rate in diagnostic radiology. Therefore the radiation protection in fluoroscopy is very important. Several feature and techniques in fluoroscopy are designed for protection to the patient during fluoroscopic procedure.
a) Protection to Patient

* A dead-man switch is a device (switch) constructed so that a circuit closing contact can only be maintained by continuous pressure on the switch by the operator. Therefore, when the machine is turned on by any means, whether by the push button at the control panel, or by the foot pedal, this switch must be held in for the machine to remain ‘on’.

* The ‘on-time’ of the fluoroscopic tube must be controlled by a timing device, and must end … alarm when the exposure exceeds 5 minutes. An audible signal must alert the user to the completion of the preset on time. This signal will remain on until the timing device is reset.

* The X-ray tube used for fluoroscopic must not produce X-rays unless a barrier is in position to intercept the entire cross-section of the useful beam. The fluoroscopic imaging assembly must be provided with shielding sufficient that the scatter radiation from the useful beam is minimized.

* Protective barriers of at least 0.25 mm lead equivalency must be used to attenuate scatter radiation above the tabletop. This shielding does not replace the lead garments worn by personnel. Scattered radiation under the table must be attenuated by at least 0.25 mm lead equivalency shielding.

* Additionally, most c-arm fluoroscopes have a warning beeper or light that activate when the beam is on, some have both. Never inactivate any warning devices, and keep one’s foot off the foot pedal whenever possible.

* Methods of limiting radiation exposure include:

o making certain that the fluoroscopy unit is functioning properly through routine maintenance,

o limiting fluoroscopic exposure time,

o reducing fields of exposure through collimation,

o keeping the X-ray source under the table by avoiding cross-table lateral visualization when possible, and

o bringing the image intensifier down close to the patient
b) Protection to personnel

There are therefore three basic ways to minimize dose:

* Reduce time of exposure

* Use the inverse square law-doubling your distance away quarter your exposure

* Use shielding by barrier

These basics known as Cardinal Principle which is important to achieved ALARA.
i) Time

Radiation dose is directly proportional to the time, those by doubling the radiation time the dose is doubled and by having the radiation time the doses halved. Many factors impact the ‘on time’ of a fluoroscopic procedure.

The exposure time is related to radiation exposure and exposure rate (exposure per unit time) as follows:

Exposure time = Exposure/Exposure rate

Exposure = Exposure rate x time

The algebraic expressions simply imply that if the exposure time is kept short, then the resulting dose to the individual is small.

Method of reducing exposure time include meticulous advanced planning of the procedure, judicious use of contrast enhancement, appropriate positio