|
Determinants of radiation dose from interventional fluoroscopy
The radiation beam in interventional fluoroscopy procedures is typically
directed at a relatively small patch of skin for a substantial length of time.
This area of skin receives the highest radiation dose of any portion of the
patient's body. The dose to this skin area may be high enough to cause a
sunburn-like injury, hair loss, or in rare cases, skin necrosis (Mettler 2002).
Threshold doses for potential radiation effects with related time of onset are
presented below (ICRP 2000). The highest doses have been reported most
frequently as a result of PTCA, radiofrequency cardiac ablation procedures,
transjugular intrahepatic portosystemic shunts (TIPS) procedures and
embolization procedures in the brain (Koenig 2001).
 |
Appearance of radiation-induced skin injury approximately 18 to 21 months
following multiple coronary angiography and angioplasty procedures - evidence
of progressive tissue necrosis (Source: www.fda.gov/cdrh/rsnaii.html) |
Potential Clinical Effects of Radiation Exposures to the Skin and Eye Lens
| |
Effects |
Threshold dose (Gy) |
Time of onset |
| Skin |
Early transient erythema |
2 |
2-24 hours |
| Main erythema reaction |
6 |
~1.5 weeks |
| Temporary epilation |
3 |
~3 weeks |
| Permanent epilation |
7 |
~3 weeks |
| Dermal necrosis |
>12 |
>52 weeks |
| Eye |
Lens opacity (detectable) |
>1-2 |
>5 years |
| Lens/cataract (debilitating) |
>5 |
>5 years |
Source: ICRP, 2000
During a procedure, several major parameters influence dose:
-
Number of images taken
-
Fluoroscopy time, field size and overlap of fields (Miller 2002)
-
Tube filtration, generator voltage and current
-
Reduced-dose pulsed fluoroscopy versus continuous fluoroscopy (Wagner 2000)
-
Distance between the X-ray tube and the patient and between the patient and the
image receptor
-
Patient body habitus
Radiation dose is optimized when imaging is performed with the least amount of
radiation required to provide adequate image quality and imaging guidance.
Optimizing patient radiation dose also provides a direct benefit to the
operator and assistants: scattered radiation in the room is directly
proportional to the patient dose. If patient dose is reduced, so is the dose to
the operator.
Back to Top
< Previous Section | Next Section > |