ANGIOGRAPHYANDINTERVENTION.COM
Radiation Dose
Patients are consented for their interventional procedure, outlining the risks and benefits of the treatment and detailing post-procedural care instructions. However, how many referrers and physicians inform their patients about radiation dose? Are interventional radiographers knowledgeable about radiation dose in the angiography suite? And how many patients do ask about radiation exposure and risk of cancer? Out of 100 patients, maybe just one.
Let us begin with what we know (what our machines tell us) and follow up with what we should know (what we need to calculate to inform patient radiation risks).
Radiation Dose Parameters on our Angiography Units
1
DOSE-AREA PRODUCT
(DAP)
Units: Gy.cm^2
Also known as kerma-area product (KAP). Refers to the total amount of radiation delivered to a person, and accounts for the rea of irradiated tissue.
Measured as the product of absorbed dose to air (Gy) and the irradiated area (cm^2).
The DAP value is independent of the distance (r) to the x-ray source, as dose decreases as 1/r^2.
DAP is linked to patients' stochastic risk.
2
AIR KERMA
(AK)
Units: Gy
When x-rays interact with matter, the energy transferred from x-rays to electrons occur through the Photoelectric Effect or Compton Effect.
Air Kerma is the kinetic energy released per unit mass when the x-ray is travelling through air.
AK is the intensity or strength of the x-ray beam.
Used to estimate Peak Skin Dose (PSD) or deterministic effects from radiation exposure.
3
FLUOROSCOPY TIME
Units: seconds
The amount of time that the operator has performed live fluoroscopy for imaging. Using either continuous or pulsed fluoroscopy.
A high fluoroscopy time can correlate with a high dose for the patient.
Fluoroscopy time only accounts for live fluoroscopy exposures and not other imaging modes such as DSA, conventional roadmap, single shot, or CBCT.
How else do we measure radiation dose in Angiography & Intervention?
Absorbed Dose - the amount of energy deposited by radiation in a mass (e.g. water, air, or tissue). Measured in milligrays (mGy).
Equivalent Dose - the absorbed dose to an organ and is adjusted to account for the effectiveness of the type of radiation (e.g. alpha, beta, gamma, x-rays).
Equivalent dose to an organ is measured in millisieverts (mSv).
Effective Dose - summation of the equivalent doses to all organs (tissue weighting factors) and thus cis calculated for the whole body. Adjusted to account for the sensitivity of the organ to radiation
Measured in millisieverts (mSv).