GUEST COMMENTARY
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the “Women in Innovation” group for safety, two
cardiologists and one nurse with breast cancer
had left-sided tumors.13 Radiation safety for the
pregnant interventional cardiologist and/or cardiac catheterization laboratory nurse/technician
is a pressing issue. U.S. federal law prohibits
discrimination against the pregnant worker, but
pregnancy should be declared to the employer as
early as feasible so that adequate fetal protection
can be undertaken. Protective garments must
provide at least 0.5 mm lead-equivalent protection throughout the entire pregnancy, and an
additional monthly fetal dose-monitoring badge
should be issued and worn at waist level under
the protective garment.14
UNDERSTANDING ADVERSE EFFECTS OF
RADIATION EXPOSURE
The adverse risks of radiation exposure may be described in terms of stochastic and deterministic effects.
The stochastic effect is the non-threshold biologic
effect of radiation that occurs by chance to a population of persons whose probability is proportional to
the dose and whose severity is independent of the
dose. Developing malignancy due to radiation exposure is a stochastic risk.
The deterministic effect is a dose-dependent
direct health effect of radiation for which a threshold is believed to exist. Developing a skin burn as a
result of a prolonged case is a deterministic effect.
Dose exposure is usually described in terms of
the following parameters:
• Fluoroscopic Time (min): This is the time during
a procedure that fluoroscopy is used but does
not include cine acquisition imaging. Therefore,
considered alone, it tends to underestimate the
total radiation dose received.
TISSUE REACTIONS
Radiation-induced hair loss and injuries of the skin
and subcutaneous tissues are collectively termed
“tissue reactions” and are rare complications of
prolonged fluoroscopic procedures. Tissue reactions may be graded; this is influenced by biological variability. In general, Grade 1 reactions are
visible but seldom clinically important, but Grade
2 reactions may be clinically important. Grades 3
and 4 tissue reactions are usually considered to be
clinically important.15,16
Notification levels are intended to make the operator aware, during the procedure, of the cumulative
radiation used. This happens at 3 Gy. The substantial
radiation dose level is a trigger level for certain processes and follow-up measures and happens at 5 Gy.
It is not an indicator of a tissue reaction or a predictor of the risk of a stochastic effect but is intended to
alert providers to the possibility of a tissue reaction.
The following process should be followed when a
substantial radiation dose level is reached:
1. At the end of the procedure, the primary operator documents the clinical necessity for exceeding any substantial radiation dose level in the
medical record.
2. Patients are promptly informed when substantial amounts of radiation were used for their
procedures and the necessity for this.
3. Patients receive follow-up to determine whether
tissue reactions occurred.
4. If a tissue reaction is identified, the patient
FIGURE 1.
should be referred to an appropriate provider
for management. In general, biopsies of these
areas must be avoided.
5. These results are reported to and reviewed by
the interventional service quality assurance
and peer review committees.
MINIMIZING X-RAY EXPOSURE
This is enshrined in the “as low as reasonably
achievable” (ALARA) principle. The level of
protection should be the best under the prevailing circumstances, maximizing the margin of
benefit over harm. Imaging requirements depend
on the specific patient and the specific procedure.
Although better-than-adequate image quality
subjects the patient to additional radiation dose
without additional clinical benefit, reducing patient radiation dose to the point at which images
are inadequate is counterproductive and results in
radiation dose to the patient without any clinical
benefit.17 Using an anthropomorphic phantom,
significant differences were identified between
different manufacturers in terms of radiation
doses in comparable views.18
Commonly employed strategies to minimize
radiation exposure are summarized below and also
in FIGURES 1 AND 2.19
PRECAUTIONS TO MINIMIZE EXPOSURE TO
PATIENT AND OPERATOR
• Utilize radiation only when imaging is necessary to support clinical care. Avoid allowing the
“heavy foot,” to step on the fluoroscopy pedal
while not looking at the image.
Commonly Employed Strategies to Minimize Radiation Exposure
• Cumulative Air Kerma (Gy): The cumulative
air kerma is a measure of X-ray energy delivered
to air at the interventional reference point (15
cm from the isocenter in the direction of the
focal spot). This measurement has been closely
associated with deterministic skin effects.
• Dose-Area Product (Gy.cm2): This is the cumulative sum of the instantaneous air kerma and the
X-ray field area. This monitors the patient dose
burden and is a good indicator of stochastic effects.
The annual occupational dose limits for catheterization laboratory personnel are as follows:
Area
Maximum Dose/Year
Whole body
50 mSv
Eye lens
50 mSV
Skin or extremities
500 mSv
Fetus
0.5 mSv/month or
5 mSv/pregnancy
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CardioSource WorldNews
February 2016