By: Mazen Khalil, MD, FSCAI and Jay Bagai, MD, FSCAI

Complex coronary and structural heart interventions (such as chronic total occlusion [CTO] percutaneous coronary intervention [PCI] and paravalvular leak closure) require prolonged radiation exposure to patients and staff. In addition, transradial PCI, which is replacing transfemoral PCI in many labs, is also associated with increased radiation exposure to the operator.1 Therefore, attention to radiation safety is becoming evermore important. Each year, several patients in the U.S. suffer permanent skin damage from fluoroscopic procedures, while adverse events for operators have also been reported.2 In this tip of the month, we will focus on adverse effects of radiation and elaborate safety practices to reduce exposure to patients and healthcare teams.

The terms commonly used to express radiation dose in the cath lab and their definitions are listed in Table 1.3 Radiation can lead to two kinds of adverse effects: deterministic (which includes skin injury, epilation, and cataracts) and stochastic (such as cancer and fetal malformations). Deterministic effects are listed in Table 2.3, 4 The deterministic effect is threshold dependent, whereas the stochastic effect is threshold independent. However, both effects are dose dependent.3 

Term

Definition

Units

Method of Measurement

Use

Peak skin dose

Absorbed dose at skin location that received the highest dose

milliGray (mGy)

Skin dosimeter (not commonly used)

Predicts risk of skin injury

Effective dose

Weighted average of the mean absorbed dose to the various body organs

Sievert (Sv); 1 Sv=100 mrem

Dosimeter worn by staff

Provides approximate measure of harm from cancer

Air kerma (AK)

Energy per unit mass absorbed by air at the “reference point” (assumed location of skin)

mGy

Calculated by fluoroscope

 

Differs from peak skin dose but is a rough estimate of the total skin dose and can estimate the risk of skin injury

AK product or dose area product (DAP)

Total energy deposition across entire exposed skin

cGy.cm2

Calculated by fluoroscope

Predicts radiation-induced cancer risk

Table 1. Measurements Used to Quantify Radiation Exposure and Risks3

Skin dose (Gy)

Prompt effect (<14 days)

Early effect

(2–8 weeks)

Midterm effect (6–52 weeks)

Long-term effect  (>40 weeks)

2–5

Transient erythema (TE)

Hair loss/erythema

Recovery

No effect

5–10

TE

Hair loss/erythema

Permanent hair
loss at high doses

Recovery, dermal atrophy/induration at higher doses

10–15

TE

Hair loss/erythema

Persistent redness,
permanent hair loss

Telangiectasia, dermal atrophy/induration

>15

TE

Hair loss/erythema

Dermal atrophy/
ulceration/dermal
necrosis necessitating
surgery

Late skin breakdown, surgical intervention likely

Table 2. Deterministic Effects of Radiation Exposure.3 A Skin Dose of Less Than 2 Gy Has Not Been Associated With Skin Injury

 

Radiation reduction techniques:

  1. Educate physicians and staff about radiation risks and radiation-reduction techniques.5
  2. Reduce radiation exposure to both the patient and the operator.3, 6
    1. Use as little radiation as possible, the As Low as Reasonably Achievable (ALARA) principle.
    2. Use a lower frame rate for fluoroscopy (4–7.5 frames/second) and cine (7.5 frames/second)
    3. Lower magnification.
    4. Minimize the distance between the patient’s body and the detector.
    5. Use fluorosave instead of cine.
    6. Avoid steep angles.
    7. Do not step on the fluoro pedal when not looking at the screen.
    8. Use collimation to decrease dose and scatter.
  3. Reduce radiation exposure to the patient.3, 6
    1. Avoid irradiating body areas, which are not of clinical interest.
    2. Maximize the distance between the X-ray tube and the patient’s skin by raising the table height.
    3. Delay elective procedures, if possible, to allow skin healing in patients who require multiple interventions.
    4. Change the C-arm angle during the case to avoid irradiating the same skin area for a prolonged time.
    5. Keep the patient’s extremities out of the beam.
    6. Have staff notify the operator when the AK exceeds 3 Gy, and then every 1 Gy thereafter.
  4. Reduce operator and staff exposure.3, 6
    1. Shield operator and room staff with use of lead aprons, lead-lined caps,7 lead glasses, removable radiation pads, and table- and ceiling-attached shields. The shielding of the left arm and legs is recommended as well. Movable screens are recommended for circulating staff. The use of suspended-operator lead shields (e.g., Zero Gravity) may provide better radiation protection and reduces orthopedic injuries.8
    2. Maintain the farthest possible distance from the X-ray tube.
    3. Keep the operator’s hands out of the path of the beam.
    4. Use radiation dosimeters to assess exposure and to provide feedback if high exposure occurs. The use of radiation-monitoring devices in real-time resulted in a 30 percent reduction of radiation exposure of the operators.9
    5. Use robotic PCI, if available. Robotic PCI leads to a significant reduction in operator radiation exposure.10
    6. Use double-lead aprons and dosimeters for pregnant operators and staff.

Quality assurance (QA) measures to reduce radiation exposure:

  1. Establish a cath lab QA program to record and review patient doses.
  2. In the event the AK exceeds 5 Gy, document it on the patient chart, inform the patient, and arrange for a follow-up to assess for skin injury.2, 4
  3. For an AK >10 Gy, have a qualified physicist calculate the skin dose.
  4. Review cases with an AK >15 Gy dose (Joint Commission sentinel event) and cases in which the patient suffers a permanent skin injury.3
  5. Review practices of staff who have high exposures. Provide education to improve techniques and consider reducing procedure numbers.
  6. Inspect lead aprons, at least yearly, for damage. 

Summary

 X-ray radiation has enabled physicians to perform lifesaving procedures, but radiation use comes at a cost. Reducing radiation exposure to the patient and staff by education, shielding, and improving techniques is of the utmost importance in maximizing the benefits and minimizing the risk of radiation.

     

References:

  1. Shah B, Bangalore S, Feit F, et al. Radiation exposure during coronary angiography via transradial or transfemoral approaches when performed by experienced operators. Am Heart J. 2013; 165(3): 286–292.
  2. Roguin A, Goldstein J, Bar O, et al. Brain and neck tumors among physicians performing interventional procedures. Am J Cardiol. 2013; 111(9): 1368–1372.
  3. Chambers CE, Fetterly KA, Holzer R, et al. Radiation safety program for the cardiac catheterization laboratory. Catheter Cardiovasc Interv. 2011; 77(4): 546–556.
  4. Balter S, Hopewell JW, Miller DL, et al. Fluoroscopically guided interventional procedures: a review of radiation effects on patients' skin and hair. Radiology. 2010; 254(2): 326–341.
  5. Georges JL, Karam N, Tafflet M, et al. Time-Course Reduction in Patient Exposure to Radiation From Coronary Interventional Procedures: The Greater Paris Area Percutaneous Coronary Intervention Registry. Circ Cardiovasc Interv. 2017; 10(8).
  6. Christopoulos G, Makke L, Christakopoulos G, et al. Optimizing Radiation Safety in the Cardiac Catheterization Laboratory: A Practical Approach. Catheter Cardiovasc Interv. 2016; 87(2): 291–301.
  7. Kuon E, Birkel J, Schmitt M, et al. Radiation exposure benefit of a lead cap in invasive cardiology. Heart. 2003; 89(10): 1205–1210.
  8. Fattal P, Goldstein JA. A novel complete radiation protection system eliminates physician radiation exposure and leaded aprons. Catheter Cardiovasc Interv. 2013; 82(1): 11–16.
  9. Christopoulos G, Papayannis AC, Alomar M, et al. Effect of a real-time radiation monitoring device on operator radiation exposure during cardiac catheterization: the radiation reduction during cardiac catheterization using real-time monitoring study. Circ Cardiovasc Interv. 2014; 7(6): 744–750.
  10. Smilowitz NR, Moses JW, Sosa FA, et al. Robotic-Enhanced PCI Compared to the Traditional Manual Approach. J Invasive Cardiol. 2014; 26(7): 318–321.

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