What are the best practices for minimizing radiation exposure and ensuring patient safety during cardiac and interventional radiography procedures, particularly for patients with impaired renal function?

Best Practices for Radiation Safety in Cardiac and Interventional Radiography

Apply the ALARA (as low as reasonably achievable) principle through two primary strategies: selecting non-radiation imaging modalities when diagnostically equivalent, and optimizing fluoroscopic technique parameters to minimize effective dose (mSv) while maintaining diagnostic image quality. 1

Imaging Modality Selection

• Prioritize non-ionizing alternatives (echocardiography, cardiac MRI) over radiation-based modalities when diagnostic utility is truly comparable, particularly in younger patients with longer life expectancy 1
• Consider that nuclear perfusion imaging may be sufficiently superior to echocardiography in certain clinical scenarios to justify the small radiation risk, depending on patient characteristics affecting image quality 1

Fluoroscopic Technique Optimization

Equipment Positioning

• Maximize distance between X-ray tube and operator while minimizing distance between patient and image detector 2
• Activate fluoroscopic beam only when actively utilizing dynamic information—never irradiate unless eyes are on the monitor 2

Dose-Sparing Parameters

• Reduce detector dose and frame rate to the minimum that yields diagnostic-quality images 1
• Use active beam collimation to limit X-ray field to minimum necessary area 2
• Minimize beam-on time through meticulous technique 1
• Utilize last image hold feature extensively to study anatomy without ongoing exposure 2
• Limit magnification to least degree required—dose increases substantially with magnification 2
• Remove grid when appropriate and reduce tube current when image quality permits 2

DSA and Acquisition Protocols

• Minimize number of digital subtraction angiography (DSA) runs to minimum consistent with accurate diagnosis 2
• Limit examination to body region of interest in CT protocols 1

Personnel Protection

Mandatory Shielding

• All personnel in procedure room must wear 0.25- or 0.5-mm lead-equivalent aprons (absorb 95% of 70 kVp and 85% of 100 kVp X-rays) 3
• Thyroid shields are non-negotiable—decrease effective operator dose by approximately 50% 3
• Leaded eye protection with side shields required for personnel near X-ray source (ceiling-mounted shields reduce operator eye exposure by factor of 19) 3
• Position circulating personnel >8 feet from X-ray source when possible 3

Special Considerations for Renal Impairment

Contrast Agent Management

• Use lowest necessary iodixanol dose in patients with pre-existing renal impairment 4
• Adequately hydrate patients before and after contrast administration 4
• Do not use laxatives, diuretics, or preparatory dehydration prior to contrast administration 4

Metformin Protocol

• Stop metformin at time of or prior to intra-arterial iodinated contrast in patients with eGFR 30-60 mL/min/1.73 m², hepatic impairment, alcoholism, or heart failure 4
• Re-evaluate eGFR 48 hours post-procedure before reinstituting metformin 4

Dose Monitoring and Follow-up

• Monitor fluoroscopy time and cumulative dose throughout procedure 2
• Procedures exceeding 50 minutes fluoroscopy time or >4 Gy to interventional reference point warrant patient follow-up at 1 and 3 months for radiation injury 2
• Facility directors should tabulate patient procedure doses and personnel doses to verify guideline compliance 1

Risk Stratification

Individual radiation cancer risk is linearly related to total effective dose (mSv) and modulated by age, gender, and life expectancy 1. Radiation-induced cancer risk is most relevant for children, young adults, and females with long life expectancy, particularly those with congenital heart disease requiring repeated evaluations 1. Risk is less relevant in patients with shorter life expectancies and significant comorbidities, as most radiation-induced cancers require minimum 5 years to emerge 1.