HDR Source Acceptance and Safety Procedures

Introduction

• Speaker: Kevin Kennedy, Medical Physicist at Austin Cancer Centers
• Topic: Acceptance of HDR (High Dose Rate) source for electron micro solectron
• Context: Austin Cancer Centers with active brachytherapy programs
  • Includes LDR prostate siting and HDR for GYN, skin, breast

HDR Source Workflow

1. Production:
   • Iridium 191 bombarded with neutrons in a reactor to produce Iridium 192
   • Transported to the destination under government agency supervision
2. Usage Duration:
   • Typically used for 3 months, decays from 11-12 curie to 4-5 curie
3. Return Process:
   • Spent source returned through proper channels
4. Safety and Regulations:
   • Refer to IAEA safety standards via provided link

Source Acceptance Process

Preparation

• Notification:
  • Email from the vendor (reciprocity request) indicating incoming source
  • Expected arrival date is specified
• Source Reception:
  • Verify shipping declaration
  • Measure transport index (dose rate at 1 meter)
• Source Exchange:
  • Service engineer replaces old source, performs safety checks
  • Physics department reviews and conducts additional tests

Return and Documentation

• Return Process:
  • Spent source sent back to the vendor with documentation
• Compliance:
  • Follow Task Group 56 and 59 guidelines
  • International colleagues should refer to local guidelines

Testing and Validation

Source Verification

• Ensure Correct Source:
  • Confirm Iridium 192 received, not Iodine 125
• Dual Position Accuracy Test:
  • Ensures source travels precisely to designated points
  • Tolerance within 1mm

Dwell Time Accuracy

• Test Procedure:
  • Check if dwell time is accurate within ±1 second
  • Highly reliable with digital systems

Source Strength Measurement

• Activity Measurement:
  • Ensure measurements align with vendor certificates
  • Typically within 1% of reported values
• Use of Air Kerma Strength:
  • Move towards specifying source strength in air kerma rather than curie

System Checks and Daily QA

• Daily Checks:
  • Source position accuracy and interrupt button functionality
  • Use of homemade film strips for cost-effective testing
• Thermal Equilibrium:
  • Ensure housing ventilation to maintain positional accuracy

Cross-Calibration and Measurements

• Equipment Calibration:
  • Well chambers and electrometers calibrated biennially
  • Survey meters calibrated annually

Excel Spreadsheet and Documentation

• Data Entry and Analysis:
  • Enter data in colored cells
  • Cross-check source activity, temperature, and pressure

Conclusion

• Q&A and Further Discussion:
  • Addressed discrepancies and methods for different systems
  • Encouragement for feedback and follow-up via email

Key Takeaways

• Adherence to safety and accuracy standards is crucial
• Regular calibration and system checks ensure reliability
• Open communication with vendors and colleagues helps resolve discrepancies