Protection Physic lecture 6

RADIATION PROTECTION PHYSICS RIT 302 RADIATION SAFETY

Advisory Agencies

• Analyze existing data to develop recommendations for dose limits.

• Recommendations can be acted on by Congress or state governments and made into law.

• Major Advisory Agencies include:

  • NCRP (National Council on Radiation Protection and Measurement)

  • Established in the U.S.

  • Primary standard setter for radiation protection.

  • ICRP (International Commission on Radiation Protection)

  • Set the first radiation protection standards globally.

  • UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation)

Regulatory Agencies

• Responsibilities include licensing users of radioactive materials and radiation-producing equipment.

• Conduct inspections and enforce laws.

• NRC (Nuclear Regulatory Commission)

  • A U.S. agency overseeing reactor-produced isotopes and naturally occurring radioactive material.

  • Regulates both medical and nonmedical practices.

  • Many states have agreements concerning licensing, inspection, and enforcement with the NRC, referred to as “agreement” states.

Other Agencies

• DOT (Department of Transportation)

  • Manages the transportation of radioactive materials.

• FDA (Food and Drug Administration)

  • Regulates machines producing ionizing radiation.

• EPA (Environmental Protection Agency)

  • Regulates the design and manufacture of electronic products (e.g., medical x-ray equipment, linear accelerators).

  • Establishes operational standards for these devices.

Regulation of Medical Events

• Radiation therapy is highly regulated.

• Majority of reported medical events relate to:

  • Wrong dose of radiation delivered.

  • Administration to wrong patient.

  • Wrong location targeted.

  • Incorrect side treated.

  • Wrong setup applied during therapy.

• Most medical events stem from human error.

Reporting Events

• New conditions for reporting therapy medical events have been in effect since May 2012.

• Facilities must report if:

  • The total delivered dose differs from the prescribed dose by 20% or more.

  • Any single fraction of a fractionated treatment exceeds the prescribed dose by 50% or more.

  • Event involves the wrong patient, treatment modality, or treatment site.

• A written report must be submitted to the department within 30 days.

  • The report should include a summary of the event, root cause, and corrective actions taken, along with the effect on the patient.

Radiation Safety Program

• Establishes standards and rules for the safe handling and usage of radiation.

• Involves a Radiation Safety Committee.

  • Should include members from each department:

  • Surgery

  • Radiation Oncology

  • Diagnostic Radiology

  • Nuclear Medicine

Radiation Safety Program - RSO

• The Radiation Safety Officer (RSO) must be a qualified Medical Physicist.

• Main responsibilities include:

  • Overseeing a comprehensive radiation safety program.

  • Overseeing activities related to:

  • Receipt of radioactive material.

  • Conducting radiation surveys.

  • Monitoring personnel and areas.

  • Conducting leak tests.

  • Designing shielding.

  • Managing emergency response procedures.

  • Decontaminating radioactive spills.

Restricted Access

• Restricted areas limit access to protect individuals from undue radiation exposure.

• Unrestricted areas have radiation levels at background levels; do not require monitoring, posting, or control measures.

Three Categories of Restricted Areas

1. Radiation Area

   • Could result in an exposure of more than 5 mrem but less than 100 mrem in 1 hour at a distance of 30 cm from the radiation source.

   • Access control is required.

   • Warning sign must be purple, magenta, or black on a yellow background stating: “Caution- Radiation Area” with a three-blade radiation symbol.

2. High-Radiation Area

   • Could result in an exposure of more than 100 mrem in 1 hour at a distance of 30 cm from the radiation source.

   • Access must be controlled with features such as door interlocks to prevent unauthorized entry.

   • Warning sign: purple, magenta, or black on a yellow background stating: “Caution- High Radiation Area” with a three-blade radiation symbol.

3. Very High Radiation Area

   • Could result in an exposure of more than 500 cGy in 1 hour at a distance of 30 cm from the radiation source.

   • Access control must include features to prevent unauthorized entry.

   • Warning sign: purple, magenta, or black on a yellow background stating: “Grave Danger, Very High Radiation Area” with a three-blade radiation symbol.

Personnel Monitoring Program

• The RSO must monitor exposure records for all individuals assigned film badges.

• Mandatory monitoring for any individual who:

  • Receives or is likely to receive 10% of the applicable radiation dose limit.

  • Enters high radiation areas.

  • Operates portable x-ray equipment.

  • Operates photo-fluoroscopic equipment.

  • Services x-ray equipment.

Dose Equivalent Limits

• Annual occupational exposure limit is set at $50 ext{ mSv}$ per year.

• General public limit is $1 ext{ mSv}$ per year.

• Embryo Fetus Exposure limits:

  • Total: $5 ext{ mSv}$

  • Per month: $0.5 ext{ mSv}$

• From NCRP Report No. 116, Limitation of Exposure to Ionizing Radiation:

  • Occupational exposures (annual): Effective dose equivalent limit (stochastic effects) $50 ext{ mSv}$ (or $5 ext{ rem}$)

  • Public exposures (annual): Effective dose equivalent limit, continuous or frequent exposure $1 ext{ mSv}$ (or $0.1 ext{ rem}$)

  • Embryo-fetus exposures:

  • Total Dose equivalent limit $5 ext{ mSv}$ (or $0.5 ext{ rem}$)

  • Dose equivalent in a month $0.5 ext{ mSv}$ (or $0.05 ext{ rem}$)

Pregnant Employee

• May choose to declare or not declare a pregnancy at any time to the RSO.

• If declared, must advise the RSO voluntarily and in writing; the employer then takes responsibility for fetal dose monitoring.

• The RSO provides instructions and evaluates the radiation work environment of the employee.

• Restrictions may be applied to certain duties, such as caring for brachytherapy patients.

• Embryo Fetus Exposure limits remain: total of $5 ext{ mSv}$ (or $0.5 ext{ rem}$), and $0.5 ext{ mSv}$ (or $0.05 ext{ rem}$) per month.

• The pregnant employee will have 2 radiation monitor badges:

  • Fetal dose monitor worn at the waist.

  • Mother’s monitor worn at the collar/chest.

Protecting the Worker

• ALARA Principle: As Low As Reasonably Achievable; exposure levels set lower than regulatory limits.

• At GVSU (Grand Valley State University), if a radiation exposure reading exceeds $50 ext{ mrem}$ on any report, the program director is notified and an investigation is conducted.

• If a student exceeds the trigger dose limit ($50 ext{ mrem}$) on any personal monitoring report, they must be removed from clinical settings immediately and counseled by the university RSO, Program Director, and Clinical Coordinator on how to avoid further exposure.

• During fluoroscopy procedures, personal monitoring devices should be worn outside of the lead shielding.