Methods of Radiation Protection Module 2 Lecture 2

Radiation Safety in the workplace

• It is the responsibility of an employer to provide the resources to ensure radiation levels for patients and workers are kept as low as possible.

• The employer must have a written policy outlining their commitment to reducing radiation exposure levels.

  • As Low As Reasonably Achievable (ALARA)

    • Synonymous with the term optimization for radiation protection (ORP)

Radiation Protection Guidelines are rooted in the philosophy of the ALARA Principle:

• Keep radiation exposure and consequent dose as low as possible

• ALARA principles should be incorporated into every health care facilities personnel radiation control program

• No safe dose levels exist for radiation-induced malignant disease so ALARA principles should always be enforced and should be the guide for therapists selecting technical exposure factors

The three Cardinal Rules of Radiation Protection under the Principles of ALARA are:

• Time

• Distance

• Shielding

______is the most effective way to increase radiation protection in radiation therapy

Distance

Reduce the amount of time the beam is on by:

Rad Therapy - Limiting the amount of repeat films on treatment machine, use appropriate techniques in CT sim.

Use as much distance as possible from the source of radiation

Rad Therapy – therapist should keep as much distance from a radioactive source (brachytherapy)

*Treatment Room Maze- takes more time to get in the room, increases the distance from the treatment machine and contains shielding in the walls (decreasing scatter radiation)

Always use shielding when possible

• Rad Therapy - Brachytherapy – lead shield

• Rad Therapy - Testicular shields when treating seminoma, concrete & lead lined walls, proper door and/or *maze

• X-ray (only) – lead apron

*Treatment Room Maze- takes more time to get in the room, increases the distance from the treatment machine and contains shielding in the walls (decreasing scatter radiation)

Applying the 3 Cardinal Rules to ourselves:

• Keep distance from patients receiving brachytherapy and minimizing time spent with them

• Always remain outside the room during simulations and treatments

  • Maze to room

  • Walls as barriers

  • Doors

Health care facilities usually adopt investigation levels, defined as level I and level II

• These levels are traditionally one tenth to three tenths the applicable regulatory limits, so way below allowable limits

  • See NCRP Report 184 overview – overall reduction in medical radiation doses

An effective radiation safety program must include:

• Employer’s responsibility:

  • Necessary resources to implement ALARA

  • Appropriate environment for ALARA program

  • Written ALARA policy statement identifying commitment to keep all employees within ALARA standards

  • Perform periodic exposure audits to determine how to lower radiation exposure in the workplace

• Radiation Workers Responsibility:

  • Beware of rules governing the workplace

  • Perform duties consistent with ALARA principles

RSO

• Radiation Safety Officer

  • Every hospital will have one

RSOs are directly responsible for the ALARA program and with regards to that program will be in charge of:

• Execution

• Enforcement

• Maintenance

Co60

radioactive source used for treatment – either in a Co60 unit (rarely used for treatment in the US) or a Gamma knife unit.

Brachytherapy

the treatment of cancer by the insertion of radioactive materials or implants either temporarily or permanently directly into the cancerous tissue and its immediate vicinity

Primalert

• will alert us when there is radioactivity in the room in the form of a radioactive source in the room or still in the patient

  • CO60 room, if the source has failed to retract back into its housing

  • In the case of HDR when the system has failed to retract the source

  • Rooms that house sources will be secure

    • Locked and badge entry

• When entering a CO60 room or a brachytherapy suite, individuals should check the _____ to make sure the flashing has ceased.

• These are located on the walls of the room.

• Primalerts should be checked daily to make sure they are operating properly (use a GM check source)

primalert

*GM check source

The GM survey meter is the most common device used for the detection of radioactive contamination. Check source is "a radioactive source, not necessarily calibrated, which is used to confirm the continuing functionality of an instrument"

When using CO60

Have an individual that has been deemed trustworthy and reliable remove the patient from the room and follow procedures for manual retraction of the source, will usually be the physicist.

When using Brachytherapy source

When treatment is complete the room should always be surveyed with a GM counter. If primalert is still flashing, the room and the patient should be surveyed, if the patient is clean, they should be removed from the room as soon as possible. The physicist usually will do the room surveys.

Warning signs:

• Entrance doors to therapy rooms must have posted signs

• For radiation levels in the room that can exceed 1 mSv in 1 hour the sign should read “Caution, High Radiation Area” (most radiation therapy rooms)

• For radiation levels in the room that can exceed 5 mSv in a 1 hour the sign should read “Grave Danger, Very High Radiation Area”

• For rooms with a radiation SOURCE – a room where a person could receive 5 Gy in 1 hour within 1 meter of the source would have a “Caution: Radioactive materials” sign.

Warning lights:

• Beam-on indicators are required on

  • Control panel

  • Entrance door

  • On the treatment unit

• Is to be illuminated when the unit is on (energized)

Door interlocks:

• Entrance door must have an interlock that will shut off the machine if the door is opened during treatment

• Also the unit must not produce radiation when the door is closed unless the operator turns the unit on

• If the treatment beam is on and the door opens, the beam should turn off. In this case, when the door closes again, the beam will stay off until the radiation therapist turns the beam on again.

Visual and Audio communication:

• Visual monitoring of the patient in the room is required at all times (by regulation)

  • Closed circuit TV system is generally used, with two systems active in case one system fails

• Audio monitoring between the therapist and patient is also required by regulation

Emergency Power-Off Switches:

• Emergency power-off switches are located at various points in the treatment room to shut power off to the machine

• To restart, the start procedure at the controls must be initiated

• For Co-60 units, mechanical means of returning the source to the head are provided

  • Therapist must be concerned with the patient first (removing them from the room), and his\her welfare next

Emergency handling Procedures for Linear Accelerator

Quality Assurance

• Frequent testing of safety devices to insure that they are working

• These tests are required either by regulation or by standard protocols