L13.2 Occup Radioprot

IAEAInternational Atomic Energy Agency

RADIATION PROTECTION INDIAGNOSTIC AND

INTERVENTIONAL RADIOLOGY

L13.2: Occupational exposure - Radioprotection measures

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

IAEA 13.2: Occupational exposure - Radioprotection measures 2

Introduction

• Subject matter: occupational exposure and regulatory aspects

• The monitoring procedures

• Investigation and follow up protocols


Topics

Personal protective equipment

Individual monitoring and exposure assessment

Investigation and follow up

Health surveillance

Records


Overview

• To become familiar with the BSS detailed requirement for radiation protection of workers in diagnostic radiology.


Part 13.2: Occupational exposure

Topic 1: Personal protective equipment




• Registrants and licensees shall ensure that workers are provided with suitable and adequate personal protective equipment which meets any relevant regulations or standards (BSS I.28).

• Protective equipment includes lead aprons, thyroid protectors, protective eye-wear and gloves. The need for these protective devices should be established by the RPO


Protective clothing:

• Gowns, aprons and thyroid protectors made of a material (such as vinyl) which contains lead

• Aprons should be equivalent to at least 0.25 mm Pb if the X Ray equipment operates up to 100 kV and 0.35 mm Pb if it operates above 100 kV

• Aprons may be of the style which is open, or contains less lead, at the back, due to the extra weight of lead required - this assumes, however, that the wearer is always facing the radiation source

• Gauntlets are heavy gloves. They have limited value because they are difficult to use and should therefore only be used where appropriate


CURTAINSCREEN AND

GOGGLES

Protective devices



• Additional protective devices should be available in fluoroscopy and interventional radiology rooms which include: • Ceiling suspended protective screens.

• Protective lead curtains mounted on the patient table.

• Protective lead curtains for the operator if the X Ray tube is placed in an over couch geometry and if the radiologist must stand near the patient



Topic 2: Individual monitoring and exposure assessment



Individual monitoring and exposure assessment (I)

• Individual dose monitoring shall be undertaken for workers who are normally exposed to radiation in controlled areas:• radiologists, medical physicists, the RPO,

radiographers and nurses • Other frequent users of X Ray systems such as

endoscopists, anaesthetists, cardiologists, surgeons etc., as well as ancillary workers who frequently work in controlled areas, shall also be monitored.


Individual monitoring and exposure assessment (II)

• Individual external doses should be determined by using individual monitoring devices: • Thermoluminescent• Film badges• Electronic dosimeters

• Worn at breast level, between the shoulders and the waist

• The monitoring period should be one month, and shall not exceed three months.

• The exchange of dosimeters and report receipt should not exceed three months


Personal dosimetry

Several personal

dosimeters are recommended

From: Avoidance of radiation injuries from interventional procedures. ICRP draft 2000


Different types of personal dosimeters…Different types of personal dosimeters…

film

termoluminescence

dosimeters (TLD)

”electronic” dosimeters


Film badge

detects beta, gamma, X Ray


TLDTLD


TLDs

whole body extremity


Individual monitoring and exposure assessment (III)

• Evaluation of dose is an important aspect of radiation protection

• It is important that workers return dosimeters on time for processing

• Delays in the evaluation of a dosimeter can result in the loss of the stored information

• Licensees should make every effort to recover any missing dosimeters


Individual monitoring when a lead apron is used (I)

• The dosimeter should be worn under the apron for estimating the effective dose

• The other body areas not protected by the apron will receive higher dose

• One dosimeter worn under the apron will yield a reasonable estimate of effective dose for most instances

• In case of high workload (interventional radiology) an additional dosimeter outside the apron should be considered by the RPO


Individual monitoring when a lead apron is used (II)

• When expected doses are high, two dosimeters are required: • 1 under the apron at waist level• 1 over the apron at collar level

• The effective dose E is given by:E = 0.5 Hw + 0.025 Hn

where: • Hw : dose at waist level under the apron • Hn : dose recorded by a dosimeter worn at neck level

over the apron• Note: The thyroid shielding allows 50% reduction of the E

• The dosimeter worn over the apron at collar level gives also an estimation of thyroid and eye lens doses


Individual monitoring and exposure assessment (IV)

• In some facilities and for some individuals with a low level of exposure (e.g.: general dental practitioners), area dosimetry to estimate the level of dose per procedure can be an acceptable alternative.

• Some X Ray systems for dental radiography, or others used in surgical theatres which use X Rays on a limited number of occasions a month may not require individual dosimetry for all staff involved although fluoroscopy in surgical theatres may lead to high dose in short time if not properly conducted

• In these cases, area dosimetry or some other individual dose evaluation per procedure could allow the RPO to estimate the typical level of risk


Special aspects of individual monitoring

• In case of loss of a dosimeter, the dose estimation may be carried out from:• recent dose history,

• co-workers dose

• or, workplace dosimetry

• Individual monitoring devices should be calibrated

• Laboratory performing personnel dosimetry should be approved by the regulatory authority


Monitoring of the workplace (I)

• Registrant and licensees shall develop programmes for monitoring of the workplace:• All survey meters used for workplace monitoring shall be

calibrated and this calibration shall be traceable to a standards dosimetry laboratory

• Initial monitoring should be conducted immediately after the installation of new radiology equipment and shall include measurements of radiation leakage from equipment, and area monitoring of useable space around radiology rooms


Monitoring of the workplace (II)

• Annual area surveys should be performed

• All radiation monitors shall be calibrated, and their warning devices and operability should be checked prior to each day of use (BSS I.37–39)



Topic 3: Investigation and follow up



Investigation levels (I)

• Employers, registrants and licensees shall, in consultation with workers or through their representatives, include in the local rules and procedures the values of any relevant investigation level, and the procedure to be followed in the event that any such value is exceeded.


Investigation levels (II)

• A suitable quantity for use as investigation level is the monthly individual effective dose.

• The dose measured outside the lead apron (at collar or shoulder level) and the dose to the hands can also be used as a quantity for an investigation level for staff in interventional radiology.


Investigation levels (III)

• Monthly values higher than say 0.5 mSv (for the dosimeter worn under the lead apron) should be investigated.

• Values higher than say 5 mSv per month in the over apron dosimeter or in the hand or finger dosimeters should also be investigated with a view to optimization.


Investigation levels (IV)

• The licensee shall conduct formal investigations, as required by the Regulatory Authority, whenever (BSS IV.18–20):• an individual effective dose exceeds

investigation levels

• any of the operational parameters related to protection or safety are out of the normal range established for operational conditions


Investigation levels (V)

• any equipment failure, severe accident or error takes place, which causes, or has the potential to cause, a dose in excess of annual dose limit

• any other event or unusual circumstance that causes, or has the potential to cause a dose in excess of the annual dose limits or the operational restrictions imposed on the installation (e.g., the significant change in workload or operating conditions of radiology equipment)


Investigation levels (VI)

• The investigation shall be initiated as soon as possible following discovery of the event, and a written report shall be prepared concerning its cause (determination or verification of any doses received, corrective actions, and instructions or recommendations to avoid recurrence)

• The report shall be submitted to the Regulatory Authority and other concerned bodies as required, as soon as possible after the investigation, or as otherwise specified and kept for a specified period.



Topic 4: Health surveillance



Health surveillance (I)

• Primary purpose is to assess the initial and continuing fitness of employees for their intended tasks

• Medical surveillance (medical examinations) to workers as specified by the Regulatory Authority.

• Counselling should be provided for women who are or may be pregnant

This is especially relevant in interventional radiology.


Health surveillance (II)

• Under normal working conditions, the doses incurred in a radiology department are lower than the dose limits.

• No specific radiation-related medical examinations are normally required for persons who are occupationally exposed to ionizing radiation, as there are no diagnostic tests which yield information relevant to exposures that are close to or below dose limits.


Health surveillance (III)

• It is therefore rare for the radiation component of the working environment of a radiology department to significantly influence the decision about the fitness of a worker to undertake work with radiation or the influence the general conditions of service

• However in the case of accidental exposure to high doses (of the order of magnitude of 0.2-0.5 Sv or higher), specific radiation-related medical investigation are necessary



Topic 5: Records



Records (I)

• The registrant or licensee should maintain:• exposure records

• medical records for each worker

• results from workplace monitoring


Record (II)

Other records to be maintained:

• The authorization or registration documents

• Training provided (initial and refresher):• Name of the person who delivered the training

• Name of the person who received the training

• Date and length of the training

• List of the topics addressed

• Copy of the certificates of training


Record (III)

Other records to be maintained:

• Results from acceptance and commissioning tests of radiology equipment

• Audits and reviews

• Installation, maintenance and repair work

• Facility modification

• Incident and accident investigation reports


Summary

• Different technical approaches can be followed to monitor the occupational exposure as well as to optimize the radiation protection

• Several operating rules can be used to investigate the radiation dose level occurring at the different working area


Where to Get More Information

• International Basic Safety Standards for Protection Against Ionizing Radiation and for the Safety of Radiation Sources. 115, Safety Standards. IAEA, February 1996.

• “1990 Recommendations of the International Commission on Radiological Protection”, Pergamon, Oxford: 1991 (ICRP 60).

• INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Report on Methodology for Investigation of Accidents involving Sources of Ionizing Radiation, IAEA, Vienna (in press).

L13.2 Occup Radioprot

Education

Transcript of L13.2 Occup Radioprot