RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY L13.2: Occupational exposure - Radioprotection measures IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Subject matter: occupational exposure and regulatory aspects
The monitoring procedures
Investigation and follow up protocols
Personal protective equipment
Individual monitoring and exposure assessment
Investigation and follow up
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 IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
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
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
Protective devices CURTAIN SCREEN AND GOGGLES
Personal protective equipment
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
Part 13.2: Occupational exposure Topic 2: Individual monitoring and exposure assessment IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
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:
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
Several personal dosimeters are recommended
From: Avoidance of radiation injuries from interventional procedures. ICRP draft 2000
Different types of personal dosimeters…
” electronic” dosimeters
Film badge detects beta, gamma, X Ray
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
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,
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)
Part 13.2: Occupational exposure Topic 3: Investigation and follow up IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
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.
Part 13.2: Occupational exposure Topic 4: Health surveillance IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
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
Part 13.2: Occupational exposure Topic 5: Records IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
The registrant or licensee should maintain:
medical records for each worker
results from workplace monitoring
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
Other records to be maintained:
Results from acceptance and commissioning tests of radiology equipment
Audits and reviews
Installation, maintenance and repair work
Incident and accident investigation reports
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).