Medical Imaging Radiation Safety and Awareness Annual Training Requirement: 2016

This module is the medical imaging radiation safety and awareness annual requirement for 2016.

Radiation Safety Management

Introduction

Radiation Health administers Queensland’s Radiation safety Act and Regulation.  It holds policy, licensing and legislative responsibility for radiation health standards and radiation safety in Queensland. Everything that we do is governed by this act.  The purpose of this legislation is to protect people and the environment from the risks associated with exposure to ionising radiation.

In Queensland, our practices are  run in accordance with:

• Radiation Safety Act 1999

• Radiation Safety Regulation 2010

• Radiation Safety Standards

The main implication of this legislation is that all premises that use radiation apparatus or radioactive materials must have a Radiation Safety and Protection Plan (RSPP).

Radiation Safety Management

THSD Radiation Safety Management

The Possession License is held by the THSD.  The Executive Director of Medical Services is the nominee, acts as the point of enquiry and is the accountable officer to Radiation Health QLD.  To ensure the Radiation Safety Act, Regulations and Standards are complied with, governance structures and appointed Radiation Safety Officers (RSOs) for each practice are in place.  Appointed RSOs, Radiation Safety Coordinators and other stakeholders regularly inform the Protection Plan nominee of radiation safety matters, issues and compliance with the Act and Regulations.  The governance structure is below.

Obligations of RSOs

Obligations of the RSOs - Audit, Advise, Report

  • Identify ways of minimising dose to staff, patients and public
  • Provision of training on radiation safety
  • Report to the PL :  regarding RSPP contraventions, breaches of radiation safety standards, radiation incidents, annual report on audit results
  • Annually review the RSPP
  • Conduct onsite inspection of ionising sources and the areas to which they are contained.  Audit QA results and assessments
  • Investigate radiation incidents and provide report
  • Assess dosemeter dose reports

Appointed Radiation Safety Officers

Mark Lee DSA and Cardiac Catheter Lab  
Annette Cotter Nuclear Medicine  
Lani Palmer Medical Imaging TTH MID, OT, pain cilinic, endoscopy, Ayr, Ingham and Palm Island
Azhar Caddy Outer Medical Imaging Charters Towers Hughenden Richmond
Diana Hill Oral Health  
Paul Morrison Laser use  

Ockert Fourie

Scott Cooper

Radiation Therapy Oncology  

If the appointed RSO is absent, report any radiation incidents or concerns to

Naomi Gibson or Gary Kershaw on 31509 or 33166

Knowledge check

The obligations of the RSOs include to: and and

Principles of radiation protection - part 1

Principles of radiation protection

The three principles of radiation protection are:

  1.  Justification - benefit outweighs the risk.  No practice should be adopted unless its introduction produces a positive net benefit.  When people are exposed to radiation its use must be justified by ensuring that it does more good than harm.
  2.  Optimisation - all exposures should be kept as low as reasonably achievable, with economic and social factors being taken into account.  Exposure is optimised for each individual, e.g. technique.
  3.  Limitation - dose limited applied; no dose limits for medical exposures; DRL

where do these comments fit?

  • occupationally exposed and members of the public should not exceed the dose limits specified
  • Medical exposures have no limits, however, DRLs are used as guidelines to ensure limited exposures.

The object of radiation protection is to prevent both the deterministic and stochastic effects of radiation.  Protection plans are based on a linear no threshold model.  

Severity of effects depend on dose, however it is assumed that there is no threshold for safe radiation and therefore any radiation exposure can potentially cause harm.  For this reason we limit our exposures and adhere to the ALARA principle.

As Low As Reasonably Achievable

Knowledge check 2

  • As
  • Low
  • As
  • Reasonably
  • Achievable

Incident reporting

What is a radiation incident?

Any unintended or ill-advised event when using an ionising radiation apparatus or source which results in, or has the potential to result in any person being exposed to radiation outside the range of that which is normally expected for that practice.

This may be due to a calibration error, operator error, process failure, equipment failure, spill or other mishap.

If in doubt about whether something is an incident - report it!

Any radiation incident, for which there is no remediation process mentioned in the THSD RSPP, or where the source is thought to be lost or stolen, must be reported to the Chief Executive.  This kind of incident is termed a reportable or dangerous event.

Radiation incidents involving patients are reported on PRIME.

Radiation incidents involving staff, visitors or equipment should be reported on the THSD workplace incident form.

If a radiation incident occurs:

  1. Report incident to supervisor and RSO.
  2. Complete a PRIME or THSD Workplace Incident Report Form.
  3. When possible complete the relevant section of the incident report form and forward to the RSO.  This form can be found on M: drive: M:\ISS\MEDICAL IMAGING SERVICES\XRAY\Radiation Safety

Ionising radiation

Ionising radiation

Ionising radiation

Isonising radiation (for example x-rays) makes up part of the electromagnetic radiation spectrum.  It is in the higher energy part of the spectrum (wavelengths shorter than 248nm (5eV), which has been shown to be potentially more harmful to humans and is therefore regulated under legislation.

Ionisation is when an electromagnetic wave travels through matter, part of its energy is absorbed by atoms in the matter.  Depending on the energy and wavelength of the wave, the atoms in the matter may lose an electron (photoelectron) thereby changing its structure and ionising the matter.

Ionising radiation is radiation with sufficient energy to remove electrons during interaction with an atom, causing it to become charged or ionised.  This may be caused by spontaneous radioactive decay or by accelerating charged particles across an electric potential (x-rays).

The ionising radiation causes harmful effects when:

  • Cells experience DNA damage and are unable able to detect and repair the damage.  These cells may go through the process of programmed cell death, or apoptosis, thus eliminating the potential genetic damage from the larger tissue.

OR

  • Cells experience a nonlethal DNA mutation that is passed on to subsequent cell divisions. This mutation may contribute to the formation of a cancer.

The effects of radiation

Deterministic (early)

In this type, there is a threshold for these effects to occur (>100mSv inc dose = inc damage).

Examples include: Skin erythema, radiation syndromes and death. 

Diagnostic x-ray practices should not result in doses above the threshold levels.

Stochastic (late)

Here is there is no threshold, so any dose - no matter how small - has the potential to cause late effects, although increased dose = increased probability of damage (but not severity). 

Examples include: leukaemia, solid cancers, genetic effects.

Dose monitoring

Ionising radiation - dose

By quantifying the radiation delivered or received, safe work practices are ensured through monitoring.

Dose is a generic term which may refer to absorbed dose, equivalent dose or effective dose.  Effective dose is meansured in Siverts (Sv).

Absorbed dose (Gy) energy absorbed by unit mass.

Equivalent dose (Sv) is radiation weighted.

Effective dose (Sv) is tissue and radiation weighted.

Throughout this module, 'dose' will mean effective dose.

Doses typical of common medical imaging examinations

ARPANSA RPS 14.1 Annex A: Approximate effective doses arising from common radiological examinations in adults.

Ionisation radiation - dose versus risk

What does a dose mean in real terms?  Compare the dose received to the time it would take to accumulate the same dose due to background radiation.  The table shows a given dose, the time equivalent of background radiation and the lifetime risk of cancer due to that dose. 

 

The risks arising from most medical imaging examinations do not pose a substantial increase in risk compared to the 1 in 3 chance of being diagnosed with cancer in a lifetime.

Ionisation radiation - risks in perspective

To help put radiation risks in perspective the table below compares scenarios which represent a 1 in a million chance of death.  It can be seen from the above table that, under normal circumstances, the risk is relatively small compared with the risk of death from other causes.

The risk from a medical imaging procedure though small, cannot be described as being nil and current policy is to keep the radiation exposure as low as is possible. Often the benefit of the diagnostic information far outweighs the radiation hazard and the risk associated with a patient's illness may be such that any additional hazard due to radiation will be insignificant.

Ionisation radiation - dose limits

Dose limits are applied to both radiation workers and members of the public.  By having dose limits in place we may avoid deterministic effects altogether and minimise the likelihood of stochastic events later.

  • Radiation workers have a dose limit of 20mSv per year averaged over 5 years.
  • Non radiation workers and the general public have a dose limit of 1mSv per year.
  • Pregnant Radiation workers have a dose limit of 1mSv for the duration of the pregnancy.
  • Dose limits do not apply to the exposure of patients as part of their diagnosis or treatment.

The table below hows the occupational and public dose limits (effective and equivalent) which are used by the radiation safety legislation. 

Those who work with ionising radiation closely, such as Radiographers, wear dose-meters to show that if radiation safety legislation is complied with it is very effective at minimising the occupational radiation dose. Most Radiographers return doses of less than 2 mSv.  Radiation workers who work in Nuclear Medicine, the DSA suite and Cardiac Catheter lab often return higher doses that the general Radiographer.

It has been proven that those staff who don’t work directly with radiation (i.e. administrative staff, operational services officers etc.) do not need to wear dose-meters.  We are required to only monitor those who are likely to return a dose of 1mSv or greater. 

Dose limits and monitoring

To monitor our exposure levels, we wear dose-meters.  Dose-meters provide proof that safe radiation practices are being undertaken and determine a dose received as a result of occupation exposure or radiation incident.  Wearing of dose-meters can also be used to determine a dose received if it is believed a staff member was exposed to ionising radiation during a radiation incident.  In the case a staff member only has one badge, the badge should be worn under lead.

  • Dose-meters are worn at chest or waist height.
  • If wearing a lead apron they are worn under the apron.
  • Some staff have two dose-meters
  •   - ‘IN’  worn under lead apron
  •   - ‘OUT’ worn outside the lead apron
  • Badges should be worn for the duration of your shift and returned to the control board at the end of your shift.
  • All badges are sent for assessment quarterly with the resulting report being displayed in the general x-ray area.  The reports are kept tin the QRMS folder maintained by the RSO.
  • Pregnant staff changed to monthly monitoring for the duration of the pregnancy.
  • Monthly monitoring of nuclear medicine staff, catheter lab and DSA staff.

Radiation and pregnancy

Pregnant staff are very safe as long as they follow radiation safety guidelines and safe work practices. The pregnant radiation worker must notify the RSO regarding her pregnancy.  The workers dosimeter will be sent for reading on a monthly basis for the duration of the pregnancy. If you have any concerns regarding possible exposure as a pregnant worker please speak to the RSO.

It is not possible to accurately measure the dose to the foetus and so it must be inferred from the exposure to the mother. Radiation protection principles limit exposure to the mother in order to achieve minimum risk to the foetus.

Due to the possible effects, dosimetry during pregnancy differs from the usual protocol.

The level of risk to pregnant women is dependent on the stage of foetal development.

It is well known that the foetus is more sensitive to the effects of radiation than the adult human. The radiation-related risks throughout pregnancy are related to the stage of pregnancy and the absorbed dose. Radiation risks are most significant during organogenesis and in the early foetal period, somewhat less in the 2nd  trimester, and least in the 3rd trimester.

The medical irradiation of pregnant patients should be justified on an individual basis.  If a diagnostic radiological examination is medically indicated in a pregnant patient, the risk to the mother from not performing the examination is usually greater than the risk of potential harm to the foetus.  Most properly performed plain film and low dose examinations pose no substantial increase in risk to the mother or foetus compared to other risks throughout the pregnancy.  However interventional radiology procedures involving extended fluoroscopy times and CT scans of the Abdomen/pelvis may result in significant doses and therefore an increased risk to the foetus.

All females of reproductive age, who are to have a radiological examination or required to assist with the examination, should be asked about the possibility of being pregnant.  General radiographic examinations remote to the foetus can be undertaken of the pregnant patient without concern. Proper collimation and suitable radiation protection should be applied.  The Radiographer shall apply all relevant dose minimisation techniques, consistent with the radiologic diagnosis sought.

Direct x-ray exposure of the foetus must be avoided unless the authorised person* for the examination has given a specific direction in relation to the irradiation of the foetus.  All pregnant patients should be counselled regarding the level of risk due to them undergoing an x-ray examination while pregnant.  This should be done by the referring doctor/authorised person.

Other radiological examinations with likely high doses, that could result in increased risk to the foetus, should have foetal dose estimates.  Pregnant staff carers are not to hold patients during an x-ray examination.

Benefits must outweigh the risk.

Knowledge check 3

  • Deterministic
    >100mSv including dose is the threshold for effects to occur.
  • Stochastic
    Any dose, regardless of sizse, has the potential to cause late effects.

Principles of radiation protection - part 2

Principles of radiation protection

As we know, there are three patient-focused principles of radiation protection: justification, optimisation and limitation.  There are also three methods used to protect ourselves from identified radiation sources:

  1.  Time
  2.  Distance
  3.  Shielding

1.  Time

Image source:

Limiting time by keeping the time exposed to radiation at a minimum.  For workers, this means reducing the time exposed to x-rays.  For example, if you are not required in the screening room, do not enter the room.  For patients, this means reducing the time exposed by reducing the acquisition frame rate, optimising exposures and monitoring and reducing screening times.

For patients – reduce exposure time by: reducing acquisition frame rate, optimising exposures, monitor and reduce screening times. 

2. Distance

The intensity of radiation decreases with the square of the distance from its source (Inverse Square Law).  Doubling distance from the source will decrease occupational dose by ¼.  If you don’t need to be close to the patient or source at the time of the examination ensure you remain outside of the room.

General rules:

  • 2 metre distance
  • Not in primary beam
  • Scattered radiation
  • Keep hands away from primary beam

Image source:

Where should staff stand?

Scatter is highest on the beam entrance side of the patient.  In the image below, the tube would be better on the other side of the patient as this would reduce the dose that the operator receives. 

Please note: due to attenuation of the beam there is least scattered radiation directly behind the image intensifier.

  • During fluoroscopy do not stand in the primary beam.
  • Dose is higher on the tube side of the patient (due to scatter).  
  • Stand as far away from the source as possible. 
  • Have II/detector as close to the patient as possible. 
  • When using mobile x-rays stand 2 meters away.

3. Shielding

Lead, concrete and water give good protection from penetrating radiation such as gamma and x-rays.  If you are required to be in the room when an x-ray is taking place (and you are not the patient),  a lead gown should be worn.

When x-ray departments are constructed consideration is given to the type of practice (i.e. type of ionising radiation being produced) that will be performed and the workload of the rooms.  Adequate shielding is provided in the walls and doors to ensure safety. This may mean that the walls are thicker or lead lining is added.  These shielding requirements are reassessed if the use of the rooms change, new equipment is installed, workloads significantly change and so on.  Further, rooms are tested for compliance every 5 years.

It is the responsibility of the Possession Licensee to provide adequate PPE, and it is your responsibility to utilise it correctly.

There have been several reported incidents in 2011 involving staff not wearing PPE, operators/nursing/support staff not wearing lead or forgetting to wear lead.  Be vigilant and look out for each other.  Make sure that when a staff member is scrubbing for the procedure that they have lead on.

Knowledge check 4

  • Time
  • Optimisation
  • Distance
  • Shielding
  • Limitation
Choose which of the following are used to protect workers from identified radiation sources.

Safe work practices

Safe work practices

This section needs work by SME

• Obligations

• Other considerations

• Safe work practices in:

  - General Radiography

  - Fluoroscopy

  - CT

  - Nuclear Medicine

 

Obligations of the Use Licensee

  •   Comply with code of practice (ARPANSA).
  •   Abide by RSPP.
  •   Undergo training prescribed in the RSPP
  •   Undertake x-ray imaging only from a valid request
  •   Work within the scope of your licence and licence restrictions.
  •   Be aware of patient and staff radiation risks.
  •   Wear your dosemeter.
  •   Wear Personal Protective Equipment when required.
  • Verbal requests may be accepted if clinically urgent and if followed immediately by a written request (from an authorised person).

  Minimising patient exposure minimises occupational exposure.

Before you start

A significant number of radiation incidents can be attributed to a failure in completing the final check.

So before you start XXXXX be sure to:

  •   Review previous examinations, images and results
  •   Room Safety and preparation
  •   Ensure you have a valid request form - appropriate examination, clinical history, signature of  approved person (as per RSPP).
  •   Give a good explanation of the examination to the patient.
  •   Patient preparation – remove any objects or clothing which may cause image artefact.
  •   Know protocol and modify if necessary.
  •   Ask all female patients (and those assisting) of reproductive age of the possibility of pregnancy.

To ensure safe work practice in general radiography, we need to keep these points in mind:

  • Exposure factors
  • Exposure creep
  • Collimation
  • PPE
  • Patient considerations

All staff who undertake or who are involved in undertaking plain film diagnostic radiography within the THSD must read Module One – Additional requirements for Plain Film – Diagnostic Radiography Practices (Including Licensed Operators) in conjunction with the RSPP.

  •   Use correct techniques and settings. (optimise exposure – kVp/mAs, bucky/grid selection, chamber selection, note ‘S’ values and ‘EXI’.)
  •   Correct use of PPE when appropriate.
    •   Aprons for those assisting.
    •   Gonadal shielding where appropriate.
  •   Paediatric protocol (pelvis)
    •   - always for males
    •   - always for females except for first presentation.
  •  Always look at patient before exposure to ensure that they have not moved or that breathing instructions have been followed correctly.
  •  Obtain necessary images.
  • Ensure images are labelled with correct patient details

  • Ensure correct sidemarkers and annotations on the film.  Try and use your sidemarkers – the routine use of electronic  sidemarkers is not supported.  If electronic sidemarkers are used, the operator’s initials must be included.  New RSPP currently awaiting approval by Radiation Health Queensland states that: “Routine use of electronic sidemarkers is not supported.  Wherever possible, lead sidemarkers shall be placed within the image field at the time of exposure.”
  •   Transfer Images and request form to PACS.
  •   Record details on RIS.

Exposure Creep

There may be no appreciable change in image quality as a result of slight over-exposures, leading to higher (unnecessary) patient doses. Take note of your exposures and of the ‘S’ values or ‘EXI’ for optimisation.  We need to be aware of our exposures and adhere to the ALARA principle.

Fluoroscopy

  • screening times
  • exposure factors - Use lowest exposure factors possible (kVp/mAs when possible, remove grids when possible, use lowest frame rate for diagnostic quality, beam-on time should be kept to minimum)
  • image magnification - Any form of geometric or electronic magnification of the image will result in increased skin dose to the patient.  Operators should use the least magnification possible to achieve the clinical answer required.
  • PPE - several radiation incidents in 2010 during fluoroscopy – operators/nursing/support staff not wearing lead or forgetting to wear lead.  Be vigilant and look out for each other.  Make sure that when a staff member is scrubbing for the procedure that they have lead on.
  • patient and II positioning

All staff who assist during radioscopic procedures on a regular basis, or use the radioscopic equipment in the THSD must read Module Three – Additional requirements for Radioscopic Procedures – Diagnostic Radiography Practices in conjunction with the RSPP.

SME TO ANSWER

Which of the dot points above should these points to into?

Standby mode when not in use (i.e. disable the machine so that it can not be accidentally activated)

Initiate an exposure to provide only a real time dynamic image or when recording images for post acquisition analysis.

Use last image hold function.

During fluroscopy

Dose is higher on the tube side of the patient due to scatter.   The operator should stand as far away from the source as possible and have II/detector as close to patient as possible.

During imaging use the greatest possible source to skin distance to reduce the patient skin entrance exposure. The patient should be positioned as close a possible to the image intensifier (II). This also minimises geometric magnification

Although the dose area product remains constant (for a fixed source – detector distance) the dose rate will increase the closer the patient is to the source. Patient dose decreases when II is close to the patient and the tube is further away

Radiation exposure is higher in oblique projections due to greater path lengths.  Furthermore lateral and oblique projections feature shorter source-skin distances and/or greater patient-II distances.

Scatter is highest on the beam entrance side of the patient. In the first image above, the tube would be better on the other side of the patient – this would reduce the dose that the operator receives.

Mitchell, E. L. and Furey, P., Prevention of radiation injury from medical imaging Journal of Vascular Surgery, 2011, Vol.53(1), pp.22S-27S

CT

Key points for consdieration:

  • Valid approved requests: All requests are to be approved by a radiologist.  Schedule 6 of the Radiation Safety Regulation 2010 states that requests for diagnostic CT scans can only be made by a Radiologist or Radiology Registrar.  This will ensure that multiphase scanning is kept to a minimum.
  • Exposure factors: Scan only the area required.  Eliminate sensitive areas where possible.

    CT slices acquired should contain the diagnostic information required for the examination.  A scout scan should be used to aid scan selection and limit the amount of subsequent cross-sectional scanning

    .  Lowest possible exposure factors should be used.

  • Safe distances
  • PPE

All staff who work in the CT room or use the CT equipment must read Module Two – Additional requirements for Computed Tomography – Diagnostic Radiography Practices in conjunction with the RSPP.

  • All doors to the scan room will be closed during examination.
  • Only when necessary to patient safety should a staff member or carer remain in the CT room whilst imaging is underway.
  • All persons required to stand in the scanning room should be counselled on where to stand.
  • At the side of the CT gantry the dose is least, as depicted on the isoexposure profiles.

In early 2009 an activity was undertaken to determine the dose received by using the side gantry position during a CT PA examination (this is the examination for which staff are usually present in the CT room during scanning).  A dose-meter was placed at the side of the gantry during 32 CT PA examinations in a 4 week period.  The dose-meter returned a result of MDL (< 70microSV) – therefore potentially a single staff member could be present in that position for ~ 500 CT PA scans before they return a result of 1mSv (the public limit) - if that was the only task contributing to their occupational dose. 

With our activity we have proven the work practice does not place staff at risk of higher occupational exposure if they follow the instruction given to stand at the side of the gantry and wear a lead gown and thyroid collar.

The CT scanner is only able to be operated by an appropriately licensed person who has received the appropriate training and is authorised to use the equipment.

Nuclear Medicine

Radiation exposure is possible from contact with patients and radioactive isotopes. 

The isotope is injected into the patient, this produces ionising radiation and the Gamma Camera in the room detects the radiation and uses the information to produce an image.  We therefore limit contact with the patient that has been recently injected with an isotope to only that which is necessary.

Any spill in the Nuclear Medicine area should be reported to the Nuclear Medicine technologist.  Special procedures are to be undertaken in the case of a radioactive spill.

Knowledge check 5

  • True
  • False
As per Schedule 6 of the Radiation Safety Regulation 2010, any professional can approve a CT.