IRMER17 & DRLs Flashcards
Identify the duty holders under IRMER17
- Employer
- Referrer
- Practitioner
- Operator
What is the role of the employer under IRMER17?
- Overall reponsability
- Provides a framwork for complaince
- Entitles other duty holders
What is the role of the referrer under IRMER17?
Supplies sufficient personal and clinical information to allow the practitioner to justify the exposure and for the patient to be identified
What is the role of the practitioner under IRMER17?
- Takes reponsability for an individual exposure
- Justification and authorisation of each exposure
- Decides appropriate imaging/therapy clinical pathway
- Ensures doses are ALARP
- must comply with employers procedures
- must be appropriately trained
What is the role of the operator under IRMER17?
Anyone who carrier out practical aspects that can affect patient dose
In some cases authorises the exposure - Generic justification
Selects equipment and methods to limit dose to patient consistent with prupose
Must comply with employers procedures
Describe Justification
Practices involving exposures to radiation must produce significant benefit to the exposed individual or to society to offset the detriment it carries
Describe Optimisation
All reasonable steps should be taken to ensure that the individual doses, as well as the number of persons exposed, are ALARP, thus maximising the net benefit
Economic and social factors should be taken into account
Describe Limitation
A system of individual dose limits should be in place to ensure that the radiation risks to individuals are acceptable
DOSE LIMITS for staff and public
DOSE CONSTRAINTS for patients having medical exposure
What are the 3 fundimental principles of radiation protection?
- Time
- Distance
- Shielding
What are the ICRP principles for the system of radiological protection?
- Justification
- Optimisation
- Limitation
Why are we interested in patient dosimetry, DRLs and patient dose audit?
PATIENT SAFETY - Benefit outweighs the risk, measuring dose to assess risk
LEGISLATIVE REQUIREMENT - IRMER17, a framwork to protect patients from the hazards of ionising radiation
OPTIMISTATION - Ensuring patient doses are ALARP for the clinical purpose
What is the definition of a diagnostic reference level?
DRLs are defined as dose levels for TYPICAL examinations for groups of STANDARD SIZED PATIENTS or STANDARD PHANTOMS and for BROADLY DEFINED types of equipment
How should DRLs be used?
- As a tool for optimisation
- As a guide to the indistinct border between good/normal practice and bad/abnormal practice
- A convenient test for identifying situations where the levels of patient doses are unnusually high
- suppliments to professional judgement
What are DRLs NOT?
- Static: They require continous updating
- Limiting (maximum) values
- A guarantee that image quality is appropriate
- A guarantee that the examination is performed at an optimised level
- Surrogates for individual dose limitation
- A defining line between good and bad practice
Where should you look for information and guidance on DRLs?
ICRP35 - DRLs in medical imaging
IPEM Report 88 - Guidance on the establishment and use of DRLs for medical imaging in x-ray examinations
How do we set NDRLs in the UK?
(previous) Set at 75th percentile value of the distribution of room means doses in the UK
Now done by median doses
When should a room be selected for Dose Audit?
Report 88 recommends to audit where:
- It has been 2 years since previous audit
- There has been a known change in equipment
- There has been a substantial change in workload or case mix
What data should you collect for patient dose audit
- Site
- Room
- Examination
- Projection
- Date range
- mAs, kVp
- dosage (KAP, DLP, MGD)
- Age at event and sex can be useful for looking at trends in caseload
This information is downloaded from CRIS
What steps should you take to ‘clean the data’ for a patient dose audit?
Remove missing entries, typos or outliers
Top and bottom 5%
Why do we remove the top and bottom 5% of doses when ‘cleaning’ data for a patient dose audit?
Because DRLs are defined for “standard sized” patients, not all the patients we examine are stanard size so we remove the top and bottom 5% to attempt to account for this
What is the outcome of a patient dose audit where the mean dosage is:
1. < LDRL
2. > LDRL
3.»_space; LDRL
Acceptable - No action
Acceptable - Optimisation Required
Unnacceptable - Investigation Required
In a patient dose audit, when is the mean dosage considered SIGNIFICANTLY higher than the LDRL?
When the mean dose exceeds the LDRL by more than 20% AND by more than 2x SEM
Why don’t we carry out an investigation whenever the mean dosage exceeds the LDRL, even by a small amount?
DRLS are NOT a hard limit
We expect 25% of examinations to have doses > DRL
DRLs are for typical examinations, standard sized patients and broadly defined types of equipment, so there are lots of variables!
What should be the aims of an investigation?
To Identify why the LDRL has been exceeded and what remedial action is required
What are the likely reasons that a DRL may have been exceeded which should be considered in an investigation?
Equipment:
Changes, faults, CR vs DR, are the QA results acceptable?
Case Mix:
Types of patients being examined
Exam Technique:
Changes in exposure parameters, patient positioning, clinical protocols
Measurement Methodology:
Must be the same as used to set LDRL (is KAP meter calibrated?)
In what areas may the case mix mean that comparison with DRLs for the general population is not appropriate?
Paediatric Radiology
Chest x-rays in a chest clinic - Patients have solid masses in lungs etc
Where expertise in a specialism means ine staff member is dealing with particular complex cases
Where DRLs can be justifiably exceeded
If your investigation finds that the LDRL has been exceeded because of the case mix, what conclusion might you draw?
That there is a sound case for NOT using the DRL in this room
If equipment is found to be the reason for the LDRL being exceeded and your findings reinforce what you expect to find, what does this suggest?
What if you did not expect the equipment to be the reason the DRL was exceeded?
That there is evidence to support the case for replacing the equipment
Critically review your QA and maintenance programmes
