IRMER17 & DRLs

Question 1

Identify the duty holders under IRMER17

Answer 1

1. Employer
2. Referrer
3. Practitioner
4. Operator

Question 2

What is the role of the employer under IRMER17?

Answer 2

• Overall reponsability
• Provides a framwork for complaince
• Entitles other duty holders

Question 3

What is the role of the referrer under IRMER17?

Answer 3

Supplies sufficient personal and clinical information to allow the practitioner to justify the exposure and for the patient to be identified

Question 4

What is the role of the practitioner under IRMER17?

Answer 4

• 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

Question 5

What is the role of the operator under IRMER17?

Answer 5

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

Question 6

Describe Justification

Answer 6

Practices involving exposures to radiation must produce significant benefit to the exposed individual or to society to offset the detriment it carries

Question 7

Describe Optimisation

Answer 7

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

Question 8

Describe Limitation

Answer 8

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

Question 9

What are the 3 fundimental principles of radiation protection?

Answer 9

1. Time
2. Distance
3. Shielding

Question 10

What are the ICRP principles for the system of radiological protection?

Answer 10

1. Justification
2. Optimisation
3. Limitation

Question 11

Why are we interested in patient dosimetry, DRLs and patient dose audit?

Answer 11

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

Question 12

What is the definition of a diagnostic reference level?

Answer 12

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

Question 13

How should DRLs be used?

Answer 13

• 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

Question 14

What are DRLs NOT?

Answer 14

• 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

Question 15

Where should you look for information and guidance on DRLs?

Answer 15

ICRP35 - DRLs in medical imaging

IPEM Report 88 - Guidance on the establishment and use of DRLs for medical imaging in x-ray examinations

Question 16

How do we set NDRLs in the UK?

Answer 16

(previous) Set at 75th percentile value of the distribution of room means doses in the UK

Now done by median doses

Question 17

When should a room be selected for Dose Audit?

Answer 17

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

Question 18

What data should you collect for patient dose audit

Answer 18

• 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

Question 19

What steps should you take to ‘clean the data’ for a patient dose audit?

Answer 19

Remove missing entries, typos or outliers

Top and bottom 5%

Question 20

Why do we remove the top and bottom 5% of doses when ‘cleaning’ data for a patient dose audit?

Answer 20

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

Question 21

What is the outcome of a patient dose audit where the mean dosage is:
1. < LDRL
2. > LDRL
3.&raquo_space; LDRL

Answer 21

Acceptable - No action
Acceptable - Optimisation Required
Unnacceptable - Investigation Required

Question 22

In a patient dose audit, when is the mean dosage considered SIGNIFICANTLY higher than the LDRL?

Answer 22

When the mean dose exceeds the LDRL by more than 20% AND by more than 2x SEM

Question 23

Why don’t we carry out an investigation whenever the mean dosage exceeds the LDRL, even by a small amount?

Answer 23

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!

Question 24

What should be the aims of an investigation?

Answer 24

To Identify why the LDRL has been exceeded and what remedial action is required

Question 25

What are the likely reasons that a DRL may have been exceeded which should be considered in an investigation?

Answer 25

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?)

Question 26

In what areas may the case mix mean that comparison with DRLs for the general population is not appropriate?

Answer 26

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

Question 27

If your investigation finds that the LDRL has been exceeded because of the case mix, what conclusion might you draw?

Answer 27

That there is a sound case for NOT using the DRL in this room

Question 28

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?

Answer 28

That there is evidence to support the case for replacing the equipment Critically review your QA and maintenance programmes