Random DR/RP Flashcards by Danni Eden

Who is responsible for implementing regulations and how is this usually done

Employer has responsibility, usually delegated to radiation protection committee

How well did you know this?

Not at all

Perfectly

Who is RPA

Radiation protection adviser - individual or body appointed by radiation employer and meeting criteria of competence specified by HSE.

How well did you know this?

Not at all

Perfectly

Advice on compliance that RPA might give

Radiation risk assessment
Designation of controlled and supervised areas
Handling of investigations
Contingency plans
Dose assessment and recording

How well did you know this?

Not at all

Perfectly

What must RPAs be consulted on

Implementation of requirements for controlled and supervised areas
Plans for future installations
Calibration and use of equipment for monitoring
Periodic testing of control and safety features and systems of work

How well did you know this?

Not at all

Perfectly

HSE graded approach

Notification (low risk) - electronic submission
Registration (includes all x-ray work) - submission, statements to agree to, small fee
Consent (licensing) - administering radionuclides, use of LINACs, more evidence and higher fee

How well did you know this?

Not at all

Perfectly

Designated area

Work area where special procedures are needed to restrict dose (access, training, work practice). Person working here likely to receive dose over threshold.

How well did you know this?

Not at all

Perfectly

Values for dose rate

Instantaneous dose rate
Dose rate (DR) - over 1 minute
Time-averaged dose rate (TADR) - over 8 hours
TADR2000 (same over 2000 hours)

How well did you know this?

Not at all

Perfectly

Requirements for designated areas

Warning signs
Systems of work to restrict exposures
Environmental monitoring
Assessment of dose (personal and environmental) to ensure dose limits not exceeded

How well did you know this?

Not at all

Perfectly

What should local rules contain

Description of area and its identification (controlled or supervised)
Name of RPS
Arrangements to restrict access
Conditions for entry for non-classified persons
Instructions for safe working
Dose investigation levels
Contingency plans

How well did you know this?

Not at all

Perfectly

RPS

Should be appointed when local rules are needed, preferably full time and sufficiently senior.

How well did you know this?

Not at all

Perfectly

Classified workers

Receive effective dose >20mSv or equivalent dose > a dose limit in a few minutes
Anyone likely to get an annual effective dose >6mSv or 3/10 any other dose limit

How well did you know this?

Not at all

Perfectly

What does classification involve

Regular medical surveillance, personal monitoring performed by an approved lab and person dose record kept on CIDI

How well did you know this?

Not at all

Perfectly

Pregnant staff

Dose to foetus should be ALARP and unlikely to exceed 1mSv - equivalent to 2mSv on abdomen

How well did you know this?

Not at all

Perfectly

Diagnostic reference levels

A dose reference level set for a specific standard examination type and standard patient
cohort
Represents an upper level for acceptable dose
National and local
Expressed in easily measurable dose quantities (ESD, CTDI, DAP)
Should be reviewed and investigated if regularly exceeded

How well did you know this?

Not at all

Perfectly

Stochastic vs tissue reactions

Stochastic: probability of effect occurring increases with dose, no threshold
Tissue reactions: no effect below threshold, above threshold severity increases with dose

How well did you know this?

Not at all

Perfectly

Classified worker limits

Effective dose > 20mSv in short period of time or equivalent dose > dose limit very quickly
Likely o get annual effective dose > 6mSv or 3/10ths another dose limit

How well did you know this?

Not at all

Perfectly

TADR2000 each area

Controlled: >3
Supervised: > 0.5
Unsupervised: <0.15
microsievert/hr

How well did you know this?

Not at all

Perfectly

3 types of personal dosimeter

TLD (thermoluminescent dosimeter)
OSL (optically stimulated luminescence)
EPD (electronic personal dosimeter)

How well did you know this?

Not at all

Perfectly

TLD material and details

Lithium Fluoride
1microGy - 10Gy
Reusable

How well did you know this?

Not at all

Perfectly

OSL material and details

Aluminium oxide Al2O3:C
10microGy - 100Gy
Irradiated electrons trapped in valence band in structure
Laser light used to read results - less signal loss than TLD, can be reread

How well did you know this?

Not at all

Perfectly

EPD

Direct read of dose and dose-rate. Audible alarms

How well did you know this?

Not at all

Perfectly

Dose for estimating skin, eye, effective

Whole body: Hp(10)
Extremity: Hp(0.07)
Lens of eye: Hp(3)

How well did you know this?

Not at all

Perfectly

How do we decrease noise

Increase no of photons to increase SNR
Use smoothing filters
Can use iterative reconstruction in CT

Principles of radiation protection

Justification
Optimisation
Limitation

Justification

Is there enough benefit to justify the procedure: benefit must outweigh risk

Optimisation

Is the dose ALARP

Limitation

Set exposure limits for doses

General principles of IRMER

Should only be carried out if necessary Alternative non-ionising measures should be considered All exposures must be justified Exposure should be ALARP

Duty holders and what legislation do they come under

IRMER Referrer Practitioner Operator MPE

Role of referrer

Refer patient Must identify paitent, give info to justify and information about breast feeding etc

Role of practitioner

Justifies exposure Confirms justification, authorises request Need ARSAC license for radionucides

Role of operator

Anyone carrying out a practical aspect of the exposure

Accidental vs unintended exposur

Accidental: patient shouldn't have been exposed at all Unintended: get higher dose or wrong area

Types of noise

Quantum noise: should dominate Electronic noise: can be significant at low doses Fixed pattern noise: pixel to pixel variations, should be low in DR because of flat fielding

KERMA

Kinetic energy released per unit mass Not necessarily dose in air because energy lost from beam is not necessarily same as energy absorbed To good approximation this is correct though: negligable Brem. and short range of electrons

What does RBE change with

Dose Dose rate Fractionation Physiological conditions Biological species

What makes a good detector

Can detect radiation Appropriate accuracy and precision Gives relevant dose quantity Appropriate range (E,D) Linear response with dose

Pros and cons of ionisation chamber

+ gives air KERMA + comes in a range of sizes - good for sensitivity and resolutiosn + linear response + stable over time -needs electrometer for read out -T/P corrections -requires careful calibration

Pros and cons of Geiger counter

+ can detect all types of radiation + increased sensitivity over ion chamber + low dose measurements + cheap -poor at high doserates due to dead time - poor energy response output

How does Geiger counter work

Sealed chamber contains gas at low P Two electrodes with high V between them Radiation creates ion pairs Electron accelerated by a high voltage causes further ionization of gas molecules therefore large number of electrons Chain reaction - pulse detected

Detriment

Measure of whole body harm -probability of fatal cancer -probability of severe genetic effects -relative length of life lost -weighted probability of non-fatal cancer

What does bit depth govern

Range of grey scales Each pixel stores discrete number related to shade of grey 4bit is 2^4 levels, 16. Numbered 0 (black) to 15 (white) Typically 12 bit

Pre-processing examples

DR: flat fielding, correcting for dead pixels CR: corret for variations in senstivity of light collecting guide

Post processing examples

Window width and level Noise reduction Edge enhancement

Cause of electronic noise

Readout electronics Thermal effects

What affects spatial resolution

Characteristics of detector (pixel size, spread of signal) Focal spot size Magnification (image intensifier)

When do risk assessment

Prior to starting a new activity but must also be reviewed regularly

Risk assessment considerations

Routine work: What radiation dose might people get? What control measures are in place/needed? Accidents: What might go wrong? What doses might people get then? What control measures are needed? What contingency plans are needed?

Who optimises exposure?

Operator

How do we use the k-edge

Match the materials of the detector with the x-ray spectrum so it is absorbed Use contrast material

What are operational quantities

Ambient dose equivalent Personal dose equivalent

Operational quantity for area monitoring

Ambient dose equivalent H*(10)

Operational quantity for personal dose

Personal dose equivalent Hp(d)

Physical quantities

KERMA, exposure, absorbed dose

Protection quanitities

Equivalent organ dose Effective dose

Employers procedures

Identify duty holders Use and review of DRLs Deal with incidents Non-medical exposures Carers and comforters