Overall Flashcards
What are the two types of radiation monitoring instrument?
Area survey meters (area monitors) and personal/individual dosimeters
What is the absorbed dose, its units and what does it not consider?
Energy per unit mass, Gray and doesn’t consider different types of radiation or biological effects
Which type of dose is the basic quantity in radiation protection and which type is related to risk?
Equivalent dose for protection and effective dose for risk
What weighting factor does equivalent dose include in its calculation?
Radiation-weighting factors to account for the specific type of radiation
What is the effective dose?
Weighted sum of mean equivalent doses to organs (who body quantity) including organ weighting factors
What is the unit for equivalent and effective dose?
Sieverts (J/kg)
Is equivalent dose referring to a particular organ/tissue or whole body dose?
Particular organ/tissue
Which types of radiation have a radiation-weighting factor of 1?
X-rays, gamma rays and electrons
What are the radiation weighting factors for protons and alpha particles?
5 for protons and 20 for alphas
Is the effective dose directly measurable?
No
Operational quantities are used for practical measurements as a substitute for what?
Effective dose
What is the concept of operational quantities?
Based on the dose equivalent to that point and relate to the type and energy of the radiation
What are the three types of operational dose quantities?
Ambient dose equivalent, directional dose equivalent and personal dose equivalent
What dose quantity is the skin dose limit in IRR17?
Equivalent dose
When do you do a radiation survey?
Verifies construction and part of prior risk assessment
What factors need to be considered for the choice of instrument?
Radiation type (including energy), dose rate, duration and geometrical precision
What are the four types of detector technologies?
Film, gas, scintillation detectors and semiconductor detectors
What are examples of gas detectors?
Ionisation chambers, proportional counters and Geiger Muller tubes (saturation detector)
What does traditional film contain?
Silver bromide crystals on a cellulose base
How does an image form on traditional film?
Radiation releases free silver to form a latent image that can be seen after developing it
What are the advantages and disadvantages of film?
Advantages: high spatial resolution, 2D dose map, permanent, no electrical connections
Disadvantages: processing required, specific range of doses, different energy response than tissue
How do gas detectors work?
Positive and negative electrodes to make an electric field and ions are attracted to electrodes and then coulombs (current) can be converted to dose
In gas detectors, when could secondary ionisation occur?
If the field is strong enough
What features changes the gas detector type?
The amount of applied voltage across the electrodes
There are 6 regions of increasing applied voltage for gas filled detectors, what are they called?
Recombination, ionisation chamber, proportional, limited proportionality, GM counter and region of continuous discharge
What does a higher applied voltage for gas-filled detectors mean for the detector?
It is more sensitive (like GM tube)
Are ionisation chambers high or low voltage and does this produce secondary ionisation?
Relatively low voltage (below 400 V) and no
Is charge proportional to dose in ionisation chambers?
Yes
Are ionisation chambers low or high sensitivity and are they suitable for high dose rates?
Low and yes
What are the advantages of thimble ionisation chambers?
High accuracy, low dose-rate dependence, linear response and stable
What are the disadvantages of ionisation chambers?
Magnitude of reading (gain) dependent on the mass or volume of air so small chambers have poor gain (high dose needed for reliability) but large chambers have poor spatial resolution
Do proportional counters produce secondary ionisation?
Yes but only some (charge multiplication of 10^3-10^4)
Do proportional counters have good sensitivity and does this make them suitable for low intensity and high dose rates?
Yes, good for low intensities but not for high dose rates
How does a GM tube work (not about the electrodes)?
Each event completely ionises the gas and creates a Townsend avalanche, with the signal being independent on initiating energy
Do GM tubes need to recover between events and this makes them unsuitable for high or low dose rates?
Yes so not suitable for high dose rates
When are gas detectors used?
Dose-rate meters (radiation surveys, leakage measurements and QA) and contamination monitors (proactive and reactive monitoring)
What are the types of solid state detectors?
Semiconductors, scintillators and thermo-luminescent detectors (TLDs)
What type of solid state detectors act as solid state ion chambers?
Semiconductor detectors
Are semiconductor detectors more sensitive than ion chambers of the same volume and why?
Yes (10^4 times) because of lower energy per ion pair and higher density
What are the advantages of semiconductor diode detectors?
Small sensitive volume, high gain (low energy threshold for ionisation) so good for low dose rates and instant read out
What are the disadvantages of semiconductor diode detectors?
Temperature dependent, subject to radiation damage and higher response to low energy photons
Where are semiconductor detectors used?
In radiotherapy for in-vivo point-dose measurements and QA
Diagnostic (everywhere in DR)
What are scintillator detectors based on?
Scintillation- light emission, where certain crystals contain activator atoms and emit light upon absorption of radiation
What material are scintillators usually made of?
High atomic number phosphors for gamma rays (plastic for beta)
What is a typical scintillation probe attached to in a gamma camera?
Photomultiplier tube
What issues does doping a scintillator crystal solve?
Poisson noise and photon wavelength-detection efficiency issues
What does doping a scintillation crystal do?
It releases the same amount of energy but spread over a larger number of photons as more excited energy levels
What are the two types of scintillator?
Inorganic (crystalline) and organic (amorphous)
What is the most used scintillator material?
Sodium iodide doped with thallium
How do thermoluminescent dosimeters (TLDs) work?
Electrons in valence bands excite to conduction band after irradiation then fall into electron traps in the lattice, and heating the crystal allows the electron to escape
What are the advantages of TLDs?
Small size, no electrical connection and approximately tissue-equivalent
What are the disadvantages TLDs?
Time needed for prep and processing, no permanent record and low accuracy (5%)
What are the two types of personal dosimetry?
Long term ‘film badge’ and real time electronic
What are deterministic effects?
Tissue/organ reactions after cell death that will occur after a threshold dose. The severity of the effect increases with dose.
What are stochastic effects?
Probabilistic effects that are random and occur from cell mutation, like cancer. The probability is proportional to the dose
What are the two methods of cell damage?
Indirect and direct action
Repair mechanisms after DNA damage may lead to what options?
Complete repair (error free) or partial repair (including incorrect repairing)
What are the potential outcomes for cells with altered DNA?
They might be non-viable (die), unable to divide (reproductive death), or give rise to a colony of mutated cells
What is the linear energy transfer (LET)?
The amount of energy that an ionising particle transfers to the material traversed per unit distance
What radiation has low LET and what has high LET?
Low LET: X-rays and gamma rays
High LET: protons and alpha particles
What are cell survival curves?
The fraction of cells that maintain reproductive integrity vs irradiated dose
What is the cell survival curve shape for high and low LET radiation?
High LET: linear
Low LET: linear quadratic
What is the linear-quadratic model for low LET radiation?
It describes the cell survival curve for low LET radiation and is defined by S, the surviving fraction
What is the equation for the linear-quadratic model for low LET radiation?
e to the power of minus alpha D minus beta D squared (D = dose)
What do alpha and beta represent in the linear-quadratic model for low LET radiation?
Alpha is the linear component, whilst beta is the quadratic component
What does the alpha/beta ratio indicate generally?
How resistant a cell is to radiation damage. High ratio = more linear cell survival curve. Low ratio = more curvature on cell survival curve
What is the alpha/beta ratio in the linear-quadratic model?
It is the dose in gray where the linear as well as the quadratic component cause the same amount of cell killing
What is the bystander effect?
Radiation induced effects in cells adjacent to cells that have been irradiated (not received direct radiation damage themselves)
What is the abscopal effect?
Distant metastases regress despite being distal to irradiated area
Organ structures can be split into parallel or serial organs. What does this mean?
Parallel organs = damage to one subunit reduces function (eg kidney)
Serial organs= damage to one subunit can result in complete breakdown of organCa
Can an organ be both parallel and serial? If so, is there example of this?
Yes but at different levels. Eg lungs are parallel at gas exchange level but serial at high level
What are deterministic effects also known as?
Tissue effects
What is the threshold in deterministic effects?
Below the threshold there is no effect
What are examples of deterministic effects?
Reddening (erythema), blistering and necrosis
Are deterministic effects reversible?
Some are but some aren’t
Can deterministic effects lead to death of an individual?
Yes if there is a loss of cells above a certain number for that tissue or organ which has created a sever lose of function that cannot be repaired
Why can secondary tissue damage occur after deterministic effects?
Blood vessel damage and replacement of viable tissue by fibrous tissue
The probability related to stochastic effects is described by what model?
The linear no threshold model
Does the severity of stochastic effects increase with the dose received?
No
What is the overkill effect and what does it mean for stochastic effects?
High acute doses kill cells so they don’t mutate, so the probability of developing conditions like cancer may decrease
What is the percentage risk per Sievert for cancer induction?
5% per Sievert
How is excess absolute risk (EAR) for stochastic effects (ie independent of background risk) usually expressed?
Often expressed per 10^4 person-years per Gray (or Sievert)
What is the relation between relative risk (RR) and excess relative risk (ERR) (proportional increase in risk above background) and how is it usually expressed?
ERR = RR -1 and it is expressed as a fraction or percentage per Gray (or Sievert)
Is there a lot of evidence and data for the cancer risk of low doses and what does this lead to in radiation protection?
No, so no ‘safe’ level or threshold, just reduced likelihood
What are the different ways of quantifying cancer risk?
Risk of developing cancer (incidence), risk of dying from cancer (mortality), loss of life expectancy, morbidity from non-fatal cancers and risk to offspring (hereditary detriment)
What are hereditary effects?
A type of stochastic effect where mutations that manifest in a descendant of the exposed person
When are radiation risks more significant for foetuses?
During organogenesis and early development (6-5 weeks)
Why is the lifetime cancer risk per unit dose higher for younger people?
There is increased rates of cell division when young and more time to see effects
How many regulations and schedules are there in IRR17?
43 regulations and 9 schedules
What is the European Directive called that IRR17 is derived from?
Basic Safety Standards (BSS) Directive 2013
What is the graded approach to informing the Health and Safety Executive (HSE) before starting work with ionising radiation?
Employers either have to notify/register/obtain consent depending on the level of work (unless they are intending to use quantities and concentrations less than specified)
What type of work falls under registration to the HSE in IRR?
Radiation generators (like x-ray devices) that are not related to practices requiring consent and other types more relevant to nuclear energy work
What type of work falls under consent to the HSE in IRR?
Administration of radioactive substances, addition of radioactive substances into products (radiopharmacy), accelerators, long term storage or disposal of radioactive waste
What are the outcomes of a risk assessment for IRR?
Action to ensure ALARP, steps to control exposure, whether personnel monitoring is needed, work procedures for pregnant people, designated of controlled areas, training needs, Local rules, appointment of RPS’ and maintenance and testing schedules
For IRR, are we more concerned about deterministic or stochastic effects?
Stochastic
What is the annual limit for the whole body dose, skin/extremities and eye lens for employees?
Whole body: 20 mSv
Extremities/skin: 500 mSv
Eye lens: 20 mSv
What is the annual limit for the whole body dose, skin/extremities and eye lens for members of the public?
Whole body: 1 mSv
Extremities/skin: 50 mSv
Eye lens: 15 mSv
What are the classification values in IRR?
If they are likely to receive 3/10ths of any dose limit for reasonably foreseeable situations, so 6 mSv per year for whole body doses and 15 mSv per year for eyes
What is the required investigation limit for a whole body dose in IRR?
15 mSv per year (lower value when set by employer)
What are dose constraints and what are they for?
They are lower than limits (0.3 mSv per year) and they are used in planning, designating areas, local rules and classifying workers
What are the requirements for classified workers?
They have to be an adult, a doctor certified they are fit for the intended work and they require medical surveillance
What are the duties of employees under IRR?
Not knowingly expose themselves or others than is necessary, PPE (use it, report defects and return it), and cooperate with employer
What are some of the areas an RPA must be consulted on by an employer?
Risk assessments, review plans and installations, designation of areas, contingency planning, recording and assessing doses, QA, PPE
Who issues certification to RPAs?
RPA2000
When should an area be designated as a controlled area?
Person working in the area is likely to receive over 6 mSv a year, and anyone entering the area has to follow special procedures to restrict exposure and the dose rate averaged over a day is over 7.5 micro Sv/h
What should the local rules contain?
Dose investigation level, key work instructions, contingency plans, description of area covered and its designation, name the RPSsW
What is the role of the RPS?
Ensure compliance with the local rules (ultimate responsibility still likes with employer)
When must a radiation employer use an Approved Dosimetry Service (approved by HSE) according to IRR?
To record and assess all significant doses received by classified workers and for accidents that have exceeded 3/10ths of any relevant dose limit (effective dose over 6 mSv)
How long does the Approved Dosimetry Service keep dose assessment record for according to IRR?
Until the individual is 75 years old, and at least 30 years old
What are the requirements for the storage of radioactive substances not in use?
They should be in a suitable receptacle (shielded, fireproof, secure) and in a suitable store (weatherproof, ventilated, labels)
What comes under the notification of certain occurrences regulation in IRR?
A certain amount of a radioactive substance has been released into the atmosphere or spilled, or is lost or stolen. Radiation generator fails to de-energise when intended. Radioactive source fails to return to safe position
What are the responsibilities of the installer under IRR for equipment containing radioactive substances and radiation generators?
They must carry out a critical examination. Consult RPA regarding plans for installation, critical examination tests and acceptability of results. Provide employer with info for use, testing and maintenance
What is the critical examination for, as described in IRR?
It is a check of all safety features and warning devices, and that there is sufficient protection for people from radiation.
Where are IRR and IRMER linked?
Equipment, where the employer must consider restricting patient dose when purchasing, installing and maintaining equipment (including QA)
What pieces of legislation backs up the need for a radiation risk assessment?
The Health and Safety at Work Act 1974
The Management of Heath and Safety at Work Regulations 1999
IRR
What work needs to be covered in a radiation risk assessment and when does it need to be done?
Routine work and reasonably foreseeable incidents and prior to work commencing
What are the 5 steps of risk assessments?
- Identify hazards
- Decide who may be harmed
- Assess the risks and take action
- Record findings
- Review risk assessments
What are some of the named sections in a generic radiation risk assessments?
Background, dose rates, controls and safety features, likelihood and severity, reasonably foreseeable incidents, special arrangements, conclusions and actions
What is the hierarchy of controls in order from most to least effective?
Elimination, substitution, engineering controls, administrative controls and PPE
What is the advantages and disadvantages of concrete as a shielding material?
Advantages: Cheap and easy to source
Disadvantages: Bulky, need more material for proper shielding
Does steel provide more or less protection than lead?
Less
What are the advantages and disadvantages of using lead for shielding?
Advantages: Compact and need less for shielding
Disadvantages: Heavy, toxic and expensive
What material is typically used for linac room shielding?
High density concrete
What is leadite?
Concrete blocks with lead in it
What shielding is used for manual afterloading brachytherapy?
No particular room shielding, might use movable shields. Patient provides enough shielding for I-125
For high dose rate (HDR) brachytherapy, what shielding considerations are there?
Thick concrete walls and maze entrances, interlocked barrier, audible alarm when source exposed, warning lights
What is the voltage range of orthovoltage radiotherapy?
50-300 kV
For orthovoltage radiotherapy, what shielding considerations are there?
Standard wall materials can be used, with lead being very efficient as an additional shielding material
What additional concerns are there for shielding proton therapy?
Neutrons are produced and materials could be activated
When should radiation surveys be performed?
When new equipment is installed and following any structural changes
What is the energy range of linacs?
6-15 MV
The use factor is the proportion of the working day that the machine is delivering radiation, what is another name for this?
Duty cycle
What is the orientation factor for primary barriers?
Proportion of beam-on time when the beam is incident on the barrier
What is the TVL of a material?
Tenth value layer = the thickness of the material to reduce the radiation intensity by a factor of 10
What is the units of instantaneous dose rate, time averaged dose rate and TADR2000?
Microsieverts per hour
What is the instantaneous dose rate (IDR) and is it measurable?
Dose rate when beam is on averaged over 1 minute and yes
How is the time averaged dose rate (TADR) calculated and what does it indicate?
IDR x duty cycle x orientation factor and it indicates worst case dose rate for a working day
What is the time average dose rate for 2000 hours (TADR2000)?
TADR x occupancy and it indicates an estimated dose rate for a worker averaged over a year
What is the units for annual dose and how is it calculated using TADR2000?
mSv and TADR2000 x 2000
Do you use a worst case or typical case for shielding calcs and why?
Reasonable worst case as undershielding is worse than overshielding
What special areas for shielding a room may need more consideration?
Joints between sheets, bricks and doors, and breaks in boundaries, like holes for cables etc
What are the features of the floor of a nuclear medicine department
Impervious, washable, chemical-resistant, curved to the walls, all joints sealed and glued to the floor
What types of ventilation systems could be used in laboratories in which radioactive aerosols or gases may be produced?
Fume hood, laminar air flow cabinet, glove box and laboratory at negative pressure relative to surrounding areas
In nuclear medicine, what should drain pipes from radioisotopes sinks and toilets do?
Go as directly as possible to main building sewer (if permitted by the Environment Agency) and no connections with other non-radioactive drains in the building
What is in an emergency kit in nuclear medicine departments?
Protective clothing, absorbent materials for wiping up, decontamination materials for persons, warning notices, portable monitoring equipment, bags for waste
What is the temperature of the helium (cryogen) in an MRI machine?
4 degrees kelvin
What are some of the hazards of the static field in MRI?
Projectiles (from translational force) from ferromagnetic materials, torque, Lenz’s law means conductive metals experience a force that will oppose motion
What are some of the hazards of the gradient field in MRI?
Magnetophosphenes (light flashes), peripheral nerve and muscle stimulation, discomfort, limb movement and sensitivity, loud noise
What are some of the hazards of the RF field in MRI?
Dielectric heating, contact burns, transdermal patches
How is RF exposure from MRI (and other non-ionising radiation) measured and its units?
Specific Absorption Rate (SAR) and Watts per kilogram
What is the MR controlled access area?
Space around scanners that must be strictly controlled and all must be screened before access (people and items)
What is the MR Environment?
It fully contains the 0.5 mT line
What are some of the concerns with implanted devices and MRI?
Movement of implant, heating, malfunction of active devices
What are the recommendations for scanning pregnant patients with MRI?
Can be scanned at any point but if possible it should be postponed until after. Heating should be minimised by remaining in normal SAR mode (less than 2 W/kg) and not using gadolinium based contrast agent
How long does a magnet quench usually take to destroy the magnetic field?
Around 30 seconds
What is the hazards from cryogens in MRI?
They may leak during a quench and cause cold burns, frostbite or asphyxiation
Why does MRI contrast use gadolinium chelate?
Free gadolinium is toxic but gadolinium is strongly paramagnetic
Why must gadolinium based contrast agents only be given to MRI patients with proper renal function?
Gadolinium chelate is still nephrotoxic and can cause nephrogenic systemic fibrosis (NSF) when the gadolinium separates from the chelate over time
What is the frequency range of diagnostic ultrasound?
1-20 MHz
What is the only type of diagnostic ultrasound that is not pulsed?
Continuous wave doppler
What wave characteristic of ultrasound is the most important for the mechanical effects?
Peak rarefaction (negative) pressure
What is the acoustic impedance? (related to ultrasound)
Constant of proportionality between wave pressure and particle velocity
For higher frequency ultrasound waves, is there more or less attenuation and does this mean more or less penetration?
More attenuation so less penetration
Why must pressure values be ‘derated’ in ultrasound calculations?
Acoustic pressure is usually measured in water so it needs to be derated for the amount absorbed by tissue
What does focusing ultrasound waves improve and why?
Lateral resolution by increasing the intensity
What is the acoustic power (related to ultrasound)?
A measurement of the rate at which energy is emitted by the transducer in watts
What is the range of acoustic power for diagnostic ultrasound?
From below 1-100s mW
Why is spatial peak time averaged (SPTA) intensity used in ultrasound?
Since it is pulsed so averaged across one complete pulse repetition period
What type of tissue heats up the most quickly from ultrasound?
Bones
What could cause the ultrasound probe to heat up?
Impedance mismatch between the probe crystals and tissue results in a lot of energy absorbed by the probe face
What type of ultrasound has the most amount of heating?
Doppler
According to ultrasound guidelines, what is the maximum temperature rise above physiological levels (37 degrees) for diagnostic scans?
1.5 degrees
What is the maximum elevation in temperature for foetuses and for how long for it to be potentially hazardous?
4 degrees for over 5 minutes
What is the thermal index (TI) in ultrasound?
Rough estimate for the increase in temperature (1 TI is approx 1 degree)
What are the subtypes of thermal indices?
TIS = soft tissue
TIB = bone at focus
TIC = bone at surface
What is the equation for thermal index?
Highest power exposing tissue anywhere in beam divided by power required to cause a max temp rise of 1 degree
What are ultrasound contrast agents?
They are microbubbles that contain a gas encapsulated in a fat or protein shell
How do ultrasound contrast agents (microbubbles) improve sensitivity?
They give back a massive reflection as the size is chosen to resonate at diagnostic frequencies
How big are ultrasound contrast agent microbubbles?
Less than 10 microns
What could happen to microbubbles (US contrast agents) at a high peak rarefaction pressure?
The microbubble oscillates too much and ruptures releasing gas (result of acoustic cavitation)
What are the safety concerns with using ultrasound contrast agents?
Injection (embolism, allergy, toxicity) and acoustic cavitation
What are the different types of cavitation with US microbubbles contrast agents?
Stable cavitation (at low pressure bubbles oscillate in size but are stable) and inertial (at high pressure bubbles will grow and implode when too big)
What can inertial cavitation of US microbubbles cause?
Large shear forces that can damage cells with high, localised pressures and temps with potential to cause free radical generation (prediction)
What does the mechanical index in ultrasound quantify?
The likelihood of the onset of inertial cavitation
Below what value of mechanical index is it not likely to cause inertial cavitation?
0.7
If the mechanical index is above 0.7, in what conditions is there more of a concern of cavitation?
Microbubble contrast agents or in the presence of gas bodies (intestines and lungs)
What is sonoporation used for in ultrasound?
It increases the absorption of drugs into cells
What is acoustic force/streaming in ultrasound?
A radiation force exerted on tissue and it can cause fluids to flow
What is the rough order of magnitude of the wavelength in metres for microwaves and UV?
Microwave = 10^-2 (ie cm)
UV = 10^-8
What is the 3 wavelength bands for UV radiation?
UVA: 315 - 400 nm
UVB: 280 - 315 nm
UVC: 100 - 280 nm
Which UV band is the most energetic and which is the most penetrative?
Most energetic: UVC
Most penetrative: UVA
Which UV band is largely responsible for sun tan effects?
UVB
Why does UVC radiation not contribute to solar UV radiation?
It gets absorbed in the outer atmosphere
What UV effects can occur on the different parts of the eye?
On the cornea: photokeratitis
On the conjunctiva: photoconjunctivitis
On the lens: cataract formation (permanent or transient)
What quantifies the UV effects on the skin?
Minimal Erythemal Dose (MED), which is the lowest UVR dose that will produce a barely detectable erythema
What are the UV effects on the skin dependent on?
UV level, duration and frequency of exposures and individual sensitivity
What are the natural protection mechanisms to UV radiation?
Skin darkening and skin thickening
What are the effects of UV on the skin?
Acute effect: Erythema (skin responds by increasing blood flow), blistering
Chronic effects: induction of skin cancer
Other: ageing, loss of elasticity, dryness, blemishes, freckles and moles
What are the beneficial and negative systemic effects of UV radiation?
Beneficial: produces vitamin D, seasonal affective disorder
Negative: compromised immune system, UVR is an immuno-suppressor
What is the dose limit to the eye and skin for UV?
30 Jm^-2
What is the maximum permissible exposure (MPE) time for UV radiation?
The dose limit (30) divided by the effective irradiance (E_eff)
What patient safety features are there for UV radiation?
Glasses, protection against bare lamps and electrical hazards, and in cabinets: doors openable from within and non-skid flooring
What does OD stand for with eye protection for UV radiation?
Optical density
What are some of the medical applications of RF (radiofrequency) and microwave?
Diathermy, physiotherapy and microwave ablation
What is diathermy and how can it be used in surgery?
Deep heating using radio and sounds waves. It can be used to seal blood vessels and cut them
How is RF/microwaves used in physiotherapy?
Heat tissue for pain relief and healing
How does microwave ablation for tumours work?
Microwave antenna inserted into a tumour and localised tissue heating around 55 degrees
Should non-life supporting medical equipment have a higher or lower immunity from E fields than life-supporting equipment?
Lower
What medical equipment can be affected by electromagnetic interference?
Electric wheelchairs, pacemakers, defibrillators, ECG monitors, syringe drivers and infusion pumps
What parts of the electromagnetic spectrum count as optical radiation?
UV, visible, infrared
What does laser stand for?
Light amplification by stimulated emission of radiation
What can the lasing medium be?
Gas, liquid, solid or semiconductor
What are the key properties of laser light?
Monochromatic (very narrow spectral range), directional (well collimated beam and parallel), coherent (in phase)
What are the types of emissions from lasers?
Continuous wave and pulsed emission (free running and triggered pulsed, these subcategories depend on speed of pulse)
What is the units of irradiance and what else can it be called?
Power divided by area, units of watts per square metre and power density
What is the units of radiant exposure and what else can it be called?
Energy divided by area, units of joules per square metre and energy density
What is the EM radiation type produced by a CO2 laser and where is it used normally?
Mid-infrared and surgery
What delivery systems are used for lasers in general surgery?
Articulated arm and optical fibre
What is a chromophore and what are the main chromophores in tissue?
A substance that absorbs light. Haemoglobin, melanin and water
Why is the blink reflex aversion response a concern for the eye hazards from lasers?
Some people have a delayed or absent response, so they don’t have the natural protection reflex
Why are lasers so much more damaging to the eye than lamps?
The light is coherent and can be focussed to a small point in the eye
What are the potential eye effects from lasers?
Photokeratitis, cataract, retinal lesion, corneal burn
What types of reflections from lasers are there?
Diffuse or specular (includes flat, convex and concave)
What are some non-beam laser hazards?
Laser plume (class 4 lasers can generate a plume of infectious tissue), fire and explosion, hazardous substances (in laser) and laser dyes are carcinogenic
What wattage defines class 4 lasers?
Anything over 0.5 W
What is the accessible emission limit (AEL) for lasers?
The maximum allowable emission for each class of laser (in watts or joules)
What is the maximum permitted exposure (MPE) for lasers?
Maximum exposure level at which adverse effects occurs (in Wm^-2 or Jm^-2) and values for eye and skin
What is the nominal ocular hazard distance (NOHD) for lasers?
Distance at which beam irradiance equals the corneal MPE (in metres)
How is the laser controlled area defined?
Usually limited by room boundaries and is closer than the NOHD, so it is where an accidental exposure may be hazardous
What are the Laser Protection Supervisor (LPS) responsibilities?
Supervision of laser environment safety and ensures local rules are followed/ They are closely involved with treatments
What are the responsibilities of the laser protection adviser (LPA)?
Advising on the laser control. Hazard analysis and risk assessments. Produce/advise on Local Rules.
When does an employer need an LPA?
When using class 3B and 4 lasers
What are the responsibilities of the Authorised Users for working with lasers?
They are approved by the Clinical Laser Expert, they have had suitable training in clinical use of laser
Is the severity of the stochastic effects dependent or independent of the dose received?
Independent
What are the ICRP’s 3 key principles of radiation protection derived from the linear no threshold model? (not time distance shielding)
Justification (net benefit), optimisation (ALARP), limitation (set well below any threshold level)
What does JOPIIR stand for, which is a requirement under EU law?
Justification of Practices Involving Ionising Radiation Regulations 2018
Does justification include societal gain as well as individual gain and why?
Yes, like screening programmes
The ALARP principle under optimisation in IRMER applies to what features?
The likelihood of incurring exposure, the number of people exposed and the magnitude of their individual doses
What does ICRP stand for? (they make recommendations and reports)
The International Commission on Radiological Protection
What type of exposures count as planned exposures? (includes non-medical exposures)
Occupational, public, medical, medical legal and emergency
Do dose limits apply to patients?
No
What is the dose a person in the UK will get from natural background radiation in a year?
2-3 mSv per year
What are some of the main sources of natural background radiation in the UK? (rough percentages for top two)
Radon (54%), medical (15%), internal (eg food), terrestrial and cosmic
For x-rays and gamma radiation, the shielding attenuation equation is the dose rate after a material of thickness ‘t’ equal to what?
The dose rate without shielding times the exponential of minus the linear attenuation coefficient times the material thickness
What is the HVL equation?
ln2 divided by the linear attenuation coefficient
What are the route of internal exposure?
Inhalation, ingestion, absorption, injection
How do you prevent internal exposure?
PPE, handle radioisotopes in designated areas, monitor contamination, decontamination kit (know where it is and how to use), prioritise stopping contamination spread and decontaminate spread
What are the Environmental Permitting Regulations (EPR) for?
Governs the amount and types of radioactive materials released to environment and protects the public, certain workers and wildlife
Where is EPR relevant in healthcare?
Nuclear medicine (radioactive patients, excreted radioactivity, unsealed sources, sealed sources for QA, waste management and brachytherapy, sealed sources for QA and calibration
Under EPR, what does a regulated site need to do?
Get a permit
What are IPEM excretion factors?
Guidance from IPEM of percentage excretion per radiopharmaceutical
For an employer to get and keep a permit for EPR, what do they need to do?
They do an environmental impact assessment (demonstrate Best Available Techniques (BAT) and what permits are appropriate), adhere to permit contents and give a pollution inventory every year
What factors are involved in if site needs a permit under EPR?
Type of tasks, radioactive materials, artificial or NORM (naturally occurring radioactive materials), activity concentration
Do the radionuclides used in nuclear medicine considered artificial or NORM (naturally occurring)?
Artificial
Are short half life radionuclides (<100s) in scope for EPR regulations?
No
Who is the regulator for the permits related to EPR?
Environmental Agency
What type of EA permits are there?
Standard (low hazard) or bespoke (must do environmental impact assessment)
In the environmental impact assessment, what needs to be calculated?
The projected annual dose to critical groups (like local family, children playing in a brook), DPUR values (dose per unit released)
There are 3 stages to an environmental impact assessment, what DPUR (dose per unit released) value for one of the critical groups means the employer has to go to stage 2?
If it is over 20 microsieverts
In the environmental impact assessment, what happens in the higher stages?
More detail for the calculation to make it more accurate, stage 3 may require a site-specific assessment
What does an EPR sealed source permit contain?
Map of site, list of specific allowed radionuclides, HASS sources (including mobile sources), required security levels, accumulation of waste, waste transfers to other premises
What can you do with Very Low Level Waste (VLLW) under an EA permit?
Can dispose some sealed sources municipally (normal bin)
What does an EPR unsealed source permit contain?
Map of site, list of specific allowed radionuclides, waste requirements (including limits on accumulation, disposal to sewer, transfers to other premises and onsite incineration)
What is the A/D values related to the EA permit? (usually related to sealed sources and HASS)
A= activity, D = activity for a dangerous source
What specific parts of an EA permit are unique to HASS (typical for brachytherapy)?
Counter-Terrorism Security Officer site visit and annual source-return (tell EA you have it), and keep EA updated on fresh and sent off sources
What are the security requirements for HASS sources dependent on?
A/D ratio and specific source types
What is covered by the Best Available Techniques (BAT) part of the environmental impact assessment?
Ways of optimising releases to environment to minimise impact on critical groups, employees, and the public. Includes measures at all levels (even basic ones)
Do all permit holders from EA have to have a BAT document?
Yes
Who is the ‘qualified expert’ for EPR?
Radioactive Waste Adviser (RWA)
When is an RWA required?
If the EA permit is for the accumulation or disposal of radioactive waste
What does CDG stand for?
The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009
What was the CDG regulations made in compliance for?
ADR European Agreement Concerning the International Carriage of Dangerous Goods by Road - not just radioactive stuff
Which class does radioactive substances count under in CDG?
Number 7
Can radioactive materials be transported using public service vehicles?
No
According to CDG, when are packages containing radioactive materials not allowed to be transported?
If the package is damaged, incorrectly labelled or if the person transporting the package is not the consignor and a transport document hasn’t been issued
All persons involved in the carriage of dangerous goods must receive appropriate training in what areas?
General awareness of regulations, safety training (radiation protection), security training
What groups of people must receive the appropriate CDG training?
Consignors, carriers and consignees
What are the three steps for transport of dangerous goods?
- Determine the type of package
- Marking and labelling
- Documentation
What are the types of packages under CDG that we will be concerned with in healthcare for radioactivity?
Excepted packages and Type A
Under CDG, do type A packages require more or less package integrity requirements than type C packages?
Less
What type of packages under CDG are subject to mandated tests at design/manufacture stage?
Type A (relevant to healthcare), also B and C
What are excepted packages under CDG?
Small quantities of radioactive material are exempt from certain requirements of the transport regulations (activity limits)
The activity limits for excepted packages under CDG are dependent on what features?
The type of isotope, the physical state (solid or liquid) and if it is in ‘special form’
What are ‘special form’ materials under CDG excepted packages and do they have higher or lower activity limits?
Generally encapsulated and unlikely to disperse and higher limits
What is the minimum package dimension for excepted packages under CDG and what must the packaging do?
10cm and must prevent leakage of radioactive material under normal conditions of transport
Surface contamination of excepted packages under CDG have to be below what activity density?
4 Bq per cm squared for gamma and beta emitters
What does the surface dose rate have to be below for excepted packages?
5 microsieverts per hour
At 10 cm away from the external surface of any unpacked article for excepted packages, what should the dose limit be below?
100 microsieverts per hour
Under CDG, are excepted and exempt the same thing and why?
No, exempt limits are lower that excepted and below this the regulations do not apply
What classifies the different categories of type A packages?
The transport index, which is the dose rate at 1 m from the package in mSv/h multiplied by 100, rounded up to the nearest decimal place (except 0)
What dose rate at 1 m in mSv/h multiplied by 100 can be classed as transport index 0?
0.05 or less
What are the category names for type A packages?
I - White
II - Yellow
III - Yellow
III - Yellow (under exclusive use)
What requirements are there for type A packages under CDG?
Minimum dimension > 10 cm ad seal for evidence it hasn’t been opened. Must be able to withstand ‘normal transport conditions’ without an increase in the max dose rate
What test conditions are there for type A packages for it to withstand ‘normal transport conditions’?
Rainfall for 1 hour (water spray test)
Dropped from a height of 1 m
Stacking
Piercing
Temperature and pressure
For liquid radiopharmaceuticals in a type A package, what is the components included in the packaging?
Lead pot directly containing material with absorbent material in metal can, polystyrene packing in metal can and cardboard box
What marking and labelling should be on type A packages?
‘Type A’ clearly marked. Consignor and consignee name and address. Two labels with: radiation trefoil, contents, activity and transport index (only yellow)
Any internal container in a type A package should have what on the label?
Radiation trefoil, isotype, activity, surface dose rate, source serial no. if applicable
What two main document types are needed for transport under CDG?
Transport document (consignment certificate) and instructions for the driver
What rules are there for people other than the driver during transport according to CDG?
No other person without the carriers permission. Only necessary people in vehicle for type A packages
Do the drivers have to be certified under CDG for radioactive materials?
Yes or very restricted on what they can carry
What is the total sum of transport indexes for a vehicle that it cannot exceed?
50
What role does the ADR require to be appointed for packages more dangerous than excepted packages?
Dangerous Goods Safety Adviser (DGSA)
Who are the duty holders under IR(ME)R?
Employer, referrer practitioner, operator (includes MPE)
What are the employers duties under IR(ME)R?
Referral criteria, entitle duty holders, QA, dose constraints for research, training, incidents, written protocols and procedures
Who is the referrer under IR(ME)R?
Registered health professional entitled under the employers procedures to refer individuals for exposure to a practitioner
Who is the practitioner under IR(ME)R?
Healthcare professional entitled by the employer to take responsibility for an individual medical exposure
What is the practitioners responsibilities under IR(ME)R?
Responsible for justification and authorisation of exposures and allocation of practical aspects (partially optimisation)
Who is the operator under IR(ME)R?
Carries out practical aspects of an exposures and must be trained and comply with employers procedures
What are the responsibilities of the operator under IR(ME)R?
Identify the patient, check pregnancy status, optimise exposure (with practitioner), monitor patients wellbeing, check justification and authorisation, comply with employers procedure, select equipment and methods
Why are MPEs a special case of an operator?
They are involved in every medical exposure
Who issues certification for MPEs (authorised assessing body)?
RPA2000
How is dose minimised in diagnostic cases?
DRLs (local and compare them), able to assess patient dose, review DRLs when consistently exceeded, written procedures, optimisation
How is dose minimised in therapeutic cases?
Radiotherapy treatment planning for every patient. Consider prognosis and verification imaging exposures
Under IR(ME)R, can responsibility be delegated and why?
No, you are either responsible or not. Tasks can be delegated while retaining responsibility
Under IR(ME)R, is a person in training or the supervisor the operator?
The supervisor
Under IR(ME)R, what is required for research exposures?
Patients consent, ethical approval, a dose constraint if exposure is not of benefit to the patient
Under IR(ME)R, is a QC programme required?
Yes
Who enforces IR(ME)R?
CQC
Are CQC inspections proactive or reactive?
Both
What are the aims of CQC inspections?
Verify employers procedures are in place and that they are being complied with, check knowledge of responsibilities of staff
Are prosecutions under IR(ME)R carried out under Criminal Law?
Yes
When are ionising radiation exposures classed as an incident under IR(ME)R and its acronym?
Significant accidental or unintended exposure (SAUE)
What does ARSAC stand for?
Administration of Radioactive Substances Advisory Committee
Who is in ARSAC?
Committee of experts, like nuclear medicine clinicians/radiologists, medical physicists and radiopharmacists
What do ARSAC do?
Advises the licensing authorities (ARSAC Support Unit, HSA) on applications from practitioners, employers and researchers who want to administer radioactive substances
Who has to hold an ARSAC licence under IR(ME)R?
Practitioners and employers to hold a licence to administer radioactive substances when it results in an effective dose over 1 micro Sievert
How long do employer and practitioners ARSAC licenses last?
5 years
How many ARSAC licenses do employers and practitioners need?
Employers: one for each radiological installation
Practitioners: Only 1
Who applies for the practitioner ARSAC licences and who is allowed to apply?
The practitioner themselves and only medically trained practitioners that are consultant grade
What are Particular Patient Licences (PPL) for?
Cases for urgent medical need where the employer and practitioner must already hold an ARSAC licence and the ARSAC will put the practitioner in contact with an experienced practitioner
When are amendments or notifications required for employer ARSAC licences?
Amendments: addition of a procedure or change of purpose of a procedure, or above DRL administration.
Notification: material changes like contact details, named persons etc
How are ARSAC involved with research/ clinical trials that include radioactive administrations?
Assessments of research studies and the trial requires ARSAC approval (certificate for each trial)
In the annual ARSAC guidance notes, how are the procedures listed and what is included for each of them?
As functional groups, including DRLs and estimated effective doses for standard sized patients and uterus doses
From the ARSAC notes for guidance, how are children doses scaled from adult doses?
Fraction of adult dose related to the childs weight
From the ARSAC guidance notes, are there recommended minimum or average activity for children?
Minimum
From the ARSAC notes for guidance, what nuclear medicine procedures require a delay in conception?
Not many in diagnostic (only high dose of I-131) but many therapeutic doses
From the ARSAC notes for guidance, what is the guidance for patients that are breastfeeding?
Possible delay test, specific written instructions including how long to interrupt breastfeeding and express and discard before the time is over, should be below 1 mSv
What is the difference between accidental and unintended exposures?
Accidental = no exposure of any kind was intended
Unintended = exposure intended but gave the wrong exposure
Who gives guidance on when statutory notification of SAUE incidents is necessary?
CQC/IR(ME)R
The CQC guidance for SAUE incidents includes a table with what headings?
Notification code, exposure category (eg intended dose range or over/ under therapy dose, miss) and criteria for notification
What are the most common causes of accidental exposures?
Often procedural errors, mistaken identity and referral issues
How is CSAUE different to SAUE in terms of reporting to the CQC?
The C stands for ‘clinically’ and SAUE events that are clinically significant need to be reported to the CQC even if they don’t meet the SAUR criteria
How quickly should the CQC be notified if an incident meets any of the SAUE criteria or is a CSAUE?
Immediately (within 2 weeks), which may be obvious straight away or after a preliminary investigation
How long after incident discovery (that fulfils the notification criteria) should a final report be sent to CQC?
12 weeks (after full investigation)
What are the investigation requirements under IR(ME)R for incidents for a final report?
Timeline, estimated dose, root cause analysis, check if part of trend, duty of candour requirements, informing referrer and practitioner, clinical impact, corrective measures, sharing learning
What is an example of an investigation tool for clinical incidents that also satisfies IRMER investigation requirements?
London Protocol
The London Protocol method is related to the swiss cheese model, what does each slice of cheese represent?
Factor types, like patient factors, team factors or work environmental factors. Each have contributory influencing factors associated with it.
Is registration a requirement for operators under IR(ME)R?
No but employer may list registration as a criteria for a particular task. They do have to be trained
What level of involvement do MPEs have in each type of practice?
Radiotherapy: closely involved
Nuclear medicine (standard therapy or diagnostic), high dose IR and CT: involved
All others: involved as appropriate
What do MPEs have to give advice on according to IR(ME)R as a minimum?
Dosimetry and QA matters relating to exposures. Physical measurements for evaluation of dose delivered. Radiological equipment.
What are the 4 key work areas for MPEs?
Optimisation, equipment management, dosimetry and regulation compliance
How long are certificates from RPA2000 valid for?
5 years
Who has developed an MPE syllabus incorporating the competency requirements and they are also the people that recognise MPEs?
The Department of Health and Social Care
Does the MPE assessment process address the suitability of an applicant to work as an MPE in any specific field?
No, it is the responsibility of the employer
What are the five questions the CQC ask of all care services? They all start with ‘are they…’ so just end the question
Safe, effective, caring, responsive to people’s needs, well-led
What is the rating system for CQC inspections?
Outstanding, good, requires improvement, inadequate
Each question of the CQC inspection is broken down into a further set of questions, what are these called?
Key lines of enquiry (KLOE)
What are some examples of information requested in advance of a CQC inspection?
Equipment maintenance info, staff training records and overview of learning from incidents
How is the CQC inspection linked to IR(ME)R legislation?
The key lines of enquiry relate to different regulations in IR(ME)R
How do the CQC take action where necessary after an inspection?
With recommendations, improvement notices and prohibition notices
What does Hp(0.07) mean on a dose report?
Dose equivalent at 0.07 mm depth is tissue, so it is the skin dose
What does Hp(10) mean on a dose report?
Dose equivalent at 10 mm depth in tissue, so it is the whole body dose
What is the MPE and spectral effectiveness (S) for 270 nm UV lamp?
30 J m^-2 and 1
