Radiology Flashcards
what is a radiograph?
image created by different absorption of x-ray photons by different tissues.
anatomy = what is the white Y shape structure found above upper 1-4?
Y shape of Ennis.
what is an xray beam a stream of?
photons
what is an electron volt?
electron accelerated through an electric field with a potential difference (voltage) of 1V gains 1eV in energy.
what are the 2 mechanisms of x-ray production?
- Bremsstrahlung (electron-nucleus interaction)
- Characteristic spectrum (electron-electron interaction)
How does Bremsstrahlung produce xrays?
with a range of engeries determined by the tube potential
How does Characteristic produce xrays?
with just afew discrete energies determined by the target material.
what are the x-ray tube components?
- Cathode
- Anode
- Filter
- Cooling oil
- Shield
- Evacuated glass tube
- Shielded metal housing
- Window
- Oil.
what is the purpose of the evacuated glass tube in the xray tube?
to get to target.
prevents xray protons going in all directions.
what is the purpose of oil in the x-ray tube?
removes heat.
What is meant by Tube Voltage (kV)?
electron energy is proportional to the potential (voltage) between anode + cathode.
what is meant by Tube Potential (kVp)?
affects both the quantity of x-rays produced and the shape of the x-ray spectrum (quality)
what is meant by Tube current (mA)?
the electrons flowing from cathode to anode form an electron current which is measured in mA. Total quantity of xrays is determined by the current (mA) and the tine for which it flows (s)
what is the intensity of x-rays proportional to?
tube current
what does the tube current and exposure time only affect?
the quantity of the x-rays
what does filtration affect?
the quality and quantity of the xrays
how does filtration increase the beam energy?
preferentially removes lower energy xrays
for a standard diagnostic x-ray tube, what should the filtration be at?
at least 2.5mmAl.
should the focal spot of xrays be large or small?
small
what would result if the focal spot of an xray is too small?
xray tube overheats.
why does there need to be heat removal in the xray tube?
- prevent damage to focal spot and target
- to prevent general overheating of the tube.
what structures in the mouth will absorb the most protons?
bones and teeth.
what is attenuation of xrays?
the total process of reducing the intensity of an xray bea,
How can attenuation be achieved to produce good contrast in an xray?
photoelectric absorption - photon energy transferred to electron.
How can attenuation be achieved to reduce contrast in an xray?
compton scatter - photon energy partially transferred to electron
what does xray energy need to be high enough to do?
traverse the tissue thickness of interest and minimise scatter.
what does xray energy need to be low enough for?
to be altenvated in the appropriate tissue.
What type of xrays can be used to gain a 3D image?
CT scans and MRI
How can you change contrast of an X-ray image?
Change the quality of the radiation (but this could increase scatter, to reduce this reduce kV, change pt orientation, compression, anti-scatter grids, air gap and reduce field size)
What are factors that affect X-ray image unsharpness?
- receptor
- geometric
- movement
How can you prevent noise in an X-ray image?
Increase the number of X-ray photons forming the image
What is noise when talking about an X-ray image?
To many photons to one area - so can no longer detect contrast differences
What is ionising radiation?
High radiation
What are the harmful effects of radiation?
- cancer
- cataracts
- skin darkening/ burns
- hair loss
- sterility
What are some beneficial effects of using radiation?
- Saves lives via radiotherapy
- early diagnosis
- sterilisation of blood products/ food stuff / dressings
What are the 3 ways in which xrays interact with tissues?
- Transmitted
- Scattered
- Absorbed
What is the purpose of transmitted xrays?
Help us to form the image we want to see
What is mean by scattered xrays?
Xrays that can be absorbed by others in the room that it wasn’t meant for
What is meant by absorbed xrays?
Absorbed xrays that deliver a radiation dose to the patient and can potentially cause harm
What are your bodies cells most at risk from damage from xrays?
During the replication stage - G2 and mitosis.
What type of cells in the body are most sensitive to damage from xrays?
Active cells - WBC and bone marrow.
What are the effects that the xrays can have on the cells in the body?
Xrays can cause ionisation of the cellular water leading to changes molecularly and the formation of chemicals that can damage chromosomes. This changes the structure and function of the cell.
What are the Effects on the body of X-ray damage dependent on?
Dose, dose rate, area irradiated and sensitivity of organs/individual
What type of radiation effects can happen in dental X-rays (but is very unlikely) ?
Stochastic
What is a stochastic effect?
Chronic, potential long term effect.
Occurs randomly but probability of effect depends on dose.
Can cause cancers, harm to future generations due too harm to reproductive organs
What are the ICRP principles for protection again radiation?
- Limitation
- Justification
- Optimisation
What is meant by ALARP?
As Low As Reasonably Possible
What does IRMER stand for?
Ionising Radiation (Medical Exposure) Regulations
Who does IRMER protect?
Protects pt from harmful effects of ionising radiation
Who is IRMER enforced by?
CQC
What does ALARP CWIF stand for?
As Low As Reasonably Practicable
Consistent With Intended Purpose
What is the fundamental premise of IRMER?
ALARP CWIP
What is the IRMER philosophy?
- avoid unnecessary exposure
- protect the pt from detrimental effects of radiation
- every exposure must be justified
- optimise exposure
- ensure quality of exposures
- written clinical evaluation for every exposure
What are the 2 main principles of IRMER ?
Justified and Optimised.
According to IRMER, what responsibility does the referrer have?
must have written referral criteria, including dose and alternatives.
According to IRMER, what responsibility does the practitioner have?
responsible for the justification and authorisation of each medical exposure.
According to IRMER, what responsibility does the operator have?
responsible for anything that can influence the outcomes (eg ID the patient, exposure factors, matching images, etc)
According to IRMER, what responsibility does the employer have?
must have written procedures for everything.
According to IRMER, should Xrays be taken during pregnancy?
only if it is justified by the practitioner that the xray is urgent and they have taken into accound the risk to the expectant mother and unborn child.
According to IRMER, what should be written in the patients note i regard to taking an xray?
- infor on radiation does
- type of xray
- exposure settings.
If there is an incident regarding radiology to a patient what should be done?
reported to CQC.
- clinically sig accidental exposure
- failure to follow procedures/ protocols
- unintended exposures
- near misses.
In what year was IRR last updated?
2017
what is IRR17 concerned with?
protection of employees and the general public
who enforced IRR17?
health and safety executive.
what is the framework for IRR17?
- consult an RPA (radiation Protection Adviser)
- notify intention to work with radiation
- Assess radiation risks before work
- manage risks
- write safety procedures
- mark and control hazardous areas
- train staff to work in hazardous areas
- supervise staff in hazardous areas
- monitor staff dose
- investigate incidents
- maintain and test engineering controls.
what is the fundermental premis of IRR17?
ALARP
according to IRR17, what is the employer responsibility?
to protect everyone from work place hazards.
according to IRR17 what is the staffs responsibility?
to follow any control measures put in place to reduce risk
If over what staff member dose in one year should an investigation take place?
Over 15mSv.
what should the employer do happen if anyone exceeds a dose limit?
- investigate
- inform the employee
- inform HSE
what is needed for radiation controlled areas?
- demarcation
- access restrictions
- local rules
- monitoring
- warning signs
- RPS
- dose assessment
what are local rules>
key work instructions for comlying with IRR17 and ALARP
what is the role of a Radiation Protection Supervisor?
appointed to ensure compliance with local rules.
Whos responsibility is it to ensure that everyone has suitable and sufficient information and training to do their work?
employer.
what are the Layers of a direct action film?
- Plastic base
- thin layer of adhesive
- emulsion
- protective layer
what makes up a direct action film packet?
- outer packet
- black paper lining
- lead foil.
what should the orientation of a xray film be?
raised dot towards the x-ray beam and towards the occlusal plane
what type of digital receptors (xray films) are solid state and phosphor plates?
PA +BW
Extraoral
what type of xrays are phosphor plates only?
occulsal and lateral obliques,
what are the 3 types of solid state sensors?
- Charge Coupled device (like @ obex)
- Complimentary metal oxide detectors
- Photostimulable phosphor storage plates ( like @ Ashwell)
In regards to characteristics of image receptors what happens if there is a larger film speed?
should decrease the dose to the patient.
In regards to characteristics of image receptors what happens if there is optical density?
degree of blackening in a radiograph
In regards to characteristics of image receptors what happens if there is fog?
- degree of blackening with zero exposure.
If there is a higher number for brightness what does this mean the xray will look like?
will look darker
If there is a lower number for brightness what does this mean the xray will look like?
will look lighter.
If there is a higher number for contrast what does this mean the xray will look like?
more shade, less contrast.
If there is a lower number for contrast what does this mean the xray will look like?
fewer shades, more contrast.
what can be used to adjust digital images?
- brightness + contrast
- magnification
- sharpening filter
- measurement (length)
- Grey scale inversion
what can be a problem with Grey scale inversion of digital imaging?
changing the image may cause mimicking of pathology
what are the advantages of digital xrays?
- instant images
- correct incorrect exposure
- lower dose to patients
- avoid chemicals
- easy storage and transfer of images
what are the disadvantages of digital xrays?
- large detectors needed
- can need wire connections
- what happens if computer fails
- overexposure can cause blooming
- manipulation can be misleading.
If the contrast in an Xray is too pale what could this have been caused by?
- too short time in developer
- too cold
- too dilute
- exhausted developer
- underdeveloped
If the contrast in an Xray is too darl what could this have been caused by?
- too long in developer
- developer to concentrated
- developer too hot
- ogged
- overexposed.
what happen to the geometric unsharpness of an xray is the penumbra is larger?
less sharp image.
how can the penumbra size be decreased to allow for ssharper xray image?
- decrease focal spot size
- increase focal spot to detector distance
- decrease object to detector distance.
what are the effects of an intensifying screen being too thick on the xray image? and why?
the xray image will be more blurred. This is because the light protons will be more spread out from the intensifying scree.
what is the bisecting angle technique for xrays?
- crown edge touching film and root diverging away.
- xray beam perpendicular to a line which bisects the angle between the long axis of the tooth and the film.
what are benifits of the bisecting angle technique for xrays?
- cheap
- quick
- more comfortable for pt
what are some disadvantages for the bisecting angle technique for xrays?
- difficult to assess line of bisection
- can cause forshortening / elongation
- fingers are irradiated
- bone levels are bot accurate.
How are occlusal xray taken?
- film held between teeth, paalle to occlusal plae.
what are occlusal xrays used to assess?
- mpacted teeth location
- trauma
- bony expansions of madible
- submandibular dict stones
What is meant by a true xray?
xray beam is perpendicular to film
what is meant by oblique xray?
xray beam angled other than right angles to film .
when is a maxillary true xray used?
never - is a usless xray as unclear view.
how is a maxillary vertex xray taken?
projects down through the vertex of the skull, along the log axis of the incisors, resulting i a cross sectional view.
Regarding the xray image what should be reported regarding a finding in the patients notes?
- location
- size
- density
- shape
- boarders/ margins
- effects o surrounding structures.
what is meant by homogeneous when talking about an xray image?
uniform in density
what is meant by heterogeneous when talking about an xray image?
not uniform in density
what is meant by unilocular when talking about an xray image?
the shape of the finding is circular.
what is meant by multilocular when talking about an xray image?
the shape of the finding has scalloped edged (many circles)
what should be states in patients notes regarding the boarders of a finding in an xray?
if they are smooth, regular or irregular.
what should be states in patients notes regarding the margins of a finding in an xray?
if they are corticated, partially corticated, well difined , or ill defined.
what effects could a finding on an xray have on surrounding structures?
- teeth displaced
- resober
- ## ID canael resorbed.
what are signs of a benign disease in an xray image?
smooth, well defined, corticated.
what are signs of a more sinister finding in an xray image?
irreguar , erosive, ill defined.
