One Doc Flashcards
OPT radiograph with 10 arrows asking for names of landmarks
Refer to radiograph in one doc
Give 2 examples of each type of bone pathology for Developmental, Inflammatory, Neoplasm, Metabolic
Developmental → tori, fibrous dysplasia. Inflammatory → dry socket, osteomyelitis. Neoplasm →osteoma,
osteosarcoma. Metabolic → osteoporosis, Rickett’s, Paget’s, Giant Cell Lesion
Give 4 differential diagnoses for a multilocular radiolucency
ameloblastoma, KCOT, Giant cell lesion, odontogenic myxoma, cherubism, aneurysmal bone cyst
What is the reason for the following errors in an OPT? Anterior distorted Blurry image Image too wide
Anteriors distorted
Pt not in focal plane.
Blurry image
Pt moved during exposure.
Image too wide
Canine guide set in front of canines.
How can positioning errors be limited
Use guides → temple rests, chin rest, bite block, hand rests, guide lights
Give 3 characteristics of a ghost image
higher, opposite side, larger/wider - Always be higher due to vertical beam angulation of -8o
- Horizontally magnified
- Usually further forward due to change in anterior-posterior position
Give 3 ways to reduce patient dose
ALARP - beam diameter no greater than 60mm at end of spacer, rectangular collimation 40x50mm, Focal Skin
Distance 20-30cm, 60-70kV, fast film F, aluminium filtration, lead absorption, limit exposures- Use E speed film or faster/direct digital as there will be fewer X-ray photons required so lower dose produced
- Use KV range from 60-70kV with Focus-skin-distance (fsd) of >200mm
- Rectangular collimating and use of film holders
What is Compton scatter vs photoelectric effect?
Compton → fogs and decreases image quality due to x-ray hitting outer electrons and losing direction and energy.
Photoelectric → complete absorption giving a white image as does not reach film. This is normalCompton scatter and absorption:
- X Ray photon interacts with over shell electrons which is greater than electron energy. The electron is ejected taking some photon energy as kinetic causing a recoil electron. Following collision, the photon has lower energy so is called a scatter photon and undergoes a change in direction
- Forward – high energy; backward – low energy
- Probability of Compton scatter occurring
- Proportional to density of material; independent of atomic number and not related to photon energy
Photoelectric effect absorption:
- X Ray photon reacts with inner shell electron which had higher energy than binding electron making the x-rah photon disappear. The difference in energy is emitted as light and energy menacing the electron is ejected as a photoelectron. This results in complete absorption of photon energy meaning the photon does not reach the film and preventing interaction with active component of image receptor – image appears white if all photons are involved and grey if some are involved
- Occurrence is propionate to:
* Atomic number; 1/photon energy and density of material
* Relatively small difference in atomic numbers results in large differences in photoelectric absorption
What metal is used for absorption in X-rays?
Lead- Lead prevents back scattered photons and absorbs scatter x-rays to prevent image degradation and absorb some of primary beam
Name another metal used in the X-ray tube head
copper/tungsten/aluminium- Copper (target surround heat conductor); tungsten (cathode filament) or aluminium (filtration)
Regarding IRR99, give 5 safety features advised
Controlled area, warning sign for controlled area, sign lights up when equipment on, light and audible sound during
exposure, exposure w/continuous pressure only, exposure stops automatically
What is ALARP?
As low as reasonably practicable → minimises exposure and dose
How is ALARp achieved
Rectangular collimation (40x50mm), FSD 20-30cm, fastest film available (F or digital), 60-70kV, aluminium filtration,
beam diameter no greater than 60mm at end of spacer
What is a radiation protection supervisor?
Ensures regulations and training are followed
What is a radiation protection advisor?
Advises on risk, regulations, training, quality etc
Compare and contrast the paralleling technique and bisecting angle technique.
Paralleling → No contact but object and receptor are parallel and beam perpendicular to receptor.
Bisecting angle → In contact but not parallel and beam perpendicular to receptor.
Why should you report radiographs? Medico-legal, best practice, IRMER2000, records, audit.Paralleling:
- Image receptor and object parallel but not in contact
- Beam is divergent/perpendicular so image receptor and object is some distance apart but with a short spacer cone which allows for short Fsd. The spacer done should always be close to patient but not touching
- Use long X-ray fsd 20cm to reduce magnification and requires film holders and stabilisation with cotton roll
Bisecting angle:
- Image receptor and object not parallel and partially in contact
- The beam is perpendicular to the image receptor and object are close together at crowns but apart at the apex
- Long fsd 20cm should still be used but can be done without film holders
Give roles for the following according to IRMER2000: ERPO
Employer – legal person, safety, make sure equipment in line with IRR99, staff follow regs.
Referrer – Check pt demographics, clinically justify radiograph, be trained.
Practitioner – Justifies exposure, benefit vs. risk, check no recent relevant radiographs.
Operator – Check pt demographics, ALARP, takes exposure, processes and reports.
- What are IRMER guidelines?
Minimising unintended, excessive or incorrect medical exposures
o Ensuring benefits outweigh the risks of each exposure (justification)
o Keeping doses in diagnostics as low as reasonably practicable for their intended use (optimisation)
- What are the 3 main principles of radiation protection?
Justification
o Optimisation – ALARP
o Dose limitation – for radiation workers and members of public not patients
- Who are the 4 personnel and roles in IRMER?
o Employer – legal person responsible for safety and making sure equipment is in line with regulations and ensuring staff are trained and follow these regulations
o Referrer - Individual requesting an examination who must take a history and conduct clinical exam prior to referral to the practitioner. Must justify exposure and examination ensuring demographics are correct
o Practitioner (IRMER practitioner) - Person responsible for confirming justification and authorisation of request in accordance with employers written procedures and must ensure doses are ALARP. Can be dentist; radiologist; specialist
o Operator:This is the person who takes and or reports radiographs – noting exposure and ensuring X-Ray are in accordance with IRMER and ALARP.
- Why should you report radiographs?
To note exactly what is seen in patients radiographs to help aid diagnosis
o Acts as a written record of patients dentition
o Details and can influence treatment planning
o Role of the operator that all radiographs must be reported (IRMER2000)
o Best practice to always report on radiographs and for medical-legal reasons o For audit purposes
