One Doc

Question 1

OPT radiograph with 10 arrows asking for names of landmarks

Answer 1

Refer to radiograph in one doc

Question 2

Give 2 examples of each type of bone pathology for Developmental, Inflammatory, Neoplasm, Metabolic

Answer 2

Developmental → tori, fibrous dysplasia. Inflammatory → dry socket, osteomyelitis. Neoplasm →osteoma,
osteosarcoma. Metabolic → osteoporosis, Rickett’s, Paget’s, Giant Cell Lesion

Question 3

Give 4 differential diagnoses for a multilocular radiolucency

Answer 3

ameloblastoma, KCOT, Giant cell lesion, odontogenic myxoma, cherubism, aneurysmal bone cyst

Question 4

What is the reason for the following errors in an OPT? Anterior distorted Blurry image Image too wide

Answer 4

Anteriors distorted
Pt not in focal plane.
Blurry image
Pt moved during exposure.
Image too wide
Canine guide set in front of canines.

Question 5

How can positioning errors be limited

Answer 5

Use guides → temple rests, chin rest, bite block, hand rests, guide lights

Question 6

Give 3 characteristics of a ghost image

Answer 6

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

Question 7

Give 3 ways to reduce patient dose

Answer 7

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

Question 8

What is Compton scatter vs photoelectric effect?

Answer 8

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

Question 9

What metal is used for absorption in X-rays?

Answer 9

Lead- Lead prevents back scattered photons and absorbs scatter x-rays to prevent image degradation and absorb some of primary beam

Question 10

Name another metal used in the X-ray tube head

Answer 10

copper/tungsten/aluminium- Copper (target surround heat conductor); tungsten (cathode filament) or aluminium (filtration)

Question 11

Regarding IRR99, give 5 safety features advised

Answer 11

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

Question 12

What is ALARP?

Answer 12

As low as reasonably practicable → minimises exposure and dose

Question 13

How is ALARp achieved

Answer 13

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

Question 14

What is a radiation protection supervisor?

Answer 14

Ensures regulations and training are followed

Question 15

What is a radiation protection advisor?

Answer 15

Advises on risk, regulations, training, quality etc

Question 16

Compare and contrast the paralleling technique and bisecting angle technique.

Answer 16

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

Question 17

Give roles for the following according to IRMER2000: ERPO

Answer 17

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.

Question 18

• What are IRMER guidelines?

Answer 18

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)

Question 19

• What are the 3 main principles of radiation protection?

Answer 19

Justification
o Optimisation – ALARP
o Dose limitation – for radiation workers and members of public not patients

Question 20

• Who are the 4 personnel and roles in IRMER?

Answer 20

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.

Question 21

• Why should you report radiographs?

Answer 21

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