Radiology Flashcards
Dose & Physics-
1. Give three ways to reduce patient dose?
- Rectangular collimation (rectangular 40x50mm)
- Focal skin distance >20cm (dose reduces with the increase of distance from the source
- lead lined film
Fastest film possible (If possible but always E or faster)- fewer x-ray photons required and so lower dose
* Focal skin distance >20cm (dose reduces with distance from source)
* Kv range 60-70kV (high tube potential reduces dose)
* Rare earth screen
- What is Compton scatter vs photelectric effect?
In Compton scatter there is interaction of the x-ray photon with loosely bound electron of the atom. The electron is ejected due to a greater energy of the photon. The photon then has lower energy after collision and undergoes change in direction hence cause scatter. Causes fogging or decreased image quality
In photoelectric effect there is interaction of the photon within the inner shell electron (higher energy). This leads to complete absorption of the photon and no scatter- there will be no interact of the x-ray with the film in this region leading to a white area on the film
what metal is used for absorption of X-rays?
Lead
Name another metal used in the X-ray tube head?
- Copper
- Tungsten
- Aluminium
- Compare and contrast the paralleling and bisecting angle technique?
- Parallel- (most commonly used)- image receptor and object parallel but not in contact- beam is divergent/perpendicular to image receptor- space between receptor and tooth/object bring risk of undue magnification (counteract by longer FSD- 20 from source to end of spacer cone (close but not touching patient)
- Bisecting angle technique- (occlusal radiography) - image receptor and object not parallel but partially in contact (at crown of tooth)- beam is 90° to long axis of the tooth and plane of image receptor (to avoid shortened or elongated image), teeth used ot gently support receptor so don’t need film holder
Regulations-
1. Regarding IRR99, give 5 safety features advised?
- Control area
- Warning sign for the controlled area
- sign lights up when the equipment is on
- Light and audible sound during exposure
- Exposure with continuous pressure only
- Exposure stops automatically
- What is ALARP?
As long as reasonably practicable - minimises exposure
How is ALARP achieved?
- Rectangular collimation
- FSD focal to skin distance of >20cm
- Beam diameter no more than 60mm at end of spacer
- Lead lined packet
- Fastest film speed possible (If possible but always E or faster)- fewer x-ray photons required and so lower dose
- Kv range 60-70kV (high tube potential reduces dose)
- Aluminium filtration system used
- What is a radiation protection supervisor?
Someone who ensures the regulations and training are followed
- What is a radiation protection advisor?
Somone who advises on radiation risk and dose assessment, regulation, training, designation of areas, equipment and periodic testing of safety features and warning devices.
What are IRMER guidelines?
- Minimise unintended, excesssive or incorrect medical exposure
- Justification. Ensure benefits outweight the risks
- Optimisation. keeping dose as low as reasonably practical
- What are the 3 main principles of radiation protection?
JOD
Justification
Optimisation
Dose limitation (for radiation workers and members of the public not patients)
- Give Roles for the following according to IRMER- employer, referrer, practitioner and operator?
- Employer- legal person responsible for safety and making sure equipment is in line with the regulations and ensuring staff are trained to follow these regulations
- 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
- Practitioner- person responsible for confirming justification and authorisation of request in accordance with employers written procedures and must **ensure doses are ALARP **
- Operator- 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 a radiograph to help aid diagnosis
- Act as a written record the patient dentition
- Details and can influence treatment planning
- IRMER specifies is it the role of operator that all radiographs must be reported
- Best practice to always report on radiograph
- For medical-legal reasons
- For audit purposes
- Give 2 examples of each type of bone pathology for developmental, inflammatory, neoplasm and metabolic?
achondroplasia, osteopetrosis
* Inflammatory- osteomyelitis, rarefying osteitis, focal sclerosing osteitis, alveolar osteitis
* Neoplasm- osteoma, osteosarcoma, osteoblastoma, ossifying fibroma
* Metabolic- osteoporosis, Paget’s disease, giant cell lesion, osteomalacia, hyperparathyrdoism
