Radiology Flashcards
1
Q
What are X-rays
A
- Form of high energy electromagnetic radiation
- Short wavelength
- Packets of energy made of photons
2
Q
What are the components of x ray tube
A
- Cathode: emits electron, typically made of tungsten
- Anode: bombarded with electron cos its positive, copper or tungsten
- vacuum
3
Q
What are the two types of x-ray collisions
A
- Continuous spectrum
- Characteristic spectrum
- Other is heat producing collisions
4
Q
What is the continuous spectrum
A
- High energy electron goes close to the nucleus
- Changes direction and loose energy
- X ray is released
5
Q
What is characteristic spectrum
A
- Knock electron out of the inner shell
- Outer shell electron fills vacancy
- Releases an x-ray
6
Q
What is critical voltage
A
- Minimum energy needed for x ray
- Tungsten 69.6 KV
7
Q
What is radiation absorbed dose
A
- Amount of energy absorbed from radiation beam
- Measured in milligray (mGy)
8
Q
What is equivalent dose (Ht)
A
- Equivalent dose = radiation absorbed dose x radiation weighting factor (Wr) for particular tissue
- For individual organs
- Measured in sievert (Sv)
- Wr for x ray is 1
9
Q
What is tissue weighting factor
A
- More risk of damage the higher the Wt
10
Q
Name some bodies
A
- ICRP (international commission on radiological protection)
- IR (ME) R (ionising radiation medical exposure regulation)(2000-2018)
- IRR (ionising radiation regulations)(1999 -> 2017)
11
Q
What are the changes in IR (ME) R
A
- Employer insure individual patient aware of risk and benefit
- Employer collect dose estimates from medical exposures
12
Q
What is IR(ME)R consist of (protects patient)
A
- Referrer (justify)
- Practitioner (take responsibility)
- Operator (exposure and process)
- Employer (ultimate responsibility)
13
Q
What are the changes of IRR
A
- How to tell health safety exec you work with IR
- Reduced does limit for lens of eye from 150 to 20msv
14
Q
What does the ICRP say
A
- Prevent deterministic and limit stochastic
- Justification: benefit outweigh the risk
- Optimization: ALARP (as low as reasonably practicable)
- Limitation: patients, radiation workers, general public (does should not exceed limits)
15
Q
What is the panoramic dose
A
- 16-26 microsivert (includes the salivary glands)
- 7-14 microsivert (without salivary glands)
- 2.7 (maybe)
16
Q
Whats the does for intra oral film
A
- 0.3-21.6 micro sivert
- 0.3 (maybe)
17
Q
Whats the maximum does
A
- 20 milisivert
18
Q
What is somatic deterministic effects
A
- Directly related to radiation received
- Dental radiation quite low so low risk of this
- Cataract, loosing fingers
19
Q
What is somatic stochastic
A
- Not directly related to radiation dose
- Random
- Malignancy
20
Q
How do x-rays cause damage
A
- Direct damage (hitting DNA)
- Indirect damage (water ionises and then damages DNA)
21
Q
What are the dose reduction techniques divided into?
A
- Equipment
- Clinical decision
- Practical technique
- Diagnostic interruption
22
Q
Tell me how to limit radiation from equipment
A
- Aluminium filtration (remove low energy photons)
- Collimator (minimise scatter radiation)
- Beam indicator device (correct distance and direction)
- Lead
- Kv,mA,time
23
Q
What happens to changing Kv
A
- Higher Kv lighter (also more penetrating)
- 70Kv
- Increasing kv more dose
24
Q
What happens when you change mA
A
- Increasing mA
- Makes it darker
25
Tell me how clinical decision reduces does
- Justification
- Evidence based selection criteria
26
What is the controlled area
- 1.5m from the tube
- Radioation protection advisor (RPA)
- Design of the x ray room or controlled area
27
What to do in malfunction
- IRR (equipment malfunction) (HSE)
- IRMER (clinical error)(IRMER )
28
What are the local rules
- RPS
- RPA
- Controlled areas
- Personal dosimetry
- Pregnant staff
29
What are the types of radiography
- Digital (direct and indirect)(Solid state sensor vs PSP)
- Conventional (manual, automatic)
30
What does conventional film consist of
- Cover
- Film (silver halide)
- Lead
31
How does silver halide work
- Developer (green silver halide converted to black)
- Fixer (black metallic fixed to plastic base)
- Wash ( washes off fixer )
- Unexposed silver not effected by developer and removed by fixer
32
What are film processing errors
- Concertraion of chemicals
- Development time
- Temperature of chemical
- Handling
33
What is PPP
- Patient preparation
- Patient positioning
- Radiation exposure
- Image processing
34
What are the two techniques taking a PA
- Paralleling technique
- Bisecting angle
35
Name some x ray errors you can see
- Overlapping (horizontal plane error)
- Elongation/ foreshortening (vertical plane error)
36
Angle for upper standard occlusal
- 60-70 degrees
- Cant tolerate PA
- Pathology
- Unerupted teeth parallax
37
Lower standard occlusal
- Lower 90 degrees (true occlusal)
- Lower 45 degree
- Salivary gland, pathology, cysts
38
How to position the head
- Laser to align the patient (canine light)
- Should me straight
39
What angle is the opg
- 5-6 degrees to stop superimposition of the hard palate
