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BDS5 > Radiology > Flashcards

Radiology Flashcards

1
Q

What are X-rays

A
  • Form of high energy electromagnetic radiation
  • Short wavelength
  • Packets of energy made of photons
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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
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3
Q

What are the two types of x-ray collisions

A
  • Continuous spectrum
  • Characteristic spectrum
  • Other is heat producing collisions
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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
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5
Q

What is characteristic spectrum

A
  • Knock electron out of the inner shell
  • Outer shell electron fills vacancy
  • Releases an x-ray
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6
Q

What is critical voltage

A
  • Minimum energy needed for x ray
  • Tungsten 69.6 KV
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7
Q

What is radiation absorbed dose

A
  • Amount of energy absorbed from radiation beam
  • Measured in milligray (mGy)
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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
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9
Q

What is tissue weighting factor

A
  • More risk of damage the higher the Wt
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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)
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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
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12
Q

What is IR(ME)R consist of (protects patient)

A
  • Referrer (justify)
  • Practitioner (take responsibility)
  • Operator (exposure and process)
  • Employer (ultimate responsibility)
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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
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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)
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15
Q

What is the panoramic dose

A
  • 16-26 microsivert (includes the salivary glands)
  • 7-14 microsivert (without salivary glands)
  • 2.7 (maybe)
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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
Q

Tell me how clinical decision reduces does

A
  • Justification
  • Evidence based selection criteria
26
Q

What is the controlled area

A
  • 1.5m from the tube
  • Radioation protection advisor (RPA)
  • Design of the x ray room or controlled area
27
Q

What to do in malfunction

A
  • IRR (equipment malfunction) (HSE)
  • IRMER (clinical error)(IRMER )
28
Q

What are the local rules

A
  • RPS
  • RPA
  • Controlled areas
  • Personal dosimetry
  • Pregnant staff
29
Q

What are the types of radiography

A
  • Digital (direct and indirect)(Solid state sensor vs PSP)
  • Conventional (manual, automatic)
30
Q

What does conventional film consist of

A
  • Cover
  • Film (silver halide)
  • Lead
31
Q

How does silver halide work

A
  • 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
Q

What are film processing errors

A
  • Concertraion of chemicals
  • Development time
  • Temperature of chemical
  • Handling
33
Q

What is PPP

A
  • Patient preparation
  • Patient positioning
  • Radiation exposure
  • Image processing
34
Q

What are the two techniques taking a PA

A
  • Paralleling technique
  • Bisecting angle
35
Q

Name some x ray errors you can see

A
  • Overlapping (horizontal plane error)
  • Elongation/ foreshortening (vertical plane error)
36
Q

Angle for upper standard occlusal

A
  • 60-70 degrees
  • Cant tolerate PA
  • Pathology
  • Unerupted teeth parallax
37
Q

Lower standard occlusal

A
  • Lower 90 degrees (true occlusal)
  • Lower 45 degree
  • Salivary gland, pathology, cysts
38
Q

How to position the head

A
  • Laser to align the patient (canine light)
  • Should me straight
39
Q

What angle is the opg

A
  • 5-6 degrees to stop superimposition of the hard palate

BDS5 (10 decks)

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