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4 Radiology > Other imaging modalities > Flashcards

Other imaging modalities Flashcards

1
Q

in CT, CBCT and MRI the patient is divided into ?

each ? is given a ? according to the amount it has attenuated (reduced) the beam

Different CT numbers give different shades of ?

  • Bone = ?
  • soft tissue = ?
  • air = ?
A

voxels

voxel
CT (Hounsfield) number

grey

white
grey
black

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2
Q

voxels can be different sizes

how does the size of the voxels affect resolution?

A

smaller voxel = higher resolution

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3
Q

voxels can be different sizes

how does the size of the voxels affect scan time and radiation dose?

A

Smaller voxels = longer scan time so higher dose

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4
Q

what is windowing?

A

manipulate the image to allow better visualisation of more subtle changes between tissues

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5
Q

this image shows

Changing the windowing of a blow out fracture

Blow out fracture - fracture of orbital floor where orbital contents can herniate into the sinus

LHS - soft tissue windowing to see muscles of the eye

RHS - hard tissue windowing to see bone more clearly

A
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6
Q

remember that all images taken need to be evaluated

A
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7
Q

when looking at CT, CBCT, MRI images the data is reconstructed into what?

A

planes - axial, coronal, sagittal and other

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8
Q

what plane is this?

A

axial

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9
Q

what plane is this?

A

sagittal

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10
Q

what plane is this?

A

coronal

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11
Q

MRI - how it works

Involves ?, ? and ?

Patient is placed in ?

? align in this field

Another magnetic field is applied at an ? & then ?

The protons ? back to their original position

This ? is measured by the ?

Cortical bone and dental hard tissues appear ? as not much ? present

Various sequences show different tissues as ? or ?

A

protons (water)
magnetic field
radiofrequency pulses

magnetic field

water protons

angle
removed

oscillate/resonate

resonance
computer

black
water

dark
bright

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12
Q

this is an MRI

A
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13
Q

in MRI with T1 weighted sequences water appears what colour?

A

dark

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14
Q

T1 weighted MRI sequences are used to view what?

A

anatomy

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15
Q

in MRI with T2 weighted sequences water appears what colour?

A

bright

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16
Q

T2 weighted MRI sequences are used to view what?

A

pathology

17
Q

advantages of MRI

A

No ionising radiation

Excellent for viewing soft tissues, cancellous bone, changes in marrow, infection, infiltration, cortex breach

Multi-planar

18
Q

disadvantages of MRI

A

Multiple contraindications
○ Pacemakers, artificial heart valves, surgical clips, 1st trimester of pregnancy

FB (foreign bodies) within the eyes and orbits

Danger of strong magnetic field

Units need to be away from car parks and other facilities

Availability and cost -> long waitlists

Scan times can be long and noisy

Claustrophobia

19
Q

what MRI view is this?

A

axial view of submandibular region

20
Q

what MRI view is this?

A

coronal

21
Q

what MRI view is this? what can be seen?

A

TMJ

disc can be seen

22
Q

what is MRI used for in dundee dental hospital?

A

TMJ disorders - particularly disc problems

Salivary gland pathology

Assessing early bone changes in patients suspected of having MRONJ - medical related osteonecrosis of the jaw

23
Q

how does ultrasound work?

A

High frequency sound waves bounce off tissues and back to the probe

Cannot travel beyond hard tissues

24
Q

remember there is limited use for ultrasound around the jaws

A
25
Q

advantages of ultrasound

A

No ionising radiation

No harmful effects

Ideal for superficial soft tissue structures

Multi-planar

Operator dependant

Real time images

Blood flow

26
Q

disadvantages of ultrasound

A

Operator dependant

Difficult to interpret

Superficial tissues

Cannot penetrate bone

27
Q

uses of ultrasound

A

Neck swelling
- Tissue of origin
- Solid/cystic
- Characteristic (benign/malignant)

Salivary glands
- Intra-glandular lesion
- Neoplasm
- Sjogren’s syndrome
- HIV
- Calculi within the salivary glands and ducts

Blood flow
- Carotid artery disease
- Relationship to lesion and lesion supply
- Guidance for biopsy/drainage

28
Q

what is radioisotope scanning?

A

Inject isotopes which are unstable and decay emitting radioactive particles or gamma radiation

29
Q

in radioisotope scanning the isotope chosen is dependant on what?

A

the tissue being imaged

30
Q

name a substance used for radioisotope scanning

A

technitium

31
Q

why is technitium used for radioisotope scanning?

A

Short half life - reduced exposure

Can be easily bound to different substances e.g. red blood cells

Taken up by thyroid and salivary glands

32
Q

in radioisotope scanning radioactive compounds concentrate more in more or less active tissues?

A

more active tissues

33
Q

in radioisotope scanning what detects radioactive emission?

A

Gamma camera

34
Q

uses of radioisotope scanning in the head and neck

A

Salivary gland function

Condylar growth in mandibular asymmetry

Thyroid

Bone metastases

Osteomyelitis (inflammation of bone or bone marrow)

35
Q

problems with nuclear medicine imaging (radioisotope scanning)

A

Poor resolution

Difficult to distinguish between different pathological processes

Radiation dose

36
Q

what is PET CT

A

Positron emission tomography combined with CT

PET scan and CT scan images superimposed on each other

37
Q

in PET CT how does it show areas where cells are more active than normal?

A

radioactive contrast given (orally, IV, inhaled)

contrast concentrates in more active areas

38
Q

compare PET CT to CT alone

A

PET CT has less detail than CT alone

39
Q

uses of PET CT

A

Diagnose and stage cancer

Radiotherapy planning

Assess effectiveness of treatment

Distinguish between active disease and scarring following treatment

4 Radiology (19 decks)

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