Alternative Imaging Modalities

Question 1

list 5 imaging modalities alternative to CBCT

Answer 1

CT
MRI
ultrasound
nucelar medicine
combo - PET-CT/PET-MRI

Question 2

what structures does CT image?

Answer 2

soft tissue and bony anatomy - can be injected w/ IV contrast to inc contrast

Question 3

CBCT - shape of beam, dose, soft tissue contrast, radiographic contrast, pt position

Answer 3

cone
lower dose
poor
not required
pt sits upright/standing

Question 4

CT - shape of beam, dose, soft tissue contrast, radiographic contrast, pt position

Answer 4

fan
higher dose than CBCT
good - “windowing”
can be used if indicated
pt lying horizontal

Question 5

what value is each CT voxel given? how does this compare to CBCT?

Answer 5

Houndsfield unit - CBCT has no value of density

Question 6

what does the min/max HF num correspond to?

Answer 6

min = black
max = white

Question 7

what does windowing do?

Answer 7

alters densities visualised in scan to optimally look at specific tissue

Question 8

what imaging modality does not use ionising radiation?

Answer 8

MRI & ultrasound

Question 9

how does cortical bone always look in MRI?

Answer 9

black - as little water content

Question 10

what appears white in T1 & T2? what is each best used for?

Answer 10

T1 = fat appears white - best for anatomy
T2 = fat and fluid is white - best for pathology

Question 11

what contrast agent is used w/ MRI?

Answer 11

gadolinium

Question 12

list 4 contraindications of MRIs

Answer 12

pacemakers
orbital foreign bodies
artificial heart valves
surgical clips

Question 13

what is MRI used to visualise in dentistry? (3)

Answer 13

TMJ
salivary glands
sinuses for malignancy

Question 14

list advanatages of ultrasound

Answer 14

no ionising radiation
good for superficial structures
shows blood flow

Question 15

list disadvantages of ultrasound

Answer 15

cannot penetrate bone
only superficial structures seen

Question 16

what use is ultrasound in dentistry?

Answer 16

neck lumps - cysts, tumours, lymph nodes
salivary gland - sjorgens, neoplasia, sialadenitis, sialoliths
guidance for biopsy
vascular - carotid artery stenosis, vascular lesions

Question 17

give 3 types of nuclear medicine - what do they stand for?

Answer 17

PET - positron emission tomography
SPECT - single photon emission CT
Scintigraphy

Question 18

what is used to identify structures in nuclear medicine?

Answer 18

gamma camera

Question 19

list 3 advantages of nuclear medicine

Answer 19

can be superimposed over other image i.e. CT
highly sensitive
can assess function - hot and cold spots

Question 20

list disadvantages of NM

Answer 20

poor resolution - so are often superimposed over other imaging
poor specificity
high radiation dose - much higher than CT

Question 21

What radioisotopes can be used in NM?

Answer 21

Technetium (99m) - can be taken up by tissues in body (bone, thyroid, salivary gland)

18-FDG - taken up by metabolically active tissues

Question 22

PET - often superimposed by? typically used for? what radioisotope used?

Answer 22

CT
cancer diagnosis when unknown primary disease
19-FDG

Question 23

what is SPECT used for in dentistry? when is this condition indicated by scan?

Answer 23

condylar hyperplasia
inc uptake suggests hyperplasia