Alternative Imaging Modalities Flashcards
list 5 imaging modalities alternative to CBCT
CT
MRI
ultrasound
nucelar medicine
combo - PET-CT/PET-MRI
what structures does CT image?
soft tissue and bony anatomy - can be injected w/ IV contrast to inc contrast
CBCT - shape of beam, dose, soft tissue contrast, radiographic contrast, pt position
cone
lower dose
poor
not required
pt sits upright/standing
CT - shape of beam, dose, soft tissue contrast, radiographic contrast, pt position
fan
higher dose than CBCT
good - “windowing”
can be used if indicated
pt lying horizontal
what value is each CT voxel given? how does this compare to CBCT?
Houndsfield unit - CBCT has no value of density
what does the min/max HF num correspond to?
min = black
max = white
what does windowing do?
alters densities visualised in scan to optimally look at specific tissue
what imaging modality does not use ionising radiation?
MRI & ultrasound
how does cortical bone always look in MRI?
black - as little water content
what appears white in T1 & T2? what is each best used for?
T1 = fat appears white - best for anatomy
T2 = fat and fluid is white - best for pathology
what contrast agent is used w/ MRI?
gadolinium
list 4 contraindications of MRIs
pacemakers
orbital foreign bodies
artificial heart valves
surgical clips
what is MRI used to visualise in dentistry? (3)
TMJ
salivary glands
sinuses for malignancy
list advanatages of ultrasound
no ionising radiation
good for superficial structures
shows blood flow
list disadvantages of ultrasound
cannot penetrate bone
only superficial structures seen
what use is ultrasound in dentistry?
neck lumps - cysts, tumours, lymph nodes
salivary gland - sjorgens, neoplasia, sialadenitis, sialoliths
guidance for biopsy
vascular - carotid artery stenosis, vascular lesions
give 3 types of nuclear medicine - what do they stand for?
PET - positron emission tomography
SPECT - single photon emission CT
Scintigraphy
what is used to identify structures in nuclear medicine?
gamma camera
list 3 advantages of nuclear medicine
can be superimposed over other image i.e. CT
highly sensitive
can assess function - hot and cold spots
list disadvantages of NM
poor resolution - so are often superimposed over other imaging
poor specificity
high radiation dose - much higher than CT
What radioisotopes can be used in NM?
Technetium (99m) - can be taken up by tissues in body (bone, thyroid, salivary gland)
18-FDG - taken up by metabolically active tissues
PET - often superimposed by? typically used for? what radioisotope used?
CT
cancer diagnosis when unknown primary disease
19-FDG
what is SPECT used for in dentistry? when is this condition indicated by scan?
condylar hyperplasia
inc uptake suggests hyperplasia
