02 (10.14) Advanced Imaging Flashcards
____ is the retrograde injection of iodinated contrast media into the ductal system of a salivary gland
Sialography
alternating areas of fusiform dilation and stricturing of the primary duct (“string of sausages”) is referred to as…
Sialodochitis
in Sialography, fat-soluble contrast agents (___) ___ diluted by saliva or absorbed across the glandular mucosa, but in cases of ductal rupture and contrast extravasation, ___ develop
- are not
- Ethiodol
- foreign body granulomata
In sialography, water-soluble contrast agents (____) ___ diluted by saliva and pass rapidly across glandular mucosa resulting in poor visualization of peripheral ducts, but do not incite an inflammatory reaction if extravasated
- Sinografin
- are
when the parotid glands are destroyed (like in Sjorgren’s syndrome) the appearance of _____ and ____ _____ in a pattern described as “________” on sialography
- punctate
- globular pseudosialectasis
- “a fruit-laden, branchless tree”
what does CT not visualize well?
-CT does not generally add to the soft tissue characterization of a lesion, although it may help in assessing the presence of soft tissue extension outside of bone or the degree of intramedullary extension within bone
what does CT stand for?
Computed Tomography
What does CT visualize?
- primary lesions and asses the presence/absence of lymph node metastases with considerable certainty
- Follow up scans enable an evaluation of the effects of treatment and allow comparison among treatments
What are the selection criteria for CT?
- extensive lesions in the mandible or maxilla (esp if sinus is involved)
- suspected malignancy
- soft tissue mass of a salivary gland
- osseous lesions affecting the TMJ
- developmental disorders affecting the mandibulomaxillofacial complex
- assessment of maxillofacial trauma
- pre-surgical implant planning, altho the radiation dose is significant
what are the different types of contrast agents used in sialography?
-fat-soluble and water-soluble
what is the ductal phase in sialography?
just when the ducts are filled with the contrast agents, the acinar phase is when the acini are filled
how much more sensitive are CT scans than plain films?
100 times
what is the orientation of the standard CT image?
-axial cross-sectional view, oriented as if looking at the patient from the floor upward, then the computer can reconstruct it into other views
what are the units of measurement in CT?
Hounsfield units (HU), according to density
what is the Hounsfield unit based off of?
water, HU=0
if a tissue has a density greater than water, how will the HU number change?
it will have a + CT number
less dense than water results in a -CT number
what is a scout Image?
displays the number and position of all slices to be obtained in the imaging study
- this facilitates spatial localization of the final slices
- also called a scannogram
which systems do not use ionizing radiation?
Ultrasound and MRI
What is MRI best for visualizing?
-soft tissues (esp compared to CT)
what does the signal strength depend on in an MRI?
Hydrogen content of the tissue (cortical bone has a very low Hyrdrogen content and fat has a high content)
on a T1-weighted image (MRI), what is bright and dark?
fat is bright (hyperintense) and cystic fluid is dark (hypointense)
on T2-weighted images…
-fat is dark and fluid is bright
when is an MRI contraindicated?
presence of implanted ferromagnetic devices (pacemakers, aneurysm clips, prosthetic joints or heart valves, hearing aids etc)
how long does it take to get an MRI?
exam may take from 15 minutes to 1.5 hours
which system has the “head coil?”
MRI
what is the selection criteria for an MRI?
Evaluation of suspected internal
derangement of the TMJ
Salivary gland disease
Assessment of soft tissue invasion by malignant disease
Evaluation of intracranial extension of inflammatory or neoplastic processes
Assessment of perineural spread of malignancy
Assessment of suspected brain tumors
Neurologic involvement with HIV
Vastly superior for identifying MS plaques and other white matter disorders
Revealing the extent and mechanism of stroke
MRI is NOT useful in examining what?
bony lesions bc of the lack of signal generated by bone
nuclear medicine
is useless
