02 (10.14) Advanced Imaging

Question 1

____ is the retrograde injection of iodinated contrast media into the ductal system of a salivary gland

Answer 1

Sialography

Question 2

alternating areas of fusiform dilation and stricturing of the primary duct (“string of sausages”) is referred to as…

Answer 2

Sialodochitis

Question 3

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

Answer 3

• are not
• Ethiodol
• foreign body granulomata

Question 4

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

Answer 4

• Sinografin

- are

Question 5

when the parotid glands are destroyed (like in Sjorgren’s syndrome) the appearance of _____ and ____ _____ in a pattern described as “________” on sialography

Answer 5

• punctate
• globular pseudosialectasis
• “a fruit-laden, branchless tree”

Question 6

what does CT not visualize well?

Answer 6

-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

Question 7

what does CT stand for?

Answer 7

Computed Tomography

Question 8

What does CT visualize?

Answer 8

• 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

Question 9

What are the selection criteria for CT?

Answer 9

• 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

Question 10

what are the different types of contrast agents used in sialography?

Answer 10

-fat-soluble and water-soluble

Question 11

what is the ductal phase in sialography?

Answer 11

just when the ducts are filled with the contrast agents, the acinar phase is when the acini are filled

Question 12

how much more sensitive are CT scans than plain films?

Answer 12

100 times

Question 13

what is the orientation of the standard CT image?

Answer 13

-axial cross-sectional view, oriented as if looking at the patient from the floor upward, then the computer can reconstruct it into other views

Question 14

what are the units of measurement in CT?

Answer 14

Hounsfield units (HU), according to density

Question 15

what is the Hounsfield unit based off of?

Answer 15

water, HU=0

Question 16

if a tissue has a density greater than water, how will the HU number change?

Answer 16

it will have a + CT number

less dense than water results in a -CT number

Question 17

what is a scout Image?

Answer 17

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

Question 18

which systems do not use ionizing radiation?

Answer 18

Ultrasound and MRI

Question 19

What is MRI best for visualizing?

Answer 19

-soft tissues (esp compared to CT)

Question 20

what does the signal strength depend on in an MRI?

Answer 20

Hydrogen content of the tissue (cortical bone has a very low Hyrdrogen content and fat has a high content)

Question 21

on a T1-weighted image (MRI), what is bright and dark?

Answer 21

fat is bright (hyperintense) and cystic fluid is dark (hypointense)

Question 22

on T2-weighted images…

Answer 22

-fat is dark and fluid is bright

Question 23

when is an MRI contraindicated?

Answer 23

presence of implanted ferromagnetic devices (pacemakers, aneurysm clips, prosthetic joints or heart valves, hearing aids etc)

Question 24

how long does it take to get an MRI?

Answer 24

exam may take from 15 minutes to 1.5 hours

Question 25

which system has the “head coil?”

Answer 25

MRI

Question 26

what is the selection criteria for an MRI?

Answer 26

 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

Question 27

MRI is NOT useful in examining what?

Answer 27

bony lesions bc of the lack of signal generated by bone

Question 28

nuclear medicine

Answer 28

is useless