Exam 2

Question 0

What features can be assessed well in a posteroanterior projection?

Answer 0

-midline and posterior facial structures -BEST projection for orbits, frontal and ethmoid sinuses, and nasal fossa -lamina papyracea -Very good for evaluating symmetry

Question 1

What facial/cranial structures are visible in the Waters’ view (occipitomental)?

Answer 1

-Medial and lateral walls of maxillary sinuses -Medial walls of orbits -Zygomatic buttresses, orbital rims, nasal bones, anterior lamina papyracea, frontal sinuses, ethmoid air cells -Only projection that differentiates between ant. and post. Ethmoid air cells

Question 2

Which features can be evaluated with a lateral projection?

Answer 2

-Anterior and posterior walls of maxillary, frontal, sphenoid and ethmoid sinuses, pterygomaxillary buttress -BEST projection for evaluating air/fluid level of maxillary sinuses -ESSENTIAL to evaluate trauma/destructive lesions of sinuses -nasopharyngeal soft tissues, airway -Relation of sphenoid sinus to sella turcica

Question 3

For standard skull projections, the source to film distance is ______. For cephalometric projections, the source to film distance is ______.

Answer 3

36-40” 60” Also, a wedge filter is used to reduce unnecessary radiation exposure and yield better image of soft tissue for cephalometric analysis.

Question 4

What features can be evaluated in a submentovertex projection?

Answer 4

-base of the skull, position/orientation of the condyles, curvature of mandible, lateral wall of maxillary sinuses, pterygoid plates. -BEST way to evaluate fractures of zygomatic arch -ONLY image in which left and right sphenoid sinuses are distinguished.

Question 5

The Reverse-Towne’s projection can be used to evaluate…

Answer 5

-Subcondylar fractures of the mandible -petrous ridges, mastoid air cells, posterolateral wall of maxillary antrum

Question 6

Fat-soluble contrast agent used in sialography

Answer 6

Ethiodol

Question 7

Water-soluble contrast agent used in sialography

Answer 7

Sinografin

Question 8

Sialographic “fruit-laden, branch less tree” is characteristic of what?

Answer 8

Degeneration of parotid gland as seen in Sjögren’s Syndrome.

Question 9

What are the selection criteria for a CT scan?

Answer 9

-extensive mand. max. lesions, esp. involving sinuses -malignancy suspected -soft tissue mass of saliv. gland (sialography) -osseous lesions affecting TMJ -developmental disorders of mand./max. facial complex -maxillofacial trauma -pre-surgical implant planning

Question 10

What is the sensitivity of CT relative to plain film systems?

Answer 10

Approximately 100 times more sensitive

Question 11

What view does the standard CT image give?

Answer 11

-Axial cross-section

Question 12

What are the units of density used to classify density of tissues and other substances in CT scans?

Answer 12

Hounsfield units

Question 13

What are the names for the reference image that diagrams the spacial location of the final CT image slices?

Answer 13

-Scout image or scannogram

Question 14

MRI images _______ tissue better than CT.

Answer 14

Soft

Question 15

Signal strength for MRI depends on the ________ content of the tissue.

Answer 15

Hydrogen

Question 16

What concerns exist with radiation exposure due to MRI?

Answer 16

None. MRI does not use ionizing radiation.

Question 17

ABSOLUTE CONTRAINDICATION to MRI is the presence of:

Answer 17

ferromagnetic devices in the patient (hearing aids, pacemakers, IUD’s, aneurysm clips, prosthetic joints or heart valves)

Question 18

MRI selection criteria include:

Answer 18

-suspected derangement of TMJ -salivary gland disease -assessment of soft tissue invasion by malignancy -evaluate intracranial inflammation or neoplasia -perineural spread of malignancy -suspected brain tumors -Neurologic involvement in HIV. MS plaques and other white matter disorders. Extent and mechanism of stroke.

Question 19

Nuclear Medicine: How are scintigraphic images obtained?

Answer 19

-inject radiopharmaceutical -wait 2 hours for uptake by target tissue -measure gamma radiation w/ gamma camera

Question 20

Radiopharmaceutical half-life range

Answer 20

12-24 hours

Question 21

What is the radiopharmaceutical of choice for bone and salivary glands?

Answer 21

-Technetium

Question 22

What are the selection criteria for nuclear medicine?

Answer 22

-detect metastasis for cancer staging purposes -localize margins for surgical treatment planning -salivary gland disorders (especially mass lesions) -evaluate biological status/extent of osteomyelitis

Question 23

radiopharmaceuticals are not concentrated in any salivary gland neoplasms unless the neoplasm is a _________.

Answer 23

Warthin’s tumor

Question 24

What are selection criteria for Ultrasound?

Answer 24

-assessment of sinus disease -assessment of extracranial carotid vasculature -assessment of salivary gland or thyroid masses

Question 25

What are the differences between CBCT and MDCT?

Answer 25

-CBCT 3-5 times less -CBCT lighter and smaller -MDCT smaller pixels, better spatial resolution -CBCT Patient seated -CBCT No cooled room required -CBCT Only 1.3-22.7% of radiation compared to MDCT

Question 26

Medical applications of Cone Beam include:

Answer 26

-CTA -Interventional radiography -Radiotherapy guidance -Mammography

Question 27

Craniofacial Imaging Applications for Cone Beam include:

Answer 27

-Infection, trauma, developmental deformities -Pre-surgical implant analysis -Pre-surgical anatomic landmark assessment -TMJ evaluation -Sinus disease -Airway space assessment -Orthodontic considerations