Final; Advanced Imaging Modalities

Question 1

This was invented in 1972 by Sir Godfrey Hounsfield and Dr. Allan Cormack sharing the Nobel Prize; it produced non-superimposed images for the first ime

Answer 1

CT; computed tomography

Question 2

What three things make CT superior to conventional radiographs

Answer 2

multiplanar and cross sectional images and 3D viewing
no superimposition of structures
many times higher sensitivity to subtle differences

Question 3

What is the principle of a CT scanner

Answer 3

internal structures of an object can be reconstructed from multiple projections of the object

Question 4

What are the three steps to image isolation of a CT scanner

Answer 4

x-ray tube is rotated around the patient
radiation transmitted through the patient is absorbed by a ring of detectors
absorbed radiation is converted to an image

Question 5

What are some current standards for the multi director CT

Answer 5

up to 64 slice scanner available
isotropic (clear, realistic) resolution
true 3D

Question 6

What are three limitations of fan beam CT in dentistry

Answer 6

expensive
substantial size; occupy large space
high radiation dose

Question 7

This was developed in the lat 1900’s using rotating gantry to which an x-ray source and detector are attached

Answer 7

cone beam computed tomography

Question 8

A cone-shaped x-ray beam is directed though the middle of the area os interest and onto what

Answer 8

an area x-ray detector (sensor) on the opposite side

Question 9

During the rotation os a cbct, multiple sequential planar projection images of what are acquired in a complete or sometimes partial arc

Answer 9

field of view (FOV)

Question 10

This type of field of view is approximately 5cm or less; dentoalveolar/TMJ

Answer 10

small; localized region

Question 11

This type of field of view is 5 to 7cm; maxilla/amndible

Answer 11

medium; single arch

Question 12

This type of field of view is 7-10cm; inferior concha to mandible

Answer 12

medium; interacrh

Question 13

This type of field of view is 10-15cm; nation to mandible

Answer 13

large; maxillofacial

Question 14

this type of field of view is greater tun 15cm; vertex of skull to inferior border of mandible

Answer 14

large; craniofacial

Question 15

What are some advantages to cbct in dental/maxillofacial imaging

Answer 15

1/4-1/5 cost of fan beam CT
significantly reduced patient exposure
segmentation

Question 16

What are some limitations and disadvantages to cbct

Answer 16

artifacts
image noise
poor soft tissue contrast

Question 17

What can cbct be used for in dental and maxillofacial applications

Answer 17

analysis of available bone for implant
impacted teeth assessment
bony and dental pathologic conditions
maxillofacial deformities
TMJ
evaluation of root canal system and nasopharyngeal airway

Question 18

This was discovered in 1946 and was used for diagnostic imaging in the 70s and 80s; introduced by Lauterbur and Mansfield; Damadian = father of modern

Answer 18

MRI and NMR

Question 19

What are the three steps to an MRI

Answer 19

magnetic field
radio-frequency pulse
relaxation

Question 20

This step of MRI; nuclei of many atoms, particularly hydrogen align with an external magnetic field (MRI machine)

Answer 20

magnetic field

Question 21

This step of MRI; generated by “transmitter coil” directed at patient cause some hydrogen atoms to absorb energy

Answer 21

radio-frequency pulse

Question 22

This step of MRI; when RF pulse is turned off, the stored energy is released from the body and detected as a signal in “receiver coil”

Answer 22

relaxation

Question 23

What is the signal in an MRI

Answer 23

essentially a map of hydrogen ion distribution in the body

Question 24

What are some relative brightness of tissued in the body in an MRI

Answer 24

white = fat, marrow, brain
grey = muscle, body fluid
black = TMJ disc, cortical bone, air

Question 25

What are three advantaged to an MRI

Answer 25

high soft tissue resolution
non-invasive
multiplanar imaging

Question 26

What are four disadvantages to an MRI

Answer 26

high cost
long imaging time
hazards with ferromagnetic metals (pace makers, etc.)
claustrophobic design

Question 27

What two applications is MRI useful for regarding dentistry

Answer 27

TMJ imaging

soft tissue disease such as neoplasia

Question 28

What two things does nuclear medicine show regarding target tissues

Answer 28

structure and function

Question 29

What are the two type of scans regarding nuclear medicine

Answer 29

scintigraphy scans

radionucleic scans

Question 30

Nuclear imaging shows what kind of imaging

Answer 30

functional

Question 31

What are the four steps of nuclear imaging

Answer 31

1. radioactive compounds such as Technetium are injected into the body
2. taken up by active tissues
3. radioactive agents pool in the target tissues and give off radioactivity
4. detected and imaged by external detectors

Question 32

What are some applications of nuclear imaging in the maxillofacial region

Answer 32

bone imaging

soft tissue imagine; salivary gland and lymph node

Question 33

This is similar to an x-ray beam needing a medium to propagate but is a wave that transmits energy

Answer 33

sound

Question 34

What are the four components to an ultrasound

Answer 34

transducer
CPU
display
printer

Question 35

What are the terms for high density structures and low density structures involving conventional radiographs

Answer 35

high; radiopaque

low; radiolucent

Question 36

What are the terms for high density structures and low density structures involving CT and CBCT

Answer 36

high; high-attenuation

low; low-attenuation

Question 37

What are the terms for high density structures and low density structures involving MRI

Answer 37

high; low-signal

low; high-signal

Question 38

What are the terms for high density structures and low density structures involving ultrasonography

Answer 38

high; hyperchoic

low; hypochoic