Imaging: CT scan

Question 1

How do CT scans produce cross-sectional images?

Answer 1

x-ray attenuation

Question 2

How are CT images read?

Answer 2

transverse images read from bottom looking up

Question 3

Advantages of CT?

Answer 3

• eliminates superimposition of tissues
• good resolution
• sensitive and specific for fracture
• all views obtained in one patient position

Question 4

Disadvantages of CT?

Answer 4

• more radiation exposure (100-1000x)
• may have reaction to contrast agents if used
• soft tissue not well visualized
• high cost

Question 5

How do magnetic resonance imaging produce images?

Answer 5

pulses of radio frequency and strong external magnet to create electromagnetic field

Question 6

Advantages of MRI?

Answer 6

good for soft tissue
no radiation exposure
see in all planes
great contrast

Question 7

Disadvantages of MRI?

Answer 7

loss of bony detail
long, expensive
can’t do if metal implants or exposure (pacemaker, welders)

Question 8

T1 images are also called

Answer 8

longitudinal magnetization

Question 9

T1 images are based on how long it takes protons to _______ back to resting state after RF pulse

Answer 9

relax

Question 10

T2 images are also called

Answer 10

transverse magnetization

Question 11

T2 images are based on how long resonating protons remain ______ following a RF pulse

Answer 11

in phase

Question 12

T1 are ____ repetition and echo times

Answer 12

short

Question 13

T2 are ____ repetition and echo times

Answer 13

long

Question 14

Fat, marrow of bone of T1 images are what?

Answer 14

bright

Question 15

areas of high water concentration in T1 images are what?

Answer 15

dark

Question 16

Fat, calcification of T2 images are what?

Answer 16

dark

Question 17

areas of high water content in T2 images are what?

Answer 17

bright

Question 18

T2 images are ideal for what injury?

Answer 18

acute trauma

Question 19

Functional MRI is based on what?

Answer 19

increased blood flow in the brain

Question 20

How does a DEXA scan work?

Answer 20

high and low energy x-ray are directed at bone. the difference in absorption b/t beams used to find bone density

Question 21

Nuclear medicine examples are

Answer 21

SPECT, PET, (with CT), Radionuclide scintigraphy (Bone scan)

Question 22

what is the radioactive tracer for radionuclide scintigraphy?

Answer 22

methylene

scan 2-3 hours after injection

Question 23

Radionuclide Scintigraphy good choice for what?

Answer 23

detecting stress fractures and follow up of metastatic bone disease

Question 24

Advantages of radionuclide scintigraphy?

Answer 24

highly sensitive
fast
not $$

Question 25

Disadvantages of radionuclide scintigraphy?

Answer 25

easily influenced by osteoblastic activity

poor specificity