Intro to Imaging

Question 1

Describe the basic principles of conventional radiography

Answer 1

heated cathode -> electrons beam b/c thermal energy -> tilted anode -> photons deflected to produce image
Electromagnetic waves transilluminate patient, behaves like shadows
Best image = beam perpendicular to object as close as possible to film

Question 2

Advantages of conventional radiography

Answer 2

inexpensive & accessible, good view of bones (fractures/joints), cardiopulmonary assessment

Question 3

Disadvantages of conventional radiography

Answer 3

ionizing radiation, avoid during pregnancy, limited soft tissue view & overlapping structures

Question 4

Describe the basic principles of CT

Answer 4

x-ray beam rotates around patient, data reconstructed by computer
water = 0
air = -1000 (black)
bone = 1000 (white)

Question 5

Advantages of CT

Answer 5

short scan time, more soft tissue detail

Question 6

Disadvantages of CT

Answer 6

ionizing radiation

Question 7

Describe the basic principles of MRI

Answer 7

imaging of protons (H+) manipulated by magnetic field
p+ align with magnet turning on -> p+ absorb wave energy and turn to RF pulse -> p+ return to magnet when RF pulse ends (intensity & duration of return = digitized tissue type)

Question 8

Advantages to MRI

Answer 8

highly manipulative, great tissue detail (brain), no known damaging effects

Question 9

Disadvantages to MRI

Answer 9

long and loud scan, enclosed (claustrophobia), no metal implants/pacemakers

Question 10

Difference between T1 and T2 weighted MRI

Answer 10

T1: water = dark (good for soft tissue)
T2: water = bright (good for contrast)

Question 11

Describe the basic principles of ultrasound

Answer 11

high frequency sound waves = echograms
image = attenuation (energy loss) + reflection (energy coming back)

Question 12

Advantages to ultrasound

Answer 12

non-ionizing waves (safe), real-time, portable & cheaper

Question 13

Disadvantages to ultrasound

Answer 13

operator dependence (training), poor image of air & bone, static images difficult to interpret

Question 14

Compare/contrast appearance of air in CT and MRI images

Answer 14

CT: black
T1-MRI: dark
T2-MRI: dark

Question 15

Compare/contrast appearance of fat in CT and MRI images

Answer 15

CT: black
T1-MRI: very bright
T2-MRI: bright

Question 16

Compare/contrast appearance of water/CSF in CT and MRI images

Answer 16

CT: grey-black
T1-MRI: dark
T2-MRI: bright

Question 17

Compare/contrast appearance of muscle in CT and MRI images

Answer 17

CT: grey
T1-MRI: dark
T2-MRI: dark

Question 18

Compare/contrast appearance of bone marrow in CT and MRI images

Answer 18

CT: gray
T1-MRI: bright
T2-MRI: intermediate

Question 19

Compare/contrast appearance of bone cortex in CT and MRI images

Answer 19

CT: white
T1-MRI: dark
T2-MRI: dark

Question 20

Define radiographic progection

Answer 20

based on direction of beam
posteroanterior, anteroposterior, lateral

Question 21

Define radiographic view

Answer 21

how image is viewed, always anterior (patient facing you)

Question 22

Describe the anatomic planes of section and explain the radiologic conventions for viewing sectional images

Answer 22

Transverse/axial: (inferior view) as if standing at supine patient’s feet
Coronal: as if patient facing you
Sagittal: standing at patient’s left side (can change to right)

Question 23

Describe how contrast media are employed to make tubular structures more visible in radiographic and CT images

Answer 23

increased density iodinated drugs enhance absorption = tissue appear whiter (angiogram, venogram, lymphangiogram)
GI tract: metal compound (barium) defines mucosa; double contrast = air + barium (more detailed, given via oral, tube, or enema)

Question 24

Describe how contrast media are employed to make tubular structures more visible in MRI images.

Answer 24

magnetically active compounds useful - gadolinium/iron oxide
(iodination = useless b/c MRI not reliant on tissue density)