Imaging

Question 1

T1 images

Answer 1

for MRI; bright on fat and contrast; dark on water/fluid/edema and bone

Question 2

T2 images

Answer 2

for MRI; bright on fat and water/fluid/edema; dark on bone

Question 3

Benefits of CT

Answer 3

remove super imposition; detail cross-sectional images; ability to reformat anatomy

Question 4

CT stands for

Answer 4

computerized tomography

Question 5

Houndsfield units

Answer 5

Scale for quantify radiodensity. Calculated based on linear attenuation coefficient.

Question 6

What’s window?

Answer 6

Contrast control. Narrow window means increase contrast; wide window means increase gray scale

Question 7

What’s level?

Answer 7

Brightness control. High (bone) vs. medium (soft tissue) vs. low (lung)

Question 8

How does MRI form?

Answer 8

MRI relies on differences in chemical properties of tissue affecting H protons subjected to a magnetic field. RF pulses, rotation of proton axis, generate image.

Question 9

What is T1 good for?

Answer 9

Anatomical detail and for use with CONTRAST agents

Question 10

What is T2 and FLAIR food for?

Answer 10

Identifying edema, and other fluids

Question 11

What is proton density good for?

Answer 11

Differentiating grey and white matter

Question 12

What is gradient echo, T2* good for?

Answer 12

Sensitive for detection of hemorrhage degradation products; confirm hemorrhage

Question 13

What is contrast use for?

Answer 13

Extracellular fluid space

Question 14

FLAIR

Answer 14

pure water appears black; “dirty” water appears white; good for detect edema.

Question 15

X-ray production

Answer 15

Negative cathod delivers electrons to positive anode; hit Tungsten atom creating high energy for X-ray

Question 16

Bremsstrahlung

Answer 16

Electrons breaking; they come close to the nucleus, then deceleration emitting energy (X-ray); produce spectrum of X-ray energies

Question 17

Characteristic X-ray

Answer 17

Incident electron knock out electron out of its shell, then replacement of missing electron create energy; produce discrete X-ray energies

Question 18

How does X-ray interact with a patient?

Answer 18

1) Goes straight, no interaction; 2) Compton scatter; 3) Photoelectric absorption

Question 19

Photoelectric absorption

Answer 19

Complete absorption of X-ray, no scatter, energy is close to the electron binding energy; produce white spot. Ejected inner shell electrons absorbed in patient.

Question 20

Compton scatter

Answer 20

Forward scatter hit detector, decrease radiographic quality; produce blurry. Ejected outer shell electrons absorbed in patient with scatter.

Question 21

What is mAs?

Answer 21

number of X-ray generated/second = radiation exposure to the patient.

Question 22

What is kVp?

Answer 22

Controls the energy or imaging characteristics of the X-ray beam generated during exposure

Question 23

Increase mAs effect?

Answer 23

increase exposure, increase motion

Question 24

Decrease mAs effect?

Answer 24

decrease exposure, decrease motion

Question 25

Increase kVp effect?

Answer 25

increase exposure, decrease contrast

Question 26

Decrease kVp effect?

Answer 26

decrease exposure, increase contrast

Question 27

kVp and mAs relationship

Answer 27

+15% kVp = x2 mAs

Question 28

If you need more contrast in image but maintain exposure, what would you do?

Answer 28

decrease kVp by 15% and double mAs

Question 29

Orthogonal view

Answer 29

At least 2 views; provide information on shape and location

Question 30

6 Roentgens signs

Answer 30

size, shape, location, number, margination, opacity

Question 31

Radiographic opacities

Answer 31

air, fat, water (soft tissue), bone, metal

Question 32

Radiopacity

Answer 32

unexposed areas of the radiographs (white)

Question 33

Radiolucency

Answer 33

exposed area of radiograph (black)

Question 34

Silhouette

Answer 34

Structures of equal density IN CONTACT, borders indistinct

Question 35

Summation

Answer 35

Structures not in contact, can have the same density, distinct

Question 36

Wavelength and frequency relationship?

Answer 36

High frequency transducer = better resolution = poor penetration Low frequency transducer = better depth penetration = resolution decreased

Question 37

Large vs. small difference in acoustic impedence

Answer 37

Large difference = more reflection Smaller difference = allow sound to pass between tissues

Question 38

Orders of abdominal organ echogenicity

Answer 38

My Cat Likes Sunny Places = Medulla (renal) < Cortex (renal) < Liver < Spleen < Prostate/Pelvis (renal) = hypo to hyper

Question 39

Most hyper // Most hypo

Answer 39

Mineral, gas, fat // water, fluid, edema

Question 40

Artifacts: reverberation

Answer 40

Sound bouncing back and forth between 2 strong reflectors (have discrete band) - Useful! - AKA comet tail, ringdown, regular arrangement of echos

Question 41

Artifacts: acoustic shadowing / dirty

Answer 41

- Useful! - Soft tissue - gas interface. 99% beam reflected and multiple reverberation artifacts occurs.

Question 42

Artifacts: acoustic shadowing / clean

Answer 42

- Useful! - Soft tissue - mineral/bone interface. It tells you 2 structures involved have large difference in acoustic impedance. Large portion of sound emitted from transducer is absorbed.

Question 43

Artifacts: acoustic enhancement

Answer 43

- Useful! - Increase echogenicity distal to an anechoic structure. - Allow us to see deeper than we normally would.

Question 44

Artifacts: edge shadowing

Answer 44

- Useless - Degrade image quality - Occurs when US beam strikes a curve surface.

Question 45

Artifacts: mirror image artifact

Answer 45

- Useless - Only confuse the actual location of the mirrored structure. - Occurs across a curved strong reflector at a gas/soft tissue interface like diaphragm/lung interface.