Midterm 2 - CT, MRI, Scintigraphy, Ultrasonography

Question 1

CT was invented by who (2) in what year?

Answer 1

Hounsfield and McLeod

1973

Question 2

Modern scanners have multiple detector arrays that are stationary around what degree of the patient?

Answer 2

360 degrees: tube rotates around patient

Question 3

The CT tube rotates around patient in the ___ plane

Answer 3

Axial

Question 4

Helical CT scanners create a ______ acquisition of data

Answer 4

Spiral

Question 5

Multi-slice scanners create data in thin slices, referred to as

Answer 5

Volumetric acquisition

This means 1) there are no gaps in acquisition of data and 2) when data is reformatted, the quality is as good as axial data.

Question 6

What are small squares of CT data that make up the image we see on axial orientation scans?

Answer 6

Pixels — picture elements

Question 7

What are comprised of pixel element PLUS depth of box?

Answer 7

Voxels — volume elements

Question 8

What kind of scanner can produce isotopic voxel?

Answer 8

Helical CT

Question 9

What is a voxel that has the same depth, width and height?

Answer 9

Isotopic voxel

In other words, the resolution of the data is the same no matter which plane you choose to see — the voxel and pixel elements have the same dimensions.

Question 10

Reformatting allows views of data from:

Answer 10

Sagittal, coronal or 3-D

Question 11

What are used to describe the shade of grey that a tissue presents on the scale on CT?

Answer 11

Hounsfield units (HU)

Question 12

HU scale ranges from

Answer 12

-1000 to 3072 HU

Question 13

Only ___ (#) HU can be assigned per pixel/voxel

Answer 13

1

Question 14

HU translate to grey scale. +1000 is going to be [lighter/darker] -1000 [lighter/darker]

Answer 14

\+1000 = lighter e.g. bone
-1000 = darker e.g. air

Question 15

What is the process of emphasizing certain ranges in the HU scale? E.g. if we want to see more bone e.g. higher value end of the HU scale OR if we want to see more soft tissue

Answer 15

Windowing

Soft tissue windows allow better viewing of the low HU end of the scale: soft tissues.

Bone windows emphasize the higher value end of HU scale: cortical and medullary bone.

Question 16

What is -1000 HU?

Answer 16

Air

Question 17

What is 0 HU?

Answer 17

Water

Question 18

What is +400 HU?

Answer 18

Cancellous bone

Question 19

What is +700 to +2000 HU

Answer 19

Cortical bone

Question 20

What is +2500 to +3000 HU

Answer 20

Metal

Question 21

When the CT detector cannot distinguish between different tissues because they are in the same pixel, its called

Answer 21

Partial Volume Effect

Machine has to decide if it will make the Pixel black or white.

Question 22

What technology uses a magnetic field?

Answer 22

MRI

Question 23

In MRI, echo time (TE) and repetition time (TR) allow what?

Answer 23

Creation of sequences known as T1 and T2

Question 24

In MRI, what is brightest for T1-weighted image? What is not bright?

Answer 24

Brightest: Fat
Not brightest: Water and fluid

Note: opposite is true for T2

Question 25

In MRI, what the high signals/low signals in T2-weighted images

Answer 25

Bright = water & fluid Not bright = fat Basically, the less free protons, the lower signals Compact tendon = low signal

Question 26

A T-2 weighted sequence can be converted to a _____ sequence

Answer 26

FLAIR, Fluid Attenuated Inversion Recovery

Question 27

What kind of image suppresses fat signal in MRI to make it appear black so that you can see tissue and fluid better?

Answer 27

STIR (short tau inversion recovery)

Question 28

Overall, T1 vs T2 vs fluid sensitive studies (FLAIR, STIR) (what are they good for)

Answer 28

T1 = evaluate anatomy T2 = find pathology FLAIR, STIR good for pathology and edematous/watery tissues

Question 29

Batteries e.g. cardiac pacemakers, insulin or infusion pumps; metals e.g. shrapnel from accidents or some high metallic tattoos; patients who can’t stay still because of seizures... these are contraindications for what procedure?

Answer 29

MRI

Question 30

Looking at an MRI, the fat is bright. What weight of MRI is it?

Answer 30

T1

Question 31

Looking at an MRI, water is bright. What weight of MRI is it?

Answer 31

T2 weighted

Question 32

Between CT and MRI which one has less risk as far as radiation exposure?

Answer 32

MRI

Question 33

How do CT and MRI refer to the tissue?

Answer 33

CT - density | MRI - signal intensity

Question 34

CT is good at ___ while MRI is good at ___

Answer 34

CT - detail | MRI - tissue differentiation

Question 35

what is faster: CT or MRI

Answer 35

CT

Question 36

What procedure can be done on patients with metal or batteries: CT or MRI

Answer 36

CT

Question 37

Is CT or MRI better for clinically unstable patients/

Answer 37

CT

Question 38

Which one requires no reformatting: CT or MRI

Answer 38

MRI because it directly acquires multiplanar images

Question 39

What type of imaging uses radioisotopes chelates to substances that are inert but processed by various tissues of the body?

Answer 39

Radionuclide Imaging AKA Scintigraphy Technetium 99m is most common and used in bone scans

Question 40

What does scintigraphy identify in organs and bones?

Answer 40

Physiological activity

Question 41

Scintigraphy characterizes areas by

Answer 41

High or low metabolic activity

Question 42

3 levels of scintigraphy scan comprehensiveness include:

Answer 42

Whole body = bony problems Limited/pin-hole = fractures 3-phase = flow, blood pool, delayed images used for infections

Question 43

Hot spot is an area of increased

Answer 43

Physiological activity

Question 44

Cold spot is an area lacking

Answer 44

Vascular supply

Question 45

20 m of Technetium-99m has an effective dose of 3 mSv in the whole body. What is the half life WITH body’s help in excretion by urinary system?

Answer 45

4.8 hour effective Includes isotope decay + help from body

Question 46

20 m of Technetium-99m has an effective dose of 3 mSv in the whole body. What is the half life WITHOUT body’s help in excretion by urinary system?

Answer 46

6 hour Raw rate of decay, no help from body

Question 47

20 m of Technetium-99m has an effective dose of 3 mSv in the whole body. What is the biological half-life??

Answer 47

24-hour

Question 48

What imaging modality uses sound waves to create images?

Answer 48

Ultrasonography

Question 49

When the sound waves bounce off internal structures, they create sound waves that bounce back which are called

Answer 49

Echoes They come back to the source and are converted into images

Question 50

How are images created in an ultrasonography scan?

Answer 50

Changes in tissue density cause sound waves to “bounce back” to the ultrasound transducer at differing rates which creates different images

Question 51

What is the wand device called in ultrasonography?

Answer 51

Transducer

Question 52

Ultrasound wave frequencies range

Answer 52

2-20 million Hz

Question 53

What poisons ultrasound image?

Answer 53

Air | Metal

Question 54

Strengths of Ultrasonography:

Answer 54

``` Internal organ evaluation Obstetrics Arteries, veins Joints MSK Cyst vs solid Cost effective ```