Introduction to Medical Imaging

Question 1

How do X-Rays work?

Answer 1

Photons from tungsten target pass through body to expose the recording plate

Question 2

X-Ray Rule:

Greater the absorption of photons by tissues, the …

Answer 2

Whiter the density will appear

Question 3

On an x ray __ will appear white

Answer 3

Bones

Question 4

On an x-ray ___ will have intermediate density

Answer 4

Soft tissues and water

Question 5

The greater thickness of bone or soft tissue on an X-ray, the ___ density

Answer 5

Whiter

Question 6

What is an AP Plain film radiograph?

What is closer to recording plate?

Answer 6

AP: Anteroposterior
goes from front to back

-back is closer to plate
So heart is farther away = enlarged

Question 7

What is a PA Plain film radiograph?

What is closer to the recording plate?

Answer 7

PA: Posteroanterior
Goes from back to front

-front is closer to recording plate so heart is closer = normal size heart

Question 8

If you want to keep an organ the right size, where would you put the plate?

Answer 8

Closer to the plate

I.e. Use AP view for kidneys

Question 9

What is fluoroscopy?

Answer 9

Real time x-ray imaging
Shows movement of structure in real time
-has c arm so the whole apparatus can be rotated to give 3D info

Question 10

When would you use fluoroscopy?

Answer 10

Is used for barium contrast studies of GI, variety of Angiographic, catheter and tube placement, fracture repair adn apparatus placement in ortho surgery

Question 11

How many frames are taken per second for a peripheral vascular study using fluoroscopy?

Answer 11

2 to 3 frames/second

Question 12

How many frames are taken per second for a coronary artery studies?

Answer 12

15-30 frames per second

Question 13

What is Digital Subtraction Angiography (DSA)?

Answer 13

Form of fluoroscopy (real time x rays)
Tissues and structures not of interest = digitally subtracted
Allows for better imaging of vessels

Question 14

What is DSA used for?

Answer 14

For diagnostics like balloon angioplasty, stent placement, guiding catheter placement

Question 15

What is the downside of DSA?

Answer 15

Invasive bc artery must be entered percutaneously

(Unlike CTA and MRA which are relatively noninvasive procedures that only require IV catheter in arm vein for contrast injection)

Question 16

What is an upside to DSA?

Answer 16

Quicker than an MR study

Question 17

How does CT work? (Basic)

Answer 17

Patient slides thru a donut, x rays pass thru patient ina helical fashion and are detected on opposite side of tube
Algorithm reconstructs in 3D image

Grayscale image can be manipulated on monitor as well

Question 18

What are the advantages and disadvantages to CT?

Answer 18

Quick, motion not a problem, gray scale can be manipulated, resolution excellent, widely available and cheaper than MRI

Disadvantages: uses ionizing radiation, must evaluate renal function if contrast used, allergy to iodine contrast

Question 19

What is the hounsfield scale?

What is middle gray? Scale for middle gray?

What is window width

Answer 19

Scale for CT

Window level; -1000 to +3095

Range of gray so-called mapped onto housnfield scale

Question 20

The narrower the width the ___ the contrast

Answer 20

Higher

Question 21

If the CT is ABOVE the window width image will appear ____

Answer 21

White

Question 22

If the CT is BELOW the window width, the image will appear ___

Answer 22

Black

Question 23

you would use a narrow window width for __

Answer 23

Soft tissue

Question 24

You would use a wide window width for __

Answer 24

Bone

Question 25

What is the window level and width for Lungs?

Answer 25

``` Level = -550 Width = 1600 ```

Question 26

What is the window level and width for soft tissue?

Answer 26

``` Level = 70 Width = 450 ```

Question 27

What is the window level and width for bone?

Answer 27

``` level = 570 Width = 3077 ```

Question 28

If you wanted more contrast and not as much detail on a CT, what would you do to the width?

Answer 28

Make it narrower will give more contrast and not as much detail

Question 29

Does a MRI use Ionizing radiation?

Answer 29

No

Question 30

How doe an MRI work?

Answer 30

Big magnet that atoms will align with It will hit tissues with radio frequency so they all go out of alignment Then relaxation time occurs where they all eat back into alignment Depending on density of tissues, return to realignment will occur at a different rate Different rate of return = different gray scale in image

Question 31

What is the difference between T1 and T2 weighted MRIs? | How will fluid appear in each?

Answer 31

T1= longitudinal relaxation time = fluid is dark T2 = transverse relaxation time = fluid is light

Question 32

What are the advantages and disadvantages to MR?

Answer 32

Advantages: no ionizing radiation, better soft tissue contrast than CT, extremely versatile Disadvantages: longer time for sequencing, more expensive, images cannot be manipulated on viewing screen, narrow matching (claustrophobia), no metal in body, no gadolinium contrast with pregnant women, increased risk for NSF in those with renal dysfunction, noisy

Question 33

What will give more depth in an angiography study? CT or MR?

Answer 33

CT

Question 34

What is nuclear medicine?

Answer 34

Radioactive molecules attached to other compounds to form radiopharmaceuticals. Administered orally or intravenously Designed to bind or be uptakes by specific cells in specific organs (esp. highly metabolic cells, i.e. CANCER) Detector used to look at hot spots

Question 35

What is one application of nuclear medicine?

Answer 35

look at breast cancer

Question 36

What is an ultrasound?

Answer 36

A non invasive imaging technique using sound waves that echo back after being reflected from tissue interfaces within the body

Question 37

When would you use a high frequency on an Ultrasound?

Answer 37

to visualize structures near the surface I.e. neck vessels, thyroid gland, breasts, and testes

Question 38

When would you use a low frequency on an Ultrasound?

Answer 38

Will have greater penetrating power, can image deeper structures in abdomen and pelvis

Question 39

How does air show up on an ultrasound?

Answer 39

Black

Question 40

What are the benefits to using ultrasound?

Answer 40

Low risk, portable, good for emergency situations, cheap

Question 41

What is barium sulfate used to visualize as a contrast agent?

Answer 41

Hollow organs I.e. for upper Gi study, colon study

Question 42

What is iodine compounds used to visualize as a contrast agent?

Answer 42

Vessels (angiography) I.e. for celiac arteriogram, hysterosalpingogram

Question 43

What kinds of contrast agents does MR use?

Answer 43

``` Intravenous gadolinium oral agents (juice, H2O) ```