Intro To Medical Imaging

Question 1

Why do we order imaging tests?

Answer 1

. Help rule in or rule out a suspected diagnosis (diagnostic)
. Detect disease early at asymptomatic stage (screening)

Question 2

Main imaging modalities

Answer 2

. x-ray
. Computerized tomography (CT/ CAT)
. Ultrasound
. Magnetic resonance imaging (MRI)
. nuclear medicine. (Scans, bone scans)

Question 3

Who made a cathode ray tube and when?

Answer 3

Wilhelm Roentgen in 1895

Question 4

How did the cathode ray tube work?

Answer 4

Invisible rays from tube made fluorescent screen glow in darkened lab (x-rays)

Question 5

How do x-rays work?

Answer 5

An x-rays generator emits x-rays that go through an object and reach an x-ray detector creating a radiograph image

Question 6

How many tissue densities are demonstrated in x-rays?

Answer 6

5 (range from black to white)

Question 7

What does density determine in x-rays?

Answer 7

How many x-rays are detected by the x-ray film

Question 8

What is black on x-ray?

Answer 8

Air, not dense, doesn’t absorb many x-rays

Question 9

What does calcium look like in x-rays?

Answer 9

White, dense, absorbs lots of x-rays

Question 10

What does fat look like in x-rays?

Answer 10

Blackish gray, more dense than air, absorbs some x-rays

Question 11

What does soft tissue/fluid look like in x-rays?

Answer 11

Whitish gray, less dense than bone, absorbs some x-rays

Question 12

What does metal look like in x-rays?

Answer 12

Really white, really dense, absorbs the most x-rays

Question 13

Antero-posterior (AP) x-rays

Answer 13

. Taken from the front side of body

. Heart is enlarged

Question 14

Posterio-anterior (PA) x-rays

Answer 14

Taken from back side

. Heart looks normal

Question 15

Science behind CT

Answer 15

. Rotating x-ray beams and detectors
. Lots of computer processing
. Images made w/ thousands of pixels
. Each pixel is small piece of tissue with particular density
. Density assigned HU nu,bear
. Oral or IV (used for venous obstruction or bleed) used to enhance image

Question 16

CT numbers

Answer 16

. Hounsfield Units (HU)

. Range between -1000 and +1000

Question 17

air HU number

Answer 17

-1000 HU

Question 18

Bone HU number

Answer 18

400-600 HU

Question 19

Fat HU number

Answer 19

-100 to -40 HU

Question 20

Water HU number

Answer 20

0 HU

Question 21

Soft tissue HU number

Answer 21

20-100 HU

Question 22

What color are dense structures on CT and why?

Answer 22

White: absorb lots of x-rays, high CT number, inc. attenuation

Question 23

What color are less dense structure on CT and why?

Answer 23

Black: absorbs fewer x-rays, low CT nu,her, dec. attenuation

Question 24

Ultrasonography

Answer 24

. Sound waves used to evaluate tissue
. No radiation
. Safe for all patients
. Used to produce still images or videos

Question 25

How does ultrasonography work?

Answer 25

Pattern of sound waves bounce back/deflected by tissue or transmission through tissue creates image

Question 26

What kind of tissue appears white on ultrasound?

Answer 26

Tissue that reflected sound waves (echogenic)

Question 27

What kind of tissues are black in ultrasound?

Answer 27

Tissue that reflects few/no sound waves (sonolucent)

Question 28

Magnetic resonance imaging (MRI)

Answer 28

. Tissue imaged analyzing potential energy in body’s H atoms
. Radiation not used
. Safety issues from presence of strong magnetic field

Question 29

How does MRI work?

Answer 29

. H atoms manipulated by magnetic field with pulsed radio frequency waves
. Computer analyzes atom response to produce image

Question 30

Nuclear medicine

Answer 30

. Uses radioactive isotope which decay to non-radioactive state in short amt of time

Question 31

How does nuclear medicine work?

Answer 31

. Isotopes have affinity for certain tissues
. Isotope injected in patient via IV
. Amt/patient of isotope uptake measured via gamma camera and produces image

Question 32

When/why should you order an x-ray?

Answer 32

. Imaging chest, abdomen, bone

. Quick, easy, inexpensive

Question 33

Disadvantages to x-ray

Answer 33

. Uses radiation

. Limited detail about area being analyzed

Question 34

Diagnoses and symptoms that would call for chest x-ray

Answer 34

. Pneumonia, bronchitis, lung tumor, pneumothorax, pleural effusion, heart/aorta abnormalities
. Symptoms include cough, shortness of breath, chest pain

Question 35

When do you order abdominal x-ray?

Answer 35

Symptoms: abdominal pain, constipation, vomiting

. Diagnoses: small bowel obstruction, large bowel obstruction, fecal impact ion, perf. Bowel

Question 36

When do you order limb x-ray?

Answer 36

. Symptoms: pain in extremity/joint
. Diagnoses: fracture, arthritis, tumor
. Good at imaging bone, fair for cartilage and soft tissue

Question 37

When do you order CT of abdomen?

Answer 37

. Symptoms: abdominal pain, pain w/ urination, blood in urine or stool, fever, fatigue
. Diagnoses: diverticulitis, appendicitis, kidney stone, pyelonephritis
. When you need more info than x-ray can give you

Question 38

When to order ultrasound?

Answer 38

. Symptoms: abdominal pain, breast lump in woman under 40, abnormal uterine bleeding, swelling of 1 leg
. Diagnoses: gall stone, breast cyst, uterine cancer, blood clots
. Screening: abdominal aorta screening in men over 65 that smoked

Question 39

How can you tell if there is an aneurysm in aorta?

Answer 39

A pseudo wall is present in ultrasound inside of aorta

Question 40

when to order MRI of lumbar spine?

Answer 40

. Symptoms: low back pain, pain travels down 1 leg to foot, numbness/tingling of foot, low back pains w/ issues controlling bowel or bladder
. Diagnoses: degenerative disc disease, herniated disc w/ radiculopathy, cauda equina syndrome

Question 41

When to order nuclear medicine study

Answer 41

. Symptoms: chest pain (cardiac), hyperactive metabolism (thyroid), pain in spine/other bones
. Diagnoses: MI, thyroid gland dysfunction/.cancer, cancer in bones