Intro to Diagnostic Imaging

Question 1

How will objects appear on X-rays?

Answer 1

-Dense objects will be radio-opaque (white)
-Non-dense objects will be radio-lucent (black/transparent)

Question 2

What is the order of tissue/material from darkest to whitest on an X-ray?

Answer 2

-Air
-Fat
-Water
-Muscle
-Bone
-Barium
-Lead

Question 3

Why is diagnostic imaging important?

Answer 3

-To localize an anatomic problem
-To identify the tissue involved
-To identify the nature of the tissue damage
-To direct treatment

Question 4

What are the different types of imaging?

Answer 4

-X-ray
-CT
-MRI
-Ultrasound
-Nuclear imaging

Question 5

How does X-ray work?

Answer 5

-A form of electromagnetic radiation, ionizing
-Made by accelerated electrons hitting a tungsten target
-Quality of image depends on kVolts, mA, and exposure time
-Depends on differential absorption by different tissues

Question 6

What is required for an X-ray?

Answer 6

A minimum of two views is required, perpendicular to one another

Question 7

What is used to screen the thoracic cavity?

Answer 7

X-ray is a highly valuable tool to screen the thoracic cavity (ex: can see pneumonia on X-ray)

Question 8

What are advantages of X-rays?

Answer 8

-Quick
-Inexpensive
-Ideal for bony changes

Question 9

What are disadvantages of X-rays?

Answer 9

-Does not show soft tissue changes
-Radiation exposure (small)

Question 10

What is Computerized (axial) Tomography (CT)?

Answer 10

-A moving x-ray
-Provides detailed planar images by progressive visual “slices”

Question 11

What are the advantages of CT?

Answer 11

-Cross sectional images
-Can enhance contrast
-Better sensitivity than plain film x-ray
-OK with metal
-Fast

Question 12

What are the disadvantages of CT?

Answer 12

-High radiation exposure
-Less sensitive than MRI

Question 13

What is magnetic resonance imaging (MRI)?

Answer 13

-Applies a powerful magnetic field to the patient
-Detects the rate of magnetization and demagnetization
-Produces “slice” images, can be in any plane

Question 14

What are the advantages of MRI?

Answer 14

-Grey scale does not apply, aka any structure can be highlighted
-No radiation exposure involved
-Can image through bone
-High sensitivity to slight tissue differences
-Can image in several planes

Question 15

What are the disadvantages of MRI?

Answer 15

-Cost
-Time lying still
-Limited tube size
-Can’t use with metal
-Can be too sensitive/not specific
-Not good for bone/calcified tissue

Question 16

What is ultrasound?

Answer 16

-Sends in ~ 35MHz range US signals
-Picks up (receiver) and examines timing and amplitude of the reflections for echo, examines frequency change for doppler
-Produces a 2D image in real time, can be moving

Question 17

What are the advantages of ultrasound?

Answer 17

-Biologically harmless
-Records and displays motion
-Required no contrast
-Portable
-Distinguishes solid from fluid

Question 18

What are the disadvantages of ultrasound?

Answer 18

-Does not penetrate bone well
-Does not go through air/gas
-Skill dependent

Question 19

What does ultrasound image well?

Answer 19

-Fetus
-Children
-Abdominal organs (gallstones, kidneys, pelvic organs/masses)
-Aorta (aortic aneurysms)
-Blood flow (with doppler)

Question 20

What is a bone scan (Skeletal scintigraphy)?

Answer 20

-Used to help diagnose problems with bones
-A tool of nuclear medicine
-A physiologic study-looking at problems with bone metabolism and how injured or broken bone is healing
-A small amount of radioactive drug injected into the bloodstream

Question 21

What are bone scans used for?

Answer 21

-Metastatic disease
-Arthritis
-Stress fractures
-Osteomyelitis
-Loosening of implants
-Multiple trauma

Question 22

How do bone scans work?

Answer 22

-Patient is given a rapidly decaying radioisotope into their veins
-Once the radiation is in the body, it can take 2-4 hours depending on what is being examined, the radioactive substance gravitates to areas of bone damage
-Once the radiation has settled a camera is used to image the bones, the dark spots on the image is the area of damage

Question 23

What is nuclear imaging?

Answer 23

A non-invasive procedure that used injected radioactive material and a PET scanner, CT scan, or MRI

Question 24

What does nuclear imaging image well?

Answer 24

-Thyroid masses (w/ radio labeled iodine)
-Bone metastases (18 fluoro deoxyglucose)
-Lung circulation and ventilation (xenon)
-Cancer
-GI diseas
-Endocrine diseases