Basic Principles

Question 1

What are the differing imaging modalities?

Answer 1

• X-ray
• Computed Tomography
• Magnetic Resonance
• Ultrasound
• Nuclear Medicine

Question 2

X-ray Overview?

Answer 2

• Uses single pulse of ionizing radiation (low radiation dose)
• Film is white to start
• Film turns dark when hit with ionizing radiation
• Two dimensional view of 3 dimensional object
• Structures can overlap and hide underlying structures
• Important to obtain more than one view

Question 3

How does density affect X-rays?

Answer 3

• Dense material blocks radiation and film brightens
• Less dense material blocks fewer rays and the film darkens
• The color depends on density of structures

Question 4

What are the five basic radiographic densities?

Answer 4

• Air (darkest)
• Fat (less dark)
• Fluid/blood/soft tissue (gray)
• Bone (white)
• Metal/contrast (most white)

Question 5

What are the different X-ray views?

Answer 5

• Anteroposterior (AP “front to back”)
• Lateral (LAT “sideview”)
• Oblique (OBL)
• Posteroanterior (PA “back to front”)

Question 6

Overview of AP view?

Answer 6

• Used if Pt is unable to stand or sit for PA
• Lower quality than PA
• Back is placed next to film
• Hear is magnified
• Borders are fuzzier

Question 7

Overview of Lateral?

Answer 7

• Usually taken in conjunction with AP view
• Allows view behind the heart (mediastinum)
• Provides 3 dimensional image

Question 8

Overview of OBL?

Answer 8

• Used mostly on limbs

Question 9

Overview of PA?

Answer 9

• Object that is closer to film has sharper borders
• Chest is placed next to film (places most important structures, heart and great vessels, closer to film)
• Heart size is minimally magnified
• Borders are sharp

Question 10

Overview of CT?

Answer 10

• Emits radiation
• Shows color in black, white, and gray
• Uses multiple “pulses” of ionizing radiation (high dose)
• X-ray tube and detector spin rapidly around patient
• Image produced is a “slice” (appear on screen as slice)

Question 11

What is Helical or spiral CT?

Answer 11

• X-ray tube continuously circles the Pt while the Pt cradle moves continuously through X-ray tube housing

Question 12

What are the CT views?

Answer 12

• Sagittal or Median
• Coronal
• Axial/Transverse/Cross-sectional

Question 13

Overview of MRI?

Answer 13

• Uses electromagnetism and radiofrequency properties
• No exposure to ionizing radiation
• Views are same as CT

Question 14

What is MRI good for?

Answer 14

• Soft Tissue (nerves, muscles, connective tissues, brain, joints)

Question 15

What is MRI bad for?

Answer 15

• People who cannot hold still

- Pt with ferrous metal

Question 16

Ultrasound Overview?

Answer 16

• Uses sound waves (similar to SONAR)
• No radiation (can’t go very deep)
• Operator dependent
• Image produced focused segment of object
• Rapid and portable

Question 17

What is U/S good for?

Answer 17

• Determining fluid vs solids
• Abdominopelvic imaging (gallbladder, kidneys, uterus, testis)
• Assessing blood flow (Doppler)

Question 18

What is U/S bad for?

Answer 18

• Things under bones (chest)
• Air filled spaces
• Deep structures

Question 19

Nuclear Medicine Overview

Answer 19

• Radioactive agent given IV
• Agent participates in physiological processes while emitting radiation
• Radiation is used to create an image

Question 20

What is the typical use of Nuclear Medicine?

Answer 20

• Typical used to detect stress fractures before being visible on X-ray

Question 21

What is Nuclear Medicine good for?

Answer 21

Detecting normal or abnormal physiological processes

Question 22

What is Nuclear Medicine bad for?

Answer 22

Showing less anatomic detail

Question 23

U/S views?

Answer 23

• Longitudinal (same as sagittal)

- Transverse (same as axial)