advantages and disadvantages of common imaging modalities

Question 1

Different Imaging Modalities

Answer 1

(1) X-ray
(2) Computed Tomography (CT)
(3) Magnetic Resonance (MR)
(4) Ultrasound (U/S)
(5) Nuclear Medicine

Question 2

What modality
Uses a single pulse of ionizing radiation
-Radiation dose is low but some views have more radiation than others.

Answer 2

X-ray

Question 3

X-ray
Good for
Bad for:

Answer 3

Good for: bones and airspaces
Bad for: soft tissue and overlapping structures

Question 4

X-ray film is _____ to start with
Turns ______ when hit with ionizing radiation (x-ray)

Answer 4

1. White
2. Dark

Question 5

Five basic radiographic densities
Air ______
Fat ______
Fluid/blood/soft tissue ______
Bone ______
Metal/contrast _____

Answer 5

(a) Air (Darkest)
(b) Fat (Less Dark)
(c) Fluid/Blood/Soft Tissue (Gray)
(d) Bone (White)
(e) Metal/Contrast (Most White)

Question 6

______ are two- dimensional representation of a three-dimensional object.
-Therefore, structures can overlap and hide underlying structures depending on the
viewpoint.
- It is important to obtain more than one view

Answer 6

X-rays

Question 7

What Xray view?
Used if patient is unable to stand or sit for a PA view
Lower quality than PA view
Back is placed next to the film
Heart is magnified and borders are fuzzier

Answer 7

Anteroposterior (AP “front to back”)

Question 8

What Xray view?
Usually taken in conjunction with a PA view
Allows viewing of structures behind the heart (mediastinum) and provides three dimensional
image.

Answer 8

Lateral (LAT “side view”)

Question 9

What xray image?
at an angle used mostly on limbs

Answer 9

Oblique (OBL)

Question 10

What xray image?
used in Chest X-ray “mostly”
1) Object that is closer to the film has sharper borders
2) Chest is placed next to the film thereby placing most of the important structures,
such as heart and great vessels, closer to the film.
3) Heart size is minimally magnified and borders are sharp

Answer 10

Posteroanterior (PA “back to front”)

Question 11

What modality?
Similar to x-ray:
(a) Emits radiation
(b) Shows color in black, white, and gray depending on density
(2) Uses multiple pulses (“shots”) of ionizing radiation
(a) Radiation dose is high

Answer 11

Computed Tomography (CT)

Question 12

What modality
Uses electromagnetism and radio frequency properties.
(a) No exposure to ionizing radiation, but time consuming

Answer 12

Magnetic resonance (MR)

Question 13

Magnetic resonance (MR)
Good for: ______________
Bad for: __________________

Answer 13

Good for: Soft tissue (nerves, muscles, connective tissue, brain, joints).
Bad for: People who cannot hold still or have ferrous metal in the body.

Question 14

What modality?
Uses sound waves (similar to SONAR)
(a) No radiation, but can’t go very deep
(b) Operator dependent
(c) Image produced is a focused segment of the object
(d) Rapid and portable

Answer 14

Ultrasound (U/S)

Question 15

Ultrasound (U/S)
Good For: ____________
Bad for: _______________

Answer 15

Good for: Determining fluid vs solids, abdominopelvic imaging (gallbladder, kidneys,
uterus, testis), assessing blood flow (Doppler).
Bad for: Things under bones (chest) and air filled chambers, deep things

Question 16

views of what modality
Longitudinal (same as sagittal)
Transverse (same as axial)

Answer 16

U/S

Question 17

What Modality
(1) Radioactive agent is given intravenously
(2) The agent participates in physiologic processes while emitting radiation
(3) The radiation is detected and is used to create an image showing the distribution of the
agent within the body.
(4) A typical use is to detect stress fractures before being visible on x-ray

Answer 17

Nuclear Medicine

Question 18

What modality?
Good for: Detecting normal or abnormal physiologic processes
Bad for: Showing less anatomic detail

Answer 18

Nuclear Medicine

Question 19

Views for what modalities
(a) Sagittal or Median
(b) Coronal
(c) Axial or Transverse or Cross-sectional

Answer 19

Ct, mri

Question 20

Computed Tomography (CT)
Good for: _________
Bad for: ________

Answer 20

Good for: Bone, airspaces, some soft tissue and overlapping structures (especially abdomen and in trauma).

Bad for: Some soft tissues (nerves, muscles, connective tissue), patients with retained metallic objects (causes artifacts).