Diagnostic Imaging

Question 1

True Positive

Answer 1

test detects something that is really there

Question 2

False Positive

Answer 2

test detects something that is not really there

Question 3

True Negative

Answer 3

test detects nothing, and nothing is there

Question 4

False Negative

Answer 4

test detects nothing, but there is something there

Question 5

Sensitivity

Answer 5

A test’s ability to identify a true positive (MRI)

snOUT - rules out

Question 6

Specificity

Answer 6

A test’s ability to identify a true negative (X-ray)

spIN - rules in

Question 7

Test that is very sensitive?

Answer 7

HIV blood tests

Question 8

Test that is very specific?

Answer 8

Home pregnancy tests

Question 9

X-rays (adv. vs. dis.)

Answer 9

A: Time and cost efficient, non-invasive, low risk, good for screening
D: may be normal when a pathology actually exists (false negative)

Question 10

Attenuation

Answer 10

Reduced strength or density of the x-ray beam as it passes through a medium

Question 11

Permeability

Answer 11

Ability of the x-ray beam to pass through substance to reach the film plate

Question 12

Radiodensity

Answer 12

X-ray absorption capacity based on substance’s composition, density and thickness

High = object is white

Question 13

What substance will all waves pass through?

Answer 13

Air

Question 14

What color does air appear on film?

Answer 14

Black

Question 15

What color does bone appear on film?

Answer 15

Gray-white

Question 16

What color does heavy metal appear on film?

Answer 16

White

Question 17

Radiographs (x-rays) are named for what?

Answer 17

the beam direction relative to the patient and patient’s position

Ex. AP (Anterioposterior) Image; x-ray tube is anterior to pt.

Question 18

ABCs of Radiology

Answer 18

Alignment, Bone Density, Cartilage, Soft Tissue

Question 19

CT (adv. vs. dis.)

Answer 19

A: Sensitive and specific for fracture; Rapid assessment of brain injury
D: Radiation exposure; Discriminates density, but limited in precise histologic differences; Small volumes of tissue image as a uniform shade of gray

Question 20

MRI (adv. vs. dis.)

Answer 20

A: Good sensitivity; Images soft tissue well; No radiation; Little distortion
D: Relatively low specificity; Expensive; Contraindicated if pt. has a ferrous metal implant or exposure

Question 21

MRI: T1 and T2 Images

Answer 21

T1 - Longitudinal

T2 - Transverse

Question 22

T1

Answer 22

How long it takes protons to relax back to resting state following an RF pulse

1ong bone will be bright

Question 23

T2

Answer 23

How long resonating protons remain “in phase” following a RF pulse

H2O is bright