Lecture 1: Be a radiology tech in 2 years

Question 1

Bayesian Analysis plus clinical example

Answer 1

pretest probability affects post-test probability. If you have a strong clinical suspicion of fracture but XR is negative, request further testing.

Question 2

x ray attenuation: definition, function of what 3 variables?

Answer 2

X ray photons are “absorbed” by matter; amount of attenuation depends on: thickness, density of material (function of atomic number), and x ray beam kVp (peak kilovoltage/energy)

Question 3

Xray: does an object of high density appear darker or brighter?

Answer 3

Brighter

Question 4

X ray radiolucency: define

Answer 4

Allows x ray to pass through without absorption, penetrates most easily. Appears dark on XR

Question 5

X ray radiodensity: define

Answer 5

Absorbs x ray beams, appears bright on XR

Question 6

Name a highly radiolucent material

Answer 6

Air, fat

Question 7

Name a material class with high radiodensity

Answer 7

heavy metal

Question 8

Which is more radiolucent: bone or water?

Answer 8

water

Question 9

Which is more radiolucent: contrast or bone?

Answer 9

Bone

Question 10

Which is more radiodense: contrast or bone?

Answer 10

contrast

Question 11

Which is more radiodense: bone or fat?

Answer 11

bone

Question 12

PACS-define

Answer 12

Picture archiving and communication system-a medical imaging technology which provides economical storage of and convenient access to images from multiple modalities (source machine types).

Question 13

DICOM-define

Answer 13

Digital Imaging and Communications in Medicine (DICOM) is a standard for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol.

Question 14

RIS-define

Answer 14

A radiology information system (RIS) is a computerized database used by radiology departments to store, manipulate, and distribute patient radiological data and imagery. The system generally consists of patient tracking and scheduling, result reporting and image tracking capabilities.

Question 15

HIS-define

Answer 15

A hospital information system (HIS) is an element of health informatics that focuses mainly on the administrational needs of hospitals

Question 16

satisfaction of search

Answer 16

phenomenon in which the detection of one radiographic finding interferes with that of others; just because you found something doesn’t mean you found everything

Question 17

Hounsfield Units: what modality of imaging? Define.

Answer 17

Measure of attenuation of x ray beam in CT scan

Question 18

Hounsfield units: reference values for water and air

Answer 18

water=0, air=-1000

Question 19

Hounsfeld units: bone, blood, muscle, fat

Answer 19

bone=1000, blood=40, muscle=10-40, fat=-50–100

Question 20

CT scan: 4 types of artifact

Answer 20

Motion, metal, partial volume averaging, beam hardening artifact

Question 21

CT scan motion artifact: example

Answer 21

Cardiac motion (less of an issue with today’s fast multislice scanners)

Question 22

CT scan: Partial volume averaging artifact

Answer 22

More of an issue with thicker slices; a substance that occupies several voxels will get “averaged” and look larger and blurrier than it would if it was centered in 1 voxel

Question 23

CT scan: metal artifact

Answer 23

Radiodense structures limits evaluation of adjacent structures, can be minimized by increasing kvp

Question 24

CT scan: beam hardening artifact

Answer 24

Appears like an area of radiolucency (very dark area on scan), low energy portion of the spectrum filtered out,

Question 25

CT contrast

Answer 25

Makes structures more radiodense, therefore brighter and easier to discern on scan. Administered orally, rectally, or intravenously.

Question 26

CT contrast risks

Answer 26

allergic reactions (mild-rash; severe-HOTN, laryngeal swelling, CV collapse); renal failure (creatinine >1,5-1.8); contrast extravasation-contrast leaks out of a ruptured vessel

Question 27

CT scan for pts on dialysis

Answer 27

IV CT contrast OK but not MRI contrast

Question 28

CT scan advantages

Answer 28

fast, high resolution, can be reformatted after scan into 3D image in any plane (multiplanar reformatting MPR)

Question 29

CT scan disadvantages

Answer 29

artifact, risks of IV contrast, RADIATION

Question 30

ionizing radiation-define and risk

Answer 30

electromagnetic waves with the energy to knock an outer shell electron out of valence shell (creates an ion); can result in damage to DNA

Question 31

ALARA

Answer 31

as low as reasonably achievable

Question 32

radiation safety compromise

Answer 32

between dose and quality of image

Question 33

Inverse Square Law of Radiation and Distance

Answer 33

radiation dose decreases as a function of the distance from the source squared

Question 34

Linear No Threshold Model: assumption/stochastic effects

Answer 34

risk is directly proportional to the dose; sum of very small exposures have the same effect as one large exposure (e.g. 1 CT scan=100 XRs)

Question 35

T1 Pulse sequence: behavior in water, fat

Answer 35

Dark in water, bright fat

Question 36

T2 Pulse sequence: behavior in water, fat

Answer 36

Water and fat bright

Question 37

PD pulse sequence: behavior in water, fat

Answer 37

Water intermediate, fat bright

Question 38

STIR pulse sequence: behavior in water, fat

Answer 38

water bright, fat dark

Question 39

MRI contrast: substance used, how administered

Answer 39

Gandolinium, intravenous contrast, bright on imaging

Question 40

CT scan contrast:

Answer 40

Iodinated

Question 41

Risks of gandolinium

Answer 41

Nephrogenic systemic fibrosis: occurs in pts with severe kidney failure or dialysis; EGFR 30-60 borderline, Gandolinium absolutely contraindicated EGFR <30

Question 42

Gandolinium absolute contraindications

Answer 42

Pregnant women, pts with EGFR <30

Question 43

MRI advantages

Answer 43

no ionizing radiation, lots of soft tissue information, sensitive to contrast, 3D data, can get angiogramswithout contrast, gandolinium not as allergenic

Question 44

MRI disadvantages

Answer 44

long scan times, motion artifact, expensive, contraindications, claustrophobia

Question 45

MRI safety: zones

Answer 45

Magnet is always on at full strength; zones: 1-public accessible; 2-supervised access, screening by MRI staff; 3-restricted area, prescreened pts and staff only; 4-magnet room

Question 46

MRI dangers

Answer 46

missile effect, field interaction with medical devices, torque on implanted devices, acoustic noise, thermal effect from absorbed RF energy and induced currents, cryogens, gandolinium risks

Question 47

MRI contraindications

Answer 47

pacemaker, nonremoveable cochlear implant, metal in the eye, noncompatible aneurysm clip, implanted electronic devices-insulin pumps, neurostimulator units, etc

Question 48

MRI possible problems

Answer 48

metallic stents, previous projectile injury, penile implants, artificial limbs, tattoos, medication patches with metal, claustrophobia

Question 49

Ultrasound benefits

Answer 49

cheap, no ionizing radiation, real time, good soft tissue detail, no artifact from metal, vascular imaging, good for MR incompatible patients

Question 50

US drawbacks

Answer 50

limited penetration, operator dependent, doesn't penetrate air or metal

Question 51

US uses

Answer 51

rotator cuff integrity, baby hips, tendon integrity, joint effusions, guidance for interventional procedures