MEDRADSC 2AA3 - Exam

How are ultrasound transducers named?

using the frequencies of sound waves sent out

What happens if frequency is too high?

poor penetration

What happens if frequency is too low?

poor resolution

ultrasound is accomplished using:

pulse echo technique

echo technique can also be known as…

echo location

do intrinsic or extrinsic factors have a greater effect on echo strength of an image?

intrinsic

T/F: Power doppler shows blood flow direction

false

spectral doppler

illustrates blood flow velocity over time as a graph

liver tissue is ____

homogenous `

red in elastography means tissue is _____

stiff

the mri machine is referred to as a _____ and a ____ in CT

bore; gantry

faraday cage

blocks outside electromagnetic influences

what is the magnetic field outside the bore known as?

fringe field

how do implanted devices affect images in MRI?

cause large distortion - susceptibility artifact

gradient field can cause ______ and _____

peripheral nerve stimulation; heating

typical B0 strength

1.5-3T

primary magnetic field in MRI

B0

what is required for a magnetic field to be produced in MRI?

odd number of protons and neutrons for a slight moving charge that inducts a MF

spin up is a _____ energy state and spin down is a ____ energy state

lower; higher

spin ____ is more natural state

up

stronger the magnet, ____ the discrepancy between ____

larger; spin up and down populations

spin up is ____ to the magnet and spin down is ____

parallel; antiparallel

how does a stronger B0 affect proton alignment?

more protons in spin up

thermal energy level effect on proton alignment

higher energy = more likely to overcome B0 and spin down

factors affecting proton alignment

thermal energy and Bo strength

when rf pulse is applied, most low energy protons move to…

midway with transverse vector

primary radionuclide production mechanism

nuclear reactor

limitation to cyclotron based production of radionuclides

short half life so the production must occur near hospital

F-18 FDG half life

110 minutes

F-18 FDG must be produced in a ….

cyclotron

half life of Tc-99

6 hours long enough for transportation but short enough for patient safety

gamma camera set up

rectilinear or planar

gamma camera creates what kind of image??

AP and 2D

SPECT function

rotating gamma camera to create 3D image

PET scan design

detectors around gantry to capture emitted photons from patients

PET can be combined with:

MRI and CT

SPECT can be combined with:

CT

when Is forearm used for DXA

obese patient or bilateral hip replacement

T score in DXA scan

likeliness of sustaining a fracture

z score in DXA scan

relative score to healthy individual of same demographic

why is fasting necessary for PET scans

so cells will uptake glucose

why shouldn’t patients exercise before a PET scan?

muscles will have increased glucose uptake

does talking affect a PET scan and how?

yes; tongue is a muscle

PET scan done _____ after injection

60-90 minutes

F-18 NaF is advantageous because…

uptake by osteolytic and osteoblastic lesions

therapeutic ratio

balancing tumour and healthy cell kill

advancements in treatment is due to ____

imaging

why is CT simulation the standard in rad therapy treatment planning?

geometric accuracy for precise beam arrangements and electron density for accurate dose

What cancers are m/c and account for over 50% of new cancers in Canada every year?

breast, lymphoma, colorectal, lung, prostate

sound

energy that moves as a wave

sound wave has cyclical changes leading to…

increases and decreases in pressure and density

compressions

areas of high pressure and density

rarefactions

areas of low pressure and density

wave classification

medium requirement for propagation, how they propagate

mechanical wave

requires medium for propagation

electromagnetic wave

exists in medium or vacuum

transverse wave

particle movement perpendicular to wave direction

longitudinal wave

particle movement parallel to wave direction

what’s another name for transverse waves?

shear waves

what type of wave is sound?

longitudinal mechanical pressure wave

Acoustic variables

mechanical changes in medium due to sound propagation

4 acoustic variables

pressure, density, particle motion, temperature

mechanical energy

physical interaction between sound and medium resulting in energy transfer and thus change in the wave

density

concentration of matter in a medium

pressure

cyclical changes in force unit/area

infrasound frequency

0-20 Hz

audible frequency

20 Hz - 20kHz

ultrasound frequency

> 20 kHz

Diagnostic frequency

2-20 MHz

What do numbers in transducer names represent

frequency sent out

high frequency results in…

poor penetration but greater resolution

low frequency results in…

poor resolution but greater penetration

propagation velocity

distance sound can travel per unit time

propogation velocity is also known as…

propagation speed

propagation velocity depends on ____ and NOT dependent on _____

physical properties of the medium; frequency of sound wave

denser the material, _____ the propagation velocity

higher

c =

square root (B/p)

what happens as bulk modulus increases?

density and propagation velocity increases

wavelength =

c/f

amplitude of sound

volume

power of sound

energy transfer over time

intensity of sound

energy transfer over an area

sound is measured in…

volts

why is sound energy measured in volts?

transducer crystals convert electrical energy to sound then back to electrical energy

amplitude of sound determines…

voltage

ultrasound uses _____ technique

pulse-echo

pulse echo may be referred to as:

echo location

pulse-echo technique

pulses of sound sent into tissues and echoes returning from tissue provide anatomic info and form basis of images

scan line

display of reflected echo per pulse of sound from transducer

real time imaging

numerous frames displayed per second

Distance =

velocity x time

intrinsic factors affecting brightness of pixel

acoustic impedance, reflection type, absorption

extrinsic factors affecting brightness of pixel

instrumentation, dynamic range, monitor changes

grey scale image

produced by various echo strength

b-mode imaging

grey scale imaging

Why does brightness vary?

differences in acoustic impedences, reflection, absorption

how many shades of grey in ultrasound images?

typically 256

strong echos are ____ and low echos are _____

white; black

A mode

graph of echo amplitudes - no image

analog to digital converter converts echo into…

binary code