Radiology Class 10

how do US work?

use of sound waves or acoustical energy in medicine to analyze and characterize tissues

what are the required components for US?

a high frequency sound wave

the ability to receive a reflected sound wave or echo

the ability to convert this “echo” into an image

how are US images produced?

sound waves are produced by a probe that contains a transducer(s)

short bursts of acoustical energy (sound) then are sent by the transducers

probe usually placed on the skin- requires transducer gel

produces real time ages

what are types of internal US?

transvaginal, transrectal, transesophageal

how do sound waves for US travel?

travel through the tissues at different speeds

some waves will travel all the way through the tissue or transmitted and some will be reflected back again

what is speed of US waves determined by?

density of the tissue

what is acoustical impedance?

how much sound is transmitted through vs how much is reflected back

what do large differences for acoustical impedance lead to?

more sound reflection

what do small differences for acoustical impedance lead to?

more sound transmission

how are US images produced?

sound waves entering fluid- most are transmitted through

sound waves entering gas or bone- most are reflected back

echoes that are reflected back are converted from sound to electrical pulses are then sent to a scanner

computer in the scanner determines the time it took for the echo to be received back

computer analyzes frequency of echo along with amplitude and produces image

what happens with echogenic or hyperchoic tissue on US?

many echoes are reflected back and look white or bright

what happens with sonolucent or hypochogenic or anechoic tissue on US?

minimal or no echoes are reflected back and look black and dark

how is the plane produced with US?

by direction that the probe is being held in relation to the tissue being evaluated

what are the most common planes for US?

long axis= sagittal or longitudinal plane

perpendicular to the long axis= transverse plane

what is viewing orientation for US?

pts head to your left

pts feet to your right

anterior is up

posterior is down

what is the doppler effect?

used to determine if (usually fluid) such as blood is moving towards or away from the transducer and at what velocity

what does red color on duplex color US mean?

fluid is moving towards the transducer

what does blue color on duplex color US mean?

fluid is moving away from the transducer

what are types of US?

a-mode, b-mode, m-mode, doppler, duplex

when is a-mode US used?

in ophthalmology

when is b-mode US used? what does it look like?

most often used, images are tiny dots

what is m-mode US?

shows moving structures- blood flow or heart valves

what is doppler US?

accesses blood flow- vascular

what is duplex US used for?

vascular- red/blue/grey scale- accesses flow

what are advantages for US?

no radiation, no long term side effects, real time images, minimal or no discomfort, small and portable

what are disadvantages for US?

difficult to penetrate bone, gas filled structures- difficult to visualize structures, obese pts- difficult to visualize structures, requires operator skill

what are indications for ordering an US?

pregnancy, ovarian cysts, appendicitis, peripheral vascular disease, masses/renal abnormalities/fatty liver disease (alcoholics)

what is the #1 cause of intercranial/subarachnoid bleed?

trauma

how long do pts need to fast for US of gallbladder?

minimum of 6 hours

how thick is a normal GB on US?

3 mm or less

what is the transverse diameter of GB on US?

< 4 cm

what is the diameter of the common bile duct on US?

4 mm

what are sonographic findings in the acute cholecystitis?

impacted stone in cystic duct or GB neck

positive sonographic murphy’s sign

thickening of GB wall (>3mm)

distention of GB lumen (>4cm)

pericholecystic fluid collections (frequent)

hyperemic GB wall on color doppler (supportive test)

*combo of multiple signs make correct dx*