Final Flashcards
TD
total diseased
TND
total not diseased
FPV
false positive
FNV
false negative
TP
total positives
TN
total negatives
total positives
true positives + false positives
total negatives
true negatives + false negatives
sensitivity
true (+) test/ Have disease
TPV/TD
how do we catch sensitivity?
lesion detection
specificity
true (-) test/Don’t have disease
TNV/TND
positive predictive value
true positives/all positives
TPV/TP
negative predictive value
true negatives/all negatives
TNV/TN
accuracy
true positives + true negatives/total tests
(TPV+TNV) / TOT
looking at benefits and risks, what do medical practices use?
benefits over the risks
what affects intensity?
power and area
what are factors of bioeffects?
- intensity
- exposure time
longer exposure times=
increases the risk of damage
for bioeffect safety, what must be kept inversely proportional?
intesity and exposure time
AIUM statement
“No independently confirmed adverse effects caused by exposure from present diagnostic ultrasound instruments have been reported in human patients in the absence of contrast agents.”
intensity changes dependant on what?
location in the beam
where is the intensity the stongest?
center and focus
where is the intensity the weakest?
periphery
what are variations of intensity?
spatial factors
temporal factors
what are the spatial factors?
spatial peak
spatial average
spatial peak
intensity at the center
spatial average
average of intensities across the beam
temportal intesity changes based on what?
moments in time
temporal factors
temporal peak
temporal average
pulse average
temporal peak
intensity at peak times
temporal average
- average intesity across entire pulse period
- includes dead zone
pulse average
- average intensity across entire pulse duration
- does NOT include dead zone
which spatial factor is higher?
spatial peak
list temporal factors from higest to lowest
- temporal peak
- pusle average
- temporal average
what is the highest out of all factors?
spatial peak
what are spatial and temporal factors used in?
research to assess the level of intensity that can cause bioeffects
organizations have set standards that ultrasound providers are to adhere to, what are they?
FDA
AIUM
acoustic output statements
maxiumum prescribes intensities
acoustic output statements AIUM
“No adverse effects have been observed for an unfocused beam having a SPTA below 100mW/cm2, and focused beam SPTA below 1 W/cm2”
acoustic output statements FDA
ISPTA = 720 mW/cm2 (upper limit)
what are the differrent intesities?
2D ultrasound-weakest
M-mode
colour doppler
PW spectral-strongest
what arre the types of bioeffects?
thermal mechanical (NON-thermal)
what does ultrasound produce?
heat
why would ultrasound heat up tissue?
attenuation
- absorption
- reflection and scattering
what does frequency not contribute to?
more intensity coming out of the probe
higher frequency sound ________ more
attenuates
more of the sound energy will be absorbed within the tissue=
more heat
acoustic output intensity
- pulser will decide intensity of outgoing signal
- can be adjusted using power dial on machine
thermal index
measure of how much the particular sound is heating up the tissue
what is thermal index most commonly associated with?
SPTA
What are the different TI standards depending on the type of tissue being assessed?
TIS-soft tissue
TIC-cranium
TIB-bone
AIUM standard soft tissue=
TIS<2
AIUM standard bone=
TIB<1.5
where is there a higher attenuation?
in bone
what adjustments must a sonographer make to maintain ALARA?
- acoutic power
- exposure time
what kind of damage can US do to cells?
sister chromatid exchange
what kind of damage can US do to plants?
- chromosomal changes
- growth rate reduction
- cell death
what kind of damage can US do to animals?
- fetal weight reduction
- postpartum mortality
- fetal tissue lesions
- hind limb paralysis
- wound repair enhancement
- tumour regression
what type of wave is sound?
a pressure wave
-particles are being pushed againsti other particles
mechanical effects
- radiation forces
- caviation
_________ will deform and disrupt objects
shear stresses
what can cause flow in a liquid?
shear stresses
how many types of caviation are there?
2 types
what is cavitation?
production and modification/behaviour of bubbles in a liquid
stable cavitation
oscillating bubbles (bigger and smaller)
- produce waves
- shear forces on nearby cells and organelles
transient cavitation
oscillating bubbles (bigger and smaller)
- “POP”!
- shock waves
- local high temperature changes
- light emission
what is particilarly dangerous in ‘gas bodies’?
mechanical effects
what are the characterstics of mechanical effects?
- already contain bubbles
- these micro-explosions hemorrhage lung/intestinal tissue
AIUM statement -mechanical effects
“No independently confirmed adverse effects caused by exposure from present diagnostic ultrasound instruments have been reported in human patients in the absence of contrast agents.”
how do contrast studies work?
we introduce microbubbles into the patient and ultrasound them
when does the risk for mechanical bioeffects become higher?
use of contrast study
when is contratt only done?
when benefits outweight the risk
AIUM-mechanical index
<1.9 (0.4-1.9)
mechanical effects formula
MI=Pr / (f)1/2
what is proportional to MI?
peak rarefactional pressure
what is inversely proportional to MI?
frequency
lower frequencies have higher_______
MI
tissue type factor
gas containing tissues will have a higher risk of cavitation
what kind of damage does MI have on humans with contrast?
premature ventricular contractions
when was X-ray fisrt seen?
1895
what is X-ray?
radiation which travels through the air in waves/particles. Some of this radiation can pass through objects, particularly soft-tissues
radiopaque
some objects are more dense (bones/calcium deposits/metal) and absorb the radiation not allowing it to pass through
radiopaque objects will show up differently than _________ soft tissues, which will allow the radiation through
radiolucent
X-ray black
fluid/air
X-ray Dark Grey
bowel
X-ray White
bone
X-ray very white
metal
X-ray radiopaque
blocks the x-rays
X-ray radiolucent
let the x-rays through
what can be correlated from X-ray with ultrasound?
- stones
- constipation (bowel obstruction)
- MSK
- surgical structures
what is the X-ray potential for harm?
- accumulation of radiation can result in cell damage that could lead to cancerous conditions
- high levels of radiation exposure can cause radiation burns
how is X-rays used in radiation therapy?
x-rays are used to kill malignant cancer cells
what are the factors for developing cancer with X-ray?
- exposure time
- age
- Gender (women are more likely)
what is fluoroscopy?
X-ray “movie” a constant beam of X-ray passing through the patient
what can you assess with fluoroscopy?
- skeletal
- digestive
- urinary
- respiratory
- reproductive systems
how does Computed Tomography (CT) work?
uses special x-ray equipment to obtain cross-sectional pictures of the body
what does CT display?
detailed images of organs, bones, other tissues
what are the uses of CT?
- lesion detection and measurment
- location of lesions and tumors
- can guide biopsy or radiation therapy or surgery
- size determination can be used to see of treament is responding
- contrast agents can be used as well, similar to US to highlight vasculature/lesions
- can be administered orally, intravenously or enema
which radiation exposure is higher risk? CT or X-ray?
CT
what is the benefit vs risk for CT vs X-ray
eternal struggle
what is the risk of CT?
very rare causes can cause allergic reactions
what are the symtoms to CT allergic reaction?
- mild itching
- Hives
- shortness of breath
- swelling of throat, face or area of contact
what is a newer form of CT?
spiral (or helical) CT scan
what is spiral CT?
X-ray machine rotates continuously around the body, following a spiral path to male cross sectional pictures of the body
what is better about spiral CT?
- better resolution than CT-better lesion detection
- faster than CT
what is Endoscopy -Colonoscopy/ Esophagogastroduodenoscopy(EGD)?
non-surgical evaluation of digestive tract
what does Endoscopy -Colonoscopy/ Esophagogastroduodenoscopy(EGD) involve?
introduction of a small camera into the digestive tract and examination of the walls
what can endoscopy detect?
abnormalities and inflammations of the walls
what is virtual endoscopy?
virtual endoscopy is a new technique that uses spiral CT/MRI
what are endoscopic views constructed from?
3D visualizations taken from the CT/MRI
CT colonography or virtual colonoscopy, is under study as a screening technique for __________
colon cancer
what is mammography?
form of X-ray used to assess breast tissue for cancer
what can mammography catch?
cancer in early stages, often before its palpable
does mammography contain radiation?
minimal and considered to be very safe
screening mammogram
- patient has no symtoms
- recommmended annually after age 40
diagnostic mammogram
- patient has a new lump, breast pain or changes to breast tissue
- this test is commonly done in conjunction with a breast ultrasound
with age, bone mineral density ______
decreases (commonly associated with osteoporosis)
what is a bone (mineral) density exam?
measures the amount of calcium within your bones
where are the most common areas of reduced BMD?
spine
hip
forearm
higher BMD=
less risk for breaking/fracturing a bone
is bone density the same as a bone scan?
no
-this is a nuclear medicine exam that involves injection
what is MRI?
creates a very strong magnetic field that aligns the atoms in the body, which are then exposed to RF waves
how does a MRI work?
This causes the protons of the atoms to produce a weak signal – “magnetic resonance” – that is picked up by the receiver in the MRI and processed in the computer
what are the pros of MRI?
- Completely painless
- Very high resolution imaging (often the gold standard)
what are the cons of MRI?
- Metal implants, pacemakers cannot go near the magnet
- Very, very expensive
- Claustrophobia
what is better seen on CT over MRI?
brain bleeding (hemorrhage)
when is MRI the gold standard?
- tendon
- ligaments
- spinal cord
- brain infarcts
what is angiogrpahy?
Use of contrast agents within the vasculature to assess patent/occluded vessels
what can angiography be used with?
X-ray (fluoroscopy)
CT
MRI
ECG (electrocardiogram) aka EKG
assessing the electrical activity of the heart
stress EKG
ECG monitoring during a stress activity
holtor monitoring
involves 24-48 hour ECG
radiotracer
Small amounts of radioactive material are placed within the body
how is radiotracer inserted into the body?
Radiotracer is either injested or inhaled, and is expected to accumulate in a particular organ (usually within an hour)
what happens once the radiotracer is in the organ?
they give off gamma rays which are picked up by special cameras
nuclear medicine is ______ tests
functional
hot spots
accumulation of radiotracer
cold spots
lack thereof
positron emission tomography is a form of what?
nuclear medicine
what does Positron emission tomography assess?
metabolic activity
what studies are PET scanning useful in?
heart
lungs
brain
Combined PET/CT
Combination of the two; mapping functionality with the anatomical image (like Duplex Sonography)
where is Combined PET/CT usually seen?
in psychological studies, showing brain activity in particular regions of the brain
combined PET/CT and cancer
Often cancerous tissue is more active than normal tissue (or may be more blood hungry), so often shows stronger on PET/CT
