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Miscellaneous
Anatomy
Diagnostic Imaging
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Megan M
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Diagnostic imaging
is tests performed to create images of the inside of the body to
diagnose
disease
radiography
x-ray
electromagnetic radiation
ionising radiation
- separates electrons from ions
how an
x-ray
works
produced in an x-ray tune by the rapid deceleration of fast moving
electrons
radiographic
image is created by the pattern of x-rays that reach the film
x-rays pass or absorb depending on the
density
of the structure
x-ray
colours
black =
radiolucent
white =
radiopaque
air
,
fat
,
soft tissue
,
bone
,
metal
x-rays
are 2D images of 3D structures
CT scans
rotating
x-ray machine
and detector
uses
x-rays
2D
cross sectional imaging
3D
reconstruction is possible
avoids superimposition that occurs on x-rays
CT scan colours
black = hypoattenuating
white = hyperattenuating
CT scans
advantages
detailed anatomical reconstructions
increasing availability
disadvantages
higher
dose of radiation
time consuming
Ultrasound
cross sectional imaging
high frequency sound waves
movement is in
real time
ultrasound
how it works
transducer
emits ultrasound waves
waves are reflected back to transducer when
boundary
between tissues is hit
returning echoes become electrical signals
computer
analyses data and displays it as an image
an
ultrasound
image
is a series of dots
the brightness is dependent on the
echo
strength
the position is dependent on the time it takes for each echo to reach the
transducer
ultrasound
allows
differentiation
of fluid from soft tissue, and can assess the internal
architecture
of soft tissue organs
this is less useful for a
bone
or
gas
as waves are immediately absorbed (bone) or immediately bounce back (gas)
ultrasound colours
black Anechoic, e.g.
fluid
white =
echogenic
, e.g. fat
hypoechoic and hyperechoic are used as comparative terms
ultrasound
Advantages
cheap
non-invasive
can see movement in real time
disadvantages
gas or bone hinders examination
expensive
MRI - magnetic resonance imaging
use of strong magnet
radiowaves are pulsed through patient
detection and analysis of returned signals provide information on tissue composition
MRI
colours
black =
hypointense
white =
hyperintense
MRI
advantages
2D
cross sectional images can be stacked
different
sequences
can be run based on tissue type
no
ionising
radiation
disadvantages
expensive
not widely available
lengthy process
nuclear scintigraphy
small amounts of radioactive
isotope
are administered to a patient
isotope collects in tissue of interest
emits
gamma rays
, detected by a gamma camera
safety issue,
ionising radiation