Download Medical Imaging

MEDICAL IMAGING
RADIOLOGY
• Radiology is a medical specialty that uses
imaging techniques to both diagnose and
treat disease visualized within the human
body.
• Imaging technologies include x-rays,
ultrasound, computed tomography, nuclear
medicine, positron emission tomography and
magnetic resonance imaging, all of which are
used to diagnose or treat diseases.
Ultrasounds
• Use of sound above human
hearing range to image body
structures, including soft tissues
• Sounds waves are reflected
(echo) off of different density
tissues differently
X-Rays
• Oldest form of imaging
• Found by German physicist
Wilhelm Rontgen, 1895
• High-energy electromagnetic
waves that pass through soft
tissue (ex. muscle) but are
absorbed by dense tissue (ex.
bone)
• Can also be used to see soft tissues with the
help of stains (ex. bismuth)
Most popular use:
• Dental x-ray exposure can be minimal but
concern over cumulative impact?
Electromagnetic radiation
- Forms of energy, some on the visible spectrum
(light)
• Some can be damaging to our DNA, in particular highenergy high-frequency waves (above colour spectrum)
• X-rays is a type of ionising radiation
CAT Scans: computerized axial
tomography scan
• An X-ray machine rotates around the patient
taking hundreds of individual pictures form
many angles
• More sensitive than an X-ray alone
• Computer re-assembles the picture into a 3-D
image, allowing for organs to be viewed
section-by-section
A CT or CAT scan (computed tomography) is a much more sensitive imaging technique
than x-ray, allowing high definition not only of the bony structures, but of the soft
tissues. Clear images of organs such as the brain, muscles, joint structures, veins and
arteries, as well as anomalies like tumors and hemorrhages may be obtained with or
without the injection of contrasting dye.
MRI
• Magnetic Resonance Imaging
An imaging technology that uses magnetism,
radio waves adn a computer to produce
images of body structures.
The MRI scanner is a tube
surrounded by a giant
circular magent.
• The magnet creates a strong magnetic filed
that aligns the protons of hydrogen atoms.
• The protons are then exposed to radio waves,
which make them spin. This spinning produces
a signal from which an image is produced.
What is MRI good for?
• Accurate disease detection throughout the
body
e.g. tumours of the brain, inflammation of the
spine, structure of the heart
CT vs. MRI
Depends on what is being diagnosed:
MRI - For brain tumour detection
- For multiple exams
- Best for soft tissues (e.g heart)
CT - For solid tumours in the chest and
abdomen
- for bone abnormalities and injuries
- cheaper than MRI
Nuclear Medicine Imaging
• Measures radiation emitted from within the
body and provides information about the
function of the organ, not just its structure
• Uses radioisotopes (unstable atoms) that are
injected into the target organ for imaging
• Large amounts of isotopes collect at site of
damage “lighting” it up
• Ex. PET scan: positron emission tomography
PET
Produces a three-dimensional image of
functional processes in the body.
Gamma rays are emitted by a positron-emitting
radionucleotide tracer, which is injected into
the patient.
Used for imaging of tumours and metastases,
also for brain and heart function
• PET scan are often used in combination with
MRI or CT scans to give a complete metabolic
and anatomic picture