1 - Introduction to Diagnostic Imaging Flashcards
What is term now used for radiology?
Diagnostic imaging
What is the difference between a radiologist and a radiographer?
RADIOLOGIST - doctor specialising in the interpretation go medical imaging
RADIOGRAPHER - technician who takes images
What are the types of diagnostic imaging?
- ionising radiation
X-ray, CT and nuclear medicine - Non-ionising radiation
ultrasound and MRI
What colour does air and fat appear as on an x-ray?
black
What colour does soft tissue appear as on an x-ray?
grey
What colour does bone appear as on an x-ray?
white
How are common agents used to contrast tissues in X-rays?
enhances the differences between tissues of similar densities
Give some commonly used contrast agent in X-rays
barium
iodine
How are contrast agents introduced into the body?
- swallowed
- via rectum
- into artery or vein
What are CT scans?
uses a combination of x-rays from many different angles to produce a cross sectional map of tissue density
What can CT differentiate between that X-ray cannot?
between water and soft tissue
What contrast agent is used in CT?
Iodine (injected into the arm vein)
What in an ultrasound?
uses high frequency sounds to make images
the sound is both produced and detected by the transducer
NOTE: completely safe, no radiation hazard
What is MRI?
Magnetic Resonance Imaging
- a strong magnet is cooled with liquid helium
- radio waves are transmitted into the patient
- listen for the return waves caused by interactions with protons (water) in the patients body
- different tissues give different intensities of returned radio waves
no ionising radiation
On MRI T1 and T2:
a) how does bone appear?
b) how does fluid appear?
c) how does fat appear?
a) black on both
b) black on T1, grey on T2
c) white on both
What is nuclear medicine used for?
(more of a physiological test than an anatomical test)
shows bone activity
can be used to observe how a cancer is destroying bone
how does nuclear medicine work?
- uses radioactive tracers that emit radiation
- different tracers go to different organs/areas of the body
- images are made by detecting the radiation coming out of the patient by a gamma camera
What is a PET scan?
Positron Emission Tomography
detects metabolic or ‘functional’ changes in the body rather than ‘structural’ changes
particularly effective in identifying whether cancer is present or not (diagnosis), if it has spread (staging) and if it is responding to treatment
What is the advantage of PET/CT over PET alone?
better anatomical localisation of cancers
faster and more specific
