Intro to radiography Flashcards
What is the role of diagnostic imaging?
Role of diagnostic imaging is to provide anatomical and physiological information which is achieved by producing a high quality image
Steps involved in x-ray interactions with matter
-The incident photon is absorbed by K-shell electron (which is then displaced
-The vacancy is filled by an L-shell electron(resulting in Kalpha emission)
-The scattered photon has less energy than the incident photon and may be scattered through any angle.
-The Compton electron(aka the recoil electron) always scattered in a forward direction.
What are 3 examples of image receptors
-Analogue-film based
-Computed radiography
-Digital radiography-built into the equipment
X-ray attenuation
-X-ray beam is homogenous
-Patients act as absorbers
-The denser the structure the more x-rays are absorbed therefore the less energy is incident to the receptor
-Less energy incident to receptor produces a dark area on the image
-Routinely:
-White on an x-ray equals dense structures like bones
-Black on an x-ray equals lucent(non-dense) structures like air
-Various shades of grey, each grey level is a different level of attenuation within the body
What type of image is it after x-ray attenuation
The picture is a differentiated x-ray energy level image
What does plain film radiography use and what are the energy levels between?
-Uses ionising radiation
-Energy levels between 55 and 150 kVp as normal
Projections in plain film radiography
-2 projections at 90 degrees to each other
What does plain film radiography show?
-Joints- Centre over the joints
-Long bones-include joint on either end
-Include soft tissue
-Demonstrate bony tissue well and some soft tissue structures
What energy level do they use up to for fluoroscopy?
They use X-rays up to 150 kVp
What does fluoroscopy produce?
-Produces real time moving images
What does fluoroscopy enable?
-Enable invasive, diagnostic, therapeutic and surgical procedures
-Cardiac, neuro, urinary
What contrast agent is used in fluoroscopy and what are the possible problems?
Uses radio-opaque contrast agents
-iodine based-can be injected or ingested
-Can cause allergic reactions-Anaphylaxis
-Can have adverse drug interactions-Metformin
What does fluoroscopy show
Bony tissue and some soft tissue structure
What power of radiation does CT use?
Uses ionising radiation up to 150 kVp
What type of image does CT produce and what was it known as before?
-Produces cross sectional images as standard
-Was known as computed axial tomography(CAT)
What can be done to the acquired image from a CT scan in terms of planes?
-Acquired image data can be reconstructed in all planes
What dimension image can a CT scan image present as?
-Can be presented as a 3D image
What does a CT scan have a higher sensitivity to?
-Higher sensitivity to changes within the densities of the body
What can a CT scan demonstrate after computer enhancement process
-Can demonstrate both bone and soft tissue using computer enhancement processes
What can CT scan be used to assess in the cranium?
-Can be used to assess ‘new bleeds’ in the cranium
What type of energy does MRI use
uses non ionising enery
What does a MRI scan produce?
-Produces ‘multi planar’ images
How does a MRI work?
-Works on the abundance of hydrogen in the body (H20)
-Utilises magnetic waves and sound waves to produce a signal
-Needs RF and magnetic shielding
-Signal is picked up and converted in to the image
What does an MRI demonstrate and not demonstrate very well?
-Can demonstrate soft tissue very well-due to the water content
-Does not demonstrate hard bones well due to little water content
What type of energy does ultrasound use?
Uses non ionising radiaiton
What is an ultrasound?
-High frequency sound waves
What is an ultrasound utilised for?
-Utilised for soft tissue imaging
How does ultrasound work?
-The sound waves penetrate the structure and are reflected back
-The image is built up from the reflected sound waves
What is doppler in ultrasound used for?
-Doppler is used to calculate blood flow
What can colour in an ultrasound image be used for?
-Colour can be overlaid to enhance the clarity of image
What energy does nuclear medicine/ radionuclide imaging use?
-Uses ionising radiation- gamma rays
How does nuclear medicine/ radionuclide imaging work?
-Radioisotope is injected, inhaled or ingested by the patient
-The isotope is attached to a pharmaceutical that is targeted for the anatomical region
-Gamma rays are detected by the gamma camera and the image is constructed by the computer
- Goes to the area of highest activity (highest function)
- higher the activity the darker the blob
What does radionuclide imaging demonstrate?
-RNI demonstrates functions and physiology mainly
