Medical Imaging Flashcards
Angiography is an example of what?
Its an example of a contrast radiograph.
A radiopaque dye is injected into the blood system to visualise blood vessels.
It’s then monitored and when it reaches an area of interest, eg coronary vessels, an image is taken.
What is an IVP?
Intravenous pilogram/urogram
Radiopaque medium is excreted via the kidneys.
A barium enema is a test that highlights the large bowel so it can be clearly seen on x Ray.
What are the types of MRI?
T1: the fat is very bright
T2 the fat signal has been suppressed so the fat appears less bright, and the WATER instead appears bright. Eg here the cerebral spinal fluid, mainly water, appears bright
State the role of diagnostic imaging
To provide anatomical & physiological information
This is achieved by producing a high quality image
How are X rays generated?
Apply an electric current across an x ray tube
The filament, when heated, will emit e-
These e will sit around the focusing cup until a pd is applied across the tube. This accelerates the electrons to the anode bc the cathode becomes - and the anode becomes +.
The amount of x-rays produced is directly proportional to the number and power of e landing on the anode
Describe attenuation in xrays and how we produce x rays.
X-Ray beam is homogenous (1 energy level)
The patient acts as an attenuator bc they absorb some radiation.
The denser the structure the more X-Rays are absorbed, so less energy will be incident to the receptor. A whiter image forms.
In less dense (lucent) structures, less x rays absorbed, more energy is incident to receptor. A darker image forms
On the x ray you can have diff grey shades. Darker grey= lower attenuation within the body. Lighter grey= higher attenuation.
Describe plain film radiography
Uses Ionising Radiation at 55-150 kVp.
Hay 2 projections/images at 90 degrees to each other so you can deduce 3d structure.
To screen joints, centre over the joint; we want the central x ray which doesn’t diverge to go straight thru the joint for a clear joint image.
To screen long bones, include joints on either end- sin joints identification becomes difficult.
Plain film x rays demonstrate bony tissue well and some soft tissue structures, but this is more limited.
Cannot get through gas, so if eg the bowel has gas, other structures in the abdomen cannot be seen clearly
Describe Fluoroscopy
Uses X-Rays up to 150kVp. Produces real time moving images
Enables invasive diagnostic, therapeutic and surgical procedures
Demonstrates bony tissue. Using contrast agents show some soft tissue structures.
Uses Radio-Opaque contrast agents:
Iodine based= is injected or ingested, but can cause allergic reactions like Anaphylaxis. Can have adverse drug interactions, eg w Metformin it can cause acidosis.
Barium Based= used orally or rectally
Normally department based but can be mobile (Operating Theatres)
Describe CT or CAT scans
Uses ionising radiation up to 150kVp
Produces cross sectional images as standard 2D, but acquired image data can be reconstructed in all planes to show a 3D image
Can use Contrast agents
Higher sensitivity to changes w/in densities of the body
Can demonstrate bone and soft tissue using computer enhancement processes (windowing)
Describe MRI scans
Does NOT use ionising radiation
Computer based imaging modality, produces ‘Multi Planar’ images
Works on the abundance of hydrogen/water in the body.
Utilises Magnetic Waves and Sound Waves to produce a signal. Signal is picked up and converted into the image
Demonstrates soft tissue very well due to water content
Doesn’t demonstrate bone well due to little water content
Describe ultrasound
No ionising radiation, instead you use high Hz sound waves for soft tissue imaging
The sound waves penetrate the structure and are reflected back. The image is built up from the ‘reflected’ sound waves
Doppler US is used to calculate blood flow
Colour can be overlaid to enhance image clarity
Mobile units- only need an electrical socket
Describe Radio Nuclide Imaging (RNI)
Uses Gamma Rays
Radioisotope is injected, inhaled or ingested by the patient
The Isotope is attached a pharmaceutical, eg glucose, that’s targeted for the anatomical region
Gamma rays are detected by the gamma camera and the image is constructed by the computer
RNI demonstrates function and physiology mainly
Advances in this field: PET now demonstrate anatomy as well as physiology
