Contrast Radiography & Modalities Flashcards
Why is contrast radiography used and provide an example:
on plain radiographs two organs of simialr densities cannot be disti guished between….
E.g. different in contrast of adjacent structures in areas such as GI tract is low, so not easy to distinguish on radiograph.
Positive - seen as…………?
White image
Negative - seen as……?
Black image
Is barium suplhate a positive or negative contrast media?
Positive contrast media
Radio-opaque means?
appears white on an x-ray
Radiolucent means…?
appears black on an x-ray
What is double contrast media and why is it used?
- This is negative and positive contrast media together.
- usually used in bladder/GI tract
- provides excellent muscosal detail
Explain how double contrast media works.
A small amount of positive contrast agent is used to coat the inner lining of the organ, which is then distended using negative contrast agent (such as air).
What drug classification is contrast media, and what checks should be made?
POM-V
date and type of contrast, quantity and concentration, administartion route, warm medium, check foreign particles, aseptic procedures, record type and amount on patient record, nursing considerations (procedure specific)
Three…..
Examples of negative contrast media:
- air
- carbon dioxide
- oxygen
What does MRI stand for?
Magnetic resonance imaging
What contrast media can be used for MRI?
Gadolinium (Gd)
Outline the process of an MRI
- body tissues become magnetized-alligning proton and hydrogen atoms.
- radiofrequency coil (RF) emits pulses of radiowaves - atoms become disoriented.
- atoms emit small radiowaves themselves as they return to their normal alignment.
- emitted radiowaves detected by RF coil and transformed into image by complex algorithms.
Patient prep for MRI
- GA
- patients screened for presence of metal implants and pacemakers
- collars, leads etc… removed (incl horse shoes)
- only trained staff to use MRI/monitor GA
Advantages of MRI
- better for soft tissue scans (brain, spinal cord, ligaments, tendons…)
- does not use ionising radiation
- uses magnetism and radio energy
- thought to be completely safe (tho GA still needed)
- planes: transverse, sagittal, oblique, dorsal
- produces cross-sectional slices through patient tissues
Disadvantages of MRI:
- high purchase and running cost
- non-ferrous GA machines, drip stands etc…
- animal must be anaesthetised as they need to be really still
What does CT stand for?
Computed Tomography
Outline CT and what it’s used for:
- used a computer and rotating x-ray device to create detailed, cross-sectional images, or slices of organs/body parts.
- ionising radiation is used.
- used for orthopaedic and body cavity details
Patient Prep - CT
- Heavy sedation or GA
- conventual GA machine sufficient
- remote monitoring
- ## no personnel allowed to reassess patient whilst CT in use
Why is scintigraphy used?
- detection of focal disease
- diagnoses abnormal conditions
- gamma camera allows hot spots of activity to be identified
Define: acoustic window
area over which sound waves are applied
Define: acoustic impedance
The degree of resistance to the passage of ultrasound waves
Define: acoustic interface
The junction between two tissues with different impedences, waves are reflected back as echoes
Explain how an ultrasound image is produced:
- when probe is applied to skin, sound waves pass through soft tissue as pressure waves
- at acoustic interfaces between organs a % of sound waves are reflected back to transducer
- returning sound waves lead to deformation of the crystal
- the change in shape is detected and converted into an electrical signal which is converted to an image on the screen.
Define the terms: anechoic, hypoechoic, hyperechoic…
- anechoic - without an echo (black)
- hypoechoic - darker than usual
- hyperechoic - brighter than usual
