Imaging Flashcards
(37 cards)
How does an x-ray work?
A beam of x-rays are projected towards the patient. Some of these are absorbed by the patient and the rest that pass through the patient are captured by a detector, which then creates a digital image.
What is gamma radiation?
Gamma rays that have occurred due to the radioactive decay of unstable isotopes.
360 degrees of rays that can’t be switched off, have to wait for the half life of the chemical to pass. Higher frequency than x-rays.
What is an isotope?
A radioactive element involved in delivery
What is a ligand?
A pharmaceutical element involved in binding
Name some properties of an ideal isotope?
Gamma emitter
Half life similar to time of examination
Easily bound to pharmaceutical component.
Radionuclide readily available at the hospital site
Radiopharmaceutical simple to prepare
What is the most common isotope currently used in hospital?
Technecium99
What is SPECT?
Single Proton Emission Computed Tomography
Gamma cameras rotate around area of interest.
Specifically effective for cardio or neurological scanning.
What is PET?
Positron Emission Tomography
Form of molecular imaging that uses radionuclides that decay by positron emission ( proton - neutron + positron)
Used to image biologically interesting processes.
Name some common PET radionuclides and their half lives?
18F - 110minutes 68GA - 68minutes 11C - 20minutes 13N- 10minutes 15O - 2minutes
What is the main risk of radiation?
Ionising radiation inducing fatal cancer
What is the benefit of using radiation in imaging?
Allows for earlier diagnosis , management of change and treatment.
What are the 5 main types of imaging used in hospitals today?
Plain radiographs (x-ray) Barium Studies CT MRI PET
What is barium sulphate?
A radio-opaque contrast used for outlining the gastrointestinal tract.
How does barium outline the GI tract?
It has a high atomic number which mean sit absorbs more photons than its surroundings. This makes it appear white on an x-ray.
Describe the different types of barium study and the tissues that each highlights?
Barium swallow and meal - oesophagus, stomach and duodenum
Barium follow through - small bowel
Barium enema - large bowel
What is the function of cross sectional imaging?
Allows the initial diagnosis and staging of disease, monitoring in response to treatment, evaluation of residual mass after treatment, recognition of complications and ability to check for disease relapse.
Describe how a computed tomography works?
X-rays used to produce a digital image of a slice of tissue, usually in the axial plane, using computing to create the image.
What are the types of contrast agents that can be used before a CT to highlight certain structures?
Oral - Iodine based contrast used to outline GI tract
Intravenous - omnipaque iodine based contrast used to outline the blood vessels or the vascularity of different tissues.
What factors are important when diagnosing and staging cancers?
Position of tumour Depth of its penetration Relationship with adjacent structures Involvement with regional lymph nodes Presence of distant metastases
What are the doses of radiation of a chest, abdominal, and pelvic CT?
Chest = 8msv
Abdomen & Pelvis = 10msv
What is the ALARA principle?
As Low As Reasonably Achievable
Must ensure whether the examination is necessary
Adequate clinical information is required before the scan can take place.
Repeat examinations are avoided.
What is MRI?
Magnetic Resonance Imaging - strong magnetic field aligns all the protons in the body in one direction.
Radiofrequency pulse displaces protons and images created by displaying the time taken for protons to relax back to their original alignment.
What are the benefits of MRI?
Excellent bone soft tissue detail
Vessels can be demonstrated
Good for brain, spine and musculoskeletal
Abdomen, pelvis and cardiac are also well demonstrated on an MRI.
What are some disadvantages of MRI?
Claustrophobic and noisy
Motion Artefact
Cannot image patients with pacemakers or aneurysm clips
