Imaging in Cancer Flashcards
Describe CT scans
- Cross section plane
- Different tissue absorb different amount of photons –HU - attenuation values relates to that of water (0) - +3000 bone to -1000 air
- Higher HU = higher density
CT contrast agents
- Gastrogafin outlines GI tract (oral)
- Oanipaque shows blood vessel or vascularity of different tissues (IV)
Mechanism of MRI scanning?
Radiofrequency excites photons causing them to tilt.
The image is generated by measuring the time taken for the photon to return back to its original state (relax)
What does MRI show?
- Bone soft tissue
- Vessels
- Brain, spine and musculoskeletal
- Abdomen and pelvis
- Cardiac scanning
Disadvantages of MRI?
- Claustrophobic and noisy
- Patient movement results in blur
- No imaging in patients with pacemaker and aneurysm clips
MRI contrast agents
Gadolinium DTPA changes in local magnetic field so alter tissue signal (IV
What cancers does the NHS screen for?
Breast, bowel and cervix
Principles of screening
- Condition fatal
- Screening at latent stage of disease
- Disease treatable
- Facilities for diagnosis available
Why is lung cancer unsuitable for screening?
Develops to rapidly
Screening test principles
- Detect disease at early stage
- Cause no harm
- High sensitivity and specificity
- Benefit to population outweigh cost
What three factors influence diagnosis and treatment of cancer?
T - relationship to adjacent structure (local spread)
N - invasion of lymph nodes
M - presence of distant metastases
Mechanism of SPECT
- Radiotracer injected in the patient (glucose and radioisotope)
- As tumour grows, requires glucose so uptake of radiotracer
- It emits gamma rays which is absorbed by rotating gamma cameras
Mechanism of PET
- Radionuclide taken up and decays by positron emission
- Proton - neutron + positron
- Emits two gamma rays which is found detected by detector
What diseases can SPECT indicate?
- Alzheimer’s disease
- Parkinson’s disease
- Myocardial perfusion
