Imaging in Cancer Flashcards
Principles of MRI
no ionising radiation
strong magnetic field aligns protons (H+) in the body in one direction
radio frequency pulse displaces protons and images created by displaying time taken for protons to “relax” back to the original alignment
Applications of MRI
Excellent for bone soft tissue detail
vessels can be demonstrated
brains, spine and musculoskeletal
abdomen & pelvis
cardiac imaging
Indications of MRI
Gadolinium DTPA is an intravenous contrast medium which causes changes in the local magnetic field and so alters the tissue signal
vascular lesions and some tumours can be more easily seen
Contraindications of MRI
claustrophobic and noisy
motion artefact
cannot image patients with pacemakers, metallic implants, prosthetic heart valves and over a certain body weight.
Patient safety issues specific to MRI
toxicity during pregnancy, claustrophobia, and hearing loss
Principles of screening
diagnose disease at an earlier stage, before symptoms start
cancer is easier to treat and most likely curable
NHS screening programme - breast, bowel, cervix
Guidlines for screening
test should detect disease at an early stage where treatment can alter outcome
test should cause no harm
test should have high sensitivity and specificity
benefit to the individual and population should outweigh the cost
Screening for breast cancer
mammography is the most common
Breast MRI is used for those at high risk for getting breast cancer. Because breast MRIs may appear abnormal even when there is no cancer, they are not used for women at average risk.
Principles of Barium Examinations
do not require computers
endoscopy & biopsy
barium sulphate is a radio-opaque contrast used for outlining the gastro-intestinal tract
high atomic number of barium absorbs more x-ray photons than surrounding tissue
appears white on the conventional radiograph
