Imaging In Cancer Flashcards
What kind of imaging can be used to detect and stage cancer?
Plain radiographs Barium studies CT MRI PET
What are three types of barium studies and what do they study?
Barium swallow and meal shows outlines the oesophagus, stomach and duodenum.
Barium follow through outlines the small intestine.
Barium enema outlines the large bowel.
How does a barium enema run through?
Patient is in left lateral position and the tube is inserted into the rectum. Barium runs into the descending colon to splenic flexure. The patient is turned onto their right side to let the barium run out. The bowel is inflated with air so the column of contrast is pushed to caecum.
What are the radiation doses of a barium meal and a barium enema?
Barium meal is 1.5mSv.
Barium enema is 7.0mSv.
Name some cross sectional imaging types and what they are useful for in imaging cancer
MRI CT PET Diagnosing and staging cancer Monitoring response Evaluation of residual mass after treatment Recognition of complications in treatment Concern for disease relapse
What is Hounsfield Unit?
Attenuation values of voxels expressed as a CT number which relates the attenuation value to that of water.
Bone is 700-3000
Air is -1000
What are two contrast agents in CT?
Oral is dilute iodine based contrast called gastrogafin to outline GI.
Intravenous is iodine based (omnipaque) to demonstrate blood vessels or vasculating tissues.
Sometimes get allergic and anaphylaxis with these contrasts.
What aspects are used to stage a cancer?
Position of tumour Depth of penetration Relationship to adjacent structures Involvement of regional lymph nodes Presence of distant metastasis TNM
What are the radiation doses for CT?
Chest is 8mSv
Pelvis is 10mSv
Abdomen is 10mSv
What is the ALARA principle?
As low as reasonably achievable
To ensure patient isn’t getting unnecessary radiation.
How does MRI image?
It uses protons in the body and how they behave. They are excited and the time taken to return to their original alignment is used to map an image. Molecular weight affects the time taken for it to revert.
What structures are good to image by MRI?
Bone Soft tissue Vessels Brain Spine Musculoskeletal Abdomen and pelvis Cardiac
What contrast agent is used for MRI?
Gadolinium DTPA is an intravenous contrast medium which alters the tissue signal
What four terms are used in imaging statistics and what do they mean?
Sensitivity is how many patients with the disease test positive.
Specificity is how many patients without the disease test negative.
Positive predictive value is how many people that are testing positive have the disease.
Negative predictive value is how many people testing negative don’t have the disease.
PPV is affected by the prevalence of the disease.
What are the WHO principles of screening?
The condition should be an important health problem
There should be a latent stage of the disease.
Should be a test/examination for the condition.
Test should be acceptable to the population.
Should be a treatment for the condition.
Facilities should be available.
