Imaging in Cancer Flashcards
What are different kinds of imaging that can be used to diagnose cancer?
Plain radiographs
Barium studies
CT
MRI
PET
What are conventional cancer diagnosis methods?
Endoscopy and biopsy
Barium examination
What is a radio-opaque used from outlining the gastro-intestine tract?
Barium sulphate
Why is barium used to outline the GI tract?
High atomic number absorbs more X-rays than surrounding tissue and appears white on radiograph
What chance does barium have of developing fatal malignancy after 10 years latent perioid?
1:2000
What are different kinds of cross sectioning imaging?
CT
MRI
PET
What can cross sectioning imaging be used for?
Initial diagnosis
Staging of the disease
Monitoring response after treatment
Evaluation of residual mass after treatment
What does CT stand up for?
Computed tomography
What happens during a CT scan?
X-rays produce a digital image of a slice of tissue
What is hounsfield unit?
Attenuation value of voxels are expressed as a CT number which relates to the attenuation value to that of water (ranges from -1000 to +3000
What are some common hounsfield values?
Air -1000
Lung -700
Fat -100
Water 0
Blood +40
Muscle +40
Calcium +150
Bone +700 to +3000
What is a voxel?
A value on a grid in a 3D space
What are contrast agents?
Substances used to enhance the visibility of internal structures in X-ray based imaging
What are the two kinds of contrast agents?
Oral
Intra-venous
What do oral contrast agents do?
Outline the GI tract
What do intra-venous contrast agents do?
Show blood vessels and vascularity of different tissues
What are contrast agents usually made of?
Usually iodine based, oral ones are diluted and known as gastrografin and IV ones are known as omnipaque
What are oral contrast agents known as?
Gastrografin
What are IV contrast agents known as?
Omnipaque
What do scans show to diagnose and stage a tumour?
Position of tumour
Depth of tumour
Relationship to adjacent structures
Involvment in regional lymph nodes
Presence of distant metastasis
What are different scans used for?
Different kinds of cancers
What kinds of cancers are CT scans used for?
Lung
Pancreatic
Renal
Adrenal
Retroperitoneal
Brain
What CT scans have the highest equilvalent dose and what value is this?
CT scans of the abdomen and pelvis which have an equilvalent dose of 10mSv
What should be considered when deciding if a scan is required?
Ensure examination is necessary
Adequate clinical information is essential for appropiate protocol
Avoid repeat examination
What does MRI stand up for?
Magnetic resonance imaging
How do MRIs work?
1) Magnetic fields align protons in the body in one direction
2) Radiofrequency pulse displaces protons and images are created displaying the time they take to reurn to their original position
What is MRI often used for?
Excellent soft tissue detail
Vessels can be demonstrated
Brain, spine and musculoskeletal
Abdomen and pelvis
Cardiac imaging
What are disadvantages of MRI?
Claustrophobic and noisy
Motion artefact
Cannot image patients with pacemakers and other electronic implants
What contrast agent can be used in an MRI and what does this do?
Gadolinium DTPA (intravenous agent) which changes local magnetic fields and so alters the tissue signal
What is screening used for?
To diagnose at an earlier stage before symptoms begin, making it more curable
What are the 3 NHS screening problem?
Breast
Bowel
Cervix
What must happen for screening to be useful?
Condition should be an important health problem
Should be a latent stage of disease
Should be a test or examination for the disease
Test should be acceptable to the population
Should be a treatment for the disease
What should screening do?
Detect disease at earliest stage
Cause no harm
High sensitivity and specificity
Benefit to individual and population outweigh the cost
