Imaging in cancer Flashcards
when is a barium swallow imaging technique used? AND EXAMPLE
only if patient can’t undergo endoscopy i.e esophageal cancer
-rarely used in real practice
Barium info
doesn’t react with the body
is excreted safely
xray beams can’t pass through Barium atoms due to high atomic number
appears white in standard xray
but in other scans it can appear black or white
can do barium swallow or barium enema
How does barium show a tumour
barium outlines the cancer in a scan
single contrast
barium outlines the lumen- can’t see a tumour however
double contrast
in addition to outlining the lumen it outlines the tumour so both are visible
CT colonography
CO2 gas inserted to open the colon up as much as possible
may have to swallow contrast dye prior
CT examination of the lumen
-fecal tagging due to dye
-tumour wouldn’t retain contrast
- improves the differentiation of residual feces from polyps and thereby false-positives can be avoided.
What does the diagnosing colonic tumours?
colonoscopy (endoscopy)
what is the best technique to see colon polyps if they can’t undergo colonoscopy?
CT colonography
cross section imaging
body in slices
includes CT, MRI & PET
Uses of cross section imaging
- initial diagnosis and staging of disease
- monitor response to treatment
- evaluating residual mass after treatment
- recognition of complications of treatment
- when there is concern for disease relapse
CT xray
body absorbs photons released by x-rays
-various angles around the body to get a 360 degree image
Voxel is how thick? and why
1 cm- reduces noise ie in radiological terms- produces a less grainy image (improves quality)
What is used to outline the GI tract?
gastrografin- dilute iodine based contrast
- not used routinely nowadays
IV CT contrast agent?
iodine based contrast
omnipaque- injected into the veins demonstrate blood vessels or the vascularity of different tissues
Risks of IV contrast use
allergic and anaphylactic reactions
diagnosis and staging system
T, N, M
T staging
TUMOURS
- very specific to particular organ
- can’t compare between structures
- shows depth or position of tumour
N staging
involves lymph nodes N= nodes
M staging
presence of distant metastases- spreading of cancer elsewhere in body
ie is there no metastasis or distant metastasis present
Brain scanning
CT, MRI
PET can’t be used- as brain is highly metabolic
which scan type is used to see the spinal cord
v intricate
MRI is only morality that can see detail
which scan type can’t be used to examine the Lungs
don’t have H+ protons and MRI depends on these so it can’t be used
which scan type can’t be used to examine the Esophagus
MRI cannot be used
what scan can’t be used to examine the liver
highly metabolic- PET can’t be used
which cancers can be diagnosed by CT imaging
lung tumour pancreatic tumour renal tumour adrenal tumour retroperitoneal tumour brain tumour
CT and staging of cancer
Assess local spread
e.g lymph nodes, adjacent organs
assess distant spread
e.g liver, lung, bone or brain metastases
CT and staging of cancer
Assess local spread
e.g lymph nodes, adjacent organs
assess distant spread
e.g liver, lung, bone or brain metastases
ALARA principle
as low as reasonably achievable- make sure examination is really necessary- avoid repeat
MRI
powerful magnet
better
quality/resolution of image
radio frequency reciever
receives
water molecule in MRI scan
a very light molecule- takes longer to get back
fat molecule in MRI scan
takes less time to be received
disadvantages of MRI
noisy
claustrophobic
can’t image patients with pacemakers, aneurysm clips
image is motion dependent- need ot stay still!
screening importance
- diagnose disease at an earlier stage
- cancer is easier to treat and most likely to be curable
- NHS screening programme- breast, bowel and cervix
no standardised screening for prostate- patient dependent
WHO principles of screening
condition should be an important health population- breast, cervix and colon cancer v common in western population (japan- stomach) nee to have high uptake
there should be a latent stage of the disease- lung cancer doesn’t have latent stage- only 6 month max 2 years really. Should be visible in imaging before it becomes a cancer
should be a test or examination for the condition- breast mamogram etc
colon- fecal stool test
test should be acceptable to the population- something people will accept to go through
there should be a treatment for the condition- cancer shouldn’t be lethal, low morality for the cancer so patients may recover
facilites for diagnosis and treatment should be available
Cancer staging- what does ‘stage’ refer to?
stage refers to the extent of your cancer, such as how large the tumor is, and if it has spread.
TNM Staging System
T refers to the size and extent of the main tumor. The main tumor is usually called the primary tumor
N refers to the the number of nearby lymph nodes that have cancer
M refers to whether the cancer has metastasised. This means that the cancer has spread from the primary tumor to other parts of the body
What stages are there?
5 stages: stage 0, I, II, III, IV
Stage 0= Abnormal cells are present but have not spread to nearby tissue.
Stage I, Stage II, and Stage III= Cancer is present. The higher the number, the larger the cancer tumor and the more it has spread into nearby tissues (in situ)
Stage IV= The cancer has spread to distant parts of the body.
‘Localised’
Cancer is limited to the place where it started, with no sign that it has spread.
genetic changes and cancer
Cancer is caused by certain changes to genes that control the way our cells function, especially how they grow and divide
Genes carry the instructions to make proteins, which do much of the work in our cells. Certain gene changes can cause cells to evade normal growth controls and become cancer.
Source of genetic changes that can cause cancer?
inherited from our parents if the changes are present in germ cells (reproductive cells of the body)
result of errors that occur as cells divide or from exposure to carcinogenic substances that damage DNA, such as certain chemicals in tobacco smoke, and radiation, such as ultraviolet rays from the sun
modalities of cancer therapy
surgery Radiation Therapy Chemotherapy Immunotherapy Targeted Therapy (targets the changes in cancer cells that help them grow, divide, and spread) Hormone therapy Stem Cell Transplant (restore blood-forming stem cells in cancer patients who have had theirs destroyed by very high doses of chemotherapy or radiation therapy) Precision Medicine
TNM staging list
Tumour
T1-4
Nodes
N0-2
Metastasis
M0-1
barium enema
enema is injected into rectum
examines colon
colon x-ray
Used in Chron’s disease
are CT and PET scans combined?
yes they are often combined to detect cancerous tumours
SPECT- what is it?
Single-photon emission computed tomography
gamma cameras rotate around area of interest
What does PET use?
radionucleides that decay by positron emission
