imaging in cancer Flashcards
what are some imaging techniques that can be used in diagnosing and staging cancer?
plain radiographs barium studies CT MRI (not imaging strictly) -endoscopy and biopsy
what colour does barium appear on the radiograph?
white
what would a barium swallow and meal allow us to look at?
oesophagus, stomach and duodenum
what would a barium enema allow us to look at?
large bowel
what would a barium follow through allow us to look at?
small bowel
how would a patient prepare for a barium meal and follow through?
fast for 4-6 hours
how would a patient prepare for a barium enema?
low residue diet for 48 hours and bowel cleansing
what happens in computed tomography (CT)
xrays produce a digital image of a slice of tissue, usually in an axial plane using computing to create the image
what is a voxel?
volume of tissue represented by a pixel in a CT slice
what is a hounsfield unit’?
the attenuation value of a voxel relative to the attenuation value of water
what contrast agents can be used in CT?
iodine based contrast agents can be used orally and intravenously
what factors are taken into account when diagnosing and staging cancer?
position of tumour depth of penetration of tumour relationship to adjacent structures - SIZE (T) involvement of regional lymph nodes (N) presence of distant metastases (M)
what kinds of tumours are diagnoed using CT?
pancreatic renal adrenal retroperitoneal brain
what is the radiation dose for chest, abdomen and pelvic CTs respectively?
chest - 8mSv
abdomen and pelvis - 10mSv
what does ALARA stand for?
as low as reasonably acheivable - aims to reduce number of exposures
what are the advantages of MRI?
excellent bone and soft tissue detail
vessels can be demonstrated
when would MRI use be indicated?
brain spine musculoskeletal abdomen pelvis cardiac imaging
what are some contraindications of MRI?
claustrophobic and noisy
hard to image lungs
cannot image patients with metal implants
what is an example of a contrast agent used in MRI?
gadolinium DTPA - some tumours and vascular lesions can be more easily seen
what should screening tests aim to acheive?
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 individual and population should outweigh the cost
