Imaging in inflammatory disorders & infection IA % + Flashcards Preview

ME2308 Principles of Disease > Imaging in inflammatory disorders & infection IA % + > Flashcards

Flashcards in Imaging in inflammatory disorders & infection IA % + Deck (10):
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Radionuclide imaging pic

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Radiography pic 2

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Gamma radiation

•Gamma rays occur due to radioactive decay of unstable isotopes

•High energy, high frequency, very similar properties to x-rays

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Properties of an ideal isotope

•Half-life similar to length of examination

Gamma emitter, rather than a or b

•Energy of g rays should be 50-300 keV

•Radionuclide should be readily available at hospital site

•Easily bound to pharmaceutical component

•Radiopharmaceutical should be simple to prepare

•Radiopharmaceutical should be eliminated in similar half-time to duration of examination

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99mTechnecium

•hydroxy-diphosphonate ⇒ bone

•dimercapto-succinic acid ⇒  kidney

•hexamethyl-propine amine oxime ⇒  brain

•macroaggregated albumin ⇒  lung

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Single photon emission computed tomography - SPECT

CT version of nuclear medicine

•Gamma cameras rotate around area of interest

•Routinely used for brain and cardiac studies

•Can be applied to any site of interest in other studies e.g. spine in bone scan or in lung scintigraphy

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Positron Emission Tomography

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Molecular imaging

•Uses radionuclides that decay by positron emission – proton ⇒  neutron + positron

•These can be used to image biologically interesting processes

•Can be used for absolute quantitation but requires arterial sampling

•All scanners now PET CT

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Half lives pic

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Physiological FDG (fluorodeoxyglucose ) uptake

•Brain

•Myocardium (muscular tissue of heart)

•Stomach (arrow)

•Liver

•Spleen

•Colon

•Urinary tract

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Radiation – risks vs benefits

Main risk is ionising radiation

•Risk of inducing fatal cancer e.g. CT abdomen & pelvis = 1:1600 (but risk is 1:4 for population and risk is relative)

Benefits

•Diagnosis, management change, treatment) should always outweigh costs (radiation, risk to patient and staff, ££)