Basics of Nuclear medicine ; radiopharmaceuticals and the Gamma camera – Flashcards
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nuclear medicine is...
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application of radioactive substances in the diagnosis and treatment of disease
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what information does nuclear medicine seek to find?
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physiological information
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under what principle does nuclear medicine work?
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using radiolabelled pharmaceuticals
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what is radioactivity
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spontaneous disintegration of an unstable nucleus with an emission of radioactive new nucleus
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radioactivity is simply
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change of nucleus
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what happens in an unstable nucleus
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emission of particles in order for the nucleus to become stable
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what are gamma rays
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high energy photons that can penetrate deeply
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what are examples of radioactive elements used to gene rate gamma rays
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TC-99m, I-123, In-111
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an ideal radionuclide that is most commonly and widely used for bone scanning
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Technetium-99m
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half life of Tc-99m
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6.02 hours
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whatr element forms clinically used Tc-99m
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molybdenum-99
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ALARA
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as low as reasonably achievable
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patient does of gamma ray should be
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ALARA
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radiopharmacy
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a sterile enviroment where the radioactive injections are customized for each patient
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osteocis
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bone
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lyomaa
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lung
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mag 3
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renal function
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DMSA
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renal structure
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nuclear medicine kits used in imaging
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osteocis, lyomaa, mag 3 and DMSA
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sestamibi
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heart/parathyroid
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tachnetium pertechnetate
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thyroid
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Tc-99m generator is called
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molybdenum99/Tc generator
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molybdenum generator structure
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alumina filled column with molybdenum bound to it
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why is Tc-99m obtained as a solution but molybdenum is bout to the alumina filled coloumn?
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molybdenum binds with strong forces to alumina than Tc-99 when saline is run through the coloum
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what concentration of saline is run through the molybdenum column in order to obtain liquid molybdenum
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0.9% sodium chloride
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what is the device used to image emitted gamma radiations called
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Gamma camera
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Gamma camera is also called
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scintillation camera
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the 3 components of a gamma camera
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a collimator, a scintillation crystal and an array of photomultiplier tubes
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collimator
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filters in order to allow the passage of appropriate gamma rays
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types of collimators
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low, medium and high energy
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most commonly used collimator
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low energy
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what gamma rays does a collimator allow to pass to the scintillation crystal?
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gamma rays that travel along a hole axis
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collimator allow _____ to pass
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gamma rays that travel along a hole axis
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what happens to gamma rays approaching the collimator at oblique angles?
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hits the septa and is absorbed
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what converts the gamma that pass the collimator successfully?
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they are converted to light photons
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what converts light photons to electrical energy?
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scintillation crystal
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what is a scintillator?
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a type of material that releases UV or visible light when radiation interacting within ir deposits energy by means of Compton scatter or photoelectric interaction
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what kind of light do scintillators release?
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UV or visible light
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when do scintillators release light?
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when radiation intercate within them in order to deposit its energy by meas of Compton scatter or photoelectric interaction
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most common scintillation crystals
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sodium Iodide doped with Thallium (NaI(Tl)
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a scintillation
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A single pulse of light that is obtained from a fluorescent crystal in response to exposure to ionising radiation
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what does the photomultiplier tube (PMT) do?
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converts visible light photons into an electrical signal
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why are the PMTs arranged closely packed together
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to minimize gaps left behind them
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how are PMT arranged
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closely packed together
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what does PMT do to the light photons before they are converted into electrical signals?
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amplifies them
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how can amplification of light photons by PMTs be adjusted
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change the voltage applied to the photomultiplier
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what is SPECT/CT?
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addition of CT onto gamma camera
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benefit of addition of CT to gamma camera
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allows better characterisation and localisation of hotspots and it is used for attenuation correction
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used for attnuation correction in gamma camera
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CT
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what is the disadvantage of attenuation of gamma camera
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server underestimation of activity in deep tissues compared to superficial tissues
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what does attenuation correction by CT do?
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maps internal organs, determines the amount of density and then decides how much has been attenuated in order to correct the loss of counts
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what attenuation correction by CT do briefly
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corrects the loss of counts
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benefit of attenuation correction by CT in gamma camera
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it can increase specificity and sensitivity
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clinical contexts of nuclear medicine use
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staging, quantification , therapy, and tumour diagnosis
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when can good image been obtained after administration of Tc-99m
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2-4 hours
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what are the most mideley used radiopharmaceuticals for skeletal imaging?
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diphosphates
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a radiotracer used in bone scanning
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Tc-99m methyl diophosphate (MDP
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osteosis is a kit supplied by IBA molecular for the preparation of
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Tc-99m oxidronate injection
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who recommends standard radiation doses
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ARSAC
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ARSAC
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administration of radioactive substances advisory committee
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recommended dose by ARSAC for bone scan
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600 to 800 MBq
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cancer which commonly spread to the bone include
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breast, prostate and lung
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what does first bone metastasis identification indicate?
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incurable cancer
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when is it not appropriat to do CT?
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if the radiographer thinks that there is a high chance the radiologist will diagnose multiple metastatic bone lesion
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thyroid uptake scan
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used to asses thyroid function
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measurement of thyroid function
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% thyroid uptake
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Iodine-131 therapy
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used in hyperthyroid patents
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thyroid ablation therapy is done with
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iodine-131
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uses of nuclear medicine in assessment of neuroendocrine tumours
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disease extent, recurrence disease,
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when is nuclear medicine particularly useful
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when other modalities are contraindicated such as in pacemaker or prostetic limbs which cannot be used in MRI
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half life of indium 111
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2.8 days
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how indium decays
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electron capture
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what kind of collimators are used for imaging indium 111
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medium energy general purpose (MEGP)
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how longs does the imaging protocol for indium 111 last?
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2 days
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Octeotide
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long lasting clinically effective somatostatin analogue
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radiolabelled form of somatostatin analogue
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In-111 pentetreotide (Octreotide)
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how radiolabelled form of somatostatin analogueis used for sensitive visualisation
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binds to somatostatin receptors
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where are somatostatin receptors found
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in endocrine cells throughout the body and tumours
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how are tumours identified by radiolabelled somatostatin analogues
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they are the hottest part
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where do carcinoids arise from
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neuroendocrine cells
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where are carcinoid most prevalent
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GIT
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where are carcinoid commonly found in the GIT?
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appendix, ilium and rectum
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type of scanning that can help diagnose carcinoid early
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octerotide scanning
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imaging modality that is highly useful for neuroendocrine imaging
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SPECT/CT
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photon energy of Tc-99m
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140 keV
