Merrill's Chapter 34 Nuclear Medicine Questions and Answers

Merrill's Chapter 34 Nuclear Medicine Questions and Answers Naturally occurring radionuclides are not used for nucmed imaging because of the high patient dose Half-life (T1/2) the time it takes the nuclide to decay to half its original activity Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:02 / 0:15 Full screen Brainpower Read More The most common radionuclide in nucmed Technetium (99mTc) One desirable characteristic on an imaging pharmaceutical primary photon energy between 100-140 KeV Scintillation detectors or gamma cameras use crystals that change radioactive emissions into light photons The crystal used in gamma cameras is made of thallium-activated sodium iodide Collimators are used in nuclear medicine to keep scatter rays from entering the camera An array of photomultiplier tubes is located to the back of the crystals Unwanted photons or "noise" are reduced by using a collimator SPECT imaging produces images similar to those done in CT Positron-emitting radionuclides have a neutron or proton deficient nucleus The radiotracers for PET scanning are chosen for its similarity to naturally occurring biochemical When a positron and an electron combine, the result is annihilation radiation of two photons of 0.511 MeV PET Scanning is an examination that can look at a patient's physiology PET scanners need to be close to the source of positrons because of the short half-lives of the nuclides If only one photon is detected and no other photon is observed during the time window of an annihilation pair when the original event is discarded Desirable properties of NM radiopharmaceuticals effective half-life longer than the exam time, suitable chemical forms for rapid localization, and primary photon energy between 100-400 KeV Typical gamma camera detector heads contain 80-100PMTs Xenon-133 lung ventilation/perfusion scan is used to evaluate pulmonary emboli The nuclear medicine test that helps diagnose Graves disease (plummer disease) due to an increased uptake of 123 Iodine is a thyroid scan