Geometric efficiency is defined as the fraction of emitted radioactivity that is incident on the detection portion of the counter, in this case, the crystal. Because the sample is essentially surrounded by the crystal, the geometric efficiency for detection of gamma rays is high. Reflected light and scattering inside the well surface and the thickness of the crystal limit the energy resolution of the standard well counter. PMT, Photomultiplier tube NaI(TI), thallium-doped sodium iodide. (A) Well counters are heavily shielded scintillation crystals used to measure and identify small amounts of radioactivity contained in small volumes such as a test tube. Thus their primary use is simply to survey for the presence of radiation and radioactivity. Limitations include that they can neither differentiate which type of radiation is being detected nor determine the exact energy of the detected radiation. There is also a battery test range that is used when the battery check button is pushed or the selector knob is switched to battery check.Īdvantages of GM counters include their durability, portability, and ability to detect many types of radiation with high sensitivity. (B) The dial reads in either counts per minute (CPM) or milliroentgens per hour (mR/hr). Note the radiation check source affixed to the side, which is used to make sure the instrument is functional.
The selector knob has various multipliers to use with the displayed reading. On the instrument, the pancake detector is located at the end of the handle and the face is covered with a red plastic cap. (A) This instrument is used for low levels of radiation or activity. Single-Photon Emission Computed Tomography (SPECT)ĭetector Head Alignment With the Axis of Rotation Image Acquisition: Memory and Matrix Sizeĭedicated Molecular Breast Imaging Cameras Crystal and Other Photon Detector Devices
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