Any probe selected for clinical use should have excellent reliability and stability. Quality control consists mainly of a check of the background value and the sensitivity of the probe. The shielding should be looked at as well. Although in our experience stability is not a problem, it is recommended that before each use, the background value and sensitivity are determined. A background count will also detect any contamination with radioactivity of the probe. It is necessary to check the sensitivity regularly, because a gradual decrease may be unnoticed. A 57Co source is convenient to use for a check of the sensitivity, but the readings should be corrected for the half-life of 270 d. Initially the source should not be too strong to avoid dead-time effects, which would cause a reduced count rate. The maximum count rate of the probe (typicaly 10,000 counts per second) should not be exceeded. After 5 years, the count rate will then have decreased to 100 counts per second. In that case, the sensitivity can still be determined with an accuracy of 3% if a counting interval of 10 seconds is used, which is acceptable. Therefore, it is recommended to obtain a new 57Co source at least every 5 years.
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Complete Guide to Preventing Skin Cancer. We all know enough to fear the name, just as we do the words tumor and malignant. But apart from that, most of us know very little at all about cancer, especially skin cancer in itself. If I were to ask you to tell me about skin cancer right now, what would you say? Apart from the fact that its a cancer on the skin, that is.