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In clinical practice, this means that it takes 4 to 5 times the half-life for a drug's serum concentration to reach steady state after regular dosing is started, stopped, or the dose changed. So, for example, digoxin has a half-life (or t 1 / 2 ) of 24–36 h; this means that a change in the dose will take the best part of a week to ...
In this situation it is generally uncommon to talk about half-life in the first place, but sometimes people will describe the decay in terms of its "first half-life", "second half-life", etc., where the first half-life is defined as the time required for decay from the initial value to 50%, the second half-life is from 50% to 25%, and so on.
Its significance is due to both its short half-life and the emission of positrons when decaying. A major medical use of fluorine-18 is: in positron emission tomography (PET) to image the brain and heart; to image the thyroid gland; as a radiotracer to image bones and seeking cancers that have metastasized from other locations in the body and in ...
The half-life of a radioactive isotope (usually denoted by t 1/2) is a more familiar concept than the mean-life, so although the equations above are expressed in terms of the mean-life, it is more usual to quote the value of 14 C 's half-life than its mean-life. The currently accepted value for the half-life of 14 C is 5,700 ± 30 years. [21]
Phosphorus-32 only exists in small quantities on Earth as it has a short half-life of 14 days and so decays rapidly. Phosphorus is found in many organic molecules , and so, phosphorus-32 has many applications in medicine , biochemistry , and molecular biology where it can be used to trace phosphorylated molecules (for example, in elucidating ...
Iodine-123 (123 I) is a radioactive isotope of iodine used in nuclear medicine imaging, including single-photon emission computed tomography (SPECT) or SPECT/CT exams. The isotope's half-life is 13.2232 hours; [1] the decay by electron capture to tellurium-123 emits gamma radiation with a predominant energy of 159 keV (this is the gamma primarily used for imaging).
Osmium is very rare, substantially more so than any element essential to life. [3] The oxide is toxic to humans. [11] oxygen: 8: 5: Ubiquitous, essential for all forms of life; essentially all biological molecules (not to mention water) contain substantial amounts of oxygen. [11] In high concentrations, oxygen toxicity can occur. palladium: 46: 2a
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.