A patient's thyroid is counted with the thyroid probe and produces 8000 counts.Then the patient is removed and background is found to be 2000 counts.The (net counts) ± (standard deviation in the net counts) in this patient is

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Background counts are a problem in most measurements of counts from a radioactive sample.Background arises from natural terrestrial and cosmic sources of radioactivity or from other nearby sources of radioactive material.The sample is usually counted in the presence of some background radiation, yielding a gross count for sample plus background, denoted by the letter C.The sample is then removed from the counter, and the background B is counted.The net, or true counts, which represents the sample only, is denoted by N and given by:
N = C - B
The standard deviation of the net counts is given by: 11ea6816_3f23_ee47_b611_c74622c44853_TB6242_11 This is an example of the rules for combinations of errors, which states that for addition or subtraction, errors add in quadrature within the square root: 11ea6816_3f23_ee48_b611_7f61178f7986_TB6242_11 Additionally, since 11ea6816_3f23_ee49_b611_d9be56debfb9_TB6242_11 and 11ea6816_3f24_155a_b611_614c64ea046c_TB6242_11 we obtain 11ea6816_3f24_155b_b611_f30a5fb0e81e_TB6242_11

A Patient's Thyroid Is Counted with the Thyroid Probe and Produces