How is net counts calculated?

Net counts are calculated by subtracting background counts from gross counts. Gross counts represent the total number of counts detected by the imaging system, including both the signal of interest and any background noise or unwanted signals. Background counts are the counts that arise from sources other than the specific signal being measured, such as inherent system noise or environmental interference.

By performing the calculation of gross counts minus background counts, you isolate the counts attributable to the actual signal of interest. This method ensures that the resulting net counts more accurately reflect the true quantitative measure of the tracer distribution in the region of interest, as it effectively removes extraneous data that could lead to misinterpretation of the results. This is particularly important in PET imaging, where the clarity of the signal is crucial for accurate diagnostic conclusions.