783620H / 1013 6. ANALYSIS METHODS
Standard reports have a “Summary of Peaks in Range” section that displays potential library matches and associated activity concentration for each peak found during analysis.
For more information on library reduction during ENV32 analyses, see Section 6.2.3.
6.2.1.5. ROI32
The ROI32 analysis engine operates on the entire spectrum, performing an ROI analysis on usermarked ROIs and a modified WAN32 analysis (no peak stripping or directed fit) on unmarked regions. You can either mark ROIs on a live or retrieved spectrum, then use the Analyze/Entire
Spectrum in Memory command; or use the Analyze/Spectrum on Disk command on a spectrum file in which ROIs have already been marked and saved.
ROI Analysis
1) The ROI center is used to calculate the ROI peak energy using the existing energy calibration. If the ROI peak energy is within the match width of a library peak, then the ROI will be used. Otherwise, the ROI will be ignored. In other words, do not mark an ROI around
unknown peaks.
2) To calculate the ROI peak background, you can set the number of background points to be used at 1, 3 or 5 on the Sample tab under Analyze/Settings/Sample Type.... If Auto back-
ground is selected, then 5 points will be used always. The background points to be used for the background calculation are within the selected ROI region, not adjacent and outside the
ROI region.
3) The background of the ROI peak is calculated as:
(22)
where:
L = the lowest-energy channel of the ROI
H = the highest-energy channel of the ROI
N = 1, 3, or 5, depending on the background method chosen, as discussed above. and the sum of background counts on the low and high end of the ROI, B
1
and B
2
, respectively, are given by:
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