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# A GAIN CALIBRATION ALGORITHM FOR POSITRON EMISSION TOMOGRAPHY

IP.com Disclosure Number: IPCOM000124116D
Publication Date: 2005-Apr-08
Document File: 5 page(s) / 60K

## Publishing Venue

The IP.com Prior Art Database

## Abstract

In an embodiment, a gain calibration algorithm includes the following steps. Find peak by a conventional method, and denote it by found_peak_location; in the range [8, 253]. Find peak_count, which is the maximum count in the neighboring 3 bins around the found_peak_location. Calculate the ratio of the normalized bin253 to peak count in percentage, denote by bp253, wherein bp253 = 100.0 * (bin253/129.0) / peak_count. If the location of the found peak is high (say greater than 60% of the target peak location), then keep the found peak, since a lower DAC will not produce a false high peak. If the energy in bin253 is small keep the found peak, since very likely this peak is valid, whether low or high.

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A GAIN CALIBRATION ALGORITHM FOR POSITRON EMISSION TOMOGRAPHY

FIELD OF THE INVENTION

[0001]               This invention relates generally, to a gain calibration algorithm in positron emission tomography (PET).

BACKGROUND OF THE INVENTION

[0002]               Conventionally, when the DAC value is so high that it pushes the peak of the energy spectrum beyond bin 252, the gain calibration algorithm will sometimes identify a false peak at the lower bin range.  Two outcomes can result from this false peak location. Firstly, the false peak falls in the “normal peak” range (20-250) and a positive DAC change will “be needed”, thus pushing the DAC value even higher.  Secondly, which is mostly the case, the false peak falls outside the normal peak range (less than 20), and the old (and high) DAC value remains the same.  In either situation, the high DAC does not get a chance to become lower as a result of the low false peak.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003]                 FIG. 1 shows a graphical representation of the DAC change in connection with the gain calibration algorithm according to one embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0004]    Various embodiments of this invention provide a gain calibration algorithm in PET.  However, the embodiments are not limited and may be implemented in connection with other medical imaging systems.

[0005]                 In an embodiment, a gain calibration algorithm includes the following steps.

[0006]               Find peak by a conventional method, and denote it by found_peak_location; in the range [8, 253].

[0007]               Find peak_count, which is the maximum count in the neighboring 3 bins around the found_peak_location.   Calculate the ratio of the normalized bin253 to peak count in percentage, denote by bp253, wherein bp253 = 100.0 * (bin253/129.0) / peak_count.

[0008]               If the location of the found peak is high (say greater than 60% of the target peak location), then keep the found peak, since a lower DAC will not produce a false high peak.  If the energy in bin253 is small keep the found peak, since very likely this peak is valid, whether low or high.

[0009]               However, when bin253 has significant energy, combined with a modest or very low peak location, then there exists a need to determine if this peak is false.  If false, then it should be replaced by a high peak location, in order to at least force the sign of the DAC change.

[0010]               The following pseudo code illustrates what conditions to intervene.

[0011]                /* will not change the found pe...