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Calculation of Noise-Effective Image Quality

IP.com Disclosure Number: IPCOM000012070D
Publication Date: 2003-Apr-04
Document File: 3 page(s) / 46K

Publishing Venue

The IP.com Prior Art Database

Abstract

PET scanners are often classified by the performance metric known as noise-effective count rate (“NECR”). The National Electrical Manufacturing Association committee has declared this metric to be broadly applicable in aiding classification of machine performance for whole-body PET. This performance metric does not account for the image reconstruction process and is for a single, simple but well-defined phantom that does not adequately represent scanner performance over the range of expected clinical application. The methods described below will allow cross-comparison between scanner designs, including use of alternative scintillator materials, by using a metric defined as noise-equivalent image quality (“NEIQ”). NEIQ uses the essence of NECR, in that the scanner performance shall be generated at multiple points on a scanner’s NECR curve.

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FIELD OF TECHNOLOGY:

Positron Emission Tomography (PET)

INVENTION TITLE:

Calculation of Noise-Effective Image Quality

PROBLEM/BACKGROUND:

It is common to classify PET scanners by the performance metric known as noise-effective count rate (“NECR”) [1].� The National Electrical Manufacturing Association (“NEMA”) committee [2] has declared this metric to be broadly applicable in aiding classification of machine performance for whole-body PET.� Using the NECR metric, the scanner performance specification, including the peak NECR, can be determined by imaging a well-defined phantom with a well-defined protocol.� See Figure 1 for an example plot of NECR as a function of activity concentration in this newly designed PET scanner.

Figure 1. NEMA count-rate curve for this PET scanner. Note in particular how the true coincidence count rate peaks at a well-defined activity concentration for this phantom.

This NECR performance metric, while considered correlated with resultant image quality due to prediction of optimal true coincidence count rates, does not account for the image reconstruction process.� Further, this method is for a single, simple but well-defined phantom that does not adequately represent scanner performance over the range of expected clinical application.� As a result, it has been determined that imaging without septa (3D) results in a higher NECR than that found while in 2D mode, although no scientific evidence shows improvement in the resultant image quality.� Indeed, most studies [2-4.] have shown that at best, 3D mode allows equivalent lesion detection with 2D mode.� The method described herein expands on the concept of NECR as a performance metric, but it can be used for protocol optimization, system design and resultant image quality assessment.

[1]        � � S.C. Strother, M.E. Casey and E.J.� Hoffman, “Measuring PET Scanner Sensitivity: Relating Count rates to Image Signal-to-Noise Ratios using Noise Equivalent Counts,” IEEE Trans. Nucl. Sci., vol. 37, pp. 783-8, 1990.

[2]        � � “Capabilities of two- and three-dimensional FDGPET for detecting small lesions and lymph nodes in the upper torso: a dynamic phantom study”, R. Raylman et al., EJNM, volume 26, issue 1 (1999) pp 39-45.

[3]        � � Farquhar TH, Llacer J, Hoh CK, et al. ROC and localization ROC analyses of lesion detection in whole-body FDG PET: effects of acquisition mode, attenuation correction and reconstruction algorithm. J Nucl Med. 1999;40:2043–2052.

[4]        � � Raylman, R.R, et al., “Capabilities of two- and three-dimensional FDG-PET for detecting small lesions and lymph nodes in the upper torso: a dynamic phantom study,” EJNM, 26 (1) 39-45 Jan 1999.

INVENTION DESCRIPTION:

The methods described below will allow cross-comparison between scanner designs, including use of alternative scintillator materials, by using a metric defined as noise-equivalent image quality (“NEIQ”).� NEIQ uses the essence of NECR, in that the scanner performance shall be generated a...