FIG. 2.

Panels illustrate the results. (A) PET deposition images for three subjects (first column) contrasted with images of activity estimated with the two methods: BW and Grayscale. The estimated images are created by multiplying the ROIs used in each method by the estimated regional specific activities. The color scale within each row is kept constant with the darkest red corresponding to the point with highest activity. Both methods assume uniform deposition within the AR, which tends to diffuse hotspots in the estimated images. However, the Grayscale method tends to reproduce location and magnitude of hotspots better than the BW method. Note that the activity on the esophagus (present in the lower two PET images) is not represented in the projections since it was not defined as an AR (see discussion). (B) The coefficient of determination of the two methods. In all subjects the description of deposition with the Grayscale method is closer to the PET image (p<0.0001) than with the BW method. (C) (Left) Projections of the ARs (at CT resolution) in blue overlaid with a projection of the deposition image (at PET resolution) in red. (Right) Projection of the estimated activity within the ARs (at CT resolution) using the Grayscale method. (D) The PI, TD, and ISC using Grayscale across lobes. Individual subject data are connected with dashed lines. The solid line is the average lobar values. No statistical difference was observed between a given lobe's TD. The LLL showed lower ISC than the lobes of the right lung (the strength of the line between the lobes under STATS indicates the strength of the P value).