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Target definition of moving lung tumors in positron emission tomography: Correlation of optimal activity concentration thresholds with object size, motion extent, and source-to-background ratio
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10.1118/1.3315369
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    Affiliations:
    1 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, University of Texas, Houston, Texas 77030
    2 Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
    3 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
    4 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Department of Biostatistics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
    5 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, University of Texas, Houston, Texas 77030
    6 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
    7 Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
    8 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and GE Healthcare, Waukesha, Wisconsin 53188
    9 Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030
    a) Author to whom correspondence should be addressed. Electronic mail: tpan@mdanderson.org; Telephone: 713–563–2714; Fax: 713–563–2720.
    Med. Phys. 37, 1742 (2010); http://dx.doi.org/10.1118/1.3315369
/content/aapm/journal/medphys/37/4/10.1118/1.3315369
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/4/10.1118/1.3315369

Figures

Image of FIG. 1.
FIG. 1.

End inspiration phase of 4D-CT, end-expiration phase of 4D-CT, and PET images of moving lung tumor. All images are coronal slices. Note the blurred appearance of the moving tumor in the PET image, which is acquired over several breathing cycles.

Image of FIG. 2.
FIG. 2.

Experimental setup. (a) Motion platform and actuator were placed on a flat tabletop with controlling laptop. (b) Phantom is placed on the table flush against a piece of Lucite anchored to the table for reproducibility. Hatch marks were placed on pieces of tape on the base and moving parts of the platform to ensure motion is accurate from scan to scan.

Image of FIG. 3.
FIG. 3.

Two spherical meshes are compared to the surface separation algorithm. From each sampling point on the “reference” mesh (in this case, the smaller sphere), the closest point on the other mesh surface is calculated.

Image of FIG. 4.
FIG. 4.

Axial, sagittal, and coronal PET images of a moving sphere, inner , motion , . PET contours are volumes segmented at different percentages of maximum activity concentration. These contours are compared to the reference volume contoured on cine CT using the surface separation algorithm. The threshold volume which minimizes the sum of squared deviations is the optimal threshold for that sphere volume, motion extent, and source-to-background.

Image of FIG. 5.
FIG. 5.

Optimal thresholds versus motion, source-to-background, and volume (denoted by different symbols). Threshold values are normalized to background. Error bars represent 1 standard deviation (3 measurements). Legend lists nominal sphere inner diameters.

Image of FIG. 6.
FIG. 6.

Optimal threshold versus source-to-background for stationary spheres. Each line represents a different sphere volume as denoted in the legend. Note the linear nature of the relationship. Error bars are 1 standard deviation (three measurements).

Image of FIG. 7.
FIG. 7.

Optimal threshold versus motion for source-to-. Each line represents a different sphere volume as denoted in the legend. Error bars are 1 standard deviation (three measurements).

Image of FIG. 8.
FIG. 8.

Optimal threshold versus volume for source-to-. Each line represents a different motion extent (0–30 mm). Error bars are 1 standard deviation (three measurements).

Image of FIG. 9.
FIG. 9.

Surfaces of regression function stated in Eq. (4). Each of the four surfaces displayed is calculated for (top) spheres of inner diameter 10, 17, 28, and 37 mm and (bottom) SBRs equal to 5:1, 20:1, 35:1, and 50:1.

Image of FIG. 10.
FIG. 10.

PET/CT images of patient 1 with PET-segmented volume (thin contour) and reference cine CT volume (thick contour). (A) 4D-CT phase image at end-expiration. (B) 4D-CT phase image at end-inspiration. (C) Maximum intensity projection. (D) Coronal PET/CT image. (E) Transverse PET/CT image.

Image of FIG. 11.
FIG. 11.

PET/CT images of patient 2 with PET-segmented volume (thin contour) and reference cine CT volume (thick contour). (A) 4D-CT phase image at end-expiration. (B) 4D-CT phase image at end-inspiration. (C) Maximum intensity projection. (D) Coronal PET/CT image. (E) Transverse PET/CT image.

Image of FIG. 12.
FIG. 12.

Reference volume for stationary sphere (inner ) compared to 35% maximum activity concentration of same volume sphere at 30 mm motion extent and source-to-. Note that the 35% threshold underestimates the axial extent of the sphere and overestimates the sagittal extent of the sphere, consistent with the findings of Okubo et al. (Ref. 18). The 35% threshold, however, underestimates the full motion envelope of the tumor.

Tables

Generic image for table
TABLE I.

Nominal and actual volumes and SBRs.

Generic image for table
TABLE II.

Regression coefficients for regression model in Eq. (2).

Generic image for table
TABLE III.

Application of threshold function to three lung cancer patients. Threshold is normalized to background measurement. Mean deviation is determined with surface separation algorithm.

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/content/aapm/journal/medphys/37/4/10.1118/1.3315369
2010-03-25
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Target definition of moving lung tumors in positron emission tomography: Correlation of optimal activity concentration thresholds with object size, motion extent, and source-to-background ratio
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/4/10.1118/1.3315369
10.1118/1.3315369
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