The combination of the new radiolabeled antibody agents and single photon emission computed tomographic (SPECT) imaging promises to significantly improve tumor detection and the delineation of disease state. SPECT quantitation with these radiopharmaceuticals will be useful for computing radionuclide therapeutic doses, monitoring therapy, and obtaining in vivo kinetic data. The clinical achievement of these goals is, however, limited by the image quality obtained when imaging the medium to high energy photon emitting radionuclides with which these agents have been labeled. The goal of this grant is to develop and test methods of three-dimensional (3-D) digital image restoration to be employed post-reconstruction which will reduce the effects of septal penetration, scatter, and spatial resolution losses while suppressing noise; all in a balanced manner. Three-D post- reconstruction filtering will be the focus of the proposed investigation because the use of a single or limited number of transfer functions should be a good approximation to use when deconvolving the images. The dependence of the transfer functions on phantom size and shape, and position within a given phantom will first be ascertained for In-111 and Ga-67. These transfer functions will then be used in the implementation and optimization of stationary and nonstationary versions of the constrained least-squares (CLS) and Metz filters. The Metz filter investigated will be our new image-dependent formulation. The optimization criteria employed will be the normalized mean square error as calculated both with and without gradient prefiltering to enhance the recovery of edges. An initial test of the performance of these filters according to standard measures of spatial resolution, image contrast, noise level, and processing time will be conducted to select those deemed suitable for further study. The selected filters will then be tested to determine their utility in facilitating tumor detection, volume estimation, and quantitation of activity. Tumor detection will be assessed via receiver operating characteristics (ROC) methods using SPECT images of the Alderson Organ Scanning Phantom. A study of volume quantitation in images of extended organs, and spheres covering a range of sizes will be conducted. A modified post- reconstruction attenuation correction technique will be developed and used to compare the quantitation of activity in terms of the linearity of quantitation, recovery coefficients, and the cross-talk index.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Diagnostic Radiology Study Section (RNM)
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University of Massachusetts Medical School Worcester
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King, Michael; Farncombe, Troy (2003) An overview of attenuation and scatter correction of planar and SPECT data for dosimetry studies. Cancer Biother Radiopharm 18:181-90
King, Michael A; Pretorius, P Hendrik; Farncombe, Troy et al. (2002) Introduction to the physics of molecular imaging with radioactive tracers in small animals. J Cell Biochem Suppl 39:221-30
Wells, R G; King, M A; Simkin, P H et al. (2000) Comparing filtered backprojection and ordered-subsets expectation maximization for small-lesion detection and localization in 67Ga SPECT. J Nucl Med 41:1391-9
Gifford, H C; King, M A; de Vries, D J et al. (2000) Channelized hotelling and human observer correlation for lesion detection in hepatic SPECT imaging. J Nucl Med 41:514-21
Gifford, H C; King, M A; Wells, R G et al. (2000) LROC analysis of detector-response compensation in SPECT. IEEE Trans Med Imaging 19:463-73
de Vries, D J; King, M A; Soares, E J et al. (1999) Effects of scatter substraction on detection and quantitation in hepatic SPECT. J Nucl Med 40:1011-23
Wells, R G; Simkin, P H; Judy, P F et al. (1999) Effect of filtering on the detection and localization of small Ga-67 lesions in thoracic single photon emission computed tomography images. Med Phys 26:1382-8
Pretorius, P H; King, M A; Pan, T S et al. (1998) Reducing the influence of the partial volume effect on SPECT activity quantitation with 3D modelling of spatial resolution in iterative reconstruction. Phys Med Biol 43:407-20
Ljungberg, M; King, M A; Hademenos, G J et al. (1994) Comparison of four scatter correction methods using Monte Carlo simulated source distributions. J Nucl Med 35:143-51
Glick, S J; Hawkins, W G; King, M A et al. (1992) The effect of intrinsic attenuation correction methods on the stationarity of the 3-D modulation transfer function of SPECT. Med Phys 19:1105-12

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