Three-dimensional fusion of pulmonary SPECT and CT images using multimodality devices.

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A phantom study was conducted to evaluate the feasibility of body contour definition using Compton scatter photons from external sources of technotium-99m pertechnotate (Tc-99m) to create a fusion image of CT and SPECT images. External sources from 1 mCi (37MBq) Tc-99m were placed on each collimator, and body-contour SPECT images were obtained using an energy window of 100 kcV±25% for detecting 90°and 180°Compton scatter photons of Tc-99m from the body surface in water-filled cylindrical and hexagonal phantoms, and in a chest phantom with a Tc-99m-avid simulated lung nodule and multimodality surface markers. In the chest phantom, each transaxial SPECT slices was registered with the corresponding CT slice using image-matching soft-ware. A summation of the registered images yielded a three-dimensional (3-D) fusion image of this phantom. This method clearly visualized the body contour on all the SPECT slices in all the phantoms except for the complex hexagonal phantom. There was no signif … More icant difference between known and SPECT-measured diameters of the cylindrical phantom. The fit of CT and SPECT images of the chest phantom was achieved with a mean alignment error of 5% in visual inspection, which was improved to 0.2% after correction of the magnification of the SPECT images according to the resultant dimensional differences. The 3-D fusion image of this phantom effectively visualized the anatomic location of the lung nodule and surface markers. This simple method effectively provided boundary information of the cold phantoms. Although further improvements of the regisration technique with CT images are desirable, the body-contour SPECT images obtained by this method has the potential for accurately creating a 3-D fusion image with CT images, and is a very feasible way anticipating the anatomical localization of a target tissue. In addition to these experimental study, the usefulness of three-dimensional Xenon-133 SPECT imaging in the evaluation of lung ventilation impairments in patients with lung cancer and in the assessment of resection targets for lung volume reduction surgery in patients with pulmonary emphysema were clinically evaluated. The associations between abnormal diaphragm/chest wall motions and regional ventilation in pulmonary emphysema was also evaluated by interstudy comparison of breathing magnetic resonance (MR) imaging and three-dimensional Xenon-133 SPECT. The results showed that this three-dimensional image was useful for the evaluation of abnormal ventilation in patients with lung cancer, and for the detection of resection targets and assessments of therapeutic effects of the reduction surgery in patients with pulmonary emphysema. The correlations between (MR) imaging and three-dimensional Xenon-133 SPECT indicate the close associations between abnormal mobility or coordination of diaphragm/chest wall motions and abnormal ventilation in each hemithorax in patients with pulmonary emphysema. Less