| Research Abstract |
Pulmonary washout study of xenon-l33 gas (Xe-133) is sensitive in detecting regional ventilatory abnormalities in both large and small airways, and has been widely used for ventilation study in various lung disease. However, the planar imaging study is difficult to obtain multidirectional views using planar imaging. and its two-dimensional character inherently limits its accuracy, because of the overlapping of Xe-133 activity among lesions, . normal lungs and chest wall. To obtain tomographic imaging for accurately assessing regional ventilation abnormalities, we developed dynamic Xe-133 single-photon emission computed tomography (SPECT) imaging acquired by a triple-detector SPECT system with a continuous repetitive rotating acquisition mode. The dynamic Xe-133 SPECT imaging provided good image quality without noticeable artifacts, despite the relatively rapid changes of Xe-133 activity in the lungs. T1/2 values and functional MTT images were used for quantitative analysis for regional
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Xe-133 washout delay. This technique was superior to chest CT scan in detecting regional ventilation abnormalities in patients with obstructive disease. Furthermore, we developed topographic three-dimensional (3D) display of Xe-133 SPECT to simplify the interpretation of multislice data of Xe-133 SPECT.The extent of Xe-133 could be quantified by Xe-133 retention index. The 3D SPECT imaging provided an overview of the distributions of Xe-133 retention sites with geometric realism, and enhanced the perception of anatomic sizes and configurations compared to multiple tomograms. This topographic 3D imaging was potential useful for selecting resection targets in candidates for LVRS and for monitoring the treatment effects on regional ventilation, and there was a good correlation between the Xe-133 retention index and lung function tests before and after the surgery. In the process of this study, we simultaneously investigated the usefulness of surface-rendering 3D images for Tc- 99m-MAA, the usefulness of pulmonary dynamic densitometry (PDD) acquired by spiral computed tomography (CT) to detect ventilation abnormalities in obstructive airway disorders, and the interactions between respiratory motions of the chest wall/diaphragm. in comparison with dynamic Xe-133 SPECT study. Thus, this modality including 3-D display can be an excellent new tool for qualifying and quantifying the nature of ventilation abnormalities in varius lung diseases . Less
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