Current status of respiratory nuclear medicine

Multimodality image fusion is now becoming popular in respiratory nuclear medical field, since scintigraphic diagnosis, based on functional image interpretation, becomes more accurate and meaningful when supported by corresponding anatomical data. Although SPECT/PET scanner-mounted X-ray tomographic systems are now being introduced for an accurate image fusion in the chest, the use of a fully automatic multi-modality image fusion algorithm may be an alternative method. Our initial attempt of this algorithm for fusion imaging of Tc-99m MAA perfusion or thallium-201 SPECT and helical CT scan has contributed to accurate interpretation of the results without user interaction, and has facilitated the understanding of the functional basis of lung parenchymal CT attenuation changes. Three-dimensional displays with functional mapping are also now being increasingly introduced to various respiratory nuclear studies. A fractal analysis has shown successful results in the analysis of technegas and 99mTc-MAA perfusion images, which will be increasingly applied for more objective assessment of the results. The feasibility of 18F-FDG PET scan in accurate staging of lung cancer and the good cost performance of this method in lung cancer strategy are repeatedly stressed by the recent studies. The feasibility of 99mTc-MAA perfusion scan in the evaluation of right-to-left shunt in patients with hepatopulmonary syndrome, and the potential of 123I-MIBG scan in the evaluation of the function status of pulmonary neuroadrenergic system are new aspects for these well established tracers. There is the first attempt of intraoperative 99mTc-colloid sentinel lymph node mapping in patients with resectable non-small cell lung cancer. This may improve the precision of pathologic staging and limit the need for mediastinal node dissection in selected patients. Radiolabeled aerosol lung scintigraphy is being increasingly applied to evaluate lung deposition of various aerosolized, therapeutic drugs. Newly developed radiotracers include L-3-123I-α-methyl-tyrosine for evaluating amino acid metabolism of lung cancer on SPECT scanner, 99mTc-labeled surfactant B for evaluating pulmonary surfactant system, Cu-DTS for imaging hypoxic tumor cells, and 18F-fluorocaptopril for evaluating the lung distribution of pulmonary angiotension converting enzyme. These will contribute to the further advancement and development of expiratory nuclear medicine. (author)