DYNAMIC PULMONARY SPECT OF XE-133 GAS WASHOUT

A triple-detector SPECT data acquisition mode of ''continuous repetiti ve rotation acquisition'' was applied to dynamic pulmonary SPECT with Xe-133 gas. Methods: Subjects included 7 healthy volunteers, 22 patien ts with a space-occupying mass lesion, 22 with obstructive lung diseas e and 10 with restrictive lung disease, Following rebreathing of Xe-13 3, equilibrium and washout SPECT images during spontaneous breathing w ere acquired every 30 sec for 5-7 min. Regional Xe-133 washout was ass essed by the real half-time (T-1/2) and mean transit time (MTT) images . Results: SPECT and MTT images represented a gravity-induced gradient of ventilation in normal lungs and detailed the distribution of heter ogeneous Xe-133 washout in patient's lungs with or without abnormaliti es on chest x-ray CT. The T-1/2 (111.4 +/- 26.4 sec) and its coefficie nt of variation (0.36 +/- 0.13) in obstructive lung diseases were sign ificantly different from those (56.8 +/- 3.9 sec and 0.16 +/- 0.15) in restrictive lung diseases (p < 0.001, p < 0.05, respectively). Compar ison of SPECT and planar studies assessed in 19 patients revealed supe riority of SPECT in detecting ventilatory abnormalities and a high cor relation of T,, between the two studies (r = 0.977, p < 0.001). Conclu sion: This modality has excellent potential for elucidating the distri bution and nature of ventilatory abnormalities.