Regional VA/Q ratios in man using 133Xe and single photon emission computed tomography (SPECT) corrected for attenuation.
We describe a technique to obtain non-invasively regional pulmonary ventilation-perfusion ratios (VA/Q) using single photon emission computed tomography (SPECT) and continuous infusion of 133Xe. Single photon transmission tomography was used for attenuation correction, for delineation of the lungs and for VA/Q calculations. Data are presented for six normal subjects and compared to those for two patients with moderate chronic obstructive pulmonary disease (COPD). The mean VA/Q for the whole lung of the normal subjects ranged from 0.49 to 0.65, group mean 0.56 +/- 0.07 (1 SD), and there was no significant difference between the right and left lung. The consistently too low VA/Q values are related to the inability to measure regional blood volume and the low resolution of the scintillation camera, giving an under-estimation of tracer input. For the normal subjects, the dispersion of VA/Q, as defined by the standard deviation of the individual distribution functions, ranged from 0.12 to 0.19. One of the patients was characterized by a low mean VA/Q of 0.35, and the other patient had a wide dispersion (SD) of VA/Q of 0.37. In the normal subjects, a consistent VA/Q gradient was found only in the ventrodorsal direction. 133Xe and SPECT can be used to obtain meaningful biological information regarding ventilation/perfusion relationships of potential clinical value.
Almquist
H
H
Department of Clinical Physiology, University Hospital, Lund, Sweden.
Jonson
B
B
Palmer
J
J
Valind
S
S
Wollmer
P
P
D000328:Adult; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015899:Tomography, Emission-Computed, Single-Photon; D014692:Ventilation-Perfusion Ratio; D014980:Xenon Radioisotopes
D014980:Xenon Radioisotopes