Comparison of99mTc-Technegas SPECT with133Xe dynamic SPECT in pulmonary emphysema

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Abstract
This study was undertaken to compare axial images of99mTc-Technegas SPECT (Technegas) with those of133Xe gas dynamic SPECT in patients with pulmonary emphysema. There were 20 patients, 19 males and 1 female. All patients except one ex-smoker were heavy smokers with a mean age of 68.1 years. For Technegas scintigraphy, the patients inhaled 505 MBq99mTc-Technegas in several tidal volume breaths in the supine position without breath holding. For133Xe gas scintigraphy, the patients inhaled 370 MBq133Xe gas.133Xe gas dynamic SPECT was performed in the equilibrium phase for the last minute of the 3 minute inhalation in a closed circuit, and in the washout phase for 6 minutes of inhalation in a semi-closed circuit, by means of a gamma camera with dual detectors (Picker model Prism 2000). Abnormal findings included heterogeneity, defects and hot spots on Technegas images and on retention images taken 3 minutes after133Xe gas washout. In 2 of 20 patients, the degree of abnormal findings on Technegas images depended on the area of133Xe gas retention in the washout phase. In 3 patients, the degrees of abnormal findings on both Technegas SPECT and133Xe gas dynamic SPECT images were equivalent. In the remaining 15 patients, more detailed findings and a greater area were shown by Technegas SPECT than133Xe gas dynamic SPECT. We conclude that in patients with pulmonary emphysema Technegas SPECT can demonstrate ventilation impairment more easily than133Xe gas dynamic SPECT.