Estimation of regional lung function in interstitial pulmonary disease using Tc-99m-Technegas and Tc-99m-macroaggregated albumin single-photon emission tomography

For quantitative evaluation of the regional lung function in patients with interstitial pulmonary disease (IP) in the sitting position, Tc-99m-Techneg as and Tc-99m-macroaggregated albumin (MAA) single-photon emission tomograp hy (SPET) studies were performed in 12 healthy controls (HC) and 42 IP pati ents. Four transverse images were prepared from the data obtained and desig nated as slices no. 1-4 from the top downward. Regions of interest (ROIs) w ere determined in the anterior and posterior parts of the lung in each slic e, and the ratio of the count per voxel in the ROIs to the count in the ent ire lung was calculated as the regional Technegas index (T). The regional p erfusion index (Q) was calculated by a similar procedure using the data of Tc-99m-MAA SPET. The ratios between T and Q (T/Q) in the anterior and poste rior regions of the lung, and the ratios of T and Q between the anterior an d posterior regions of the lung (Tp/Ta and Qp/Qa) were examined. In the HC group, T/Q decreased but Tp/Ta and Qp/Qa increased from the upper re the lo wer lung fields. When IP patients were classified into (I) those in whom T/ Q decreased from the upper to the lower lung fields, (II) those in whom it was similar in all slices, (III) those in whom it increased from slice 3 to slice 4, and (IV) those in whom it increased from slice 2 to slices 3 and 4, this classification was more closely correlated with %VC than with %DLCO or PaO2. When the patients were classified according to Tp/Ta and Qp/Qa in to (A) those in whom the values were greater in the lower than the upper lu ng field, (B) those in whom the values were similar in all slices, and (C) those in whom the values were smaller in lower than in upper lung fields, c ategories B and C were observed frequently even in patients whose %VC was i n the normal range. This method is considered to be an effective means to e valuate the progression and pathology of IP and to detect early impairment of lung function.