Gallium-67 lung index computerization in interstitial pneumonitis

To improve ease of use, precision, and reduce interobserver variability of the 67Ga lung index, we developed and tested a computer method that yields similar numeric values and uses previous indexing principles, except that the computer matrix unit is the fractional area assessed. Patients were referred for suspected interstitial lung disease. Fifty-three image studies were available for both manual and computer indexing. Linear regression analysis gave a correlation of 0.884. Decision matrix analysis of 58 different nonimmunosuppressed patients resulted in 93% sensitivity and 76% specificity. Receiver operating characteristic curve analysis showed that the ideal index cutoff was 50. Because there is tighter control over 67Ga uptake intensity and spatial distribution assessment, the computerized 67Ga index appears to perform better than the manual analysis.