SLIDING THIN SLAB, MINIMUM INTENSITY PROJECTION TECHNIQUE IN THE DIAGNOSIS OF EMPHYSEMA - HISTOPATHOLOGIC-CT CORRELATION

PURPOSE: To assess the accuracy of sliding thin slab, minimum intensit y projection technique in the detection of emphysema. MATERIALS AND ME THODS: In 29 patients without radiographic evidence of emphysema and w ho were undergoing lung resection, focal spiral computed tomography (C T) was performed in the lobe to be resected. Ten contiguous 1-mm-thick CT scans and sliding thin slab, minimum intensity projection images w ith slab thicknesses of 3-, 5-, and 8 mm were generated. From each ima ge, the presence and extent of emphysema were recorded before histopat hologic analysis was performed. To familiarize readers with the appear ance of normal lung parenchyma on sliding thin slab, minimum intensity projection images, five asymptomatic volunteers underwent scanning wi th a similar protocol. RESULTS: Emphysema was present on both thin-sec tion CT scans and sliding thin slab, minimum intensity projection imag es in 13 patients. In all cases, sliding thin slab, minimum intensity projection images improved conspicuity of small areas of hypoattenuati on. When thin-section CT scans were negative (n = 16), sliding thin sl ab, minimum intensity projection images enabled identification of foca l zones of hypoattenuation in four cases with histologic confirmation of emphysema. Sensitivity of thin-section CT (62%) and sliding thin sl ab, minimum intensity projection technique (81%) were significantly di fferent (P < .01); specificity for both was 100%. Emphysema was easier to detect on 8-mm-thick slabs because of better suppression of vascul ar structures. CONCLUSION: The sliding thin slab, minimum intensity pr ojection technique enabled improved detection of mild forms of emphyse ma.