Comparison of computed density and macroscopic morphometry in pulmonary emphysema.

TLDR

The study aimed to determine whether the relative area of low‑attenuation lung on high‑resolution CT could quantify macroscopic emphysema and to identify how many scans are needed for accurate measurement. Researchers performed 1‑cm‑interval HRCT scans on 63 subjects, calculated the relative area below eight attenuation thresholds (–900 to –970 HU) using a semiautomatic method, and compared these values to morphometric measurements from paper‑mounted lung sections taken every 1–2 cm, also testing the effect of reducing scan numbers at the –950 HU threshold. Only the –950 HU threshold showed no significant difference between CT and morphometric data, and because patient‑to‑patient variation was large, no optimal scan interval could be recommended.

Abstract

High-resolution computed tomography (HRCT) scans were obtained at 1 cm intervals in 63 subjects referred for surgical resection of a cancer or for transplantation to find out whether the relative area of lung occupied by attenuation values lower than a threshold would be a measurement of macroscopic emphysema. Using a semiautomatic procedure, the relative areas occupied by attenuation values lower than eight thresholds ranging from -900 to -970 HU were calculated on the set of scans obtained through the lobe or the lung to be resected. The extent of emphysema was quantified by a computer-assisted method on horizontal paper-mounted lung sections obtained every 1 to 2 cm. The only level for which no statistically significant difference was found between the HRCT and the morphometric data was -950 HU. To determine the number of scans sufficient for an accurate quantification, we recalculated the relative area occupied by attenuation values lower than -950 HU on progressively fewer numbers of scans and investigated the departure from the results obtained with 1 cm intervals. Because of wide variations in this departure from patient to patient, a standard cannot be recommended as the optimal distance between scans.