Tc-99m MAA SPECT in pectus excavatum: assessment of perfusion volume changes after correction by the Nuss procedure

The Nuss procedure is a minimally invasive technique for the repair of pectus excavatum. This investigation attempted to assess the impact of this corrective protocol on pulmonary functional volume through analysis of distribution volume data derived from Tc-99m MAA SPECT.

SPECT was performed in 3 patients before and 6 months after completion of the Nuss procedure. Before the clinical application of SPECT, phantom experiments were conducted to establish the threshold level based on the volume calculation program. Haller's index, a quantitative index of chest-wall deformity, was also obtained by x-ray CT.

A threshold level of 30% was the most accurate determinant of pulmonary volume. Preoperative and postoperative Tc-99m MAA distribution volumes (MAA volume in mL) were 2812 and 3107 (an increase of 10%), 2212 and 2410 (9%), and 2341 and 2872 (23%), respectively. In all patients, MAA volume increased after corrective intervention. Changes were most striking in the left lung, which is affected to a greater extent by dislocation of the heart. Morphologic improvement in the lungs was also demonstrated by Haller's CT index in all patients, which decreased from 4.35, 3.52, and 10.67, preoperatively, to 3.45, 2.75, and 4.25, respectively, postoperatively.

MAA volume assessment is an easy, suitable approach for detection of favorable changes produced by the Nuss procedure in pectus excavatum.