Detection of chronic rejection by quantitative ventilation scintigrams in lung-transplanted patients: a pilot study

The suspicion of chronic rejection [bronchiolithis obliterans syndrome (BOS)] is usually based on deteriorating forced expired volume in 1 s. It is however, desirable to develop more sensitive methods as increased anti-inflammatory therapy is thought to stop progression of the rejection. The aim of the present study was to develop quantitative tools based on ventilation scintigrams, to diagnose BOS. Sixteen double-lung-transplanted patients participated, six developing BOS and 10 who did not develop BOS. They were investigated with planar posterior-anterior (99m)Tc-Technegas (Tetley Manufacturing Ltd, Sydney, Australia) ventilation scintigraphy at baseline, 6 months to 1 year post-transplantation, and at a follow-up examination 3-4-year post-transplant or in the BOS patients close to the time of the diagnosis. An automatic region of interest (ROI) was drawn on each lung in the scintigraphic image at baseline and also applied to the follow-up investigation. The area inside the ROI was subdivided into stripes 10.8 mm high and squares 10.8 x 10.8 mm wide. Corresponding stripes and squares in baseline and follow-up were analysed regarding differences in relative retention. The results show that the square analysis is superior. Applying chosen cut-off values for square element differences, 6/6 right and 5/6 left BOS lungs were identified and one left and one right lung of patients not developing BOS were misclassified. We conclude that the square element difference appears to be a promising method to diagnose BOS.