Abstract
Planar perfusion scintigraphy with Tc99m-labelled macroaggregated albumin (Tc99m-MAA) is often used for pre-therapy quantification of regional lung perfusion in lung cancer patients, particularly in patients with poor respiratory function. However, subdividing lung parenchyma in rectangular regions of interests, as done on planar images, is a poor reflection of true lobar anatomy. New tridimensional methods using SPECT and SPECT/CT have been introduced, including a semi-automatic lung segmentation software (Hermes Medical Solutions). The present study evaluates inter- and intraobserver agreement of quantification using a SPECT/CT software, and compares results of regional lung contribution obtained with SPECT/CT and planar scintigraphy. Methods: Thirty (30) lung cancer patients underwent ventilation perfusion (V/Q) scintigraphy with Tc99m-MAA and Tc99m-Technegas. Regional lung contribution to perfusion and ventilation was measured on both planar scintigraphy and SPECT/CT using a semi-automatic lung segmentation software by two observers. Interobserver and intraobserver agreement for SPECT/CT software were assessed using intra-class correlation coefficient (ICC), Bland Altman plots, and absolute differences of measurements. Measurements from planar and tridimensional methods were compared using paired sample t-tests, and mean absolute differences. Results: ICC were in the excellent range (above 0.9) for both interobserver and intraobserver agreement using the SPECT/CT software. Bland Altman analyses showed very narrow limits of agreement. Absolute differences were below 2.0% in 96% of both interobserver and intraobserver measurements. There was a statistically significant difference between planar and SPECT/CT methods (P<.001) for quantification of perfusion and ventilation for all right lung lobes, with a maximal mean absolute difference of 20.7% for the right middle lobe. There was no statistically significant difference for quantification of perfusion and ventilation for left lung lobes using both methods, however absolute differences reached 12.0%. Total right and left lung contribution were very similar using both methods, with a mean difference of 1.2% for perfusion and 2.0% for ventilation. Conclusion: Quantification of regional lung perfusion and ventilation using a SPECT/CT-based lung segmentation software is highly reproducible. This tridimensional method yields statistically significant differences in measurements for right lung lobes when compared to planar scintigraphy. We recommend that SPECT/CT based quantification be used for all lung cancer patients undergoing pre-therapy evaluation of regional lung function.