Lung perfusion quantification using a SPECT/CT-based semi-automated segmentation workflow rather than planar perfusion scintigraphy

Introduction: Predicting postoperative lung function prior to surgical resection or lung transplantation is of paramount importance in surgical planning. In this setting, lung perfusion quantification has been established as a useful marker of postoperative lung function. Traditionally, lung perfusion has been determined using 2D planar perfusion scintigraphy. However, planar imaging does not account for the obliquity of the lung fissures. As such, planar imaging provides non-anatomic quantification of lung regions (upper, middle, and lower) rather than individual lobes, a limitation of particularly importance when planning partial lung resection. Quantification using SPECT/CT overcomes these limitations by enabling anatomic 3D lung segmentation guided by the accompanying CT. Herein, we study a novel method to quantify pulmonary perfusion using SPECT/CT and validate the method against planar imaging for whole lungs.

Methods: In this single center study of 8 patients, SPECT/CT imaging of the chest was acquired after intravenous injection of technetium-99m–labeled macroaggregated albumin (X mCi). The CT was obtained in shallow respiration to optimize registration between the CT and SPECT . A semi-automated quantification segmentation workflow (SPECT Lung Quant, MIM software Inc, Beachwood, OH, USA) was applied to the SPECT and CT data to calculate anatomic lobar perfusion counts and percentages. Following SPECT/CT, planar images of the chest were obtained in the anterior and posterior projections; whole lung and regional perfusion (upper, middle, lower) were calculated. Whole lung and regional perfusion from the SPECT/CT and planar methods were compared using the Pearson correlation.

Results: There was strong correlation of whole lung pulmonary perfusion between the SPECT/CT and the planar method (right and left lung Pearson r² =0.98: p-value <0.001). Regional perfusion on planar imaging did not correlate as strongly with lobar perfusion on SPECT/CT. For example, the right upper lobe perfusion SPECT/CT and planar methods showed no statistically significant correlation (Pearson r² = 0.37; p-value = 0.11).

Conclusions: SPECT/CT lung perfusion quantification provides the ability to quantify lobar pulmonary perfusion. A strong correlation of whole lung perfusion between SPECT/CT and a planar method supports the validity of the SPECT measurements. In our primary institution, pulmonary perfusion with SPECT/CT using this semi-automated segmentation workflow has replaced planar imaging. Referring physicians are preferentially sending their patients for these SPECT/CT studies. We expect lobar perfusion data from SPECT/CT to impact pre-operative planning and better predict postoperative clinical outcomes in patients with compromised lung function.