Role of quantitative CT in predicting postoperative FEV1 and chronic dyspnea in patients undergoing lung resection

Abstract

Lung resection is the mainstay of treatment in patients with early stage non-small cell lung cancer. However, lung cancer patients often suffer from comorbidities and the respiratory reserve should be carefully evaluated preoperatively in order to avoid postoperative complications. Forced expiratory volume in 1 second (FEV1) is considered to be an index that depicts the patient's respiratory efficacy and its prediction has a key role in the preoperative evaluation of lung cancer patients with impaired lung function. Prediction of postoperative FEV1 is currently possible with the use of perfusion radionuclide lung scanning.Quantitative CT is the analysis of data acquired during normal chest CT scan using the system's software. By applying a dual threshold of -500 to -910 Hounsfield Units, functional lung volumes are estimated and postoperative FEV1 can be predicted by reducing the preoperative measurement by the fraction of the part to be resected.Studies have shown that preoperative predictions correlate well with the actual postoperative measurements. Additionally, quantitative CT results are in good agreement with perfusion scintigraphy predictions. Newer radiological techniques such as perfusion MRI and co-registered SPECT/CT have also been used in the preoperative evaluation with similar results.In conclusion, chest CT which is obligatory for staging, can be used for quantitative analysis of the already available data. It is technically simple, providing an accurate prediction of postoperative FEV1. Thus, quantitative CT appears to be a useful tool in the preoperative evaluation of lung cancer patients undergoing lung resection.

Figure 1

Quantitative Ct Volume Estimations. (A): Chest CT scan of a patient with a tumor in the left upper lobe. (B): and (C): Quantitative analysis of functional lung parenchyma of both lungs, using the dual threshold of -500 to -910 HU. Areas in blue correspond to voxels within these attenuation limits. Total functional lung volume of both lungs is estimated to be 3932.99 mL.

Figure 2

Volumetric Analysis of the Resected Lobe (Same Patient as in Figure 1). (A): Fissure identification between left upper and lower lobe. (B): Delineation of the region of interest (limits of the lobe to be resected) in all transaxial images. (C): and (D): Volumetric analysis of the left upper lobe. Regional functional lung volume is estimated to be 1173.14 mL.

Figure 3

Quantitative Analysis of a Patient With a Tumor Causing Atelectasis of the Left Upper Lobe. (A): Chest CT scan. (B): Volumetric analysis of both lungs. Total functional lung volume is estimated to be 3972 mL. (C): Regional functional lung volume of the left upper lobe is only 9 mL due to the atelectasis. In this case, predicted postoperative FEV₁ is very similar to the preoperative measurement.