Functional Assessment of Individual Lung Lobes with MDCT Images

Abstract

CT is an effective modality for evaluating the structure inside the body and the 3-D shape of organs of interest because of ability of high spatial resolution and of high acquisition speed. However, CT is weak to evaluate a function of organs because CT only maps X-ray absorption coefficients of materials constructing human body. Therefore, study of functional imaging of organs by using CT images will be a breakthrough of image diagnosis. This chapter introduces a novel method for estimating pulmonary function using MDCT. The human lung is composed of five anatomical compartments called “lung lobes.” The right lung is segmented into three lung lobes (the upper, middle and lower lobes), and the left lung is segmented into two lung lobes (the upper and lower lobes). Thoracic surgeries such as a living-donor lobar lung transplantation (LDLLT) (Date et al., 2003a) and the lobectomy (Kirby et al., 1993) often operate by a lung lobe. LDLLT is an operation that transplants the right and left lower lobes of two living donors to a recipient. In this surgery, predicting the postoperative forced vital capacity (FVC) of a recipient is necessary to select the adequate donors. The lobectomy is a treatment that extirpates lung lobe. This surgery excises the diseased region such as lung or improves breathing function by reducing the lung capacity that overexpands by emphysema. In this surgery, predicting the postoperative FVC is necessary to investigate the effectiveness of the surgery, too. Since these surgeries treatment lobe by lobe, the prediction should be based on individual lung lobes. Although a spirometry, which is widely used in a clinical field, enables us to measure the FVC of whole lung, it is not available for the FVCs of the individual lung lobes. Date et al. have proposed a method for approximating FVCs of individual lung lobes by determining the contribution ratio to FVC of the whole lung (Date et al., 2003b). The contribution ratio is determined from the number of lung segments occupied in the lung lobe. The FVC of recipients that underwent the LDLLT measured at 6 months was correlated well with the grafts FVCs of donors estimated by their method (r = 0.802). However, the method does not consider the variation of the lobar function among subjects. To consider such variation, a tracheal tube can measure the FVCs of the right and the left lung respectively. However, the method is invasive due to the use of anesthesia and the tracheal tube, and it still cannot measure the FVCs of the individual lung lobes. This chapter proposes a novel method for measuring the FVCs of individual lung lobes by using volume data acquired from CT scanner. This approach is based on an assumption that the FVC of whole lung can be expressed as the change of lung lobe volumes between