Evaluation of pulmonary function using single-breath-hold dual-energy computed tomography with xenon: Results of a preliminary study

Abstract

Xenon-enhanced dual-energy computed tomography (xenon-enhanced CT) can provide lung ventilation maps that may be useful for assessing structural and functional abnormalities of the lung. Xenon-enhanced CT has been performed using a multiple-breath-hold technique during xenon washout. We recently developed xenon-enhanced CT using a single-breath-hold technique to assess ventilation. We sought to evaluate whether xenon-enhanced CT using a single-breath-hold technique correlates with pulmonary function testing (PFT) results. Twenty-six patients, including 11 chronic obstructive pulmonary disease (COPD) patients, underwent xenon-enhanced CT and PFT. Three of the COPD patients underwent xenon-enhanced CT before and after bronchodilator treatment. Images from xenon-CT were obtained by dual-source CT during a breath-hold after a single vital-capacity inspiration of a xenon-oxygen gas mixture. Image postprocessing by 3-material decomposition generated conventional CT and xenon-enhanced images. Low-attenuation areas on xenon images matched low-attenuation areas on conventional CT in 21 cases but matched normal-attenuation areas in 5 cases. Volumes of Hounsfield unit (HU) histograms of xenon images correlated moderately and highly with vital capacity (VC) and total lung capacity (TLC), respectively (r=0.68 and 0.85). Means and modes of histograms weakly correlated with VC (r=0.39 and 0.38), moderately with forced expiratory volume in 1 second (FEV1) (r=0.59 and 0.56), weakly with the ratio of FEV1 to FVC (r=0.46 and 0.42), and moderately with the ratio of FEV1 to its predicted value (r=0.64 and 0.60). Mode and volume of histograms increased in 2 COPD patients after the improvement of FEV1 with bronchodilators. Inhalation of xenon gas caused no adverse effects. Xenon-enhanced CT using a single-breath-hold technique depicted functional abnormalities not detectable on thin-slice CT. Mode, mean, and volume of HU histograms of xenon images reflected pulmonary function. Xenon images obtained with xenon-enhanced CT using a single-breath-hold technique can qualitatively depict pulmonary ventilation. A larger study comprising only COPD patients should be conducted, as xenon-enhanced CT is expected to be a promising technique for the management of COPD. Abbreviations: COPD = chronic obstructive pulmonary disease, CT = computed tomography, DLCO/VA = diffusing capacity divided by the alveolar volume, FEV1 = forced expiratory volume in 1 second, FEV1 % pred = FEV1 as a percentage of predicted, FVC = forced vital capacity, HU = Hounsfield unit, PFT = pulmonary function test, TLC = total lung capacity, V50/V25 = maximal expiratory flow at 50% and 25% of FVC, VC = vital capacity, xenon-enhanced CT = xenon-enhanced dual-energy computed tomography.