Xenon-Enhanced Dual-Energy CT of Patients With Asthma: Dynamic Ventilation Changes After Methacholine and Salbutamol Inhalation

Department of Radiology, Seoul National University Hospital and Institute of Radiation Medicine, Seoul National University Medical Research Center, 101 Daehangno Jongno-gu, Seoul 110-744, Korea.
American Journal of Roentgenology (Impact Factor: 2.73). 11/2012; 199(5):975-81. DOI: 10.2214/AJR.11.7624
Source: PubMed


The purpose of this study was to evaluate the use of xenon-enhanced dual-energy CT of the chest to assess ventilation changes after methacholine and salbutamol inhalation in subjects with asthma and healthy subjects.
Twenty-five subjects with asthma and 10 healthy subjects underwent three-phase (basal, after methacholine inhalation, after salbutamol inhalation) xenon-enhanced chest CT. Each phase was composed of wash-in and washout scans. For visual analysis, two radiologists evaluated ventilation defects and gas trapping lobe by lobe on a 10-point scale. Total ventilation defect and gas trapping scores were calculated by adding ventilation defect and gas trapping scores. Xenon and total lung volume were quantified automatically. Total xenon concentration index was calculated as total xenon concentration divided by lung volume. Repeated measures analysis of variance and Student t test were used for comparisons of total ventilation defect score, total gas trapping score, and total xenon concentration index between the two groups. The Friedman test was used for within-group analysis.
In the basal state, subjects with asthma had a higher total ventilation defect score (p = 0.004) and higher total gas trapping score (p = 0.05) than did healthy subjects. On washout images, total ventilation defect score, total gas trapping score, and total xenon concentration index after methacholine and salbutamol inhalation were statistically different between the two groups (p < 0.05). However, total xenon concentration index on wash-in images was not significantly different between the two groups. In within-group analysis, total ventilation defect score and total gas trapping score in subjects with asthma and total ventilation defect score in healthy subjects increased significantly after methacholine inhalation and decreased significantly after salbutamol inhalation (p < 0.05).
Xenon-enhanced chest CT may be a useful technique for visualizing dynamic changes in airflow in response to methacholine and salbutamol inhalation in patients with asthma. Optimization of the protocol for radiation exposure is warranted.

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    • "Xenon ventilation CT using dual source and dual energy is a new technique for functional lung imaging which visualises lung ventilation and allows quantification of regional ventilation defects as well as gas trapping behind obstructed airways [21, 22]. Using this technique, abnormalities of regional ventilation were found to be highly associated with measures of asthma control, airway hyperreactivity (as assessed by methacholine-induced bronchoconstriction) and subsequent bronchodilator response to salbutamol, but not with baseline FEV1 in a group of asthmatic subjects [23]. "
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    ABSTRACT: Image analyses include computed tomography (CT), magnetic resonance imaging, and xenon ventilation CT, which is new modality to evaluate pulmonary functional imaging. To examine the usefulness of dual-energy xenon ventilation CT in asthmatic patients. A total of 43 patients 18 years or older who were nonsmokers were included in the study. Xenon CT images in wash-in and wash-out phases were obtained at baseline and after inhalation of methacholine and salbutamol. The degrees of ventilation defects and xenon trappings were evaluated through visual analysis. Ventilation defects and xenon trapping were significantly increased and decreased after methacholine challenge and salbutamol inhalation, respectively (P < .005). The ventilation abnormalities were not significantly related to the percentage of forced expiratory volume in 1 second (FEV1) or the ratio of FEV1 to forced vital capacity. Xenon trappings after salbutamol inhalation were negatively related to the scores of the asthma control test, wheezing, or night symptoms, with statistical significance (P < .05), whereas, FEV1 showed no significant correlation with symptom scores. Baseline FEV1 was significantly lower and dyspnea and wheezing were more severe in the non-full reversal group than in the full reversal group after salbutamol inhalation in xenon CT (P < .05). The degree of ventilation defects were positively correlated with FEV1 improvement after 3 months of treatment (P = .02). The results of this study suggest that xenon ventilation CT can be used as a new method to assess ventilation abnormalities in asthma, and these ventilation abnormalities can be used as novel parameters that reflect the status of asthma control and symptom severity.
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