title: Evaluation of pulmonary function using breathing chest radiography with a dynamic flat panel detector: primary results in pulmonary diseases.
abstract: OBJECTIVE
  Dynamic flat panel detectors (FPD) permit acquisition of distortion-free radiographs with a large field of view and high image quality. The present study was performed to evaluate pulmonary function using breathing chest radiography with a dynamic FPD. We report primary results of a clinical study and computer algorithm for quantifying and visualizing relative local pulmonary airflow.
  
  
  METHODS
  Dynamic chest radiographs of 18 subjects (1 emphysema, 2 asthma, 4 interstitial pneumonia, 1 pulmonary nodule, and 10 normal controls) were obtained during respiration using an FPD system. We measured respiratory changes in distance from the lung apex to the diaphragm (DLD) and pixel values in each lung area. Subsequently, the interframe differences (D-frame) and difference values between maximum inspiratory and expiratory phases (D-max) were calculated. D-max in each lung represents relative vital capacity (VC) and regional D-frames represent pulmonary airflow in each local area. D-frames were superimposed on dynamic chest radiographs in the form of color display (fusion images). The results obtained using our methods were compared with findings on computed tomography (CT) images and pulmonary functional test (PFT), which were examined before inclusion in the study.
  
  
  RESULTS
  In normal subjects, the D-frames were distributed symmetrically in both lungs throughout all respiratory phases. However, subjects with pulmonary diseases showed D-frame distribution patterns that differed from the normal pattern. In subjects with air trapping, there were some areas with D-frames near zero indicated as colorless areas on fusion images. These areas also corresponded to the areas showing air trapping on computed tomography images. In asthma, obstructive abnormality was indicated by areas continuously showing D-frame near zero in the upper lung. Patients with interstitial pneumonia commonly showed fusion images with an uneven color distribution accompanied by increased D-frames in the area identified as normal on computed tomography images. Furthermore, measurement of DLD was very effective for evaluating diaphragmatic kinetics.
  
  
  CONCLUSIONS
  This is a rapid and simple method for evaluation of respiratory kinetics for pulmonary diseases, which can reveal abnormalities in diaphragmatic kinetics and regional lung ventilation. Furthermore, quantification and visualization of respiratory kinetics is useful as an aid in interpreting dynamic chest radiographs.
authors.affiliation: Department of Radiology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan. rie44@mhs.mp.kanazawa-u.ac.jp
authors.forename: Rie
authors.initials: R
authors.lastname: Tanaka
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sanada
authors.forename: Nobuo
authors.initials: N
authors.lastname: Okazaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Masaki
authors.initials: M
authors.lastname: Fujimura
authors.forename: Masahide
authors.initials: M
authors.lastname: Yasui
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsui
authors.forename: Kazuya
authors.initials: K
authors.lastname: Nakayama
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nanbu
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsui
mesh_terms: D000328:Adult; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D013902:Radiography, Thoracic / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D014963:X-Ray Intensifying Screens