title: Normal spectrum of pulmonary parametric response map to differentiate lung collapsibility: distribution of densitometric classifications in healthy adult volunteers.
abstract: OBJECTIVE
  Pulmonary parametric response map (PRM) was proposed for quantitative densitometric phenotypization of chronic obstructive pulmonary disease. However, little is known about this technique in healthy subjects. The purpose of this study was to describe the normal spectrum of densitometric classification of pulmonary PRM in a group of healthy adults.
  
  
  METHODS
  15 healthy volunteers underwent spirometrically monitored chest CT at total lung capacity (TLC) and functional residual capacity (FRC). The paired CT scans were analyzed by PRM for voxel-by-voxel characterization of lung parenchyma according to 4 densitometric classifications: normal lung (TLC ≥ -950 HU, FRC ≥ -856 HU); expiratory low attenuation area (LAA) (TLC ≥ -950 HU, FRC < -856 HU); dual LAA (TLC<-950 HU, FRC < -856 HU); uncharacterized (TLC < -950 HU, FRC ≥ -856 HU).
  
  
  RESULTS
  PRM spectrum was 78 % ± 10 % normal lung, 20 % ± 8 % expiratory LAA, and 1 % ± 1 % dual LAA. PRM was similar between genders, there was moderate correlation between dual LAA and spirometrically assessed TLC (R = 0.531; p = 0.042), and between expiratory LAA and VolExp/Insp ratio (R = -0.572; p = 0.026).
  
  
  CONCLUSIONS
  PRM reflects the predominance of normal lung parenchyma in a group of healthy volunteers. However, PRM also confirms the presence of physiological expiratory LAA seemingly related to air trapping and a minimal amount of dual LAA likely reflecting emphysema.
  
  
  CONCLUSIONS
  • Co-registration of inspiratory and expiratory computed tomography allows dual-phase densitometry. • Dual-phase co-registered densitometry reflects heterogeneous regional changes in lung function. • Quantification of lung in healthy subjects is needed to set reference values. • Expiratory low attenuation areas <30 % could be considered within normal range.
authors.affiliation: Section of Cardiothoracic Imaging, Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA. mariosilvamed@gmail.com.|Section of Radiology, Department of Surgical Sciences, University Hospital of Parma, Via Gramsci 14, 43126, Parma, Italy. mariosilvamed@gmail.com.
authors.forename: Mario
authors.identifier: http://orcid.org/0000-0002-2538-7032
authors.initials: M
authors.lastname: Silva
authors.affiliation: Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Waehringer Guertel 18-20, A-1090, Vienna, Austria.
authors.forename: Stefan F
authors.initials: SF
authors.lastname: Nemec
authors.affiliation: Pneumologie, CHU de Charleroi - Hôpital Vésale, Rue de Gozé 706, 6110, Montigny-le-Tilleul, Belgium.
authors.forename: Valerie
authors.initials: V
authors.lastname: Dufresne
authors.affiliation: Section of Cardiothoracic Imaging, Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
authors.forename: Mariaelena
authors.initials: M
authors.lastname: Occhipinti
authors.affiliation: Section of Cardiothoracic Imaging, Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
authors.forename: Benedikt H
authors.initials: BH
authors.lastname: Heidinger
authors.affiliation: Imbio, 227 Colfax Ave North, Suite 144, Minneapolis, MN, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Chamberlain
authors.affiliation: Section of Cardiothoracic Imaging, Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Bankier
mesh_terms: D000328:Adult; D000368:Aged; D003720:Densitometry; D045853:Exhalation / Q000502:physiology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008168:Lung / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D001261:Pulmonary Atelectasis / Q000473:pathology / Q000503:physiopathology; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000473:pathology / Q000503:physiopathology; D012129:Respiratory Function Tests; D014057:Tomography, X-Ray Computed / Q000379:methods; D014109:Total Lung Capacity / Q000502:physiology
keywords: Densitometry; Healthy subjects; Lung; Obstructive lung diseases; Volumetric computed tomography