Characteristic crescentic subpleural lung zones with high ventilation (V)/perfusion (Q) ratios in interstitial pneumonia on V/Q quotient SPECT.
OBJECTIVE
Nonspecific interstitial pneumonia (NSIP) and usual IP (UIP) preferentially involve subpleural lung zones (SPLZ), and may result in characteristic regional lung function impairment. The aim of this study was to characterize cross-sectional lung ventilation (V)-perfusion (Q) imbalance in these disorders on automated V/Q quotient single photon emission computed tomography (SPECT).


METHODS
99mTc-technegas/macroaggregated albumin SPECT-derived V/Q quotient SPECT and V/Q profile were automatically built for assessment of cross-sectional lung V-Q imbalance in 38 patients with NSIP or UIP. The findings of V/Q quotient SPECT were correlated with lung CT morphology. The results were compared with 12 healthy nonsmoker controls and 48 patients with chronic obstructive pulmonary disease.


RESULTS
V/Q quotient SPECT showed 81 crescentic SPLZ with high V/Q ratios in 32 patients (84%) with NSIP or UIP, which were not observed in controls and patients with chronic obstructive pulmonary disease. Sixty-three (77.7%) of them were located at high-attenuation areas (reticular and/or ground-glass opacities) with or without small cystic air spaces (honeycombing and/or traction bronchiectasis) on CT, and 12 (14.8%) at normal lung areas. V/Q profile at the lung sections with crescentic SPLZ with high V/Q ratios showed flattened peaks with broadened V/Q ratio distribution compared with controls, and standard deviation of V/Q ratios in the entire lungs was significantly correlated with partial oxygen arterial blood pressure (P = 0.0009) and predicted diffusing capacity of the lungs for carbon monoxide (P = 0.0139). Five of eight patients with NSIP or UIP and with worsening of hypoxemia showed an extension of SPCZ with high V/Q ratios on follow-up V/Q quotient SPECT, without significant changes on CT.


CONCLUSIONS
A high prevalence of crescentic SPLZ with high V/Q ratios is a characteristic feature of lung V-Q imbalance causing alveolar gas exchange impairment in NSIP and UIP.
Suga
Kazuyoshi
K
Department of Radiology, St. Hill Hospital, Ube, Yamaguchi, Japan. sugar@sthill-hp.or.jp
Kawakami
Yasuhiko
Y
Koike
Masahiro
M
Iwanaga
Hideyuki
H
Matsunaga
Naofumi
N
D000328:Adult; D000368:Aged; D000418:Albumins / Q000737:chemistry; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D014692:Ventilation-Perfusion Ratio
D000418:Albumins; D015609:Organotechnetium Compounds