Early emphysematous changes in asymptomatic smokers: detection with 3He MR imaging.
OBJECTIVE
To prospectively compare apparent diffusion coefficient (ADC) measurements derived from diffusion-weighted hyperpolarized helium 3 (3He) magnetic resonance (MR) imaging with functional and structural findings using spirometric tests and thin-section computed tomography (CT) of the lungs in asymptomatic smokers and healthy nonsmokers of similar age.


METHODS
All studies were HIPAA compliant and were approved by the institutional review board. Informed consent was obtained. Ventilation and diffusion-weighted 3He MR images were obtained in healthy subjects: 11 smokers (five women, six men; mean age, 47 years+/-18 [standard deviation]; range, 23-73 years) and eight nonsmokers (<100 cigarettes in lifetime) (four women, four men; mean age, 46 years+/-16; range, 23-69 years). Mean ADC values for smokers and nonsmokers were compared with spirometric values, diffusing capacity of the lung for carbon monoxide (Dlco), age, and pack-years with Spearman rank correlation coefficient (rs) and multiple linear regression analysis. Mean ADC value and thin-section CT emphysema index of relative area less than -950 HU (RA950) were compared on a regional basis by using linear mixed-effect models.


RESULTS
Mean ADC values and number of pack-years were significantly correlated (rs=0.60; 95% confidence interval (CI): 0.21, 1.00; P=.007); relationship remained significant after adjustment for age (P=.003). Dlco was strongly correlated with pack-years (rs=-0.63; 95% CI: -0.97, -0.29; P=.004). Negative correlations between mean ADC values and percentage predicted Dlco (rs=-0.79; 95% CI: -0.93, -0.64; P<.001) and the ratio of forced expiratory volume in 1 second to forced vital capacity (rs=-0.72; 95% CI: -0.92, -0.52; P=.001) were statistically significant. Correlations between spirometric values or RA950 and number of pack-years were not significant (.05 level).


CONCLUSIONS
Correlations between mean ADC values and pulmonary function test measurements for diagnosing emphysema, especially Dlco, were statistically significant.
Fain
Sean B
SB
Department of Radiology, University of Wisconsin, J3/110 CSC Medical Physics, 600 Highland Ave, Madison, WI 53792, USA. sfain@wisc.edu
Panth
Shilpa R
SR
Evans
Michael D
MD
Wentland
Andrew L
AL
Holmes
James H
JH
Korosec
Frank R
FR
O'Brien
Matthew J
MJ
Fountaine
Harvey
H
Grist
Thomas M
TM
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002248:Carbon Monoxide; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D042241:Early Diagnosis; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006371:Helium; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007554:Isotopes; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011653:Pulmonary Diffusing Capacity / Q000502:physiology; D011656:Pulmonary Emphysema / Q000175:diagnosis* / Q000503:physiopathology; D012907:Smoking / Q000503:physiopathology; D013147:Spirometry; D014057:Tomography, X-Ray Computed / Q000379:methods; D014797:Vital Capacity / Q000502:physiology
D007554:Isotopes; D006371:Helium; D002248:Carbon Monoxide