Effects of diffusion time on short-range hyperpolarized (3)He diffusivity measurements in emphysema.
OBJECTIVE
To characterize the effect of diffusion time on short-range hyperpolarized (3)He magnetic resonance imaging (MRI) diffusion measurements across a wide range of emphysema severity.


METHODS
(3)He diffusion MRI was performed on 19 lungs or lobes resected from 18 subjects with varying degrees of emphysema using three diffusion times (1.6 msec, 5 msec, and 10 msec) at constant b value. Emphysema severity was quantified as the mean apparent diffusion coefficient (ADC) and as the percentage of pixels with ADC higher than multiple thresholds from 0.30-0.55 cm(2)/sec (ADC index). Quantitative histology (mean linear intercept) was obtained in 10 of the lung specimens from 10 of the subjects.


RESULTS
The mean ADCs with diffusion times of 1.6, 5.0, and 10.0 msec were 0.46, 0.40, and 0.37 cm(2)/sec, respectively (P < 0.0001, analysis of variance [ANOVA]). There was no relationship between the ADC magnitude and the effect of diffusion time on ADC values. The mean linear intercept correlated with ADC (r = 0.91-0.94, P < 0.001) and ADC index (r = 0.78-0.92, P < 0.01) at all diffusion times.


CONCLUSIONS
Decreases in ADC with longer diffusion time were unrelated to emphysema severity. The strong correlations between the ADC at all diffusion times tested and quantitative histology demonstrate that ADC is a robust measure of emphysema.
Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63105, USA. gieradad@wustl.edu
David S
DS
Gierada
Jason C
JC
Woods
Andrew J
AJ
Bierhals
Seth T
ST
Bartel
Jon H
JH
Ritter
Cliff K
CK
Choong
Nitin A
NA
Das
Cheng
C
Hong
Thomas K
TK
Pilgram
Yulin V
YV
Chang
Richard E
RE
Jacob
James C
JC
Hogg
Richard J
RJ
Battafarano
Joel D
JD
Cooper
Bryan F
BF
Meyers
G Alexander
GA
Patterson
Dmitriy A
DA
Yablonskiy
Mark S
MS
Conradi
D000368:Aged; D000704:Analysis of Variance; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006371:Helium; D006801:Humans; D066298:In Vitro Techniques; D007554:Isotopes; D008297:Male; D011656:Pulmonary Emphysema / Q000473:pathology*
D007554:Isotopes; D006371:Helium