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.
Gierada
David S
DS
Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63105, USA. gieradad@wustl.edu
Woods
Jason C
JC
Bierhals
Andrew J
AJ
Bartel
Seth T
ST
Ritter
Jon H
JH
Choong
Cliff K
CK
Das
Nitin A
NA
Hong
Cheng
C
Pilgram
Thomas K
TK
Chang
Yulin V
YV
Jacob
Richard E
RE
Hogg
James C
JC
Battafarano
Richard J
RJ
Cooper
Joel D
JD
Meyers
Bryan F
BF
Patterson
G Alexander
GA
Yablonskiy
Dmitriy A
DA
Conradi
Mark S
MS
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