Multiple regression method for pulmonary apparent diffusion coefficient measurement by hyperpolarized 3He MRI.
OBJECTIVE
To develop and validate a new multiple regression technique for the separation of flip angle effect in pulmonary apparent diffusion coefficient (ADC) measurement.


METHODS
Hyperpolarized (3)He MRI (HP (3)He MRI) ADC measurements were performed on phantom, pig, and human models. The diffusion-sensitization sequence is modified from a standard gradient echo (GRE) sequence with a nonlinear progression in the bipolar gradient amplitude with each image. In the self-diffusion phantom experiment, four images were acquired with base gradient factor b(0) = 0.15 second/cm(2); in the pig and human experiment, six images were acquired with base gradient factor b(0) = 1.4 second/cm(2).


RESULTS
The self-diffusion coefficient measured in the phantom experiment was 1.98 +/- 0.16 cm(2)/second. The measured uncertainty curve was consistent with the theoretically predicted curve. The measured in vivo ADC values (three coronal slices in the supine direction) were 0.20/0.16/0.13 cm(2)/second and 0.20/0.18/0.16 cm(2)/second for pig and human experiments, respectively.


CONCLUSIONS
With the introduction of a nonlinear progression in the diffusion-sensitization gradients, the multiple regression technique is capable of separating the flip angle effect in ADC measurement. In addition, this technique can perform a rigorous measurement uncertainty analysis and provide the optimal scan parameters that yield best noise performance.
Yu
Jiangsheng
J
Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Ishii
Masaru
M
Kadlecek
Stephen
S
Lipson
David A
DA
Emami
Kiarash
K
Clark
Timothy W
TW
Rajaei
Sheeva
S
Rizi
Rahim R
RR
D000280:Administration, Inhalation; D000328:Adult; D000465:Algorithms; D000818:Animals; D005260:Female; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007554:Isotopes; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011653:Pulmonary Diffusing Capacity; D012044:Regression Analysis; D013552:Swine
D007554:Isotopes; D006371:Helium