Validation of surface-to-volume ratio measurements derived from oscillating gradient spin echo on a clinical scanner using anisotropic fiber phantoms.
A diffusion measurement in the short-time surface-to-volume ratio (S/V) limit (Mitra et al., Phys Rev Lett. 1992;68:3555) can disentangle the free diffusion coefficient from geometric restrictions to diffusion. Biophysical parameters, such as the S/V of tissue membranes, can be used to estimate microscopic length scales non-invasively. However, due to gradient strength limitations on clinical MRI scanners, pulsed gradient spin echo (PGSE) measurements are impractical for probing the S/V limit. To achieve this limit on clinical systems, an oscillating gradient spin echo (OGSE) sequence was developed. Two phantoms containing 10 fiber bundles, each consisting of impermeable aligned fibers with different packing densities, were constructed to achieve a range of S/V values. The frequency-dependent diffusion coefficient, D(ω), was measured in each fiber bundle using OGSE with different gradient waveforms (cosine, stretched cosine, and trapezoidal), while D(t) was measured from PGSE and stimulated-echo measurements. The S/V values derived from the universal high-frequency behavior of D(ω) were compared against those derived from quantitative proton density measurements using single spin echo (SE) with varying echo times, and from magnetic resonance fingerprinting (MRF). S/V estimates derived from different OGSE waveforms were similar and demonstrated excellent correlation with both SE- and MRF-derived S/V measures (ρ  ≥  0.99). Furthermore, there was a smoother transition between OGSE frequency f and PGSE diffusion time when using teffS/V=9/64f, rather than the commonly used teff= 1/(4f), validating the specific frequency/diffusion time conversion for this regime. Our well-characterized fiber phantom can be used for the calibration of OGSE and diffusion modeling techniques, as the S/V ratio can be measured independently using other MR modalities. Moreover, our calibration experiment offers an exciting perspective of mapping tissue S/V on clinical systems.
Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA.|Sackler Institute of Graduate Biomedical Sciences, NYU School of Medicine, New York, New York, USA.
Gregory
http://orcid.org/0000-0002-8336-7486
G
Lemberskiy
Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA.
Steven H
http://orcid.org/0000-0003-3361-3789
SH
Baete
Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA.
Martijn A
http://orcid.org/0000-0002-0636-234X
MA
Cloos
Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA.
Dmitry S
http://orcid.org/0000-0002-4213-3050
DS
Novikov
Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, USA.
Els
http://orcid.org/0000-0002-1384-8591
E
Fieremans
D016880:Anisotropy; D017352:Echo-Planar Imaging / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D009991:Oscillometry / Q000379:methods*; D019047:Phantoms, Imaging; D011095:Polyethylenes / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene
OGSE diffusion; STEAM diffusion; anisotropic diffusion phantom; magnetic resonance fingerprinting; surface to volume ratio