Non-parametric intravoxel incoherent motion analysis of the thyroid gland.
OBJECTIVE
To implement a protocol for intravoxel incoherent motion (IVIM) of the thyroid, to determine base parameters in healthy volunteers, and to provide preliminary experience on clinical applicability in one patient.


METHODS
Eight healthy volunteers underwent 3T MRI using a diffusion weighted echo-planar imaging sequence with 12 different b-values between 0-800 s/mm2. The IVIM parameters diffusion coefficient D, pseudo-diffusion coefficient D*, perfusion fraction Fp, and the optimal b-values thresholds were calculated for each thyroid lobe, muscle tissue and the cerebrospinal fluid (CSF) using a non-parametric multi-step algorithm and compared with a Student's t-test. A p-value <0.05 was considered significant.


RESULTS
Mean values for healthy thyroid tissue were: D 1.01 ± 0.13 × 10-3mm2/s, D* 71.0 ± 52.5 × 10-3mm2/s and Fp17.1 ± 4.2%; for muscle: D 0.50 ± 0.21 × 10-3mm2/s, D* 58.3 ± 99.2 × 10-3mm2/s and Fp26.5 ± 9.3%; and for CSF D 2.18 ± 0.93 × 10-3mm2/s, D* 99.2 ± 41.2 × 10-3mm2/s and Fp74.6 ± 12.7%. The optimal b-value threshold separating diffusion and perfusion effects in thyroid ranged between 0-70 s/mm2. Healthy thyroid tissue showed similar Fpcompared to muscle, both lower than CSF.


CONCLUSIONS
The proposed IVIM protocol provides surrogate markers on cellular diffusion restriction and perfusion; thereby providing a more comprehensive description of tissue properties compared to conventional DWI.
Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Switzerland.
Anton S
AS
Becker
Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Switzerland.
Moritz C
MC
Wurnig
Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Switzerland.
Tim
T
Finkenstaedt
Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Switzerland.
Andreas
A
Boss
Anatomy; Medical imaging; Medicine; Pathology; Physiology