Korean J Radiol.  2020 Feb;21(2):218-227. 10.3348/kjr.2019.0232.

B-Value Optimization in the Estimation of Intravoxel Incoherent Motion Parameters in Patients with Cervical Cancer

Affiliations
  • 1Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong. eyplee77@hku.hk
  • 2Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Switzerland.

Abstract


OBJECTIVE
This study aimed to find the optimal number of b-values for intravoxel incoherent motion (IVIM) imaging analysis, using simulated and in vivo data from cervical cancer patients.
MATERIALS AND METHODS
Simulated data were generated using literature pooled means, which served as reference values for simulations. In vivo data from 100 treatment-naïve cervical cancer patients with IVIM imaging (13 b-values, scan time, 436 seconds) were retrospectively reviewed. A stepwise b-value fitting algorithm calculated optimal thresholds. Feed forward selection determined the optimal subsampled b-value distribution for biexponential IVIM fitting, and simplified IVIM modeling using monoexponential fitting was attempted. IVIM parameters computed using all b-values served as reference values for in vivo data.
RESULTS
In simulations, parameters were accurately estimated with six b-values, or three b-values for simplified IVIM, respectively. In vivo data showed that the optimal threshold was 40 s/mm² for patients with squamous cell carcinoma and a subsampled acquisition of six b-values (scan time, 198 seconds) estimated parameters were not significantly different from reference parameters (individual parameter error rates of less than 5%). In patients with adenocarcinoma, the optimal threshold was 100 s/mm², but an optimal subsample could not be identified. Irrespective of the histological subtype, only three b-values were needed for simplified IVIM, but these parameters did not retain their discriminative ability.
CONCLUSION
Subsampling of six b-values halved the IVIM scan time without significant losses in accuracy and discriminative ability. Simplified IVIM is possible with only three b-values, at the risk of losing diagnostic information.

Keyword

Cervical cancer; Magnetic resonance imaging; Diffusion-weighted imaging; Intravoxel incoherent motion; b-values

MeSH Terms

Adenocarcinoma
Carcinoma, Squamous Cell
Humans
Magnetic Resonance Imaging
Reference Values
Retrospective Studies
Uterine Cervical Neoplasms*
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