Assessment of Cervical Cancer with a Parameter-Free Intravoxel Incoherent Motion Imaging Algorithm

To evaluate the feasibility of a parameter-free intravoxel incoherent motion (IVIM) approach in cervical cancer, to assess the optimal b-value threshold, and to preliminarily examine differences in the derived perfusion and diffusion parameters for different histological cancer types.

After Institutional Review Board approval, 19 female patients (mean age, 54 years; age range, 37-78 years) gave consent and were enrolled in this prospective magnetic resonance imaging study. Clinical staging and biopsy results were obtained. Echo-planar diffusion weighted sequences at 13 b-values were acquired at 3 tesla field strength. Single-sliced region-of-interest IVIM analysis with adaptive b-value thresholds was applied to each tumor, yielding the optimal fit and the optimal parameters for pseudodiffusion (D^*), perfusion fraction (F_p) and diffusion coefficient (D). Monoexponential apparent diffusion coefficient (ADC) was calculated for comparison with D.

Biopsy revealed squamous cell carcinoma in 10 patients and adenocarcinoma in 9. The b-value threshold (median [interquartile range]) depended on the histological type and was 35 (22.5-50) s/mm² in squamous cell carcinoma and 150 (100-150) s/mm² in adenocarcinoma (p < 0.05). Comparing squamous cell vs. adenocarcinoma, D^* (45.1 [25.1-60.4] × 10^-3 mm²/s vs. 12.4 [10.5-21.2] × 10^-3 mm²/s) and F_p (7.5% [7.0-9.0%] vs. 9.9% [9.0-11.4%]) differed significantly between the subtypes (p < 0.02), whereas D did not (0.89 [0.75-0.94] × 10^-3 mm²/s vs. 0.90 [0.82-0.97] × 10^-3 mm²/s, p = 0.27). The residuals did not differ (0.74 [0.60-0.92] vs. 0.94 [0.67-1.01], p = 0.32). The ADC systematically underestimated the magnitude of diffusion restriction compared to D (p < 0.001).

The parameter-free IVIM approach is feasible in cervical cancer. The b-value threshold and perfusion-related parameters depend on the tumor histology type.