Intravoxel incoherent motion MR imaging for prostate cancer: an evaluation of perfusion fraction and diffusion
Yuxi Pang1, Baris Turkbey, Marcelino Bernardo
1Philips Healthcare, BU-MR, Cleveland, Ohio, USA.
Abstract:
There has been a resurgent interest in intravoxel incoherent motion (IVIM) MR imaging to obtain perfusion as well as diffusion information on lesions, in which the diffusion was modeled as Gaussian diffusion. However, it was observed that this diffusion deviated from expected monoexponential decay at high b-values and the reported perfusion in prostate is contrary to the findings in dynamic contrast-enhanced (DCE) MRI studies and angiogenesis. Thus, this work is to evaluate the effect of different b-values on IVIM perfusion fractions (f) and diffusion coefficients (D) for prostate cancer detection. The results show that both parameters depended heavily on the b-values, and those derived without the highest b-value correlated best with the results from DCE-MRI studies; specifically, f was significantly elevated (7.2% vs. 3.7%) in tumors when compared with normal tissues, in accordance with the volume transfer constant (K(trans); 0.39 vs. 0.18 min(-1)) and plasma fractional volume (v(p) ; 8.4% vs. 3.4%). In conclusion, it is critical to choose an appropriate range of b-values in studies or include the non-Gaussian diffusion contribution to obtain unbiased IVIM measurements. These measurements could eliminate the need for DCE-MRI, which is especially relevant in patients who cannot receive intravenous gadolinium-based contrast media.
Insights
Intravoxel incoherent motion (IVIM) MRI shows promise for prostate cancer detection. Optimizing b-values is crucial for accurate perfusion and diffusion measurements, potentially replacing dynamic contrast-enhanced MRI.
Area of Science:
- Magnetic Resonance Imaging
- Medical Physics
- Oncology
Background:
- Intravoxel incoherent motion (IVIM) MRI offers simultaneous diffusion and perfusion data.
- Standard IVIM models assume Gaussian diffusion, which may not hold true at high b-values.
- Previous IVIM studies in prostate cancer showed discrepancies with dynamic contrast-enhanced MRI (DCE-MRI).
Purpose of the Study:
- To investigate the impact of varying b-values on IVIM-derived perfusion fraction (f) and diffusion coefficient (D).
- To evaluate the efficacy of IVIM parameters in detecting prostate cancer.
- To compare IVIM findings with established DCE-MRI metrics.
Main Methods:
- Prostate MRI was performed using IVIM sequences with a range of b-values.
- IVIM parameters (f and D) were calculated using different b-value sets.
- IVIM results were correlated with DCE-MRI parameters (K(trans) and v(p)).
Main Results:
- IVIM parameters (f and D) were significantly influenced by the chosen b-values.
- IVIM parameters derived without the highest b-value showed the best correlation with DCE-MRI.
- Tumor regions exhibited significantly elevated f (7.2%) compared to normal tissue (3.7%), aligning with higher K(trans) and v(p).
Conclusions:
- The selection of appropriate b-values is critical for obtaining reliable IVIM measurements in prostate cancer.
- Incorporating non-Gaussian diffusion models may improve IVIM accuracy.
- Optimized IVIM could potentially serve as an alternative to DCE-MRI, especially for patients contraindicated for contrast agents.
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