Temporal evolution of perfusion parameters in brain metastases treated with stereotactic radiosurgery: comparison of intravoxel incoherent motion and dynamic contrast enhanced MRI

Abstract

Intravoxel incoherent motion (IVIM) is a magnetic resonance imaging (MRI) technique that is seeing increasing use in neuro-oncology and offers an alternative to contrast-enhanced perfusion techniques for evaluation of tumor blood volume after stereotactic radiosurgery (SRS). To date, IVIM has not been validated against contrast enhanced techniques for brain metastases after SRS. In the present study, we measure blood volume for 20 brain metastases (15 patients) at baseline, 1 week and 1 month after SRS using IVIM and dynamic contrast enhanced (DCE)-MRI. Correlation between blood volume measurements made with IVIM and DCE-MRI show poor correlation at baseline, 1 week, and 1 month post SRS (r = 0.33, 0.14 and 0.30 respectively). At 1 week after treatment, no significant change in tumor blood volume was found using IVIM or DCE-MRI (p = 0.81 and 0.41 respectively). At 1 month, DCE-MRI showed a significant decrease in blood volume (p = 0.0002). IVIM, on the other hand, demonstrated the opposite effect and showed a significant increase in blood volume at 1 month (p = 0.03). The results of this study indicate that blood volume measured with IVIM and DCE-MRI are not equivalent. While this may relate to differences in the type of perfusion information each technique is providing, it could also reflect a limitation of tumor blood volume measurements made with IVIM after SRS. IVIM measurements of tumor blood volume in the month after SRS should therefore be interpreted with caution.

Application of a Simplified Method for Estimating Perfusion Derived from Diffusion-Weighted MR Imaging in Glioma Grading

“…These distinct correlation results are in line with theoretical expectations: SPF and f associated tissue perfusion originates from the randomly orientated capillary network as the contribution from macrovascular structures is spoiled by applying the magnetic pulsed gradients (Le Bihan and Turner, 1992 ), whereas v p measurement accounts for all types of vessels within the vascular bed regardless of vessel size (Sourbron and Buckley, 2011 ). Though a straightforward comparison between SPF and v p has not been reported, a recently published study showed a positive correlation between f and v p ( r = 0.33) on untreated brain metastases (Kapadia et al, 2017 ), similar to our observations ( ρ = 0.362). In addition, SPF also showed a strong correlation with D* ( ρ = 0.716) and K trans ( ρ = 0.607).…”

“…First, the most common clinical concern is whether there is a clear relationship between the perfusion properties derived from IVIM and other imaging techniques using intravascular tracers including DCE MR imaging and dynamic susceptibility contrast (DSC) MR imaging (Koh et al, 2011 ; Iima and Le Bihan, 2016 ). Several studies have been conducted to evaluate the relationship and inconsistent results have been reported: results from most studies showed significant correlations between IVIM and DCE/DSC MR imaging (Federau et al, 2014 ; Suh et al, 2014 ; Togao et al, 2016 ; Kapadia et al, 2017 ), whereas some studies reported no correlation (Bisdas et al, 2015 ; Wu et al, 2015 ). Second, a large number of b -values are needed to fully characterize biexponential signal attenuation and provide more data support for parameter estimation.…”

Advanced Magnetic Resonance Imaging Techniques in Management of Brain Metastases

“…The slow decaying component on the other hand represents the diffusion properties of the tissue (48). The microvascular fraction can also be measured with a simplified IVIM model that focuses on large diffusion b-values (49), and has been used in several pilot studies investigating human brain metastases (45, 46). Figure 2 shows perfusion and ADC maps of microvascular fraction quantification with IVIM for two patients with brain metastases, one having radiation necrosis, and the other with tumor recurrence (46).…”

“…Most studies have focused on differentiating brain metastases from other brain tumors such as high and low-grade gliomas (38, 53, 71, 74–81). Assessing tumor response to therapy and attempting to perform such evaluation early after the treatment has been less explored; however, this topic has been gaining significant attention recently (21, 25, 45, 58, 68, 69, 82). Management of treatment-induced late-effects, specifically differentiating radiation necrosis from tumor progression or recurrence, has also been attempted with qMRI techniques.…”

“…Conventional radiotherapy results in an initial increase in perfusion (94, 95); in contrast, stereotactic radiosurgery (SRS) induces a significant reduction in perfusion within a few hours after treatment due to damage to the vascular endothelium (96). These changes can be quantified with perfusion measurement techniques such as IVIM and DCE-MRI (45, 48, 97). Kapadia et al (45) measured an increase in perfusion index (measured with IVIM) four weeks after treatment ( f = 0.08 ± 0.02, 0.10 ± 0.03 at baseline and 4 weeks post-SRS, respectively).…”