Technical Note: Development of a cranial phantom for assessing perfusion, diffusion, and biomechanics

Abstract

Purpose: A novel cranial phantom was developed to simulate the relationships among factors such as blood perfusion, water diffusion, and biomechanics in intracranial tissue. Methods: The cranial phantom consisted of a high-density polypropylene filter (mimicking brain parenchyma) with intra-and extrafilter spaces (mimicking cerebral artery and vein, respectively), and a capacitor space (mimicking the cerebrospinal fluid space). Pulsatile and steady flow with different flow rates were applied to the cranial phantom using a programmable pump. On 3.0-T MRI, the measurements of the internal pressure in the phantom, apparent diffusion coefficient (ADC) with mono-exponential analysis in the filter, and total simulated cerebral blood flow (tSCBF) into the phantom were synchronized with the pulsatile flow. We obtained their maximum changes during the pulsation period (DP, DADC, and DtSCBF, respectively). Then, the compliance index (CI) was calculated by dividing the volume change (DV) by the DP in the phantom. Moreover, the same measurements were repeated after the compliance of the phantom was reduced by increasing the water volume in the capacitor space. Under steady flow conditions, we determined the regional SCBF (rSCBF) and perfu-sion-related and restricted diffusion coefficients (D* and D, respectively) with biexponential analysis in the filter. Results: The internal pressure, ADC, and tSCBF varied over the pulsation period depending on the input flow. Moreover, the DP, DADC, DtSCBF, and rSCBF increased with the input flow rate. Compared to the high compliance condition, in the low compliance condition, the DP and DADC were higher by factors of 2.5 and 1.3, respectively, and the CI was smaller by a factor of 2.7, whereas the DV was almost unchanged. The D* was strongly affected by the input flow. Conclusion: Our original phantom models the relationships among the blood perfusion, water diffu-sion, and biomechanics of the intracranial tissue, potentially facilitating the validation of novel MRI techniques and optimization of imaging parameters. © 2017 American Association of Physicists in Medicine [https://doi.org/10.1002/mp.12182].