Optical Access to Arteriovenous Cerebral Microcirculation Through a Transparent Cranial Implant

Abstract

Background and Objective Microcirculation plays a critical role in physiologic processes and several disease states. Laser speckle imaging (LSI) is a full‐field, real‐time imaging technique capable of mapping microvessel networks and providing relative flow velocity within the vessels. In this study, we demonstrate that LSI combine with multispectral reflectance imaging (MSRI), which allows for distinction between veins and arteries in the vascular flow maps produced by LSI. We apply this combined technique to mouse cerebral vascular network in vivo, comparing imaging through the skull, to the dura mater and brain directly through a craniectomy, and through a transparent cranial “Window to the Brain” (WttB) implant. Study Design/Materials and Methods The WttB implant used in this study is made of a nanocrystalline Yttria‐Stabilized‐Zirconia ceramic. MSRI was conducted using white‐light illumination and filtering the reflected light for 560, 570, 580, 590, 600, and 610 nm. LSI was conducted using an 810 nm continuous wave near‐infrared laser with incident power of 100 mW, and the reflected speckle pattern was captured by a complementary metal‐oxide‐semiconductor (CMOS) camera. Results Seven vessel branches were analyzed and comparison was made between imaging through the skull, craniectomy, and WttB implant. Through the skull, MSRI did not detect any vessels, and LSI could not image microvessels. Imaging through the WttB implant, MSRI was able to identify veins versus arteries, and LSI was able to image microvessels with only slightly higher signal‐to‐noise ratio and lower sharpness than imaging the brain through a craniectomy. Conclusions This study demonstrates the ability to perform MSRI‐LSI across a transparent cranial implant, to allow for cerebral vascular networks to be mapped, including microvessels. These images contain additional information such as vein‐artery separation and relative blood flow velocities, information which is of value scientifically and medically. The WttB implant provides substantial improvements over imaging through the murine cranial bone, where microvessels are not visible and MSRI cannot be performed. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Theranostic cranial implant for hyperspectral light delivery and microcirculation imaging without scalp removal

“…Therefore, brain imaging has been predominantly demonstrated in rodent open-skull and thinned skull models. Likewise, in our own prior studies we have found that optical imaging through the intact skull of mice diminishes detection of the intrinsic optical signals [24][25][26][27] . Moreover, the optical properties of the inhomogeneous cranial bone overlap with those of brain tissue and jointly these factors decrease the accuracy and reliability of the data.…”

“…Conventional cranial prosthesis including titanium, alumina, and acrylic 37 , have not provided the requisite combination of transparency and toughness required for clinically-viable transparent cranial implants. To address this challenge, our group has previously introduced a transparent nanocrystalline yttria-stabilized-zirconia cranial implant material, which possesses the mechanical strength and biocompatibility which are prerequisites for a clinically-viable permanent cranial implant for patients [24][25][26][27][38][39][40][41][42][43][44][45][46] . This implant has been referred to in the literature as the "Window to the Brain" (WttB) implant.…”

Agarose Gel Characterization for the Fabrication of Brain Tissue Phantoms for Infrared Multispectral Vision Systems

“…The availability of such phantoms will pave the way for designing and characterizing novel infrared multispectral imaging systems for cerebral hemodynamics monitoring, such as directly monitoring the intracranial site of the patient [24,25]. As far as we know, this is the first work that reports the optical characterization of a brain tissue-like phantom within the infrared range (i.e., 800-820 nm) using agarose.…”

Acoustically transparent alumina-based cranial implants enhance ultrasound transmission through a combined mechano-acoustic resonant effect

“…Ceramics of 8 mol yttria stabilized zirconia (8YSZ) have been proposed as an acoustic window-to-the-brain (AWttB) that transmits up to 80.8% of the ultrasonic energy at certain thicknesses; this effect depends on a resonant behavior related to the ultrasound wavelength in the material [13]. The use of this specific material responded to a double intended use in which the window can be translucent for both optical and acoustical [13] energies for new opto-acoustic applications, besides the already presented in Optics [20]. Although 8YSZ transmits light at 1 mm thickness [21], it needs to be clarified if its transmission level is enough at the average human cranium thickness, which ranges from about 3 mm to 15 mm [22].…”