Use of a Blood Substitute to Determine Instantaneous Murine Right Ventricular Thickening With Optical Coherence Tomography

Abstract

Background-A satisfactory imaging technique to determine regional wall thickening of the murine myocardium is not available. Although cardiovascular imaging with light offers a novel solution, application is problematic because scattering by erythrocytes causes significant optical attenuation. Methods and Results-Optical coherence tomography (OCT) is a technique for detailed resolution imaging of highly scattering biological tissues. To reduce the high level of blood scattering, a method was devised whereby murine blood was replaced with a hemoglobin-based blood substitute. The scattering and absorption properties of in vitro preparations of whole blood and dilutions of blood with a blood substitute were determined with a spectrophotometer and an inverse-adding doubling algorithm. OCT imaging of the same dilutions demonstrated a significant reduction in scattering at a hematocrit Ͻ5%. A fiber-optic OCT imaging system was used to image the murine right midventricular free wall before and after isovolumic replacement with blood substitute. Strong light attenuation prevented full thickness imaging before replacement, whereas visualization of the full ventricular thickness was possible after replacement. Baseline and imaging hematocrits were 52.4Ϯ3.8% and 3.7Ϯ1.2%, respectively. End-systolic and end-diastolic thickness values were 0.458Ϯ0.051 mm and 0.352Ϯ0.047 mm. Percent thickening fraction was 30.8Ϯ7.5%. Conclusion-Optical imaging of the intact beating murine right ventricle was substantially improved by isovolumic blood replacement with a hemoglobin-based blood substitute. Although the current study has been directed toward imaging the murine heart, a blood substitute may be applied to various optical diagnostic and therapeutic techniques under investigation in cardiovascular medicine.

Optical Coherence Tomography: Real-time Imaging of Bronchial Airways Microstructure and Detection of Inflammatory/Neoplastic Morphologic Changes

“…In addition, enhanced vascular supply within the inflamed region contributes to reduced imaging capability, as whole blood induces strong attenuation of light. This originates from the absorption of light by hemoglobin and the scattering properties of RBC (15). In contrast, invasive neoplastic changes seem as featureless images on OCT, reflecting total loss of local architecture characteristic of tumor infiltration seen on subsequent histologic examination.…”

MR imaging of caveolin gene-specific alterations in right ventricular wall thickness

“…While the method does not permit instantaneous measurement of right ventricular wall thickening as is possible with optical coherence tomography [14] the MRI method does not require the introduction of any agent other than the anesthetic. We believe MRI will continue to be a powerful noninvasive tool for studies of the RV of genetically altered mice.…”

“…Right ventricle wall thicknesses measured by the two different methods were comparable (0.41F0.11 mm with TEE and 0.46F0.10 mm with MRI). Another recent study employed optical coherence tomography and a hemoglobin-based blood substitute to measure instantaneous RV wall thickening during the cardiac cycle in mice [14]. The end diastolic and end systolic RV wall thicknesses were 0.458F0.051 and 0.352F0.047 mm, respectively.…”

Optical coherence tomography—current technology and applications in clinical and biomedical research

“…First patient studies indicate the general safety of this method [197,198]. Nevertheless, research continues to eliminate the risk of ischemia completely, for instance by matching the refractive index of the blood serum with that of the red blood cells [199] or by using oxygen-carrying flushing liquids [200,201]. An important step was the introduction of high-speed FD-OCT systems, since it enabled the acquisition of large sampling volumes during relatively short flushing periods [36,195].…”