Differential pathlength factor informs evoked stimulus response in a mouse model of Alzheimer’s disease

Abstract

Abstract. Baseline optical properties are typically assumed in calculating the differential pathlength factor (DPF) of mouse brains, a value used in the modified Beer-Lambert law to characterize an evoked stimulus response. We used spatial frequency domain imaging to measure in vivo baseline optical properties in 20-month-old control (n ¼ 8) and triple transgenic APP/PS1/tau (3xTg-AD) (n ¼ 5) mouse brains. Average μ a for control and 3xTg-AD mice was 0.82 AE 0.05 and 0.65 AE 0.05 mm −1 , respectively, at 460 nm; and 0.71 AE 0.04 and 0.55 AE 0.04 mm −1 , respectively, at 530 nm. Average μ 0 s for control and 3xTg-AD mice was 1.5 AE 0.1 and 1.7 AE 0.1 mm −1 , respectively, at 460 nm; and 1.3 AE 0.1 and 1.5 AE 0.1 mm −1 , respectively, at 530 nm. The calculated DPF for control and 3xTg-AD mice was 0.58 AE 0.04 and 0.64 AE 0.04 OD mm, respectively, at 460 nm; and 0.66 AE 0.03 and 0.73 AE 0.05 OD mm, respectively, at 530 nm. In hindpaw stimulation experiments, the hemodynamic increase in brain tissue concentration of oxyhemoglobin was threefold larger and two times longer in the control mice compared to 3xTg-AD mice. Furthermore, the washout of deoxyhemoglobin from increased brain perfusion was seven times larger in controls compared to 3xTg-AD mice (p < 0.05).

Intrinsic, widefield optical imaging of hemodynamics in rodent models of Alzheimer’s disease and neurological injury

“…The current delivered to the rodent paw ranges from 0.5 to 1.5 mA. 26 , 110 – 113 A higher current will typically lead to a larger hemodynamic response. However, care must be taken to not exceed a current that causes pain, as this response differs from a traditional NVC response.…”

Structured illumination diffuse optical tomography for noninvasive functional neuroimaging in mice

“…37 Although the technique can provide 3-D tomographic reconstructions of absorption heterogeneities, 35,36 thus far the implementations in rodent neuroimaging, for example to monitor stroke, 38 cortical spreading depressions, 39 or Alzheimer's disease, 40,41 have required invasive surgeries prior to imaging or have not been used in applications with fast dynamics (∼1 s). Additionally, although SFDI is commonly used to assess baseline optical properties, [42][43][44] our technique compares the light fall-offs as a function of effective distance in the optical measurements versus a finite element forward model, which will be easily translatable to calculating optical properties in complex geometries.…”

Diffuse optical spectroscopic method for tissue and body composition assessment

“…13 Not surprisingly, there are some efforts to develop and commercialize NIRS approaches to measure the key elements of body composition. 14,15 As suggested in animal and human studies, 16,17 current commercial efforts are, however, limited due to their reliance on continuous-wave NIRS and their dependence on substantial assumptions about tissue scattering, optical pathlength, and composition. Advancements in time-and frequency-domain diffuse optical methods, in combination with broadband time-independent NIRS, has reduced reliance on many of these assumptions 18 and allowed for multiple physiological variables to be assessed with a single multi-modality device.…”