HemoSYS: An Image‐based Toolkit for Quantifying Hemodynamics in the Microcirculation

Objective To develop an easy‐to‐use image‐based toolkit for quantifying spatiotemporal hemodynamic changes in the healthy and pathologic microcirculation. Methods We combined the capabilities of two well‐known image processing platforms: Matlab ® (MathWorks, MA) and ImageJ into a single framework, and created an interactive graphical user interface (GUI) to manage all aspects of user interactions. The resulting toolkit for quantifying hemodynamic changes, HemoSYS, can be utilized without any prior programming knowledge, and consists of five analysis modules: propagation, clustering, coupling, perturbation, and Fourier. We demonstrate the utility of HemoSYS by using it to quantify hemodynamic changes within the tumor microenvironment (TME) of a murine breast cancer model. To acquire multi‐variable microcirculatory dynamics of the TME, we used a multi‐contrast optical imaging system and obtained wide field (i.e. 5 × 7 mm 2 ) images of tumor extent via fluorescence (FL) imaging of GFP tagged tumor cells, and concurrent image‐sequences of tumor microvasculature or blood volume (BV) via hemoglobin‐based intrinsic optical signal (IOS) imaging, intravascular oxygen saturation (HbSat) via IOS imaging, and blood flow (BF) via laser speckle contrast (LSC) imaging every 30 seconds, for 1 hour. Results Fig. 1 shows a schematic of HemoSYS illustrating its input data and capabilities. Using HemoSYS on a cohort of 5 animals, we identified the tumor extent and interrogated: (i) the propagation characteristics of an acute hypoxic episode; (ii) the formation and cessation of clusters with distinct microcirculatory dynamics; (iii) the dysregulation of blood flow; (iv) the multi‐variable hemodynamic response to carbogen gas inhalation;and (v) the heterogeneity of microcirculatory dynamics in the frequency domain. Conclusion HemoSYS (freely available upon request) enables characterization of hemodynamic changes in microvascular beds using a systems biology approach. It can be used by anyone interested in quantifying hemodynamic changes from imaging data because it does not require any programming experience. While we demonstrated its utility using wide‐field optical imaging data, HemoSYS could be readily modified to accept input data from additional imaging modalities such as MR, PET, and Photoacoustic imaging. We believe that HemoSYS will become a tool‐of‐choice for image‐based characterization of the microcirculation in any preclinical disease model or tissue bed. Support or Funding Information This work was supported by NCI 1R01CA196701, 5R01CA138264 and a Kavli Neuroscience Distinguished Fellowship (JS).Schematic of HemoSYS illustrating its inputs and capabilities. HemoSYS accepts a broad range of inputs, from static images indicating an area of interest (e.g. the tumor extent) to multiple image‐sequences showing concurrent spatiotemporal changes in multiple hemodynamic variables (e.g. BV, HbSat and BF). One can then interactively use HemoSYS’s five modules (i.e. propagation, clustering, coupling, perturbation and Fourier) to quantify and characterize the underlying microcirculation.