Introduction to pCRT

pCRT (alternatively called rCRT) is an algorithmically calculated metric of peripheral perfusion that is analogous to CRT (Capillary Refill Time). The acronyms stand for polarized CRT or reflective CRT, in reference to the use of polarizers and diffusely reflected light in the master’s thesis [1] which this library is based upon.

CRT is defined as the time it takes for a region of skin (typically a finger or the forearm) to return to its original color after enough pressure is applied to cause bleaching [2]. CRT is usually measured by the examiner’s own visual assessment and a chronometer, while pCRT is measured through the use of a digital camera and digital video processing, resulting in increased reproducibility and allowing for measurements on all skin phototypes [1].

This library (pyCRT) initially sought merely to reimplement the MATLAB routines developed by Pantojo & Cunha for the aforementioned master’s thesis, but over time its features grew beyond the original work’s scope.

Algorithm for calculation

PyrCRT’s data model

References

[1] (1,2)

de Souza, Raquel Pantojo, and George Cunha Cardoso. “Skin color independent robust assessment of capillary refill time.” arXiv preprint arXiv:2102.13611 (2021).

[2]

Pickard, Amelia, Walter Karlen, and J. Mark Ansermino. “Capillary refill time: is it still a useful clinical sign?.” Anesthesia & Analgesia 113.1 (2011): 120-123.