Diffuse optical spectroscopy imaging (DOSI) has shown great potential for the early detection of non-responding
tumors during neoadjuvant chemotherapy in breast cancer, already one day after therapy starts. Patients with rectal
cancer receive similar chemotherapy treatment. The rectum geometry and tissue properties of healthy and tumor
tissue in the rectum and the requirement of surface contact impose constraints on the probe design.
In this work we present the design of a DOSI probe with the aim of early chemotherapy/radiotherapy
effectiveness detection in rectal tumors. We show using Monte Carlo simulations and phantom measurements that
the colon tissue can be characterized reliably using a source-detector separation in the order of 10 mm. We present a
design and rapid prototype of a probe for DOSI measurements that can be mounted on a standard laparoscope and
that fits through a standard rectoscope. Using predominantly clinically approved components we aim at fast clinical
translation.
The use of near-infrared time-resolved spectroscopy (TRS-20, Hamamatsu Corporation) in two resistance type exercise applications in human subjects is described. First, using isometric flexion of the biceps, we compared the magnitude and relevance of tissue hemoglobin concentration and oxygen saturation (stO2) changes when assuming constant scattering versus continuous measurement of reduced scattering coefficients at three wavelengths. It was found that the assumption of constant scattering resulted in significant errors in hemoglobin concentration assessment during sustained isometric contractions. Secondly, we tested the effect of blood flow restriction (BFR) on oxygenation in a muscle (vastus medialis oblique, VMO) and in the prefrontal cortex (PFC) of the brain. The BFR training technique resulted in considerably more fatigability in subjects, and correlated with reduced muscle stO2 between sets of exertion. Additionally, exercise with BFR resulted in greater PFC deoxygenation than a condition with equivalent work performance but no BFR. These experiments demonstrate novel applications for diffuse optical spectroscopy in strength testing and targeted muscle rehabilitation.
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