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A noncontact electron multiplying charge-coupled-device (EMCCD)-based speckle contrast diffuse correlation tomography (scDCT) technology has been recently developed in our laboratory, allowing for noninvasive three-dimensional measurement of tissue blood flow distributions. One major remaining constraint in the scDCT is the assumption of a semi-infinite tissue volume with a flat surface, which affects the image reconstruction accuracy for tissues with irregular geometries. An advanced photometric stereo technique (PST) was integrated into the scDCT system to obtain the surface geometry in real time for image reconstruction. Computer simulations demonstrated that a priori knowledge of tissue surface geometry is crucial for precisely reconstructing the anomaly with blood flow contrast. Importantly, the innovative integration design with one single- EMCCD camera for both PST and scDCT data collection obviates the need for offline alignment of sources and detectors on the tissue boundary. The in vivo imaging capability of the updated scDCT is demonstrated by imaging dynamic changes in forearm blood flow distribution during a cuff-occlusion procedure. The feasibility and safety in clinical use are evidenced by intraoperative imaging of mastectomy skin flaps and comparison with fluorescence angiography. [ABSTRACT FROM AUTHOR]

This study used a hybrid near-infrared diffuse optical instrument to monitor tumor hemodynamic responses to chemoradiation therapy for early prediction of treatment outcomes in patients with head and neck cancer. Forty-seven patients were measured once per week to evaluate the hemodynamic status of clinically involved cervical lymph nodes as surrogates for the primary tumor response. Patients were classified into two groups: complete response (CR) (n = 29) and incomplete response (IR) (n = 18). Tumor hemodynamic responses were found to be associated with clinical outcomes (CR/IR), wherein the associations differed depending on human papillomavirus (HPV-16) status. In HPV-16 positive patients, significantly lower levels in tumor oxygenated hemoglobin concentration ([HbO2]) at weeks 1 to 3, total hemoglobin concentration at week 3, and blood oxygen saturation (StO2) at week 3 were found in the IR group. In HPV-16 negative patients, significantly higher levels in tumor blood flow index and reduced scattering coefficient (μ's) at week 3 were observed in the IR group. These hemodynamic parameters exhibited significantly high accuracy for early prediction of clinical outcomes, within the first three weeks of therapy, with the areas under the receiver operating characteristic curves (AUCs) ranging from 0.83 to 0.96. [ABSTRACT FROM AUTHOR]

We report a low-cost compact diffuse speckle contrast flowmeter (DSCF) consisting of a small laser diode and a bare charge-coupled-device (CCD) chip, which can be used for contact measurements of blood flow variations in relatively deep tissues (up to ∼8 mm). Measurements of large flow variations by the contact DSCF probe are compared to a noncontact CCD-based diffuse speckle contrast spectroscopy and a standard contact diffuse correlation spectroscopy in tissue phantoms and a human forearm. Bland-Altman analysis shows no significant bias with good limits of agreement among these measurements: 96.5% ± 2.2% (94.4% to 100.0%) in phantom experiments and 92.8% in the forearm test. The relatively lower limit of agreement observed in the in vivo measurements (92.8%) is likely due to heterogeneous reactive responses of blood flow in different regions/volumes of the forearm tissues measured by different probes. The low-cost compact DSCF device holds great potential to be broadly used for continuous and longitudinal monitoring of blood flow alterations in ischemic/hypoxic tissues, which are usually associated with various vascular diseases. [ABSTRACT FROM AUTHOR]

Occlusion calibrations and gating techniques have been recently applied by our laboratory for continuous and absolute diffuse optical measurements of forearm muscle hemodynamics during handgrip exercises. The translation of these techniques from the forearm to the lower limb is the goal of this study as various diseases preferentially affect muscles in the lower extremity. This study adapted a hybrid near-infrared spectroscopy and diffuse correlation spectroscopy system with a gating algorithm to continuously quantify hemodynamic responses of medial gastrocnemius during plantar flexion exercises in 10 healthy subjects. The outcomes from optical measurement include oxy-, deoxy-, and total hemoglobin concentrations, blood oxygen saturation, and relative changes in blood flow (rBF) and oxygen consumption rate (r...O2). We calibrated rBF and r...O2 profiles with absolute baseline values of BF and ...O2 obtained by venous and arterial occlusions, respectively. Results from this investigation were comparable to values from similar studies. Additionally, significant correlation was observed between resting local muscle BF measured by the optical technique and whole limb BF measured concurrently by a strain gauge venous plethysmography. The extensive hemodynamic and metabolic profiles during exercise will allow for future comparison studies to investigate the diagnostic value of hybrid technologies in muscles affected by disease. [ABSTRACT FROM AUTHOR]

Our first step to adapt our recently developed noncontact diffuse correlation tomography (ncDCT) system for three-dimensional (3-D) imaging of blood flow distribution in human breast tumors is reported. A commercial 3-D camera was used to obtain breast surface geometry, which was then converted to a solid volume mesh. An ncDCT probe scanned over a region of interest on the mesh surface and the measured boundary data were combined with a finite element framework for 3-D image reconstruction of blood flow distribution. This technique was tested in computer simulations and in vivo human breasts with low-grade carcinoma. Results from computer simulations suggest that relatively high accuracy can be achieved when the entire tumor is within the sensitive region of diffuse light. Image reconstruction with a priori knowledge of the tumor volume and location can significantly improve the accuracy in recovery of tumor blood flow contrasts. In vivo imaging results from two breast carcinomas show higher average blood flow contrasts (5.9- and 10.9-fold) in the tumor regions compared to the surrounding tissues, which are comparable with previous findings using diffuse correlation spectroscopy. The ncDCT system has the potential to image blood flow distributions in soft and vulnerable tissues without distorting tissue hemodynamics. [ABSTRACT FROM AUTHOR]

Knowledge of tissue blood flow (BF) changes after free tissue transfer may enable surgeons to predict the failure of flap thrombosis at an early stage. This study used our recently developed noncontact diffuse correlation spectroscopy to monitor dynamic BF changes in free flaps without getting in contact with the targeted tissue. Eight free flaps were elevated in patients with head and neck cancer; one of the flaps failed. Multiple BF measurements probing the transferred tissue were performed during and post the surgical operation. Postoperative BF values were normalized to the intraoperative baselines (assigning "1") for the calculation of relative BF change (rBF). The rBF changes over the seven successful flaps were 1.89 ± 0.15, 2.26 ± 0.13, and 2.43 ± 0.13 (mean ± standard error), respectively, on postoperative days 2, 4, and 7. These postoperative values were significantly higher than the intraoperative baseline values (p < 0.001), indicating a gradual recovery of flap vascularity after the tissue transfer. By contrast, rBF changes observed from the unsuccessful flaps were 1.14 and 1.34, respectively, on postoperative days 2 and 4, indicating less flow recovery. Measurement of BF recovery after flap anastomosis holds the potential to act early to salvage ischemic flaps. [ABSTRACT FROM AUTHOR]