Head and neck cancer accounts for 3 to 5% of all cancers in the United States. Primary or salvage surgeries are extensive and often lead to major head and neck defects that require complex reconstructions with local, regional, or free tissue transfer flaps. 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 flap were 1.14 and 1.34 respectively on postoperative days 2 and 4, indicating a less flow recovery. Measurement of BF recovery after flap anastomosis holds the potential to act early to salvage ischemic flaps.
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.
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.
Technologies currently available for the monitoring of electrical stimulation (ES) in promoting blood circulation and tissue oxygenation are limited. This study integrated a muscle stimulator with a diffuse correlation spectroscopy (DCS) flow-oximeter to noninvasively quantify muscle blood flow and oxygenation responses during ES. Ten healthy subjects were tested using the integrated system. The muscle stimulator delivered biphasic electrical current to right leg quadriceps muscle, and a custom-made DCS flow-oximeter was used for simultaneous measurements of muscle blood flow and oxygenation in both legs. To minimize motion artifact of muscle fibers during ES, a novel gating algorithm was developed for data acquisition at the time when the muscle was relaxed. ES at 2, 10, and 50 Hz were applied for 20 min on each subject in three days sequentially. Results demonstrate that the 20-min ES at all frequencies promoted muscle blood flow significantly. However, only the ES at 10 Hz resulted in significant and persistent increases in oxy-hemoglobin concentration during and post ES. This pilot study supports the application of the integrated system to quantify tissue hemodynamic improvements for the optimization of ES treatment in patients suffering from diseases caused by poor blood circulation and low tissue oxygenation (e.g., pressure ulcer).
The dual-wavelength diffuse correlation spectroscopy (DCS) flow-oximeter is an emerging technique enabling simultaneous measurements of blood flow and blood oxygenation changes in deep tissues. High signal-to-noise ratio (SNR) is crucial when applying DCS technologies in the study of human tissues where the detected signals are usually very weak. In this study, single-mode, few-mode, and multimode fibers are compared to explore the possibility of improving the SNR of DCS flow-oximeter measurements. Experiments on liquid phantom solutions and in vivo muscle tissues show only slight improvements in flow measurements when using the few-mode fiber compared with using the single-mode fiber. However, light intensities detected by the few-mode and multimode fibers are increased, leading to significant SNR improvements in detections of phantom optical property and tissue blood oxygenation. The outcomes from this study provide useful guidance for the selection of optical fibers to improve DCS flow-oximeter measurements.
A noncontact diffuse correlation spectroscopy (DCS) probe has been developed using two separated optical paths for the source and detector. This unique design avoids the interference between the source and detector and allows large source-detector separations for deep tissue blood flow measurements. The noncontact probe has been calibrated against a contact probe in a tissue-like phantom solution and human muscle tissues; flow changes concurrently measured by the two probes are highly correlated in both phantom (R2 = 0.89, p<10−5) and real-tissue (R2 = 0.77, p<10−5, n = 9) tests. The noncontact DCS holds promise for measuring blood flow in vulnerable (e.g., pressure ulcer) and soft (e.g., breast) tissues without distorting tissue hemodynamic properties.
All-Reflected Fourier Transform Imaging Spectrometer (ARFTIS) is a novel type of instrument based on Fourier
transform spectroscopy. ARFTIS will offer high luminous flux and high spectral resolution, well suited to remote sensing
with low energy. But there is nearly not any method of convenient spectrum calibration for this kind of instrument. In
this paper, we analyze the spectrum calibration principle of ARFTIS and the cause of the calibration error. We reached
the result that the calibration error is getting bigger with the increase of spectrum peak wavelength of the calibration light.
By these we develop three convenient spectrum calibration methods used in Visible/Near-Infrared waveband, which are
the Monochromatic Method, the Average Method and the Weighted Average Method respectively. We apply these
methods to ARFTIS calibrate experiment. According to the experiment results, The Monochromatic Method can
calibrate by using only one group of data, but with a little lower calibration precision. However the Weighted Average
Method can provide a higher calibration precision than the other two methods. So, the Monochromatic method and the
Weighted Average Method both have good application value for ARFTIS calibration.
The Computed-Tomography Imaging Interferometer (CTII) is a novel imaging spectrometer, which combines the
advantages of the conventional Fourier Transform Imaging Spectrometer (FTIS) and the ordinary
Computed-Tomography Imaging Spectrometer (CTIS). CTII obtains multi-angle projection interferograms by rotating
Dove prism placed in the collimating light beams. The image reconstruction is carried out by using
computed-tomography reconstruction algorithm named Radon transform. However, in experiments, images
reconstructed from the raw projection-interferogram sequences, are badly distorted. To solve this problem, we find when
Dove prism is rotated, its rotation center is not coincident to the optic axis of CTII. Therefore, the raw
projection-interferogram sequences have a few deviations to the ideal sequences. And then we find the deviations follow
certain law, so it is possible to rectify the raw projection-interferogram sequences. In this paper, two methods, the Linear
rectification method and the Cosine rectification method are proposed. The Linear rectification method uses an image
processing method, gets the dither value at each rotation angle, and rectifies the raw images. The Cosine rectification
method supposes the dither follows cosine change; the detail is presented in this paper. Finally, the reconstruction images
are presented. The reconstruction results show these two rectification methods are feasible and effective.
The definition and classifications of the UV communication are described in the paper. The UV channel
consists of three sections: propagation loss section, scattering section and background-noise section. The
principle of selecting the wave band of UV communication is analyzed. The LOS and NLOS (a) transmission
models are presented, and the two configurations are well proved by outdoor experiments. The experiment
results also show that the communication distance of LOS can go up to 5kms, and NLOS(a) can reach 2kms
with the UV detectors at present.
In this paper, we introduce a new approach of simultaneous acquisition of hyper-spectral image by means of using
Computed Tomography Imaging Interferometer. Detecting rapidly varying targets both spatially and spectrally using
imaging spectrometer is an international phenomenon in remote sensing in recent years and worthwhile in many domains
such as pollution inspection and biochemical arms detection. Computed Tomography Imaging Interferometer (CTII) we
put forward previously is a kind of imaging spectrometer with merits of high resolution, high throughout and high
signal-to-noise rate. In our current work, some transmogrifications have been brought into the existed model of CTII. More
channels are constructed in the new type of CTII-Simultaneous CTII (SiCTII). The rotation system in each channel is made
irrotianal. Snapshot can be brought in the acquisition by means of opening and closing channels simultaneously. The
Algebraic Reconstruction Technique (ART) and Artificial Neural Network (ANN) are considered in the image
reconstruction. Referring to the characteristics of SiCTII, a conclusion can be made that SiCTII is a kind of imaging
spectrometer for rapid acquisition and can be applied in the instances, in which the spatial resolution is not highly
demanded and rapid data acquisition is demanded.
We introduce our latest research of the computed tomography Fourier transform imaging spectrometer that combines the advantages of both the computed tomography imaging spectrometer and the Fourier transform imaging spectrometer. In our previous work, there were still some problems such as the optical aberration in the optical system. Therefore, some significant improvements are made on the optical configuration of our new system. In this paper, the computational simulation of our new system is introduced. Both the interferogram-projection cube and the spectrum-projection cube are generated in the simulation experiment, and the filtered back projection algorithm is adopted in the image reconstruction. The results of the simulation demonstrate the feasibility of our new system.
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