Noninvasive assessment of bowel blood perfusion using intraoperative laser speckle flowgraphy.

PURPOSE: Laser speckle flowgraphy (LSFG) is a noninvasive method for quantitative evaluation of blood flow using the mean blur rate (MBR) as the blood flow index. We investigated whether LSFG can intraoperatively detect the demarcation line after vessel dissection and reduce the incidence of anastomotic leakage (AL). METHODS: This study included 36 patients who underwent left-sided colorectal surgery. First, we compared the demarcation line (determined by LSFG) with the transection line (TL) at which the marginal vessels were divided. We then measured the MBR on both sides of the TL to determine where the MBR changed significantly. We investigated the presence or absence of significant differences between the MBR on the proximal side and that on the distal side of the TL. Finally, we retrospectively compared the patient characteristics and AL rates in the LSFG group (n = 36) and control group (n = 87). RESULTS: In total, 58.3% (21/36) of the demarcation lines determined by LSFG matched the TL. The median distance between the demarcation line determined by LSFG and the TL was 0.0 mm (0.0-12.1 mm). The MBR sharply decreased at the TL in 80.6% (29/36) of cases. The median MBR was significantly lower on the distal than proximal side. The AL rate was not significantly lower in the LSFG group than in the control group. CONCLUSION: LSFG accurately detected the demarcation line during surgery. However, LSFG did not reduce the incidence of AL.

Detection of Site-Specific Blood Flow Variation in Humans during Running by a Wearable Laser Doppler Flowmeter.

Wearable wireless physiological sensors are helpful for monitoring and maintaining human health. Blood flow contains abundant physiological information but it is hard to measure blood flow during exercise using conventional blood flowmeters because of their size, weight, and use of optic fibers. To resolve these disadvantages, we previously developed a micro integrated laser Doppler blood flowmeter using microelectromechanical systems technology. This micro blood flowmeter is wearable and capable of stable measurement signals even during movement. Therefore, we attempted to measure skin blood flow at the forehead, fingertip, and earlobe of seven young men while running as a pilot experiment to extend the utility of the micro blood flowmeter. We measured blood flow in each subject at velocities of 6, 8, and 10 km/h. We succeeded in obtaining stable measurements of blood flow, with few motion artifacts, using the micro blood flowmeter, and the pulse wave signal and motion artifacts were clearly separated by conducting frequency analysis. Furthermore, the results showed that the extent of the changes in blood flow depended on the intensity of exercise as well as previous work with an ergometer. Thus, we demonstrated the capability of this wearable blood flow sensor for measurement during exercise.

Comparative evaluation of pulpal blood flow during incisor intrusion.

AIM: The aim of the present study was to evaluate and compare changes in pulpal blood flow (PBF) as a result of maxillary incisor intrusion achieved by one of two methods (utility arches or mini-implants). MATERIALS AND METHODS: Thirty subjects were divided into three groups, the first of which underwent maxillary incisor intrusion using utility arches (UA) and a second group, intrusion via mini-implants (MI). The third group acted as a control. An intrusive force of 100 g was applied to the upper incisors in the treatment groups, whereas no force was applied to the anterior teeth in the control group. A laser Doppler flowmeter (LDF) was used to measure PBF at baseline (T0) and during incisor intrusion at 24 hours (T1), three days (T2), seven days (T3) and three weeks (T4). Statistical changes in PBF were assessed by the Wilcoxon Signed Rank and Mann-Whitney U tests, with significance set at p < 0.05. RESULTS: The mean PBF in the UA and MI groups decreased significantly from T0 to T1 (p < 0.001), slightly increased at T2 and continued to increase gradually at T3. PBF attained levels similar to those measured prior to intrusion at T4. No significant changes in PBF were observed in the control group over the course of the study. The only statistically significant difference between the UA and MI groups were at T1 and T2, at which time the MI group had lower PBF values (p < 0.001). CONCLUSIONS: Despite slight regressive changes in pulpal tissue observed over the short-term, PBF values tended to return to initial levels within three weeks, indicating that changes observed in PBF with the UA and MI intrusion methods are reversible. Although the changes in PBF could not be directly related to the method of intrusion employed, in general, a more severe drop in PBF was observed in the MI group during the first three days of intrusion.

Self-mixing dual-frequency laser Doppler velocimeter.

A self-mixing (SM) dual-frequency (DF) laser Doppler velocimeter (LDV) (SM DF-LDV) is proposed and studied, which integrates the advantages of both the SM-LDV and the DF-LDV. An optically injected semiconductor laser operated in a dual-frequency period-one (P1) dynamical state is used as the light source. By probing the target with the light-carried microwave generated from the beat of the two optical frequency components, the spectral broadening in the Doppler signal due to the speckle noise can be significantly reduced. Together with an SM configuration, the SM DF-LDV has the advantages of direction discriminability, self-alignment, high sensitivity, and compact setup. In this study, speckle noise reduction and direction discriminability with an SM DF-LDV are demonstrated. The signal-to-noise ratios (SNRs) at different feedback powers are investigated. Benefiting from the high sensitivity of the SM configuration, an SNR of 23 dB is achieved without employing an avalanched photodetector or photomultiplier tube. The velocity resolution and the SNR under different speckle noise conditions are studied. Average velocity resolution of 0.42 mm/s and SNR of 22.1 dB are achieved when a piece of paper is rotating at a transverse velocity of 5 m/s. Compared with a conventional single-frequency LDV (SF-LDV), the SM DF-LDV shows improvements of 20-fold in the velocity resolution and 8 dB in the SNR.

High speed, wide velocity dynamic range Doppler optical coherence tomography (Part IV): split spectrum processing in rotary catheter probes.

We report a technique for blood flow detection using split spectrum Doppler optical coherence tomography (ssDOCT) that shows improved sensitivity over existing Doppler OCT methods. In ssDOCT, the Doppler signal is averaged over multiple sub-bands of the interferogram, increasing the SNR of the Doppler signal. We explore the parameterization of this technique in terms of number of sub-band windows, width and overlap of the windows, and their effect on the Doppler signal to noise in a flow phantom. Compared to conventional DOCT, ssDOCT processing has increased flow sensitivity. We demonstrate the effectiveness of ssDOCT in-vivo for intravascular flow detection within a porcine carotid artery and for microvascular vessel detection in human pulmonary imaging, using rotary catheter probes. To our knowledge, this is the first report of visualizing in-vivo Doppler flow patterns adjacent to stent struts in the carotid artery.

Angiogenic factors and uterine Doppler velocimetry in early- and late-onset preeclampsia.

OBJECTIVE: To assess correlations between maternal serum levels of pro- and anti-angiogenic factors with uterine perfusion in women with early- compared with late-onset preeclampsia, and in healthy pregnant women. DESIGN: Case-control study. SETTING: Antenatal care clinic located within a hospital (São Bernardo do Campo, Brazil). POPULATION: We enrolled 54 preeclamptic and 54 healthy control women who were coming for routine ultrasound at 28-36 weeks' gestation. METHODS: All participants had uterine artery and umbilical Doppler studies and a blood sample to assess maternal serum levels of soluble fms-like tyrosine kinase-1, soluble endoglin, adiponectin and plasminogen activator inhibitor-1. All angiogenic factors were measured using enzyme-linked immunosorbent assay. MAIN OUTCOME MEASURES: Levels of pro- and anti-angiogenic factors in maternal serum, and uterine artery Doppler findings. RESULTS: Concentrations of soluble fms-like tyrosine kinase-1 and soluble endoglin were significantly higher in preeclamptic than control women (p < 0.0001 and p < 0.0001, respectively), especially in those with early-onset (<34 weeks) preeclampsia. These two anti-angiogenic mediators were significantly correlated with increased uterine artery Doppler in the preeclamptic women. Plasminogen activator inhibitor-1 levels were significantly higher in preeclampsia (p = 0.03) but unrelated to uterine artery resistance. Adiponectin levels were similar in cases and controls, independent of body mass index and unrelated to uterine artery resistance. CONCLUSION: Preeclamptic patients have increased soluble fms-like tyrosine kinase-1 and soluble endoglin serum levels and this increase is directly correlated with uterine artery resistance, especially in those with early-onset preeclampsia.

Analysis of four-dimensional Mie imaging using fiber-based endoscopes.

This work reports the demonstration and analysis of four-dimensional (4D) imaging measurements in two-phase flows using fiber-based endoscopes (FBEs). Such 4D measurements resolve the droplet distribution in two-phase flows in all three spatial directions and with a temporal resolution of up to 5 kHz. Demonstration measurements were performed in a measurement volume of 85 mm × 85 mm × 85 mm discretized into 64 × 64 × 64 voxels to illustrate FBEs' potential for facilitating practical implementation of 4D tomographic measurements. Mathematical analyses were performed to quantify the fundamental advantage of FBEs to enhance the reconstruction fidelity.

Full-range Fourier domain Doppler optical coherence tomography based on sinusoidal phase modulation.

A novel full-range Fourier domain Doppler optical coherence tomography (full-range FD-DOCT) using sinusoidal phase modulation for B-M scan is proposed. In this sinusoidal B-M scan, zero optical path difference (OPD) position does not move corresponding to lateral scanning points in contrast to linear B-M scan. Since high phase sensitivity arises around the zero OPD position, the proposed full-range FD-DOCT can achieve easily high velocity sensitivity without mirror image around the zero OPD position. Velocity sensitivity dependent on the OPD and the interval of scanning points is examined, and flow velocity detection capability is verified through Doppler imaging of a flow phantom and an in vivo biological sample.

The effect of vascular pedicle preservation on blood flow and clinical outcome following ulnar nerve transposition.

PURPOSE: To evaluate the efficacy of a technique to preserve the extrinsic vascular supply to the ulnar nerve after transposition and its effect on blood flow and clinical outcome. METHODS: We included 36 patients with cubital tunnel syndrome. The patients were randomly selected to undergo vascular pedicles-sparing surgery for anterior ulnar nerve transposition (VP group) or nerve transposition and artery ligation (non-VP group). Blood flow to the ulnar nerve was estimated intraoperatively at 3 locations in the cubital tunnel before and after transposition using a laser Doppler flowmeter. Clinical results at 3, 6, and 12 months after surgery were also compared between the 2 groups. RESULTS: The blood flow before ulnar nerve transposition was not significantly different between the groups. Blood flow at all 3 locations after the ulnar nerve transposition was significantly higher in the VP group than in the non-VP group. Blood flow in the non-VP group reduced to values between 28% and 52% from the pre-transposition baseline values. After surgery, no significant differences were observed in the clinical results between the groups, except for the Disabilities of the Arm, Shoulder and Hand scores at 12 months after surgery, which was greater in the non-VP group. CONCLUSIONS: The procedure of preserving the extrinsic vascular pedicles can prevent compromise of blood flow to the ulnar nerve immediately after nerve transposition. However, this procedure had no correlation to improved recovery of ulnar nerve function after surgery. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic II.

Doppler-based flow rate sensing in microfluidic channels.

We design, fabricate and experimentally demonstrate a novel generic method to detect flow rates and precise changes of flow velocity in microfluidic devices. Using our method we can measure flow rates of ~2 mm/s with a resolution of 0.08 mm/s. The operation principle is based on the Doppler shifting of light diffracted from a self-generated periodic array of bubbles within the channel and using self-heterodyne detection to analyze the diffracted light. As such, the device is appealing for variety of "lab on chip" bio-applications where a simple and accurate speed measurement is needed, e.g., for flow-cytometry and cell sorting.

Changes in maxillary incisor dental pulp blood flow during intrusion by mini-implants.

AIM: The aim of this clinical study was to identify changes in pulpal blood flow (PBF) in human central incisors resulting from short- and long-term intrusive orthodontic forces from mini-implants. MATERIALS AND METHODS: A total of 40 sound upper central and lateral incisors in 20 patients scheduled for intrusion for orthodontic reasons were divided into two groups. From each group, 20 teeth were subjected to intrusive force from mini-implants (Group 1 = Light Force: 40 g; Group 2 = Heavy Force: 120 g), whereas the remaining 20 contralateral teeth were not subjected to forces from mini-implants and served as controls. Laser-Doppler flowmetry (LDF) measurements were recorded at baseline and at 3 days and 3 weeks following intrusion. RESULTS: PBF decreased significantly at 3 days (Light Force Group: 7.72 ± 0.50; Heavy Force Group: 7.72 ± 0.52) and then increased towards baseline at 3 weeks (Light Force Group: 10.37 ± 0.58; Heavy Force Group: 10.31 ± 0.45) following intrusion. CONCLUSIONS: In other words, despite slight regressive changes in pulpal tissue in the short-term, PBF improved after 3 weeks following intrusion by mini-implants, indicating that the changes observed in PBF is reversible, even following radical incisor intrusion.

Changes in maxillary molar pulp blood flow during orthodontic intrusion.

INTRODUCTION/OBJECTIVE: The aim of this prospective study was to evaluate the effects of maxillary first molar intrusion on pulpal blood flow (PBF) in humans as recorded by laser Doppler flowmetry (LDF). MATERIALS AND METHODS: Maxillary first molars of 16 participants were divided into two groups. In the study group, 20 teeth in 10 participants were subjected to an intrusive force of 100 g delivered from mini-implants for 6 months. A control group of 6 subjects (12 teeth) received no orthodontic treatment. LDF measurements were recorded at baseline and at 3 days, 3 weeks, 3 months and 6 months during intrusion. Data was analysed using the Wilcoxon Signed Rank and Mann-Whitney U tests, with a level of p < 0.05 considered statistically significant. RESULTS: No significant changes in PBF perfusion units (PU) were observed in the control group over the course of the study. However, PBF in the study group was significantly higher at TO (8.7 ± 0.9 PU) when compared with T1 (6.1 ± 0.6 PU, p < 0.001) and T2 (6.0 ± 0.6 PU, p < 0.001). PBF did not vary significantly between T1 and T2 (p = 0.073) or between T3 and T4 (p = 0.262). Moreover, PBF at the end of the study (T4) was similar to baseline PBF values for both groups (study group: p = 0.687; control group: p = 0.525). CONCLUSIONS: Despite significant short-term regressive changes in pulpal tissue during continuous molar intrusion with mini-implants and an applied force of 100 g, blood vessel function was maintained throughout intrusion, as indicated by LDF measurements of PBF, which tended to return to baseline values by the end of the observation period. These results highlight the changes that can occur in molar vascularity, especially during six months of intrusion.

Extendable, miniaturized multi-modal optical imaging system: cortical hemodynamic observation in freely moving animals.

Observation of brain activities in freely moving animals has become an important approach for neuroscientists to understand the correlation between brain function and behavior. We describe an extendable fiber-optic-based multi-modal imaging system that can concurrently carry out laser speckle contrast imaging (LSCI) of blood flow and optical intrinsic signal (OIS) imaging in freely moving animals, and it could be extended to fluorescence imaging. Our imaging system consists of a multi-source illuminator, a fiber multi-channel optical imaging unit, and a head-mounted microscope. The imaging fiber bundle delivers optical images from the head-mounted microscope to the multi-channel optical imaging unit. Illuminating multi-mode fiber bundles transmit light to the head-mounted microscope which has a mass of less than 1.5 g and includes a gradient index lens, giving the animal maximum movement capability. The internal optical components are adjustable, allowing for a change in magnification and field of view. We test the system by observing hemodynamic changes during cortical spreading depression (CSD) in freely moving and anesthetized animals by simultaneous LSCI and dual-wavelength OIS imaging. Hemodynamic parameters were calculated. Significant differences in CSD propagation durations between the two states were observed. Furthermore, it is capable of performing fluorescence imaging to explore animal behavior and the underlying brain functional activity further.

Ultrasonically encoded photoacoustic flowgraphy in biological tissue.

Blood flow speed is an important functional parameter. Doppler ultrasound flowmetry lacks sufficient sensitivity to slow blood flow (several to tens of millimeters per second) in deep tissue. To address this challenge, we developed ultrasonically encoded photoacoustic flowgraphy combining ultrasonic thermal tagging with photoacoustic imaging. Focused ultrasound generates a confined heat source in acoustically absorptive fluid. Thermal waves propagate with the flow and are directly visualized in pseudo color using photoacoustic computed tomography. The Doppler shift is employed to calculate the flow speed. This method requires only acoustic and optical absorption, and thus is applicable to continuous fluid. A blood flow speed as low as 0.24 mm·s(-1)} was successfully measured. Deep blood flow imaging was experimentally demonstrated under 5-mm-thick chicken breast tissue.

Comparison of CCD-equipped laser speckle flowgraphy with hydrogen gas clearance method in the measurement of optic nerve head microcirculation in rabbits.

The aim of this study was to verify the correlation between mean blur rate (MBR) obtained with CCD-equipped laser speckle flowgraphy (LSFG) and capillary blood flow (CBF) obtained by the hydrogen gas clearance method in rabbit optic nerve head (ONH). Using Japanese white rabbits under systemic anesthesia, a hydrogen electrode was inserted an area of the ONH free from superficial capillaries. MBR was measured with LSFG near the hydrogen electrode. CBF and MBR were measured in the range of 32.4-83.5 mL/min/100 g and 3.5-6.0, respectively. MBR and CBF were significantly correlated (r = 0.73, P < 0.01, n = 14). After inhalation of carbon dioxide (CO(2)) or intravenous administration of endothelin-1 (ET-1), MBR and CBF were changed in the relative range of 0.74-1.27 and 0.76-1.35, respectively. The relative changes in MBR and CBF induced by CO(2) and ET-1 were also significantly correlated (r = 0.67, P < 0.01). The current results suggest that MBR may correlate with CBF and also change with CBF, as an index of blood flow in the ONH, linearly.

Self-mixing laser Doppler flow sensor: an optofluidic implementation.

We present the miniaturization of self-mixing interferometry (SMI) into a microfluidic circuit using an optical fiber, forming an optofluidic device that can be used as a component in lab on a chip systems. We characterize the performance of the device as a fluid velocity (and hence flow) sensor, showing it to produce good accuracy and correlation with theory over a range of velocities from 0.5 to 60 mm/s and almost four decades of scatterer concentration. SMI in an optofluidic system has the advantage that only a single path to the optical inspection point is needed, as the laser source is also the receiver of light. In addition, the same system that is used for measuring fluid velocity can be used to measure other quantities such as particle size. The configuration presented is inherently easy to optically align due to the self-aligned property of SMI and divergent nature of light exiting the embedded optical fiber, providing for low-cost manufacturing.

A comparative study of colour and perfusion between two different post surgical scars. Do the laser Doppler imager and the colorimeter measure the same features of a scar?

BACKGROUND/PURPOSE: The purpose of this study was to investigate the influence of different located post surgical scars on both perfusion and redness. The pattern of change and correlation between perfusion and redness of post surgical scars is also examined. METHODS: In this study, we measured redness and perfusion of the abdominal and breast scar of 24 women undergoing breast reconstruction with Deep Inferior Epigastric Perforator Free Flap surgery with the Minolta Chromameter CR-400/410 and the Moor Instruments laser Doppler imager 12IR, respectively, at different intervals post-operatively. RESULTS: The laser Doppler imager gives significantly higher values for the abdominal compared with the breast scar. There was no consistent correlation found between perfusion and redness at the different test moments for both locations. The scores of both parameters were significantly associated after 9 months follow-up for both locations. CONCLUSION: Scars closed with higher mechanical force show higher perfusion and prolonged activity; and more redness is associated with more perfusion for both post surgical scars. Nevertheless, there was no consistent correlation found between these parameters making the laser Doppler imager and the Colorimeter still non-replaceable instruments.

Effect of tooth isolation on laser Doppler readings.

AIM: To measure differences between single (STI) and multiple teeth isolation (MTI), pulpal blood flow (PBF) was assessed using laser Doppler flowmetry (LDF). METHODOLOGY: Pulpal blood flow of twenty maxillary incisors with no restorations or abnormal responses to sensitivity tests in healthy patients between 24 and 42 years of age was measured in perfusion units (PU). STI (isolation of only the tooth undergoing blood flow assessment) and MTI (isolation including the maxillary right to the maxillary left canine) recordings were taken with regular blood flow (RBF) and with local infiltration (LI) with vasoconstrictor. anova and Tukey HSD tests were used for statistical analysis. RESULTS: The mean PBF with regular blood flow conditions was significantly different between single tooth isolation [5.53 PU (SD ± 2.98)] and multiple tooth isolation [2.85 PU (SD ± 2.13)] (P < 0.01). When local anaesthesia was administered (LI), the PBF was significantly different between single tooth isolation [2.95 PU (SD ± 2.48)] and multiple tooth isolation [1.32 PU (SD ± 0.70)] (P < 0.05). Significant differences in PBF also existed between single tooth isolation under regular blood flow conditions and with local anaesthesia (P < 0.01), between single tooth isolation under regular blood flow conditions and multiple tooth isolation with local anaesthesia (P < 0.01), and between multiple tooth isolation under regular blood flow conditions and with local anaesthesia (P < 0.05). CONCLUSIONS: Pulpal blood flow measurements could be obtained with multiple teeth isolation and single tooth isolation. Multiple teeth isolation blocked signal contamination better. Single tooth isolation provided significantly different readings for regular blood flow and LI conditions and may therefore provide an option for pulpal blood flow assessment with LDF.

Optical multi-point measurements of the acoustic particle velocity with frequency modulated Doppler global velocimetry.

To reduce the noise of machines such as aircraft engines, the development and propagation of sound has to be investigated. Since the applicability of microphones is limited due to their intrusiveness, contactless measurement techniques are required. For this reason, the present study describes an optical method based on the Doppler effect and its application for acoustic particle velocity (APV) measurements. While former APV measurements with Doppler techniques are point measurements, the applied system is capable of simultaneous measurements at multiple points. In its current state, the system provides linear array measurements of one component of the APV demonstrated by multi-tone experiments with tones up to 17 kHz for the first time.