Highly parallel Monte-Carlo simulations of the acousto-optic effect in heterogeneous turbid media

The development of a highly parallel simulation of the acousto-optic effect is detailed. The simulation supports optically heterogeneous simulation domains under insonification by arbitrary monochromatic ultrasound fields. An adjoint method for acousto-optics is proposed to permit point-source/point-detector simulations. The flexibility and efficiency of this simulation code is demonstrated in the development of spatial absorption sensitivity maps which are in broad agreement with current experimental investigations. The simulation code has the potential to provide guidance in the feasibility and optimization of future studies of the acousto-optic technique, and its speed may permit its use as part of an iterative inversion model

Cerebral and Peripheral Tissue Oxygenation in Children Supported on ECMO for Cardio-Respiratory Failure

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for patients with cardio-respiratory failure. Establishing, maintaining and weaning from ECMO may increase the risk for intracranial injury. We used a dual channel near infrared system to monitor cerebral and peripheral tissue oxygenation in 3 venoarterial (VA) and 1 venovenous (VV) ECMO patients undergoing manipulations in the ECMO circuit flows. Spectral analysis was performed on the oxyhaemoglobin data collected from these patients with the aim of comparing oscillations at range of frequencies appearing in the two measurement sites

A Hybrid Multi-Distance Phase and Broadband Spatially Resolved Spectrometer and Algorithm for Resolving Absolute Concentrations of Chromophores in the Near-Infrared Light Spectrum

For resolving absolute concentration of tissue chromophores in the human adult brain with near-infrared spectroscopy it is necessary to calculate the light scattering and absorption, at multiple wavelengths with some depth resolution. To achieve this we propose an instrumentation configuration that combines multi-distance frequency and broadband spectrometers to quantify chromophores in turbid media by using a hybrid spatially resolved algorithm. Preliminary results in solid phantoms as well as liquid dynamic homogeneous and inhomogeneous phantoms and in-vivo muscle measurements showed encouraging results

Cerebral blood flow and oximetry response to blood transfusion in relation to chronological age in preterm infants

OBJECTIVE: Preterm infants frequently receive blood transfusion (BT) and the aim of this study was to measure the effect of BT on cerebral blood flow and oxygenation in preterm infants in relation to chronological age. PATIENTS: Preterm infants undergoing intensive care recruited to three chronological age groups: 1 to 7 (Group 1; n=20), 8 to 28 (Group 2; n=21) & ≥29days of life (Group 3; n=18). METHODS: Pre and post-BT anterior cerebral artery (ACA) time averaged mean velocity (TAMV) and superior vena cava (SVC) flow were measured. Cerebral Tissue Haemoglobin Index (cTHI) and Oxygenation Index (cTOI) were measured from 15-20min before to 15-20min post-BT using NIRS. Vital parameters and blood pressure were measured continuously. RESULTS: Mean BP increased significantly, and there was no significant change in vital parameters following BT. Pre-BT ACA TAMV was higher in Group 2 and 3 compared to Group 1 (p<0.001). Pre-BT ACA TAMV decreased significantly (p≤0.04) in all 3 groups; pre-BT SVC flow decreased significantly in Group 1 (p=0.03) and Group 3 (p<0.001) following BT. Pre-BT cTOI was significantly lower in Group 3 compared to Group 1 (p=0.02). cTHI (p<0.001) and cTOI (p<0.05) increased significantly post-BT in all three groups. PDA had no effect on these measurements. CONCLUSION: Baseline cTOI decreases and ACA TAMV increases with increasing chronological age. Blood transfusion increased cTOI and cTHI and decreased ACA TAMV in all groups. PDA had no impact on the baseline cerebral oximetry and blood flow as well as changes following blood transfusion

Analysis of the Changes in the Oxidation of Brain Tissue Cytochrome-c-Oxidase in Traumatic Brain Injury Patients during Hypercapnoea A Broadband NIRS Study

Using broadband near-infrared spectroscopy (NIRS) and cerebral micro-dialysis (MD), we investigated cerebral cellular metabolism and mitochondrial redox states, following hypercapnoea in 6 patients with traumatic brain injury (TBI). In all patients hypercapnoea increased intracranial pressure and cerebral blood flow velocity measured with transcranial Doppler. Despite the likely increase in cerebral oxygen delivery, we did not see an increase in the oxidation status of cytochrome-c-oxidase [oxCCO] in every patient. Analysis of the NIRS data demonstrated two patterns of the changes; Group A (n = 4) showed an increase in [oxCCO] of 0.34(+/-0.34)mu M and Group B (n = 2) a decrease of 0.40(+/- 0.41)mu M. Although no obvious association was seen between the Delta[oxCCO] and the MD, measured changes in lactate and pyruvate concentrations. Further work using model informed data interpretation may be helpful in understanding the multimodal signals acquired in this heterogeneous patient group

Pilot Study to Detect Changes in Blood Flow in the External Auditory Meatus During Hemodialysis

Blood flow to internal organs is reported to fall during haemodialysis (HD). As such, there non‐invasive monitoring devices are required to detect changes in perfusion, which could then be used for therapeutic interventions. We report on a pilot study monitoring blood flow in the outer auditory meatus. We measured the maximum pulse wave amplitude and indicators of blood flow by analysing red and green colour changes in the outer auditory meatus from video recordings made using an otoscope fitted with a digital camera during haemodialysis treatments. We studied 61 patients, 43 (71.5%) male, mean age 64.9 ± 12.7 years. Weight fell from 72.8 ± 22.5 pre‐dialysis to 71.5 ± 22.1 kg post‐dialysis (p < 0.001). Blood pressure did not significantly change (pre‐dialysis 142 ± 29/ 67 ± 18 to 143 ± 25/68 ± 17 mmHg post‐dialysis). The maximum pulse wave amplitude in the external auditory meatus fell from 0.21 (0.1–0.55) to 0.14 (0.04–0.4) after 90 min, p < 0.001, and remained low thereafter, and the change at the end of the dialysis session was associated with percentage weight loss (r = −0.37, p = 0.003). Green and red pixel values did not change (pre‐dialysis 0.339 (0.333–0.345) to 0.302 (0.291–0.33) post, and 0.301 (0.293–0.328) pre‐dialysis to 0.339 (0.334–0.347), respectively). This pilot study showed that the maximum pulse wave amplitude measured in the external auditory meatus fell during the dialysis session, and that the fall was associated with fluid removal. This could potentially lead to the development of a monitoring device which could fit in the ear and record during the dialysis session

Limited open reduction and Ilizarov external fixation in the treatment of distal tibial fractures

The authors reviewed 31 distal tibial fractures (16 involving the tibial plafond) treated with Ilizarov external fixation. The study population was composed of 19 males and 12 females, with an average age of 54. The fractures were classified according to the AO classification: A1 (3), A2 (6), A3 (6), C1 (2), C2 (8), C3 (6). There were six open injuries. In 14 pilon cases, open reduction of the intra-articular fragments and bone grafting via a limited incision was performed. Clinical follow-up averaged 28 months (range 18-42). All but one fracture united with an average healing time of 13.9 weeks. Nearly all patients with AO type A fracture had excellent or good functional scores. The 14 cases of AO C2 and C3 group had five (38%) good results, five (38%) fair results and three (24%) poor results. This method yielded results comparable with previous studies using open reduction and internal fixation. Twenty-nine percent of the patients had pin track infection, which remained the most important complication of this method. © 2003 Elsevier Ltd. All rights reserved.postprin

The importance of a device specific calibration for smartphone colorimetry

In order for a smartphone-based colorimetry system to be generalizable, it must be possible to account for results from multiple phones. A move from device-specific space to a device independent space such as XYZ space allows results to be compared, and means that the link between XYZ values and the physical parameter of interest needs only be determined once. We compare mapping approaches based on calibration data provided in image metadata, including the widely used open-source software dcraw, to a separate calibration carried out using a colorcard. The current version of dcraw is found to behave suboptimally with smartphones and should be used with care for mapping to XYZ. Other metadata approaches perform better, however the colorcard approach provides the best results. Several phones of the same model are compared and using an xy distance metric it is found that a device-specific calibration is required to maintain the desired precision

Active routing service for the next-generation network/ISDN3

In recent years, a new routing method, known as active routing, has been emerging. This involves using active packets to configure customized network paths. Based on a Markov decision model, this paper presents an active routing service for active networks in general and the next generation network, called ISDN3, in particular. Our aim is to determine the active routing policy so as to minimize the network cost. Theoretical analysis is presented to show the advantages of our proposal as compared with three other approaches.published_or_final_versio

ISDN3: The next generation networks

Two generations of Integrated Services Digital Network (ISDN), namely ISDN1 and ISDN2, have been developed in the last century. In our view, the convergence of ATM, Internet and active networks will form the basis for the next generation networks called ISDN3. In this paper, we first review ISDN1 and ISDN2 as well as the Internet and active networks. We then discuss some fundamental questions related to the design of ISDN3. Finally, we compare ISDN3 with ISDN1 and ISDN2, and outline what ISDN3 might look like.published_or_final_versio