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Biomedical subjects

R H Taylor

Publications and source records attributed to R H Taylor.

At least 19 recordsLinked to original sources
PubMed2004

Discharge reductions--value for money?

Through the Nuclear Liabilities Management Authority White Paper, the UK Government and the Regulators have signalled a commitment to further improving the operation of the regulatory regime and to its operating within the principles of proportionality, transparency, consistency and accountability which underpin the Government's approach to regulation in general. Particular emphasis is placed upon ensuring that there is greater consistency in the treatment of risk and hazard; proportionate and cost effective delivery of public, worker and environmental protection; and an open and transparently applied regulatory system. The paper uses the historical record of radioactive discharges from BNFL's Sellafield reprocessing site in the UK and seeks to identify what have been the key drivers for change, particularly over the past 20 years of significant discharge reductions. The paper examines the current context for ongoing and future discharges from the site, and the incorporation of the use of the concepts of best practicable environmental option and best practicable means. Intergovernmental commitments such as the OSPAR Sintra and Bremen statements and the developing UK policy framework are also considered, together with BNFL's work with a wide range of 'green' stakeholders. The paper outlines the principal components of BNFL's decision-making processes for discharge control and abatement; and how these interact with the relevant external pressures. It then analyses whether the overall drivers and outcomes align with the declared desire of the UK Government to ensure that the taxpayer receives value for money in the new national arrangements for managing historic nuclear liabilities.

Environmental Exposure↗
PubMed2004

Pharmacokinetics of levobupivacaine 0.25% following caudal administration in children under 2 years of age.

BACKGROUND: Levobupivacaine, the S(-)enantiomer of racemic bupivacaine is less cardiotoxic than racemic bupivacaine and the R(+)enantiomer dexbupivacaine, while retaining similar local anaesthetic properties and potency to racemic bupivacaine. The pharmacokinetic profiles of the two bupivacaine enantiomers differs and that of racemic bupivacaine may be age dependent. We examined the pharmacokinetics of levobupivacaine after its single shot caudal epidural administration in children. METHODS: An open-label phase 2 study was undertaken to examine the pharmacokinetics of levobupivacaine 0.25% 2 mg kg(-1) in 49 children aged less than 2 yr, after single shot caudal epidural administration. Plasma concentrations were determined at intervals up to 60 min after caudal injection. RESULTS: Time to peak plasma concentration (T(max)) ranged between 5 and 60 min (median 30 min) and was reached later in children aged less than 3 months (P<0.005). Peak plasma concentration (C(max)) ranged between 0.41 and 2.12 micro g ml(-1) (median 0.80, mean (SD) 0.91 (0.40) micro g ml(-1)). CONCLUSION: After the caudal epidural administration of levobupivacaine 2 mg kg(-1) in children less than 2 yr of age, C(max) was within the accepted safe range for racemic bupivacaine. T(max) varied and occurred later in some children, particularly those aged less than 3 months. Sampling in future pharmacokinetic studies in this age group should extend beyond 60 min.

Age Factors↗
PubMed2001

System for robotically assisted percutaneous procedures with computed tomography guidance.

We present the prototype of an image-guided robotic system for accurate and consistent placement of percutaneous needles in soft-tissue targets under CT guidance inside the gantry of a CT scanner. The couch-mounted system consists of a seven-degrees-of-freedom passive mounting arm, a remote center-of-motion robot, and a motorized needle-insertion device. Single-image-based coregistration of the robot and image space is achieved by stereotactic localization using a miniature version of the BRW head frame built into the radiolucent needle driver. The surgeon plans and controls the intervention in the scanner room on a desktop computer that receives DICOM images from the scanner. The system does not need calibration, employs pure image-based registration, and does not utilize any vendor-specific hardware or software features. In the open air, where there is no needle-tissue interaction, we systematically achieved an accuracy better than 1 mm in hitting targets at 5-8 cm from the fulcrum point. In the phantom, the orientation accuracy was 0.6 degrees, and the distance between the needle tip and the target was 1.04 mm. Experiments indicated that this robotic system is suitable for a variety of percutaneous clinical applications.

Biopsy, Needle↗
PubMed2001

Software framework for a surgical guidance system using magnetic markers.

Use of active, optical tracking Surgical Guidance systems provides line of sight problems to the surgeon. We plan to use a new magnetic system, 'Aurora' from Northern Digital Inc. (Canada) and Mednetix AG (Switzerland), in intra-operative fluoroscopy to develop an integrated system for surgical guidance. Here we outline the modules developed for use with this system, including a novel registration method.

Algorithms↗
PubMed2000

Optimization of multiple-isocenter treatment planning for linac-based stereotactic radiosurgery.

OBJECTIVE: Computer-assisted treatment planning for linac-based radiosurgery is still an open research problem, especially for multiple-isocenter procedures, primarily due to its high complexity and computational requirements. This paper focuses on the optimization of multiple-isocenter treatment planning for linac systems, and addresses several important issues associated with multiple isocenters, such as dose conformality, homogeneity, and optimization of isocenter position and dose. METHODS: The key idea behind our approach is that the desired dose distribution can be decomposed into a number of fundamental components. In the current paper, an analytical form, the so-called Ellipsoidal Dose Distribution Estimation (EDDE) model, represents each component. We establish ways (arc configurations) to achieve such ellipsoidal doses of arbitrary position, orientation, and size. Since the EDDE model is described by relatively few parameters, it allows very quick estimation of the dose distribution corresponding to a particular isocenter and thus makes the optimization of isocenter position very efficient. It is further used in a framework for optimal treatment planning, in which a number of ellipsoidal dose distributions, each corresponding to a different isocenter, are optimally placed to cover the target while sparing healthy tissue. RESULTS: The general ellipsoidal dose distribution of linac-based radiosurgery is summarized as a mathematical model with the aid of supporting experiments. Comparisons between the EDDE-optimized and clinically implemented plans are made, revealing the superior performance of the former. In addition, a dramatic reduction in planning time is achieved using the EDDE model. CONCLUSION: The proposed EDDE model is a useful and effective dose model in multiple-isocenter treatment planning for linac-based radiosurgery.

Brain Neoplasms↗
PubMed2000

A C-arm fluoroscopy-guided progressive cut refinement strategy using a surgical robot.

We describe a new method to cut a precise, high-quality femoral cavity in Revision Total Hip Replacement surgery (RTHR) using a surgical robot and an intra-operative C-arm fluoroscope. With respect to previous approaches, our method contains several new features. (1) We describe a novel checkerboard plate designed to correct the geometric distortion within fluoroscopic images. Unlike previous distortion correction devices, the plate does not completely obscure any part of the image, and the distortion correction algorithm works well even when there are some overlaid objects in the field of view. (2) Also included are a novel corkscrew fiducial object designed to be integrated with the robot end-effector, and a 6D pose estimation algorithm based on the two-dimensional (2D) projection of the corkscrew, used in robot-imager registration and imager co-registration. (3) In addition, we develop a cavity location algorithm, which utilizes image subtraction and 2D anatomy contour registration techniques. (4) Finally, we propose a progressive cut refinement strategy, which progressively improves the robot registration during the procedure. We have conducted several experiments, in both simulated and in vitro environments. The results indicate that our strategy is a promising method for precise orthopedic procedures like total hip replacement.

Algorithms↗
PubMed2000

Vertical diplopia following local anaesthetic cataract surgery: predominantly a left eye problem?

PURPOSE: Vertical diplopia is an uncommon but disappointing complication of otherwise successful local anaesthetic cataract surgery. We studied strabismus patterns in a group of such patients to identify the nature and extent of extraocular muscle involvement. METHODS: A retrospective review identified 15 cases of vertical diplopia following local anaesthetic cataract surgery between July 1994 and January 1998. Peribulbar anaesthesia was used in all cases and given by right-handed professionals. RESULTS: All cases had otherwise successful cataract surgery (mean age 80.5 years; median pre-operative VA 6/18; median post-operative VA 6/9). The mean level of vertical diplopia was 7.2 prism dioptres (PD) in the primary position (range 2-25 PD). The left inferior rectus (IR) was paretic in 6 cases and restricted in 5 cases. The left superior rectus (SR) was not affected in any of the cases. The right IR was restricted in a single case. The right SR was paretic in 2 cases and restricted in a single case. None of the cases had clinical involvement of the oblique muscles. Eleven of the cases were managed successfully with prisms. Two of the cases required strabismus surgery. CONCLUSIONS: The incidence of left eye extraocular muscle involvement was greater than right eye involvement, although this did not reach statistical significance (73% vs 27%; p = 0.075). This may be due to the more difficult access of right-handed individuals giving left eye peribulbar injections with the needle tract being directed more closely to the muscle cone. The IR muscle is more commonly affected than the SR (80% vs 20%; p = 0.019). An equal incidence of paretic and restricted rectus muscle pathology was found in this study (53% vs 47%; p = 0.818). The exact aetiology of muscle injury is unknown but could be due to direct muscle or nerve trauma, anaesthetic toxicity, periocular haemorrhage or a combination of these.

Aged↗
PubMed2000

Chlorine, chloramine, chlorine dioxide, and ozone susceptibility of Mycobacterium avium.

Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.

AIDS-Related Opportunistic Infections↗
PubMed1999

Human vs robotic organ retraction during laparoscopic Nissen fundoplication.

BACKGROUND: Advances in technique and instrumentation have enabled surgeons to perform an increasing number of complicated procedures through laparoscopy. However, these efforts have often been compromised by the exertion of excessive force when anatomical structures are retracted to create a clear view of the anatomy. Here, we present a comparative study of human and robotic performance in force-controlled organ retraction during laparoscopic Nissen fundoplication (LNF). METHODS: Six female pigs (20-25 kg) were anesthetized, intubated, and placed on mechanical ventilation; pneumoperitoneum (13 mmHg CO2) was established. A force-sensing retractor (FSR) was constructed to record the forces applied in retracting the stomach during dissection of the esophageal hiatus. The FSR was calibrated using known forces and then operated by either human alone or robot under human guidance using the FSR data. The esophageal hiatus was visualized and dissected, and LNF was completed. RESULTS: Less force was needed for robotic (74.3 +/- 10.5 g; mean +/- standard deviation) than for human (108.9 +/- 34.3 g) retraction (p = 0.007) to obtain an optimal view of the esophageal hiatus. No significant differences were observed for retraction setup time (robot, 14.3 +/- 0.8 min; human, 13.7 +/- 9.9 min; mean +/- SD) or hiatal dissection time (robot, 14.0 +/- 3.0 min; human, 14.0 +/- 6.1 min; mean +/- SD). CONCLUSIONS: These preliminary results illustrate our continuing effort to develop and evaluate an automated surgical assistant for laparoscopy. As more personnel-intensive advanced laparoscopic procedures are performed, robotic retraction is likely to offer a superior alternative to human retraction; it minimizes the forces exerted on the organs while maintaining excellent anatomical view.

Animals↗
PubMed1999

The epidemiology of pediatric glaucoma: the Toronto experience.

BACKGROUND: This study was conceived to provide an insight into the spectrum of glaucoma in the pediatric population. We also set out to compare the success of disease control and the prognosis for vision within the different diagnostic subgroups. This is the largest single population of children with glaucoma that has been so described and compared. METHODS: The charts of children who were first seen between birth and age 16 years and who attended the Hospital for Sick Children with any form of glaucoma between January 1974 and January 1995 were reviewed and entered into the study. RESULTS: Data are presented for 306 children. Congenital glaucoma was the most common subtype, accounting for 38%. Patients with congenital glaucoma were young, had surgery, and had more operations than any other group except those with aniridia. Goniotomy offered a cure in 47.8% of the patients. A bimodal distribution reflected their visual performance. Patients with aphakic glaucoma, the next most prevalent group (20%), presented at an older age (4.5 years). Surgical intervention was performed in 50% of these children. Nearly all patients with Sturge-Weber syndrome (80%) had surgery. The following glaucoma groups were associated with a poor visual outcome: aniridia, anterior segment developmental anomalies involving the cornea, uveitis with glaucoma other than steroid induced, retinopathy of prematurity, and persistent hyperplastic primary vitreous. Steroid-induced glaucoma and anterior segment dysgenesis, excluding Peters anomaly, had uniformly good outcomes. CONCLUSION: The ability to control glaucoma in childhood and visual prognosis is highly variable. Particular diagnostic categories do consistently well and some do poorly.

Adolescent↗
PubMed1999

Brachytherapy optimal planning with application to intravascular radiation therapy.

We have been studying brachytherapy planning with the objective of minimizing the maximum deviation of the delivered dose from prescribed dose bounds for treatment volumes. A general framework for optimal treatment planning is presented and the minmax optimization is formulated as a linear program. Dose rate calculations are based on the dosimetry formulation of the American Association of Physicists in Medicine, Task Group 43. We apply the technique to optimal planning for intravascular brachytherapy of intimal hyperplasia using ultrasound data and 192Ir seeds. The planning includes determination of an optimal dwell-time sequence for a train of seeds that deliver radiation while stepping through the vessel lesion. The results illustrate the advantage of this strategy over the common approach of delivering radiation by positioning a single train of seeds along the whole lesion.

Algorithms↗
PubMed1999

Computer-integrated revision total hip replacement surgery: concept and preliminary results.

This paper describes an ongoing project to develop a computer-integrated system to assist surgeons in revision total hip replacement (RTHR) surgery. In RTHR surgery, a failing orthopedic hip implant, typically cemented, is replaced with a new one by removing the old implant, removing the cement and fitting a new implant into an enlarged canal broached in the femur. RTHR surgery is a difficult procedure fraught with technical challenges and a high incidence of complications. The goals of the computer-based system are the significant reduction of cement removal labor and time, the elimination of cortical wall penetration and femur fracture, the improved positioning and fit of the new implant resulting from precise, high-quality canal milling and the reduction of bone sacrificed to fit the new implant. Our starting points are the ROBODOC system for primary hip replacement surgery and the manual RTHR surgical protocol. We first discuss the main difficulties of computer-integrated RTHR surgery and identify key issues and possible solutions. We then describe possible system architectures and protocols for preoperative planning and intraoperative execution. We present a summary of methods and preliminary results in CT image metal artifact removal, interactive cement cut-volume definition and cement machining, anatomy-based registration using fluoroscopic X-ray images and clinical trials using an extended RTHR version of ROBODOC. We conclude with a summary of lessons learned and a discussion of current and future work.

Algorithms↗