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Biomedical subjects

B L Davies

Publications and source records attributed to B L Davies.

At least 19 recordsLinked to original sources
PubMed2006

Preoperative planning and intraoperative guidance for accurate computer-assisted minimally invasive hip resurfacing surgery.

Hip resurfacing is an alternative to total hip replacement (THR) and is particularly suitable for the younger, more active patient. However, it is a more demanding procedure. This paper describes a system that enables the surgeon to plan the surgery preoperatively with optimally sized and placed components, and then transfer this plan to an intraoperative system that registers computer models to the real patient and tracks surgical tools, allowing the surgeon to ensure that the bone is resected correctly and that the components are fitted in accordance with the plan. The paper describes a series of instruments used with the system which are locked to the bone. These instruments serve the dual purpose of soft tissue retraction and bone immobilization. The system will shortly be the subject of laboratory and clinical evaluation. Registration, a cornerstone of the tracked instrument system, has been tested, and accuracy measures are provided. Experimental results for the remainder of the system will be provided after clinical trials.

Arthroplasty↗
PubMed2002

A computer assisted surgical trainer for transurethral resection of the prostate.

PURPOSE: We developed a realistic and reusable computer assisted surgical training system for transurethral resection of the prostate. MATERIALS AND METHODS: A disposable prostate model is housed in a model abdomen. A software program that provides a 3-dimensional (D) illustration of the prostate model was developed. Resectoscope position with reference to the model is tracked by infrared emitting diodes attached to it, which in turn are monitored by an optical tracker. Movement of the loop in relation to the resectoscope is measured by a potentiometer attached to the working element. RESULTS: Resectoscope position was shown on the monitor superimposed on a 3-D image of the prostate model in real time. A 2-D image showed the amount of tissue resected and the proximity of the loop to the capsule. A series of thumbnail images were shown and the highlighted image represented the current position of the resectoscope. It is intended that this system should be interactive, providing continuous feedback on the progress of resection and acting as an interactive training aid. During the course of validating the system several problems were noted, mainly with model movement and permanent deformation of the model during resection. CONCLUSIONS: This system can exist as a stand-alone training aid after the problems have been addressed. The potential application of an in vivo system for routine transurethral prostate resection has great implications for training and quality control.

Computer Simulation↗
PubMed2001

The first clinical application of a "hands-on" robotic knee surgery system.

The performance of a novel "hands-on" robotic system for total knee replacement (TKR) surgery is evaluated. An integrated robotic system for accurately machining the bone surfaces in TKR surgery is described. Details of the system, comprising an "active constraint" robot, called Acrobot, a "gross positioning" robot, and patient clamps, are provided. The intraoperative protocol and the preoperative, CT-based, planning system are also described. A number of anatomical registration and cutting trials, using plastic bones, are described, followed by results from two preliminary clinical trials, which demonstrate the accuracy achieved in the anatomical registration. Finally, the first clinical trial is described, in which the results of the anatomical registration and bone cutting are seen to be of high quality. The Acrobot system has been successfully used to accurately register and cut the knee bones in TKR surgery. This demonstrates the great potential of a "hands-on" robot for improving accuracy and increasing safety in surgery.

Arthroplasty, Replacement, Knee↗
PubMed2001

A multiple focused probe approach for high intensity focused ultrasound based surgery.

To produce deep-seated surgical lesions using ultrasound requires high power and intensity levels at the target sites. Conventionally, large transducers are used which require big apertures and so are generally suitable only for extra-corporeal access. Such transducers also result in strong off-focus maxima, where the resulting hot spots can destroy normal tissue whilst deep-seated large tissue volumes are being ablated. This paper describes a new approach in which it is proposed that multiple probes are used simultaneously, each at a relatively low power, to result in an overlapping focused region of high temperature without strong off-focus hot spots. Robotic techniques could be used to move the individual probes in coordination to sweep out the desired region of tissue ablation. Simulation and planning are the key to quality prediction for high intensity focused ultrasound (HIFU). Simplified two-dimensional and three-dimensional models of HIFU probes have been developed to study the characteristics of various multi-probe configurations. Preliminary simulation results show that the multi-probe system can be arranged successfully to minimise off-focus hot spots. Experimental results are presented which validate the modality and confirm this positive finding. Further prediction studies and planning will be necessary to achieve the most appropriate desired treatment, by varying the pulse duration and spacing.

Computer Simulation↗
PubMed2000

A robotic system for blood sampling.

A robotic system to take blood samples autonomously from the forearm is presented and preliminary results are discussed which demonstrate its feasibility. Force/position profiles, while pressing a flat-headed probe against the surface of the skin, enable the determination of a vein's location to within 1 mm on a phantom. When a needle is inserted, the characteristic force/position profile, on puncturing the vein wall, is distinctive enough to implement automatic needle withdrawal to prevent overshoot. Future developments of the project are presented that provide both an autonomous blood sampling robot and a force-feedback surgical trainer.

Analog-Digital Conversion↗
PubMed1999

Automated prostate recognition: a key process for clinically effective robotic prostatectomy.

Clinical trials of PROBOT, a robotic system for prostate surgery, have shown that robotic surgery of soft tissue can be successful. Monitoring of the progress of the resection has shown to be a necessary feature of an effective robotic system for prostate surgery. It should provide the surgeon with a reliable method of assessing the cavity during resection. An automatic system for intraoperative monitoring of the progress of the resection during robotic prostatectomy consists of two subsystems: real-time intraoperative imaging of the prostate and automatic identification of the contour of the gland on each image. The development of a fully automatic scheme for prostate recognition on transurethral ultrasound scans is reported. A genetic algorithm has been developed to automatically adjust a model of the prostate boundary until an optimum fit to the prostate in a given image is obtained. An analysis of its performance on 22 different ultrasound images showed an average error of 6.21 mm. Use of a genetic algorithm and a constrained prostate model have shown to be a robust way to automatically identify the prostate in ultrasound images. The scheme is able to produce approximate prostate boundaries, without any human intervention, on ultrasound scans of varying quality. In addition to soft tissue robotic surgery, the genetic algorithm technique is also applicable to a wide range of computer assisted surgical techniques.

Humans↗
PubMed1999

A computer-assisted training/monitoring system for TURP structure and design.

A generic framework for a computer-assisted system for both soft tissue endoscopic surgery and surgical training is being researched and developed. The concept demonstrator is a specific system for transurethral prostatic resection (TURP). The main novelty of the research is that it is not confined to an in vitro trainer system. An in vivo monitoring version of the system, for use in the operating theater, is also being researched. This paper presents the framework's structure and design using the United Modeling Language. It also discusses and justifies the underlying information technologies chosen to implement this approach. Object-oriented concepts and well-proven mathematical tools have been adopted as the foundation of this research and development. The rationale for having chosen such tools is presented. The objectives are to arrive at a system which is modular, general, and reusable.

Computer Simulation↗
PubMed1997

Electromagnetic compatibility aspects of active robotic systems for surgery: the robotic prostatectomy experience.

The paper discusses the susceptibility to electromagnetic interference (EMI) of active robots for surgery, which are safety-critical systems. The high EMI environment of an operating room in the presence of an electrosurgical generator is considered. Experience of a surgeon assistant robot for prostatectomies in improving the immunity to EMI is described. It has been found that effective isolation of the robotic system hardware from grounded metal objects provides significant improvements to safety by its immunity to EMI, in minimising the flow of high-frequency current to ground through the system hardware.

Electromagnetic Fields↗
PubMed1997

Active compliance in robotic surgery--the use of force control as a dynamic constraint.

Robotic surgery can be carried out automatically by using a robot to move the cutting tool under position control. However, although the surgeon can observe the procedure on a visual display and has the ability to stop the operation in an emergency, he has little direct contact with the task. An alternative approach is to involve the surgeon more directly, by his moving a robot using active force control. The robot is then used to allow motion in preprogrammed regions, by the surgeon back-driving the robot motors, while preventing motion in prohibited areas. This active constraint robot (or ACROBOT) is described in this paper applied to knee surgery, in which the knee bones are accurately machined to allow the fitting of prosthetic knee implants. The ACROBOT is, however, ideally suited to a range of surgical procedure, because it allows the surgeon to feel the forces exerted during cutting and take appropriate action. This ability to be in direct control, while being constrained to cut within a permitted region, enhances safety and makes the system more acceptable to the medical community. The system of programmable constraint also allows the ACROBOT to provide the traditional benefits of robot surgery, namely the ability to machine complex geometrical surfaces very accurately and to make repetitive motions tirelessly. The system also has a potential for minimally invasive procedures. In knee surgery, for example, the robot could operate through a small incision in the skin and excise a volume into which a small, specially designed, unicompartmental prosthesis could fit.

Arthroplasty, Replacement, Knee↗
PubMed1997

The Probot--an active robot for prostate resection.

As men age, their prostates can enlarge, causing urinary difficulty. Surgery to correct this [transurethral resection of the prostate (TURP)] is a skilled and time-consuming operation requiring many repetitive motions of a cutter. A robot has been developed to perform these motions, relieving the surgeon of much of the burden of surgery. This robot has been tried both in the laboratory and later on human subjects and has proved itself capable of performing prostate resection. The Probot system consists of on-line imaging and three-dimensional prostate model construction, an appropriate surgeon-computer interface, a counterbalanced mounting frame and a computer controlled robot.

Computer Graphics↗
PubMed1993

Electronic fetal monitoring: a Canadian survey.

OBJECTIVES: To determine the current status of electronic fetal monitoring (EFM) in Canadian teaching and nonteaching hospitals, to review the medical and nursing standards of practice for EFM and to determine the availability of EFM educational programs. DESIGN: National survey in 1989. PARTICIPANTS: The directors of nursing at the 737 hospitals providing obstetric care were sent a questionnaire and asked to have it completed by the most appropriate staff member. The response rate was 80.5% (593/737); 44 hospitals did not have deliveries in 1988 and were excluded. The remaining hospitals varied in size from 8 to 1800 (mean 162.1) beds and had 1 to 7500 (mean 617.1) births in 1988; 18.8% were teaching hospitals. RESULTS: Of the 549 hospitals 419 (76.3%) reported having at least 1 monitor (range 1 to 30; mean 2.6); the mean number of monitors per hospital was higher in the teaching hospitals than in the nonteaching hospitals (6.2 v. 1.7). Manitoba had the lowest mean number of monitors per hospital (1.1) and Ontario the highest (3.7). In 71.8% of the hospitals with monitors almost all of the obstetric patients were monitored at some point during labour. However, 21.6% of the hospitals with monitors had no policy on EFM practice. The availability of EFM educational programs for physicians and nurses varied according to hospital size, type and region. CONCLUSIONS: Most Canadian hospitals providing obstetric services have electronic fetal monitors and use them frequently. Although substantial research has questioned the benefits of EFM, further definitive research is required. In the meantime, a national committee should be established to develop multidisciplinary guidelines for intrapartum fetal assessment.

Canada↗
PubMed1993

The use of ultrasound in automated prostatectomy.

A new way of applying transurethral ultrasound scanning in the common surgical procedure of the transurethral resection of the prostate is described. The scanning is incorporated as part of a robotic procedure for surgery, so that the overall time spent in an operation can be further shortened, and a safe and accurate operation can be achieved. The prostate dimensions obtained pre-operatively by the transrectal method and those obtained operatively are compared. A robotic system, which was developed specifically to remove prostatic adenoma automatically, is discussed. The system, called a motorized frame, is briefly described, together with its predecessor, a manual frame, in relation to ultrasound measurements. Sizing of the prostate pre-operatively using transrectal ultrasound methods is discussed, using both the manual and the motorized frame. The shortcomings of transrectal ultrasound for use in a robotic procedure are highlighted.

Humans↗
PubMed1991

The development of a surgeon robot for prostatectomies.

The removal of prostatic tissue through transurethral resection of the prostate (TURP) is an operation that can require considerable skill from a surgeon as well as being a lengthy procedure. The potential for using robotic techniques was investigated in a preliminary feasibility study using a standard six axis 'Puma' robot. This led to the construction of a manually operated 'safety frame' which has been shown to be effective through clinical trials on 30 patients. A special-purpose robot, based on the design of the manual frame, has now been constructed. Some of the safety issues are discussed which make this procedure an ideal candidate for a robotic device.

Equipment Design↗
PubMed1990

The efficacy of incentive spirometers in post-operative protocols for low-risk patients.

Incentive spirometry offered no statistically significant advantages to pulmonary function when compared to unstructured or structured deep breathing and coughing exercise programs, for patients at low risk of developing pulmonary complications. The additional cost of incentive spirometer equipment does not seem warranted in these patients. Furthermore, patients with or without an incentive spirometer were willing to comply with a structured breathing exercise program with the same frequency of practice sessions. Patients in this diagnostic category did not require a technical device to reward and motivate them for performing maximal inspiratory manoeuvres.

Adult↗
PubMed1988

Insertion and recovery of a new retrievable vena caval filter. Work in progress.

A new retrievable inferior vena cava (IVC) filter was tested in nine pigs. Insertion was through a 14 French sheath using both the femoral and jugular approaches. All insertions were successful, and there was a 100% postinsertion IVC patency rate (8/8 pigs at one week and 1/1 pig at one month). Addition of an apical hook to the filter design allowed transjugular retrieval of two filters at one week postinsertion. Three of nine filters migrated to the upper IVC. The filter's design allows paraxial blood flow despite trapped thrombus and inhibits filter tilting. In vitro, the filter captured 95% to 100% of 5 X 5 mm clots. If problems with migration can be solved, the new filter may provide effective short- and long-term prophylaxis against pulmonary embolism.

Animals↗
PubMed1987

Use of perceived effort ratings to control exercise intensity in young healthy adults.

The purpose of this study was to evaluate the use of the rating of perceived exertion (RPE) as a means of regulating the intensity of exercise during running. The subjects were healthy, relatively fit young adults (16 men and 12 women). Estimates of effort were recorded using the Borg 6-20 Scale whilst the maximal oxygen uptake of the subjects was measured as they ran on an electrically driven treadmill. In a further session, the same subjects were requested to run on the treadmill at constant exercise intensity based on their interpretation of levels 9, 13 and 17 of the Borg Scale. They regulated their running speed and the treadmill gradient but had no knowledge of performance from the equipment display panel. A linear regression analysis was carried out to examine the relationship between heart rate, perceived exertion and relative metabolic demand. This revealed that the rating of perceived exertion was at least as good a predictor of exercise intensity as heart rate in both the graded exercise test and effort production test. The results support the view that RPE may be used to predict relative metabolic demand, especially at higher workloads and could be a useful medium for controlling intensity of effort during vigorous exercise in such subjects.

Adult↗