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Biomedical subjects

G D Bell

Publications and source records attributed to G D Bell.

At least 19 recordsLinked to original sources
PubMed1998

Device for measuring the forces exerted on the shaft of an endoscope during colonoscopy.

Colonoscopy involves advancing a flexible endoscope into and along the entire length of the colon. The procedure can be painful and carries the risk of perforating the organ, yet very little is known of the forces involved. A device to measure the forces exerted on the endoscope during colonoscopy is described. The device features a handle designed in the shape of a hinged split cylinder that locks around the endoscope, gripping it tightly. The handle has two parts, an inner part that grips the endoscope, and an outer part that is gripped by the endoscopist. The two parts are joined together by members that transmit the forces through to the endoscope. One of the members incorporates strain gauges that measure the torque applied to the endoscope, as well as the push and pull forces. The handle can easily be unlocked and moved along the endoscope as the colonoscopy proceeds. The device is used to measure the forces applied to the endoscope during 11 routine colonoscopies, and summary results are presented. These are believed to be the first accurate measurements of the forces exerted during colonoscopy.

Colonoscopes↗
PubMed1998

Non-radiological technique for 3D imaging of intestinal endoscopes: computerised graphical 3D representation of endoscope and skeleton.

Colorectal cancer is a common malignancy but as yet there is no agreement regarding the optimal method for screening. Colonoscopy is theoretically the investigation of choice. The examination can, however, be difficult to perform and the average trainee requires at least 200 supervised examinations to become proficient. Colonoscopy takes on average about half an hour per patient and sedation is normally required because of painful instrument looping. The authors previously developed a non-radiological method of visualising the path of the endoscope using magnetic drive coils under the patient and a chain of sensors in the biopsy channel of the instrument. The computer-generated grey-scale images produced in real time were deemed unsatisfactory and the anatomical markers confusing. A new computer graphics system is described in which a much more realistic endoscope and, if necessary, skeleton can be produced. The wire-frame octagonal representation should help in the detailed analysis of colonoscopy using existing endoscopes and aid in future computer design and testing of novel instruments incorporating worm or snake-like properties.

Colonoscopy↗
PubMed1998

Clinical practice--breath tests.

The underlying principle of the two non-invasive radio-labelled urea breath tests is similar. Both are positive when the patient's stomach is colonised by Helicobacter pylori because the organism's urease enzyme splits the orally administered urea isotope to labelled CO2 which is then detected in the expired breath. The tests thus reflect active infection and are ideally suited to monitoring the success or failure of different eradication therapies as well as studying rates of acquisition and re-infection/late recrudescence post treatment. [13C]-urea should always be used in children since it is the stable non-radioactive isotope but the [14C]-urea breath test is suitable for most adults, since the dose of radioactivity is minimal.

Adult↗
PubMed1998

Biopsy specimen appearances of ischaemic gastritis in splanchnic arterial insufficiency.

A 74 year old man presented with a one month history of epigastric discomfort, anorexia, weight loss, and postprandial vomiting. The diagnosis of ischaemia was made on endoscopic biopsies from the stomach and duodenum. He was too ill for major vascular surgery and died eight days after admission. Postmortem examination confirmed the diagnosis of splanchnic arterial insufficiency caused by atheroma and thrombosis. Ischaemic gastritis is rare but could easily be missed in unrepresentative biopsy specimens. Prompt diagnosis with revascularisation surgery is the only hope for long term survival.

Aged↗
PubMed1997

Adaptive filtering, modelling and classification of knee joint vibroarthrographic signals for non-invasive diagnosis of articular cartilage pathology.

Interpretation of vibrations or sound signals emitted from the patellofemoral joint during movement of the knee, also known as vibroarthrography (VAG), could lead to a safe, objective, and non-invasive clinical tool for early detection, localisation, and quantification of articular cartilage disorders. In this study with a reasonably large database of VAG signals of 90 human knee joints (51 normal and 39 abnormal), a new technique for adaptive segmentation based on the recursive least squares lattice (RLSL) algorithm was developed to segment the non-stationary VAG signals into locally-stationary components; the stationary components were then modelled autoregressively, using the Burg-Lattice method. Logistic classification of the primary VAG signals into normal and abnormal signals (with no restriction on the type of cartilage pathology) using only the AR coefficients as discriminant features provided an accuracy of 68.9% with the leave-one-out method. When the abnormal signals were restricted to chondromalacia patella only, the classification accuracy rate increased to 84.5%. The effects of muscle contraction interference (MCI) on VAG signals were analysed using signals from 53 subjects (32 normal and 21 abnormal), and it was found that adaptive filtering of the MCI from the primary VAG signals did not improve the classification accuracy rate. The results indicate that VAG is a potential diagnostic tool for screening for chondromalacia patella.

Adult↗
PubMed1997

Parametric representation and screening of knee joint vibroarthrographic signals.

We have been investigating analysis of knee joint vibration or vibroarthrographic (VAG) signals as a potential tool for noninvasive diagnosis and monitoring of cartilage pathology. In this paper, we present a comprehensive comparative study of different parametric representations of VAG signals. Dominant poles and cepstral coefficients were derived from autoregressive models of adaptively segmented VAG signals. Signal features and a few clinical features were used as feature vectors in pattern classification experiments based on logistic regression analysis and the leave-one-out method. The results using 51 normal and 39 abnormal signals indicated the superior performance of cepstral coefficients in VAG signal classification with an accuracy rate of 75.6%. With 51 normal and 20 abnormal signals limited to chondromalacia patella, cepstral coefficients again gave the highest accuracy rate of 85.9%.

Algorithms↗
PubMed1997

Real-time magnetic three-dimensional imaging of flexible endoscopy.

Because of the variability of the colonic anatomy from patient to patient, colonoscopy may be technically difficult to perform and teach, and lesions may be localized inaccurately by the endoscopist. Endoscopists understandably have abandoned fluoroscopy as an adjunct because of its expense, complexity, and potential hazard. The authors have developed a novel method of magnetic imaging that gives real-time views in simulated three dimensions of the endoscope configuration and the location of its tip in the abdomen. The system is inherently safe and easy to use, although it currently requires a catheter to be inserted into the instrumentation channel. Preliminary experience suggests that this approach will be a significant help to endoscopists performing colonoscopy, particularly to those who are currently learning or less experienced.

Clinical Competence↗
PubMed1996

Tissue culture-propagated orf virus vaccine protects lambs from orf virus challenge.

Twenty, eight-day-old specific pathogen-free (SPF) lambs were vaccinated by a single scarification approximately 4 cm in length on the inner right thigh with a double-pronged applicator. The titre of live virus in the vaccine was 10(7.2) TCID50/ml and the estimated dose per lamb was 0.04 ml. Three months and six months later 10 of the vaccinated lambs and five age-matched unvaccinated control specific pathogen free lambs were challenged by a single scarification with virulent virus on the inner left thigh in the same way. After the vaccination all 20 lambs developed lesions characteristic of orf virus infection that had largely resolved four weeks later, when they all had reciprocal ELISA antibody titres > or = 3200 that persisted in all but one of them until they were challenged. After the challenge, the development of lesions in the vaccinated and unvaccinated sheep was compared daily for four weeks by means of a clinical scoring system. Both groups of vaccinated lambs had significantly lower (P < 0.01) total clinical scores after challenge at three months and six months than the unvaccinated lambs.

Animals↗
PubMed1996

Symptomatic and endoscopic duodenal ulcer relapse rates 12 months following Helicobacter pylori eradication treatment with omeprazole and amoxycillin with or without metronidazole.

AIM: To determine the effect of Helicobacter pylori eradication with omeprazole and amoxycillin, with or without metronidazole, on the 12-month course of duodenal ulcer disease. METHODS: In a randomized; double-blind study, conducted in 19 hospitals, 105 H. pylori positive duodenal ulcer patients were healed and symptom-free following either omeprazole dual therapy (omeprazole 40 mg o.m.+amoxycillin 500 mg t.d.s., OA, eradication rate 46%, n = 52) or omeprazole triple therapy (omeprazole 40 mg o.m.+amoxycillin 500 mg t.d.s.+metronidazole 400 mg t.d.s., OAM, eradication rate 92%, n = 53) for 2 weeks, followed by 2 weeks of omeprazole 20 mg o.m. and a 12-month untreated follow-up period, after which time all patients were endoscoped. Endoscopic and symptomatic relapse rates, and effect on H. pylori status measured using 13C-urea breath test, were determined. RESULTS: During the 12-month untreated follow-up period, the life-table endoscopic relapse rates were 12% (95% CI: 2-22%) and 2% (95% CI: 0-6%) for OA and OAM patients, respectively. By 12 months, life-table symptomatic relapse rates were 22% (95% CI: 13-37%) and 19% (95% CI: 8-30%) for OA and OAM, respectively. In the 12 months untreated follow-up period, 2/69 (3%, 95% CI: 0-7%) patients rendered H. pylori negative had an endoscopic relapse at the end of the 12-month follow-up period, compared with 5/31 (16%, 95% CI: 3-29%) patients remaining H. pylori positive (P = 0.03 between H. pylori positive and negative groups). Twelve of 69 (17%, 95% CI: 8-26%) patients rendered H. pylori negative relapsed symptomatically, compared with 9/31 (29%, 95% CI: 13-45%) patients remaining H. pylori positive (P = N.S. between groups). There was a significant improvement in epigastric pain (P = 0.0001), nausea and vomiting (P < 0.05) between entry to the study and 1, 6 and 12 months post-treatment for both treatment groups. CONCLUSIONS: OAM eradicates H. pylori in significantly more patients than OA, but successful H. pylori eradication with either OAM or OA predisposes to low endoscopic and symptomatic relapse rates for duodenal ulcer patients when followed up for 12 months.

Adult↗
PubMed1996

Screening of vibroarthrographic signals via adaptive segmentation and linear prediation modeling.

This paper proposes a noninvasive method to diagnose chondromalacia patella at its early stages by recording knee vibration signals (also known as vibroarthrographic or VAG signals) over the mid-patella during normal movement. An adaptive segmentation method was developed to segment the nonstationary VAG signals. The least squares modeling method was used to reduce the number of data samples to a few model parameters. Model parameters along with a few clinical parameters and a signal variability parameter were then used as discriminant features for screening VAG signals by applying logistic and discriminant algorithms. The system was trained using ten normal and eight abnormal signals. It correctly screened a separate test set of ten normal and eight abnormal signals except for one normal signal. The proposed method should find use as an alternative technique for diagnosis of knee joint pathology or as a test before arthroscopy or major knee surgery.

Algorithms↗
PubMed1996

Conference report: duodenal ulcer trials reported at the European Helicobacter pylori Study Group, Edinburgh 1995.

The abstracts from the 8th International Workshop on Gastro-duodenal Pathology and Helicobacter pylori held in Edinburgh, 7-9 July 1995, are published in Gut 1995; 37 (Suppl. 7). I was privileged to act as reporter to the Plenary Workshop on Duodenal Ulcer Trials chaired by Prof. Seppala. Prof. Roy Pounder and I felt that in such a fast moving field as Helicobacter pylori there would be some merit in briefly reviewing the eight excellent papers presented at the Workshop. The main reason for this being that six of the presentations were well conducted randomized prospective clinical trials of H. pylori eradication therapy and the other two had important clinical messages.

Clinical Trials as Topic↗
PubMed1996

Helicobacter pylori reinfection after apparent eradication--the Ipswich experience.

The reported rate of Helicobacter pylori reinfection following eradication therapy is highly variable. In Ipswich, the 14C-urea breath test (UBT) has been used since 1986 as a tool to study H. pylori eradication and reinfection. Updated results from 1182 patients in whom the organism had apparently been successfully eradicated, following a number of different eradication regimens between October 1986 and 31 March 1995, are presented. During this period, 57 "reinfections' were observed, of which 45 had occurred within 6 months of treatment. After the first year, the 'reinfection' rate was less than 0.6% per year. The criterion for eradication of the infection was a UBT (2-hour area under curve) of less than 40 at least 1 month after treatment. The treatment regimens were arbitrarily divided into five groups with eradication rates of: less than 20%, 20-39%, 40-59%, 60-79% and over 80%. In these groups, the 6-month 'reinfection' rates were 28.0%, 15.8%, 16.4%, 4.6% and 1.7%, respectively (p < 0.001). These and other data presented in the paper strongly suggest that, in Westernized countries, most so-called reinfections in adults are in fact the late recrudescence of a suppressed infection rather than a true reinfection. Our data also suggest that the true reinfection rate is particularly low if the eradication therapy chosen has an efficacy of more than 85%. Several effective and well-tolerated 1-week triple H. pylori eradication regimens are now available, and we would advocate their use in preference to the less effective dual regimens where initial eradication rates are lower and there is consequently a higher risk of 'reinfection'. We would predict that even in developing countries with a high prevalence of metronidazole-resistant H. pylori, the 'reinfection' rate would be low if a combination of omeprazole, amoxycillin and clarithromycin were to be used.

Adult↗
PubMed1996

Relationships of the vibromyogram to the surface electromyogram of the human rectus femoris muscle during voluntary isometric contraction.

The relationship between vibromyographic (VMG) and electromyographic (EMG) signals during isometric contraction of the human rectus femoris muscles was studied. The method of least squares was used to obtain the best-fitting linear regression model to the root mean squared (RMS) values of the VMG and the EMG. It is shown that for the rectus femoris of four subjects, a linear VMG versus EMG relationship exists during 20-80% of the maximum voluntary contraction (MVC) at 30 degrees, 60 degrees, and 90 degrees of knee joint flexion angles. The relation between the VMG and the EMG may be explained by the order recruitment of motor units and by the "onion-skin" phenomenon of the firing rates of recruited motor units in the regulation of muscle force production as reported in electro-neurophysiologic studies.

Adult↗
PubMed1995

Protection of the bovine fetus from bovine viral diarrhoea virus by means of a new inactivated vaccine.

A model is described for the validation of vaccines designed to protect the bovine fetus from bovine viral diarrhoea virus (BVDV). The fetopathic nature of the challenge strain of virus was confirmed and the method used to test a commercial vaccine (Bovidec) developed from a Compton prototype. Heifers were vaccinated two or three times about the time of impregnation and challenged when they were between 25 and 80 days of gestation. There was no evidence of a viraemia in the heifers after the challenge, or of infection with BVDV of 13 liveborn calves or two aborted fetuses.

Abortion, Veterinary↗