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Biomedical subjects

S Aldridge

Publications and source records attributed to S Aldridge.

At least 19 recordsLinked to original sources
PubMed2006

Degradation of tetraphenylphosphonium bromide at high pH and its effect on radionuclide solubility.

Recently, tetraphenylphosphonium bromide (TPPB) has been used to remove technetium from some radioactive waste streams. However, before TPPB could be approved for use it was necessary to show that TPPB and its degradation products would not have a significant detrimental effect on post-closure performance of a radioactive waste repository. TPPB is known to be stable at neutral pH, however, under alkaline conditions it degrades by an alkaline hydrolysis mechanism to triphenylphosphonium oxide (TPPO). Degradation can also occur by radiolysis to produce triphenylphosphine (TPP). The kinetics of the alkaline hydrolysis degradation of TPPB is described and the solubility of europium, iodine, nickel, technetium(VII) and uranium(VI) in aqueous solutions of TPPB and its degradation products is reported. These results were used to support the use of TPPB in removing technetium from some waste streams.

Hydrolysis↗
PubMed2004

Toxicity and early biochemical outcomes from 125iodine prostate brachytherapy in the UK. A prospective study.

AIMS: Transperineal interstitial prostate brachytherapy is increasingly available to patients with early prostate cancer in the U.K., but limited data are available about the toxicity and early results in the U.K. prostate cancer population. We describe our experience and results from prostate brachytherapy to date. MATERIALS AND METHODS: Two hundred and fifty-five patients were treated at St Luke's Cancer Centre, Guildford, U.K., between March 1999 and November 2002. Of these, over 3 months of follow-up data were available for 216 patients. Patients were assessed at 6 weeks and then at 3, 6, 9 and 12 months after implant, and at 6 monthly intervals thereafter. Prostate-specific antigen (PSA), International Prostate Symptom Score (IPSS) and toxicity, including catheter use, was recorded prospectively. RESULTS: Median PSA at 1, 2 and 3 years was 0.5, 0.4 and 0.1 ng/ml, respectively. Ninety-five per cent of patients experienced temporary deterioration in their urinary symptoms, which persisted at clinically significant levels (IPSS increase >3 points) for 9 months after implant. The severity of urinary symptoms (IPSS) after implant was most closely related to IPSS at presentation (P<0.001). Acute urinary retention (AUR) occurred in 20 (9.3%) patients, with a further 26 (12.1%) patients using clean intermittent self-catheterisation (CISC) to reduce voiding frequency associated with chronic retention. Median duration of catheter use was 4 weeks. Multivariate analysis revealed that urodynamic status, prostate volume and IPSS score were independently significant (P<0.05) predictors of post-implant catheter use. Twelve patients (5.6%) reported either rectal urgency or mild, self-limiting rectal bleeding. CONCLUSION: Brachytherapy was tolerated well, with self-limiting urinary, bowel and sexual toxicity in most patients. Postoperative catheter use in our population is closely linked to pre-implant IPSS score, baseline prostate volume and urodynamic obstruction status. This work confirms the prognostic value of urodynamic assessment, which adds useful prognostic information to assessment of known risk factors such as prostate volume and IPSS.

Aged↗
PubMed2001

An intercomparison of IMRT delivery techniques: a case study for breast treatment.

Intensity-modulated radiotherapy beams can be delivered using a multileaf collimator by one of two methods: either by superposition of a series of multiple-static fields, or by moving the collimators while the beam is on to produce 'dynamically' modulated beams. The leaf trajectories in this dynamic mode are given by a series of linear steps between control points defining each collimator position at known intervals throughout an exposure. The complexity of the resulting modulation is limited in the first case by the number of fields superposed and in the second case by the number of control points defined. Results are presented for an experimental study that investigates the effect of changing both the number of fields for the multiple-static technique, and the number of control points for a dynamic 'close-in' technique. All deliveries studied are clinical intensity-modulated breast fields. The effect of using a universal wedge in conjunction with the multileaf collimator is also studied, together with a comparison of the relative efficiency, time taken and the absolute dosimetric accuracy of the various delivery options. It is shown that all delivery techniques produce equivalent dose distributions when using 15 control points, with 10 control points being sufficient to produce an adequate breast compensator distribution. Except for the case of a four-control-point dynamic delivery, the universal wedge makes no significant difference to the dose distribution. However, it makes the delivery less efficient. The close-in interpreter consistently produces deliveries that are more efficient than the more conventional sliding-window technique and faster than the multiple-static-field technique. Finally the close-in technique is compared to the more 'standard' leaf-sweep technique and shown to be equivalent.

Breast Neoplasms↗
PubMed1999

Tomotherapy.

Tomotherapy is delivery of intensity-modulated, rotational radiation therapy using a fan-beam delivery. The NOMOS (Sewickley, PA) Peacock system is an example of sequential (or serial) tomotherapy that uses a fast-moving, actuator-driven multileaf collimator attached to a conventional C-arm gantry to modulate the beam intensity. In helical tomotherapy, the patient is continuously translated through a ring gantry as the fan beam rotates. The beam delivery geometry is similar to that of helical computed tomography (CT) and requires the use of slip rings to transmit power and data. A ring gantry provides a stable and accurate platform to perform tomographic verification using an unmodulated megavoltage beam. Moreover, megavoltage tomograms have adequate tissue contrast and resolution to provide setup verification. Assuming only translational and rotational offset errors, it is also possible to determine the offsets directly from tomographic projections, avoiding the time-consuming image reconstruction operation. The offsets can be used to modify the leaf delivery pattern to match the beam to the patient's anatomy on each day of a course of treatment. If tomographic representations of the patient are generated, this information can also be used to perform dose reconstruction. In this way, the actual dose distribution delivered can be superimposed onto the tomographic representation of the patient obtained at the time of treatment. The results can be compared with the planned isodose on the planning CT. This comparison may be used as an accurate basis for adaptive radiotherapy whereby the optimized delivery is modified before subsequent fractions. The verification afforded tomotherapy allows more precise conformal therapy. It also enables conformal avoidance radiotherapy, the complement to conformal therapy, for cases in which the tumor volume is ill-defined, but the locations of sensitive structures are adequately determined. A clinical tomotherapy unit is under construction at the University of Wisconsin.

Dose Fractionation, Radiation↗
PubMed1998

Process modelling and simulation for managing clinical care in the community.

'Care in the Community' is an easy catch phrase but a difficult goal. It is a phrase that addresses a current growth area within health care, and one that comes complete with an impressive array of political, economic and social factors that would seem to support the notion of a continuing trend. Technology, specifically information systems, however, has not been successfully cast in a supporting role. There are many reasons for this lack of success but a major one is the mismatch between the understanding of what is required to support the clinical care processes and the specifications of the current systems supplied. Specifically the interest here is in the use and assessment of two computer science techniques, i.e. process modelling and simulation, as suitable means of capturing and communicating requirements so as to bridge the divided and power differential between users and developers of information systems.

Community Health Nursing↗
PubMed1996

Cell death induced by cytopathic bovine viral diarrhoea virus is mediated by apoptosis.

Cells infected with two closely related isolates of bovine viral diarrhoea virus (BVDV), one cytopathic (CP) and one non-cytopathic (NCP), were examined for signs of apoptosis. The results from labelling DNA using terminal transferase and biotinylated dUTP and by observing oligonucleosomal-sized DNA fragmentation indicated that the CP strain of BVDV induced apoptosis in cell culture but the NCP strain did not. Induction of apoptosis correlated with infected cells undergoing apoptosis rather than interactions between infected and uninfected cells and the induction of apoptosis by CP BVDV was a dominant trait in cells co-infected with both types of virus.

Animals↗
PubMed1995

Late diagnosis of congenital sensorineural hearing impairment: why are detection methods failing?

This study was designed to look in detail at the paths to diagnosis for a group of 197 children with congenital sensorineural hearing impairment (SNHI), who were diagnosed between 1989 and 1991 in the state of Victoria, Australia. Despite the existence of universal infant screening at 7-9 months by distraction test or questionnaire, the median age at diagnosis for the study group was 18.0 months, with median age at aid fitting of 20.8 months, and median age at commencement of specialised intervention programmes of 22.3 months. Parent questionnaires completed for 143 (73%) of these children showed that 49% had known risk factors for hearing loss yet only 20% of them had been referred for audiological assessment before the 7-9 month screen. Only 63% of those eligible for the 7-9 month screen had received it. Of those children who were screened by distraction test 46% passed as did 57% of those screened by questionnaire. Twenty four parents (17%) described how they had initially 'denied' their own observations of their infants' abnormal hearing behaviour. When concerns were raised with professionals, 10% of parents were falsely reassured without audiological assessment. Detection methods are failing through a combination of poor screen test efficacy, incomplete population coverage, and parental and professional denial.

Age Factors↗
PubMed1989

A controlled study of hand function in nodal and erosive osteoarthritis.

Hand function using a standardised test of activities of daily living was assessed in (a) 57 patients (53 female, four male; mean age 69 years) with established (that is, symptom onset greater than 10 years before) nodal generalised osteoarthritis (NGOA); (b) 10 patients (nine female, one male; mean age 70 years) with established erosive osteoarthritis (EOA); and (c) 52 matched controls (48 female, four male; mean age 71 years) with asymptomatic, clinically normal hands. Although significant differences between controls and patient groups were observed for individual tasks, only minor global impairment was seen, the worst function occurring in patients with EOA. There was no consistent correlation between tested aspects of hand function and extent of radiographic change assessed by summated graded score for separate osteoarthritic features in individual joints. In controls increasing age correlated with longer time to complete all tasks and weaker power grip; a similar, less pronounced correlation occurred in patients. Differences between controls and patients with NGOA were most apparent in younger subjects; in the elderly (greater than 80 years) hand function was essentially the same. This study shows good functional outcome for patients with NGOA, and suggests that the OA process is of little functional importance to the aging hand.

Activities of Daily Living↗
PubMed1988

Left ventricular aneurysm formation: an iatrogenic cause for the third mogul.

Two cases of left ventricular pseudoaneurysm formation developing post-operatively after mitral valve replacement are reported. The chest radiographs showed an abnormal protuberance on the left heart border at the site of the "third mogul". The definitive diagnosis of this protuberance, resulting from the development of a left ventricular aneurysm, was made on angiography in each case. This site is unusual for left ventricular aneurysm formation, with the exception of the annular subvalvular aneurysm described in the negro population. Relevant aetiological factors in the development of these post-operative left ventricular pseudoaneurysms are considered. Since pseudoaneurysms are more prone to rupture than true aneurysms, it is concluded that early diagnosis of development of these left ventricular pseudoaneurysms should be made.

Female↗
PubMed1979

Glucose movement into rat interine fluid.

The uterine horns of anaesthetized rats were cannulated and 2.5 ml 0.9% NaCl at 37 degrees C were recirculated for up to 90 min. Glucose appeared in the medium, reaching a concentration of approximately 1 mM. Various aspects of the transport process were examined, and it is suggested that the glucose is mainly derived from the plasma, and probably enters the uterine lumen by a process involving facilitated diffusion.

Animals↗
PubMed1979

The movement of pyruvate, lactate and lactate dehydrogenase into rabbit oviductal fluid.

Pyruvate, lactate and lactate dehydrogenase appeared linearly in 2 ml 0.9% NaCl recirculated through the rabbit oviduct for 4 h in vivo. In oviducts from rabbits injected 3 days previously with 100 i.u. hCG, the rate of appearance of all three constituents was considerably reduced. It is considered unlikely that the lactate dehydrogenase secreted brings about the interconversion of pyruvate and lactate in the oviduct lumen.

Animals↗
PubMed1979

The movement of amino acids into rabbit oviductal fluid.

Twenty-three amino acids appeared linearly in oviduct fluid to reach an average concentration 27% of that in the plasma, with glycine and alanine present in greatest amount. In contrast, the concentration of urea in the fluid approached its plasma concentration after 1 h, and remained at this level for the duration of the experiment. The oviduct was unable to bring the overall uphill transport of amino acids from plasma to oviduct lumen. The amounts of amino acids appearing in the oviduct lumen of rabbits injected 3 days previously with hCG were mostly similar to those of the controls, but the movements of 6 neutral amino acids appeared to be enhanced relative to their plasma concentrations following ovulation.

Amino Acids↗