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Biomedical subjects

D Hamilton

Publications and source records attributed to D Hamilton.

At least 55 records · Page 3Linked to original sources
PubMed1996

Self-hypnotic relaxation during interventional radiological procedures: effects on pain perception and intravenous drug use.

The authors evaluated whether self-hypnotic relaxation can reduce the need for intravenous conscious sedation during interventional radiological procedures. Sixteen patients were randomized to a test group, and 14 patients were randomized to a control group. All had patient-controlled analgesia. Test patients additionally had self-hypnotic relaxation and underwent a Hypnotic Induction Profile test. Compared to controls, test patients used less drugs (0.28 vs. 2.01 drug units; p < .01) and reported less pain (median pain rating 2 vs. 5 on a 0-10 scale; p < .01). Significantly more control patients exhibited oxygen desaturation and/or needed interruptions of their procedures for hemodynamic instability. Benefit did not correlate with hypnotizability. Self-hypnotic relaxation can reduce drug use and improve procedural safety.

Aged↗
PubMed1996

Event-related potential prolongation in Alzheimer's disease signifies frontal lobe impairment: evidence from SPECT imaging.

BACKGROUND: The N2 and P3 components of auditory event-related potentials (ERPs) and single-photon emission computed tomographic (SPECT) images are separate independent biological markers of cerebral function and are abnormal in Alzheimer's disease (AD). The relationship between ERP N2 and P3 latencies and regional cerebral perfusion abnormalities in AD is unknown. METHODS: ERP and SPECT data were obtained one week apart in 18 patients with "probable" AD of mild or moderate severity, and 12 healthy age-matched elderly controls. Average premotor frontal, anterior temporal, inferior parietal, and occipital cortical/cerebellar perfusion ratios were calculated from the SPECT data and correlations with ERP N2 and P3 latencies derived for AD and control groups separately. RESULTS: ERP N2 latency was correlated significantly with the average frontal perfusion ratio (r = -.59; p < .009), but correlations with average temporal, parietal, and occipital ratios were nonsignificant in the AD group. Similarly, ERP P3 latency was correlated significantly with the average frontal perfusion ratio (r = -.65; p < .004), but not with the other perfusion ratios in the AD group. In the control group, a partial correlation between the average frontal perfusion ratio and the ERP N2 latency was noted (r = -.52; p < .09), but no other ERP/SPECT correlations approached statistical significance. CONCLUSION: ERP N2 and P3 latency delay in AD is a function of differential frontal lobe hypoperfusion.

Aged↗
PubMed1996

Sodium picosulphate compared with polyethylene glycol solution for large bowel lavage: a prospective randomised trial.

Mechanical efficiency, patient acceptability and minimal biochemical perturbation are important factors in the choice of lavage solution for bowel preparation. This prospective randomised trial of 59 patients compared a polyethylene glycol bowel lavage solution (Klean Prep) to a sodium picosulphate solution (Picolax) considering their efficacy from both colonoscopists' and radiologists' points of view, patient acceptibility, and plasma biochemical changes. The sodium picosulphate solution was more acceptable to patients than the polyethylene glycol, and resulted in significantly less nausea and vomiting (p = 0.0025), and far fewer consumption difficulties (p < 0.0001). Mean plasma biochemical changes were significantly different for magnesium (p < 0.001), chloride (p < 0.01) and potassium (p < 0.02). Because neither lavage solution displayed a marked advantage for the colonoscopist or radiologist, and sodium picosulphate was more acceptable to patients, sodium picosulphate is the preferred solution for bowel preparation. The changes in plasma biochemistry values are unlikely to cause clinical problems.

Adolescent↗
PubMed1996

Interpretation of captopril transplant renography using a feed forward neural network.

UNLABELLED: Severe renal artery stenosis (RAS) is a relatively uncommon complication after renal transplantation but is a curable cause of hypertension, which demands reliable early diagnosis to reduce morbidity, mortality and graft loss. Captopril renography has been used for a number of years as a method of detecting RAS but controversy still exists as to the diagnostic accuracy of this test and as to the most appropriate interpretation criteria with which to establish a positive result. METHODS: This report presents the results of using artificial neural networks to impartially assess these interpretation criteria. Data comprised 31 99mTc-MAG3 captopril renography investigations undertaken on hypertensive renal transplant patients with a suspected diagnosis of RAS. Each renogram study was correlated with an arteriogram as the "gold standard". Training of the network was performed using the round-robin technique. RESULTS: An accuracy of 95% could be achieved by considering perfusion index, time-to-peak activity, accumulation index and excretion index for both pre- and post-challenge studies. This varied as the parameters were either included or excluded. CONCLUSION: Artificial neural network analysis is a useful technique to evaluate the most appropriate criteria for interpreting captopril transplant renography investigations.

Antihypertensive Agents↗
PubMed1995

A feed forward neural network for classification of bull's-eye myocardial perfusion images.

Identification of hypoperfused areas in myocardial perfusion single-photon emission tomography studies can be aided by bull's-eye representation of raw counts, lesion extent and lesion severity, the latter two being produced by comparison of the raw bull's-eye data with a normal data base. An artificial intelligence technique which is presently becoming widely popular and which is particularly suitable for pattern recognition is that of artificial neural network. We have studied the ability of feed forward neural networks to extract patterns from bull's-eye data by assessing their capability to predict lesion presence without direct comparison with a normal data base. Studies were undertaken on both simulation data and on real stress-rest data obtained from 410 male patients undergoing routine thallium-201 myocardial perfusion scintigraphy. The ability of trained neural networks to predict lesion presence was quantified by calculating the areas under receiver operating characteristic curves. Figures as high as 0.96 for non-preclassified patient data were obtained, corresponding to an accuracy of 92%. The results demonstrate that neural networks can accurately classify patterns from bull's-eye myocardial perfusion images and detect the presence of hypoperfused areas without the need for comparison with a normal data base. Preliminary work suggests that this technique could be used to study perfusion patterns in the myocardium and their correlation with clinical parameters.

Computer Simulation↗
PubMed1995

Identification of a hypoperfused segment in bull's-eye myocardial perfusion images using a feed forward neural network.

Artificial neural networks are computer systems which can be trained to recognize similarities in patterns and which learn by example; one of the more straightforward types being the feed forward neural network (FFNN). We previously reported the use of FFNNs for classification of hypoperfusion patterns in bull's-eye representation of 201Tl single photon emission tomography myocardial perfusion studies and showed that, when such an image was divided into 24 segments, FFNNs could detect perfusion defects without direct comparison to a normal data base. This has been extended in this investigation to assess the ability of an FFNN, trained on data in which only a single segment was hypoperfused, to detect this abnormal segment when the hypoperfusion pattern of the other segments in the image varied. The results indicated that the network could reliably determine whether a segment was normally or under perfused, with accuracies of 99% and 100%, respectively, if all other segments were normally perfused. It could also reliably detect a normally perfused segment, even if other segments were hypoperfused, with accuracies of 95% and 98%. The network was less reliable, however, in detecting a hypoperfused segment when other segments were also hypoperfused, showing accuracies of only 74% and 88%.

Blood Flow Velocity↗
PubMed1994

The renal transplant perfusion index: reduction in the error and variability.

For 15 years, perfusion indices derived from scintigraphic studies have proved useful in the serial evaluation of renal transplants and they have recently been confirmed as being more sensitive than Doppler ultrasound as an indicator of vascular rejection and cyclosporin toxicity. In the calculation of these indices, correction for administered activity is often accomplished using activity measurements made over a convenient artery which, therefore, has a critical influence on the value of the index obtained. In this communication, a theoretical assessment is made of the error and variability introduced into the calculation of the perfusion index, because of inadequate spatial sampling of activity in these narrow arteries and the consequential inconsistencies in the measurement of the arterial tracer activity. Using numerical simulation, it is shown that the errors in repeat studies on the same patient may be as high as 39% and between patients as high as 53%. These figures can be reduced to below 18% and 21%, respectively, by constructing a region of interest (ROI) to extend over as much of the arterial width as possible rather than relying only on the maximum pixel count. Further reduction to below 12% and 10% is possible by utilising a 128 x 128 acquisition matrix instead of 64 x 64 and drawing the ROI over the aorta instead of the iliac artery.

Humans↗
PubMed1994

Overview of a quality assurance/quality control compliance program consistent with FDA regulations and policies for somatic cell and gene therapies: a four year experience.

Somatic cell and gene therapy involve the application of biological technologies to an individual patient through the use of living cells which provide a therapeutic benefit (Aliski, 1991). Various forms of cellular and gene therapies are being developed and evaluated in an increasing number of clinical trials for congenital and acquired disorders. The potential and progress of these therapeutic applications have resulted in an increasing effort by the Food and Drug Administration (FDA) to develop the regulatory framework under which these therapeutic approaches would insure safety and efficacy, the primary mandate of the FDA. Over five years ago Cellcor began to define the parameters, specifications, and conditions relevant to a Quality Assurance/Quality Control (QA/QC) program that has evolved to insure safety and maximize the efficacy of applications of the company's ex vivo technology, autolymphocyte therapy. Autolymphocyte therapy is an outpatient form of somatic cell immunotherapy based upon the infusion of T cells that have been activated ex vivo using a combination of previously generated autologous cytokines and an anti-CD3 monoclonal antibody. We have been able to demonstrate the feasibility for the safe, controlled, and consistent preparation and delivery of a cellular therapy by application of relevant GMP regulations. This presentation reviews aspects of this program and chronicles our experience which at present amounts to over 4400 in fusions for over 700 patients. This program provides a high degree of assurance that a cellular therapy program can be carried out in a multisite mode involving hundreds of patients through the strict adherence to cGMP as set forth in existing regulations.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Transplantation↗
PubMed1994

The importance of the perfusion index in the evaluation of captopril renography for transplant renal artery stenosis.

Severe renal artery stenosis (RAS) is a relatively uncommon complication following renal transplantation but is a curable cause of hypertension which demands reliable early diagnosis to reduce morbidity, mortality and graft loss. Captopril renography has been used for a number of years as a method of detecting RAS mainly in native kidneys, with only a few studies concerning the transplant situation. Controversy still exists as to the diagnostic accuracy of this test and as to the most appropriate interpretation criteria with which to establish a positive result. This paper reports the evaluation of 26 captopril renography investigations on hypertensive renal transplant patients with a suspected diagnosis of RAS. Each renogram study was correlated with an arteriogram as the 'gold standard' which was undertaken within 28 days of the renography. A sensitivity of 92%, a specificity of 86% and an accuracy of 88% were achieved by including a consideration of the change in perfusion to the kidney between pre- and post-challenge studies. It is concluded that captopril renography is a useful screening test for the detection of transplant renal artery stenosis (TRAS).

Captopril↗
PubMed1994

Inter-beat changes in left ventricular function with cardiomyoplasty as measured using MUGA scanning.

Dynamic cardiomyoplasty is a new surgical technique that uses electrically stimulated skeletal muscle to partially replace or reinforce the heart muscle in the treatment of advanced heart failure. Clinical experience with cardiomyoplasty is limited, which has precluded definitive conclusions about its value. We have studied the effect of cardiomyoplasty on the heart muscle when the skeletal muscle was being stimulated to coincide with alternate natural beats. The left ventricular function was assessed using radionuclide angiography during the beat immediately following skeletal muscle stimulation and during the beat immediately before stimulation. When the supported beat is compared with the unsupported beat, the results demonstrate that cardiomyoplasty improves the global and regional ejection fraction. The regurgitation index remains unchanged. The systolic peak emptying rate improves but the diastolic peak filling rate worsens. This latter finding provides additional information regarding the diastolic function of the heart following cardiomyoplasty, which is presently not well understood.

Adult↗
PubMed1994

The effect of indigenous bacterial populations on buccal epithelial cells on subsequent microbial adhesion in vitro.

Despite the numerous investigations on the adhesion of microorganisms to buccal epithelial cells, it is difficult to correlate different results, as disparate adherence values have been reported for a given organism. As one reason for this disparity may be the indigenous or natural bacterial populations on human buccal epithelial cells, the effect of the latter on subsequent microbial adherence in vitro was examined. There was a highly significant correlation between the degree of natural bacterial colonization on pooled buccal epithelial cells from 8 healthy donors and the adhesion of a single isolate each of Streptococcus mitis, Escherichia coli and Actinomyces naeslundii. However, no such relationship could be established for Candida albicans, Streptococcus milleri and another isolate of Streptococcus mitis. As in previous studies, variation in adherence values was found, both between samples from different donors, and from the same donor over time, but to a far lesser degree in pooled samples from different donors. These results imply that natural bacterial populations on buccal epithelial cells may affect the adhesion values derived from laboratory experimentation, and hence such data should be interpreted with caution.

Actinomyces↗
PubMed1994

Anodyne imagery: an alternative to i.v. sedation in interventional radiology.

OBJECTIVE: Pain and anxiety are to be expected in patients undergoing interventional procedures, and they are usually treated by IV conscious sedation. Insufficient treatment of pain and anxiety can cause cardiovascular strain and restlessness, which may jeopardize the success of the procedure. On the other hand, pharmacologic oversedation can provoke respiratory and cardiovascular depression, thereby increasing the procedural risks and delaying the patient's recovery. We therefore evaluated a nonpharmacologic method, which we call anodyne imagery (anodyne: able to soothe or relieve pain; soothing the feelings; relaxing), as an alternative to the use of drugs in interventional radiology. SUBJECTS AND METHODS: Anodyne imagery technique consists of conditioned relaxation, induction of a trance state, and guided processing of the patient's internal imagery. An intrapatient comparison of drug use was made in five patients who had equivalent procedures with and without anodyne imagery and an intergroup comparison was made between a group of 16 other patients undergoing anodyne imagery and a group of 16 control patients matched for factors affecting use of drugs and recruited from 100 interventional cases analyzed for patterns of drug use. For statistical analysis, drug unit scores (weighting: 1 mg of midazolam = 1 unit and 50 micrograms of fentanyl = 1 unit) were compared within patients by paired t-test and between groups of patients by analysis of variance in two-sided tests, with p less than .05 considered to be significant. RESULTS: The 100 patients who did not have anodyne imagery received 0-6 mg of midazolam (median, 1.4 mg), 0-500 micrograms of fentanyl (median, 80 micrograms), and 0.5-9 drug units (median, 2.5). Drug administration was insignificantly affected by the physician conducting the procedure, the type of procedure, or the patient's age, but significantly increased with longer table times. Ten of the 21 patients undergoing anodyne imagery associated fear-provoking images with their interventional procedure that were generally intense, vivid, and dramatic. Intrapatient comparison showed significantly lower median drug use with anodyne imagery than without (0.1 vs 5.3 drug units, p = .01). Intergroup comparison also yielded significantly lower median drug use during procedures with anodyne imagery than without (0.2 vs 2.6 drug units, p = .0001). CONCLUSION: Patients having interventional radiologic procedures frequently experience intense and frightening imagery related to the procedure. Our initial experience with anodyne imagery suggests that this alternative method of analgesia can mitigate patients' anxiety and fears and reduce the amount of drugs used during interventional radiologic procedures, and thereby has the potential to improve procedural safety and increase the speed of recovery.

Aged↗
PubMed1994

The discriminant value of semiquantitative SPECT data in mild Alzheimer's disease.

UNLABELLED: In most semiquantitative SPECT studies, overlap between groups of patients with Alzheimer's disease (AD) and age-matched elderly controls is such that single posterior cortical perfusion measurements lack sensitivity. In the present study, the value of a combination of semiquantitative temporoparietal SPECT parameters was examined. METHODS: Supratentorial transaxial perfusion measurements were obtained in frontal, anterior temporal, posterior temporoparietal and occipital cortical areas in both hemispheres, in a baseline population of 10 healthy elderly controls and 30 mild to moderately impaired AD patients, as well as in a prospective group of 15 patients with mild cognitive impairment, 12 patients with a diagnosis of probable AD and individual cases of multi-infarct dementia, dementia-frontal type and paranoid psychosis. A linear discriminant function (LDF) was calculated from the baseline subjects' data to classify control and AD subjects individually. RESULTS: Highly significant hypoperfusion was noted in both the anterior temporal and posterior temporoparietal regions of interest in the AD group compared with controls, but with significant overlap. Using an LDF incorporating these perfusion measurements in both hemispheres, 10/10 (100%) controls and 26/30 (87%) AD baseline subjects were correctly classified. Using the baseline LDF in the prospective 15 mildly impaired cases, 11/12 new mild AD cases and none of the 3 non-AD cases were classified in the AD group. CONCLUSION: These results support the use of a combination of semiquantitative SPECT perfusion estimates from cortical areas with predictable pathological involvement in AD in a linear discriminant format in the clinical assessment of patients with suspected AD.

Aged↗
PubMed1993

Erythromycin improves emptying of the denervated stomach after oesophagectomy.

Oesophagectomy, necessitating vagotomy, is associated with delayed gastric emptying. Cisapride and erythromycin have prokinetic effects and improve emptying of the innervated stomach. Their effect on the denervated stomach following oesophagectomy is unknown. The effect of pyloroplasty, cisapride and erythromycin on the rate of gastric emptying after oesophagectomy was studied using a radiolabelled meal. Oesophagectomy was associated with a marked delay in gastric emptying (56 per cent of the test meal remaining after 4 h) compared with age- and sex-matched normal controls (16 per cent; P < 0.001). Erythromycin improved the rate of gastric emptying to preoperative control values (18 per cent). Cisapride had no significant effect on gastric emptying. After pyloroplasty, 32 per cent of the label remained at 4 h (P = 0.065). The mean(s.e.m.) half-emptying time in patients receiving erythromycin was 94(29) min, which was similar to control values, 55(3) min (P = 0.26). Erythromycin may have a role in the treatment of gastric stasis following oesophagectomy or truncal vagotomy.

Aged↗
PubMed1993

Image processing of videofluoroscopy of patients with velopharyngeal insufficiency and hypernasal speech.

Eleven patients with hypernasal speech and velopharyngeal insufficiency (VPI), together with five normals, were evaluated by videofluoroscopy to assess velopharyngeal movement, velar lift and lateral pharyngeal wall movement. Computer processing of the images obtained was used to compensate for initial poor quality images by contrast and edge enhancement techniques and to provide objective measurement of the movements involved. It was demonstrated that objective computer aided analysis of videofluoroscopic images is feasible and may provide additional subtle diagnostic information when nasendoscopy is unavailable. In addition, results obtained showed an increased degree of velar lift and lateral pharyngeal wall movement for the more severely affected patients. These suggest a compensatory mechanism in operation for the more severe cases of VPI.

Child↗