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Biomedical subjects

R L Atkinson

Publications and source records attributed to R L Atkinson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cerebrovascular biomodelling: a technical note.

BACKGROUND: Recently computed tomographic angiography (CTA) and MR angiography (MRA) have been used to image cerebrovascular structures. Although CTA and MRA are accurate and sensitive imaging modalities, limitations have been identified in relation to image interpretation. Stereolithographic (SL) biomodelling is a new technology that allows three-dimensional (3D) CT and MR data to be used to accurately manufacture solid plastic replicas of anatomical structures. A prospective trial of SL biomodelling in cerebrovascular surgery has been performed to investigate the feasibility and clinical utility of this new display medium. METHODS: Fifteen patients with cerebral aneurysms and 1 patient with a cerebral arteriovenous malformation (AVM) were selected. 3D CT and/or MR angiograms were acquired and 19 solid anatomical biomodels manufactured using the rapid prototyping technology of stereolithography. The biomodels were used for patient education, diagnosis, operative planning and surgical navigation. RESULTS: The biomodels replicated the CTA and MRA source data. The accuracy of one biomodel was verified by comparison with a post mortem specimen, which corresponded exactly in the x and y planes but differed by 2 mm in the z plane. The ability to closely study an overview of complex cerebrovascular anatomy from any perspective on a solid biomodel was reported to enhance the surgeon's understanding, particularly when conventional images were equivocal. Cerebrovascular biomodels were found to be useful when positioning the patient's head for surgery, for selecting the best aneurysm clip and for the simulation of clipping. Patient informed consent was anecdotally improved. Disadvantages of the technology were the cost and manufacturing time. CONCLUSIONS: Cerebrovascular biomodelling may have utility in complex cases or when the standard imaging is felt to be equivocal.

Adult↗
PubMed1999

Stereolithographic biomodelling in cranio-maxillofacial surgery: a prospective trial.

Stereolithographic (SL) biomodelling is a new technology that allows three-dimensional (3-D) computed tomography (CT) data to be used to manufacture solid plastic replicas of anatomical structures (biomodels). A prospective trial with the objective of assessing the utility of biomodelling in complex surgery has been performed. Forty-five patients with craniofacial, maxillofacial, skull base cervical spinal pathology were selected. 3-D CT or MR scanning was performed and the data of interest were edited and converted into a form acceptable to the rapid prototyping technology SL. The data were used to guide a laser to selectively polymerize photosensitive resin to manufacture biomodels. The biomodels were used by surgeons for patient education, diagnosis and operative planning. An assessment protocol was used to test the hypothesis that 'biomodels in addition to standard imaging had greater utility in the surgery performed than the standard imaging alone'. Biomodels significantly improved operative planning (images 44.09%, images with biomodel 82.21%, P < .01) and diagnosis (images 65.63%, images with biomodel 95.23%, P < .01). Biomodels were found to improve measurement accuracy significantly (image measurement error 44.14%, biomodel measurement error 7.91%, P < .05). Surgeons estimated that the use of biomodels reduced operating time by a mean of 17.63% and were cost effective at a mean price of $1031 AUS. Patients found the biomodels to be helpful for informed consent (images 63.53%, biomodels 88.54%, P < .001). Biomodelling is an intuitive, user-friendly technology that facilitated diagnosis and operative planning. Biomodels allowed surgeons to rehearse procedures readily and improved communication between colleagues and patients.

Cephalometry↗
PubMed1999

Initial weight loss as a predictor of response to obesity drugs.

BACKGROUND: Initial weight loss has been used as a predictor of long-term response to obesity drugs. Discontinuation of drugs has been recommended if weight loss is not > or =1.81 kg (4 lb) in the first month of treatment. OBJECTIVE: We compared the weight loss response at 6 months of patients losing > or =1.81 kg (responders) vs. < 1.81 kg (non-responders) in the first month of treatment with the combination of fenfluramine and phentermine. DESIGN: Outcomes at 6 months in 975 patients treated in a comprehensive program of phentermine (15-30 mg/d) d,l-fenfluramine (20-60 mg/d), were compared for responders vs. non-responders. RESULTS: In the total population, first month weight loss highly correlated with % reduction in body mass index (BMI) after 6 months of treatment (P<0.001). The reduction in baseline BMI after 6 months treatment was greater for the responders (15.9% vs. 10%, P<0.02). However, the North American Association for the Study of Obesity (NAASO) guidelines for drug treatment of obesity state that a 5% weight loss produces significant health benefits, and may be used as a criteria for success. At 6 months, 76%, 37% and 14% of the non-respondents had lost > or = 5%, > or = 10% and > or = 15% of baseline BMI, respectively. After 6 months treatment the reductions in serum cholesterol, triglycerides and LDL-cholesterol were 0.55, 0.31 and 0.42 mmol/L, respectively, (P< or =0.006), for the non-responders. Adverse effects after 6 months of treatment and the dropout rates after 1 y of treatment were not significantly different for the two groups. CONCLUSIONS: Although, the first month weight loss predicted the long-term response to phen-fen treatment, it was inadequate in identifying the non-responders and may unnecessarily preclude potential beneficiaries of the treatment.

Adult↗
PubMed1999

Biomodel-guided stereotaxy.

OBJECTIVES: To simplify the practice of stereotactic surgery by using an original method, apparatus, and solid anatomic replica for trajectory planning and to validate the method and apparatus in a laboratory and clinical trial. METHODS: The patient is marked with fiducials and scanned by using computed tomography or magnetic resonance imaging. The three-dimensional data are converted to a format acceptable to stereolithography. Stereolithography uses a laser to polymerize photosensitive resin into a solid plastic model (biomodel). Stereolithography can replicate blood vessels, soft tissue, tumor, and bone accurately (<0.8 mm). A stereotactic apparatus is referenced to fiducials replicated in the biomodel. The trajectory for the intervention is determined and saved. The apparatus is attached to the patient fiducials, and the intervention is replicated. RESULTS: Three types of apparatus (template, Brown-Roberts-Wells frame, and D'Urso frame) were tested on phantoms and patients requiring the excision/biopsy of tumors. The localization errors determined from the phantom studies were template, 0.82 mm; Brown-Roberts-Wells frame, 1.17 mm; and D'Urso frame, 0.89 mm. The surgeons reported that clinical use of the template and D'Urso frame was accurate and ergonomic. The Brown-Roberts-Wells frame was more difficult to use and somewhat inaccurate. CONCLUSION: Biomodel-guided stereotaxy has significant advantages. It is performed quickly; it is based on simple, intuitive methodology; it enhances visualization of anatomy and trajectory planning; it enhances patient understanding; it uses inexpensive equipment; it does not require rigid head fixation; and it has greater versatility than known techniques. Disadvantages are biomodel cost and a manufacturing time of 12 to 24 hours.

Biopsy↗
PubMed1998

Stereolithographic (SL) biomodelling in craniofacial surgery.

BACKGROUND: Stereolithographic (SL) biomodelling allows 3D CT to be used to generate solid plastic replicas of anatomical structures (biomodels). Case reports in the literature suggest that such biomodels may have a use in craniofacial surgery but no large series or assessment of utility has been reported. A prospective trial to assess the utility of biomodelling in craniofacial surgery has been performed. METHODS: Forty patients with complex craniofacial abnormalities were selected and 3D CT scanning performed. The data of interest was used to guide a laser to selectively polymerise photosensitive resin to manufacture SL biomodels. The biomodels were used for patient education, diagnosis and operative planning. An assessment protocol was designed to test the hypothesis that biomodels in addition to standard imaging had greater utility in the surgery performed than the standard imaging alone. RESULTS: Anecdotally surgeons found biomodelling useful in 40 complex craniofacial operations. The formal assessment of the first 10 cases suggested biomodels improved operative planning (image 76%, image with biomodel 97%, P < 0.01) and diagnosis (image 82.5%, image with biomodel 99.25%, P < 0.01). Surgeons estimated that the use of biomodels had reduced operating time by a mean of 16% and were cost effective at a mean price of $1100 AUS. CONCLUSION: Biomodelling was reported as an intuitive, user-friendly technology that facilitated diagnosis, operative planning and communication between colleagues and patients. Limitations of the technology were manufacturing time and cost.

Attitude of Health Personnel↗
PubMed1998

Sleep apnea in obese miniature pigs.

We postulated that three extremely obese Yucatan miniature pigs would have more sleep apnea than three nonobese Yucatan miniature pigs. Pigs were studied with the use of electroencephalograms, inductance plethysmography, oximetry, expired nasal CO2, or thermistors. All of the obese pigs, but none of the nonobese pigs, had both sleep apnea (8.5, 10.3, and 97.0 in obese pigs vs. O apnea + hypopnea/h in all nonobese pigs; P < 0.05) and oxyhemoglobin desaturation episodes during sleep [9.4 +/- 3.0 vs. 0 + 0.53 (SD) mean desaturation episodes/h in obese pigs vs. nonobese pigs, respectively; P < 0.05]. Two of the extremely obese pigs had obstructive sleep apnea, whereas the third obese pig had central sleep apnea. We conclude that sleep apnea occurs in extremely obese Yucatan minipigs and suggest that this animal can be used as a model for sleep apnea in obesity.

Animals↗
PubMed1997

Long-term drug treatment of obesity in a private practice setting.

This study evaluated the long-term efficacy and safety of the combination of phentermine and fenfluramine for the treatment of obesity in a private practice setting. A total of 1388 consecutive, qualified patients presenting to a private general internal medicine practice in Charlotte, NC, were enrolled with eligibility criteria including: age 18 years to 60 years, 20% over "desirable" bodyweight or body mass index > 27, no serious medical or psychiatric disease, and no contraindications to drug therapy. Patients were instructed in diet, exercise, and behavior modification techniques and received phentermine (15 mg/day to 30 mg/day) and fenfluramine (20 mg/day to 60 mg/day) continuously for over 3 years. Average duration of treatment was 15.9 months, and average weight loss at the last visit was 11.6 kg, or 11.7% of initial bodyweight. For patients completing 1 year of drug treatment, mean weight loss was 16.5 kg, or 16% of initial weight. Weight loss persisted for 2 years, but partial regain was seen at 3 years. The dropout rates were 18% at 6 months, 39% at 1 year, 68% at 2 years, and 78% at 3 years. At 1 year, blood pressure of hypertensive patients fell from 151/95 mm Hg to 127/78 mm Hg, and serum cholesterol and triglycerides of hyperlipidemic patient fell by 0.750 mmol/L (29 mg/dL) and 0.937 mmol/L (83 mg/dL), respectively. Adverse events were modest. We conclude that, in a private practice setting, long-term treatment of obesity with the combination of phentermine, fenfluramine, and a weight maintenance program is generally safe and effective. More research is needed to determine efficacy and safety for longer than 3 years.

Adolescent↗
PubMed1997

Association of adenovirus infection with human obesity.

We previously reported that chickens infected with the avian adenovirus SMAM-1 developed a unique syndrome characterized by excessive intra-abdominal fat deposition accompanied by paradoxically low serum cholesterol and triglyceride levels. There have been no previous reports of avian adenoviruses infecting humans. We screened the serum of 52 humans with obesity in Bombay, India, for antibodies against SMAM-1 virus using the agar gel precipitation test (AGPT) method. Bodyweights and serum cholesterol and triglyceride levels were compared in SMAM-1-positive (P-AGPT) and SMAM-1-negative (N-AGPT) groups. Ten subjects were positive for antibodies to SMAM-1, and 42 subjects did not have antibodies. The P-AGPT group had a significantly higher bodyweight (p < 0.02) and body mass index (p < 0.001) (95.1 +/- 2.1 kg and 35.3 +/- 1.5 kg/m2, respectively) compared with the N-AGPT group (80.1 +/- 0.6 kg and 30.7 +/- 0.6 kg/m2, respectively). Also, the P-AGPT group had significantly lower serum cholesterol (p < 0.02) and triglyceride (p < 0.001) values (4.65 mmol/L and 1.45 mmol/L, respectively) compared with the N-AGPT group (5.51 mmol/L and 2.44 mmol/L, respectively). Two subjects positive for SMAM-1 antibodies had antibodies against each others' serum, suggesting the presence of antigens in one or both. When these two serum samples were inoculated into chicken embryos, macroscopic lesions compatible with SMAM-1 infection developed. The inoculation of serum from N-AGPT subjects did not produce such lesions. The presence of increased obesity, antibodies to SMAM-1, reduced levels of blood lipids, and viremia that produces a typical infection in chicken embryos suggests that SMAM-1, or a serologically similar human virus, may be involved in the cause of obesity in some humans.

Adenoviridae↗
PubMed1997

Metyrapone pre-treated inferior petrosal sinus sampling in the differential diagnosis of ACTH-dependent Cushing's syndrome.

BACKGROUND: Inferior petrosal sinus sampling (IPSS) is a useful investigative technique in the differential diagnosis of ACTH-dependent Cushing's syndrome. Diagnostic accuracy is improved by the administration of corticotrophin releasing-factor (CRF) during the procedure to stimulate ACTH secretion. We hypothesized that, given the unavailability of CRF in Australia, stimulation of ACTH secretion from tumorous corticotrophs with metyrapone treatment before IPSS may be useful. AIMS: To describe our clinical experience with a novel diagnostic test, and to compare results between IPSS with and without metyrapone pre-treatment. SETTING: Metropolitan, Australian university teaching hospital. PATIENTS: 18 patients were studied on 21 occasions: three with Cushing's disease without metyrapone treatment prior to IPSS (M-), 11 with Cushing's disease with metyrapone pretreatment (M+), three with ectopic ACTH syndrome, and one with pseudo-Cushing's syndrome. TREATMENT: Patients received oral metyrapone, median dose 750 mg 6 hourly, for 24 h before IPSS. RESULTS: No major side effects were noted. Metyrapone increased serum 11-deoxycortisol concentration to a median of 400 nmol/l (range 36-1310) on the morning of the test. Radiological confirmation of correct catheter placement was shown in 36/42 inferior petrosal sinuses (86%). Median peak central: peripheral ACTH ratios were 9.8 for M- pituitary adenomas (range 5.7-13.6), 12.9 for the technically successful M+ pituitary adenomas (range 8-54.1), and 1.6 for M+ ectopic ACTH syndrome cases (range 1.2-3.4). Repeat studies in unoperated patients with ectopic ACTH syndrome showed ratios < 1.6. IPSS showed median peak ACTH concentrations of 190 ng/l for M- pituitary adenomas (range 83-205), 595 ng/l for the technically successful M+ pituitary adenomas (range 80-7630; P = 0.035 compared to M-), and 62 ng/l for M+ ectopic ACTH syndrome cases (range 47-220). IPSS correctly identified the pituitary source of ACTH production in all cases of Cushing's disease (except one technical failure where MRI revealed a lesion). MRI scanning correctly identified a lesion in 3/14 operated Cushing's disease cases. IPSS correctly lateralized 1/3 M- and 7/8 M+ Cushing's disease cases where the procedure was technically successful and surgical descriptions adequate. Pituitary exploration revealed a visible lesion in 75% of cases corresponding to the side predicted by IPSS; 'blind' hemi-hypophysectomy was performed on the side predicted from IPSS in the remainder. All cases of Cushing's disease were cured or improved following surgery, with a median follow-up of 2.8 years (range 0.7-5.9). CONCLUSIONS: Metyrapone pre-treated inferior petrosal sinus sampling is safe, and appears to induce high ACTH output from pituitary corticotroph adenomas. The technique has allowed accurate localization and treatment of pituitary corticotroph microadenomas.

ACTH Syndrome, Ectopic↗
PubMed1997

Use of drugs in the treatment of obesity.

Obesity has become an epidemic in the United States and in many other countries of the world. Obesity is a chronic disease, not a failure of willpower. Diet, exercise, and behavioral modification of lifestyle are rarely successful over the long term. Medications have been used sparingly, because of concerns about addiction and ineffectiveness, but used chronically, obesity drugs are effective. The two main categories of obesity drugs are centrally active adrenergic and serotonergic agents. These drugs reduce appetite, enhance satiety, and increase energy expenditure. Use of single agents produces modest weight loss and use of combinations increases loss, but few patients reach their goal weight. Co-morbidities associated with obesity resolve or are reduced in severity with weight loss. Adverse events of major concern are changes in brain biochemistry and primary pulmonary hypertension. Published guidelines for use of obesity medications recommend they be used only for medically significant obesity.

Adrenergic Agents↗
PubMed1997

Differential regulation of the p80 tumor necrosis factor receptor in human obesity and insulin resistance.

Previous studies have shown that tumor necrosis factor (TNF)-alpha production from adipose tissue is elevated in rodent and human obesity and plays an important role in insulin resistance in experimental animal models. In this study, we examined the adipose expression of both TNF receptors (TNFR1 and TNFR2) in human obesity and demonstrated that obese female subjects express approximately twofold more TNFR2 mRNA in fat tissue and approximately sixfold more soluble TNFR2 in circulation relative to lean control subjects. In contrast, TNFR1 expression and protein levels were similar in these subjects. TNFR2 expression levels in adipose tissue were strongly correlated with BMI (r = 0.65, P < 0.001) and level of hyperinsulinemia (P < 0.001), an indirect measure of insulin resistance, as well as level of TNF-alpha mRNA expression in fat tissue (r = 0.56, P < 0.001). These results suggest that TNFR2 might play a role in human obesity by modulating the actions of TNF-alpha.

Adipose Tissue↗
PubMed1996

Role of nutrition planning in the treatment for obesity.

The most sensible eating plans are those that involve a wide selection of foods with a modest percentage of kilocalories as fat. The dietary pyramid developed by the US Government is an excellent basis for the construction of an eating plan for life. Patients should be encouraged to develop healthy eating habits that they can maintain indefinitely, as the early inevitable consequence of finishing a diet is regain of any weight that has been lost when the patient goes back to their old eating habits. The unfortunate fact is that individuals with the disease of obesity must behave differently than those who do not. This usually means that obese persons must eat differently than lean persons, and they must do this for their entire lives. Food is a critical part of the social fabric of our society. The physician, usually in combination with a knowledgeable and empathetic dietitian or other nutritional education resource, can help obese patients choose the series of compromises in eating plans and activity levels that can be maintained for life but still allow a reasonable quality of life.

Dietary Services↗
PubMed1996

High prevalence of gastric trichobezoars (hair balls) in Wistar-Kyoto rats fed a semi-purified diet.

Gastric trichobezoars (hair balls) are frequently found in rabbits but are rarely reported in rats. Several Wistar-Kyoto rats fed a semi-purified diet developed anorexia and abdominal tenderness. Proteolysis therapy with fresh papaya and commercially prepared enzyme was attempted in these rats but was not successful. The prevalence of trichobezoars at necropsy was 100%. We conclude that semi-purified diets contribute to trichobezoar formation in rats, but proteolysis therapy is not effective in dissolving the trichobezoars.

Animals↗
PubMed1995

Combined drug treatment of obesity.

Pharmacological treatment of obesity has been neglected as a viable therapeutic option for many years. Recent long term studies with combinations of obesity drugs gives promise that drugs may play a role in weight maintenance, which classically has been the most difficult aspect of treating obesity. Currently available obesity drugs include centrally acting adrenergic agents and serotonin agonists. Drugs still in development include a lipase inhibitor that produces fat malabsorption, a combined adrenergic-serotonergic reuptake inhibitor, various gut-central nervous system peptides, and a number of beta-3 agonists. Any of these obesity drugs given alone produces modest weight loss, and for most, weight loss continues for as long as medication is given. The most successful drug regimens to date are combinations of phentermine and fenfluramine or of ephedrine, caffeine, and/or aspirin. The former combination produces reduction in body weight and complications of obesity for 2 to almost 4 years in clinical trials to date. More research is needed to document long term efficacy and particularly the long term safety of these and other combinations.

Adrenergic Agents↗