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Biomedical subjects

R A Cooper

Publications and source records attributed to R A Cooper.

At least 55 records · Page 3Linked to original sources
PubMed2000

Vascular endothelial growth factor (VEGF) expression is a prognostic factor for radiotherapy outcome in advanced carcinoma of the cervix.

The aim of the study was to evaluate VEGF expression in tumour biopsies as a prognostic factor for radiotherapy outcome in advanced carcinoma of the cervix. A retrospective study was carried out on 100 patients. Pre-treatment tumour VEGF expression was examined immunohistochemically in formalin-fixed, paraffin-embedded biopsies using a widely available commercial antibody. A semi-quantitative analysis was made using a scoring system of 0, 1, 2, and 3, for increasing intensity of staining. High VEGF expression was associated with a poor prognosis. A univariate log rank analysis found a significant relationship with overall survival (P = 0.0008) and metastasis-free survival (P = 0.0062), but not local control (P = 0.23). There was no correlation between VEGF expression and disease stage, tumour differentiation, patient age, or tumour radiosensitivity (SF2). In a Cox multivariate analysis of survival VEGF expression was the most significant independent prognostic factor (P = 0.001). After allowing for VEGF only SF2 was a significant prognostic factor (P = 0.003). In conclusion, immunohistochemical analysis of VEGF expression is a highly significant and independent prognostic indicator of overall and metastasis-free survival for patients treated with radiotherapy for advanced carcinoma of the cervix. It is also a rapid and easy method that could be used in the clinical setting, to identify patients at high risk of failure with conventional radiotherapy who may benefit from novel approaches or chemoradiotherapy.

Adenocarcinoma↗
PubMed2000

Wheelchair armrest strength testing.

There are about 1.4 million manual wheelchair users, 100,000 electric-powered wheelchair users, and 60,000 electric-powered scooter users. The current study was undertaken to determine if the fasteners of a clamp-type armrest receiver were prone to failure. The first test was used to examine the potential misalignment of the armrest receiver components that attach it to the frame. The second test was to evaluate the entire armrest using the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America armrest static strength standard. Finally, we conducted three fatigue tests. The first fatigue test was performed by repeating the static stability tests multiple times. The last two tests were a modified version of the double-drum wheelchair fatigue test used to apply repeated loading and vibration simultaneously. A paired t-test showed that there is no statistically significant difference (p = 0.08), with a confidence of 95%, between critical alignment measurements. The armrest including the receiver passed the standard requirement of a force of 760 N being applied outward at 15 degrees. During fatigue testing, we found that armrests did not exhibit any visible or functional damage. Upon completion of the tests, the armrests and receivers functioned properly. At about 100,289 cycles on a double-drum test machine, three bolts failed on each armrest receiver when the screws were loosened to have only five threads engaged prior to commencing the test. The design of the armrest tested was in compliance with existing national and international standards. Currently, both International Standards Organization and American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society committees are developing standards for seating systems that will include static, impact, and fatigue strength testing of devices like lateral torso supports, lateral hip support, etc. Methods similar to those explored in this study should be considered. This study may help manufacturers when designing products and purchasers or regulatory agencies when attempting to evaluate the safety and quality of armrest assemblies.

Equipment Design↗
PubMed2000

Analysis of position and isometric joysticks for powered wheelchair driving.

The control interface is one of the most critical components of the electric-powered wheelchair (EPW). The control interface must accommodate the user's limitations and maximize the user's abilities. This study extended Fitts' Law for target-acquisition to a continuously updated target. The extended Fitts' Law was used to examine EPW driving with a standard position sensing joystick and a prototype isometric joystick (IJ). The extended Fitts' Law provides insight into the difficulty of performing target-acquisition tasks with an EPW. The test results showed significant differences (p < 0.05) among the two types of joysticks for selected measures of information processing capacity, movement time, root-mean-square-error, and average velocity while performing turning maneuvers. The mean values indicate that the IJ may provide superior turning performance.

Algorithms↗
PubMed2000

Road loads acting on manual wheelchairs.

A barrier to performing more in-depth analyzes during the wheelchair design process is a lack of dynamic reaction force and moment data, and the instrumentation to collect this data. Instrumentation was developed to collect the dynamic force and moment data. New data collections methodologies and analysis techniques were implemented to facilitate computer-aided-engineering for wheelchair designs. Data were collected during standardized wheelchair fatigue tests, while driving over a simulated road course within a laboratory, and while driving in the community. Seventeen subjects participated in this study. Based upon the three test conditions, a pseudo-statistical distribution of the force and moment data at both a caster and rear wheel was developed. The key parameters describing the distribution and the extremums of the data (minima and maxima) were compared using analysis of variance. The results showed that the force and moment distributions and extreme values were similar for the both sets of human trials (i.e., simulated road course and field trials). However, the standardized testing (i.e., wheelchair fatigue testing) differed from both human trials. The force/moment data gathered during this study are suitable for inputs in finite element analysis and dynamic modeling. Our results suggest that the fatigue tests should be modified to change the magnitude and increase the frequency of the forces and moments imparted on the wheelchair. The data reported from this study can be used to improve wheelchair standards and to facilitate computer-aided-engineer in wheelchair design.

Acceleration↗
PubMed2000

Frequency analysis of kinematics of racing wheelchair propulsion.

The purpose of this study was to describe the frequency content of racing wheelchair propulsion motion data. The selection of the filter corner frequency in previous kinematic analyses of manual wheelchair propulsion was commonly based on gait literature. An estimate of the frequency separating the signal and the noise was determined to make recommendations for low-pass digital filters. The global (noncoordinate specific) cutoff frequency was 6 Hz. The directional cutoff frequencies were 5.1, 3.9, and 5.6 Hz, in the anterior-posterior, superior-inferior and medial-lateral directions, respectively. Recommendations for the corner frequencies of low-pass Butterworth digital filters based on the cutoff frequency are higher than the corner frequencies used in previous studies of manual wheelchair propulsion kinematic data. This study provides a foundation for the data reduction of manual wheelchair propulsion kinematic data that is independent of gait literature.

Adult↗
PubMed2000

Accuracy and complication rates of US-guided vacuum-assisted core breast biopsy: initial results.

PURPOSE: To determine the accuracy and complications of vacuum-assisted core breast biopsy performed with ultrasonographic (US) guidance. MATERIALS AND METHODS: US-guided, vacuum-assisted breast biopsy with an 11-gauge device was performed in 71 lesions in 67 consecutive women (age range, 23-82 years; mean age, 52.9 years). Vacuum-assisted core biopsy findings were compared with excisional biopsy, mammographic follow-up, and clinical follow-up findings (follow-up, 1-19 months; mean, 9.2 months). Procedural complications and treatment were noted. RESULTS: Of 71 lesions, 18 (25%) were diagnosed as malignant at core biopsy; one (1%), as premalignant; 30 (42%), as specific benign; and 22 (31%), as nonspecific benign. Of 18 malignant diagnoses, one (6%) was benign at excision. The premalignant specimen was benign at excision. Of 52 benign findings, 51 (98%) were proved benign at excision, mammographic follow-up, or clinical follow-up. One benign finding was carcinoma at excision. In this case, the specimen did not include the carcinoma because of a technical problem recognized at the time of the percutaneous procedure. Five (7%) of 71 biopsies resulted in bleeding beyond 10 minutes. One (1%) patient experienced a vasovagal response. CONCLUSION: According to these data, US-guided vacuum-assisted core breast biopsy is accurate. There may be a slightly higher risk of bleeding, which may be related to the lack of breast compression during the procedure, when compared with biopsy performed with stereotactic guidance.

Adult↗
PubMed2000

Evaluation of a manual wheelchair interface to computer games.

The sedentary lifestyle of many people with spinal cord injury (SCI) has lead to cardiovascular diseases being a major health concern. A suitable exercise program may help improve the SCI individual's cardiovascular fitness level. GAMEWheels is an interface between a custom wheelchair roller system and a computer that enables an individual to control computer video games by driving his or her wheelchair. The purpose of Phase 1 was to evaluate the design of the GAMEWheels system and to determine the type of computer video game that is likely to motivate wheelchair users to exercise. Phase 2 included physiologic testing of wheelchair users and the GAMEWheels system to investigate whether the system elicits an exercise training response. Thirty-five subjects were recruited to evaluate the GAMEWheels by playing three commercial computer games (Phase 1) and to identify the computer game that they would prefer to use when exercising. The feedback from Phase 1 was used with test subjects to verify that the GAMEWheels system elicits an exercise training effect (Phase 2). Phase 2 included 10 subjects using the GAMEWheels system to play Need for Speed II. During game play, physiologic data were collected and the subjects' oxygen consumption and heart rate were analyzed. Analysis showed that the GAMEWheels system induced nine subjects to reach their training zone, defined as 50% and 60% of their maximum oxygen consumption and heart rate, respectively. This study demonstrates that the GAMEWheels system elicits an exercise training response.

Adult↗
PubMed2000

Radiotherapy for carcinoma of the posterior pharyngeal wall.

Posterior pharyngeal carcinoma has an extremely poor prognosis regardless of the method of treatment. The purpose of this study was to assess the local control and survival in patients with carcinoma of the posterior pharyngeal wall treated with definitive radiotherapy and to determine prognostic factors which may be relevant to the current UICC staging classification. Between January 1991 and December 1995, 22 patients with a mean age of 60 years (range 44-82) received definitive radiotherapy, using a homogeneous technique, for carcinoma of the posterior pharyngeal wall. The median follow-up was 42 months (range 25-66). The overall 3-year survival and local control for the whole group was 50% and 73% respectively. Patients with early stage (T1 and T2) disease had a significantly better overall 3-year survival rate of 77% compared to 11% for patients with advanced stage (T3 and T4) disease (p=0.0010). Similarly, patients with early stage disease had a significantly improved 3-year local control rate compared to patients with more advanced stage disease (92% and 44% respectively, p=0.0080). Patients with node positive disease had an inferior survival rate of 29% compared to 60% for those with node negative disease though the difference did not reach statistical significance. In addition only one patient with initial node negative disease had isolated nodal relapse. There was no significant late morbidity. For patients with early stage disease we have obtained local control and survival rates comparable to other groups with a once daily, short fractionation radiotherapy scheme but with reduced morbidity. In late stage disease altered fractionation schemes should be considered in order to achieve better local control and survival. Isolated nodal relapse was not a significant problem in this cohort of patients. Outcome correlates with primary tumour size and this is reflected in the current UICC staging classification.

Adult↗
PubMed1999

Changes in oxygenation during radiotherapy in carcinoma of the cervix.

PURPOSE: The aim of this study was to investigate changes in tumor oxygenation, assessed by polarographic needle electrode measurements, following fractionated external beam radiotherapy in carcinoma of the cervix. METHODS AND MATERIALS: Normal and tumor tissue oxygenation was measured in 19 patients prior to radiotherapy and after 40-45 Gy of external beam radiotherapy delivered in 20 fractions over 4 weeks. All measurements were performed during anesthesia. RESULTS: There was no significant difference in the level of normal tissue oxygenation pre- and post radiotherapy. The individual patient median tumor pO2 values ranged from 0 to 31 mmHg pre-radiotherapy and 1 to 61 mmHg post-radiotherapy. The mean of the 19 median pO2 values increased from 8 (SD +/- 10) mmHg to 20 (+/- 20) mmHg following external beam radiotherapy. The increase was significant by paired Wilcoxon test (p = 0.011). There was also a significant fall in the proportion of values < 5 mmHg (p = 0.040). Although this value remained constant, or fell, in the majority of patients (15/19), it increased in 4 tumors. Tumor size pre- and postradiotherapy did not correlate with the level of pretreatment oxygenation; neither did the change in tumor size and change in level of oxygenation. CONCLUSION: The level of tumor oxygenation increased in the majority of patients (15/19) following 40-45 Gy of radiotherapy in carcinoma of the cervix.

Adult↗
PubMed1999

A high ratio of apoptosis to proliferation correlates with improved survival after radiotherapy for cervical adenocarcinoma.

PURPOSE: A retrospective study was made of the role of apoptosis in determining radiotherapy outcome in 39 adenocarcinoma of the cervix. A comparison was also made of the detection of apoptosis by morphology and the TdT dUtp nick end-labeling (TUNEL) assay. METHODS AND MATERIALS: The level of apoptosis was assessed in paraffin-embedded sections by cell morphology, the TUNEL assay, and a combination of the two. A total of 2,000 cells were counted per section, to obtain apoptotic (AI) and mitotic (MI) indices. RESULTS: Patients with a high AI had a higher survival rate than those with a low AI, however, the difference was not significant. Using a ratio of apoptosis to proliferation indices, patients with an AI:MI > median had significantly better survival than those with AI:MI < median. This was true where the AI was quantified by morphology alone (p = 0.030) or in combination with the TUNEL assay (p = 0.008). Where the AI was quantified by a combination of morphology and TUNEL, the 5-year survival rates for women with AI:MI greater or less than the median were 81% and 25%, respectively. CONCLUSION: A high ratio of AI:MI in adenocarcinoma of the cervix indicates a good prognosis. A combination of the TUNEL assay and morphology provided the best discrimination between outcome groups.

Adenocarcinoma↗
PubMed1999

Does salivary gland scintigraphy predict response to pilocarpine in patients with post-radiotherapy xerostomia?

This study was undertaken to determine whether standard salivary gland scintigraphy may be used for the objective assessment of salivary gland sialogogues, in particular oral pilocarpine, in the treatment of post-radiotherapy xerostomia. Nine patients, with xerostomia following radiotherapy to the head and neck region underwent salivary gland scintigraphy with technetium-99m pertechnetate (40 MBq) both before and following 1 month of oral pilocarpine (5 mg tds). For each scan, the percentage uptake in the first 14 min, the peak uptake, time to peak uptake and the percentage of activity excreted following lemon juice stimulation were calculated. The results were correlated with the subjective response as assessed by questionnaire and visual analogue scale. We found no correlation between subjective response and any of the four scan parameters analysed. We could not identify any parameter that predicted those patients who would respond to pilocarpine. In addition, only one parameter, the percentage of activity excreted following stimulation, correlated with previous dose of radiotherapy to the gland. In conclusion, in this study salivary gland scintigraphy did not appear to correlate with or predict response to oral pilocarpine. However, future studies might consider performing salivary gland scintigraphy prior to radiotherapy as well as at differing time points following the commencement of pilocarpine.

Administration, Oral↗
PubMed1999

Fatigue-life of two manual wheelchair cross-brace designs.

OBJECTIVE: To compare the durability of two designs of cross-braces for folding manual wheelchairs and to determine the nature of wheelchair cross-brace failures. DESIGN: Fatigue testing of two folding wheelchair cross-brace designs (one with a rectangular cross-section and the other with a circular cross-section). A total of 20 cross-brace pairs were tested. RESULTS: The cross-braces with a circular cross-section endured a mean +/- SD of 100,159 +/- 45,814 cycles before experiencing a fatigue failure, whereas the cross-braces with a rectangular cross-section endured an average of 261,254 +/- 160,741 cycles. A t test showed significant differences (p = .01) in fatigue-life between cross-braces with a circular cross-section versus cross-braces with a rectangular cross-section. All 20 cross-braces experienced similar fatigue failures that would develop at the bolt hole where the two cross-braces connect to form a hinge. CONCLUSION: The results suggest that the rectangular cross-brace design has a longer fatigue-life than the circular cross-brace design. People should regularly inspect the cross-brace for cracks. The area around the bolt forming the hinge should be inspected carefully. If a crack is observed, the cross-brace should be replaced immediately.

Persons with Disabilities↗
PubMed1999

Wheelchair pushrim kinetics: body weight and median nerve function.

OBJECTIVES: Individuals who use manual wheelchairs are at high risk for median nerve injury and subsequent carpal tunnel syndrome (CTS). To gain a better understanding of the mechanism behind CTS in manual wheelchair users, this study examined the relation between (1) pushrim biomechanics and function of the median nerve, (2) pushrim biomechanics and subject characteristics, and (3) median nerve function and subject characteristics. DESIGN: Case series. SETTING: Biomechanics laboratory and an electromyography laboratory. PARTICIPANTS: Thirty-four randomly recruited individuals with paraplegia who use a manual wheelchair for mobility. INTERVENTION: Subjects propelled their own wheelchair on a dynamometer at 0.9m/sec and 1.8m/sec. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system. Bilateral nerve conduction studies focusing on the median nerve were also completed. MAIN OUTCOME MEASURES: Pearson's correlation coefficients between subject characteristics, median nerve conduction studies, and propulsion biomechanics; a regression model of nerve conduction studies incorporating subject characteristics and pushrim biomechanics. RESULTS: Subject weight was significantly related to median nerve latency (r = .36, p = .03) and median sensory amplitude (r = -.43, p = .01). Height was also significantly related to median sensory amplitude (r = -.58, p = .01). Subject weight was significantly related to the peak resultant force applied to the pushrim (r = .59, p < .001). Height, weight, and weight-normalized pushrim forces were successfully incorporated into a linear regression model predicting median sensory amplitude (r = .63, p < .05) and mean median latency (r = .54, p < .05). CONCLUSION: This study found subject weight to be related to pushrim forces and median nerve function. Independent of subject weight, pushrim biomechanics were also related to median nerve function. Through weight loss and changes in pushrim biomechanics, it may be possible to prevent median nerve injury in manual wheelchair users.

Adult↗
PubMed1999

Evaluation of selected ultralight manual wheelchairs using ANSI/RESNA standards.

OBJECTIVES: To provide data for clinicians and wheelchair users to compare the durability, strength, stability, and cost effectiveness of four different ultralight wheelchair models, and to compare the results of this study with those published for lightweight wheelchairs. DESIGN: Standards testing and cost-effectiveness analysis of four wheelchair models from different manufacturers (12 wheelchairs total). RESULTS: There were significant differences (p< or =.05) in the fatigue life and value (equivalent cycles per dollar) among the ultralight wheelchairs tested. There was also a significant difference (p< or =.05) in rearward stability tilt angle for the least and most stable configurations. There were no differences in forward and lateral stability. The ultralight wheelchairs (1,009,108 cycles) had significantly (p< or =.05) higher fatigue lives than previously reported for lightweight wheelchairs (187,370 cycles). The lightweight wheelchairs had a mean value of 210 cycles per dollar compared to 673 cycles per dollar for the ultralight wheelchairs. The difference in value for the lightweight and ultralight wheelchairs was statistically significant (p< or =.05). CONCLUSION: There were differences in the fatigue life and value among the four models of ultralight manual wheelchairs tested. This indicates that ultralight manual wheelchairs are not all of equal quality. The fatigue life and value of the ultralight manual wheelchairs were significantly higher than those previously reported for lightweight manual wheelchairs. This indicates that ultralight wheelchairs may be of higher quality than lightweight manual wheelchairs. Clinicians and consumers should seriously consider selecting an ultralight manual wheelchair to meet their wheelchair mobility needs.

Cost-Benefit Analysis↗
PubMed1999

Tumour vascularity is a significant prognostic factor for cervix carcinoma treated with radiotherapy: independence from tumour radiosensitivity.

The aim of the study was to investigate the relationship between intrinsic radiosensitivity and vascularity in carcinoma of the cervix given radiotherapy, and assess whether more refined prognostic information can be gained by combining the two parameters. A retrospective study was carried out on 74 patients with locally advanced carcinoma of the cervix. Formalin-fixed, paraffin-embedded tumour biopsies were stained with anti-factor VIII using immunohistochemistry. Vascularity was scored using the intra-tumour microvessel density (IMD), or 'hot-spot', technique. For the same patients, the measurement of intrinsic radiosensitivity (SF2) had been made previously on the same pretherapy samples. Patients were stratified by the median IMD and SF2 scores. Women with radioresistant and highly vascular tumours had poorer 5-year survival (P = 0.0005, P = 0.035 respectively) and local control (P = 0.012, P = 0.077 respectively) than those with radiosensitive and poorly vascular tumours. No significant correlation was seen between IMD and SF2. Multivariate analysis (including tumour stage and patient age) showed that only SF2 and IMD were significant prognostic factors for survival. Patients with both a radioresistant and highly vascular tumour had a 5-year survival level of 18% compared to 77% for those patients with a radiosensitive and poorly vascularized tumour. Tumour angiogenesis and cellular radiosensitivity are independent prognostic factors for cervix carcinoma treated with radiotherapy. Allowing for tumour radiosensitivity increases the prognostic significance of vascularity measurements in cervix tumours.

Adult↗