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Biomedical subjects

S Symons

Publications and source records attributed to S Symons.

9 recordsLinked to original sources
PubMed2006

Identification of penumbra and infarct in acute ischemic stroke using computed tomography perfusion-derived blood flow and blood volume measurements.

BACKGROUND AND PURPOSE: We investigated whether computed tomography (CT) perfusion-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. METHODS: Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n=16) and those without (n=9). Penumbra was operationally defined as tissue with an admission CBF <25 mL x 100 g(-1) x min(-1) that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points. RESULTS: For recanalized patients, CBF was significantly lower (P<0.05) for infarct (13.3+/-3.75 mL x 100 g(-1) x min(-1)) than penumbra (25.0+/-3.82 mL x 100 g(-1) x min(-1)). CBV in the penumbra (2.15+/-0.43 mL x 100 g(-1)) was significantly higher than contralateral (1.78+/-0.30 mL x 100 g(-1)) and infarcted tissue (1.12+/-0.37 mL x 100 g(-1)). Logistic regression using an interaction term (CBFxCBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better (P<0.05) fit than CBF or CBV alone, suggesting that the CBV threshold for infarction varies with CBF. For patients without recanalization, CBF and CBV for infarcted regions were 15.1+/-5.67 mL x 100 g(-1) x min(-1) and 1.17+/-0.41 mL x 100 g(-1), respectively. CONCLUSIONS: We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.

Acute Disease↗
PubMed2005

Cochlear implantation in cochlear otosclerosis.

OBJECTIVES/HYPOTHESIS: The objective was to correlate implant performance in cochlear otosclerosis to 1) matched control samples, 2) severity of otic capsule involvement, 3) prior ipsilateral surgery, and 4) programming issues. STUDY DESIGN: Retrospective case controlled study. METHODS: Study cohort comprised 30 individuals. Diagnosis was based on prior ear surgery (stapedectomy [n = 18] or fenestration [n = 2]) and/or pathognomonic radiological findings. High-resolution computed tomography images of the temporal bones were assessed by two radiologists and graded (range, 0-3) for the extent of otosclerosis. Operative records were reviewed. Performance, programming visits, and the number of electrode deactivations at 6 months and at 1 year after implantation were determined for the individuals with otosclerosis and compared with a group of matched control subjects. A within-group comparison correlating severity of otosclerosis to the above was carried out. RESULTS: Implant performance in individuals with cochlear otosclerosis was not significantly different from those without. Previous surgery on the side of implantation did not alter performance. Programming difficulty as reflected in the number of visits and electrode deactivation for sound quality reasons were comparable. Deactivation for facial nerve stimulation occurred exclusively in otosclerotics with the most severe radiological disease (grade 3) and was only with non-modiolar hugging electrodes (n = 5). There was no observed difference between the radiological extent of otosclerosis and implant performance. CONCLUSION: Individuals with severe otosclerosis considering cochlear implantation can be counseled to expect similar benefit to those without, regardless of whether prior surgery occurred on the side of implantation or of severity of otic capsule involvement. There is a significant risk of facial nerve stimulation in otosclerotics with grade 3 disease.

Case-Control Studies↗
PubMed2001

Hospital versus home management of children with buckle fractures of the distal radius. A prospective, randomised trial.

Our aim was to determine whether children with buckle fractures of the distal radius could be managed at home after initial hospital treatment. There were 87 patients in the trial: 40 had their short-arm backslab removed at home three weeks after the initial injury, and 47 followed normal practice by attending the fracture clinic after three weeks for removal of the backslab. Clinical examination six weeks after the injury showed no significant difference in deformity of the wrist, tenderness, range of movement and satisfaction between the two groups. Fourteen (33%) of the hospital group compared with five (14%) (p = 0.04) of those managed in the community stated that they had problems with the care of their child's fracture. It was found that both groups, given a choice, would prefer to remove their child's backslab at home (p < 0.001). Our findings show that it is clinically safe to manage children with buckle fractures within the community.

Ambulatory Care↗
PubMed2000

Development and duration of radiographic signs of bone healing in children.

OBJECTIVE: Few articles report the evaluation of pediatric fracture healing and dating based on radiographic appearance. We established a timetable for expected radiographic changes visible during bone healing in otherwise healthy children. MATERIALS AND METHODS: We examined 707 radiographs of fractured forearms in 141 patients. Each fracture was assessed by a pediatric radiologist who was unaware of the timing of the initial injury. Assessment included the following features: fracture margins, fracture gap, periosteal reaction, callus, bridging, and remodeling. The time interval between injury and the appearance of the radiographic features and the duration of radiographic signs were determined and correlated with age, sex, angulation, displacement, and location. RESULTS: Sclerosis at the fracture margins was evident in 85% of fractures 5 weeks after injury. Widening of the fracture gap was observed in 62% of fractures at 6 weeks. Periosteal reaction was evident on all images by 4 weeks, and after 7 weeks, periosteal reaction was separable from cortex in only 10% of fractures. Fracture callus had a density equal to or greater than that of adjacent cortex 10 weeks after injury in 90% of fractures. CONCLUSION: A wide variation exists in the appearance and duration of the radiographic signs of bone healing. Marginal sclerosis should be an expected radiographic sign of normal bone healing. Applying maximum and minimum time spans to objective radiographic signs may aid in fracture dating.

Adolescent↗
PubMed1998

A Comparison of Self-Explanation and Elaborative Interrogation.

The purpose of the present study was to examine the effectiveness of two learning strategies, self-explanation and elaborative interrogation, for the retention of scientific facts. University students (N = 55) were asked to learn facts about the cardiovascular system using one of three approaches. Self-explanation participants were required to explain what the facts meant to them and how they related to their prior knowledge. Elaborative interrogation participants answered "why" the facts made sense. Finally, the control group simply repeated the facts aloud. Self-explanation participants significantly outperformed elaborative interrogation and repetition control participants on measures of cued recall and recognition. Elaborative interrogation was no more effective than repetition. Results were discussed in terms of the practicality and flexibility of each approach. Copyright 1998 Academic Press.

Journal Article↗
PubMed1991

Measurements of contact currents in radiofrequency fields.

Radiofrequency electromagnetic fields can affect human health not only by direct interactions but indirectly through induction of charges on isolated or poorly grounded conductive (metallic) objects located in these fields. A person who touches such an object may perceive a tingling or prickling sensation or heat, or experience pain or electric shock. For sufficiently large objects, these phenomena can occur at field strengths that are relatively low and below the health protection limits based on direct interactions. We describe a method and circuitry developed to evaluate steady-state contact currents that may flow through a person touching conductive objects and give a summary of experimental tests performed. The method is simple and viable for field tests aimed at preventing pain, shock, and burn hazards in radiofrequency electromagnetic fields except those related to spark discharges. The method is applicable up to about 30 MHz.

Electric Injuries↗