Biomedical subjects

Steve McLaughlin

Publications and source records attributed to Steve McLaughlin.

9 recordsLinked to original sources

PubMed2007

Error analysis of ultrasonic tissue doppler velocity estimation techniques for quantification of velocity and strain.

Recent work in the field of Doppler tissue imaging has focused mainly on the quantification of results involving the use of techniques of strain and strain-rate imaging. These results are based on measuring a velocity gradient between two points, a known distance apart, in the region-of-interest. Although many recent publications have demonstrated the potential of this technique in clinical terms, the method still suffers from low repeatability. The work presented here demonstrates, through the use of a rotating phantom arrangement and a custom developed single element ultrasound system, that this is a consequence of the fundamental accuracy of the technique used to estimate the original velocities. Results are presented comparing the performance of the conventional Kasai autocorrelation velocity estimator with those obtained using time domain cross-correlation and the complex cross-correlation model based estimator. The results demonstrate that the complex cross-correlation model based technique is able to offer lower standard deviations of the velocity gradient estimations compared with the Kasai algorithm.

Algorithms↗

PubMed2006

Serologic response to inactivated poliovirus vaccine: a randomized clinical trial comparing 2 vaccination schedules in Puerto Rico.

BACKGROUND: The World Health Organization (WHO) recommends the discontinuation of oral poliovirus vaccine after eradication of wild poliovirus. Studies assessing inactivated poliovirus vaccine (IPV) immunogenicity in tropical countries, using the WHO Expanded Programme on Immunization (EPI) schedule, have been limited. METHODS: We conducted a randomized clinical trial in Ponce, Puerto Rico. Infants were assigned to 1 of 2 study arms: those in the EPI arm received IPV at 6, 10, and 14 weeks of age, and those in the US arm received IPV at 2, 4, and 6 months of age. Neutralizing antibody titers against poliovirus types 1, 2, and 3 were tested on serum specimens obtained before administration of the first dose of IPV and 28-45 days after administration of the last dose of IPV. RESULTS: Seroconversion rates for the EPI (n=225) and US (n=230) arms, respectively, were 85.8% and 99.6% for poliovirus type 1 (P<.001), 86.2% and 100% for poliovirus type 2 (P<.001), and 96.9% and 99.1% for poliovirus type 3 (P=.08). Seroconversion rates were lower among infants in the EPI arm who had high maternal antibody levels for all 3 poliovirus types (P<.001). CONCLUSIONS: The EPI schedule resulted in lower seroconversion rates for poliovirus types 1 and 2. These results are relevant for tropical countries planning to use IPV in a posteradication environment.

Antibodies, Viral↗

PubMed2006

The use of the fractional Fourier transform with coded excitation in ultrasound imaging.

Medical ultrasound systems are limited by a tradeoff between axial resolution and the maximum imaging depth which may be achieved. The technique of coded excitation has been used extensively in the field of RADAR and SONAR for some time, but has only relatively recently been exploited in the area of medical ultrasound. This technique is attractive because allows the relationship between the pulse length and the maximum achievable spatial resolution to be changed. The work presented here explores the possibility of using the fractional Fourier transform as an effective means for the processing of signals received after the transmission of linear frequency modulated chirps. Results are presented which demonstrate that this technique is able to offer spatial resolutions similar to those obtained with a single cycle duration signal.

Algorithms↗

PubMed2005

Empirical mode decomposition and tissue harmonic imaging.

Empirical mode decomposition (EMD) is a relatively new technique used in the analysis of nonlinear and nonstationary time series. Previous signal-processing methods used for medical ultrasound have been based on the assumption of a linear time-invariant system. More recently, the technique of tissue harmonic imaging (THI) has become prevalent. This technique relies on the nonlinear propagation of the sound wave through the medium to disperse the signal energy into the harmonic frequencies of the transmitted signal. In this paper, results are presented from using EMD to process received ultrasound echo signals that have passed through nonlinear media. The Hilbert spectrum is used to demonstrate an interpretation of the physical process underlying THI that is based on the concept of intrawave frequency modulation, rather then the spreading of signal energy into harmonic frequencies. The technique of EMD is shown to be able to produce superior results to the bandpass filtering method of THI, even when the band width of the transducer was such that the second harmonic would be suppressed.

Artifacts↗

PubMed2004

Carcinoma of the anal canal: a local experience and review of the literature.

BACKGROUND: Through the 1970s patients presenting with anal canal carcinoma were managed with a surgical approach--abdomino-perineal resection. Since then, the pioneering work of Nigro et al. and a series of large clinical trials have clearly demonstrated that combined chemotherapy and radiotherapy result in greater local control, colostomy-free survival and increase in overall patient survival. The aim of the present study is to determine how widely the combined modality approach has been adopted in routine clinical practice and what outcomes are achieved in this setting. METHODS: All patients with anal cancer treated at three tertiary referral centres over an 11-year period (1991-2001) were identified. Data were collected by a retrospective record review. RESULTS: Our search identified a total of 50 patients: 22 men and 28 women, with a median age of 62 years. Four patients had metastatic disease diagnosed at presentation. Nine patients (18%) were at least 75 years of age and three were known to be HIV positive. Median potential follow up is 52 months. Of the 46 patients treated for cure, 38 received a combination of chemotherapy and radiation, with 79% achieving a complete response. Efficacy was maintained in treated elderly patients (> or =75 years). The 5-year survival of the 38 patients with local or locoregional disease who received combined chemoradiation modality was 63%. CONCLUSIONS: Overall this series demonstrates that combined chemotherapy and radiotherapy has been adopted as standard treatment with outcome data similar to those reported in the randomized clinical trials. Where possible elderly patients should receive combined modality therapy.

Aged↗

PubMed2002

Nasal positive-pressure technique for nasal foreign body removal in children.

Nasal foreign bodies in children are often encountered in emergency medicine and many methods of removal exist. This study examines the nasal positive pressure technique, a method not previously described in the literature. A retrospective chart review of nasal foreign body removal using the nasal positive pressure technique was conducted, as well as, a follow-up telephone survey of patient's parents. Nine patients were identified over a 1-year period. The average time from triage to discharge was 34 minutes (15-106 minutes). No sedation, consultation or complications were recorded. Five of the 9 parents completed the survey. All 5 (100%) described the procedure less traumatic than an injection, and 4 (80%) described the procedure similar or less traumatic than an oral pharyngeal exam with a tongue depressor. Nasal positive pressure technique for nasal foreign body removal is a safe and efficient method, and it is relatively nontraumatic in the view of parents.

Child, Preschool↗

PubMed2002

An approach to fulfilling the systems-based practice competency requirement.

The Accreditation Council for Graduate Medical Education (ACGME)-identified core competency of systems-based practice requires the demonstration of an awareness of the larger context and system of health care, and the ability to call on system resources to provide optimum care. This article describes an approach to teaching and fulfilling the requirement of this core competency in an emergency medicine residency. Beginning residents are oriented to community resources that are important to the larger context of care outside the emergency department. Each resident completes a community project during his or her residency. Readings and discussions concerning community-oriented medical care and the literature of research and injury prevention in emergency medicine precede the project development. Several projects are described in detail. Such projects help to teach not only awareness of the community resources of the greater context of medical practice outside the emergency department, but also how to use those resources. Projects could be a main component of a resident portfolio. This approach to teaching the core competency of systems-based practice is proposed as an innovative and substantial contribution toward satisfying the requirement of the core competency.

Clinical Competence↗

PubMed2002

Teaching communications and professionalism through writing and humanities: reflections of ten years of experience.

Both professionalism and interpersonal communication are core competencies for emergency medicine residents as well as residents from other specialties. The authors describe a weekly, small-group seminar lasting one year for emergency medicine residents that incorporates didactic materials, case studies, narrative expression (stories and poems), and small-group discussion. Examples of cases and narrative expressions are provided and a rationale for utilizing the format is explained. A theoretical model for evaluation measures is also included.

Communications Media↗

PubMedDate not supplied

Discovery and development of anticancer agents from plants.

A novel in vitro assay for the discovery of anticancer agents was used to examine aqueous and organic extracts from 1847 plants collected mainly in the U.S. Southwest and West. The assay results were separated into 5 categories: inactive (62%), equally active (36%), equally active and potent (0.5%), solid tumor selective (1.4%), and human selective (0.8%). Extracts from the latter three categories were fractionated using the in vitro assay to biodirect each step. Psorothamnus emoryi extracts were solid tumor selective and yielded two active compounds upon fractionation: dalrubone and 5-methoxydalrubone. Calocedrus decurrens was equally active and potent and yielded deoxypodophyllotoxin as the active compound. Linanthus floribundus was human selective and yielded strophanthidin as the active compound. The potential of this assay to discover novel anticancer agents from the active extracts is discussed.

Animals↗