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Biomedical subjects

John Pitts

Publications and source records attributed to John Pitts.

5 recordsLinked to original sources
PubMed2003

Comparison of cardiac MRI on 1.5 and 3.0 Tesla clinical whole body systems.

RATIONALE AND OBJECTIVES: A cardiac imaging pilot study was performed on 1.5 and 3.0 Tesla (T) whole body magnetic resonance units equipped with identical gradient sets and geometrically equivalent body coils. The goals were to compare the signal-to-noise (SNR) and contrast-to-noise (CNR) ratios on matched studies conducted at both field strengths and demonstrate the potential for functional and morphologic cardiac evaluation at 3.0 T. METHODS: Short axis cine true fast imaging with steady precession (True FISP) was compared at 1.5 and 3.0 T using the body coil in transmit-receive mode and transmit-only with single loop and phased array receiver coils. SNR of the myocardium and CNR of the ventricular blood and myocardium were calculated from a quantitative region of interest analysis of these data. Additionally at 3.0 T, long axis and 4-chamber cine as well as "dark blood" imaging are demonstrated with sequence and parameter settings comparable to current state of the art for cardiac evaluation at 1.5 T. RESULTS: The 3.0 T data consistently demonstrates increases in SNR when all imaging conditions are closely matched but the increase has a large variability ranging from 20 to 85% depending on the radiofrequency coil configuration. Ventricular blood-myocardium CNR greater than 30 is obtained at 3.0 T, which is comparable to an optimized 1.5 T acquisition despite the specific absorption rate limitation of flip angle to nearly one half the value. The increased SNR at 3.0 T improves detection of fine anatomic detail, such as the chordae tendineae and mitral valve structure. CONCLUSIONS: Increased specific absorption rate can be a limiting fact; however, we have demonstrated that 3.0 T cardiac imaging shows gains in SNR while maintaining the CNR. The SNR gain is advantageous, and phased array coil technology is key for improving cardiac magnetic resonance imaging at 3.0 T.

Aged↗
PubMed2002

Enhancing reliability in portfolio assessment: discussions between assessors.

This paper reports the reliability in assessments of a series of portfolios assembled by a cohort of participants attending a course for prospective general practice trainers. Initial individual assessments are compared with open discussion between random pairs of assessors to produce paired composite scores, and analysed using kappa statistics. Overall reliability of a global pass/refer judgement improved from a kappa of 0.26 (fair) using individual assessment, to 0.5 (moderate) with paired discussants.

Cohort Studies↗
PubMed2001

Enhancing reliability in portfolio assessment: 'shaping' the portfolio.

This paper reports a follow-on project that assessed a series of portfolios assembled by a cohort of participants attending a course for prospective general practice trainers. In an attempt to enhance reliability, a framework for defining and addressing problems using a reflective practice model was offered to participants. The reliability of the judgements made by a panel of assessors about individual 'components', together with an overall global judgement about performance were studied. The reliability of individual assessors' judgements (i.e. their consistency) was moderate, but inter-rater reliability did not reach a level that could support making a safe summative judgement. Despite offering a possible structure for demonstrating reflective processes, the levels of reliability reached were similar to the earlier work and other subjective assessments generally, and perhaps reflected individuality of personal agendas of both the assessed and the assessors, and variations in portfolio structure and content; even agreement among the assessors about evidence of the framework being used was poor. Suggestions for approaches in the future are made. The conclusion remains that while portfolios might be valuable as resources for learning, as assessment tools they should be treated as problematic.

Journal Article↗