A pilot study to assess the feasibility of measurement of adrenal gland volume by magnetic resonance imaging.

BACKGROUND: Repeated computed tomography (CT) assessment of the adrenal glands is associated with a significant radiation burden. The increasing capabilities of magnetic resonance (MR) volumetric analysis of the adrenals make this a potentially alternative technique in man. PURPOSE: To determine whether MR imaging could be used to measure adrenal volume, and to determine the intra- and interobserver variation and repeatability of MR volume imaging of adrenals in healthy human subjects. MATERIAL AND METHODS: This was a single-cohort, sequential design, three-part study involving four MRI examinations per subject following ethical approval and informed consent. Information was collected on four healthy subjects (three male and one female). Two different investigators estimated the area of the adrenal gland for each of the 3-mm contiguous slices (and consequently adrenal volume). In order to estimate inter- and intrareader variability, a repeated-measures mixed model was fitted with adrenal volume as the dependent variable. In order to estimate any bias between readers, Bland-Altman methodology was applied. RESULTS: Intraobserver variation for adrenal gland volume is approximately 5% of a 3-cm(3 )adrenal gland. Interobserver variation is approximately 9% of a 3-cm(3) adrenal gland. Potential variation in measurement for adrenal volume from all sources equates to approximately 14% of a 3-cm(3) adrenal gland. Verification of image reading by a second investigator (consensus reading) reduces variability. CONCLUSION: Analysis of adrenal gland volume using MRI is a potentially reliable technique that could be used to assess a pathological change in adrenal size.

A statistical assessment of QT data following placebo and moxifloxacin dosing in thorough QT studies.

The ICH guidelines indicate that a single "thorough QT study" should be conducted to evaluate the effects of new drugs on cardiac repolarization. A positive control, such as moxifloxacin, is required to be assessed as part of the thorough QT study to validate the assay sensitivity of each study. In order to better understand the effect of moxifloxacin, a meta-analysis of nine thorough QT studies has been undertaken to assess the overall moxifloxacin effect. The data was analyzed using a repeated measures mixed model to test various covariance structures to identify the most suitable model for this and future meta-analyses of thorough QT studies.