Minimum detectable change in water diffusion using 3-T magnetic resonance imaging.

The objective of this study was to determine the minimum change in fractional anisotropy (FA), mean diffusivity (MD), and transverse diffusivity (TD) that can be detected in a repeated diffusion tensor imaging (DTI) session with 95% confidence, i.e., the minimum detectable change (MDC). During each of three sessions, six DTI sets were collected from eight volunteers using a 3-T MR scanner, and maps of FA, MD, and TD were generated. Mean FA, MD, and TD were recorded for regions of interest placed within the corpus callosum, corticospinal tract, putamen, optic radiation, and ventricular cerebral spinal fluid. An analysis of variance was performed to calculate MDC. MDC decreased as data were averaged over scans. With three averages, MDC was lowest within the corticospinal tract and putamen, where MDC was 0.04 for FA, below 30 x 10(-6) and 40 x 10(-6) mm2/s, respectively, for MD, and below 40 x 10(-6) mm2/s for TD. No improvement was observed beyond three averages. Our results suggest that DTI can be used clinically in individual patients to detect changes in FA, MD, and TD over repeated sessions associated with neurological disease with 95% confidence, or in research to investigate changes in white matter connections in individual subjects that accompany behavioral change, such as learning.

Short-term exposure evaluation of adult smokers switching from conventional to first-generation electrically heated cigarettes during controlled smoking.

This randomized, controlled study in 110 male and female adult smokers evaluated biomarkers of tobacco smoke exposure (carbon monoxide [CO], carboxyhemoglobin [CO-Hb], nicotine, urine mutagenicity) under controlled smoking conditions when adult smokers of 1 conventional cigarette brand (CC1) were switched to an electrically heated cigarette smoking system (EHCSS) or a low-tar conventional cigarette (CC2). Baseline exposure was determined while all subjects smoked CC1. Subjects then were stratified for gender and cigarette consumption and randomized to 1 of 5 groups-EHCSS1, EHCSS2, CC1, CC2, or no smoking-and monitored for 8 days. Compared to baseline, biomarkers of exposure on day 8 decreased 53% to 93% (P < .0001) for EHCSS groups and 18% to 39% (P < .02) for CC2. Environmental tobacco smoke arising from the smoking activities of the different study groups was measured in the air of a separate smoking room over 1-hour periods. Concentrations of respirable suspended particulates in both EHCSS groups were about 90% lower than in the CC1 and CC2 groups, similar to the 95% reduction in the no-smoking group. CO was undetectable in the EHCSS and no-smoking groups. Results from this short-term clinical study indicate that switching from a conventional cigarette to a first-generation EHCSS reduces the generation of environmental tobacco smoke and can reduce the exposure to the measured, potentially harmful constituents in tobacco smoke if smokers do not compensate by numbers of cigarettes. The study design was found to be suitable for the evaluation of the exposure of adult smokers to the measured smoke constituents and to allow the differentiation of different cigarette designs.