Subregional analysis of striatum iron in Parkinson's disease and rapid eye movement sleep behaviour disorder.

The loss of dopamine in the striatum underlies motor symptoms of Parkinson's disease (PD). Rapid eye movement sleep behaviour disorder (RBD) is considered prodromal PD and has shown similar neural changes in the striatum. Alterations in brain iron suggest neurodegeneration; however, the literature on striatal iron has been inconsistent in PD and scant in RBD. Toward clarifying pathophysiological changes in PD and RBD, and uncovering possible biomarkers, we imaged 26 early-stage PD patients, 16 RBD patients, and 39 age-matched healthy controls with 3 T MRI. We compared mean susceptibility using quantitative susceptibility mapping (QSM) in the standard striatum (caudate, putamen, and nucleus accumbens) and tractography-parcellated striatum. Diffusion MRI permitted parcellation of the striatum into seven subregions based on the cortical areas of maximal connectivity from the Tziortzi atlas. No significant differences in mean susceptibility were found in the standard striatum anatomy. For the parcellated striatum, the caudal motor subregion, the most affected region in PD, showed lower iron levels compared to healthy controls. Receiver operating characteristic curves using mean susceptibility in the caudal motor striatum showed a good diagnostic accuracy of 0.80 when classifying early-stage PD from healthy controls. This study highlights that tractography-based parcellation of the striatum could enhance sensitivity to changes in iron levels, which have not been consistent in the PD literature. The decreased caudal motor striatum iron was sufficiently sensitive to PD, but not RBD. QSM in the striatum could contribute to development of a multivariate or multimodal biomarker of early-stage PD, but further work in larger datasets is needed to confirm its utility in prodromal groups.

Development of Learning Curves for Bronchoscopy: Results of a Multicenter Study of Pulmonary Trainees.

BACKGROUND: There are currently no reference standards for the development of competence in bronchoscopy. RESEARCH QUESTION: The aims of this study were to (1) develop learning curves for bronchoscopy skill development and (2) estimate the number of bronchoscopies required to achieve competence. STUDY DESIGN AND METHODS: Trainees from seven North American academic centers were enrolled at the beginning of their pulmonology training. Performance during clinical bronchoscopies was assessed by supervising physicians using the Ontario Bronchoscopy Assessment Tool (OBAT). Group-level learning curves were modeled using a quantile regression growth model, where the dependent variable was the mean OBAT score and the independent variable was the number of bronchoscopies performed at the time the OBAT was completed. RESULTS: A total of 591 OBAT assessments were collected from 31 trainees. The estimated regression quantiles illustrate significantly different learning curves based on trainees' performance percentiles. When competence was defined as the mean OBAT score for all bronchoscopies rated as being completed without need for supervision, the mean OBAT score associated with competence was 4.54 (95% CI, 4.47-4.58). Using this metric, the number of bronchoscopies required to achieve this score varied from seven to 10 for the 90th percentile of trainees and from 109 to 126 for the lowest 10th percentile of trainees. When competence was defined as the mean OBAT score for the first independent bronchoscopy, the mean was 4.40 (95% CI, 4.20-4.60). On the basis of this metric, the number of bronchoscopies required varied from one to 11 for the 90th percentile of trainees and from 83 to 129 for the lowest 10th percentile of trainees. INTERPRETATION: We were able to generate learning curves for bronchoscopy across a range of trainees and centers. Furthermore, we established the average number of bronchoscopies required for the attainment of competence. This information can be used for purposes of curriculum planning and allows a trainee's progress to be compared with an established norm.