Who explicitly requests the ordering of computed tomography for emergency department patients? A multicenter prospective study.

Emergency department (ED) computed tomography (CT) use has increased substantially in recent years, resulting in increased radiation exposure for patients. Few studies have assessed which parties contribute to CT ordering in the ED. The objective of this study was to determine the proportion of CT scans ordered due to explicit requests by various stakeholders in ED patient care. This is a prospective, observational study performed at three university hospital EDs. CT scans ordered during research assistant hours were eligible for inclusion. Attending emergency physicians (EPs) completed standardized data forms to indicate all parties who had explicitly requested that a specific CT be performed. Forms were completed before the CT results were known in order to minimize bias. Data were obtained from 77 EPs regarding 944 CTs. The parties most frequently requesting CTs were attending EPs (82.0 %, 95 % CI 79.4-84.3), resident physicians (28.6 %, 95 % CI 25.8-31.6), consulting physicians (24.4 %, 95 % CI 21.7-27.2), and admitting physicians (3.9 %, 95 % CI 2.9-5.4). In the 168 instances in which the attending EP did not explicitly request the CT, requests most commonly came from consulting physicians (51.2 %, 95 % CI 43.7-58.6), resident physicians in the ED (39.9 %, 95 % CI 32.8-47.4), and admitting physicians (8.9 %, 95 % CI 5.5-14.2). EPs were the sole party requesting CT in 46.2 % of cases while multiple parties were involved in 39.0 %. Patients, families, and radiologists were uncommon sources of such requests. Emergency physicians requested the majority of CTs, though nearly 20 % were actually not desired by them. Admitting, consulting, and resident physicians in the ED were important contributors to CT utilization.

Predicting Progression from Mild Cognitive Impairment to Alzheimer's Disease using MRI-based Cortical Features and a Two-State Markov Model.

Magnetic resonance imaging (MRI) has a potential for early diagnosis of individuals at risk for developing Alzheimer's disease (AD). Cognitive performance in healthy elderly people and in those with mild cognitive impairment (MCI) has been associated with measures of cortical gyrification [1] and thickness (CT) [2], yet the extent to which sulcal measures can help to predict AD conversion above and beyond CT measures is not known. Here, we analyzed 721 participants with MCI from phases 1 and 2 of the Alzheimer's Disease Neuroimaging Initiative, applying a two-state Markov model to study the conversion from MCI to AD condition. Our preliminary results suggest that MRI-based cortical features, including sulcal morphometry, may help to predict conversion from MCI to AD.

The reliability and heritability of cortical folds and their genetic correlations across hemispheres.

Cortical folds help drive the parcellation of the human cortex into functionally specific regions. Variations in the length, depth, width, and surface area of these sulcal landmarks have been associated with disease, and may be genetically mediated. Before estimating the heritability of sulcal variation, the extent to which these metrics can be reliably extracted from in-vivo MRI must be established. Using four independent test-retest datasets, we found high reliability across the brain (intraclass correlation interquartile range: 0.65-0.85). Heritability estimates were derived for three family-based cohorts using variance components analysis and pooled (total N > 3000); the overall sulcal heritability pattern was correlated to that derived for a large population cohort (N > 9000) calculated using genomic complex trait analysis. Overall, sulcal width was the most heritable metric, and earlier forming sulci showed higher heritability. The inter-hemispheric genetic correlations were high, yet select sulci showed incomplete pleiotropy, suggesting hemisphere-specific genetic influences.

Inter- and intra-fraction motion in stereotactic body radiotherapy for spinal and paraspinal tumours using cone-beam CT and positional correction in six degrees of freedom.

INTRODUCTION: Stereotactic body radiotherapy (SBRT) for spinal tumours delivers high doses per fraction to targets in close proximity to neural tissue. With steep dose gradients, small changes in position can confer significant dosimetric impact on adjacent structures. We analysed positioning error in consecutively treated patients on a strict image-guidance protocol with online correction in 6 degrees of freedom (6-DOF). METHODS: Set-up error, residual error post-correction and intra-fraction motion for 30 courses of spinal SBRT in 27 patients were assessed using cone-beam CT. Positional error was corrected in x, y and z translational planes and rotational axes using a robotic couch, applying 2 mm and 2° action levels. Linear mixed-effects model assessed whether positional error was influenced by factors such as vertebral level, immobilisation device and treatment duration. RESULTS: Sixty-two fractions were delivered with 225 image registrations. Median treatment duration was significantly longer for patients treated with static-field intensity-modulated radiotherapy compared with volumetric-modulated arc treatment--40 min versus 28 min, respectively (P = 0.01). Across all fractions, the median residual positional error after initial correction was greatest in the x translational plane (0.5 mm; 95% confidence interval (CI) 0.3-0.6) and y rotational axis (0.25°; 95% CI 0.1-0.3). Median intra-fraction error was also greatest in the x-plane (0.7 mm; 95% CI 0.5-1.0) and y-axis (0.4°; 95% CI 0.2-0.5). CONCLUSION: With strict immobilisation, image-guidance and 6-DOF correction, our current practice of applying 3-mm planning margins for target volumes and critical structures appears safe. Lower image-guidance action thresholds plus verification with end-to-end testing would be recommended before further reducing margins.