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Background ‘Syndemic’ refers to socially produced, intertwined, and co-occurring epidemics. Syndemic theory is increasingly used to understand the population-level relationships between sexual health (including HIV) and mental health (including problematic substance use) epidemics. Syndemic-informed clinical interventions are rare. Methods We therefore asked 22 sexual health practitioners from six sexual health clinics in British Columbia, Canada to define the word ‘syndemic’ and then asked how the theory related to their clinical practice. Results Responses to syndemic theory ranged widely, with some practitioners providing nuanced and clinically informed definitions, others expressing a vague familiarity with the term, and others still having no prior knowledge of it. Where practitioners acknowledged the relevance of syndemic theory to their practice, they articulated specific ways in which syndemics create moral distress, that is, feeling that the most ethical course of action is different from what they are mandated to do. While some practitioners routinely used open-ended questions to understand the social and economic contexts of patients’ sexual health needs, they described an uneasiness at potentially having surfaced concerns that could not be addressed in the sexual health clinic. Many observed persistent social, mental health, and substance use-related needs among their patients, but were unable to find feasible solutions to these issues. Conclusions We therefore propose that interventions are needed to support sexual health practitioners in addressing psychosocial health needs that extend beyond their scope of practice, thereby reducing ‘syndemic moral distress’.

Linear scaling is used to convert raw computed tomography (CT) pixel values into Hounsfield units corresponding to different tissue values. Analysis of a benchmarking study, presented here, where the same CT scan was imported into and then exported from multiple radiotherapy treatment planning systems, found inconsistencies in HU scaling parameter values exported along with the images, particularly when images were exported using the Radiation Therapy Oncology Group format. Several methods of estimating conversion parameters, based on estimating pixel values corresponding to air and water within the image, for pelvic CT images from a large multi-centre trial were compared against original Digital Imaging and Communications in Medicine export parameters. In general using the mean of a sample region at the centroid of the bladder to estimate the value of water was more accurate than using the minimum or maximum or a single value at the centroid. Accuracy of methods of air estimation tested were dependent in part on features of the CT scanners and treatment planning systems, making it difficult to pick one method as superior that was independent of scanner and treatment planning system type. Based on the above analysis, methods for estimating air and water were selected for use in performing linear scaling of a set of pelvic CT images prior to their use in an interpatient image registration application. The selected methods were validated against a more recent and homogeneous dataset. Estimation error was found to be much lower within the validation set.