Existing quantitative imaging biomarkers (QIBs) are associated with known biological tissue characteristics and follow a well-understood path of technical, biological and clinical validation before... Show moreExisting quantitative imaging biomarkers (QIBs) are associated with known biological tissue characteristics and follow a well-understood path of technical, biological and clinical validation before incorporation into clinical trials. In radiomics, novel data-driven processes extract numerous visually imperceptible statistical features from the imaging data with no a priori assumptions on their correlation with biological processes. The selection of relevant features (radiomic signature) and incorporation into clinical trials therefore requires additional considerations to ensure meaningful imaging endpoints. Also, the number of radiomic features tested means that power calculations would result in sample sizes impossible to achieve within clinical trials. This article examines how the process of standardising and validating data-driven imaging biomarkers differs from those based on biological associations. Radiomic signatures are best developed initially on datasets that represent diversity of acquisition protocols as well as diversity of disease and of normal findings, rather than within clinical trials with standardised and optimised protocols as this would risk the selection of radiomic features being linked to the imaging process rather than the pathology. Normalisation through discretisation and feature harmonisation are essential pre-processing steps. Biological correlation may be performed after the technical and clinical validity of a radiomic signature is established, but is not mandatory. Feature selection may be part of discovery within a radiomics-specific trial or represent exploratory endpoints within an established trial; a previously validated radiomic signature may even be used as a primary/secondary endpoint, particularly if associations are demonstrated with specific biological processes and pathways being targeted within clinical trials. Show less
De Rooij, N.K.; Claessen, M.H.G.; Van der Ham, I.J.M.; Post, M.W.M.; Visser-Meily, J.M.A. 2017
Post-stroke navigation complaints are frequent (about 30%) and intervention is possible, but there is no assessment instrument to identify patients with navigation complaints. We therefore studied... Show morePost-stroke navigation complaints are frequent (about 30%) and intervention is possible, but there is no assessment instrument to identify patients with navigation complaints. We therefore studied the clinical validity of the Wayfinding Questionnaire (WQ) in a cross-sectional study with 158 chronic stroke patients and 131 healthy controls. Patients with low (more navigation complaints) versus normal WQ scores were compared for demographics, stroke characteristics, emotional and cognitive complaints, and health-related quality of life (HRQoL). Actual navigation performance of 78 patients was assessed in a virtual reality setting. Effect sizes (d) were calculated. WQ responses (22 items) of stroke patients were compared with those of controls (discriminant validity). Results showed that patients with a low WQ score (n = 49, 32%) were more often women (p = 0.013) and less educated (p = 0.004), reported more cognitive complaints (d = 0.69), more emotional problems (d = 0.38 and 0.52), and lower HRQoL (d = 0.40 and 0.45) and, last but not least, performed worse on the navigation ability tasks (d = 0.23–0.80). Patients scored lower than controls on 21/22 WQ items, predominantly with small to medium effect sizes (d = 0.20–0.51). We conclude that the WQ is valid as a measure of navigation complaints in stroke patients, and thus strongly advocate its use in stroke care. Show less
Krogt, H. van der; Klomp, A.; Groot, J.H. de; Vlugt, E. de; Helm, F.C.T. van der; Meskers, C.G.M.; Arendzen, J.H. 2015
In the Antelope study availability, use and diagnostic accuracy of spiral CT in patients clinically suspected of PE was investigated. This study was divided in two separate phases, starting with a... Show moreIn the Antelope study availability, use and diagnostic accuracy of spiral CT in patients clinically suspected of PE was investigated. This study was divided in two separate phases, starting with a prospective evaluation of available diagnostic techniques part of the diagnostic consensus strategy in The Netherlands in a specifically designed algorithm. Phase I showed that in a direct comparison with the gold standard sensitivity and specificity of spiral CT is too low to endorse its role as a single test to exclude pulmonary embolism. Also spiral CT had a limited added value as a second procedure following ventilation-perfusion scintigraphy. The accuracy of CT was significantly better in cases with interobserver agreement and good image quality. The available data of phase I was used for a cost-effectiveness analysis. Combined with recent literature data two new strategies were proposed and studied independently. Phase II showed in a prospective clinical management study that spiral CT can be used safely as a first line test to rule out pulmonary embolism in clinically suspected patients. It is also possible to reliably determine an alternative diagnosis in 25% of all patients. A new questionnaire showed that since 1997 the use of spiral CT has increased considerably. Show less
