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Background: Neuroimaging-based biomarkers have the potential to improve etiological diagnosis of cognitive impairment in elderly inpatients. However, there is a relative lack of studies on neuroimaging-based biomarkers in hospitalized geriatric patients, as the vast majority of neuroimaging studies in dementia have focused on memory clinic outpatients. An important aspect of study planning is a priori estimation of the rate of screen failures., Objective: To report on the rate and causes of screen failures in a prospective study on the utility of neuroimaging (PET, MRI) for the etiological diagnosis of newly manifested cognitive impairment in acutely hospitalized geriatric patients., Methods: Ten acute care geriatrics clinics with 802 beds participated in the study. The potential recruitment rate had been estimated to 5 patients/100 beds/week., Results: Seventeen months of pre-screening resulted in 322 potential participants. 109 of these patients were enrolled, i.e., the screen failure rate was 66%. 58% of the screen failures were due to refusal of participation by the patient, most often due to lack of interest in clarifying the cause of the cognitive impairment or due to reluctance to engage in additional diagnostic procedures associated with physical stress. 42% of pre-screened patients were excluded because of violation of the eligibility criteria., Conclusion: Enrollment for neuroimaging studies presents considerable additional challenges in acutely hospitalized geriatric patients compared to outpatient settings. Low rate of approaching potential candidates by attending geriatricians and a high rate of screen failures have to be anticipated in the study design.