RecruitingDevice studyHemorrhage Elimination During Lumbar Puncture Using Ultrasound Measurements (HELPUS)This is a clinical trial to determine the extent to which ultrasound-assisted lumbar puncture using a standardized procedure, including use of ultrasound to ascertain the presence of cerebrospinal fluid (CSF) at L3 - L5 and the optimal needle insertion distance, increases the acquisition rate of CSF that is interpretable for patient management.