title: MRI measurements of intracranial pressure in the upright posture: The effect of the hydrostatic pressure gradient.
abstract: OBJECTIVE
  To add the hydrostatic component of the cerebrospinal fluid (CSF) pressure to magnetic resonance imaging (MRI)-derived intracranial pressure (ICP) measurements in the upright posture for derivation of pressure value in a central cranial location often used in invasive ICP measurements.
  
  
  METHODS
  Additional analyses were performed using data previously collected from 10 healthy subjects scanned in supine and sitting positions with a 0.5T vertical gap MRI scanner (GE Medical). Pulsatile blood and CSF flows to and from the brain were quantified using cine phase-contrast. Intracranial compliance and pressure were calculated using a previously described method. The vertical distance between the location of the CSF flow measurement and a central cranial location was measured manually in the mid-sagittal T1 -weighted image obtained in the upright posture. The hydrostatic pressure gradient of a CSF column with similar height was then added to the MR-ICP value.
  
  
  RESULTS
  After adjustment for the hydrostatic component, the mean ICP value was reduced by 7.6 mmHg. Mean ICP referenced to the central cranial level was -3.4 ± 1.7 mmHg compared to the unadjusted value of +4.3 ± 1.8 mmHg.
  
  
  CONCLUSIONS
  In the upright posture, the hydrostatic pressure component needs to be added to the MRI-derived ICP values for compatibility with invasive ICP at a central cranial location.
authors.affiliation: Department of Radiology, University of Miami, Miami, Florida, USA.
authors.forename: Noam
authors.initials: N
authors.lastname: Alperin
authors.affiliation: Department of Radiology, University of Miami, Miami, Florida, USA.
authors.forename: Sang H
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Radiology, University of Miami, Miami, Florida, USA.
authors.forename: Ahmet M
authors.initials: AM
authors.lastname: Bagci
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology*; D005260:Female; D006801:Humans; D006874:Hydrostatic Pressure; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007427:Intracranial Pressure / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011187:Posture / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: CSF flow; hydrostatic pressure gradient; intracranial pressure; phase contrast; upright posture