MR-intracranial pressure (ICP): A method to measure intracranial elastanceand pressure noninvasively by means of MR imaging: Baboon and human study

PURPOSE: To develop a noninvasive method for intracranial elastance and int racranial pressure (ICP) measurement. MATERIALS AND METHODS: Intracranial volume and pressure changes were calcul ated from magnetic resonance (MR) imaging measurements of cerebrospinal flu id (CSF) and blood flow. The volume change was calculated from the net tran scranial CSF and blood volumetric flow rates. The change in pressure was de rived from the change in the CSF pressure gradient calculated from CSF velo city. An elastance index was derived from the ratio of pressure to volume c hange. The reproducibility of the elastance index measurement was establish ed from four to five measurements in five healthy volunteers. The elastance index was measured and compared with invasive ICP measurements in five pat ients with an intraventricular catheter at MR imaging. False-positive and f alse-negative rates were established by using 25 measurements in eight heal thy volunteers and six in four patients with chronically elevated ICP. RESULTS: The mean of the fractional SD of the elastance index in humans was 19.6%. The elastance index in the five patients with intraventricular cath eters correlated well with the invasively measured ICP (R-2 = 0.965; P < .0 05). MR imaging-derived ICPs in the eight healthy volunteers were 4.2-12.4 mm Hg, all within normal range. Measurements in three of the four patients with chronically elevated ICP were 20.5-34.0 mm Hg, substantially higher th an the normal limit. CONCLUSION: MR imaging-derived elastance index correlates with ICP over a w ide range of ICP values. The sensitivity of the technique allows differenti ation between normal and elevated ICP.