Measurements acquired through the smartphone application. A: Coronal MRI section with moderate enlarged ventricles with virtual placement of the guide on the skull surface. Angulation of catheter trajectory (red dotted line) is measured at 10° deviation from 90° (light blue dotted line) tilting the guiding tube towards the midline. The catheter length (green dotted line) is measured at 67 mm. B: Coronal CT reconstruction along body axis with the measurements revealing an angulation of 5.2° deviation from rectangular with the guiding tube tilt towards the midline and a catheter length of 69 mm.