New Stereotactic Frame System for Neurosurgery

Aims:

This study will evaluate a new stereotactic device (D1 stereotactic system) designed to address shortcomings of current stereotactic systems by using a novel surface-mounted stereotactic system that is comparatively small, lightweight, user-friendly, and comparable in precision and accuracy to current clinical systems.

Methods:

Subjects will be recruited exclusively from adult subjects with a neurological disease. These subjects will be identified preoperatively from DBS clinical subjects. Each subject will undergo an evaluation by the Mayo Clinic Deep Brain Stimulation Committee (comprised of neurologists, neuropsychologists, psychiatrists, neurosurgeons, and radiologists) to receive a DBS surgery at Mayo Clinic - Rochester for the treatment of a neurological disease. All subjects will be pre-screened against the standard Mayo Clinic inclusion/exclusion criteria for DBS surgery through face-to-face interviews. Once a subject has been identified, the Study Coordinator will contact the subject for interest in participation in the study.

Step-by-Step Schedule:

Skull Anchor Key Attachment Location: St. Mary Hospital - Subject Preparation Room

1. Superior portion of the head, the hair is clipped off in the area where Skull Anchor Key would be placed. The clipped area and surrounding region is prepped in usual sterile fashion. This begins subject participation in the protocol.
2. The MR Localizer Box is placed upside down and the Skull Anchor Key is placed within its slot in the MR Localizer Box and screwed in using MR compatible screws.
3. The apparatus is positioned on the subject head and allowed to rest such that the Skull Anchor Key is midline and the ear bars lie parallel to the external auditory meatus taking caution to prevent the bottom surface of the Skull Anchor Key or the safety caps from becoming non sterile.
4. The Z value of the ear bars is adjusted such that the ear probes are at same horizontal level as the external auditory meatus. The ear bars are gently pushed into the external auditory meatus on both sides such that it is snug but comfortable to the subject. (NOTE: If required, the Y position of the ear bars may be readjusted at this step in situations such as the anterior N fiducial bars hitting the forehead of the subject).
5. After confirming accurate initial placement of the MR Localizer Box, the sites of skull screw and pins placement are marked using a surgical pen with the guide Skull Anchor Key which has holes instead of screws and pins acting as reference guide. The MR Localizer Box is then removed and each of the pen marked site receives an injection of local anesthetic.
6. Following local anesthetic application, the ear bars are removed from the ear while an assistant supports the MR Localizer Box. The MR Localizer Box is gradually lowered to allow the pins to penetrate scalp until it rests on the bone. At this point, titanium self-tapping screws are gently screwed in through the hole on each of the 2 angled legs of the Skull Anchor Key until the Skull Anchor Key is level and secure.
7. The subject is then transferred to the MR/CT Imaging Facility for target planning.

MRI Acquisition and Target Planning Location: St. Mary Hospital - Neuroradiology Facility

1. Once in MR suite, the subject rests their head in a custom made MR headrest which sits within the lower portion of RF coil. The headrest holds the axis of MR Localizer Box parallel to the axis of MR gantry and allows the frame to be held securely during the MR imaging.
2. The subject is positioned in a MR scanner in a supine position.
3. An anatomical image volume is acquired. The field of view region is adjusted to ensure the MR Localizer Box fiducials are visible in the MR images and then all images are acquired.
4. The images are then transferred to the surgical planning computer.
5. Following image acquisition, the images are reviewed by the surgical team to judge whether they are suitable for surgical planning. (If found unsuitable, the imaging and review is repeated.) Once satisfactory images are obtained, the subject is moved to the subject preparation room where the MR Localizer Box is detached from the KEY.
6. A DBS surgical plan, comprised of the electrode stereotactic target coordinates and an optimal trajectory is created by the navigational software. The plan is documented and shared with the surgical team.
7. The subject is then transferred to the operating room for DBS electrode implantation.

DBS Electrode Implantation Location: St. Mary Hospital - Operating Room

1. The subject is shifted to the operating room.
2. The D1 stereotactic device is attached to the Skull Anchor Key and the X, Y, Z, Arc and Collar angles will be adjusted based on MR planned coordinates.
3. Standard procedure is followed for making the incision and burr hole, putting in the DBS electrode, electrophysiologic target confirmation (as required) and securing the electrode in place.
4. A C-arm is then used to obtain a lateral view radiograph to confirm correct placement of the DBS electrode as assessed by the alignment of the tip of the DBS electrode with X-ray reticules on the stereotactic device.
5. Above steps are repeated for additional DBS electrode insertion.
6. After securing the last DBS electrode the stereotactic device is removed from the KEY. All DBS electrodes are then coiled and secured under the skin or are tunneled beneath the skin of the scalp and neck for battery placement as currently practiced. All surgical incisions are then sutured.
7. The CT Localizer Box is attached to the Skull Anchor Key to acquire a post-operative CT scan.
8. The subject is then transferred to the Neuroradiology Facility for post-operative CT imaging.

CT Confirmation and CT Localizer Box and KEY Removal Location: St. Mary Hospital - Neuroradiology Facility

1. With the subject in the CT imaging room the subject is positioned supine in the CT scanner to acquire a postoperative anatomical image volume to confirm the placement of the DBS electrode placement using planning software normally used for neurosurgical procedures.
2. Immediately following the CT scan, the subject is taken to the preparation room for removal of the CT Localizer Box, the Skull Anchor Key, and post-removal treatments. The self-tapping titanium screws are removed and the surgical site is treated appropriately.

Power Statement:

This is a pilot study with a unique subject cohort.

Data Analysis Plan:

The effectiveness of the D1 Stereotactic System in accurately implanting DBS electrodes in adults approved for DBS surgery at Mayo Clinic for treatment of a neurological disease will be evaluated by analyzing the following:

1. A 3D Euclidian distance error between the MR planned coordinate (XP, YP, ZP) and CT confirmed actual DBS coordinate (XA, YA, ZA) will be calculated. The 3D distance error comparable or lower to conventional system will be accounted as success criteria. Unpaired t-test will be used to determine whether the difference is significantly different or not.
2. A trajectory accuracy will be determined by comparing Collar Angle (CA) and Arc Angle (AA) between MR planned angles (CAP and AAP) and CT confirmed actual angles (CAA and AAA). The non-significant difference between MR planned and CT confirmed angles will be accounted as success criteria. Paired t-test will be used for 10 patient data.
3. Operating room time will be counted and compared to conventional procedure (using Leksell frame). The average operating room time will be compared between conventional procedure and D1 Stereotactic System procedure. Significantly lower operating room time will be accounted as success criteria.
4. Comfort level questionnaire will be given to each subject after DBS surgery and removal of the device to assess their overall experience with device and surgery.

Data Exclusion Criteria: If any surgical plan is changed in operating room (i.e., target coordinate, trajectory), the data will be excluded. However, the change of DBS electrode depth will be accounted as valid data.