Purpose Fluoroscopic systems in modern interventional suites have the ability to perform flat panel detector CT (FDCT) and navigational guidance. FDCT data acquired in the interventional suite can be fused with MR data in order to allow navigational guidance towards targets defined on MR. This system could be used for intracranial access or spinal procedure guidance in the interventional suite. We aim to evaluate the accuracy of this system and to report the radiation doses associated with single pass needle placement in a deep brain stimulator (DBS) phantom.

Materials and methods An established head phantom with deep brain stimulator lead targets was imaged with an iso-volumetric T2 weighted inversion recovery sequence. The head phantom was placed into a Mayfield Integra headrest system and attached to the procedure table. An 8s FDCT was performed (Siemens, DynaCT) and the CT and MR data sets were automatically fused using the integrated guidance system (iGuide, Siemens). A DBS target was selected on the MR data set. An entry site was selected on the CT data set to visualize the pre-drilled burr hole. The flat panel detector was automatically moved to the correct in-line or “bull’s-eye” projection. The table was manually shimmed to line up the projected targets and entry site. A 10 cm, 19G needle was advanced by hand in a single pass using laser crosshair guidance. Radial error was visually assessed against measurement markers on the target. A second FDCT was performed and the radial error was measured from the center of the planned target to the needle. Air kerma and dose area product (DAP) were recorded. 10 needles were placed using CT-MR fusion and 10 needles were placed without MR fusion, skipping all MR steps and targeting based off of the FDCT.

Results Mean target depth was 83.12 mm (SD 20.59). For MR fusion mean visual radial error to the absolute center of the target was 2.55 mm (SD 1.04 mm), mean visual radial error to the 3 mm diameter spherical target was 1.10 mm (SD 0.97 mm), and mean radial error by CT as measured to the planned target point was 2.60 mm (SD 1.05 mm). With CT only targeting, corresponding radial errors were 2.95 mm (1.67 mm), 1.65 mm  (1.37 mm), and 3.00 mm (1.68 mm). Mean total air kerma was 122.19 mGy and mean total DAP was 3272 uGy-m2. The operator was only in the room for a mean flouro time of 0.16 min with an air kerma of 1.21 and DAP of 17.28. CT1 had a mean air kerma of 60.39 and DAP of 1624.88 and CT2 had a mean air kerma of 60.58 and DAP 1629.84. In practice CT2 could possibly be omitted.

Conclusions Navigational guidance for single pass needle placement in the interventional suite using FDCT with or without fusion to pre-procedural MRI is associated with a radial error of approximately 2.5–3.0 mm at a depth of approximately 80 mm and acceptable radiation to the patient and operator. This system could be used to accurately target sub centimeter intracranial lesions or provide guidance for spinal procedures.

Disclosures M. Mabray: None. S. Datta: 5; C; Siemens. P. Lillaney: None. T. Moore: 5; C; Siemens. S. Gehrisch: 5; C; Siemens. J. Talbott: None. P. Larson: None. D. Cooke: None.