Tomosynthesis and cone-beam CT on a mobile C-arm for image-guided interventions

Purpose: A prototype mobile C‐arm capable of real‐time fluoroscopy, tomosynthesis, and cone‐beam CT (CBCT) has been developed for intraoperative guidance of minimally invasive procedures. This work investigates the imaging performance, radiation dose, and image acquisition / reconstruction time associated with a range of 3D imaging techniques. In addition, protocols for intraoperative use are developed for implementation in clinical research trials. Method and Materials: Imaging performance was assessed in terms of spatial resolution as well as soft‐tissue and bony detail visualization in phantoms and cadavers. Image reconstruction via 3D filtered backprojection was performed across a range of tomosynthesis angle (10°–178°) and number of projections (5–200). The corresponding radiation dose was evaluated analytically and experimentally (using a Farmer chamber in cylindrical head and body phantoms) to quantify peripheral, central, and organ dose (e.g., dose to the eyes). Acquisition / reconstruction times were benchmarked in relation to operational time constraints. Results: CBCT images exhibited sub‐mm spatial resolution and soft‐tissue visibility (∼20 HU) sufficient for interventional guidance at a central dose of 10 mGy. Tomosynthesis offered a useful, high‐speed adjuvant to CBCT, providing visualization of high‐contrast features at a fairly limited arc — e.g., visualization of the clivus (skull base) achieved at angles down to ∼30° (central dose ∼1.6 mGy). Reconstruction times were ∼62 sec (full CBCT volume, 0.8 mm voxels) and ∼20 sec (tomosynthesis “slab,” 0.4 mm voxels), respectively.Conclusion:C‐arm tomosynthesis and CBCT provide a valuable addition to the image guidance arsenal. The former offers fast, low‐dose 3D images sufficient for guidance with respect to high‐contrast bony features. The latter offers sub‐mm spatial resolution and soft‐tissue visibility at the cost of time and dose. Deployment of the C‐arm prototype in clinical research trials promises increased surgical precision, with protocols for intraoperative imaging consistent with operational time and dose constraints. © 2007, American Association of Physicists in Medicine. All rights reserved.