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Purpose: To characterize the 3D imaging performance and radiation dose for a prototype slot‐beam configuration on an intraoperative O‐arm™ Surgical Imaging System (Medtronic Inc., Littleton, MA) and identify potential improvements in soft‐tissue image quality for surgical interventions. Methods: A slot collimator was integrated with the O‐arm™ system for slot‐beam axial CT. The collimator can be automatically actuated to provide 1.2° slot‐beam longitudinal collimation. Cone‐beam and slot‐beam configurations were investigated with and without an antiscatter grid (12:1 grid ratio, 60 lines/cm). Dose, scatter, image noise, and soft‐tissue contrast resolution were evaluated in quantitative phantoms for head and body configurations over a range of exposure levels (beam energy and mAs), with reconstruction performed via filtered‐backprojection. Qualitative imaging performance across various anatomical sites and imaging tasks was assessed with anthropomorphic head, abdomen, and pelvis phantoms. Results: The dose for a slot‐beam scan varied from 0.02–0.06 mGy/mAs for head protocols to 0.01–0.03 mGy/mAs for body protocols, yielding dose reduction by ∼1/5 to 1/3 compared to cone‐beam, owing to beam collimation and reduced x‐ray scatter. The slot‐beam provided an ∼6–7× reduction in scatter‐to‐primary ratio (SPR) compared to the cone‐beam, yielding SPR ∼20–80% for head and body without the grid and ∼7–30% with the grid. Compared to cone‐beam scans at equivalent dose, slot‐beam images exhibited an ∼2.5× increase in soft‐tissue contrast‐to‐noise ratio (CNR) for both grid and gridless configurations. For slot‐beam scans, a further ∼10–30% improvement in CNR was achieved when the grid was removed. Slot‐beam imaging could benefit certain interventional scenarios in which improved visualization of soft tissues is required within a fairly narrow longitudinal region of interest (±7 mm in z)––for example, checking the completeness of tumor resection, preservation of adjacent anatomy, or detection of complications (e.g., hemorrhage). While preserving existing capabilities for fluoroscopy and cone‐beam CT, slot‐beam scanning could enhance the utility of intraoperative imaging and provide a useful mode for safety and validation checks in image‐guided surgery. Conclusions: The 3D imaging performance and dose of a prototype slot‐beam CT configuration on the O‐arm™ system was investigated. Substantial improvements in soft‐tissue image quality and reduction in radiation dose are evident with the slot‐beam configuration due to reduced x‐ray scatter. [ABSTRACT FROM AUTHOR]

Purpose: Intraoperative imaging plays an increased role in support of surgical guidance and quality assurance for interventional approaches. However, image quality sufficient to detect complications and provide quantitative assessment of the surgical product is often confounded by image noise and artifacts. In this work, we translated a three‐dimensional model‐based image reconstruction (referred to as "Known‐Component Reconstruction," KC‐Recon) for the first time to clinical studies with the aim of resolving both limitations. Methods: KC‐Recon builds upon a penalized weighted least‐squares (PWLS) method by incorporating models of surgical instrumentation ("known components") within a joint image registration–reconstruction process to improve image quality. Under IRB approval, a clinical pilot study was conducted with 17 spine surgery patients imaged under informed consent using the O‐arm cone‐beam CT system (Medtronic, Littleton MA) before and after spinal instrumentation. Volumetric images were generated for each patient using KC‐Recon in comparison to conventional filtered backprojection (FBP). Imaging performance prior to instrumentation ("preinstrumentation") was evaluated in terms of soft‐tissue contrast‐to‐noise ratio (CNR) and spatial resolution. The quality of images obtained after the instrumentation ("postinstrumentation") was assessed by quantifying the magnitude of metal artifacts (blooming and streaks) arising from pedicle screws. The potential low‐dose advantages of the algorithm were tested by simulating low‐dose data (down to one‐tenth of the dose of standard protocols) from images acquired at normal dose. Results: Preinstrumentation images (at normal clinical dose and matched resolution) exhibited an average 24.0% increase in soft‐tissue CNR with KC‐Recon compared to FBP (N = 16, P = 0.02), improving visualization of paraspinal muscles, major vessels, and other soft‐tissues about the spine and abdomen. For a total of 72 screws in postinstrumentation images, KC‐Recon yielded a significant reduction in metal artifacts: 66.3% reduction in overestimation of screw shaft width due to blooming (P < 0.0001) and reduction in streaks at the screw tip (65.8% increase in attenuation accuracy, P < 0.0001), enabling clearer depiction of the screw within the pedicle and vertebral body for an assessment of breach. Depending on the imaging task, dose reduction up to an order of magnitude appeared feasible while maintaining soft‐tissue visibility and metal artifact reduction. Conclusions: KC‐Recon offers a promising means to improve visualization in the presence of surgical instrumentation and reduce patient dose in image‐guided procedures. The improved soft‐tissue visibility could facilitate the use of cone‐beam CT to soft‐tissue surgeries, and the ability to precisely quantify and visualize instrument placement could provide a valuable check against complications in the operating room (cf., postoperative CT). [ABSTRACT FROM AUTHOR]

Transplantation of adipose-derived mesenchymal stem cells (ADSCs) has become a promising approach for bone regeneration therapies, particularly in elderly patients. However, poor cell survival in vivo after implantation due to the ischemic tissue environment has been one of the major limitations of the effectiveness of this strategy. Hypoxia Inducible Factor-1α (HIF-1α) plays an important role in angiogenic-osteogenic coupling during bone regeneration, as it is a critical mediator of the adaptive cell response to hypoxia. DMOG treatment has been demonstrated to stabilize cellular expression of HIF-1α in cells, as well as enhance osteogenic and angiogenic capacity of MSCs. By therapeutically targeting both osteogenesis and vascularization via DMOG preconditioned MSCs, this tissue-engineering approach sought to yield superior bone quality and integration, thereby increasing rates of spinal fusion. We aimed to demonstrate that preconditioning adipose (ADSC)-derived (AD) MSCs with DMOG prior to implantation will prolong survival in vivo and improve spinal fusion outcomes in a rat model. In vivo study via a rat posterolateral spinal fusion model. Syngeneic 6-8 week old Lewis rats. Manual palpation scoring was performed by blinded researchers as follows: 0 = non-fused; 1 = partial fusion, some motion across operative joint; and, 2 = fused, no motion across the operated joint. MicroCT images were used to assess fusion mass volume (mm^3) via ImageJ software and determine CT fusion score (0 = non-fused; 1 = unilateral fusion; 2 = bilateral fusion). ADSCs were isolated from the inguinal fat pads of syngeneic 6-8 week old Lewis rats and cultured in vitro. When passage 1 (P1) ADSCs reached approximately 80% confluency they were pre-conditioned for 24 hours with 1 ng of DMOG (Fisher Scientific). After pre-conditioning, 2 × 10^6 ADSCs were seeded onto Vitoss (Stryker) bone graft substitute scaffolds for subsequent transplantation. Posterolateral spinal fusion surgery at L4-L5 was performed on 18 female Lewis rats divided into 2 experimental groups: [1] Vitoss+ADSCs pre-conditioned with DMOG; and, [2] Vitoss+non pre-conditioned ADSCs. Fusion was evaluated eight weeks post-surgery. Manual palpation scoring evaluated the motion across the operated joint, and MicroCT images were assessed for fusion mass volume and CT fusion. Preliminary microCT imaging data suggest that DMOG pre-conditioned ADSCs (n=12) yielded significantly higher fusion mass volumes than non-preconditioned ADSCs (n=6) (23.49 mm^3 vs. 15.39 mm^3, respectively, p=.001). DMOG pre-conditioned ADSCs showed a trend towards higher rates of fusion and manual palpation scores compared to non-conditioned ADSCs (1.16 vs. 0.50, respectively, p=.06; and 1.25 vs. 0.66, respectively, p>.05). In our rat posterolateral fusion model, DMOG pre-conditioned ADSCs displayed an increased fusion mass volume, CT fusion rates, and manual palpation score compared to non-conditioned ADSCs. Ongoing histological studies will evaluate whether there are any differences in the quality of bone formed within the fusion masses. Future studies will also compare whether these results are also similar in bone marrow-derived MSCs. Dimethyloxaloylglycine (Investigational/Not approved) [ABSTRACT FROM AUTHOR]