Axel Krieger

Virtual surgical planning, flow simulation, and 3-dimensional electrospinning of patient-specific grafts to optimize Fontan hemodynamics

Background: Despite advances in the Fontan procedure, there is an unmet clinical need for patient‐specific graft designs that are optimized for variations in patient anatomy. The objective of this study is to design and produce patient‐specific Fontan geometries, with the goal of improving hepatic flow distribution (HFD) and reducing power loss (Ploss), and manufacturing these designs by electrospinning. Methods: Cardiac magnetic resonance imaging data from patients who previously underwent a Fontan procedure (n = 2) was used to create 3‐dimensional models of their native Fontan geometry using standard image segmentation and geometry reconstruction software. For each patient, alternative designs were explored in silico, including tube‐shaped and bifurcated conduits, and their performance in terms of Ploss and HFD probed by computational fluid dynamic (CFD) simulations. The best‐performing options were then fabricated using electrospinning. Results: CFD simulations showed that the bifurcated conduit improved HFD between the left and right pulmonary arteries, whereas both types of conduits reduced Ploss. In vitro testing with a flow‐loop chamber supported the CFD results. The proposed designs were then successfully electrospun into tissue‐engineered vascular grafts. Conclusions: Our unique virtual cardiac surgery approach has the potential to improve the quality of surgery by manufacturing patient‐specific designs before surgery, that are also optimized with balanced HFD and minimal Ploss, based on refinement of commercially available options for image segmentation, computer‐aided design, and flow simulations.

Novel, 3D Display of Heart Models in the Postoperative Care Setting Improves CICU Caregiver Confidence

Background: Postoperative care delivered in the pediatric cardiac intensive care unit (CICU) relies on providers’ understanding of patients’ congenital heart defects (CHDs) and procedure performed. Novel, bedside use of virtual, three-dimensional (3D) heart models creates access to patients’ CHD to improve understanding. This study evaluates the impact of patient-specific virtual 3D heart models on CICU provider attitudes and care delivery. Methods: Virtual 3D heart models were created from standard preoperative cardiac imaging of ten patients with CHD undergoing repair and displayed on a bedside tablet in the CICU. Providers completed a Likert questionnaire evaluating the models’ value in understanding anatomy and improving care delivery. Responses were compared using two-tailed t test and Mann-Whitney U test and were also compared to previously collected CICU provider responses regarding use of printed 3D heart models. Results: Fifty-three clinicians (19 physicians, 34 nurses/trainees) participated; 49 (92%) of 53 and 44 (83%) of 53 reported at least moderate to high satisfaction with the virtual 3D heart’s ability to enhance understanding of anatomy and surgical repair, respectively. Seventy-one percent of participants felt strongly that virtual 3D models improved their ability to manage postoperative problems. The majority of both groups (63% physicians, 53% nurses) felt that virtual 3D heart models improved CICU handoffs. Virtual 3D heart models were as effective as printed models in improving understanding and care delivery, with a noted provider preference for printed 3D heart models. Conclusions: Virtual 3D heart models depicting patient-specific CHDs are perceived to improve understanding and postoperative care delivery in the CICU.

Development of a shoulder-mounted robot for MRI-guided needle placement: phantom study

AbstractPurposeThis paper presents new quantitative data on a signal-to-noise ratio (SNR) study, distortion study, and targeting accuracy phantom study for our patient-mounted robot (called Arthrobot). Arthrobot was developed as an MRI-guided needle placement device for diagnostic and interventional procedures such as arthrography.nMethodsWe present the robot design and inverse kinematics. Quantitative assessment results for SNR and distortion study are also reported. A respiratory motion study was conducted to evaluate the shoulder mounting method. A phantom study was conducted to investigate end-to-end targeting accuracy. Combined error considering targeting accuracy, respiratory motion, and structure deformation is also reported.ResultsThe SNR study showed that the SNR changes only 2% when the unpowered robot was placed on top of a standard water phantom. The distortion study showed that the maximum distortion from the ground truth was 2.57%. The average error associated with respiratory motion was 1.32xa0mm with standard deviation of 1.38xa0mm. Results of gel phantom targeting studies indicate average needle placement error of 1.64xa0mm, with a standard deviation of 0.90xa0mm.ConclusionsNoise and distortion of the MR images were not significant, and image quality in the presence of the robot was satisfactory for MRI-guided targeting. Combined average total error, adding mounting stability errors and structure deformation errors to targeting error, is estimated to be 3.4xa0mm with a standard deviation of 1.65xa0mm. In clinical practice, needle placement accuracy under 5xa0mm is considered sufficient for successful joint injection during shoulder arthrography. Therefore, for the intended clinical procedure, these results indicate that Arthrobot has sufficient positioning accuracy.

An endoscopic 3D structured illumination imaging system for robotic anastomosis surgery (Conference Presentation)

Surgical 3D endoscopy based on structured illumination has been built and evaluated for application in minimally invasive anastomosis surgery which offers advantages of smaller incision, low risk of infection, quick recovery times and reduced blood loss. When combined with robotic manipulations, surgeons can perform surgical tasks with higher precision and repeatability. For reconstructive surgery such as anastomosis, a supervised laparoscopic anastomosis using a surgical robot has recently been reported with an open-surgery approach using a large 3D camera. To push the technology into minimally-invasive setting, we report an endoscopic 3D system based on structured illumination technique to assist the surgical robot, particularly in anastomosis surgery. The recorded structural profile achieves a high depth quantification of 250 um for static objects, with 25 mm depth of field. The proposed system can be integrated into a flexible holding arm to move in accordance with the surgical robotic arm. We characterize the system performance using multiple porcine intestinal tissue samples with variations in surface textures, tissue pigmentation and thickness.

Development and Feasibility of a Robotic Laparoscopic Clipping Tool for Wound Closure and Anastomosis.

This paper reports the design, development, and initial evaluation of a robotic laparoscopic clipping tool for single manipulator wound closure and anastomosis (tubular reconnection). The tool deploys biodegradable clips and clasps with the goal of (i) integrating grasping and suturing into a single device for single hand or manipulator use, (ii) applying the equivalent of interrupted sutures without the need of managing suture thread, and (iii) allowing for full six degrees-of-freedom (DOFs) laparoscopic control when mounted on a robot arm. The specifications, workflow, and detailed design of the robotic laparoscopic tool and injection molded bio-absorbable T shaped clip and locking clasp are reported. The clipping tool integrates forceps to grab and stabilize tissue and a clip and clasp applier to approximate and fixate the tissue. A curved needle is advanced on a circular needle path and picks up and drags clips through tissue. The clip is then tightened through the tissue and a clasp is clamped around the clip, before the clip is released from the needle. Results of several bench test runs of the tool show: (a) repeatable circular needle drive, (b) successful pick-up and deployment of clips, (c) successful shear of the clip to release the clip from the needle, and (d) closure of clasp on clip with an average of 2.0 N holding force. These data indicate that the robotic laparoscopic clipping tool could be used for laparoscopic wound closure and anastomosis.