Publications by authors named "Naren Nimmagadda"

6 Publications

  • Page 1 of 1

Patient-specific, touch-based registration during robotic, image-guided partial nephrectomy.

World J Urol 2021 Jun 16. Epub 2021 Jun 16.

Department of Urology, Vanderbilt Institute for Surgery and Engineering (VISE), Vanderbilt University Medical Center, Nashville, TN, USA.

Image-guidance during partial nephrectomy enables navigation within the operative field alongside a 3-dimensional roadmap of renal anatomy generated from patient-specific imaging. Once a process is performed by the human mind, the technology will allow standardization of the task for the benefit of all patients undergoing robot-assisted partial nephrectomy. Any surgeon will be able to visualize the kidney and key subsurface landmarks in real-time within a 3-dimensional simulation, with the goals of improving operative efficiency, decreasing surgical complications, and improving oncologic outcomes. For similar purposes, image-guidance has already been adopted as a standard of care in other surgical fields; we are now at the brink of this in urology. This review summarizes touch-based approaches to image-guidance during partial nephrectomy, as the technology begins to enter in vivo human evaluation. The processes of segmentation, localization, registration, and re-registration are all described with seamless integration into the da Vinci surgical system; this will facilitate clinical adoption sooner.
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http://dx.doi.org/10.1007/s00345-021-03745-yDOI Listing
June 2021

MOSES Technology for Holmium Laser Enucleation of the Prostate: A Prospective Double-Blind Randomized Controlled Trial.

J Urol 2021 Jul 22;206(1):104-108. Epub 2021 Feb 22.

Department of Urology, Vanderbilt University Medical Center, Nashville, Tennessee.

Purpose: Holmium laser enucleation of the prostate has proven to be efficacious and safe for the treatment of benign prostatic hyperplasia. New laser technologies, such as the MOSES™ pulse laser system, improve energy delivery and may improve operative times. We sought to prospectively evaluate holmium laser enucleation of the prostate using MOSES technology in a double-blind randomized controlled trial.

Materials And Methods: This is a single-center, prospective, double-blind, randomized controlled trial comparing holmium laser enucleation of the prostate using MOSES technology to holmium laser enucleation of the prostate. Patients were randomized in a 1:1 fashion. The study was powered to evaluate for a difference in operative time. Secondary end points included enucleation, morcellation, and hemostasis times, as well as blood loss, functional outcomes and complications 6 weeks postoperatively.

Results: A total of 60 patients were analyzed without difference in preoperative characteristics in either group (holmium laser enucleation of the prostate using MOSES technology: 30/60, 50%, holmium laser enucleation of the prostate: 30/60, 50%). Shorter total operative time was seen in the holmium laser enucleation of the prostate using MOSES technology group compared to the holmium laser enucleation of the prostate group (mean: 101 vs. 126 minutes, p <0.01). This difference remained significant on multiple linear regression. Additionally, the holmium laser enucleation of the prostate using MOSES technology group had shorter enucleation times (mean: 68 vs. 80 minutes, p=0.03), hemostasis time (mean: 18 vs. 29 minutes, p <0.01), and less blood loss (mean: -6.3 vs. -9.0%, p=0.03), measured by a smaller change in hematocrit postoperatively, compared to the traditional holmium laser enucleation of the prostate. There was no difference in functional or safety outcomes at followup.

Conclusions: We report the results of a prospective, double-blind, randomized controlled trial comparing holmium laser enucleation of the prostate using MOSES technology to traditional holmium laser enucleation of the prostate. MOSES technology resulted in an improvement in operative time and a reduction in blood loss with comparable functional outcomes and complications compared to traditional holmium laser enucleation of the prostate.
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http://dx.doi.org/10.1097/JU.0000000000001693DOI Listing
July 2021

Transurethral Anastomosis after Transurethral Radical Prostatectomy: A Phantom Study on Intraluminal Suturing With Concentric Tube Robots.

IEEE Trans Med Robot Bionics 2020 Nov 29;2(4):578-581. Epub 2020 Oct 29.

Department of Mechanical Engineering, Vanderbilt University.

Current surgical approaches to radical prostatectomy are associated with high rates of erectile dysfunction and incontinence. These complications occur secondary to the disruption of surrounding healthy tissue, which is required to expose the prostate. The urethra offers the least invasive access to the prostate, and feasibility has been demonstrated of enucleating the prostate with an endoscope using Holmium laser, which can itself be aimed by concentric tube robots. However, the transurethral approach to radical prostatectomy has thus far been limited by the lack of a suitable means to perform an anastomosis of the urethra to the bladder after prostate removal. Only a few intraluminal anastomotic devices currently exist, and none are small enough to pass through the urethra. In this paper we describe a new way to perform an anastomosis in the small luminal space of the urethra, harnessing the dexterity and customizability of concentric tube manipulators. We demonstrate a successful initial proof-of-concept anastomosis in an anthropomorphic phantom of the urethra and bladder.
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http://dx.doi.org/10.1109/tmrb.2020.3034735DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694552PMC
November 2020

Accuracy of Touch-Based Registration During Robotic Image-Guided Partial Nephrectomy Before and After Tumor Resection in Validated Phantoms.

J Endourol 2021 03 11;35(3):362-368. Epub 2020 Nov 11.

Department of Urology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.

Image-guided surgery (IGS) allows for accurate, real-time localization of subsurface critical structures during surgery. No prior IGS systems have described a feasible method of intraoperative reregistration after manipulation of the kidney during robotic partial nephrectomy (PN). We present a method for seamless reregistration during IGS and evaluate accuracy before and after tumor resection in two validated kidney phantoms. We performed robotic PN on two validated kidney phantoms-one with an endophytic tumor and one with an exophytic tumor-with our IGS system utilizing the da Vinci Xi robot. Intraoperatively, the kidney phantoms' surfaces were digitized with the da Vinci robotic manipulator via a touch-based method and registered to a three-dimensional segmented model created from cross-sectional CT imaging of the phantoms. Fiducial points were marked with a surgical marking pen and identified after the initial registration using the robotic manipulator. Segmented images were displayed via picture-in-picture in the surgeon console as tumor resection was performed. After resection, reregistration was performed by reidentifying the fiducial points. The accuracy of the initial registration and reregistration was compared. The root mean square (RMS) averages of target registration error (TRE) were 2.53 and 4.88 mm for the endophytic and exophytic phantoms, respectively. IGS enabled resection along preplanned contours. Specifically, the RMS averages of the normal TRE over the entire resection surface were 0.75 and 2.15 mm for the endophytic and exophytic phantoms, respectively. Both tumors were resected with grossly negative margins. Point-based reregistration enabled instantaneous reregistration with minimal impact on RMS TRE compared with the initial registration (from 1.34 to 1.70 mm preresection and from 1.60 to 2.10 mm postresection). We present a novel and accurate registration and reregistration framework for use during IGS for PN with the da Vinci Xi surgical system. The technology is easily integrated into the surgical workflow and does not require additional hardware.
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http://dx.doi.org/10.1089/end.2020.0363DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7987368PMC
March 2021

Comparing the accuracy of the da Vinci Xi and da Vinci Si for image guidance and automation.

Int J Med Robot 2020 Dec 1;16(6):1-10. Epub 2020 Sep 1.

Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, USA.

Background: Current laparoscopic surgical robots are teleoperated, which requires high fidelity differential motions but does not require absolute accuracy. Emerging applications, including image guidance and automation, require absolute accuracy. The absolute accuracy of the da Vinci Xi robot has not yet been characterized or compared to the Si system, which is now being phased out. This study compares the accuracy of the two.

Methods: We measure robot tip positions and encoder values assessing accuracy with and without robot calibration.

Results: The Si is accurate if the setup joints are not moved but loses accuracy otherwise. The Xi is always accurate.

Conclusion: The Xi can achieve submillimetric average error. Calibration improves accuracy, but excellent baseline accuracy of the Xi means that calibration may not be needed for some applications. Importantly, the external tracking systems needed to account for setup joint error in the Si are no longer required with the Xi.
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http://dx.doi.org/10.1002/rcs.2149DOI Listing
December 2020

Capacitive coupling reduces instrumentation-related infection in rabbit spines: a pilot study.

Clin Orthop Relat Res 2012 Jun;470(6):1646-51

Department of Orthopaedics, University of Maryland, 22 S Greene Street, S11B, Baltimore, MD 21201, USA.

Background: Postoperative spine infections cause considerable morbidity. Patients are subjected to long-term antibiotic regimens and may require further surgery. Delivery of electric current through instrumentation can detach biofilm, allowing better antibiotic penetration and assisting in eradicating infection.

Question/purposes: We asked (1) whether capacitive coupling treatment in combination with a single dose of antibiotics would reduce infection rates when compared with antibiotics alone in a rabbit spine infection model, (2) whether it would decrease the overall bacterial burden, and (3) whether there was a time-dependent response based on days treated with capacitive coupling.

Methods: Thirty rabbits were subjected to a well-established spine infection model with a single dose of intravenously administered systemic ceftriaxone (20 mg/kg of body weight) prophylaxis. Two noncontiguous rods were implanted inside dead space defects at L3 and L6 challenged with 10(6) colony-forming units of Staphylococcus aureus. Rabbits were randomly treated with a capacitive coupling or control device. Instrumentation and soft tissue bacterial growth were assessed after 7 days.

Results: Sites treated with capacitive coupling showed a decrease in the incidence of positive culture: 36% versus 81% in the control group. We observed no difference in the soft tissue's infectious burden. Overall bacterial load was not decreased with capacitive coupling.

Conclusions: Capacitive coupling in conjunction with antibiotics reduced the instrumentation-related infection rate compared with antibiotics alone.

Clinical Relevance: Capacitive coupling noninvasively delivers an alternating current that may detach biofilm from instrumentation. Treatment of infection may be successful without removal of instrumentation, allowing for improved stability and overall decreased morbidity.
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http://dx.doi.org/10.1007/s11999-011-2231-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3348327PMC
June 2012
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