Alexander Squires

Advances in Haptics, Tactile Sensing, and Manipulation for Robot-Assisted Minimally Invasive Surgery, Noninvasive Surgery, and Diagnosis

The developments of medical practices and medical technologies have always progressed concurrently. The relatively recent developments in endoscopic technologies have allowed the realization of the “minimally invasive” form of surgeries. The advancements in robotics facilitate precise surgeries that are often integrated with medical image guidance capability. This in turn has driven the further development of technology to compensate for the unique complexities engendered by this new format and to improve the performance and broaden the scope of the procedures that can be performed. Medical robotics has been a central component of this development due to the highly suitable characteristics that a robotic system can purport, including highly optimizable mechanical conformation and the ability to program assistive functions in medical robots for surgeons to perform safe and accurate minimally invasive surgeries. In addition, combining the robot-assisted interventions with touch-sensing and medical imaging technologies can greatly improve the available information and thus help to ensure that minimally invasive surgeries continue to gain popularity and stay at the focus of modern medical technology development. This paper presents a state-of-the-art review of robotic systems for minimally invasive and noninvasive surgeries, precise surgeries, diagnoses, and their corresponding technologies.

Magic Angle–Enhanced MRI of Fibrous Microstructures in Sclera and Cornea With and Without Intraocular Pressure Loading

PURPOSE The structure and biomechanics of the sclera and cornea are central to several eye diseases such as glaucoma and myopia. However, their roles remain unclear, partly because of limited noninvasive techniques to assess their fibrous microstructures globally, longitudinally, and quantitatively. We hypothesized that magic angle-enhanced magnetic resonance imaging (MRI) can reveal the structural details of the corneoscleral shell and their changes upon intraocular pressure (IOP) elevation. METHODS Seven ovine eyes were extracted and fixed at IOP = 50 mm Hg to mimic ocular hypertension, and another 11 eyes were unpressurized. The sclera and cornea were scanned at different angular orientations relative to the main magnetic field inside a 9.4-Tesla MRI scanner. Relative MRI signal intensities and intrinsic transverse relaxation times (T2 and T2*) were determined to quantify the magic angle effect on the corneoscleral shells. Three loaded and eight unloaded tendon samples were scanned as controls. RESULTS At magic angle, high-resolution MRI revealed distinct scleral and corneal lamellar fibers, and light/dark bands indicative of collagen fiber crimps in the sclera and tendon. Magic angle enhancement effect was the strongest in tendon and the least strong in cornea. Loaded sclera, cornea, and tendon possessed significantly higher T2 and T2* than unloaded tissues at magic angle. CONCLUSIONS Magic angle-enhanced MRI can detect ocular fibrous microstructures without contrast agents or coatings and can reveal their MR tissue property changes with IOP loading. This technique may open up new avenues for assessment of the biomechanical and biochemical properties of ocular tissues in aging and in diseases involving the corneoscleral shell.

Robotic System for MRI-Guided Focal Laser Ablation in the Prostate

MRI-conditional robotic platforms have proved to be an effective approach for image-guided interventions. In this study, a computer-assisted, pneumatically actuated robot is designed, built, and tested for MRI-guided prostate cancer focal laser ablation (FLA). The robotic manipulator provides two active planar degrees of freedom (DoFs) by using a customized CoreXY frame and one passive rotational DoF. A remote insertion mechanism improves the surgical workflow by keeping the patients inside the scanner during needle insertion. The robotic manipulator is tested in a 3T MR scanner to evaluate its MR compliance, and the results demonstrated that the signal-to-noise ratio (SNR) variation is less than 8%. The in-scanner template positioning accuracy test demonstrates that the manipulator achieves high targeting accuracy with a mean error of 0.46 mm and a standard deviation of 0.25 mm. Phantom studies have shown that the needle insertion accuracy of the manipulator is within 2 mm (mean = 1.7 mm, standard deviation = 0.2 mm).

A Simple and Inexpensive Stereotactic Guidance Frame for MRI-Guided Brain Biopsy in Canines

A magnetic resonance imaging (MRI) guided stereotactic system was developed to provide veterinarians a method to accomplish minimally invasive stereotactic brain biopsies and procedures involving the cerebrum in canines. While MR-guided procedures are prevalent for humans, they are less common in animal practices. The system was designed to minimize fabrication costs in an effort to make such procedures more accessible in the veterinary field. A frame constrained the head without the need for punctures and supported registration and guidance attachments. Location data for registration and relevant structures were selected by the clinician, and a reverse kinematic analysis program generated the settings of the stereotactic arch to guide a needle to the desired location. Phantom experiments and three cadaver trials showed an average targeting error of <3 mm using the system.

Robot for MRI-Guided ALS Spinal Therapy

Limited treatment options are available for treating Amyotrophic Lateral Sclerosis (ALS) (1). Small animal models have shown promise in halting neurodegeneration associated with ALS where cellular therapeutics are delivered to the ventral horn of the spinal cord (2), although this procedure is invasive and requires multi-level laminectomy and dissection of the dura mater (Fig. 1). We hypothesized that SpinoBof, a robotic needle guidance platform (Fig. 2) could deliver cellular therapeutics to the ventral horn percutaneously under MRI guidance, enhancing upon existing invasive and time-consuming techniques for targeting injection sites.Copyright

SpinoTemplate: A Platform for MRI-Guided Spinal Cord Injections

Patients with amyotrophic lateral sclerosis have limited treatment options and a 20% survival rate within five years of diagnosis. Small animal models show promise for halting the associated neurodegeneration when cellular therapeutics are delivered to the ventral horn of the spinal cord. A template-based guidance system was developed to facilitate percutaneous injections under MRI guidance to improve upon existing invasive and time-consuming surgical techniques. Procedure duration was 30min plus 5min per insertion, with a mean error of <2mm.