Biomedical subjects

Louis L Whitcomb

Publications and source records attributed to Louis L Whitcomb.

8 recordsLinked to original sources

PubMed2006

A preliminary analysis and model of prostate injection distributions.

PURPOSE: Understanding the internal dynamics of prostate injections, particularly injection pattern distribution is a key step to developing new therapies for prostate disease that may be best served with a direct injection approach. Due to excellent properties involving liquid contrast agents, MRI can be used for targeting and monitoring of injections into organs and tissues. MATERIALS AND METHODS: Eleven intraprostatic injections were performed in vivo with canines using a custom transrectal guiding and imaging system for use in a standard 1.5 T MR scanner. In addition, 25 injections were performed on excised cadaveric human prostates, using a MedRad Spectris injector system. MRI was used to guide the injections and monitor intraparenchymal injection distribution. RESULTS: T1 and T2-weighted MR images were correlated with histology to produce three-dimensional data sets that can be used to analyze trends in injection patterns. This analysis was used to develop strategies for injection prediction such as gadolinium pre-injections and diffusion-weighted imaging guidance. In addition, a rough model of prostate injections is described, and a preliminary injection guide is developed that takes into account the individual clinician's goals for therapy. CONCLUSIONS: MR visualization of injected therapeutic agents allows for prediction and monitoring of drug distributions, possibly improving efficacy and reducing side effects. Injection analysis and modeling may be used to assist in optimizing clinical treatments that require or would benefit from focal parenchymal injections into the prostate.

Animals↗

PubMed2006

Transrectal prostate biopsy and fiducial marker placement in a standard 1.5T magnetic resonance imaging scanner.

PURPOSE: We investigated the accuracy and feasibility of a system that provides transrectal needle access to the prostate concurrent with 1.5 Tesla MRI which previously has not been possible. MATERIALS AND METHODS: In 5 patients with previously diagnosed prostate cancer, MRI guided intraprostatic placement of gold fiducial markers (4 procedures) and/or prostate biopsy (3 procedures) was performed using local anesthesia. RESULTS: Mean procedure duration was 76 minutes and all patients tolerated the intervention well. Procedure related adverse events included self-limited hematuria and hematochezia following 3 of 8 procedures (all resolved in less than 1 week). Mean needle placement accuracy was 1.9 mm for the fiducial marker placement studies and 1.8 mm for the biopsy procedures. Mean fiducial marker placement accuracy was 4.8 mm and the mean fiducial marker placement accuracy transverse to the needle direction was 2.6 mm. All patients who underwent the procedure were able to complete their course of radiotherapy without delay or complication. CONCLUSIONS: While studies of clinical usefulness are warranted, transrectal 1.5 T MRI guided prostate biopsy and fiducial marker placement is feasible using this system, providing new opportunities for image guided diagnostic and therapeutic prostate interventions.

Biopsy, Needle↗

PubMed2005

Design of a novel MRI compatible manipulator for image guided prostate interventions.

This paper reports a novel remotely actuated manipulator for access to prostate tissue under magnetic resonance imaging guidance (APT-MRI) device, designed for use in a standard high-field MRI scanner. The device provides three-dimensional MRI guided needle placement with millimeter accuracy under physician control. Procedures enabled by this device include MRI guided needle biopsy, fiducial marker placements, and therapy delivery. Its compact size allows for use in both standard cylindrical and open configuration MRI scanners. Preliminary in vivo canine experiments and first clinical trials are reported.

Animals↗

PubMed2003

Task performance in stapedotomy: comparison between surgeons of different experience levels.

OBJECTIVES: Two steps in stapedotomy are particularly challenging: (1) micropick fenestration of the stapes footplate (SF) and (2) crimping of the stapes prosthesis (SP) to the incus. We conducted trials to determine if experience correlates with differences in performance for these tasks. METHODS: In a surgical model of stapedotomy, performance was measured for 3 experienced and 3 novice surgeons. For fenestration, we measured ability to target the fenestration and force applied to the SF. For crimping, we measured crimp quality, movement of the SP during crimping, and force applied to the SF. RESULTS: Experienced surgeons demonstrated significantly better ability to target the fenestration and, during crimping, caused less SP movement and a significantly lower rate of SP dislodgment. CONCLUSIONS: Clear differences in task performance are measurable between more and less experienced surgeons during critical steps of stapedotomy. CLINICAL SIGNIFICANCE: The observed differences in task performance may contribute to an understanding of maneuvers that increase the risk of inadequate prosthesis placement and cochlear trauma-factors likely responsible for variable hearing results with strapedotomy.

Clinical Competence↗

PubMed2003

System for MR image-guided prostate interventions: canine study.

The purpose of this study was to demonstrate the use of a transrectal system that enables precise magnetic resonance (MR) image guidance and monitoring of prostate interventions. The system used a closed-bore 1.5-T MR imaging unit and enables one to take advantage of the higher signal-to-noise ratio achieved with traditional magnet designs, which is crucial for accurate targeting and monitoring of prostate interventions. In the first of the four canine studies, reliable needle placement, with all needles placed within 2 mm of the desired target site, was achieved. In two other studies, MR imaging was used to monitor distribution of injected contrast agent solution (gadopentetate dimeglumine mixed with trypan blue dye) in and around the prostate, thereby confirming that solution had been delivered to the desired tissue and also detecting faulty injections. In the final study, accurate placement and MR imaging of brachytherapy seeds in the prostate were demonstrated. The described system provides a flexible platform for a variety of minimally invasive MR image-guided therapeutic and diagnostic prostate interventions.

Animals↗

PubMed2002

Robot-assisted stapedotomy: micropick fenestration of the stapes footplate.

OBJECTIVE: Micropick fenestration of the stapes footplate, a difficult step in stapedotomy, was selected for trials evaluating the potential for robotic assistance (RA) to improve clinical measures of surgical performance. STUDY DESIGN: In a surgical model of stapedotomy, we measured accuracy of fenestration to a desired point location and force applied to the stapes footplate. Performance variables were measured for 3 experienced and 3 less-experienced surgeons. RESULTS: RA significantly reduced the maximum force applied to the stapes footplate. For fenestration targeting, RA significantly improved accuracy for less-experienced surgeons and significantly worsened targeting for more-experienced surgeons. CONCLUSIONS: RA significantly improves performance for micropick fenestration in a surgical model of stapedotomy. For certain tasks, RA differentially affects performance for users of different experience levels. CLINICAL SIGNIFICANCE: These are the first results showing quantitative improvements in performance during simulated ear surgery using RA and differential effects of RA on performance for users of different experience levels.

Clinical Competence↗

PubMedDate not supplied

Robotically assisted prostate brachytherapy with transrectal ultrasound guidance--Phantom experiments.

PURPOSE: To report the preliminary experimental results obtained with a robot-assisted transrectal ultrasound (TRUS)-guided prostate brachytherapy system. METHODS AND MATERIALS: The system consists of a TRUS unit, a spatially coregistered needle insertion robot, and an FDA-approved treatment planning and image-registered implant system. The robot receives each entry/target coordinate pair of the implant plan, inserts a preloaded needle, and then the seeds are deposited. The needles/sources are tracked in TRUS, thus allowing the plan to be updated as the procedure progresses. RESULTS: The first insertion attempt was recorded for each needle, without adjustment. All clinically relevant locations were reached in a prostate phantom. Nonparallel and parallel needle trajectories were demonstrated. Based on TRUS, the average transverse placement error was 2 mm (worst case 2.5 mm, 80% less than 2 mm), and the average sagittal error was 2.5 mm (worst case 5.0 mm, 70% less than 2.5 mm). CONCLUSIONS: The concept and technical viability of robot-assisted brachytherapy were demonstrated in phantoms. The kinematically decoupled robotic assistant device is inherently safe. Overall performance was promising, but further optimization is necessary to prove the possibility of improved dosimetry.

Brachytherapy↗

PubMedDate not supplied

An interventional magnetic resonance imaging technique for the molecular characterization of intraprostatic dynamic contrast enhancement.

The biological characterization of an individual patient's tumor by noninvasive imaging will have an important role in cancer care and clinical research if the molecular processes that underlie the image data are known. Spatial heterogeneity in the dynamics of magnetic resonance imaging contrast enhancement (DCE-MRI) is hypothesized to reflect variations in tumor angiogenesis. Here we demonstrate the feasibility of precisely colocalizing DCE-MRI data with the genomic and proteomic profiles of underlying biopsy tissue using a novel MRI-guided biopsy technique in a patients with prostate cancer.

Biopsy↗