Evaluation of a robotic technique for transrectal MRI-guided prostate biopsies

Item does not contain fulltextOBJECTIVES: To evaluate the accuracy and speed of a novel robotic technique as an aid to perform magnetic resonance image (MRI)-guided prostate biopsies on patients with cancer suspicious regions. METHODS: A pneumatic controlled MR-compatible manipulator with 5 degrees of freedom was developed in-house to guide biopsies under real-time imaging. From 13 consecutive biopsy procedures, the targeting error, biopsy error and target displacement were calculated to evaluate the accuracy. The time was recorded to evaluate manipulation and procedure time. RESULTS: The robotic and manual techniques demonstrated comparable results regarding mean targeting error (5.7 vs 5.8 mm, respectively) and mean target displacement (6.6 vs 6.0 mm, respectively). The mean biopsy error was larger (6.5 vs 4.4 mm) when using the robotic technique, although not significant. Mean procedure and manipulation time were 76 min and 6 min, respectively using the robotic technique and 61 and 8 min with the manual technique. CONCLUSIONS: Although comparable results regarding accuracy and speed were found, the extended technical effort of the robotic technique make the manual technique - currently - more suitable to perform MRI-guided biopsies. Furthermore, this study provided a better insight in displacement of the target during in vivo biopsy procedures.01 februari 201

A robotic device for MRI-guided prostate brachytherapy

One of the treatment options for prostate cancer is brachytherapy with iodine-125 sources. In prostate brachytherapy a high radiation dose is delivered to the prostate with a steep dose fall off to critical surrounding organs. The implantation of the iodine sources is currently performed under ultrasound guidance, but MRI (Magnetic Resonance Imaging) offers a better image quality that could be employed to further improve source placement precision and prostate dose distribution. Due to the limited amount of space inside a closed bore MRI scanner the currently used manual implantation technique is impossible. Therefore a robotic device, which can be placed between the patient’s legs, is being developed. Prostate motion is one of the main causes of seed misplacement. Because this motion is more or less random there is no practical solution to take it into account during planning of the treatment (chapter 2). To diminish prostate motion a new needle insertion method was developed. Instead of pushing the needle into the prostate, the needle is tapped into the prostate with a high velocity. A tapping device was built and tested on a piece a beef (chapter 3). The tests showed less beef motion with higher needle insertion velocities. After the phantom experiments a clinical study was performed to compare prostate motion during needle insertion for pushing and tapping the needle into the prostate (chapter 4). The mean prostate motion was 5.6~mm when the needle was pushed and 0.9 mm when the needle was tapped into the prostate. We expect that prostate movement will be further reduced when the tapping device is operated at higher momentums. To be able to deliver the iodine seeds at the pre-planned position a good image of the prostate, the needle and the seeds is necessary. The only currently available commercial MRI compatible needles are made of titanium, which still gives a rather large artefact at the tip. This makes it difficult to determine the exact position of the delivered seeds (dimensions 4.5 x 0.8 mm), which is of importance for accurate dose delivery in the prostate. In chapter 5 a simulation study was performed to investigate the influence of different needle materials on the seed artefact. Only with a plastic needle it was possible to distinguish the seed artefact. When the middle of the seed position is taken as the middle of the seed artefact, the seed position can be determined with an accuracy of 0.4 mm on Gradient Echo images. In chapter 6 the first prototype of the MRI compatible robotic device is described. MRI compatibility tests proved the working of the robotic device in a magnetic field without distorting the MR images. In the near future pre-clinical experiments will be performed to test the functionality and the needle and seed placement accuracy of the robotic device. Thanks to the new needle insertion method and the MRI-guidance we think that more accurate seed placement and therefore a better dose distribution is possible than currently achieved

Design considerations for patient-specific bone fixation plates: a literature review

In orthopedic surgery, patient-specific bone plates are used for fixation when conventional bone plates do not fit the specific anatomy of a patient. However, plate failure can occur due to a lack of properly established design parameters that support optimal biomechanical properties of the plate. This review provides an overview of design parameters and biomechanical properties of patient-specific bone plates, which can assist in the design of the optimal plate. A literature search was conducted through PubMed and Embase, resulting in the inclusion of 78 studies, comprising clinical studies using patient-specific bone plates for fracture fixation or experimental studies that evaluated biomechanical properties or design parameters of bone plates. Biomechanical properties of the plates, including elastic stiffness, yield strength, tensile strength, and Poisson’s ratio are influenced by various factors, such as material properties, geometry, interface distance, fixation mechanism, screw pattern, working length and manufacturing techniques. Although variations within studies challenge direct translation of experimental results into clinical practice, this review serves as a useful reference guide to determine which parameters must be carefully considered during the design and manufacturing process to achieve the desired biomechanical properties of a plate for fixation of a specific type of fracture. Graphical Abstract: [Figure not available: see fulltext.]Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Biomaterials & Tissue Biomechanic

3D printed patient-specific fixation plates for the treatment of slipped capital femoral epiphysis: Topology optimization vs. conventional design

Orthopedic plates are commonly used after osteotomies for temporary fixation of bones. Patient-specific plates have recently emerged as a promising fixation device. However, it is unclear how various strategies used for the design of such plates perform in comparison with each other. Here, we compare the biomechanical performance of 3D printed patient-specific bone plates designed using conventional computer-aided design (CAD) techniques with those designed with the help of topology optimization (TO) algorithms, focusing on cases involving slipped capital femoral epiphysis (SCFE). We established a biomechanical testing protocol to experimentally assess the performance of the designed plates while measuring the full-field strain using digital image correlation. We also created an experimentally validated finite element model to analyze the performance of the plates under physiologically relevant loading conditions. The results indicated that the TO construct exhibited higher ultimate load and biomechanical performance as compared to the CAD construct, suggesting that TO is a viable approach for the design of such patient-specific bone plates. The TO plate also distributed stress more evenly over the screws, likely resulting in more durable constructs and improved anatomical conformity while reducing the risk of screw and plate failure during cyclic loading. Although differences existed between finite element analysis and experimental testing, this study demonstrated that finite element modelling can be used as a reliable method for evaluating and optimizing plates for SCFE patients. In addition to enhancing the mechanical performance of patient-specific fixation plates, the utilization of TO in plate design may also improve the surgical outcome and decrease the recovery time by reducing the plate and incision sizes.Biomaterials & Tissue Biomechanic

Prostate biopsies assisted by comanipulated probe-holder: first in man

International audiencePurpose: a comanipulator for assisting endorectal prostate biopsies is evaluated through a first-in man clinical trial. This lightweight system, based on conventional robotic components, possesses 6 degrees of freedom. It uses 3 electric motors and 3 brakes. It features a free mode, where its low friction and inertia allow for natural manipulation of the probe and a locked mode, exhibiting both a very low stiffness and a high steady state precision. Methods: Clinical trials focusing on the free mode and the locked mode of the robot are presented. The objective is to evaluate the practical usability and performance of the robot during clinical procedures. A research protocol for a prospective randomized clinical trial has been designed. Its specific goal is to compare the accuracy of biopsies performed with and without the assistance of the comanipulator. Results:The accuracy is compared between biopsies performed with and without the assistance of the comanipulator, across the 10 first patients included in the trial. Results show a statistically significant increase of the precision.. This work is partially funded french state funds managed by the ANR within the Investissements d'Avenir programme (Labex CAMI) under reference ANR-11-LABX-0004. 2 Marie-Aude Vitrani et al