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

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

Will focal therapy become a standard of care for men with localized prostate cancer?

The current treatment choice for men with localized prostate cancer lies between active surveillance and radical therapy. The difference between these two extremes of care is 5% in terms of cancer-related absolute mortality at 8 years. It is generally accepted that this small difference will decrease for men diagnosed in the prostate-specific-antigen era. Radical therapy is associated with considerable adverse effects (e.g. incontinence, impotence, rectal problems) because it treats the whole gland, and damages surrounding structures in up to half of men. Men are being diagnosed at a younger age with lower-risk disease, and many have unifocal or unilateral disease. We propose a new concept whereby only the tumor focus and a margin of normal tissue are treated. This paradigm might decrease adverse effects whilst, at the same time, retaining effective cancer control. The arguments for and against active surveillance and radical therapy are reviewed in this article, with focal therapy presented as a means for bridging these two approaches