Flexible needle steering has aroused a lot of research interest in recent years. It has the potential to correct targeting errors, which may be caused by needle bending, tissue deformation, or error ...in insertion angle. In addition, control and planning based on a steering model can guide the needle to some areas that are currently not amenable to needles because of obstacles, such as bone or sensitive tissues. Thus, there is a clear motivation for needle steering. In this paper, a spring-beam-damper model is proposed to describe the dynamics during the needle-tissue contact procedure. Considering tissue inhomogeneity, depth-varying mean parameters are proposed to calculate the spring and damper effects. Local polynomial approximations in finite depth segments are adopted to estimate the unknown depth-varying mean parameters. Based on this approach, an online parameter estimator has been designed using the modified least-square method with a forgetting factor. Some preliminary experiments have been carried out to verify the steering model with the online parameter estimator. The details are given in this paper. Finally, conclusions and future studies are given at the end.
In this paper, we present needle insertion forces and motion trajectories measured during actual brachytherapy needle insertion while implanting radioactive seeds in the prostate glands of 20 ...different patients. The needle motion was captured using ultrasound images and a 6 degree-of-freedom electromagnetic-based position sensor. Needle velocity was computed from the position information and the corresponding time stamps. From in vivo data we found the maximum needle insertion forces to be about 15.6 and
8.9
N
for
17
gauge
(
1.47
mm
)
and
18
gauge
(
1.27
mm
)
needles, respectively. Part of this difference in insertion forces is due to the needle size difference (17G and 18G) and the other part is due to the difference in tissue properties that are specific to the individual patient. Some transverse forces were observed, which are attributed to several factors such as tissue heterogeneity, organ movement, human factors in surgery, and the interaction between the template and the needle. However, theses insertion forces are significantly responsible for needle deviation from the desired trajectory and target movement. Therefore, a proper selection of needle and modulated velocity (translational and rotational) may reduce the tissue deformation and target movement by reducing insertion forces and thereby improve the seed delivery accuracy. The knowledge gleaned from this study promises to be useful for not only designing mechanical/robotic systems but also developing a predictive deformation model of the prostate and real-time adaptive controlling of the needle.
In traditional prostate brachytherapy procedures for a low-dose-rate (LDR) radiation seed implant, stabilizing needles are first inserted to provide some rigidity and support to the prostate. Ideally ...this will provide better seed placement and an overall improved treatment. However, there is much speculation regarding the effectiveness of using regular brachytherapy needles as stabilizers. In this study, we explored the efficacy of two types of needle geometries (regular brachytherapy needle and hooked needle) and several clinically feasible configurations of the stabilization needles. To understand and assess the prostate movement during seed implantation, we collected in vivo data from patients during actual brachytherapy procedures. In vitro experimentation with tissue-equivalent phantoms allowed us to further understand the mechanics behind prostate stabilization. We observed superior stabilization with the hooked needles compared to the regular brachytherapy needles (more than 40% in bilateral parallel needle configuration). Prostate movement was also reduced significantly when regular brachytherapy needles were in an angulated configuration as compared to the parallel configuration (more than 60%). When the hooked needles were angulated for stabilization, further reduction in prostate displacement was observed. In general, for convenience of dosimetric planning and to avoid needle collision, all needles are desired to be in a parallel configuration. In this configuration, hooked needles provide improved stabilization of the prostate. On the other hand, both regular and hooked needles appear to be equally effective in reducing prostate movement when they are in angulated configurations, which will be useful in seed implantation using a robotic system. We have developed nonlinear spring-damper model for the prostate movement which can be used for adapting dosimetric planning during brachytherapy as well as for developing more realistic haptic devices and training simulators.
Elderly patients with symptomatic Achilles tendinopathy who develop insertional ruptures develop are at risk of persistent pain and poor functional outcome. Extensive debridement of the tendinopathy ...creates a defect that adds to the difficulty of Achilles insertional rupture repair. Complete excision of the tendinopathy segment was proposed to minimize persistent pain. Reconstruction of the defect using modified flexor hallucis longus transfer might better restore Achilles function. Five patients older than 50 years (mean age, 58.8 years) who had symptomatic Achilles tendinopathy and subsequently had insertional ruptures were treated. The outcome was assessed at an average of 28.8 months after the reconstruction. There was good pain relief. All patients were able to do single-leg stance. Cybex isokinetic testing showed plantar flexion peak torque deficits of 10.9% and 3.9% when tested at 60 degrees /second and 120 degrees /second, respectively. The Functional Ambulation Performance score indicated a near normal gait pattern. The American Orthopaedic Foot and Ankle Society hindfoot score improved from 64.4 to 94.4. There was no major surgical complication and no re-rupture. Excision of Achilles tendinopathy segment followed by modified flexor hallucis longus transfer can achieve good pain relief and functional recovery in elderly patients with symptomatic Achilles tendinopathy who have Achilles insertional ruptures develop.
A novel Gaussian mixture model (GMM)-based region and gradient active contour model is proposed for general object boundary tracking and the purpose of boundary tracking for anal muscle layers. ...Motion information is extracted from adjacent slice and is used to guide the first step of boundary tracking procedure. The idea is that GMM is introduced into the statistical feature computation for object region and background region, thereby providing an accurate model for regional pixel intensity description. Expectation-maximization algorithm and K-means algorithm are used for parameter solutions of GMM. Based on the available region information, gradient information and the self-constraints of the contour, a unifying active contour model is proposed. The proposed active contour models and tracking algorithm were tested on synthetic images and simulated ultrasound images to evaluate some generic features of the model for boundary tracking. Furthermore, it was applied to perform boundary tracking of anal muscle layers. The tracking results were evaluated by three experts. The results showed that the proposed method has a good performance for boundary tracking on anal wall ultrasound image.
Robot-Assisted Prostate Brachytherapy Yu, Yan; Podder, Tarun; Zhang, Yongde ...
Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006,
2006, Letnik:
9, Številka:
Pt 1
Book Chapter, Journal Article
Recenzirano
Odprti dostop
In contemporary brachytherapy procedures, needle placement at the desired target is challenging due to a variety of reasons. A robot-assisted brachytherapy system can improve the needle placement and ...seed delivery resulting in enhanced patient care. In this paper we present a 16 DOF (degrees-of-freedom) robotic system (9DOF positioning module and 7DOF surgery module) developed and fabricated for prostate brachytherapy. Techniques to reduce needle deflection and target movement have been incorporated after verifying with extensive experiments. Provisions for needle motion and force feedback have been included into the system for improving the robot control and seed delivery. Preliminary experimental results reveal that the prototype system is quite accurate (sub-millimeter) in placing brachytherapy needles.
Prostate diseases are very common in adult and elderly men, and prostate boundary detection from ultrasonographic images plays a key role in prostate disease diagnosis and treatment. However, because ...of the poor quality of ultrasonographic images, prostate boundary detection still remains a challenging task. Currently, this task is performed manually, which is arduous and heavily user dependent. To improve the efficiency by automating the boundary detection process, numerous methods have been proposed. We present a review of these methods, aiming to find a good solution that could efficiently detect the prostate boundary on ultrasonographic images.
A full description of various methods is beyond the scope of this article; instead, we focus on providing an introduction to the different methods with a discussion of their advantages and disadvantages. Moreover, verification methods for estimating the accuracies of the algorithms reported in the literature are discussed as well.
From the investigation, we summarize several key issues that might be confronted and project possible future research.
Those model-based methods that minimize user involvement but allow for interactive guidance of experts will likely be most immediately successful.
Wafer‐scale polymer nanofabrillar structures have been fabricated using the combination of colloidal nanolithography, deep‐silicon etching, and nanomolding to mimic the nanostructure of gecko ...foot‐hairs. The artificial surface features densely packed polymeric nanofibrils with super‐hydrophobic, water‐repellent, and “easy‐to‐clean” characteristics. The lateral dimension of the nanofibrils is as small as 250 nm and an aspect‐ratio as high as 10:1 has been achieved without lateral collapse between neighboring fibrils. The method allows both fabrication of synthetic structures over a large area and direct integration of a flexible membrane to assist the array of nanofibrils in making intimate contact with uneven surfaces. A single nanofibril exhibits a mean adhesive force ranging from (0.91 ± 0.34) nN to (1.35 ± 0.37) nN. In the macroscopic scale, the nanostructured surface can adhere firmly to a smooth glass substrate and inherits the in‐use, self‐cleaning property of the setal nanostructures found in gecko lamellae.
A flexible membrane covered by high aspect‐ratio of polymeric nanostructures has been fabricated to emulate the morphology of gecko's foot‐pads. The nanostructured surface adheres firmly to a smooth surface and inherits the self‐cleaning property of the setal nanostructures found in gecko lamellae.
Purpose
There is a need for methods which enable precise correlation of histologic sections with in vivo prostate images. Such methods would allow direct comparison between imaging features and ...functional or histopathological heterogeneity of tumors. Correlation would be particularly useful for validating the accuracy of imaging modalities, developing imaging techniques, assessing image-guided therapy, etc. An optimum prostate slicing method for accurate correlation between the histopathological and medical imaging planes in terms of section angle, thickness and level was sought.
Methods
Literature review (51 references from 1986–2009 were cited) was done on the various sectioning apparatus or techniques used to slice the prostate specimen for accurate correlation between histopathological data and medical imaging. Technology evaluation was performed with review and discussion of various methods used to section other organs and their possible applications for sectioning prostatectomy specimens.
Results
No consensus has been achieved on how the prostate should be dissected to achieve a good correlation. Various customized sectioning instruments and techniques working with different mechanism are used in different research institutes to improve the correlation. Some of the methods have convincingly shown significant potential for improving image-specimen correlation. However, the semisolid consistent property of prostate tissue and the lack of identifiable landmarks remain challenges to be overcome, especially for fresh prostate sectioning and microtomy without external fiducials.
Conclusions
A standardized optimum protocol to dissect prostatectomy specimens is needed for the validation of medical imaging modalities by histologic correlation. These standards can enhance disease management by improving the comparability between different modalities.
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