The overall mechanism weights 900 g so that its manipulation, once mounted on the KUKA LWR arm, is practicable. Ergonomic design ease its maneuverability by external exerted forces. Safety concerns have led the development of a disposable and attachable needle sleeve. It offers the possibility to decouple the needle from the mechanism in an easy and rapid manner. By enclosing a force sensor, sensory information, concerning the force exerted by the ultra- sound probe on the patient’s skin, can be provided.
6 Conclusion
The study of this project was to present and explore a novel manipulator for minimally invasive ultrasound guided breast biopsy, identifying the reasons and motivations for automating such procedure and its impact on the medical workflow outcomes. The research also sought to introduce the practicability of assisting and sustaining professionals in the field through an innovative needle steering mechanism.
Many previously developed RCM mechanisms have shown enhancing lesion targeting by of- fering improved accuracy and precision for needle steering, but not many have been proven conclusive for breast biopsy purposes.
The research sought to developed a needle steering manipulator compatible with a multi-DOF serial arm for automated breast biopsy procedure. This was done in the context of the MURAB project, searching to improve precision and effectiveness of biopsy gathering for cancer dia- gnostic operations.
The requirements for such apparatus were deducted from an extended literature study, and a novel design was based upon these. Using rapid prototyping techniques, this design was realized. The controlled needle steering mechanism has proven accurate and precise with ac- ceptable uncertainties, considering the used materials and components, lying in the range of 1 to 2 mm. Nevertheless, the 6 to 8 mm play felt at the end effector due to the gearbox’s backlash needs to be accounted for. The ultrasound transducer can be housed and properly aligned with the needle for its real time imaging and possible path planning. Also, the use of force sensing favors the mimick of the studied and demonstrated biopsy ’hand-held’ technique. Fail scenarios has led to design a detachable and disposable needle sleeve, and a mechanism that can be decoupled. Its kinematic structure allows for easy sterilization and hygienic solu- tions. The apparatus also offers an attachment so that it can be mounted on the KUKA LWR robotic arm, and is light enough to be operated by it.
Although the realized and evaluated prototype did not entirely cover the desired area of interest for breasts with different anatomical structures, a design concept for improved workspace was proposed. Their differences solely lie in minor dimension changes in the ultrasound trans- ducer’s housing, as was observed in Figure 3.20.
Using his overview about MIS robots, (Kuo et al., 2012) work has led towards careful study of kinematic design consideration . The division of the mechanism into proximal and distal parts, such as in (Taylor et al., 1995b) work, proved to be indeed befitting for medical purposes, and offer a valuable solution for changing the working point of the manipulator. Likewise to (Dav- ies et al., 2000), the mechanism was design such that a remote center of motion is obtained by kinematic arrangement of the joints of the manipulator so that future legislation approval is prospective. Studying, combining and proposing a multitude of concepts has led towards empirical findings, demonstrating the impact minimally invasive manipulators could have on the outcome of automated guided breast biopsies. This study offers an evaluative perspective for the needle steering manipulator realized by rapid prototyping, which whom limitations due to printing tolerances need to be considered.
Although the limitation of prototype realization to 3D printing and use of cheap components, the presented novel needle steering manipulator for minimally invasive guided breast biopsy has proven to be particularly accurate and precise. The development of such mechatronic sys- tem demonstrated that repeated and precise lesion targeting has great potential for automated breast biopsy procedures.
CHAPTER 6. CONCLUSION 47
6.1 Future work
The development of a clinically suitable guided needle steering mechanism for the MURAB project is an ongoing project. What can be found in this paper is the first step towards a com- mercial and FDA approved product.
As was already discussed in Section 3.2.1.4, transition from laboratory to clinical practice for needle guidance devices can be challenging. Due to strict regulatory concerns, it is crucial to consider safety as the main requisite of the undertaken development assignment.
In addition to the covered safety measures for making the mechanism intrinsically safer, controller electronics of the manipulator can be designed such that power supply and cable integrity are monitored. Kinematic safety and unwanted motion in case of power failure can be ensured by implementing emergency brakes on the primary DOF, as well as providing re- dundant position encoders for each actuated joints. It can be also imagined that redundancy to the emergency brakes can be achieved through gravity balance of the needle steering system. Although a Proof of Concept (PoC) was delivered, and satisfactory possibility for lesion tar- geting provided, the overall performance of the manipulator can be improved by enhanced realization of the product. Indeed, considering the obtained accuracy, precision, robustness and low denoted uncertainties were obtained through ABS material assembly conception, with the use of rapid 3D printing prototyping, the exploit of further precise manufactured components could lead to even better targeting performances.
Further study on the workflow of ultrasound guided breast biopsies in clinical institutes should be performed, involving the input of radiologist concerning conventional practices. This could, in turn, permit for further appropriate size synthesis of the mechanism, ensuing towards a fit- ter and more suitable mechanism workspace.
The prototype presented in this paper lays groundwork for the development of a clinically ap- proved mechanism allowing for robotically assisted ultrasound guided breast biopsy, and could lead towards the development of a revolutionizing system in the integration of robotic systems for cancer diagnostic operations.
A Appendix
A.1 Coordinates of point B
Solving forxBandyB, the coordinates of point B with respect to the coordinates of point A can be obtained: a2=(xB−xA)2+(yB−yA)2 b2=(xB−xC)2+(yB−yC)2 Such that xB=(x2A+y2A−xC2−yC2−a2+b2)/(2·(xA−xC))−((yA−yC)·(x2A·yA+yA·xC2+x2A·yC−yA·yC2− y2A·yC+xA·((x2A−2·xA·xC+y2A−2·yA·yC+xC2+yC2−a2+2·a·b−b2)·(−x2A+2·xA·xC −y2A+2·yA·yC−xC2−yC2+a2+2·a·b+b2))(1/2)+xC2·yC−xC·((xA2−2·xA·xC+y2A−2· yA·yC+xC2+yC2−a2+2·a·b−b2)·(−x2A+2·xA·xC−y2A+2·yA·yC−xC2−yC2+a2+2·a· b+b2))(1/2)−yA·a2+yA·b2+yC·a2−yC·b2+y3A+yC3−2·xA·yA·xC−2·xA·xC·yC))/(2 ·(xA−xC)·(x2A−2·xA·xC+yA2−2·yA·yC+xC2+yC2)) yB=(x2A·yA+yA·xC2+x2A·yC−yA·yC2−y2A·yC+xA·((x2A−2·xA·xC+y2A−2·yA·yC+xC2+yC2− a2+2·a·b−b2)·(−x2A+2·xA·xC−y2A+2·yA·yC−xC2−yC2+a2+2·a·b+b2))(1/2)+xC2· yC−xC·((x2A−2·xA·xC+y2A−2·yA·yC+x2C+yC2−a2+2·a·b−b2)·(−x2A+2·xA·xC−y2A +2·yA·yC−xC2−yC2+a2+2·a·b+b2))(1/2)−yA·a2+yA·b2+yC·a2−yC·b2+y3A+yC3−2 ·xA·yA·xC−2·xA·xC·yC)/(2·(x2A−2·xA·xC+y2A−2·yA·yC+xC2+yC2))
APPENDIX A. APPENDIX 49