Increasing the precision of the biopsy with robots: two case studies

Robotics is a rapidly advancing field and its introduction in healthcare can have a multitude of benefits for clinical practice. Especially applications depending on the radiologist’s accuracy and precision, such as percutaneous interventions, may profit. Percutaneous interventions are relatively simple and the quality of the procedure increases a lot by introducing robotics due to the improved accuracy and precision. This paper provides the description of two robotic systems for percutaneous interventions: breast biopsy and prostate biopsy. The systems presented here are complete prototypes in an advanced state ready to be tested in clinical practice.https://youtu.be/KZxfRtg0afg https://www.youtube.com/watch?v=AB3Qa6LyHP

MRI and Stereo Vision Surface Reconstruction and Fusion

Breast cancer, the most commonly diagnosed cancer in women worldwide, is mostly detected through a biopsy where tissue is extracted and chemically examined or pathologist assessed. Medical imaging plays a valuable role in targeting malignant tissue accurately and guiding the radiologist during needle insertion in a biopsy. This paper proposes a computer software that can process and combine 3D reconstructed surfaces from different imaging modalities, particularly Magnetic Resonance Imaging (MRI) and camera, showing a visualization of important features and investigates its feasibility. The development of this software aims to combine the detectability of MRI with the physical space of the camera. It demonstrates that the registration accuracy of the proposed system is acceptable and has potential for clinical application

Dual-Speed MR Safe Pneumatic Stepper Motors

In breast cancer detection it is essential to perform precise interventions to determine the diagnosis. Robotic systems actuated by MR safe pneumatic stepper motors could improve accuracy to target the tumor. The achievable accuracy or speed is limited due to long pneumatic tubes connecting the motors to the electromagnetic valves in the control room. This paper presents the design of two dual-speed stepper motors in order to solve this limitation. The linear motor measures 50x32x14 mm (excluding racks) and has step sizes 1.7 mm and 0.3 mm. The maximum speed under load is 20 mm/s, measured force is 24 N and positioning accuracy is 0.1 mm. The rotational motor measures Ø30x32 mm (excluding axles) and has step sizes 10° and 12.9°. Under load its maximum angular speed is 229 °/s or 38.2 RPM, maximum torque is 74 N mm and positioning accuracy is 1°. By operating the valves in a coordinated way high-speed and precise position control can be achieved. With these specifications the motors have high potential to actuate MR safe surgical robots

Miniaturization of MR Safe Pneumatic Rotational Stepper Motors

Pneumatic rotational stepper motors can be used to actuate MR (magnetic resonance) safe robotic systems. This paper describes novel techniques to minimize the volumetric size and/or step size of such motors in order to cope with the limited space requirements while still delivering high precision. Three designs are presented: the R-10 measures 1.0 cm 3, has step size 12.9° and torque 1.2 N mm. The R-40 measures 25.6 cm 3, has step size 1.01° and torque 470 N mm. The R-54 measures 46.7 cm 3, has step size 1.01 m° and torque 240 N mm. The particularly small step size in the R-54 motor is achieved by using a high-reduction planetary gear.These three motors demonstrate that small-scale rotational stepper motors with a wide range of step sizes and good torque characteristics can be constructed that surpass state-of-art designs by a considerable margin. This allows the advancement of MR safe robotics towards more compact and versatile designs, and also overcome certain existing limitations by combining multiple motors with different specifications

Magnetic Resonance Pneumatic Stepper Motor With Multiple Concentric Shafts Output

Pneumatic stepper motors can be used to actuate MR safe robotics and other devices. Due to tight space requirements inside the MRI scanner it is useful to combine several individual stepper motors into a single device with an efficient shared actuator mechanism, called the multiple concentric shaft pneumatic stepper motor. The demonstrated "multi-motor" prototype has six geared shafts driven by four pneumatic cylinders and is controlled by five pneumatic lines. The dimensions are 58 x 25 mm (excluding shafts) and the maximum torque at 1.5 bar system pressure is in the range 56 N mm to 114 N mm. The maximum unloaded stepping frequency is 50 Hz when using 0.3 m tubes and drops to 12 Hz when using 5.1 m tubes and 15 N mm load on each shaft. The positioning accuracy is two steps and the most efficient path planning algorithm needs 1.7 times as many steps as six separate single-axis motors. An examplatory 6-DOF manipulator design concept driven by the proposed motor requires an order of magnitude fewer components than state-of-art robotic systems with comparable kinematics. While the multi-motor concept offers significant advantages in motor dimensions and pneumatic tube count, the dynamic performance is fundamentally poor, accuracy is compromised and the coaxial output shafts requires thoughtful kinematic design of robotic systems to make effective use of the motor

Stormram 3: A Magnetic Resonance Imaging-Compatible Robotic System for Breast Biopsy

Stormram 3 is an MRI-compatible robotic system that can perform MR guided breast biopsies of suspicious lesions. The base of the robot measures 160x180x90 mm and it is actuated by five custom pneumatic linear stepper motors, driven by a valve manifold outside the Faraday cage of the MRI scanner. All parts can be rapidly prototyped with 3-D printing or laser-cutting, making the design suitable for other applications such as actuation in hazardous environments. Based on the choice of materials, the robot (with the exception of the needle) is inherently MR-safe. Measurements show that the maximum force of the T-49 actuator is 70 N, at a pressure of 0.3 MPa. The Stormram 3 has an optimized repeatability which is lower than 0.5 mm, and can achieve a positional accuracy in the order of 2 mm

Design and characterization of Stormram 4: an MRI-compatible robotic system for breast biopsy

Targeting of small lesions with high precision is essential in an early phase of breast cancer for diagnosis and accurate follow up, and subsequently determines prognosis. Current techniques to diagnose breast cancer are suboptimal, and there is a need for a small, MRI-compatible robotic system able to target lesions with high precision and direct feedback of MRI. Therefore, the design and working mechanism of the new Stormram 4, an MRI-compatible needle manipulator with four degrees of freedom, will be presented to take biopsies of small lesions in the MRI scanner. Its dimensions (excludign racks and needle) are 72x51x40 mm, and the system is driven by two linear and two curved pneumatic stepper motors. The T-26 linear motor measures 26x21x16 mm, has a step size of 0.25 mm and can exert 63 N at 0.65 MPa. The workspace has a total volume of 2.2 L. Accuracy measurements have shown that the mean positioning error is \SI{0.7}{\mm}, with a reproducibility of \SI{0.1}{\mm}. Consequently, these preliminary results show that the robot might be able to target millimeter-sized lesions for the MRI-guided breast biopsy procedure

Sunram 5: A Magnetic Resonance-Safe Robotic System for Breast Biopsy, Driven by Pneumatic Stepper Motors

Sunram 5 is the fifth generation MR safe robotic system for breast biopsy. It has five degrees of freedom and is driven by six linear and curved pneumatic stepper motors plus three singular cylinders, all constructed by rapid prototyping techniques. A stepper motor consists of two or three pneumatic cylinders that act on a straight or curved toothed rack. The design, production and evaluation of both single pneumatic cylinders and various types stepper motors are described in detail in this chapter, including design aspects such as the optimal geometries of cylinders, pistons, seals and teeth. Control strategies are also discussed such as how multiple motors inside the Sunram 5 can be controlled to achieve both high speed and high accuracy, despite the relatively low stepping frequencies associated with long pneumatic lines between controller and motor in an MRI setting. This way, Sunram 5 provides fast and precise needle insertions under near-realtime MRI guidance, resulting in improved accuracy and efficiency in MRI-guided breast biopsy procedures