In breast cancer patients, some nodules are only visible on MRI, thus, requiring MRI-guidance to perform the biopsy. MRI interventions are cumbersome due to the magnetic field and the constrained working space. An MR safe robotic system actuated by pneumatic stepper motors may enable these procedures, improving both accuracy and image-guided navigation. A compact multipurpose pneumatic stepper motor has been designed with outer dimensions$(45 \times 40\times 15)\mathbf{mm}^{\mathbf{3}}$. This is configurable as a linear, rotational or curved stepper motor with a customizable step size and radius of curvature. Five copies of these motors actuate the Sunram 7 biopsy robot, of which the moving part (without protruding racks and tubes) measures$(130 \times 65\times 55)\mathbf{mm}^{\mathbf{3}}$. After manually choosing the target location and angle of approach, the needle is robotically inserted into the breast and the integrated pneumatic biopsy gun is fired to sample tissue from the lesion. The maximum torque of the presented motor is 0.61 N m at 6 bar which can be achieved using 13-teeth polycarbonate gears. Using 17-teeth gears for higher accuracy and a more convenient working pressure of 2 bar the maximum torque is 0.28 N m. The accuracy in free air of the Sunram 7 robot is 1.69mm and 1.72mm in X and Z-direction respectively, with a resulting 2-D error of 2.54 mm. The workspace volume is 4.1 L. When targeting 10 mm-sized lesions in phantoms under MRI guidance, Sunram 7 achieved a success rate of 68%. The minimum interval between two successive biopsies was 5:47 minutes. The presented multipurpose stepper motor has distinct advantages over previous designs in terms of robustness, customizability, printability and ease of integration in MR safe robotics. The Sunram 7 is able to perform accurate MRI-guided biopsies in a large workspace volume while reducing the intervention time when compared to the gold standard (i.e., MRI-guided free-hand biopsy).

Absolute position detection in sensorless electric stepper motors potentially allows for higher space efficiency, improved shock resistance, simplified installation, reduced number of parts and lowered cost. A prototype is demonstrated measuring 42 × 42 × 34 mm3with seven coils arranged in a star configuration. The rotor is ϕ 25.8 × 12.5 mm2and has 51 teeth which are irregularly spaced. At the driver side, the coil currents are measured during motion in order to reconstruct the absolute position of the motor. Calibration and smoothing techniques are used to reduce systematic and stochastic measurement errors, respectively. The motor is able to detect and correct its position after externally-induced stalls at the tested motor speeds from 40 rpm to 108 rpm. The holding torque is 0.23 N m at an armature current of 1 A; on average the torque is 7% lower than that of a reference bipolar stepper motor with the same dimensions. The results show that dynamic position sensing and correction are possible for a range of velocities, but not at standstill. The driver requires seven current sensors and sufficient computational power, and proper calibration of motor intrinsics is required beforehand. The presented technology could make existing 3-D printers and other machines with open-loop stepper motors more robust and increase the range of operating speeds and accelerations, without the adverse side-effects of increased complexity and cost associated with dedicated position sensors.

Breast cancer affects one out of eight women. Ultrasound (US) plays an important role in the diagnostic workflow, especially during the biopsy phase, in which tissue is extracted from the lesion for further analysis. The extension from 2D to 3D US acquisitions has multiple benefits including enhanced lesion localization and improved registration with MRI data. Current commercial 3D US systems lack the ability to preserve the breast’s original shape. Robotic US scanners follow tailored trajectories and produce high quality volumes by accurate localization of 2D slices captured with a conventional linear probe. Current methods require a patient specific model to plan the scanning trajectory.In this study we investigate how to change the direction of the scanning trajectory based on US feedback, such that no patient specific model is required to perform a scan. In our method, the scanning trajectory is kept tangent to the breast based on confidence maps of the US images and an estimation of current radius of curvature of the surface. We evaluated our approach on a realistic breast phantom. The robot revolves around the breast without prior knowledge of its shape. In ten scans, the RMS error between the probe’s scanning plane and the breast’s surface normal is 12.6° out-of-plane, and 4.3° in-plane. A 3D US reconstruction shows the acquired data. This is a step forward to fully autonomous, high quality robotic US volume acquisitions.

Breast cancer is one of the most diagnosed types of cancer worldwide. Volumetric ultrasound breast imaging, combined with MRI can improve lesion detection rate, reduce examination time, and improve lesion diagnosis. However, to our knowledge, there are no 3D US breast imaging systems available that facilitate 3D US - MRI image fusion. In this paper, a novel Automated Cone-based Breast Ultrasound System (ACBUS) is introduced. The system facilitates volumetric ultrasound acquisition of the breast in a prone position without deforming it by the US transducer. Quality of ACBUS images for reconstructions at different voxel sizes (0.25 and 0.50 mm isotropic) was compared to quality of the Automated Breast Volumetric Scanner (ABVS) (Siemens Ultrasound, Issaquah, WA, USA) in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and resolution using a custom made phantom. The ACBUS image data were registered to MRI image data utilizing surface matching and the registration accuracy was quantified using an internal marker. The technology was also evaluated in vivo. The phantom-based quantitative analysis demonstrated that ACBUS can deliver volumetric breast images with an image quality similar to the images delivered by a currently commercially available Siemens ABVS. We demonstrate on the phantom and in vivo that ACBUS enables adequate MRI-3D US fusion. To our conclusion, ACBUS might be a suitable candidate for a second-look breast US exam, patient follow-up, and US guided biopsy planning.

Cardiovascular diseases remain as the most common cause of death worldwide. Remotely manipulated robotic systems are utilized to perform minimally invasive endovascular interventions. The main benefits of this methodology include reduced recovery time, improvement of clinical skills and procedural facilitation. Currently, robotic assistance, precision, and stability of instrument manipulation are compensated by the lack of haptic feedback and an excessive amount of radiation to the patient. This paper proposes a novel master-slave robotic platform that aims to bring the haptic feedback benefit on the master side, providing an intuitive user interface, and clinical familiar workflow. The slave robot is capable of manipulating conventional catheters and guidewires in multi-modal imaging environments. The system has been initially tested in a phantom cannulation study under fluoroscopic guidance, evaluating its reliability and procedural protocol. As the slave robot has been entirely produced by additive manufacturing and using pneumatic actuation, MR compatibility is enabled and was evaluated in a preliminary study. Results of both studies strongly support the applicability of the robot in different imaging environments and prospective clinical translation.

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 cm3, has step size 12.9° and torque 1.2 N mm. The R-40 measures 25.6 cm3, has step size 1.01° and torque 470 N mm. The R-54 measures 46.7 cm3, 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.

Breast cancer is the most frequently life-threatening diagnosed type of cancer among women. Early and accurate diagnosis by acquiring a tissue sample using biopsy techniques is essential. However, small lesions only visible by MRI are often missed in standard methods, indicating the need for a robotic-assisted biopsy system that is MRI-compatible. Existing proof-of-concepts are difficult to employ due to large sizes and/or actuation complexities. Therefore, a compact pneumatically-actuated 5 DOF MRI-compatible robot was further developed and controlled by a computerized valve manifold. Accuracy and efficiency measurements have been performed using two different PVC breast phantoms with embedded fish oil capsules (mimicking lesions) inside a 0.25T MRI scanner. Preliminary results show that the end-effector was able to hit the targeted capsules, and that the position accuracy is in the range of 4.7-7.3 mm. The developed robotic system has potential to perform MRI-guided breast biopsies accurately and improve the clinical workflow.

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 (excluding racks and needle) are 72×51×40 mm, and the system is driven by two linear and two curved pneumatic stepper motors. The T-26 linear motor measures 26×21×16 mm, has a nominal step size of 0.25 mm and the measured maximum force is 63N at 0.65 MPa. The workspace has a total volume of 2.2 L. Accuracy measurements have shown that the mean positioning error is 0.7 mm, with a reproducibility of 0.1 mm. Velocity measurements with 5 m long tubes show a maximum stepping frequency of 8 Hz (maximum force) to 30 Hz (unloaded). These results show that the robot might be able to target lesions with sub-millimeter accuracy within reasonable time for the MRI-guided breast biopsy procedure.