Design and implementation of autonomous robotic scanning of the breast

Breast cancer is the most common type of cancer in women worldwide, with nearly 1.7 million new cases diagnosed in 2012.[1] Improvement of breast biopsy methods, allowing early detection and reliable diagnosis, can reduce the mortality rate significantly.[2] The MURAB project stands for MRI and Ultrasound Robotic Assisted Biopsy and aims to improve breast biopsy. Image modalities such as ultrasound and MRI are used to locate the lesion. MRI breast biopsy provides higher resolution images but is significantly more complicated than ultrasound guided biopsy and causes increased discomfort for the patient and increased intervention time and costs. The MURAB project aims to reduce these drawbacks using the advantages of both imaging modalities. Images of both modalities will be registered and will provide input during the robotic assisted biopsy while using real-time ultrasound guidance to guide the biopsy needle to the lesion. The main aim of this research project is to design and implement the ultrasound scanning phase during which the breast of the patient is autonomously scanned by a LWR4+ lightweight robotic arm (KUKA industrial robots, Germany) in order to acquire 2D ultrasound images. The design and implementation in this study consists of 1) autonomous initialization of scanning using visual servoing, 2) automatic trajectory planning and 3) contact control using force feed-back to maintain a constant contact pressure between the robot probe and the patient while keeping the probe normal to the breast surface. Experiments were performed using breast phantoms. Results showed that during initialization of the scanning motion the robot is steered to the correct start position with an accuracy of 1.6 mm. It was possible to automatically plan the trajectory, after which the robotic arm made contact with the breast phantom. The contact pressure of 5N was maintained during the full scan and the probe was kept normal to the surface with an average deviation of seven degrees. These results are promising for further implementation and fine tuning of the scanning phase using a robot arm designed for breast biopsy applications. The MURAB project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 688188. References [1] World Cancer Research Fund International (2012), Breast cancer statistics. http://www.wcrf.org/int/cancer-facts-figures/ data-specific-cancers/breast-cancer-statistics [2] Khatib, Oussama MN, and Atord Modjtabai. "Guidelines for the early detection and screening of breast cancer." World Health Organization. Technical Publications Series 30 (2006)

Automated robotic breast ultrasound acquisition using ultrasound feedback

Current challenges in automated robotic breast ultrasound (US) acquisitions include keeping acoustic coupling between the breast and the US probe, minimizing tissue deformations and safety. In this paper, we present how an autonomous 3D breast US acquisition can be performed utilizing a 7DOF robot equipped with a linear US transducer. Robotic 3D breast US acquisitions would increase the diagnostic value of the modality since they allow patient specific scans and have a high reproducibility, accuracy and efficiency. Additionally, 3D US acquisitions allow more flexibility in examining the breast and simplify registration with preoperative images like MRI. To overcome the current challenges, the robot follows a reference- based trajectory adjusted by a visual servoing algorithm. The reference trajectory is a patient specific trajectory coming from e.g. an MRI. The visual servoing algorithm commands in-plane rotations and corrects the probe contact based on confidence maps. A safety aware, intrinsically passive framework is utilised to actuate the robot. The approach is illustrated with experiments on a phantom, which show that the robot only needs minor pre-procedural information to consistently image the phantom while relying mainly on US feedback

Targeted lymph node biopsy in mediastinoscopy using 3D FDG-PET/CT movies: a feasibility study

In non-small-cell lung cancer, positive lymph nodes with increased fluorodeoxyglucose (FDG) uptake may be missed by mediastinoscopy. Lack of pathological confirmation may lead to radical, but unnecessary lung surgery. To minimize these false-negative results, the feasibility and potential value of three-dimensional (3D) FDG-PET/computed tomography (CT) movies were investigated to improve targeted lymph node biopsy during mediastinoscopies. PET/CT images were rendered in 3D volumes with multiplanar reconstructions and maximum intensity projections and reviewed in 3D 'fly-through' and 'fly-around' movies. These movies were developed and optimized by the Departments of Surgery and Nuclear Medicine. Twenty-two consecutive patients with non-small-cell lung cancer were included, of whom eight were FDG-PET positive for mediastinal lymph nodes. 3D FDG-PET/CT movies were presented to surgeons before mediastinoscopy. Surgical consequences were investigated, including sensitivity and the negative predictive value of mediastinoscopy. Results were compared with those of a retrospective study in which 3D techniques were not used. During mediastinoscopies, the 3D-PET/CT movies were found to be helpful in the surgical localization of FDG-positive lymph nodes. It led to more confidence in the surgical approach. The sensitivity and negative predictive value were 86 and 94%, respectively. Although not statistically significant, these results were higher compared with those of the retrospective study (75 and 92%, respectively). 3D FDG-PET/CT guidance during mediastinoscopy is feasible. The movies seem to lead to targeted biopsy of lymph nodes. They may reduce false-negative mediastinoscopies and improve staging of lung cancer. 3D FDG-PET/CT can be seen as a promising tool for further implementation of image-guided surgery

Scanning multiple mice in a small-animal PET scanner: Influence on image quality

To achieve high throughput in small-animal positron emission tomography (PET), it may be advantageous to scan more than one animal in the scanner’s field of view (FOV) at the same time.\ud \ud However, due to the additional activity and increase of Poisson noise, additional attenuating mass, extra photon scattering, and radial or axial displacement of the animals, a deterioration of image quality can be expected. In this study, the NEMA NU 4-2008 image quality (NU4IQ) phantom and up to three FDG-filled cylindrical “mouse phantoms” were positioned in the FOV of the Siemens Inveon small-animal PET scanner to simulate scans with multiple mice. Five geometrical configurations were examined. In one configuration, the NU4IQ phantom was scanned separately and placed in the center of the FOV (1C). In two configurations, a mouse phantom was added with both phantoms displaced radially (2R) or axially (2A). In two other configurations, the NU4IQ phantom was scanned along with three mouse phantoms with all phantoms displaced radially (4R), or in a combination of radial and axial displacement (2R2A). Images were reconstructed using ordered subset expectation maximization in 2 dimensions (OSEM2D) and maximum a posteriori (MAP) reconstruction. Image quality parameters were obtained according to the NEMA NU 4-2008 guidelines. Optimum image quality was obtained for the 1C geometry. Image noise increased by the addition of phantoms and was the largest for the 4R configuration. Spatial resolution, reflected in the recovery coefficients for the FDG-filled rods, deteriorated by radial displacement of the NU4IQ phantom (2R, 2R2A, and 4R), most strongly for OSEM2D, and to a smaller extent for MAP reconstructions. Photon scatter, as indicated by the spill-over ratios in the non-radioactive water- and air-filled compartments, increased by the addition of phantoms, most strongly for the 4R configuration. Application of scatter correction substantially lowered the spill-over ratios, but caused an over-correction for the recovery coefficients of the FDG-filled rods when the phantom was displaced radially. Image noise was not substantially influenced by scatter correction. In conclusion, when scanning 2 mice, axial displacement (2A) is preferable above to radial displacement (2R) since for axial displacement, the recovery coefficients are higher and spill-over ratios are lower, whereas image noise remains similar. In the case of scanning 4 mice, combined axial and radial displacement (2R2A) is preferable to just radial displacement (4 R)

Ultrasound-guided breast biopsy using an adapted automated cone-based ultrasound scanner: a feasibility study.

BACKGROUND: Among available breast biopsy techniques, ultrasound (US)-guided biopsy is preferable because it is relatively inexpensive and provides live imaging feedback. The availability of magnetic resonance imaging (MRI)-3D US image fusion would facilitate US-guided biopsy even for US occult lesions to reduce the need for expensive and time-consuming MRI-guided biopsy. In this paper, we propose a novel Automated Cone-based Breast Ultrasound Scanning and Biopsy System (ACBUS-BS) to scan and biopsy breasts of women in prone position. It is based on a previously developed system, called ACBUS, that facilitates MRI-3D US image fusion imaging of the breast employing a conical container filled with coupling medium. PURPOSE: The purpose of this study was to introduce the ABCUS-BS system and demonstrate its feasibility for biopsy of US occult lesions. METHOD: The biopsy procedure with the ACBUS-BS comprises four steps: target localization, positioning, preparation, and biopsy. The biopsy outcome can be impacted by 5 types of errors: due to lesion segmentation, MRI-3D US registration, navigation, lesion tracking during repositioning, and US inaccuracy (due to sound speed difference between the sample and the one used for image reconstruction). For the quantification, we use a soft custom-made polyvinyl alcohol phantom (PVA) containing eight lesions (three US-occult and five US-visible lesions of 10 mm in diameter) and a commercial breast mimicking phantom with a median stiffness of 7.6 and 28 kPa, respectively. Errors of all types were quantified using the custom-made phantom. The error due to lesion tracking was also quantified with the commercial phantom. Finally, the technology was validated by biopsying the custom-made phantom and comparing the size of the biopsied material to the original lesion size. The average size of the 10-mm-sized lesions in the biopsy specimen was 7.00 ± 0.92 mm (6.33 ± 1.16 mm for US occult lesions, and 7.40 ± 0.55 mm for US-visible lesions). RESULTS: For the PVA phantom, the errors due to registration, navigation, lesion tracking during repositioning, and US inaccuracy were 1.33, 0.30, 2.12, and 0.55 mm. The total error was 4.01 mm. For the commercial phantom, the error due to lesion tracking was estimated at 1.10 mm, and the total error was 4.11 mm. Given these results, the system is expected to successfully biopsy lesions larger than 8.22 mm in diameter. Patient studies will have to be carried out to confirm this in vivo. CONCLUSION: The ACBUS-BS facilitates US-guided biopsy of lesions detected in pre-MRI and therefore might offer a low-cost alternative to MRI-guided biopsy. We demonstrated the feasibility of the approach by successfully taking biopsies of five US-visible and three US-occult lesions embedded in a soft breast-shaped phantom

Production and clinical evaluation of breast lesion skin markers for automated three-dimensional ultrasonography of the breast: a pilot study

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