Kaiguo Yan

A real-time prostate cancer detection technique using needle insertion force and patient-specific criteria during percutaneous intervention

In this article, the authors present a novel real-time cancer detection technique by using needle insertion forces in conjunction with patient-specific criteria during percutaneous interventions. Needle insertion experiments and pathological analysis were performed for developing a computer-aided detection (CAD) model. Backward stepwise regression method was performed to identify the statistically significant patient-specific factors. A baseline force model was then developed using these significant factors. The threshold force model that estimated the lower bound of the cancerous tissue forces was formulated by adding an adjustable classifier to the baseline force model. Tradeoff between sensitivity and specificity was obtained by varying the threshold value of the classifier, from which the receiver-operating characteristic (ROC) curve was generated. Sequential quadratic programming was used to optimize the CAD model by maximizing the area under the ROC curve (AUC) using a set of model-training patient data. When the CAD model was evaluated using an independent set of model-validation patient data, an AUC of 0.90 was achieved. The feasibility of cancer detection in real time during percutaneous interventions was established.

Needle Steering Modeling and Analysis using Unconstrained Modal Analysis

Precise needle placement is very important for a number of percutaneous interventions. Poor placement may cause tissue damage, misdiagnosis, poor dosimetry and tumor seeding. Yet precise needle placement is hard to achieve in real practice due to tissue heterogeneity and elastic stiffness, unfavorable anatomic structures, needle bending, inadequate sensing, tissue/organ deformation and movement, and poor maneuverability. To date, there are few effective physical-based needle steering systems exist that can correct the needle deflection in real time. In addition, many procedures are currently not amenable to needles because of obstacles, such as bone or sensitive tissues, which lie between feasible entry points and potential targets. Thus, there is a clear motivation for needle steering in order to provide accurate and dexterous targeting. In this paper, a spring-beam-damper system is proposed to model the system dynamics while applying steering force on the needle end. Instead of using the traditional finite element method, unconstrained model analysis is adopted to derive the system dynamic equations. The modeling procedure and analysis method are given in details. Experiment had also been carried out to verify the accuracy of the proposed model. Conclusions and future works are given in subsequent sections

Clinical study of a noninvasive multimodal sono-contrast induced spectroscopy system for breast cancer diagnosis.

PURPOSE To present a noninvasive multimodal sono-contrast induced spectroscopy (SCIS) system for breast cancer detection. METHODS An IRB approved clinical study was carried out to evaluate its diagnostic power. A total of 66 subjects were enrolled with informed consent. The study data were grouped into healthy breast tissue (26), histologically proven cancer (14), and benign mass (26). The diffuse reflectance optical intensity and low intensity focused ultrasound (LIFU) signals, as well as ultrasound images, were collected during each study. The ratio of optical intensities at wavelengths 685 and 830 nm was analyzed using wavelet technique to compare the LIFU effects in cancer and noncancerous tissues. The ultrasound images were also processed to obtain tissue texture parameters, such as correlation, energy, contrast, homogeneity, etc. Backward stepwise regression method was performed to identify the statistically significant factors correlating to tissue types (cancer vs benign mass). RESULTS Comparison of the optical signals showed that LIFU induced transitory fluctuation in noncancerous tissue, but not in malignant tissue, as quantified by the ratio of mean absolute deviation (RMAD) of the high frequency component. Statistical analysis revealed that the RMAD ratios were significantly different in tumor vs noncancerous masses (p ≪ 0.01). For tissue texture parameters, energy and correlation were found to statistically correlate with the tissue types. A cancer characterization model was developed using the weighted factors to differentiate the tumor from the benign mass. Trade-off between sensitivity and specificity was obtained by varying the threshold value that estimated the upper-bound of the cancer output factor, from which the receiver-operating characteristic (ROC) curve was generated. The characterization model was optimized using ten modeling datasets and verified using another ten validation datasets randomly generated from the database. The optimization results show that an AUC of 0.93 can be achieved. With threshold 0.3, sensitivity of 96.0%, specificity of 84.1%, and negative predictive value (NPV) of 97.3% can be achieved. CONCLUSIONS The feasibility of the multimodal system in characterizing breast cancer vs benign mass is established.

MO‐D‐AUD B‐04: Parameter Optimization for Brachytherapy Robotic Needle Insertion and Seed Deposition

Purpose: To investigate influence of different needle insertion and seed deposition techniques for roboticbrachytherapy. To find optimal sets of low, normal and high translational and rotational velocities of the needle for decreasing insertion force, needle deflection and OR time, and increasing seed placement accuracy. Method and Materials: We have developed EUCLIDIAN — a fully automatic robotic prostate brachytherapy system. Robotic system parameters were optimized via preclinical experiments using two types of polyvinylchloride and tissue phantoms, cannula and stylet single‐axis force sensors, and six‐axis force‐torque sensor. Cannula sensor measures the force on the cannula during insertion, withdraw, and axial force exerted by tissue at rest. Stylet sensor measures the force while seed is expelled from the cartridge, during seed travel through the cannula, and at the moment when seed is deposited into tissue. Position of the needle tip and consequently deposition depth into the phantom was measured using optical encoders on the cannula and stylet motors. Cannula and stylet translational velocity range was 5–120 mm/s, and cannula rotation range was 0–30 rev/s. Force patterns were analyzed based on the experimental data. Results: According to the criteria for minimizing insertion force and OR time while maximizing seed deposition precision, it was found that best performances were achieved when cannula and stylet normal speed was 70 ± 10 mm/s and optimal high speed was 100 ± 10 mm/s. Optimal cannula rotation speed range was 15–25 rev/s. In order to avoid seed jam in the cartridge, optimal speed for pushing seed out of the cartridge was 2–5 mm/s. Conclusion: Optimal parameters were programmed in the EUCLIDIAN configuration files. Seed deposition techniques have significant influence on reduction of insertion force, needle deflection and seed deposition accuracy. Future investigation will be on adaptive parameter tuning for specific clinical encounters. Acknowledgement: Supported by NCI‐R01‐CA091763.

A multimodal sono-contrast NIR spectroscopy system for breast cancer Diagnosis: System design and safety considerations

This paper presents a novel multimodal imaging system, which combines optical spectroscopy, ultrasonography and acoustic radiation force (ARF) for improving diagnosis of breast cancer based on noninvasive interrogation of vasculature. System design including both hardware and software is described in detail. Patient safety related considerations are also addressed in this paper. Calibrations and tests have been performed accordingly. Based on safety guidelines, the maximum exposure to skin for laser was controlled within 0.2 W·cm−2; exposure from ARF fields were maintained below the FDA diagnostic limit (0.72 W·cm−2), and electrical leakage was controlled below 300 µA. This multimodal system has the potential to improve tumor detection by deploying ARF to produce a measurable difference in the dynamic behavior of the tissue blood supply environment as interrogated by optical spectroscopy, which was demonstrated to be highly diagnostic in a murine tumor model. Pilot clinical study is being carried out.

Hazard analysis of EUCLIDIAN: An image-guided robotic brachytherapy system

Robotic assistance can help clinicians to improve the flexibility of needle insertion and accuracy of seed deposition. However, the robotic platform is a safety critical system for its automated operational mode. Thus, it is important to perform Hazard Identification & Safety Insurance Control (HISIC) for securing the safety of a medical robotic system. In this paper, we have performed HISIC for our robotic platform, called Endo-Uro Computer Lattice for Intratumoral Delivery, Implementation, and Ablation with Nanosensing (ECLIDIAN). The definition and requirements of the system are described by Unified Modeling Language (UML). Failure Mode and Effect Analysis (FMEA) are executed for the principles of HISIC, such as hazard identification, safety insurance control, safety critical limit, monitoring and control. FMEA combined with UML can also be implemented to ensure reliability of the human operation. On the basis of safety control index and fuzzy mathematics, safety effective value is outlined to assess the validity of safety insurance control for robotic system. The above principles and methods are feasible and effective for hazard analysis during the development of the robotic system.

Sono-contrast spectroscopy for breast cancer detection

In a preclinical study, we demonstrated that blood flow and tissue oxygenation could be manipulated by focused ultrasound; the effects of such manipulation were interrogated via optical spectroscopy at wavelengths where oxy- and deoxy-hemoglobin display different extinction properties. We have designed a clinical breast scanner based on these noninvasive techniques. In addition to the focused ultrasound field intersecting with the volume of optical illumination and points of spectral collection, a diagnostic quality breast imaging probe is incorporated into the scanhead to achieve image guidance. Experimental confirmation of the system performance of the focused ultrasound field properties, diagnostic imaging capabilities and NIR spectroscopy subsystem has been carried out to demonstrate readiness for a clinical study involving 200 patients who are scheduled to undergo ultrasound-guided biopsy to rule out breast cancers.

SU‐EE‐A2‐05: Tissue Ablation by Medium Intensity Focused Ultrasound for Breast Cancer Treatment: Preliminary Study

Purpose: Focused ultrasonicradiation is known for its ability to induce thermal effects for therapy deep in tissue without surgical intervention. To design a medium intensity focused ultrasound (MIFU) system with distributed ultrasound transducers for breast cancer therapy, physical properties of the acoustic field must be fully characterized. Method and Materials: Custom made ultrasound transducers and driving system were calibrated with 1MHz sine wave input (1mW power). Calibrated gain of RF amplifier was utilized for ultrasound power control. Numerical simulation of the ultrasoundradiation field was carried out with Rayleigh‐Sommerfold integral. The mathematical model for simulation was verified by measuring the acoustic output with a hydrophone. Heat distribution model was established based on the simulated ultrasound field. The heating experiment was implemented under different control strategies (duty cycle, pulse repetition) with tissue‐mimicking phantoms (12W each transducer) and animal tissue phantoms (20W each transducer).Results: The output power for MIFU can be controlled accurately with calibration of ultrasound driving system. The focal length of the transducer was found to be 6.9cm with resonance frequency 1MHz. At −6dB focal zone, the beam width was 0.3cm and the focal zone depth was about 3cm. The mathematical model of the ultrasound field was quite comparable with the measured results. In the simulation of ultrasound fields generated by two orthogonal transducers, the area of −6dB focal zone was 6mm×6mm. The mathematical model of thermal field distribution was verified with heating experiment. The temperature of the target point rose up to 65°C from ambient temperature within 3 minutes of sonication. Significant lesion was visible in the tissue ablation experiment. Conclusion: From the mathematical model and experimental results, it appears that MIFU can potentially be used for soft tissue ablation such as treating breast cancer with better skin sparing. Acknowledgement: Supported by NCI‐R33‐CA107860.

SU‐GG‐I‐166: Design and Evaluation of an Optical Tactile Imaging Device for Tumor Detection

Purpose: To present a novel tactile imagingdevice for cancer detection. Method and Materials: Unlike traditional tactile devices, which are formed of pressuresensor array, this new device uses an optical waveguide and total internal reflection principle to maximize the tactile resolution. In order to emulate the detection range of the human tactile sensation, a multi‐layer polydimethylsiloxane waveguide has been fabricated as a sensing probe. The elastic modulus of each layer has been matched to the dermis, epidermis, and subcutaneous of the human finger. The light is illuminated under the critical angle for full reflection within the waveguide. When a waveguide is compressed by an object, the contact area of the waveguide deforms, which causes the light to scatter. The scattered light is then captured by a high resolution camera. The applied forces can be detected by measuring changes in the amount of diffused light. To test the performance of the proposed device, a realistic tissue phantom with hard inclusions is developed. Total of nine inclusions with different diameters and depth were placed in the phantom. We estimated the diameter and the depth of the inclusions with the tactile imagingdevice. We also performed experiments using the mice with globus tumors. We grew three different sizes of tumors and imaged them using the proposed device.Results: The result showed that the proposed sensor can estimate the inclusion diameter within 4.09% and the inclusion depth within 7.55%. The mice test results show that the proposed device successfully detects the tumors. In the animal study, the sensor detected a subsurface tumor as small as 2.74 mm. Conclusion: A novel tactile imagingdevice for tumor identification has been designed and experimentally evaluated to be effective.

Investigation of acoustic radiation force for radio-protecting normal tissues during radiation therapy

Radiation therapy (radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to erradicate malignant cells. Normal tissue tolerance is currently a major dose-limiting factor. As molecular oxygen plays a critical role in creating the radiation damage, we propose a novel approach, that is, the use of acoustic radiation force (ARF) to suppress the normal tissue oxygenation, for the purpose of protecting the normal tissue and increasing its tolerance during radiotherapy. This paper investigated the effects of ARF on tissue oxygenation. Both subcutaneous tissue and tumor were studied for comparison. Experiments have been carried out using a murine model. Preliminary results showed that ARF can effectively suppress normal tissue oxygenation, and at the same time had negligible effect on the tumor oxygenation. Further investigation is ongoing to characterize the time course of oxygen changes with different ultrasound parameters (frequency, intensity, ultrasound pulse duration, etc.), for the purpose of optimal control of tissue oxygenation.