Path planning for robot-assisted active flexible needle using improved Rapidly-Exploring Random trees.

In robot-assisted needle-based medical procedures, path planning for a flexible needle is challenging with regard to time consumption and searching robustness for the solution due to the nonholonomic motion of the needle tip and the presence of anatomic obstacles and sensitive organs in the intended needle path. We propose a novel and fast path planning algorithm for a robot-assisted active flexible needle. The algorithm is based on Rapidly-Exploring Random Trees combined with reachability-guided strategy and greedy heuristic strategy. Linear segments are taken into consideration to the paths, and insertion orientations are relaxed by the introduction of the linear segments. The proposed algorithm yields superior results as compared to the commonly used algorithm in terms of computational speed, form of path and robustness of searching ability, which potentially can make it suitable for the real-time intraoperative planning for clinical procedures.

Novel irradiated axial rotational flap model in the rodent.

IMPORTANCE: Patients who require extensive surgical resection of head and neck tumors often have a history of treatment with radiation and chemotherapy. Chemoradiation-induced damage to the skin and soft tissues can cause complications following surgical reconstruction. OBJECTIVE: To design an easily reproducible rodent rotational skin flap and to evaluate the effects of radiation exposure on flap viability. DESIGN AND SETTING: Ten rats at a tertiary university medical center received 40-Gy irradiation to the abdominal wall. Following a recovery period of 1 month, a 3 × 8-cm fasciocutaneous flap based axially on the inferior epigastric vessel was raised and rotated 60° into a contralateral deficit. Five nonirradiated rats underwent the identical procedure as a control. Animals were killed 7 days postoperatively, areas of flap necrosis were documented by an observer blinded to the grouping, and histological specimens were taken to compare flap viability and vessel density. MAIN OUTCOMES AND MEASURES: Flap revascularization and microvascular density. RESULTS: Six of 10 rats in the irradiated group had necrosis of the distal flap ranging from 1 to 6 cm from the distal edge, whereas none of the animals in the control group exhibited necrosis (P < .001). Histologic analysis revealed collagen and vascular changes in the irradiated skin. Vascular density analysis revealed a significant difference between radiated and nonradiated flaps; P = .004, .03, and .01 in the distal, middle, and proximal segments of the flap, respectively. CONCLUSIONS AND RELEVANCE: This novel rat axial rotational flap model demonstrates increased flap necrosis and a decrease in vascular density due to the effects of radiation exposure. With use of a linear electron accelerator, a dose of 40 Gy can be delivered to the skin without resulting in devastating gastrointestinal adverse effects. LEVEL OF EVIDENCE: NA.

Acoustic radiation force and optical spectroscopy for assessing tumor vessel normalization during anti-angiogenic therapy.

Molecular oxygen is the best known mediator of radiation damage during radiation therapy. This paper investigates techniques for enhancing tumor oxygenation by use of anti-angiogenic therapy for better radiosensitivity. A noninvasive monitoring technique, Acoustic radiation force (ARF)-induced optical spectroscopy, was proposed in this paper to track tumor oxygen changes during anti-angiogenic therapy. Male NCR-NUM nude mice bearing human U87 glioblastoma (ATCC) xenografts on the right hind limb were used for the study. An anti-angiogenic regimen using the drug AZD2171 (AsraZeneca) was found capable of improving tissue oxygenation during the first week of drug treatment. The optical spectroscopy technique was shown to be able to track tumor oxygenation changes during anti-angiogenic therapy, as verified by direct pO2 measurement. By using anti-angiogenic therapy to improve tumor oxygenation prior to radiotherapy, tissue oxygenation may be altered in a way that favors radiation therapy.

Geant4 estimation model of high Z atom concentration for tumor vessel ablation.

In our novel technique of tumor vessels treatment, High Z (HZ) contrast atoms are injected into the blood vessel and the tumor region is irradiated with "narrowband" fluorescence photon (FP) beam tuned to the "resonance energies". Theoretically, this technique guarantees a dose 10(2) - 10(3) higher than that achieved in conventional radiation therapy (RT). Meanwhile, this high dose is confined to a region of tens of micrometers. This will minimize the side effects caused by the high dose to the surrounding tissues. The FPs are generated by electrons impinging onto target made of the same material as the HZ contrast. In order to support the experiment, an estimation model has been developed based on Geant4 Monte Carlo (MC) simulation. This model takes into account physical and biological factors, which can be determined separately. In this work, the derivation of the model was described in detail, and four HZ atoms, gadolinium (Gd), platinum (Pt), gold (Au) and uranium (U) were evaluated using the model. The scaling law for the capability to yield FPs from IEs had been deduced for these HZ atoms. The results also showed that the minimum molar concentration required for apoptosis of tumor endothelial cells (ECs) for Gd, Pt, Au and U in normal experimental condition were 220.44 nmol/ml, 55.57 nmol/ml, 49.78 nmol/ml and 9.05 nmol/ml, respectively.

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.

'Smart' needle for percutaneous surgery: influential factor investigation.

Precise needle insertion is important for a number of percutaneous interventions. Yet it is difficult to achieve in practice due to target movement and needle deflection. Preliminary design and simulation of 'Smart Needle' are presented in this paper for active needle steering. This smart needle is designed to use piezoelectric actuators to adjust the needle tip position. Some simulations have been carried out to investigate the influences of the factors, such as input voltage, the length and thickness of the piezoelectric actuators etc. on the produced needle tip deflection. This information is useful in designing an effective smart needle that will need less electrical input in order to achieve certain needle displacement.

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.