A medical instrument has a set of opposing jaws that can be articulated, both left and right, from centerline. The instrument has a proper bend radius and support for the jaw actuation member and cutter driving member. The bendable support for the drive members comprises tightly wound coil springs. Another embodiment of the invention controls the degree of articulation at the handle of the laparoscopic instrument. A further embodiment of the invention incorporates a locking mechanism to prevent motion of the wrist while the user performs other operations on the device. The locking mechanism also includes an indexing feature with which the user can index and choose the necessary amount of angle between preset angles.

Method and apparatus for articulating the wrist of a laparoscopic grasping instrument

Methods and apparatus are provided for non-continuous circumferential treatment of a body lumen. Apparatus may be positioned within a body lumen of a patient and may deliver energy at a first lengthwise and angular position to create a less-than-full circumferential treatment zone at the first position. The apparatus also may deliver energy at one or more additional lengthwise and angular positions within the body lumen to create less-than-full circumferential treatment zone(s) at the one or more additional positions that are offset lengthwise and angularly from the first treatment zone. Superimposition of the first treatment zone and the one or more additional treatment zones defines a non-continuous circumferential treatment zone without formation of a continuous circumferential lesion. Various embodiments of methods and apparatus for achieving such non-continuous circumferential treatment are provided.

Methods and apparatus for performing a non-continuous circumferential treatment to a body lumen

A system and method for heat ablation of tissue in which energy is sequentially applied to at least two electrodes inserted into tissue. The system is comprised of a radiofrequency (RF) source for supplying RF energy, at least two electrodes configured to apply RF energy to tissue, at least one return electrode for returning the RF energy to the RF source, and a controller configured to sequentially apply the RF energy to each of the at least two electrodes. The sequential delivery of energy is determined by the measured current and voltage, the calculated impedance at each of the electrodes and the timing for each electrode. An internal load may be activated with the previously activated channel and remain on until the next channel is activated to avoid the generator from having an open circuit.

Electrosurgical system employing multiple electrodes and method thereof

Radiofrequency ablation is an interventional technique that in recent years has come to be employed in very different medical fields, such as the elimination of cardiac arrhythmias or the destruction of tumors in different locations. In order to investigate and develop new techniques, and also to improve those currently employed, theoretical models and computer simulations are a powerful tool since they provide vital information on the electrical and thermal behavior of ablation rapidly and at low cost. In the future they could even help to plan individual treatment for each patient. This review analyzes the state-of-the-art in theoretical modeling as applied to the study of radiofrequency ablation techniques. Firstly, it describes the most important issues involved in this methodology, including the experimental validation. Secondly, it points out the present limitations, especially those related to the lack of an accurate characterization of the biological tissues. After analyzing the current and future benefits of this technique it finally suggests future lines and trends in the research of this area.

https://link.springer.com/content/pdf/10.1186%2F1475-925X-5-24.pdf

Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future.

Superparamagnetic nanoparticles (SPIONs) could enable cancer theranostics if magnetic resonance imaging (MRI) and magnetic hyperthermia treatment (MHT) were combined. However, the particle size of SPIONs is smaller than the pores of fenestrated capillaries in normal tissues because superparamagnetism is expressed only at a particle size <10 nm. Therefore, SPIONs leak from the capillaries of normal tissues, resulting in low accumulation in tumors. Furthermore, MHT studies have been conducted in an impractical way: direct injection of magnetic materials into tumor and application of hazardous alternating current (AC) magnetic fields. To accomplish effective enhancement of MRI contrast agents in tumors and inhibition of tumor growth by MHT with intravenous injection and a safe AC magnetic field, we clustered SPIONs not only to prevent their leakage from fenestrated capillaries in normal tissues, but also for increasing their relaxivity and the specific absorption rate. We modified the clusters with folic acid (FA) and polyethylene glycol (PEG) to promote their accumulation in tumors. SPION clustering and cluster modification with FA and PEG were achieved simultaneously via the thiol-ene click reaction. Twenty-four hours after intravenous injection of FA- and PEG-modified SPION nanoclusters (FA-PEG-SPION NCs), they accumulated locally in cancer (not necrotic) tissues within the tumor and enhanced the MRI contrast. Furthermore, 24 h after intravenous injection of the NCs, the mice were placed in an AC magnetic field with H = 8 kA/m and f = 230 kHz (Hf = 1.8×10(9) A/m∙s) for 20 min. The tumors of the mice underwent local heating by application of an AC magnetic field. The temperature of the tumor was higher than the surrounding tissues by ≈6°C at 20 min after treatment. Thirty-five days after treatment, the tumor volume of treated mice was one-tenth that of the control mice. Furthermore, the treated mice were alive after 12 weeks; control mice died up to 8 weeks after treatment.

/pdf/superparamagnetic-nanoparticle-clusters-for-cancer-5avr7y50v9.pdf

Superparamagnetic nanoparticle clusters for cancer theranostics combining magnetic resonance imaging and hyperthermia treatment.

We measured the ex vivo electrical conductivity of eight human metastatic liver tumours and six normal liver tissue samples from six patients using the four electrode method over the frequency range 10 Hz to 1 MHz. In addition, in a single patient we measured the electrical conductivity before and after the thermal ablation of normal and tumour tissue. The average conductivity of tumour tissue was significantly higher than normal tissue over the entire frequency range (from 4.11 versus 0.75 mS cm−1 at 10 Hz, to 5.33 versus 2.88 mS cm−1 at 1 MHz). We found no significant correlation between tumour size and measured electrical conductivity. While before ablation tumour tissue had considerably higher conductivity than normal tissue, the two had similar conductivity throughout the frequency range after ablation. Tumour tissue conductivity changed by +25% and −7% at 10 Hz and 1 MHz after ablation (0.23–0.29 at 10 Hz, and 0.43–0.40 at 1 MHz), while normal tissue conductivity increased by +270% and +10% at 10 Hz and 1 MHz (0.09–0.32 at 10 Hz and 0.37–0.41 at 1 MHz). These data can potentially be used to differentiate tumour from normal tissue diagnostically.

/pdf/electrical-conductivity-measurement-of-excised-human-3qahz00wsj.pdf

Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation

Purpose: Finite element method (FEM) models are commonly used to simulate radio frequency (RF) tumor ablation. Prior FEM models of RF ablation have either ignored the temperature dependent effect of microvascular perfusion, or implemented the effect using simplified algorithms to reduce computational complexity. In this FEM modeling study, the authors compared the effect of different microvascular perfusion algorithms on ablation zone dimensions with two commercial RF electrodes in hepatic tissue. They also examine the effect of tissue type and inter-patient variation of perfusion on ablation zone dimensions. Methods and Materials: The authors created FEM models of an internally cooled and multi-tined expandable electrode. RF voltage was applied to both electrodes (for 12 or 15 min, respectively) such that the maximum temperature in the model was 105 °C. Temperature dependent microvascular perfusion was implemented using three previously reported methodologies: cessation above 60 °C, a standard first-order Arrhenius model with decreasing perfusion with increasing degree of vascular stasis, and an Arrhenius model that included the effects of increasing perfusion at the ablation zone boundary due to hyperemia. To examine the effects of interpatient variation, simulations were performed with base line and ±1 standard deviation values of perfusion. The base line perfusion was also varied to simulate the difference between normal and cirrhotic liver tissue. Results: The ablation zone volumes with the cessation above 60 °C perfusion algorithm and with the more complex Arrhenius model were up to 70% and 25% smaller, respectively, compared to the standard Arrhenius model. Ablation zone volumes were up to ∼175% and ∼100% different between the simulations where −1 and +1 standard deviation values of perfusion were used in normal and cirrhotic liver tissue, respectively. Conclusions: The choice of microvascular perfusion algorithm has significant effects on final ablation zone dimensions in FEM models of RF ablation. The authors also found that both interpatient variation in base line tissue perfusion and the reduction in perfusion due to cirrhosis have considerable effect on ablation zone dimensions.

/pdf/effects-of-variation-in-perfusion-rates-and-of-perfusion-47vtg26ng7.pdf

Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation

Three methods of creating large thermal lesions with cool-tip cluster electrodes were compared. Three cluster electrodes were arranged 4 cm apart in a triangular array. Eight lesions were created ex vivo in fresh bovine liver (from a butcher) with each method: sequential ablation (three electrodes, 12 minutes each); simultaneous activation of electrodes (12 minutes); and rapid switching of power between electrodes (12 minutes), for which an electronic computer-controlled switch was developed. For sequential, rapid switching, and simultaneous methods, lesion volumes were 137.5 cm3± 22.2, 116.4 cm3± 15.2, and 22.3 cm3± 6.4 (P < .05), respectively, and final temperatures at lesion center were 80°C ± 5, 97°C ± 8, and 41°C ± 3 (P < .001), respectively. Because of electrical interference between electrodes, simultaneous method led to little heating at the center between the electrodes and created small discontinuous lesions. Rapid switching created large round lesions by employing multiple electrodes concurrent...

Large-volume radiofrequency ablation of ex vivo bovine liver with multiple cooled cluster electrodes.

In vitro measurements of temperature-dependent specific heat of liver tissue.

A method, a system and an electrode array for radio frequency ablation. The electrode array allows for rapid ablation of a strip of tissue in an organ providing a barrier to blood loss during resection operations. The electrode array (10) comprises a set of elongate electrodes (14) for insertion through tissue of an organ and a holder (12) positioning the electrodes-with respect to each other to define a surface (18) partitioning the organ (22) whereby a partition of ablated tissue may be created across an organ to reduce blood loss during resection of a portion of the organ on one side of the partition.

David J. Schutt

Papers

Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation

Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation

Large-volume radiofrequency ablation of ex vivo bovine liver with multiple cooled cluster electrodes.

In vitro measurements of temperature-dependent specific heat of liver tissue.

Electrode array for tissue ablation