Design and evaluation of a pneumatic actuation unit for a wasp-inspired self-propelled needle.

Transperineal laser ablation is a minimally invasive thermo-ablative treatment for prostate cancer that requires the insertion of a needle for accurate optical fiber positioning. Needle insertion in soft tissues may cause tissue motion and deformation, resulting in tissue damage and needle positioning errors. In this study, we present a wasp-inspired self-propelled needle that uses pneumatic actuation to move forward with zero external push force, thus avoiding large tissue motion and deformation. The needle consists of six parallel 0.25-mm diameter Nitinol rods driven by a pneumatic actuation system. The pneumatic actuation system consists of Magnetic Resonance (MR) safe 3D-printed parts and off-the-shelf plastic screws. A self-propelled motion is achieved by advancing the needle segments one by one, followed by retracting them simultaneously. The advancing needle segment has to overcome a cutting and friction force, while the stationary needle segments experience a friction force in the opposite direction. The needle self-propels through the tissue when the friction force of the five stationary needle segments overcomes the sum of the friction and cutting forces of the advancing needle segment. We evaluated the prototype's performance in 10-wt% gelatin phantoms and ex vivo porcine liver tissue inside a preclinical Magnetic Resonance Imaging (MRI) scanner in terms of the slip ratio of the needle with respect to the phantom or liver tissue. Our results demonstrated that the needle was able to self-propel through the phantom and liver tissue with slip ratios of 0.912-0.955 and 0.88, respectively. The prototype is a promising step toward the development of self-propelled needles for MRI-guided transperineal laser ablation as a method to treat prostate cancer.

Therapeutic prostate cancer interventions: a systematic review on pubic arch interference and needle positioning errors.

INTRODUCTION: This study focuses on the quantification of and current guidelines on the hazards related to needle positioning in prostate cancer treatment: (1) access restrictions to the prostate gland by the pubic arch, so-called Pubic Arch Interference (PAI) and (2) needle positioning errors. Next, we propose solution strategies to mitigate these hazards. METHODS: The literature search was executed in the Embase, Medline ALL, Web of Science Core Collection*, and Cochrane Central Register of Controlled Trials databases. RESULTS: The literature search resulted in 50 included articles. PAI was reported in patients with various prostate volumes. The level of reported PAI varied between 0 and 22.3 mm, depending on the patient's position and the measuring method. Low-Dose-Rate Brachytherapy induced the largest reported misplacement errors, especially in the cranio-caudal direction (up to 10 mm) and the largest displacement errors were reported for High-Dose-Rate Brachytherapy in the cranio-caudal direction (up to 47 mm), generally increasing over time. CONCLUSIONS: Current clinical guidelines related to prostate volume, needle positioning accuracy, and maximum allowable PAI are ambiguous, and compliance in the clinical setting differs between institutions. Solutions, such as steerable needles, assist in mitigating the hazards and potentially allow the physician to proceed with the procedure.This systematic review was performed in accordance with the PRISMA guidelines. The review was registered at Protocols.io (DOI: dx.doi.org/10.17504/protocols.io.6qpvr89eplmk/v1).

Bioinspired medical needles: a review of the scientific literature.

Needles are commonly used in medical procedures. However, current needle designs have some disadvantages. Therefore, a new generation of hypodermic needles and microneedle patches drawing inspiration from mechanisms found in nature (i.e. bioinspiration) is being developed. In this systematic review, 80 articles were retrieved from Scopus, Web of Science, and PubMed and classified based on the strategies for needle-tissue interaction and propulsion of the needle. The needle-tissue interaction was modified to reduce grip for smooth needle insertion or enlarge grip to resist needle retraction. The reduction of grip can be achieved passively through form modification and actively through translation and rotation of the needle. To enlarge grip, interlocking with the tissue, sucking the tissue, and adhering to the tissue were identified as strategies. Needle propelling was modified to ensure stable needle insertion, either through external (i.e. applied to the prepuncturing movement of the needle) or internal (i.e. applied to the postpuncturing movement of the needle) strategies. External strategies include free-hand and guided needle insertion, while friction manipulation of the tissue was found to be an internal strategy. Most needles appear to be using friction reduction strategies and are inserted using a free-hand technique. Furthermore, most needle designs were inspired by insects, specifically parasitoid wasps, honeybees, and mosquitoes. The presented overview and description of the different bioinspired interaction and propulsion strategies provide insight into the current state of bioinspired needles and offer opportunities for medical instrument designers to create a new generation of bioinspired needles.

Design and evaluation of an MRI-ready, self-propelled needle for prostate interventions.

Prostate cancer diagnosis and focal laser ablation treatment both require the insertion of a needle for biopsy and optical fibre positioning. Needle insertion in soft tissues may cause tissue motion and deformation, which can, in turn, result in tissue damage and needle positioning errors. In this study, we present a prototype system making use of a wasp-inspired (bioinspired) self-propelled needle, which is able to move forward with zero external push force, thereby avoiding large tissue motion and deformation. Additionally, the actuation system solely consists of 3D printed parts and is therefore safe to use inside a magnetic resonance imaging (MRI) system. The needle consists of six parallel 0.25-mm diameter Nitinol rods driven by the actuation system. In the prototype, the self-propelled motion is achieved by advancing one needle segment while retracting the others. The advancing needle segment has to overcome a cutting and friction force while the retracting needle segments experience a friction force in the opposite direction. The needle self-propels through the tissue when the friction force of the five retracting needle segments overcomes the sum of the friction and cutting forces of the advancing needle segment. We tested the performance of the prototype in ex vivo human prostate tissue inside a preclinical MRI system in terms of the slip ratio of the needle with respect to the prostate tissue. The results showed that the needle was visible in MR images and that the needle was able to self-propel through the tissue with a slip ratio in the range of 0.78-0.95. The prototype is a step toward self-propelled needles for MRI-guided transperineal laser ablation as a method to treat prostate cancer.

Focal therapy for localized cancer: a patent review.

INTRODUCTION: Conventional cancer treatments such as radical surgery and systemic therapy targeting the organ or organ system might have side effects because of damage to the surrounding tissue. For this reason, there is a need for new instruments that focally treat cancer. AREAS COVERED: This review provides a comprehensive overview of the patent literature on minimally and noninvasive focal therapy instruments to treat localized cancer. The medical section of the Google Patents database was scanned, and 128 patents on focal therapy instruments published in the last two decades (2000-2021) were retrieved and classified. The classification is based on the treatment target (cancer cell or network of cancer cells), treatment purpose (destroy the cancerous structure or disable its function), and treatment means (energy, matter, or a combination of both). EXPERT OPINION: We found patents describing instruments for all groups, except for the instruments that destroy a cancer cell network structure by applying matter (e.g. particles) to the network. The description of the different treatment types may serve as a source of inspiration for new focal therapy instruments to treat localized cancer.

Design of a Flexible Wasp-Inspired Tissue Transport Mechanism.

Tissue transport is a challenge during Minimally Invasive Surgery (MIS) with the current suction-based instruments as the increasing length and miniaturisation of the outer diameter requires a higher pressure. Inspired by the wasp ovipositor, a slender and bendable organ through which eggs can be transported, a flexible transport mechanism for tissue was developed that does not require a pressure gradient. The flexible shaft of the mechanism consists of ring magnets and cables that can translate in a similar manner as the valves in the wasp ovipositor. The designed transport mechanism was able to transport 10wt% gelatine tissue phantoms with the shaft in straight and curved positions and in vertical orientation against gravity. The transport rate can be increased by increasing the rotational velocity of the cam. A rotational velocity of 25 RPM resulted in a transport rate of 0.8 mm/s and increasing the rotation velocity of the cam to 80 RPM increased the transport rate to 2.3 mm/s though the stroke efficiency decreased by increasing the rotational velocity of the cam. The transport performance of the flexible transport mechanism is promising. This means of transportation could in the future be an alternative for tissue transport during MIS.