Microsulis pMTA Case Study

Introduction

Talking through use of the device in a CT Suite Environment. The Microsulis pMTA is a Microwave ablation device. Interventional radiologists use it to control local tumours by volume ablation in the liver, lung, bone, kidney and any other sites. The device consists of a trolley-mounted microwave generator and local cooling station (LCS) that delivers microwave energy through a 1.8mm close-cooled needle. Runfold Medical was approached by Microsulis to help develop a laboratory prototype into a production-ready medical device with regulatory approvals

Phase 0: November 2007

Solid state microwave source (left) compared with Sulis V unit (right). To understand the product fully, its design requirements and risk assessment, we undertook a feasibility study. Initially, this was to determine the suitability of the existing Sulis V microwave generator for the new product, and to establish if we could meet the cooling requirements for the product. We also carried out studies with potential end users at Basingstoke hospital to help us fully understand their product requirements.

Phase 1: February 2008

Complete System Concept Using Exisiting Sulis V Unit Based on the feasibility and end user study, and an extensive set of product requirements we proposed a number of concept designs. At this stage, we kept the concepts very open to encourage debate and explore potential areas for product innovation - including a complete re-design of the microwave ablation system. We also drew up concepts to show the pMTA as an add-on to the existing system.

Phase 2: September 2008

Alongside concept development, we engineered a suitable disposable pump and pump drive mechanism. This compact reciprocating pump could pump over six litres per hour at pressures of up to 8 Bar, and we designed and manufactured a prototype tool for the disposable pump head in eight weeks.

We also manufactured proof-of-concept prototypes for both the Local Cooling Station and Applicator. Taking the original applicator design developed by Bath University we also manufactured a small number of prototype applicator devices.

Applicator Handle Concept. Alongside this, we developed a functional prototype LCS, and refined the positive displacement pump into a robust pump drive unit.

Early prototype manufacture allowed a greater understanding of the complexities of manufacture for the applicator, as well as providing important opportunities for the client to demonstrate a working product. These prototypes were used commercially to demonstrate to investors and gauge interest within the radiology community.

Phase 3: January 2009

FiniteElementAnalysisOfDisposablePumpHead

We completely re-designed the LCS and Applicator proof-of-concept prototypes in very tight timescales. Taking into account user feedback on the prototype applicators, we developed a new more ergonomic and simpler to manufacture design and used injection moulded parts to develop a custom waterproof housing for the microwave components.

This new design incorporated a right-angled handle, essential for use with CT gantries.

Prototpye pump drive units undergoing 14 week life testing.

Simplifying the LCS allowed for a dramatic reduction in size, while combining the electrical and mechanical connections into a simple twist cartridge design also improved device usability.

The complete pMTA system includes a modified Sulis V Microwave generator, a local cooling station, and a disposable applicator. At this stage we implemented a design freeze to keep a tight control of any changes as the product was finalised.

Phase 4: August 2009

1st Generation prototype applicator.

We tested safety, functionality and reliability of the LCS extensively to verify the design met the product requirements. This included 60601 electrical safety and EMC testing. We applied the same process to the applicator with the added complexity of sterilisation validation.

We focused all verification testing on proving equivalence to a predicate device. Some minor modifications and improvements were necessary to both the Applicator and LCS, and we achieved these without delay to the project milestones.

For the Applicator and LCS, design verification involves a large range of requirements including;

Final Design1

Performance, Safety, Regulatory, Sterility and Reliability. We had to manage all of these and cross-reference them to the risk management plan - a process that we started at the concept stage of the project.
These tests and their corresponding reports form the basis of the regulatory submission - in this case for both CE submission and FDA approval.

October 2009

The pMTA project achieved its first regulatory submissions less than two years after the initial feasibility study.

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