Medical Verification and Validation of PT systems



Regulations and standards for medical devices are of particularly importance when system software is concerned. Cosylab is a specialist in the medical verification and validation process.



The particle systems for which Cosylab offers products, services and solutions are very software-intensive. It is known that software is very different in nature and behavior from hardware. Even complex digital hardware systems (composed of discrete logic) are not comparable to software. The two main reasons for this are 1. the complexity of software, with its enormous number of possible internal states, and 2. the common software development process, which is more flexible and less constrained than hardware design. The first factor determines that it is practically impossible to test a software module in all its internal states, leaving room for latent bugs. The second factor also influences reliability.

The nature of software allows for late changes, changes that can introduce unnoticed side effects. So there is a risk of overconfidence on the side of inexperienced software teams near the end of the project. If these two aspects are not addressed properly, software cannot be considered reliable enough for medical devices, especially when there is a risk to people associated with it.

That’s why the regulations and standards for medical devices take special care of software: to ensure that, although the possibility of bugs cannot be totally eliminated, their probability can be reduced and its associated risk mitigated; with good processes, proper testing, risk management and validation. There is an international standard that deals with this: “IEC62304: Medical device software -- Software life cycle processes.”


When software quality is in an organization’s DNA, applying medical processes is a natural as breathing. Cosylab has made medical processes second nature

 

Software cannot exist without the associated hardware, and its proper operation in the context of the whole system cannot be judged without testing them together. Yet, in a system that is as complex as a Particle Therapy System, there are many different subsystems or components that may contain software, and it is impractical or impossible to execute the full set of tests for every software module, all integrated and operating in the final machine. That is why this is never done in that way, and there is always a strategy to hierarchize and segregate testing into different levels, according to the system level architecture and the “V-model”, in order to make testing effective and practicable. This is the purpose of the set of activities usually referred to as “Verification and Validation”: to Verify, at different system levels, that the build system works as specified, and to Validate that it is capable of fulfilling its intended purpose. More about verification and validation of Programmable Electrical Medical Systems can be found in the standard IEC60601-1, section 14, and informative annex H.


Cosylab offers a wide range of V&V related services: