Certification Standards - Using Event-B for Critical Device Software Systems - page 307

A.2.2 IEC 62304—Process Requirements for Medical Device
Software

The IEC 62304 [ 11 ] standard specifies a framework of the life cycle processes for
medical devices, which helps to design a safe system. All necessary requirements
for each life cycle process are provided by the IEC 62304. Life cycle process is
divided into a subset of activities and is controlled by the risk management and
quality management. The risk-management process is defined by the ISO 14971
standard and quality management is defined by the ISO 13485 standards.
The ISO 14971 and ISO 13485 standards [ 18 ] provide risk-based quality man-
agement that determines the required rigour of software quality assurance from the
risk, which appears from a medical device in form of undesired behaviour of the
system. Software can be an important part of a medical device providing safety and
effectiveness of the software-based a medical device requires to fulfil requirements
and to use of software without any risk. When a software is contributing to a haz-
ard, which is determined by hazard identification activity of the risk-management
process. Hazards could be indirectly caused by software, which can be considered
that software is a contributing factor. The use of software to control risk is made
during the risk control activity and risk management process under consideration of
the ISO 14971 and ISO 13485 standards, respectively. The software-development
process consists of a number of activities related to the service or maintenance of a
medical device system, including software updates. All these activities are also con-
sidered as an important task of the software-development process. The IEC 62304
mentions six sub-activities for the architectural design step, which are as follows:
•

Realisation of the requirements

• Interface design

• Specification of functional and non-functional software components

• Specification of the environment of software components

• Partitioning due to the risk mitigation strategy

• Verification of the architecture

The software safety classification ranges from A—no harm or injury—to C—
death or severe injury is possible. The classification defines the principle level of
rigour, and consequently, the efforts to be undertaken, is required for all software
development and maintenance activities [ 10 ]. The IEC 62304 standards provide
assurance for medical software system and guarantees that the software does not
contribute to hazardous failure of the system due to its systematic safety-oriented
process and implementation of the functional requirements are performed carefully
for the required activities. The requirement analysis, architecture, design, imple-
mentation and integration are main phases of the development process for handling
the complexity of a system. Each phase of the development process is controlled
by the IEC 62304, which recommends activities to plan, track, control and com-
municate possible problems to prevent the risk of systematic errors. The complete
process development with risk management for a medical device is described in [ 8 ,
11 ].