Question

A safety-critical software system for treating cancer patients has two principal components: A radiation therapy machine that delivers controlled doses of radiation to tumour sites. This machine is controlled by an embedded software system. A treatment database that includes details of the treatment given to each patient. Treatment requirements are entered in this database and are automatically downloaded to the radiation therapy machine. Identify three hazards that may arise in this system. For each hazard, suggest a defensive requirement that will reduce the probability that these hazards will result in an accident. Explain why your suggested defence is likely to reduce the risk associated with the hazard.

Short answer

Implement verification systems, strong authentication, and data synchronization to mitigate risks.

Step-by-step solution

Identify Hazard 1

One hazard could be an incorrect dosage of radiation being administered to a patient due to software malfunction or input error. If the software miscalculates the dosage, it can endanger the patient's health by administering too much or too little radiation.

Defensive Requirement for Hazard 1

Implement a secondary verification system that cross-checks the input dosage with a set of standard values before the machine administers radiation. This secondary check would require approvals from multiple sources (e.g., a healthcare professional) to ensure the dosage is safe.

Reason Behind Defensive Requirement 1

By having an independent verification system that requires manual approval, the likelihood of a wrong dosage being administered is reduced, decreasing the risk of harm due to software errors or data entry mistakes.

Identify Hazard 2

Another hazard could be unauthorized access to the treatment database, which may lead to manipulation or deletion of critical treatment information.

Defensive Requirement for Hazard 2

Implement strong user authentication protocols, including biometric verification and a multi-factor authentication (MFA) system, to ensure that only authorized personnel can access the database.

Reason Behind Defensive Requirement 2

Strong authentication measures significantly reduce the risk of unauthorized access, thereby protecting the integrity of patient treatment data and preventing data loss or alteration.

Identify Hazard 3

A third hazard might be the failure to update the treatment database with the latest patient information due to a data transmission error or delay.

Defensive Requirement for Hazard 3

Introduce a data synchronization protocol that automatically checks and re-transmits data at regular intervals to ensure the treatment database is always updated with the most current information.

Reason Behind Defensive Requirement 3

By having a mechanism that ensures data is consistently synchronized, the risk of administering outdated treatment protocols is minimized, safeguarding against potential treatment errors.

Key concepts

Radiation Therapy Machines

Radiation therapy machines are pivotal in cancer treatment as they precisely deliver radiation to targeted tumor areas. These machines play a crucial role in treating patients by damaging the DNA of cancer cells, slowing their growth or killing them. The precision required in this process makes these machines safety-critical, as any deviation in the dosage can lead to severe consequences for patients. To maintain accuracy, these machines are controlled by sophisticated systems that ensure the correct amount of radiation is used. Regular maintenance and thorough checks are essential to ensure optimal functioning and patient safety.

Embedded Software Systems

Embedded software systems are at the heart of modern radiation therapy machines, managing their operations. These are complex programs embedded within the machine hardware, tasked with controlling the dose, timing, and targeting of radiation beams. They must operate with high reliability and accuracy to prevent any misadministration of radiation. A malfunction in the software could lead to serious patient harm, such as overdose or underdose of radiation. Therefore, software testing, validation, and periodic updates are crucial to maintain safety and efficacy in such critical environments.

Treatment Databases

Treatment databases are essential components in radiation therapy as they hold detailed patient treatment information. These databases store data such as treatment plans, administered doses, and patient progress notes. The data is automatically downloaded to radiation machines to ensure treatments are personalized and precise. To maintain data integrity, these databases should employ robust security measures, such as encryption and regular backups. This prevents data loss and ensures that treatment regimens reflect the most current patient information, avoiding errors in ongoing cancer treatments.

Hazard Identification

Hazard identification is a crucial process in developing safety-critical systems like radiation therapy machines. It involves recognizing potential risks that could lead to safety incidents, such as incorrect dosage calculations or data breaches. Thorough hazard analysis helps in pinpointing vulnerabilities within the system, allowing for the design and implementation of mitigation strategies. Regular hazard assessments ensure that emerging risks, as well as existing ones, are continuously managed, therefore keeping patient safety as a top priority. This proactive approach helps in averting costly and harmful accidents in medical settings.

Defensive Requirements

Defensive requirements are protective measures integrated into systems to counteract identified hazards. In the context of radiation therapy, these include mechanisms such as redundancy checks, secure authentication protocols, and data synchronization processes. Each defensive measure targets a specific hazard, reducing the chances of its occurrence. For instance, implementing multi-factor authentication can prevent unauthorized access, while regular data synchronization ensures accuracy in treatment records. By designing systems with these safeguards, risks are minimized, ensuring high reliability and safety in critical medical procedures.