The QA process in Radiotherapy

How it develops and the future by Görgen Nilsson, CTO and founder of ScandiDos

When IMRT was introduced in early 2000 it was found that the old routines using machine QA were insufficient to ensure that treatment was delivered as planned. PT-verification was implemented but the systems to run it were slow and not very accurate. The lack of sufficient and efficient QA had a big impact on the implementation of IMRT, especially outside US where reimbursements did not justify the additional time or make it possible with current manpower to implement the film-based and later 2D based QA technology.

When VMAT was introduced in 2008, the situation was much better from a QA perspective. ScandiDos had already introduced Delta4PT, a 3D QA solution. Requirements for accuracy, efficiency and tools to find the cause of discrepancy could now be addressed. Physicists could now be confident in introducing the new therapy safely which made the introduction of the VMAT technique fast. An important part was also the 4D tools that made it possible to quickly find out about the shortcomings in the TPS and improvements could be done by the TPS vendors expediently.

Today, with VMAT treatments continuously increasing, the demand to speed up the patient specific QA process increases. This demand puts a high workload on the physicists who use advanced MU-checks as an alternative to PT-Verification, others simply stop doing patient specific QA or use log files as pseudo-verification. None of those solutions are sufficient and should not have to be used. Independent verification must be used to gain safety and confidence and no one should have to trust solutions with limited accuracy.

Today, several new ideas are competing to verify treatment delivery; EPID based solutions are offered by several vendors. In many of the cases the solution has been to combine with log-file data to complement with time resolved information. Due to rather low investment cost many customers are attracted to begin using EPID and log-file based QA. It is important to understand that log file data is not independent data but rather the feedback data that is used to run the therapy in the first place. EPID based solutions are limited in accuracy and is expected to both miss important errors and to report ghost-errors, especially when delivering VMAT treatments. Several users are concerned about the lifetime of the EPID when used continuously in EPID dosimetry and one publication is specifying a lifetime of 32 months. EPID will thereby become a very expensive solution in the long run.

Even if the above solutions had offered accuracy and been economical, these solutions still don’t offer the time savings that is desired. To save time, you first need to have a solution that only indicates error when there is an error -it has to be a good measurement system. Ghost-errors are very frustrating and cost a lot of valuable time.  When you finally get a correct indication on a real error you have stopped trusting the data you get from the system.  Another factor when talking time and efficiency is the analysis of real errors. You have to find the cause of errors and the measurement solution must have the “toolbox” required to do it. If not, the task becomes very complicated, time becomes a major factor and the pressure to continue to treat is high…

The future is thereby independent and automated verification without compromises on quality!

So, before you decide on how the QA should be done in your clinic make sure you know the difference between QA systems and the benefits the Delta4 Discover can offer to eliminate risk, ensure safety and time savings!

Görgen Nilsson,
CTO ScandiDos AB