I Q M - Integral Quality Monitor
I Q M: Simplicity and Design
The IQM is a transmission detector fixed to the Linac gantry for continous dose measurements during patient treatment. The wedge-shaped ion chamber detector design is based on an idea by Canadian physicists in the year 2002.
IQM as transmission detector although appears to belongs to the same class of devices as PTW DAVID, IBA Dolphin and ScandiDos Discover, but with a stringent simplicity designed for long term undisturbed operation. All detector sytems mentioned are based on continuous check principle i.e comparing actual measurements with a reference data set.
The first device introduced to the market was PTW DAVID in 2005, as a battery operated ion chamber device with wireless Bluetooth connection. The idea was born in Germany as cooperation of 2 university hospitals in Oldenburg and Goettingen. IQM however was planned to come with more sophisticated software, running in the background, for fast treatment error detetction and treatment reporting - this allows a double check mechanism on a continuous basis.
IQM is a compact device, lightweight and robust and does not need user attention as the software runs automatically in the background. So it is ideal for high volume patient treatments, typically in hospitals as in India.
dose.point has now developed eight (8) reference customers with orders from Asia Pacific region. This first level installations shall further allow research cooperation with iRT from our leading therapy providers in Japan, Korea and India. These KOL centers shall contribute with their long term experience to the ongoing IQM product improvements and further development.
IQM has been in R&D over the past 14 years. IQM is an ideal device for the state-of-the-art, yet safe, treatment some 10 yars ago, as the simple detector design was sufficient for the coarse Linac beam shaping mechanics at that time. The idea was to have a device which is able to stop the irraditaion in case of detected error.
Now we are in 2016, and the beam delivery has improved dramatically with huge improvements in the delivery systems. Currently the IQM is manufactured with year 2002 detector layout on current highly dynamic treatment methods of 2016 and beyond. IQM might face competition with established and experienced dosimetry companies, and also Varian and Elekta, offering their own dose monitoring solution based on EPIDs.
For the sake of good order to understand EPID systems –please note the Detector systems with multiple detectors (as spin-offs from 2D-Arrays) offer much better resolution. The vast improvement in CPU speed allows fast error detection as well. However: the detectors mounted to the Linac collimator are bulky, heavy and with shorter time on battery power, and EPID based systems are complex due to the high radiation load on semiconductor detectors. Array detectors with some 1500 and more detectors even allow dose reconstructions as additional benefit, but need skilled personnel and QA on its own.
IQM is, however, going the simple way:
Modern Linacs a complex machines and driven by sophisticated software including self test routines, making the beam delivery more reliable and safe. In particular for ARC treatments the linacs deliver beams in flexible patterns assuring correct dosage at the end of each treatment fraction. As a consequence there is no static reference data set available, which in particular is a challenge for simple detector systems as IQM. For modern treatment methods using thin MLC with high resolution movement for optimized tumor shaping the IQM detector designs requires special software for data processing, as the big ion chamber can not distinguish between field size, field shape, field position and dose rate variations. But due to chamber volume and integration time the dose measurement is highly precise, which is a main benefit.
For all Systems on the market there is the benchmark for high true irradiation error detetction. But there is another i.e : the capability for avoiding false negative and false positive alarms. In the first case true errors are not detected, in the 2nd a correct beam delivery is detected as wrong. The 2nd case is disturbing, as it shows linac malfunctions which in reality are not.
In order to make the IQM detector capable of reliable error detection on modern Linacs there are ongoing software development tasks since a couple of months. It looks as the software complexity is increasing in order to cover all cases for all treatment approaches on all tumor types with all required software settings. IQM software might require similar to linac manufacturers safety and performance software updates/upgrades, as they are expected to be installed during remote linac service and maintenance criteria.
The IQM principle is a great idea, that requires further data for its proven clinical use. In daily operation the system has to run some 16 hours with a plurality of completely different treatment cases.
The software, developed by experts in the Toronto Princess Margarete Cancer Center, should certainly allow solution in accordance with clinical requirements.
Summary:
In conclusion educating our customers : Together with IQM, DAVID, DOLPHIN and Discover there are increasing solutions emerging for fast treatment verifications possible. The EPID based solutions from Varian and Elekta as mentioned above, and pure software solutions based on dynamic log file analysis as Qualiformed LinacWatch. So there is a bundle of options with different technical approaches for customers, from pure error detection up to 3D/4D dose reconstruction after each delivered fraction.
IQM is an elegant and simple device, which does not require any user interaction. The publications for pre-clinical tests show promising results, and pending continued software improvements in order to make IQM fit for daily clinical use.
Accordingly, our eight (8) leading Asia Pacific hospitals as Reference Hospitals will thus contribute to the perfectioning of IQM hardware and software to a easy-to-use solution. The IQM for Japan was installed end of May, 7 more IQM pending for Korea and India. One more project in Hongkong for installation end of 2016, and 3 systems have arrived already in Australia.
dose.point Asia Pacific is based in Singapore and exclusive representation for iRT in all AP countries without China, so Australia, Japan, Korea, India, Hong Kong, Taiwan, Thailand and more.