Clinical Proof

"Recent publications suggest the clinical benefit of IMRT for a large number of treatment paradigms(¹). It can be expected on the basis of currently available reports that highly conformal radiotherapy as provided by IMRT improves clinical outcome for at least 50 % of all RT patients.

It is the goal of the Department of Radiation Oncology at the University Medical Center Mannheim, University of Heidelberg, to offer all our eligible patients this higher quality of therapy. IMRT was established clinically in early 2002 at our department, and currently all of our 4 LINACs are capable of delivering IMRT treatments. Improved IMRT and particularly the newly available modality VMAT offers the possibility to reduce the delivery times for intensity modulated treatments enormously. Therefore, we have recently clinically introduced the VMAT technology into our clinical routine based on the most advanced Monte-Carlo treatment planning system currently available.

The many dynamical degrees of freedom in VMAT treatments require, however, rigorous machine-related QA and currently still pre-treatment QA that has to be as efficient as possible given the increasing number of patients treated. Since today not only field borders but also delivered dose is mainly defined by a linear accelerator's collimator, the ideal solution, however, is advanced on-line monitoring of the relevant treatment parameters, particularly delivered fluence/dose below the collimator. Therefore, we are currently evaluating the performance of the COMPASS system, first using the MatriXX-based pre-treatment configuration. It has been shown that this system can achieve the necessary precision in plan verification while shortening the time required for pre-treatment QA.

On the basis of these evaluations we are planning to introduce the COMPASS into our clinical routine workflow when the system will be capable of monitoring rotational deliveries in the on-line modality.

COMPASS with Transmission Detector will offer - for the first time ever - an ultimate end-to-end test to independently verify any treatment technique (including complex treatments such as static IMRT/VMAT) on a daily basis and to visualize dosimetric outcome. In its final implementation, this unique QA tool does not require extra pre-treatment QA-time, does not strain on EPIDs and will be usable for every deliverable field including all noncoplanar orientations up to the full deliverable field size on the largest collimators in clinical use (40x40 cm) currently not covered by EPID dosimetry.”

Prof. Dr. Frank Lohr

Universität Heidelberg

Universitätsmedizin Mannheim

(¹) l.Veldeman et al., Lancet Oncology 9,2008 367-375

UMM
Universitätsmedizin Mannheim

"At the Radiotherapy Department of the University Medical Center Groningen we replaced film dosimetry by COMPASS software with MatriXX detector for pre-treatment verification in February 2009. Since the implementation of this unique QA method we clinically verified about 80 patient plans using COMPASS. COMPASS was primarily used for QA of complex IMRT treatment plans for H&N but also in some other cases like sarcomas, carcinomas of the skin and prostate."

All QA results were within clinical criteria which shows that we have a stable linear accelerator, a reliable and well configured TPS and a stable QA system. With COMPASS it was possible to avoid false non passing verifications which appeared in some cases using film and which caused time consuming final verification.

By irradiating QA plans on a regular basis and analyzing them with COMPASS we were able to improve the control of critical IMRT parameters, mainly the MLC calibration. This enables us to apply COMPASS as a pure calculational verification for some routine cases, thus again reducing the time needed for a single patient. An important reason to introduce the calculational verification is to shorten the time until the start of treatment. Moreover, the application of COMPASS measurement based verification for sample patients at various moments in time allows us to further control stability of delivery.

With the increased flexibility in allocation of our physicist´s time, we are now in the process of commissioning the new rotational modality VMAT which will enable us to increase the number of patients treated with modulated modality. We expect COMPASS to play a decisive role in the optimization and verification of VMAT as well."

Erik Korevaar, PhD
Medical Physicist
Department of Radiation Oncology
University Medical Center Groningen
The Netherlands
Tel.: 31 50 36 11 230
Fax: 31 50 36 11 692
E.W.Korevaar(at)rt.umcg.nl