Volume 34, Issue 6, June 2007
Index of content:
- Therapy Continuing Education Course: Room M100E
- CE‐Therapy: Quality Assurance for Advanced RT Technologies: The Challenge for Clinical RT Trials
TH‐A‐M100E‐01: Introduction To: Quality Assurance for Advanced RT Technologies‐The Challenge for RT Clinical Trials34(2007); http://dx.doi.org/10.1118/1.2761615View Description Hide Description
We as medical physicists have a crucial role to play in ensuring that all patients on radiotherapy protocols are treated comparably. Without this comparability, the validity of outcome results from the pooled patient data may be jeopardized. Advances in radiation therapy technology and delivery techniques have naturally led to the desire to incorporate such new tools into clinical trials, yet standardized quality assurance (QA) procedures are not fully developed and widely practiced. Although several task groups within the AAPM have been formed to set standards for QA for these new technologies, a major challenge is to conduct clinical trials that involve both the old and new technologies without overwhelming individual physicists with additional testing. National and international multi‐institutional clinical trials uniquely challenge the medical physics community to maintain comparability while at the same time requiring or permitting patient treatments that incorporate advanced technologies such as IMRT, image guided radiotherapy,imagefusion, and other techniques.
The AAPM Working Group on Clinical Trials presents this continuing education symposium in order to discuss the efforts underway to design QA methods for advanced radiotherapy technologies especially in the context of clinical trials with the intent to address the issue of comparability and standardization of protocol data. We will present the work of Task Group 113, an important player in these efforts, on providing guidance as to physics practice standards for QA for radiotherapy clinical trials. The task group's recommendations on QA procedures and reporting methods are intended to facilitate highly consistent protocol treatments and data submission.
The Working Group on clinical trials has identified several topics that pose significant challenges with respect to consistency of physics practices: dose calculations with heterogeneity corrections, localization verification, imagefusion techniques, and the treatment of moving targets. In this course, the history and the current state of the art will be described for each topic. The discussion about these areas should be of interest whether or not one is involved in clinical trials.
Learning objectives for the entire CE course:
1. Understand the quality assurance issues facing Medical Physicists using advanced technologies and how these relate to clinical trial data validity.
2. Learn what Task Group 113 is doing to address the accuracy and consistency of data we send to quality assurance review centers.
3. Understand the problems and potential solutions to controversies in quality assurance measures for imagefusion, target motion, patient localization, and heterogeneity corrections.
34(2007); http://dx.doi.org/10.1118/1.2761616View Description Hide Description
Imaging studies acquired at multiple times and using different modalities are important components to many clinical trials. Imaging is used for staging and protocol eligibility, for radiation therapy target definition, for adaptive radiation treatmentdelivery, for assessing response to therapy, and for outcome analysis. Currently co‐registration of CT, MR and PET scans may be important for any of these purposes; in the future, molecular and biomarker imaging may be incorporated.
The challenges for the QA centers are to verify that institutions participating in protocols requiring image registration have the tools and expertise to perform the registrations, and to verify the appropriate registration for individual protocol patients. There are many software systems, many with multiple methods, available for image registration.
One method to credential institutions is by benchmarking. QARC's “fusion” benchmark has the institution download a DICOM MR and a DICOM CT scan set. The datasets are to be registered, the small lesion on the MR scan is to be outlined, and the geometrical center of the lesion on the CT scan is to be reported (lesion not visible on CT). Results from more than 40 institutions will be discussed.
An increasing number of protocols require PETimaging. Registration of PETimaging is problematic, except for PET/CT. Since the DICOM standard does not includes specifications for SUV calculations, currently only ACRIN, by using the manufacturers' workstations, is able to receive PETimages and recalculate SUVs. Ideally these PETimages would be registered with the planning CT in radiotherapy protocols.
More and more protocols propose requiring IGRT, particularly for few fraction treatments. For protocol participation, institutions need to demonstrate the reproducibility and accuracy of the imaging system used to adapt the daily treatment to the daily target position. Extensive questionnaires (QARC) and submission of representative patient data (RTOG) are required by the QA centers. The variety of systems — MV CT, kV CT, Tomotherapy, Cyberknife, ultrasound — provide a challenge for the QA center.
An even greater challenge is how to provide QA for individual patient treatments. If CT/CT or CT/MR registration is used for target delineation, how can the QA center assess the registration? Do they need to redo it themselves? What tools can be developed to register and verify CT/PET registration? For adaptive radiotherapy, what is the benefit of reviewing the daily assessment of required repositioning? And at what cost?
1. Understand the issues faced by the QA centers in reviewing image registrations.
2. Understand the difference between credentialing and providing individual patient QA for image registration.
3. Become familiar with the current strategies of QA for image registration by the QA centers.
34(2007); http://dx.doi.org/10.1118/1.2761617View Description Hide Description
In mid‐2006, the National Cancer Institute (NCI) published updated guidelines for the use of intensity‐modulated radiation therapy(IMRT) on clinical trials, specifically when the target volume included the thoracic region or other areas in which respiratory motion could have a significant effect. In addition to requiring heterogeneity corrections, the NCI now requires that the clinical protocol address the localization and immobilization of both the patient and the tumor.Imaging must be performed in a manner that provides a representation of the target volume without motion artifact. Procedures must be defined to document reproducible daily position of the patient and target. Some form of credentialing is required.
The Radiological Physics Center (RPC) has been enlisted to participate in the credentialing process for institutions participating in certain cooperative group trials in which respiratory motion is an issue. To accomplish this, the RPC has constructed several phantoms that mimic the thoracic and abdominal region, and which can be placed on a moving platform to simulate respiratory motion. The combination of phantom and moving platform have been used to evaluate compensation techniques for respiratory motion at several institutions. The techniques employed and the results of these measurements will be described as well as those reported in the literature.
1. Review the structure supporting cooperative group clinical trials in the US.
2. Become familiar with the NCI guidelines for the use of IMRT in clinical trials.
3. Learn about the effects of respiratory motion during thoracic treatments.
4. Understand the information derived from the RPC's moving anthropomorphic phantoms.
This research is supported by grants CA 10953 and 81647 awarded by NCI, DHHS.
34(2007); http://dx.doi.org/10.1118/1.2761618View Description Hide Description
Clinical trials rely on accurate dose reporting, both for the planning target volumes and organs at risk (OAR). Until recently, clinical trials have not mandated that heterogeneity corrections be applied in dose calculations. Therefore history of prescription and reported doses has been for homogenous water equivalent media. The reticence is attributed to lack of confidence in commercial treatment planning algorithms and in lack of direction as how to change prescriptions when accounting for heterogeneous media. Thorax irradiation is the most challenging example of where corrections and prescription changes are difficult but necessary. Two well reported studies, RTOG‐8808 and RTOG‐9311, required complementary parallel calculations performed. One set was the prescribed and treated homogeneous (water) based calculations, and the other was retrospective heterogeneous CT‐based calculations, but using the homogeneous based MU. The calculations demonstrated major variations in the doses that would have been reported depending if heterogeneity corrections were exclusively used. This was confirmed by dosimetric studies showing the failure of algorithms of the 1990s, particularly in regions of non‐equilibrium. As OAR, particularly lung volume, were often the limiting factor, dose calculations to the lung itself had to be accurate. High energy‐small fields had the largest deviations. The commercial introduction of superposition and Monte Carlo algorithms has remedied the situation by providing accurate calculations, provided they are implemented properly. Simultaneously, publication of AAPM's Report of TG‐65 (Inhomogeneity Corrections) gave direction to physicists as how to work with clinician partners to transition to correction based plans and change prescriptions accordingly.
From this lecture the physicist will learn;
1. the history of corrections for clinical trials,
2. progression of algorithms,
3. methods for making the transition to using heterogeneity corrections.
34(2007); http://dx.doi.org/10.1118/1.2761619View Description Hide Description
Paralleling the introduction of Intensity Modulated Radiation Therapy(IMRT) in the early to mid 1990s, Image Guided Radiation Therapy(IGRT) is an important but problematic new tool for the RadiationOncology community. The challenges are similar to IMRT in that IGRT is a general classification that covers many different approaches with numerous variations. Where IMRT ranges from tomotherapy to conventional MLC‐based dose delivery with many different treatment planning approaches, IGRT covers a broad spectrum of techniques ranging from stereoscopic x‐ray imaging with rigid‐body fusion to cone‐beam volume imaging with deformable registration. Thus, like IMRT, guaranteeing the safe and effective use of this new modality in a clinical trial setting will require procedures that are as comprehensive as the ones currently in place for IMRT. As quality assurance techniques are developed for routine clinical use of advanced technologies like IGRT, they must also be appropriately standardized for use in clinical trials.
Image Guidance is defined here as the steps of obtaining daily in‐room images of the patient in the treatment position, matching or fusing these images to the ones obtained during the treatment planning process, and the procedure of manually or automatically changing the patient's position based on the fusioninformation. Notice that this description does not consider the patient as a deformable object. Using this simple definition, two Radiation Therapy Oncology Group (RTOG) protocols employ IGRT for targeting the lesion. Both of these protocols require institutions to verify their IGRT methodology through a credentialing process. This process is aimed at guaranteeing that each institution understands the protocol requirements relative to the use of their fusion software or manual shift capabilities.
This presentation will discuss the process used by the RTOG to credential institutions for the use of IGRT in their protocols, and it will present the problems and considerations that will have to be addressed as the definition of IGRT expands to include moving targets and deformable fusion.
1. To develop a working definition of IGRT that includes imagefusion and patient repositioning.
2. To understand how IGRT is currently being used in RTOG protocols.
3. To understand how the RTOG credentials institutions to use daily imaging and imagefusion in clinical trails.
4. To describe future challenges and to outline how they might be addressed.
34(2007); http://dx.doi.org/10.1118/1.2761620View Description Hide Description
The goal of AAPM Task Group 113 is to provide guidance to physicists, QA centers, and others involved in clinical trials on methods to improve the consistency and quality of data generated for trials involving external beam radiotherapy.
To date, there are no universally agreed upon standards for the physics practices related to clinical trials. In addition, as treatment techniques become more sophisticated, it is even more challenging to comprehensively maintain consistency across multiple institutions. Since hundreds of institutions may be involved in clinical trials, it is critical to review the entire treatment planning and delivery process and to identify areas where improvements can be made to ensure that high quality and consistent data are acquired from all institutions treating patients on clinical trials.
This presentation will focus on factors that impact data quality for the treatment planning and delivery process. In addition, methods to help individual physicists improve the consistency of clinical trials will be discussed. The scope of the task group includes image acquisition for volume definition, treatment planning systems, patient localization, treatment guidance and delivery, and credentialing for clinical trials.
1. To describe the goals of TG♯113 Physics Practice Standards for Clinical Trials.
2. To highlight factors that directly impact clinical trials that involve IMRT and IGRT.