THURSDAY, SEPTEMBER 3, 2009 TEACHING LECTURE S 125

Treatment verification QA337 speaker

IS WHAT YOU HAVE PLANNED WHAT YOU GET?N. Jornet11 HOSPITAL DE LA SANTA CREU I SANT PAU, Radiofísica i Radioprotecció,Barcelona, Spain

During the last decades, the use of CT images for planning and the imple-mentation of accurate 3D dose calculation algorithms have provided us withknowledge about the doses to both the PTV and the organs at risk (OAR).This has led in turn to an improvement in treatment techniques aiming at tar-get coverage while minimizing the dose to OAR. Time and effort are used tooptimize the dose distribution to achieve these objectives. The dose-volumehistograms obtained in the planning are then reported and correlated withlocal control or recurrence and also with short and long term toxicity. Theresults of these studies are also used as objectives and constraints to designfuture treatment techniques.But are we certain that the planned dose distri-bution is what the patient receives? What is the distribution of the absorbeddose in the tissues and organs? Ideally, we should be able to correlate thedelivered dose with changes in cell or tissue properties either by direct mon-itoring of these changes or indirect functional/biological imaging. Althoughseveral research groups are working on these lines, these tools are not yetavailable for routine clinical practice. Therefore, treatment planning is stillused for dose-volume correlations with control rates and toxicity.There areseveral factors that can lead to discrepancies between the planned dose dis-tribution and the dose distribution delivered to the patient:1. Insufficiently accurate dose calculation algorithms or beam data used bythe treatment planning system.2. Pitfalls in beam delivery causing a lack of agreement between the fluencedelivered by the treatment machine and that calculated by the planning sys-tem.3. Changes in patient anatomy: intra and interfractions patient and/or, organmovement, differences in tissue composition and density and in patient posi-tioning.This presentation will focus on strategies to minimize the differences betweenplanning and delivery. Involvement of all the radiotherapy department staff,in particular the radiation therapy technologists (RTT), is crucial to guaranteenot only the success of an individual patient’s treatment but also to obtainreliable data for clinical trials or for intradepartmental studies on responseand toxicity.The presentation will also address techniques such as IMRT andnovel high energy treatment units that have challenged us to rethink and re-formulate QA during treatment delivery. A short overview on possible futuretreatment delivery QA will also be provided.

338 speaker

GEOMETRIC VERIFICATION AND THE ROLE OF THE THERAPEU-TIC RADIOGRAPHERN. Howes11 NORTHAMPTON GENERAL HOSPITAL NHS TRUST, NorthamptonshireCentre for Oncology, Northampton, United Kingdom

In a time when the complexity for planning and treating the radiation oncologypatient increases, the potential for treatment errors occurring subsequentlyincreases. This requires the promotion of improved control mechanisms toguarantee optimal treatment quality. Regardless of how accurately treat-ment is planned, radiotherapy delivery errors not only have the potential toincrease treatment toxicity but may also undermine the confidence of the pa-tient that their treatment is being delivered accurately. Any healthcare profes-sional involved with radiotherapy planning, dosimetry and treatment deliveryhas an obligation to ensure the certainty of treating the tumour volume asplanned and prescribed. This is the process of radiotherapy verification andit must incorporate both geometric and dosimetric verification in all stagesof the patient pathway process. However, it must be remembered that nocomputer system or QA tool can compensate for a team member’s error injudgement, misinterpretation of physical concepts or technical limitations, orsubstandard planning and delivery of treatment.Therapeutic radiographersoperate at the patient and radiation-technology interface of cancer manage-ment and treatment, practising within an ethical, legal and professional frame-work. Tumour localisation and treatment plan verification precede accurateand safe treatment delivery, and the therapeutic radiographer has responsi-bility for the complex techniques used in this area of practice. It is essentialthat a multi disciplinary approach be applied to the verification process, withclearly defined roles and responsibilities, following a well-structured trainingand competency-based programme. The role of the therapeutic radiographerin treatment verification is paramount and they are often considered to be inthe best position to assess accuracy, for example online geometric correc-tions, since they have a complete ’picture’ of patient set-up and history tohand. The enhanced role extension of therapeutic radiographers in the area

of geometric verification is proving to be beneficial in terms of improved jobsatisfaction, as well as providing a more efficient service to patients withoutcompromising the quality of service delivery.This lecture will explore the areaand considerations of geometric verification, incorporating the associated roleof the therapeutic radiographer with particular reference to the UK scene.