ESTRO 2021 Abstract Book

S167

ESTRO 2021

N. Shusharina 1 , T. Bortfeld 1 1 Massachusetts General Hospital , Radiation Oncology, Boston, USA

Abstract Text

We present a new approach that deals with delineation uncertainties of the clinical target volume (CTV). Instead of a contour-based binary CTV we introduce and test a continuum distribution of probability to find tumorous cells at a certain distance from the surface of the gross tumor volume (GTV) and call it the clinical target distribution (CTD). We introduce and test a model where the probability to find the tumor in adjacent voxels is correlated. The CTD was incorporated in treatment plan optimization algorithms through tumor control probability (TCP) model by considering the probabilities of voxels being tumorous and adapting the model to define the objective optimization function though the weighted sum approach. Voxel probabilities were derived through the series of shells around the GTV, with certain probabilities that there is tumor outside the shell. For the outermost shell with the probability 0%, it is absolutely certain that there are no tumorous voxels at further distances. We implemented the CTD in a commercial treatment planning system and tested it in two synthetic and two clinical cases. The CTD-based plans were compared with the plans optimized to deliver the same dose to traditionally defined CTV. For both synthetic and clinical cases, the CTD-based plans were superior in terms of a tradeoff between coverage of the radiation target and sparing of critical organs. We showed that CTD allows the treatment planner to find the most suitable expansion of the high dose region beyond the visible GTV. In summary, a concept of continuum clinical target distribution increases flexibility of definition of the microscopic disease extension that is reflected in superior treatment plans. CTD allows to find the most suitable tradeoff between target coverage and sparing of healthy organs, without modifying or redrawing the CTV. Owing to the variable probabilities afforded by the CTD, a more clinically meaningful sparing of critical structure becomes possible. SP-0255 Prioritised MCO to automatically balance dose extensions for uncertanties in GTV contours an d microscopic disease against does in OARs S. Korreman USA SP-0256 Higher education for advancing clinical practice - Examining the degrees of "preparation" N. Harnett 1 1 Princess Margaret Cancer Centre, Radiation Medicine, TORONTO, Canada Abstract Text Much has been written on the development of expertise – how it is developed, when it is developed, what it looks like. Seen as the pinnacle of professional practice, expertise has been well-described and studied in depth. However, over the past 50 years or so, categories of practice that scale beyond “expertise” in a particular field have surfaced in response to changing pressures or system goals, as well as to needs of those being served by any professional group. Radiation Therapy is one such profession where the changing landscape has resulted in opportunities to imagine how practitioners can be elevated to practice levels that exceed the expectations of the standard scope of practice. While the concept is logical and exciting, there are many questions inherent in the development of this new cadre of health care providers. Defining what “advanced practice” is presents challenges, as is evident in the various descriptions that can be found in the international literature. In addition to that challenge, once advanced practice is imagined and defined, leaders must turn to how advanced practice can be attained. The natural tendency is to assume that there is a need for MORE of something – more knowledge, more practice, more thinking – but where to get “more” isn’t always so straight forward. As has been the path for health care professions that have gone before us, we gravitate to the concept of higher education as the solution that will help us achieve our practice goals – critical thinking, scholarship, advanced competence, etc. But is there an alignment between what higher education is and what we expect from our newly minted advanced practitioners? In this session, we will examine what we know about each of these topics to gain insight into the question “Is higher always better?” Abstract not available Symposium: Opportunities for RTTs in higher education: Making the right choice

SP-0257 Preparing for a clinical academic career H. McNair United Kingdom

Abstract not available

SP-0258 Training RTTs for leadership C. Washington 1 1 Memorial Sloan Kettering Cancer Center, Radiation Oncology, New York, USA

Abstract Text The development of practical leadership skills is essential in facilitating operations through the provision of