ESTRO 2022 - Abstract Book

S613

Abstract book

ESTRO 2022

Teaching lecture: MRI: From basic to state-of-the-art acquisition protocols

SP-0680 MRI: From basic to state-of-the-art acquisition protocols

R. Tijssen 1

1 Catharina Hospital Eindhoven, Radiotherapy, Eindhoven, The Netherlands

Abstract Text In this lecture we will cover all the pulse sequences that we frequently use for radiotherapy planning (MR-sim) and online MR-guidance (MR-Linac). We will see how contrast is formed and how changes to the readout affect the geometric accuracy of our images. We’ll start easy by exploring standard T1- and T2-weighted sequences and increase complexity as we go along and discuss the inner workings of DWI, 4D-MRI, and real-time tumor tracking. We’ll end with a few research examples that show where the field is heading.

Learning objectives - Understand how T1 and T2 contrast is generated - Know how diffusion weighting is achieved - Know that the imaging readout determines the geometric accuracy of the resulting images - Learn how 4D-MRI is are acquired

Literature - Bernstein. Handbook of MRI pulse sequences. Elsevier Academic press, 2004

- Brown. Magnetic Resonance Imaging: Physical Principles and Sequence design. Wiley-Blackwell, 2014 - Liney & vd Heide. MRI for Radiotherapy planning, delivery, and response assessment. Springer, 2019

Teaching lecture: Immobilisation in the rapidly changing world of radiotherapy: Now and into the future

SP-0681 Immobilisation in the rapidly changing world of radiotherapy: Now and into the future

D. Callens 1

1 University Hospitals Leuven, Radiation Oncology, Leuven, Belgium

Abstract Text To contemplate about the future, the past should be reflected upon and the present to be evaluated.

In the ancient days of radiation treatment, early 20th century, primitive (non-standardized) ways of positioning were adopted due to the fairly short KV-exposure time upon superficial skin leasions and large margins because of treatment uncertainties. The eye of the therapist could have been seen as the surveyor of intrafraction movements when radiotherapy was still in its infancy. The rise of isocentric treatments, thanks to (gantry-mounted) accelerators and the upcoming use of simulators since the 1950s, made the immobilisation techniques change accordingly. Nowadays, we’re working in an image-based radiotherapy environment. Thanks to IGRT, debates could be initiated about the added value of very strict positioning devices when using portal or on-board imaging. Recently a paradigm shift occurred from tattoo-laser alignment towards surface guided positioning. Considering recent advancements in hypofractionation this could be a way to go in the observation and correction of intrafraction movements. In addition to SGRT, MR-Linac systems have a far-reaching influence on the assessment of anatomical intrafraction variations. Next to hypofractionation, the clinical use of particle therapy becomes more prevalent. In these settings, immobilisation remains unquestionably crucial. In the near future, a hypothesis is that FLASH-therapy may become a routine treatment in RO departments. Ultra high dose rates lead to short exposure times. Therefore, will we still need/want to offer rigid positioning devices to our patients or will patient comfort be our only priority? - A brief travel through time in patient positioning evolutions - An overview of thought-provoking recent literature of immobilisation techniques/devices in the light of current developments cf. hypofractionation, particle therapy, … - The benefits of using SGRT in modern day radiotherapy - An overview of captivating literature of immobilisation techniques/devices in the light of future (r)evolutions cf. MR- Linac, FLASH-therapy, - A thought experiment on patient positioning techniques in the (near) future What this teaching lecture offers:

The objectives of this teaching leacture:

- By the end of the lecture, participants should be able to evaluate and enhance their intern departmental immobilisation practices with the provided knowledge, in the light of current and future advancements

This lecture focuses on a target audience of RTT’s. However, anyone interested in positioning our patients, now and in the future of clinical radiotherapy is welcome.