ESTRO 2022 - Abstract Book

S298

Abstract book

ESTRO 2022

Figure 2. DVH comparison for CT vs syCT for plan 1, target 1

Conclusion Calculation on SyCT and MRI-based SyCT is in good agreement with the reference plan when the treatment field is within a homogeneous area; calculation on syCT for targets with different densities can affect the accuracy of the plan dosimetry.

PD-0334 Feasibility of magnetic resonance-guided stereotactic ablative body radiotherapy of liver cancer

M. Picton 1 , V. Batumalai 1 , D. Crawford 2 , C. Pagulayan 3 , L. Hogan 2 , U. Jelen 2 , C. Loo 2 , N. Dunkerley 2 , L. Geddes 2 , S. Sampaio 2 , M. Heinke 2 , T. Twentyman 2 , M. Jameson 2 , J. de Leon 2 1 GenesisCare, Radiation Therapy , Sydney, Australia; 2 GenesisCare, Radiation Therapy, Sydney, Australia; 3 GensisCare, Radiation Therapy, Sydney, Australia Purpose or Objective Stereotactic ablative body radiotherapy (SABR) is an effective treatment method for liver cancer. However, tumour motion and proximity of organs at risk (OAR) can be a limiting factor when delivering high doses of radiation. Magnetic resonance (MR) guided adaptive radiotherapy (MRgART) can improve the accuracy and dose coverage of tumour volumes. This study assessed the feasibility of MRgART for liver cancer. Materials and Methods Five patients with liver cancer were treated with MRgART. Image sequencing included a T2 Navigated scan which produced images at expiration. A balance turbo fast field echo (BTFFE) image was also acquired every fraction to measure liver motion for the ITV margin. All plans were prescribed to 50Gy in 5 fractions. Plans were adapted in real time for every fraction with treatment time and dosimetric criteria recorded. Results Median patient age was 61 years (range 54-85 years). Twenty-five fractions (adapted plans) were delivered to a total of five patients. Dosimetric parameters are summarised in Table 1. Median dose to 98% of the gross tumour volume and planning target volume were 52.4 Gy and 46.5 Gy, respectively. OAR targets were met for all twenty-five fractions. The median time from ‘patient set-up’ to ‘beam-off’ time was 49.3 minutes (range 39.2-57.0 minutes). All patients completed treatment with no interruptions.

Conclusion