3D Monte Carlo dosimetry of intraoperative electron radiation therapy (IOERT)

Abstract

This paper studies the feasibility of using Monte Carlo (MC) for treatment planning of intraoperative electron radiation therapy (IOERT) procedure to get 3D dose by using patient's CT images. Methods: The IOERT treatment planning was performed using the following successive steps:I) The Mobetron 1000® machine was modelled with the EGSnrc MC codes. II) The MC model was validated with measurements of percentage depth doses and profiles for three energies (12, 9, 6) MeV. III) CT images were imported as DICOM files. IV) Contouring of the planning target volume (PTV) and the organs at risk was done by the radiation oncologist. V) The medical physicist with the radiation oncologist, had chosen the same parameters of IOERT procedures like energy, applicator (type, size) and using or not bolus. VI) Finally, dose calculation and analysis of 3D maps was carried out. Results: The tuning process of the MC model provides good results, as the maximum value of the root mean square deviation (RMSD) was less than 3% between the MC simulated PDDs and the measured PDDs. The contouring and dose analysis review were easy to conduct for the classical treatment planning system. The radiation oncologist had many tools for dose analysis such as DVH and color wash for all the slides. Summation of the 3D dose of IOERT with other radiotherapy plans is possible and helpful for total dose estimation. Archiving and documentation is as good as treatment planning system (TPS). Conclusions: The method displayed in this paper provides a step forward for IOERT Dosimetry and allows to obtain accurate dosimetry of treated volumes.

FLASH radiotherapy treatment planning and models for electron beams

“…Currently, there are dedicated UHDR HEE devices [11,12,[19][20][21]26] and converted medical linacs repurposed for UHDR HEE [13,14] (see Figure 2), albeit often with beam characteristics different from those used to treat patients. For example, some UHDR machines produce Gaussian beams with FWHM that can range from a few to about 15 cm, or even more [27][28][29][30]. Others produce smaller but flat beams for preclinical treatments and in vivo studies.…”

“…Computer speed has increased enough to make MC methods become the gold standard for electron linac treatment head simulations, beam modelling in the TPS, and dose calculation of electron beams in patient anatomies [55]. Consequently, approaches based on MC methods are well established for HEE RT for these tasks and most recent research and clinical HEE beam models apply MC codes for particle transport in the treatment head as well as particle transport and dose computations in the patient [16,28,29,55,56].…”

Treatment Planning in Intraoperative Radiation Therapy (IORT): Where Should We Go?

“…Nonetheless, dose calculation algorithms in current systems may lack the accuracy that characterizes analogous devices dedicated to EBRT. Monte Carlo dose calculation is currently implemented in treatment planning systems dedicated to electron-beam IORT [ 4 , 5 , 6 , 9 , 10 ]. However, most systems still employ suboptimal, simplified algorithms that cannot guarantee a dosimetric accuracy at the same level of systems developed for advanced photon-beam modulated techniques.…”

“…The time is probably ripe for a change. Availability of accurate dose calculation algorithms for clinical use, such as real-time Monte Carlo calculation [ 4 , 5 , 6 ], the prospected coming of radically new irradiation schemes such as FLASH therapy [ 7 ], and the possibility to use in-room imaging [ 8 ] call for an evolution of treatment planning systems in IORT.…”

Intraoperative computed tomography imaging for dose calculation in intraoperative electron radiation therapy: Initial clinical observations

“…A further step in IOERT dose calculation involves the use of a specific commercial treatment planning system (TPS) [4,5] or other solutions developed for this purpose [6] that take account of tissue heterogeneity by means of computed tomography (CT) studies. However, the actual treatment field can deviate from that foreseen in the TPS when using preoperative CT studies owing to variations in the patient's position, surgical access, tumour resection and IOERT parameters.…”