Dynamic electron arc radiotherapy (DEAR): a feasibility study

Abstract

Compared to other radiation therapy modalities, clinical electron beam therapy has remained practically unchanged for the past few decades even though electron beams with multiple energies are widely available on most linacs. In this paper, we present the concept of dynamic electron arc radiotherapy (DEAR), a new conformal electron therapy technique with synchronized couch motion. DEAR utilizes combination of gantry rotation, couch motion, and dose rate modulation to achieve desirable dose distributions in patient. The electron applicator is kept to minimize scatter and maintain narrow penumbra. The couch motion is synchronized with the gantry rotation to avoid collision between patient and the electron cone. In this study, we investigate the feasibility of DEAR delivery and demonstrate the potential of DEAR to improve dose distributions on simple cylindrical phantoms. DEAR was delivered on Varian's TrueBeam linac in Research Mode. In conjunction with the recorded trajectory log files, mechanical motion accuracies and dose rate modulation precision were analyzed. Experimental and calculated dose distributions were investigated for different energies (6 and 9 MeV) and cut-out sizes (1×10 cm(2) and 3×10 cm(2) for a 15×15 cm(2) applicator). Our findings show that DEAR delivery is feasible and has the potential to deliver radiation dose with high accuracy (root mean square error, or RMSE of <0.1 MU, <0.1° gantry, and <0.1 cm couch positions) and good dose rate precision (1.6 MU min(-1)). Dose homogeneity within ±2% in large and curved targets can be achieved while maintaining penumbra comparable to a standard electron beam on a flat surface. Further, DEAR does not require fabrication of patient-specific shields. These benefits make DEAR a promising technique for conformal radiotherapy of superficial tumors.

Part 2: Dynamic mixed beam radiotherapy (DYMBER): Photon dynamic trajectories combined with modulated electron beams

“…Another extension would be to deliver the electron beams with arcs or dynamic trajectories to possibly reduce delivery time. For this purpose, a technique similar to dynamic electron arc radiotherapy (DEAR) could be utilized, but with pMLC collimation instead of applicator based collimation to maintain clinical workflow. Finally, energy modulation could also be used for photon beams as conventional treatment units usually support multiple photon beam energies .…”

An investigation of a novel reusable radiochromic sheet for 2D dose measurement

“…[17][18][19][20] With the advent of new sophisticated electron treatment techniques, such as dynamic electron arc radiotherapy (DEAR), it is now possible to resolve the discrepancies between treatment plans and delivered distributions that can arise when treating a curved surface such as the chest wall. 21 With this new technology comes the need for appropriate verification methods, of which the reusable bolus sheet introduced in this work is a strong fit.…”

Dynamic trajectory‐based couch motion for improvement of radiation therapy trajectories in cranial SRT

“…The investigation of simultaneous couch and gantry radiotherapy is currently a very active field of research. Several recent publications [2][3][4][5][6][7] have illustrated principles and methods. Yang et al 2 supply the motivation for this research in the creation of a cost function analysis of the patient anatomy, which produces an overlap map as a guide for designing a patient support system and gantry trajectory.…”

“…Popescu et al 6 present a method for partial-breast irradiation with two subarcs of simultaneous couch and gantry motion that was selected based on trial-and-error. Rodrigues et al 5 present an electron arc radiotherapy method combining gantry and couch motion. A previous patent by Van Heteran et al 8 involves the rotation of the couch along a longitudinal axis, which includes no means for selection of couch position.…”