In vivo range verification in particle therapy

Abstract

Exploitation of the full potential offered by ion beams in clinical practice is still hampered by several sources of treatment uncertainties, particularly related to limitations of our ability to locate the position of the Bragg peak in the tumour. To this end, several efforts are ongoing to improve the characterization of patient position, anatomy and tissue stopping power properties prior to treatment, as well as to enable in-vivo verification of the actual dose delivery, or at least beam range, during or shortly after treatment. This contribution critically reviews methods under development or clinical testing for verification of ion therapy, based on pre-treatment range and tissue probing as well as detection of secondary emissions or physiological changes during and after treatment, trying to disentangle approaches of general applicability from those more specific to certain anatomical locations. Moreover, it discusses future directions, which could benefit from integration of multiple modalities or address novel exploitation of the measurable signals for biologically adapted therapy.

Technical Note: Machine learning approaches for range and dose verification in proton therapy using proton‐induced positron emitters

“…For the classification task, the confusion matrix and receiver operating characteristic (ROC) were used. 48 For the regression task, mean squared error (MSE) and mean absolute error (MAE) were selected to assess the performance, shown in formula (4). After averaging over all training data (n = 200, m = 302), MSE reveals the mean prediction error of dose profiles (e.g.,ŷ i represents the predicted dose at a given depth), while MAE (n = 200) reveals the mean prediction error of range profiles (e.g., between a predicted ranger i and an actual range r i ).…”

“…A major challenge in proton therapy is how to accurately monitor the location of Bragg peak and dose distribution . The rational is that the spatial distribution of secondary signals correlates with both dose distribution and proton range.…”

“…A major challenge in proton therapy is how to accurately monitor the location of Bragg peak and dose distribution. [1][2][3][4] The rational is that the spatial distribution of secondary signals correlates with both dose distribution and proton range. A number of methods have been explored, including positron radioisotope, 5-10 prompt gamma (PG), [11][12][13][14][15] acoustic wave, 16,17 and Cherenkov photons.…”

Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: A Theoretical Study

“…Thanks to the efforts of many research institutions during the last decades, several solutions towards in vivo range verification have been proposed and tested [6], [12]. Two examples thereof are Positron Emission Tomography (PET) [13] and Prompt Gamma-ray Imaging (PGI) [14].…”

“…Two examples thereof are Positron Emission Tomography (PET) [13] and Prompt Gamma-ray Imaging (PGI) [14]. The first one has been extensively tested in clinical settings, but is challenged by the correlation of activity to dose as well as the metabolic washout effect [12], [15], except in the case of in-beam PET of short-lived nuclides [16].…”