Impact of beam angle choice on pencil beam scanning breath-hold proton therapy for lung lesions

Gorgisyan, Jenny; Perrin, Rosalind; Lomax, Anthony; Persson, G.; Engelholm, Svend Aage; Weber, Damien Charles; Rosenschöld, Per Munck af

doi:10.1080/0284186x.2017.1287950

Cited by 18 publications

(33 citation statements)

References 21 publications

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“…It just shows that even dramatic anatomical changes do not need to substantially reduce the advantage of protons. Indeed, similar robustness to anatomical changes have been found by a number of authors through a similarly careful selection of beam angles, 16,17 the use of robust optimizaton 18 or through reduced in-field modulation of plans. 19 Myth 2: the Bragg peak is the sharpest gradient The distal fall-off of a Bragg peak in water is indeed sharp, as seen in Figures 1 and 3.…”

supporting

confidence: 57%

Myths and realities of range uncertainty

Lomax

2019

The British Journal of Radiology

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Range uncertainty is a much discussed topic in proton therapy. Although a very real aspect of proton therapy, its magnitude and consequences are sometimes misunderstood or overestimated. In this article, the sources and consequences of range uncertainty are reviewed, a number of myths associated with the effect discussed with the aim of putting range uncertainty into clinical context and attempting to de-bunk some of the more exaggerated claims made as to its consequences.

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supporting

confidence: 57%

Myths and realities of range uncertainty

Lomax

2019

The British Journal of Radiology

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“…Briefly put, instead of warping and accumulating the dose distribution on each image phase, our approach deforms the calculational dose grid as a function of time, the vectors for this deformation being extracted from 4D imaging such as 4DCT or 4DMRI (Boye et al). This approach allows to model motion effects at much higher temporal resolutions than the conventional approach, and many studies on the effects of motion and the effectiveness of motion mitigation strategies have been conducted using this 4D dose calculation (Bernatowicz et al (2013), Bernatowicz et al (2016), Knopf et al (2011), Knopf et al (2013), Dueck et al (2016), Gorgisyan et al (2017), Zhang et al (2012), Zhang et al (2013), Zhang et al (2014), Zhang et al (2015), Zhang et al (2016), Zhang et al (2017)). As such, and as is the case for all other components of a treatment planning system, such a 4DDC needs to be commissioned and verified, particularly its ability to model the complex effects of the temporal interplays between the delivery dynamics of PBS proton therapy and motion of the patient.…”

Section: Introductionmentioning

confidence: 99%

Experimental validation of a deforming grid 4D dose calculation for PBS proton therapy

et al. 2018

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The aim of this study was to verify the temporal accuracy of the estimated dose distribution by a 4D dose calculation (4DDC) in comparison to measurements. A single-field plan (0.6 Gy), optimised for a liver patient case (CTV volume: 403cc), was delivered to a homogeneous PMMA phantom and measured by a high resolution scintillating-CCD system at two water equivalent depths. Various motion scenarios (no motion and motions with amplitude of 10 mm and two periods: 3.7 s and 4.4 s) were simulated using a 4D Quasar phantom and logged by an optical tracking system in real-time. Three motion mitigation approaches (single delivery, 6[Formula: see text] layered and volumetric rescanning) were applied, resulting in 10 individual measurements. 4D dose distributions were retrospectively calculated in water by taking into account the delivery log files (retrospective) containing information on the actually delivered spot positions, fluences, and time stamps. Moreover, in order to evaluate the sensitivity of the 4DDC inputs, the corresponding prospective 4DDCs were performed as a comparison, using the estimated time stamps of the spot delivery and repeated periodical motion patterns. 2D gamma analyses and dose-difference-histograms were used to quantify the agreement between measurements and calculations for all pixels with [Formula: see text]5% of the maximum calculated dose. The results show that a mean gamma score of 99.2% with standard deviation 1.0% can be achieved for 3%/3 mm criteria and all scenarios can reach a score of more than 95%. The average area with more than 5% dose difference was 6.2%. Deviations due to input uncertainties were obvious for single scan deliveries but could be smeared out once rescanning was applied. Thus, the deforming grid 4DDC has been demonstrated to be able to predict the complex patterns of 4D dose distributions for PBS proton therapy with high dosimetric and geometric accuracy, and it can be used as a valid clinical tool for 4D treatment planning, motion mitigation selection, and eventually 4D optimisation applications if the correct temporal information is available.

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“…A possibility to avoid high RBE within or close to critical structures is the choice of beam angles that avoid positioning of the Bragg peak close to or inside critical structures. If motion is considered as well, other beam angles might be preferred [23] and a careful consideration of both effects is necessary. In our opinion, the most relevant open question concerns the inclusion of additional patients with different motion characteristics.…”

Section: Discussionmentioning

confidence: 99%