Quantification of dose perturbations induced by external and internal accessories in ocular proton therapy and evaluation of their dosimetric impact

Carnicer, A.; Angellier, G.; Thariat, Juliette; Sauerwein, W.; Caujolle, Jean‐Pierre; Hérault, J.

doi:10.1118/1.4807090

Cited by 15 publications

(8 citation statements)

References 31 publications

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“…Substantial recent improvements in on-board imaging systems, patient positioning, and patient immobilization have led to increased use of radiopaque implanted fiducial markers in proton therapy to many disease sites, with the goal of improving target coverage and/or normal tissue sparing. However, recent studies revealed that some commonly used markers, even those less than 1 mm in size, can cause severe cold spots (Figure 7), compromising target coverage (Newhauser et al , 2007a; Newhauser et al , 2007c; Carnicer et al , 2013). The severity of the cold spots varies with fiducial size, material composition, and mass density.…”

Section: Proton Interaction Mechanismsmentioning

confidence: 99%

“…Several studies reported that implanted metallic fiducials can cause dose shadows that may compromise local tumor control for certain diseases, e.g. , prostate carcinoma and uveal melanoma (Newhauser et al , 2007a; Newhauser et al , 2007c; Giebeler et al , 2009; Cheung et al , 2010; Huang et al , 2011; Matsuura et al , 2012; Zhang et al , 2012; Carnicer et al , 2013). …”

Section: Proton Transport Calculationsmentioning

confidence: 99%

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The physics of proton therapy

2015

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The physics of proton therapy has advanced considerably since it was proposed in 1946. Today analytical equations and numerical simulation methods are available to predict and characterize many aspects of proton therapy. This article reviews the basic aspects of the physics of proton therapy, including proton interaction mechanisms, proton transport calculations, the determination of dose from therapeutic and stray radiations, and shielding design. The article discusses underlying processes as well as selected practical experimental and theoretical methods. We conclude by briefly speculating on possible future areas of research of relevance to the physics of proton therapy.

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Section: Proton Interaction Mechanismsmentioning

confidence: 99%

Section: Proton Transport Calculationsmentioning

confidence: 99%

The physics of proton therapy

2015

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“…The density of the tantalum material is not taken into account in both EYEPLAN and EOPP TPS where only an average of eye density of 1.05 g.cm −3 is assumed, although this value may be adjusted and vary among the centers 13,63 . The degree of disturbance can be high as raised by Carnicer et al 64 who established an underdose shadow of up to 20% downstream of their location associated with an overdose on either side of the beam paths and a shift reduction of 1.1 mm of the intended range along the central axis of the beam. Newhauser et al 65 reported dose perturbations between 22% and 82%, when investigating various clip positions and orientations.…”

Section: Discussionmentioning

confidence: 99%

Three‐dimensional MRI‐based treatment planning approach for non‐invasive ocular proton therapy

et al. 2021

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Purpose To develop a high‐resolution three‐dimensional (3D) magnetic resonance imaging (MRI)‐based treatment planning approach for uveal melanomas (UM) in proton therapy. Materials/methods For eight patients with UM, a segmentation of the gross tumor volume (GTV) and organs‐at‐risk (OARs) was performed on T1‐ and T2‐weighted 7 Tesla MRI image data to reconstruct the patient MR‐eye. An extended contour was defined with a 2.5‐mm isotropic margin derived from the GTV. A broad beam algorithm, which we have called πDose, was implemented to calculate relative proton absorbed doses to the ipsilateral OARs. Clinically favorable gazing angles of the treated eye were assessed by calculating a global weighted‐sum objective function, which set penalties for OARs and extreme gazing angles. An optimizer, which we have named OPT’im‐Eye‐Tool, was developed to tune the parameters of the functions for sparing critical‐OARs. Results In total, 441 gazing angles were simulated for every patient. Target coverage including margins was achieved in all the cases (V95% > 95%). Over the whole gazing angles solutions space, maximum dose (Dmax) to the optic nerve and the macula, and mean doses (Dmean) to the lens, the ciliary body and the sclera were calculated. A forward optimization was applied by OPT’im‐Eye‐Tool in three different prioritizations: iso‐weighted, optic nerve prioritized, and macula prioritized. In each, the function values were depicted in a selection tool to select the optimal gazing angle(s). For example, patient 4 had a T2 equatorial tumor. The optimization applied for the straight gazing angle resulted in objective function values of 0.46 (iso‐weighted situation), 0.90 (optic nerve prioritization) and 0.08 (macula prioritization) demonstrating the impact of that angle in different clinical approaches. Conclusions The feasibility and suitability of a 3D MRI‐based treatment planning approach have been successfully tested on a cohort of eight patients diagnosed with UM. Moreover, a gaze‐angle trade‐off dose optimization with respect to OARs sparing has been developed. Further validation of the whole treatment process is the next step in the goal to achieve both a non‐invasive and a personalized proton therapy treatment.

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“…However, we previously measured the dose received due to secondary neutrons in conditions of ocular PT as 2.5 mSv. [35][36][37] It is possible that we missed other confounding causes of cataracts. 38,39…”

Section: Discussionmentioning

confidence: 99%