Hybrid 3D analytical linear energy transfer calculation algorithm based on precalculated data from Monte Carlo simulations

Deng, Wei; Ding, Xiaoning; Younkin, James E.; Shen, Jiajian; Bues, Martin; Schild, Steven E.; Patel, Samir H.; Liu, Wei

doi:10.1002/mp.13934

Cited by 23 publications

(30 citation statements)

References 42 publications

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“…High linear energy transfer (LET) may appear in the distal fall-off regions of a proton beam and may cause unexpected AEs to nearby OARs. At our institution, every plan will receive a second dose and LET calculation [66][67][68] after the plan is generated by our TPS (Eclipse TM ).…”

Section: Discussionmentioning

confidence: 99%

“…High linear energy transfer (LET) may appear in the distal fall‐off regions of a proton beam and may cause unexpected AEs to nearby OARs. At our institution, every plan will receive a second dose and LET calculation 66–68 after the plan is generated by our TPS (Eclipse TM ). The physicists and the attending physician will then check for overlap of high dose (at least 50% of the prescription dose) and high LET (at least 6 keV/µm) in nearby OARs during the LET‐guided plan evaluation.…”

Section: Discussionmentioning

confidence: 99%

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Beam angle comparison for distal esophageal carcinoma patients treated with intensity‐modulated proton therapy

Feng

Sio

Rule

et al. 2020

J Applied Clin Med Phys

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Purpose: To compare the dosimetric performances of intensity-modulated proton therapy (IMPT) plans generated with two different beam angle configurations (the Right-Left oblique posterior beams and the Superior-Inferior oblique posterior beams) for the treatment of distal esophageal carcinoma in the presence of uncertainties and interplay effect. Methods and Materials: Twenty patients' IMPT plans were retrospectively selected, with 10 patients treated with the R-L oblique posterior beams (Group R-L) and the other 10 patients treated with the S-I oblique posterior beams (Group S-I). Patients in both groups were matched by their clinical target volumes (CTVs-high and low dose levels) and respiratory motion amplitudes. Dose-volume-histogram (DVH) indices were used to assess plan quality. DVH bandwidth was calculated to evaluate plan robustness. Interplay effect was quantified using four-dimensional (4D) dynamic dose calculation with random respiratory starting phase of each fraction. Normal tissue complication probability (NTCP) for heart, liver, and lung was calculated, respectively, to estimate the clinical outcomes. Wilcoxon signed-rank test was used for statistical comparison between the two groups. Results: Compared with plans in Group R-L, plans in Group S-I resulted in significantly lower liver D mean and lung V 30Gy[RBE] with slightly higher but clinically acceptable spinal cord D max. Similar plan robustness was observed between the two groups. When interplay effect was considered, plans in Group S-I performed statistically better for heart D mean and V 30Gy[RBE] , lung Dmean and V 5Gy[RBE] , and liver D mean , with slightly increased but clinically acceptable spinal cord D max. NTCP for liver was significantly better in Group S-I. Conclusions: IMPT plans in Group S-I have better sparing of liver, heart, and lungs at the slight cost of spinal cord maximum dose protection, and are more interplayeffect resilient compared to IMPT plans in Group R-L. Our study supports the routine use of the S-I oblique posterior beams for the treatments of distal esophageal carcinoma.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Beam angle comparison for distal esophageal carcinoma patients treated with intensity‐modulated proton therapy

Feng

Sio

Rule

et al. 2020

J Applied Clin Med Phys

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“…A large number of time-consuming computations were needed for this study. In order to speed up the calculation, we migrated our in-house developed treatment planning system (TPS) to a Graphic Processing Unit (GPU)-based computing platform, including the following three components: (a) a modified ray-casting-based dose and linear energy transfer (LET) calculation engine, 59,64 with the enhanced capability to account for inhomogeneity more accurately 65 ; (b) voxel- wise worst-case-based 3D, [10][11][12][13][14][15][16][17]20,[25][26][27][28]66,67,68 4D, 19 and LETguided 26,69 robust optimization; and (c) DVH-band method 20,61,63 to quantify plan robustness. The TPS was highly parallelized using Compute Unified Device Architecture (CUDA).…”

Section: C Graphic Processing Unit (Gpu)-accelerated Treatment Plamentioning

confidence: 99%

Intensity‐modulated proton therapy (IMPT) interplay effect evaluation of asymmetric breathing with simultaneous uncertainty considerations in patients with non‐small cell lung cancer

et al. 2020

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Purpose Intensity‐modulated proton therapy (IMPT) is sensitive to uncertainties from patient setup and proton beam range, as well as interplay effect. In addition, respiratory motion may vary from cycle to cycle, and also from day to day. These uncertainties can severely degrade the original plan quality and potentially affect patient’s outcome. In this work, we developed a new tool to comprehensively consider the impact of all these uncertainties and provide plan robustness evaluation under them. Methods We developed a comprehensive plan robustness evaluation tool that considered both uncertainties from patient setup and proton beam range, as well as respiratory motion simultaneously. To mimic patients' respiratory motion, the time spent in each phase was randomly sampled based on patient‐specific breathing pattern parameters as acquired during the four‐dimensional (4D)‐computed tomography (CT) simulation. Spots were then assigned to one specific phase according to the temporal relationship between spot delivery sequence and patients’ respiratory motion. Dose in each phase was calculated by summing contributions from all the spots delivered in that phase. The final 4D dynamic dose was obtained by deforming all doses in each phase to the maximum exhalation phase. Three hundred (300) scenarios (10 different breathing patterns with 30 different setup and range uncertainty scenario combinations) were calculated for each plan. The dose‐volume histograms (DVHs) band method was used to assess plan robustness. Benchmarking the tool as an application’s example, we compared plan robustness under both three‐dimensional (3D) and 4D robustly optimized IMPT plans for 10 nonrandomly selected patients with non‐small cell lung cancer. Results The developed comprehensive plan robustness tool had been successfully applied to compare the plan robustness between 3D and 4D robustly optimized IMPT plans for 10 lung cancer patients. In the presence of interplay effect with uncertainties considered simultaneously, 4D robustly optimized plans provided significantly better CTV coverage (D95%, P = 0.002), CTV homogeneity (D5%‐D95%, P = 0.002) with less target hot spots (D5%, P = 0.002), and target coverage robustness (CTV D95% bandwidth, P = 0.004) compared to 3D robustly optimized plans. Superior dose sparing of normal lung (lung Dmean, P = 0.020) favoring 4D plans and comparable normal tissue sparing including esophagus, heart, and spinal cord for both 3D and 4D plans were observed. The calculation time for all patients included in this study was 11.4 ± 2.6 min. Conclusion A comprehensive plan robustness evaluation tool was successfully developed and benchmarked for plan robustness evaluation in the presence of interplay effect, setup and range uncertainties. The very high efficiency of this tool marks its clinical adaptation, highly practical and versatile nature, including possible real‐time intra‐fractional interplay effect evaluation as a potential application for future use.

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“…On the other hand, analytical LET calculation methods [15,[51][52][53][54][55][56] have been used in clinical practice owing to their high efficiency, acceptable computational accuracy, and other historical reasons. The widely used 1D LET models [13,51,52] only consider the LET variation along the beam direction and assume uniform LET values in the lateral direction.…”

Section: Analytical Methods Versus MC Simulationsmentioning

confidence: 99%

A Critical Review of LET-Based Intensity-Modulated Proton Therapy Plan Evaluation and Optimization for Head and Neck Cancer Management

Deng

Yang

Liu

et al. 2021

International Journal of Particle Therapy

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In this review article, we review the 3 important aspects of linear-energy-transfer (LET) in intensity-modulated proton therapy (IMPT) for head and neck (H&N) cancer management. Accurate LET calculation methods are essential for LET-guided plan evaluation and optimization, which can be calculated either by analytical methods or by Monte Carlo (MC) simulations. Recently, some new 3D analytical approaches to calculate LET accurately and efficiently have been proposed. On the other hand, several fast MC codes have also been developed to speed up the MC simulation by simplifying nonessential physics models and/or using the graphics processor unit (GPU)–acceleration approach. Some concepts related to LET are also briefly summarized including (1) dose-weighted versus fluence-weighted LET; (2) restricted versus unrestricted LET; and (3) microdosimetry versus macrodosimetry. LET-guided plan evaluation has been clinically done in some proton centers. Recently, more and more studies using patient outcomes as the biological endpoint have shown a positive correlation between high LET and adverse events sites, indicating the importance of LET-guided plan evaluation in proton clinics. Various LET-guided plan optimization methods have been proposed to generate proton plans to achieve biologically optimized IMPT plans. Different optimization frameworks were used, including 2-step optimization, 1-step optimization, and worst-case robust optimization. They either indirectly or directly optimize the LET distribution in patients while trying to maintain the same dose distribution and plan robustness. It is important to consider the impact of uncertainties in LET-guided optimization (ie, LET-guided robust optimization) in IMPT, since IMPT is sensitive to uncertainties including both the dose and LET distributions. We believe that the advancement of the LET-guided plan evaluation and optimization will help us exploit the unique biological characteristics of proton beams to improve the therapeutic ratio of IMPT to treat H&N and other cancers.

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Hybrid 3D analytical linear energy transfer calculation algorithm based on precalculated data from Monte Carlo simulations

Cited by 23 publications

References 42 publications

Beam angle comparison for distal esophageal carcinoma patients treated with intensity‐modulated proton therapy

Beam angle comparison for distal esophageal carcinoma patients treated with intensity‐modulated proton therapy

Intensity‐modulated proton therapy (IMPT) interplay effect evaluation of asymmetric breathing with simultaneous uncertainty considerations in patients with non‐small cell lung cancer

A Critical Review of LET-Based Intensity-Modulated Proton Therapy Plan Evaluation and Optimization for Head and Neck Cancer Management

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