Dosimetric Multicenter Planning Comparison Studies for Stereotactic Body Radiation Therapy: Methodology and Future Perspectives

Giglioli, F.R.; Garibaldi, Cristina; Blanck, Oliver; Villaggi, E.; Russo, S.; Esposito, Marco; Marino, C.; Stasi, M.; Mancosu, P.

doi:10.1016/j.ijrobp.2019.10.041

Cited by 23 publications

(25 citation statements)

References 41 publications

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“…Thus, comparison of plan quality considering several distinct parameters is not easy. Mathematical scores that combine dosimetric parameters have been proposed following different strategies [17,19,20,[29][30][31][32][33][34] and their use is highly recommended to objectively compare treatment plans [18]. In [33] a special index was defined to evaluate simultaneously plan modulation, PTV coverage and dose to heart for breast treatments; in [34] a quality index was defined combining PTV coverage, dose conformity, dose fall-off and the cord maximum dose for spinal cases.…”

Section: Discussionmentioning

confidence: 99%

“…Generally, although mathematical scores of plan quality are necessary and useful tools of analysis, the users should be aware of some critical issues in their definition. Critical issues are, among others, the choice of parameters to be included in the score, the relative weights and when used, the linear scoring assigned to each parameter [18]. To the best of our knowledge, no previous work has evaluated the criticality of the choice of these parameters and weights.…”

Section: Discussionmentioning

confidence: 99%

“…However, it is well known that different parameters/metrics may show conflicting results when comparing the two examined solutions. The use of a single quality index is, therefore, highly recommended to reduce variability in plan quality evaluation [18]. To this purpose, a mathematical score was defined in this work, through a combination of dosimetric and efficiency parameters following the suggestions in [17,19,20].…”

Section: Introductionmentioning

confidence: 99%

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Performance assessment of a new optimization system for robotic SBRT MLC-based plans

Calusi

Doro²,

Cataldo³

et al. 2020

Physica Medica

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A B S T R A C TPurpose: To assess the performance of a new optimization system, VOLO, for CyberKnife MLC-based SBRT plans in comparison with the existing Sequential optimizer. Methods: MLC-plans were created for 25 SBRT cases (liver, prostate, pancreas and spine) using both VOLO and Sequential. Monitor units (MU), delivery time (DT), PTV coverage, conformity (nCI), dose gradient (R50%) and OAR doses were used for comparison and combined to obtain a mathematical score (MS) of plan quality for each solution. MS strength was validated by changing parameter weights and by a blinded clinical plan evaluation. The optimization times (OT) and the average segment areas (SA) were also compared. Results: VOLO solutions offered significantly lower mean DT (−19%) and MU (−13%). OT were below 15 min for VOLO, whereas for Sequential, values spanned from 8 to 160 min. SAs were significantly larger for VOLO: on average 10 cm 2 versus 7 cm 2 . VOLO optimized plans achieved a higher MS than Sequential for all tested parameter combinations. PTV coverage and OAR sparing were comparable for both groups of solutions. Although slight differences in R50% and nCI were found, the parameters most affecting MS were MU and DT. VOLO solutions were selected in 80% of cases by both physicians with 88% inter-observer agreement. Conclusions: The good performance of the VOLO optimization system, together with the large reduction in OT, make it a useful tool to improve the efficiency of CK SBRT planning and delivery. The proposed methodology for comparing different planning solutions can be applied in other contexts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Performance assessment of a new optimization system for robotic SBRT MLC-based plans

Calusi

Doro²,

Cataldo³

et al. 2020

Physica Medica

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“…Stereotactic body radiation therapy (SBRT), as a new fractionation, has been proven useful and widely used for the clinical treatments of various anatomical sites. [1][2][3][4] With precise beam delivery, SBRT can achieve superior local control rates. [4][5][6][7] Compared with the conventional fractionation, SBRT is characterized by higher fractional dose, fewer fractions, and longer delivery time.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

et al. 2021

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The induced radioactivity in stereotactic body radiation therapy with a flattening-filter-free 10 MV beam model (10 FFF SBRT) was investigated for the risk to therapists. Methods: This study was performed on a Varian TrueBeam linac. The induced radioisotopes were identified by γ spectroscopy. The dose rate from the induced activity was measured for 12 treatment cycles in 4 h continuously. The impacts of the characteristic factors of 10 FFF SBRT on the dose rate were investigated, including monitor units (MU), beam rate, field size, and flattening filter. The dose rate was compared between the SBRT plans and conventional fractionation plans. A mathematical model was used to analyze the results and estimate the annual dose to therapists. Results: (a) The induced radioisotopes included 24 Na, 28 Al, 38 Cl, 56 Mn, 66 Cu, 187 W, and 196 Au. (b) In 4 h, the total dose contribution ratios were more than 70% for 28 Al, about 20% for 56 Mn, and 10% for all other long-lived radioisotopes, combining doses at the isocenter and end of the treatment couch. (c) The dose rate showed a nonlinear growth with increasing MU and beam rate. The variation of the dose rate was complicated with the jaw field and not sensitive to the MLC field. The removal of the flattening filter reduced the dose rate by about 40%. The dose level of SBRT was two to three times that of conventional fractionation. (d) The estimated annual dose to therapists was up to 0.20 mSv/y. Conclusions: The induced radioactivity in 10 FFF SBRT was higher compared with that in 10 MV conventional fractionation. More MU and higher beam rate were the primary factors that caused the increase. The therapists should wait longer after beam-off to reduce the occupational dose. In addition, aluminum and manganese should be less used in the treatment room.

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“…Dose distributions for stereotactic body radiotherapy (SBRT) are often heterogeneous when treatment doses are prescribed to lower isodose lines (IDL), i.e., from 70% to 90%, to create more rapid dose fall off [1][2][3]. The difficulty is in characterizing and reporting these dose distributions within the tumor that are typically delivered at a high dose per fraction [4].…”

Section: Introductionmentioning

confidence: 99%

Revisiting the formalism of equivalent uniform dose based on the linear-quadratic and universal survival curve models in high-dose stereotactic body radiotherapy

Chan

Chiang

2020

Strahlenther Onkol

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Purpose To examine the equivalent uniform dose (EUD) formalism using the universal survival curve (USC) applicable to high-dose stereotactic body radiotherapy (SBRT). Materials and methods For nine non-small-cell carcinoma cell (NSCLC) lines, the linear-quadratic (LQ) and USC models were used to calculate the EUD of a set of hypothetical two-compartment tumor dose–volume histogram (DVH) models. The dose was varied by ±5%, ±10%, and ±20% about the prescription dose (60 Gy/3 fractions) to the first compartment, with fraction volume varying from 1% and 5% to 30%. Clinical DVHs of 21 SBRT treatments of NSCLC prescribed to the 70–83% isodose lines were also considered. The EUD of non-standard SBRT dose fractionation (EUDSBRT) was further converted to standard fractionation of 2 Gy (EUDCFRT) using the LQ and USC models to facilitate comparisons between different SBRT dose fractionations. Tumor control probability (TCP) was then estimated from the LQ- and USC-EUDCFRT. Results For non-standard SBRT fractionation, the deviation of the USC- from the LQ-EUDSBRT is largely limited to 5% in the presence of dose variation up to ±20% to fractional tumor volume up to 30% in all NSCLC cell lines. Linear regression with zero constant yielded USC-EUDSBRT = 0.96 × LQ-EUDSBRT (r2 = 0.99) for the clinical DVHs. Converting EUDSBRT into standard 2‑Gy fractions by the LQ formalism produced significantly larger EUDCFRT than the USC formalism, particularly for low $$\alpha /\beta$$ α / β ratios and large fraction dose. Simplified two-compartment DVH models illustrated that both the LQ- and USC-EUDCFRT values were sensitive to cold spot below the prescription dose with little volume dependence. Their deviations were almost constant for up to 30% dose increase above the prescription. Linear regression with zero constant yielded USC-EUDCFRT = 1.56 × LQ-EUDCFRT (r2 = 0.99) for the clinical DVHs. The clinical LQ-EUDCFRT resulted in median TCP of almost 100% vs. 93.8% with USC-EUDCFRT. Conclusion A uniform formalism of EUD should be defined among the SBRT community in order to apply it as a single metric for dose reporting and dose–response modeling in high-dose-gradient SBRT because its value depends on the underlying cell survival model and the model parameters. Further investigations of the optimal formalism to derive the EUD through clinical correlations are warranted.

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Dosimetric Multicenter Planning Comparison Studies for Stereotactic Body Radiation Therapy: Methodology and Future Perspectives

Cited by 23 publications

References 41 publications

Performance assessment of a new optimization system for robotic SBRT MLC-based plans

Performance assessment of a new optimization system for robotic SBRT MLC-based plans

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

Revisiting the formalism of equivalent uniform dose based on the linear-quadratic and universal survival curve models in high-dose stereotactic body radiotherapy

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