An Integrated Physical Optimization Framework for Proton Stereotactic Body Radiation Therapy FLASH Treatment Planning Allows Dose, Dose Rate, and Linear Energy Transfer Optimization Using Patient-Specific Ridge Filters

Liu, Ruirui; Zhou, Jun; Wahl, Niklas; Liu, Wei; Kang, Minglei; Zhou, Jun; Yang, Xiaofeng; Baltazar, Filipa; Palkowitsch, Martina; Higgins, Kristin; Dynan, William S.; Bradley, Jeffrey D.; Lin, Liyong

doi:10.1016/j.ijrobp.2023.01.048

Cited by 23 publications

(35 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Compared with the representative pilot study of employing TBs alone for FLASH planning, 38 the cooperation of the SESOBPs and the TBs in this method could not only accomplish FLASH dose rate based on the high current of the high-energy beams but also exploit the sharp distal dose falloff of the BPs to reduce radiation exposure of the OARs at the distal edge of the targets. In contrast with using tailored BPs or SESOBPs of FLASH dose rate by customized range compensators 23 or pin-shaped RFs, 25,26 respectively, to obtain high LET effect, the proposed hybrid planning method is more applicable for proton ART.When replanning is required due to patient anatomical changes during the treatment course, the hybrid TB-SESOBP plan can be adapted by simply re-selecting the RFs from the pre-designed RF set if necessary and then re-conducting the optimization process based on current patient anatomy.…”

Section: Discussionmentioning

confidence: 99%

“…Alternative approaches have been proposed for FLASH planning using spread-out single-energy proton beams, in which patient-specific range compensators were used to pull back the BPs to the target exit edge and pin-shaped ridge filters (RFs) were customized to spread out the BPs to the proximal edge of the target. [24][25][26] Nevertheless, either using the customized range compensators alone or combining the patient-specific pin-shaped RFs and range compensators for FLASH planning has limitations in adapting to patient anatomical changes that often occur during the treatment courses, such as tumor regression, since a time-consuming process for re-making the range compensators and/or pin-shaped RFs may be required.…”

Section: Introductionmentioning

confidence: 99%

“…In these studies, the uniform range shifters (RSs) and patient‐specific universal range compensators were employed to align the BPs of the high‐energy proton beams to the distal edge of the target from multiple beam directions, which demonstrated improved OAR sparing with sufficient target dose coverage and comparable FLASH dose rate coverage compared to the TB‐only planning. Alternative approaches have been proposed for FLASH planning using spread‐out single‐energy proton beams, in which patient‐specific range compensators were used to pull back the BPs to the target exit edge and pin‐shaped ridge filters (RFs) were customized to spread out the BPs to the proximal edge of the target 24–26 . Nevertheless, either using the customized range compensators alone or combining the patient‐specific pin‐shaped RFs and range compensators for FLASH planning has limitations in adapting to patient anatomical changes that often occur during the treatment courses, such as tumor regression, since a time‐consuming process for re‐making the range compensators and/or pin‐shaped RFs may be required.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Feasibility study of hybrid inverse planning with transmission beams and single‐energy spread‐out Bragg peaks for proton FLASH radiotherapy

Yang

Chang

et al. 2023

Medical Physics

View full text Add to dashboard Cite

Background: Ultra-high dose rate (FLASH) proton planning with only transmission beams (TBs) has limitations in normal tissue sparing. The single-energy spread-out Bragg peaks (SESOBPs) of the FLASH dose rate have been demonstrated feasible for proton FLASH planning. Purpose: To investigate the feasibility of combining TBs and SESOBPs for proton FLASH treatment. Methods: A hybrid inverse optimization method was developed to combine the TBs and SESOBPs (TB-SESOBP) for FLASH planning. The SESOBPs were generated field-by-field from spreading out the BPs by pre-designed general bar ridge filters (RFs) and placed at the central target by range shifters (RSs) to obtain a uniform dose within the target.The SESOBPs and TBs were fully placed field-by-field allowing automatic spot selection and weighting in the optimization process. A spot reduction strategy was conducted in the optimization process to push up the minimum MU/spot assuring the plan deliverability at beam current of 165 nA. The TB-SESOBP plans were validated in comparison with the TB only (TB-only) plans and the plans with the combination of TBs and BPs (TB-BP plans) regarding 3D dose and dose rate (dose-averaged dose rate) distributions for five lung cases. The FLASH dose rate coverage (V 40Gy/s ) was evaluated in the structure volume receiving > 10% of the prescription dose. Results: Compared to the TB-only plans, the mean spinal cord D 1.2cc drastically reduced by 41% (P < 0.05), the mean lung V 7Gy and V 7.4 Gy moderately reduced by up to 17% (P < 0.05), and the target dose homogeneity slightly increased in the TB-SESOBP plans. Comparable dose homogeneity was achieved in both TB-SESOBP and TB-BP plans. Besides, prominent improvements were achieved in lung sparing for the cases of relatively large targets by the TB-SESOBP plans compared to the TB-BP plans. The targets and the skin were fully covered with the FLASH dose rate in all three plans. For the OARs, V 40Gy/s = 100% was achieved by the TB-only plans while V 40Gy/s > 85% was obtained by the other two plans. Conclusion:We have demonstrated that the hybrid TB-SESOBP planning was feasible to achieve FLASH dose rate for proton therapy. With pre-designed general bar RFs,the hybrid TB-SESOBP planning could be implemented for proton adaptive FLASH radiotherapy. As an alternative FLASH planning approach to TB-only planning, the hybrid TB-SESOBP planning has great potential in dosimetrically improving OAR sparing while maintaining high target dose homogeneity.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Feasibility study of hybrid inverse planning with transmission beams and single‐energy spread‐out Bragg peaks for proton FLASH radiotherapy

Yang

Chang

et al. 2023

Medical Physics

View full text Add to dashboard Cite

show abstract

“…The base of the range modulator is shaped to act as a range compensator to match the distal contour of the tumor. It has been shown that this set-up could easily achieve dose rate of at least 40 Gy/s [18,7].…”

Section: Introductionmentioning

confidence: 98%

“…To plan a conformal PBS FLASH treatment it is therefore necessary to optimize a patient-specific range modulator and the weights of the PBS spots. Several methods have already been proposed [13,7,18]. Although different, they are based on two common principles:…”

Section: Introductionmentioning

confidence: 99%

Optimization of patient-specific range modulators for conformal FLASH proton therapy

Deffet¹,

Souris²,

Sterpin³

2023

Preprint

View full text Add to dashboard Cite

Background: In proton therapy, current pencil beam scanning (PBS) systems cannot deliver intensity modulated proton therapy (IMPT) treatment with a FLASH dose rate. A promising approach to enable FLASH conformal proton therapy is to passively degrade a single energy layer using a patient-specific range modulator. This range modulator can be seen as a combination of a ridge filter and a range shifter to achieve both uniformity and conformality. Several studies have already proved the feasibility of this approach. However, in those published works, the optimization of the range modulators is more akin to dose mimicking as it is not performed with respect to the constraints used to design the original IMPT plan. In addition, a complex simulation pipeline with an external dose engine is required to deal with the parameterized geometries of the range modulators. Purpose: We propose an innovative method to directly optimize the geometrical characteristics of the range modulator and the treatment plan with respect to user defined constraints, similarly to state-of-the-art IMPT inverse planning. Methods: The kind of range modulators proposed in this study is a voxelized object which can be placed in the CT for dose computation, which simplifies the simulation pipeline. Both the geometrical characteristics of the range modulator and the weights of the PBS spots were directly optimized with respect to constraints on the dose using a first-order method. A modified Monte Carlo dose engine was used to provide an estimate of the gradient of the relaxed constraints with respect to the elevation values of the range modulator. Results: Assessed on a head and neck case, dose conformity logically appeared to be significantly degraded compared to IMPT. We then demonstrated that this degradation came mainly from the use of a large range shifter and therefore from physical limitations inherent in the passive degradation of beam energy. The geometry of the range modulator, on the other hand, was shown to be very close to being optimal. PBS dose rates were computed and discussed with respect to FLASH objectives. Conclusions: The voxelized range modulators optimized with the proposed method were proven to be optimal on a head and neck case characterized by two rather large volumes, with irregular contours and variable depths. The optimized geometry differed from conventional ridge filters as it was arbitrarily set by the optimizer. This kind of range modulators can be directly added in the CT for dose computation and is well suited for 3D printing.

show abstract

Optimal minimum MU for intensity‐modulated proton therapy with pencil‐beam scanning proton beams

Yi,

Mossahebi,

Jatczak

et al. 2024

J Applied Clin Med Phys

View full text Add to dashboard Cite

PurposeA higher minimum monitor unit (minMU) for pencil‐beam scanning proton beams in intensity‐modulated proton therapy is preferred for more efficient delivery. However, plan quality may be compromised when the minMU is too large.This study aimed to identify the optimal minMU (OminMU) to improve plan delivery efficiency while maintaining high plan quality.MethodsWe utilized clinical plans including six anatomic sites (brain, head and neck, breast, lung, abdomen, and prostate) from 23 patients previously treated with the Varian ProBeam system. The minMU of each plan was increased from the current clinical minMU of 1.1 to 3–24 MU depending on the daily prescribed dose (DPD). The dosimetric parameters of the plans were evaluated for consistency against a 1.1‐minMU plan for target coverage as well as organs‐at‐risk dose sparing. DPD/minMU was defined as the ratio of DPD to minMU (cGy/MU) to find the OminMU by ensuring that dosimetric parameters did not differ by >1% compared to those of the 1.1‐minMU plan.ResultsAll plans up to 5 minMU showed no significant dose differences compared to the 1.1‐minMU plan. Plan qualities remained acceptable when DPD/minMU ≥35 cGy/MU. This suggests that the 35 cGy/MU criterion can be used as the OminMU, which implies that 5 MU is the OminMU for a conventional fraction dose of 180 cGy. Treatment times were decreased by an average of 32% (max 56%, min 7%) and by an average of 1.6 min when the minMU was increased from 1.1 to OminMU.ConclusionA clinical guideline for OminMU has been established. The minMU can be increased by 1 MU for every 35 cGy of DPD without compromising plan quality for most cases analyzed in this study. Significant treatment time reduction of up to 56% was observed when the suggested OminMU is used.

show abstract

An Integrated Physical Optimization Framework for Proton Stereotactic Body Radiation Therapy FLASH Treatment Planning Allows Dose, Dose Rate, and Linear Energy Transfer Optimization Using Patient-Specific Ridge Filters

Cited by 23 publications

References 45 publications

Feasibility study of hybrid inverse planning with transmission beams and single‐energy spread‐out Bragg peaks for proton FLASH radiotherapy

Feasibility study of hybrid inverse planning with transmission beams and single‐energy spread‐out Bragg peaks for proton FLASH radiotherapy

Optimization of patient-specific range modulators for conformal FLASH proton therapy

Optimal minimum MU for intensity‐modulated proton therapy with pencil‐beam scanning proton beams

Contact Info

Product

Resources

About