Impact of radiobiological models on the calculation of the therapeutic parameters of Grid therapy for breast cancer

Mahmoudi, Farshid; Chegeni, Nahid; Bagheri, Ali; Asl, Jafar Fatahi; Batiar, Mohammad Taghi

doi:10.1016/j.apradiso.2021.109776

Cited by 1 publication

(2 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the fractionated doses investigated within this work are outside the limits that are well defined by a classical linear‐quadratic (LQ) model, the use of an LQ model has been shown to still accurately model relative TR when compared against modified LQ formalisms 16 . This proof‐of‐concept work also does not incorporate the bystander effect into the cell survival model, which has been proposed as another prominent mechanism associated with GRID in addition to the dose‐volume effect 64 . While the presented work focuses on dosimetric aspects with GRID, future work will aim to develop predictive models of the therapeutic response from a given GRID treatment that will likely require the bystander effect as an additional component to the cell radiosensitivity as demonstrated by Peng et al 65 …”

Section: Discussionmentioning

confidence: 97%

“…16 This proof -of -concept work also does not incorporate the bystander effect into the cell survival model, which has been proposed as another prominent mechanism associated with GRID in addition to the dosevolume effect. 64 While the presented work focuses on dosimetric aspects with GRID, future work will aim to develop predictive models of the therapeutic response from a given GRID treatment that will likely require the bystander effect as an additional component to the cell radiosensitivity as demonstrated by Peng et al 65 There are also notable uncertainties within the reported 𝛼∕𝛽 ratios assumed in this work from other published studies. As presented in Table 4, the optimal collimation and spot spacing for a particular cell line are largely dependent on the cell's specific 𝛼 and 𝛽 radiosensitivity characteristics.…”

Section: Limitations Of Biological Modelingmentioning

confidence: 94%

See 1 more Smart Citation

The dosimetric enhancement of GRID profiles using an external collimator in pencil beam scanning proton therapy

Smith

Nelson

et al. 2022

Medical Physics

View full text Add to dashboard Cite

The radiobiological benefits afforded by spatially fractionated (GRID) radiation therapy pairs well with the dosimetric advantages of proton therapy. Inspired by the emergence of energy-layer specific collimators in pencil beam scanning (PBS), this work investigates how the spot spacing and collimation can be optimized to maximize the therapeutic gains of a GRID treatment while demonstrating the integration of a dynamic collimation system (DCS) within a commercial beamline to deliver GRID treatments and experimentally benchmark Monte Carlo calculation methods. Methods: GRID profiles were experimentally benchmarked using a clinical DCS prototype that was mounted to the nozzle of the IBA-dedicated nozzle system. Integral depth dose (IDD) curves and lateral profiles were measured for uncollimated and GRID-collimated beamlets. A library of collimated GRID dose distributions were simulated by placing beamlets within a specified uniform grid and weighting the beamlets to achieve a volume-averaged tumor cell survival equivalent to an open field delivery. The healthy tissue sparing afforded by the GRID distribution was then estimated across a range of spot spacings and collimation widths, which were later optimized based on the radiosensitivity of the tumor cell line and the nominal spot size of the PBS system. This was accomplished by using validated models of the IBA universal and dedicated nozzles. Results: Excellent agreement was observed between the measured and simulated profiles. The IDDs matched above 98.7% when analyzed using a 1%/1mm gamma criterion with some minor deviation observed near the Bragg peak for higher beamlet energies. Lateral profile distributions predicted using Monte Carlo methods agreed well with the measured profiles; a gamma passing rate of 95% or higher was observed for all in-depth profiles examined using a 3%/2mm criteria. Additional collimation was shown to improve PBS GRID treatments by sharpening the lateral penumbra of the beamlets but creates a trade-off between enhancing the valley-to-peak ratio of the GRID delivery and the dosevolume effect. The optimal collimation width and spot spacing changed as a function of the tumor cell radiosensitivity, dose, and spot size. In general, a spot spacing below 2.0 cm with a collimation less than 1.0 cm provided a superior dose distribution among the specific cases studied. Conclusions:The ability to customize a GRID dose distribution using different collimation sizes and spot spacings is a useful advantage, especially to maximize the overall therapeutic benefit. In this regard, the capabilities of the DCS, and perhaps alternative dynamic collimators, can be used to enhance GRID treatments. Physical dose models calculated using Monte Carlo methods were 2684

show abstract

Section: Discussionmentioning

confidence: 97%