Effect of dose-delivery time for flattened and flattening filter-free photon beams based on microdosimetric kinetic model

Nakano, Hisashi; Kawahara, Daisuke; Ono, Kaoru; Akagi, Yukio; Hirokawa, Yutaka

doi:10.1371/journal.pone.0206673

Cited by 12 publications

(14 citation statements)

References 32 publications

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“…Furthermore, it has been shown that the dose administration time affects the relative biological effectiveness (RBE) during photon irradiation. As a result, it was stated that the effects of dosing time are important and should be considered in radiation therapy 17 .…”

Section: Discussionmentioning

confidence: 99%

Comparison of radiotherapy techniques with flattening filter and flattening filter-free in lung radiotherapy according to the treatment volume size

Arslan

Sengul

2020

Sci Rep

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In external radiotherapy (RT), the use of flattening filter-free (FFF) radiation beams obtained by removing the flattening filter (FF) in standard linear accelerators is rapidly increasing, and the benefits of clinical use are the issue of research. Advanced treatment techniques have increased the interest in the operation of linear accelerators in FFF mode. The differences of the beams with non-uniform dose distribution created by removing FF compared to the beams with uniform dose distribution used as a standard were examined. These differences were compared in the treatment plans of lung patients who have different planning target volumes (PTV). Clinac IX linear accelerator units were used. Twenty patients with previously completed treatment were divided into two groups depending on the size of the target volume. All patients underwent two different intensity-modulated RT (IMRT) plans using FF and FFF beams. The Wilcoxon Signed-Rank test was used to compare two different techniques (Significance p < 0.05). There was no statistically significant difference between the two techniques when looking at the D2%(Gy), D98%(Gy), D50%(Gy), homogeneity (HI), and conformity index (CI) data for both groups. When the critical organ doses were evaluated, there was a statistically significant difference only in the V20(%) values of the lungs, but these differences were not very large. Monitor unit (MU) data were found to be lower in FF planning, and treatment time was lower in FFF planning. Except for shorter treatment times, and of the lungs V20(%) value, in standard fractionated RT of lung cancer, there was no significant difference between the use of FFF and FF techniques for large and small target volumes.

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Section: Discussionmentioning

confidence: 99%

Comparison of radiotherapy techniques with flattening filter and flattening filter-free in lung radiotherapy according to the treatment volume size

Arslan

Sengul

2020

Sci Rep

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“…The irradiation applied in radiotherapy can be interrupted due to a linear accelerator's mechanical problems, sometimes for a long term 34 . Moreover, irradiation techniques such as a respiratory gating system used to attain tumor control for lung cancer require a large absorbed dose per fraction, a protracted dose‐delivery time, and a long interruption time 10,14 . Figure 5 provides the results of our calculation of the interruption times' effects on the RBE.…”

Section: Discussionmentioning

confidence: 99%

“…34 Moreover, irradiation techniques such as a respiratory gating system used to attain tumor control for lung cancer require a large absorbed dose per fraction, a protracted dose-delivery time, and a long interruption time. 10,14 Figure 5 provides the results of our calculation of the interruption times' effects on the RBE. A several-minutes-long interruption had no significant effect on the RBE within 3%, but a ≥10% reduction of the RBE occurred when the 8-Gy fourfield irradiation was interrupted for 30 or 60 min.…”

Section: A | the Interruption Time's Effects On The Sf With Two-andmentioning

confidence: 99%

“…3,4 The dose-delivery time's effects on radiobiological effectiveness were evaluated with single-field photon beams and a microdosimetric kinetic (MK) model; [5][6][7][8][9] the surviving fraction (SF) was increased by prolonging the dose-delivery time, and the relative biological effectiveness was decreased. 10 Fractionated irradiation with multiple-field is used clinically to cover radiation targets with the prescribed dose but prevent toxicity to surrounding normal tissues. 11 When multiplefield irradiation is applied, the prescribed dose is not administered consecutively; there is an interruption time (an interval between radiation fields) used so that irradiation interruption occurs at several sites/operations, for example, the gantry, collimator, couch rotation, and patient repositioning within each field.…”

Section: Introductionmentioning

confidence: 99%

“…With SLDR, lessening photon beams' cell‐killing effect on relative biological effectiveness (RBE) may be possible by increasing the irradiation dose‐delivery time 3,4 . The dose‐delivery time's effects on radiobiological effectiveness were evaluated with single‐field photon beams and a microdosimetric kinetic (MK) model; 5‐9 the surviving fraction (SF) was increased by prolonging the dose‐delivery time, and the relative biological effectiveness was decreased 10 …”

Section: Introductionmentioning

confidence: 99%

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Radiobiological effects of the interruption time with Monte Carlo Simulation on multiple fields in photon beams

Nakano

Kawahara

Tanabe

et al. 2020

J Applied Clin Med Phys

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Purpose The interruption time is the irradiation interruption that occurs at sites and operations such as the gantry, collimator, couch rotation, and patient setup within the field in radiotherapy. However, the radiobiological effect of prolonging the treatment time by the interruption time for tumor cells is little evaluated. We investigated the effect of the interruption time on the radiobiological effectiveness with photon beams based on a modified microdosimetric kinetic (mMK) model. Methods The dose‐mean lineal energy y D (keV/µm) of 6‐MV photon beams was calculated by the particle and heavy ion transport system (PHITS). We set the absorbed dose to 2 or 8 Gy, and the interruption time (τ) was set to 1, 3, 5, 10, 30, and 60 min. The biological parameters such as α 0, β 0, and DNA repair constant rate (a + c) values were acquired from a human non‐small‐cell lung cancer cell line (NCI‐H460) for the mMK model. We used two‐field and four‐field irradiation with a constant dose rate (3 Gy/min); the photon beams were paused for interruption time τ. We calculated the relative biological effectiveness (RBE) to evaluate the interruption time's effect compared with no interrupted as a reference. Results The y D of 6‐MV photon beams was 2.32 (keV/µm), and there was little effect by changing the water depth (standard deviation was 0.01). The RBE with four‐field irradiation for 8 Gy was decreased to 0.997, 0.975, 0.900, and 0.836 τ = 1, 10, 30, 60 min, respectively. In addition, the RBE was affected by the repair constant rate (a + c) value, the greater the decrease in RBE with the longer the interruption time when the (a + c) value was large. Conclusion The ~10‐min interruption of 6‐MV photon beams did not significantly impact the radiobiological effectiveness, since the RBE decrease was <3%. Nevertheless, the RBE's effect on tumor cells was decreased about 30% by increasing the 60 min interruption time at 8 Gy with four‐field irradiation. It is thus necessary to make the interruption time as short as possible.

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Medical application of particle and heavy ion transport code system PHITS

Furuta

Sato

2021

Radiol Phys Technol

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Effect of dose-delivery time for flattened and flattening filter-free photon beams based on microdosimetric kinetic model

Cited by 12 publications

References 32 publications

Comparison of radiotherapy techniques with flattening filter and flattening filter-free in lung radiotherapy according to the treatment volume size

Comparison of radiotherapy techniques with flattening filter and flattening filter-free in lung radiotherapy according to the treatment volume size

Radiobiological effects of the interruption time with Monte Carlo Simulation on multiple fields in photon beams

Medical application of particle and heavy ion transport code system PHITS

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