Radiation Therapy of Large Intact Breasts Using a Beam Spoiler or Photons with Mixed Energies

Lief, Eugene P.; Hunt, Margie; Hong, Linda; Amols, Howard

doi:10.1016/j.meddos.2007.02.002

Cited by 8 publications

(6 citation statements)

References 16 publications

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“…Utilization of higher energy photons (10-18MV) is a practical way to reduce these radiation hot spots particularly in large breasts. The main disadvantage of this approach is under dosing of superficial subcutaneous tissues in the buildup region of the beams (Ellen et al, 1999;Baird et al, 2001;Lief et al, 2007) and so an important question is: what proportion of high energy photons should be used in radiotherapy of the intact breast to achieve acceptable hot spots and at the same time adequate target coverage?…”

Section: Breast Radiotherapy With Mixed Energy Photons; a Model For Optimal Beam Weightingmentioning

confidence: 99%

Breast Radiotherapy with Mixed Energy Photons; a Model for Optimal Beam Weighting

Birgani

Fatahiasl²,

Hosseini³

et al. 2015

Asian Pacific Journal of Cancer Prevention

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Utilization of high energy photons (>10MV) with an optimal weight using a mixed energy technique is a practical way to generate a homogenous dose distribution while maintaining adequate target coverage in intact breast radiotherapy. This study represents a model for estimation of this optimal weight for day to day clinical usage. For this purpose, treatment planning computed tomography scans of thirty-three consecutive early stage breast cancer patients following breast conservation surgery were analyzed. After delineation of the breast clinical target volume (CTV) and placing opposed wedge paired isocenteric tangential portals, dosimeteric calculations were conducted and dose volume histograms (DVHs) were generated, first with pure 6MV photons and then these calculations were repeated ten times with incorporating 18MV photons (ten percent increase in weight per step) in each individual patient. For each calculation two indexes including maximum dose in the breast CTV (D max ) and the volume of CTV which covered with 95% Isodose line (V CTV, 95%IDL ) were measured according to the DVH data and then normalized values were plotted in a graph. The optimal weight of 18MV photons was defined as the intersection point of D max and V CTV, 95%IDL graphs. For creating a model to predict this optimal weight multiple linear regression analysis was used based on some of the breast and tangential field parameters.The best fitting model for prediction of 18MV photons optimal weight in breast radiotherapy using mixed energy technique, incorporated chest wall separation plus central lung distance (Adjusted R2=0.776). In conclusion, this study represents a model for the estimation of optimal beam weighting in breast radiotherapy using mixed photon energy technique for routine day to day clinical usage.

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Section: Breast Radiotherapy With Mixed Energy Photons; a Model For Optimal Beam Weightingmentioning

confidence: 99%

Breast Radiotherapy with Mixed Energy Photons; a Model for Optimal Beam Weighting

Birgani

Fatahiasl²,

Hosseini³

et al. 2015

Asian Pacific Journal of Cancer Prevention

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“…In radiation therapy that employs high energy photon beams, different types of boluses are used to adjust the final dose delivered to superficial tissues and to modulate dose distribution near the irradiated surface. The role of boluses in dose distribution during neck and head cancer treatment [1][2][3] and in breast radiation therapy [4][5][6] has been investigated. The air gap often forms under the bolus because of either daily variations in body surface shape or daily differences in bolus settings.…”

Section: Introductionmentioning

confidence: 99%

The air gap between bolus and skin affects dose distribution in helical and direct tomotherapy

et al. 2020

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Aim: To modify the final dose delivered to superficial tissues and to modulate dose distribution near irradiated surface, different boluses are used. Air gaps often form under the bolus affecting dose distribution. This study aimed to evaluate the effect of an air gap under the bolus radiation on dose delivery. Materials and methods: To evaluate the impact of the air gap, both helical tomotherapy (HT) and direct tomotherapy (DT) were performed in a simulation study. Results: The maximum dose to bolus in DT plans was bigger than that used in HT plans. The maximum dose delivered to the bolus depended on the air gap size. However, the maximum dose to bolus in all HT plans was within the acceptable value range. Acceptable value was set to up to 107% of the prescription dose. In the simulation performed in this study, the acceptable air gap under bolus was up to 15 mm and below 5 mm in HT and DT plans, respectively. Conclusions: HT technique is a good choice, but DT technique can be also used if the bolus position can be reproduced accurately. Thus, the reproducibility of the bolus position between planning and treatment is very important.

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“…The use of high-energy beams is a practical way to reduce hot spots in the radiation therapy. However, subcutaneous tissues that are in the buildup region do not receive enough doses [3,4].…”

Section: Introductionmentioning

confidence: 99%

Calculating Weighting Factors for Mixing Megavoltage Photon Beams to Achieve Desirable Dose Distribution in Radiotherapy

et al. 2019

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Background: In radiotherapy, low-energy photon beams are better adapted to the treated volume, and the use of high-energy beams can reduce hot spots in the radiation therapy. Therefore, mixing low and high energies with different ratios can control the rate of hotspots, as well as the dose distribution of the target volume.Material and Methods: The percentage depth doses (PDDs) were calculated at various depths, by using a fitted double exponential equation. Then, using quality factor equation and PDD of a 10×10 cm2 field, the amount of energy equivalent to each PDD and the value of weighting factors of 6, 18 MV energies were calculated to produce different energies. To validate the mathematical model, dosimetry of 10 MV energy was used. For this purpose, PDDs and dose Profile of 10 MV obtained from the mix were compared with ones obtained from the measurementResults: The value of weighting factor of 6 MV energy required for the 10 ×10 cm2 field to create dose distribution of 15 MV energy using 6 and 18 MV energies was obtained as equal to 0.57. Comparison of percentage depth dose curves and dose profile shows good agreement with the practical measurements of 10 MV for 10×10 cm2 field using gamma index.Conclusion: The simultaneous use of high and low photon energies with different weighting factors to achieve desirable energy makes possible the treatment of tumors located at various depths without the need for different modes of energy in the accelerator leading to a decrease in the cost of the equipment and a safer treatment of the cancerous patients.

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Radiation Therapy of Large Intact Breasts Using a Beam Spoiler or Photons with Mixed Energies

Cited by 8 publications

References 16 publications

Breast Radiotherapy with Mixed Energy Photons; a Model for Optimal Beam Weighting

Breast Radiotherapy with Mixed Energy Photons; a Model for Optimal Beam Weighting

The air gap between bolus and skin affects dose distribution in helical and direct tomotherapy

Calculating Weighting Factors for Mixing Megavoltage Photon Beams to Achieve Desirable Dose Distribution in Radiotherapy

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