Jaw position uncertainty and adjacent fields in breast cancer radiotherapy

Hedin, Emma; Bäck, Anna; Chakarova, R.

doi:10.1120/jacmp.v16i6.5673

Cited by 5 publications

(8 citation statements)

References 18 publications

(25 reference statements)

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“…The MC method was independent from the treatment planning system and was used as a third method to compare the dosimetric performance of AAA and AXB in the extreme cases selected. The accelerator model, designed within the EGSnrc code package, was developed earlier and validated by the same experimental data used for configuration of AAA and AXB [11][12][13]. Tissue segmentation was performed by 9 material table with a more detailed presentation of bone tissue types [14,15].…”

Section: Calculation Algorithmsmentioning

confidence: 99%

Impact of lung density on the lung dose estimation for radiotherapy of breast cancer

Hedin¹,

Bäck²,

Chakarova³

2017

Physics and Imaging in Radiation Oncology

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Background and purpose: To investigate the impact of the clinical implementation of a deterministic particle transport method on the lung dose evaluation for radiotherapy of breast cancer focusing on dosimetric effects of the lung density. Material and methods: Fourteen patients with left sided breast cancer having both deep inspiration breath hold (DIBH) and free breathing CT scans were studied. Lung density variations for 157 patients treated under DIBH were quantified and the cases with the lowest lung densities for breast and for loco regional treatment added to the study. Dose calculations were performed with the class-b type algorithm AAA and the deterministic algorithm Acuros XB. Monte Carlo method was utilized as reference. Differences in the dose distributions were evaluated by comparing DVH parameters. Results: Lung density variations between 0.08 and 0.3 g/cm 3 and between 0.02 and 0.25 g/cm 3 were found for loco-regional and tangential breast treatments under DIBH, respectively. Lung DVH parameters for patients with medium and high lung density obtained by the different algorithms agreed within 3%. Larger differences were observed for low lung density cases where the correction based algorithm underestimated V 10Gy and overestimated V 40Gy by up to 5%. The least affected parameter, V 20Gy , deviated by less than 2% for all cases and densities. Conclusions: Dosimetric constrains for lung based on V 20Gy required minimum changes due to implementation of the new algorithm regardless of breathing technique or type of treatment. Evaluation criteria utilizing V 10Gy or V 40Gy needed reconsideration, especially for treatments under DIBH involving low lung density.

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Section: Calculation Algorithmsmentioning

confidence: 99%

Impact of lung density on the lung dose estimation for radiotherapy of breast cancer

Hedin¹,

Bäck²,

Chakarova³

2017

Physics and Imaging in Radiation Oncology

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“…Adjuvant RT following lumpectomy or mastectomy is performed to reduce locoregional recurrence and improve survival [1][2][3]. Traditionally, two opposing tangential and anterior elds are mainly used for the chest wall area and supraclavicular nodes, respectively [4][5][6][7]. The anterior eld should be precisely matched with the two tangential elds to avoid hot and cold spots in the junction region.…”

Section: Introductionmentioning

confidence: 99%

“…The anterior eld should be precisely matched with the two tangential elds to avoid hot and cold spots in the junction region. Several approaches have been proposed to improve inhomogeneities in the junction region [7][8][9][10][11][12][13][14][15][16][17][18]. Intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) for breast cancer treatment have been proposed to provide better dosimetric results and to improve dose conformity to the target [9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…Patient motion can affect the accuracy of dose delivery and is signi cant for achieving a successful treatment. Field edges with a steep dose gradient may have a signi cant impact on the dose distribution in the junction region [6][7][8]. A perfect alignment in the junction region between adjacent elds is di cult to accomplish even when a phantom is used.…”

Section: Introductionmentioning

confidence: 99%

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Improved robustness in the junction region for postoperative breast cancer including supraclavicular nodes using hybrid VMAT

Miura¹,

Doi²,

Nakao³

et al. 2021

Preprint

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Purpose To improve the hybrid VMAT treatment plan robustness for postoperative breast cancer patients considering small patient motion shifts during treatment using a 3D-CRT with a dose gradient in the junction region. Methods Locoregional supraclavicular nodes of breast cancer patients were planned using 3D-CRT and VMAT. A 3D-CRT plan with a dose gradient on the cranial side was applied by shifting the jaw to reduce hot or cold spots. The VMAT plan was optimized based on the results of the 3D-CRT plan calculation. Hybrid plans were created by the sum of the 3D-CRT and VMAT plans. To simulate patient motion, the plans were recalculated with the VMAT plan simulating isocenter superiorly (separation) or inferiorly (overlap) shifted by 1, 2, and 3 mm. The shifted plans were compared with the non-shifted plans considering the clinical target volume (CTV) (D98% or D2%). Results The D2% value of the CTV with perfectly aligned fields for the hybrid VMAT plan with high- or low-dose gradients on the 3D-CRT plan increased from 102.8%/102.9–107.2%/105.7%, 114.9%/110.9%, and 122.2%/115.5% for each 1 mm, 2 mm, and 3 mm overlapped shift, respectively. The value of D98% to the CTV with perfectly aligned fields decreased from 95.7%/95.6–90.0%/93.1%, 81.2%/88.4%, and 72.8%/83.5% for each 1 mm, 2 mm, and 3 mm separated shift, respectively. Conclusions By employing a 3D-CRT plan with a low dose gradient on the cranial side, the dose differences can be decreased. A more robust treatment delivery option can be achieved for breast cancer treatment using our proposed hybrid VMAT.

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“…While a steep penumbra is normally desired, it cannot be easily softened on a typical linac to smooth out the junction. Clinical consequences of setup and machine uncertainties on the dose distribution in the junction region were described, e.g., by Holupka et al and Rosenthal et al The impact on the dose volume histograms (DVH) of the uncertainties of the jaw positions in the junction in the four‐fields monoisocentric breast radiotherapy was discussed recently by Hedin et al…”

Section: Introductionmentioning

confidence: 99%

MLC‐based penumbra softener of EDW borders to reduce junction inhomogeneities

Szpala

Kohli

2017

J Applied Clin Med Phys

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Junctions of fields are known to be susceptible to developing cold or hot spots in the presence of even small geometrical misalignments. Reduction of these dose inhomogeneities can be accomplished through decreasing the dose gradients in the penumbra, but currently it cannot be done for enhanced dynamic wedges (EDW). An MLC‐based penumbra softener was developed in the developer mode of TrueBeam linacs to reduce dose gradients across the side border of EDWs. The movement of each leaf was individually synchronized with the movement of the dynamic Y jaw to soften the penumbra in the same manner along the entire field border, in spite of the presence of the dose gradient of the EDW. Junction homogeneity upon field misalignment for side‐matched EDWs was examined with the MV imager. The fluence inhomogeneities were reduced from about 30% per mm of shift of the field borders for the conventional EDW to about 2% per mm for the softened‐penumbra plan. The junction in a four‐field monoisocentric breast plan delivered to the Rando phantom was assessed with film. The dose inhomogeneities across the junction in the superior‐inferior direction were reduced from about 20% to 25% per mm for the conventional fields to about 5% per mm. The dose near the softened junction of the breast plan with no shifts did not deviate from the conventional plan by more than about 4%. The newly‐developed softened‐penumbra junction of EDW (and/or open) fields was shown to reduce sensitivity to misalignments without increasing complexity of the planning or delivery. This methodology needs to be adopted by the manufacturers for clinical use.

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Jaw position uncertainty and adjacent fields in breast cancer radiotherapy

Cited by 5 publications

References 18 publications

Impact of lung density on the lung dose estimation for radiotherapy of breast cancer

Impact of lung density on the lung dose estimation for radiotherapy of breast cancer

Improved robustness in the junction region for postoperative breast cancer including supraclavicular nodes using hybrid VMAT

MLC‐based penumbra softener of EDW borders to reduce junction inhomogeneities

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