AAA and PBC calculation accuracy in the surface build-up region in tangential beam treatments. Phantom and breast case study with the Monte Carlo code penelope

Panettieri, Vanessa; Barsoum, Pierre; Westermark, Mathias; Brualla, L.; Lax, Ingmar

doi:10.1016/j.radonc.2009.05.010

Cited by 88 publications

(72 citation statements)

References 33 publications

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“…It was shown that as the curvature of the region that the MOSFETmeasuring position is located in increases, the radiation dose increases in the same cross-section, and this tendency is attributed to the angle dependency of the MOSFET itself according to the attachment position [18,24]. In addition, we confirmed that, although the absorbed dose in the build-up area is very important for tangential irradiation, one of the radiation-therapy techniques for breast cancer, there is a radiation-dose difference that depends on the radiation-dose-calculation algorithm of the instrument that is used for the computerized treatment plan [25,26]; therefore, an additional verification of the treatment plan that uses algorithms that are different from the adaptive convolution algorithm that was used in this experiment is needed. Regarding post-mastectomy radiation therapy for the chest wall, the recommendation stipulates the delivery of at least 80 % of the prescribed dose for the surface dose on the chest wall [27]; however, a lesser dose than what is recommended was delivered to most of the points when a bolus was not used.…”

Section: Discussionsupporting

confidence: 59%

Chest-wall Surface Dose During Post-mastectomy Radiation Therapy, with and without Nonmagnetic Bolus: A Phantom Study

Choi¹,

Hong²,

Park³

et al. 2016

Journal of Magnetics

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For mastectomy patients, sufficient doses of radiation should be delivered to the surface of the chest wall to prevent recurrence. A bolus is used to increase the surface dose on the chest wall, whereby the surface dose is confirmed with the use of a virtual bolus during the computerized treatment-planning process. The purpose of this study is an examination of the difference between the dose of the computerized treatment plan and the dose that is measured on the bolus. Part of the left breast of an Anderson Rando phantom was removed, followed by the attainment of computed tomography (CT) images that were used as the basis for computerized treatment plans that were established with no bolus, a 3 mm-thick bolus, a 5 mm-thick bolus, and a 10 mm-thick bolus. For the computerized treatment plan, a prescribed dose regimen was dispensed daily and planning target volume (PTV) coverage was applied according to the RTOG 1304 guidelines. Using each of the established computerized treatment plans, chest-wall doses of 5 points were measured; this chest-wall dose was used as the standard for the analysis of this study, while the level of significance was set at P < 0.05. The measurement of the chest-wall dose with no bolus is 1.6 % to 10.3 % higher, and the differences of the minimum average and the maximum average of the five measurement points are −13.8 and −1.9, respectively (P < 0.05); however, when the bolus was used, the dosage was measured as 3.7 % to 9.2 % lower, and the differences of the minimum average and the maximum average are 7.4 and 9.0, −1.2 and 17.4, and 8.1 and 19.8 for 3 mm, 5 mm, and 10 mm, respectively (P < 0.05). As the thickness of the bolus is increased, the differences of the average surface dose are further increased. There are a variety of factors that affect the surface dose on the chest wall during post-mastectomy radiation therapy, for which verification is required; in particular, a consideration of the appropriate thickness and the number of uses when a bolus is used, and which has the greatest effect on the surface dose on the chest wall, is considered necessary.

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Section: Discussionsupporting

confidence: 59%

Chest-wall Surface Dose During Post-mastectomy Radiation Therapy, with and without Nonmagnetic Bolus: A Phantom Study

Choi¹,

Hong²,

Park³

et al. 2016

Journal of Magnetics

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“…( 8 – 14 ) For dose distribution calculations in heterogeneous media, and especially at interfaces, the AAA algorithm has been shown to be consistently more accurate than the pencil beam convolution (PBC) algorithm. ( 9 , 10 , 14 – 16 ) …”

Section: Introductionmentioning

confidence: 99%

Validation of the Eclipse AAA algorithm at extended SSD

Hussain

Villarreal-Barajas

Brown

et al. 2010

J Applied Clin Med Phys

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The accuracy of dose calculations at extended SSD is of significant importance in the dosimetric planning of total body irradiation (TBI). In a first step toward the implementation of electronic, multi‐leaf collimator compensation for dose inhomogeneities and surface contour in TBI, we have evaluated the ability of the Eclipse AAA to accurately predict dose distributions in water at extended SSD. For this purpose, we use the Eclipse AAA algorithm, commissioned with machine‐specific beam data for a 6 MV photon beam, at standard SSD (100 cm). The model was then used for dose distribution calculations at extended SSD (179.5 cm). Two sets of measurements were acquired for a 6 MV beam (from a Varian linear accelerator) in a water tank at extended SSD: i) open beam for 5 × 5, 10 × 10, 20 × 20 and 40×40 cm2 field sizes (defined at 179.5 cm SSD), and ii) identical field sizes but with a 1.3 cm thick acrylic spoiler placed 10 cm above the water surface. Dose profiles were acquired at 5 cm, 10 cm and 20 cm depths. Dose distributions for the two setups were calculated using the AAA algorithm in Eclipse. Confidence limits for comparisons between measured and calculated absolute depth dose curves and normalized dose profiles were determined as suggested by Venselaar et al. The confidence limits were within 2% and 2 mm for both setups. Extended SSD calculations were also performed using Eclipse AAA, commissioned with Varian Golden beam data at standard SSD. No significant difference between the custom commissioned and Golden Eclipse AAA was observed. In conclusion, Eclipse AAA commissioned at standard SSD can be used to accurately predict dose distributions in water at extended SSD for 6 MV open beams.PACS numbers: 87.53.Kn, 87.55.D‐, 87.55.de, 87.56.ng

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“…Panettieri et al. investigated the dose in the buildup region of AAA and found that it underestimated the predictions of MC calculations severely in the first 2 mm of tissue, particularly when the beam was delivered at a wide angle as is the case in breast radiotherapy 27. Since AXB has been shown to agree more closely with MC calculations in the buildup region,13 it is consistent that it should estimate the mean dose in the superficial 5 mm to be hotter.…”

Section: Discussionmentioning

confidence: 86%

Clinical implementation of AXB from AAA for breast: Plan quality and subvolume analysis

Guebert

Conroy

Weppler

et al. 2018

J Applied Clin Med Phys

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PurposeTwo dose calculation algorithms are available in Varian Eclipse software: Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB). Many Varian Eclipse‐based centers have access to AXB; however, a thorough understanding of how it will affect plan characteristics and, subsequently, clinical practice is necessary prior to implementation. We characterized the difference in breast plan quality between AXB and AAA for dissemination to clinicians during implementation.MethodsLocoregional irradiation plans were created with AAA for 30 breast cancer patients with a prescription dose of 50 Gy to the breast and 45 Gy to the regional node, in 25 fractions. The internal mammary chain (IMCCTV) nodes were covered by 80% of the breast dose. AXB, both dose‐to‐water and dose‐to‐medium reporting, was used to recalculate plans while maintaining constant monitor units. Target coverage and organ‐at‐risk doses were compared between the two algorithms using dose–volume parameters. An analysis to assess location‐specific changes was performed by dividing the breast into nine subvolumes in the superior–inferior and left–right directions.ResultsThere were minimal differences found between the AXB and AAA calculated plans. The median difference between AXB and AAA for breastCTV V 95%, was <2.5%. For IMCCTV, the median differences V 95%, and V 80% were <5% and 0%, respectively; indicating IMCCTV coverage only decreased when marginally covered. Mean superficial dose increased by a median of 3.2 Gy. In the subvolume analysis, the medial subvolumes were “hotter” when recalculated with AXB and the lateral subvolumes “cooler” with AXB; however, all differences were within 2 Gy.ConclusionWe observed minimal difference in magnitude and spatial distribution of dose when comparing the two algorithms. The largest observable differences occurred in superficial dose regions. Therefore, clinical implementation of AXB from AAA for breast radiotherapy is not expected to result in changes in clinical practice for prescribing or planning breast radiotherapy.

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AAA and PBC calculation accuracy in the surface build-up region in tangential beam treatments. Phantom and breast case study with the Monte Carlo code penelope

Cited by 88 publications

References 33 publications

Chest-wall Surface Dose During Post-mastectomy Radiation Therapy, with and without Nonmagnetic Bolus: A Phantom Study

Chest-wall Surface Dose During Post-mastectomy Radiation Therapy, with and without Nonmagnetic Bolus: A Phantom Study

Validation of the Eclipse AAA algorithm at extended SSD

Clinical implementation of AXB from AAA for breast: Plan quality and subvolume analysis

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