Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields

Hsu, Shu-Hui; Moran, Jean M.; Chen, Yu; Kulasekere, R.; Roberson, Peter L.

doi:10.1118/1.3377769

Cited by 23 publications

(22 citation statements)

References 52 publications

(58 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The density within these contours was overridden with the density of the surrounding dermal tissue (1.07 g/cm 3 ). As the calculation grid is generally considered a determinative parameter for dose calculation accuracy in the build-up region [14], the calculations were performed for both the clinically used 4 mm, as well as for a 1 mm calculation grid. Within these computations, the fluence density grid always equaled the calculation grid.…”

Section: Methodsmentioning

confidence: 99%

“…The dose-effect relation of temporary alopecia is, however, poorly investigated and, to our knowledge, the available data remain limited to permanent alopecia [12,13]. Furthermore, plan optimization and evaluation for the hair follicle volume is impeded by the known inaccuracies of the treatment planning system in calculating build-up doses [14]. In order to overcome these issues, our study combines a dosimetric study and a prospective phase II trial for the treatment of patients with brain metastases, relating the measured and computed dose reductions to temporary alopecia and hair loss related QOL.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hair-sparing whole brain radiotherapy with volumetric arc therapy in patients treated for brain metastases: dosimetric and clinical results of a phase II trial

et al. 2014

View full text Add to dashboard Cite

PurposeTo report the dosimetric results and impact of volumetric arc therapy (VMAT) on temporary alopecia and hair-loss related quality of life (QOL) in whole brain radiotherapy (WBRT).MethodsThe potential of VMAT-WBRT to reduce the dose to the hair follicles was assessed. A human cadaver was treated with both VMAT-WBRT and conventional opposed field (OF) WBRT, while the subcutaneously absorbed dose was measured by radiochromic films and calculated by the planning system. The impact of these dose reductions on temporary alopecia was examined in a prospective phase II trial, with the mean score of hair loss at 1 month after VMAT-WBRT (EORTC-QOL BN20) as a primary endpoint and delivering a dose of 20 Gy in 5 fractions. An interim analysis was planned after including 10 patients to rule out futility, defined as a mean score of hair loss exceeding 56.7. A secondary endpoint was the global alopecia areata severity score measured with the “Severity of Alopecia Tool” (SALT) with a scale of 0 (no hair loss) to 100 (complete alopecia).ResultsFor VMAT-WBRT, the cadaver measurements demonstrated a dose reduction to the hair follicle volume of 20.5% on average and of 41.8% on the frontal-vertex-occipital medial axis as compared to OF-WBRT. In the phase II trial, a total of 10 patients were included before the trial was halted due to futility. The EORTC BN20 hair loss score following WBRT was 95 (SD 12.6). The average median dose to the hair follicle volume was 12.6 Gy (SD 0.9), corresponding to a 37% dose reduction compared to the prescribed dose. This resulted in a mean SALT-score of 75.ConclusionsCompared to OF-WBRT, VMAT-WBRT substantially reduces hair follicle dose. These dose reductions could not be related to an improved QOL or SALT score.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hair-sparing whole brain radiotherapy with volumetric arc therapy in patients treated for brain metastases: dosimetric and clinical results of a phase II trial

et al. 2014

View full text Add to dashboard Cite

show abstract

“…The dosimetric resolution of AAA calculation (~2.5 mm) needs to be considered when comparing with the near surface dose values reported from the Attix, EBT2 and MC measurements/calculation (48 µm -1 mm). For build-up region dosimetry, the estimated uncertainties of 2% and 2.7% have been reported for the Attix chamber and EBT2 film, respectively [8,12]. Table 5.…”

Section: Monte Carlo Simulationmentioning

confidence: 99%

“…However, the accuracy of the dose prediction by a TPS in the build-up region is reduced leading to broader tolerance limits [6,7]. Several factors influence the TPS near surface dose prediction: dose calculation algorithm and its electron contamination model, initial commissioning of TPS build-up region dose calculation, clinical dose calculation parameters and treatment plan complexity [8].…”

Section: Introductionmentioning

confidence: 99%

In vivoand phantom measurements versus Eclipse TPS prediction of near surface dose for SBRT treatments

Cho

Ralston

Tin

et al. 2014

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Abstract. This study reports on Gafchromic EBT2 film skin dose measurements for lung stereotactic body radiotherapy. These measurements were compared to near surface skin doses predicted by Eclipse treatment planning system (TPS) using the Analytical Anisotropic Algorithm (AAA) for a 6 MV photon beam. The accuracy of the predicted near surface dose for 3×3, 5×5 and 10×10 cm 2 fields was assessed using an Attix chamber and EBT2 film in a Virtual Water phantom and compared to Monte Carlo calculation. The maximum near surface dose and its location were identified from the patient's treatment plan. For phantom measurements, the TPS dose (nominal 0 mm depth) was higher than the Attix chamber data by up to 24.0 % but in closer agreement with the EBT2 film measurement, which was up to 10.3 % higher than the Attix data. The MC calculated dose values were higher than the Attix data by up to 3.5% for the depths up to 2 mm. The maximum patient skin dose estimated from in vivo EBT2 film measurements was 7.5 -19.5 Gy per course and depended on the number of overlapping fields, beam weight and/or contact with immobilisation devices. The TPS predicted dose for patient plans was mostly higher than the in vivo dose, by as much as 69.3%, but in two cases was lower, by as much as -23.1%.

show abstract

“…Planar dose from measurement was compared with planar dose from TPS for all planning with DTA and DD criteria 2 mm/2% and 90% for the passing rate [21,9,22]. The greatest deviation of GI value for IMRT of 70 segments at a depth of 1.5 cm has a positive sign (+), meaning that CGR of 0.4 cm is higher than 0.2 cm.…”

Section: Gamma Index Evaluationmentioning

confidence: 99%

Homogeneous and inhomogeneous material effect in gamma index evaluation of IMRT technique based on fan beam and Cone Beam CT patient images

Wibowo

Waliyyulhaq

Pawiro

2017

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Patient-specific Quality Assurance (QA) technique in lung case Intensity-Modulated Radiation Therapy (IMRT) is traditionally limited to homogeneous material, although the fact that the planning is carried out with inhomogeneous material present. Moreover, the chest area has many of inhomogeneous material, such as lung, soft tissue, and bone, which inhomogeneous material requires special attention to avoid inaccuracies in dose calculation in the Treatment Planning System (TPS). Recent preliminary studies shown that the role of Cone Beam CT (CBCT) can be used not only to position the patient at the time prior to irradiation but also to serve as planning modality. Our study presented the influence of a homogeneous and inhomogeneous materials using Fan Beam CT and Cone Beam CT modalities in IMRT technique on the Gamma Index (GI) value. We used a variation of the segment and Calculation Grid Resolution (CGR). The results showed the deviation of averaged GI value to be between CGR 0.2 cm and 0.4 cm with homogeneous material ranging from -0.44% to 1.46%. For inhomogeneous material, the value was range from -1.74% to 0.98%. In performing patientspecific IMRT QA techniques for lung cancer, homogeneous material can be implemented in evaluating the gamma index.

show abstract

Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields

Cited by 23 publications

References 52 publications

Hair-sparing whole brain radiotherapy with volumetric arc therapy in patients treated for brain metastases: dosimetric and clinical results of a phase II trial

Hair-sparing whole brain radiotherapy with volumetric arc therapy in patients treated for brain metastases: dosimetric and clinical results of a phase II trial

In vivoand phantom measurements versus Eclipse TPS prediction of near surface dose for SBRT treatments

Homogeneous and inhomogeneous material effect in gamma index evaluation of IMRT technique based on fan beam and Cone Beam CT patient images

Contact Info

Product

Resources

About