Biological effective dose evaluation in gynaecological brachytherapy: LDR and HDR treatments, dependence on radiobiological parameters, and treatment optimisation

Bianchí, C.; Botta, Francesca; Conte, L.; Vanoli, Paolo; Cerizza, L.

doi:10.1007/s11547-008-0291-4

Cited by 11 publications

(6 citation statements)

References 9 publications

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“…As seen in figure 4, a large portion of 169 Yb's electron and photon fluence spectra is below 1 keV in energy; by using a high cut-off, these particles were not transported and thus the differences in RBE as a function of source proximity was not seen in their work. Additionally, the work Currently, the prevalence of RBE-weighting in the treatment planning process is not ubiquitous despite numerous suggestions in literature [6,7,10,18,19,30,32,[50][51][52][53][54][55][56][57][58][59]. Contrary to previous works, this study sought to determine how RBE changed as a function of distance from the source and the resulting impact on a treatment plan.…”

Section: Discussionmentioning

confidence: 99%

Maximum RBE change in ¹⁹²Ir, ¹²⁵I, and ¹⁶⁹Yb brachytherapy and the corresponding effect on treatment planning

Nusrat

Karim-Picco²,

Pang³

et al. 2020

Biomed. Phys. Eng. Express

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Purpose: The purpose of this study was to examine RBE variation as a function of distance from the radioactive source, and the potential impact of this variation on a realistic prostate brachytherapy treatment plan. Methods: Three brachytherapy sources ( 125 I, 192 Ir, and 169 Yb) were modelled in Geant4 Monte Carlo code, and the resulting electron energy spectrum in water in 3D space around these sources was scored (voxel size of 2 mm 3 ). With this energy spectrum, microdosimetric techniques were used to calculate the maximum RBE, RBE M , as a function of distance from the source. RBE M of 125 I relative to 192 Ir was calculated in order to validate simulations against literature; all other RBE M calculations were done by normalizing electron fluence at various distances to the source position. In order to examine the impact of RBE M variation in treatment planning, a realistic 192 Ir prostate plan was re-evaluated in terms of RBE instead of absorbed dose. Results: The RBE M of 125 I, 192 Ir, and 169 Yb at 8 cm away from the source was 0.994 (+/−0.002), 1.030 (+/−0.003), and 1.066 (+/−0.008), respectively. RBE M in the HDR prostate treatment plan exhibited several hot (+3.6% in RBE M ) spots. Conclusions: The large increase RBE M observed in 169 Yb has not yet been described in the literature. Despite the presence of radiobiological hotspots in the HDR treatment, these variations are likely nominal and clinically insignificant. 103Pd. These sources have different energy spectra and therefore have different mean energies (table 1).Since it is known that lower energy particles are more damaging, the question of whether RBE changes and if so by how much has been posed many times before [6][7][8][9][10]. In this section, the previous works on RECEIVED

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Section: Discussionmentioning

confidence: 99%

Maximum RBE change in ¹⁹²Ir, ¹²⁵I, and ¹⁶⁹Yb brachytherapy and the corresponding effect on treatment planning

Nusrat

Karim-Picco²,

Pang³

et al. 2020

Biomed. Phys. Eng. Express

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“…Currently, the prevalence of RBE-weighting in the treatment planning process is not ubiquitous despite numerous suggestions in literature. 24,77,78,88,89,101,103,[114][115][116][117][118][119][120][121][122][123] Contrary to previous works, this study sought to determine how RBE changed as a function of distance from the source and the resulting impact on a treatment plan. In contradiction to 125 I, the RBE M of 192 Ir and 169 Yb was found to increase with distance away from the source by approximately 3% and 7%, respectively, at 8 cm (Figure 4.3).…”

Section: Discussionmentioning

confidence: 99%

Quantifying Radiobiological Variation in Cancer Radiotherapy Using Monte Carlo Simulation and Doped Plastic Scintillators

Nusrat¹

2021

Preprint

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This dissertation examines the extent to which radiobiological variations occur in photon radiotherapy, and then presents a novel methodology and detector prototype to measure this variation. In the first section, I examine the change in maximum RBE (RBEM) outside the primary field in open and composite 6 MV x-ray beams. This is done using Monte Carlo simulation and microdosimetric techniques. It was found that when comparing an open 10 10 cm2 6 MV beam to a composite 10 10 cm2 beam comprising one hundred 1x 1 cm2 beamlets, the out-of-field increase in RBE occurs much closer to the field edge in the composite case. This finding may have consequences for IMRT cases in which large amount of scattered radiation may be causing a higher than expected effective dose to organs at risk. In the second section, the maximum RBE variation is examined in the context of brachytherapy. The sources examined include 192Ir, 125I, and 169Yb. It was determined that maximum RBE of 125I relative to the source position did not vary significantly as distance from the source was increased, however, 192Ir and 169Yb were found to exhibit RBEM increases of 3.0% and 6.6% at a distance of 8 cm, respectively. Also, the impact of this variation on an HDR 192Ir prostate treatment plan was examined; it was found that RBEM hotspots of +3.6% occur at the treatment plan’s periphery. In the third part, the impact of lead doping on plastic scintillator response is quantified, a major step required for the development of the LET detector prototype. In this stage, 4 differently doped plastic scintillators were obtained, and measurements were conducted in low and medium LET beams. Using Geant4 Monte Carlo and the measured scintillator responses, the scintillator parameters: kB and L0 were determined as a function of dopant concentration and effective atomic number. Finally, the uniquely energy dependent scintillators were combined into a detector prototype used to measure the LET spectra produced by five low energy photon beams. These beams included four orthovoltage energies (100, 180, 250, and 300 kVp) along with an 192Ir HDR source. In this proof-of-principle work, the detector prototype and technique was found to accurately determine the LET spectra and the mean LET for all beams with the exception of the 100 kVp orthovoltage beam. Potential applications for the real-time LET detector prototype and technique described in this dissertation include LET measurement in radiotherapy, allowing for biologically optimized treatment plans improving patient care. This technique and prototype also has numerous applications in non-medical fields such as health physics, space travel dosimetry, and nuclear safety.

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“…The parameters used for calculations have been chosen in agreement with existing literature [8, 12, 17]. Generic values of 10 Gy and 3 Gy have been assumed for the fractionation sensitivities of tumors and normal tissues, respectively.…”

Section: Methodsmentioning

confidence: 99%

Clinical Investigations Biological effective dose evaluation and assessment of rectal and bladder complications for cervical cancer treated with radiotherapy and surgery

Beskow¹,

Ågren-Cronqvist²,

Lewensohn³

et al. 2012

jcb

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PurposeThis study aims to retrospectively evaluate dosimetric parameters calculated as biological effective dose in relation to outcome in patients with cervical cancer treated with various treatment approaches, including radiotherapy with and without surgery.Material and methodsCalculations of biological effective dose (BED) were performed on data from a retrospective analysis of 171 patients with cervical carcinoma stages IB-IIB treated with curative intent, between January 1989 and December 1991. 43 patients were treated only with radiotherapy and 128 patients were treated with a combination of radiotherapy and surgery. External beam radiotherapy was delivered with 6-21 MV photons from linear accelerators. Brachytherapy was delivered either with a manual radium technique or with a remote afterloading technique. The treatment outcome was evaluated at 5 years.ResultsThe disease-specific survival rate was 87% for stage IB, 75% for stage IIA and 54% for stage IIB, while the overall survival rates were 84% for stage IB, 68% for stage IIA and 43% for stage IIB. Patients treated only with radiotherapy had a local control rate of 77% which was comparable to that for radiotherapy and surgery patients (78%). Late complications were recorded in 25 patients (15%). Among patients treated with radiotherapy and surgery, differences in radiation dose calculated as BED10 did not seem to influence survival. For patients treated with radiotherapy only, a higher BED10 was correlated to a higher overall survival (p = 0.0075). The dose response parameters found based on biological effective dose calculations were D50 = 85.2 Gy10 and the normalized to total dose slope of the dose response curve γ = 1.62 for survival and D50 = 61.6 Gy10 and γ = 0.92, respectively for local control.ConclusionsThe outcome correlates with biological effective dose for patients treated with radiation therapy alone, but not for patients treated with radiotherapy and surgery. No correlations were found between BED and late toxicity from bladder and rectum.

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Biological effective dose evaluation in gynaecological brachytherapy: LDR and HDR treatments, dependence on radiobiological parameters, and treatment optimisation

Abstract: The efficacy of a treatment may vary as a result of several factors. Customised radiobiological evaluation is a useful adjunct to clinical evaluation in planning equivalent treatments that satisfy all dosimetric constraints.

Cited by 11 publications

References 9 publications

Maximum RBE change in ¹⁹²Ir, ¹²⁵I, and ¹⁶⁹Yb brachytherapy and the corresponding effect on treatment planning

Maximum RBE change in ¹⁹²Ir, ¹²⁵I, and ¹⁶⁹Yb brachytherapy and the corresponding effect on treatment planning

Quantifying Radiobiological Variation in Cancer Radiotherapy Using Monte Carlo Simulation and Doped Plastic Scintillators

Clinical Investigations Biological effective dose evaluation and assessment of rectal and bladder complications for cervical cancer treated with radiotherapy and surgery

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Biological effective dose evaluation in gynaecological brachytherapy: LDR and HDR treatments, dependence on radiobiological parameters, and treatment optimisation

Abstract: The efficacy of a treatment may vary as a result of several factors. Customised radiobiological evaluation is a useful adjunct to clinical evaluation in planning equivalent treatments that satisfy all dosimetric constraints.

Cited by 11 publications

References 9 publications

Maximum RBE change in 192Ir, 125I, and 169Yb brachytherapy and the corresponding effect on treatment planning

Maximum RBE change in 192Ir, 125I, and 169Yb brachytherapy and the corresponding effect on treatment planning

Quantifying Radiobiological Variation in Cancer Radiotherapy Using Monte Carlo Simulation and Doped Plastic Scintillators

Clinical Investigations Biological effective dose evaluation and assessment of rectal and bladder complications for cervical cancer treated with radiotherapy and surgery

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Maximum RBE change in ¹⁹²Ir, ¹²⁵I, and ¹⁶⁹Yb brachytherapy and the corresponding effect on treatment planning

Maximum RBE change in ¹⁹²Ir, ¹²⁵I, and ¹⁶⁹Yb brachytherapy and the corresponding effect on treatment planning