Microdosimetric Evaluation of Current and Alternative Brachytherapy Sources—A Geant4-DNA Simulation Study

Famulari, Gabriel; Pater, Piotr; Enger, Shirin A.

doi:10.1016/j.ijrobp.2017.09.040

Cited by 31 publications

(47 citation statements)

References 47 publications

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“…Maximum femoral head dose for 169 Yb‐based RSBT was calculated for the patient with bone closest to the HR‐CTV and was 50.1 Gy EQD2 , with a brachytherapy dose of 6.9 Gy EQD2 and an EBRT dose of 43.2 Gy EQD2 . The α / β value of 3 Gy has was used 42 and the radiobiological effectiveness of 169 Yb was set to 1.13 43 . The dose enhancement factor for 169 Yb in bone is not known, and, assuming it is between 2 and 3, the maximum femoral head dose would be 63.1 Gy EQD2 (19.9 Gy EQD2 from RSBT and 43.2 Gy EQD2 from EBRT) and 80.8 Gy EQD2 (37.6 Gy EQD2 from RSBT and 45 Gy EQD2 from EBRT), respectively.…”

Section: Discussionmentioning

confidence: 99%

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the ¹⁶⁹Yb Isotope

et al. 2020

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Purpose: To assess the capability of an intracavitary 169 Yb-based helical multishield rotating shield brachytherapy (RSBT) delivery system to treat cervical cancer. The proposed RSBT delivery system contains a pair of 1.25 mm thick platinum partial shields with 45°and 180°emission angles, which travel in a helical pattern within the applicator. Methods: A helically threaded tandem applicator with a 45°tandem curvature containing a helically threaded catheter was designed. A 0.6 mm diameter 169 Yb source with a length of 10.5 mm was simulated. A 37-patient treatment planning study, based on Monte Carlo dose calculations using MCNP5, was conducted with high-risk clinical target volumes (HR-CTVs) of 41.2-192.8 cm 3 (average AE standard deviation of 79.9 AE 35.8 cm 3 ). All patients were assumed to receive 25 fractions of 1.8 Gy of external beam radiation therapy (EBRT) before receiving 5 fractions of high-dose-rate brachytherapy (HDR-BT). For each patient, 192 Ir-based intracavitary (IC) HDR- BT, 192 Ir-based intracavitary/interstitial (IC/IS) HDR-BT using a hybrid applicator with eight IS needles, and 169 Yb-based RSBT plans were generated. Results: For the IC, IC/IS, and RSBT treatment plans, 38%, 84%, and 86% of the plans, respectively, met the planning goal of an HR-CTV D 90 (minimum dose to hottest 90%) of 85 Gy EQD2 (a/ b = 10 Gy). Median (25th percentile, 75th percentile) treatment times for IC, IC/IS, and RSBT were 11.71 (6.62, 15.40) min, 68.00 (45.02, 80.02) min, and 25.30 (13.87, 35.39) min, respectively. 192 Ir activities ranging from 159.1-370 GBq (4.3-10 Ci) and 169 Yb activities ranging from 429.2-999 GBq (11.6-27 Ci) were used, which correspond to the same clinical ranges of dose rates at 1 cm off-source-axis in water. Extra needle insertion and planning time beyond that needed for intracavitary-only approaches was accounted for in the IC/IS treatment time calculations. Conclusion: 169 Yb-based RSBT for cervical cancer met the HR-CTV D 90 goal of 85 Gy in a greater percentage of the patients considered than IC/IS (86% vs 84%, respectively) and can reduce overall treatment time relative to IC/IS. 169 Yb-based RSBT could be used to replace IC/IS in instances where IC/IS treatment is not available, especially in instances when HR-CTV volumes are ≥30 cm 3 .

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Section: Discussionmentioning

confidence: 99%

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the ¹⁶⁹Yb Isotope

et al. 2020

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“…Differences in relative biological effectiveness (RBE) between 192 Ir and 169 Yb were not taken into account in this work, since all photon‐emitting sources are assigned an RBE of unity in the clinic. However, a previous study showed that 169 Yb has an RBE of ~1.1 relative to 192 Ir for HDR BT applications . Prescription doses, and thus delivery times, may need to be adjusted to account for the differences in RBE values.…”

Section: Discussionmentioning

confidence: 99%

“…However, a previous study showed that 169 Yb has an RBE of~1.1 relative to 192 Ir for HDR BT applications. 52 Prescription doses, and thus delivery times, may need to be adjusted to account for the differences in RBE values.…”

Section: Discussionmentioning

confidence: 99%

A novel ¹⁶⁹Yb‐based dynamic‐shield intensity modulated brachytherapy delivery system for prostate cancer

Famulari

Duclos²,

Enger

2019

Medical Physics

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Purpose Intensity modulated brachytherapy (IMBT) is a novel high dose rate brachytherapy (HDR BT) technique which incorporates static or dynamic shielding to increase tumor coverage and/or spare healthy tissues. The purpose of this study is to present a novel delivery system (AIM‐Brachy) design that can enable dynamic‐shield IMBT for prostate cancer. Methods The AIM‐Brachy system dynamically controls the rotation of platinum shields, placed within interstitial catheters, which partially collimate the radiation emitted from an 169Yb source. Conventional HDR BT (10 Ci 192Ir) and IMBT (18 Ci 169Yb) plans were generated for 12 patients using an in‐house column generation‐based optimizer, coupled to a Geant4‐based dose calculation engine, RapidBrachyMC. Treatment plans were normalized to match the same PTV D90 coverage as the clinical plan. Intershield attenuation effects were taken into account. A sensitivity analysis was performed to evaluate the dosimetric impact of systematic longitudinal source positioning errors (±1 mm, ±2 mm, and ±3 mm) and rotational errors (±5∘, ±10∘, and ±15∘) on clinically relevant parameters (PTV D90 and urethra D10). Results The platinum shield reduced the dose rate on the shielded side at 1 cm to 18.1% of the dose rate on the unshielded side. For equal PTV D90 coverage, the urethral D10 was reduced by 13.3% ± 4.7%, without change to other plan quality indices (PTV V100, V150, V200, bladder V75, rectum V75, HI, COIN). Delivery times for HDR BT and IMBT were 9.2 ± 1.6 min and 18.6 ± 4.0 min, respectively. In general, the PTV D90 was more sensitive to source positioning errors than rotational errors, while the urethral D10 was more sensitive to rotational errors than source positioning errors. For a typical range of positioning errors (±1 mm, ±5∘), the overall tolerance was <2%. Conclusions The AIM‐Brachy system was proposed to deliver dynamic‐shield IMBT for prostate cancer with the potential to create a low dose tunnel within the urethra. The urethra‐sparing properties are desirable to minimize the occurrence and severity of urethral strictures or, alternatively, to provide a method for dose escalation.

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“…In the RSBT plans, to use the dose gradients enabled by RSBT, catheters were placed in a ring abutting the urethra gradient margin, in a ring around the outer edge of the PTV, and in a uniform manner in the remaining area of the PTV (Figure 1). Twenty 91.0 GBq 153 Gd sources were modeled as 153 Gd in Gd 2 O 3 with an activity of 2,442 GBq of 153 Gd per gram of Gd 2 O 3 [14,25,26]. The 192 Ir source was modeled after the VariSource (Varian Medical Solution, Inc., Palo Alto, CA) with an activity of 370 GBq.…”

Section: Methodsmentioning

confidence: 99%

“…Physical dose for the PTV was converted to equivalent dose in 2 Gy fractions (EQD2) using the following parameters: α/β ratio of 3.41 Gy [29,30], treatment repair half-time of 1.9 hours [31], and RBE ratio of 1.15 for the 153 Gd used for RSBT and 1.00 for the 192 Ir used for HDR-BT [32]. The EQD2 was calculated for each voxel in the PTV as [33–35]: EQD2=D(αβRBE+G[D.(t)]D)(αβ+2),and G[D˙(t)]=2D2∫tstarttstopdtD˙(t)∫tstarttdt′D˙(t′)e−μ(t−t′), Where is the total dose delivered between t start and t stop , which are the times when brachytherapy starts and stops, respectively, D˙(t)…”

Section: Methodsmentioning

confidence: 99%

Effectiveness of Rotating Shield Brachytherapy for Prostate Cancer Dose Escalation and Urethral Sparing

Adams

Hopfensperger

Kim

et al. 2018

International Journal of Radiation Oncology*Biology*Physics

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Microdosimetric Evaluation of Current and Alternative Brachytherapy Sources—A Geant4-DNA Simulation Study

Cited by 31 publications

References 47 publications

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the ¹⁶⁹Yb Isotope

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the ¹⁶⁹Yb Isotope

A novel ¹⁶⁹Yb‐based dynamic‐shield intensity modulated brachytherapy delivery system for prostate cancer

Effectiveness of Rotating Shield Brachytherapy for Prostate Cancer Dose Escalation and Urethral Sparing

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Microdosimetric Evaluation of Current and Alternative Brachytherapy Sources—A Geant4-DNA Simulation Study

Cited by 31 publications

References 47 publications

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the 169Yb Isotope

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the 169Yb Isotope

A novel 169Yb‐based dynamic‐shield intensity modulated brachytherapy delivery system for prostate cancer

Effectiveness of Rotating Shield Brachytherapy for Prostate Cancer Dose Escalation and Urethral Sparing

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Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the ¹⁶⁹Yb Isotope

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the ¹⁶⁹Yb Isotope

A novel ¹⁶⁹Yb‐based dynamic‐shield intensity modulated brachytherapy delivery system for prostate cancer