Asymmetric dose–volume optimization with smoothness control for rotating‐shield brachytherapy

Liu, Yunlong; Flynn, R; Kim, Yusung; Wu, Xiaodong

doi:10.1118/1.4897617

Cited by 12 publications

(48 citation statements)

References 54 publications

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“…Optimized treatment plans were generated for all patients using the POGS method and the previously investigated CPLEX method . The same objective function, with the same input parameters and beamlets, was minimized for each patient with both methods.…”

Section: Methodsmentioning

confidence: 99%

“…Optimized treatment plans were generated for all patients using the POGS method and the previously investigated CPLEX method. 15 The same objective function, with the same input parameters and beamlets, was minimized for each patient with both methods. A total variation term was included in the objective function as a regularization term, resulting in smoothly varying emission times along each keyway.…”

Section: E Treatment Plan Evaluationmentioning

confidence: 99%

“…Liu et al used a commercial optimization solver called CPLEX. 15,16 In order to efficiently solve the ADOS optimization problem, an optimization method based on the proximal graph solver (POGS), 17 which is a solver using the alternating direction method of multipliers (ADMM), was designed. For this purpose, the closed-form formulas for the proximal operators used in POGS were derived.…”

Section: Introductionmentioning

confidence: 99%

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Fast dose optimization for rotating shield brachytherapy

Cho

Dadkhah

et al. 2017

Medical Physics

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Purpose To provide a fast computational method, based on the proximal graph solver (POGS) – A convex optimization solver using the alternating direction method of multipliers (ADMM), for calculating an optimal treatment plan in rotating shield brachytherapy (RSBT). RSBT treatment planning has more degrees of freedom than conventional high-dose-rate brachytherapy due to the addition of emission direction, and this necessitates a fast optimization technique to enable clinical usage. Methods The multi-helix RSBT (H-RSBT) delivery technique was investigated for five representative cervical cancer patients. Treatment plans were generated for all patients using the POGS method and the commercially available solver IBM ILOG CPLEX. The rectum, bladder, sigmoid colon, high-risk clinical target volume (HR-CTV), and HR-CTV boundary were the structures included in our optimization, which applied an asymmetric dose-volume optimization with smoothness control. Dose calculation resolution was 1 × 1 × 3 mm3 for all cases. The H-RSBT applicator had 6 helices, with 33.3 mm of translation along the applicator per helical rotation and 1.7 mm spacing between dwell positions, yielding 17.5° emission angle spacing per 5 mm along the applicator. Results For each patient, HR-CTV D90, HR-CTV D100, rectum D2cc, sigmoid D2cc, and bladder D2cc matched within 1% for CPLEX and POGS methods. Also, similar EQD2 values between CPLEX and POGS methods were obtained. POGS was around 18 times faster than CPLEX. For all patients, total optimization times were 32.1–65.4 s for CPLEX and 2.1–3.9 s for POGS. Conclusions POGS reduced treatment plan optimization time approximately 18 times for RSBT with similar HR-CTV D90, organ at risk (OAR) D2cc values, and EQD2 values compared to CPLEX, which is significant progress toward clinical translation of RSBT.

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Section: Methodsmentioning

confidence: 99%

Section: E Treatment Plan Evaluationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fast dose optimization for rotating shield brachytherapy

Cho

Dadkhah

et al. 2017

Medical Physics

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“…Figure 9 shows the delivery efficiency curves by P-RSBT-5 and P-RSBT-60 for the anchor plans computed by two different dose optimizers: one was the ADOS method 1 in which emission time smoothness is enforced by the L 2 -norm, and the other was based on the inverse planning by simulated annealing (IPSA) technique where no smoothness was enforced. The HR-CTV D 90 's of the anchor plans using ADOS and IPSA were 91.4 and 94.0 Gy 10 , respectively.…”

Section: Discussionmentioning

confidence: 99%

Paddle‐based rotating‐shield brachytherapy

et al. 2015

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Purpose: The authors present a novel paddle-based rotating-shield brachytherapy (P-RSBT) method, whose radiation-attenuating shields are formed with a multileaf collimator (MLC), consisting of retractable paddles, to achieve intensity modulation in high-dose-rate brachytherapy. Methods: Five cervical cancer patients using an intrauterine tandem applicator were considered to assess the potential benefit of the P-RSBT method. The P-RSBT source used was a 50 kV electronic brachytherapy source (Xoft Axxent™). The paddles can be retracted independently to form multiple emission windows around the source for radiation delivery. The MLC was assumed to be rotatable. P-RSBT treatment plans were generated using the asymmetric dose-volume optimization with smoothness control method [Liu et al., Med. Phys. 41(11), 111709 (11pp.) (2014)] with a delivery time constraint, different paddle sizes, and different rotation strides. The number of treatment fractions (fx) was assumed to be five. As brachytherapy is delivered as a boost for cervical cancer, the dose distribution for each case includes the dose from external beam radiotherapy as well, which is 45 Gy in 25 fx. The high-risk clinical target volume (HR-CTV) doses were escalated until the minimum dose to the hottest 2 cm 3 (D 2cm 3) of either the rectum, sigmoid colon, or bladder reached their tolerance doses of 75, 75, and 90 Gy 3 , respectively, expressed as equivalent doses in 2 Gy fractions (EQD2 with α/ β = 3 Gy). Results: P-RSBT outperformed the two other RSBT delivery techniques, single-shield RSBT (S-RSBT) and dynamic-shield RSBT (D-RSBT), with a properly selected paddle size. If the paddle size was angled at 60• , the average D 90 increases for the delivery plans by P-RSBT on the five cases, compared to S-RSBT, were 2.2, 8.3, 12.6, 11.9, and 9.1 Gy 10 , respectively, with delivery times of 10, 15, 20, 25, and 30 min/fx. The increases in HR-CTV D 90 , compared to D-RSBT, were 16.6, 12.9, 7.2, 3.7, and 1.7 Gy 10 , respectively. P-RSBT HR-CTV D 90 -values were insensitive to the paddle size for paddles angled at less than 60• . Increasing the paddle angle from 5• to 60• resulted in only a 0.6 Gy 10 decrease in HR-CTV D 90 on average for five cases when the delivery times were set to 15 min/fx. The HR-CTV D 90 decreased to 2.5 and 11.9 Gy 10 with paddle angles of 90• and 120• , respectively. Conclusions: P-RSBT produces treatment plans that are dosimetrically and temporally superior to those of S-RSBT and D-RSBT, although P-RSBT systems may be more mechanically challenging to develop than S-RSBT or D-RSBT. A P-RSBT implementation with 4-6 shield paddles would be sufficient to outperform S-RSBT and D-RSBT if delivery times are constrained to less than 15 min/fx.

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“…Dose distribution conformity and sensitive healthy tissue avoidance can be considerably improved through the use of rotating shield brachytherapy (RSBT) in conjunction with a 153 Gd radiation source that is amenable to partial shielding within an interstitial needle ( 192 Ir is not). 30–33 The sources rotate during delivery in an optimized fashion, 34,35 directing dose away from sensitive structures and into the targeted tissue.…”

Section: Introductionmentioning

confidence: 99%

Multisource Rotating Shield Brachytherapy Apparatus for Prostate Cancer

Dadkhah

Hopfensperger

Kim

et al. 2017

International Journal of Radiation Oncology*Biology*Physics

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Purpose To present a novel multisource rotating shield brachytherapy (RSBT) apparatus for the simultaneous precise angular and linear positioning of partially-shielded 153Gd brachytherapy sources in interstitial needles for the treatment of locally-advanced prostate cancer. It is designed to lower the dose to nearby healthy tissues, the urethra in particular, relative to conventional high-dose-rate brachytherapy (HDR-BT) techniques. Methods and Materials Following needle implantation through the patient template, an angular drive mechanism is docked to the patient template. Each needle is coupled to a multisource afterloader catheter by a connector passing through a shaft. The shafts are rotated about their axes by translating a moving template between two stationary templates. Shafts’ surfaces and moving template holes are helically threaded with the same pattern such that translation of the moving template causes simultaneous rotation of the shafts. The rotation of each shaft is mechanically transmitted to the catheter/source/shield combination, inside the needles, via several key/keyway pairs. The catheter angles are simultaneously incremented throughout treatment, and only a single 360° rotation of all catheters is needed for a full treatment. For each rotation angle, source depth in each needle is controlled by a multisource afterloader, which is proposed as an array of belt-driven linear actuators, each of which drives a wire that controls catheter depth in a needle. Results Treatment plans demonstrated RSBT with the proposed apparatus reduced urethral D0.1cc below that of conventional HDR-BT by 31% for urethral dose gradient volume within 3 mm of the urethra surface. Treatment time to deliver 20 Gy with the proposed multisource RSBT apparatus using nineteen 62.4 GBq 153Gd sources is 122 min. Conclusions The proposed RSBT delivery apparatus enables a mechanically feasible urethra-sparing treatment technique for prostate cancer in a clinically reasonable timeframe.

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Asymmetric dose–volume optimization with smoothness control for rotating‐shield brachytherapy

Cited by 12 publications

References 54 publications

Fast dose optimization for rotating shield brachytherapy

Fast dose optimization for rotating shield brachytherapy

Paddle‐based rotating‐shield brachytherapy

Multisource Rotating Shield Brachytherapy Apparatus for Prostate Cancer

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