A new plan quality objective function for determining optimal collimator combinations in prostate cancer treatment with stereotactic body radiation therapy using CyberKnife

Varnava, Maria; Sumida, Iori; Mizuno, Hirokazu; Shiomi, Hiroya; Сузукі, Осаму; Yoshioka, Yasuo; Ogawa, Kazuhiko

doi:10.1371/journal.pone.0208086

Cited by 7 publications

(7 citation statements)

References 32 publications

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“…More collimators also obviously increased nodes, beams, EFTT, GI, and dose to normal brain and decreased the MUs and HI, although improved PTV coverage produced slightly higher PTV D min . These results are consistent with those of Varnava et al, who conjectured that 2 collimators can do the same as the 10 collimators (17).…”

Section: Discussionsupporting

confidence: 93%

Comparison of Two Cyberknife Planning Approaches for Multiple Brain Metastases

Song

Zhao

et al. 2022

Front. Oncol.

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PurposeTo compare the delivery efficiency, plan quality, and planned treatment volume (PTV) and normal brain dosimetry between different Cyberknife planning approaches for multiple brain metastases (MBM), and to evaluate the effects of the number of collimators on the related parameters.MethodsThe study included 18 cases of MBM. The Cyberknife treatment plans were classified as Separate or Combined. For the Separate plan, each lesion was targeted by the collimator auto-selection method (Conformality 2/3 collimators). For the Combined plan, a PTV including all PTVs was targeted by the collimators. Monitor units (MUs), number of nodes and beams, estimated fraction treatment time (EFTT), new conformity index (nCI), dose gradient index (GI), homogeneity index (HI), PTV minimum/maximum dose (Dmax/Dmin), volume doses (D2% and D98%), maximum doses to lenses, optic nerves, and brainstem as well as normal brain 3, 6, 10, and 12 Gy (V3Gy–V12Gy) were compared.ResultsCompared to the Combined plan, the Separate plan had fewer nodes and beams, shorter EFTT, smaller PTV Dmin, normal brain dose, and GI, and larger HI. The Separate plan with 2 collimators also had worse PTV coverage. In the Combined plan, more collimators increased beams, EFTT, GI, and normal brain dose but improved the PTV Dmin. Among treatments based on the Separate approach, there were obvious differences between plans for most of the items except the nCI. Fewer collimators resulted in significantly reduced beams, EFTT, PTV D98%, and normal brain dose with improved GI, although PTV Dmin and MUs were decreased while HI was increased.ConclusionBoth approaches met the requirements for SRS/HFSRT. We found that Separate plans improved treatment efficiency and normal tissue dosimetry.

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Section: Discussionsupporting

confidence: 93%

Comparison of Two Cyberknife Planning Approaches for Multiple Brain Metastases

Song

Zhao

et al. 2022

Front. Oncol.

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“…When CK is used, it generally takes 35–50 min to deliver prostate SBRT, including a 5‐min setup time. 24 , 25 However, in our study, the average BOT was only 17 min for CK. The VOLO optimizer, a new optimization algorithm for CK, can reduce the BOT more than the previous Sequential optimization algorithm.…”

Section: Discussioncontrasting

confidence: 60%

“…When CK is used, it generally takes 35–50 min to deliver prostate SBRT, including a 5‐min setup time 24,25 . However, in our study, the average BOT was only 17 min for CK.…”

Section: Discussionmentioning

confidence: 66%

Plan comparison of prostate stereotactic radiotherapy in spacer implant patients

Oki

Uehara

Mizonobe

et al. 2021

J Applied Clin Med Phys

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In prostate stereotactic body radiation therapy (SBRT), hydrogel spacers are increasingly used. This study aimed to perform a dosimetry comparison of treatment plans using CyberKnife (CK), commonly used for prostate SBRT, Helical TomoTherapy (HT), and TrueBeam (TB) in patients with hydrogel spacer implantations. The data of 20 patients who received hydrogel spacer implantation for prostate SBRT were retrospectively analyzed. The prescription dose was 36.25 Gy in five fractions to 95% of the planning target volume (PTV; D95). The conformity index (CI), gradient index (GI), homogeneity index (HI), and dose‐volume histogram (DVH) were analyzed for the three modalities, using the same PTV margins. The monitor unit (MU) and the beam‐on‐time (BOT) values were subsequently compared. The CI of TB (0.93 ± 0.02) was significantly superior to those of CK (0.82 ± 0.03, p < 0.01) and HT (0.86 ± 0.03, p < 0.01). Similarly, the GI value of TB (3.59 ± 0.12) was significantly better than those of CK (4.31 ± 0.43, p < 0.01) and HT (4.52 ± 0.24, p < 0.01). The median doses to the bladder did not differ between the CK and TB (V18.1 Gy: 16.5% ± 4.5% vs. 15.8% ± 4.4%, p = 1.00), but were significantly higher for HT (V18.1 Gy: 33.2% ± 7.3%, p < 0.01 vs. CK, p < 0.01 vs. TB). The median rectal dose was significantly lower for TB (V18.1 Gy: 5.6% ± 4.5%) than for CK (V18.1 Gy: 11.2% ± 6.7%, p < 0.01) and HT (20.2% ± 8.3%, p < 0.01). TB had the shortest BOT (2.6 min; CK: 17.4 min, HT: 6.9 min). TB could create treatment plans dosimetrically comparable to those of CK when using the same margins, in patients with hydrogel spacers.

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“…For lung and liver SBRT, the therapeutic ratio is essential to ensure adequate coverage of moving targets while sparing the surrounding normal tissues. The amount of irradiated volume in CyberKnife treatment depends on applied motion management strategy, adopted safety margins, and beam collimator selection 4–6 . Most of the CyberKnife treatment retrospective studies have focused on improving tracking accuracy and reducing the planning target volume (PTV) margins 1,7–11 .…”

Section: Introductionmentioning

confidence: 99%

“…This collimator allows 12‐field diameters to be used without a manual exchange of collimators 16 . At our institution, in order to improve the plan quality and time efficiency, one collimator is used for small tumors in CKS treatment and two collimator combinations (small and large) are used for the large tumors in CKS treatment 4,6,17 . We previously analyzed the intrafractional dose uncertainty in the CyberKnife XLT treatment, and found that the plan robustness is better with large collimator 12 .…”

Section: Introductionmentioning

confidence: 99%

Integrating CVH and LVH metrics into an optimization strategy for the selection of Iris collimator for Cyberknife Xsight lung tracking treatment

Xiao

Chang

Zhang

et al. 2021

J Applied Clin Med Phys

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PurposeWe conducted this study to construct a target coverage‐volume histogram (CVH) and leakage‐volume histogram (LVH) metrics and optimization strategy for the selection of the Iris collimator in Cyberknife Xsight lung tracking treatment through a retrospective analysis of target structures and clinical data.Methods and MaterialsCVH and LVH metrics were retrospectively analyzed for 37 lung cancer patients. CVH and LVH were the same as dose‐volume histogram (DVH), but with a coverage and leakage replacing dose. For each patient, Iris collimator was optimized and selected based on CVH and LVH metrics. The CVH and LVH metrics were then compared to ascertain differences in 95% (C95) or 90% (C90) of the target coverage thresholds. The planning target volume (PTV) C95 and C90 coverage, absolute mean leakage value, leakage/coverage ratio, selected collimator diameter (Φ), Φ/length of the long axis of PTV (Amax), and Φ/length of the short axis (Amin) of PTV were compared. The correlation of the absolute mean leakage value, leakage/coverage ratio, Φ/Amin and Φ/Amax were evaluated.ResultsFor each patient, the PTV C95 coverage (70.45 vs 63.19) and C90 coverage (77.25 vs 69.96) were higher in the C95 coverage threshold group compared to the C90 coverage threshold group. The leakage/coverage ratio (0.56 vs 0.69) and absolute mean leakage value (0.56 vs 0.61) were lower in C90 coverage threshold group than in C95 coverage threshold group. The Spearmen correlation test showed the Φ/Amin were significantly correlated with leakage/coverage ratio and absolute mean leakage value. Upon analysis of the selected collimator diameters, the mean value of Φ/Amin of the optimized collimator diameters was found to be 1.10.ConclusionThe CVH and LVH analysis is able to quantitatively evaluate the tradeoff between target coverage and normal tissue sparing.

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A new plan quality objective function for determining optimal collimator combinations in prostate cancer treatment with stereotactic body radiation therapy using CyberKnife

Cited by 7 publications

References 32 publications

Comparison of Two Cyberknife Planning Approaches for Multiple Brain Metastases

Comparison of Two Cyberknife Planning Approaches for Multiple Brain Metastases

Plan comparison of prostate stereotactic radiotherapy in spacer implant patients

Integrating CVH and LVH metrics into an optimization strategy for the selection of Iris collimator for Cyberknife Xsight lung tracking treatment

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