Dosimetric comparison of fractionated radiosurgery plans using frameless Gamma Knife ICON and CyberKnife systems with linear accelerator–based radiosurgery plans for multiple large brain metastases

OBJECTIVEFor patients with multiple large brain metastases with at least 1 target volume larger than 10 cm3, multifractionated stereotactic radiosurgery (MF-SRS) has commonly been delivered with a linear accelerator (LINAC). Recent advances of Gamma Knife (GK) units with kilovolt cone-beam CT and CyberKnife (CK) units with multileaf collimators also make them attractive choices. The purpose of this study was to compare the dosimetry of MF-SRS plans deliverable on GK, CK, and LINAC and to discuss related clinical issues.METHODSTen patients with 2 or more large brain metastases who had been treated with MF-SRS on LINAC were identified. The median planning target volume was 18.31 cm3 (mean 21.31 cm3, range 3.42–49.97 cm3), and the median prescribed dose was 27.0 Gy (mean 26.7 Gy, range 21–30 Gy), administered in 3 to 5 fractions. Clinical LINAC treatment plans were generated using inverse planning with intensity modulation on a Pinnacle treatment planning system (version 9.10) for the Varian TrueBeam STx system. GK and CK planning were retrospectively performed using Leksell GammaPlan version 10.1 and Accuray Precision version 1.1.0.0 for the CK M6 system. Tumor coverage, Paddick conformity index (CI), gradient index (GI), and normal brain tissue receiving 4, 12, and 20 Gy were used to compare plan quality. Net beam-on time and approximate planning time were also collected for all cases.RESULTSPlans from all 3 modalities satisfied clinical requirements in target coverage and normal tissue sparing. The mean CI was comparable (0.79, 0.78, and 0.76) for the GK, CK, and LINAC plans. The mean GI was 3.1 for both the GK and the CK plans, whereas the mean GI of the LINAC plans was 4.1. The lower GI of the GK and CK plans would have resulted in significantly lower normal brain volumes receiving a medium or high dose. On average, GK and CK plans spared the normal brain volume receiving at least 12 Gy and 20 Gy by approximately 20% in comparison with the LINAC plans. However, the mean beam-on time of GK (∼ 64 minutes assuming a dose rate of 2.5 Gy/minute) plans was significantly longer than that of CK (∼ 31 minutes) or LINAC (∼ 4 minutes) plans.CONCLUSIONSAll 3 modalities are capable of treating multiple large brain lesions with MF-SRS. GK has the most flexible workflow and excellent dosimetry, but could be limited by the treatment time. CK has dosimetry comparable to that of GK with a consistent treatment time of approximately 30 minutes. LINAC has a much shorter treatment time, but residual rotational error could be a concern.

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The role of diffusion tensor imaging tractography for Gamma Knife thalamotomy planning

Journal of Neurosurgery ◽

10.3171/2016.7.gks161553 ◽

2016 ◽

Vol 125 (Supplement_1) ◽

pp. 129-138 ◽

Cited By ~ 9

Author(s):

João Gabriel Ribeiro Gomes ◽

Alessandra Augusta Gorgulho ◽

Amanda de Oliveira López ◽

Crystian Wilian Chagas Saraiva ◽

Lucas Petri Damiani ◽

...

Keyword(s):

Treatment Planning ◽

Gamma Knife ◽

Treatment Time ◽

Diffusion Tensor ◽

Pyramidal Tract ◽

Planning System ◽

Treatment Planning System ◽

Motor Complications ◽

Clinical Series

OBJECTIVEThe role of tractography in Gamma Knife thalamotomy (GK-T) planning is still unclear. Pyramidal tractography might reduce the risk of radiation injury to the pyramidal tract and reduce motor complications.METHODSIn this study, the ventralis intermedius nucleus (VIM) targets of 20 patients were bilaterally defined using Iplannet Stereotaxy Software, according to the anterior commissure–posterior commissure (AC-PC) line and considering the localization of the pyramidal tract. The 40 targets and tractography were transferred as objects to the GammaPlan Treatment Planning System (GP-TPS). New targets were defined, according to the AC-PC line in the functional targets section of the GP-TPS. The target offsets required to maintain the internal capsule (IC) constraint of < 15 Gy were evaluated. In addition, the strategies available in GP-TPS to maintain the minimum conventional VIM target dose at > 100 Gy were determined.RESULTSA difference was observed between the positions of both targets and the doses to the IC. The lateral (x) and the vertical (z) coordinates were adjusted 1.9 mm medially and 1.3 mm cranially, respectively. The targets defined considering the position of the pyramidal tract were more medial and superior, based on the constraint of 15 Gy touching the object representing the IC in the GP-TPS. The best strategy to meet the set constraints was 90° Gamma angle (GA) with automatic shaping of dose distribution; this was followed by 110° GA. The worst GA was 70°. Treatment time was substantially increased by the shaping strategy, approximately doubling delivery time.CONCLUSIONSRoutine use of DTI pyramidal tractography might be important to fine-tune GK-T planning. DTI tractography, as well as anisotropy showing the VIM, promises to improve Gamma Knife functional procedures. They allow for a more objective definition of dose constraints to the IC and targeting. DTI pyramidal tractography introduced into the treatment planning may reduce the incidence of motor complications and improve efficacy. This needs to be validated in a large clinical series.

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Independent verification of treatment planning system calculations

Nukleonika ◽

10.2478/nuka-2021-0006 ◽

2021 ◽

Vol 66 (2) ◽

pp. 47-53

Author(s):

Edyta Dąbrowska-Szewczyk ◽

Anna Zawadzka ◽

Beata Brzozowska ◽

Agnieszka Walewska ◽

Paweł Kukołowicz

Keyword(s):

Treatment Planning ◽

Three Dimensional ◽

Conformal Radiotherapy ◽

Target Volume ◽

Planning System ◽

Treatment Planning System ◽

Rank Test ◽

Average Dose ◽

Independent Verification ◽

The Mean

Abstract Purpose According to the available international recommendations, at least one independent verification of the calculations of number of monitor unit (MU) is required for every patient treated by teleradiotherapy. The aim of this study was to estimate the differences of dose distributions calculated with two treatment planning systems: Eclipse (Varian) and Oncentra MasterPlan (Elekta). Materials and methods The analysis was performed for 280 three-dimensional conformal radiotherapy treatment (3D-CRT) plans with photon beams from Varian accelerators: CL 600C/D X6 MV (109 plans), CL 2300C/D X6 MV (43 plans), and CL 2300C/D X15 MV (128 plans). The mean doses in the planning target volume (PTV) and doses at the isocenter point obtained with Eclipse and Oncentra MasterPlan (OMP) were compared with Wilcoxon matched-pairs signed rank test. Additionally, the treatment planning system (TPS) calculations were compared with dosimetric measurements performed in the inhomogeneous phantom. Results Data were analysed for 6 MV plans and for 15 MV plans separately, independently of the treatment machine. The dose values calculated in Eclipse were significantly (p <0.001) higher compared to calculations of OMP system. The average difference of the mean dose to PTV was (1.4 ± 1.0)% for X6 MV and (2.5 ± 0.6)% for X15 MV. Average dose disparities at the isocenter point were (1.3 ± 1.9)% and (2.1 ± 1.0)% for X6 MV and X15 MV beams, respectively. The largest differences were observed in lungs, air cavities, and bone structures. Moreover the variation in dosimetric measurements was less as compared to Eclipse calculations. Conclusions OMP calculations were introduced as the independent MU verification tool with the first action level range equal to 3.5%.

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RADI-33. DISTRIBUTED FRAMELESS GAMMA KNIFE RADIOSURGERY: A NEW TREATMENT PARADIGM FOR PATIENTS WITH BRAIN METASTASES

Neuro-Oncology Advances ◽

10.1093/noajnl/vdz014.125 ◽

2019 ◽

Vol 1 (Supplement_1) ◽

pp. i28-i28

Author(s):

Ankur Patel ◽

Jameson Mendel ◽

Aaron Plitt ◽

Lucien Nedzi ◽

Robert Timmerman ◽

...

Keyword(s):

Brain Metastases ◽

Gamma Knife ◽

Treatment Time ◽

Gamma Knife Radiosurgery ◽

Median Number ◽

Treatment Session ◽

Normal Brain ◽

Single Session ◽

Treatment Paradigm ◽

Number Of Treatment

Abstract INTRODUCTION: Stereotactic radiosurgery (SRS) has excellent efficacy for patients with limited intracranial disease. Its use in patients with >10 brain metastases remains controversial. Nonetheless, cancer patients are living longer due to advancements in systemic therapeutics and avoiding the neurocognitive toxicities of whole brain radiation therapy is critical. Recent reports suggest that SRS may be effective in patients with ≥10 metastases. Treating large numbers of brain metastases in a single Gamma Knife radiosurgery (GKRS) treatment session poses several challenges. Treatment of metastases in close proximity to one another leads to an increased dose to normal brain, potentially increasing the risk of necrosis. Furthermore, single session treatment of multiple metastases may last several hours, causing significant patient discomfort. Here, we describe a novel treatment paradigm to address these issues: distributed frameless GKRS. Patients with ≥6 brain metastases undergo multi-session frameless GKRS with both temporal and spatial distribution over 2–5 sessions, decreasing treatment time per day and not treating adjacent metastases simultaneously. METHODS: We evaluated all patients with brain metastases who underwent distributed frameless SRS, using the Gamma Knife ICON, between January 2017 and November 2018. Fifty-one patients with 1097 unique lesions were included in this analysis. RESULTS: Mean patient age was 58.8 (range 29–89) years. Median follow-up was 4.1 (range: 0–20.4) months. The median number of metastases treated was 5 (range: 1–19) per treatment session and 11.5 (range: 3–82) per treatment course. The median number of treatment sessions per treatment course was 3 (range: 2–10). The median number of treatment courses, per patient, was 1 (range: 1–4). The median margin dose was 15 Gy. The median overall survival was 5.9 (range: 0.2–20.9) months. CONCLUSIONS: Distributed frameless Gamma Knife radiosurgery is technically feasible and should be considered in lieu of single session GKRS for patients with ≥6 brain metastases.

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Dosimetric performance of two linear accelerator-based radiosurgery systems to treat single and multiplebrain metastases

British Journal of Radiology ◽

10.1259/bjr.20190004 ◽

2019 ◽

Vol 92 (1100) ◽

pp. 20190004 ◽

Cited By ~ 2

Author(s):

Yoshihiro Ueda ◽

Shingo Ohira ◽

Hideya Yamazaki ◽

Nobuhisa Mabuchi ◽

Naokazu Higashinaka ◽

...

Keyword(s):

Brain Metastasis ◽

Brain Metastases ◽

Stereotactic Radiosurgery ◽

Linear Accelerator ◽

Planning System ◽

Treatment Planning System ◽

Multiple Brain Metastases ◽

Volumetric Arc Therapy ◽

Significant Difference ◽

Single Brain Metastasis

Objective: To evaluate and compare the dosimetric plan quality for noncoplanar volumetric arc therapy of single and multiple brain metastases using the linear accelerator-based radiosurgery system HyperArc and a robotic radiosurgery system. Methods: 31 tumors from 24 patients were treated by stereotactic radiosurgery using the CyberKnife system. CT images, structure sets, and dose files were transferred to the Eclipse treatment planning system for the HyperArc system. Dosimetric parameters for both plans were compared. The beam-on time was calculated from the total monitor unit and dose rate. Results: For normal brain tissue, the received volume doses were significantly lower for HyperArc than for CyberKnife_G4 and strongly correlated with the planning target volume (PTV) for cases of single brain metastasis. In addition, the difference in volume dose between CyberKnife_G4 and HyperArc was proportional to the PTV. For multiple brain metastases, no significant difference was observed between the two stereotactic radiosurgery systems, except for high-dose region in the normal tissue. In low dose for brain minus PTV, when the maximum distance among each target was above 8.0 cm, HyperArc delivered higher dose than CyberKnife_G4. The mean ± SDs for the beam-on time were 15.8 ± 5.3 and 5.6 ± 0.8 min for CyberKnife_G4 and HyperArc, respectively (p < .01). Conclusion: HyperArc is best suited for larger targets in single brain metastasis and for smaller inter tumor tumor distances in multiple brain metastases. Advances in knowledge: The performance of HyperArc in comparison with CyberKnife_G4 was depended on defined margin and tumor distances.

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Dosimetric characterization of hypofractionated Gamma Knife radiosurgery of large or complex brain tumors versus linear accelerator–based treatments

Journal of Neurosurgery ◽

10.3171/2016.7.gks16881 ◽

2016 ◽

Vol 125 (Supplement_1) ◽

pp. 97-103 ◽

Cited By ~ 9

Author(s):

Peng Dong ◽

Angélica Pérez-Andújar ◽

Dilini Pinnaduwage ◽

Steve Braunstein ◽

Philip Theodosopoulos ◽

...

Keyword(s):

Brain Tumors ◽

Gamma Knife ◽

Linear Accelerator ◽

Maximum Diameter ◽

Conformity Index ◽

Normal Brain ◽

Gradient Index ◽

Prescription Dose ◽

The Mean ◽

Prescription Isodose

OBJECTIVENoninvasive Gamma Knife (GK) platforms, such as the relocatable frame and on-board imaging, have enabled hypofractionated GK radiosurgery of large or complex brain lesions. This study aimed to characterize the dosimetric quality of such treatments against linear accelerator–based delivery systems that include the CyberKnife (CK) and volumetric modulated arc therapy (VMAT).METHODSTen patients treated with VMAT at the authors' institution for large brain tumors (> 3 cm in maximum diameter) were selected for the study. The median prescription dose was 25 Gy (range 20–30 Gy) in 5 fractions. The median planning target volume (PTV) was 9.57 cm3 (range 1.94–24.81 cm3). Treatment planning was performed using Eclipse External Beam Planning V11 for VMAT on the Varian TrueBeam system, Multiplan V4.5 for the CyberKnife VSI System, and Leksell GammaPlan V10.2 for the Gamma Knife Perfexion system. The percentage of the PTV receiving at least the prescription dose was normalized to be identical across all platforms for individual cases. The prescription isodose value for the PTV, conformity index, Paddick gradient index, mean and maximum doses for organs at risk, and normal brain dose at variable isodose volumes ranging from the 5-Gy isodose volume (V5) to the 15-Gy isodose volume (V15) were compared for all of the cases.RESULTSThe mean Paddick gradient index was 2.6 ± 0.2, 3.2 ± 0.5, and 4.3 ± 1.0 for GK, CK, and VMAT, respectively (p < 0.002). The mean V15 was 7.5 ± 3.7 cm3 (range 1.53–13.29 cm3), 9.8 ± 5.5 cm3 (range 2.07–18.45 cm3), and 16.1 ± 10.6 cm3 (range 3.58–36.53 cm3) for GK, CK, and VMAT, respectively (p ≤ 0.03, paired 2-tailed t-tests). However, the average conformity index was 1.18, 1.12, and 1.21 for GK, CK, and VMAT, respectively (p > 0.06). The average prescription isodose values were 52% (range 47%–69%), 60% (range 46%–68%), and 88% (range 70%–94%) for GK, CK, and VMAT, respectively, thus producing significant variations in dose hot spots among the 3 platforms. Furthermore, the mean V5 values for GK and CK were similar (p > 0.79) at 71.9 ± 36.2 cm3 and 73.3 ± 31.8 cm3, respectively, both of which were statistically lower (p < 0.01) than the mean V5 value of 124.6 ± 67.1 cm3 for VMAT.CONCLUSIONSSignificantly better near-target normal brain sparing was noted for hypofractionated GK radiosurgery versus linear accelerator–based treatments. Such a result supports the use of a large number of isocenters or confocal beams for the benefit of normal tissue sparing in hypofractionated brain radiosurgery.

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Prolonged survival in a subgroup of patients with brain metastases treated by gamma knife surgery

Journal of Neurosurgery ◽

10.3171/sup.2005.102.s_supplement.0262 ◽

2005 ◽

Vol 102 (Special_Supplement) ◽

pp. 262-265

Author(s):

C. P. Yu ◽

Joel Y. C. Cheung ◽

Josie F. K. Chan ◽

Samuel C. L. Leung ◽

Robert T. K. Ho

Keyword(s):

Brain Metastases ◽

Gamma Knife ◽

Patient Survival ◽

Gamma Knife Surgery ◽

Prolonged Survival ◽

Organ Involvement ◽

Lesion Volume ◽

Content Type ◽

The Mean ◽

Fine Print

Object. The authors analyzed the factors involved in determining prolonged survival (≥ 24 months) in patients with brain metastases treated by gamma knife surgery (GKS). Methods. Between 1995 and 2003, a total of 116 patients underwent 167 GKS procedures for brain metastases. There was no special case selection. Smaller and larger lesions were treated with different protocols. The mean patient age was 56.9 years, the mean number of initial lesions was 3.15, and the mean lesion volume was 10.45 cm.3 The mean follow-up time was 9.2 months. The median patient survival was 8.68 months. One-, 2-, 3-, 4-, and 5-year actuarial survival rates were 31.8%, 19.8%, 14.6%, 7.7%, and 6.9%, respectively. Patient age, number of lesions at presentation, and lesion volume had no influence on patient survival. Twenty-three (19.8%) patients survived for 24 months or more. Certain factors were associated with increased survival time. These were stable primary disease (21 of 23 patients), a long latency between diagnosis of the primary tumor and the occurrence of brain metastases (mean 28.4 months, median 16 months), absence of third-organ involvement, and repeated local procedures. Ten patients underwent repeated GKS (mean 3.4 per patient). Seven patients required open surgery for local treatment failures (recurrence or radiation necrosis). Two patients had both. Fifteen patients underwent repeated procedures. Conclusions. Aggressive local therapy with GKS, repeated GKS, and GKS plus surgery can achieve increased survival in a subgroup of patients with stable primary disease, no third-organ involvement, and long primary-brain secondary intervals.

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Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

Radiation Oncology ◽

10.1186/s13014-021-01858-7 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Vanessa Da Silva Mendes ◽

Lukas Nierer ◽

Minglun Li ◽

Stefanie Corradini ◽

Michael Reiner ◽

...

Keyword(s):

Prostate Cancer ◽

Target Volume ◽

Planning System ◽

Treatment Planning System ◽

Target Coverage ◽

Treatment Delivery ◽

Ptv Margin ◽

Delivery Times ◽

Low Field ◽

Treatment Plans

Abstract Background The aim of this study was to evaluate and compare the performance of intensity modulated radiation therapy (IMRT) plans, planned for low-field strength magnetic resonance (MR) guided linear accelerator (linac) delivery (labelled IMRT MRL plans), and clinical conventional volumetric modulated arc therapy (VMAT) plans, for the treatment of prostate cancer (PCa). Both plans used the original planning target volume (PTV) margins. Additionally, the potential dosimetric benefits of MR-guidance were estimated, by creating IMRT MRL plans using smaller PTV margins. Materials and methods 20 PCa patients previously treated with conventional VMAT were considered. For each patient, two different IMRT MRL plans using the low-field MR-linac treatment planning system were created: one with original (orig.) PTV margins and the other with reduced (red.) PTV margins. Dose indices related to target coverage, as well as dose-volume histogram (DVH) parameters for the target and organs at risk (OAR) were compared. Additionally, the estimated treatment delivery times and the number of monitor units (MU) of each plan were evaluated. Results The dose distribution in the high dose region and the target volume DVH parameters (D98%, D50%, D2% and V95%) were similar for all three types of treatment plans, with deviations below 1% in most cases. Both IMRT MRL plans (orig. and red. PTV margins) showed similar homogeneity indices (HI), however worse values for the conformity index (CI) were also found when compared to VMAT. The IMRT MRL plans showed similar OAR sparing when the orig. PTV margins were used but a significantly better sparing was feasible when red. PTV margins were applied. Higher number of MU and longer predicted treatment delivery times were seen for both IMRT MRL plans. Conclusions A comparable plan quality between VMAT and IMRT MRL plans was achieved, when applying the same PTV margin. However, online MR-guided adaptive radiotherapy allows for a reduction of PTV margins. With a red. PTV margin, better sparing of the surrounding tissues can be achieved, while maintaining adequate target coverage. Nonetheless, longer treatment delivery times, characteristic for the IMRT technique, have to be expected.

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Dose assessment to the Bladder during Intracavitary Brachytherapy of the Cervix using Gafchromic films

International Journal of Scientific Research in Science Engineering and Technology ◽

10.32628/ijsrset173486 ◽

2017 ◽

pp. 97-105

Author(s):

J. Avevor ◽

S. N. A. Tagoe ◽

J. H. Amuasi ◽

J. J. Fletcher ◽

I. Shirazu

Keyword(s):

Treatment Planning ◽

Maximum Dose ◽

Mean Difference ◽

Planning System ◽

Treatment Planning System ◽

In Vivo Dosimetry ◽

Intracavitary Brachytherapy ◽

Gafchromic Films ◽

System Verification ◽

The Mean

Intracavitary brachytherapy procedures are used for cervical cancer treatment, by the insertion of radioactive implants directly into the diseased tissues. During the treatment process, the bladder together with surrounding tissues are exposed to radiations. Clinical complications do results from high doses received by parts of the bladder during intracavitary brachytherapy of the cervix. The aim of this study is to assess the dose delivered to the bladder using Gafchromic films and compare it with the optimized dose calculated by the Brachy Prowess 4.60 Treatment Planning System (TPS) reports for empirical validation and system verification. Fletcher suite applicators were used to perform thirty (30) different clinical insertions on the constructed cervix phantom and results evaluated. The mean difference between the doses calculated by the TPS and the doses measured by the Gafchromic film for the bladder at the distance of 0.5cm from the edge of the film was 16.3 % (range -35.33 to +39.37). At a distance of 1.5cm for the bladder, the mean difference was 19.4% (range -49.48 to +30.39). The TPS calculated maximum dose was typically higher than the measured maximum dose. However, in some cases, the measured doses were found to be higher than the doses calculated by the TPS. This is due to positional inaccuracies of the sources during treatment planning. It is recommended that in vivo dosimetry be performed in addition to computation.

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Evaluation of Auto-Planning for Left-Side Breast Cancer After Breast-Conserving Surgery Based on Geometrical Relationship

10.21203/rs.3.rs-92221/v2 ◽

2020 ◽

Author(s):

Yijiang Li ◽

Han Bai ◽

Danju Huang ◽

Feihu Chen ◽

Xuhong Liu ◽

...

Keyword(s):

Breast Cancer ◽

Correlation Coefficient ◽

Dose Distribution ◽

Breast Conserving Surgery ◽

Target Volume ◽

Planning System ◽

Treatment Planning System ◽

Geometric Information ◽

Ipsilateral Lung ◽

Geometrical Relationship

Abstract Purpose: This study aimed to evaluate (1) the performance of the Auto-Planning module embedded in the Pinnacle treatment planning system (TPS) with 30 left-side breast cancer plans and (2) the dose-distance correlations between dose-based patients and overlap volume histogram-based (OVH) patients. Method: A total of 30 patients with left-side breast cancer after breast-conserving surgery were enrolled in this study. The clinical manual-planning (MP) and the Auto-Planning (AP) plans were generated by Monaco and by the Auto-Planning module in Pinnacle respectively. The geometric information between organ at risk (OAR) and planning target volume (PTV) of each patient was described by the OVH. The AP and MP plans were ranked to compare with the geometry-based patients from OVH. The Pearson product-moment correlation coefficient (R) was used to describe the correlations between dose-based patients (APs and MPs) and geometry-based patients (OVH). Dosimetric differences between MP and AP plans were evaluated with statistical analysis. Result: The correlation coefficient (mean R = 0.71) indicated that the AP plans have a high correlation with geometry-based patients from OVH, whereas the correlation coefficient (mean R = 0.48) shows a weak correlation between MP plans and geometry-based patients. For different indicators, the dose distribution of V5Gy in the ipsilateral lung (AP: mean R = 0.82; MP: mean R = 0.58) is more relevant to geometry-based patients compared to the dose distribution of in the heart (AP: mean R = 0.4; MP: mean R = 0.19). The dosimetric comparison revealed a statistically significant improvement in ipsilateral lung V5Gy and V10Gy and in the heart V5Gy of AP plans compared to MP plans. Conclusion: The overall results of AP plans were superior to MP plans. The dose distribution in AP plans was more consistent with the distance-dose relationship described by OVH. After eliminating the interference of human factors, the AP was able to provide more stable and objective plans for radiotherapy patients.

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