Dataset Information

Implications of a high-definition multileaf collimator (HD-MLC) on treatment planning techniques for stereotactic body radiation therapy (SBRT): a planning study.

ABSTRACT:

Purpose

To assess the impact of two multileaf collimator (MLC) systems (2.5 and 5 mm leaf widths) on three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and dynamic conformal arc techniques for stereotactic body radiation therapy (SBRT) of liver and lung lesions.

Methods

Twenty-nine SBRT plans of primary liver (n=11) and lung (n=18) tumors were the basis of this study. Five-millimeter leaf width 120-leaf Varian Millennium (M120) MLC-based plans served as reference, and were designed using static conformal beams (3DCRT), sliding-window intensity-modulated beams (IMRT), or dynamic conformal arcs (DCA). Reference plans were either re-optimized or recomputed, with identical planning parameters, for a 2.5-mm width 120-leaf BrainLAB/Varian high-definition (HD120) MLC system. Dose computation was based on the anisotropic analytical algorithm (AAA, Varian Medical Systems) with tissue heterogeneity taken into account. Each plan was normalized such that 100% of the prescription dose covered 95% of the planning target volume (PTV). Isodose distributions and dose-volume histograms (DVHs) were computed and plans were evaluated with respect to target coverage criteria, normal tissue sparing criteria, as well as treatment efficiency.

Results

Dosimetric differences achieved using M120 and the HD120 MLC planning were generally small. Dose conformality improved in 51.7%, 62.1% and 55.2% of the IMRT, 3DCRT and DCA cases, respectively, with use of the HD120 MLC system. Dose heterogeneity increased in 75.9%, 51.7%, and 55.2% of the IMRT, 3DCRT and DCA cases, respectively, with use of the HD120 MLC system. DVH curves demonstrated a decreased volume of normal tissue irradiated to the lower (90%, 50% and 25%) isodose levels with the HD120 MLC.

Conclusion

Data derived from the present comparative assessment suggest dosimetric merit of the high definition MLC system over the millennium MLC system. However, the clinical significance of these results warrants further investigation in order to determine whether the observed dosimetric advantages translate into outcome improvements.

SUBMITTER: Tanyi JA

PROVIDER: S-EPMC2716348 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Publications

Implications of a high-definition multileaf collimator (HD-MLC) on treatment planning techniques for stereotactic body radiation therapy (SBRT): a planning study.

Tanyi James A JA Summers Paige A PA McCracken Charles L CL Chen Yiyi Y Ku Li-Chung LC Fuss Martin M

Radiation oncology (London, England) 20090710

<h4>Purpose</h4>To assess the impact of two multileaf collimator (MLC) systems (2.5 and 5 mm leaf widths) on three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and dynamic conformal arc techniques for stereotactic body radiation therapy (SBRT) of liver and lung lesions.<h4>Methods</h4>Twenty-nine SBRT plans of primary liver (n=11) and lung (n=18) tumors were the basis of this study. Five-millimeter leaf width 120-leaf Varian Millennium (M120) MLC-based plans served as re ...[more]

PMID: 19591687

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Project description:BackgroundTo investigate the effect of stereotactic body radiation therapy (SBRT) on pulmonary oligometastases and to analyze the clinical factors and dose parameters affecting local recurrence-free survival (LRFS) and overall survival (OS).MethodsThis study retrospectively enrolled a total of 84 patients (148 lesions) treated in our department from May 2015 to November 2018. Pulmonary oligometastases was defined as up to 5 metastatic lesions in the lung and with both the primary tumor and any extra-thoracic metastases being controlled. Patients receiving a BED10 (biological effective dose, α/β =10) of SBRT ≥75 Gy and a dose/fraction ≥4 Gy were enrolled. The patient group consisted of 52 men (61.9%) and 32 women (38.1%), with a median age 56 years (range, 29-80 years). Median tumor diameter was 1.71cm (range, 1.2-5.0 cm). The BED10 was 75-119 Gy in 4-15 fractions. Univariate and multivariate Cox regression analyses were performed on factors predicting the outcomes.ResultsAll patients completed the treatment as planned, and the median follow-up time was 20.3 months. The median OS for the entire group was 34.3 months, with an actuarial 1-, 2-, 3- and 5-year OS of 74.7%, 59.4%, 49.7%, and 36.8%, respectively. Among the 148 lesions in the whole group, 19 (12.8%) lesions had local recurrence (LR). The median LRFS time for all patients was 56.9 months. The LRFS rate was 93.6%, 83.5%, 81.4%, and 76.6% at 1, 2, 3, and 5 years, respectively. No patient developed acute grade 3 or 4 toxicity. On univariate analysis, age ≥63 years old, primary site of colorectal cancer, BED10 <85.2 Gy, pathological type of adenocarcinoma, planning target volume (PTV) min BED10 <76.6 Gy, and gross tumor volume (GTV) ≥8.8 cc, were significantly associated with poorer LRFS. Multivariate analysis showed that age ≥63 years old, primary site of colorectal cancer, and PTV min BED10 <76.6 Gy were significant risk factors affecting LRFS.ConclusionsSBRT is feasible for pulmonary oligometastasis with favorable local control and minimal toxicity. Multiple dose parameters, instead of a prescription dose only, in combination with clinical parameters, should be considered for optimal local control.

Project description:PurposeReal-time tumor tracking through active correction by the multileaf collimator or treatment couch offers a promising strategy to mitigate delivery uncertainty due to intrafractional tumor motion. This study evaluated the performance of MLC and couch tracking using the prototype iTools Tracking system in TrueBeam Developer Mode and the application for abdominal cancer treatments.MethodsExperiments were carried out using a phantom with embedded Calypso transponders and a motion simulation platform. Geometric evaluations were performed using a circular conformal field with sinusoidal traces and pancreatic tumor motion traces. Geometric tracking accuracy was retrospectively calculated by comparing the compensational MLC or couch motion extracted from machine log files to the target motion reconstructed from real-time MV and kV images. Dosimetric tracking accuracy was measured with radiochromic films using clinical abdominal VMAT plans and pancreatic tumor traces.ResultsGeometrically, the root-mean-square errors for MLC tracking were 0.5 and 1.8 mm parallel and perpendicular to leaf travel direction, respectively. Couch tracking, in contrast, showed an average of 0.8 mm or less geometric error in all directions. Dosimetrically, both MLC and couch tracking reduced motion-induced local dose errors compared to no tracking. Evaluated with five pancreatic tumor motion traces, the average 2%/2 mm global gamma pass rate of eight clinical abdominal VMAT plans was 67.4% (range: 26.4%-92.7%) without tracking, which was improved to 86.0% (range: 67.9%-95.6%) with MLC tracking, and 98.1% (range: 94.9%-100.0%) with couch tracking. In 16 out of 40 deliveries with different plans and motion traces, MLC tracking did not achieve clinically acceptable dosimetric accuracy with 3%/3mm gamma pass rate below 95%.ConclusionsThis study demonstrated the capability of MLC and couch tracking to reduce motion-induced dose errors in abdominal cases using a prototype tracking system. Clinically significant dose errors were observed with MLC tracking for certain plans which could be attributed to the inferior MLC tracking accuracy in the direction perpendicular to leaf travel, as well as the interplay between motion tracking and plan delivery for highly modulated plans. Couch tracking outperformed MLC tracking with consistently high dosimetric accuracy in all plans evaluated, indicating its clinical potential in the treatment of abdominal cancers.

Dataset Information

Implications of a high-definition multileaf collimator (HD-MLC) on treatment planning techniques for stereotactic body radiation therapy (SBRT): a planning study.

Purpose

Methods

Results

Conclusion

Publications

Implications of a high-definition multileaf collimator (HD-MLC) on treatment planning techniques for stereotactic body radiation therapy (SBRT): a planning study.

Similar Datasets

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