Institutional experience with SRS VMAT planning for multiple cranial metastases Journal Article

   


Authors: Ballangrud, A.; Kuo, L. C.; Happersett, L.; Lim, S. B.; Beal, K.; Yamada, Y.; Hunt, M.; Mechalakos, J.
Article Title: Institutional experience with SRS VMAT planning for multiple cranial metastases
Abstract: Background and Purpose: This study summarizes the cranial stereotactic radiosurgery (SRS) volumetric modulated arc therapy (VMAT) procedure at our institution. Materials and Methods: Volumetric modulated arc therapy plans were generated for 40 patients with 188 lesions (range 2-8, median 5) in Eclipse and treated on a TrueBeam STx. Limitations of the custom beam model outside the central 2.5 mm leaves necessitated more than one isocenter pending the spatial distribution of lesions. Two to nine arcs were used per isocenter. Conformity index (CI), gradient index (GI) and target dose heterogeneity index (HI) were determined for each lesion. Dose to critical structures and treatment times are reported. Results: Lesion size ranged 0.05-17.74 cm3 (median 0.77 cm3), and total tumor volume per case ranged 1.09-26.95 cm3 (median 7.11 cm3). For each lesion, HI ranged 1.2-1.5 (median 1.3), CI ranged 1.0-2.9 (median 1.2), and GI ranged 2.5-8.4 (median 4.4). By correlating GI to PTV volume a predicted GI = 4/PTV0.2 was determined and implemented in a script in Eclipse and used for plan evaluation. Brain volume receiving 7 Gy (V7 Gy) ranged 10-136 cm3 (median 42 cm3). Total treatment time ranged 24-138 min (median 61 min). Conclusions: Volumetric modulated arc therapy provide plans with steep dose gradients around the targets and low dose to critical structures, and VMAT treatment is delivered in a shorter time than conventional methods using one isocenter per lesion. To further improve VMAT planning for multiple cranial metastases, better tools to shorten planning time are needed. The most significant improvement would come from better dose modeling in Eclipse, possibly by allowing for customizing the dynamic leaf gap (DLG) for a special SRS model and not limit to one DLG per energy per treatment machine and thereby remove the limitation on the Y-jaw and allow planning with a single isocenter. © 2018 American Association of Physicists in Medicine.
Keywords: cranial metastases; vmat; srs
Journal Title: Journal of Applied Clinical Medical Physics
Volume: 19
Issue: 2
ISSN: 1526-9914
Publisher: American College of Medical Physics  
Date Published: 2018-03-01
Start Page: 176
End Page: 183
Language: English
DOI: 10.1002/acm2.12284
PROVIDER: scopus
PMCID: PMC5849827
PUBMED: 29476588
DOI/URL:

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042390892&doi=10.1002%2facm2.12284&partnerID=40&md5=6baf1ba58b3fdb2619ec27d5edae9118
Notes: Article -- Export Date: 2 April 2018 -- Source: Scopus
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MSK Authors
  1. Yoshiya Yamada
    479 Yamada
  2. Li Cheng Kuo
    63 Kuo
  3. Seng Boh Lim
    90 Lim
  4. Laura Happersett
    89 Happersett
  5. Kathryn Beal
    221 Beal
  6. Ase M Ballangrud-Popovic
    103 Ballangrud-Popovic
  7. James G Mechalakos
    164 Mechalakos
  8. Margie A Hunt
    287 Hunt
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