Determination of action thresholds for electromagnetic tracking system‐guided hypofractionated prostate radiotherapy using volumetric modulated arc therapy

Zhang, Pengpeng; Mah, Dennis; Happersett, Laura; Cox, Brett; Hunt, Margie; Mageras, G.

doi:10.1118/1.3596776

Cited by 17 publications

(16 citation statements)

References 34 publications

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“…Several techniques were reported: continuous EPID, 89 CBCT before and after treatment, 90 and electromagnetic tracking system. 27,[91][92][93][94][95] Kupelian et al 91 using electromagnetic tracking (single responder) with Calypso system showed that intrafraction motion was not only strongly patient dependent but also changed between treatment fractions. The same approach made it possible to determine anisotropic character of intrafraction motion leading to margins for the LR, SI and AP axes of 8.4, 10.8 and 14.7 mm for skin mark-only set-up and 1.3, 2.3 and 2.8 mm using the online set-up correction.…”

Section: Accounting For Intrafraction Motionmentioning

confidence: 99%

Target margins in radiotherapy of prostate cancer

Yartsev

2016

BJR

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We reviewed the literature on the use of margins in radiotherapy of patients with prostate cancer, focusing on different options for image guidance (IG) and technical issues. The search in PubMed database was limited to include studies that involved external beam radiotherapy of the intact prostate. Post-prostatectomy studies, brachytherapy and particle therapy were excluded. Each article was characterized according to the IG strategy used: positioning on external marks using room lasers, bone anatomy and soft tissue match, usage of fiducial markers, electromagnetic tracking and adapted delivery. A lack of uniformity in margin selection among institutions was evident from the review. In general, introduction of pre- and in-treatment IG was associated with smaller planning target volume (PTV) margins, but there was a lack of definitive experimental/clinical studies providing robust information on selection of exact PTV values. In addition, there is a lack of comparative research regarding the cost-benefit ratio of the different strategies: insertion of fiducial markers or electromagnetic transponders facilitates prostate gland localization but at a price of invasive procedure; frequent pre-treatment imaging increases patient in-room time, dose and labour; online plan adaptation should improve radiation delivery accuracy but requires fast and precise computation. Finally, optimal protocols for quality assurance procedures need to be established.

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Section: Accounting For Intrafraction Motionmentioning

confidence: 99%

Target margins in radiotherapy of prostate cancer

Yartsev

2016

BJR

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“…Prostate motion and its impact on margins and delivered dose distributions in radiotherapy are well studied. [2][3][4][5][6][7] Dynamic multileaf collimator (DMLC) tracking is a method to compensate for intrafraction target motion by real-time adaption of the MLC aperture to the targets movement. [8][9][10][11][12][13][14][15][16][17] Other methods of motion compensation, not covered in this study, include beam gating, moving the source, and couch tracking.…”

Section: Introductionmentioning

confidence: 99%

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

et al. 2013

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Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments. Methods: Prostate IMAT plans were delivered with either a high-definition MLC (HDMLC) or a Millennium MLC (M-MLC) (0.25 and 0.50 cm central leaf width, respectively), with and without DMLC tracking, to a dosimetric phantom that reproduced four prostate motion traces. The plan complexity was varied by applying leaf position constraints during plan optimization. A subset of the M-MLC plans was converted for delivery with the HDMLC, isolating the effect of the different leaf widths. The gamma index was used for evaluation. Tracking errors caused by target localization, leaf fitting, and leaf adjustment were analyzed. Results: The gamma pass rate was significantly improved with DMLC tracking compared to no tracking (p < 0.001). With DMLC tracking, the average gamma index pass rate was 98.6% (range 94.8%-100%) with the HDMLC and 98.1% (range 95.4%-99.7%) with the M-MLC, using 3%, 3 mm criteria and the planned dose as reference. The corresponding pass rates without tracking were 87.6% (range 76.2%-94.7%) and 91.1% (range 81.4%-97.6%), respectively. Decreased plan complexity improved the pass rate when static target measurements were used as reference, but not with the planned dose as reference. The main cause of tracking errors was leaf fitting errors, which were decreased by 42% by halving the leaf width. Conclusions: DMLC tracking successfully compensated for the prostate motion. The finer leaf width of the HDMLC improved the tracking accuracy compared to the M-MLC. The tracking improvement with limited plan complexity was small and not discernible when using the planned dose as reference.

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“…We have previously reported a methodology to prospectively calculate a patient specific action window for electromagnetic-tracking (Calypso R ) guided VMAT delivery. 17 Intra-fraction motion traces from the Calypso database were linked to a VMAT delivery. Cumulative dose was calculated for the simulated delivery assuming rigid transformation, and checked to determine whether dose constraints in the clinical protocol were violated due to the motion.…”

Section: Iie Motion Management Strategymentioning

confidence: 99%