Evaluation of Unity 1.5 T MR‐linac plan quality in patients with prostate cancer

Tanaka, Shohei; Ishizawa, Miyu; Katsuta, Yoshiyuki; Arai, Kazuhiro; Takahashi, Hideya; Xiao, Yong; Takahashi, Noriyoshi; Sato, Kiyokazu; Takeda, Ken; Jingu, Keiichi

doi:10.1002/acm2.14122

Cited by 2 publications

(3 citation statements)

References 29 publications

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“…OAR dose limits for planning followed our institutional standard which is based off of the criteria published by the PACE B clinical trial and Tanaka et al. ( 26 , 58 ).…”

Section: Methodsmentioning

confidence: 99%

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Simulating an intra-fraction adaptive workflow to enable PTV margin reduction in MRIgART volumetric modulated arc therapy for prostate SBRT

Snyder,

Smith,

Aubin

et al. 2024

Front. Oncol.

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PurposeThis study simulates a novel prostate SBRT intra-fraction re-optimization workflow in MRIgART to account for prostate intra-fraction motion and evaluates the dosimetric benefit of reducing PTV margins.Materials and methodsVMAT prostate SBRT treatment plans were created for 10 patients using two different PTV margins, one with a 5 mm margin except 3 mm posteriorly (standard) and another using uniform 2 mm margins (reduced). All plans were prescribed to 36.25 Gy in 5 fractions and adapted onto each daily MRI dataset. An intra-fraction adaptive workflow was simulated for the reduced margin group by synchronizing the radiation delivery with target position from cine MRI imaging. Intra-fraction delivered dose was reconstructed and prostate DVH metrics were evaluated under three conditions for the reduced margin plans: Without motion compensation (no-adapt), with a single adapt prior to treatment (ATP), and lastly for intra-fraction re-optimization during delivery (intra). Bladder and rectum DVH metrics were compared between the standard and reduced margin plans.ResultsAs expected, rectum V18 Gy was reduced by 4.4 ± 3.9%, D1cc was reduced by 12.2 ± 6.8% (3.4 ± 2.3 Gy), while bladder reductions were 7.8 ± 5.6% for V18 Gy, and 9.6 ± 7.3% (3.4 ± 2.5 Gy) for D1cc for the reduced margin reference plans compared to the standard PTV margin. For the intrafraction replanning approach, average intra-fraction optimization times were 40.0 ± 2.9 seconds, less than the time to deliver one of the four VMAT arcs (104.4 ± 9.3 seconds) used for treatment delivery. When accounting for intra-fraction motion, prostate V36.25 Gy was on average 96.5 ± 4.0%, 99.1 ± 1.3%, and 99.6 ± 0.4 for the non-adapt, ATP, and intra-adapt groups, respectively. The minimum dose received by the prostate was less than 95% of the prescription dose in 84%, 36%, and 10% of fractions, for the non-adapt, ATP, and intra-adapt groups, respectively.ConclusionsIntra-fraction re-optimization improves prostate coverage, specifically the minimum dose to the prostate, and enables PTV margin reduction and subsequent OAR sparing. Fast re-optimizations enable uninterrupted treatment delivery.

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“…OAR dose limits for planning followed our institutional standard which is based off of the criteria published by the PACE B clinical trial and Tanaka et al. ( 26 , 58 ).…”

Section: Methodsmentioning

confidence: 99%

“…Prostate PTV margins ranging from 2 mm to greater than 10 mm have been reported in the literature and this variation often coincides with the type of pretreatment imaging used and whether intra-fraction adaptions are applied ( 25 ). Most commonly, PTV margins fall within the range of 4 to 6 mm ( 22 , 26 – 28 ). Keizer et al.…”

Section: Introductionmentioning

confidence: 99%

Simulating an intra-fraction adaptive workflow to enable PTV margin reduction in MRIgART volumetric modulated arc therapy for prostate SBRT

Snyder,

Smith,

Aubin

et al. 2024

Front. Oncol.

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“…There are currently three institutions in Japan in which 1.5 Tesla MR-Linac has been installed ( 22 , 23 ). In Japan, treatment using 1.5 Tesla MR-Linac started in December 2021 ( 22 ).…”

Section: Tesla Mr-linac In Japan and Future Prospects Of 15 Tesla Mr-...mentioning

confidence: 99%

Beginning of clinical treatment using the 1.5 Tesla MR-Linac system in Japan: a narrative review

Takahashi,

Tanaka,

Umezawa

et al. 2024

Transl Cancer Res

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Background and Objective In the field of radiation therapy, image-guided radiotherapy (IGRT) technology has been gradually improving and highly accurate radiation treatment has been possible. Research on IGRT using 1.5 Tesla magnetic resonance imaging (MRI) began in 1999, and a radiation therapy device called 1.5 Tesla magnetic resonance linear accelerator (MR-Linac), which combines a linear accelerator with 1.5 Tesla MRI, was developed in Europe. The aim of this review is to present an overview of 1.5 Tesla MR-Linac with a review of the literature and our experience. Methods Reports related to 1.5 Tesla MR-Linac were searched for in PubMed and are discussed in relation to our experience. Key Content and Findings The 1.5 Tesla MR-Linac enables IGRT using 1.5 Tesla MRI, further enhancing the precision of radiation therapy. Position verification by cone-beam computed tomography (CBCT) is performed in many institutions, but soft tissue contrast is often unclear in CBCT images of the abdomen and mediastinal organs. Since the 1.5 Tesla MR-Linac allows position verification using MRI, position verification can be performed using clear MRI even in regions where CBCT is unclear. With the 1.5 Tesla MR-Linac, it is possible to perform online adaptive radiotherapy (ART) using 1.5 Tesla MRI. Online ART is a method in which images are acquired while the patient is on the treatment table. The method is based on the current condition of the organs in the body on that day and an optimal treatment field is recreated. Additionally, it allows monitoring of tumor motion using cine images obtained by 1.5 Tesla MRI during the delivery of X-ray radiation. A previous report showed that patients with prostate cancer who received radiotherapy by MR-Linac had fewer side effects than those in patients who received conventional CBCT radiation therapy. Conclusions The 1.5 Tesla MR-Linac obtained CE-mark certification in Europe in August 2018 and it has been used for clinical treatment. In Japan, clinical treatment using this device started in 2021. By using 1.5 Tesla MR-Linac, patients can be provided with higher precision radiotherapy. In this review, we provide an overview of 1.5 Tesla MR-Linac.

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Evaluation of Unity 1.5 T MR‐linac plan quality in patients with prostate cancer

Cited by 2 publications

References 29 publications

Simulating an intra-fraction adaptive workflow to enable PTV margin reduction in MRIgART volumetric modulated arc therapy for prostate SBRT

Simulating an intra-fraction adaptive workflow to enable PTV margin reduction in MRIgART volumetric modulated arc therapy for prostate SBRT

Beginning of clinical treatment using the 1.5 Tesla MR-Linac system in Japan: a narrative review

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