Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer

Wahlstedt, Isak; Andratschke, Nicolaus; Behrens, Carsten; Ehrbar, Stefanie; Gabryś, Hubert S.; Schüler, Helena Garcia; Gückenberger, Matthias; Smith, Abraham George; Tanadini‐Lang, Stephanie; Tascón-Vidarte, José D.; Vogelius, I.R.; Timmeren, Janita E. van

doi:10.1016/j.radonc.2022.03.013

Cited by 19 publications

(9 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, despite longer treatment times, patients have reported high satisfaction when undergoing MRIgRT [ 56 ]. While some studies have shown that beam gating may only have small dosimetric impacts on online-adaptive MRIgRT, these studies did, in fact, implement “manual gating”, where dose delivery was interrupted in the majority of patients to initiate 3D couch corrections after large displacements noticed on the onboard MRI [ 58 ].…”

Section: Limitations Of Mrigrtmentioning

confidence: 99%

MRI-Guided Radiation Therapy for Prostate Cancer: The Next Frontier in Ultrahypofractionation

Benitez,

Steinberg,

Cao

et al. 2023

Cancers

View full text Add to dashboard Cite

Technological advances in MRI-guided radiation therapy (MRIgRT) have improved real-time visualization of the prostate and its surrounding structures over CT-guided radiation therapy. Seminal studies have demonstrated safe dose escalation achieved through ultrahypofractionation with MRIgRT due to planning target volume (PTV) margin reduction and treatment gating. On-table adaptation with MRI-based technologies can also incorporate real-time changes in target shape and volume and can reduce high doses of radiation to sensitive surrounding structures that may move into the treatment field. Ongoing clinical trials seek to refine ultrahypofractionated radiotherapy treatments for prostate cancer using MRIgRT. Though these studies have the potential to demonstrate improved biochemical control and reduced side effects, limitations concerning patient treatment times and operational workflows may preclude wide adoption of this technology outside of centers of excellence. In this review, we discuss the advantages and limitations of MRIgRT for prostate cancer, as well as clinical trials testing the efficacy and toxicity of ultrafractionation in patients with localized or post-prostatectomy recurrent prostate cancer.

show abstract

Section: Limitations Of Mrigrtmentioning

confidence: 99%

MRI-Guided Radiation Therapy for Prostate Cancer: The Next Frontier in Ultrahypofractionation

Benitez,

Steinberg,

Cao

et al. 2023

Cancers

View full text Add to dashboard Cite

show abstract

“…Combining reduced PTV margins and online adaptive re-planning may further reduce treatment related toxicities. However, long treatment session times associated with MRIgART and intra-fraction motion limit the extent to which PTV margins can be reduced without intra-fraction compensation ( 29 , 42 , 43 ). MRIgART with daily re-planning commonly uses prostate PTV margins ranging between 3 and 5 mm ( 44 – 48 ) with 5 mm in all directions except for 3 mm in the posterior direction remaining a standard ( 43 , 49 – 51 ).…”

Section: Introductionmentioning

confidence: 99%

“…MRIgART with daily re-planning commonly uses prostate PTV margins ranging between 3 and 5 mm ( 44 – 48 ) with 5 mm in all directions except for 3 mm in the posterior direction remaining a standard ( 43 , 49 – 51 ). While techniques such as gating and/or baseline shift corrections can be used in conjunction with reduced PTV margins, this will add additional time to already long treatment sessions and therefore is impractical for some patients ( 42 , 43 ). This may be especially impactful on systems such as the Elekta Unity which does not support couch movement during treatment and thus, users must wait for baseline shift plans to be re-optimized or re-calculated prior to resuming treatment if target excursions occur ( 52 , 53 ).…”

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.

View full text Add to dashboard Cite

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.

show abstract

“…This is of particular importance for ultra-hypofractionated treatment regimes (Finazzi et al 2020b) or single fraction treatments (Finazzi et al 2020c, Palacios et al 2022 for which dose inhomogeneities do not average out over the course of treatment. Recently, Xiong et al (2022) and Wahlstedt et al (2022) derived first-order approximations of the intrafractionally accumulated dose delivered in online adaptive MRgRT to the prostate and close-by OARs in presence of residual target motion within a gating window. They neglected interplay effects and assumed the shift-invariance of dose distributions (McCarter andBeckham 2000, Sharma et al 2012) in photon therapy and convolved a static dose distribution with the target trajectories observed on planar sagittal cine MR images acquired at MRIdian MRlinacs (ViewRay Inc., Oakwood Village, Ohio, USA).…”

Section: Introductionmentioning

confidence: 99%

Continuous time-resolved estimated synthetic 4D-CTs for dose reconstruction of lung tumor treatments at a 0.35 T MR-linac

Rabe,

Paganelli,

Schmitz

et al. 2023

Phys. Med. Biol.

View full text Add to dashboard Cite

Objective. To experimentally validate a method to create continuous time-resolved estimated synthetic 4D-computed tomography datasets (tresCTs) based on orthogonal cine MRI data for lung cancer treatments at a magnetic resonance imaging (MRI)-guided linear accelerator (MR-linac).Approach. A breathing porcine lung phantom was scanned at a CT scanner and 0.35 T MR-linac. Orthogonal cine MRI series (sagittal/coronal orientation) at 7.3 Hz, intersecting tumor-mimicking gelatin nodules, were deformably registered to mid-exhale 3D-CT and 3D-MRI datasets. The time-resolved deformation vector fields were extrapolated to 3D and applied to a reference synthetic 3D-CT image (sCTref), while accounting for breathing phase-dependent lung density variations, to create 82s-long tresCTs at 3.65 Hz. Ten tresCTs were created for ten tracked nodules with different motion patterns in two lungs. For each dataset, a treatment plan was created on the mid-exhale phase of a measured ground truth (GT) respiratory-correlated 4D-CT dataset with the tracked nodule as gross tumor volume (GTV). Each plan was recalculated on the GT 4D-CT, randomly sampled tresCT, and static sCTref images. Dose distributions for corresponding breathing phases were compared in gamma (2%/2mm) and dose-volume histogram (DVH) parameter analyses.Main results. The mean gamma pass rate between all tresCT and GT 4D-CT dose distributions was 98.6%. The mean absolute relative deviations of the tresCT with respect to GT DVH parameters were 1.9%, 1.0%, and 1.4% for the GTV D 98%, D 50%, and D 2%, respectively, 1.0% for the remaining nodules D 50%, and 1.5% for the lung V 20 Gy. The gamma pass rate for the tresCTs was significantly larger (p<0.01), and the GTV D 50% deviations with respect to the GT were significantly smaller (p<0.01) than for the sCTref.Significance. The results suggest that tresCTs could be valuable for time-resolved reconstruction and intrafractional accumulation of the dose to the GTV for lung cancer patients treated at MR-linacs in the future.

show abstract

Gating has a negligible impact on dose delivered in MRI-guided online adaptive radiotherapy of prostate cancer

Cited by 19 publications

References 29 publications

MRI-Guided Radiation Therapy for Prostate Cancer: The Next Frontier in Ultrahypofractionation

MRI-Guided Radiation Therapy for Prostate Cancer: The Next Frontier in Ultrahypofractionation

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

Continuous time-resolved estimated synthetic 4D-CTs for dose reconstruction of lung tumor treatments at a 0.35 T MR-linac

Contact Info

Product

Resources

About