Fiducial marker based intra-fraction motion assessment on cine-MR for MR-linac treatment of prostate cancer

Keizer, Doeke; Pathmanathan, A.; Andreychenko, Anna; Kerkmeijer, Linda G.W.; Zyp, Jochem R.N. van der Voort van; Tree, A.; Berg, C.A.T. Van den; Boer, J.C.J. de

doi:10.1088/1361-6560/ab09a6

Cited by 35 publications

(47 citation statements)

References 41 publications

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“…Arc 4 is not included, as there is no IGRT performed after completion of the fourth arc delivery. greatest in the SI and AP directions, and was of similar magnitude in these two directions though slightly more pronounced anteriorly-posteriorly, which is consistent with prior reports (8,16,23,25). Greater intra-fractional displacement has also been reported, up to 2.0 ± 1.8 mm (SI) and 1.9 ± 2.0 mm (AP) based on pre-and post-treatment orthogonal imaging (19).…”

Section: Discussionsupporting

confidence: 90%

“…Our large patient numbers provide weight to our conclusions regarding average target displacement and required margins. Indeed, our standard deviations of 0.5-0.9 mm for prostate displacement are smaller than those reported in many published datasets, including those which found smaller mean directional displacements, as standard deviations of up to 2 mm have been reported (8,9,16,19,25). Importantly, the calculated margins reflect a scenario in which intra-fractional shifts are not applied in real-time.…”

Section: Discussioncontrasting

confidence: 71%

“…Image-guidance using solely pre-treatment setup, however, is not sensitive to intra-fractional changes in target positioning during dose delivery, which can be significant (14). Variables affecting intra-fractional target motion include bladder and rectal filling, treatment time, target size, and tissue density (15)(16)(17)(18). Rectal and bladder filling are generally the greatest contributors to prostate displacement, and as a result, prostate displacement tends to be greatest in the superior-inferior (SI) and anterior-posterior (AP) directions (9,(17)(18)(19)(20).…”

Section: Introductionmentioning

confidence: 99%

“…Multiple image-guided motion management strategies exist (22), and a wide range of required prostate radiotherapy margins have been proposed based on varied techniques. However, the numbers of patients included in studies to estimate required margins are relatively modest, and proposed margins based on data from the intra-fractional, interarc kilovoltage (kV) imaging method is lacking (8,9,16,19,20,(23)(24)(25)(26)(27).…”

Section: Introductionmentioning

confidence: 99%

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Clinical Assessment of Prostate Displacement and Planning Target Volume Margins for Stereotactic Body Radiotherapy of Prostate Cancer

et al. 2020

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Purpose: To assess the optimal planning target volume (PTV) margins for stereotactic body radiotherapy (SBRT) of prostate cancer based on inter-and intra-fractional prostate motion determined from daily image guidance. Methods and Materials: Two hundred and five patients who were enrolled on two prospective studies of SBRT (8 Gy × 5 fractions) for localized prostate cancer treated at a single institution between 2012 and 2017 had complete inter-and intra-fractional shift data available. All patients had scheduled kilovoltage planar imaging during SBRT with rigid registration to intraprostatic fiducials prior to each of four half-arcs delivered per fraction, as well as cone beam CT verification of anatomy prior to each fraction. Inter-and intra-fractional shift data were obtained to estimate the required PTV margins based on the classic van Herk formula. Inter-and intra-fractional motion were compared between patients with and without severe toxicities using the independent two-sample Wilcoxon test. Results: The margins required to account for inter-fractional motion were estimated to be 0.99, 1.52, and 1.45 cm in lateral (LR), longitudinal (SI), and vertical (AP) directions, respectively. The margins required to account for intra-fractional motion were estimated to be 0.19, 0.27, and 0.31 cm in LR, SI and AP directions, respectively. Large intra-fractional shifts were mostly observed in the SI and AP directions, with 2.0 and 5.4% of patients experiencing average intra-fractional motion >3 mm in the SI and AP directions, respectively, compared with none experiencing mean shifts >3 mm in the LR direction. Six patients experienced grade 3 gastrointestinal or genitourinary toxicity. There were no significant differences in mean inter-or intra-fractional motion in any of the cardinal directions compared to patients without severe toxicity (inter-fractional p = 0.46-0.99, intra-fractional p = 0.10-0.84). Levin-Epstein et al. Prostate Displacement and SBRT Margins Conclusion: The inter-and intra-fractional margins estimated from this study are in line with prior reported values. Intra-fractional prostate motion was generally small with larger margins required for the SI and AP directions, notably just slightly exceeding the commonly used 3 mm posterior PTV margin even with realignment between half-arcs. Development of severe toxicity was not significantly associated with the degree of inter-or intra-fractional motion.

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Section: Discussionsupporting

confidence: 90%

Section: Discussioncontrasting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Clinical Assessment of Prostate Displacement and Planning Target Volume Margins for Stereotactic Body Radiotherapy of Prostate Cancer

et al. 2020

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“…However, fiducial markers seem to only result in insignificant dosimetric benefits in comparison to markerless registration strategies if daily CT imaging is available ( 12 ). The advent of hybrid MR-linear accelerators may further reduce anatomic and dosimetric deviations during the course of hypofractionated prostate radiotherapy, e.g., by utilizing the superior soft tissue contrast and the possibility for real-time prostate tracking: MR-guided imaging concepts would thereby allow to compensate for both interfractional and intrafractional motion ( 39 , 40 ). In contrast to focusing on the dosimetric consequences of underlying anatomic pelvic alterations, novel position correction strategies have been proposed that guide repositioning based on the accumulated doses during treatment ( 41 ).…”

Section: Discussionmentioning

confidence: 99%

Dosimetric Impact of the Positional Imaging Frequency for Hypofractionated Prostate Radiotherapy – A Voxel-by-Voxel Analysis

et al. 2020

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Background To investigate deviations between planned and applied treatment doses for hypofractionated prostate radiotherapy and to quantify dosimetric accuracy in dependence of the image guidance frequency. Methods Daily diagnostic in-room CTs were carried out in 10 patients in treatment position as image guidance for hypofractionated prostate radiotherapy. Fraction doses were mapped to the planning CTs and recalculated, and applied doses were accumulated voxel-wise using deformable registration. Non-daily imaging schedules were simulated by deriving position correction vectors from individual scans and used to rigidly register the following scans until the next repositioning before dose recalculation and accumulation. Planned and applied doses were compared regarding dose-volume indices and TCP and NTCP values in dependence of the imaging and repositioning frequency. Results Daily image-guided repositioning was associated with only negligible deviations of analyzed dose-volume parameters and conformity/homogeneity indices for the prostate, bladder and rectum. Average CTV T did not significantly deviate from the plan values, and rectum NTCPs were highly comparable, while bladder NTCPs were reduced. For non-daily image-guided repositioning, there were significant deviations in the high-dose range from the planned values. Similarly, CTV dose conformity and homogeneity were reduced. While TCPs and rectal NTCPs did not significantly deteriorate for non-daily repositioning, bladder NTCPs appeared falsely diminished in dependence of the imaging frequency. Conclusion Using voxel-by-voxel dose accumulation, we showed for the first time that daily image-guided repositioning resulted in only negligible dosimetric deviations for hypofractionated prostate radiotherapy. Regarding dosimetric aberrations for non-daily imaging, daily imaging is required to adequately deliver treatment.

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Real time volumetric MRI for 3D motion tracking via geometry‐informed deep learning

et al. 2022

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Purpose: To develop a geometry-informed deep learning framework for volumetric MRI with sub-second acquisition time in support of 3D motion tracking, which is highly desirable for improved radiotherapy precision but hindered by the long image acquisition time. Methods: A 2D-3D deep learning network with an explicitly defined geometry module that embeds geometric priors of the k-space encoding pattern was investigated, where a 2D generation network first augmented the sparsely sampled image dataset by generating new 2D representations of the underlying 3D subject. A geometry module then unfolded the 2D representations to the volumetric space. Finally, a 3D refinement network took the unfolded 3D data and outputted high-resolution volumetric images. Patient-specific models were trained for seven abdominal patients to reconstruct volumetric MRI from both orthogonal cine slices and sparse radial samples. To evaluate the robustness of the proposed method to longitudinal patient anatomy and position changes, we tested the trained model on separate datasets acquired more than one month later and evaluated 3D target motion tracking accuracy using the model-reconstructed images by deforming a reference MRI with gross tumor volume (GTV) contours to a 5-min time series of both ground truth and model-reconstructed volumetric images with a temporal resolution of 340 ms. Results: Across the seven patients evaluated, the median distances between model-predicted and ground truth GTV centroids in the superior-inferior direction were 0.4 ± 0.3 mm and 0.5 ± 0.4 mm for cine and radial acquisitions, respectively. The 95-percentile Hausdorff distances between model-predicted and ground truth GTV contours were 4.7 ± 1.1 mm and 3.2 ± 1.5 mm for cine and radial acquisitions, which are of the same scale as cross-plane image resolution. Conclusion:Incorporating geometric priors into deep learning model enables volumetric imaging with high spatial and temporal resolution, which is particularly valuable for 3D motion tracking and has the potential of greatly improving MRI-guided radiotherapy precision.

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Fiducial marker based intra-fraction motion assessment on cine-MR for MR-linac treatment of prostate cancer

Cited by 35 publications

References 41 publications

Clinical Assessment of Prostate Displacement and Planning Target Volume Margins for Stereotactic Body Radiotherapy of Prostate Cancer

Clinical Assessment of Prostate Displacement and Planning Target Volume Margins for Stereotactic Body Radiotherapy of Prostate Cancer

Dosimetric Impact of the Positional Imaging Frequency for Hypofractionated Prostate Radiotherapy – A Voxel-by-Voxel Analysis

Real time volumetric MRI for 3D motion tracking via geometry‐informed deep learning

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