Bringing online adaptive radiotherapy to a standard C-arm linac
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PROVIDER: S-EPMC11239695 | biostudies-literature | 2024 Jun
REPOSITORIES: biostudies-literature
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Project description:PurposeA hybrid magnetic resonance linear accelerator (MRL) can perform magnetic resonance imaging (MRI) with high soft-tissue contrast to be used for online adaptive radiotherapy (oART). To obtain electron densities needed for the oART dose calculation, a computed tomography (CT) is often deformably registered to MRI. Our aim was to evaluate an MRI-only based synthetic CT (sCT) generation as an alternative to the deformed CT (dCT)-based oART in the abdominal region.MethodsThe study data consisted of 57 patients who were treated on a 0.35 T MRL system mainly for abdominal tumors. Simulation MRI-CT pairs of 43 patients were used for training and validation of a prototype convolutional neural network sCT-generation algorithm, based on HighRes3DNet, for the abdominal region. For remaining test patients, sCT images were produced from simulation MRIs and daily MRIs. The dCT-based plans were re-calculated on sCT with identical calculation parameters. The sCT and dCT were compared in terms of geometric agreement and calculated dose.ResultsThe mean and one standard deviation of the geometric agreement metrics over dCT-sCT-pairs were: mean error of 8 ± 10 HU, mean absolute error of 49 ± 10 HU, and Dice similarity coefficient of 55 ± 12%, 60 ± 5%, and 82 ± 15% for bone, fat, and lung tissues, respectively. The dose differences between the sCT and dCT-based dose for planning target volumes were 0.5 ± 0.9%, 0.6 ± 0.8%, and 0.5 ± 0.8% at D2% , D50% , and D98% in physical dose and 0.8 ± 1.4%, 0.8 ± 1.2%, and 0.6 ± 1.1% in biologically effective dose (BED). For organs-at-risk, the dose differences of all evaluated dose-volume histogram points were within [-4.5%, 7.8%] and [-1.1 Gy, 3.5 Gy] in both physical dose and BED.ConclusionsThe geometric agreement metrics were within typically reported values and most average relative dose differences were within 1%. Thus, an MRI-only sCT-based approach is a promising alternative to the current clinical practice of the abdominal oART on MRL.
| S-EPMC10018672 | biostudies-literature
Project description:IntroductionOnline adaptive magnetic resonance-guided radiotherapy (MRgRT) is a promising treatment modality for pancreatic cancer and is being employed by an increasing number of centers worldwide. However, clinical outcomes have only been reported on a small scale, often from single institutes and in the context of clinical trials, in which strict patient selection might limit generalizability of outcomes. This study presents clinical outcomes of a large, international cohort of patients with (peri)pancreatic tumors treated with online adaptive MRgRT.MethodsWe evaluated clinical outcomes and treatment details of patients with (peri)pancreatic tumors treated on a 1.5 Tesla (T) MR-linac in two large-volume treatment centers participating in the prospective MOMENTUM cohort (NCT04075305). Treatments were evaluated through schematics, dosage, delivery strategies, and success rates. Acute toxicity was assessed until 3 months after MRgRT started, and late toxicity from 3-12 months of follow-up (FU). The EORTC QLQ-C30 questionnaire was used to evaluate the quality of life (QoL) at baseline and 3 months of FU. Furthermore, we used the Kaplan-Meier analysis to calculate the cumulative overall survival.ResultsA total of 80 patients were assessed with a median FU of 8 months (range 1-39 months). There were 34 patients who had an unresectable primary tumor or were medically inoperable, 29 who had an isolated local recurrence, and 17 who had an oligometastasis. A total of 357 of the 358 fractions from all hypofractionated schemes were delivered as planned. Grade 3-4 acute toxicity occurred in 3 of 59 patients (5%) with hypofractionated MRgRT and grade 3-4 late toxicity in 5 of 41 patients (12%). Six patients died within 3 months after MRgRT; in one of these patients, RT attribution could not be ruled out as cause of death. The QLQ-C30 global health status remained stable from baseline to 3 months FU (70.5 at baseline, median change of +2.7 [P = 0.5]). The 1-year cumulative overall survival for the entire cohort was 67%, and that for the primary tumor group was 66%.ConclusionOnline adaptive MRgRT for (peri)pancreatic tumors on a 1.5 T MR-Linac could be delivered as planned, with low numbers of missed fractions. In addition, treatments were associated with limited grade 3-4 toxicity and a stable QoL at 3 months of FU.
| S-EPMC10579578 | biostudies-literature
Project description:BackgroundThe stomach is one of the most deformable organs. Its shape can be easily affected by breathing movements, and daily diet, and it also varies when the body position is different. The susceptibility of stomach has made it challenging to treat gastric cancer using the conventional image-guided radiotherapy, i.e., the techniques based on kilovoltage X-ray imaging. The magnetic resonance imaging guided radiotherapy (MRgRT) is usually implemented using a hybrid system MR-LINAC. It is feasible to implement adaptive radiotherapy using MR-LINAC for deformable organs such as stomach. In this case report, we present our clinical experience to treat a gastric cancer patient using MR-LINAC.Case descriptionThe patient is a 58-year-old male who started having black stools with no apparent cause a year ago. Gastroscopy result showed pancreatic cancer, pathology: adenocarcinoma on gastric cancer biopsy, adenocarcinoma on gastric body minor curvature biopsy. The patient was diagnosed with gastric cancer (adenocarcinoma, cTxN+M1, stage IV, HER-2 positive). The patient was treated in 25 fractions with radiotherapy using MR-LINAC with online adaptive treatment plans daily. The target area in daily MR images varied considerably when compared with the target area on the CT simulation images. During the course of treatment, there have even been instances where the planned target area where the patient received radiotherapy did not cover the lesion of the day.ConclusionOnline adaptive MRgRT can be a meaningful innovation for treating malignancies in the upper abdomen. The results in the current study are promising and are indicative for further optimizing online adaptive MRgRT in patients with inoperable tumors of the upper abdomen.
| S-EPMC10514477 | biostudies-literature
Project description:IntroductionMR-guided adapted radiotherapy (MRgART) using a high field MR-linac has recently become available. We report the estimated delivered fractional dose of the first five prostate cancer patients treated at our centre using MRgART and compare this to C-Arm linac daily Image Guided Radiotherapy (IGRT).MethodsPatients were treated using adapted treatment plans shaped to their daily anatomy. The treatments were recalculated on an MR image acquired immediately prior to treatment delivery in order to estimate the delivered fractional dose. C-arm linac non-adapted VMAT treatment plans were recalculated on the same MR images to estimate the fractional dose that would have been delivered using conventional radiotherapy techniques using a daily IGRT protocol.Results95% and 93% of mandatory target coverage objectives and organ at risk dose constraints were achieved by MRgART and C-arm linac delivered dose estimates, respectively. Both delivery techniques were estimated to have achieved 98% of mandatory Organ At Risk (OAR) dose constraints whereas for the target clinical goals, 86% and 80% were achieved by MRgART and C-arm linac delivered dose estimates.ConclusionsProstate MRgART can be delivered using the a high field MR-linac. Radiotherapy performed on a C-arm linac offers a good solution for prostate cancer patients who present with favourable anatomy at the time of reference imaging and demonstrate stable anatomy throughout the course of their treatment. For patients with critical OARs abutting target volumes on their reference image we have demonstrated the potential for a target dose coverage improvement for MRgART compared to C-arm linac treatment.
| S-EPMC7210377 | biostudies-literature
Project description:Bladder tumour-focused magnetic resonance image-guided adaptive radiotherapy using a 1.5 Tesla MR-linac is feasible. A full online workflow adapting to anatomy at each fraction is achievable in approximately 30 min. Intra-fraction bladder filling did not compromise target coverage with the class solution employed.
| S-EPMC9092067 | biostudies-literature
Project description:Background and purposeIn this report, we describe our implementation and initial clinical experience using 4D-MRI driven MR-guided online adaptive radiotherapy (MRgOART) for abdominal stereotactic body radiotherapy (SBRT) on the Elekta Unity MR-Linac.Materials and methodsEleven patients with abdominal malignancies were treated with free-breathing SBRT in three to five fractions on a 1.5 T MR-Linac. Online adaptive plans were generated using Adapt-To-Position (ATP) or Adapt-To-Shape (ATS) workflows based on motion averaged or mid-position images derived from a pre-beam 4D-MRI. A high performance server positioned on the local MR-Linac machine network was utilized for 4D-MR image reconstruction. A parallel contour editing approach was employed in the ATS workflow. Intravoxel incoherent motion (IVIM) and T2 mapping sequences were acquired during adaptive planning in both ATP and ATS workflows for treatment response monitoring. Adaptive plans were delivered under real-time cine image motion monitoring.ResultsThe shortest 4D-MRI time-to-image was the motion averaged image, followed by mid position and respiratory binned images. In this cohert of patients, 50% of treatments utilized the ATS workflow; the remaining treatments utilized the ATP workflow. Mid-position images were utilized as daily planning images for two of the eleven patients. The mean daily adaptive plan secondary dose calculation and ArcCheck 3D Gamma passing rates were 97.5% (92.1-100.0%) and 99.3% (96.2-100.0%), respectively. The median overall treatment times for abdominal SBRT was 46 and 62 min for ATP and ATS workflows, respectively.ConclusionWe have successfully implemented and utilized a 4D-MRI driven MRgOART process with ATP and ATS workflows for free-breathing abdominal SBRT on a 1.5 T Elekta Unity MR-Linac.
| S-EPMC7256110 | biostudies-literature
Project description:ObjectiveWe proposed a scheme for automatic patient-specific segmentation in Magnetic Resonance (MR)-guided online adaptive radiotherapy based on daily updated, small-sample deep learning models to address the time-consuming delineation of the region of interest (ROI) in the adapt-to-shape (ATS) workflow. Additionally, we verified its feasibility in adaptive radiation therapy for esophageal cancer (EC).MethodsNine patients with EC who were treated with an MR-Linac were prospectively enrolled. The actual adapt-to-position (ATP) workflow and simulated ATS workflow were performed, the latter of which was embedded with a deep learning autosegmentation (AS) model. The first three treatment fractions of the manual delineations were used as input data to predict the next fraction segmentation, which was modified and then used as training data to update the model daily, forming a cyclic training process. Then, the system was validated in terms of delineation accuracy, time, and dosimetric benefit. Additionally, the air cavity in the esophagus and sternum were added to the ATS workflow (producing ATS+), and the dosimetric variations were assessed.ResultsThe mean AS time was 1.40 [1.10-1.78 min]. The Dice similarity coefficient (DSC) of the AS model gradually approached 1; after four training sessions, the DSCs of all ROIs reached a mean value of 0.9 or more. Furthermore, the planning target volume (PTV) of the ATS plan showed a smaller heterogeneity index than that of the ATP plan. Additionally, V5 and V10 in the lungs and heart were greater in the ATS+ group than in the ATS group.ConclusionThe accuracy and speed of artificial intelligence-based AS in the ATS workflow met the clinical radiation therapy needs of EC. This allowed the ATS workflow to achieve a similar speed to the ATP workflow while maintaining its dosimetric advantage. Fast and precise online ATS treatment ensured an adequate dose to the PTV while reducing the dose to the heart and lungs.
| S-EPMC10289262 | biostudies-literature
Project description:PurposeAssessment of the accuracy of geometric tests of a linac used in external beam therapy is crucial for ensuring precise dose delivery. In this paper, a new simulation-based method for assessing accuracy of such geometric tests is proposed and evaluated on a set of testing procedures.MethodsLinac geometry testing methods used in this study are based on an established design of a two-module phantom. Electronic portal imaging device (EPID) images of fiducial balls contained in these modules can be used to automatically reconstruct linac geometry. The projection of the phantom modules fiducial balls onto the EPID detector plane is simulated for assumed nominal geometry of a linac. Then, random errors are added to the coordinates of the projections of the centers of the fiducial balls and the linac geometry is reconstructed from these data.ResultsReconstruction is performed for a set of geometric test designs and it is shown how the dispersion of the reconstructed values of geometric parameters depends on the design of a geometric test. Assuming realistic accuracy of EPID image analysis, it is shown that for selected testing plans the reconstruction accuracy of geometric parameters can be significantly better than commonly used action thresholds for these parameters.ConclusionsProposed solution has the potential to improve geometric testing design and practice. It is an important part of a fully automated geometric testing solution.
| S-EPMC6753736 | biostudies-literature
Project description:Intrafraction motion during magnetic resonance (MR)-guided dose delivery of esophageal cancer tumors was retrospectively analyzed. Deformable image registration of cine-MR series resulted in gross tumor volume motion profiles in all directions, which were subsequently filtered to isolate respiratory and drift motion. A large variability in intrafraction motion patterns was observed between patients. Median 95% peak-to-peak motion was 7.7 (3.7 - 18.3) mm, 2.1 (0.7 - 5.7) mm and 2.4 (0.5 - 5.6) mm in cranio-caudal, left-right and anterior-posterior directions, relatively. Furthermore, intrafraction drift was generally modest (<5mm). A patient specific approach could lead to very small margins (<3mm) for most patients.
| S-EPMC10068261 | biostudies-literature
Project description:The MR-Linac (MRL) provides a novel treatment modality that enables online adaptive treatments, but also creates new challenges for patient positioning in a laser-free environment. The accuracy and duration of prostate patient set-up on the MRL using two different methods for patient alignment was determined to establish standard of practice on the MRL. Differences in set-up accuracy were significant in the longitudinal direction and are accounted for in online plan adaption. Both methods recorded similar set-up times. The vendor recommended alignment method involves less manipulation of the patient and will be adopted as the standard positioning method for prostate and other pelvic patients on the MRL in future.
| S-EPMC7042150 | biostudies-literature