Seminal vesicle intrafraction motion during the delivery of radiotherapy sessions on a 1.5 T MR-Linac

Purpose To evaluate seminal vesicle (SV) intrafraction motion using cinematic magnetic resonance imaging (cine-MR) during the delivery of online adaptive MR-Linac radiotherapy fractions, in preparation of MR-guided extremely hypofractionated radiotherapy for intermediate to high-risk prostate cancer patients. Material and Methods Fifty prostate cancer patients were treated with 5 × 7.25 Gy on a 1.5 Tesla MR-Linac. 3D Cine-MR imaging was started simultaneously and acquired over the full beam-on period. Intrafraction motion in this cine-MR was determined for each SV separately with a previously validated soft-tissue contrast-based tracking algorithm. Motion statistics and coverage probability for the SVs and prostate were determined based on the obtained results. Results SV motion was automatically determined during the beam-on period (approx. 10 min) for 247 fractions. SV intrafraction motion shows larger spread than prostate intrafraction motion and increases over time. This difference is especially evident in the anterior and cranial translation directions. Significant difference in rotation about the left–right axis was found, with larger rotation for the SVs than the prostate. Intra-fraction coverage probability of 99% can be achieved when using 5 mm isometric expansion for the left and right SV and 3 mm for the prostate. Conclusion This is the first study to investigate SV intrafraction motion during MR-guided RT sessions on an MR-Linac. We have shown that high quality 3D cine-MR imaging and SV tracking during RT is feasible with beam-on. The tracking method as described may be used as input for a fast replanning algorithm, which allows for intrafraction plan adaptation

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The autonomy of the contracting partner. An argument for heuristic contractarian business ethics

Due to the domain characteristics of business ethics, a contractarian theory for business ethics will need to be essentially different from the contract model as it is applied to other domains. Much of the current criticism of contractarian business ethics (CBE) can be traced back to autonomy, one of its three boundary conditions. After explaining why autonomy is so important, this article considers the notion carefully vis à vis the contracting partners in the contractarian approaches in business ethics. Autonomy is too demanding a condition for the realm of CBE. But a less stringent version of the contract may be possible, a version which uses the contract as a heuristic device, which merely requires moral responsibility. Furthermore, it is argued that views of (human) agency and the moral subject should be made explicit in such a theory. © Springer 2006

Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac

Purpose: To evaluate prostate intrafraction motion using MRI during the full course of online adaptive MR-Linac radiotherapy (RT) fractions, in preparation of MR-guided extremely hypofractionated RT. Material and methods: Five low and intermediate risk prostate cancer patients were treated with 20 × 3.1 Gy fractions on a 1.5T MR-Linac. Each fraction, initial MRI (Pre) scans were obtained at the start of every treatment session. Pre-treatment planning MRI contours were propagated and adapted to this Pre scan after which plan re-optimization was started in the treatment planning system followed by dose delivery. 3D Cine-MR imaging was started simultaneously with beam-on and acquired over the full beam-on period. Prostate intrafraction motion in this cine-MR was determined with a previously validated soft-tissue contrast based tracking algorithm. In addition, absolute accuracy of the method was determined using a 4D phantom. Results: Prostate motion was completely automatically determined over the full on-couch period (approx. 45 min) with no identified mis-registrations. The translation 95% confidence intervals are within clinically applied margins of 5 mm, and plan adaption for intrafraction motion was required in only 4 out of 100 fractions. Conclusion: This is the first study to investigate prostate intrafraction motions during entire MR-guided RT sessions on an MR-Linac. We have shown that high quality 3D cine-MR imaging and prostate tracking during RT is feasible with beam-on. The clinically applied margins of 5 mm have proven to be sufficient for these treatments and may potentially be further reduced using intrafraction plan adaptation guided by cine-MR imaging

In patients eligible for meniscal surgery who first receive physical therapy, multivariable prognostic models cannot predict who will eventually undergo surgery

Purpose Although physical therapy is the recommended treatment in patients over 45 years old with a degenerative meniscal tear, 24% still opt for meniscal surgery. The aim was to identify those patients with a degenerative meniscal tear who will undergo surgery following physical therapy. Methods The data for this study were generated in the physical therapy arm of the ESCAPE trial, a randomized clinical trial investigating the effectiveness of surgery versus physical therapy in patients of 45-70 years old, with a degenerative meniscal tear. At 6 and 24 months patients were divided into two groups: those who did not undergo surgery, and those who did undergo surgery. Two multivariable prognostic models were developed using candidate predictors that were selected from the list of the patients' baseline variables. A multivariable logistic regression analysis was performed with backward Wald selection and a cut-off of p < 0.157. For both models the performance was assessed and corrected for the models' optimism through an internal validation using bootstrapping technique with 500 repetitions. Results At 6 months, 32/153 patients (20.9%) underwent meniscal surgery following physical therapy. Based on the multivariable regression analysis, patients were more likely to opt for meniscal surgery within 6 months when they had worse knee function, lower education level and a better general physical health status at baseline. At 24 months, 43/153 patients (28.1%) underwent meniscal surgery following physical therapy. Patients were more likely to opt for meniscal surgery within 24 months when they had worse knee function and a lower level of education at baseline at baseline. Both models had a low explained variance (16 and 11%, respectively) and an insufficient predictive accuracy. Conclusion Not all patients with degenerative meniscal tears experience beneficial results following physical therapy. The non-responders to physical therapy could not accurately be predicted by our prognostic models.Orthopaedics, Trauma Surgery and Rehabilitatio