A single reference measurement can predict liver tumor motion during respiration

AimTo evaluate liver tumor motion and how well reference measurement predicts motion during treatment.Material and methodsThis retrospective study included 20 patients with colorectal cancer that had metastasized to the liver who were treated with stereotactic ablative radiotherapy. An online respiratory tumor tracking system was used. Tumor motion amplitudes in the superior-inferior (SI), latero-lateral (LL), and anterior-posterior (AP) directions were collected to generate patient-specific margins. Reference margins were generated as the mean motion and 95th percentile of motion from measurements recorded for different lengths of time (1, 3, and 5[[ce:hsp sp="0.25"/]]min). We analyzed the predictability of tumor motion in each axis, based on the reference measurement and intra-/interfraction motions.ResultsAbout 96,000 amplitudes were analyzed. The mean tumor motions were 9.9[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]4.2[[ce:hsp sp="0.25"/]]mm, 2.6[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]0.8[[ce:hsp sp="0.25"/]]mm, and 4.5[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]1.8[[ce:hsp sp="0.25"/]]mm in the SI, LL, and AP directions, respectively. The intrafraction variations were 3.5[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]1.8[[ce:hsp sp="0.25"/]]mm, 0.63[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]0.35[[ce:hsp sp="0.25"/]]mm, and 1.4[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]0.65[[ce:hsp sp="0.25"/]]mm for the SI, LL, and AP directions, respectively. The interfraction motion variations were 1.32[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]0.79[[ce:hsp sp="0.25"/]]mm, 0.31[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]0.23[[ce:hsp sp="0.25"/]]mm, and 0.68[[ce:hsp sp="0.25"/]]±[[ce:hsp sp="0.25"/]]0.62[[ce:hsp sp="0.25"/]]mm for the SI, LL, and AP directions, respectively. The Pearson's correlation coefficients for margins based on the reference measurement (mean motion or 95th percentile) and margins covering 95% of the motion during the whole treatment were 0.8–0.91, 0.57–0.7, and 0.77–0.82 in the SI, LL, and AP directions, respectively.ConclusionLiver tumor motion in the SI direction can be adequately represented by the mean tumor motion amplitude generated from a single 1[[ce:hsp sp="0.25"/]]min reference measurement. Longer reference measurements did not improve results for patients who were well-educated about the importance of regular breathing. Although the study was based on tumor tracking data, the results are useful for ITV delineation when tumor tracking is not available

Dosimetric comparison of MRI-based HDR brachytherapy and stereotactic radiotherapy in patients with advanced cervical cancer: A virtual brachytherapy study

AimTo evaluate the treatment plans of 3D image-guided brachytherapy (BT) and stereotactic robotic radiotherapy with online image guidance – CyberKnife (CK) in patients with locally advanced cervix cancer.Methods and materialsTen pairs of plans for patients with locally advanced inoperable cervical cancer were created using MR based 3D brachytherapy and stereotaxis CK. The dose that covers 98% of the target volume (HR CTV D98) was taken as a reference and other parameters were compared.ResultsOf the ten studied cases, the dose from D100 GTV was comparable for both devices, on average, the BT GTV D90 was 10–20% higher than for CK. The HR CTV D90 was higher for CK with an average difference of 10–20%, but only fifteen percent of HR CTV (the peripheral part) received a higher dose from CK, while 85% of the target volume received higher doses from BT. We found a significant organ-sparing effect of CK compared to brachytherapy (20–30% lower doses in 0.1[[ce:hsp sp="0.25"/]]cm3, 1[[ce:hsp sp="0.25"/]]cm3, and 2[[ce:hsp sp="0.25"/]]cm3).ConclusionBT remains to be the best method for dose escalation. Due to the significant organ-sparing effect of CK, patients that are not candidates for BT could benefit from stereotaxis more than from classical external beam radiotherapy

Cardiac Radiosurgery for Malignant Ventricular Tachycardia

Abstract Ventricular tachycardia is a frequent cause of mortality after myocardial infarction. Current treatment includes the implantation of cardioverter defibrillators and adjunctive therapies such as catheter ablation or cardiac surgery. In patients where standard treatment fails, preclinical data showed that radiosurgery ablation of the ectopic substrate might be a viable option. Authors present a case report of cardiac radiosurgery in a patient with malignant ventricular tachycardia. Stereotactic radiosurgery system CyberKnife was used; the applied dose was 25 Gy in one fraction. Within the follow-up period of 120 days, no signs of toxicity were noted no episode of malignant arrhythmia has been detected. This case report demonstrates that stereotactic radiosurgery of recurrent ventricular tachycardia after inefficient catheter ablation might be a viable option for patients unsuitable for cardiosurgical intervention. Further research on this topic is highly warranted

New results on light nuclei, hyperons and hypernuclei from HADES (HADES collaboration)

International audienceIn March 2019 the HADES experiment recorded 14 billion Ag+Ag collisions at √sNN = 2.55 GeV as a part of the FAIR phase-0 physics program. In this contribution, we present and investigate our capabilities to reconstruct and analyze weakly decaying strange hadrons and hypernuclei emerging from these collisions. The focus is put on measuring the mean lifetimes of these particles

Hyperon signatures in the PANDA experiment at FAIR

We present a detailed simulation study of the signatures from the sequential decays of the triple-strange pbar p -> Ω+Ω- -> K+ΛbarK- Λ -> K+pbarπ+K-pπ- process in the PANDA central tracking system with focus on hit patterns and precise time measurement. We present a systematic approach for studying physics channels at the detector level and develop input criteria for tracking algorithms and trigger lines. Finally, we study the beam momentum dependence on the reconstruction efficiency for the PANDA detector