Intra-fraction motion represents a crucial issue in the era of precise radiotherapy in several settings, including breast irradiation. To date, only few data exist on real-time measured ...intra-fraction motion in breast cancer patients. Continuous surface imaging using visible light offers the capability to monitor patient movements in three-dimensional space without any additional radiation exposure. The aim of the present study was to quantify the uncertainties of possible intra-fractional motion during breast radiotherapy.
One hundred and four consecutive patients that underwent postoperative radiotherapy following breast conserving surgery or mastectomy were prospectively evaluated during 2028 treatment sessions. During each treatment session the patients' motion was continuously measured using the Catalyst™ optical surface scanner (C-RAD AB, Sweden) and compared to a reference scan acquired at the beginning of each session. The Catalyst system works through an optical surface imaging with light emitting diode (LED) light and reprojection captured by a charge coupled device (CCD) camera, which provide target position control during treatment delivery with a motion detection accuracy of 0.5 mm. For 3D surface reconstruction, the system uses a non-rigid body algorithm to calculate the distance between the surface and the isocentre and using the principle of optical triangulation. Three-dimensional deviations and relative position differences during the whole treatment fraction were calculated by the system and analyzed statistically.
Overall, the maximum magnitude of the deviation vector showed a mean change of 1.93 mm ± 1.14 mm (standard deviation SD) (95%-confidence interval: 0.48-4.65 mm) and a median change of 1.63 mm during dose application (beam-on time only). Along the lateral and longitudinal axis changes were quite similar (0.18 mm ± 1.06 mm vs. 0.17 mm ± 1.32 mm), on the vertical axis the mean change was 0.68 mm ± 1.53 mm. The mean treatment session time was 154 ± 53 (SD) seconds and the mean beam-on time only was 55 ± 16 s. According to Friedman's test differences in the distributions of the three possible directions (lateral, longitudinal and vertical) were significant (p < 0.01), in post-hoc analysis there were no similarities between any two of the three directions.
The optical surface imaging system is an accurate and easy tool for real-time motion management in breast cancer radiotherapy. Intra-fraction motion was reported within five millimeters in all directions. Thus, intra-fraction motion in our series of 2028 treatment sessions seems to be of minor clinical relevance in postoperative radiotherapy of breast cancer.
Purpose/Objective:
Reproducible patient positioning remains one of the major challenges in modern radiation therapy. Recently, optical surface scanners have been introduced into clinical practice in ...addition to well-established positioning systems, such as room laser and skin marks. The aim of this prospective study was to evaluate setup errors of the optical surface scanner Catalyst HD (C-RAD AB) in different anatomic regions.
Material/Methods:
Between October 2016 and June 2017 a total of 1902 treatment sessions in 110 patients were evaluated. The workflow of this study included conventional setup procedures using laser-based positioning with skin marks and an additional registration of the 3-dimensional (3D) deviations detected by the Catalyst system. The deviations of the surface-based method were then compared to the corrections of cone beam computed tomography alignment which was considered as gold standard. A practical Catalyst setup error was calculated between the translational deviations of the surface scanner and the laser positioning. Two one-sided t tests for equivalence were used for statistical analysis.
Results:
Data analysis revealed total deviations of 0.09 mm ± 2.03 mm for the lateral axis, 0.07 mm ± 3.21 mm for the longitudinal axis, and 0.44 mm ± 3.08 mm vertical axis for the Catalyst system, compared to −0.06 ± 3.54 mm lateral, 0.53 ± 3.47 mm longitudinal, and 0.19 ± 3.49 mm vertical for the laser positioning compared to cone beam computed tomography. The lowest positional deviations were found in the cranial region, and larger deviations occurred in the thoracic and abdominal sites. A statistical comparison using 2 one-sided t tests showed a general concordance of the 2 methods (P ≤ 0.036), excluding the vertical direction of the abdominal region (P = 0.198).
Conclusion:
The optical surface scanner Catalyst HD is a reliable and feasible patient positioning system without any additional radiation exposure. From the head to the thoracic and abdominal region, a decrease in accuracy was observed within a comparable range for Catalyst and laser-assisted positioning.
Background and purpose
Reperfusion treatment in patients presenting with large vessel occlusion (LVO) and minor neurological deficits is still a matter of debate. We aimed to compare minor stroke ...patients treated with endovascular thrombectomy (EVT) and intravenous thrombolysis (IVT) or IVT alone.
Methods
Patients enrolled in the German Stroke Registry–Endovascular Treatment (GSR‐ET) and the Safe Implementation of Treatments in Stroke–International Stroke Thrombolysis Registry (SITS‐ISTR) between June 2015 and December 2019 were analyzed. Minor stroke was defined as National Institutes of Health Stroke Scale (NIHSS) score ≤5, and LVO as occlusion of the internal carotid, carotid‐T, middle cerebral, basilar, vertebral or posterior cerebral arteries. GSR‐ET and SITS‐ISTR IVT‐treated patients were matched in a 1:1 ratio using propensity‐score (PS) matching. The primary outcome was good functional outcome at 3 months (modified Rankin Scale score 0–2).
Results
A total of 272 GSR‐ET patients treated with EVT and IVT (age 68.6 ± 14.0 years, 43.4% female, NIHSS score 4 interquartile range 2–5) were compared to 272 IVT‐treated SITS‐ISTR patients (age 69.4 ± 13.7, 43.4% female, NIHSS score 4 2–5). Good functional outcome was seen in 77.0% versus 82.9% (p = 0.119), mortality in 5.9% versus 7.9% (p = 0.413), and intracranial hemorrhage in 8.8% versus 12.5% (p = 0.308) of patients in the GSR‐ET versus the SITS‐ISTR IVT group, respectively. In a second PS‐matched analysis, 624 GSR‐ET patients (IVT rate 56.7%) and 624 SITS‐ISTR patients (IVT rate 100%), good outcome was more often observed in the SITS‐ISTR patients (68.2% vs. 80.9%; p < 0.001), and IVT independently predicted good outcome (odds ratio 2.16, 95% confidence interval 1.43–3.28).
Conclusions
Our study suggests similar effectiveness of IVT alone compared to EVT with or without IVT in minor stroke patients. There is an urgent need for randomized controlled trials on this topic.
Figure 2 The benefit of endovascular thrombectomy (EVT) treatment for minor stroke patients (NIHSS ≤5) is still unknown. We matched German Stroke Registry–Endovascular Treatment (GSR‐ET) patients treated with EVT, with or without intravenous thrombolysis (IVT) treatment, to Safe Implementation of Treatments in Stroke –International Stroke Thrombolysis Register (SITS‐ISTR) patients treated with IVT alone. Our observational results suggest that the efficacy is similar between treatment options, and EVT appears to be safe for this patient group.
Coherent epitaxial growth allows us to produce strained crystalline films with structures that are unstable in the bulk. Thereby, the overlayer lattice parameters in the interface plane, (a, b), ...determine the minimum-energy out-of-plane lattice parameter, . We show by means of density-functional total energy calculations that this dependence can be discontinuous and predict related first-order phase transitions in strained tetragonal films of the elements V, Nb, Ru, La, Os, and Ir. The abrupt change of can be exploited to switch properties specific to the overlayer material. This is demonstrated for the example of the superconducting critical temperature of a vanadium film which we predict to jump by 20% at a discontinuity of .
Strained Fe–Co films have recently been demonstrated to exhibit a large magnetocrystalline anisotropy (MCA) and thus to be of potential interest as magnetic storage material. Here, we show by means ...of density‐functional (DF) calculations, that chemical order can remarkably enhance the MCA. We also investigate the effect of relaxation perpendicular to the applied strain and evaluate the strain energy as a function of Co concentration and substrate lattice parameter. On this basis, favourable preparation routes for films with a large perpendicular anisotropy are suggested.
Background and purpose
The radiation dose received by the heart during adjuvant left-sided breast irradiation plays a crucial role in development of late toxicity. Although the absolute risk of ...cardiotoxicity can be reduced with modern irradiation techniques, cardiotoxic chemotherapy increases the risk of late damage. Thus, the radiation dose to the heart should be minimized. This study evaluated the influence of different amplitudes of inspiration breath hold (IBH) during simulated left-sided breast irradiation on cardiac doses compared to free breathing (FB).
Patients and methods
CT data of 11 lung cancer patients were retrospectively used as left-sided pseudo-breast cancer cases. Two CT scans were used, one during IBH and one during FB, and two treatment plans were generated. Relevant heart, lung, and left anterior descending artery (LAD) parameters were derived from dose–volume histograms. The normal tissue complication probabilities (NTCPs) for the heart were calculated based on the relative seriality model. Inspiration depth was quantified using chest volume and diameter, and correlated thereafter to a possible sparing of heart tissue.
Results
Mean reduction of heart dose for IBH compared to FB was 40 % (1.65 vs. 0.99 Gy;
p
= 0.007). Maximum dose to the heart and LAD could be decreased by 33 % (
p
= 0.011) and 43 % (
p
= 0.024), respectively. The mean anteroposterior shift was 5 mm (range 0.9–9.5 mm). Significant negative correlations between the relative change in LAD mean dose and the mean thoracic diameter and volume change, as well as with the absolute change in thoracic diameter were seen. The NTCP for cardiac mortality could be decreased by about 78 % (
p
= 0.017).
Conclusion
For left-sided breast cancer patients, cardiac doses can be significantly decreased with tangential irradiation and IBH.
•Ab initio calculation of the surface relaxation of metals.•Surface energy and surface stress of transition metals.•Surface energy and surface stress of simple metals and light actinides.
We ...investigated surface properties of metals by performing first-principles calculations. A systematic database was established for the surface relaxation, surface energy (γ), and surface stress (τ) for metallic elements in the periodic table. The surfaces were modeled by multi-layered slab structures along the direction of low-index surfaces. The surface energy γ of simple metals decreases as the atomic number increases in a given group, while the surface stress τ has its minimum in the middle. The transition metal series show parabolic trends for both γ and τ with a dip in the middle. The dip occurs at half-band filling due to a long-range Friedel oscillation of the surface charge density, which induces a strong stability to the Peierls-like transition. In addition, due to magnetic effects, the dips in the 3d metal series are shallower and deeper for γ and τ, respectively, than those of the 4d and 5d metals. The surface stress of the transition metals is typically positive, only Cr and Mn have a negative τ for the (100) surface facet, indicating that they are under compression. The light actinides have an increasing γ trend according to the atomic number. The present work provides a useful and consistent database for the theoretical modelling of surface phenomena.
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Patients with left-sided breast cancer frequently receive deep inspiration breath-hold (DIBH) radiotherapy to reduce the risk of cardiac side effects. The aim of the present study was to analyze ...intra-breath-hold stability and inter-fraction breath-hold reproducibility in clinical practice.
Overall, we analyzed 103 patients receiving left-sided breast cancer radiotherapy using a surface-guided DIBH technique. During each treatment session the vertical motion of the patient was continuously measured by a surface guided radiation therapy (SGRT) system and automated gating control (beam on/off) was performed using an audio-visual patient feedback system. Dose delivery was automatically triggered when the tracking point was within a predefined gating window. Intra-breath-hold stability and inter-fraction reproducibility across all fractions of the entire treatment course were analyzed per patient.
In the present series, 6013 breath-holds during beam-on time were analyzed. The mean amplitude of the gating window from the baseline breathing curve (maximum expiration during free breathing) was 15.8 mm (95%-confidence interval: 8.5-30.6 mm) and had a width of 3.5 mm (95%-CI: 2-4.3 mm). As a measure of intra-breath-hold stability, the median standard deviation of the breath-hold level during DIBH was 0.3 mm (95%-CI: 0.1-0.9 mm). Similarly, the median absolute intra-breath-hold linear amplitude deviation was 0.4 mm (95%-CI: 0.01-2.1 mm). Reproducibility testing showed good inter-fractional reliability, as the maximum difference in the breathing amplitudes in all patients and all fractions were 1.3 mm on average (95%-CI: 0.5-2.6 mm).
The clinical integration of an optical surface scanner enables a stable and reliable DIBH treatment delivery during SGRT for left-sided breast cancer in clinical routine.
This study demonstrates for the first time that the microelectrode array (MEA) technique allows analysis of electrical activity of islets isolated from human biopsies. We have shown before that this ...method, i.e., measuring beta cell electrical activity with extracellular electrodes, is a powerful tool to assess glucose responsiveness of isolated murine islets. In the present study, human islets were shown to exhibit glucose-dependent oscillatory electrical activity. The glucose responsiveness could be furthermore demonstrated by an increase of insulin secretion in response to glucose. Electrical activity was increased by tolbutamide and inhibited by diazoxide. In human islets bursts of electrical activity were markedly blunted by the Na(+) channel inhibitor tetrodotoxin which does not affect electrical activity in mouse islets. Thus, the MEA technique emerges as a powerful tool to decipher online the unique features of human islets.Additionally, this technique will enable research with human islets even if only a few islets are available and it will allow a fast and easy test of metabolic integrity of islets destined for transplantation.
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