12,048 research outputs found
Monitoring Frequency of IntraâFraction Patient Motion Using the ExacTrac System for LINACâbased SRS Treatments
Purpose: The aim of this study was to investigate the intraâfractional patient motion using the ExacTrac system in LINACâbased stereotactic radiosurgery (SRS).
Method: A retrospective analysis of 104 SRS patients with kilovoltage imageâguided setup (Brainlab ExacTrac) data was performed. Each patient was imaged preâtreatment, and at two time points during treatment (1st and 2nd midâtreatment), and bony anatomy of the skull was used to establish setup error at each time point. The datasets included the translational and rotational setup error, as well as the time period between image acquisitions. After each image acquisition, the patient was repositioned using the calculated shift to correct the setup error. Only translational errors were corrected due to the absence of a 6D treatment table. Setup time and directional shift values were analyzed to determine correlation between shift magnitudes as well as time between acquisitions.
Results: The average magnitude translation was 0.64 ± 0.59 mm, 0.79 ± 0.45 mm, and 0.65 ± 0.35 mm for the preâtreatment, 1st midâtreatment, and 2nd midâtreatment imaging time points. The average time from preâtreatment image acquisition to 1st midâtreatment image acquisition was 7.98 ± 0.45 min, from 1st to 2nd midâtreatment image was 4.87 ± 1.96 min. The greatest translation was 3.64 mm, occurring in the preâtreatment image. No patient had a 1st or 2nd midâtreatment image with greater than 2 mm magnitude shifts.
Conclusion: There was no correlation between patient motion over time, in direction or magnitude, and duration of treatment. The imaging frequency could be reduced to decrease imaging dose and treatment time without significant changes in patient position
NonClassicality Criteria in Multiport Interferometry
Interference lies at the heart of the behavior of classical and quantum
light. It is thus crucial to understand the boundaries between which
interference patterns can be explained by a classical electromagnetic
description of light and which, on the other hand, can only be understood with
a proper quantum mechanical approach. While the case of two-mode interference
has received a lot of attention, the multimode case has not yet been fully
explored. Here we study a general scenario of intensity interferometry: we
derive a bound on the average correlations between pairs of output intensities
for the classical wavelike model of light, and we show how it can be violated
in a quantum framework. As a consequence, this violation acts as a
nonclassicality witness, able to detect the presence of sources with
sub-Poissonian photon-number statistics. We also develop a criterion that can
certify the impossibility of dividing a given interferometer into two
independent subblocks.Comment: 5 + 3 pages, published versio
Non-linear matter power spectrum from Time Renormalisation Group: efficient computation and comparison with one-loop
We address the issue of computing the non-linear matter power spectrum on
mildly non-linear scales with efficient semi-analytic methods. We implemented
M. Pietroni's Time Renormalization Group (TRG) method and its Dynamical 1-Loop
(D1L) limit in a numerical module for the new Boltzmann code CLASS. Our
publicly released module is valid for LCDM models, and optimized in such a way
to run in less than a minute for D1L, or in one hour (divided by number of
nodes) for TRG. A careful comparison of the D1L, TRG and Standard 1-Loop
approaches reveals that results depend crucially on the assumed initial
bispectrum at high redshift. When starting from a common assumption, the three
methods give roughly the same results, showing that the partial resumation of
diagrams beyond one loop in the TRG method improves one-loop results by a
negligible amount. A comparison with highly accurate simulations by M. Sato &
T. Matsubara shows that all three methods tend to over-predict non-linear
corrections by the same amount on small wavelengths. Percent precision is
achieved until k~0.2 h/Mpc for z>2, or until k~0.14 h/Mpc at z=1.Comment: 24 pages, 7 figures, revised title and conclusions, version accepted
in JCAP, code available at http://class-code.ne
Wallpaper Fermions and the Nonsymmorphic Dirac Insulator
Recent developments in the relationship between bulk topology and surface
crystal symmetry have led to the discovery of materials whose gapless surface
states are protected by crystal symmetries. In fact, there exists only a very
limited set of possible surface crystal symmetries, captured by the 17
"wallpaper groups." We show that a consideration of symmetry-allowed band
degeneracies in the wallpaper groups can be used to understand previous
topological crystalline insulators, as well as to predict new examples. In
particular, the two wallpaper groups with multiple glide lines, and
, allow for a new topological insulating phase, whose surface spectrum
consists of only a single, fourfold-degenerate, true Dirac fermion. Like the
surface state of a conventional topological insulator, the surface Dirac
fermion in this "nonsymmorphic Dirac insulator" provides a theoretical
exception to a fermion doubling theorem. Unlike the surface state of a
conventional topological insulator, it can be gapped into topologically
distinct surface regions while keeping time-reversal symmetry, allowing for
networks of topological surface quantum spin Hall domain walls. We report the
theoretical discovery of new topological crystalline phases in the AB
family of materials in SG 127, finding that SrPb hosts this new
topological surface Dirac fermion. Furthermore, (100)-strained AuY and
HgSr host related topological surface hourglass fermions. We also
report the presence of this new topological hourglass phase in
BaInSb in SG 55. For orthorhombic space groups with two glides, we
catalog all possible bulk topological phases by a consideration of the allowed
non-abelian Wilson loop connectivities, and we develop topological invariants
for these systems. Finally, we show how in a particular limit, these
crystalline phases reduce to copies of the SSH model.Comment: Final version, 6 pg main text + 29 pg supplement, 6 + 13 figure
Early Posttreatment Audiometry Underestimates Hearing Recovery after Intratympanic Steroid Treatment of Sudden Sensorineural Hearing Loss
Objective. To review our experience with intratympanic steroids (ITSs) for the treatment of idiopathic sudden sensorineural hearing loss (ISSNHL), emphasizing the ideal time to perform follow-up audiograms. Methods. Retrospective case review of patients diagnosed with ISSNHL treated with intratympanic methylprednisolone. Injections were repeated weekly with a total of 3 injections. Improvement was defined as an improved pure-tone average â„20âdB or speech-discrimination score â„20%. Results. Forty patients met the inclusion criteria with a recovery rate of 45% (18/40). A significantly increased response rate was found in patients having an audiogram >5 weeks after the first dose of ITS (9/13) over those tested â€5 weeks after the first dose of ITS (9/27) (P = 0.03). Conclusions. Recovery from ISSNHL after ITS injections occurs more frequently >5 weeks after initiating ITS. This may be due to the natural history of sudden hearing loss or the prolonged effect of steroid in the inner ear
KELT-18b: Puffy Planet, Hot Host, Probably Perturbed
We report the discovery of KELT-18b, a transiting hot Jupiter in a 2.87-day orbit around the bright (V = 10.1), hot, F4V star BD+60 1538 (TYC 3865-1173-1). We present follow-up photometry, spectroscopy, and adaptive optics imaging that allow a detailed characterization of the system. Our preferred model fits yield a host stellar temperature of 6670 ± 120 K and a mass of 1.524^(+0.069)_(-0.068) Mâ, situating it as one of only a handful of known transiting planets with hosts that are as hot, massive, and bright. The planet has a mass of 1.18 ± 0.11 M_J, a radius of 1.570^(+0.042)_(-0.036) R_J, and a density of 0.377 ± 0.040 g cm^(-3), making it one of the most inflated planets known around a hot star. We argue that KELT-18b's high temperature and low surface gravity, which yield an estimated ~600 km atmospheric scale height, combined with its hot, bright host, make it an excellent candidate for observations aimed at atmospheric characterization. We also present evidence for a bound stellar companion at a projected separation of ~1100 au, and speculate that it may have contributed to the strong misalignment we suspect between KELT-18's spin axis and its planet's orbital axis. The inferior conjunction time is 2457542.524998 ± 0.000416 (BJD_(TDB)) and the orbital period is 2.8717510 ± 0.0000029 days. We encourage RossiterâMcLaughlin measurements in the near future to confirm the suspected spinâorbit misalignment of this system
- âŠ