181 research outputs found
Radiotherapy in the treatment of gastrointestinal stromal tumor
Gastrointestinal stromal tumors (GISTs) are uncommon mesenchymal tumors of the gastrointestinal tract. Up to one-third of GISTs are malignant with a high rate of metastasis. Surgical resection is the mainstay of care for patients with resectable disease. Imatinib mesylate, a selective tyrosine kinase inhibitor, is the current standard of care for GISTs that cannot be completely resected or in cases of metastatic GIST. Although often overlooked, radiation therapy is a viable option for select patients with GIST. We report the case of a patient with unresectable GIST who was treated with local radiotherapy and achieved long-term response. We also present a review of the literature regarding the use of radiotherapy in the treatment of GIST. GIST has been shown to be a radiosensitive tumor. Radiotherapy can offer long-term local control and should be considered in the adjuvant or palliative setting. The role of radiotherapy delivered concurrently with imatinib in the treatment of GIST may warrant further investigation
Collision geometry scaling of Au+Au pseudorapidity density from sqrt(s_NN) = 19.6 to 200 GeV
The centrality dependence of the midrapidity charged particle multiplicity in
Au+Au collisions at sqrt(s_NN) = 19.6 and 200 GeV is presented. Within a simple
model, the fraction of hard (scaling with number of binary collisions) to soft
(scaling with number of participant pairs) interactions is consistent with a
value of x = 0.13 +/- 0.01(stat) +/- 0.05(syst) at both energies. The
experimental results at both energies, scaled by inelastic p(pbar)+p collision
data, agree within systematic errors. The ratio of the data was found not to
depend on centrality over the studied range and yields a simple linear scale
factor of R_(200/19.6) = 2.03 +/- 0.02(stat) +/- 0.05(syst).Comment: 5 pages, 4 figures, submitted to PRC-R
Centrality and pseudorapidity dependence of elliptic flow for charged hadrons in Au+Au collisions at sqrt(sNN) = 200 GeV
This paper describes the measurement of elliptic flow for charged particles
in Au+Au collisions at sqrt(sNN)=200 GeV using the PHOBOS detector at the
Relativistic Heavy Ion Collider (RHIC). The measured azimuthal anisotropy is
presented over a wide range of pseudorapidity for three broad collision
centrality classes for the first time at this energy. Two distinct methods of
extracting the flow signal were used in order to reduce systematic
uncertainties. The elliptic flow falls sharply with increasing eta at 200 GeV
for all the centralities studied, as observed for minimum-bias collisions at
sqrt(sNN)=130 GeV.Comment: Final published version: the most substantive change to the paper is
the inclusion of a complete description of how the errors from the hit-based
and track-based analyses are merged to produce the 90% C.L. errors quoted for
the combined results shown in Fig.
Au+Au Reactions at the AGS: Experiments E866 and E917
Particle production and correlation functions from Au+Au reactions have been
measured as a function of both beam energy (2-10.7AGeV) and impact parameter.
These results are used to probe the dynamics of heavy-ion reactions, confront
hadronic models over a wide range of conditions and to search for the onset of
new phenomena.Comment: 12 pages, 14 figures, Talk presented at Quark Matter '9
The Landscape of Particle Production: Results from PHOBOS
Recent results from the PHOBOS experiment at RHIC are presented, both from
Au+Au collisions from the 2001 run and p+p and d+Au collisions from 2003. The
centrality dependence of the total charged particle multiplicity in p+p and
d+Au show features, such as Npart-scaling and limiting fragmentation, similar
to p+A collisions at lower energies. Multiparticle physics in Au+Au is found to
be local in (pseudo)rapidity, both when observed by HBT correlations and by
forward-backward pseudorapidity correlations. The shape of elliptic flow in
Au+Au, measured over the full range of pseudorapidity, appears to have a very
weak centrality dependence. Identified particle ratios in d+Au reactions show
little difference between the shape of proton and anti-proton spectra, while
the absolute yields show an approximate m_T scaling.Comment: 8 Pages, 11 Figures, Plenary talk at Quark Matter 2004, Oakland, CA,
January 11-18, 200
Rapidity and k_T dependence of HBT correlations in Au+Au collisions at 200 GeV with PHOBOS
Two-particle correlations of identical charged pion pairs from Au+Au
collisions at sqrt(s_NN) = 200 GeV were measured by the PHOBOS experiment at
RHIC. Data for the most central (0--15%) events were analyzed with
Bertsch-Pratt (BP) and Yano-Koonin-Podgoretskii (YKP) parameterizations using
pairs with rapidities of 0.4 < y < 1.3 and transverse momenta 0.1 < k_T < 1.4
GeV/c. The Bertsch-Pratt radii decrease as a function of pair transverse
momentum. The pair rapidity Y_pipi roughly scales with the source rapidity
Y_YKP, indicating strong dynamical correlations.Comment: 5 pages, 2 figures. To appear in the proceedings of Seventeenth
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted
to Journal of Physics G: Nuclear and Particle Physic
Elliptic Flow in Au+Au Collisions at RHIC
Elliptic flow is an interesting probe of the dynamical evolution of the dense
system formed in the ultrarelativistic heavy ion collisions at the Relativistic
Heavy Ion Collider (RHIC). The elliptic flow dependences on transverse
momentum, centrality, and pseudorapidity were measured using data collected by
the PHOBOS detector, which offers a unique opportunity to study the azimuthal
anisotropies of charged particles over a wide range of pseudorapidity. These
measurements are presented, together with an overview of the analysis methods
and a discussion of the results.Comment: Presented at Hot Quarks 2004; 7 pages, 6 figure
The significance of the fragmentation region in ultrarelativistic heavy ion collisions
We present measurements of the pseudorapidity distribution of primary charged
particles produced in Au+Au collisions at three energies, sqrt(s_{NN}) = 19.6,
130, and 200 GeV, for a range of collision centralities. The centrality
dependence is shown to be non-trivial: the distribution narrows for more
central collisions and excess particles are produced at high pseudorapidity in
peripheral collisions. For a given centrality, however, the distributions are
found to scale with energy according to the "limiting fragmentation"
hypothesis. The universal fragmentation region described by this scaling grows
in pseudorapidity with increasing collision energy, extending well away from
the beam rapidity and covering more than half of the pseudorapidity range over
which particles are produced. This approach to a universal limiting curve
appears to be a dominant feature of the pseudorapidity distribution and
therefore of the total particle production in these collisions.Comment: 5 pages, 4 figure
Ratios of charged antiparticles to particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV
We have measured the ratios of antiparticles to particles for charged pions,
kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) =
130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06
(syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to
an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6
smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.Comment: 4 page
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