Search results for "positron"
showing 10 items of 1346 documents
Viable tumor in postchemoradiation neck dissection specimens as an indicator of poor outcome
2010
Management of the neck in patients treated with primary chemoradiation for cancer of the laryngopharynx with a clinically positive neck remains an area of controversy. The neck may be managed in 1 of 3 ways: by observation, by planned neck dissection, or by salvage neck dissection. Observation of the neck can be done in patients who have a complete or near-complete response to treatment and have a negative positron emission tomography (PET) scan result. Evidence for this approach comes from recent studies that have reported low regional recurrence rates.1–6 Planned neck dissection was carried out in the past in patients with N2 and N3 neck disease irrespective of the response to chemoradiat…
Choline PET/CT Features to Predict Survival Outcome in High Risk Prostate Cancer Restaging: A Preliminary Machine-Learning Radiomics Study
2020
Background Radiomic features are increasingly utilized to evaluate tumor heterogeneity in PET imaging but to date its role has not been investigated for Cho-PET in prostate cancer. The potential application of radiomics features analysis using a machine-learning radiomics algorithm was evaluated to select 18F-Cho PET/CT imaging features to predict disease progression in PCa. Methods We retrospectively analyzed high-risk PCa patients who underwent restaging 18F-Cho PET/CT from November 2013 to May 2018. 18F-Cho PET/CT studies and related structures containing volumetric segmentations were imported in the "CGITA" toolbox to extract imaging features from each lesion. A Machine-learning model h…
A case of post-traumatic complex auditory hallucinosis treated with rTMS.
2010
Previous studies of auditory hallucinations in schizophrenia found that the hallucinations were reduced by the application of transcranial magnetic stimulation (rTMS). Here we describe a case of traumatic brain injury associated with continuous music hallucinations. An MRI scan showed a structural lesion of the right temporal pole and a PET scan indicated a hyperactive area of the posterior right temporal lobe. We hypothesized that rTMS applied to the right temporal area would reduce this activity and the corresponding hallucinations. The patient's music hallucinations were significantly reduced by rTMS treatment. A PET scan following treatment also indicated that rTMS treatment reduced bra…
Prediction of Normal Organ Absorbed Doses for [177Lu]Lu-PSMA-617 Using [44Sc]Sc-PSMA-617 Pharmacokinetics in Patients With Metastatic Castration Resi…
2018
In vivo pharmacokinetic analysis of [Sc]Sc-PSMA-617 was used to determine the normal organ-absorbed doses that may result from therapeutic activity of [Lu]Lu-PSMA-617 and to predict the maximum permissible activity of [Lu]Lu-PSMA-617 for patients with metastatic castration-resistant prostate carcinoma. Methods Pharmacokinetics of [Sc]Sc-PSMA-617 was evaluated in 5 patients with metastatic castration-resistant prostate carcinoma using dynamic PET/CT, followed by 3 static PET/CT acquisitions and blood sample collection over 19.5 hours, as well as urine sample collection at 2 time points. Total activity measured in source organs by PET imaging, as well as counts per milliliter measured in bloo…
Evidence of Two Resonant Structures in e+e−→π+π−hc
2017
The cross sections of e(+)e(-) -> pi(+) pi(-) hc at center-of-mass energies from 3.896 to 4.600 GeVare measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e(+)e(-) -> pi(+) pi(-) J/psi and e(+)e(-) -> pi(+) pi(-) psi (2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e(+)e(-) -> pi(+) pi(-) hc cross sections around 4.22 and 4.39 GeV/c(2), which we call Y(4220)and Y(4390), respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4(- 4.5)…
Positronics of radiation-induced effects in chalcogenide glassy semiconductors
2015
Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.
Positron annihilation probing of crystallization effects in TAS-235 glass affected by Ga additions
2014
Abstract Crystallization effects in Te20As30Se50 glass known also as TAS-235 affected by Ga additions to Ga2Te20As28Se50 and Ga5Te20As25Se50 compositions are probed with positron annihilation spectroscopy in the measuring modes exploring positron lifetimes and Doppler broadening of annihilation line. Occurring of cubic-phase Ga2Se3 droplets with character nanoscale sizes in partially-crystallized Ga2Te20As28Se50 alloy is shown to be associated with agglomeration of intrinsic free-volume voids, this process being enhanced over microcrystalline scale in Ga5Te20As25Se50 alloy. Crystallization changes in the void structure of TAS-235 glass are considered in terms of free-volume evolution under …
Positron annihilation studies of recrystallization in the subsurface zone induced by friction in magnesium—effect of the inhomogeneity on measured po…
2013
The discussion of the positron annihilation studies of crystal structure defects, like vacancies, dislocations, grain boundaries and the defect depth profile, is presented. The role of the positron implantation depth and positron diffusion in such studies has been considered in detail. For description of the measured annihilation characteristics the proposed theoretical models take into account both effects. The annealing studies of defects created in pure magnesium by compression or dry sliding-wear were used for demonstration of the discussed thesis. The positron lifetime measurements were applied for monitoring open volume defects behavior. It was demonstrated that annealing at the tempe…
Positron Annihilation with Electrons of Admixture Atoms in Some Binary Nickel Alloys
2005
Weighted difference curves have been shortly presented as a proper tool allowing to analyze in another way two-detector Doppler spectra regarding positron annihilation with admixture electrons in some nickel alloys. The analysis of low and middle momentum parts of Doppler spectra for investigated alloys reflects the annihilation of positrons with admixture electrons. There is no distinct signal of annihilations with admixture electrons from the positron lifetime data for well-annealed samples.
Defects in Martensitic Stainless Steel 1.4031 (EN) Exposed to Friction as Seen by Positron Annihilation
2010
We present experimental results of measurements of the Doppler broadening of annihilation line and positron annihilation lifetimes in martensitic stainless steel 1.4031 (EN) samples exposed to the dry sliding under different loads. In particular, we tested the subsurface zone under the worn surfaces. As a main result, we obtained information about the defect profiles in this zone and the total extent of the damage region induced by the dry sliding.