[en] Most previous scattering correction techniques for PET are based on assumptions made for a single transaxial plane and are independent of axial variations. These techniques will incorrectly estimate the scattering fraction for volumetric PET imaging systems since they do not take the cross-plane scattering into account. In this paper, the authors propose a new point source scattering deconvolution method (2-D). The cross-plane scattering is incorporated into the algorithm by modeling a scattering point source function. In the model, the scattering dependence both on axial and transaxial directions is reflected in the exponential fitting parameters and these parameters are directly estimated from a limited number of measured point response functions. The authors' results comparing the standard in-plane point source deconvolution to the authors' cross-plane source deconvolution show that for a small source, the former technique overestimates the scatter fraction in the plane of the source and underestimate the scatter fraction in adjacent planes. In addition, the authors also propose a simple approximation technique for deconvolution

[en] We have observed a strong non-linear effect in copper cluster ions induced damage in silicon. Copper cluster ions Cu_n (n=1,2,...,7) were extracted from a source of negative ions by cesium sputtering. P-type silicon wafers were irradiated with copper cluster ions at an atomic dosage range of 8x10¹² to 1x10¹⁵ atoms/cm² at the energy of 6 keV/atom. The quantitative characterization of the cluster ion induced damage was performed by Rutherford backscattering spectrometry/channeling analysis. Comparison with analytical overlapping model shows very good agreement

[en] We observed as much as 50% more damage for Au-cluster ion implantation in Si as compared with that of the Au monomer in the energy range of 6 keV/atom. This is contrary to the literature where the linear damage result was reported. In this experiment, small gold clusters Au_n with n from 1 to 4 were used. Energy of 6 keV per Au atom was applied to bombard the Si single-crystal surface. The radiation damage was characterized by Rutherford backscattering spectrometry/channeling in the number of Si atom displacements per Au atom. We have also studied this non-linear effect in a wide range of fluences from 8x10¹² to 1.2x10¹⁵ Au-atoms/cm² and observed a fluence-dependent effect. At higher fluence, sputtering and overlapping of the damage will reduce the damage efficiency, therefore reducing the non-linear effect. This could be the reason that earlier publication did not observe the non-linear effect

[en] We investigated the delivery of small cluster ions using a source of negative ions by cesium sputtering (SNICS). The negative cluster ions of B_n, C_n, Si_n, Co_n, Cu_n, Ge_n, Au_n, GeB_n and SiB_n have been extracted by SNICS. Adequate beam current of some small clusters was obtained by changing several parameters for cluster ion yield. After a comprehensive study of the operation parameters, such as target material selection, target geometry, sputtering voltage and current, the small cluster ion current can be increased by several orders of magnitude, with little change on the monomer ion yield

[en] A practical triple energy window technique (TEW) is proposed, which is based on using the information in two lower energy windows and one single calibration, to estimate the scatter within the photopeak window. The technique is basically a conventional dual-window technique plus a modification factor, which can partially compensate object-distribution dependent scatters. The modification factor is a function of two lower scatter windows of both the calibration phantom and the actual object. In order to evaluate the technique, a Monte Carlo simulation program, which simulates the PENN-PET scanner geometry, was used. Different phantom activity distributions and phantom sizes were tested to simulate brain studies, including uniform and nonuniform distributions. The results indicate that the TEW technique works well for a wide range of activity distributions and object sizes. The comparisons between the TEW and dual window techniques show better quantitative accuracy for the TEW, especially for different phantom sizes. The technique is also applied to experimental data from a PENN-PET scanner to test its practicality

[en] Maximum likelihood position estimation of a scintillation event in a gamma-ray imaging detector has been described using two independent one-dimensional estimates in x and y. This approximation is only valid when the sampled light-spread function is separable, and spatial distortion is observed when this constraint is violated. The authors have investigated recursive calculation of the 2-D position estimate using a sequence of one-dimensional estimates. Mean phototube response functions have been computed from Monte Carlo simulations of the light-spread function, and position have been estimated for scintillation events using recursive estimation

[en] By taking account of the high-order corrections to the paraxial approximation of a Gaussian beam, it has been verified that for a focused laser beam propagating in vacuum, there indeed exists a subluminous wave phase velocity region surrounding the laser beam axis. The magnitude of the phase velocity scales as V_φm∼c(1+b/(kw₀)²), where V_φm is the phase velocity of the wave, c is the speed of light in vacuum, w₀ is the beam width at focus. This feature gives a reasonable explanation for the mechanism of capture and acceleration scenario

[en] The ¹⁰B(α, p)¹³C nuclear reaction shows great potential in boron depth profiling due to its large cross-section and a narrow resonance in the MeV energy range. Unfortunately, the existing cross-section data on this reaction are too rough for depth profiling. We present an accurate measurement of the cross-section of the (α, p) reaction on ¹⁰B using a boron thin film on a Si substrate, high-resolution detection and careful analysis of the proton spectra. Angular distributions of the cross-section at the resonant energy E_r=1512 keV are also presented. The sharp resonance at 1512 keV was used to measure the B depth distribution in a borophosphosilicate glass (BPSG) thin film. The boron concentration profiles are compared with SIMS measurement and are found in good agreement

[en] Quantitative measurements of Cerebral Blood Flow (CBF) are performed in a volume imaging PET Scanner by means of moderate activity infusions. In equilibrium infusions, activations are measured by scanning over 10 minutes with 16 minute activations. Typical measured whole brain CBF values are 37±8 ml/min/100g, close to the value of 42 ml/min/100g reported by other groups using this method. For ramped infusions, scanning over 4 minutes with 5 minute activations results in whole brain CBFs of 49 ± 9 ml/min/100g, close to the Kety and Schmidt value of 50 ml/min/100g. Both equilibrium and ramped infusion methods have been used to study face and word memory in human subjects. Both methods were able to detect significant activations in regions implicated in human memory. The authors conclude that precise quantitation of regional CBF is achieved using both methods, and that ramped infusions also provide accurate measures of CBF. In addition a simplified protocol for ramped infusion studies has been developed. In this method the whole brain tissue time activity curve generated from dynamic scanning is replaced by an appropriately scaled camera coincidence countrate curve. The resulting whole brain CBF values are only 7% different from the dynamic scan and fit results. Regional CBFs (rCBF) may then be generated from the summed image (4.25 minutes) using a count density vs flow lookup table

[en] When high energy heavy ions bombard a single crystal, such as MeV Si implantation in Si, the surface region becomes vacancy-rich, while interstitials are mostly distributed near the range of the implants. We have demonstrated that vacancy retards while interstitial enhances boron thermal diffusion in silicon. In this paper we will show experimental results on the modification of boron diffusivity by point defect engineering, and its application in ultra-shallow junction (10 nm) formation. In this paper, we will also show cluster ion, such as GeB and SiB, implantation in silicon, and two-stage annealing in forming ultra shallow junction in Si. RBS, channeling, nuclear reaction, and secondary ion mass spectrometry are used for this studies