Impact of random and scattered coincidences from outside of field of view on positron emission tomography/computed tomography imaging with different reconstruction protocols

Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.

Quantification of the impact of TOF and PSF on PET images using the noise-matching concept: clinical and phantom study

This study was to assess quantitatively the accuracy of ^(18)F-FDG PET/CT images reconstructed by TOF+PSF and TOF only, considering the noise-matching concept to minimize probable bias in evaluating algorithm performance caused by noise. PET images of similar noise level were considered. Measurements were made on an inhouse phantom with hot inserts of Φ10–37 mm, and oncological images of 14 patients were analyzed. The PET images were reconstructed using the OSEM, OSEM+TOF and OSEM+TOF+PSF algorithms. Optimal reconstruction parameters including iteration, subset, and FWHM of post-smoothing filter were chosen for both the phantom and patient data. In terms of quantitative accuracy, the recovery coefficient(RC) was calculated for the phantom PET images. The signal-to-noise ratio(SNR),lesion-to-background ratio(LBR), and SUV_(max)were evaluated from the phantom and clinical data. The smallest hot insert(Ф10 mm) with 2:1 activity concentration ratio could be detected in the PET image reconstructed using the TOF and TOF+PSF algorithms, but not the OSEM algorithm. The relative difference for SNR between the TOF+PSF and OSEM showed significantly higher values for smaller sizes, while SNR change was smaller for Ф22–37 mm inserts both 2:1 and 4:1 activity concentration ratio. In the clinical study, SNR gains were 1.6 ± 0.53 and 2.7 ± 0.74 for the TOF and TOF+PSF, while the relative difference of contrast was 17 ± 1.05 and 41.5 ± 1.85% for the TOF only and TOF+PSF, respectively. The impact of TOF+PSF is more significant than that of TOF reconstruction, in smaller inserts with low activity concentration ratio. In the clinical PET/CT images, the use of the TOF+PSF algorithm resulted in better SNR and contrast for lesions, and the highest SUV_(max)was also seen for images reconstructed with the TOF+PSF algorithm.

Combined Effects of Exposure to Noise and Vibration on Human Postural Equilibrium under Simulated Driving Conditions

There is little information about drivers’body balance responses to combined exposure of noise and vibration.To fill the gap,this study aims to investigate the combined effects of exposure to noise and whole-body vibration(WBV)on the body balance under simulated driving conditions.For this purpose,30 male participants were exposed to noise level at 85 dB(A)and two vibration levels(0.87 and 1.3 m/s^(2))in five sessions.The design of the study was repeated-measures,and it attempted to assess the effects of 40 minutes of exposure to noise and/or WBV.Moreover,the participants’fatigue was measured with the Borg scale(CR 10).The findings revealed there was a significant change in body sway after WBV and combined noise and WBV exposure(p<0.05).However,no significant difference was found in exposure to noise alone(p>0.05).The effect sizes of exposure to noise,WBV(1.3 m/s^(2)),and combined noise and WBV(1.3 m/s^(2))on body balance were 0.035,0.425,and 0.635,respectively.Also,single exposure to WBV caused more fatigue than single exposure to noise(p<0.05).Combined noise and WBV exposure descriptively caused more fatigue in comparison with the influence of WBV alone.The study concluded that the combined effects of exposure to noise and vibration are more than the sum of them.So,some synergistic effects may be observed in human body balance.It is essential to increase drivers’awareness and revise current health care interventions about new possible effects of combined exposures.

Synthesis and Development of Gd³⁺-ALGDG₂-C595 as MR Imaging Contrast Agent

Magnetic Resonance imaging (MR imaging) as a powerful non-invasive modality is of high global interest for early cancer detection. The aim of this study was the synthesis of nanodendrimer and its conjugate with monoclonal antibody C595 against breast cancer cell, followed by its chelating with gadolinium for its magnetic property. First, anti-MUC-1 monoclonal antibody C595 was coupled to a biodegradable biocompatible Anionic Linear Globular Dendrimer G2 (having polyethylene glycol core and citric acid shell). Then prepared nanocomplex loaded by gadolinium to make novel agent of functional MR imaging. Anticancer effects and MR imaging parameters of the prepared nanoconjugate was investigated under in vitro conditions doing performing several studies such as evaluation of monoclonal antibody C595 binding to mucine-1 (MUC-1) cell, its purification, size of nanoconjugate and relaxivity measurements. The obtained data showed a powerful relaxations as well as selective MUC-1 antigen binding to the cell. Based on the findings from the present research Gd3+-ALGDG2-C595 nano-probe may be a potential breast molecular imaging and therapeutic agent. However, further investigations by in vivo studies and clinical trials are in the pipeline.

<i>In Vitro</i>Studies of NIPAAM-MAA-VP Copolymer-Coated Magnetic Nanoparticles for Controlled Anticancer Drug Release

Thermosensetive poly(N-isopropylacrylamide)-based magnetic nanoparticles were synthesized by free radical polymerization of N-isopropylacrylamide (NIPPAMs), methacrylic acid (MAA), and vinyl pyrrolidone (VP) in the presence of methylene-bis-acrylamide as cross linking agent. The Fe3O4 magnetic nanoparticls were prepared by chemical precipitation of Fe salts in the ratio of 1:2 under alkaline and inert condition. Thermosensitive crosslinked P (NI-PAAM-MAA-VP) copolymers were characterized by FT-IR and H-NMR. The pH and thermosensitive copolymer was used for preparation of drug loaded magnetic nanoparticles, and doxorubicin (DOX) was used as a typical anticancer drug. The amount of the loaded drug and drug release amount were determined by UV measurements. Scanning electron microscopy (SEM) and lower critical solution temperature (LCST) were used to determine the particle surface morphology and the phase transition temperature of the nanoparticles respectively. The release behavior of DOX at pH = 7.4 and 37°C was studied. The result indicated that this thermosensetive magnetic nanoparticle has a high drug loading capacity and favorable linear release property for DOX without initial burst release. Thus this system is promising for the application in targeted smart anticancer drug delivery.

How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

It is well known that inter-crystal scattering and penetration(ICS-P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated crystal.In this study,the effect of ICS-P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation.A ^(99m)Tc pencil-beam toward central crystal element was utilized.Beam incident angle was assumed to vary from 0° to 45° in 5° steps.The effects of various crystal configurations such as pixel-size,pixel-gap,and crystal material were studied.The influence of photon energy on the crystal identification(CI) was also investigated.Position detection accuracy(PDA) was defined as a factor indicating performance of the crystal.Furthermore,a set of ^(99m)Tc point-source simulations was performed in order to calculate peak-to-valley(PVR) ratio for each configuration.The results show that the CsI(Na)manifests higher PDA than NaI(TI) and YAP(Ce).In addition,as the incident angle increases,the crystal becomes less accurate in positioning of the events.Beyond a crystal-dependent critical angle,the PDA monotonically reduces.The PDA reaches 0.44 for the CsI(Na) at 45° beam angle.The PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam irradiations.In addition,the PVRs derived from flood images linearly correlate their corresponding PDAs.In conclusion,quantitative assessment of ICS-P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.

Optimization of Sputtering Parameters for the Deposition of Low Resistivity Indium Tin Oxide Thin Films

Indium tin oxide （ITO） thin films have been deposited using RF sputtering technique at different pressures, RF powers, and substrate temperatures. Variations in surface morphology, optical properties, and film resistances were measured and analyzed. It is shown that a very low value of sheet resistance （1.96 Ω/sq.） can be achieved with suitable arrangement of the deposition experiments. First, at constant RF power, deposition at different pressure values is done, and the condition for achieving minimum sheet resistance （26.43 Ω/sq.） is found. In the next step, different values of RF powers are tried, while keeping the pressure fixed on the previously found minimum point （1-2 Pa）. Finally, the minimum resistivity is obtained by sweeping the substrate temperatures, while keeping RF power and the working pressure at their optimum values. Furthermore, the effects of process parameters on properties, such as the surface morphology and the optical transmission, are discussed. Although the point of minimum resistivity does not coincide with that of the maximum transparency of ITO film, relatively acceptable values of transmittance （approximately 75% on a glass substrate with intrinsic transparency of 89%） can be obtained.

内外联合照射剂量计算方法的研究

目的基于TG-43U1号报告剂量算法开发体元化的铱-192后装剂量计算程序，通过该程序将两个不同治疗计划系统的内外照射计算结果叠加、计算并显示总剂量分布。方法在开发的后装铱-192刘量计算程序中，根据Nucletron Plato治疗计划系统中读取的后装治疗计划的治疗信息（放射源强度、驻留位置、驻留时间等），重建出参照ADAC治疗计划系统坐标的后装源驻留位置，并重新计算后装治疗计划的三维剂量分布。计算结果经开发的程序转换并输入到ADAC计划系统，在ADAC中重建后装剂量分布并和ADAC外照射计划的剂量分布结果相叠加。结果根据TG-43U1号报告算法编写的程序剂量计算结果和Nucletron的Plato治疗计划系统得到的计算结果完全一致，误差〈0．1％。同时，该计算结果可以在ADAC计划系统上和其他外照射计划进行叠加。结论笔者编写的铱-192后装剂量计算程序能使不同治疗计划系统的内外照射计算结果叠加，有一定的临床使用价值。

A new three-dimensional elastography using phase based shifted Fourier transform

Elastography is an imaging technique with the ability to determine low quantities of some of the mechanical properties of tissues.The aim of our research is to design a new 3D algorithm using the Shifted Fourier Transform(SFT)to perform a quasi-static elastography.Our innovative idea is implementation of a 3D convolution instead of using three 2D convulsions.At first,we collected the raw data from Abaqus engineering software in the form of breast tissue with a coefficient of elasticity of healthy tissue and tumor tissue with a coefficient of elasticity of tumor tissue.The primary raw data consists of a number of points with x,y and z specified for tumor and healthy breast tissue.At this step,we simulated the displacements in directions of x,y and z at each point of the prescribed tissues for 15 mm displacement of probe in–Y direction then we collected 1831 points for tumor and 4186 points for breast before and after pressure.After applying a novel reconstruction algorithm,we convolved all images with the 3D Gabor filters to obtain phases,represented displacements of the breast and tumor images for before and after pressure.To reach this goal,we designed a Gabor filter bank based on the dimensions of the input images in different scales,directions,and deviations.Using the 3D SFT,we calculated the displacements of the breast and tumor tissues followed by 3D elastogram representation of the images.Finally,we implemented a 2D analysis of SFT in order to investigate validation of the 3D SFT.In 2D algorithm,we used three two-dimensional convulsions in XY,YZ and XZ planes.The results obtained from the small displacements marked by circles,confirmed the accuracy of the 3D SFT algorithm.These areas of interest are the tumor areas in the 2D analysis.