SPECT、CT对脊柱关节病的诊断价值

为探讨CT、SPECT对脊柱关节病（SpA）的诊断价值，将临床诊断为SpA的102例患者，包括强直性脊柱炎（AS）63例，未分化脊柱关节病(uSpA）39例，分别进行CT骶髂关节扫描及SPECT全身及骶髂关节局部骨显像。结果显示，SPECT对AS的诊断总阳性率为50.8%（32／63），而且随着病情的发展而下降。CT对检查uSpA的阳性率仅为15.4%（6／39），远低于SPECT的阳性率82.1%(32/39)。因此，SPECT作为早期诊断SpA尤其是uSpA较敏感，并可作为AS治疗监测的重要手段，对临床SpA诊治具有重要意义。     

The pinhole SPECT for animal model of bone metastasis with SPC-A-1BM human pulmonary adenocarcinoma bone metastasis cell line

The study was to investigate the role of pinhole single photon emission computed tomography （SPECT）, the human pulmonary adenocarcinoma bone-seeking metastasis cell line SPC-A-1BM was used. These cells form typical osteolytic bone metastases when inoculated into the arterial circulation of NIH-Beige-Nude-XD （BNX） mice v/a the left ventricle. In order to evaluate the irradiation impact of ^99mTc-MDP versus X-ray on cells growth, we used six groups of SPC-A-IBM cells in our imaging scheme and irradiated by various doses of ^99mTc-MDP （37, 74, 111, 370, 740 MBq） and X-ray（40 kV, 2 mA, 6 s） respectively. The cell＇s number of each group was well recorded in different exposure time（ 4, 8, 12, 24, 48, 72, 96 hours ）. After that, SPC-A-1BM cells （1×106） were inoculated into the mice via left ventricle. We compared the results obtained with those different doses of ^99mTc-MDP using pinhole SPECT and conventional X-ray skeletal surveys. The data show that the cell-survival number of 111 MBq group has insignificant difference with that of X-ray and the dose is adequate to have an ideal image. Besides, it is important that the chromosome of the cells in the group of 111 MBq showed no irradiation-related damages in our test. These results implied that ^99mTc-MDP pinhole SPECT may provide another way other than conventional X-ray skeletal surveys in detecting bone metastasis of pulmonary adenocarcinoma in BNX mice.     

High-resolution SPECT for small-animal imaging

1Introduction The rapid advance in molecular biology and the increasing use of transgenic mice as models of human biology and diseases have led to significant interests in the development of noninvasive,high-resolution,in vivo imaging techniques for small animals[1-4].Medi-cal imaging techniques including ultrasound(US),computed tomography(CT),magnetic resonance im-aging(MRI),positron emission tomography(PET),and single-photon emission computed tomography(SPECT),are contributing to this …     

SPECT/CT活度定量中校准体模和重建方法的选择

本文探讨了SPECT/CT校准体模和重建方法的选择,以用于临床SPECT/CT的准确活度定量。分别对活度已知的点源、大圆柱、小圆柱3种校准体模进行SPECT/CT扫描,然后对每个断层数据依次采用4种重建方法（FBP、OSEM、OSEM+AC、OSEM+AC+SC）进行重建,并据此计算校准因子。将小圆柱作为活度定量的对象进行定量误差计算。OSEM+AC和OSEM+AC+SC的平均相对定量误差均小于10%,FBP和OSEM的平均相对定量误差均大于20%。OSEM+AC的平均相对定量误差在采用小圆柱做校准体模时与OSEM+AC+SC无显著差异,而在采用大圆柱和点源时,分别较OSEM+AC+SC的小3.38%和6.48%（P<0.05）。3种体模的对比中,采用OSEM+AC时差异不显著,采用其他重建方法时差异显著。采用OSEM+AC+SC时,小圆柱作校准体模的定量误差较大圆柱和点源的结果分别小3.92%和6.42%（P<0.05）。结果表明,基于CT和迭代算法的衰减校正可有效提升活度定量准确性,但散射校正的效果不佳;校准体模应尽可能与目标定量对象相似。合理选择校准体模和重建方法,可有效提升SPECT/CT的活度定量准确性。     

Monte-Carlo simulation of pinhole collimator of a small field of view gamma camera for small animal imaging

Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022% and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the wade-off between sensitivity and resolution.     

Point spread functions for a small gamma camera with pinhole collimator

A set of point spread functions (PSF) has been obtained by means of Monte-Carlo simulation for a small gamma camera with a pinhole collimator of various hole diameters. The FOV (field of view) of the camera is expended from 45 mm to 70 mm in diameter. The position dependence of the variances of PSF is presented, and the acceptance for the 140 keV gamma rays is explored. A phantom of 70 mm in diameter was experimentally imaged in the camera with effective FOV of only 45 mm in diameter.     

Evaluation of suspected local recurrence in lung cancer and head & neck cancer: A comparison between 99mTc-HL91 SPECT and CT for biopsy proven lesions

CT has rather low accuracy for the follow-up of rumors after therapy. This study was to determine whether the diagnostic accuracy can be improved with 99mTc-HL91 SPECT in comparison with parallel results of CT imaging. Thirty patients of lung cancer or head & neck cancer, suspected of recurrences on clinical symptoms and CT during clinical follow-up after therapy, underwent 99mTc-HL91 SPECT. The radioactivity ratios of tumor to normal tissues (T/NT) were calculated using the region of interest technique. Results of 99mTc-HL91 SPECT were verified by histopathology. The 99mTc-HL91 average uptake ratios of T/NT in the group of recurrent lesions and non-recurrent lesions were 1.58±0.16 and 1.18±0.14, respectively. A significant difference was found between T/NT data of the two phases (t=4.87, P<0.001). The 99mTc-HL91 SPECT shows sensitivity of 72.73%, specificity of 89.47% and accuracy of 83.83% for differentiating recurrent lesion, while the CT shows sensitivity of 63.63%, specificity of 84.21% and accuracy of 76.67%. A combination of 99mTc-HL91 SPECT and CT for 21 patients with lung cancers or head & neck cancers with congruent results shows sensitivity of 100%, specificity of 94.12% and accuracy of 95.23%. It is concluded that 99mTc-HL91 SPECT may play a role in differentiating recurrent lesions in patients with lung cancer and head & neck cancer. Furthermore, the combination of CT and 99mTc-HL91 SPECT is a more effective method for diagnosing recurrence of lung cancer and head & neck cancer.     

脑外伤患者的SPECT显像与CT对比观察

对４８例脑外伤２进行了＾９９ｍＴｃ－ＥＣＤ ＳＰＥＣＴ脑血流灌注显像。其中４１例在ＳＰＥＣＴ检查的前后两周同时行脑ＣＴ检查，结果ＳＰＥＣＴ对轻、中、重型外伤的检出率分别为６０％、９０％和１００％；而ＣＴ分别为１０％、６０％和１００％，同一病人中ＳＰＥＣＴ比ＣＴ发现的病灶早、数目多，范围大。对脑外伤综合征及后遗症ＳＰＥＣＴ检出率分别为８０％和９０％，ＣＴ分别为２５％和７１．４２％。显然ＳＰＥＣＴ探测     

450keV锥束CT系统的散射校正研究

在450keV锥束工业CT成像系统中,对投影数据进行适当的散射校正是一步重要的数据校正.结合国内外散射校正方法研究的现状,对一种用散射校正板来进行散射校正方法的原理和实现进行了深入的研究.实验结果表明,这种校正方法能够对450KeV锥束CT成像系统进行有效地散射校正.     

Performance evaluation of the backprojection filtered （BPF） algorithm in circular fan-beam and cone-beam CT

In this article we introduce an exact backprojection filtered （BPF） type reconstruction algorithm for cone-beam scans based on Zou and Pan＇s work. The algorithm can reconstruct images using only the projection data passing through the parallel PI-line segments in reduced scans. Computer simulations and practical experiments are carded out to evaluate this algorithm. The BPF algorithm has a higher computational efficiency than the famous FDK algorithm. The BPF algorithm is evaluated using the practical CT projection data on a 450 keV X-ray CT system with a flat-panel detector （FPD）. From the practical experiments, we get the spatial resolution of this CT system. The algorithm could achieve the spatial resolution of 2.4 lp/mm and satisfies the practical applications in industrial CT inspection.     

透射式CT与自射线式CT检测核废物桶蒙特卡罗模拟

用蒙特止罗方法对透射式CT（TCT）和自射线式CT（ECT）检测核废物进行模拟实验,用TCT的模拟结果对ECT的模拟结果进行材料吸收系数校正,可以较为准确地确定核废物桶中放射性活度的绝对分布,并可确定放射性核素的种类。     

Kalypso: a software package for molecular dynamics simulation of atomic collisions at surfaces

A suite of graphically-oriented computer programs (Kalypso) has been developed for molecular dynamics simulations of projectile collisions with metallic targets. The features of the package include free-boundary or periodic targets, many-body potentials, a variety of inelastic loss models, and the ability to carry out simulations of fluence-dependent processes.     

^99mTc-3P4 -RGD2 radiotracers for SPECT/CT of esophageal tumor

In recent years,several RGD（Arg-Gly-Asp）-based radiotracers have already been successfully tested in human for the visualization of integrin αvβ3,demonstrating its feasibility in tumor diagnosis.In this paper,we evaluated the 99mTc-3P4-RGD2 single photon emission computed tomography/computerized tomography（SPECT/CT）in patients suffering from space occupying disease of esophagus.40 patients（34 males and 6 female;mean age： 58.3 years） with a suspected space occupying lesion of esophagus were included,thus finally obtaining their definite pathologic diagnosis（malignant,n=32;benign,n=8）.All patients underwent endoscopic,barium esophagography and SPECT/CT imaging preoperatively.The chest SPECT was performed at 4 h after administration of99mTc-3P4-RGD2 with a dose of 939±118 MBq.The diagnosis precision,sensitivity and specificity among these methods were compared.The relationship between radioactive uptake and clinical pathological stage of esophageal carcinoma was discussed by calculating the tumor to normal esophagus（T/N）.Meanwhile,the integrin αvβ3 expression was assessed immunohistochemically in postoperative esophageal tissues.31 patients were diagnosed as esophageal carcinoma;and 1,leiomyosarcoma;and 6.leimyoma;and 2,esophageal tuberculosis.The accuracy,sensitivity and specificity of barium esophagography,endoscopic and SPECT/CT imaging are 92.5/93.8/87.5%,97.5/96.9/100%,and 90/90.6/87.5%,respectively.Abnormal accumulation of radiotracer in 29 malignant lesions is observed.The SPECT/CT imaging displayed the region of radioactive uptake and lesions matched extremely with the T/N ratio from 1.31 to 2.79（mean 2.04）.A case with pulmonary metastases and a case with mediastinal lymph node metastases were found which were missed by barium esophagography and endoscopic.The99mTc-3P4-RGD2 uptake of the esophageal carcinoma masses had no relevance to the tumor pathologic classification（P〉0.05）.There was a significant positive correlation between T/N ratio and positive cell percentage of integrin αvβ3（r=0.976）,demonstrating the certain clinical potential in the diagnosis of esophageal carcinoma.     

同步辐射微束X射线荧光CT的计算机模拟

同步辐射微束X射线荧光CT是一种能无损、高空间分辨和高灵敏地探测样品内部元素含量和分布的新技术,是在建的上海光源(SSRF)硬X射线微聚焦及应用光束线站可开展的实验方法之一.本文简要介绍了同步辐射微束X射线荧光CT的基本原理和实验技术发展,对同步辐射微束X射线荧光CT实验进行了计算机模拟,用滤波反投影算法(FBP)、代数重构算法(ART)和加吸收修正的FBP算法重构了模拟样品的图像.对各种重构方法得到的图像质量进行了分析和比较,讨论了其适用性.     

高能CT检测中图像重建算法的积分因子仿真计算

针对核装置的具体情况,设计一种提高其图像指标的算法。利用核装置的大量先验知识并结合蒙特卡罗程序来修正CT检测中图像重建算法的积分因子,通过图像重建仿真实验验证了该算法可有效抑制散射与串扰对图像重建的影响,大幅提高了检测结果的精度。     

Evaluation of theoretical critical angle including mass effects for channeling by computer simulation

The calculated critical angles using the theory included mass effects of Zheng et al. for the axial channeling of ion have been investigated by the computer simulations, making comparisons with the theory of Lindhard and the precise formula of Barrett’s numerical simulations. The computer simulations employing the ACOCT program code, which treats the atomic collisions three-dimensionally and is based on the binary collision approximation (BCA), were carried out for the channeling of He, Ne, Ar, Kr, Xe and Rn ions incident along the 〈1 0 0〉 axis in Al, Cu, Ag and Pt crystals. A slight dependence of the channeling critical angle on the atomic number of incident ion in the ACOCT results is in agreement with that in the calculated ones using the theory of mass effects. The average critical angles in the ACOCT results for the channeling of six rare gas ions are approximately 5.0/Z₂ times the magnitude of the theoretical critical angles with mass effects, where Z₂ is the atomic number of crystal atom. Besides, the results show that the calculated critical angles using the theory with mass effects are substantially larger than those using the theory of Lindhard, the Barrett’s formula and the formula by the ACOCT simulations for He ions impinging on Al, Cu, Ag and Pt crystals, and that the channeling critical angles in the ACOCT results agree well with those in the calculated ones using Barrett’s formula for 0.6-50 MeV He ions incident on Cu and Ag crystals and 5-50 MeV He ions impinging on Al and Pt crystals.     

工业CT三维可视化系统设计与实现

在系统分析的基础上，给出了针对工业CT的三维可视化系统体系结构设计与实现，对关键的交互速度问题提出了自适应精度法解决方案，并对未来研究提出了方向。     

Comparison between beam-stop and beam-hole array scatter correction techniques for industrial X-ray cone-beam CT

In industrial X-ray cone-beam computed tomography, the inspection of large-scale samples is important because of increasing demands on their quality and long-term mechanical resilience. Large-scale samples, for example made of aluminum or iron, are strongly scattering X-rays. Scattered radiation leads to artifacts such as cupping, streaks, and a reduction in contrast in the reconstructed CT-volume. We propose a scatter correction method based on sampling primary signals by employing a beam-hole array (BHA). In this indirect method, a scatter estimate is calculated by subtraction of the sampled primary signal from the total signal, the latter taken from an image where the BHA is absent. This technique is considered complementary to the better known beam-stop array (BSA) method. The two scatter estimation methods are compared here with respect to geometric effects, scatter-to-total ratio and practicability. Scatter estimation with the BHA method yields more accurate scatter estimates in off-centered regions, and a lower scatter-to-total ratio in critical image regions where the primary signal is very low. Scatter correction with the proposed BHA method is then applied to a ceramic specimen from power generation technologies. In the reconstructed CT volume, cupping almost completely vanishes and contrast is enhanced significantly.     

Atomic-scale simulation of displacement cascades and amorphization in β-SiC

Molecular dynamics (MD) methods with a modified Tersoff potential have been used to simulate Si displacement cascades with energies up to 50 keV and to compare clustering behavior for Si and Au recoils in β-SiC (3C). The results show that the lifetime of the thermal spike is very short compared to that in metals, and that the surviving defects are dominated by C interstitials and vacancies for Si displacement cascades. Only 19% of the interstitial population is contained in clusters, with the largest cluster containing only four interstitial atoms for energetic Si recoils. The energy dependence of stable defect formation exhibits a power-law relationship. The high energy Si recoil generates multiple sub-cascades and forms dispersed defect configurations. These results suggest that in-cascade amorphization in SiC does not occur with any high degree of probability during the lifetime of Si cascades. On the other hand, large disordered domains are created in the cascades produced by 10 keV Au recoils. Structure analysis indicates that these highly disordered regions have amorphous characteristics. The data for the cluster spectra have been used to calculate the relative cross-sections for in-cascade amorphization (or clustering) and defect-stimulated amorphization. The ratios of these cross-sections for Si and Au are in excellent agreement with those derived from a fit of the direct-impact/defect-stimulated model to experimental data.     

MD simulation of ion implantation damage in AlGaAs: III. Defect accumulation and amorphization

The defect accumulation and amorphization in (0 0 1)Al_xGa_1−xAs due to irradiation with 200 keV Ar ions at 20 K is investigated with the help of classical molecular dynamics computer simulation using a modified Tersoff potential. The amount of disorder as a function of the number of displacements per atom has been calculated for x = 0, 0.2, 0.5, 0.75, 0.9 and 1.0. The results reasonably agree with the corresponding RBS data from the literature for x ? 0.9, however, they completely disagree in the case of x = 1. An artificial increase of thermally activated processes shows that thermal annealing during the irradiation may be responsible for the outstanding behavior of AlAs. In addition, the structure of the damage is investigated by visualizing the amorphous clusters and their evolution. It is shown that dynamic annealing does exist. It is negligible for x = 0 but it becomes more and more important with increasing Al content x. Furthermore, it is shown that the generation of damage is supported by pre-damage. This effect dominates the dynamic annealing for x ? 0.5.