Pore structure of ore granular media by computerized tomography image processing

The pore structure images of ore particles located at different heights of leaching column were scanned with X-ray computerized tomography (CT) scanner, the porosity and pore size distribution were calculated and the geometrical shape and connectivity of pores were analyzed based on image process method, and the three dimensional reconstruction of pore structure images was realized. The results show that the porosity of ore particles bed in leaching column is 42.92%, 41.72%, 39.34% at top, middle and bottom zone, respectively. Obviously it has spatial variability and decreases appreciably along the height of the column. The overall average porosity obtained by image processing is 41.33% while the porosity gotten from general measurement method in laboratory is 42.77% showing the results of both methods are consistent well. The pore structure of ore granular media is characterized as a dynamical space network composed of interconnected pore bodies and pore throats. The ratio of throats with equivalent diameter less than 1.91 mm to the total pores is 29.31%, and that of the large pores with equivalent diameter more than 5.73 mm is 2.90%.

The possible value of ~18F-FDG positron emission tomography/computerized tomography imaging in detection of atherosclerotic plaque

Objective：To evaluate the clinical value with positron emission tomography/computerized tomography（PET/CT） imaging for the detection of vulnerable plaque in atherosclerotic lesions. Methods：Sixty people with a age of over 60[mean age （69.2 ± 7.1）years] underwent three dimension（3D） whole-body fluorine-18-2-fluoro-2-deoxy-D-glucose（^18F-FDG） PET/CT imaging and were evaluated retrospectively, including 6 cases assessed as normal and 54 cases with active atherosclerotic plaque. Fifty-four cases with SUVs and CT values in the aortic wall of high-FDG-uptake were measured retrospectively. These high-FDG-uptake cases in the aortic wall were divided into three groups according their CT value. Cases in group 1 had high uptake in atherosclerotic lesions of the aortic wall with CT value of less than 60 Hu（soft plaque）. Cases in group 2 had high uptake with CT value between 60-100 Hu （intermediate plaque）, Cases in group 3 had high uptake with CT value more than 100 Hu（calcified plaque）, Group 4 was normal. Results： In group 1, there were 42 high-FDG-uptake sites （average SUV 1.553 ± 0.486）. In group 2, there were 30 high-FDG-uptake sites（average SUV 1.393 ± 0.296）. In group 3, there were 36 high-FDG-uptake sites（average SUV 1.354 ± 0.189）. In group 4, there were 33 normal-FDG-uptake sites （average SUV was 1.102 ± 0.141）, The SUVs showed significant difference among the four groups（F = 678.909, P = 0.000）. There were also significant difference found between the normal-FDG-uptake group and the high-FDG-uptake groups（P = 0.000, 0.000, 0.001, respectively）. Conclusion：Different degrees of ^18F-FDG uptake in active large atherosclerotic plaque were shown in different stages of atherosclerotic plaque formation. The soft plaque had the highest FDG uptake in this study. This suggested that ^18F- FDG PET/CT imaging may be of great potential value in early diagnosis and monitoring of vulnerable soft plaque in atherosclerotic lesions.

A controlled study of positron-emission-tomography and positron-emission-tomography/computed tomography in differential diagnosis of solitary pulmonary nodules—report of 60 cases

The differential diagnosis of solitary pulmonary nodules （SPNs） remains a challenge. It is acknowledged that combining positron-emission tomography （PET） and computed tomography （CT） offers the most reliable noninvasive method for the diagnosis of SPNs. Since Townsend et al1 developed integrated PET/CT in 1999, this technique has increasingly been introduced into clinical practice. To date, nuclear medicine physicians have usually undertaken PET/CT diagnosis, but the question is surfacing as how to make full use of the information of CT image to improve the accuracy of SPN diagnosis. To answer this question, we performed a retrospective study on 60 patients with SPNs.

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Effects of Carbon Nanotubes on Mechanical and 2D-3D Microstructure Properties of Cement Mortar

To study the influence of multi-wall carbon nanotubes （MWCNTs） on the mechanical and microstructural properties of cementitious composites, 0.00, 0.02, 0.08, 0.10, and 0.20 wt% of multi-wall carbon nanotubes were added into cement mortar, in which the cement-sand ratio was 1：1.5. The flexural and compressive strengths of cement mortar at the age of 3, 7, 28 and 90 d and the fracture performance at the age of 28 d were determined, its 2D micrograph was tested by means of SEM, and the 3D defects distribution was firstly determined with or without CNTs by means of XCT （X-ray computerized tomography）. The results showed that 0.08 wt% of CNTs improved the compressive strength and flexural strength by 18% and 19~A, respectively, and a significant improvement of its fracture property was observed. Moreover lower addition of carbon nanotubes to cement mortars can improve its microstructure and decrease the defects significantly compared to the cement mortar without CNTs. With the increase of the content of CNTs, the mechanical properties of cement mortars presented to be declined largely due to the agglomeration of CNTs.

Micromechanical analysis of damage evolution in splitting test of asphalt mixtures

A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was used to simulate the damage evolution of asphalt mixture through splitting test. Aggregates were modeled to be linearly elastic, and the mastics were modeled to be plastically damaged. The splitting test simulation results show that the material heterogeneity, the properties of aggregates and air voids have significant effects on the damage evolution approach. The damage behavior of asphalt mixture considering material heterogeneity is quite different from that of the conventional hypothesis of homogeneous material. The results indicate that the proposed method can be extended to the numerical analysis for the other micromechanical behaviors of asphalt concrete.

COMPARISON OF EFFECTS OF ACUPUNCTURE ON CEREBRAL INFARCTION IN DIFFERENT PARTS

92 cases of acute cerebral infarction confirmed by CT were assigned to cerebral hemi sphere surface infarction group and cerebral hemisphere deep infarction gioup according to infarction parts. The two groups were further divided randomly into acupuncture groups and simp1e drug control groups, respectively, i. e, surface infarction acupuncture group, surface infarction control group, deep infarction acupuncture group and deep infarction control group. Changes of nervous function be fore and after treatment were investigated in the 4 groups. Results indicated that acupuncture treatment had a definite therapeutic effect on acute cerebral infarction, but it had different effects on cereral infarction of different parts, that is, the therapeutic effect of acupuncture on cerebral surface infarction was superi or to that on deep infarction. It is suggested that effects of acupuncture are related closely with the in farction part.

Preliminary study on CT perfusion imaging in guiding biopsy of pulmonary lumps

Background CT perfusion imaging （CTP） has been proved to be a powerful functional imaging technique. This study aimed to evaluate the value of CTP in guiding biopsy of pulmonary lumps. Methods A total of 147 patients with pulmonary lumps who had CT guided biopsies were enrolled in this study from February 2005 to June 2007. The patients were assigned to 3 groups： 33 cases guided by CTP as group 1, 45 cases guided by contrast-enhanced scan of CT as group Ⅱ, and 69 cases guided by plain scan of CT as group Ⅲ. Each group was subdivided into central and peripheral types according to the location of the lumps. The achievement ratio of biopsy, the accuracy in grouping, and grading of lung cancer, and the incidence of complication were compared. Results The total achievement ratios of biopsy from group Ⅰ to Ⅲ were 100% （33/33）, 91% （41/45）, and 80% （55/69） respectively, and the difference was statistically significant between group Ⅰ and Ⅲ （P 〈0.05）. For the central type, they were 100% （18/18）, 88% （15/17）, and 79% （11/14） respectively, and the difference was also statistically significant between group Ⅰand Ⅲ （P 〈0.05）. For the peripheral type, they were 100% （15/15）, 93% （26/28）, and 80% （44/55） respectivelies, and the difference was not statistically significant among the three groups. The total accuracies in grouping and grading of lung cancer from group Ⅰ to Ⅲ were 100% （27/27）, 91% （31/34）, and 72% （33/46） respectively, and the difference was statistically significant between group Ⅰ and Ⅲ and between group Ⅱ and Ⅲ （P 〈0.05）. For the central type, they were 100% （16/16）, 94% （16/17）, and 70% （8/12） respectively, and the difference was statistically significant between group Ⅰ and Ⅲ （P〈0.05）. For the peripheral type, they were 100% （11/11）, 88% （15/17）, and 72% （26/36） respectively, and the difference was statistically significant between group Ⅰ and Ⅲ （P 〈0.05）. The total incidence of complication from group Ⅰ to Ⅲ were 15% （5/33）, 27% （12/45）, and 43% （30/69） respectively, and the difference was statistically significant between group Ⅰ and Ⅲ （P 〈0.01）. For the central type, they were 11% （2/18）, 24% （4/17）, and 57% （8/14） respectively, and the difference was statistically significant between group Ⅰ and Ⅲ （P 〈0.01）. For the peripheral type, they were 20% （3/15）, 29% （8/28）, and 40% （22/55） respectively, and no statistically significant difference was found among the three groups. Conclusions CTP guided biopsy of pulmonary lumps using multi-detector row CT has the potential to improve the accuracy of histopathological diagnosis with a lower risk and higher achievement ratio. More research and technical improvements are needed before it is widelv used.

肌骨影像学发展方向

1895年,德国物理学家伦琴(Roentgen)发现X线,当时照的第一张人体X线片就是他夫人的手。由于人体骨骼含钙多,密度高,与周围组织对比明显,因此非常适合X线成像。从常规X线摄片,到CT、MRI,再到PET-CT、PET-MRI以及分子影像学,100多年来,医学影像学已成为骨科必不可少的检查方法,在各种骨科疾病的诊断、治疗和随访中发挥着不可替代的作用。医学影像学科包括放射学和核医学。

Diagnostic value of CTA and MRA in intracranial traumatic aneurysms

Objective： To investigate the diagnostic value of computerized tomographic angiography （ CTA ） and magnetic resonance angiography （ MRA ） for intracranial traumatic aneurysms （TAs）. Methods： CTA and MRA of six patients with intracranial TAs verified by digital subtraction angiography （DSA） and surgery were retrospectively analysed. All patients were examined by nonenhanced computerized tomography （CT） and two by CTA. The source data were reconstructed by volume rendering （VR） and multi-planar reconstruction （MPR） from CTA. Four of them had maxhnum intensity project （MIP） from MRA. Results ： Of the six patients, a total of seven TAs were detected by CTA and MRA examinations. Five cases had only one TA and one case had two TAs. The average diameter was 2.3 cm （1.1-3.3 cm）. CTA demonstrated two TAs appeared at the cavernous segment of the internal carotid artery （ICA） and the middle cerebral artery （MCA） respectively. MCA TA was definitely and dearly demonstrated on VR images, whereas VR images failed to depict the cavernous ICA TA, which was detected on MPR images. Two TAs were found irregular saccular shape,irregular margin of parent artery and wide neck on CTA. Four MRA examinations demonstrated five TAs, including the cavernous segment ICA TAs （2 cases）, the supraclinoid segment ICA TA （1 case ）, and the cavernous segment associated with opposite side of the petrosal segment ICA TA （1 case）. In a cavernous ICA TA, MRA only revealed aneurysm body, whereas aneurysm neck and distal segment of the parent artery were not revealed. In the remaining cases, MRA clearly depicted aneurysm body and parent artery, whereas the neck was not displayed. ICA TAs showed irregular capsnle-like high signal intensity on MRA images. Four TAs exhibited irregular distal segment of the parent artery. TAs at the supraclinoid segment or MCA failed to find fracture signs on nonenhanced CT. Conclusions： Both CTA and MRA examinations are the effective non-invasive method of imageology for diagnosing intracranlal TAs, while CTA is more eligible for diagnosing TAs after nonenhanced CT has demonstrated skull base fractures.