ISSN 1004-4140
CN 11-3017/P

2014  Vol. 23  No. 6

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Spectral CT
Abstract:
Objective: The purpose of the study was to discuss the application value of spectral CT in preoperative imaging evaluation of the living donor's vessels in pediatric liver transplantation. Methods: Preoperational spectral CT scan was performed for 30 living donors. CTA were performed, both monochromatic and combined energetic, on their hepatic artery and vein, also the portal vein. The donor's total volume and the planning cutting part was measured respectively and compared with the real replanting liver volume. Result: The monochromatic CTA imaging quality of the liver vessels at 50 ke V is better than the combined one (P < 0.001). And the anatomical variation of the donor's liver vessels could be shown very clear by CTA. Conclusion: As one of the methods of the preoperative evaluation of the living donor's liver in pediatric liver transplantation, the monochromatic CTA could show high quality contrast image between the vessels and the soft tissues, and guarantee the quality of vessel reconstruction image and the accuracy of assessment.
Abstract:
Objective: To investigate the clinical value of dual energy CT lung perfusion imaging (DEPI) combined with CT pulmonary angiography (CTPA) in patients with highly suspected pulmonary embolism (PE). Methods: Fifty subjects suspected of pulmonary embolism underwent dual-energy CT pulmonary perfusion imaging. The CTPA, DEPI, and both of fusion image were acquired using the Lung Perfusion Blood Volume (PBV) software. Through DEPI, CTPA and both combined detection of three methods, χ2 test were used for the detection of three methods on pulmonary lobe level, pulmonary segment level and sub-segment level respectively to compare the different test results and analyzed whether the statistically significant difference in the test results. Results: Analysis the χ2 test results found that DEPI, CTPA and combined detection of pulmonary embolism results showed no significant difference (P > 0. 05) in lung lobe level; In the pulmonary segment and sub-segment level, three methods were statistically significant (P < 0. 05) , especially the joint detection can improve the detection rate of isolated sub-segmental with pulmonary embolism in the sub-segment level. Conclusion: Combined DEPI and CTPA, can not only improve the sensitivity of pulmonary embolism but also keep the higher specificity. It also plays an important role in early and accurate diagnosis to help clinical treatment and estimate prognosis for pulmonary embolism.
Abstract:
Objective: To investigate the correlation between diabetes and the formation of coronary atherosclerotic plaque in DSCT angiography. Methods: The patients underwent DSCT coronary angiography, on the basis of questionnaires, were divided into diabetes group (n = 300) and non-diabetes group (n = 300) first, then diabetes group, which was divided into two groups:group 1, duration of diabetes less than or equal to 5 years (n = 180) and group 2, duration of diabetes more than 5 years (n = 120). Two groups were observed and compared the incidence rate of plaque, distribution characteristics and types. Results: The incidence rate of 3 coronary artery vascular lesions was 27.5% in diabetes group and 20.6.0% in non diabetes group. Incidence rate of diffuse lesions was 43.8% in diabetes group, 17.4% in non diabetes group, the difference between the two groups were statistically significant (P < 0.05). Comparison of the degree of coronary artery stenosis: Severe stenosis was 7.9% and occlusion was 4.8% in diabetes group; those were 3.7% and 1.9% respectively in non diabetes. Severe stenosis was 12.2% and occlusion was 7.8% in group 2; those were 0.93%, 0% in group 1, the difference between the two groups were statistically significant (P < 0.05). Plaque types: occurrence rate of mixed plaque was 51.4% in diabetes group and 38.9% in non diabetes group. The incidence of non calcified plaque was 43.8% in diabetes group, 53.7% in non-diabetes group, the difference between the two groups were statistically significant (P < 0.05). occurrence rate of mixed plaque was 63.3% in group 2 and 31.5% in group 1, The difference between the two groups were statistically significant (P < 0.05). that both diabetes and duration of diabetes were independent risk factor for mixed plaque. Mixed plaque was increased with the duration of diabetes increasing through statistical analysis. Conclusion: DSCTCA can evaluate the relationship between the diabetes and coronary artery plaque. Coronary plaque involvement is wider, Luminal stenosis is more serious, Incidence rate of mixed plaque is higher and having more risk prone to cardiovascular events in diabetes, and will be more serious with longer duration of diabetes.
CT Theory
Abstract:
The detector for whole-body-scan PETs used currently in clinical is commonly loop structure, sinogram (sinogram, also known as Sino) using the traditional method of fan beam structure if projection line is complete and rules. Along with the progress of the design concept for panel-PET, the projection of the panel-PET is Incomplete and irregular, it is of great significance to develop parallel-beam algorithm suited for panel-structure PET. Based on the structure of a breast panel-PET developed by our Lab, and base on rotating acquisition mode, an algorithm of parallel beam for breast panel-PET sinogram construction is put forward. To confirm the correctness of this algorithm, animal experiments were carried out to test and verify. Firstly, signals of animal rats were collected, then sinograms are constructed by the algorithm proposed in this paper, finally functional images of animal rats are reconstructed through those sinograms.Resultsshow that the proposed algorithm is correct indicating its feasible for panel-PET imaging reconstruction.
Abstract:
The experimental study of CT imaging was carried out when the activity of radiation source is very low in the case of CT detection for luggage CT inspection system. The method of adding and averaging was used to reduce the effect of statistical fluctuation and noise. And the quality of CT image is improved. Experiments show that for weak signal conditions, using the method of adding and averaging, CT imaging has high quality and can realize property identification requirements. In addition, the A/D quantization error is also analyzed.
Geotomography
Abstract:
Stereotomography is a new reflection tomography method based on the slopes of locally coherent seismic events. It can provide accurate velocity macromodels for prestack depth migration. We study the implementation methods for picking travel times and slopes using hyperbolic stack in common midpoint gather and common offset gather, representing the discrete velocity model using B-spline function, tracing rays with the numerical solution of ray equation, calculating picked data based ray theory, determining ray parameters, solving the inverse problem, etc., and then provide the algorithm flow of stereotomography. Based on the experiments with Marmousi model, we test and analyze the main factors of stereotomography like the initial velocity model, the amount of picked data, discrete grid scale, smoothing weight for velocity model, and summarize their influences on the results of stereotomography.
Abstract:
In wide angle reflection/refraction seismic sounding data processing, filtering and denoising methods based on Fourier transform and wavelet denoising method are still used. In view of the problem that there are inherent defects using the Fourier transform to process non-steady state seismic signal and that there not are the orthogonality, tight branch, and symmetry in wavelet transform at the same time, multi-wavelet denoising method is given, which has orthogonality, symmetry, compact, and overcomes the defect of traditional wavelet. Graphical user interface software is written based on the multi-wavelet in this paper. The software can show quickly and easily wide angle reflection/refraction seismic record section, can do adaptive threshold denoising in the multi-wavelet domain. Examples show that the methods and software in this paper are effective and feasible.
Industrical CT
Abstract:
Phantom is widely used to evaluate CT image quality objectively. Currently, only DIGIDENT Phantom is exclusively used in evaluating image performance of Dental CT. This phantom was recommended by "YY/T 0795-2010 Particular specification for oral cavity X-ray equipment for digital tomography". Although most of image parameters can be tested by this phantom, there are still disadvantages with it. For example, no module for slice thickness measurement and the density resolution and spatial resolution module can be improved. Hence, this paper proposed an innovative phantom which can not only be used to evaluate image quality of dental CT, but also be suitable for the dual-energy subtraction experiment. By experimental verification, the performance of this phantom is much better than existed DIGIDENT Phantom when evaluating dental CT's image quality. A new phantom design and evaluation way were presented, which will contribute to the development of dental CT phantom.
Abstract:
3D X-ray Microscope is becoming a widely used imaging tool in many research and industrial fields such as biology, geology, material science, etc, due to its capability of achieving sub-micron spatial resolution and showing internal structures non-destructively. This paper introduces a newly developed X-ray Microscope (nano Voxel-2000) by Tianjin Sanying precision Instruments Ltd.. The system configuration and imaging technologies of the instrument are presented and discussed. One of the most important index for microscopes is resolution. nano Voxel-2000 is of a spatial resolution up to 500 nm. It can scan samples with different scales and fields of view via a multiple lens-coupled CCD detector system, and realize image reconstruction at different resolution scales. In addition, typical applications of the 3D X-ray Microscope in material science and geology are explored, and quantitative analysis on image data such as the morphology of material structures, interior structure information, etc. is presented. It is expected that this article can play a role in attracting more colleagues to carry out research with 3D X-ray Microscopy.
Abstract:
In radiation imaging application, huge image data is produced in DR and CT imaging. Image processing methods used in this area include image reconstruction, visualization, image enhancement, image compression and image defects detection and etc. Often people need pinpoint some area in an image and process this area. These areas are called ROI (region of image). The selection and edit of ROI is a functionality often used in radiation image processing. Various ROIs and applications are introduced in this article.
Abstract:
Positron emission tomography technology is an emerging nuclear medicine imaging technique that can provide the physiological metabolic level of functional imaging, has wide application in many fields, such as disease diagnosis, pathology research, and drug research and so on. The core of PET technology is detector and scan structures design. Scanning structures include ring-static scanning, ring-dynamic scanning, flatbed-static scanning, flatbed-dynamic scanning and so on. A variety of detector structures have developed: PMT coupled to a single crystal, PMT coupled multi-block crystals, PSPMT coupled crystal array, SPM coupled crystal array and so on. The author began to engage in medical PET studies from 1983, this paper reviews several PET machines that author has developed, and describe the development of the PET detector and scan structures.
Medical CT
Abstract:
Objective: To explore the value of CT urography (CTU) on diagnosis of urinary tuberculosis. Methods: A retrospective analysis was carried out in TB patients clinically confirmed whom had underwent CTU or IVP, image data were compared with pathological findings. Results: 79 cases were included in the study. CTU examination revealed 46 cases of positive diagnosis in 50, 13 cases of positive diagnosis were found in 29 cases of IVP examination. The diagnosis accuracy of CTU is higher than that of IVP. CTU signs of urinary tuberculosis are: multiple or single round hypodense in renal parenchyma, renal calcification, uneven caliectasis, urothelial thickening and "beaded" change, bladder contracture. Conclusion: CTU can accurately reflect the different pathological changes of urinary tuberculosis. It can be used as first-line screening tool, especially for patients with poor renal function or whose IVP with poor developing, to provide more diagnostic information.
Abstract:
Objection: Analysis and research on MRI subtraction technology combined with the clinical value of DWI in preoperative TN staging of rectal cancer can. Methods: Collected during 2010.8-2013.12 by surgery and pathology confirmed in our primary 53 patients with rectal cancer, The selected patients were confirmed by colonoscopy biopsy for 46 cases of patients with rectal cancer, 7 cases of suspicious. Including conventional MRI sequence TSE-T1 WI, T2 WI, diffusion imaging (DWI) can imaging and inversion recovery frequency saturation (SPIR) sequence. All patients were multiple enhanced scan, and ensure that there is a bearing insufflate long axis of the plane must be perpendicular to the masses, to subtract the same level images of before and after enhancement scanning. By two high venture experts asked to read, and preoperative TN staging. Pathological reference standard is a standard with Dukes staging.MRI subtraction technique in colorectal cancer using Kappa. test preoperative staging and pathologic results consistency difference, statistical processing using SPASS19.0. Results: 53 patients for colorectal cancer, MRI subtraction technique combining DWI for colorectal cancer detection rate of 100%, can correct the T staging in 49 cases, low stage 1 case, high stage (3 cases) , T staging accuracy was 92.5% (49/53). According to the preoperative MRI tips, surgical removal of lymph nodes 283, 53 patients with postoperative disease inspection in 36 cases with lymph node metastasis, 184 metastatic lymph nodes, DWI combined with conventional sequence can reliability evaluation of preoperative lymph node metastasis. Conclusion: MRI subtraction technique combining DWI convenient, quick, can in colorectal cancer diagnosis and preoperative TN staging accuracy is high, is worth popularization and application.
Abstract:
Objective: To explore the feasibility of adaptive statistical iterative reconstruction (ASIR) technique in 64-slice CT of hip with low tube current application. Methods: Of 106 patients with 64 row helical CT scan of hip, 53 patients were treated with conventional tube current of 220 m As scanning, and were reconstructed with filtered back projection (FBP) , 53 patients were treated with low tube current of 50 m As scanning and were reconstructed with 30% of adaptive statistical iterative reconstruction (ASIR).The radiation dose, image noise (S D value) and signal-to-noise ratio of different reconstruction images of two groups were compared respectively at the same level. Results: The CTDIvol value was (15.55 ± 0.20) m Gy in the conventional group and (3.56 ± 0.15) m Gy in the low tube current group, the CTDIvol in the low tube current group was 77.1% of that in the conventional group, the DLP was (297.82 ± 2.9) m Gy·cm in the conventional group and (67.59 ± 3.3) m Gy·cm in the low tube current group, the DLP in the low tube current group was 77.3% of that in the conventional group. Compared with the conventional group, the radiation dose of low tube current group was reduced greatly (P< 0.05). The image quality with excellent、good、bad was 49, 4 and 0 cases, respectively, in the conventional group. 42, 11 and 0 cases in the low tube current group, difference of image quality between two groups were no statistically significant (P> 0.05). The difference of image noise value and SNR between two groups were statistically significant, respectively (P< 0.05). Conclusion: It is feasible to apply 30% of ASIR technology in 64 row helical CT of hip with low-current of 50 m A, resulting with the reduction of radiation dose, meanwhile, the image quality can meet the need of clinical diagnosing.
Abstract:
Objective: To investigate the MSCT imaging features of the red pulp type splenic hamartoma. Methods: Retrospective analysis of the clinical and CT imaging data of 13 cases of red pulp type SH confirmed by operation and pathology, All patients underwent 64 slice spiral CT plain scanning and enhanced scanning. Results: 13 cases were solitary, a total of 13 lesions, diameter of 4.6~10.5 cm, the plain CT scan showed is density in 9 cases, the state is not clear, showed slightly low density lesion in 4 cases, the realm of clear, all cases without fat component and calcification, cystic necrosis, rare, enhanced scan showed 9 patients with lesions density showed diffuse irregular, inhomogeneous patchy enhancement, scan showed slightly low density lesions of 4 cases showed diffuse irregular, uneven patches enhanced obviously, time delay lesions showed homogeneous enhancement in delayed phase of progressive, lesion density close to or equal to the surrounding normal splenic parenchymal density, which was misdiagnosed as malignant tumor of splenic hemangiomas, 1 cases in each. Conclusion: SH is different from the other organs of the hamartoma, has its own characteristics, intralesional often no fat component and calcification, when found in the spleen of solitary mass, enhanced lesions showed diffuse irregular, inhomogeneous enhancement patch or plaque, with the delay time is progressive uniform enhancement, should first consider splenic hamartoma, and more for the red pulp type.
Review
Abstract:
γ-ray CT is one of the non-destructive technologies increasingly applied for radioactive waste assay in recent years. The radioactive sources in the target objects can be identified, quantitified and located by γ-ray CT, offering the bases for further disposal and management of the radioactive waste. In this paper, the application background of γ-ray CT for radioactive waste assay is briefly described, and the mathematical models, system designs of the technology are summarized, as well as its main performance indices and influencing factors. Furthermore, the research developments in key techniques about the algorithms and correction methods for radioactivity image reconstruction are introduced in detail. Finally, an outlook to future developments of the technology is given.
Abstract:
Seismic array is a seismic observation system originally built for detecting underground nuclear explosions. Nowadays, seismic array has been developed into the study of the Earth's interior structure, and then greatly promotes the development of seismology. This article gives an introduction to the various seismic array techniques such as beam-forming method, slant stacking techniques,Nth root slant stack process, frequency-wave number analysis and phase-weighted stack, and discusses the advantages and disadvantages of the techniques. As to the detecting of weak but coherent arrivals, phase-weighted stack and its applications will be discussed. It turned out to be a great improvement of the signal-to-noise ratio (SNR) in different degree. These array data of high quality make it possible to research the fine-scale structure tomography of Earth's interior.
Abstract:
Oil shale is one of the world's most popular unconventional resources. Affected by the oil crisis, the world is searching for alternative resources urgently. Many countries are paying more and more attention on this clean energy's exploration technology not far behind that America may twist the situation that its natural gas comes from imports mostly relying on shale gas revolution. This paper discusses the present situation and progress of oil shale exploration and exploitation: (1) Oil shale is a kind of high-ash and high-organic source rock, its sedimentary environments are divided into three types which are marine facies, lake facies and continental facies and its deposit types contain offshore and inland lake type. (2) The oil shale resources are very abundant in the world especially America, and also China. However, oil shale has lower exploitable reverse than the proved one. (3) Well logging methods include log R method, resistivity method, and density method on the basis of its logging response characteristics such as high nature gamma, high electronic resistivity, high interval transit-time and low density. (4) Seismic methods include sweetness prediction method and rock physics model method. (5) When evaluating oil shale, it is evaluating oil content mainly and methods which can be used include cracking process, logging evaluation and pyrolysis method. (6) Shale oil production is the difficulty of oil shale exploration and development; it can be divided into four types: strip mining with retorting processing, underground mining with retorting processing, the modified in-situ mining and in-situ thermal conversion processing technology. The results of this paper are good references for understanding the characteristics, development, key technologies and further promotion of oil shale.