CT理论与应用研究

Attenuation Based Governing Equations for Automatic mAs and kVp Controls in Medical X-ray CT Imaging

ZHENG Xiao-ming

2016, 25(6): 625-632. doi: 10.15953/j.1004-4140.2016.25.06.01

Abstract(519) PDF(3)

Abstract:
Automatic exposure control based on noise index has been commonly implemented in current medical X-ray CT scanners in order to minimise radiation dose to patients while maintaining image quality for patient diagnosis. Automatic peak voltage control is also desirable as it is an important scanning parameter that has significant impact on both image quality and radiation dose. In this paper, a general attenuation based governing equation for simultaneous automatic controls of both mA s and kV p is presented which was derived from the first principle of radiation dose and image quality optimisation. This equation can be applied separately for automatic mA s control only or automatic kV p control only. The equation for automatic mA s control only states that the mA s should be increased by 3.8% for every 1cm increase of the patient body's sectional thickness if the peak voltage is kept constant. For automatic kV p control only, the equation states that the peak voltage should be increased by 1.53% percent on average for every 1 cm increase of the patient's body sizes if the mA s is kept as a constant. For a constant body thickness, the equation states that the average percentage mA s reduction should be 2.49 times the percentage peak voltage increase. The implementation of these equations in medical CT scanners has been described in a recent Australian patent.

Application of CT Dual Energy Imaging with High Concentration Contrast in Ophthalmic Artery Vascular Examination

CAO Wei, LIU Hong, WANG Fan, HUANG Hai-dong

2016, 25(6): 633-638. doi: 10.15953/j.1004-4140.2016.25.06.02

Abstract(402) PDF(3)

Abstract:
Objective: To explore the application value of iodine contrast agent with high concentration in the ophthalmic artery angiography in dual source dual energy CT angiography. Methods: From March 2014 to December 2015, 80 patients(160 eyes) with brain CTA were selected in our hospital. 80 patients were randomly divided into observation group and control groups, Judgment and analysis of the two groups of dual energy CT angiography and spiral CT subtraction, the former uses the Bayer 370 mg I/m L contrast agent, the latter uses the GE 350 mg I/m L contrast agent. Results: The ophthalmic artery CT angiography images of all subjects showed clear, full of each vessel filling well. After the measurement, the intracranial segment of the observation group, the optic nerve canal segment, the diameter of the orbital segment and other ocular artery were significantly more than the control group(P<0.05), Diameter(mm) were: 1.26 ±0.16, 1.21 ±0.18, 1.12 ±0.14. The detection rate of plaque in the observation group and the control group were 28.8% and 2.5%, the observation group was significantly higher than that of the control group(P<0.05). Conclusion: Using dual source spiral CT dual energy CT angiography applied in the judgment of the ophthalmic artery disease showed good effect. Can effectively judge the diameter of the ophthalmic artery and plaque situation, so as to guide the treatment.

A Feasibility Study on Coronary Angiography with Flash Technique of Dual-source Computed Tomography by Double Low Technical and Manual Trigger Scanning

GUO Hai-dong, ZHAO Sheng, GUO Xiu-ling, LIU Ai-shi

2016, 25(6): 639-646. doi: 10.15953/j.1004-4140.2016.25.06.03

Abstract(415) PDF(5)

Abstract:
Objective: To investigate the application of low tube voltage, low-volume contrast media and manual trigger scanfor coronary artery CT angiography with Flash scan modeon dual-source CT equipment about patients with low weight and low heart rate, through contrast with prospectively ECG-triggering sequentia and normal-volume contrast media. Methods: 48 patients were scanned with a prospectively ECG-triggering sequential or Flash CCTA protocol on DSCT. All patients were divided into two groups: the weight and heart ratein Group A was less then 65 kg and 65 beats per min, the injection rate and volume of contrast in Group A was 5.0 mL/s and 20 mL(350 mg I/m L), scanned with Flash scan mode, Tube voltage was 70 kV; the weight in Group B was less than 65 kg, the heart ratein in Group B was less than 65 beats per min, the injection rate and volume of contrastin in Group B was 5.0 mL/s and 50 mL(350 mg I/m L), scanned with a prospectively ECG-triggering sequential, Tube voltage was 100 kV. The raw data were reconstructed with sinogram affirmed iterative reconstruction(SAFIRE) technique. The differences of sex, age, HR,weight, BMI, CTDI_VOL, DLP and ED were compared. Besides, the CT value, noise, signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR) between the two Groups of the aortic root, left main coronary artery and the proximalsegment of each coronary arteries were compared. And Image quality(Ⅰ~Ⅳ) between the two Groups was compared. Results: There were no significant differences in sex, age, HR, weight and BMI between the two Groups(all P > 0.05), while there were no significant differences in the CT value, noise, SNR and CNR of the aortic root, left main coronary artery and the proximalsegment of each coronary arteries between the two groups(all P > 0.05). The CTDI_VOL, DLP and ED in Group B was higher than Group A(all P > 0.05). The scores of image quality showed no significant difference between the two Groups. They more than 96%. Conclusion: For patients with low weight and low heart rate, the use of tube voltage as 70 kV and low-volume contrast media in DSCT is feasible. The radiation dose and contrastdosage can be much lower.

Experimental Study of Effective Displacement Characteristics of Different Displacing Methods in Tight Oil Reservoir

PAN Wei-yi, LANG Dong-jiang, LUN Zeng-min, LV Cheng-yuan, ZHAO Shu-xia, WANG Hai-tao, ZHAO Qing-min

2016, 25(6): 647-652. doi: 10.15953/j.1004-4140.2016.25.06.04

Abstract(431) PDF(6)

Abstract:
Tight oil is an important unconventional hydrocarbon resource. Its low recovery of primary production induces the necessities of enhanced oil recovery researches. Due to the complex pore structure of tight oil reservoir, the contribution of different pores is different. So it is necessary to study effective displacement in different pores and optimize development mode. In this study, nuclear magnetic resonance(NMR) and core flood tests were conducted to experimentally simulate different displacing methods(CO₂ flooding and waterflooding), and to evaluate effective displacement of different pores. The tests results indicated that effective displacement of different pores of CO₂ flooding and waterflooding increases with an increasing pressure drawdown. Most of the oil in large pores was displaced. As the pore radius turned small, displaced oil gradually decreased. In the pores with radius less than 0.01 μm, effective displacement of CO₂ flooding was better than that of waterflooding. In tight oil reservoir CO₂ was easier to enter the small pores to enhance oil recovery.

Study on Data Processing of Sub-bottom Profile Based on the Chirp Signal in Order to Distinguish Thin Layer

YANG Li, ZHANG Bao-jin, WEN Peng-fei, ZHANG Ru-wei, XUE Hua, GU Yuan

2016, 25(6): 653-660. doi: 10.15953/j.1004-4140.2016.25.06.05

Abstract(354) PDF(2)

Abstract:
Sub-bottom profiler based on Chirp signal is widely used in the fields of engineering investigation, geological hazard assessment, gas hydrate investigation and deep sea resources exploration because of its high resolution. Due to the narrow bandwidth of the Chirp signal, the side lobe of cross-correlation result is serious. Conventional extraction envelope processing can suppress side lobe, but the resolution of the data is low. In this paper, the different theoretical models and the actual data are processed by the method of mutual correlation, extracting amplitude envelope and linear frequency extraction and their results are remarkable.

Spatial Registration of X-ray CT Projection Images

BAI Juan-juan, YANG Yu-shuang, WANG Hai-peng

2016, 25(6): 661-670. doi: 10.15953/j.1004-4140.2016.25.06.06

Abstract(490) PDF(7)

Abstract:
The relative displacement among X-ray source, rotation stage, and detector in X-ray computed tomography(X-ray CT) imaging process are difficult to eliminate. This causes spatial misalignment of the projection and flat-field images, which directly affects the accuracy of flat-field subtraction and the subsequent CT reconstruction. In this paper, the quantitative spatial displacement was obtained between each projection image and the detector using a cross-correlation method. The projection images registrations were carried out according to the calculated displacement. As this method is very sensitive to image gray value, a polynomial fitting method was used to correct the non-uniform illumination in the original CT image. The numerical results based on real CT data have demonstrated that this method can effectively correct the misalignment of CT projection images, caused by relative movement among the X-ray source, the rotation stage and the detector.

A Registration and Evaluation Algorithm for the Calibration of Point Extraction Precision Based on ICT Equipment

CHEN Si, LI Jing, LI Shi-gen, LI Shou-tao, CHEN Yun-bin, ZHANG Xiao-li

2016, 25(6): 671-678. doi: 10.15953/j.1004-4140.2016.25.06.07

Abstract(420) PDF(4)

Abstract:
Reverse modeling based on CT measuring data is widely used in military, automotive, aviation, aerospace and other fields. At present, there is a lack of relevant research to verify the accuracy of the points based on industrial ICT equipment. A kind of registration and evaluation algorithm for the calibration of point extraction precision based on ICT equipment is presented. On the basis of many registration algorithms, a method that contains manual original registration and auto accurate registration is described. Two set of data for registration are obtained from ICT equipment and 3D optical scanner. The Modified Hausdorff distance between each two correlative points is used to verify the algorithm accuracy. The calculation steps of seven parameters and ICP(Iterative Closest Point) algorithms are presented detailed to demonstrate how to complete the original registration and accurate registration. The evaluation value for point-cloud data extraction accuracy based on CT equipment is calculated and the applicability of registration process is validated as self-designed standard parts for example.

3T Magnetic Resonance Imaging Evaluate the Efficacy after Percutaneous Coronary Intervention in Coronary Heart Disease

YANG Yang, SHEN Bi-xian, ZENG Zhi-bin

2016, 25(6): 679-686. doi: 10.15953/j.1004-4140.2016.25.06.08

Abstract(346) PDF(3)

Abstract:
Objective: Myocardial remodeling and time course and magnitude of infact involution after acute myocardial infarction undergoing selective percutaneous coronary intervention(PCI) opterations are not completely knowed in humans. This subject is to explore the changes and correlations of relative amount of hyperenhancement, global left ventricular function and regional wall thickening by using 3T cardiac magnetic resonance. Method: To collect patients with acute myocardial infarction in our hospital from August 2014 to March 2016. They were examination by MRI before PCI operation and reexamine at one week and half year after PCI operation. To observe and compare the changes of relative amount of hyperenhancement, global left ventricular function and regional wall thickening in three groups. Result: Comparison of relative amount of hyperenhancement: relative amount of hyperenhancement was reduced by about 30% during the first week after operation, which were respectively(13.1 ±7.6)%,(9.4 ±6.6)%,(8.9 ±6.4)% at the time before PCI operation, one week after PCI operation and half year after operation, the difference was statistically significant(P<0.05). Comparison of global left ventricular function: the global left ventricular function increase gradually by time. LVEF were respectively(43.9 ±10.9)%,(46.7 ±10.8)%,(52.3 ±12.5)% at the time before PCI operation, one week after PCI operation and half year after operation. LVEDV were respectively(161.4 ±54.0)mL,(1.686 ±53.0)mL,(168.5 ±52.6)mL. LVSDV were respectively(91.62 ±43.5)mL,(91.3 ±43.7)mL,(82.5 ±43.4) mL. he difference was statistically significant(P<0.05). The changes of regional wall thickening: Regional wall thickening was increased by remote segments,adjacent segment and which transmural extent of hyperenhancement is 1%~25%, 26%~50%, 51%~75% and no significant change by which transmural extent of hyperenhancement is 75%~100%.Regional wall thickening decreased progressively with increasing transmural extent of hyperenhancement(P<0.05). Conclusion: The efficacy of PCI operation may reduce the relative amount of hyperenhancement, improve regional left ventricular function and regional wall thickening. 3T magnetic resonance can accurately evaluate the efficacy of PCI in patients with coronary heart disease.

Analysis of Complications and Treatment of CT-guided Radiofrequency Ablation of Lung Tumours

GUAN Li-jun, JIA Guang-zhi, ZHANG Chun-long, LI Xiao-guang

2016, 25(6): 687-694. doi: 10.15953/j.1004-4140.2016.25.06.09

Abstract(495) PDF(3)

Abstract:
Objective: To evaluate the value of CT-guided percutaneous RFA therapy of lung tumours and analyze complications. Methods: Fourty-eight patients with pathologically proved lung neoplasms that comprised 43 primary lung cancers initially underwent CT-guided percutaneous RFA treatment and subsequently the near-term efficacy. Results: Our experiments have indicated an initial increase in lesion size at immediate follow-up CT. The density of 54 lesions was lowered. Among total 54 lesions of 48 patients, RFA resulted in complete necrosis of 54 lesions, which appears as devascularization and enhancement of residual tumors on postcontrast CT images. Radiologically assessed through measurements of the lesions on axial CT scans in the lung window setting lesions had CR 61%(33/54) and PR 39%(21/54) at 3 month follow-up. No severe complications related to the procedure occurred in the group patients. Conclusion: CT-guided percutaneous RFA in treating lung neoplasms is safe and effective, which has recently received wide attention for the promising results achieved, and can serve as a new approach to the treatment of lung neoplasm.

The Application of Lung Volume Measurement with Gemstone HDCT Low-dose Dual Phase Scanning in Patients with Coal Workers Pneumoconiosis

DENG Mao-song, ZHANG Shu-hui, WANG Xu, WU Ge, YIN Xiao-ming, LI Bao-ping, QU Yin-e

2016, 25(6): 695-701. doi: 10.15953/j.1004-4140.2016.25.06.10

Abstract(404) PDF(5)

Abstract:
Objective: To investigate the application value of HDCT low-dose dual phase scanning measurement of lung volume in patients with coal workers pneumoconiosis. Methods: Totally 30 cases of male patients with coal workers pneumoconiosis underwent low-dose chest examination with HDCT at inspiratory and expiratory phase, image reconstruction using adaptive statistical iterative reconstruction(ASIR), and all patients underwent pulmonary function tests(PFT) within 3 days after the CT scanning. The control group from the usual male patients who underwent routine dose with 64 rows of VCT chest scanning about 30 cases. Each the noise of the image and each scan volume CT dose index(CTDI, DLP, ED) was converted. The subjective image quality score between the two groups to compare the nonparametric Mann-Whitney U test. With paired samples t test to compare different scan dose and breathing state between the two groups of image noise, the volumetric CT dose index. The Pearson correlation analysis inspection throughout the lung volume index(Vin, Vex, Vin-Vex, Vex/Vin, Vin-Vex/Vin100%) and PFT index(FVC, FEV1, FEV1/FVC%). Results: All the subjective image quality evaluation in middle rating above, the image noise between two groups of the scanned without statistical significance; The sam of radiation dose of low-dose scan using ASIR technology dual phase scanning with HDCT lower than the routine dose in a single scan with VCT. Correlation was found between the lung volume index(Vin, Vex, Vex/Vin, Vin-Vex/Vin 100%) and PFT index(FVC, FEV1, FEV1/FVC%) in Coal workers pneumoconiosis patients. The Vex, Vex/Vin had a better correlation with PFT index(P<0.01). Conclusion: HDCT low-dose dual phase scanning of lung volume index can be used for assessment of lung function in patients with coal workers pneumoconiosis, and its clinical application value is high.

Radiological Diagnosis of Nasopharyngeal Non-Hodgkin's Lymphoma

WANG Li, FENG Feng, FU Ai-yan

2016, 25(6): 703-710. doi: 10.15953/j.1004-4140.2016.25.06.011

Abstract(386) PDF(2)

Abstract:
Objective: To investigate the radiological findings of nasopharyngeal non-Hodgkin's lymphoma(NHL). Materials and Methods: The CT images of 22 patients and MRI images of 6 patients with pathologically confirmed nasopharyngeal NHL were retrospectively analyzed. All nasopharyngeal NHL were assessed for morphology,necrosis,local invasion and lymphadenopathy. Results: 16 cases presented the walls of nasopharynx symmetrically or general symmetrically diffuse thickening, and 12 cases presented soft tissue masses on the hanging posterior and(or) lateral walls of nasopharynx. 25 cases were homogeneous. 14 cases invaded the oropharynx, palatine and/or lingual radix tonsil swollen in 4. 2 invaded the laryngopharynx. 4 invaded nasal cavity. 1 invaded clivus and adjacent muscles. Lymphadenopathy was found in 17, with necrosis in 4. Conclusions: There were typical features of nasopharyngeal NHL on MRI or CT. Nasopharyngeal NHL usually invaded mutiple walls of nasopharynx, and more than half were lymphadenopathy. Both of the tumour at nasopharynx and lymphadenopathy were homogeneous, necrosis uncommon. Skull base or the deep structures invasion were rare. The lesions could spread down invading the other parts of Waldeyer ring.

CT Diagnosis of Basal Cell Adenoma of the Parotid Gland in the Parapharyngeal Space

HE Jia-wei, WANG Si-wei, LI Ruo-mei, SHENG Mao

2016, 25(6): 711-716. doi: 10.15953/j.1004-4140.2016.25.06.12

Abstract(356) PDF(2)

Abstract:
Objective: CT feature of the basal cell adenoma of parotid gland in parapharyngeal space and its main points of identification from neurilemmoma of parapharyngeal space were discussed. Method: An infrequent CT feature of one example of basal cell adenoma in parapharyngeal space was reported and analyzed. All literatures on this disease diagnosed by CT were reviewed from 2010 in China. Among them there were only four articles reporting more than 10 samples with detailed data and full description. Totally there were 77 samples and 83 lesions. In this paper, the number, sizes, locations of parotid gland, cystic degeneration and calcification of those lesions were subtotaled. Result: 94.8% of them were single disease, 86.7% of them were located in superficial lobe, 92.8% of them were smaller than 3 cm, 60.2% of them were cystic degeneration and 2.4% of them were calcification. Basal cell adenoma of parotid gland in parapharyngeal space was located in the superficial side to the posterior belly of digastric muscle and fat ingression in parapharyngeal space happened. Conclusion: CT feature of the basal cell adenoma of parotid gland in parapharyngeal space shows some certain characteristics. Posterior belly of digastric muscle is the boundary to identify the basal cell adenoma and the neurilemmoma in parapharyngeal space.

Effect of Volume Helical Shuttle Mode with ASiR Technique on the Quality of CT Perfusion Imaging in Liver Tumor

YANG Xiao-feng, ZHA Yun-fei, LI Liang

2016, 25(6): 717-723. doi: 10.15953/j.1004-4140.2016.25.06.13

Abstract(373) PDF(4)

Abstract:
Objective: To investigate the effect of VHS mode with ASi R on the quality of CT perfusion images of liver tumors. Methods: Twenty-eight patients with liver tumor underwent first-pass perfusion CT with volume helical shuttle technique. The raw date had been reconstructed by using FBP, the slice thickness being 2.5 mm. The CT values of aorta and the image noise were recorded for both groups. The parametric maps for the permeability surface(PS), blood volume(BV), blood flow(BF), transit time mean(MTT) were calculated. Paired samples t test or Wilcoxon signed sum test was used to analyze the difference.Image quality was assessed by two radiologists. Results: Compared with FBP reconstruction technique, 40% ASi R demonstrates low image noise((13.20 ±1.65) vs(10.9 ±1.49), P<0.01), with no statistical difference in CT values of aorta((58.33 ±9.19) vs(58.77 ±9.30), P=0.258). All the functional parameters of CT perfusion between two groups, including PS, BV, BF and MTT, showed no statistical difference. 40% ASi R group as quality score(4.14 ±0.36) higher than that of group FBP(3.79 ±0.48), the difference was statistically significant(P=0.001); Conclusion: Application of ASi R demonstrates no influence parameters acquired from CT perfusion with VHS mode in liver tumor, though the noise is lower than FBP.

Current State and Progress of Coronary Angiography in Multi-slice Spiral Computed Tomography Imaging Techniques

LIANG Yu, ZHANG Xiao-qin

2016, 25(6): 725-735. doi: 10.15953/j.1004-4140.2016.25.06.14

Abstract(413) PDF(8)

Abstract:
Multislice computed tomography angiography has been increasingly used in the detection and diagnosis of coronary artery disease because of its rapid technical evolution. Technical developments of multislice CT imaging enable improved diagnostic value in the detection of coronary artery disease, and this indicates that multislice CT can be used as a reliable less-invasive alternative to invasive coronary angiography in selected patients. In addition, multislice CT angiography has played a significant role in the prediction of disease progression and cardiac events. Despite promising results reported in the literature, multislice CT has the disadvantage of having a high radiation dose which could contribute to the radiation-induced malignancy. A variety of strategies have been currently undertaken to reduce the radiation dose associated with multislice CT coronary angiography while in the meantime acquiring diagnostic images. In this article, we will review the technical developments, radiation dose associated with multislice CT coronary angiography, and strategies to reduce radiation dose. The diagnostic and prognostic value of multislice CT angiography in coronary artery disease is briefly discussed, and future directions of multislice CT angiography in the diagnosis of coronary artery disease will also be highlighted.

The Research Status of MSCT in the Small Bowel Obstruction

KUANG Lian-qin, ZHANG Chun-lai, TANG Shuang-yue, CHENG Cheng, WANG Yi

2016, 25(6): 737-744. doi: 10.15953/j.1004-4140.2016.25.06.15

Abstract(369) PDF(3)

Abstract:
Due to the high incidence of small bowel obstruction, early accurate diagnosis and comprehensive evaluations are very important for choice of the treatment methods. Multi-slice spiral computed tomography(MSCT) has very high accuracy in the evaluation of whether there is any obstruction; obstructive sites, severity degrees and causes, and can also provide useful information for secondary intestinal ischemia. The present research situations of MSCT in evaluation of the small bowel obstruction were reviewed in this article.

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2016 Vol. 25, No. 6