ISSN 1004-4140
CN 11-3017/P

## 2022 Vol. 31, No. 2

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2022, 31(2): 135-148. doi: 10.15953/j.1004-4140.2022.31.02.01
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With the deepening of exploration and development, due to the limitation of the resolution of the conventional seismic data, it is difficult to meet the needs of exploration and development. Since the attenuation degree of different frequency components of seismic signals is different, the frequency decomposing technology can be applied to perform differential compensation on each frequency component to improve the resolution of seismic data. However, the conventional frequency division technology generally not only holds low frequency division accuracy but also shows modal aliasing, thus it cannot be well applied to seismic data processing. To solve these problems, this paper proposes a high-resolution processing method for seismic data based on adaptive variational modal decomposition (VMD). The multi-objective bat algorithm is applied to the variational modal decomposition, and the VMD parameters are optimized by the fitness function constructed using power spectrum entropy, energy difference, and sample entropy. The model test results show that the optimized VMD method holds high frequency division accuracy and strong anti-noise ability, and also can avoids modal aliasing, When the optimized VMD method is applied to high-resolution processing of seismic data, the model and actual data test results show that the resolution of processed seismic data is effectively improved.
2022, 31(2): 149-162. doi: 10.15953/j.1004-4140.2022.31.02.02
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Taking the rock slope of the subway deep foundation pit as the research object, elastic wave CT is used to preliminarily judge the type and spatial distribution of rock mass diseases in foundation pit, which is then verified by geological radar. Furtherly the a watershed algorithm is adopted to analyze the wave velocity distribution obtained by elastic wave CT in order to extract the detailed sound velocity change at the rock cave and delineate its range. On this basis, based on the coordinate information of elastic wave CT three-dimensional spatial wave velocity database, combined with the spatial coordinate information obtained by watershed algorithm, the modeling database is constructed, after imported into GOCAD software, the three-dimensional geological visualization model is established after processing and analysis. The rock mass disease model established in this paper is highly consistent with geological drilling, peephole imaging and field observation. The proposed rock disease identification method and modeling technology can not only provide an important reference for rock mass support but also provide a basis for water disaster prevention of urban underground engineering.
2022, 31(2): 163-172. doi: 10.15953/j.ctta.2021.032
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To solve the problem of severe streak artifacts in sparse-view computed tomography (CT) reconstruction, in this paper we propose a method which is based on the adversarial residual dense deep neural network to acquire high-quality sparse-view CT reconstruction. The UNet that combines residual connectioin, dense connection, adversarial mechanism and attention mechanism is designed, which is trained through large-scale training data composed of streak artifact images and high-quality images to suppress streak artifacts. First, the filtered back projection (FBP) algorithm is used to reconstruct CT images with streak artifacts from sparse projections, then these images are inputed into the deep network, which can suppress streak artifacts to output high-quality images. The experimental results show that, compared with the existing deep learning algorithms, the image reconstructed by the proposed new network possesses higher accuracy and can suppress streak artifacts better.
2022, 31(2): 173-185. doi: 10.15953/j.ctta.2021.052
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Light field imaging plays a vital role in three-dimensional reconstruction, synthetic aperture de occlusion, and holographic imaging. The light field dense reconstruction algorithm can make up for the shortage of light field imaging hardware and realize the dense reconstruction of the sparse light field. Based on the basic principle of two-dimensional optical flow and the light field biplane model, a new mathematical model of a four-dimensional light field optical flow constraint equation is proposed in this paper. The position coordinates of the new viewing angle are determined by using the light field optical flow solved by the constraint equation, and the intensity values of the new coordinates are obtained point by point through interpolation calculation and image inversion, so as to finally obtain a high-quality new viewing angle synthetic images. The experimental results show that the proposed method can realize high-quality reconstruction of the texture, shadow, and color information in the extended baseline scene. The quantitative evaluation results show that the algorithm can accomplish the task of dense light field reconstruction in complex settings. This algorithm in this paper is only applicable to the case of linear optical flow constraint and one-dimensional viewing angle light field. The subsequent related research will focus on the case of nonlinear optical flow constraint and multi-dimensional viewing angle light field.
2022, 31(2): 186-194. doi: 10.15953/j.1004-4140.2022.31.02.05
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Objective: To explore the feasibility of low-dose scanning for COVID-19 patients by using the method of high-pitch combined with ASIR, and compare the diffrence of radiation dose and image quality. Methods: 91 patients diagnosed with COVID-19 in our hospital were collected as the low-dose group while 91 cases of undiagnosed COVID-19 patients who were screened for COVID-19 in our hospital during the same period were selected as the conventional dose group. High-pitch combined with ASIR was performed on the low-dose group while conventional dose group was scanned by common pitch and reconstructed by FBP. In order to compare the differnce of the image quality and radiation dose between the two groups, we recorded the radiation dose and performed subjective and objective evaluation of image quality of the two groups.Results: There was statistical differences in radiation dose between the two groups, and the radiation dose of the low-dose group was significantly lower than that of the conventional dose group (the ED was reduced by about 52%). There was no statistical difference in the image quality scores between the two groups; There was no statistical difference in the objective evaluation of images between the two groups . Conclusion: Low dose scanning with high-pitch combined with ASIR for COVID-19 patients can evidently reduce the radiation dose without significant decrease in image quality.
2022, 31(2): 195-202. doi: 10.15953/j.ctta.2021.011
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Objective: To evaluate the incidence and patterns of AMCA amony normal population. Methods: 331 cases of normal people who underwent Abdomen & Pelvis enhanced CT scan in RuiJin Hospital North Area from January, 2021 to June, 2021 were retrospectively collected for the present study and 97 cases were found to have got AMCA. Multiplanar reconstruction was performed on the original images of venous phase to record how the AMCA originated and the adjacency relationship between the accompanying veins and pancreas. The diameter of AMCA starting point and the distance to the nearest point of pancreas were also measured. Results: The incidence of AMCA was 29.3％ (97/331). Among the 97 cases, 66.0％ (64/97) occurred in superior mesenteric artery, 17.5％ (17/97) occurred in inferior mesenteric artery and 6.5％(16/97) occurred in inferior pancreaticoduodenal artery. The average diameter of AMCA was (2.0±0.24)mm, the minimum distance to pancreas was (2.1±1.4)mm. Accompanying vein was observed in all the 97 AMCA cases, 72.2％ (70/97) converged towards inferior mesenteric vein, 20.6％ (20/97) converged towards superior mesenteric vein, 6.2％ (6/97) converged towards splenic vein, and 1％ (1/97) converged towards jejunal vein. Conclusion: Multi-slice spiral CT contrast enhancement scan can clearly show the origin and the adjacency relationship between the accompanying veins and pancreas of ACMA. It can provide accurate evaluation of blood vessels before operation.
2022, 31(2): 203-210. doi: 10.15953/j.ctta.2021.033
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Objective: To investigate the optimal dosage of contrast agent in three-dimensional dynamic enhanced magnetic resonance angiography (3D CE-MRA) in the imaging of arterial lesions of both lower limbs. Methods: 45 patients who underwent 3D CE-MRA angiography of lower extremity arteries in our hospital were randomly divided into three groups A, B and C. The gadolinium dosages of the three groups were respectively 0.1 mmol/kg, 0.2 mmol/kg and 0.3 mmol/kg. They were injected intravenously with saline at the ratio of 1:1. The images of different dose scanning schemes were scored subjectively and objectively. Subjective scoring: the lower limb arteries were divided into femoral artery, popliteal artery and calf artery (posterior tibial artery, anterior tibial artery and common peroneal artery). The quality of MIP reconstruction images was evaluated, and the overall venous overlap scoring of calf and foot vessels was also carried out. Finally, the differences of the three scanning schemes were compared by Wilcoxon test.The objective scoring is to measure and calculate the signal intensity Si, signal-to-noise ratio SNR and contrast-to-noise ratio of the original enhanced images of the three groups, compare the horizontal signal intensity differences of femoral artery, popliteal artery and calf artery, and compare the differences of the three scanning schemes by t-test. Results: When the contrast medium dosage was 0.1 mmol/kg, the image quality scores of femoral artery, popliteal artery and calf artery were (3.35±0.25), (2.97±0.25), (2.35±1.15) respectively; When the dosage of contrast agent was 0.2 mmol/kg, the scores of the above parts were (3.75±0.35), (3.55±0.32), (2.97±0.70) respectively; When the dosage of contrast agent was 0.3 mmol/kg, the scores of the above parts were (3.90±0.41), (3.83±0.52), (3.10±0.75) respectively. 33.33% of the images in group A did not meet the diagnostic needs, while all the images in group B and C met the diagnostic needs. There was significant difference between group A and group B, and there was no significant difference between group B and group C. B The Si, SNR and CNR of femoral artery and popliteal artery in group C were significantly higher than those in group A, and there was no significant difference between group B and C. The images of group B and C were better than those of group A. Conclusion: Appropriate increase of the contrast medium dosage is helpful to improve the 3D CE-MRA imaging quality of both lower limb arteries. The contrast medium dosage of 0.2 mmol/kg is reliable and accurate for the evaluation of blood vessels, and can provide accurate and reliable imaging basis for the formulation of treatment plan for patients with peripheral artery diseases.
2022, 31(2): 211-217. doi: 10.15953/j.ctta.2021.060
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Purpose: To compare the effect of radiation dose and tube potential on image quality of CT through the task-based image quality assessment parameters. Methods: We scanned Gammex 464 (the ACR quality assurance phantom) with GE Revolution Apex CT. Three radiation doses (5, 10, 20 mGy) and three tube potentials (80, 100, 120 kVp) were used to reconstruct nine sets of image. Bone and acrylic inserts from module 1 of the phantom was selected for the measurement of task-based transfer function (TTF, representing spatial resolution) and TTF50% was recorded for each set of images. Module 3 was selected for the measurement of noise power spectrum (NPS, representing image noise) and noise value, spatial frequency (f-peak) and NPS peak value were recorded for each set of images. Detestability index (${d}'$ representing lesion detestability) was furtherly calculated based on TTF and NPS of images. The effect of radiation dose and tube potential on image quality was evaluated by One-way Anova analysis. Multiple comparisons for P value were corrected by FDR. Results: Compared with radiation dose, the effect of tube potential on TTF50% was more obvious, but there was no significant difference between them in bone and acrylic substances. Noise and NPS peak significantly decreased with the increase of both radiation dose and tube potential but no statistical difference was found. Compared with tube potential, radiation dose showed greater impact on f-peak, but no statistical difference was found. d’ was significantly improved as radiation dose increased; while no statistical difference was found under different tube potentials. Conclusion: Image quality is predominantly influenced by radiation dose rather than tube potential. Image noise and lesion detestability is signifcantly improved as radiation dose elevates. Image quality could be comprehensively inflected by the task-based image quality assessment.
2022, 31(2): 219-226. doi: 10.15953/j.ctta.2021.041
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Objective: To compare the image quality between virtual monochromatic images (VMI) of dual-source dual-energy CT (DECT) and conventional CT images. Siemens SOMATOM Force dual source dual energy CT was adopted in the scanning of the high contrast resolution CTP 528 component and low contrast resolution CTP 515 component of image quality control phantom catphan 500. Dual-tube dual-energy scanning scheme was used to reconstruct low, medium and high-level VMI (group A: 40 keV, group B: 70 keV, group C: 100 keV) and a single tube scanning scheme was used to reconstruct conventional images (Group D: 120 kVp). Two radiologiss carried out the measurement of high resolution by the smallest line pair one could distinguish and low-contrast sensitivity was measured by the smallest diameter under 1% contrast. Mean noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also evaluated for each group. Results: The image consistency of the two radiologists turned out well (high reolution and low-contrast sensitivity: Kappa coefficient=0.667; noise parameter: Spearman r = 0.920). Among all images, D group performed the best in high resolution (6 lp/cm) and A and B groups showed the best low-contrast sensitivity (diameter of 4 mm). C group had the lowest noise (2.333±0.289) and highest SNR (37.944±3.949). Mean noise and SNR were found significantly difference among the four groups. B group showed the highest CNR (3.361±0.875), but no statistical significance was found among the groups. Conclusion: Compared with conventional CT, VMI images from DECT could improve image quality while retain low-contrast sensitivity; image noise decreases while SNR increases as VMI elevates.
2022, 31(2): 227-235. doi: 10.15953/j.ctta.2021.018
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Objective: To investigate the CT findings of pulmonary infarction (PI) secondary to acute pulmonary embolism (APE). Method: The clinical and CT data of 41 patients with PI secondary to APE were analyzed retrospectively. The number, location, shape, margin of PI, pleural effusion and dynamic changes were summarized. Results: CT features of PI: (1) Number and location: Among the total 79 PI lesions, 18 patients had single lesion and 23 patients had multiple lesions. All lesions were located under the pleura and connected to the pleura with a broad base, 46.8% (37/79) were located in the lower lobe of the right lung, 36.7% (29/79) in the lower lobe of the left lung, 3.8% (3/79) in the upper lobe, 6.3% (5/79) in the middle lobe of the right lung, and 6.3% (5/79) in the lingual segment of the upper lobe of the left lung. (2) Shape: 45.6% (36/79) of the lesions showed Reversed Halo Sign (RHS), 36.7% (29/79) displayed consolidation of oval, wedge or hump, 17.7% (14/79) revealed ground glass opacity. (3) Bronchovascular bundles in PI: Bronchovascular bundles were found in 79.7% (63/79) of PI. In 21.3% (16/79) of the cases, there was no bronchovascular bundle in the lesion because of its small size; (4) After enhancement, there was no enhancement shown in the 79 PI lesions. (5) All 79 lesions changed into patchy or linear during the end of the treatment period. (6) Pleural effusion: 63.4% (26/41) of patients had pleural effusion, among whom 42.3% (11/26) had bilateral pleural effusion, and 57.7% (15/26) had unilateral pleural effusion. Conclusion: The imaging manifeatations of PE secondary to API hole certain characteristics. For single or multiple lesions under the pleura, with RHS, consolidation of wedge or hump, bronchovascular bundles, APE secondary to API should be considered. In addition, pleural effusion is helpful for diagnosis.
2022, 31(2): 237-243. doi: 10.15953/j.ctta.2021.039
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Objective: To explore the application value of CT bilateral lower extremity volume measurement in the grading of secondary lower extremity lymphedema. Materials and methods: Patients with secondary lower extremity lymphedema who were admitted to our hospital and underwent CT of both lower extremities were collected from June 2019 to January 2020. The clinician completed the multiple-circumference measurement of lower extremity within one week of CT scanning, and recorded the volumes of both lower extremities, thighs and calfs obtained by CT bilateral lower extremity volume measurement and clinical multiple-circumference method, respectively. Based on the percentage enlargement in the volume of the affected side compared with the healthy side, the grading of the whole lower extremity, thigh and calf was obtained by CT and clinical measurement results,respectively. Kappa analysis was used to compare the consistency between CT and clinical in the grading of whole lower extremity. Results: Thirty-eight patients were finally enrolled. The volumes of lower extremities measured respectively by CT bilateral lower extremity volume measurement and clinical multiple-circumference method were (cm3): the affected side (9984±2217 and 11308±2373), the healthy side (7154±1417 and 8265±1704). The CT grading of whole lower extremity was 1 case in preclinical stage, 6 cases of mild, 14 cases of moderate, and 17 cases of severe. The clinical grading of whole lower extremity was 1 case in preclinical stage, 8 cases of mild, 11 cases of moderate, and 18 cases of severe. The consistency between CT and clinical in grading of whole lower extremity is excellent (Kappa=0.878). Conclusion: CT bilateral lower extremity volume measurement can be used as an imaging tool in the grading of secondary lower extremity lymphedema.
2022, 31(2): 244-250. doi: 10.15953/j.1004-4140.2022.31.02.12
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Objective: To explore the application of noise index combined with automatic tube current regulation technology in the one-stop scanning of chest and lumbar QCT physical examination. Method: 100 patients who unferwent thoracic CT and lumbar QCT scan in our medical examination were prospectively collected and randomly divided into two groups( conventional dose group and ow dose group). There were 50 patients in the conventianl group (noise index set to NI=8.5) and 50 patients in the low dose group (noise index set to NI=14). Their height, weight and BMI were recorded, as well as the mean BMD of L1, L2 in both radiation and low dose groups, and L1, L2 in the conventional dose group. The differences of radiation dose and mean bone mineral density between the two groups were compared. Results: The average scanning dose was 387.65 mGy in the conventional dose group and 73.18 mGy in the low dose group. There was statistical differences in radiation dose between the two groups. The mean bone mineral density (BMD) of L1 and L2 was 119.71 in the conventional dose group, and that of L1 and L2 was 123.65 in the low dose group. There was no statistical difference between the two groups. Conclusion: Low dose CT scan of thoracic and lumbar spine can not only meet the needs of lung screening and bone mineral density assessment but also greatly reduce radiation dose. It can be widely used in physical examination.
2022, 31(2): 251-258. doi: 10.15953/j.1004-4140.2022.31.02.13
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Objective: To investigate the value of multi-slice spiral CT (MSCT) signs in differential diagnosis of pathological types of acute appendicitis. Methods: 78 patients with acute appendicitis confirmed through surgery and pathology in our hospital from October 2018 to September 2019 were retropectively analyzed. All patients underwent multi-slice spiral CT examination before operation while some patients with unclear appendicitis were performed curved surface reconstruction (CPR), then we analyzed the differences of MSCT signs in different types of appendicitis. Results: Among the 78 patients, 28 were simple appendicitis, 33 were suppurative appendicitis and 17 were gangrenous appendicitis. In the variance analysis, the difference between the appendiceal lumen diameter and the peripheral fat density in the three pathological types of appendicitis was statistically significant. In Spearman's rank correlation analysis, the P values of periappendiceal exudation, appendiceal bezoar, extraluminal effusion, mesangial thickening and intraluminal effusion were all less than 0.05, but their Rs values were different. Among them, periappendiceal exudation and mesangial thickening showed strong correlation with appendiceal typing. Conclusion: MSCT showed that signs including appendiceal lumen diameter, peripheral fat density, mesangial thickening and periappendiceal exudation held quite strong clinical guiding significance in the differential diagnosis of pathological types of acute appendicitis.
2022, 31(2): 259-267. doi: 10.15953/j.1004-4140.2022.31.02.14
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Objective: To analyze the imaging features of primary testicular tumor. Methods: The CT imaging data of 46 cases of testicular tumor confirmed by pathology were retrospectively reviewed. Combined with the other data, the location, attenuation, size, shape, edge, and enhancement patterns of lesions were comprehensively analyzed. Result: All 46 cases of testicular tumor were unilateral. There were 24 cases of seminoma, among whom 16 cases showed uneven mild septal enhancement; 10 cases of endodermal sinus tumor, and 8 cases showed multiple tortuous and thickened blood vessels; 4 cases of teratoma, spot or irregular calcification; 2 cases of mixed germinoma, obvious heterogenous enhancement with no calcification or fat; 2 cases of leiomyoma with clear border, homogeneous density and nhomogeneous enhancement in enhanced scan; 3 cases of diffuse large B cell lymphoma, 2 cases showed clear boundary, uniform density and homogeneous enhancement, 1 case of patchy low density area, with unclear boundary, persistent enhancement, the low density area showed no enhancement; 1 case of malignant mesenchymal cell tumor with thick calcification and moderate enhancement of solid components, accompanied by retroperitoneal lymph node and lung metastasis. Conclusion: CT can distinguish the imaging features of different types of testicular tumors, and have high value in the diagnosis and differential diagnosis of testicular tumors. Thus CT can provide a more accurate basis for clinical treatment.