A retrospective study on 55 subjects with surrenal gland tumors diagnosed by CT showed that the tumors are commonly benign and pheocromocytoma was detected lately with a large size (> 3 cm, accounted for 73.5%). Heterogenous structure of the tumors before and after the injection of the contrasts showed characterustic sign of pheocromocytoma. The CT procedure has had a sensitivity of 100% and a positive predictive value of 89%. In the diagnosis of ganglion metastasis, these ratios were 2/3 and 99% respectively, in the evaluation of infiltration into the liver and the right kidney, these ratios were 58.30% and 95% respectively
Tomography, X-Ray Computed ; Neoplasms ; methods

A fast non-local means image denoising algorithm is presented based on the single motif of existing computed tomography images in medical archiving systems. The algorithm is carried out in two steps of prepossessing and actual possessing. The sample neighborhood database is created via the data structure of locality sensitive hashing in the prepossessing stage. The CT image noise is removed by non-local means algorithm based on the sample neighborhoods accessed fast by locality sensitive hashing. The experimental results showed that the proposed algorithm could greatly reduce the execution time, as compared to NLM, and effectively preserved the image edges and details.
Algorithms ; Tomography, X-Ray Computed ; methods

In the load capacity test of CT diagnosis table top, by analyzing the easy destroy area and related test data for the table top, using a simple mechanical auxiliary support structure in local area of the table top to solve the insufficient loading strength problem of table top and obtain significant results during the actual product usage.
Tomography, X-Ray Computed ; instrumentation ; methods

OBJECTIVE: To build a helical CT projection data restoration model at random low-dose levels. METHODS: We used a noise estimation module to achieve noise estimation and obtained a low-dose projection noise variance map, which was used to guide projection data recovery by the projection data restoration module. A filtering back-projection algorithm (FBP) was finally used to reconstruct the images. The 3D wavelet group residual dense network (3DWGRDN) was adopted to build the network architecture of the noise estimation and projection data restoration module using asymmetric loss and total variational regularization. For validation of the model, 1/10 and 1/15 of normal dose helical CT images were restored using the proposed model and 3 other restoration models (IRLNet, REDCNN and MWResNet), and the results were visually and quantitatively compared. RESULTS: Quantitative comparisons of the restored images showed that the proposed helical CT projection data restoration model increased the structural similarity index by 5.79% to 17.46% compared with the other restoration algorithms (P < 0.05). The image quality scores of the proposed method rated by clinical radiologists ranged from 7.19% to 17.38%, significantly higher than the other restoration algorithms (P < 0.05). CONCLUSION The proposed method can effectively suppress noises and reduce artifacts in the projection data at different low-dose levels while preserving the integrity of the edges and fine details of the reconstructed CT images.
Algorithms ; Artifacts ; Tomography, Spiral Computed ; Tomography, X-Ray Computed/methods*

This study was conducted to establish the values for optimal fixed scan delays and diagnostic scan delays associated with the bolus-tracking technique using various contrast material injection durations in canine abdominal multi-phase computed tomography (CT). This study consisted of two experiments employing the crossover method. In experiment 1, three dynamic scans at the porta hepatis were performed using 5, 10 and 15 sec injection durations. In experiment 2, two CT scans consisting of five multi-phase series with different scan delays of 5 sec intervals for bolus-tracking were performed using 5, 10 and 15 sec injection duration. Mean arrival times to aortic enhancement peak (12.0, 15.6, and 18.6 sec for 5, 10, and 15 sec, respectively) and pancreatic parenchymal peak (17.8, 25.1, and 29.5 sec) differed among injection durations. The maximum mean attenuation values of aortas and pancreases were shown at the scan section with 0 and 5, 0 and 10 and 5 and 10 sec diagnostic scan delays during each injection duration, respectively. The optimal scan delays of the arterial and pancreatic parenchymal phase in multi-phase CT scan using fixed scan delay or bolus-tracking should be determined with consideration of the injection duration.
Animals ; Aorta ; Dogs* ; Liver* ; Methods ; Pancreas* ; Tomography, X-Ray Computed

Cerebrovascular Circulation ; physiology ; Humans ; Microcomputers ; Tomography, X-Ray Computed ; methods

OBJECTIVETo propose a new method for effectively and rapidly removing the ring artifacts in CT images based on image post-processing.

METHODSThe CT image with ring artifacts in the Cartesian coordinate was first transformed into an image with line artifacts in the polar coordinate. The image in the polar coordinate was then filtered by designing a one-dimensional filter to calculate the mean and variance of each pixel after filtering, which were compared with the variance threshold value and the pixel threshold value to determine the position of the artifacts for corrections accordingly. Finally, the polar coordinate image was converted into Cartesian coordinate image.

RESULTSSimulated and actual CT data experimental results demonstrated the efficiency of this method for removing artifacts, retaining the image fidelity and reducing the processing time.

CONCLUSIONThe new method can accurately recognize the position of the artifacts and effectively remove them to facilitate the clinical diagnosis.

Computed Tomography(CT) is one of the successful methods, in which mathematical theories are combined with engineering technology. Volume CT will replace the cross-sectional CT that has been widely used. In this paper two new cone vertex orbits, which are circle-and-arc and regular triangular pyramid lines, have been proposed and their complete conditions for exact reconstruction have been obtained. After having studied circle-and-n-line cone vertex orbit which is one of the important orbits in volume CT, we have given a better proof about the complete condition in circle-and-line and circle-and-2-line cone vertex orbit and have obtained some proper conclusions. Finally, we extend the above results to circle-and-n-line vertex orbit. These results will be useful for the design of direct volume imaging.
Algorithms ; Artifacts ; Computer Simulation ; Tomography, X-Ray Computed ; methods

A new adaptively hybrid filtering algorithm is proposed to reduce the artifacts caused by metal in CT image. Firstly, the method is used to preprocess the projection data of metal region and is reconstruct by filtered back projection (FBP) method. Then the expectation maximization algorithm (EM) is performed on the iterative original metal project data. Finally, a compensating procedure is applied to the reconstructed metal region. The simulation result has demonstrated that the proposed algorithm can remove the metal artifacts and keep the structure information of metal object effectively. It ensures that the tissues around the metal will not be distorted. The method is also computational efficient and effective for the CT images which contains several metal objects.
Algorithms ; Artifacts ; Metals ; Tomography, X-Ray Computed ; methods

A non-invasive detecting and analyzing method which used to monitor the working condition of rotating anode X-ray was proposed. Based on the NI development environment, accelerometer, 24-bit high resolution data acquisition card and personal computer were connected to construct the system for collecting the vibration signal of X-ray tube. Results demonstrate that the system could acquire and store the vibration data of X-ray tube quickly and efficiently. The characteristics of vibration, were extracted and processed, which proposed a new approach to detect the malfunction of rotating anode X-ray early and effectively.
Equipment Design ; Software ; Tomography, X-Ray Computed ; instrumentation ; methods ; Vibration