Computed tomography angiography (CTA) is a useful approach for diagnosing vascular diseases. In this paper, we proposed a reconstruction algorithm for dual-source spiral CT with variable pitch. The projection data are collected by the double-source double-multislice spiral CT (DSDMS-CT). However, the pitch of the DSDMS-CT is variable other than being constant. We have developed a new formula performing interpolation along Z-axis for dual-source spiral CT with variable pitch. The dual-source spiral CT with variable pitch can chase contrast bolus more flexibly and more effectively. The simulation results show the correctness and efficiency of the proposed algorithm.
Algorithms ; Coronary Angiography ; methods ; Humans ; Tomography, Spiral Computed ; instrumentation ; methods

The upper slicing system is the main components of the optical system in MSCT. This paper focuses on the design of upper slicing system and its accuracy analysis to improve the accuracy of imaging. The error of slice thickness and ray center by bearings, screw and control system were analyzed and tested. In fact, the accumulated error measured is less than 1 microm, absolute error measured is less than 10 microm. Improving the accuracy of the upper slicing system contributes to the appropriate treatment methods and success rate of treatment.
Computer Simulation ; Equipment Design ; Tomography, Spiral Computed ; instrumentation ; methods

The QUASAR Penta-guide Phantom with fiducial markers was scanned, and the CT images were transferred to Pinnacle workstation. Skin and target volumes were contoured and transferred to TomoPlan treatment planning system. The phantom was scanned with Megavoltage CT (MVCT). MVCT images were matched to the planning CT. Automatic adjustment of treatment couch was completed. It was found that the green laser coincided with the etched center crosshairs in lateral and longitudinal directions with an error less than 2 mm. However 2 mm vertical tabletop lag was found, but could be eventually corrected. Verifications for specific patients with head and pelvic tumors were also completed, the residual setup error were analyzed. The automatic movement of tabletop after image match is satisfactory.
Humans ; Radiotherapy Planning, Computer-Assisted ; instrumentation ; methods ; Radiotherapy, Intensity-Modulated ; instrumentation ; methods ; Tomography, Spiral Computed ; instrumentation ; methods

The present paper introduces the components and operating principle of Sensation 16 CT date measuring system (DMS), analyzes the fixed position of modules and channels in array detector modules (ADM), the Checkup table, Tuneup table and IRS table in ICS Syngo Service. The author also puts forward a solution of manual handling of defective channels.
Artifacts ; Radiographic Image Interpretation, Computer-Assisted ; methods ; Software ; Tomography, Spiral Computed ; instrumentation

According to the structural characteristics of spiral CT systems and our experiences, some relevant solutions to common malfunctions in daily maintenance are suggested.
Computers ; Equipment Design ; Equipment Failure ; Equipment Failure Analysis ; methods ; Humans ; Maintenance ; Tomography, Spiral Computed ; instrumentation

OBJECTIVETo evaluate the feasibility and accuracy of using Megavoltage CT(MVCT) for head and neck dose calculation.

METHODSThe cheese Phantom was imaged using MVCT scanner, and the MVCT value density calibration curve was established. Conventional CT and MVCT image of nasopharyngeal carcinoma was acquired respectively, and IMRT plan was designed on conventional CT image of NPC patient. The conventional CT plan was copied to MVCT image. The dose distribution was calculated for tumor and normal tissue using the MVCT value density calibration curve, and compared with that of conventional CT. Ten NPC patients were collected for dose verification of IMRT plan on MVCT images.

RESULTSThe MVCT numbers depended linearly on the electron density of the sample, and the stability of the MVCT numbers to electron density was good.The error between the measured dose and calculated dose in measured point was less than 3%.The isodose distribution was well agreement with that calculated by planning system.

CONCLUSIONSPerforming dose recalculation using MVCT of Tomotherapy in head and neck region was feasible.and the dose distributions on kVCT and MVCT were in excellent agreement.

Algorithms ; Head and Neck Neoplasms ; radiotherapy ; Humans ; Phantoms, Imaging ; Radiosurgery ; instrumentation ; methods ; Radiotherapy Dosage ; Tomography, Spiral Computed ; instrumentation

OBJECTIVETo study regular patterns of cone artifact resulted from interpolation algorithm of spiral CT.

METHODSBased on the principle of interpolation algorithm and back-projection reconstruction, a mathematical model of the reconstructed image was established to clarify the relation of the scanning parameters and the characteristics of the scanned object with the cone artifact. Experiments were carried out by a set of acrylic phantoms on siemens plus 4 CT scanners.

RESULTSThe artifact in the image was directly proportional to the table increment per gantry rotation of the scanner, and was positively correlated to the tangent of half cone-angle and inversely to the radii in the reconstruction plane of the phantom. The theoretical analysis was validated by experimental results.

CONCLUSIONThe cone artifact is related to the scanning parameters and the characteristics of the scanned object.

Algorithms ; Artifacts ; Computer Simulation ; Image Processing, Computer-Assisted ; methods ; standards ; Models, Theoretical ; Phantoms, Imaging ; Tomography, Spiral Computed ; instrumentation ; methods

Recently, the availability of multidetector-row CT (MDCT) and continuous refinement in three-dimensional (3D) imaging process have greatly expanded the role of CT in evaluating patients with gastrointestinal diseases. MDCT is the latest advancement in CT technology and is now more readily available. This imaging modality can offer full examination of the entire intestinal tract as well as powerful information about the bowel itself and its surrounding structures, which are inherent advantages of CT over conventional barium or optical endoscopic studies. In most cases, MDCT with various 3D technologies can make an easy, rapid, and accurate diagnosis by one-stop imaging, and enables to avoid other examinations. Therefore, knowledge and awareness of valuable clinical applications and proper scan technique of MDCT imaging is essential to achieve the diagnostic goal of one-step imaging.
Barium Sulfate/diagnostic use ; Colonic Neoplasms/diagnosis/radiography ; Colonic Polyps/diagnosis/radiography ; Colonography, Computed Tomographic/instrumentation/*methods ; *Enema ; Humans ; Imaging, Three-Dimensional ; Tomography, Spiral Computed/instrumentation/*methods

Multidetector-row computed tomography (MDCT) is useful for the evaluation of malignant biliary obstruction because it allows faster scanning, which decreases motion and breathing artifacts, as well as thinner collimation. In addition, MDCT leads to improved 3-dimensional assessment of vascular structures and biliary tree. The purpose of this pictorial essay is to introduce scanning techniques and image acquisition methods for the evaluation of malignant biliary obstruction and to highlight the unique display of diagnostic information by multiplanar reformations of the biliary tract with MDCT.
Humans ; Imaging, Three-Dimensional ; Pancreas/*radiography ; Pancreatic Diseases/*radiography ; Pancreatic Neoplasms/*radiography ; Tomography, Spiral Computed/instrumentation/*methods

CT colonography is a promising technique that provides both multiplanar and endoluminal perspective of the air-filled, distended, cleaned colon. "Virtual colonoscopy" refers to computer-simulated 3D endoscopic visualization of the colonic mucosal surface. Unlike barium enema and conventional colonoscopy, CT colonography can give cross- sectional and endoluminal images of the colon and enables to image extracolic abnormality. CT colonography offers potential advantages over colonoscopy in that it causes little discomfort to the patient, and does not need sedation. It is more accurate in spatial location of lesions and creates no complication. To date, most studies assessing CT colonography have focused in technical development, less aggressive bowel preparation, and computer-aided diagnosis of polyp detection. In the future, CT colonography would be a diagnostic and screening tool for the colorectal polyp and cancer.
Humans ; Imaging, Three-Dimensional ; Liver Diseases/diagnosis/*radiography ; Lung Volume Measurements ; Pulmonary Veins/radiography ; Tomography, Spiral Computed/instrumentation/*methods