PURPOSE: To determine the physical properties of a newly developed cone beam computed tomography (CBCT). MATERIALS AND METHODS: We measured and compared the imaging properties for the indirect-type flat panel detector (FPD) of a new CBCT and the single detector array (SDA) of conventional helical CT (CHCT). RESULTS: First, the modulation transfer function (MTF) of the CBCT were superior to those of the CHCT. Second, the noise power spectrum (NPS) of the CBCT were worse than those of the CHCT. Third, detective quantum efficiency (DQE) of the indirect-type CBCT were worse than those of the CHCT at lower spatial frequencies, but were better at higher spatial frequencies. Although the comparison of contrast-to-noise ratio (CNR) was estimated in the limited range of tube current, CNR of CBCT were worse than those of CHCT. CONCLUSION: This study shows that the indirect-type FPD system may be useful as a CBCT detector because of high resolution.
Cone-Beam Computed Tomography* ; Noise ; Tomography, Spiral Computed

PURPOSE: We compared the contrast enhancement patterns of hepatocellular carcinomas(HCC), hemangiomas, and metastasis on two phase imagings to determine the value of two phase dynamic CT in the differential diagnosis. MATERIALS AND METHODS: Two phases spiral volumetric CT scan were obtained 45 seconds and 6 minutes after bolus injection of contrast material in 106 patients. A bolus of 100 mL of nonionic contrast material was administered intravenously at a injection rate of 2 mL/sec. RESULT:In Hepatocollular carcinoma, 47% were totally hyperdense and 30% were totally hypodense in early phase, and 82% were totally hypodense in late phase. In hemangioma, 90% were peripherally hyperdense in early phase, 52% were isodense and 27% were totally hyperdense in late phase. In metastatic liver malignancies, 65% were hypodense and 32% were peripherally hyperdense in early phase, and 79% were hypodense in late phase. CONCLUSION: Two phases spiral volumetric CT scaning is considered to be heplful in the differential diagnosis of hepatic tumors.
Diagnosis, Differential* ; Hemangioma ; Humans ; Liver ; Neoplasm Metastasis ; Spiral Cone-Beam Computed Tomography ; Tomography, Spiral Computed*

Aiming at the problem of timeliness of CBCT reconstruction, a CBCT fast short scan reconstruction method is proposed. At the same time, the image reconstruction process in which a new attenuation compensation algorithm is applied to improve image quality. When performing FDK three-dimensional reconstruction of a single-frame acquisition image, the Parker-weighted image is calculated in real time, and a new attenuation compensation algorithm is applied in the back projection process to complete the short scan Parker-weighted reconstruction. This method simulates the CBCT synchronous acquisition and reconstruction process by establishing collection and reconstruction threads. Under the premise of satisfying the reconstruction quality, the reconstruction can be completed within 1 to 2 seconds after the patient collection is completed, which achieves the purpose of real-time.
Algorithms ; Cone-Beam Computed Tomography ; Humans ; Image Processing, Computer-Assisted ; Spiral Cone-Beam Computed Tomography

OBJECTIVE: To quantitatively analyze image quality of two sets of phantom (CatPhan504 and Cheese) Megavoltage computed tomography (MVCT) images acquired by Helical Tomotherapy with three scanning modes (Fine, Normal and Coarse), and to explore and validate a semi-automatic quality assurance procedure for MVCT images of Helical Tomotherapy. METHODS: On Helical Tomotherapy, CatPan504 and Cheese phantoms were scanned with three pitch levels (Fine, Normal, Coarse: 4 mm, 8 mm, 12 mm/circle) respectively. Pylinac, Matlab and Eclipse were used to calculate and compare spatial resolution, noise level and low contrast resolution of images obtained under three scanning modes respectively. The spatial resolution can be evaluated by the blurring of line-pair CT value in the images of CatPhan504's CTP528 module. The noise level can be evaluated by the integral non-uniformity in the images of Cheese's uniformity module. the low contrast resolution can be evaluated by contrast-to-noise ratio of both phantoms' plug-in module, or visibility of the region of interest (Supra-Slice) in the images of CatPhan504's CTP515 module. RESULTS: Analyses on CatPhan504's line pair module(CTP528 module) showed that the first three line pairs(the gap size are 0.500 cm, 0.250 cm and 0.167 cm respectively) could be clearly observed but blurring began to occur from the fourth line pair(the gap size is 0.125 cm) under Coarse mode. Meanwhile, the first four line pairs were all observable under the Normal and Fine modes. Integral non-integrity index(the value negatively correlated with the noise level) were 0.155 7, 0.136 8 and 0.122 9 for Coarse, Normal and Fine modes respectively. None of the Supra-Slice in CatPhan504's CTP515 module could be observed under three imaging modes. Low contrast contrast-to-noise ratio of Cheese phantom was similar under three modes and the insert visibility exhibited nearly linear growth with the increasing difference between CT average value of the insert material and background. CONCLUSION Superiority and inferiority of three image modes in terms of the three image quality index was not consistent. Evaluation results above could provide reference for more rational decision on scanning modes selection of helical tomotherapy, which was based on image visualization demands in clinical practice. The proposed method could also provide guidance for similar image quality assessment and periodic quality assurance.
Cone-Beam Computed Tomography ; Phantoms, Imaging ; Radiotherapy, Intensity-Modulated ; Tomography, Spiral Computed ; Tomography, X-Ray Computed

Recent research in endodontics has highlighted the need for three-dimensional imaging in the clinical arena as well as in research. Three-dimensional imaging using computed tomography (CT) has been used in endodontics over the past decade. Three types of CT scans have been studied in endodontics, namely cone-beam CT, spiral CT, and peripheral quantitative CT. Contemporary endodontics places an emphasis on the use of cone-beam CT for an accurate diagnosis of parameters that cannot be visualized on a two-dimensional image. This review discusses the role of CT in endodontics, pertaining to its importance in the diagnosis of root canal anatomy, detection of peri-radicular lesions, diagnosis of trauma and resorption, presurgical assessment, and evaluation of the treatment outcome.
Cone-Beam Computed Tomography ; Dental Pulp Cavity ; Diagnosis ; Endodontics* ; Imaging, Three-Dimensional* ; Spiral Cone-Beam Computed Tomography ; Tomography, X-Ray Computed ; Treatment Outcome

After over one decade development, cone beam computed tomography (CBCT) has been widely accepted for clinical application in almost every field of dentistry. Meanwhile, the radiation dose of CBCT to patient has also caused broad concern. According to the literature, the effective radiation doses of CBCTs in nowadays market fall into a considerably wide range that is from 19 microSv to 1073 microSv and closely related to the imaging detector, field of view, and voxel sizes used for scanning. To deeply understand the potential risk from CBCT, this report also reviewed the effective doses from literatures on intra-oral radiograph, panoramic radiograph, lateral and posteroanterior cephalometric radiograph, multi-slice CT, and so on. The protection effect of thyroid collar and leaded glasses were also reviewed.
Cone-Beam Computed Tomography ; Dentistry ; Eyeglasses ; Glass ; Humans ; Radiation Dosage ; Radiation Protection ; Thyroid Gland ; Tomography, Spiral Computed

This article briefly describes the imaging performance standards of the kilovolt X-ray image guidance system used in radiotherapy, analyzes the main aspects that should be considered in the image quality of X-IGRT system, and focuses on parameters that should be considered in the imaging performance evaluation criteria of the CBCT X-IGRT. The purpose is to sort out the imaging performance evaluation standards of kilovolt X-IGRT system, clarify the image quality requirements of X-IGRT equipment, and reach a consensus when evaluating the imaging performance of X-IGRT system.
Radiotherapy Planning, Computer-Assisted/methods* ; Cone-Beam Computed Tomography/methods* ; Spiral Cone-Beam Computed Tomography ; Radiotherapy, Intensity-Modulated/methods* ; Radiotherapy, Image-Guided/methods*

Noninvasive, high-resolution MRI has shown its efficacy in the visualization of carotid atherosclerotic plaque characteristics. MRI is the only noninvasive option for thin plaque cap, active inflammation, fissured/injured plaque and intraplaque hemorrhage, is also useful in monitoring the response after statin therapy, and has the potential to image a coronary plaque and to determine its composition. New contrast agents and targeted molecular imaging open a window for MRI detection of thrombi and assessment of atherosclerotic activity and plaque vulnerability. Currently, multidetector CT is capable of the noninvasive detection of coronary stenosis and coronary calcifications. High resolution CT may be beneficial in the detection of noncalcified vulnerable coronary plaques, and more reliable with the use of newer high-speed volume CT scanners.
Atherosclerosis ; Cone-Beam Computed Tomography ; Contrast Media ; Coronary Stenosis ; Hemorrhage ; Hydroxymethylglutaryl-CoA Reductase Inhibitors ; Inflammation ; Magnetic Resonance Imaging* ; Molecular Imaging ; Plaque, Atherosclerotic* ; Tomography, Spiral Computed

The purpose of this study provides measurements of radiation dose from MDCT of head, chest, abdomen and pelvic examinations. A series of dose quantities that are measured of patient weight to compare the dose received during MDCT examinations. Data collected included: weight together with CT dose descriptors, volume CT dose index (CTDIvol) and dose length product (DLP). The effective dose was also estimated and served as collective dose estimation data. Data from 1,774 adult patients attending for a CT examination of the head (n=520) or chest (n=531) or abdomen (n=724) was obtained from spiral CT units using a same CT protocol. Mean values of CTDIvol was a range of 48.6 mGy for head and 6.9, 10.5 mGy for chest, abdomen examinations, respectively. And mean values of DLP was range of 1,604 mGy.cm for head, 250 mGy.cm for chest, 575 mGy.cm for abdomen examinations, respectively. Mean effective dose values for head, chest, abdominal CT were 3.6, 4.2, and 8.6 mSv, respectively. The degree of CTDIvol and DLP was a positive correlation with weight. And there was a positive correlation for weight versus CTDIvol (r2=0.62), DLP (r2=0.694) in chest. And head was also positive correlation with weight versus CTDIvol (r2=0.691), DLP (r2=0.741). We conclude that CTDIvol and DLP is an important determinant of weight within the CT examinations. The results for this study suggest that CT protocol should be tailored according to patient weight.
Abdomen ; Adult ; Antineoplastic Combined Chemotherapy Protocols ; Cone-Beam Computed Tomography ; Cytarabine ; Gynecological Examination ; Head ; Humans ; Subject Headings ; Thioguanine ; Thorax ; Tomography, Spiral Computed

OBJECTIVETo study the value of compute tomography (CT)-based quantitative assessment in the diagnosis of pneumoconiosis.

METHODSSixty patients with pneumoconiosis and 40 healthy volunteers (control) underwent CT scanning at the levels of the top of the aortic arch, tracheal carina, and 3 cm and 6 cm below the tracheal carina. All the CT images were analyzed with density histograms for a specific region to calculate the mean lung CT value (ME) and pixel index for assessment of lung density changes.

RESULTSAt the levels of the top of the aortic arch and 6 cm below the tracheal carina, the pixel indices in the 10 CT threshold density intervals within -832 to -352 HU was all significantly higher in pneumoconiosis group than in the control group (P<0.05). At the levels of the tracheal carina and 3 cm below the tracheal carina, the 11 pixel indices in the CT threshold density intervals within -880 to -352 HU were also significantly higher in pneumoconiosis group (P<0.05). At all the 4 scan levels, the pixel indices in the 10 intervals between -880 and -352 HU were all significantly higher in pneumoconiosis group (P<0.05).

CONCLUSIONCT density histograms allow quantitative evaluation of lung fibrosis in patients with pneumoconiosis for diagnostic purposes.

Adult ; Aged ; Case-Control Studies ; Humans ; Male ; Middle Aged ; Pneumoconiosis ; diagnostic imaging ; Pulmonary Fibrosis ; diagnostic imaging ; Spiral Cone-Beam Computed Tomography ; Tomography, X-Ray Computed ; methods