- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A weighted rebinned backprojection-Filtration algorithm from partially beam-blocked data for a single-scan cone-beam CT with hybrid type scatter correction
摘要： Purpose: Scatter contamination constitutes a dominant source of degradation of image quality in cone-beam computed tomography (CBCT). We have recently developed an analytic image reconstruction method with a scatter correction capability from the partially blocked cone-beam data out of a single scan. Despite its easy implementation and its computational efficiency, the developed method may result in additional image artifacts for a large cone angle geometry due to data inconsistency. To improve the image quality at a large cone angle, we propose a weighted rebinned backprojection-filtration (wrBPF) algorithm in conjunction with a hybrid type scatter correction approach. Methods: The proposed method uses a beam blocker array that provides partial data for scatter correction and image reconstruction and that only blocks the beam within a limited cone angle. This design allows a chance to keep the image quality at larger cone angles by use of data redundancy since the projection data corresponding to larger cone angles are not blocked. However, the scatter correction would not be straightforward. In order to correct for the scatter in the projections at larger cone angles, we propose a novel scatter correction method combining a measurement-based and a convolution-based method. We first estimated the scatter signal using a measurement-based method in the partially beam-blocked regions, and then optimized the fitting parameters of a convolution-kernel that can be used for scatter correction in the projections at larger cone angles. For image reconstruction, we developed a wrBPF with butterfly filtering. We have conducted an experimental study to validate the proposed algorithm for image reconstruction and scatter correction. Results: The experimental results revealed that the developed reconstruction method makes full use of the benefits of partial beam-blocking for scatter correction and image reconstruction and at the same time enhances image quality at larger cone angles by use of an optimized convolution-based scatter correction. Conclusions: The proposed method that enjoys the advantages of both measurement-based and convolution-based methods for scatter correction has successfully demonstrated its capability of reconstructing accurate images out of a single scan in circular CBCT.
关键词： X-ray beam-blocker,Cone-beam CT,Image reconstruction,Scatter correction,BPF
更新于2025-09-23 15:23:52
-
Optimization of X-ray image acquisition and reconstruction for a C-arm CBCT system with a flat-panel detector
摘要： A modern cone-beam computed tomography (CBCT) system with a C-arm gantry incorporating a large-area flat-panel detector is an important imaging tool widely used for diagnosis and image-guidance in spine surgery, orthopedic and interventional suite, and image-guided radiation therapy. In this study, the experimental prototype CBCT imaging platform consists of a benchtop system that is integrated with a cone-beam X-ray tube, a collimator, an anti-scatter grid, and a large-area TFT-based flat-panel detector. The different projection images in the C-arm CT system were usually acquired at short scanning angles with a constant interval for various exposure conditions. The performance of CT imaging quality was performed using the Feldkamp, Davis and Kress (FDK) reconstruction algorithm through acquired two-dimensional projection images at different scanning angles and projection numbers. Quantitative analysis of the image quality was performed by using the cone-beam CT phantom for spatial resolution, low-contrast resolution, noise, and two different phantoms, such as the head and pelvis.
关键词： Flat-panel X-ray detector,3D image reconstruction,Cone-beam CT system,C-arm CT system
更新于2025-09-23 15:23:52
-
Variation of patient imaging doses with scanning parameters for linac-integrated kilovoltage cone beam CT
摘要： To evaluate the Elekta kilovoltage CBCT doses and the associated technical protocols with patient dosimetry estimation. Image guidance technique with cone-beam CT (CBCT) in radiation oncology on a daily basis can deliver a significant dose to the patient. To evaluate the patient dose from LINAC-integrated kV cone beam CT imaging in image-guided radiotherapy. CT dose index (CTDI) were measured with PTW TM30009 CT ion chamber in air, in head phantom and body phantom, respectively; with different combinations of tube voltage, current, exposure time per frame, collimator and gantry rotation range. Dose length products (DLP) were subsequently calculated to account for volume integration effects. The CTDI and DLP were also compared to AcQSim? simulator CT for routine clinical protocols. Both CTDIair and CTDIw depended quadratically on the voltage, while linearly on milliampere x seconds (mAs) settings. It was shown that CTDIw and DLP had very close relationship with the collimator settings and the gantry rotation ranges. Normalized CTDIw for Elekta XVI? CBCT was lower than that of ACQSim simulator CT owing to its pulsed radiation output characteristics. CTDIw can be used to assess the patient dose in CBCT due to its simplicity for measurement and reproducibility. Regular measurement should be performed in QA & QC program. Optimal image parameters should be chosen to reduce patient dose during CBCT.
关键词： CT dose index,image-guided radiotherapy,dose-length product,Cone-beam CT
更新于2025-09-23 15:22:29
-
Computed tomography criteria for the use of advanced localization techniques in minimally invasive thoracoscopic lung resection
摘要： Background: The significant improvement of patient outcomes from minimally invasive lung surgery has led to the development of advanced lung nodule localization techniques to help manage patients with small suspicious lung nodules or to help resect patients with small pulmonary metastases. However, there are no clear computed tomography (CT) criteria to guide the use of advanced localization techniques for this group of patients. Methods: We conducted a retrospective chart review of patients who had undergone initial wedge resection of single or multiple lung nodules. We collected demographics, surgical information and surgical outcomes as well as CT scan features. Multiple logistic regression was performed to determine which factors were most predictive of the need for advanced localization techniques. Results: A total of 45 patients (73%) were resected by direct identification alone while 17 patients (27%) required advanced localization techniques. Of those requiring advanced localization, 11 patients had cone beam CT, 3 patients had transbronchial localization using electromagnetic navigation and 3 patients had preoperative CT guided wire localization. Patients requiring advanced localization had significantly smaller lung nodules at 0.8 cm compared to 1.4 cm (P=0.01), nodules that were further away from the pleura at 1.3 cm compared 0.1 cm (P<0.001) and were more likely to have ground glass nodules (P=0.01) compared to patients who were resected by direct identification alone. Multiple logistic regression confirmed that nodule size, distance to pleura and ground glass attenuation were predictive factors for requiring advanced localizing techniques. Every patient was treated with minimally invasive lung resection. A 1.3-cm or greater solitary pulmonary nodule less than 5 mm from the pleura can be removed without advanced techniques with a 96% success rate. Conclusions: Overall, in patients undergoing resection of a suspicious primary or metastatic lung nodule, advanced localization techniques should be considered in those with small non-solid nodules, which are not near the pleural surface on CT scan.
关键词： computed tomography guided localization (CT guided localization),navigation bronchoscopy,cone beam computed tomography (cone beam CT),lung cancer,Lung nodule
更新于2025-09-19 17:15:36
-
Evaluation of Radiation Dose for Dual Energy CBCT Using Multi-Grid Device
摘要： The paper discusses radiation dose of dual energy CT on which copper modulation layer, is mounted in order to improve diagnostic performance of the dual energy CT. The radiation dose is estimated using MCNPX and its results are compared with that of the conventional dual energy CT system. CT X-ray spectra of 80 and 120 kVp, which are usually used for thorax, abdominal, head, and neck CT scans, were generated by the SPEC78 code and were used for the source specification ‘SDEF’ card for MCNPX dose modeling. The copper modulation layer was located 20 cm away from a source covering half of the X-ray window. The radiation dose was measured as changing its thickness from 0.5 to 2.0 mm at intervals of 0.5 mm. Since the MCNPX tally provides only normalized values to a single particle, the dose conversion coefficients of F6 tally for the modulation layer-based dual energy CBCT should be calculated for matching the modeling results into the actual dose. The dose conversion coefficient is 7.2*104 cGy/output that is obtained from dose calibration curve between F6 tally and experimental results in which GAFCHORMIC EBT3 films were exposed by an already known source. Consequently, the dose of the modulation layer-based dual energy cone beam CT is 33～40% less than that of the single energy CT system. On the basis of the results, it is considered that scattered dose produced by the copper modulation layer is very small. It shows that the modulation layer-based dual energy CBCT system can effectively reduce radiation dose, which is the major disadvantage of established dual energy CT.
关键词： Beam hardening effect,Modulation layer,Monte Carlo Simulation,Dual energy cone beam CT,Dose evaluation
更新于2025-09-11 14:15:04
-
Analysis of Beam Hardening of Modulation Layers for Dual Energy Cone-beam CT
摘要： Dual energy cone-beam CT can distinguish two materials with different atomic compositions. The principle of dual energy cone-beam CT based on modulation layer is that higher energy spectrum can be acquired at blocked x-ray window. To evaluate the possibility of modulation layer based dual energy cone-beam CT, we analyzed x-ray spectrum for various thicknesses of modulation layers by Monte Carlo simulation. To compare with the results of simulation, the experiment was performed on prototype cone-beam CT for 50～100 kVp with CdTe XR-100T detector. As the result of comparing, the mean energy of energy spectrum for 80 kVp are well matched with that of simulation. The mean energy of energy spectrum for 80 and 120 kVp were increased as 1.67 and 1.52 times by 2.0 mm modulation layer, respectively. We realized that the virtual dual energy x-ray source can be generated by modulation layer.
关键词： Dual energy cone-beam CT,Monte Carlo simulation,Beam hardening effect,Modulation layer
更新于2025-09-11 14:15:04
-
Scatter Correction in Cone Beam CT for Metal Additive Manufacturing Components
摘要： This paper provides an x-ray scatter correction method for cone beam computed tomography (CT) to reduce cupping artifacts and image inhomogeneity of metal additive manufacturing (AM) components. Firstly, projections in 360° were obtained by a cone beam CT system. Secondly, the corresponding virtual CT system was built on Geant4 to obtain scatter photons. Different from previous studies, the geometry of the metal AM component was set by importing a CAD model of the component into Geant4, which can not only assure the accuracy of geometry but also simplify the de?nition of the geometry. Finally, the corresponding scatter photons were subtracted from the experimental projections in 360° to obtain corrected projections. Corrected reconstruction images were acquired via an FDK algorithm. In the corrected images, the average sum of squares of deviation of regions of interest was about 79.5% of that in the uncorrected images. Corrected images showed that cupping-shaped artifacts and image inhomogeneity were effectively reduced.
关键词： scatter correction,CADMesh,Geant4,metal additive manufacturing,cone beam CT
更新于2025-09-10 09:29:36
-
Feasibility of 4DCBCT-based proton dose calculation: An ex vivo porcine lung phantom study
摘要： Inter-fractional variations of breathing pattern and patient anatomy introduce dose uncertainties in proton therapy. One approach to monitor these variations is to utilize the cone-beam computed tomography (CT, CBCT) scans routinely taken for patient positioning, reconstruct them as 4DCBCTs, and generate ‘virtual CTs’ (vCTs), combining the accurate CT numbers of the diagnostic 4DCT and the geometry of the daily 4DCBCT by using deformable image registration (DIR). In this study different algorithms for 4DCBCT reconstruction and DIR were evaluated. For this purpose, CBCT scans of a moving ex vivo porcine lung phantom with 663 and 2350 projections respectively were acquired, accompanied by an additional 4DCT as reference. The CBCT projections were sorted in 10 phase bins with the Amsterdam-shroud method and reconstructed phase-by-phase using first a FDK reconstruction from the Reconstruction Toolkit (RTK) and again an iterative reconstruction algorithm implemented in the Gadgetron Toolkit. The resulting 4DCBCTs were corrected by DIR of the corresponding 4DCT phases, using both a morphons algorithm from REGGUI and a b-spline deformation from Plastimatch. The resulting 4DvCTs were compared to the 4DCT by visual inspection and by calculating water equivalent thickness (WET) maps from the phantom’s surface to the distal edge of a target from various angles. The optimized procedure was successfully repeated with mismatched input phases and on a clinical patient dataset. Proton treatment plans were simulated on the 4DvCTs and the dose distributions compared to the reference based on the 4DCT via gamma pass rate analysis. A combination of iterative reconstruction and morphons DIR yielded the most accurate 4DvCTs, with median WET differences under 2 mm and 3%/3 mm gamma pass rates per phase between 89% and 99%. These results suggest that image correction of iteratively reconstructed 4DCBCTs with a morphons DIR of the planning CT may yield sufficiently accurate 4DvCTs for daily time resolved proton dose calculations.
关键词： Adaptive proton therapy,Cone-beam CT,Proton therapy,Dose monitoring
更新于2025-09-09 09:28:46
-
Investigation of the Prevalence of Retromolar Canals: A Cone Beam CT Study
摘要： The retromolar canal (RMC) is a collateral branch of the mandibular canal. This branch seems to be involved in the innervation of the third molar, retromolar trigon and part of the buccal mucosa and fibres of the buccinator and temporalis muscles. The prevalence of RMC in osseous and CBCT studies was reported between 1.7 %-72 %. This study aims to investigate the prevalence of RMCs in a Turkish population using cone beam CT. 340 CBCT images of hemimandibles of 170 patients, with a mean age of 37 (range, 16-80), that clearly identified the course of the mandibular canal in the posterior mandible were selected retrospectively from the archived records of our Oral and Maxillofacial Radiology Department. The sagittal, coronal, axial and pseudopanoramic images were used for assessing the RMCs. This variant was found in 19 out of 170 patients (11 %). Of the 340 CBCT examinations in 170 patients, 20 showed the presence of a RMC (5 %). It was present unilaterally in 18 patients (95 %) and bilaterally in one patient (5 %). There was no difference in the presence of RMCs with regard to sex and sides of the mandible (p>0.05). Clinicans should be aware of RMC and this anatomical variance should be taken into consideration while planning surgery around this region. When there is any suspicion of the RMC presence CBCT is the best imaging modality to visualize the three-dimensional structure of this variant.
关键词： Anatomic variation,Cone beam CT,Retromolar canal
更新于2025-09-04 15:30:14