Journal of X-Ray Science and Technology - Volume 27, issue 1
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: BACKGROUND: Some patients cannot be imaged with cone-beam CT for image-guided radiation therapy because their size, pose, or fixation devices cause collisions with the machine. OBJECTIVE: To investigate imaging trajectories that avoid such collisions by using virtual isocenter and variable magnification during acquisition while yielding comparable image quality. METHODS: The machine components most likely to collide are the gantry and kV detector. A virtual isocenter trajectory continuously moves the patient during gantry rotation to maintain an increased separation between the two. With dynamic magnification, the kV detector is dynamically moved to increase clearance for an angular…range around the potential collision point while acquiring sufficient data to maintain the field-of-view. Both strategies were used independently and jointly with the resultant image quality evaluated against the standard circular acquisition. RESULTS: Collision avoiding trajectories show comparable contrast and resolution to standard techniques. For an anthropomorphic phantom, the RMSE is <7×10- 4 , multi-scale structural similarity index is >0.97, and visual image fidelity is >0.96 for all trajectories when compared to a standard circular scan. CONCLUSIONS: The proposed trajectories avoid machine-patient collisions while providing comparable image quality to the current standard thereby enabling CBCT imaging for patients that could not otherwise be scanned.
Abstract: BACKGROUND: Computer aided detection (CADe) of pulmonary nodules from computed tomography (CT) is crucial for early diagnosis of lung cancer. Self-learned features obtained by training datasets via deep learning have facilitated CADe of the nodules. However, the complexity of CT lung images renders a challenge of extracting effective features by self-learning only. This condition is exacerbated for limited size of datasets. On the other hand, the engineered features have been widely studied. OBJECTIVE: We proposed a novel nodule CADe which aims to relieve the challenge by the use of available engineered features to prevent convolution neural networks (CNN)…from overfitting under dataset limitation and reduce the running-time complexity of self-learning. METHODS: The CADe methodology infuses adequately the engineered features, particularly texture features, into the deep learning process. RESULTS: The methodology was validated on 208 patients with at least one juxta-pleural nodule from the public LIDC-IDRI database. Results demonstrated that the methodology achieves a sensitivity of 88% with 1.9 false positives per scan and a sensitivity of 94.01% with 4.01 false positives per scan. CONCLUSIONS: The methodology shows high performance compared with the state-of-the-art results, in terms of accuracy and efficiency, from both existing CNN-based approaches and engineered feature-based classifications.
Keywords: Computer aided detection (CADe), computed tomography (CT) imaging, pulmonary nodules, deep learning, image features analysis
Abstract: Performing X-ray computed tomography (CT) examinations with less radiation has recently received increasing interest: in medical imaging this means less (potentially harmful) radiation for the patient; in non-destructive testing of materials/objects such as testing jet engines, the reduction of the number of projection angles (which for large objects is in general high) leads to a substantial decreasing of the experiment time. In the experiment, less radiation is usually achieved by either (1) reducing the radiation dose used at each projection angle or (2) using sparse view X-ray CT, which means significantly less projection angles are used during the examination. In…this work, we study the performance of the recently proposed sinogram-based iterative reconstruction algorithm in sparse view X-ray CT and show that it provides, in some cases, reconstruction accuracy better than that obtained by some of the Total Variation regularization techniques. The provided accuracy is obtained with computation times comparable to other techniques. An important feature of the sinogram-based iterative reconstruction algorithm is that it is simpler and without the many parameters specific to other techniques.
Abstract: We evaluate the impact of denoising and Metal Artefact Reduction (MAR) on 3D object segmentation and classification in low-resolution, cluttered dual-energy Computed Tomography (CT). To this end, we present a novel 3D materials-based segmentation technique based on the Dual-Energy Index (DEI) to automatically generate subvolumes for classification. Subvolume classification is performed using an extension of Extremely Randomised Clustering (ERC) forest codebooks, constructed using dense feature-point sampling and multiscale Density Histogram (DH) descriptors. Within this experimental framework, we evaluate the impact on classification accuracy and computational expense of pre-processing by intensity thresholding, Non-Local Means (NLM) filtering, Linear Interpolation-based MAR (LIMar) and…Distance-Driven MAR (DDMar) in the domain of 3D baggage security screening. We demonstrate that basic NLM filtering, although removing fewer artefacts, produces state-of-the-art classification results comparable to the more complex DDMar but at a significant reduction in computational cost - bringing into question the importance (in terms of automated CT analysis) of computationally expensive artefact reduction techniques. Overall, it was found that the use of MAR pre-processing approaches produced only a marginal improvement in classification performance (< 1%) at considerable additional computational cost (> 10×) when compared to NLM pre-processing.
Abstract: BACKGROUND: During the MRI examination, pediatric patients sleep under the sedation so that the image artifacts caused by the patient motion could be minimized. However, the sedative injection at the buttocks might cause a difficulty in the diagnosis of the buttock diseases using the MRI manifestations. OBJECTIVE: This study aims to explore the imaging characteristics of MR for the pediatric patients with the sedative injected at the buttocks in order to correctly diagnose the diseases. METHODS: MR imaging data of 64 pediatric patients injected with the sedative at the buttocks were retrospectively collected, including 8 cases…of buttock disease. The imaging manifestations were analyzed and compared. RESULTS: Out of 64 patients, 8 were diagnosed as the buttock diseases. MR imaging manifestations of the sedatives injected at the buttocks were the locally patchy and streaky long T1 and long T2 signals and were different from what were shown for the normal tissues and diseases. CONCLUSION: The sedative injected at the buttocks has the MRI manifestations different from the normal tissues and diseases. Correctly understanding the MRI manifestations for the pediatric patients with the injection of sedative at the buttocks would reduce the chances of the misdiagnosis on the diseases.
Keywords: Magnetic resonance imaging, sedative, buttocks, pediatric patients
Abstract: BACKGROUND: SPECT MPI (Single photon emission computed tomography myocardial perfusion imaging) is an essential tool for diagnosis of cardiovascular disease, but it also involves considerable exposure to ionizing radiation. OBJECTIVE: To determine the radioprotective potential of lipoic acid free and nano-capsule against 99m Tc-MIBI-induced injury in cardiovascular tissue. METHODS: The radioprotective ability was assessed by blood count, histopathology and heart enzymes in different groups of mice. Hearts of mice from all groups were dissected and prepared for oxidative stress analysis of superoxide dismutase (SOD) and malondialdehyde (MDA). Furthermore, levels of DNA damage in heart and bone…marrow cells were evaluated by alkaline comet assay technique. The same measurements were estimated after treating the mice with lipoic acid. RESULTS: Comparing mice injected by radiopharmaceutics with control group showed a significant depression in the count of white blood cells (WBC) by about 40 % at 24 &72 hrs post-radiopharmaceutical administration. Moreover, platelets count was decreased by 27% at 72 hrs post-radiopharmaceutical administration. Radiation also dropped in super oxide dismutase (SOD) and increased in activity of heart enzymes and level of MDA (Malondialdehyde). Additionally, histopathological observation was characterized by focal necrosis of cardiac myocytes. 99m Tc-MIBI induced DNA damage had significant increase. Nevertheless, pretreatment with free and lipoic acid nano-capsules (LANC’s) prevented the reduction induced in WBCs and platelets, and improved their counts significantly. Conversely pre-treatment with lipoic acid free and nano-capsule significantly increased the activity of SOD and decreased the level of MDA and therefore protected the cardiovascular tissues and reduced DNA strand-break, consequently and enhanced the body weight of the mice. CONCLUSIONS: These findings highlight the efficacy of lipoic acid free and nano-capsule as a radio protector.
Keywords: Lipoic acid free and nano-capsule, Radioprotection, 99mTc-MIBI, Antioxidant, DNA damage
Abstract: OBJECTIVE: To assess the difference in absorbed organ dose and image quality for head-neck CT angiography using organ dose modulation compared with 3D smart mA modulation in different body mass indices (BMIs) using an adaptive statistical iterative reconstruction (ASiR-V) algorithm. METHODS: Three hundred patients underwent head-neck CTA were equally divided into three groups: A (18.5 kg/m2 ≦BMI < 24.9 kg/m2 ), B (24.9 kg/m2 ≦BMI < 29.9 kg/m2 ) and C (29.9 kg/m2 ≦BMI≦34.9 kg/m2 ). The groups were randomly subdivided into two subgroups (n = 50): A1-A2, B1-B2 and C1-C2. The patients in subgroups A1, B1 and C1 underwent organ dose modulation with the ASiR-V algorithm, while other…patients underwent 3D smart mA modulation. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all head-neck CT angiography images were calculated. Images were then subjectively evaluated. Mean values of several indices including dose-length product (DLP) were computed. The DLP was converted to the effective dose (ED). SNR, CNR and ED in groups A, B, and C were compared in statistical data analysis. RESULTS: SNR, CNR, and subjective image scores show no statistical differences in three groups (P > 0.05). However, there is significant difference of ED values (P < 0.05) . For example, in subgroup A1 mean ED values are 15.30% and 23.66% lower than those in subgroup A2 at thyroid gland and eye lens, respectively. Similar patterns also exist in groups B (B1 vs. B2) and C (C1 vs. C2). CONCLUSIONS: Using organ dose modulation and applying the ASiR-V algorithm can more effectively reduce the radiation dose in head-neck CT angiography than using 3D smart mA modulation, while maintaining image quality. Thus, using organ-based dose modulation has the additional benefit of reducing dose to the thyroid gland and eye lens.
Keywords: Organ dose modulation, 3D smart mA modulation, radiation dose, image quality, head-neck CT angiography
Abstract: BACKGROUND: Due to large dimensional matrix multiplications, the existing iterative algorithms for cone beam computed tomography (CBCT) reconstruction often face problems of heavy computational workload and large volume of memory usage. OBJECTIVE: This study proposes and tests an iterative algorithm of 3DA-TVAL3 for fast reconstruction of CBCT images using undersampled measurement data and the reduced amount of computer memories. METHODS: In order to reduce computational workload and computer memories based on the sparsity of the CBCT measurement matrix, the proposed iterative algorithm applies elementwise scalar multiplications in the iterative computation to search for optimal solution. Through…a number of tests on three different CT data sets with different number of projections, the reconstruction performance of the proposed algorithm is compared with that of two accelerated iterative algorithms and the conventional FDK algorithm. RESULTS: The visual and quantitative evaluations using the normalized mean square error, peak signal to noise ratio and structural similarity metrics demonstrated the faster computational time and the higher image quality of using the proposed 3DA-TVAL3 algorithm than using other conventional algorithms under comparison. CONCLUSIONS: The proposed 3DA-TVAL3 algorithm can perform efficient and fast computation of CBCT reconstruction using the reduced amount of computer memories.
Abstract: In this study, we designed mobile X-ray equipment that generates high-power X-rays, using an internal power source by means of a super-capacitor, and evaluated its safety. The proposed X-ray equipment uses the charging voltage of a battery to store high density energy, supplementing the electric charge of the super-capacitor, which can instantly release a large amount of energy. Further, pulse frequency modulation was applied to produce high voltage and thereby improve energy efficiency. The developed mobile X-ray equipment enables to generate an output of 30 kW and, therefore, can be applied to many diagnostic fields. In addition, various devices and control…circuits were employed to ensure convenience and safety of using the equipment in clinical applications. This study analyzed the error ranges regarding tube voltage, tube current, irradiation time, coefficient variation, half-value layer, and the output characteristics. The results showed that the proposed X-ray equipment was able to generate 800mR X-ray power under the condition of 30 kW. The coefficient variation was less than 0.05 at all measurement points, which indicates that it is possible to generate the equal amount of X-ray when the driving conditions are same. Results also showed 51.25% of transmittance at 3.5mmAL in the case of the wire, which is thicker than a common reference of 2.3mmAL and indicates that this new mobile equipment is possible to generate X-rays with relatively high permeability. In conclusion, the findings in this study suggest that the new equipment can generate consistent high-power X-rays and, therefore, can be used safely by minimizing unnecessary re-taking of images and radiation exposure.
Keywords: Mobile X-ray, super-capacitor, coefficient variation, half-value layer
Abstract: BACKGROUND: Numerous techniques had been proposed to reduce radiation exposure in computed tomography (CT) including the use of radiation shielding. OBJECTIVE: This study aims to evaluate efficacy of using a bismuth breast shield and optimized scanning parameter to reduce breast absorbed doses from CT thorax examination. METHODS: Five protocols comprising the standard CT thorax clinical protocol (CP1) and four modified protocols (CP2 to CP5) were applied in anthropomorphic phantom scans. The phantom was configured as a female by placing a breast component on the chest. The breast component was divided into four quadrants, where 2…thermoluminescence dosimeters (TLD-100) were inserted into each quadrant to measure the absorbed dose. The bismuth shield was placed over the breast component during CP4 and CP5 scans. RESULTS: The pattern of absorbed doses in each breast and quadrant were approximately the same for all protocols, where the 4th quadrant > 3rd quadrant > 2nd quadrant > 1st quadrant. The mean absorbed dose value in CP3 was reduced to almost 34% of CP1’s mean absorbed dose. It was reduced even lower to 15% of CP1’s mean absorbed dose when the breast shield was used in CP5. CONCLUSION: This study showed that CT radiation exposure on the breast could be reduced by using a bismuth shield and low tube potential protocol without compromising the image quality.
Keywords: Computed tomography, bismuth shielding, organ equivalent dose, scan
protocols, tube potential, breast