Journal of X-Ray Science and Technology - Volume 25, issue 5
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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: It is often unrealistic to assume that the subject remains stationary during a computed tomography (CT) imaging scan. A patient rigid motion can be decomposed into a translation and a rotation around an origin. How to minimize the motion impact on image quality is important. OBJECTIVE: To eliminate artifacts caused by patient rigid motion during a CT scan, this study investigated a new method based on frequency domain analysis to estimate and compensate motion impact. METHODS: Motion parameters was first determined by the magnitude correlation of projections in frequency domain. Then, the estimated parameters were…applied to compensate for the motion effects in the reconstruction process. Finally, this method was extended to helical CT. RESULTS: In fan-beam CT experiments, the simulation results showed that the proposed method was more accurate and faster on the performance of motion estimation than using Helgason-Ludwig consistency condition method (HLCC). Furthermore, the reconstructed images on both simulated and human head experiments indicated that the proposed method yielded superior results in artifact reduction. CONCLUSIONS: The proposed method is a new tool for patient motion compensation, with a potential for practical application. It is not only applicable to motion correction in fan-beam CT imaging, but also to helical CT.
Keywords: CT, fan-beam, frequency domain, motion artifacts
Abstract: Objective of this study is to present and test a new method for metal artifact reduction (MAR) by segmenting raw CT data (sinogram). The artifact suppression technique incorporates two steps namely, metal projection segmentation in the sinogram and replacement of segmented regions by new values using an interpolation method. The proposed segmentation algorithm uses the sinogram instead of reconstructed CT slices. First, one of the best and newest region-based geometric active contour models is used to detect projection data affected by metal objects (missing projections). Then, the Hough-transform method is applied to detect all sinusoidal-like curves belonging to metal objects.…Finally, a post image processing technique is used aiming to increase accuracy of the segmentation process. To provide a proof of performance, CT data of two patients with metallic teeth filling and pelvis prosthesis were included in the study as well as CT data of a phantom with metallic teeth inserts. Accuracy was determined by comparing mean, variance, mean squared error (MSE) and, peak signal to noise ratio (PSNR) as evaluation measurements of distortion in phantom images with respect to metallic teeth (original and suppressed) and without metallic teeth inserts. Quantitative results showed an average improvement of 12 dB in terms of PSNR and 517 in terms of MSE when the new MAR method was applied to remove metal artifacts. Qualitative improvement was also assessed by comparing uncorrected clinical images with artifact suppressed images. Moreover, qualitative comparison of the results of the proposed new method with the existing methods of MAR showed the superiority of the new method tested in this study.
Keywords: Active contour models, Hough transform, metal artifact reduction, sinogram
Abstract: PURPOSE: To develop and test a deep learning based computer-aided diagnosis (CAD) scheme of mammograms for classifying between malignant and benign masses. METHODS: An image dataset involving 560 regions of interest (ROIs) extracted from digital mammograms was used. After down-sampling each ROI from 512×512 to 64×64 pixel size, we applied an 8 layer deep learning network that involves 3 pairs of convolution-max-pooling layers for automatic feature extraction and a multiple layer perceptron (MLP) classifier for feature categorization to process ROIs. The 3 pairs of convolution layers contain 20, 10, and 5 feature maps, respectively. Each convolution layer is…connected with a max-pooling layer to improve the feature robustness. The output of the sixth layer is fully connected with a MLP classifier, which is composed of one hidden layer and one logistic regression layer. The network then generates a classification score to predict the likelihood of ROI depicting a malignant mass. A four-fold cross validation method was applied to train and test this deep learning network. RESULTS: The results revealed that this CAD scheme yields an area under the receiver operation characteristic curve (AUC) of 0.696±0.044, 0.802±0.037, 0.836±0.036, and 0.822±0.035 for fold 1 to 4 testing datasets, respectively. The overall AUC of the entire dataset is 0.790±0.019. CONCLUSIONS: This study demonstrates the feasibility of applying a deep learning based CAD scheme to classify between malignant and benign breast masses without a lesion segmentation, image feature computation and selection process.
Keywords: Computer aided diagnosis (CAD), deep learning, breast mass classification, convolution neuron networks
Abstract: When testing small size and high density objects with a broad field-of-view (FOV) industrial CT system, multiple objects are always assembled evenly onto the turntable for detecting to improve test efficiency. However, the maximum X-ray’s penetrating path through the materials increases, which means the CT system should collocate with a high energy X-ray source and wide-dynamic range detectors to complete the CT scanning. In this study, we proposed and tested a novel and efficient CT scanning method based on linear-arrangement and synchronous-rotating multi-turntables without enhancing the energy of X-ray source and wide-dynamic range of detectors for the CT system. With…this modality, multiple objects are assembled onto multiple synchronous-rotating turntables respectively, and X-rays within the FOV merely penetrate one single object when scanning. The corresponding filtered back projection algorithm for image reconstruction is deduced. The computer simulation and experimental results verified the feasibility of this novel method and the scanning time was reduced to 5–8 minutes when completing the scanning of 3 to 5 group objects.
Keywords: Computed tomography, test efficiency, multi-turntables, synchronous rotating, image reconstruction
Abstract: Plasma cooling due to hard x-ray radiation from the Runaway electrons is an important issue in tokamaks. Thus, developing effective methods to reduce the Runaway electrons and the emitted hard x-ray is also important for optimal tokamak plasma operation. In this study, we investigated the effects of external fields on hard x-ray intensity and the Magnetohydrodynamic (MHD) activity. In other words, we presented the effects of positive biased limiter and Resonant Helical Field (RHF) on the MHD fluctuations and hard x-ray emission from the Runaway electrons. MHD activity and hard x-ray intensity were analyzed using Wavelet transform in the presence…of external fields and without them. The experimental results showed that the MHD activity and therefore the hard x-ray intensity could be controlled by the external electric and magnetic fields.
Abstract: Osteoblastoma is a rare benign primary bone tumor, which occurs in any part of the skeleton. Extraskeletal osteoblastoma is rather rare. We presented an extremely rare case of extraskeletal osteoblastoma located in the breast. The tumor recurred 7 months later after resection and transformed to aggressive osteoblastoma. The histopathological features, ultrasonic manifestations and ultrasonic differential diagnoses of the primary and recurrent tumors were discussed. The recommended treatment of the tumor is surgical excision. Due to its tendency of recurrence and potential malignant transformation, adequate resection and careful follow up is essential.
Keywords: Extraskeletal osteoblastoma, breast tumor, ultrasound, cancer diagnose, cancer recurrence
Abstract: BACKGROUND: Ultrasound (US) and computed tomography (CT) are common diagnostic imaging methods for detecting and diagnosing papillary thyroid microcarcinoma (PTMC). However, single-source dual-energy spectral computed tomography (spectral CT) reduces beam hardening artefacts and optimizes contrast, which may add value in detecting PTMC. OBJECTIVE: To investigate values of applying single-source dual-energy spectral CT for diagnosing PTMCs, in comparison with high frequency ultrasound and conventional polychromatic images. METHODS: Thirty-one patients with suspected PTMC underwent contrast-enhanced dual-energy spectral CT. The images were analyzed by two experienced radiologists. Noise and contrast-noise-ratio (CNR) were compared between conventional CT and spectral CT.…Ultrasonography was also performed by an experienced radiologist with a 7 to 12-MHz linear array transducer. Detection and diagnostic sensitivity were determined and compared. RESULTS: Forty-six pathologically-confirmed PTMC lesions were detected in 31 patients. Spectral CT had lower noise and higher CNR than conventional CT (P < 0.05). US detected more tumors (45/46 [97.8%] than conventional CT images (40/46 [87.0%]) or spectral CT images (44/46 [95.7%]). Among them, 30 (65.2%), 36 (78.3%), and 40 (87.0%) lesions were diagnosed correctly by conventional CT, spectral CT and US, respectively. Spectral CT had higher sensitivity than conventional CT (P = 0.031). However, there was no significant difference between spectral CT and US diagnostic sensitivities (P = 0.125). CONCLUSION: Single-source dual-energy spectral CT was superior to conventional polychromatic images and similar to high frequency ultrasound in detecting and diagnosing for PTMCs. CT had advantages in detecting level VI and VII lymph nodes. Spectral CT and US provided good results for PTMC, and aid preoperative diagnosis.
Abstract: BACKGROUND: Optimizing scan parameters for double inversion recovery (DIR) sequences remains difficult. OBJECTIVE: To evaluate a new method for optimizing DIR sequence scan parameters using T1 mapping and a newly developed analysis algorithm. METHODS: Twelve healthy volunteers underwent T1 mapping and DIR magnetic resonance imaging. The following steps were used for image optimization including: 1) measurement of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) T1 values to create a T1 map; 2) calculation of optimized scan parameters by using a developed analysis algorithm; 3) performance assessment of DIR magnetic resonance imaging by using…the calculated optimized imaging parameters. Additionally, we used scan parameters from previous studies to obtain DIR images in order to evaluate our new method. The contrast between GM and suppressed tissues was compared between these images and those obtained using the optimized parameters. RESULTS: Using our optimization method, WM and CSF regions were suppressed uniformly for all scan conditions. The contrast was significantly higher in images obtained using this optimization method compared to those obtained using previously published parameters (p < 0.01). CONCLUSIONS: It is possible to obtain superior DIR images by using an optimization method that involves T1 mapping and a newly developed analysis algorithm.
Abstract: Iterative reconstruction algorithms for computed tomography (CT) through total variation (TV) regularization can provide accurate and stable reconstruction results. TV minimization is the L 1 -norm of gradient-magnitude images and can be regarded as a convex relaxation method to replace the L 0 norm. In this study, a fast and efficient algorithm, which is named a weighted difference of L 1 and L 2 (L 1 - αL 2 ) on the gradient minimization, was proposed and investigated. The new algorithm provides a better description of sparsity for the optimization-based algorithms than TV minimization algorithms. The alternating direction…method is an efficient method to solve the proposed model, which is utilized in this study. Both simulations and real CT projections were tested to verify the performances of the proposed algorithm. In the simulation experiments, the reconstructions from the proposed method provided better image quality than TV minimization algorithms with only 7 views in 180 degrees, which is also computationally faster. Meanwhile, the new algorithm enabled to achieve the final solution with less iteration numbers.
Keywords: Computed tomography, image reconstruction, difference of L1 and L2 minimization, alternating direction method
Abstract: Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare renal tumor composed of epithelial and stromal cells. In this study, we report a rare case of MESTK, which was pathologically benign but complicated with renal vein and inferior vena cava tumor thrombus. The 50-year-old female patient was admitted to hospital for a mass on the left kidney. Computed tomography showed a 32 mm×18 mm mass with slight delayed enhancement in the left renal sinus, and neoplastic thrombus was detected in left renal vein and inferior vena cava. A preoperative diagnosis of renal leiomyoma was made by needle biopsy and…a laparoscopic radical nephrectomy with thrombectomy was performed. Histologically, the tumor and thrombus were composed of proliferative spindle cells and a small amount of tubular structures. Both kinds of the cells were well differentiated with no atypia or mitosis of nuclei. Immunohistochemical staining showed positive for CK, Ki-67 in the tubular cells and desmin, actin, estrogen receptors, progesterone receptors in the spindle cells. Finally, the diagnosis of MESTK was established. No recurrence or metastasis was found in the patient with a followed-up period of 12 months after the surgery. Due to the difficulty in diagnosis of MESTK, documentation with more cases of MESTK is needed to further understand its pathogenesis, biological behavior, preoperative diagnosis and optimal management of patient treatment.
Keywords: Mixed epithelial and stromal tumor of the kidney, benign, inferior vena cava tumor thrombus, case report