Conversion from dose-length product to effective dose in computed tomography venography of the lower extremities

For radiation dose assessement of computed tomography (CT), effective dose (ED) is often estimated by multiplying the dose-length product (DLP), provided automatically by the CT scanner, by a conversion factor. We investigated such conversion in CT venography of the lower extremities performed in conjunction with CT pulmonary angiography. The study subjects consisted of eight groups imaged using different scanners and different imaging conditions (five and three groups for the GE and Siemens scanners, respectively). Each group included 10 men and 10 women. The scan range was divided into four anatomical regions (trunk, proximal thigh, knee and distal leg), and DLP was calculated for each region (regional DLP). Regional DLP was multiplied by a conversion factor for the respective region, to convert it to ED. The sum of the ED values for the four regions was obtained as standard ED. Additionally, the sum of the four regional DLP values, an approximate of the scanner-derived DLP, was multiplied by the conversion factor for the trunk (0.015 mSv/mGy/cm), as a simplified method to obtain ED. When using the simplified method, ED was overestimated by 32.3%−70.2% and 56.5%−66.2% for the GE and Siemens scanners, respectively. The degree of overestimation was positively and closely correlated with the contribution of the middle and distal portions of the lower extremities to total radiation exposure. ED/DLP averaged within each group, corresponding to the conversion factor, was 0.0089−0.0114 and 0.0091−0.0096 mSv/mGy/cm for the GE and Siemens scanners, respectively. In CT venography of the lower extremities, ED is greatly overestimated by multiplying the scanner-derived DLP by the conversion factor for the trunk. The degree of overestimation varies widely depending on the imaging conditions. It is recommended to divide the scan range and calculate ED as a sum of regional ED values.

Three-dimensional Alignment of the Upper Extremity in the Standing Neutral Position in Healthy Subjects

Background: Though alignment of the spine and lower extremities in the standing neutral position has been evaluated, a few studies evaluating the alignment of the upper extremities have also been made. This study assessed the normal alignment of the upper extremities in the standing neutral position and clarified the three-dimensional angular rotations of the upper extremity joints.Methods: Computed tomography (CT) images of 158 upper extremities from 79 healthy volunteers were prospectively acquired in the standing neutral position using an upright CT scanner. Three-dimensional coordinate systems of the thorax, scapula, humerus, and forearm were designated, and three-dimensional angular rotations of the scapulothoracic, glenohumeral, and elbow joints were calculated.Results: The mean angle of the scapulothoracic joint was 8.5° ± 5.9° of upward rotation, 28.7° ± 5.9° of internal rotation, and 7.9° ± 5.2° of anterior inclination. The mean angle of the glenohumeral joint was 4.4° ± 5.9° of abduction, 9.4° ± 12.3° of internal rotation, and 0.3° ± 4.4° of extension. The mean angle of the elbow joint was 9.6° ± 3.7° of valgus, 88.8° ± 14.3° of pronation, and 15.4° ± 4.2° of flexion. Correlations in angular rotation values were found, and interactions for keeping the upper extremities in a neutral position were observed.Conclusions: This study clarified the three-dimensional angular rotation of upper extremity joints in the standing neutral position using an upright CT scanner. Our results may provide important insights for the functional evaluation of upper extremity alignment.

Evaluation of Diagnostic Performance of MDCT Coronary Angiography in Comparison with Conventional Coronary Angiography

Background: Coronary artery disease is now becoming increasingly prevalent than before especially in younger age groups. We in the current study tried to evaluate the potential of 128 slice MDCT coronary angiography for the detection of stenotic coronary lesions by comparing the results of computed tomographic coronary angiography to a gold standard set by Conventional coronary angiography. Methods: A total of n=30 patients with clinically suspected Coronary artery disease. They were evaluated with 128 Slice CT Scanner (PHILIPS INGENUITY) and conventional coronary angiography. All patients were examined with a 128 slice MDCT scanner (Philips Ingenuity 128 slice Netherlands) using standard cardiac CT protocol. Gantry rotation time was 400 ms with a half sector acquisition protocol and multisector reconstruction permitting an effective temporal resolution between 50 and 200 ms depending on patient heart rate. Results: In the n=30 Patients included in the study with CCA, the n=450 coronary segments included in the study were found to contain a total number of n=138 stenoses among them non-significant stenoses. The accuracy of MDCT detection of coronary stenoses greater than 50% diameter of vessel lumen is about 94.78. When raising the threshold for stenosis from 50% to 70% of the vessel lumen, so that only hemodynamic relevant stenoses enter the evaluation, the sensitivity decreases from 88%. The MDCT detection in the patient group with heart rates below 60 beats per minute higher values for sensitivity 93% and specificity 97% were observed, compared to sensitivity 87% and specificity 93% of the patient group with heart rates above 60 beats per minute. Conclusion:The present study revealed that a high negative predictive value (98.08%)suggests that 128- Slice MDCT coronary angiography is a good screening modality for evaluation of patients with mild to intermediate-risk factors who might otherwise require invasive angiography.

Deep learning-based extended field of view computed tomography image reconstruction: influence of network design on image estimation outside the scan field of view

The problem of data truncation in Computed Tomography (CT) is caused by the missing data when the patient exceeds the Scan Field of View (SFOV) of a CT scanner. The reconstruction of a truncated scan produces severe truncation artifacts both inside and outside the SFOV. We have employed a deep learning-based approach to extend the field of view and suppress truncation artifacts. Thereby, our aim is to generate a good estimate of the real patient data and not to provide a perfect and diagnostic image even in regions beyond the SFOV of the CT scanner. This estimate could then be used as an input to higher order reconstruction algorithms [1]. To evaluate the influence of the network structure and layout on the results, three convolutional neural networks (CNNs), in particular a general CNN called ConvNet, an autoencoder, and the U-Net architecture have been investigated in this paper. Additionally, the impact of L1, L2, structural dissimilarity and perceptual loss functions on the neural network’s learning have been assessed and evaluated. The evaluation of data set comprising 12 truncated test patients demonstrated that the U-Net in combination with the structural dissimilarity loss showed the best performance in terms of image restoration in regions beyond the SFOV of the CT scanner. Moreover, this network produced the best mean absolute error, L1, L2, and structural dissimilarity evaluation measures on the test set compared to other applied networks. Therefore, it is possible to achieve truncation artifact removal using deep learning techniques.

Dual-Layer Spectral CTA for TAVI Planning Using a Split-Phase Protocol and Low-keV Virtual Monoenergetic Images: Improved Image Quality in Comparison with Single-Phase Conventional CTA

Purpose Adaptation of computed tomography protocols for transcatheter aortic valve implantation (TAVI) planning is required when a first-generation dual-layer spectral CT scanner (DLCT) is used. The purpose of this study was to evaluate the objective image quality of aortic CT angiography (CTA) for TAVI planning using a split-phase technique with reconstruction of 40 keV virtual monoenergetic images (40 keV-VMI) obtained with a DLCT scanner. CT angiography obtained with a single-phase protocol of a conventional single-detector CT (SLCT) was used for comparison. Materials and Methods 75 CTA scans from DLCT were retrospectively compared to 75 CTA scans from SLCT. For DLCT, spiral CTA without ECG-synchronization was performed immediately after a retrospectively ECG-gated acquisition covering the heart and aortic arch. For SLCT, spiral CTA with retrospective ECG-gating was performed to capture the heart and the access route simultaneously in one scan. Objective image quality was compared at different levels of the arterial access route. Results 40 keV virtual monoenergetic images of DLCT showed a significantly higher mean vessel attenuation, SNR, and CNR at all levels of the arterial access route. With 40 keV-VMI of DLCT, the overall mean aortic attenuation of all six measured regions was 589.6 ± 243 HU compared to 492.7 ± 209 HU of SLCT (p < 0.01). A similar trend could be observed for SNR (23.6 ± 18 vs. 18.6 ± 9; p < 0.01) and CNR (21.1 ± 18 vs. 16.4 ± 8; p < 0.01). No deterioration was observed for vascular noise (27.8 ± 9 HU vs. 28.1 ± 8 HU; p = 0.599). Conclusion Using a DLCT scanner with a split-phase protocol and 40 keV-VMI for TAVI planning, higher objective image quality can be obtained compared to a single-phase protocol of a conventional CT scanner. Key Points: Citation Format

Human Umbilical Cord-Derived Mesenchymal Stem Cells Alleviate Acute Lung Injury Caused by Severe Burn via Secreting TSG-6 and Inhibiting Inflammatory Response

Objectives To investigate whether hUC-MSCs attenuated severe burn-induced ALI and the effects were based on TSG-6 secreted from hUC-MSCs. Method Rat model was established and evaluated as follows：Anires2005 animal pulmonary function tester for pulmonary function; micro-CT scanner for lung imaging manifestations; cytokine expression was measured by ELISA assay, and both inflammatory cell infiltration and lung injury were assessed by immunohistochemistry assay. Results In vitro, TSG-6 levels in serum from the burn group were significantly increased than that of the sham group. In vivo, TSG-6 levels of lung tissues and serum in the burn+ hUC-MSCs group were significantly increased than those of that in the burn group. Higher parameters of airway resistance（Ri, Re, etc）were markedly decreased, and the disordered lung texture and funicular density shadows were significantly improved after hUC-MSCs administration. Both in lung tissues and serum, increased levels of proinflammatory cytokines（TNF-α, IL-1β, IL-6）were remarkably decreased, but anti-inflammatory cytokine IL-10 increased after hUC-MSCs administration (p<0.05). These significant positive effects after hUC-MSCs transplantation did not occur in the Burn+siTSG-6 group. Conclusion Intra-tracheal implantation of hUC-MSCs has been an effective treatment for severe burn-induced ALI via promoting TSG-6 secretion and inhibiting inflammatory reaction in lung tissue.

TÌM HIỂU MỘT SỐ ĐẶC ĐIỂM LÂM SÀNG, X-QUANG, CẮT LỚP VI TÍNH CỦA BỆNH NHÂN GÃY KÍN DUPUYTREN ĐƯỢC KẾT XƯƠNG BÊN TRONG TẠI BỆNH VIỆN TRUNG ƯƠNG QUÂN ĐỘI 108

Mục tiêu: Gãy Dupuytren là một tổn thương đặc biệt vùng cổ chân, là một tổn thương thường gặp trên lâm sàng. Mục tiêu của nghiên cứu này là tìm hiểu đặc điểm lâm sàng, XQ, CT Scanner của loại gãy này. Đối tượng, phương pháp: Đối tượng nghiên cứu gồm 38 BN gãy kín Dupuytren, được phẫu thuật kết xương bên trong từ 9/2015-6/2020 tại Bệnh viện TWQĐ 108. Có 22 nam và 16 nữ, tuổi trung bình 46,26 tuổi (22-72), trong đó gãy ở chân trái là 23 BN, gãy chân phải là 15 BN. Nguyên nhân tổn thương là TNGT gặp ở 20 BN, do TNLĐ gặp ở 2 BN, do ngã gặp ở 13 BN, do TNTT gặp ở 3 BN. Các BN được chụp XQ thẳng, nghiêng. Chụp CT Scanner được thực hiện ở 20 BN gãy 3 mắt cá. Các đặc điểm lâm sàng, XQ, CT Scanner được thu thập và phân tích. Kết quả: 20 BN gãy 3 mắt cá, 17 BN gãy 2 mắt cá, 1 BN gãy mắt cá ngoài đơn thuần. Có 2 BN gãy loại I, 8 BN gãy loại II, 4 BN gãy loại III, 2 BN gãy loại IV theo phân loại gãy mắt cá sau của Bartonicek. Có 23 BN gãy kiểu Weber B và 13 BN kiểu Weber C. Tất cả BN đều có hình ảnh tổn thương mộng chày mác và bán trật xương sên ra ngoài. Cơ chế tổn thương chính là xoay ngoài (33/38 BN). Chẩn đoán gãy mắt cá sau dựa vào đường gãy chéo vát trên phim XQ tư thế nghiêng của 20 BN và hình ảnh đường viền kép ở 4 BN và hình núi mờ ở 16 BN trên phim X quang thẳng. CT Scan cho thấy kích thước, vị trí gãy, hình ảnh lún, chèn mảnh gãy nhỏ, di lệch lớn của mảnh gãy mắt cá sau ngay trên diện khớp. Kết luận: Gãy Dupuytren với các tổn thương đặc trưng: Gãy mắt cá ngoài, gãy mắt cá trong hoặc đứt dây chằng Delta; doãng mộng chày mác, có hoặc không có kèm gãy mắt cá sau. Cơ chế tổn thương chủ yếu là xoay ngoài cổ chân. XQ có thể chẩn đoán được gãy Dupuytren, tuy nhiên XQ có một số hạn chế trong chẩn đoán tổn thương gãy mắt cá sau, vì vậy nên chụp CT Scans để đánh giá gãy mắt cá sau.

Finite element modelling of UHPC under pulsating load using X-ray computed tomography based fiber distributions

The benefits of including fibers in ultra-high performance concrete (UHPC) are attributed to their good bond with the matrix and, hence, an optimal utilization of their properties. At the same time, though, fiber reinforcement may contribute to anisotropy in the composite material and induce weak areas. The influence of the fibers’ orientation on the material properties is a matter of current scientific discourse and it is known to play a vital role in structural design. In the case studies presented herein, mechanical laboratory tests using pulsating load regimes on UHPC with a strength of more than 200 MPa were simulated by use of finite element models. The orientations of the fibers were measured for each test sample prior to failure using an X-ray computed tomography (CT) scanner, and these orientations are explicitly implemented into the model. The paper discusses the methodology of merging data retrieved by CT image processing and state-of-the-art FE simulation techniques Moreover, the CT scanning was carried out throughout the testing procedure, which further enables the comparison of the mechanical tests and the FE models in terms of damage propagation and failure patterns. The results indicate that the overall fiber configuration and behavior of the samples can be realistically modelled and validated by the proposed CT-FE coupling, which can enhance the structural analysis and design process of elements produced with steel fiber reinforced and UHPC materials.

Virtual Non-Contrast versus True Non-Contrast Computed Tomography: Initial Experiences with a Photon Counting Scanner Approved for Clinical Use

The present study evaluates the diagnostic reliability of virtual non-contrast (VNC) images acquired with the first photon counting CT scanner that is approved for clinical use by comparing quantitative image properties of VNC and true non-contrast (TNC) images. Seventy-two patients were retrospectively enrolled in this study. VNC images reconstructed from the arterial (VNCa) and the portalvenous (VNCv) phase were compared to TNC images. In addition, consistency between VNCa and VNCv images was evaluated. Regions of interest (ROI) were drawn in the following areas: liver, spleen, kidney, aorta, muscle, fat and bone. Comparison of VNCa and VNCv images revealed a mean offset of less than 4 HU in all tissues. The greatest difference between TNC and VNC images was found in spongious bone (VNCv 86.13 HU ± 28.44, p < 0.001). Excluding measurements in spongious bone, differences between TNC and VNCv of 10 HU or less were found in 40% (VNCa 36%) and differences of 15 HU or less were found in 72% (VNCa 68%) of all measurements. The underlying algorithm for the subtraction of iodine works in principle but requires adjustments. Until then, special caution should be exercised when using VNC images in routine clinical practice.

Quality Assessment of Mobile Cone-beam Computerized Tomography Scanner Made in Thailand: A Phantom Study

Background: In 2011, the National Science and Technology Development Agency had successfully developed the first local-made mobile conebeam computed tomography (CBCT) scanner, called MobiiScan. Before a computed tomography (CT) scanner can be used in clinical practice, it must pass a quality assurance process. Objective: To assess the performance of MobiiScan before it can be further evaluated in human subjects. Materials and Methods: Images from scanning of an imaging phantom by MobiiScan were compared to a commercial 64-slice (GE Discovery CT750 HD) and a mobile (Neurologica CereTom) CT scanner, which were used as controls. Spatial resolution, uniformity, noise, accuracy of CT number, and geometric accuracy were examined by three investigators. Results: According to the bone scanning protocol, spatial resolution of the images produced by MobiiScan was comparable to the mobile scanner, but it was less than the 64-slice scanner. In addition, the signal uniformity of MobiiScan was poorer compared to the controls. MobiiScan produced more noise than the mobile and the 64-slice scanners at the 120-kVp mode, but less noise than the 64-slice scanner at the 80-kVp mode. Using the brain protocol, the spatial resolution from the MobiiScan was higher than the mobile scanner, but comparable to the 64-slice scanner. Although the signal uniformity of the MobiiScan was superior compared to the controls, the noise production was more than the controls. At all settings, the MobiiScan gave underrated distances and inaccurate CT numbers. However, it delivered very low radiation doses. Conclusion: MobiiScan had a good spatial resolution and delivered low radiation dose, which suggested that it could be used for bone examination as intended by the creator. However, its noise production and inaccurate CT numbers suggest that MobiiScan should not be used to diagnose soft tissue problems. It is recommended that the hardware and software should be adjusted to provide a better signal uniformity, lower noise level, accurate CT number, and geometric accuracy. Keywords: X-ray computed tomography; Cone-beam computed tomography; Craniofacial abnormalities; Radiologic phantom; MobiiScan