Journal of X-Ray Science and Technology - Volume 28, issue 2

Authors: Mu, Junxu | Tang, Xiaobin | Liu, Yunpeng | Hang, Shuang | Li, Huan | Zhou, Wei | Dang, Peng | Lai, Sheng

Article Type: Research Article

Abstract: BACKGROUND: Modern industrial facilities urgently need effective wireless communication technology to monitor instruments and equipment, but electromagnetic interference and physical shielding often exist in these fields, thereby preventing traditional communication methods from working correctly. OBJECTIVE: As a special wireless optical communication technology, X-ray communication (XCOM) is expected to solve the problem of signal transmission under this extreme condition. Our goal was to prove the feasibility of XCOM for signal transmission under metal barrier condition. METHODS: The Monte Carlo method was used to simulate the transmission characteristics of X-ray beam under metal barrier conditions, and the communication …performance of XCOM was evaluated. Moreover, the experimental demonstration system of XCOM was developed to test the penetration and communication performance of XCOM under metal shield. RESULTS: X-ray with energy above 150 keV could achieve a bit error rate of less than 10–4 after passing through a 20 mm iron, whereas X-ray with energy above 250 keV could maintain excellent communication performance after passing through a 30 mm iron. The experimental test results were consistent with the theoretical calculation. CONCLUSIONS: As a new wireless optical communication technology, X-ray communication is expected to solve the problem of signal transmission under physical shielding conditions. Show more

Keywords: X-ray communication, physical shielding, transmission characteristics of x-ray, communication performance

DOI: 10.3233/XST-190587

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 187-196, 2020

Authors: Wang, Zhiqiong | Xin, Junchang | Zhang, Qianqian | Gao, Sa | Ma, ChunXiao | Ren, Jie | Zhang, Hao | Qian, Wei | Zhu, Wancheng | Zhang, Xia | Liu, Jiren

Article Type: Research Article

Abstract: BACKGROUND: Breast cancer is a common disease in women. Early detection and early treatment can reduce breast cancer mortality. Studies have shown that breast cancer microcalcifications is one of the important clinical manifestations of early breast cancer, and sometimes even the only manifestation. When the mammography image shows typical malignant microcalcification, it can be diagnosed as breast cancer without any other signs of malignancy. In the aided diagnosis of microcalcifications, it is a crucial step to automatically find and locate regions of interest containing microcalcifications. However, the existing feature extraction method for microcalcifications only extracts features in the time domain …or wavelet domain, and does not completely represent all the information of the region of interest. An extraction method based on the combination of Dual-Tree Complex Wavelet Transform (DTCWT) and texture features is proposed in the paper. METHODS: First, the processing operations including denoising, enhancement, and edge detection were performed on mammograms. Sub-image segmentation is then performed. DTCWT features and texture features are extracted for each sub-image.DTCWT features are combined with texture features, and then genetic algorithm is used for feature optimization. The features are classified by the Extreme Learning Machine (ELM) to achieve rapid detection and automatic extraction of ROI with microcalcifications. The experimental results verify that the feature model proposed in this paper has the highest detection rate for ROI regions. The ROI region extracted by the proposed feature model was used as subsequent experimental data. Three different methods were used to detect the microcalcifications, including Top-hat, wavelet transform, and methods combining Top-Hat and wavelet transform. RESULTS: The method was applied to 100 mammograms from the mammograms database of women in Northeast China. In the automatic extraction of ROI, the accuracy, sensitivity, specificity, positive accuracy and negative accuracy of the proposed model combined with DTCWT were 95.92%, 96.71%, 92.20%, 93.65%, 96.33%, respectively. When the Top-hat algorithm was used for microcalcifications detection, the sensitivity reached 89.6%, and the false positive detection rate was 2.6. When the wavelet transform algorithm was used for microcalcifications detection, the sensitivity was 91.1%, and the false positive detection rate was 3.28. When the combined algorithm was used for microcalcifications detection, the sensitivity was 86.7%, and the false positive detection rate decreased to 1.35. CONCLUSIONS: The proposed model combined with DTCWT features achieves better result in the automatic extraction of ROI. Moreover, in the subsequent detection of microcalcifications based on three methods, the three methods achieved better results in sensitivity and false positive detection rate, respectively. Show more

Keywords: Breast Cancer, Microcalcifications, DTCWT, ELM, Mammogram

DOI: 10.3233/XST-190583

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 197-218, 2020

Authors: Lifton, Joseph | Liu, Tong

Article Type: Research Article

Abstract: X-ray sources with acceleration voltages of 450 kV typically have large focal spot sizes that lead to low spatial resolution computed tomography (CT) data. In this work a method to improve the spatial resolution of 450 kV CT is developed. The proposed method relies on using vertical subpixel detector shifting and deconvolution to generate a projection-set that has double the number of pixels in the direction parallel to the axis of rotation. The results show that the proposed method is able to increase the 10% modulation transfer function of the considered system from 3 lp/mm to 4 lp/mm. In addition, …a scan of a metal additively manufactured component with periodic features of approximately 200 μm is used to demonstrate the method; small features that were not fully resolved in a conventional scan become resolvable when the proposed method is used. Show more

DOI: 10.3233/XST-190595

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 219-230, 2020

Authors: Wang, Xin-Hua | Liu, Zheng-Jun | Xu, Jian-Bo | Li, Fang-Qian | Li, Wen-Li | Cao, Wu-Teng | Zhou, Zhi-Yang

Article Type: Research Article

Abstract: PURPOSE: To explore whether volumetric measurements of 3D-CUBE sequences based on baseline and early treatment time can predict neoadjuvent chemotherapy (NCT) efficacy of locally advanced rectal cancer (LARC). MATERIAL AND METHOD: 73 patients with LARC were enrolled from February 2014 to January 2018. All patients underwent MRIs during the baseline period before NCT (BL-NCT) and the first month of NCT (FM-NCT), and tumor volume (TV) was measured using 3D-CUBE, and tumor volume reduction (TVR) and tumor volume reduction rate (TVRR) were calculated. In addition, tumor invasion depth, tumor maximal length, range of tumor involvement in the circumference of …intestinal lumen and distance from inferior part of tumor to the anal verge were measured using baseline high-spatial-resolution T2-weighted MRIs. All patients were categorized into sensitive and insensitive groups based on post-surgical pathology after completion of the full courses of NCT. The receiver operating characteristic (ROC) curve was used to analyze the value of different MRI parameters in predicting efficacy of NCT. RESULTS: Statistically significant differences in TV of BL-NCT, TVR and TVRR from BL-NCT to FM-NCT were detected between sensitive and insensitive groups (P  < 0.05, respectively). The areas under the curves (AUC) of ROC of TVR and TVRR in predicting efficacy of NCT (0.890 [95% CI, 0.795∼0.951], 0.839 [95% CI, 0.735∼0.915]) were significantly better than that of TV (0.660 [95% CI, 0.540∼0.767]) (P  < 0.05, respectively). CONCLUSION: Reconstruction of 3D-CUBE volume in the first month of NCT is necessary, and both TVR and TVRR can be used as early predictors of NCT efficacy. Show more

Keywords: Magnetic resonance imaging, 3D-CUBE sequence, rectal cancer, neoadjuvant chemotherapy

DOI: 10.3233/XST-190594

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 231-241, 2020

Authors: Soda, Rikana | Hatanaka, Shogo | Hariu, Masatsugu | Shimbo, Munefumi | Yamano, Takafumi | Nishimura, Keiichiro | Kondo, Shuichi | Utsumi, Nobuko | Takahashi, Takeo

Article Type: Research Article

Abstract: OBJECTIVE: Since most radiation treatment plans are based on computed tomography (CT) images, which makes it difficult to define the targeted tumor volume located near a metal implant, this study aims to evaluate and compare three treatment plans in order to optimally reduce geometrical uncertainty in external radiation treatment of localized prostate cancer. METHODS: Experimental subjects were three prostate patients with bilateral hip prosthesis who had undergone radical radiotherapy. The treatment plans were five-field three-dimensional conformal radiation therapy (3D-CRT), fixed 5-field intensity-modulated radiation therapy (IMRT) using similar gantry angles, and single-arc volumetric modulated arc therapy (VMAT). The monitor …units (MUs), dose volume histograms (DVHs), the dose indices of planning target volume (PTV), clinical target volume (CTV) and rectum were compared among the three techniques. The geometrical uncertainties were evaluated by shifting the iso-center (2– 10 mm in the anterior, posterior, left, right, superior, and inferior directions). The CTV and rectum dose indexes with and without the iso-center shifts were compared in each plan. RESULTS: The Conformity Index of PTV were 1.35 in 3D-CRT, 1.12 in IMRT, and 1.04 in VMAT, respectively. The rectum doses in 3D-CRT are also higher than those in IMRT and VMAT. The iso-center shift little affected the CTV dose when smaller than the margin size. The rectum dose increased especially after a posterior shift. Additionally, this dose increase was larger in the VMAT plan than in the 3D– CRT plan. However, the VMAT achieved a superior rectum DVH to that of 3D– CRT, and this effect clearly exceeded the rectum-dose increase elicited by the iso-center shift. CONCLUSION: For radiotherapy treatment of localized prostate cancer in patients with hip prosthesis, the dose distribution was better in the VMAT and Metal Artifact Reduction (MAR)–CT image methods than the conventional methods. Because the anatomical structure of the male pelvic region is relatively constant among individuals, we consider that VMAT is a valid treatment plan despite analyzing just three cases. Show more

Keywords: Radiation therapy, metal artifact reduction technique, localized prostate cancer, computed tomography, Volumetric Modulated Arc Therapy

DOI: 10.3233/XST-190598

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 243-254, 2020

Authors: Chen, Yang | Dai, Xiaoting | Duan, Huihong | Gao, Lei | Sun, Xiwen | Nie, Shengdong

Article Type: Research Article

Abstract: BACKGROUND: Low dose computed tomography (LDCT) reduces radiation damage to patients. However, with the decrease of radiation dose, LDCT images of the lung often appear some serious problems such as poor contrast, noise and streak artifacts. OBJECTIVE: To improve the quality of lung LDCT images, this study proposed and investigated a new denoising method based on classification training structure combined dictionary for lung LDCT images. METHODS: First, top-hat transform and anisotropic diffusion with a shock filter (ADSF) algorithm are used to enhance the image contrast and image details. Second, an adaptive dictionary is trained and used …for noise reduction. Third, more image details are extracted from the residual image by using the atom activity measurement. The final result is obtained by combining the dictionary denoising result with the extracted detail information. The proposed method is then validated by both simulated and clinical lung LDCT images. Four metrics including Contrast-to-Noise Ratio (CNR), Noise Suppression Index (NSI), Edge Preserving Index (EPI), and Blurring Index (BI) are computed to quantitatively evaluate image quality. RESULTS: The results showed that the CNR, NSI, EPI, and BI of our method reached 8.953, 0.9500, 0.7230 and 0.0170, respectively. Noise and streak artifacts can be removed from lung LDCT images while keeping and retaining more details. CONCLUSIONS: Comparing with the results of other methods tested using the same dataset, this study demonstrated that our new method significantly improved quality of the lung LDCT images. Show more

Keywords: Low-dose computed tomography (LDCT), top-hat transform, anisotropic diffusion with shock filter (ADSF), spare representation, image quality improvement

DOI: 10.3233/XST-190605

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 255-270, 2020

Authors: Yi, Fang | Liu, Siling | Lei, Lei | Liu, Ousheng | Zhang, Lingling | Peng, Qian | Lu, Yanqin

Article Type: Research Article

Abstract: OBJECTIVE: To evaluate the changes of maxillary expansion and upper airway structure after microimplant assisted rapid palatal expansion (MARPE) using cone-beam computed tomography (CBCT). METHODS: This retrospective study included 19 subjects (15 females and 4 males) aged 15–29 years old (mean, 19.95±4.39 years) with maxillary transverse deficiency treated with MARPE. CBCT was performed at the initial diagnosis and 3 months after MARPE treatment. Measurements were taken to evaluate the amount of total expansion, skeletal expansion, and dental expansion at the maxillary first premolar (P1), second premolar (P2), first molar (M1), second molar (M2) regions and upper airway changes. …RESULTS: After MARPE treatment, the maxillary skeletal base expansion, skeletal expansion, alveolar expansion and dental expansion were achieved at the P1, P2, M1, M2 region. The nasopharyngeal volume significantly increased 8.48% after MARPE treatment compared with that before the treatment (P  < 0.05). The change of nasal lateral width (NLW) was also significantly different before and after MARPE (P  < 0.05). However, there were no statistically significant change in the oropharyngeal, palatopharyngeal, glossopharyngeal and airway total volume (all P  > 0.05). CONCLUSIONS: MARPE can produce more transverse bone expansion, relieve maxillary transverse deficiency and improve upper airway ventilation. Show more

Keywords: Cone-beam computed tomography (CBCT), microimplant assisted rapid palatal expansion (MARPE), bone expansion, upper airway, maxillary transverse deficiency

DOI: 10.3233/XST-190597

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 271-283, 2020

Authors: Ge, Yu-xi | Li, Jie | Zhang, Jun-qin | Duan, Shao-feng | Liu, Yan-kui | Hu, Shu-dong

Article Type: Research Article

Abstract: OBJECTIVE: To investigate the value of CT-based radiomics signature for preoperatively discriminating mucinous adenocarcinoma (MA) from nomucinous adenocarcinoma (NMA) in rectal cancer and compare with conventional CT values. METHOD: A total of 225 patients with histologically confirmed MA or NMA of rectal cancer were retrospectively enrolled. Radiomics features were computed from the entire tumor volume segmented from the post-contrast phase CT images. The maximum relevance and minimum redundancy (mRMR) and LASSO regression model were performed to select the best preforming features and build the radiomics models using a training cohort of 155 cases. Then, predictive performance of the …models was validated using a validation cohort of 70 cases and receiver operating characteristics (ROC) analysis method. Meanwhile, CT values in post- and pre-contrast phase, as well as their difference (D-values) of tumors in two cohorts were measured by two radiologists. ROC curves were also calculated to assess diagnostic efficacies. RESULTS: One hundred and sixty-three patients were confirmed by pathology as NMA and 62 cases were MA. The radiomics signature comprised 19 selected features and showed good discrimination performance in both the training and validation cohorts. The areas under ROC curves (AUC) are 0.93 (95% confidence interval [CI]: 0.89–0.98) in training cohort and 0.93 (95% CI: 0.87–0.99) in validation cohort, respectively. Three sets of CT values of MA in pre- and post-contrast phase, and their difference (D-value) (31±7.0, 51±12.6 and 20±9.3, respectively) were lower than those of NMA (37±5.6, 69±13.3 and 32±11.7, respectively). Comparing to the radiomics signature, using three sets of conventional CT values yielded relatively low diagnostic performance with AUC of 0.84 (95% CI: 0.78–0.88), 0.75 (95% CI: 0.69–0.81) and 0.78 (95% CI: 0.72–0.83), respectively. CONCLUSION: This study demonstrated that CT radiomics features could be utilized as a noninvasive biomarker to identify MA patients from NMA of rectal cancer preoperatively, which is more accurate than using the conventional CT values. Show more

Keywords: Rectal cancer, mucinous adenocarcinoma, radiomics, CT

DOI: 10.3233/XST-190614

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 285-297, 2020

Authors: Chen, Si-Ying | Wu, Wen-Fang | Di, Cong | Zhao, Xin-Xiang

Article Type: Research Article

Abstract: OBJECTIVE: To investigate the correlation between carotid artery stenosis (CAS) measured by magnetic resonance imaging (MRI) and the coronary stenosis (CS) determined by computed tomography angiography (CTA). METHODS: In this prospective study, 42 subjects diagnosed with coronary artery disease (CAD) underwent MRI and CTA examinations. The severity degree and number of CAS, the score, detection rate and type of carotid plaque, and also the severity degree and number of CS were assessed. Spearman’s rank correlation test was used to evaluate the correlation between CAS and CS. RESULTS: CS was detected in 42 (100%) subjects, while CAS …was detected in 36 (85.7%) subjects. Distribution of CAS severity grades in multiple-vessel group was significantly different from other groups, which with more moderate and severe stenosis (p  < 0.05). A positive and significant correlation between the CAS severity and CS severity (r = 0.612, p  < 0.05), and the number of involved coronary vessels (r  = 0.572, p  < 0.05) were observed, respectively. Both detection rate (r = 0.587, p  < 0.05) and score (r = 0.735, p  < 0.05) of carotid plaque showed a good correlation with the number of involved coronary vessels. After carotid MRI, 71 carotid plaques were detected in 42 subjects, with an incidence rate of 9.9% in subjects with mild CS, 18.3% in moderate CS and 71.8% in severe CS. CONCLUSION: Correlation between CAS measured by MRI and CS determined by CTA was identified in present study. These results indicated that the non-invasive CAS evaluation employing the MRI may be clinically useful for the assessment of CS. Show more

DOI: 10.3233/XST-190619

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 299-309, 2020

Authors: Duan, Hui-Hong | Gong, Jing | Sun, Xi-Wen | Nie, Sheng-Dong

Article Type: Research Article

Abstract: BACKGROUND: Automatic segmentation of pulmonary airway tree is a challenging task in many clinical applications, including developing computer-aided detection and diagnosis schemes of lung diseases. OBJECTIVE: To segment the pulmonary airway tree from the computed tomography (CT) chest images using a novel automatic method proposed in this study. METHODS: This method combines a two-pass region growing algorithm with gray-scale morphological reconstruction and leakage elimination. The first-pass region growing is implemented to obtain a rough airway tree. The second-pass region growing and gray-scale morphological reconstruction are used to detect the distal airways. Finally, leakage detection is performed …to remove leakage and refine the airway tree. RESULTS: Our methods were compared with the gold standards. Forty-five clinical CT lung image scan cases were used in the experiments. Statistics on tree division order, branch number, and airway length were adopted for evaluation. The proposed method detected up to 12 generations of bronchi. On average, 148.85 branches were extracted with a false positive rate of 0.75%. CONCLUSIONS: The results show that our method is accurate for pulmonary airway tree segmentation. The strategy of separating the leakage detection from the segmenting process is feasible and promising for ensuring a high branch detected rate with a low leakage volume. Show more

Keywords: Pulmonary airway, segmentation, region growing, morphological reconstruction, skeleton analysis

DOI: 10.3233/XST-190627

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 311-331, 2020

Authors: Zhang, Shuqing | Gu, Xiaowen | Liu, Jia | Kumar PS, Sanjeev | Fang, Xiangming | Yin, Jianbing | Jiang, Jianqin | Qian, Cheng | Hu, Xiaoyun | Cui, Lei

Article Type: Research Article

Abstract: OBJECTIVE: To investigate the measurement reproducibility of the maximum diameter on MRI routine sequence (T1 WI, T2 WI, DWI) and CT in peripheral and central lung cancer, and to provide reference standard for evaluating treatment responses for lung cancer. METHODS: 53 patients with lung cancer underwent CT and 3.0T MR scanning. The maximum diameter was measured according to the RECIST1.1 standard on images of CT (lung and enhanced mediastinal window), MRI T2 -BLADE, axial T1 -VIBE and DWIb0 , DWIb300 , DWIb800 , respectively. The reproducibility of the diameters was analyzed with intraclass correlation coefficient (ICC), and the …distribution of measurement points with the Bland-Altman method. The difference analysis was assessed by paired samples t -test and nonparametric rank sum test, P  < 0.05 is considered statistically significant. RESULTS: Reproducibility of diameters derived from routine MRI and CT was good (ICC > 0.75). For peripheral lung cancer, there was no significant difference in diameters between CT and MRI. While for central lung cancer, there was significant difference in diameters measured between using CT and each MRI sequence. However, the diameters derived from T1 -VIBE and T2 -BLADE were not significantly different from all DWI sequences. CONCLUSIONS: For peripheral lung cancer, the measurement on CT and routine MRI sequences can potentially replace each other after comprehensive consideration of examination purposes, but for central lung cancer, alternative use of CT and MRI in evaluating treatment responses for lung cancer should needs extra attention. The diameter measurement of lung cancer on DWI is consistent with that on T1 WI and T2 WI, suggesting that DWI can provide functional and morphological information. Show more

Keywords: Lung cancer, computed tomography, MRI, diameter

DOI: 10.3233/XST-190613

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 333-344, 2020

Authors: Li, Xiaohu | Li, Zhijie | Li, Jianying | Song, Jian | Yu, Yongqiang | Liu, Bin

Article Type: Research Article

Abstract: OBJECTIVE: To demonstrate the value of optimizing non-contrast head imaging tasks by using the multiple virtual monochromatic spectral imaging (VMSI) sets in dual-energy spectral computed tomography (CT) and determine the optimal energy levels for various tasks in imaging head. MATERIALS AND METHODS: This retrospective study includes 55 patients (29 women and 26 men, average age of 54.5±12.3years) who underwent non-contrast head CT in spectral imaging mode. For each patient, 21 VMSI sets from 40 to 140 keV at 5 keV intervals and 120 kVp-like image were reconstructed. Signal-to-noise ratio (SNR) for gray matter (GM) and white matter (WM), contrast-to-noise ratio (CNR) …between GM and WM, subcalvarial artifact index (SAI) and posterior fossa artifact index (PFAI) were measured by placing regions-of-interest (ROIs) in nine areas of the brain. Two radiologists subjectively rated the image quality in terms of GM-WM differentiation, beam hardening artifacts in the subcalvarial space, and posterior fossa. The overall image noise was evaluated using a 5-point Likert scale. Measurement data were then statistically analyzed. RESULTS: The optimal energy level for viewing the supratentorial brain and reducing beam hardening artifacts in the subcalvarial space and posterior fossa was 65 keV and 75 keV, respectively. All corresponding measurements at these energy levels were significantly better than those measured at other energy levels (all P  < 0.05). CONCLUSIONS: Dual-energy spectral CT imaging provides a set of virtual monochromatic spectral imaging and can be selected on-demand to optimize the imaging tasks in non-contrast head CT. VMSI reconstruction of dual-energy unenhanced head CT scans at 65–75 keV enables to maximize image quality. Show more

Keywords: Signal-to-noise ratio, computed tomography x-ray, artifact

DOI: 10.3233/XST-190617

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 345-356, 2020

Authors: Zhang, Zejian | Zhang, Yixiang | Wang, Xisheng | Fang, Liekui | Chen, Dong | Peng, Naixiong | Thakker, Parth | Wang, Qinjun | Zhang, Yuanyuan

Article Type: Research Article

Abstract: INTRODUCTION: To report the management and outcome of one case of pediatric patient sustaining high-grade blunt renal trauma. We present and discuss the clinical characteristics and radiologic features of the patient. PATIENTS AND METHODS: A 10 years old child was admitted for serious blunt renal trauma formed a huge urinoma in the right renal after injury gradually in 2018. We treated the patient with synchronous percutaneous nephrostomy drainage and retrograde ureteral catheterization. A retrospective review was performed of this case, including the clinical features, imaging studies and short-term follow-up. A literature review was also performed to highlight the …principals of diagnosis and treatment of severe blunt renal trauma in children. RESULTS: After drainage, the symptoms of abdominal distension gradually disappeared, and the physical examination shows that the abdomen gradually reduced to normal. The huge urinoma was cured by synchronous drainge. No complications occurred in short-term follow-up. COMMENTS: The choice of surgical treatment is based on the degree and location of renal trauma. Grade IV injuries are a heterogeneous group and management should be tailored to the patient, especially among pediatric patients. Persistent urinary extravasation and/or symptomatic urinoma is a common complication of high-grade renal trauma, which will be amenable to ureteral stent placement or percutaneous drainage. For huge urinoma, synchronous percutaneous nephrostomy drainage and retrograde ureteral catheterization can relieve symptoms quickly. Show more

Keywords: Renal Trauma, Grade IV laceration, Pediatric, Urinoma, Percutaneous drainage

DOI: 10.3233/XST-190611

Citation: Journal of X-Ray Science and Technology, vol. 28, no. 2, pp. 357-367, 2020