Bremsstrahlung Produced by 5 keV Electrons Incident on Al2O3 and MgO Samples at Air Pressures of 30, 50, and 100 Pa.

Bremsstrahlung spectra produced by 5 keV electrons incident on Al2O3 and MgO targets at air pressures of 30, 50, and 100 Pa have been compared with results produced using pyPENELOPE, a program designed to simulate electron microscopy. The comparisons showed that the experimental results were in good agreement with the results simulated using pyPENELOPE, except near the Duane-Hunt limit, where the bremsstrahlung amplitudes were consistently greater than PENEPMA predicted. The discrepancies may be due to charging effects, which are not simulated by PENEPMA, the Monte Carlo code on which pyPENELOPE is based. If so, the phenomena could potentially impact the accuracy of energy dispersive X-ray spectrometry measurements.

Novel MRI signs of ruptured disc in the cervical spine with intraoperative comparisons.

OBJECTIVES: To evaluate the diagnostic performance of two novel MRI signs for extruded disc (ED) and uncontained ED (ruptured disc, RD) in the cervical spine using intraoperative findings as reference. METHODS: This retrospective study included patients who underwent cervical spine MRI and surgery for disc pathology with intraoperative confirmation of RD from September 1, 2016, to January 31, 2021. Two radiologists determined whether the disc was extruded or ruptured with and without the aid of two novel MRI signs suggesting RD (sign 1: blurred margin of the disc; sign 2: mushroom-shaped disc). The diagnostic performance was analyzed using surgical findings as reference. Intra- and interobserver agreements were measured for each MRI sign. RESULTS: A total of 91 patients totaling 131 discs were enrolled (mean age: 56.02 ± 12.93; range: 26-88; 62 men and 29 women), of whom 62 were surgically confirmed with RD. When the diagnosis was based exclusively on existing ED definitions, ED was diagnosed with 62.9-79.0% sensitivity and 80.2% accuracy, whereas RD was diagnosed with 35.5-45.2% sensitivity and 67.9-71.0% accuracy. However, when the two novel MRI signs were used as an aid in the diagnosis, ED was diagnosed with 95.2-96.8% sensitivity and 84.0-88.5% accuracy, while RD was diagnosed with 95.2-96.8% sensitivity and 84.0-89.3% accuracy. Intra- and interobserver agreement was substantial (k = 00.77-0.86, 0.69-0.79, respectively, p < 0.001). CONCLUSIONS: The detection of two novel MRI signs on preoperative MRI can lead to a more accurate RD diagnosis. KEY POINTS: • The diagnostic sensitivity of MRI for cervical ruptured disc is very low (about 35-45 %) using the standardized definition of lumbar disc nomenclature. • Two novel MRI signs can lead to a more accurate diagnosis of the surgically confirmed ruptured disc in the cervical spine. • These two novel MRI signs showed substantial intra-and interobserver reliabilities.

Enhancement parameters of contrast-enhanced computed tomography for pancreatic ductal adenocarcinoma: Correlation with pathologic grading.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDA) is a malignancy with a high mortality rate and short survival time. The conventional computed tomography (CT) has been worldwide used as a modality for diagnosis of PDA, as CT enhancement pattern has been thought to be related to tumor angiogenesis and pathologic grade of PDA. AIM: To evaluate the relationship between the pathologic grade of pancreatic ductal adenocarcinoma and the enhancement parameters of contrast-enhanced CT. METHODS: In this retrospective study, 42 patients (Age, mean ± SD: 62.43 ± 11.42 years) with PDA who underwent surgery after preoperative CT were selected. Two radiologists evaluated the CT images and calculated the value of attenuation at the aorta in the arterial phase and the pancreatic phase (VAarterial and VApancreatic) and of the tumor (VTarterial and VTpancreatic) by finding out four regions of interest. Ratio between the tumor and the aorta enhancement on the arterial phase and the pancreatic phase (TARarterial and TARpancreatic) was figured out through dividing VTarterial by VAarterial and VTpancreatic by VApancreatic. Tumor-to-aortic enhancement fraction (TAF) was expressed as the ratio of the difference between attenuation of the tumor on arterial and parenchymal images to that between attenuation of the aorta on arterial and pancreatic images. The Kruskal-Wallis analysis of variance and Mann-Whitney U test for statistical analysis were used. RESULTS: Forty-two PDAs (23 men and 19 women) were divided into three groups: Well-differentiated (n = 13), moderately differentiated (n = 21), and poorly differentiated (n = 8). TAF differed significantly between the three groups (P = 0.034) but TARarterial (P = 0.164) and TARpancreatic (P = 0.339) did not. The median value of TAF for poorly differentiated PDAs (0.1011; 95%CI: 0.01100-0.1796) was significantly higher than that for well-differentiated PDAs (0.1941; 95%CI: 0.1463-0.3194). CONCLUSION: Calculation of TAF might be useful in predicting the pathologic grade of PDA.