A Systematic Study of the Factors Affecting the Surface Quality of Chemically Vapor-Deposited Diamond during Chemical and Mechanical Polishing.

Diamond surfaces must be of high quality for potential use in semiconductors, optical windows, and heat conductivity applications. However, due to the material's exceptional hardness and chemical stability, it can be difficult to obtain a smooth surface on diamond. This study examines the parameters that can potentially influence the surface quality of chemically vapor-deposited (CVD) diamonds during the chemical and mechanical polishing (CMP) process. Analysis and experimental findings show that the surface quality of polished CVD diamonds is significantly influenced by the crystal structure and the growth quality of the diamond. In particular, when the surface roughness is below Ra 20 nm, the pores and grain boundaries on CVD diamond obstruct surface roughness reduction during mechanical polishing. To obtain a smooth polished surface, careful consideration of the size of diamond abrasives and polishing methods is also a prerequisite. Chemical mechanical polishing is a novel method to achieve a surface quality with roughness below Ra 3 nm, as in this method, the anisotropy of the CVD diamond allows the uneven steps to be efficiently erased. However, the chemical actions of polishing slurry should be controlled to prevent the formation of chemical etching pits.

The Application of Multiple Magnetic Resonance Scanning Techniques in Evaluating the Stability of Intracranial Aneurysms.

Purpose: To evaluate the stability of unruptured intracranial aneurysm (UIA) with high-resolution magnetic resonance imaging of the vessel wall (HR-VWI). Materials and Methods: A total of 92 UIA patients were enrolled. After MRA, HR-VWI imaging, the reconstruction of volume rendering (VR) and maximum intensity projection (MIP) were performed to observe the location and size of aneurysms, AR value (ratio of aneurysm height to aneurysmal diameter), SR value (ratio of maximum tumor depth to proximal parent artery diameter), and signal intensity were measured. Results: There were 7 aneurysms with UIA located in the anterior cerebral artery, 31 aneurysms with UIA in the middle cerebral artery, 1 aneurysm with UIA in the posterior cerebral artery, 18 aneurysms with UIA in the anterior communication, 5 aneurysms with UIA in the posterior communication, 34 aneurysms with UIA in the intracranial segment of the internal carotid artery and 3 aneurysms with UIA in the vertebral artery. Among them, 8 patients had more than two multiple aneurysms. The lesion size was 2-38mm (6.3 ± 5.09). There are 46 aneurysms with wall enhancement: the maximum SR value was 7.03 and the minimum 1.2, and the maximum AR value was 7.5 and the minimum 1.0. Fifty-five aneurysms showed no enhancement of the tumor wall. The maximum SR value was 4.55 and the minimum 0.58, and the maximum AR value was 4.0 and the minimum 0.6, respectively. Patients were divided into a stable group and an unstable group according to the aneurysm wall. The enhancement rate, SR value, and AR value in the stable aneurysm group were significantly lower than those in the unstable aneurysm group (P < 0.05). Conclusion: MRA and HR-VWI can objectively reflect the stability of aneurysms by judging the morphology, SR value, and signal enhancement of UIA, and can provide a certain basis for diagnosis and treatment, which has become routine examination.

The Role of Computed Tomography in The Diagnosis of Rare Congenital Heart Disease: Interrupted Aortic Arch.

Interrupted aortic arch (IAA) is a rare congenital anomaly of the aortic arch and an anatomical interruption of the lumen between the ascending and descending aorta. Computed tomography (CT) has become a reliable noninvasive diagnostic method for congenital IAA. The purpose of this study was to investigate the imaging features of IAA and improve the understanding and diagnosis of the disease. The imaging features and postoperative pathological data of 25 patients with IAA confirmed by dual-source computed tomography (DSCT) angiography were analyzed in this retrospective study. Among the 25 patients with IAA, 15 were type A, seven were type B, 0 were types C and D, and two were type E. The diameter of the pulmonary artery trunk in type A was larger than that in type B (P < 0.05). However, there were no significant differences between types A and B along the ascending aorta diameter, descending aorta, ascending aorta/descending aorta ratio, left pulmonary artery main trunk diameter, right pulmonary artery main trunk diameter, left pulmonary artery trunk/pulmonary artery trunk ratio, right pulmonary artery trunk/pulmonary artery trunk ratio, and left pulmonary artery trunk/right pulmonary artery trunk ratio. The imaging findings of IAA have typical and specific signs, and the types of IAA are not comprehensive. One type of patient identification can be added: Patients who are dissected between the left common carotid artery and left subclavian artery opening, and the descending aorta is circulated by the chest collaterals. Patients with a wide pulmonary artery in the IAA are usually type A patients. Patients with IAA after surgical repair require lifetime follow up, mainly to monitor left ventricular outflow tract obstruction and recurrent aortic coarctation. This study was approved by the Ethics Committee of Kunming Yan'an Hospital (Kunming City, Yunnan Province, China), and consent was waived because of the retrospective data collection.

Combined dynamic DCE-MRI and diffusion-weighted imaging to evaluate the effect of neoadjuvant chemotherapy in cervical cancer.

PURPOSE: To prospectively investigate changes in quantitative parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and the apparent diffusion coefficient (ADC) of diffusion-weighted imaging (DWI) in patients with cervical cancer before and after neoadjuvant chemotherapy (NACT). METHODS: Thirty-eight patients with cervical cancer underwent DCE-MRI and DWI 1 week before and 4 weeks after NACT. The patients were classified into 2 groups: significant reaction (sCR) group and the non-sCR group. DCE-MRI parameters and ADC values were measured and compared between the 2 groups. RESULTS: Before NACT, the mean Ktrans value was higher, but the mean Ve was lower, in the sCR group compared with the non-sCR group; these differences were statistically significant (p<0.05). After NACT, the mean Ktrans value and the delta (i.e., changed) value of Ktrans were significantly lower in the sCR group compared with the non-sCR group (p<0.05). However, the mean ADC and the delta value of the mean ADC between the 2 groups were slightly higher in the sCR group compared with the non-sCR group (p<0.05). The area under the curve of pre-mean Ktrans, DKtrans, and pre-mean Ktrans combined with post-mean ADC values were 0.801, 0.955, and 0.878, respectively (p<0.05). The optimal cutoff values for distinguishing sCR from non-sCR were pretreatment Ktrans (0.7020 min-1) and DKtrans (0.0437 min-1). CONCLUSIONS: Quantitative parameters (pre-mean Ktrans, DKtrans, and pre-mean Ktrans) combined with post-mean ADC could predict treatment efficacy more precisely. However, quantitative DCE-MRI combined with DWI could not significantly improve prognostic efficacy.