This study investigated the effectiveness of a new method for measuring the actual focal spot position of a diagnostic x-ray tube using a high-precision antiscatter grid and a digital x-ray detector in which grid magnification, which is directly related to the focal spot position, was determined from the Fourier spectrum of the acquired x-ray grid’s image. A systematic experiment was performed to demonstrate the viability of the proposed measurement method. The hardware system used in the experiment consisted of an x-ray tube run at 50 kVp and 1 mA, a flat-panel detector with a pixel size of 49.5 µm, and a high-precision carbon-interspaced grid with a strip density of 200 lines/inch. The results indicated that the focal spot of the x-ray tube (Jupiter 5000, Oxford Instruments) used in the experiment was located approximately 31.10 mm inside from the exit flange, well agreed with the nominal value of 31.05 mm, which demonstrates the viability of the proposed measurement method. Thus, the proposed method can be utilized for system’s performance optimization in many x-ray imaging applications.

Background Increased prevalence of nonalcoholic fatty liver disease (NAFLD) and inflammatory bowel disease (IBD) has been reported; however, the effects of NAFLD on the outcome of IBD remains unclear. We investigated whether the presence of NAFLD could influence the outcomes of patients with IBD. Methods We recruited 3,356 eligible patients with IBD into our study between November 2005 and November 2020. Hepatic steatosis and fibrosis were diagnosed using hepatic steatosis index (HSI) of ≥30 and fibrosis-4 (FIB-4) of ≥1.45, respectively. Primary outcome was clinical relapse, defined based on the following: IBD-related admission, surgery, or first use of corticosteroids, immunomodulators, or biologics agents for IBD. Results Prevalence of NAFLD in patients with IBD was 16.7%. Patients with hepatic steatosis and advanced fibrosis were older, had a higher body mass index, and were more likely to have diabetes (all p<0.05). Multivariate cox regression analysis revealed that hepatic steatosis was independently associated with an increased risk of relapse in patients with ulcerative colitis (UC) (hazard ratio [HR] 1.697, 95% confidence interval [CI] 1.291-2.230; p<0.001) and Crohn’s disease (CD) (HR 1.536, 95% CI 1.130-2.087; p=0.006). Advanced liver fibrosis was not associated with an increased risk of clinical relapse in patients with UC or CD (all p>0.05). Conclusion Hepatic steatosis was independently associated with increased risks of clinical relapse in patients with UC and CD, whereas fibrotic burden in the liver was not. Future studies should investigate whether the assessment and therapeutic intervention of NAFLD will improve clinical outcomes of patients with IBD.