Coronary stent imaging in photon counting computed Tomography: Optimization of reconstruction kernels in a phantom.

PURPOSE: Imaging stents and in-stent stenosis remains a challenge in coronary computed tomography angiography (CCTA). In comparison to conventional Computed Tomography, Photon Counting CT (PCCT) provides decisive clinical advantages, among other things by providing low dose ultra-high resolution imaging of coronary arteries. This work investigates the image quality in CCTA using clinically established kernels and those optimized for the imaging of cardiac stents in PCCT, both for in-vitro stent imaging in 400 µm standard resolution mode (SRM) and 200 µm Ultra High Resolution Mode (UHR). METHODS: Based on experimental scans, vascular reconstruction kernels (Bv56, Bv64, Bv72) were optimized. In an established phantom, 10 different coronary stents with 3 mm diameter were scanned in the first clinically available PCCT. Scans were reconstructed with clinically established and optimized kernels. Four readers measured visible stent lumen, performed ROI-based density measurements and rated image quality. RESULTS: Regarding the visible stent lumen, UHR is significantly superior to SRM (p < 0.001). In all levels, the optimized kernels are superior to the clinically established kernels (p < 0.001). One optimized kernel showed a significant reduction of noise compared to the clinically established kernels. Overall image quality is improved with optimized kernels. CONCLUSIONS: In a phantom study PCCT UHR with optimized kernels for stent imaging significantly improves the ability to assess the in-stent lumen of small cardiac stents. We recommend using UHR with an optimized sharp vascular reconstruction kernel (Bv72uo) for imaging of cardiac stent.

[Diagnostic and prognostic significance of α-fetoprotein in hepatocellular carcinoma]. / Diagnostische und prognostische Bedeutung des α-Feto-Proteins beim hepatozellulären Karzinom.

BACKGROUND: Hepatocellular carcinoma (HCC) is an aggressive tumor with a growing socioeconomic burden. International guidelines do not predominantly recommend the pretherapeutic determination of the alpha-fetoprotein (AFP) concentration. Regarding the prognostic value of AFP, the European study data are not sufficiently meaningful. OBJECTIVE: This study aimed to demonstrate possible aspects of the AFP level and to investigate the prognostic value of AFP levels as well as to provide impetus for future prospective studies. MATERIAL AND METHODS: At the time of data retrieval the prospective liver databank showed 1382 entries. All patients with a histologically confirmed HCC were included resulting in 92 final entries. For these patients, information on T, N, M and G stages, R status as well as sex, age and etiology of the HCC were available. For data analysis the patient population was divided into six groups based on three cut-off values. Furthermore, a survival analysis was performed using Kaplan-Meier and a multifactorial analysis of the influencing factors regarding outcome. RESULTS: The AFP serum level showed a statistically significant correlation with the tumor diameter (T1/T2 vs. T3/T4) and grading (G1/G2 vs. G3/G4). The survival prognosis was significantly lower in patients with higher AFP values (p < 0.05). The median survival time for patients with AFP levels >8 µg/l was 35 months, with AFP levels >200 µg/l or >400 µg/l showed a reduced median survival of 15 months and 11 months, respectively. High AFP levels were a significant influencing factor for the outcome independent of the T stage, age and R status of patients in comparison to low AFP levels. CONCLUSION: Taking the present results into consideration, the AFP level can have a therapeutic usefulness. Therapeutic consequences could be derived from the height of the measured AFP concentration, with respect to the treatment strategy. Therefore, preoperative and postoperative determination of the AFP serum level is recommended in all HCC patients.