Biomedical subjects

Andreas Kopp

Publications and source records attributed to Andreas Kopp.

3 recordsLinked to original sources

PubMed2005

First performance evaluation of a dual-source CT (DSCT) system.

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

Coronary Angiography↗

PubMed2004

Clinical evaluation of a computer simulated prediction model of contrast enhancement of the liver in spiral CT.

OBJECTIVE: A software program was developed simulating a compartmental model of blood circulation based on differential equations. The aim of this study was to compare software-simulated levels of hepatic enhancement with the true values in patients and to test how many patients reach the simulated hepatic enhancement level. METHODS: As software program the CT application software carebolus 2 (Siemens, Forchheim, Germany) was used. Hepatic contrast-enhancement curves were simulated prior to CT examinations to evaluate a patient specific time delay after contrast application. At the time delay, when the simulation curve showed an enhancement threshold of 40 Hounsfield Units (HU), the CT spiral scan was started applying 120 ml contrast media with 2 ml/s. The simulated curves were compared with the empiric curves of each patient. RESULTS: 25 of 28 patients (89%) achieved 40 HU. The mean enhancement of empiric patients curves was 46.32 +/- 11.9 HU, the mean simulated enhancement was 46.62 +/- 4.3 HU S.D. (P= 0.48). 4.4 values per patient liver could be compared with the simulation curve (122 points for 28 patients): 50% of the patient curves were within a range of 5 HU compared with the simulation curve. CONCLUSION: Software simulation of contrast enhancement curves of the liver is a feasible and valuable method to predict individual liver enhancement curves. Improvements concerning the integration of cardiovascular parameters and preexisting liver parenchymal diseases into the simulation software have to be arranged.

Adult↗

PubMedDate not supplied

Effects of tamoxifen on transcriptional level of transforming growth factor beta (TGF-beta) isoforms 1 and 2 in tumor tissue during primary treatment of patients with breast cancer.

Tamoxifen action in breast cancer is believed to be mediated in part by regulation of transforming growth factor beta (TGF-beta) isoforms in tumor tissue. However, the pattern of this regulation and its relation ship to clinical data are not yet clearly understood. Tumor tissue was derived from 10 patients with breast cancer before and following primary treatment with tamoxifen over a period of 1-12 days, preceding tumor ectomy. Each tissue sample was processed for semiquantitative assessment of the mRNA expression levels of the TGF-beta isoforms 1 and 2 using competitive RT-PCR. The results of mRNA quantification were then related to the estrogen receptor-alpha (ER-alpha) and progesterone receptor (PR) status of the tumors as well as to the clinical course during the first 5-6 postoperative years in patients who additionally received adjuvant tamoxifen therapy. TGF-beta 1 mRNA and TGF-beta 2 mRNA expression was detectable in all examined samples. During treatment with tamoxifen, the TGF-beta 2 mRNA level changed in 8 cases, increasing seven times and decreasing once, whereas the TGF-beta 1 mRNA level changed in only two cases, increasing once and decreasing once. Our data do not provide evidence of a strong correlation between the occurrence of tamoxifen-related induction of TGF-beta 2 mRNA expression and the ER-alpha or PR status. The prediction sensitivity of the response to adjuvant therapy, to which relapse-free survival during post-operative follow-up over 5-6 years was attributed, increased when the tamoxifen-related up-regulation of the TGF-beta 2 mRNA level was considered to predict response, in addition to the ER-alpha- and/or PR-rich receptor status. We conclude that tamoxifen predominantly induces an up-regulation of TFG-beta 2 expression on the transcriptional level in breast cancer, which may predict clinical response independently of the ER-alpha/PR status in some cases.

Antineoplastic Agents, Hormonal↗