Biomedical subjects

Stefan Adams

Publications and source records attributed to Stefan Adams.

6 recordsLinked to original sources

PubMed2006

Multi-detector CT in the evaluation of patients with recurrence of rectal cancer.

The advantages of multiplanar reconstruction in rectal cancer recurrence diagnostics using medium resolution multi-detector CT are evaluated. We included 40 patients after a rectal cancer operation in this study. During follow-up ten patients developed a recurrence. All patients received a minimum of two CT-examinations in their follow-up program. A total of 131 CT-scans were evaluated. Each examination was reviewed by two experienced radiologists in respect to recurrence. Each examination was presented in axial reconstruction with a slice thickness of 8mm with an increment of 7 mm and a slice thickness of 3 mm with an increment of 2 mm. The thin slices were used for the multi-planar reconstruction. Multi-planar reconstructions showed better results for the detection of recurrence than axial reconstruction. A reduced slice thickness did not lead to better results in axial reconstruction. Multi-planar reconstruction showed a sensitivity of 0.88, a specificity of 1.0 and an accuracy of 0.97. Our axial reconstruction results were: 0.86, 0.96, and 0.93, respectively. Sensitivity and accuracy showed a significant increase after the first and second examinations. Multi-planar reconstructions allow for better detection of rectal cancer recurrence when compared to axial reconstructions. Thinner axial slice thickness shows no diagnostic advantage.

Adult↗

PubMed2006

Diagnostic value of proton MR spectroscopy in peripheral arterial occlusive disease: a prospective evaluation.

OBJECTIVE: The objective of the present study was to determine the detectability of metabolic alterations in patients with peripheral arterial occlusive disease (PAOD) using proton MR spectroscopy (hydrogen-1 MR spectroscopy). SUBJECTS AND METHODS: Twenty-seven people were included in this study: 10 patients with PAOD and a pain-free walking distance of less than 200 m served as the patient group and 17 young healthy subjects served as a control group. Hydrogen-1 MR spectroscopy was performed on a 1.5-T scanner using an extremity coil and a point-resolved spectroscopy (PRESS) sequence (TR/TE, 1,500/30; 256 repetitions). For the patient group, a voxel was localized in the gastrocnemius muscle of the diseased leg. The data were processed using standard 1H MR spectroscopy tools. The identification of resonances detected on all MR spectra was made: intramyocellular lipids at 1.2 ppm, extramyocellular lipids at 1.6 ppm, lactate at 4.1 ppm, glucose with two main peaks at 3.4 and 3.8 ppm, choline at 3.2 ppm, and creatine at 3.0 and 3.9 ppm. To avoid operator bias, three spectral intensities were measured after correcting baseline and phase of MR spectra each time. The creatine signal was used as an internal reference; thus, all spectra were scaled relative to creatine. We compared the resultant intensity ratios between the two groups using the Mann-Whitney U test. RESULTS: The lactate-creatine quotient was higher in the patient group, with a ratio of 1.6, than in the control group, with a ratio of 0.6. The glutamate-creatine ratio was higher in the patient group than in the control group (1.3 vs 0.8, respectively). All other ratios were higher in the control group. The best ratio for differentiating between healthy subjects and patients with PAOD was the glucose-lactate ratio. The patient group had a glucose-lactate quotient of 5.4, whereas the control group had a glucose-lactate quotient of 21.5 (p = 0.001). CONCLUSION: Proton MR spectroscopy has the potential to allow identification of patients who have PAOD on the basis of altered muscle metabolism.

Adult↗

PubMed2004

Antifluorite-type lithium chromium oxide nitrides: synthesis, structure, order, and electrochemical properties.

Antifluorite-type lithium chromium oxide nitrides were prepared by solid-state reaction of Li(3)N, Li(2)O, and Cr(2)N. Depending on the reaction time and starting Li/Cr and O/Cr ratios, either an ordered or a disordered phase (or mixtures of both) is obtained. The formation of the former is favored by short reaction times and low Cr/O ratios whereas the formation of the latter is favored by higher Cr/O ratios and longer reaction times. The two phases were characterized, and the first one was confirmed to be the already reported Li(14)Cr(2)N(8)O phase, whereas the stoichiometry of the second is Li(10)CrN(4)O(2). Interestingly, even if both contain cationic vacancies in the structure, electrochemical lithium intercalation could only be achieved for Li(10)CrN(4)O(2). This phase exhibits a reversible capacity of 160 mAh/g very stable upon cycling. Bond valence and first-principles DFT calculations were carried out to understand the absence of lithium insertion in Li(14)Cr(2)N(8)O. Li-Li repulsion and destabilization of the tetrahedral CrN(4) units induced by occupation of the potential sites, as well as the absence of energetically favorable pathways for transport of the ions to these sites, are suggested to be the reasons.

Journal Article↗

PubMed2003

Mixed alkali effect in glasses.

We have applied the bond-valence technique to reverse Monte Carlo produced structural models of mixed alkali phosphate glasses in order to elucidate the mixed alkali effect (MAE) in glasses. For the first time, the MAE is reproduced and understood directly from structural models in quantitative agreement with available experimental results. The two types of alkali ions are randomly mixed and have distinctly different conduction pathways of low dimensionality. This implies that A ions tend to block the pathways for the B ions and vice versa, and this is the main reason for the MAE.

Journal Article↗

PubMed2003

PET with 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG) in patients with cancer of unknown primary (CUP): influence on patients' diagnostic and therapeutic management.

25 patients with cancer of unknown primary (CUP) were studied using PET-FDG. Whole-body-PET scans were performed based on previous morphological information. All patients underwent conventional diagnostic modalities prior to and after the PET-study. True positive results were obtained in 12/25 patients (48%) and the primary identified by PET was confirmed by further procedures. True negative results were obtained in 8/25 patients (32%) and no primary tumor was found by PET or other clinical investigations. False positive results were obtained in 5/25 patients (20%). No false negative results were obtained. In 11 patients having CT compared with PET the primary tumor was exclusively localized by PET in 8 patients (73%) and also by CT in 3 patients (27%); CT was unable to identify the tumor in 8/11 patients detected by PET. PET affected management and directed treatment in 11/25 patients (44%). The sensitivity of PET-FDG was 100%, specificity 61%. These observations demonstrate that PET-FDG is a highly sensitive method to detect CUP. Correctly classified patients in an early stage of disease may lead to benefit from a more targeted therapy with prolonged survival time. In cases of advanced disease PET might not decisively influence survival time.

Adult↗

PubMed2002

Magnetic resonance imaging of bone marrow metastasis with fluid-fluid levels from small cell neuroendocrine carcinoma of the urinary bladder.

Fluid-fluid levels have been reported as an extremely infrequent and non-specific condition in many benign and malignant bone lesions. We present the first reported MRI findings of bone marrow metastasis with fluid-fluid levels from small cell neuroendocrine carcinoma of the urinary bladder to the lumbar spine. Radiologists should be aware of the MRI appearance of these extraordinary lesions in order to provide a complete differential diagnosis and to guide clinicians in adequate treatment.

Bone Marrow Neoplasms↗