[Small animal MRI: clinical MRI as an interface to basic biomedical research]. / Experimentelle Kleintier-MRT: Klinische MRT-Systeme als Schnittstelle zur biomedizinischen Grundlagenforschung.

The demand for highly resolved small animal MRI for the purpose of biomedical research has increased constantly. Dedicated small animal MRI scanners working at ultra high field strengths from 4.7 to 7.0 T and even above are MRI at its best. However, using high resolution RF coils in clinical scanners up to 3.0 T, small animal MRI can achieve highly resolved images showing excellent tissue contrast. In fact, in abundant experimental studies, clinical MRI is used for small animal imaging. Mostly clinical RF coils in the single-loop design are applied. In addition, custom-built RF coils and even gradient inserts are used in a clinical scanner. For the reduction of moving artifacts, special MRI-compatible animal ECG und respiration devices are available. In conclusion, clinical devices offer broad availability, are less expense in combination with good imaging performance and provide a translational nature of imaging results.

Incidental detection of breast cancer by 68Ga-DOTATOC-PET/CT in women suffering from neuroendocrine tumours.

AIM: Somatostatin receptor (sstr) imaging using 68Ga-DOTATOC-PET/CT in neuroendocrine tumors (NET) is promising, suggesting a more sensitive detection of lesions with a low sstr-expression. This is also important for other sstr positive tumors, especially breast cancer whose incidence and age-range is similar to that of NET. PATIENTS, METHODS: The PET/CT data of 33 consecutive women with NET (age: 33-78 years, mean 59) who underwent whole-body staging with 68Ga-DOTATOC was retrospectively analyzed for breast lesions. The data was read separately, side-by-side and as fused images. Focal tracer uptake in the breast was semiquantitatively analyzed by comparing the lesional SUVmax to normal breast tissue using Wilcoxon's rank sum test. Breast cancer lesions were compared visually to concomitant NET-lesions. RESULTS: In six of 33 patients (18%) breast lesions were observed on the CT-scans and classified in four patients (12%) as suspicious. The same lesions also showed a pathological tracer uptake on the corresponding PET-scan, visually and semiquantitatively (p<0.01). Histological reevaluation of the suspicious lesions revealed two patients with NET metastases. Two patients had primary breast cancer with lower tracer uptake than concomitant abdominal NET-lesions. Breast cancer diagnosis resulted in a change of the therapeutic regimen. CONCLUSION: 68Ga-DOTATOC-PET/CT not only improves the staging of NET-patients, but also increases the chance to detect sstr-positive breast cancer. Although these lesions may show a lower tracer uptake than NET, they must not be overlooked or misinterpreted as metastases. Further imaging and clarification by histopathology is warranted, as the confirmation of a secondary malignoma has great impact on further therapeutic proceedings.

Tracking of primary human hepatocytes with clinical MRI: initial results with Tat-peptide modified superparamagnetic iron oxide particles.

The transplantation of primary human hepatocytes is a promising approach in the treatment of specific liver diseases. However, little is known about the fate of the cells following application. Magnetic resonance imaging (MRI) could enable real-time tracking and long-term detection of transplanted hepatocytes. The use of superparamagnetic iron oxide particles as cellular contrast agents should allow for the non-invasive detection of labelled cells on high-resolution magnetic resonance images. Experiments were performed on primary human hepatocytes to transfer the method of detecting labelled cells via clinical MRI into human hepatocyte transplantation. For labelling, Tat-peptide modified nano-sized superparamagnetic MagForce particles were used. Cells were investigated via a clinical MR scanner at 3.0 Tesla and the particle uptake within single hepatocytes was estimated using microscopic examinations. The labelled primary human hepatocytes were clearly detectable by MRI, proving the feasibility of this new concept. Therefore, this method is a useful tool to investigate the effects of human hepatocyte transplantation and to improve safety aspects of this method.

Impact of image fusion and attenuation correction by SPECT-CT on the scintigraphic detection of parathyroid adenomas.

AIM: In addition to planar parathyroid scintigraphy, SPECT and image fusion with CT/MR improve adenoma detection in primary hyperparathyroidism (pHPT). This study evaluated the use of a hybrid SPECT-CT device concerning image fusion and attenuation correction (AC). PATIENTS, METHODS: The data of 26 patients with pHPT, preoperatively examined by (99m)Tc-sestamibi dual-phase scintigraphy plus SPECT-CT (low-dose CT), was retrospectively evaluated by two observers in a consensus reading. The images of planar scintigraphy, non-attenuation corrected SPECT (SPECT(NAC)), attenuation corrected SPECT (SPECT(AC)) and SPECT(AC)-CT were interpreted and compared to the results of surgery. The effect of AC on focus intensity was semiquantified by determination of the tumor-to-background (TB) ratio for SPECT(AC) and SPECT(NAC). Finally, the TB(AC)/TB(NAC)-ratio was calculated for each focus and correlated to the distance of a focus from the body surface. RESULTS: 20/26 (77%) patients were positive in planar scintigraphy. One focus was detected by SPECT only. AC of SPECT-data increased image contrast but had no impact on the detection rate. Additional SPECT(AC)-CT image fusion facilitated the localization of three mediastinal foci. In the semiquantitative analysis an increase in TB after AC was observed, although there was no strong correlation between depth of the focus (16-60 mm) and the TB(AC)/TB(NAC)-ratio (r = 0.213, p = 0.353). CONCLUSION: The detection rate of planar scintigraphy is only slightly improved by SPECT imaging. Due to the low spatial resolution of the CT component, the benefit of image fusion is limited to mediastinal foci. However, as TB and image contrast is measurably improved after AC there is a potential to improve the sensitivity of parathyroid SPECT.

Baseline levels of selected trace elements in Colorado oil shale region animals.

Baseline levels of boron, fluorine, molybdenum, and copper are described for 18 mule deer (Odocoileus hemionus) and for 45 composite samples of deer mice (Peromyscus maniculatus) from the Piceance Creek Basin, Rio Blanco County, Colorado. These data were collected before oil shale mining took place, and can be used to compare with levels found after mining is initiated. The data can thus be used to monitor changes in levels in animal tissues and as a basis for mitigating possible harmful effects due to the mining. Mean ppm (+/- S.D.) dry basis of each element is presented for selected tissues of each species. Results are also presented by habitat type for deer mice and by age for mule deer. Significant differences (P < 0.05) in molybdenum levels in deer mice were found between habitats. Significant differences (P < 0.05) were found between fawns and adult mule deer for boron levels, but not for the other elements. A need to standardize bone selection for analysis of fluorine was indicated. Kidneys appeared to be the organ of choice for baseline sampling of molybdenum and copper, and livers may be the organ of choice when toxic levels are suspected.

Postinterventional MRI findings following MRI-guided laser ablation of osteoid osteoma.

OBJECTIVE: To evaluate postinterventional magnetic resonance imaging (MRI) characteristics following MRI-guided laser ablation of osteoid osteoma (OO). MATERIALS AND METHODS: 35 patients treated with MRI-guided laser ablation underwent follow-up MRI immediately after the procedure, after 3, 6, 12, 24, 36, and up to 48 months. The imaging protocol included multiplanar fat-saturated T2w TSE, unenhanced and contrast-enhanced T1w SE, and subtraction images. MR images were reviewed regarding the appearance and size of treated areas, and presence of periablation bone and soft tissue changes. Imaging was correlated with clinical status. RESULTS: Mean follow-up time was 13.6 months. 28/35 patients (80%) showed a postinterventional "target-sign" appearance consisting of a fibrovascular rim zone and a necrotic core area. After an initial increase in total lesion diameter after 3 months, a subsequent progressive inward remodeling process of the zonal compartments was observed for up to 24 months. Periablation bone and soft tissue changes showed a constant decrease over time. MR findings correlated well with the clinical status. Clinical success was achieved in 32/35 (91%). CONCLUSIONS: Evaluation of long-term follow-up MRI after laser ablation of OO identified typical postinterventional changes and thus may contribute to the interpretation of therapeutic success and residual or recurrent OO in suspected cases.

Morphological analysis and differentiation of benign cystic neoplasms of the pancreas using computed tomography and magnetic resonance imaging.

PURPOSE: To evaluate morphologic characteristics and establish a standardized diagnostic algorithm to differentiate benign cystic pancreatic tumors (CPTs) in non-pancreatitis patients using multidetector computed tomography (CT) and magnetic resonance imaging (MRI). MATERIALS AND METHODS: Patients with histopathologically proven CPTs who had undergone MRI and/or CT and subsequent tumor resection in our institution were retrospectively identified. Images were analyzed for morphology and enhancement patterns by three independent blinded observers. Preoperative image findings were correlated with histopathological results. Based on the evaluated morphologic parameters, a standardized diagnostic algorithm was designed to help characterize the lesions. RESULTS: A total of 62 consecutive patients with 64 CPTs were identified from the surgical database (21 intraductal papillary mucinous neoplasms; 10 mucinous cystic neoplasms; 12 serous microcystic adenomas; 3 serous oligocystic adenomas; 6 solid pseudopapillary tumors; 12 neuroendocrine neoplasms). The overall averaged accuracy for the 3 observers was 89.9 % for CT and 93.1 % for MRI with increasing overall accuracy in relation to the experience of the observer (88.2 %, 91.5 %, and 93.8 %, respectively). Overall, the generalized kappa value was 0.69 (CT, 0.64; MRI, 0.76); p < 0.001). The accuracy of the standardized diagnostic algorithm was 91.1 %. CONCLUSION: It is possible to characterize benign CPTs with MRI and CT, while MRI appears to be superior to CT. Diagnostic accuracy depends on the observer's experience. The standardized algorithm can aid in the differential diagnosis but still needs to be tested in other patient populations.

Volume measurement of liver metastases using multidetector computed tomography: comparison of lesion diameter and volume segmentation - a phantom study.

PURPOSE: To compare lesion volume determination by applying diameter measurement and three different segmentation algorithms at different slice thicknesses reconstructed from computed tomography (CT) of a phantom model for hepatic colorectal metastases. MATERIALS AND METHODS: Based on CT attenuation measurements obtained retrospectively from 20 patients with colorectal liver metastases, a phantom model was designed with a sponge soaked with a dilution of contrast agent and 6 embedded polyamide spheres (diameter, 8 - 30 mm) to simulate the contrast behavior of liver metastases. CT scans were obtained and reconstructed at different slice thicknesses (0.625/1.25/2.5/3.75 mm; increment, 1). One observer performed software-aided volume determination using the maximum diameter, manual segmentation, seed point method, and threshold method six times for each lesion in a randomized order. Statistical analysis revealed the absolute and relative differences from the actual lesion volumes and the intraobserver differences as well as the influence of slice thickness for each method. RESULTS: The mean relative differences of the seed point method (1.2 - 5.9%) and manual segmentation (2.6 - 4.9%) were significantly lower than the threshold method (5.4 - 12.8%) and diameter measurement (12.3 - 18.5%; p < 0.01). Volume determination by manual segmentation and the seed point method benefited from the use of thin-slice CT datasets. The intraobserver variation was lowest when using the manual segmentation (1.5 - 3.3%) and the seed point method (2.2 - 3.9%; p < 0.001). CONCLUSION: Manual segmentation and the seed point method for thin CT slices were the methods with the lowest volume differences and intraobserver variation.

Phosphate ester cleavage in ribose-5-phosphate induced by OH radicals in deoxygenated aqueous solution. The effect of Fe(II) and Fe(III) ions.

The reaction of OH radicals and H atoms with ribose-5-phosphate (10(-2) M) in deoxygenated aqueous solution at room temperature (dose-rate 2-1 X 10(17) eV/ml-min, dose 5 X 10(18)-15 X 10(18) eV/ml) leads to the following dephosphorylation products (G-values): ribo-pentodialdose 1 (0-2), 2-hydroxy-4-oxoglutaraldehyde 2 (0-06), 5-deoxy-erythro-pentos-4-ulose 3 (0-1) and 3-oxoglutaraldehyde 4 (0-06). In addition, some minor phosphate free products (total G=0-09) are formed. G(inorganic phosphate) =1-3 and G(H2O2)=0-3. On the addition of 10(-3) M (Fe(III) ions, G (1) and G (3) increase to 0-6 and 0-4 respectively. In the presence of 10(-3) M Fe(II), G(1) and G(3) change to 0-4 and 0-8, respectively. The other dephosphorylation products are suppressed by the iron ions. G(1) also increases on the addition of increasing amounts of H2O2. Each product can be assigned a precursor radical formed by hydrogen abstraction from C-5, C-4 or C-3 of the ribose-5-phosphate molecule. Products 1 and 2 are formed by oxydative dephosphorylation of an alpha-phospho radical with preceeding H2O elimination for product 2. Elimination of H3PO4 from a beta-phospho radical leads to product 3; product 4 is formed by elimination of two molecules of H2O from its precursor radical and hydrolytic cleavage of an enol phosphate bond. Deuterium-labelling experiments and the effects of the iron ions and of H2O2 support the mechanisms proposed. The importance of the dephosphorylation mechanisms for the formation of strand breaks in DNA is discussed with special reference to the effects of the radiosensitizers.