Abstract:
Our aim was to evaluate the intrabony friction heat produced by implant drills, using different drill materials and methods of cooling. Four pilot drills and 4 form drills were used. The following combinations of drill material and cooling supply were tested: steel and external cooling; steel and internal cooling; steel coated with zirconium nitride and external cooling; and zirconium oxide and external cooling. The handpiece that supported the drill was fixed in a lifting device. Specimens of bovine ribs were fixed below the handpiece, and the drill speed was set to 1200rpm. The vertical force was adjusted to 1kg for pilot drills and 0.5kg for implant drills. Intrabony temperature during drilling was measured at depths of 4, 8, and 12mm parallel to the drill, and the depth was limited to 13mm. There were no significant differences in heat generation between the drill materials (p>.05), but the differences between groups with internal or external cooling supplies were significant (p≤.05). The method of cooling affected the development of the intrabony temperature during preparation of the site of the implant, but the drill material seemed to play no particular role.

Abstract:
The rate of microsatellite mutation is dependent upon both the allele length and the repeat motif, but the exact nature of this relationship is still unknown. We analysed data on the inheritance of human Y-chromosomal microsatellites in father-son duos, taken from 24 published reports and comprising 15,285 directly observable meioses. At the six microsatellites analysed (DYS19, DYS389I, DYS390, DYS391, DYS392 and DYS393), a total of 162 mutations were observed. For each locus, we employed a maximum likelihood approach to evaluate one of several single-step mutation models on the basis of the data. For five of the six loci considered, a novel logistic mutation model was found to provide the best fit according to Akaike's Information Criterion. This implies that the mutation probability at the loci increases (non-linearly) with allele length at a rate that differs between upward and downward mutations. For DYS392, the best fit was provided by a linear model in which upward and downward mutation probabilities increase equally with allele length. This is the first study to empirically compare different microsatellite mutation models in a locus-specific fashion.

Abstract:
The stepwise mutation model (SMM) is a simple, widely used model to describe the evolutionary behaviour of microsatellites. We apply a Markov chain description of the SMM and derive the marginal and joint properties of this process. In addition to the standard SMM, we also consider the normalised allele process. In contrast to the standard process, the normalised process converges to a stationary distribution. We show that the marginal stationary distribution is unimodal. The standard and normalised processes capture the global and the local behaviour of the SMM, respectively.

Abstract:
Conventional histological examination of NSLNs fails to detect lymphatic spread in penile cancer. Step-section technique at 3 section levels, rather than immunohistochemistry, helps to safely detect minimal metastatic disease. The prognostic relevance is still unclear and has to be investigated in larger cohort studies.

Abstract:
PURPOSE: Quantification of tumour burden in oncology requires accurate and reproducible image evaluation. The current standard is one-dimensional measurement (e.g. RECIST) with inherent disadvantages. Volumetric analysis is discussed as an alternative for therapy monitoring of lung and liver metastases. The aim of this study was to investigate the accuracy of semi-automated volumetric analysis of artificial lymph node metastases in a phantom study. MATERIALS AND METHODS: Fifty artificial lymph nodes were produced in a size range from 10 to 55mm; some of them enhanced using iodine contrast media. All nodules were placed in an artificial chest phantom (artiCHEST(®)) within different surrounding tissues. MDCT was performed using different collimations (1-5mm) at varying reconstruction kernels (B20f, B40f, B60f). Volume and RECIST measurements were performed using Oncology Software (Siemens Healthcare, Forchheim, Germany) and were compared to reference volume and diameter by calculating absolute percentage errors. RESULTS: The software performance allowed a robust volumetric analysis in a phantom setting. Unsatisfying segmentation results were frequently found for native nodules within surrounding muscle. The absolute percentage error (APE) for volumetric analysis varied between 0.01 and 225%. No significant differences were seen between different reconstruction kernels. The most unsatisfactory segmentation results occurred in higher slice thickness (4 and 5mm). Contrast enhanced lymph nodes showed better segmentation results by trend. CONCLUSION: The semi-automated 3D-volumetric analysis software tool allows a reliable and convenient segmentation of artificial lymph nodes in a phantom setting. Lymph nodes adjacent to tissue of similar density cause segmentation problems. For volumetric analysis of lymph node metastases in clinical routine a slice thickness of ≤3mm and a medium soft reconstruction kernel (e.g. B40f for Siemens scan systems) may be a suitable compromise for semi-automated volumetric analysis.

Abstract:
PURPOSE: To compare the reproducibility (r) of CT value measurement of pulmonary nodules using volumetry software (LungCare, LC) and manual ROIs (mROI). MATERIALS AND METHODS: 54 artificial nodules in a chest phantom were scanned three times with CT. CT values were measured with LC and mROI. The intrascan-r was assessed with three measurements in the first scan, and the interscan-r with measurements in three consecutive scans (one observer). Intrascan-r und interobserver-r (two obs.) were assessed in the first scan and in contrast-enhanced CT of 51 nodules from 15 patients (kernels b50f and b80f). Intrascan-r and interscan-r were described as the mean range and interobserver-r as the mean difference of CT values. The significance of differences was tested using t-test and sign test. RESULTS: Reproducibility was significantly higher for volumetry-based measurements in both artificial and patient nodules (range 0.11 vs. 6.16 HU for intrascan-r, 2.22 vs. 7.03 HU for interscan-r, difference 0.11 vs. 18.42 HU for interobserver-r; patients: 1.78 vs. 13.19 HU (b50f-Kernel) and 1.88 vs. 27.4 HU (b80f-Kernel) for intrascan-r, 3.71 vs. 22.43 HU for interobserver-r). Absolute CT values differed significantly between convolution kernels (pat./mROI: 29.3 [b50f] and 151.9 HU [b80f] pat./LC: 5 [b50f] and 147 HU [b80f]). CONCLUSION: The reproducibility of volumetry-based measurements of CT values in pulmonary nodules is significantly higher and should therefore be recommended, e. g. in dynamic chest CT protocols. Reproducibility does not depend on absolute CT values.

Abstract:
The primary objective of this study was to evaluate, if in multidetector computed tomography (MDCT) of the wrist a good image quality can be maintained while radiation dose is substantially reduced. In a second approach one solely parameter change that allows for the best trade-off between dose reduction and image quality should be identified. Twenty wrist specimens were examined with a 16-slice MDCT in different parameter combinations: 120 and 100kV, 100, 70 and 40electronicmAs, pitch factor 0.9 and 1.5. Images were reconstructed in four standard planes (slice thickness 1.0mm, increment 0.5mm, hard kernel) resulting into a total number of 960 images. Two observers evaluated image quality in a blinded and randomized consensus scheme. Detail quality of corticalis, spongiosa, articular surface and soft tissues was graded according to a four-point scale (1=excellent, 2=good, 3=sufficient, and 4=poor). The scan protocol with the best trade-off between radiation exposure and image quality had a parameter constellation of 100kV, 70electronicmAs (78effectivemAs) and a pitch of 0.9 (DLP 63mGycm). This represented a dose reduction of 55%. A solely decrease of voltage lead to a dose reduction of 36% without any loss of image quality. An increase of the pitch factor to 1.5 and a decrease from 70 to 40mAs caused the most distinct impairment of image quality. In MDCT of the wrist good image quality could be maintained while radiation dose was considerably reduced. A reduction of voltage offers the best result for a solely parameter change.