Penetration Coefficients of Commercial Nanolimes and a Liquid Mineral Precursor for Pore-Imitating Test Systems-Predictability of Infiltration Behavior

Nanolimes have been commercially available for over a decade as a remineralization agent for natural stone to combat deterioration. While they have been applied successfully and studied extensively, their penetration abilities in different materials have not yet been readily quantifiable in situ and in real time. Using two transparent pore-imitating test systems (acrylic glass (PMMA) and polydimethylsiloxane (PDMS)) and light microscopy, the penetration coefficients (PCs) of two nanolimes (CaLoSiL (CLS) and Nanorestore Plus (NRP)), as well as their solvents, were determined experimentally in square channels of about 100 µm diameter. Their PCs and those for a previously published glass-resin-based test system were also predicted based on measurable material parameters or literature values using the Lucas-Washburn equation. Additionally, a liquid mineral precursor (LMP) of calcium carbonate based on complex coacervation (CC) was investigated as an alternative to the solid particle dispersions of nanolime. In general, the dispersions behaved like their pure solvents. Overall, trends could be reasonably well predicted with both literature and experimentally determined properties using the Lucas-Washburn equation. In absolute terms, the prediction of observed infiltration behavior was satisfactory for alcohols and nanolimes but deviated substantially for water and the aqueous LMP. The commercially available PMMA chips and newly designed PDMS devices were mostly superior to the previously published glass-resin-based test system, except for the long-term monitoring of material deposition. Lastly, the transfer of results from these investigated systems to a different, nontransparent mineral, calcite, yielded similar PC values independently of the original data when used as the basis for the conversion (all PC types and all material/liquid combinations except aqueous solutions in PDMS devices). This knowledge can be used to improve the targeted design of tailor-made remineralization treatments for different application cases by guiding solvent choice, and to reduce destructive sampling by providing a micromodel for pretesting, if transferability to real stone samples proves demonstrable in the future.

[Arthroscopic management of tibial plateau fractures]

Since the mid 1980 s the arthroscopically and radiologically controlled management of tibial plateau fractures is an established part of arthroscopic surgery of the knee. The aim of this study is to analyse the results of this method in our patient population. Between January 1, 1994 and December 31, 1998 59 patients were operated under arthroscopic and radiologic control. Of the 59 tibial plateau fractures there were concomitant ligamentous injuries in 21 cases. In 34 cases an additional arthroscopic procedure was performed (partial meniscectomy 19 times, a meniscal repair 7 times. An arthroscopic procedure was necessary because of chondral lesions 14 times, and in 10 cases a rupture of the ACL was found, which was treated by resection). None of the 8 patients with lateral wedge fracture had a concomitant intraarticular lesion. The intraoperative use of Endobon provided good mechanical stability, but it is not always necessary. The negative aspect of Endobon, however, is the high cost. The number of complications in our series was low (3 intra- and 6 postoperative complications). The average follow-up interval was 48 months. According to the Lysholm-Score, 41 patients investigated obtained an average of 84 points. Because of its good results this procedure can be recommended when conducted by an experienced arthroscopic surgeon. However, the range of indications is limited to special tibial plateau fractures. In case of intraoperative problems or complications we recommend an early change to conventional methods of internal fixation of tibial plateau fractures.

Computer-aided detection of clustered microcalcifications in digitized mammograms

RATIONALE AND OBJECTIVES

We investigated a computer-aided detection (CAD) scheme for clustered microcalcifications in digitized mammograms.

METHODS

A multistage CAD scheme was developed and tested. To increase sensitivity, the scheme uses a Gaussian band-pass filter and nonlinear threshold. A multistage local minimum searching routine and a multilayer topographic feature analysis are used to reduce the false-positive detection rate. One hundred ten digitized mammograms were used in this preliminary test, with 55 images containing one or two verified microcalcification clusters.

RESULTS

The CAD scheme achieved 100% sensitivity and had an average false-positive detection rate of 0.18 per image.

CONCLUSION

The CAD scheme performs as well as many published schemes and has some unique advantages to further improve detection sensitivity and specificity of future CAD schemes.

Selection of processing algorithms for digital image compression: a rank-order study

RATIONALE AND OBJECTIVES

We investigated non-receiver operating characteristic (non-ROC) methods for the selection of processing algorithms for digital image compression.

METHODS

We performed a multipoint, rank-order study with 20 posteroanterior chest images, each processed using four different algorithms. Seven radiologists reviewed these alongside the digitized noncompressed image. Observers were forced to rank order the similarity and/or difference of the processed images to the nonprocessed image in each case.

RESULTS

A two-way analysis of variance of the rankings was statistically significant (p = .025), indicating that one processing scheme yielded images that were clearly perceived as the most similar to the nonprocessed images. The selected processing scheme was not the one that yielded the lowest quantitative difference from the nonprocessed images as measured by root mean square error.

CONCLUSION

Non-ROC study designs that are highly sensitive to small differences among similar images can be used to select processing algorithms.

Use of a latex cover sheath for transesophageal echocardiography (TEE) instead of regular disinfection of the echoscope?

Better visualization of cardiac structures is an advantage of transesophageal echocardiography (TEE). Because of this, the transesophageal approach is an essential window in the assessment of various cardiovascular disorders. Quick consecutive access to this instrument should not be delayed by time-consuming cleansing procedures of the probe. In this study we used a sterile latex condom in routine TEE examinations as a barrier to contamination of the echoscope, observing practical use and the incidence of perforations. Defects were detected after the procedure by visual inspection and by an airtightness test. Maneuvers or situations associated with an increased likelihood of injury were checked for. In 180 studies a total of 168 patients were consecutively examined; insertion was feasible in all but one case (99.5%). We found 8 of 181 (4.4%) sheaths defective following the procedure. Visual inspection was less sensitive (only 3 of 8) for finding defects than an airtightness test (8 times). Teeth in situ and/or a bite guard are the only sharp edges during insertion and removing the probe; these seem to be the main risk factors in latex perforation. Application of a cover sheath for each examination saves approximately two-thirds of the time otherwise necessary for a cleansing bath, and easy handling of cover sheaths for TEE make them an alternative to regular disinfection in general. For reasons of safety we recommend checking each used cover sheath after examination for holes so as not to jeopardize the following patient by the possible spread of germs from contaminated probes. Not only visual inspection but also a second method, for example, an airtightness test, is mandatory.

[Tibial intramedullary nailing without open drilling]

By means on the basis of a prospective study of 33 osteosynthesis with the unreamed tibia nail (UTN) the following conclusions were found: 1. A technical simple, intramedullary solid strength bearing device in only two diameters is available, therefore costs for stock keeping are low. Systematic interlocking of the nail is necessary. Regarding the multiplicity of indication as well as the mechanical character the UTN is close to the principle of the internal fixator. 2. As a result of its solid constitution remarkable hollow cavities do not exist, so that retention of hematoma or secretions is limited (prophylaxis of infection). 3. In case of a closed nailing procedure the less rigid fracture fixation is favourable for the biology of the bone healing (fracture hematoma, less traumatic procedure without reaming of the medullary cavity, etc.). 4. The frequently observed breakage of interlocking bolts leads spontaneously to a dynamisation favourable as to time and therefore to a better bone healing process (callus formation). 5. Time intervals of bony fractures consolidation are significantly shorter compared to the exclusive osteosynthesis with the external fixator [3]. 6. The unreamed tibia nail is an implant for both primary stabilisation of closed diaphyseal fractures of the tibia with soft tissue injury and for secondary procedure/treatment for example after external fixator osteosynthesis or initial non-operative treatment. Early change of procedure seems to be of importance.

Correlation of caffeine elimination and Child's classification in liver cirrhosis

Apparent pharmacokinetic parameters of caffeine elimination from the circulation were determined in 27 patients with histologically confirmed liver cirrhosis, 8 patients with miscellaneous liver disease, and 8 patients with other than liver disease. The usefullness of this quantitative test to assess the severity of liver cirrhosis was compared to the Child-Turcotte or Child-Pugh classification score as well as to the galactose elimination capacity of these patients. Using reversed-phase high pressure liquid chromatography caffeine, paraxanthine, theophylline, and theobromine were analysed in blood plasma collected before and after an oral dose of caffeine. Compared to apparent caffeine pharmacokinetics in patients with normal livers or miscellaneous liver disease, cirrhosis was characterized by a statistically significant reduction in apparent caffeine clearance and prolongation in half-life. The reduced apparent plasma disappearance rate of caffeine in cirrhotics was related to the retarded formation of paraxanthine which was the main metabolite of caffeine in blood plasma both in the absence or presence of liver disease. The apparent caffeine clearance in cirrhosis decreased with increasing Child-Turcotte classification score: Child's class A patients differed significantly from Child's class B or Child's class C patients, whereas the difference between Child's class B and C patients did not reach statistical significance (Wilcoxon's rank test). In addition there was a strong correlation between the Child-Pugh classification score and apparent caffeine clearance (P less than 0.001). However, no correlation existed between Child's classification and galactose elimination capacity. Our data emphasize the value of the Child-Turcotte or Child-Pugh classification in assessing the severity of liver cirrhosis in a simpler and less time-consuming way than using quantitative liver function tests.