Absolute quantification of PET brain imaging requires the measurement of an arterial input function (AIF), typically obtained invasively via an arterial cannulation. We present an approach to automatically calculate an image-derived input function (IDIF) and cerebral metabolic rates of glucose (CMRGlc) from the [18F]FDG PET data using an integrated PET/MRI system. Ten healthy controls underwent test-retest dynamic [18F]FDG-PET/MRI examinations. The imaging protocol consisted of a 60-min PET list-mode acquisition together with a time-of-flight MR angiography scan for segmenting the carotid arteries and intermittent MR navigators to monitor subject movement. AIFs were collected as the reference standard. Attenuation correction was performed using a separate low-dose CT scan. Assessment of the percentage difference between area-under-the-curve of IDIF and AIF yielded values within ±5%. Similar test-retest variability was seen between AIFs (9 ± 8) % and the IDIFs (9 ± 7) %. Absolute percentage difference between CMRGlc values obtained from AIF and IDIF across all examinations and selected brain regions was 3.2% (interquartile range: (2.4-4.3) %, maximum < 10%). High test-retest intravariability was observed between CMRGlc values obtained from AIF (14%) and IDIF (17%). The proposed approach provides an IDIF, which can be effectively used in lieu of AIF.
The aim of this study was to evaluate whether coating titanium discs with selenium in the form of sodium selenite decreased bacterial adhesion of Staphylococcus aureus and Staph. epidermidis and impeded osteoblastic cell growth. In order to evaluate bacterial adhesion, sterile titanium discs were coated with increasing concentrations of selenium and incubated with bacterial solutions of Staph. aureus (ATCC 29213) and Staph. epidermidis (DSM 3269) and stained with Safranin-O. The effect of selenium on osteoblastic cell growth was also observed. The adherence of MG-63 cells on the coated discs was detected by staining with Safranin-O. The proportion of covered area was calculated with imaging software. The tested Staph. aureus strain showed a significantly reduced attachment on titanium discs with 0.5% (p = 0.011) and 0.2% (p = 0.02) selenium coating. Our test strain from Staph. epidermidis showed a highly significant reduction in bacterial adherence on discs coated with 0.5% (p = 0.0099) and 0.2% (p = 0.002) selenium solution. There was no inhibitory effect of the selenium coating on the osteoblastic cell growth. Selenium coating is a promising method to reduce bacterial attachment on prosthetic material.
s u m m a r yObjective: Cartilage restoration in joints with an early stage of osteoarthritis (OA) is an important clinical challenge. In this study, a compartmentalized, early-stage OA was generated surgically in sheep stifle joints, and this model was used to evaluate a matrix-associated cell transplantation approach for cartilage repair. Method: Eighteen sheep were operated twice. During the first operation, a unicompartmental OA in a stable joint was induced by creating a critical-size defect. The second operation served as a regeneration procedure. The eighteen sheep were divided into three groups. One group was treated with spongialization (SPONGIO), while the two others had spongialization followed by implantation of a hyaluronan matrix with (MACT) or without chondrocytes (MATRIX). The follow-up took place 4 months after the second operation. Gross Assessment of Joint Changes score and Brittberg score were used for the macroscopic evaluation, Mankin score, O'Driscoll score, and immunohistochemistry for collagen type I and type II for histological evaluation. Results: The MACT group achieved significantly better results in both macroscopic and histological examinations. In the regeneration area, a Mankin score of 7.88 (6.20; 9.55) [mean (upper 95% confidence interval; lower 95% confidence interval)] was reached in the MACT group, 10.38 (8.03; 12.72) in the MATRIX group, and 10.33 (8.80; 11.87) in the SPONGIO group. The O'Driscoll score revealed a highly significant difference in the degree of defect repair: 15.92 (14.58; 17.25) for the MACT group compared to the two other groups [5.04 (1.21; 8.87) MATRIX and 6.58 (5.17; 8.00) SPONGIO; P < 0.0001]. Conclusion: This study demonstrates promising results toward the development of a biological regeneration technique for early-stage OA.
Background One of the most commonly identified pathogens responsible for orthopaedic implant infection is Staphylococcus epidermidis, which can form biofilms on surfaces. Currently, orthopaedic implants made of various surface materials are available, each with features influencing osseointegration, biocompatibility, and adherence of bacteria to the surface, which is the first step in biofilm formation. The aim of this experimental study was to investigate the effect of a high tribologic-resistant 2.5-µm zirconium nitride top coat on an antiallergic multilayer ceramic-covered cobalt-chromium-molybdenum surface on the formation of S. epidermidis biofilm compared with other commonly used smooth and rough orthopaedic implant surface materials. Questions/purposes (1) When evaluating the surfaces of a cobalt-chromium-molybdenum (CoCrMo) alloy with a zirconium (Zr) nitride coating, a CoCrMo alloy without a coating, titanium alloy, a titanium alloy with a corundum-blasted rough surface, and stainless steel with a corundum-blasted rough surface, does a Zr coating reduce the number of colony-forming units of S. epidermidis in an in vitro setting? (2) Is there quantitatively less biofilm surface area on Zr-coated surfaces than on the other surfaces tested in this in vitro model? Methods To determine bacterial adhesion, five different experimental implant surface discs were incubated separately with one of 31 different S. epidermidis strains each and subsequently sonicated. Twenty test strains were obtained from orthopaedic patients undergoing emergency hip prosthesis surgeries or revision of implant infection and 10 further strains were obtained from the skin of healthy individuals. Additionally, one reference strain, S. epidermidis DSM 3269, was tested. After serial dilutions, the number of bacteria was counted and expressed as colony-forming units (CFUs)/mL. For biofilm detection, discs were stained with 0.1% Safranin-O for 15 minutes, photographed, and analyzed with computer imaging software. Results The lowest bacterial count was found in the CoCrMo + Zr surface disc (6.6 x 104 CFU/mL ± 4.6 x 104 SD) followed by the CoCrMo surface (1.1 x 105 CFU/mL ± 1.9 x 105 SD), the titanium surface (1.36 x 105 CFU/mL ± 1.8 x 105 SD), the rough stainless steel surface (2.65 x 105 CFU/mL ± 3.8 x 105 SD), and the rough titanium surface (2.1 x 105 CFU/mL ± 3.0 x 105 SD). The mean CFU count was lower for CoCrMo + Zr discs compared with the rough stainless steel surface (mean difference: 2.0 x 105, p = 0.021), the rough titanium alloy surface (mean difference: 1.4 x 105, p = 0.002), and the smooth titanium surface (mean difference: 7.0 x 104, p = 0.016). The results of biofilm formation quantification show that the mean covered area of the surface of the CoCrMo + Zr discs was 19% (± 16 SD), which was lower than CoCrMo surfaces (35% ± 23 SD), titanium alloy surface (46% ± 20 SD), rough titanium alloy surface (66% ± 23 SD), and rough stainless steel surface (58% ± 18 SD). Conclusions These results demonstrate that a multilayer, ceramic-covered, CoCrMo surface with a 2.5-µm zirconium nitride top coat showed less S. epidermidis biofilm formation compared with other surface materials used for orthopaedic implants. Clinical Relevance CoCrMo with a 2.5-µm zirconium nitride top coat seems to be a promising surface modification technology able to reduce bacterial attachment on the surface of an implant and, hence, may further prevent implant infection with S. epidermidis biofilm formation.
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