RESUMO
The collective self-organization of cells into three-dimensional structures can give rise to emergent physical properties such as fluid behavior. Here, we demonstrate that tissues growing on curved surfaces develop shapes with outer boundaries of constant mean curvature, similar to the energy minimizing forms of liquids wetting a surface. The amount of tissue formed depends on the shape of the substrate, with more tissue being deposited on highly concave surfaces, indicating a mechano-biological feedback mechanism. Inhibiting cell-contractility further revealed that active cellular forces are essential for generating sufficient surface stresses for the liquid-like behavior and growth of the tissue. This suggests that the mechanical signaling between cells and their physical environment, along with the continuous reorganization of cells and matrix is a key principle for the emergence of tissue shape.
Assuntos
Proliferação de Células , Forma Celular , Osteoblastos/citologia , Engenharia Tecidual , Animais , Técnicas de Cultura de Células , Células Cultivadas , Cinética , Camundongos , Modelos Biológicos , Tensão SuperficialRESUMO
PURPOSE: We compared the targeting accuracy and reliability of two different electromagnetic navigation systems for manually guided punctures in a phantom. MATERIALS AND METHODS: CT data sets of a gelatin filled plexiglass phantom were acquired with 1, 3, and 5âmm slice thickness. After paired-point registration of the phantom, a total of 480 navigated stereotactic needle insertions were performed manually using electromagnetic guidance with two different navigation systems (Medtronic Stealth Station: AxiEM; Philips: PercuNav). A control CT was obtained to measure the target positioning error between the planned and actual needle trajectory. RESULTS: Using the Philips PercuNav, the accomplished Euclidean distances were 4.42â±â1.33âmm, 4.26â±â1.32âmm, and 4.46â±â1.56âmm at a slice thickness of 1, 3, and 5âmm, respectively. The mean lateral positional errors were 3.84â±â1.59âmm, 3.84â±â1.43âmm, and 3.81â±â1.71âmm, respectively. Using the Medtronic Stealth Station AxiEM, the Euclidean distances were 3.86â±â2.28âmm, 3.74â±â2.1âmm, and 4.81â±â2.07âmm at a slice thickness of 1, 3, and 5âmm, respectively. The mean lateral positional errors were 3.29â±â1.52âmm, 3.16â±â1.52âmm, and 3.93â±â1.68âmm, respectively. CONCLUSION: Both electromagnetic navigation devices showed excellent results regarding puncture accuracy in a phantom model. The Medtronic Stealth Station AxiEM provided more accurate results in comparison to the Philips PercuNav for CT with 3âmm slice thickness. One potential benefit of electromagnetic navigation devices is the absence of visual contact between the instrument and the sensor system. Due to possible interference with metal objects, incorrect position sensing may occur. In contrast to the phantom study, patient movement including respiration has to be compensated for in the clinical setting. KEY POINTS: â¢âCommercially available electromagnetic navigation systems have the potential to improve the therapeutic range for CT guided percutaneous procedures by comparing the needle placement accuracy on the basis of planning CT data sets with different slice thickness. Citation Format: â¢âPutzer D, Arco D, Schamberger B etâal. Comparison of Two Electromagnetic Navigation Systems For CT-Guided Punctures: A Phantom Study. Fortschr Röntgenstr 2016; 188: 470â-â478.
Assuntos
Biópsia por Agulha/instrumentação , Ablação por Cateter/instrumentação , Fenômenos Eletromagnéticos , Biópsia Guiada por Imagem/instrumentação , Imagens de Fantasmas , Técnicas Estereotáxicas/instrumentação , Tomografia Computadorizada por Raios X/instrumentação , Conjuntos de Dados como Assunto , Precisão da Medição Dimensional , Desenho de Equipamento , Sistemas de Informação em Radiologia/instrumentação , Reprodutibilidade dos Testes , SoftwareRESUMO
Epidemiologic studies and in vitro experiments indicate that low density lipoprotein (LDL) subtypes differ concerning their atherogenic potential. Small, dense LDL are more atherogenic than large, buoyant LDL. LDL apheresis is a potent therapeutic modality to lower elevated LDL-cholesterol. It is unknown whether such therapy induces a shift in the LDL subtype distribution. In this study we evaluated the influence of LDL apheresis on the LDL subtype distribution in patients with CHD and familial hypercholesterolemia (FH, n = 22), combined hyperlipidemia (CHLP, n = 6), or Lp[a]-hyperlipoproteinemia (Lp[a]-HLP, n = 4) regularly treated by LDL apheresis (immunoadsorption (n = 14), HELP apheresis (n = 8), dextran sulfate adsorption (n = 7), cascade filtration (n = 3)). On the basis of 6 LDL subfractions (d 1.020;-1.057 g/mL) isolated by density gradient ultracentrifugation the LDL-density profile was determined in each patient before and after apheresis. There was a relative increase of LDL-subfractions 1, 2, and 3 (P < 0.01, P < 0. 05, and P < 0.01, respectively) and a concomitant decrease of LDL subfractions 5 and 6 (P < 0.05) after apheresis. Subgroup analysis indicates that the degree of the small, dense LDL reduction was much more prominent in patients with CHLP compared to patients with FH or Lp[a]-HLP, whereas the type of apheresis technique had no effect. The extent of small, dense LDL reduction correlated with the preapheresis concentrations of small, dense LDL and triglycerides but not with the extent of triglyceride reduction.We conclude that LDL apheresis not only decreases LDL mass, but also improves LDL-density profile, particularly in patients with CHLP.