Formation of Poly(ethylene phosphates) in Polycondensation of H3PO4 with Ethylene Glycol. Kinetic and Mechanistic Study

Conditions of synthesis of poly(ethylene phosphates) in reaction of H3PO4 with HOCH2CH2OH (EG), the actual path of polycondensation, and structure of the obtained polymers (mostly oligomers) and kinetics of reaction are described. Preliminary kinetic information, based on the comparison of the MALDI-TOF-ms and 31P{1H} NMR spectra as a function of conversion is given as well. Because of the dealkylation process fragments derived from di- and triethylene glycols are also present in the repeating units. Structures of the end groups (-CH2CH2OH or -OP(O)(OH)2) depend on the starting ratio of [EG]0/[H3PO4]0, although even at the excess of EG the acidic end groups prevail because of the dealkylation process. In MALDI-TOF-ms products with Pn equal up to 21 have been observed. The average polymerization degrees (Pn) are lower and have been calculated from the proportion of the end groups.

Regional cardiac motion and strain estimation in three-dimensional echocardiography: A validation study in thick-walled univentricular phantoms

Automatic quantification of regional left ventricular deformation in volumetric ultrasound data remains challenging. Many methods have been proposed to extract myocardial motion, including techniques using block matching, phase-based correlation, differential optical flow methods, and image registration. Our lab previously presented an approach based on elastic registration of subsequent volumes using a B-spline representation of the underlying transformation field. Encouraging results were obtained for the assessment of global left ventricular function, but a thorough validation on a regional level was still lacking. For this purpose, univentricular thick-walled cardiac phantoms were deformed in an experimental setup to locally assess strain accuracy against sonomicrometry as a reference method and to assess whether regions containing stiff inclusions could be detected. Our method showed good correlations against sonomicrometry: r2 was 0.96, 0.92, and 0.84 for the radial (εRR), longitudinal (εLL), and circumferential (εCC) strain, respectively. Absolute strain errors and strain drift were low for εLL (absolute mean error: 2.42%, drift: −1.05%) and εCC (error: 1.79%, drift: −1.33%) and slightly higher for εRR (error: 3.37%, drift: 3.05%). The discriminative power of our methodology was adequate to resolve full transmural inclusions down to 17 mm in diameter, although the inclusion-to-surrounding tissue stiffness ratio was required to be at least 5:2 (absolute difference of 39.42 kPa). When the inclusion-to-surrounding tissue stiffness ratio was lowered to approximately 2:1 (absolute difference of 22.63 kPa), only larger inclusions down to 27 mm in diameter could still be identified. Radial strain was found not to be reliable in identifying dysfunctional regions.Heyde B., Cygan S., Choi H.F., Lesniak-Plewinska B., Barbosa D., Elen A., Claus P., Loeckx D., Kaluzynski K., D’hooge J., ''Regional cardiac motion and strain estimation in three-dimensional echocardiography: A validation study in thick-walled univentricular phantoms'', IEEE transactions on ultrasonics, ferroelectrics, and frequency control, vol. 59, no. 4, pp. 668-682, April 2012.status: publishe

Three-dimensional cardiac motion and strain estimation: A validation study in thick-walled univentricular phantoms

Automatic quantification of regional left ventricular function in volumetric ultrasound data remains challenging. Our lab previously presented such an approach based on elastic registration of subsequent volumes using a b-spline representation of the underlying transformation field. Good results were obtained for the assessment of global function, but a thorough validation on a regional level was still lacking. For this purpose, univentricular thick-walled cardiac phantoms were designed and mounted in an experimental setup to (i) locally assess strain accuracy against two reference methods: sonomicrometry and simulations through finite element modeling (FEM); and (ii) to assess whether regions containing stiff inclusions could be detected. Our method showed good correlations against sonomicrometry: R2 was 0.95, 0.92 and 0.84 in the radial (R), longitudinal (L) and circumferential (C) direction respectively. Furthermore, the predicted apex-base gradients by FEM were best resolved in the circumferential direction. Finally, the discriminative power of our methodology was adequate to resolve inclusions up to 17mm in diameter, although enough stiffness difference with the surrounding tissue was needed.Heyde B., Cygan S., Choi H.F., Lesniak-Plewinska B., Barbosa D., Elen A., Claus P., Loeckx D., Kaluzynski K., D'hooge J., ''Three-dimensional cardiac motion and strain estimation: a validation study in thick-walled univentricular phantoms'', IEEE international ultrasonics symposium, pp. 1534-1537, October 11-14, 2010, San Diego, California, USA.status: publishe