MasterOnline Periodontology and Implant Therapy-revisited after seven years: A case study of the structures and outcomes in a blended learning CPD.

INTRODUCTION: There is a great need for postgraduate training and continuing professional development (CPD), specifically in the field of periodontology. Despite the plenty of periodontal CPDs, there is a lack of information about the performance of CPDs in a blended learning setting. This study is a case study of the structures and outcomes in a blended learning CPD programme in periodontology, the MasterOnline Periodontology and Implant Therapy hosted by the University of Freiburg's Dental School. MATERIAL AND METHODS: The structures of the blended learning CPD were analysed with the aims to (i) make explicit how various innovative educational methods and ICT tools can be successfully applied to a Web-supported postgraduate periodontology training programme, (ii) identify the programme's impact on learning transfer in students' dental practices and (iii) identify other outcomes, synergies and any changes required during the existence. Using qualitative interviewing, the various types of learning transfer and elements of the study programme that foster transfer could be exemplified. RESULTS: A period of 7 years was analysed. In this duration, 50 students successfully graduated to a master of science. Qualitative interviews were performed with six students and four teachers affirming the learning transfer in a blended learning setting. CONCLUSIONS: This case study shows that blended learning can be a successful approach for CPD in dentistry.

Imaging considerations for in vivo 13C metabolic mapping using hyperpolarized 13C-pyruvate.

One of the challenges of optimizing signal-to-noise ratio (SNR) and image quality in (13)C metabolic imaging using hyperpolarized (13)C-pyruvate is associated with the different MR signal time-courses for pyruvate and its metabolic products, lactate and alanine. The impact of the acquisition time window, variation of flip angles, and order of phase encoding on SNR and image quality were evaluated in mathematical simulations and rat experiments, based on multishot fast chemical shift imaging (CSI) and three-dimensional echo-planar spectroscopic imaging (3DEPSI) sequences. The image timing was set to coincide with the peak production of lactate. The strategy of combining variable flip angles and centric phase encoding (cPE) improved image quality while retaining good SNR. In addition, two aspects of EPSI sampling strategies were explored: waveform design (flyback vs. symmetric EPSI) and spectral bandwidth (BW = 500 Hz vs. 267 Hz). Both symmetric EPSI and reduced BW trended toward increased SNR. The imaging strategies reported here can serve as guidance to other multishot spectroscopic imaging protocols for (13)C metabolic imaging applications.

The quantitative 19F-imaging of albumin at 1.5 T: a potential in-vivo tool.

19F-MR-imaging has been used to quantitate albumin concentration in a phantom at 1.5 T. The experimentally derived relationship between albumin concentration and the T1 relaxation time of a fluorinated marker, tetrafluorosuccinic acid (TFSA) was used to calculate the albumin concentration from a quantitative 19F T1 map acquired using a gradient echo sequence. There was close correlation between calculated and actual BSA concentrations (r = 0.99, SE = 0.15). The potentially interfering effect of paramagnetic species on T1 relaxation times was also investigated. Relaxivity data show that albumin concentration measurements should be performed prior to any contrast agent administration.

In vivo 13 carbon metabolic imaging at 3T with hyperpolarized 13C-1-pyruvate.

We present for the first time dynamic spectra and spectroscopic images acquired in normal rats at 3T following the injection of (13)C-1-pyruvate that was hyperpolarized by the dynamic nuclear polarization (DNP) method. Spectroscopic sampling was optimized for signal-to-noise ratio (SNR) and for spectral resolution of (13)C-1-pyruvate and its metabolic products (13)C-1-alanine, (13)C-1-lactate, and (13)C-bicarbonate. Dynamic spectra in rats were collected with a temporal resolution of 3 s from a 90-mm axial slab using a dual (1)H-(13)C quadrature birdcage coil to observe the combined effects of metabolism, flow, and T(1) relaxation. In separate experiments, spectroscopic imaging data were obtained during a 17-s acquisition of a 20-mm axial slice centered on the rat kidney region to provide information on the spatial distribution of the metabolites. Conversion of pyruvate to lactate, alanine, and bicarbonate occurred within a minute of injection. Alanine was observed primarily in skeletal muscle and liver, while pyruvate, lactate, and bicarbonate concentrations were relatively high in the vasculature and kidneys. In contrast to earlier work at 1.5 T, bicarbonate was routinely observed in skeletal muscle as well as the kidney and vasculature.

Hyperpolarized 129Xe NMR as a probe for blood oxygenation.

Optically enhanced NMR with (129)Xe and (3)He is emerging as a novel and promising technique for medical imaging of lungs and other tissues. Here it is shown that hyperpolarized (129)Xe NMR provides a powerful means of measuring blood oxygenation quantitatively and noninvasively. The interaction of xenon with hemoglobin is responsible for an oxygen-dependent NMR shift of (129)Xe in red blood cells, in sharp contrast to the current model of xenon-hemoglobin binding. This effect could be exploited in brain functional studies, and in the assessment of conditions and diseases affected by blood oxygenation.

On the oxygenation-dependent (129)Xe T (1) in blood.

The spin-lattice relaxation time, T(1), of hyperpolarized (129)Xe in blood is sensitive to blood oxygenation. In particular, it has been shown that (129)Xe T(1) is shorter in venous blood than in arterial blood. We have studied the T(1) of hyperpolarized (129)Xe dissolved in human blood as a function of blood oxygenation level, sO(2), in the physiological oxygenation range. We show that the (129)Xe relaxation rate, T(1)(-1), varies in a nonlinear fashion as a function of sO(2). This finding suggests that direct interaction of xenon with the paramagnetic heme group of deoxyhemoglobin is not the dominant oxygenation-dependent relaxation mechanism for (129)Xe in blood. These results corroborate the idea that the oxygenation-dependence of (129)Xe T(1) is determined by conformational changes of hemoglobin induced by oxygen binding.

Spin-lattice relaxation of laser-polarized xenon in human blood.

The nuclear spin polarization of 129Xe can be enhanced by several orders of magnitude by using optical pumping techniques. The increased sensitivity of xenon NMR has allowed imaging of lungs as well as other in vivo applications. The most critical parameter for efficient delivery of laser-polarized xenon to blood and tissues is the spin-lattice relaxation time (T1) of xenon in blood. In this work, the relaxation of laser-polarized xenon in human blood is measured in vitro as a function of blood oxygenation. Interactions with dissolved oxygen and with deoxyhemoglobin are found to contribute to the spin-lattice relaxation time of 129Xe in blood, the latter interaction having greater effect. Consequently, relaxation times of 129Xe in deoxygenated blood are shorter than in oxygenated blood. In samples with oxygenation equivalent to arterial and venous blood, the 129Xe T1s at 37 degrees C and a magnetic field of 1.5 T were 6.4 s +/- 0.5 s and 4.0 s +/- 0.4 s, respectively. The 129Xe spin-lattice relaxation time in blood decreases at lower temperatures, but the ratio of T1 in oxygenated blood to that in deoxygenated blood is the same at 37 degrees C and 25 degrees C. A competing ligand has been used to show that xenon binding to albumin contributes to the 129Xe spin-lattice relaxation in blood plasma. This technique is promising for the study of xenon interactions with macromolecules.

Perfluorocarbon emulsions as intravenous delivery media for hyperpolarized xenon.

The use of perfluorooctyl bromide (PFOB) emulsions as delivery media for hyperpolarized xenon has been investigated. Emulsion droplet size was controlled by varying the content of egg yolk phospholipid (EYP), which served as an emulsifier. Hyperpolarized 129Xe nuclear magnetic resonance (NMR) spectra of the dissolved gas were obtained. The NMR spectra were found to be correlated strongly with the emulsion droplet size distribution. The NMR line width is determined by xenon exchange between the PFOB droplets and the aqueous environment. Our findings show that, in a 1.5-Tesla field, relatively narrow 129Xe NMR spectra are obtained for droplet sizes larger than 5 microm. Preliminary results on animal models show that PFOB emulsions have potential as hyperpolarized 129Xe carriers for in vivo magnetic resonance applications.

In vivo hyperpolarized 129Xe NMR spectroscopy in tumors.

The first in vivo hyperpolarized 129Xe NMR study in experimental tumors is presented. Hyperpolarized 129Xe was dissolved in solutions, and was injected intratumorally in GH-3 prolactinomas in rats and RIF-1 fibrosarcomas in mice. The 129Xe NMR spectra and apparent spin-lattice relaxation times in the two tumor types present characteristic differences. These differences are discussed in terms of xenon exchange between the carrier medium and the tissue compartments.