Enteric MRI contrast agents: comparative study of five potential agents in humans.

We compared the effectiveness of 1 mM Geritol, 12% corn oil emulsion, Kaolin-pectin, single contrast oral barium sulfate, and effervescent granules as enteric magnetic resonance imaging (MRI) contrast agents. Five volunteers were recruited. Each volunteer ingested for examinations, separated by at least one week, either 500 ml of each of the liquid preparations or two packets of the CO2 granules (producing 400 ml of CO2 per packet). Abdominal MR images were then obtained using a 1.5 T Magnetom imager and SE 550/22, SE 2000/45/90 and FISP 40/18/40 degrees pulse sequences. The oil emulsions were best tolerated. Barium sulfate caused the greatest amount of nausea, followed by Geritol and Kaolin-pectin. With FISP 40/18/40 degrees, 60%-80% of the small bowel was well delineated using oil emulsion, Kaolin-pectin, or barium sulfate. We conclude that oil emulsion was by far the best enteric MR contrast agent in our study. Good delineation of the small bowel and pancreas can be achieved using oil emulsion and gradient echo pulse sequences. The lack of side-effects and the excellent taste make it highly acceptable to human subjects.     

Geometrical modelling of foam structures using implicit functions

Mechanical, thermo-mechanical, and fluid dynamic simulations of open-cell foams require an accurate geometry model. Usually, models are derived from computer- tomography (CT) data which do not allow analysing systematically variation and optimisation of the geometry. On the other hand, entirely computer generated models are mostly assembled of primitive objects like cylinders. This disregards strut thickness variations and node rounding which are observed in real open-cell foams. This paper presents an approach to generate models of ceramic open-cell foams using simple objects with variable thickness generated by implicit functions. This approach can also account for cavities within struts and nodes, which are observed in many real foam structures. The specific rounding at the foam nodes can be modelled by applying the transformation of Blinn. The quality of the generated foam models is verified using CT data of real foams.     

Barium sulfate suspension as a negative oral MRI contrast agent: in vitro and human optimization studies

In vitro proton spectroscopy with line-width measurements and MR imaging were performed on various concentrations of commercially available single contrast (SC), double contrast, oral and rectal barium sulfate suspensions, as well as potassium sulfate, barium chloride, barium hydroxide, and 97% pure barium sulfate suspensions. Approximately 500 ml of 20%, 40%, 60%, and 70% w/w suspensions of SC oral barium sulfate suspensions were administered to four normal volunteers, respectively, and MR images were obtained at both 1.5 T and 0.15 T. Subsequently, 500 ml of 60% w/w suspensions of SC oral barium sulfate suspensions were administered to five normal volunteers and imaged at 1.5 T. All of the inert suspensions produced line-width broadening but the SC oral barium sulfate suspension at 50% and 70% stayed in suspension even after hours of standing undisturbed. As much as 80% of the small bowel and the entire colon were well visualized using the combination of 60% or 70% w/w SC barium sulfate suspensions with SE 550/22 and FISP pulse sequences. The effect was less at 0.15 T and also with the SE 2000/45/90 pulse sequences. We conclude that barium sulfate suspensions are useful as oral MRI contrast agents.     

Paramagnetic oil emulsions as oral magnetic resonance imaging contrast agents

The combination of a paramagnetic agent with an oil emulsion can uniformly enhance the small bowel. We discovered that the entire small bowel becomes homogeneously brighter than its surroundings when imaged with all commonly utilized pulse sequences. We have tried various combinations of ferric ammonium citrate, ferrous sulfate, gadolinium-DPTA and corn oil, olive oil and peanut oil. All paramagnetic oil emulsions tested were uniformly distributed throughout the small bowel, but the enhancement effect is much stronger with the ferric ammonium citrate and gadolinium-DPTA oil emulsions. We have also developed a mixture of Geritol, corn oil, ice cream and milk, which uniformly coats the small bowel wall, has good enhancement effect, tastes good, and is nutritious. With this dietary contrast, retroperitoneal structures including the pancreas can be well delineated. We conclude that the combination of a paramagnetic agent with an oil emulsion can work as a safe and effective magnetic resonance imaging (MRI) oral contrast agent with high patient acceptance.     

An ultrasonic device for continuous measurement of cervical dilation during labour

This paper describes ultrasonic apparatus for continuous registration of cervical dilation during the first stage of labour.The techniques used ensure maximum safety for the patients and do not influence the normal birth process     

Proton magnetic resonance spectra of some 6- and 7-substituted 2-amino-4-hydroxypteridines

The conformations in solution of 6-phenyltetrahydropterin, 6,7-diphenyltetrahydropterin and 6-7, dimethyltetrahydropterin have been determined from their proton magnetic resonance spectra. The 6-phenyltetrahydropterin has the reduced pyrazine ring in a half chair conformation with the phenyl ring in the equatorial position. Both the 6,7-diphenyl- and 6,7-dimethyltetrahydropterins are of the cis configuration and have one substituent in an axial position. The enzymatic activity of these cofactors may be related to these conformations.     

Iron-mediated synthetic routes to unsymmetrically substituted, sterically congested benzophenones

A new synthetic route to unsymmetrically substituted benzophenones, relying upon iron-mediated reactions in all of the key steps, is described. The key buiding block, eta6-2-chloro-carbomethoxybenzene-eta5-cyclopentadienyl iron hexafluorophosphate (4), is reacted with a variety of substituted phenols, providing diaryl ether complexes (6). After hydrolysis of the ester functionalities, these complexes are subjected to Friedel-Crafts conditions. The efficiency of this intramolecular acylation reaction is very much dependent upon the substituents on the phenols. If these are appropriately chosen, xanthone complexes are isolated in fair to good yields. Regioselective ring-opening, using oxygen-nucleophiles, delivers substituted benzophenone complexes. After regioselective nucleophilic addition of cyanide ion, performed in the presence of DDQ, highly substituted benzophenones are isolated. To demonstrate the applicability of the new route, a formal synthesis of the benzophenone moiety of the protein kinase C inhibitor Balanol (3) is described.     

Inclusion of thiazyl radicals in porous crystalline materials

The incorporation of benzodithiazolyl (BDTA) and methylbenzodithiazolyl (MBDTA) radicals into porous hybrid frameworks via gas phase diffusion revealed that inclusion appeared selective for the MIL53(Al) framework against a range of other potential hosts. Both PXRD and EPR studies are consistent with retention of a π*-π* dimer motif for BDTA in MIL53(Al)@BDTA whereas MBDTA in MIL53(Al)@MBDTA appears to be monomeric. The guests are readily released by the addition of solvent (CH(2)Cl(2)).