ZIB

Hits per page

hits 1 - 2 | 2 hits

Sorting

Electronic Resource

Field strength and dose dependence of contrast enhancement by gadolinium-based MR contrast agents (1999)

Rinck, P. A. ; Muller, R. N.

Springer

European radiology 9 (1999), S. 998-1004

add to mindlist on the mindlist

Details

ISSN: 1432-1084

Keywords: Key words: MR imaging ; Contrast agents ; MR field strength

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract. The relaxivities r1 and r2 of magnetic resonance contrast agents and the T1 relaxation time values of tissues are strongly field dependent. We present quantitative data and simulations of different gadolinium-based extracellular fluid contrast agents and the modulation of their contrast enhancement by the magnetic field to be able to answer the following questions: How are the dose and field dependences of their contrast enhancement? Is there an interrelationship between dose and field dependence? Should one increase or decrease doses at specific fields? Nuclear magnetic relaxation dispersion data were acquired for the following contrast agents: gadopentetate dimeglumine, gadoterate meglumine, gadodiamide injection, and gadoteridol injection, as well as for several normal and pathological human tissue samples. The magnetic field range stretched from 0.0002 to 4.7 T, including the entire clinical imaging range. The data acquired were then fitted with the appropriate theoretical models. The combination of the diamagnetic relaxation rates (R1 = 1/T1 and R2 = 1/T2) of tissues with the respective paramagnetic contributions of the contrast agents allowed the prediction of image contrast at any magnetic field. The results revealed a nearly identical field and dose-dependent increase of contrast enhancement induced by these contrast agents within a certain dose range. The target tissue concentration (TTC) was an important though nonlinear factor for enhancement. The currently recommended dose of 0.1 mmol/kg body weight seems to be a compromise close to the lower limits of diagnostically sufficient contrast enhancement for clinical imaging at all field strengths. At low field contrast enhancement might be insufficient. Adjustment of dose or concentration, or a new class of contrast agents with optimized relaxivity, would be a valuable contribution to a better diagnostic yield of contrast enhancement at all fields.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003300050781

Permalink

Library	Location	Call Number	Volume/Issue/Year	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

Electronic Resource

Relationship between structure and rheological properties in the melt of polymers containing spherical inclusions (1995)

Bardollet, P. ; Bousmina, M. ; Muller, R.

New York, NY : Wiley-Blackwell

Polymers for Advanced Technologies 6 (1995), S. 301-308

add to mindlist on the mindlist

Details

ISSN: 1042-7147

Keywords: polymer blends ; melt rheology ; crosslinked rubber ; structured latex ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: The linear viscoelastic behavior of model rubbertoughened polymer melts has been studied. The most significant influence of the dispersed crosslinked rubber phase on the melt rheology of the blends is the existence of a secondary plateau for the storage modulus G′ at low frequencies. This behavior was ascribed to a percolation phenomenon, leading to the formation of a threedimensional network of inclusions, and contributing to the elasticity at low frequencies of the blend. Two different systems were investigated: (a) a polystyrene matrix with crosslinked and structured latex particles and (b) silicon oil matrices with homogeneous crosslinked PMMA particles. An initial shearing history was found to influence the dynamic mechanical properties of the molten blends and in particular to lower the lowfrequency plateau value for G′. During a subsequent annealing, the plateau modulus increases again. These results are in agreement with the assumption of a particle network.

Additional Material: 13 Ill.