sepharose and gadolinium-chloride

The availability of adapted phantoms mimicking different body parts is fundamental to establishing the stability and reliability of magnetic resonance imaging (MRI) methods. The primary purpose of such phantoms is the mimicking of physiologically relevant, contrast-creating relaxation times

Topics: Alginates; Brain; Carrageenan; Cross-Linking Reagents; Magnetic Resonance Imaging; Microscopy, Electron, Scanning; Phantoms, Imaging; Printing, Three-Dimensional; Reproducibility of Results; Sepharose

A 3.0-T MRI phantom (called the CAGN-3.0T phantom) having human-equivalent relaxation times and human-equivalent conductivity was developed.. The ingredients of the phantom are carrageenan (as a gelatinizer), agarose (as a T2-relaxation modifier), GdCl3 (as a T1-relaxation modifier), NaCl (as a conductivity modifier), and NaN3 (as an antiseptic). Numerous samples with varying concentrations of agarose, GdCl3, and NaCl were prepared, and T1 and T2 values were measured using 3.0-T MRI.. The T1 values of the CAGN-3.0T phantom were unaffected by NaCl, while the T2 values were only slightly affected. Based on the measured data, empirical formulae were devised to express the relationships between the concentrations of agarose, GdCl3, and NaCl and the relaxation times. The formula for expressing the conductivity of the CAGN-3.0T phantom was obtained.. By adjustments to the concentrations of agarose, GdCl3, and NaCl, the relaxation times and conductivity of almost all types of human tissues can be simulated by CAGN-3.0T phantoms. The phantoms have T1 values of 395-2601 ms, T2 values of 29-334 ms, and conductivity of 0.27-1.26 S/m when concentrations of agarose, GdCl3, and NaCl are varied from 0 to 2.0 w/w%, 0 to 180 μmol/kg, and 0 to 0.7 w/w%, respectively. The CAGN-3.0T phantom has sufficient strength to replicate the torso without using reinforcing agents, and can be cut with a knife into any shape.

Topics: Electric Impedance; Gadolinium; Humans; Magnetic Resonance Imaging; Phantoms, Imaging; Sepharose; Sodium Chloride

A phantom has previously been developed containing carrageenan, agarose and gadolinium chloride (called CAG phantom) for MRI with 1.5 T. T(1) and T(2) relaxation times of this phantom are independently changeable by varying concentrations of relaxation-time modifiers to simulate relaxation times of the various types of human tissues. The CAG phantom has a T(1) value of 202-1904 ms and a T(2) value of 38-423 ms, when the GdCl(3) concentration is varied from 0-140 micromol/kg and the agarose concentration is varied from 0-1.6%. A new phantom has now been developed (called CAGN phantom), made by adding an electric conductive agent, NaCl, to the CAG phantom for use in the areas of MRI and hyperthermia research. Dielectric properties of the CAGN phantom were measured and the results of experiments were expressed by the Cole-Cole equation in the frequency range of 5-130 MHz. The relationship between the conductivity of the CAGN phantom and the concentration of NaCl was expressed by a linear function in the frequency range of 1-130 MHz. The linear function involves a parameter of frequency and, when the frequency is 10 MHz, the conductivity of the CAGN phantom can be changed from 0.27-1.26 Sm(-1) by increasing the NaCl concentration from 0-0.7%. The CAGN phantom developed can be employed in basic experiments for non-invasive temperature measurement using MRI and as a loading phantom for MRI with up to 3 T.

Topics: Carrageenan; Electric Conductivity; Gadolinium; Gels; Humans; Hyperthermia, Induced; Magnetic Resonance Imaging; Models, Biological; Phantoms, Imaging; Sepharose; Sodium Chloride

The authors developed a phantom, designated as the CAGN phantom, compatible for MRI and hyperthermia that is useful in the fundamental studies of non-invasive MR thermometry. The ingredients of this phantom are carrageenan, GdCl3 as a T1 modifier, agarose as a T2 modifier, NaCl as a conductivity modifier, NaN3 as an antiseptic and distilled water. Another phantom that was developed, the CAG phantom, has relaxation times that are adjustable to those of any human tissue. To use this phantom for electromagnetic heating, NaCl was added to change the conductivity of the phantom and clarified the relationship between the conductivity and NaCl concentration. This study examined the relationship between relaxation times and NaCl concentration of the CAGN phantom. The results showed that both T1 and T2 values were affected by NaCl and the experimental results led to the empirical formulae expressing the relationship between the relaxation rates (1/T1, 1/T2) and the concentrations of GdCl3, agarose and NaCl. The appropriate concentrations of T1 and T2 modifiers were calculated from these empirical formulae when making a specified phantom that has the required relaxation times and NaCl concentration.

Topics: Algorithms; Carrageenan; Electric Conductivity; Electromagnetic Phenomena; Gadolinium; Humans; Hyperthermia, Induced; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Phantoms, Imaging; Sepharose; Sodium Azide; Sodium Chloride; Water

A new tissue-equivalent MRI phantom based on carrageenan gel was developed. Carrageenan gel is an ideal solidifying agent for making large, strong phantoms in a wide variety of shapes. GdCl(3) was added as a T(1) modifier and agarose as a T(2) modifier. The relaxation times of a very large number of samples were estimated using 1.5-T clinical MRI equipment. The developed phantom was found to have a T(1) value of 202-1904 ms and a T(2) value of 38-423 ms when the GdCl(3) concentration was varied from 0-140 mumol/kg and the agarose concentration was varied from 0-1.6% in a carrageenan concentration that was fixed at 3%. The range of measured relaxation times covered those of all types of human tissue. Empirical formulas linking the relaxation time with the concentration of the modifier were established to enable the accurate and easy calculation of the modifier concentration needed to achieve the required relaxation times. This enables the creation of a phantom having an arbitrary combination of T(1) and T(2) values and which is capable of retaining its shape.

Topics: Carrageenan; Gadolinium; Gels; Humans; Magnetic Resonance Imaging; Phantoms, Imaging; Sepharose

A tissue-equivalent test material for MRI has been produced from a polysaccharide gel, agarose, containing gadolinium chloride chelated to EDTA. By varying the amounts of each constituent, the T1 and T2 of the material can be varied independently. As a result, the entire range of in vivo tissue relaxation times can be covered. Through the mathematical modelling of the 1H relaxation theories for both the gel and chelated paramagnetic ion, it has been possible to create a material with relaxation properties and behaviour predictable as functions of both the Larmor frequency and temperature. The similarity of the material to in vivo tissues, in terms of its biological and physical NMR characteristics, makes it an excellent tissue-equivalent substance, in addition to being an accurate calibration standard for routine MRI.

Topics: Edetic Acid; Gadolinium; Magnetic Resonance Imaging; Models, Theoretical; Polysaccharides; Sepharose