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MRI phantoms - are there alternatives to agar?

Hellerbach A, Schuster V, Jansen A, Sommer J - PLoS ONE (2013)

Bottom Line: With such characteristics, it was even possible to embed sensitive objects and retrieve them after testing.This was demonstrated with a fiber phantom for Diffusion Weighted MRI applications.Since Carbomer-980 and Carbopol-974P are non-hazardous, they are also suitable for multimodal setups (e.g., MRI as well as ultrasonic imaging).

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Psychotherapy, Philipps-University Marburg, Marburg, Germany. hellerba@med.uni-marburg.de

ABSTRACT
The suitability of different gelling agents as MRI phantoms was evaluated in terms of homogeneity, gel stability and reproducibility. Time and effort for preparation were also taken into account. The relaxation times of various gel compositions were estimated. Carbomer-980 and Carbopol-974P were determined to be promising novel phantom materials. These gelling agents are readily available, inexpensive and easy to handle given that thermal treatment is not required. Furthermore, the viscoelasticity of their polymer network is pH-dependent. With such characteristics, it was even possible to embed sensitive objects and retrieve them after testing. This was demonstrated with a fiber phantom for Diffusion Weighted MRI applications. Since Carbomer-980 and Carbopol-974P are non-hazardous, they are also suitable for multimodal setups (e.g., MRI as well as ultrasonic imaging).

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Effect of contrast agents on image homogeneity.T2 image of Carbopol-974P phantom (0.5% Carbopol-974P, spin echo sequence with TE = 50 ms and TR = 3000 ms). A Phantom without contrast agent. B Phantom with 0.20 ml Endorem and C phantom with 0.012 g manganese nitrate.
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pone-0070343-g004: Effect of contrast agents on image homogeneity.T2 image of Carbopol-974P phantom (0.5% Carbopol-974P, spin echo sequence with TE = 50 ms and TR = 3000 ms). A Phantom without contrast agent. B Phantom with 0.20 ml Endorem and C phantom with 0.012 g manganese nitrate.

Mentions: Relaxation times of all gelling agents are listed in Table 1. Sodium alginate had relaxation times similar to those of human tissue, whereas T1 and T2 relaxation times of other gelling agents were longer than those of human tissue. For comparison T1 and T2 relaxation times of different biological tissues measured at 37°C and 3 T are presented in Table 2[23]. Relaxation times could be adjusted by the addition of contrast agents. T1 and T2 modification in different samples is summarized in Table 3. For analysis of variation in T1 and T2 relaxation times, only phantoms with a solid gel structure were used. Relaxometry fit curves of three different samples are shown in Fig. 3. Without adding a contrast agent, T2 relaxation time was similar to that of free water. Manganese nitrate and Endorem reduced T2 relaxation time to a value similar to that obtained from human tissue. Depending on the concentration, T2 modifiers had a strong influence on gel homogeneity (Fig. 4). Another way to reduce T2 relaxation time was to increase the concentration of the gelling agent. Table 4 shows the dependence of relaxation time on Carbomer-980 concentration. The higher the concentration the lower the T2 relaxation time, but concentration higher than 1.5% affects also gel homogeneity. pH had a strong effect on viscosity of Carbomer-980 gels, but a less drastic effect on T1 and T2 relaxation times (Table 5).


MRI phantoms - are there alternatives to agar?

Hellerbach A, Schuster V, Jansen A, Sommer J - PLoS ONE (2013)

Effect of contrast agents on image homogeneity.T2 image of Carbopol-974P phantom (0.5% Carbopol-974P, spin echo sequence with TE = 50 ms and TR = 3000 ms). A Phantom without contrast agent. B Phantom with 0.20 ml Endorem and C phantom with 0.012 g manganese nitrate.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3734012&req=5

pone-0070343-g004: Effect of contrast agents on image homogeneity.T2 image of Carbopol-974P phantom (0.5% Carbopol-974P, spin echo sequence with TE = 50 ms and TR = 3000 ms). A Phantom without contrast agent. B Phantom with 0.20 ml Endorem and C phantom with 0.012 g manganese nitrate.
Mentions: Relaxation times of all gelling agents are listed in Table 1. Sodium alginate had relaxation times similar to those of human tissue, whereas T1 and T2 relaxation times of other gelling agents were longer than those of human tissue. For comparison T1 and T2 relaxation times of different biological tissues measured at 37°C and 3 T are presented in Table 2[23]. Relaxation times could be adjusted by the addition of contrast agents. T1 and T2 modification in different samples is summarized in Table 3. For analysis of variation in T1 and T2 relaxation times, only phantoms with a solid gel structure were used. Relaxometry fit curves of three different samples are shown in Fig. 3. Without adding a contrast agent, T2 relaxation time was similar to that of free water. Manganese nitrate and Endorem reduced T2 relaxation time to a value similar to that obtained from human tissue. Depending on the concentration, T2 modifiers had a strong influence on gel homogeneity (Fig. 4). Another way to reduce T2 relaxation time was to increase the concentration of the gelling agent. Table 4 shows the dependence of relaxation time on Carbomer-980 concentration. The higher the concentration the lower the T2 relaxation time, but concentration higher than 1.5% affects also gel homogeneity. pH had a strong effect on viscosity of Carbomer-980 gels, but a less drastic effect on T1 and T2 relaxation times (Table 5).

Bottom Line: With such characteristics, it was even possible to embed sensitive objects and retrieve them after testing.This was demonstrated with a fiber phantom for Diffusion Weighted MRI applications.Since Carbomer-980 and Carbopol-974P are non-hazardous, they are also suitable for multimodal setups (e.g., MRI as well as ultrasonic imaging).

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Psychotherapy, Philipps-University Marburg, Marburg, Germany. hellerba@med.uni-marburg.de

ABSTRACT
The suitability of different gelling agents as MRI phantoms was evaluated in terms of homogeneity, gel stability and reproducibility. Time and effort for preparation were also taken into account. The relaxation times of various gel compositions were estimated. Carbomer-980 and Carbopol-974P were determined to be promising novel phantom materials. These gelling agents are readily available, inexpensive and easy to handle given that thermal treatment is not required. Furthermore, the viscoelasticity of their polymer network is pH-dependent. With such characteristics, it was even possible to embed sensitive objects and retrieve them after testing. This was demonstrated with a fiber phantom for Diffusion Weighted MRI applications. Since Carbomer-980 and Carbopol-974P are non-hazardous, they are also suitable for multimodal setups (e.g., MRI as well as ultrasonic imaging).

Show MeSH