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Thermal Excitation of Gadolinium-Based Contrast Agents Using Spin Resonance.

Dinger SC, Fridjhon P, Rubin DM - PLoS ONE (2016)

Bottom Line: The shorter relaxation time is found to significantly increase the rate of thermal energy deposition.The experimental results show a statistically significant thermal response for two out of the four contrast agents tested.The results are compared to the simulated estimates via analysis of a detailed model of the system.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical & Information Engineering, University of Witwatersrand, Johannesburg, Gauteng, South Africa.

ABSTRACT
Theoretical and experimental investigations into the thermal excitation of liquid paramagnetic contrast agents using the spin resonance relaxation mechanism are presented. The electronic spin-lattice relaxation time τ1e of gadolinium-based contrast agents, which is estimated at 0.1 ns, is ten orders of magnitude faster than the relaxation time of protons in water. The shorter relaxation time is found to significantly increase the rate of thermal energy deposition. To the authors' knowledge this is the first study of gadolinium based contrast agents in a liquid state used as thermal agents. Analysis shows that when τ1e and other experimental parameters are optimally selected, a maximum theoretical heating rate of 29.4 °C.s-1 could be achieved which would suffice for clinical thermal ablation of neoplasms. The experimental results show a statistically significant thermal response for two out of the four contrast agents tested. The results are compared to the simulated estimates via analysis of a detailed model of the system. While these experimentally determined temperature rises are small and thus of no clinical utility, their presence supports the theoretical analysis and strongly suggests that the chemical structure of the selected compounds plays an important role in this mechanism of heat deposition. There exists an opportunity for the development of alternative gadolinium-based compounds with an order of magnitude longer τ1e in a diluted form to be used as an efficient hyperthermia agent for clinical use.

No MeSH data available.


Related in: MedlinePlus

Mean temperature rise over a ninety second interval for the six tested substances, with each mean value obtained over thirty experiments and a linear regression line fitted.Standard error bars shown at every 8 s.
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pone.0158194.g003: Mean temperature rise over a ninety second interval for the six tested substances, with each mean value obtained over thirty experiments and a linear regression line fitted.Standard error bars shown at every 8 s.

Mentions: Multiple recordings at 0.2 s intervals were logged for each condition, with 30 experiments in total to accommodate the small temperature changes and measurement noise. The thirty sample average of the recorded temperature changes for each of the six substances, each with the DC magnetic field ‘On’ and ‘Off’ conditions, is shown in Fig 3. It is noted that each result is centered by subtracting the average initial value, approximately 37°C, from the dataset. The centralisation enables comparison between substances as well as the comparison of slopes for each substance.


Thermal Excitation of Gadolinium-Based Contrast Agents Using Spin Resonance.

Dinger SC, Fridjhon P, Rubin DM - PLoS ONE (2016)

Mean temperature rise over a ninety second interval for the six tested substances, with each mean value obtained over thirty experiments and a linear regression line fitted.Standard error bars shown at every 8 s.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920350&req=5

pone.0158194.g003: Mean temperature rise over a ninety second interval for the six tested substances, with each mean value obtained over thirty experiments and a linear regression line fitted.Standard error bars shown at every 8 s.
Mentions: Multiple recordings at 0.2 s intervals were logged for each condition, with 30 experiments in total to accommodate the small temperature changes and measurement noise. The thirty sample average of the recorded temperature changes for each of the six substances, each with the DC magnetic field ‘On’ and ‘Off’ conditions, is shown in Fig 3. It is noted that each result is centered by subtracting the average initial value, approximately 37°C, from the dataset. The centralisation enables comparison between substances as well as the comparison of slopes for each substance.

Bottom Line: The shorter relaxation time is found to significantly increase the rate of thermal energy deposition.The experimental results show a statistically significant thermal response for two out of the four contrast agents tested.The results are compared to the simulated estimates via analysis of a detailed model of the system.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical & Information Engineering, University of Witwatersrand, Johannesburg, Gauteng, South Africa.

ABSTRACT
Theoretical and experimental investigations into the thermal excitation of liquid paramagnetic contrast agents using the spin resonance relaxation mechanism are presented. The electronic spin-lattice relaxation time τ1e of gadolinium-based contrast agents, which is estimated at 0.1 ns, is ten orders of magnitude faster than the relaxation time of protons in water. The shorter relaxation time is found to significantly increase the rate of thermal energy deposition. To the authors' knowledge this is the first study of gadolinium based contrast agents in a liquid state used as thermal agents. Analysis shows that when τ1e and other experimental parameters are optimally selected, a maximum theoretical heating rate of 29.4 °C.s-1 could be achieved which would suffice for clinical thermal ablation of neoplasms. The experimental results show a statistically significant thermal response for two out of the four contrast agents tested. The results are compared to the simulated estimates via analysis of a detailed model of the system. While these experimentally determined temperature rises are small and thus of no clinical utility, their presence supports the theoretical analysis and strongly suggests that the chemical structure of the selected compounds plays an important role in this mechanism of heat deposition. There exists an opportunity for the development of alternative gadolinium-based compounds with an order of magnitude longer τ1e in a diluted form to be used as an efficient hyperthermia agent for clinical use.

No MeSH data available.


Related in: MedlinePlus