Giuseppe Carluccio PhD, Abstract Co-Author: Nothing to Disclose

Yu-Shin Ding PhD, Abstract Co-Author: Nothing to Disclose

Christopher M. Collins PhD, Presenter: Nothing to Disclose

Though MRI-induced temperature increase should not dramatically affect qualitative appearance of PET images such as used in locating metastatic masses, it may cause enough increase in metabolic rate to affect results of quantitative, dynamic studies. Thus, in these studies use of low-SAR sequences should be advised until conclusive experiments regarding the quantitative effects of MR-induced temperature increase on PET signal can be performed.

With the recent introduction of multimodality MR/PET imaging systems, it is technically possible that RF heating (SAR) from MRI could cause temperature increase resulting in metabolic change affecting uptake of metabolism-specific radiotracers (such as FDG) and thereby influencing the PET image.

We performed advanced numerical simulations of the 3D human body in an MRI system and the resulting SAR, temperature distribution, and metabolic rates throughout the body before and after application of an MRI sequence reaching “normal mode” limits on SAR for a period of 40 minutes.

Distributions of metabolic rate (Q) before and after application of a high-SAR sequence for 40 minutes show little qualitative difference to the eye, but quantitative maps of the difference and percent difference between them show notable increase in metabolic rate in some high-metabolism organs (e.g., approaching 20% in thyroid), and even greater percent increase in some low-metabolic rate tissues (e.g., approaching 45% in muscle at rest in some high-SAR locations).

Carluccio, G, Ding, Y, Collins, C, Numerical Investigation of the Potential for MR-induced Temperature Increase to Affect Distributions of Temperature, Metabolic Rate, and FDG Uptake in MR/PET.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006300.html