Effects of air susceptibility on proton resonance frequency MR thermometry
- نوع فایل : کتاب
- زبان : انگلیسی
- مؤلف : Markus N. Streicher · Andreas Schنfer · Enrico Reimer · Bibek Dhital · Robert Trampel · Dimo Ivanov · Robert Turner
- چاپ و سال / کشور: 2011
Description
Object The temperature dependence of the proton resonance frequency (PRF) is often used in MR thermometry. However, this method is prone to even very small changes in local magnetic field strength. Here, we report on the effects of susceptibility changes of surrounding air on the magnetic field inside an object and their inferred effect on the measuredMR temperature. Materials and methods MR phase thermometry was performed on spherical agar phantoms enclosed in cylindrical containers at 7T. The air susceptibility inside the cylindrical container was changed by both heating the air and changing the gas composition. Results Changing the temperature of surrounding air from 23 to 69.C caused an apparent MR temperature error of 2 K. When ambient air was displaced by 100% oxygen, the MR temperature error increased to 40 K. The magnetic field shift and therefore error in inferred MR temperature scales linearly with volume susceptibility change and has a strong and nontrivial dependence on the experimental configuration. Conclusion Air susceptibility changes associated with oxygen concentration changes greatly affect PRFMR thermometry measurements. Air temperature changes can also affect thesemeasurements, but to a smaller degree. For uncalibrated MR thermometry, air susceptibility changes may be a significant source of error.
Magn Reson Mater Phy DOI 10.1007/s10334-011-0249-8 Received: 10 December 2010 / Revised: 11 February 2011 / Accepted: 8 March 2011
