Absolute MR thermometry using nanocarriers

Roel Deckers, Sara M. Sprinkhuizen, Bart J. Crielaard, Johannes H. Ippel, Rolf Boelens, Chris J.G. Bakker, Gert Storm, Twan Lammers, Lambertus W. Bartels

Research output: Contribution to journalArticleAcademicpeer-review

5 Citations (Scopus)
42 Downloads (Pure)

Abstract

Accurate time‐resolved temperature mapping is crucial for the safe use of hyperthermia‐mediated drug delivery. We here propose a magnetic resonance imaging temperature mapping method in which drug delivery systems serve not only to improve tumor targeting, but also as an accurate and absolute nano‐thermometer. This method is based on the temperature‐dependent chemical shift difference between water protons and the protons in different groups of drug delivery systems. We show that the chemical shift of the protons in the ethylene oxide group in polyethylene glycol (PEG) is temperature‐independent, whereas the proton resonance of water decreases with increasing temperature. The frequency difference between both resonances is linear and does not depend on pH and physiological salt conditions. In addition, we show that the proton resonance of the methyl group in N‐(2‐hydroxypropyl)‐methacrylamide (HPMA) is temperature‐independent. Therefore, PEGylated liposomes, polymeric mPEG‐b‐pHPMAm‐Lac2 micelles and HPMA copolymers can provide a temperature‐independent reference frequency for absolute magnetic resonance (MR) thermometry. Subsequently, we show that multigradient echo MR imaging with PEGylated liposomes in situ allows accurate, time‐resolved temperature mapping. In conclusion, nanocarrier materials may serve as highly versatile tools for tumor‐targeted drug delivery, acting not only as hyperthermia‐responsive drug delivery systems, but also as accurate and precise nano‐thermometers.
Original languageEnglish
Pages (from-to)283-290
JournalContrast media & molecular imaging
Volume9
Issue number4
DOIs
Publication statusPublished - 2014

Keywords

  • Drug delivery
  • Liposomes
  • Micelles
  • MR thermometry
  • Polymers

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