A method to convert MRI images of temperature change into images of absolute temperature in solid tumours. (September 2013)

• Record Type: Journal Article
• Authors: Davis, Ryan M.; Viglianti, Benjamin L.; Yarmolenko, Pavel; Park, Ji-Young; Stauffer, Paul; Needham, David; Dewhirst, Mark W.
• Is Part Of: International journal of hyperthermia. Volume 29:Number 6(2013)
• Page Start: 569
• Page End: 581
• Publication Date: 2013-09
• Subjects: Thermotherapy -- Periodicals; 615.832
• DOI: 10.3109/02656736.2013.790091
• Languages: English
• ISSNs: 0265-6736

Abstract

<abstract> <title>Abstract</title> <p> <italic>Purpose</italic>: During hyperthermia (HT), the therapeutic response of tumours varies substantially within the target temperature range (39–43 °C). Current thermometry methods are either invasive or measure only temperature change, which limits the ability to study tissue responses to HT. This study combines manganese-containing low temperature sensitive liposomes (Mn-LTSL) with proton resonance frequency shift (PRFS) thermometry to measure absolute temperature in tumours with high spatial and temporal resolution using MRI.</p> <p> <italic>Methods</italic>: Liposomes were loaded with 300 mM MnSO<sub>4</sub>. The phase transition temperature (T<sub>m</sub>) of Mn-LTSL samples was measured by differential scanning calorimetry (DSC). The release of manganese from Mn-LTSL in saline was characterised with inductively coupled plasma atomic emission spectroscopy. A 2T GE small animal scanner was used to acquire dynamic T<sub>1</sub>-weighted images and temperature change images of Mn-LTSL in saline phantoms and fibrosarcoma-bearing Fisher-344 rats receiving hyperthermia after Mn-LTSL injection.</p> <p> <italic>Results</italic>: The T<sub>m</sub> of Mn-LTSL in rat blood was 42.9 ± 0.2 °C (DSC). For Mn-LTSL samples (0.06 mM–0.5 mM Mn<sup>2+</sup> in saline) heated monotonically from 30 °C to 50 °C, a peak in the rate of MRI signal enhancement occurred at 43.1° ± 0.3 °C. The same peak in signal enhancement rate was observed during heating of fibrosarcoma tumours (<italic>N</italic> = 3) after injection of Mn-LTSL, and the peak was used to convert temperature change images into absolute temperature. Accuracies of calibrated temperature measurements were in the range 0.9–1.8 °C.</p> <p> <italic>Conclusion</italic>: The release of Mn<sup>2+</sup> from Mn-LTSL affects the rate of MR signal enhancement which enables conversion of MRI-based temperature change images to absolute temperature.</p> </abstract>