Measuring Temperature Induced Phase Change Kinetics in Subcutaneous Adipose Tissues Using Near Infrared Spectroscopy, MR Imaging and Spectroscopy and OCT

Amir Y Sajjadi,Stefan A Carp,Dieter Manstein

doi:10.1038/s41598-017-18145-9

Abstract

Monitoring phase transition in adipose tissue and formation of lipid crystals is important in Cryo-procedures such as Selective Cryolipolysis (SC). We exploited a Near-Infrared Spectroscopy (NIRS) method to monitor the onset of fat phase transition (freezing/melting) in human abdominal adipose tissue. The changes in optical scattering were compared to Differential Scanning Calorimetry (DSC) measurements as the gold standard method for measuring phase transition. For some samples, concurrent in vitro measurements of optical scattering using NIRS and the MR signal parameters (T2*) as well as spectral parameters using MR Spectroscopy were performed in a 3 T MR scanner during a cooling/heating cycle. To further investigate phase-transition in adipose tissue in microscopic level, an identical cooling/heating procedure was replicated on a small piece of fat harvested from the same tissue while being imaged under Optical Coherence Tomography (OCT). For all methods, their relationship with temperature shows inflexions in a narrow range, characteristic of lipid phase transition. In particular, the good agreement between DSC and Optical measurements suggests that such NIRS methods can be used to improve dosimetry and to minimize variations of clinical outcome for cryo-procedures.

Highlights

Monitoring phase transition in adipose tissue and formation of lipid crystals is important in Cryoprocedures such as Selective Cryolipolysis (SC)
This procedure is proved to be effective for removal of subcutaneous fat[11], it is conceivable that real time monitoring of onset and distribution of fat freezing can improve the dosimetry of the treatment and further minimize any variation of treatment efficacy
During the cooling trace the optical scattering progressively increases, but the increase substantially accelerates once the sample goes under ~10 degrees C

Summary

Introduction

Monitoring phase transition in adipose tissue and formation of lipid crystals is important in Cryoprocedures such as Selective Cryolipolysis (SC). To further investigate phase-transition in adipose tissue in microscopic level, an identical cooling/heating procedure was replicated on a small piece of fat harvested from the same tissue while being imaged under Optical Coherence Tomography (OCT). For all methods, their relationship with temperature shows inflexions in a narrow range, characteristic of lipid phase transition. Studies have shown that multiple additional pre/post treatment options such as massage can enhance the efficacy of the outcome[9,10] This procedure is proved to be effective for removal of subcutaneous fat[11], it is conceivable that real time monitoring of onset and distribution of fat freezing can improve the dosimetry of the treatment and further minimize any variation of treatment efficacy. For some samples we performed Magnetic Resonance Imaging (MRI)/Spectroscopy (MRS) measurements as well as Optical Coherence Tomography

Methods

Results

Discussion

Conclusion