Positron annihilation lifetime spectroscopy of adipose, hepatic, and muscle tissues

Abstract

Can positron annihilation lifetime spectroscopy (PALS) be employed to discriminate different types of soft tissues? This work reports our experimental measurements of the three components of positron annihilation lifetime spectra for three types of bovine, non-fixated soft tissues: adipose, hepatic, and muscle. These three components of PALS spectra correspond to contributions from annihilation lifetimes of para-positronium (p-Ps), positron, and ortho-positronium (o-Ps). We also report a benchmark comparison between PALS and X-ray phase-contrast imaging, which is the current state-of-the-art for soft tissue imaging and analysis. Our measurements showed that the joint probability of annihilation from p-Ps and positron in the soft tissues increases with electron density of the tissue and hence correlates well with the mean voxel values measured by X-ray phase-contrast computed tomography. Notably, the o-Ps lifetime in adipose tissue (2.53±0.01 ns) was approximately 25% longer than in hepatic (2.03±0.02 ns) and muscle tissues (2.00±0.01 ns). The significance here is that the o-Ps lifetime is a viable non-invasive probe for analyzing and discriminating the different soft tissues with a strong sensitivity to the lipid content of the tissue.

Developing a novel positronium biomarker for cardiac myxoma imaging

“…Observed differences in o-Ps lifetime between both adipose and myxoma tissue and myxoma cell cultures vs tissues can originate from different intramolecular void structure and free radicals and oxygen concentration. It was shown by studies of various biological samples that each of this factor is contributing to o-Ps lifetime values [54][55][56][57][58][59][60]. Detailed understanding of the relative contribution of various electron-positron annihilation mechanisms requires further systematic investigations.…”

First positronium image of the human brainin vivo

“…The resolution of 10 ps is much smaller than the range of oPs lifetime values for various tissues, ranging from about 1.4 ns to 2.9 ns [10, 12, 25–27, 64]. It is also smaller than differences observed in the oPs mean lifetime between healthy and cancer tissues, ranging from 50 ps to 700 ps [9, 10, 13, 28, 65, 66].…”

Positronium Physics and Biomedical Applications

“…In highly hydrated organs (lens) or tissues (myoma), the mean o-Ps lifetime is below or around ∼2 ns (Sane et al, 2010;Zgardzinska et al, 2020). In adipose tissue this time is significantly increased (Avachat et al, 2022;Moskal et al, 2021a,b) confirming the observation from biological systems that structural characteristic and molecular composition determine positronium annihilation.…”

“…Further studies on complex biological systems like biological membranes or proteins moved positronium research towards structural biology and showed that this approach was efficient in the study of biological reactions (such as electron transfer (Jean and Ache, 1977)), phase transition of lipids (Chow et al, 1981;Jean and Hancock, 1982;Stinson et al, 1980) macromolecule structure (Handel et al, 1976), hydratation (Akiyama et al, 2007Gregory et al, 1992;Handel et al, 1980) and porosity (Chamerski et al, 2017;Pamula et al, 2006) of biological samples. Nowadays, after many years of focused research, PALS appears to be a promising technique in the investigation of the structure of macromolecules (Chen et al, 2012) and clinical samples (Avachat et al, 2022;Moskal et al, 2021a,b;Zgardzinska et al, 2020).…”