Applications of positron annihilation to dermatology and skin cancer

Abstract

Positronium annihilation lifetime experiments have been performed to investigate the interaction between skin cancer and positronium for human skin samples. Positronium annihilation lifetime is found to be shorter and intensity is found to be less for the samples with basal cell carcinoma and squamous cell carcinoma than the normal skin samples. These results indicate a reduction of free volume in the molecular level for the skin with cancer with respect to the skin without cancer. Positron annihilation spectroscopy may be potentially developed as a new noninvasive and external method for dermatology clinics, early detection of cancer, and nano-PET technology in the future. However, the sun's UV-radiation can cause skin damage including wrinkles, lowered immunity against infection, aging skin disorders, and also lead to cancer [2]. The possible mechanisms for UV skin damage are collagen breakdown, the formation of free radicals, interfering with DNA repair, and inhibiting the immune system. The current method to diagnose skin cancer uses an invasive biopsy which is surgically excised from human body for pathological analysis [3]. This is a destructive technique which can cause a scar in the skin. Therefore, to develop a non-invasive and external technique to detect skin diseases is becoming one of most significant research areas for dermatology and skin cancer.Currently, one of the most practical methods in detecting cancer is Positron Emission Tomography (PET), which uses nuclear medicine containing positron emitters to generate positron annihilation radiation inside human body and then utilizes the gamma energy imaging technology to detect tumors [4]. However, PET is mainly for internal use and the detection focuses on the size (in mm) of tumor. The important information about molecular interaction between positron and cancer has not been investigated in current PET technique. Positron annihilation spectroscopy (PAS) has been recently developed to determine defects at a size in the order of 0.1-2 nm in polymeric materials [5] since the positronium (Ps, a bound atom consisting of a positron and an electron) was found to preferentially exist in free volumes.Recently we discovered that in a variable energy positron beam experiment the positron annihilation rate is significant lower for skin samples with cancer cells of basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) comparing with the skin without cancer cells [6]. However, those beam experiments were performed under high vacuum condition and the skin samples were dried. A more realistic measurement for skin system is for the skin in the presence of water molecules. In this paper we report

Detection of Atomic Scale Changes in the Free Volume Void Size of Three-Dimensional Colorectal Cancer Cell Culture Using Positron Annihilation Lifetime Spectroscopy

“…Positron annihilation lifetime spectroscopy (PALS) provides a direct measurement of the free volume void sizes in polymers and biological systems at the molecular level, and this free volume is critical to understand physical and mechanical properties of complex biomolecular systems as collagen [3], porcine eye lens [4], rat brain sections [5] and human skin [6].…”

“…Thus, PALS has been proposed as a potential tool to detect cancer formation at the early stages of tumor development [6], [7]. However, cellular composition of tissue samples varies from the same organism and may involve changes in the void sizes [8].…”

New Porosimetric Method Based on the 3γ Annihilation Rate. Applications to Materials Science and Medical Imaging

“…PALS techniques were applied successfully to investigate some living biological systems [25][26][27][28]. As it was mentioned above both factors: void sizes and concentration influence the 3γ fraction.…”

Human Tissue Investigations Using PALS Technique - Free Radicals Influence

“…PALS techniques were applied, however, in a very limited number of papers concerning living biological systems [10][11][12][13][14][15]. As the oPs lifetime reflects changes in the material structure, it * corresponding author; e-mail: bozena.jasinska@umcs.pl should be connected to the morphology of the cells of the living organisms [16].…”