Ultrasonic detection of anti cancer treatment success using tissue acoustic properties and parametric imaging

Abstract

In cancer therapy the estimation of the tissue response is of importance for its therapeutic success. However, the efficacy cannot be assessed easily during the treatment. Today Biopsy and nuclear medicine are the current procedures for estimating the content of apoptotic cells within a tumor. It has been observed that ultrasound backscatter from collections of cancerous cells that are undergoing cell death due to chemo- or radiation therapy show increased intensity and alterations in signal characteristics. Acoustic attenuation, backscatter intensity and spectral features are tissue acoustic properties that can be applied for a parametric imaging - based method to estimate the treatment response of cancerous tissue. Diagnostic ultrasound does not harm the human body and therefore can be applied continuously during chemo- or radiation therapy. In this study ultrasound in the range between 10 and 55 MHz was used to investigate the treatment dependent changes in ultrasound backscatter signals of cervix carcinoma cells (HeLa). The data collection was performed at 6 time points during the treatment. The scanning procedure allowed the simultaneous acquisition of backscatter signals obtained from the cell pellet and a reference signal estimated by a flat quartz cylinder. From the normalized power spectra of the ultrasound radio frequency signals backscatter coefficients and spectral slopes were computed. Applying a Gaussian form factor model the effective scatterer size and acoustic concentration were derived using two different methods. Results of the data analysis showed decreasing effective scatterer sizes of 10% to 15% for both methods and frequency ranges. In concordance the acoustic concentration and integrated backscatter coefficients increased continuously throughout the treatment time by 230% for signals acquired with a 20 MHz transducer and by over 300 % when using a 40 MHz transducer. The detected changes are linked to structural cell changes when undergoing apoptosis. This study contributes towards a non-invasive method for estimating the response in cancer therapy.