In a spinning position of a spinning machine a longitudinal fibre array first is refined in a drafting process, and the refined fibre array then is subject to a twist imparting process, and is taken off the twist-imparting zone as a yarn. The baseline and treatment ultrasounds are compared, and as a result a damage map representing cell death within the treatment area can be constructed. A second portion of the defined volume is scanned at a high-density sampling rate, higher than the low-density sampling rate, to obtain at least one high-density frame. The formed pegylated liposomes contain the hydrophobic photosensitizer within the lipid bilayer membrane. The repeater re-transmits the original BTS signal as well as a time delayed version of the signal.