  Samples of uterine leiomyomatis and normal tissues taken from patients after
surgery were investigated using the Positron Annihilation Lifetime Spectroscopy
(PALS). Significant differences in all PALS parameters between normal and
diseased tissues were observed. For all studied patients, it was found that the
values of the free annihilation and ortho-positronium lifetime are larger for
the tumorous tissues than for the healthy ones. For most of the patients, the
intensity of the free annihilation and ortho-positronium annihilation was
smaller for the tumorous than for the healthy tissues. For the first time, in
this kind of studies, the $3\gamma$ fraction of positron annihilation was
determined to describe changes in the tissue porosity during morphologic
alteration.
