The data presented in this study, although preliminary, suggest a potential validity of biomagnetism in the differentiation of uterine myomas. This is not unexpected as malignant tissues, by virtue of their rapid expansion, vascularity and thus increased ionic movements produce magnetic fields of higher intensity than normal tissues [15
It is well known that tumor hyperemia is related to new blood vessel growth (neovascularization) as well as to dilatation of previously existing vessels. Viable tumor cells release diffusible angiogenic factors, which stimulate new capillary growth and endothelial mitosis in vivo [21
] even when tumor cell proliferation has been arrested by irradiation [22
]. Folkman et al
] proposed a hypothesis that "once tumor take occurs", every further increase in tumor cell population must be preceded by an increase in new capillaries which converge upon the tumor in early growth. According to this concept, a small focus of tumor cells could not increase indefinitely without the induction of angiogenesis. Furthermore, there is strong evidence that growth of solid tumors beyond a few millimeters in diameter depends on the induction of functional microcirculation from the surrounding host tissue. It is obvious that malignant tumor induces growth of the independent and characteristic vascular network on its own. The tumor vasculature is highly heterogeneous and does not conform to standard normal vascular organization (i.e. artery, to arteriole, to capillaries, to postcapillary venule, to venule, to vein). A key difference between normal and tumor vessels is that the latter are dilated, saccular and tortuous, and may contain tumor cells within the endothelial lining of the vessel wall [24
It has been well established in previous studies that low uterine artery PI values are present in uteri with myomas. This may be an effect of increased uterine size and not necessarily an effect of the myomas per se. Differences in the uterine artery PI values might also reflect differences in the women's menstrual status (pre-menopausal vs menopausal women). In this study all women were pre-menopausal and the difference in PI values between the two groups is more likely to be explained by the difference in the myoma size.
Doppler velocimetry studies on myoma vessels (both capsule and core vessels) have shown that PI values < 1.0 are common in uterine myomas and do not indicate malignancy. This eliminates the role of Doppler study in the discrimination of benign uterine myomas from other malignant pelvic tumors. Biomagnetic recordings obtained from benign and malignant tumors of various organs (eg breast, ovary) proved to be helpful in the differentiation of the tumor's biologic behavior [12
]. Further biomagnetic studies on uterine myomas might elucidate the value of biomagnetism in the differential diagnosis of benign and malignant pelvic tumors.
The data presented in the study, although preliminary, justify a novel approach to biomagnetism and suggest that this imaging modality of measuring the magnetic activity of uterine artery circulation can be potentially exploited in follow up of women with myomas. It is a non-invasive procedure, reliable, rapid and easy to interpret. Furthermore, it is totally harmless and well tolerated by women. It is true that SQUID biomagnetometry needs special equipment, a suitable prepared room and a good methodological knowledge, but once these requirements have been met, the method is rewarding. A further refinement of the equipment so as to be more sensitive and easily moved to the patients' bedside could be most helpful in clinical practice. Nevertheless, further studies in large numbers of women are needed in order to evaluate the role of biomagnetometry in the differentiation of pelvic tumors and to investigate its potential role as an adjunct procedure to established diagnostic methods.