Scientific research at Sheba includes a study of pregnancy after transplantation of cryopreserved ovarian tissue in a patient with ovarian failure after chemotherapy;[20] a study of alginate-based stem cell biomaterial injected into heart attack victims that may repair heart tissue;[21] and a study showing that heavy cell phone users are subject to a higher risks of benign and malignant tumors of the salivary gland.[22] The Israeli company Ventor Technologies developed a novel type of heart valve which can be implanted by catheterization rather than open-heart surgery at Sheba.