A pharmaceutically acceptable implant system comprising a collection of pharmaceutically acceptable, covalently-crosslinked hydrogel particles having a radioopaque agent covalently attached to a plurality of the particles in the collection, with the radioopaque agent being present in the collection at a concentration of at least about 0.1% w/w. The implantable materials may be used, for instance, in an iatrogenic site and for fiducial marking.埋込み可能な材料を医原性部位で用いることができる。用途には、基準マーキングのための放射線不透過性材料が含まれる。
