This invention, coat doing the iron oxide nano grain where magnetism improves by the fact that annealing it does with the hydrophilic material making use of the salt, the manner which prepares the living body compatibility iron oxide nano grain, and the magnetic resonance image which includes the iron oxide nano grain which is prepared because of this (magnetic resonance imaging and MRI) regards the contrast medium. Although the inside carboxymethyl dextran of the hydrophilic material (Carboxymethyl dextran, CM - dextran), is stabilized the iron oxide nano grain which was heat-treated, at the same time plays the image effect it is most efficient.< Choice figure >Drawing 1本発明は、塩を用いてアニーリングすることで磁性が向上された酸化鉄ナノ粒子を親水性物質でコーティングして生体適合性酸化鉄ナノ粒子を調製する方法、及びこれにより調製される酸化鉄ナノ粒子を含む磁気共鳴画像(magnetic resonance imaging、MRI)造影剤に関する。親水性物質のうちカルボキシメチルデキストラン(Carboxymethyl dextran、CM‐デキストラン)が、熱処理された酸化鉄ナノ粒子を安定化させ、且つ造影効果を奏するのに最も効率的である。【選択図】図1
