Digest Journal of Nanomaterials and Biostructures Vol. 7, No. 4, October-December 2012, p. 1793-1798 Co x Zn x-1 Fe 2 O 4 NANOPARTICLES FERRITE SERIES AS MAGNETIC RESONANCE IMAGING CONTRAST AGENTS C. P. CONSTANTIN a , T. SLATINEANU b , M. PALAMARU b , A. IORDAN b , O. F. CALTUN a* a Faculty of Physics and Carpath Center, Alexandru Ioan Cuza University, Bd. Carol I. Nr. 11, Iasi, 700506 Romania b Faculty of Chemistry, Alexandru Ioan Cuza University, Bd. Carol I. Nr. 11, Iasi, 700506 Romania Contrast agents are used in magnetic resonance imaging to influence the magnetic relaxation process so that lesions, structures or vessel – otherwise would poorly identifiable – can be visualized. The most commonly used media are the paramagnetic contrast agents, which have their strongest effect on the T1, by shortening T1 relaxation time in tissues where they accumulate. To this purpose a lot of in vitro and in vivo studies on ferrite nanoparticles and iron oxides have been conducted. In our study a series of Co x Zn x-1 Fe 2 O 4 ferrites, with x= 0; 0.2; 0.4; 0.6; 0.8; 1 were obtained by sol-gel method. Ferrite nanoparticles were dispersed in agarose gels and scanned with a medical MRI APERTO (Hitachi, Japan) device (0,4 Tesla). Basic T1 and T2 weighted sequences were obtained. Images were analyzed using a commercial program, Spin Software, to highlight the influence of particles on image contrast by attributing different colors to different intensity of pixels. For small values of x, contrast was enhanced in T2 weighted sequences while for higher values of x a positive T1 contrast was shown. (Recieved October 16, 2012; Accepted November 10, 2012) Keywords: Nanoparticles, Contrast agent, Magnetic resonance imaging 1. Introduction Magnetic resonance imaging (MRI) is a technique used for imaging benign or malignant tumors. This technique is based on the relaxation of magnetic nuclear moments in a high intensity magnetic field (0.2-3T) [1]. When subject to a magnetic field, the magnetic moments will align on 2 energy layers (E 1 - low energy and E 2 - high energy, ∆E=γћB o ). Most of the moments will align on the E 1 level. When a radiofrequency pulse sequence is applied two relaxation fenomena occur – transverse and longitudinal, which are characterized by their respective relaxation times [2]. The contrast in such imaging techniques is given by different relaxation times. For many tissues contrast is similar in plain images. To increase tissue discrimination contrast agents have been used [3]. Contrast agents use magnetic nanoparticles in order to influence relaxation times. Gadolinium based agents - paramagnetic and influencing longitudinal relaxation – are commonly used. To be eligible as contrast agents nanoparticles must have certain properties such as: reduced toxicity for both the environment and the patient, a capability to influence one of the relaxation times and a sufficiently long permanence time in the tissue to be examined [4]. The development of new environmentally friendly technologies to obtain new contrast agents is of special interest. To this end we study the properties of materials such as ferrite, iron * Corresponding author: caltun@uaic.ro