Mixed sensors coupled to tuned flux transformer could more effective than classical tuned coils in detecting MRI signals on a very low field range. In order to compare later on their effectiveness, first, a very low field head MRI system (8.4 mT) is developed. Homogeneity, gradients strength, excitation and reception coils were adjusted. A homogeneity of 84 ppm was achieved in a quasi-open configuration. The amplitude of each gradient was 100 times lower than at high field but sufficiently high to achieve a resolution of less 2 mm x 2 mm x 2 mm. Images with a 3D imaging acquisition without pre-polarization technique nor magnetic shielding room were achieved.