Particles spawning with an offset from the image set in planar region.

Hello, I am having a particle system on which I have put a custom image to the planar region in order to spawn particles on the shape of this image. Although I do have managed to do that. Then, when I change on the Sprite-Emitter the Rendering Strategy from the default Render as dots to Use Age the particles the particles spawn with an offset on Y axis (vertical, they spawn upper than the dots). Do you have any suggestions of what might be doing this?

Thank you very much in Advance.