For MRI imaging, during quadrature detection, if sine carrier has phase shift about some angle, what would change on the image? I could imagine real and imaginary parts of signal separetely but i can't exactly decide the image combining both. How quadrature and in phase images combine together to form the resulting image?
It depends on a sequence used. For simple cases:
You have to keep in mind that the signal received by NRI receiver is frequency domain signal. So it is converted to spatial domain by FFT. FFT is a complex transformation. It needs phase of each frequency component on its input. Wrong or missing phase on FFT input leads to bad artifacts, actually, it damages the image.
In most simple cases, the phase information is dropped out after FFT.