We describe the development of the RAPID-SI technique and its implementation on a 3 T Siemens scanner. In-vivo studies demonstrate the performance of this technique in terms of acquisition time, signal-to-noise ratio, and data analysis. The results are compared to the CSI technique. Compared to CSI, RAPID reduces the acquisition time by a factor of R and provides accurate quantification results. The SNR of RAPID at the acquisition level is lower by √R and increased by data pre-processing. Quantification results of RAPID-SI are comparable to the CSI ones. The study shows that RAPID-SI provides accurate metabolite quantification results while significantly reducing acquisition time in obtaining MRSI data similar to CSI in terms of resolution and sensitivity.