Radiology
MRI uses strong magnetic fields to align atomic nuclei (usually hydrogen protons) within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the radio frequency signal generated as the nuclei return to their baseline states. The radio signals are collected by small antennae, called coils, placed near the area of interest. An advantage of MRI is its ability to produce images in axial, coronal, sagittal and multiple oblique planes with equal ease. MRI scans give the best soft tissue contrast of all the imaging modalities. With advances in scanning speed and spatial resolution, and improvements in computer 3D algorithms and hardware, MRI has become an important tool in musculoskeletal radiology and neuroradiology.
Prostate biopsy
Since the mid-1980s, TRUS biopsy has been used to diagnose prostate cancer in essentially a blind fashion because prostate cancer cannot be seen on ultrasound due to poor soft tissue resolution. However, multi-parametric magnetic resonance imaging (mpMRI) has since about 2005 been used to better identify and characterize prostate cancer. A study correlating MRI and surgical pathology specimens demonstrated a sensitivity of 59% and specificity of 84% in identifying cancer when T2-weighted, dynamic contrast enhanced, and diffusion-weighted imaging were used together. Many prostate cancers missed by conventional biopsy are detectable by MRI-guided targeted biopsy. In fact, a side-by-side comparison of TRUS versus MRI-guided targeted biopsy that was conducted as a prospective, investigator-blinded study demonstrated that MRI-guided biopsy improved detection of significant prostate cancer by 17.7%, and decreased the diagnosis of insignificant or low-risk disease by 89.4%.