By: Dan Sperling, MD
Diffusion weighted magnetic resonance imaging (DWI-MRI) has tremendous diagnostic value for conditions throughout the body, not just the prostate. Diffusion weighting is one of parameters that distinguish unhealthy tissue from normal tissue. It gives qualitative and quantitative information about the random motion of water molecules in tissues, and can give functional insight into the disease state of a tumor and its surrounding architecture. It has two advantages over other types of cancer imaging: it does not require use of a contrast agent, and there is no exposure to radiation. I want to share some of the diverse ways that magnetic resonance imaging, using DWI, is being used besides detecting prostate cancer.
Metastatic bone cancer: If cancer spreads from an organ such as the prostate into the bones, early and accurate detection is critical in order to quickly intervene, as bone lesions can be very painful. Some particular types of lesions are not well detected by bone scintigraphy, the conventional imaging for bone disease. PET and CT scans are also sometimes used, but all of these tests involve exposure to radiation. One MRI functional parameter, Diffusion Weighted Imaging (DWI) is more widely available than PET/CT, and it has already demonstrated usefulness in this area, and research continues on ways to improve DWI-MRI scans for bone lesions.
Focal lesions in the liver: DWI-MRI can differentiate between benign liver lesions and cancerous ones. In addition, it can reveal how well a treatment is working by documenting changes in the lesion after treatment.
Lung cancer: The current imaging gold standard for non-small cell lung cancer (NSCLC), the most common type of lung cancer, is called 18F-FDG-PET/CT. As far as telling the difference between NSCLC and noncancerous nodules in the lungs, it increasingly appears that DWI-MRI delivers equivalent results. Although PET/CT may be superior for characterizing aggression, DWI-MRI has potential for predicting how well a tumor will respond to chemo/radiotherapy.
Gastrointestinal cancer: DWI-MRI also appears to be competitive with FDG-PET/CT in detecting a rare type of gastrointestinal cancer called peritoneal carcinomatosis (PC). This malignancy affects the thin layer of tissue that surrounds the organs in your abdominal cavity, and may be a result of spread from another cancer of the digestive system. The ability to identify the presence of multiple lesions by imaging spares patients from how such tumors used to be discovered through exploratory surgery.
As you can see, DWI-MRI has a wide range of applications. As more powerful magnets are developed, and software refined, it will prove to be a huge benefit to employ imaging that does not require contrast agents, and especially for patients who need frequent repeat imaging, does not involve radiation exposure.