Magnetic resonance imaging of the genitourinary tract.

MRI is in its infancy as a clinical imaging tool. It is undergoing intensive investigation in various areas of the body. Evaluation of the brain and spine is superb, and in some areas of the brain, like the posterior fossa, it is thought to be superior to CT. Evolving indications for body scanning include staging of pelvic malignancies, evaluation of liver malignancy, evaluation and staging of musculoskeletal problems, and, to a lesser degree, staging of renal malignancies and evaluation of vascular disease. The main problem in body imaging stems from image degradation because of respiratory motion that is transmitted to upper abdominal organs. Respiratory gating of image acquisition or utilization of short heavily T1-weighted pulse sequences will likely overcome this problem in due time. Minimizing motion artifact will make MR images comparable to, if not better than, CT images with regard to transverse anatomic display, and MR images have the added advantage of multiplanar scanning, which can be done directly, without need of additional computer reconstruction time and without having to move the patient. The second major problem in MRI is the lack of understanding of equipment potential. Unlike conventional radiography and CT, in which the behavior of the X-ray beam is understood with regard to image formation, in MRI new parameters are used to generate images. As stated earlier, MR signal intensity is due to hydrogen concentration, T1 and T2 relaxation times of the tissue, and flow of protons through the imaged volume. How these factors are weighted depends on pulse sequence selection, and thus image contrast and information content of the scans change. On the surface, these images display anatomic information as do other imaging modalities, but manipulation of pulse sequences may ultimately lead to the ability to demonstrate physiologic and chemical parameters previously unavailable in imaging. Current research is geared to help extract this data by testing new pulse sequences, using different types of receiver RF coils, and using MR-specific contrast materials. Minor MRI problems such as long scan times are being dealt with to decrease time to an acceptable length. The nonvisualization of soft tissue calcifications will probably remain a problem that may have to be weighed against other known advantages. At this time further research and clinical experience are the key to what is needed in MRI, to gain further knowledge with regard to imaging physiologic phenomena, such as flow and spectroscopy, and possibly to monitor the chemical basis of disease.(ABSTRACT TRUNCATED AT 400 WORDS)