Imaging the Urinary Tract: Fundamentals of Ultrasound, Computed Tomography, and Magnetic Resonance Imaging

Minimally invasive image-guided techniques in the field of urology have evolved rapidly over the past decades. With increasingly sophisticated interventions targeted to the urinary tract, there is an increased demand for more effective diagnostic imaging tests to support the urologist and interventional radiologist in both the identification of disease and guidance for procedural planning. The growth of noninvasive diagnostic imaging has allowed for accurate identification of urinary tract disease, in response to treatment and treatment-related complications. Grayscale ultrasound and Doppler ultrasound have been in the clinical mainstream for years; however, the development of contrast-enhanced ultrasound has resulted in a quantum leap over grayscale imaging for renal mass evaluation, rivaling that of MRI and CT. Computed tomography continues to be the first-line choice for the evaluation of many clinical scenarios where urologic disease is known or suspected. Dual-energy CT shows promise in characterization of stone disease and in renal and adrenal mass evaluation, among other potential applications. Employment of dose reduction techniques in CT over the past decade has resulted in significant decreases in radiation exposure to patients. MRI continues to evolve rapidly, with technologic advances leading to better image quality and decreased acquisition times. Prostate MRI continues to push the limitations of current MR technology; however, with the use of 3T magnets, long diffusion times, and meticulous attention to other technical parameters, high-quality imaging of the prostate is now a clinical reality. ET-CT can provide whole-body assessment for extent of disease and response to therapy in a patient with a known urologic malignancy. PET-CT and PET-MRI are also used for detection of prostate cancer recurrence, employing novel radiotracers such as Axumin® and prostate-specific membrane antigen (PSMA).