The pace of innovation in diagnostic radiology has increased exponentially, in tandem with computer advances and the rapid evolution of microprocessing power. Imaging of the urinary tract, as a result, has become more flexible and precise, with new procedures offering a great selection of options and the implementation of new imaging algorithms. Ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) provide higher soft-tissue contrast resolution than conventional radiography, as well as multiplanar imaging capability, resulting in significant advances in almost all areas of uroradiology. In academic centers, metabolic and molecular imaging techniques have become the focus of new research and have begun to enter the realm of daily clinical practice. While imaging advances have produced new algorithms for approaching diagnostic evaluation, appropriate use of imaging in each individual case also depends greatly on the equipment and professional talent available. One imaging modality or protocol may offer specific advantages over another, depending on the clinical question, and the importance of a collaborative approach from the medical team cannot be overemphasized.
In summary, ever-changing uroradiology remains indispensable in the diagnosis and treatment of patients with urologic disorders. This chapter discusses the imaging techniques used in uroradiology and summarizes the advantages and disadvantages of the various techniques and concludes with a brief discussion comparing imaging methods.
X-rays are electromagnetic waves with photon energies that typically fall between those of gamma (γ) rays and ultraviolet radiation. Radiography is possible because tissues differ in their ability to absorb x-rays. A radiopaque contrast medium is frequently employed to enhance soft-tissue contrast.
Although newer imaging techniques have largely replaced conventional radiography for diagnosis of many urologic problems, general radiography remains useful for some urologic disorders; therefore, the urologist should be familiar with x-ray equipment and uroradiologic techniques. The basic types of uroradiologic studies are plain (conventional) abdominal films (also known as kidney–ureter–bladder [KUB] films), intravenous urograms (IVUs), cystourethrograms, urethrograms, and angiograms. These studies are described separately in sections that follow.
Basic Equipment and Techniques
1. Radiography fluoroscopy
Many conventional x-ray units contain both radiographic and fluoroscopic capabilities. These require a high-voltage power supply, an x-ray tube, a collimating device, and an x-ray detector or film. Fluoroscopic units also use an electronic image intensifier and an image display system. Today, most radiology departments have become completely “filmless” as digital recording, displaying, and archiving of images are replacing film-based techniques.
Image intensifiers, coupled to videocameras, electronically augment the ordinary dim fluoroscopic image.
Conventional recording of an x-ray image uses film and intensifying screens. The image intensifier and camera can be used to capture dynamic and static images. Real-time images are now typically recorded using conventional or digital video. Conventional spot or cine images may ...