Radiology is a specialty of medicine concerned with obtaining and interpreting images of the body for diagnosis, treatment planning, and monitoring, and with performing image-guided procedures. Its techniques include X-rays, computed tomography, magnetic resonance imaging, ultrasound, and nuclear medicine imaging. Despite its name, radiology is not limited to techniques that use ionizing radiation: magnetic resonance imaging and ultrasound do not use it. A radiologist is a physician trained in the clinical application and interpretation of these examinations. (radiologyinfo.org)
Scope and clinical practice
Diagnostic radiology evaluates bodily structures and disease-related changes through imaging. Radiologists relate imaging findings to the clinical question, medical history, other examinations, and laboratory results. Their work includes interpreting examinations, communicating findings to referring clinicians, and helping determine whether further investigation is appropriate. Subspecialties include breast imaging, neuroradiology, musculoskeletal imaging, abdominal imaging, cardiovascular imaging, emergency radiology, and pediatric radiology. (radiologyinfo.org)
Interventional radiology uses imaging to guide instruments within the body for diagnostic or therapeutic purposes. It therefore combines image interpretation with procedural care rather than functioning solely as an image-reading service. (radiologyinfo.org)
Radiological practice involves several professions. Radiologic technologists operate imaging equipment and acquire images, while diagnostic medical physicists contribute to equipment performance, quality control, and radiation-dose assessment. These roles are distinct from the physician’s responsibility for clinical interpretation. (radiologyinfo.org)
Principal imaging techniques
The main techniques differ in the physical signals they measure and the information they provide.
- Radiography: Produces a static projection image by recording X-rays transmitted through the body. Differences in transmission create contrast between structures. Applications include skeletal examinations, dental imaging, and mammography. (fda.gov)
- Fluoroscopy: Uses X-ray imaging to display movement and guide procedures, including the placement of instruments and devices within the body. (fda.gov)
- Computed tomography (CT): Records X-ray measurements from multiple directions and uses computer processing to reconstruct cross-sectional images. These images can also support three-dimensional representations. (nibib.nih.gov)
- Magnetic resonance imaging (MRI): Uses strong magnetic fields and radiofrequency excitation to detect signals from atomic nuclei, principally hydrogen nuclei in biological tissues. It provides detailed soft-tissue images without ionizing radiation. Its physical basis is nuclear magnetic resonance. (nibib.nih.gov)
- Ultrasonography: Uses high-frequency sound waves and their returning echoes to image internal structures. It can provide real-time images and does not use ionizing radiation. Probes may be applied to the skin or positioned within the body. (nibib.nih.gov)
- Nuclear medicine imaging: Detects radiation emitted by administered radioactive tracers to investigate bodily functions and diagnose disease. Major methods include positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Hybrid systems combine these measurements with CT or MRI to relate functional information to anatomical location. (nibib.nih.gov)
Image-guided procedures
Interventional radiologists use modalities such as fluoroscopy, ultrasound, and CT to navigate needles, catheters, and other instruments to a target. Diagnostic procedures include image-guided biopsy, in which tissue is collected for examination. Therapeutic procedures include drainage of fluid collections, angioplasty and stent placement, embolization to block selected blood vessels, and thermal or cryogenic ablation of tissue. These procedures are generally performed through small access points rather than the larger incisions associated with open surgery. (radiologyinfo.org)
Contrast materials and safety
Contrast agents improve the visibility of selected tissues, vessels, or organs. Common examples include iodine-based materials for X-ray examinations and CT, and gadolinium-based agents for MRI. Their use introduces considerations separate from those of the imaging equipment itself, including possible allergic-like reactions and risks associated with impaired kidney function. Serious reactions are uncommon. (radiologyinfo.org)
Radiography, fluoroscopy, CT, and nuclear medicine imaging involve ionizing radiation. Such radiation can damage DNA and carries a potential increase in lifetime cancer risk. Some prolonged interventional fluoroscopy procedures can also deliver doses sufficient to cause tissue injury. Radiation protection rests on justification—establishing that an examination serves a clinical purpose—and optimization—using exposure appropriate to the task while maintaining adequate image quality. (fda.gov)
The absence of ionizing radiation does not eliminate all hazards. MRI safety depends on the interaction of its magnetic and radiofrequency fields with the patient, equipment, implants, and surrounding objects; relevant risks include heating and the attraction of ferromagnetic objects. (radiologyinfo.org)
References
- Diagnostic Radiology Professionsradiologyinfo.org
- What does a radiologist do?radiologyinfo.org
- Interventional Radiologyradiologyinfo.org
- Radiographyfda.gov
- Medical X-ray Imagingfda.gov
- Computed Tomography (CT)nibib.nih.gov
- Godfrey N. Hounsfield - Nobel Lecturenobelprize.org
- Magnetic Resonance Imaging (MRI)nibib.nih.gov
- Ultrasoundnibib.nih.gov
- Nuclear Medicinenibib.nih.gov
- Patient Safety - Contrast Materialradiologyinfo.org
- MRI Safetyradiologyinfo.org