Fluoroscope Health Article

Definition

A fluoroscope is an x-ray device that allows live images to be projected onto a viewing monitor during diagnostic and interventional procedures.

Purpose

A fluoroscope is used for real-time imaging of various anatomical areas during a diagnostic or interventional procedure. Fluoroscopy produces a live image of the area of interest, and can be used to view such motion as blood flow and catheter insertion. In contrast, radiography, or x-ray imaging, produces a still image on film.

Specific procedures that use fluoroscopy include aneurysm repair, hip and knee replacement, arthroscopy, catheter placement, needle biopsy, location of foreign bodies, swallowing studies, fracture reduction, discography, lithotripsy, brachytherapy, pacemaker insertion, endoscopic retrograde cholangiopancreatography (ERCP), and gastrointestinal evaluation (e.g., bowel studies). Fluoroscopy may also be used to detect bone cancer or digestive cancers, and digestive ulcers; however, computed tomography (CT) imaging is now routinely used to detect these conditions.

Description

The term fluoroscope generally refers to a mobile radiographic/fluoroscopic unit, also called a mobile C-arm because of its shape. A mobile C-arm system consists of two wheeled units: one carries the imaging arm, x-ray generator, and control console, and the other carries the image display monitors and image processing and recording devices. The imaging arm, which is shaped like the letter C, has an x-ray tube mounted on one end and an image intensifier mounted on the other end. The x-ray generator supplies the power to the x-ray tube, which emits x rays that pass through the patient and are absorbed by the image intensifier. The image intensifier is a phosphor screen that converts the x rays into light, which is then scanned and transmitted by a charge-coupled device (CCD) camera to a display monitor.

Fluoroscopy is also performed using larger stationary radiographic/fluoroscopic systems that include a patient table, an x-ray generator, an x-ray tube, an image intensifier, and an image display system configured in a shielded room. The term fluoroscope may be used to refer to the components of this stationary system that perform fluoroscopy, but it is most commonly used in reference to a mobile system.

Fluoroscopy is performed in surgical, orthopedic, critical care, emergency care, and diagnostic radiology settings. In addition, mobile fluoroscopes are used to image patients on stretchers, beds, or examination/procedure tables when they cannot be transported to the radiology department.

Scaled-down compact fluoroscopes that can be handheld are also available and are designed for fast, continuous imaging of the extremities at various angles. Mini C-arms may be used in the emergency department, during surgery, in a physician's office, in sports medicine and physical therapy, and in the field such as an accident site.

In 2000, a fluoroscope with a navigational or surgical guidance computer was introduced to improve instrumentplacement and imaging during minimally invasive surgical procedures, particularly those involving the spine.

Operation

The fluoroscope is maneuvered in such a way that the patient, and the anatomical area of interest, is positioned between the x-ray tube and the image intensifier. The operator uses the control console to set imaging parameters. The intensity of the x rays is controlled with the milliamperage (mA) setting, and the energy and intensity of the x rays are controlled with the peak kilovoltage (kVp) setting. A typical fluoroscopy image setting is 70 kVp at 2 mA. Most mobile C-arms have capabilities for magnified views, automatic brightness stabilization to maintain a constant brightness during the exam, and last-image hold to freeze the last acquired image on the monitor.

During fluoroscopic imaging, the patient is exposed to radiation; continuous fluoroscopy for long periods (e.g., during a surgical procedure) can deliver a significant radiation dose. Therefore, most systems have a pulsed fluoroscopy mode, which allows the x-ray output to be pulsed for periods ranging from 10 milliseconds to 30 times per second, and displays the image acquired with each pulse. Although the image on the monitor may be jumpy, radiation exposure to the patient can be reduced by as much as 75% with this mode. Dose reduction is especially important in pediatric patients and young adult patients of reproductive age. Clinical staff are also exposed to radiation, and portable radiation shields, lead aprons, and radiation badges should be worn by all staff present during fluoroscopy.

All images displayed on the monitor can be saved to a disk, video disk, compact disk, or tape. Some systems have digital capabilities that allow storage in digital memory or on a computer network. A videocassette recorder or digital recorder can be used to record several minutes of real-time fluoroscopy. Snapshot images can also be printed as hard copy using video printers, thermal printers, or a multi-format camera (a camera that records and prints multiple images; for example, four images on one film).