Fluoroscopy is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object.
It allows visualization of internal structures and function of a patient, so that the pumping action of the heart or the motion of swallowing, for example, can be watched.
It is useful for both diagnosis and therapy and occurs in general radiology, interventional radiology, and image-guided surgery.
A fluoroscope consists of an X-ray source and a fluorescent screen, between which a patient is placed.
Most fluoroscopes have included X-ray image intensifiers and cameras to improve the image’s visibility and make it available on a remote display screen.
Fluoroscopy produces live pictures with recording and playback.
Fluoroscopy is similar to radiography and X-ray computed tomography (X-ray CT) in that it generates images using X-rays.
Modern radiography, CT, and fluoroscopy now use digital imaging with image analysis software and data storage and retrieval.
Fluoroscopy source projects from below leading to horizontally mirrored images, and in keeping with historical displays the grayscale remains inverted, that is radiodense objects such as bones are dark whereas traditionally they would be bright.
X-rays can penetrate a wider variety of objects but they are invisible to the naked eye, and must be converted into a form that is visible.
Classic film-based radiography achieves this by the variable chemical changes that the X-rays induce in the film, and classic fluoroscopy achieves it by fluorescence, in which certain materials convert X-ray energy into visible light.
As the X-rays pass through the patient, they are attenuated by varying amounts as they pass through or reflect off the different tissues of the body, casting an X-ray shadow of the radiopaque tissues such as bone tissue on the fluorescent screen.
Images on the screen are produced as the unattenuated or mildly attenuated X-rays from radiolucent tissues interact with atoms in the screen through the photoelectric effect, giving their energy to the electrons.
While much of the energy given to the electrons is dissipated as heat, a fraction of it is given off as visible light.
All forms of digital X-ray imaging-radiography, fluoroscopy, and CT, the conversion of X-ray energy into visible light can be achieved by electronic sensors, such as flat panel detectors, which convert the X-ray energy into electrical signals: small bursts of electric current that convey information that a computer can analyze, store, and output as images.
Fluoroscopy renders moving pictures during a surgery or any other procedure.
Fluoroscopy is used in orthopaedic surgery and podiatric surgery to guide fracture reduction and in use in certain procedures that have extensive hardware.
In urology, fluoroscopy is used in retrograde pyelography and micturating cystourethrography to detect various abnormalities related to the urinary system.
Fluoroscopy is used to confirm needle and guide wire location when placing a nephrostomy.
Fluoroscopy is used for diagnostic angiography, percutaneous coronary interventions, (pacemakers, implantable cardioverter defibrillators, and cardiac resynchronization devices).
A barium swallow exam taken via fluoroscopy.
Fluoroscopy can be used to examine the digestive system using a substance that is opaque to X-rays (usually barium sulfate or gastrografin), which is introduced into the digestive system either by swallowing or as an enema.
Liver biopsy is performed under fluoroscopic guidance at many centers.
Angiography of the leg, heart, and cerebral vessels.
Placement of a peripherally inserted central catheter.
Placement of a weighted feeding tube (e.g. Dobhoff) into the duodenum after previous attempts without fluoroscopy have failed.
Discography, an invasive diagnostic procedure for evaluation for intervertebral disc pathology.
In lumbar puncture, fluoroscopy helps to guide where the needles of the spinal tap can go, and may reduce the number of attempts required for a successful lumbar puncture.
Fluoroscopy is also used in airport security scanners to check for hidden weapons or bombs.
Fluoroscopy was discontinued in shoe-fitting because the radiation exposure risk outweighed the trivial benefit.
Modern improvements in screen phosphors, digital image processing, image analysis, and flat panel detectors have increased image quality while minimizing the radiation dose.
Modern fluoroscopes use caesium iodide (CsI) screens and produce noise-limited images, ensuring that the minimal radiation dose results while still obtaining images of acceptable quality.
Because the patient must be exposed to a continuous source of X-rays instead of a momentary pulse, a fluoroscopy procedure generally subjects a patient to a higher absorbed dose of radiation than an ordinary radiograph.
Only important applications such as health care, bodily safety, food safety, nondestructive testing, and scientific research meet the risk-benefit threshold for use. In the first half of the 20th century, shoe-fitting fluoroscopes were used in shoe stores, but their use was discontinued because it is no longer considered acceptable to use radiation exposure, however small the dose, for nonessential purposes. Much research has been directed toward reducing radiation exposure, and recent advances in fluoroscopy technology such as digital image processing and flat panel detectors, have resulted in much lower radiation doses than former procedures.
Fluoroscopic procedures pose a potential for increasing the patient’s risk of radiation-induced cancer.
In addition to the cancer risk radiation effects have also been observed ranging from mild erythema, equivalent of a sunburn, to more serious burns.
Radiation doses to the patient depend greatly both on the size of the patient and length of the procedure, with typical skin dose rates quoted as 20–50 mGy/min.
Exposure times vary depending on the procedure being performed, ranging from minutes to hours.
Image intensifiers have been introduced that increase the brightness of the screen, so that the patient can be exposed to a lower dose of X-rays.
Within the XRII, five mini components make up this intensifier, which are:
Most imaging centers now use nonionic contrast. exclusively.
Negative radiographic contrast agents are air and carbon dioxide (CO2).