How Fluoroscopy Works | Indications and Physics of X-ray Fluoroscopy

What is fluoroscopy?

Fluoroscopy is a medical imaging exam that uses X-rays to create dynamics images of the inside of the body (i.e real-time imaging and short movies of the body). This allows doctors (e.g. interventional radiologist, surgeons, etc) to see internal organs, vessels, tissues, and abnormalities. Since the x-rays pass through the body the images are made are projections through the body and often include x-ray contrast agents such as iodine, barium and air.

What are the reasons for a fluoroscopy exam?

Fluoroscopy is a type of medical imaging that uses X-rays to create real-time images of the inside of the body. It is used to diagnose and treat a variety of conditions, including cancer, heart disease, gastrointestinal disorders, and musculoskeletal problems. Fluoroscopy can also be used to guide minimally invasive procedures such as biopsies and catheterizations. The main reasons for using fluoroscopy are to identify abnormalities in the body, assess organ function, and monitor the progress of treatments. Fluoroscopy can also be used to detect foreign objects in the body or guide surgeons during complex operations. In addition, it can help doctors diagnose diseases such as pneumonia or tuberculosis by providing detailed images of the lungs. Finally, fluoroscopy can be used to evaluate joint movement and alignment in order to diagnose musculoskeletal problems such as arthritis or fractures.

What is the difference between a CT scan and fluoroscopy?

Computed Tomography (CT) scans and fluoroscopy are two different imaging techniques used to diagnose medical conditions. A CT scan is a type of imaging that uses X-rays to create detailed 3D images of the body, while fluoroscopy is an imaging technique that uses X-rays to create real-time 2D images of the body. The main difference between CT scan and fluoroscopy is that CT is fully volumetric and better for low contrast imaging, such as imaging blood in the brain during stroke triage or changes in the gray and white matter which occur hours to days after a stroke. Modern CT scanners also do have real-time fluoroscopic imaging modes. However, traditional fluoroscopy has a higher frame rate and higher spatial resolution than CT and there are many clinical tasks where the higher frame-rate and spatial resolution of an x-ray fluoroscopy system outweigh the benefits of CT.

What happens during a fluoroscopy exam?

A fluoroscopy exam is a type of medical imaging procedure that uses X-rays to create real-time images of the body. During the exam, a radiologist and radiologic technologists (sometimes improperly called technicians) will use a fluoroscope, which is an X-ray device which produces x-rays and uses an image receptor to measure the x-rays that pass through the body in order to view inside the body in real-time.

Typically, the patient will be asked to lie on a table and may be given contrast material to help make certain areas more visible. The radiologist or technician will then move the fluoroscope around the area being examined while taking pictures. These images are then displayed on the monitor in real time, allowing the doctor to see what’s happening inside the body as it happens. Fluoroscopy exams can be used to diagnose and treat many conditions, including: heart disease, gastrointestinal issues, and other vascular issues.

Are you sedated for a fluoroscopy exam?

During a fluoroscopy exam, you may be sedated in order to reduce any discomfort or anxiety. Sedation can range from minimal to moderate depending on the procedure and your individual needs. If you are sedated for a fluoroscopy exam, you will likely receive an intravenous medication that will help you relax and make the procedure more comfortable. The amount of sedation used is tailored to each individual patient and their specific needs. After the procedure, you may experience some drowsiness or confusion as the effects of the medication wear off. It is important to have someone available to drive you home after your appointment if you have been sedated for a fluoroscopy exam.

What are the benefits of Fluoroscopy?

The benefits of angiography and non-invasive procedures using real-time imaging from fluoroscopy include the ability to see inside the body more clearly especially as objects are moving. This can help doctors diagnose and treat medical problems more accurately, than with radiography alone. Additionally, fluoroscopy exams are often less invasive than other types of procedures. This means patients are less likely to experience any pain or discomfort during the procedure.

What examinations might include fluoroscopy, i.e. what procedures are included in diagnostic fluoroscopy?

There are a wide range of applications for real-time tracking that can be done under x-ray guidance by the projection images that can be acquired by the fluoroscope. These procedures include:

  1. Barium swallow or upper gastrointestinal (GI) series which looks at the esophagus, stomach, and small intestine. The patient drinks a solution containing barium, which shows up on the X-ray images and helps to outline the digestive tract.
  2. Hysterosalpingography which is used to examine the uterus and fallopian tubes. Iodinated contrast is injected through the cervix, and the images produced by the fluoroscope allow the doctor to see the shape and size of the uterus and fallopian tubes and check for any blockages or abnormalities.
  3. Arthrography which is used to look at joints such as the shoulder, hip, or knee. Iodinated contrast is injected into the joint, and the fluoroscope is used to produce images that show the inside of the joint and any problems such as torn cartilage or arthritis.
  4. Angiography is used to look at the blood vessels and can be used to diagnose problems such as blockages or aneurysms. A special dye is injected into the blood vessels, and the fluoroscope is used to produce images that show the inside of the blood vessels and any problems.
  5. Myelography is used to evaluate the spinal cord and has been replaced to a large extent by CT or MRI examinations but fluoroscopic guidance can still be used to guide the contrast injection.
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What interventional procedures include fluoroscopy?

Fluoroscopy is used for a number of interventional procedures including: joint, spine, neuro interventions and cardiac catheterizations. These procedures include:

  1. Biopsies: During a biopsy, a small sample of tissue is removed and examined under a microscope. Fluoroscopy can be used to guide the biopsy needle to the correct location and ensure that an adequate sample is obtained.
  2. Stent placement: A stent is a small metal mesh tube that is used to hold open a blocked or narrowed blood vessel. Fluoroscopy is used to guide the stent to the correct location and ensure that it is properly placed.
  3. Balloon angioplasty: This procedure is used to widen a blocked or narrowed blood vessel. A small balloon is inflated inside the blood vessel, and fluoroscopy is used to guide the balloon to the correct location and ensure that it is properly inflated.
  4. Vertebroplasty: This procedure is used to stabilize a fractured vertebra (bone in the spine). Fluoroscopy is used to guide the needle to the correct location and ensure that the cement is properly injected into the vertebra.
  5. Radiofrequency ablation: This procedure is used to destroy tissue, such as a tumor or abnormal cells. Fluoroscopy is used to guide the needle (or set of needles) to the correct location and ensure that the radiofrequency energy is delivered to the targeted tissue.
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How do I get ready for fluoroscopy?

Getting ready for fluoroscopy is an important step in ensuring a successful procedure. First, you should make sure to wear comfortable clothing that does not have any metal components, such as zippers or buttons. You may also be asked to remove jewelry and other metal objects from your body. Additionally, you should inform your doctor of any allergies or medical conditions that could affect the procedure. Before the procedure begins, you will be asked to lie on a table and the radiologic technologist will position you so that the area of interest can be seen clearly. During the procedure, you may be asked to hold your breath or move into different positions so that the radiologic technologist (and potentially interventional staff such as interventional radiologist) can get a better view of the area being examined. Afterward, you may need to wait for a few minutes while the radiologist reviews the images before being allowed to leave. Following these steps will help ensure that your fluoroscopy experience is safe and successful.

Can fluoroscopy be done without contrast?

Yes, fluoroscopy can be performed without contrast and the dynamic acquisition is used to track either motion of the patient themselves such as intentional joint motion to observe the joint articulation or to track other objects in the field of view such as biopsies or injections which are performed using fluoroscopy for needle guidance.

What are the components of a fluoroscopy system?

The fundamental components of a modern fluoroscopy system are shown in this figure. Where the x-rays are generated by the x-ray tube and pass through the filters, collimator, anti-scatter grid and finally the remnant beam is measured on a flat panel detector.

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  1. X-ray tube and Generator: This is the source of the X-rays that are used to produce the images. The X-ray tube is located in the head of the fluoroscopy machine, and it generates X-rays when a high voltage current is passed through it. The generator is the source of the high tube potential in order to power the x-ray tube.
  2. Beam Filtration: In many x-ray systems there are beam filters which can be added from the side such that additional beam filtration can be added over areas which have lower attenuation within the anatomy itself.
  3. Collimator: This is a device that is used to shape the X-ray beam and control the size and shape of the area being imaged. The collimator is located between the X-ray tube and the patient and can be adjusted to change the size and shape of the beam.
  4. Image Receptor (Image Intensifier or Flat Panel Detector (FPD) ): The image receptor converts the remnant x-ray beam to a digital image that is displayed on the monitors.
  5. Dedicated image processing: The raw image data is typically processed through a number of digital image enhancement algorithms before being displayed to the user.
  6. Control panel and footswitch: This is the device that is used to control the fluoroscopy machine and adjust the settings such as the X-ray tube voltage, current, and exposure time. The control panel is typically located on the front of the fluoroscopy machine and includes buttons, switches, and joystick type control that can be used to adjust the settings. The foot pedal is often used also to control the x-ray on and off while the hands are in use.
  7. Patient table: This is the table that the patient lies on during the exam. The patient table is typically equipped with a system of motors and gears that allow it to be moved in various directions and positions to help the interventionalist achieve the best possible view of the area being imaged.
  8. Gantry: Typically a fluoroscopy system has a C shape gantry that is often called a C-arm. In some specialized configurations two C-arm systems are mounted on the same system in what is termed a bi-plane system as it is possible to achieve two views at once.
  9. The x-ray radiation dose is monitored during the acquisition and displayed for the users to read out during the procedure.
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What is pulsed fluoroscopy?

Pulsed fluoroscopy is an imaging technique used for medical diagnosis and interventional guidance, and is the basis of all modern fluoroscopy acquisitions. By pulsing the radiation in short bursts, it reduces the amount of radiation that a patient is exposed to, thus reducing the radiation dose compared with a continuous mode fluoroscopy acquisition.

Unlike traditional X-ray imaging (i.e. CR and DR), pulsed fluoroscopy allows physicians to observe rapid movements and identify subtle abnormalities since it has inherently high temporal resolution. It also helps them to differentiate between normal and abnormal structures in organs or soft tissues. This type of imaging is often used for all the procedures mentioned in this post including: catheterizations, biopsies and imaging of the digestive tract or urinary system. Pulsed fluoroscopy is an effective diagnostic tool that improves patient care by providing detailed images with reduced radiation exposure compared with continuous fluoroscopy. In pulsed fluoroscopy if the same x-ray flux can be achieved in a faster time it can reduce the motion blur as the acquisition is faster.

What are the image receptors used for fluoroscopy?

The image receptors for fluoroscopy are the devices that are used to capture and record the X-ray images produced by the fluoroscopy system. There are two main types of image receptors used in fluoroscopy:

  1. Image intensifier: This is a device that is used to amplify the X-ray image and make it visible on a monitor. The image intensifier is located between the patient and the monitor, and it converts the X-ray image into an electronic signal that can be displayed on the monitor.
  2. Flat panel detector (FPD): This is a newer type of image receptor that is increasingly being used in place of the image intensifier. The FPD is a solid-state device that consists of a matrix of photodiodes that are used to detect the X-ray photons and convert them into an electronic signal. The FPD has several advantages over the image intensifier, including better spatial resolution, faster image acquisition, and the ability to capture images in digital format.
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Both image intensifiers and FPDs can be found in fluoroscopy systems, and the FPDs are increasingly replacing image intensifiers. The image intensifier can be easily distinguished from the flat panel systems as the image intensifier is significantly larger and is more of a cylinder shape than the rectangular shape of the flat panel detectors.

Image intensifiers for fluoroscopy

Image intensifiers revolutionized interventional imaging and for many years were the state of the art for an interventional x-ray imaging suite. Image intensifiers are a type of image receptor that is used in fluoroscopy to capture and record X-ray images. The image intensifier first converts the x-ray signal to light and then to electrons (photocathode). The electrons are then accelerated and incident on a fluorescent screen. An image intensifier consists of a photocathode, a microchannel plate, and a fluorescent screen. The fluorescent screen emits light in proportion to the intensity of the X-ray energy that was deposited, producing a visible image that can be captured by a digital video camera. Flat panel detectors are increasingly replacing image intensifiers for fluoroscopy systems.

Flat panel detectors for fluoroscopy

Flat panel detectors (FPDs) are a type of image receptor that is used in fluoroscopy to convert the remnant x-ray beam into digital X-ray images. FPDs are solid-state devices that consist of a matrix of photodiodes on an amorphous silicone substrate that are used to detect the X-ray photons and convert them into an electronic signal.

FPDs have several advantages over the traditional image intensifiers, including:

  1. Better spatial resolution: FPDs have a higher detector element density, which means they can produce images with finer detail especially for non magnification modes.
  2. Fast image acquisition: FPDs can capture images very quickly, which makes them well-suited for use in dynamic imaging situations such as interventional procedures.
  3. Direct digital image capture: FPDs can capture images in digital format, which allows for easy storage, retrieval, and manipulation of the images. They do not require an additional camera in order to generate the image
  4. Improved patient dose: FPDs typically are efficient in converting the x-rays to images. One example of the reduced dose efficiency of image intensifiers is the thin metal outer shell that the x-rays need to pass through before they are incident on the photocathode.

Overall, FPDs offer many benefits over traditional image intensifiers and are becoming increasingly common in fluoroscopy systems. In first world locations it is likely that image intensifiers will become increasingly less common.

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