FLUOROSCOPY

What is fluoroscopy?
X-RAYS IN MOTION "Viewing dynamic studies of the human body"
Fluoroscopy is a technique for obtaining "live" X-ray images of a living patient - it is like an X-ray TV camera. The Radiologist uses a switch to control an X-Ray beam that is transmitted through the patient. The X-rays then strike a fluorescent plate that is coupled to an "image intensifier" that is (in turn) coupled to a television camera. The Radiologist can then watch the images "live" on a TV monitor.


HISTORY OF FLOUROSCOPY

Thomas Edison, 1896
Screen (zinc-cadmium sulfide) placed over patient’s body in x-ray beam
Radiologist looked directly at screen
Red goggles-30 minutes before exam
1950 image intensifiers developed
www.cerebromente.org.br/.../xray-fluoroscope.JPG

PRESENTLY
Fluoro viewed at same level of brightness as radiographs (100-100 lux)
X-ray tube under table/over table or in c-arm
Image intensifier above patient in carriage
Carriage also has the power drive control, spot film selection and tube shutters

Courtesy of Scott Sorenson, 2000









Purpose of Fluoroscopy
The principal advantage of image intensified fluoro is an increased brightness
Sometimes requires that the room be dark so that the image can be visualized better

Human vision structures designed for vision


Rods: Sensitive to low light levels. Used in night vision (scotopic vision)
Cones: Sensitive to bright light levels. Daylight vision (phototopic vision)

Fluoroscopic technique
Maximum detail is desired, Image brightness must be high, Controlled by automatic brightness control (ABC) Generally high kVp and low mA are preferred kVp relates to the body part being examined mA is around 5 Much lower than hundreds of mA usually used for static imaging

Components of the image intensifier tube Input phosphor

Glass envelope
Photocathode
Electrostatic lenses
Anode
Output phosphor

Glass envelope
Surrounds all of the components and provides mechanical support of internal components has a vacuum tube.

Input phosphor
Receives incident x-rays from the x-ray tube and converts them into light Composed of cesium iodide

Photocathode
Attached to the input phosphor by an adhesive layer, Converts light from input phosphor to electrons by photoemission Negative portion of the tube

Anode
Positive portion of the tube. A circular plate with a hole in it in which electrons are focused to which goes to the output phosphor

Electrostatic focusing lenses
Focuses electron path form photocathode to anode by means of repulsion

Output phosphor
Converts electrons from anode to light


Multifield Image Intensification
Gives the fluoroscopist the ability to magnify the video image of the body part examined. Sometimes referred to as a “Mag” view Electrostatic focusing lenses focus electrons in a smaller area on the output phosphor which makes the resulting image larger than the original.


(Cross section of the II-TV system illustrates the various components that are used to create the highly amplified output light image. A four stage process (x-rays to light; light to electrons; electrons to light; light to electronic signal) is shown)

What are the types of fluoroscopic tests?
Fluoroscopy, as an imaging tool, enables physicians to look at many body systems. Fluoroscopy may be performed to evaluate specific areas of the body, including the bones, muscles, and joints, as well as solid organs such as the heart, lung, or kidneys.


Fluoroscopic exams include the following types of tests: barium swallow, upper GI series, small bowel series, barium enema, hystersalpingogram, intravenous pyelogram, voiding cystourethregram, myleogram, arthrogram, biopsy, lumbar punctures and facet injections

Fluoroscopy Equipment
Fluoroscopic table




C-arm

Linear Tomography

For Linear Tomography, X-ray images are collected while the X-ray tube moves through a range of positions, generating images with a range of exposure angles.

(fig. 1)
Siemens Iconos R 200 X-ray machine with Linear Tomography capability. (From:
http://www.siemens.com)


PURPOSE OF LINEAR TOMOGRAPHY

Tomography can be defined as the radiographic technique that employs motion to show anatomical structures lying in a plane of tissue while blurring or eliminating the detail in images of structures above and below the plane of interest.


PRINCIPLES OF LINEAR TOMOGRAPHY

Tomographic principle: you must have 2 of the 3 elements in synchronous movement during your exposure (for tomography, this would be the tube and image receptor, while the patient lies still as in fig.1).

The motion of X-ray tube and film in linear tomography.
(fig.2)








The angle of movement is called the tomographic angle. You must have an adjustable fulcrum (pivot point) that allows you to change the area of beam focus. This is the "cm" adjustment you make between tomo slices, and should be adjusted to the height of the anatomy of interest. object Plane: region in which the image exhibits satisfactory recorded detail, and is controlled by the level of the fulcrum. This region will show the least amount of radiographic motion, thus will appear clearly defined on the radiograph. Anything above or below this plane will be blurred due to tube/receptor motion. (fig.3)

(fig.3)















Details from other planes in the object which would otherwise contribute confounding detail to the image, are blurred and effectively removed from visual consideration in the image. A variety of tomography techniques have been developed, which differ primarily in the manner in which the X-ray source and film move.

Linear tomography is one of the most basic techniques As the tube and film move from the first position to the second, all points in the object plane project to the same position on X-ray film.


(fig.4)













To complete the tomographic calculation, the relative positions of the X-ray tube, imager and subject must be precisely known. In the typical case the patient and imager are stationary and only the X-ray tube moves (as shown in fig.1)
Section thickness: Consider the diagrams below in which the the width of the object plane is controlled by the exposure (or tomographic) angle as seen in the diagram. The exposure angle is inversely proportional to section thickness. As exposure angle increases, section thickness decreases (fig.5). If you want the whole anatomy to appear more focused, you would have a narrow exposure angle (10 degrees for example), giving you a "thicker" cut (fig.6) The thinner your slice, the more detail for small parts will be visible.

(fig.5)


(fig.6)
















A tomogram showing the kidneys














Equipment used