FLUOROSCOPY EQUIPMENT

Learning Objectives By the end of this Lecture the student will be able to: Differentiate between fluoroscopic and radiographic examinations List the basic components of the fluoroscopic system and identify the function of each component Describe a typical basic fluoroscopic image Intensifier Describe advantages of image intensified fluoroscopy over conventional screen fluoroscopy Identify uses of dynamic and static fluoroscopic recording systems Discus digital fluoroscopic image acquisition Differentiate between conventional fluoroscopy, image intensifier fluoroscopy, and digital fluoroscopy

References Websites http://www.e-radiography.net/ Bushberg, The Essentials of Physics and Medical Imaging, Williams & Wilkins Publisher. Positioning in Radiography: By k.C.Clarke. Text book of radiographic positioning and related anatomy;bykenneth L.Bontrager,5th edition Websites http://www.e-radiography.net/

FLUOROSCOPY History Purpose: Invented by Thomas A. Edison in 1896 Conventional film radiography is restricted to static patient exams. If dynamic events need to e studied such as movement contrast materials through gastrointestinal tract (GIT) the image must be viewed directly using a dynamic method. Purpose: To perform dynamic studies. Visualize anatomical structures in real time or motion. View the motion and function of anatomic organs.

Fluoroscopic systems Conventional fluoroscopic systems Earliest fluoroscopic systems used phosphor screens where the transmitted x-ray caused scintillations that were viewed directly.

Fluoroscopic systems Direct Fluoroscopy In older fluoroscopic examinations radiologist stands behind screen and view the image.

Fluoroscopic systems Conventional fluoroscopic systems The images of this type were of very poor quality for a number of reasons:- - Poor light output by the fluorescent screen - Low efficiency of the light conversion mechanism - Poor spatial resolution for that fluorescent screens are no longer used since they gave high radiation dose to the operator.

Fluoroscopic with image intensifiers What is an Image Intensifier ? A complex electronic imaging device that receives the remnant beam and converts it to light and increases the intensity of the light. The image intensifier tube is contained in a glass envelope in a vacuum and mounted in a metallic container which provides protection for the components.

Fluoroscopic with image intensifiers

Image Intensifier Schematics Fluoroscopic with image intensifiers Image Intensifier Schematics

Input Phosphor Constructed of cesium iodide. Responsible for converting the incident photon’s energy to a burst of visible light photon. Similar to intensifying screens in cassettes. Standard size varies from 10 - 35 cm. Normally used to identify the II tubes.

Photocathode Thin metal layer bonded directly to the input phosphor. Usually made of Cesium and Antimony compounds that respond to light stimulation. Responsible for Photoemission. Electron emission after light stimulation The number of electrons emitted is directly proportional to the intensity of light intensity of the incident x-ray photon.

Electrostatic Focusing Lenses A series of lenses inside the II tube to maintain proper focus of the photoelectrons emitted from the photocathode. They contain a positive charge. They are located along the length of the II tube. The focusing lenses assist in maintaining the kinetic energy of the photoelectrons to the output phosphor.

Output Phosphor Usually constructed of zinc cadmium sulfide crystals. Serves to increase illumination of the images by converting photoelectrons to light photons.

Spot Film Device Used to make permanent images during the radiographic examination. Film is positioned b/w the patient and the image intensifier. When the film is needed, the radiologist actuates the control that brings the cassette in position. This changes the tube from fluoroscopic mA to radiographic mA. During fluoroscopy, the tube is operated at less than 5 mA.

TV MONITORS This practical and efficient viewing system was employed because of the limitations of the mirror optic viewing system. TV monitors: 1. Enables viewing by multiple persons. 2. Monitors may be located in remote locations other than the radiographic room. 3. Image brightness and contrast can be manipulated. 4. Images may be stored on different medium for reviewing at a later time.

Fluoroscopy -Modes of operation Manual Mode Allow the use to select the exact MA and KVp required AEC Mode Allow the unit to drive the KVp and MA to optimize dose and image quality Pulsed Digital mode Modifies the fluoroscopic output by cutting by cutting out exposure between pulses With the pulsed mode, it can be set to produce less than the conventional 25 or 30 images per second. This reduces the exposure rate.

Fluoroscopy Units Smaller facilities may use one fluoroscopic system for a wide variety of procedures Larger facilities have several units dedicated to specific applications, such as: Gastrointestinal units Remote fluoroscopy rooms Peripheral angiography units Cardiology catheterization units Biplane angiography units Mobile fluoroscopy – C arms units

Fluoroscopy Units 1/An over table model Where the x-ray tube is placed above the table top, and the image intensifier under the table surface.

Fluoroscopy Units 2/An under table model Where the x-ray tube is placed under the table surface , and the image intensifier over the table top.

Fluoroscopy Units An under table model

Fluoroscopy Units The table have the ability to tilt from horizontal to vertical

Fluoroscopy Units 3/Single or bi-planar cine –fluoroscopy model Where the x-ray tube and image intensifier are fixed to c-arms. Mostly used in surgical theatres.

Fluoroscopy Units Remote control systems

Digital Fluoroscopy Digital fluoroscopy is currently most commonly configured as a conventional fluoroscopy system This method uses digital detector technologies (eg, flat-panel "direct" detection of x rays and charge- coupled device technology) The analog video signal is converted to a digital format with an analog-to-digital converter (ADC).

Radiation Protection General Rule (ALARA Principle) As Low Reasonably Achievable

Radiation Protection more exposure Time Longer usage

Radiation Protection TIME Take foot off fluoro pedal if physician is not viewing the TV monitor Use last image hold (freeze frame) Five-minute timer Use pulsed fluoro instead of continuous fluoro Pulsed Low-Dose provides further reduction with respect to Normal Dose continuous mode: Use record mode only when a permanent record is required Record beam-on time for review

Radiation Protection Distance Distance is large factor for reducing exposure. Inverse Square law “ When you double the distance the exposure rate is decreased by 4 times ”

Radiation Protection DISTANCE - One step back from tableside: cuts exposure by factor of 4 - Move Image Int. close to patient: less patient skin exposure less scatter - Source to Skin Distance (SSD): 38 cm for stationary fluoroscopes 30 cm for mobile fluoroscopes

Radiation Protection X-ray Tube Position Position the X-ray tube under the patient not above the patient. The largest amount of scatter radiation is produced where the x-ray beam enters the patient. By positioning the x-ray tube below the patient, you decrease the amount of scatter radiation that reaches your upper body.

Radiation Protection Shielding Increasing the amount of shielding around a source of radiation will decrease the amount of radiation exposure. To avoid scatter Be sure to shield all directions. - + Shielding

Radiation Protection Lead aprons: cut exposure by factor of 20 SHIELDING Lead aprons: cut exposure by factor of 20 Proper storage (hanging vs. folding)

Part No...., Module No....Lesson No Module title Radiation Protection Protection tools Eye goggles curtain Lead Apron thyroid shield IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Radiation Protection Collimation Collimate tightly to the area of interest. Reduces the patient’s total entrance skin exposure. Improves image contrast. Scatter radiation to the operator will also decrease.

Radiation Protection Safety in Fluoroscopy Familiarity with specific fluoro units Factors influencing dose: patient size kVp, mA and time tube - patient distance (SSD) Image Intensifier - patient distance image magnification vs. patient dose x-ray field collimation oblique's vs. perpendicular views

Radiation Protection Safety in Fluoroscopy Standard Operating Procedures - each clinical protocol / procedure - modes of operation, image recording - emphasis on minimizing duration - risk / benefit on a case-by-case basis Equipment quality control - periodic PMs - prompt calibrations - post radiation output values - check aprons, shields, gloves annually

Final Summary Golden rules” Radiation Protection Final Summary Golden rules” Keep the II close to the patient Do not overuse magnification modes Keep the x-ray tube at maximal distance from patient Use higher kVp where possible Wear protective aprons and radiation monitors, and know where scatter is highest Keep your distance, as far as is practicable