Mobile Fluoroscopy Safety

Protecting the patient from scatter radiation is vitally important, but we also need to protect ourselves as well as all of the medical peronal in the surgical suite.  Fluoroscopy contributes to the highest occupational dose of all the modalities, which is most commonly scatter radiation from the patient.  The scatter radiation is produced mainly from the patient thickness, so the thicker the patient, the higher the scatter radiation.  We can help prevent the excessive production of scatter radiation by C-Arm positioning, orientation during set-up, as well as correctly positioning the staff in the surgical suite.  The furthest distance away from the C-Arm, the safer everyone will be, which describes the inverse square law: Radiation intensity is inversly proportional to the square of the distance from the source.  This theory means that if you double the distance from the source of the radiation, you will decrease your dose by four times.  The same is true ...

There are a wide variety of factors that help you reduce the dose to the patient which is minimizing the radiation exposure.  Time, distance and shielding are the cardinal principals of any technologist, but there are other important things we need to remember to make sure we are providing a diagnostic image to the Radiologist, while limiting the dose to the patient.  As low as reasonably achievable is the moto that the technologist stands by, so in Fluoscopy procedures, we need to take other concepts into consideration to make sure the dose is kept as low as possible.  The entrance to skin exposure (ESE) is the measurment of radiation output at the point of skin entry for x-rays and fluoroscopic examinations.  The FDA has set a maximum ESE for fluoroscopy at 10 R/min and 20 R/min for high level fluoroscopy, so there are a variety of techniques as well as equipment set up that the technologist needs to be aware of to ensure low doses to the patients.  The ESE wi...

Fluoroscopy is different than conventional radiography when it comes to who is being exposed to ionizing radiation.  During a conventional exam, such as a chest x-ray, the only person who is being directly exposed is the patient, or a possible family member staying with the patient to console or comfort them.  In Fluoroscopy however, everyone who is in the surgery suite or all the members in the fluro room are being exposed for the duration of the examination.  For example, during a surgical procedure when a C-Arm is being used, the surgeon, anesthesiologist, the technologist, surgical technologist, nursing staff, and others in the room are being exposed during the entire duration of th fluoro procedure.  It is vitally important to protect them and minimize the scatter radiation exposure to ensure their dose is as low as reasonably achievable.  There a many devices that are available to protect them, such as lead aprons, thyroid shields, lead gloves and lead gla...

According to the FDA, the minimum source to skin distance for mobile fluoroscopic equipment is 12 inches, or 30 cm.  The angulation and position of the C-Arm will determine the dose the patient will receive in a examination or surgical procedure.  There is an exception for extremities, since it may be impossible to get a diagnostic image at that distance, so it is allowed to reduce to 7.5 inches in those cases.  The entrance skin exposure is inversly related to the source to skin distance, so keeping the exposure as low as possible is the goal of the technologist.  Distance is one of the greatest ways to limit exposure, along with controlling the radiation field by limiting the beam dimensions.  The FDA enforces that the length or width of the beam shall not exceed the image receptor by more than 3% of the souce to image distance.  This beam restriction is to ensure that only the area of interest is irradiated, and to limit the patient exposure and dose....

The Fluoroscopic C-Arm has a variety of locks and angle indicators and positioning handles that help manuever the machine during surgical procedures.  The machine is typically positioning in a 90 degree angle from the patient and perpendicular to the surgical table with the patient in a supine or AP projection.   It has the capabilty to be manueverd in a variety of positons and orientations, which can be controlled by a serious of braking handles.  The movement mechanisms allow the angle and distance locators using a color coded system to help simultaneously move the machine in a variety of directions.  Orbital rotation allow it to move for lateral and oblique positions, while overscanning will allow the machine to move over the body of the patient, and underscanning will scan under the body of the patient.  It can also be adjusted in the horizontal axis, which allows the technologist to move the image receptor to face the floor, while the x-ray tube faces ...

There has been a transition from film screen fluoroscopy to digital fluoroscopy in the medical imaging industry.  It uses a digitized signal to produce a computer generated digital image displayed on a cathode ray tube screen. In the digital system, the x-ray tube is much higher than the standard fluoroscopic system, so to control the light exposure from the output screen, so the optical system needs to be equipped with an adjustable iris diaphragm.   The incoming analog voltage signal from the camera is processed by an analog to digital converter which changes the analog signal to a digital binary equivalent. It can than be processed and stored in a computer and then be manipulated and copied without loosing without loosing signal quality.  The digital system is able to rapidly changing image content in real time, while adding and subtracting from the image to create a more diagnostic image.  It has the capability to be in either a constant or pulsed mode, and ...

Once the output screen of the image intensifier produces light, it must be transferred to an image viewer and recorded.  This occurs in an optical coupling device will transfer and distribute the light from the outlook window of the image intensifier to multiple viewing and recording systems.  When the light from the output screen leaves the output window, it enters the optical coupling system, and strikes a beam splitting mirror.  From here, some of the light passes through the mirror to a video system, while some is reflected by the mirror. Then the mirror will direct the light from the output screen to a television screen or cine camera.  They can be directed to various systems, which allows various viewing and recording options simultaneously.  A residual image is the replica of light image from the output phosphor, and is read by an electron beam at the cathode.  The heated cathode will then emit a thermionic electron cloud that is focused into an elec...

The image intensifier has several components which all have a unique function for the Mobile Fluoroscopy C-Arm unit.  These include the input phosphor, photo-cathode, electrostatic focusing lens, anode, output phosphor, and glass envelope.  When an x-ray exits a patient, the remnant beam is formed and strikes the input phosphor, which absorbs the x-ray photons and emits light photons.  These light photons strike the photo-cathode, absorbs the light photons while emitting photo-electrons. The photo-electrons are then directed as well as accelerated by the electrostatic focusing lens toward the anode.  After passing through the center whole of the anode, the photo-electrons react with the output phosphor, which converts them into light photons. The primary purpose of this process it to produce a brighter image without increasing the radiation dose to the patient. The total brightness gain is the measurement of the image intensifies ability to create the brightest image...

There are several components that make up the mobile Fluoroscopic unit, such as the control panel, C-Arm and monitor.  The control panel is a vital component of radiation protection and shielding, as it controls the orientation, collimation and contrast.  The collimator protects the patient by decreasing the exiting x-ray beam, as well as providing optimal display of relavent anatomy.  The beam hardening filter component and the shutters that adjust the field of view and limits the scatter radiation in the collimator, are components that reduce the dose to the patient. By using the proper collimation, you are able to expose only the pertinent anatomy while adjusting exposure factors to create the correct brightness and and contrast in the image.  Reducing the patient dose, while creating the optimal diagnostic image is the goal for any fluoroscopic exam.