Lecture 2 - Fluoro Machine PDF

Overview of the Fluoroscopy Machine Prof. Feliz Niña G. Perez, RRT, MSRT History Thomas Edison invented the fluoroscope in 1896 Had a zinc-cadmium sulfide screen It has served valuable tool in medical imaging 1960s the image intensifier entered routine clinical service...

Overview of the Fluoroscopy Machine Prof. Feliz Niña G. Perez, RRT, MSRT History Thomas Edison invented the fluoroscope in 1896 Had a zinc-cadmium sulfide screen It has served valuable tool in medical imaging 1960s the image intensifier entered routine clinical service  Overview The image intensifier is a Fluoroscopy is a medical complex device that imaging technique that receives the image-forming uses X-rays to create a xray beam, converts it to real-time video of the light and increases the inside of the body. It's also light intensity for better known as "fluoro". viewing  Diagnostic fluoroscopy Diagnostic fluoroscopy is a procedures are performed daily modality that involves in radiology suites across the visualizing the anatomy using country. radiation in real time. Therefore, patient doses have a potential for being great, increasing the chance of adverse reactions.  Interventional fluoroscopy is a type of medical imaging that guides minimally invasive medical procedures. It's used to evaluate dynamic biological processes, such as the movement of a body part, instrument, or contrast agent.  An X-ray The beam passes The X-ray healthcare through the images are provider can How it works body part transmitted see the body being to a monitor part in examined motion  Healthcare providers use fluoroscopy to help monitor and diagnose certain conditions and as imaging guidance for certain procedures. Evaluating specific areas Diagnosing Guiding of the body, health treatments, Helping with such as What it's used problems, such as orthopedic bones, for such as heart implants or surgery muscles, or intestinal injections joints, organs, disease and blood vessels  Imaging chain components 01 02 03 X-ray Flat panel Monitor: Displays source: Emits an detector (FPD)/ the digital images X-ray beam that Image-intensifier as a continuous X- passes through the Tube: A image ray image, similar patient's body receptor that to an X-ray movie converts the X-ray signal into digital images  The imaging chain of interventional Components: fluoroscopy involves an X- -High Voltage Generator ray source, a flat panel -X-Ray Tube (XRT) detector/Image-intensifier Tube, and a monitor. The -X-Ray Image Intensifier chain produces real-time X- (XRII) ray images that guide -Video Camera/Monitor medical procedures Imaging Chain Components 1. X-ray image intensifier (II) It converts: low intensity X-ray photon fluence to high fluence of Visible Photons *Fluence = # of particles Image-Intensifier Tube Tube components are contained within a It receives the image- glass or metal forming xray beam envelope that and converts it into provides structural visible-light image of support and high intensity maintains the vacuum.  Diagram of an image intensifier and evacuated insert tube X-rays pass through the input window of the vacuum element and strike the input screen, producing light that stimulates the photocathode to emit electrons, which are ejected into the electronic lens system. The electronic lens system adds energy to the image-carrying electrons, while minifying the image onto a small output screen. The electron image is finally converted back to light at the output screen. The combination of energy input and minification in the electron optics yields an image 5 to 10 thousand times as bright as the image emerging from the input screen. The light image is detected by a CCD or CMOS camera to produce a digital video signal that is re-created on a display monitor in the examination room.  Input Phosphor Xrays that exit the patient and are incident on the image- intensifier tube are transmitted through the glass envelope and interact with the input phosphor) Energy converted into visible light Input Phosphor converts: X-Rays to Light Most commonly used phosphor: Cesium Iodide (CsI) crystals grown in a dense needle-like structure (approx. 300 µm) prevents lateral light spread 2. Photocathode Next active element of the II tube Bonded directly to input phosphor It is a thin metal layer usually composed of cesium and antimony compounds that responds to stimulation of input phosphor It emits electrons when illuminated by visible light from input phosphor (Photoemission) Photocathode converts: Light to Electrons Light photons strike a very thin bi- or multi-alkali photocathode Electrons: Released through photoelectric effect Repulsed from photocathode Accelerated towards anode by 25-30 kV Photoemission is electron emission that follows visible light stimulation. It takes many light photons to cause the emission of 1 electron. The number of electron emitted by the photocathode is directly proportional to the intensity of light that reaches it.  25, 000 V is maintained across the tube between photocathode and anode so that electrons produced by photoemission will be accelerated to anode. Electron Optics It maintains proper electron travel Focus the electrons generated in the active area of the input onto the fixed size output screen. Electrostatic Focusing Lens – are responsible for the pattern of electrons emitted from the large cathode end of the II tube must be reduced to the small output phosphor  Flux gain is the ratio of the number of light photons at the output phosphor to the number of xrays at the input phosphor Flux Gain  Minification Gain is the increased illumination of the image is attributable to the multiplication of light photons at the output phosphor compared with xrays at the input phosphor Minification Brightness gain is the ability of the II to Gain and increase the illumination level of the Brightness image. It is simply the product of the minification and flux gain. Gain  Intensification - two mechanisms: Electronic (or Flux) Gain - KE gained by electrons from acceleration (~50 typically) Minification Gain- reduction of large X-ray image at Input Phosphor (e.g. 40 cm) to a smaller diameter Output Phosphor (e.g. 2.5 cm) 402/2.52 = 256 Brightness Gain = (Electronic Gain).(Minification Gain)  Internal scatter radiation in the form of xrays, electrons and particulary light can reduce the contrast of image intensifiers through process called veiling glare.  Site where accelerated electrons interact and produce visible light Output Output Phosphor converts: Phosph Electrons to Light Electron beam focused by or electrodes onto a thin powder phosphor Optical System couples XRII to video camera includes: Collimating Lens to shape the Lens to focus the image divergent light from the onto the video camera Output Phosphor Aperture to limit the amount of light reaching the video camera  a. Replacement for the II tube, optical system, 2. Flat-Panel and cameras. Detector (i) Directly converts x-rays into a digital form. (ii) Carbon fiber covers reduce x-ray attenuation and increase DQE compared to II. FPD a. Indirect systems have a b. Direct systems have a phosphor layer that absorbs semiconductor (e.g., the x-rays and converts a selenium) that produces x- fraction of their energy into ray-induced charge directly, light and a photodiode that which is captured by the converts the x-ray-induced electronics within the same light from the phosphor into dexel as the x-ray absorption a corresponding charge. event.  Video Camera captures the XRII output image, and converts it to an analogue electrical signal that conforms to a recognized video format (e.g. NTSC/PAL/SECAM) Older Video Cameras - Photoconductive target scanned by electron beam Modern Video Cameras- Charge-Coupled Device (CCD)  In interventional procedures, the X-ray tube is positioned beneath the patient to minimize the amount of scattered radiation reaching the medical staff, as the majority of scatter radiation originates from the patient's entrance side where the X-ray beam first enters the body, which is the top when the tube is positioned underneath the patient; this design prioritizes radiation protection for healthcare workers.