Fluoroscopic Imaging PDF

Fluoroscopic Imaging Jack Pearse Session Aims Understand the Compare and contrast underpinning physical fixed and mobile principals of fluoroscopic imaging. fluoroscopic imaging....

Fluoroscopic Imaging Jack Pearse Session Aims Understand the Compare and contrast underpinning physical fixed and mobile principals of fluoroscopic imaging. fluoroscopic imaging. Explore image Consider radiation generation and protection in optimisation features fluoroscopic imaging. in fluoroscopic imaging. What is Fluoroscopy? “Fluoroscopy is a type of medical imaging that shows a continuous X-ray image on a monitor, much like an X-ray movie” (FDA, 2020) Digital Fluoroscopy systems produce video x-ray sequences of anatomy, when combined with the use of contrast media soft tissue structures and vasculature can also be demonstrated. This can provide both anatomical and physiological information. The modality can be used for both diagnosis and in support of intervention. Modern digital fluoroscopic systems utilise flat panel x-ray detectors, but they are often still referred to as Image Intensifiers, which was the name of the original technology that they were based on. Why use fluoroscopy? Imparts anatomical and physiological information. Can be diagnostic or therapeutic. Allows for dynamic guidance of clinicians. Facilitates less invasive operative procedures. Uses contrast agent so body can be seen in detail Provides structural anatomical detail and physiological detail To make sure everything is functioning s it should  Can you think of any fluoroscopic procedures? Common Applications: Orthopaedic – Arthrograms & theatre procedures. Angiography – Cardiac, cerebral, peripheral. GI Tract – Barium swallows, meals and enemas. Endoscopy – ERCP & OGD. Urology – Ureteroscopy, nephrostomy insertions, PCNL. Interventional Radiology – Line insertions, Embolisations, PTC. And many more! HSG- gynae examination Stent insertions RIG insertions Proctogram  Fixed Systems Fixed systems are installed in a specific room or suite- room is designed to undertake fluoroscopy These are typically used for longer screening cases. Variety of styles including floor mounted, ceiling mounted and biplane (2 c arms- allows imaging from multiple positions at once) Mobile Systems Portable- can be difficult to find place for it Usually used to support theatre cases and shorter or less complex interventions. Less reliant on xray cases  Comparison of System Advantages Mobile Systems Fixed Systems Does not require custom More reliable x-ray generators. room design. Usually more features. Can be moved between theatres. Often better built in radiation protection. Can be replaced mid- Room is designed to allow procedure without moving uninhibited movement of c-arm. patient – minimal disruption X-ray Generation The mechanism for X-ray generation is similar in fluoroscopy to conventional x-ray systems. In fluoroscopy however there are a number of modes that are utilised for different methods of imaging: Continuous fluoroscopy- holding down button, higher dose+higher heat on anode and xray tube 4 ½ frames per second Pulsed fluoroscopy- usually 3 frames per second, sequence of imaging but not smooth, doesn’t need to expose every frame, more general, slower e.g. pacemaker insertion High-Dose “Acquisitions”- higher frame rate, higher/large exposure, higher dose, clearer smoother image, captures every moment, higher diagnostic moments e.g. barium swallow Single high-dose image- one frame clear as possible, usually seperate pedal e.g picc line Anode Heat Dissipation High-speed rotational anodes. - gives chance for each spot to cool down, to change position of focal spot, evenly distributes heat on the anode Oil or water-cooled systems. Range of focal spot sizes to balance detail with anode heating depending on application- finer the focus the more the focal spot is being hit by electrons, causing more heat to smaller areas of the anode The more X-rays produced, the more radiation exposure to patient and those in the room. Higher wear on the anode – heating effect - Continuous high wear would lead to less Efficiently in the anode to produce xray - Radiographers must inhibit radiation protection habits Image Intensifier System (Seeram, 2019)  The Image Intensifier X-rays that pass through the patient reach the input phosphor. The input phosphor emits light. This light reaches the photo emissive layer (photocathode) which emits electrons towards the anode. These electrons reach the output phosphor which itself produces an amplified light signal. This light signal is recorded by a camera. Made up of a few layers Input phosphor- take X-rays and converts into light energy Photo cathode- light is converted into electrons, focused across image intensifier, emits electrons towards anode Output phosphor- Reach an output phosphor which converts it back into light The light is recorded by a camera  X- Input Photo- Tube rays Phosph Light Cathode or Electr ons Output Phosph Electron Camera Light Anode or s Devic Output e  Flat Panel Detectors (FPDs) Similar to plain film direct digital receptors. The input x-rays that have passed through the patient are converted into electrons via a Selenium photoconductor. This charge is transmitted/mapped against to a thin-film transistor (TFT) array. This array is arranged in a matrix with each transistor mapped to a pixel. Turns the amount of X-rays reached, into a proportional electrical charge Comparison Advantages and Disadvantages of Flat Panel Detector Systems Advantages Disadvantages FPDs usage tends to Higher initial cost. utilise a lower dose. Shape of detector There is a greater can sometimes be field of view with more awkward FPDs. to position. (This Higher image can be true of quality. both II and FPDs) Contrast Media Positive Media Negative Media Radiopaque Radiolucent Has a higher atomic Has a lower atomic number than surrounding number than surrounding tissues tissues Denser- Attenuates more Attenuates less x-rays x-rays Appears “Hypodense on Appears “Hyperdense” on image” image Double contrast involved using both together- not performed in angiography Contrast Media Contrast Media Double-Contrast Imaging Uses both positive and negative contrast together! Can be used in Barium meal and Barium Enema investigations. Positive- shows densely Negative- shows darker Double-contrast Image Digital Subtraction Angiography Setting we can use to tidy up the image (computer processing function that allows higher signal to noise ratio) Removes background info to make area of interest clearer (Fujihara, 2017) Digital Subtraction Angiography This is a process used in angiography to remove distracting detail and anatomical structures from the image. The operator begins acquiring the images before injecting contrast. The computer system uses the initial frames to create a “mask” demonstrating the background anatomy. For subsequent images (when the contrast is injected) the information from the “mask” is removed, leaving only the new information [contrast] visible on the screen. This creates a simpler image as anatomy not under scrutiny such as bones are not visible on the image to cause any distraction. This process can only work on anatomy that is not moving.  Visual Representation of Subtraction Computer 0 0 100 0 0 0 0 100 0 0 0 0 0 0 0 takes 0 0 100 0 0 0 0 100 0 0 0 0 0 0 0 reference 100 100 100 100 100 Subtract 100 100 100 100 100 0 0 0 0 0 image before > = 0 0 100 0 0 0 0 100 0 0 anything 0 0 0 0 0 0 0 100 0 0 changes- tells 0 0 100 0 0 0 0 0 0 0 the computer Pre Mask Final Image what doesn’t Contrast need to be in 100 Image 0 100 0 0 0 0 100 0 0 100 0 0 0 0 the image- 0 100 100 0 0 0 0 100 0 0 0 100 0 0 0 Mask is taken 100 100 200 100 100 100 100 100 100 100 0 0 100 0 0 away 0 0 100 100 0 Subtract 0 0 100 0 0 = 0 0 0 100 0 > New contrast 0 0 100 0 100 0 0 100 0 0 0 0 0 0 100 stays on image where Post Mask DSA Image we don’t see Contrast the original Image Can you see why movement prevents this process? frame (bone) Roadmapping (Castro-Afonso et al., 2017) roadmapping refers to a technique used to help guide medical procedures by overlaying a real- time moving image (fluoroscopic image) onto a previously acquired static image of the same region. This allows clinicians to navigate instruments, such as catheters or guidewires, through the patient’s body with higher precision. Here’s a detailed explanation: How Roadmapping Works: 1. Initial Image Acquisition: First, a static image or “roadmap” is created by injecting a contrast agent into the patient’s blood vessels or other structures of interest. This contrast enhances visibility of specific areas such as blood vessels, bile ducts, or other pathways in the body. 2. Overlay Technique: Once the roadmap image is obtained, it is stored and displayed on the monitor. Then, the fluoroscopic system overlays real-time X-ray images onto the static roadmap. This allows the physician to see both the current position of the instrument (like a catheter or stent) and the roadmap of the anatomy, all at once. 3. Navigating Instruments: Using the roadmap, clinicians can guide tools through the anatomy, avoiding critical structures or narrowing areas (stenosis). It is particularly useful in vascular procedures like angioplasty or stenting, as it provides a reference image of the blood vessels. 4. Contrast Optimization: Roadmapping also reduces the need for repeated injections of contrast agents, as the original image provides a clear view of the anatomy throughout the procedure. This helps in minimizing patient exposure to both contrast agents and radiation. Applications of Roadmapping in Fluoroscopy 1. Interventional Cardiology: In procedures like angioplasty or placing stents in coronary arteries, roadmapping helps doctors navigate through arteries to the site of a blockage or narrowing. 2. Neurovascular Procedures: Used in treating conditions like aneurysms or blockages in the brain’s blood vessels. Roadmapping allows precise navigation to avoid sensitive brain tissue while treating a target area. 3. Endovascular Surgery: Roadmapping assists in placing devices inside blood vessels, such as embolic agents, grafts, or coils, with extreme accuracy, which is critical in procedures like aneurysm repair. Advantages of Roadmapping Increased Precision: Provides a clearer view for the physician to navigate tools, reducing the risk of injury to surrounding tissues. Reduced Radiation Exposure: As the static roadmap can serve as a reference, fewer real-time X- ray images are needed, thus lowering radiation exposure. Less Contrast Agent: The ability to reference a previous image reduces the need for multiple contrast injections, which can be harmful, especially in patients with kidney problems. Limitations Registration Errors: If the patient moves or if there’s a change in anatomy (e.g., vessel spasms), the roadmap and real-time images may not align perfectly, leading to inaccuracies. Complex Anatomy: In some cases, the roadmap may not provide sufficient detail, particularly in highly complex anatomical regions, requiring additional imaging. In summary, roadmapping in fluoroscopy provides a valuable tool in guiding interventional procedures with greater accuracy and safety, making it easier to navigate instruments within the body while reducing the need for excessive radiation and contrast.  Biplane Systems Bi-plane systems are digital fluoroscopy systems that have multiple c- arms, allowing the clinician to take simultaneous images in multiple planes. With traditional systems, the radiographer must manoeuvre between the positions sequentially in order to gain an appreciation of the anatomy in 3 dimensions. Takes PA and lateral at same time Can see positions in real time A PA image of the heart Benefits of using Biplane imaging: Quicker, better angles Doesn’t disrupt procedure/ equipment position Saves time, contamination risks Lower radiation- saves positioning shots when changing angles Can see fast moving anatomy A lateral image of the Less contrast needed- one heart injection would be enough for Radiation Protection The room in which the fluoroscopic imaging takes place is designated a “Controlled Area”. The controlled area should be demarked with warning signs. There should be local radiation rules associated with the room or system. Workers within the controlled area should wear lead PPE and undergo dose monitoring.  Radiation Protection Some procedures such as cardiac angioplasties can incur a high dose, due to prologued screening time and high framerate. Therefore, deterministic effects can be caused to the patient. Skin erythema can be induced following an exposure of over 2Gy cumulatively to an individual area of skin. Trusts will have follow-up procedures for patients whose “skin dose” reaches a certain level within a case. Xray: Stochastic risks- overtime the radiation can lead to cancer Can’t be entirely avoided Fouroscopy: Deterministic efffect- skin Threshold levels Record skin dose to keep track of quality assurance Methods of reducing dose. Using a “low dose fluoroscopy” setting. Collimation. Reduce exposure factors. Increase SID. Reduce OID. Staff stand further from primary beam (Inverse-square law). Reduce pulse/frame rate – switching from continuous to pulse etc Using shallow angles. Lead shielding. These can be fixed to the machine, removable or even disposable sterile shields. Staging the procedure. Exposure Factor Control In fluoroscopy the exposure factors are adjusted automatically by the system by default, rather than the user setting specific exposure factors. There are various systems for how these factors are controlled. Two systems of note are Automatic Brightness Control (ABC) Automatic Dose Rate Control (ADRC)  Fluoroscopy Dose Settings Fluoroscopy systems will usually include a setting that refers to a general implication of dose imparted such as “Fluoro –” or “Low Fluoro”. These settings alter the method in which the ABC functions. Lower dose settings will skew the exposure factors in favour of higher kVp but lower mA, this results in lower image contrast but a lower dose. Where possible, the radiation used should be as low as reasonably practicable, however “higher dose” settings may be appropriate for large patients, if image quality is (Axelsson, Automatic Brightness Control (ABC) Similarly in nature to the use of automatic exposure chambers (AECs) in conventional radiography, fluoroscopy automatically adjusts kVp and mAs via a system called Automatic Brightness Control (ABC). In image intensifier systems this is achieved by measuring the intensity of the output phosphor (light) and adjusting the exposure factors to maintain a present brightness level. Adjusts brightness compared to what’s needed too bright = brings exposure down Too dark = brings exposure up Automatic Dose Rate Control (ADRC) Modern systems utilise a system called ADRC. With ADRC the exposure factors are algorithmically controlled. The system estimates anatomical thickness and applies initial setting based on the program selected. After each x-ray pulse, the system measures the pixel data against its parameters under the setting, adjusting accordingly for the next pulse to provide the programmed “optimal” exposure. After each run, the estimated patient thickness is updated based on the data and the starting exposure is updated. Changing programmes adjusts the algorithm applied. (Gislason-Lee et al., 2013) Reading the input of X-rays If selected ap thorax but angled tube 30 in one direction, ADRC would see that and would estimate Adjusts according to thickness and initial activity setting Image Quality – Further Considerations If your surgeon/radiologist/advanced practitioner is having trouble interpreting the images, before reaching for the Fluoro + button, consider: Screen Position Cleanliness of screens Lighting of the room Display settings This is done to To avoid extra unnecessary radiation dose Collimation Just as in conventional radiography, collimation is utilised to reduce irradiation of unnecessary anatomy and reduce scatter. There are a variety of collimation configurations that are found within fluoroscopy systems, such as independent side collimators, paired collimators and iris collimators. Collimation Linear Collimation Iris Collimation Depending on system, these Adjustments to collimation collimators may be paired or affect the full circumference of each side may move image. independently. E.g. ERCP Image “Flare” Reduces dose to patient The less dense aspect of the Filtration has been applied to the upper image is too bright. (Ignore left lung. Resulting in more even Filtration Unlike conventional x-ray systems, fluoroscopy systems will usually have a filter or filters that can be positioned within the field of view to attenuate a section of the Reduces skin dose by filtering soft radiation from a section of the incidental beam. Reduces “flare” on the image. Improving visibility. Filtration Exposure Lock High density objects within the fluoroscopic field of view, such as metallic structures (commonly occurs with operating tables) can cause the ABC to attempt to compensate unnecessarily by increasing the x-ray exposure. Many systems will have a “technique lock” button that allows the exposure to be locked at a previously used level or override and set manual parameters. Some systems have settings for use when a large bolus of contrast is delivered such as for a left ventriculogram or aortogram, whereby the exposure is locked after a set number of frames before the contrast fills the image, preventing the ramping up of exposure factors in compensation.  Key 1. Height Control Panel Adjustment 2. Technique Lock + Exposure Adjustments 3. Subtraction 4. Roadmap 1 5. High Dose Image 6. Pulsed 2 15 Fluoroscopy 16 17 7. Continuous Fluoroscopy 18 8. Increased mA 9. Magnification 3 4 8 12 10.Mirror Image + Flip 5 9 11 13 Superior/Inferior 11.Reduce Motion 6 7 10 14 Blur 12.Iris Collimator Adjustment 13.Rotate Paired Filters