ANGIOGRAPHYANDINTERVENTION.COM
X-ray Equipment
Detector
X-ray Tube
Monitors
Table-side Control Modules
Ceiling or Floor-mounted C-arm
Table
Angiography units are complex and sophisticated x-ray machines. A typical angiography suite or interventional catheter lab consists of a C-arm which is either ceiling or floor-mounted. The top of the C-arm is the image intensifier (older generation systems) or flat-panel detector (modern generation systems), and the bottom of the C-arm is the x-ray tube. A table for the patient is free-floating on a floor-mounted base and holds a high weight limit (e.g. Philips Azurion is 250kg with 500 N for CPR at any point of the table). There are table-side control modules attached to the table and in-room monitors, as well as control modules and monitors in the Control Room (behind lead screens and lead-lined walls).
A skillful operator (physician or interventional radiographer) involves being able to "drive" the angiography unit with ease, efficiency, and precision. This includes the mechanical movements of the unit itself - the table amd the C-arm - and the image processing capabilities of the unit - such as Roadmapping, magnification, collimation, filters, and fluoroscopy controls.
Each system allows for different fluoroscopy levels ranging from low pulse rates (7.5 pps) to higher pulse rates (15 pps). Note that this increases image quality and dose to the patient.
Magnification from 40 FDD to 20 FDD, for example, focuses onto the region of interest (ROI) with an increase in size, but also an increase in dose to the patient. TIP: Using the digital magnification function on modern angiography systems will allow for a magnification of the anatomy or ROI and will not change the exposure and dose to the patient.
Fluoroscopy store function allows for last-image hold (LIH) replay of the fluoroscopy scene and can be used a reference image or roadmap (if contrast is present).
Conventional roadmap or Navigate (Philips Healthcare) function uses the peak opacification of contrast as a roadmap, where the vessel is bright, and the background is dark grey. This is the DSA function on Siemens angiography units. Navigate on Philips Healthcare angiography units can be activated by pressing "Roadmap ON" twice, or the appearance can be changed from DSA to Navigate on the touchscreen console (under "Roadmap").
Angiographic Imaging Modes
01
DSA
Digital Subtraction Angiography (DSA) involves acquisition of an initial frame, known as the mask, and where the subsequent frames are subtracted from the mask. This removes the background and leaves only the new information, such as the flow of contrast. "Stitching" or "stacking" can add frames together to be used as a roadmap.
02
CONVENTIONAL ROADMAP
The peak opacification of contrast (bright area) and summation of all frames. Useful as an alternative to DSA as a roadmap technique. Less than 50% of the radiation dose compared to DSA. User does not have the ability to go through the series frame by frame.
03
FLUOROSCOPY/
LAST-IMAGE HOLD
Live fluoroscopy is either continuous or pulsed fluoroscopy (pulses per second [pps]). Fluoroscopy shows live dynamic imaging of the region of interest and can be used to visualize contrast through a vessel or cavity. Frames can be reviewed and also "stacked" or "stitched" for use as a reference or roadmap.
04
SINGLE SHOT/EXPOSURE
A single x-ray shot or exposure can be performed, with a set kVp and mAs. This is a single frame image and is used to better visualise the region of interest and/or contrast within the vessel or cavity. This can be used as a reference image.
05
CBCT
Cone Beam Computed Tomography (CBCT) is used to acquire a CT volumetric scan of the region of interest. This can be performed as non-contrast, arterial, portal venous, or delayed. Some units can do Dual-phase CBCT. The volume, flow rate, and delay can be determined on the injector and system. "EmboGuide" (Philips Healthcare) or SyngoVia (Siemens) can be used to track vessels and measure volumes.
06
IMAGE FUSION
External datasets from CT angiograms or Magnetic Resonance Angiograms (MRA) can be imported onto the angiography system, perform a work-up of the 3D model, calibrate the patient on-table (with angled single exposures), and fuse the dataset to the live fluoroscopy. Minimises contrast injector runs and DSA.
07
3DRA
3D Rotation Angiography (3DRA) is useful during cerebral studies where the C-arm can be used to perform a CT around the ROI with a contrast injection. 2D frames are visualised rotating around the ROI. Multi-planar reconstructions can be used to generate a 3D volume of the vessels.
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