UUUU.3.2.1 X-Ray Angiography

UUUU.3.2.1 X-Ray Angiography (Current)
Prev	UUUU.3 Radiation Dose Overview	Next

X-Ray Angiography (XA) systems perform diagnostic and interventional procedures, typically in a catheterization lab (cath lab). These angiography procedures primarily involve imaging of the blood vessels and organs of the body (arteries, veins, and heart chambers) by injecting a radio-opaque contrast agent into the blood.

XA equipment is also used for electrophysiology (EP) procedures in the EP lab, where catheters and wire electrodes are passed through blood vessels to assess and treat the heart's electrical activity. The use of fluoroscopically-guided procedures in the cath lab for minimally invasive surgical interventions led to the definition of the term "interventional", which includes interventional radiology (IR) and cardiology (IC) procedures that do not always use angiography techniques but require the same type of XA equipment to visualize instruments inside the body. They are performed in the so-called interventional lab or in hybrid operating rooms. Finally, image-guided surgical procedures may use similar XA imaging techniques on smaller mobile equipment.

The equipment used in all these procedures typically includes the X-Ray Source and X-Ray Detector mounted on a C-Arm, and the technical data related to the Source and Detector is collected automatically. The mechanical data related to the gantry is known (e.g., positioner angles), while the data related to the table may be known if the table is integrated with the gantry but may be unknown on mobile C-Arms. These concepts are developed in more detail in Section UUUU.4.9.

A general XA procedure workflow is as follows:

The procedure starts,
1. Patient and procedure information is provided to the equipment by the DICOM Modality Worklist or manually entered by the operator.
2. Equipment settings like protocols, patient position relative to the table, etc., are then provided to the equipment by the operator.
During the procedure, X-Ray exposures are performed.
1. XA has two main X-Ray exposure modes: Fluoroscopy and Acquisition. Fluoroscopy is typically low dose and is used to place the instruments (catheters, guidewires, needles). Acquisition is typically higher dose (so-called cine run) and is used to achieve higher image quality.
2. For each X-Ray exposure, dose and other related information is collected and recorded in an Irradiation Event (for both Fluoroscopy and Acquisitions).
3. When the two X-Ray sources of a biplane system are activated simultaneously during the X-Ray exposure, it results in two Irradiation Events, one for Plane A and one for Plane B.
4. Optionally, one or more RDSRs are created during the procedure if there is an external dose consumer system that needs to process and display the information as the procedure goes. These RDSRs contain information of the Irradiation Events that were recorded until that time in the procedure.
  - Each RDSR Instance defines its Scope of Accumulation which indicates the period of irradiation reported in that RDSR Instance (e.g., Procedure Step To This Point, or an individual Irradiation Event). Each RDSR Instance includes information of all the Irradiation Events within its scope of accumulation, as well as Accumulated Dose Data within that same scope.
During the procedure, images are generated.
1. X-Ray exposures always result in images (i.e., XA 2D projection images) that are displayed on the equipment and have corresponding Irradiation Events.
  - Images resulting from Fluoroscopy exposures are shown on the screen to the operator but may or may not be a persistent DICOM object.
  - Images resulting from Acquisition exposures are shown on the screen to the operator and are typically persistent DICOM objects.
  - XA 2D projection images can be multi-frame or single frame.
  - X-Ray exposures of two X-Ray sources of a biplane system activated simultaneously result into two XA 2D projection images, one for Plane A and one for Plane B.
2. XA 2D projection images may be processed to create new images (e.g., subtracted images), also stored as XA 2D images. No new X-Ray exposures were involved. The new images may include a reference to the Irradiation Event UIDs of the XA 2D images they were created from.
3. 3D cone-beam (CBCT) reconstructions may be created from XA 2D projections and stored as X-Ray 3D images. No new X-Ray exposures were involved. The new 3D cone-beam reconstructions may include a reference to the Irradiation Event UIDs of the XA 2D images they were created from.
4. DICOM XA images are stored in one or more DICOM Series grouping related images in a Series.
5. The Irradiation Event details are always kept regardless of whether the XA 2D images are persistently stored or deleted during the procedure.
The procedure ends.
Following the procedure, one or more RDSR Instances are created from the irradiation data collected during the procedure.
1. These RDSRs contain information for long-term storage and distribution to dose information management systems and cross-institutional systems such as dose registries. They are used to perform relevant dose QA analysis, produce related reports, and support medical regulations.
2. Each RDSR Instance defines its scope of accumulation which indicates the period of irradiation reported in that RDSR Instance (the Study, the Series, the Performed Procedure Step). Each RDSR Instance includes information of all the Irradiation Events within its scope of accumulation, as well as Accumulated Dose Data within that same scope.
3. There will typically be an RDSR with a scope that covers all of the Irradiation Events during that Study.
4. These RDSRs are stored in a new DICOM Series different from the one where the XA images are stored.
Optionally, additional images are created from the existing data.
1. No new X-Ray exposures are involved in the creation of additional images (e.g., processed XA 2D images, 3D cone-beam reconstructions).
2. The new images may include a reference to the Irradiation Event UIDs of the XA 2D images they were created from.
3. The RDSR is not updated to reference these images produced after the creation of the RDSR.
Subsequent dose analysis is performed.
1. Dose analysis is based on the information of the Irradiation Events contained in the RDSRs, not on the image metadata.
2. Images are associated with one or more Irradiation Events, but there may be Irradiation Events with no images (e.g., images that come for Fluoroscopy, or deleted Acquisition images).
3. There may be also one Irradiation Event that ultimately results in multiple images (e.g., original and processed images, 3D reconstructions, etc.). See Section UUUU.4.1.4 for the importance to use the Irradiation Event UIDs in the RDSRs.

See also Annex FFF Enhanced XA/XRF Encoding Examples (Informative) and Annex TTT X-Ray 3D Angiographic Image Encoding Examples (Informative) for more information about X-Ray Angiography.

Prev	Up	Next
UUUU.3.2 Real-World Scenarios of Radiation Dose Reporting	Home	UUUU.3.2.2 Radiofluoroscopy