Researchers in Germany and Siemens Healthineers have developed a protocol to reduce artefacts caused by irregular breathing patterns during clinical 4D CT scanning, according to their paper, publishing in the journal Medical Physics and a report in Physics World.
Respiration-correlated CT imaging, or 4D CT, is an essential part of radiotherapy planning for thoracic and abdominal tumors. Clinical 4D CT images are often affected by artefacts, however, mainly due to irregular breathing patterns during data acquisition. A research team has now successfully validated a prototype implementation of an intelligent 4D CT (i4DCT) scanning protocol that produces fewer motion artefacts, demonstrating that breathing signal-guided 4D CT is feasible for clinical applications.
The researchers, at the University Medical Center Hamburg-Eppendorf in Germany and Siemens Healthineers, utilized online breathing curve analysis and respiratory signal-guided 4D CT protocols to develop the i4DCT concept. In a feasibility study, they compared images of a motion phantom recorded using routine spiral 4D CT and i4DCT.
4D CT images are used for dose calculation and optimization, to define motion-adapted safety margins, and to perform 4D dose reconstruction and quality assurance after radiation treatment. When images are degraded by artefacts, it may be necessary for a patient to have an additional CT scan, exposing them to a second high radiation dose and potentially delaying their radiotherapy.
The i4DCT concept enables automated selection of CT beam-on/beam-off periods, by adapting data acquisition to a patient’s individual breathing pattern, instead of the patient having to adapt to the scanner. The i4DCT workflow consists of an initial learning period to establish a reference patient-specific breathing cycle representation, followed by online breathing signal-guided sequence mode scanning.
Featured image: Comparison of routine spiral 4D CT and i4DCT imaging for regular and irregular breathing patterns. Left: normalized programmed breathing curves; green: beam-on periods; grey: beam-off periods; red: breathing pause. Right: images reconstructed at maximum inhalation; the arrow shows an artefact caused by the breathing pause. (Courtesy: Med. Phys. 10.1.1002/mp.14106)