Research presented earlier this month at SNM’s 58th annual meeting examined how nongated PET corrected with information from a 4D CT scan may improve imaging in patients who do not benefit from gated PET scans. The 4D CT scan is used in an alternative way to assess tumor and normal organ motion.
“Breathing irregularities can lead to significantly underestimated lesion activity in respiratory-gated PET imaging,” said Boon-Keng Teo, PhD, an assistant professor of radiation oncology at the University of Pennsylvania in Philadelphia. “Nongated PET imaging corrected with 4D computed tomography may be more effective for imaging patients with irregular breathing. This could potentially lead to a more robust and quantitatively accurate reading of active tumors.”
In respiratory gating systems, sensors placed on or around a patient monitor the phase of the breathing cycle. They then transmit information about a patient’s breathing to the scanning technology for image processing. Instead of creating one fluid image that shows so-called motion artifacts, respiratory-gated PET imaging is much like a series of photos taken during different phases of the respiratory cycle that are grouped together to create a series of images corresponding to each phase. The problem is that patients with respiratory disease, heart conditions, or other serious diseases are likely to breathe unevenly. Respiratory gating systems are designed to work with normal even breathing patterns but not with irregular respiratory cycles.
The researchers conducted phantom studies to compare respiratory-gated PET imaging with nongated PET imaging corrected with 4D CT and complex data processing to produce very high-resolution images of structural anatomy during different phases of the breathing cycle. Phantom studies were performed with inanimate objects that were moved in a controlled manner to simulate tumors in respiratory motion. Various degrees of motion irregularities were simulated to study their impact on the accuracy of 4D PET for suppressing motion artifacts. The 4D PET and CT studies were conducted in succession with a hybrid PET/CT system.
The researchers found that nongated PET with 4D CT imaging can be an alternative to respiratory-gated PET imaging for determining tumor activity in patients with highly irregular breathing. These findings could change imaging protocols for patients with uneven breathing and potentially improve overall accuracy in detecting and evaluating tumors, which could help clinicians plan appropriate treatments.
— Source: SNM