Iterative model reconstruction lowers dose in cardiac CT

Knowledge-based iterative model reconstruction (IMR) can provide improved image quality at super-low-dose cardiac CT with 20 percent of the standard tube current, according to a study published in the January 2014 issue of Academic Radiology.

The use of cardiac CT has raised concerns because of the ionizing radiation it emits, which can lead to stochastic risks. While dose saving techniques have been created for the modality, iterative reconstruction algorithms for CT have also been developed to reduce quantum noise and radiation dose. Iterative model reconstruction is the latest of these techniques. Lead author Seitaro Oda, MD, of Kumamoto University in Kumamoto, Japan, and colleagues wrote of IMR: “It applies a knowledge-based approach that yields improved image quality and virtually noise-free images through the iterative minimization of the penalty-based cost function.”

Oda and colleagues created a study to investigate IMR’s effects on quantitative and qualitative image evaluation by comparing images acquired at low-radiation doses and images obtained at standard radiation doses with convolution-filtered back projection (FBP) reconstruction.

The retrospective study included 23 patients who underwent electrocardiography-gated cardiac CT with dose modulation. The researchers compared full-dose images reconstructed with FBP and the low-dose images reconstructed with FBP and IMR techniques. Once they were established, objective and subjective image quality parameters were compared among the three varying CT images.

The study’s findings revealed no significant difference in CT attenuation among the three reconstructions. Of the three reconstructions, the mean image noise of the low-dose IMR were significantly the lowest. The contrast-to-noise ratio of the low-dose IMR was better than the other two reconstructions. It also had the highest visual evaluation score.

“The IMR algorithm yields images of significantly improved quantitative quality and acceptable subjective quality at LD cardiac CT at 20 percent of the standard tube current. This may potentially benefit subgroups such as low-risk patients and young patients by radiation exposure saving,” wrote Oda and colleagues.

Further clinical studies must be performed to evaluate the authors’ research techniques and confirm their preliminary findings, they concluded.