Inspiration breath-hold data acquisition for thoracic PET/CT without respiratory gating system: A phantom study for quantitative assessment.

Objectives Respiratory motion artifact on PET/CT disturbs accurate diagnosis of lesions. To reduce this artifact, respiratory gated PET/CT Imaging was reported to be useful. As a simple alternative, we propose an inspiration breath-hold PET data acquisition method without respiratory gating system.

Methods In this method, patients are asked to hold breath in inspiratory state for 10-15sec then allowed to breathe freely for next 15sec. Repeating this cycle 6-12times during dynamic PET data acquisition, frames showing good registration with inspiratory CT were selected by visual inspection and merged to obtain PET images in inspiratory state. With this method, inspiratory PET images could be obtained without a respiratory gating system. We investigated quantitatively of the PET images acquired by this method using a hot lesions phantom. Radioactivity concentration was measured on the images obtained by different acquisition times, and compared with the reference imager (300sec).

Results On the images obtained by acquisition time of 20sec, radioactivities of all spheric hot lesions were overestimated by 30%, compared with the reference image. However, by merging the images, image quality was improved and the overestimation was reduced to 10% and 5% in the images by acquisition time of 60 and 120 sec.

Conclusions This method could provide inspiratory PET images in good quality without any system by additional 5min. Quantitativity of the merged PET image was well preserved for the lesion sizes studied. Considering the image quality obtained with this method and that maximal SUV are usually used for evaluating regional uptake in clinical situation, this method could be clinically useful.