Abstract
305
Objectives PET/CT imaging following Y90 microsphere radioembolization is a growing area of interest in molecular imaging. High resolution imaging of the liver is made difficult because of the large range of motion in this region because of normal respiratory function. Use of amplitude-based gating with PET imaging has shown to be an efficient way to balance improved motion correction with minimal count loss or increases in scan time [1]. Further, our team has shown quantitative improvements to Y90 PET imaging and dosimetry calculations when using amplitude-based gating PET/CT [2]. This work, to our knowledge is the first to examine the potential impact amplitude-based gating has on diagnostic image quality using the Kao criteria for diagnostic assessment of Y90 PET/CT images.
Methods 11 patients were imaged using PET/CT following radioembolization of the liver using Y90 microspheres using standard PET/CT and amplitude-based gating. Quantitative comparison of SUVs between standard PET/CT and amplitude-based gating images was performed for regions of interest covering the entire liver (based on a 30% of maximum threshold) and individual primary lesions. A binary scale based on the Kao criteria (Table 1) was created to assess diagnostic quality of the Y90 images with interpretation performed by a board certified nuclear medicine physician. Thresholds for noise spike and bleeding were set to 25% of maximum values.
Results Quantitative assessment shows that SUVs differ significantly between gated and standard PET/CT (p<0.05). Average SUV measurements were 19% higher in images acquired using amplitude-based gating with maximum changes in mean values of 62% and 37% for global and regional lesion assessments, respectively. Diagnostic interpretation showed no statistical difference between ratings when comparing standard PET images to those acquired using amplitude-based gating (p<0.05).
Conclusions Amplitude-based gating significantly increases measured SUVs in PET images affected by respiratory motion. Use of this technique reduces the overall number of counts in the image but the increased image noise does not negatively impact diagnostic image quality compared to standard Y90 PET/CT imaging. Figure 1 shows a comparison of data with increased noise spike seen in gated images but significant loss of image quality due to motion blur using standard PET/CT. $$graphic_A4CAA279-7286-48E3-8405-5FA98004F4B8$$