Effects of image noise, respiratory motion, and motion compensation on 3D activity quantification in count-limited PET images

W. Siman, O. R. Mawlawi, J. K. Mikell, F. Mourtada, S. C. Kappadath

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The aims of this study were to evaluate the effects of noise, motion blur, and motion compensation using quiescent-period gating (QPG) on the activity concentration (AC) distribution - quantified using the cumulative AC volume histogram (ACVH) - in count-limited studies such as 90Y-PET/CT. An International Electrotechnical Commission phantom filled with low 18F activity was used to simulate clinical 90Y-PET images. PET data were acquired using a GE-D690 when the phantom was static and subject to 1-4 cm periodic 1D motion. The static data were down-sampled into shorter durations to determine the effect of noise on ACVH. Motion-degraded PET data were sorted into multiple gates to assess the effect of motion and QPG on ACVH. Errors in ACVH at AC90 (minimum AC that covers 90% of the volume of interest (VOI)), AC80, and ACmean (average AC in the VOI) were characterized as a function of noise and amplitude before and after QPG. Scan-time reduction increased the apparent non-uniformity of sphere doses and the dispersion of ACVH. These effects were more pronounced in smaller spheres. Noise-related errors in ACVH at AC20 to AC70 were smaller (<15%) compared to the errors between AC80 to AC90 (>15%). The accuracy of ACmean was largely independent of the total count. Motion decreased the observed AC and skewed the ACVH toward lower values; the severity of this effect depended on motion amplitude and tumor diameter. The errors in AC20 to AC80 for the 17 mm sphere were -25% and -55% for motion amplitudes of 2 cm and 4 cm, respectively. With QPG, the errors in AC20 to AC80 of the 17 mm sphere were reduced to -15% for motion amplitudes <4 cm. For spheres with motion amplitude to diameter ratio >0.5, QPG was effective at reducing errors in ACVH despite increases in image non-uniformity due to increased noise. ACVH is believed to be more relevant than mean or maximum AC to calculate tumor control and normal tissue complication probability. However, caution needs to be exercised when using ACVH in post-therapy 90Y imaging because of its susceptibility to image degradation from both image noise and respiratory motion.

Original languageEnglish
Pages (from-to)448-464
Number of pages17
JournalPhysics in medicine and biology
Volume62
Issue number2
DOIs
StatePublished - Jan 21 2017

Keywords

  • dose volume histogram
  • gated respiratory motion
  • quantitative Y PET/CT

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