The influence of minimal misalignment on the repeatability of PET images examined by the repositioning of point sources

Akira Maebatake, Keishin Morita, Go Akamatsu, Yuji Tsutsui, Kazuhiko Himuro, Shingo Baba, Masayuki Sasaki

Research output: Contribution to journalArticle

Abstract

We aimed to evaluate the influence of minimal misalignment of a hot spot on the repeatability of PET images using repositioning of point sources. Methods: Point sources with an inner diameter of 1 mm were made with 1 μL of 18F solution. Seven point sources were placed on the x-axis in the field of view. For fixed-position imaging, PET data were acquired for 10 min 5 times serially. For variable-position imaging, PET data were acquired for 10 min each with the point sources placed at 0, ±0.5, and ±1.0 mm in the x-axis direction. The data were reconstructed using ordered-subsets expectation maximization (OSEM) and OSEM plus point-spread function (PSF). The image matrix was 128 x 128, 200 x 200, 256 x 256, 400 x 400, and 512 x 512 pixels. The normalized maximum count (rMax), the coefficient of variance (CVmax), and the full width at half maximum were analyzed. Results: The hot spots on OSEM images far from the center became faint and broad, whereas those on OSEM1PSF images became small and dense. Although rMax was overestimated at the 5-cm position on OSEM images, rMax at other positions was overestimated on OSEM+PSF images with a matrix of at least 256 x 256. rMax showed a similar pattern in fixed- and variable-position images. CVmax in fixed-position OSEM images was less than 2%, irrespective of matrix size. In contrast, CVmax in variable-position images was higher than in fixed-position images. CVmax was higher for OSEM+PSF images than for OSEM images. The full width at half maximum increased at positions far from the center on OSEM images but was stable at all positions on OSEM+PSF images. Conclusion: The repeatability of the small hot spot was affected by the minimal misalignment, especially on OSEM+PSF images. Precise positioning is necessary if PET is to be used as a biomarker. Professionals should recognize that PSF correction worsens the repeatability of the small hot spot although improving the spatial resolution of PET images.

Original languageEnglish
Pages (from-to)55-59
Number of pages5
JournalJournal of nuclear medicine technology
Volume47
Issue number1
DOIs
Publication statusPublished - Mar 1 2019

All Science Journal Classification (ASJC) codes

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

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