Annals of Nuclear Medicine

, Volume 24, Issue 7, pp 507–514

Importance of gated CT acquisition for the quantitative improvement of the gated PET/CT in moving phantom

  • Y. Sakaguchi
  • T. Mitsumoto
  • T. Zhang
  • K. Mitsumoto
  • Y. Tachiya
  • N. Ohya
  • M. Sasaki
Original Article

DOI: 10.1007/s12149-010-0388-4

Cite this article as:
Sakaguchi, Y., Mitsumoto, T., Zhang, T. et al. Ann Nucl Med (2010) 24: 507. doi:10.1007/s12149-010-0388-4

Abstract

Objective

The aim of this study was to investigate the utility of gated PET/CT and CT attenuation correction (AC) for the quantitation of radioactivity.

Methods

An ellipse phantom containing six spheres, ranging from 10 to 37 mm in diameter, was filled with 36.7 kBq/mL of F-18. The respiratory motion was simulated by a motor-driven plastic platform to move the phantom with a displacement of 2 cm in the craniocaudal direction at a frequency of 15/min. With the phantom at rest, PET/CT data were acquired and used as a standard (nonmotion). With the phantom in motion, PET data were acquired in both the static and gated modes (sPET and gPET, respectively). Helical CT (HCT), slow CT (SCT), average CT (ACT), and four-dimensional CT (4DCT) were acquired and used to correct attenuation. On both PET and CT images, the maximum radioactivity, dimensions, and CT numbers were measured on the central slices.

Results

In nonmotion, recovery coefficients whose spheres were 22 mm or smaller gradually decreased. Regarding motion, the PET counts of the spheres in the static acquisition were lower than those acquired in nonmotion with either type of CTAC (sPET–HCT: −43.8%, sPET–SCT: −51.4%, sPET–ACT: −49.5%). Gated acquisition of PET significantly improved the PET counts (gPET–HCT: −30.1%) (p < 0.05), while additional gated acquisition of CT significantly improved them further (gPET–4DCT: −15.2%) (p < 0.01). The dimensions of sPET were overestimated, but those of gPET were close to the standard values. The SCT significantly overestimated the dimensions, and the water density area decreased (p < 0.01). The 4DCT images were similar to the HCT images.

Conclusions

In respiratory motion, PET acquisition in the static mode underestimated the radioactivity and overestimated the dimensions. Neither SCT nor ACT improved these errors. Although PET acquisition in the gated mode improved the quantification of PET/CT images, the additional gated CT acquisition using 4DCT is required for further improvement.

Keywords

Respiration motionGatedPET/CT4DCTAttenuation correction

Copyright information

© The Japanese Society of Nuclear Medicine 2010

Authors and Affiliations

  • Y. Sakaguchi
    • 1
  • T. Mitsumoto
    • 1
  • T. Zhang
    • 1
  • K. Mitsumoto
    • 2
  • Y. Tachiya
    • 2
  • N. Ohya
    • 3
  • M. Sasaki
    • 1
  1. 1.Division of Radiological Science, Department of Health SciencesGraduate School of Medical Sciences, Kyushu UniversityFukuokaJapan
  2. 2.Radiological Science Course, Department of Health SciencesSchool of Medicine, Kyushu UniversityFukuokaJapan
  3. 3.Department of Medical TechnologyKyushu University HospitalFukuokaJapan