Does a novel penalized likelihood reconstruction of 18F-FDG PET-CT improve signal-to-background in colorectal liver metastases?

Eur J Radiol. 2015 Oct;84(10):1873-8. doi: 10.1016/j.ejrad.2015.06.025. Epub 2015 Jun 29.

Abstract

Purpose: Iterative reconstruction algorithms are widely used to reconstruct positron emission tomography computerised tomography (PET/CT) data. Lesion detection in the liver by 18F-fluorodeoxyglucose PET/CT (18F-FDG-PET/CT) is hindered by 18F-FDG uptake in background liver parenchyma. The aim of this study was to compare semi-quantitative parameters of histologically-proven colorectal liver metastases detected by 18F-FDG-PET/CT using data based on a Bayesian penalised likelihood (BPL) reconstruction, with data based on a conventional time-of-flight (ToF) ordered subsets expectation maximisation (OSEM) reconstruction.

Methods: A BPL reconstruction algorithm was used to retrospectively reconstruct sinogram PET data. This data was compared with OSEM reconstructions. A volume of interest was placed within normal background liver parenchyma. Lesions were segmented using automated thresholding. Lesion maximum standardised uptake value (SUVmax), standard deviation of background liver parenchyma SUV, signal-to-background ratio (SBR), and signal-to-noise ratio (SNR) were collated. Data was analysed using paired Student's t-tests and the Pearson correlation.

Results: Forty-two liver metastases from twenty-four patients were included in the analysis. The average lesion SUVmax increased from 8.8 to 11.6 (p<0.001) after application of the BPL algorithm, with no significant difference in background noise. SBR increased from 4.0 to 4.9 (p<0.001) and SNR increased from 10.6 to 13.1 (p<0.001) using BPL. There was a statistically significant negative correlation between lesion size and the percentage increase in lesion SUVmax (p=0.03).

Conclusions: This BPL reconstruction algorithm improved SNR and SBR for colorectal liver metastases detected by 18F-FDG-PET/CT, increasing the lesion SUVmax without increasing background liver SUV or image noise. This may improve the detection of FDG-avid focal liver lesions and the diagnostic performance of clinical 18F-FDG-PET/CT in this setting, with the largest impact for small foci.

Keywords: Colorectal liver metastases; Positron emission tomography; Reconstruction; Signal-to-background; Signal-to-noise.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms
  • Artifacts
  • Bayes Theorem
  • Colorectal Neoplasms / pathology
  • Female
  • Fluorodeoxyglucose F18 / administration & dosage*
  • Humans
  • Image Processing, Computer-Assisted / methods*
  • Image Processing, Computer-Assisted / statistics & numerical data
  • Likelihood Functions
  • Liver Neoplasms / diagnostic imaging
  • Liver Neoplasms / secondary*
  • Male
  • Middle Aged
  • Multimodal Imaging / methods*
  • Multimodal Imaging / statistics & numerical data
  • Positron-Emission Tomography / methods*
  • Positron-Emission Tomography / statistics & numerical data
  • Radiopharmaceuticals / administration & dosage*
  • Retrospective Studies
  • Signal-To-Noise Ratio
  • Tomography, X-Ray Computed / methods*
  • Tomography, X-Ray Computed / statistics & numerical data

Substances

  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18