Abstract

BackgroundAccurate staging is crucial for treatment selection and prognosis prediction in patients with rectal cancer. Point spread function (PSF) reconstruction can improve spatial resolution and signal-to-noise ratio of PET imaging. The aim of this study was to evaluate the effectiveness of 18F-FDG PET/CT with PSF reconstruction for initial staging in rectal cancer compared with conventional PET/CT and pelvic MRI.MethodsA total of 59 patients with rectal cancer underwent preoperative 18F-FDG PET/CT and pelvic MRI. The maximum standardized uptake value (SUVmax) and lesion to background (L/B) ratio of possible metastatic lymph nodes, and metabolic tumor volumes (MTVs) of primary tumors were calculated. For N and T (T1-2 vs T3-4) staging, sensitivities, specificities, positive predictive values, negative predictive values, and accuracies were compared between conventional PET/CT [reconstructed with ordered subset expectation maximization (OSEM)], PSF-PET/CT (reconstructed with OSEM+PSF), and pelvic MRI. Histopathologic analysis was the reference standard.ResultsFor N staging, PSF-PET/CT provided higher sensitivity (78.6%) than conventional PET/CT (64.3%), and pelvic MRI (57.1%), and all techniques showed high specificity (PSF-PET: 95.4%, conventional PET: 96.7%, pelvic MRI: 93.5%). SUVmax and L/B ratio were significantly higher in PSF-PET/CT than conventional-PET/CT (p < 0.001). The accuracy for T staging in PSF-PET/CT (69.4%) was not significantly different to conventional PET/CT (73.5%) and pelvic MRI (73.5%). MTVs of PSF and conventional PET showed a significant difference among T stages (p < 0.001), with higher values in advanced stages. In M staging, both PSF and conventional PET/CT diagnosed all distant metastases correctly.ConclusionsPSF-PET/CT produced images with higher lesion-to-background contrast than conventional PET/CT, which allowed improved detection of lymph node metastasis without compromising specificity, and showed comparable diagnostic value to MRI in local staging. PSF-PET/CT is likely to have a great value for initial staging in rectal cancer.

Highlights

  • Accurate staging is crucial for treatment selection and prognosis prediction in patients with rectal cancer

  • The latest PET scanners generally equipped with Point spread function (PSF) reconstruction, which can be used only by changing its reconstruction algorithm, without additional image acquisition. 18F-FDG PET/CT using PSF reconstruction has already been reported to improve the sensitivity of nodal staging for malignancies such as lung or breast cancer [15,16,17]

  • The aim of this study was to evaluate the effectiveness of 18F-FDG PET/CT using PSF reconstruction for the initial staging in patients with rectal cancer, and compare it to both pelvic MRI and 18F-FDG PET/CT using ordered subset expectation maximization (OSEM) reconstruction

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Summary

Introduction

Accurate staging is crucial for treatment selection and prognosis prediction in patients with rectal cancer. Point spread function (PSF) reconstruction can improve spatial resolution and signal-to-noise ratio of PET imaging. The aim of this study was to evaluate the effectiveness of 18F-FDG PET/CT with PSF reconstruction for initial staging in rectal cancer compared with conventional PET/CT and pelvic MRI. PSF reconstruction corrects photon mis-positioning (parallax effect) while gamma rays pass in the scintillation detectors at both non-oblique and oblique angles. This algorithm can improve the spatial resolution and signal-to-noise ratio of PET images [13, 14], leading to higher detection rates for small lesions. The utility of PSF for in rectal cancer has not been adequately clarified

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