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
Summary
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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