Abstract
BackgroundProstate-specific membrane antigen (PSMA) radiotracers such as [18F]PSMA-1007 used with positron emission tomography-computed tomography (PET-CT) is promising for initial staging and detection of recurrent disease in prostate cancer patients. The block-sequential regularization expectation maximization algorithm (BSREM) is a new PET reconstruction algorithm, which provides higher image contrast while also reducing noise. The aim of the present study was to evaluate the influence of different acquisition times and different noise-suppressing factors in BSREM (β values) in [18F]PSMA-1007 PET-CT regarding quantitative data as well as a visual image quality assessment.We included 35 patients referred for clinical [18F]PSMA-1007 PET-CT. Four megabecquerels per kilogramme were administered and imaging was performed after 120 min. Eighty-four image series per patient were created with combinations of acquisition times of 1–4 min/bed position and β values of 300–1400. The noise level in normal tissue and the contrast-to-noise ratio (CNR) of pathological uptakes versus the local background were calculated. Image quality was assessed by experienced nuclear medicine physicians.ResultsThe noise level in the liver, spleen, and muscle was higher for low β values and low acquisition times (written as activity time products (ATs = administered activity × acquisition time)) and was minimized at maximum AT (16 MBq/kg min) and maximum β (1400). There was only a small decrease above AT 10. The median CNR increased slowly with AT from approximately 6 to 12 and was substantially lower at AT 4 and higher at AT 14–16. At AT 4–6, many images were regarded as being of unacceptable quality. For AT 8, β values of 700–900 were considered of acceptable quality.ConclusionsAn AT of 8 (for example as in our study, 4 MB/kg with an acquisition time of 2 min) with a β value of 700 performs well regarding noise level, CNR, and visual image quality assessment.
Highlights
Prostate-specific membrane antigen (PSMA) radiotracers such as [18F]PSMA-1007 used with positron emission tomography-computed tomography (PET-CT) is promising for initial staging and detection of recurrent disease in prostate cancer patients
Positron emission tomography-computed tomography (PET-CT) is a widely accepted imaging technique for initial staging and for detecting sites of disease recurrence in patients with prostate cancer; this has been the case since the introduction of prostate-specific membrane antigen (PSMA) radiotracers [3]
The PET-CT systems were equipped with time-of-flight and configured with four rings of detector blocks with lutetium yttrium oxyorthosilicate crystals coupled to an array of Silicon photomultiplier (SiPM)
Summary
Prostate-specific membrane antigen (PSMA) radiotracers such as [18F]PSMA-1007 used with positron emission tomography-computed tomography (PET-CT) is promising for initial staging and detection of recurrent disease in prostate cancer patients. The block-sequential regularization expectation maximization algorithm (BSREM) is a new PET reconstruction algorithm, which provides higher image contrast while reducing noise. Positron emission tomography-computed tomography (PET-CT) is a widely accepted imaging technique for initial staging and for detecting sites of disease recurrence in patients with prostate cancer; this has been the case since the introduction of prostate-specific membrane antigen (PSMA) radiotracers [3]. Compared to ordered subset expectation maximization (OSEM), BSREM can maintain a low noise level as the number of iterations increases This reduces the need of “stopping early” as a strategy for noise control and allow for more iterations while keeping the noise level at clinical acceptable levels. BSREM have been shown to increase the quantitative accuracy of standardized uptake value (SUV) measurements, in small lesions [9]
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