Abstract
The aim of the study was to analyze the use of block sequential regularized expectation maximization (BSREM) with different β-values for the detection of brain metastases in digital fluorine-18 labeled 2-deoxy-2-fluoro-D-glucose (18F-FDG) PET/CT in lung cancer patients. We retrospectively analyzed staging/restaging 18F-FDG PET/CT scans of 40 consecutive lung cancer patients with new brain metastases, confirmed by MRI. PET images were reconstructed using BSREM (β-values of 100, 200, 300, 400, 500, 600, 700) and OSEM. Two independent blinded readers (R1 and R2) evaluated each reconstruction using a 4-point scale for general image quality, noise, and lesion detectability. SUVmax of metastases, brain background, target-to-background ratio (TBR), and contrast recovery (CR) ratio were recorded for each reconstruction. Among all reconstruction techniques, differences in qualitative parameters were analyzed using non-parametric Friedman test, while differences in quantitative parameters were compared using analysis of variances for repeated measures. Cohen’s kappa (k) was used to measure inter-reader agreement. The overall detectability of brain metastases was highest for BSREM200 (R1: 2.83 ± 1.17; R2: 2.68 ± 1.32) and BSREM300 (R1: 2.78 ± 1.23; R2: 2.68 ± 1.36), followed by BSREM100, which had lower accuracy owing to noise. The highest median TBR was found for BSREM100 (R1: 2.19 ± 1.05; R2: 2.42 ± 1.08), followed by BSREM200 and BSREM300. Image quality ratings were significantly different among reconstructions (p < 0.001). The median quality score was higher for BSREM100-300, and both noise and metastases’ SUVmax decreased with increasing β-value. Inter-reader agreement was particularly high for the detectability of photopenic metastases and blurring (all k > 0.65). BSREM200 and BSREM300 yielded the best results for the detection of brain metastases, surpassing both BSREM400 and OSEM, typically used in clinical practice.
Highlights
Brain metastases (BM) are the most frequent intracranial tumors in adults
The aim of our study was to compare block sequential regularized expectation maximization (BSREM) with different β-values and ordered subset expectation maximization (OSEM) algorithms, in order to define which reconstruction algorithm is most appropriate for brain metastases detection in digital 18 labeled 2-deoxy-2-fluoro-D-glucose (18F-FDG) positron-emission tomography (PET)/computed tomography (CT)
The mean number of BM detected was 1.63 ± 1.48 per patient at clinical 18F-FDG PET/ CT with B SREM400 reconstruction versus 4.42 ± 5.93 at magnetic resonance imaging (MRI). BSREM300 reconstruction showed the highest mean number of BM detected per patient (1.75 ± 1.46; median = 1; 1–7)
Summary
Brain metastases (BM) are the most frequent intracranial tumors in adults. Lung cancer, breast cancer, melanoma, renal cell carcinoma (RCC), and colorectal cancer (CRC) are the most common solid tumors associated with BM. BM are associated with higher morbidity and mortality, independently of the type of primary tumor, with an overall survival of less than 2 years [1]. BM occur in approximately 10–20% of lung cancer patients with metastatic disease and approximately 30–50% of patients with non-small-cell lung cancer (NSCLC) will eventually develop BM [2,3,4]. BM are diagnosed more frequently in small-cell lung cancer (SCLC) compared to other types of lung cancer and are present at initial staging already in approximately 10% of patients [5, 6]. In NSCLC patients, adenocarcinoma subtype, advanced nodal status, advanced tumor stage, and young patient age are known risk factors for the metachronous development of BM [7,8,9]. The reported overall survival at 60 months is 68% in stage IB, while it is less than 10% in stage IVB [4]
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