Evaluation of tumor heterogeneity based on texture parameters has recently attracted much interest in the PET imaging community. However, the impact of reconstruction settings on texture parameters is unclear, especially relating to time-offlight and point-spread function modeling. Their effects on 55 texture features (TFs) and 6 features based on first-order statistics (FOS) were investigated. Standardized uptake value (SUV) measures were also evaluated as peak SUV (SUV peak ), maximum SUV, and mean SUV (SUV mean ). Methods: This study retrospectively recruited 20 patients with lesions in the lung who underwent whole-body 18 F-FDG PET/CT. The coefficient of variation (COV) of each feature across different reconstructions was calculated. Results: SUV peak , SUV mean , 18 TFs, and 1 FOS were the most robust (COV # 5%) whereas skewness, cluster shade, and zone percentage were the least robust (COV . 20%) with respect to reconstruction algorithms using default settings. Heterogeneity parameters had different sensitivities to iteration number. Twenty-four parameters including SUV peak and SUV mean exhibited variation with a COV less than 5%; 28 parameters, including maximum SUV, showed variation with a COV in the range of 5%-10%. In addition, skewness, cluster shade, and zone percentage were the most sensitive to iteration number. In terms of sensitivity to full width at half maximum (FWHM), 15 TFs and 1 FOS had the best performance with a COV less than 5%, whereas SUV peak and SUV mean had a COV between 5% and 10%. Grid size had the largest impact on image features, which was demonstrated by only 11 features, including SUV peak and SUV mean , having a COV less than 10%. Conclusion: Different image features have different sensitivities to reconstruction settings. Iteration number and FWHM of the gaussian filter have a similar impact on the image features. Grid size has a larger impact on the features than iteration number and FWHM. The features that exhibited large variations such as skewness in FOS, cluster shade, and zone percentage should be used with caution. The entropy in FOS, difference entropy, inverse difference normalized, inverse difference moment normalized, low gray-level run emphasis, high gray-level run emphasis, and low gray-level zone emphasis are the most robust features.
The use of radiotherapy, either in the form of stereotactic radiosurgery (SRS) or whole-brain radiotherapy (WBRT), remains the cornerstone for the treatment of brain metastases (BM). As the survival of patients with BM is being prolonged, due to improved systemic therapy (i.e., for better extra-cranial control) and increased use of SRS (i.e., for improved intra-cranial control), patients are clinically manifesting late effects of radiotherapy. One of these late effects is radiation necrosis (RN). Unfortunately, symptomatic RN is notoriously hard to diagnose and manage. The features of RN overlap considerably with tumor recurrence, and misdiagnosing RN as tumor recurrence may lead to deleterious treatment which may cause detrimental effects to the patient. In this review, we will explore the pathophysiology of RN, risk factors for its development, and the strategies to evaluate and manage RN.
Four cytokine receptor genes are located on Chr21q22.11, encoding the a and b subunits of the interferon-a receptor (IFNAR1 and IFNAR2), the b subunit of the interleukin 10 receptor (IL10RB) and the second subunit of the interferon-g receptor (IFNGR2). We previously reported that two variants in IFNAR1 were associated with susceptibility to malaria in Gambians. We now present an extensive fine-scale mapping of the associated region utilizing 45 additional genetic markers obtained from public databases and by sequencing a 44 kb region in and around the IFNAR1 gene in 24 Gambian children (12 cases/12 controls). Within the IFNAR1 gene, a newly studied C-G single-nucleotide polymorphism (IFNAR1 272354c-g) at position À576 relative to the transcription start was found to be more strongly associated with susceptibility to severe malaria. Association was observed in three populations: in Gambian (P ¼ 0.002), Kenyan (P ¼ 0.022) and Vietnamese (P ¼ 0.005) case-control studies. When all three studies were combined, using the Mantel-Haenszel test, the presence of IFNAR1 À576G was associated with a substantially elevated risk of severe malaria (N ¼ 2444, OR ¼ 1.38, 95% CI: 1.17-1.64; P ¼ 1.7 Â 10 À4 ). This study builds on previous work to further highlight the importance of the type-I interferon pathway in malaria susceptibility and illustrates the utility of typing SNPs within regions of high linkage disequilibrium in multiple populations to confirm initial positive associations.
This study highlights the potential of (68) Ga-DOTA-peptide PET/CT as a new molecular biomarker for newly diagnosed undifferentiated NPC, and less so for recurrent NPC and metastatic nodes. This potentially opens up new diagnostic and therapeutic options in the management of undifferentiated NPC.
BackgroundThe understanding of early events following TB exposure is limited by traditional tests that rely on detection of an immune response to infection, which is delayed, or on imaging tests with low sensitivity for early disease. We investigated for evidence of lung abnormalities in heavily exposed TB contacts using PET/MRI.Methods30 household contacts of 20 index patients underwent clinical assessment, IGRA testing, chest x-ray and PET/MRI scan using 18-F-FDG. MRI images were examined by a radiology/nuclear medicine dual-qualified physician using a standardised report form, while PET/MRI images were examined independently by another radiology/nuclear medicine dual-qualified physician using a similar form. Standardised uptake value (SUV) was quantified for each abnormal lesion.ResultsIGRA was positive in 40%. PET/MRI scan was abnormal in 30%, predominantly FDG uptake in hilar or mediastinal lymph nodes and lung apices. We did not identify any relationship between PET/MRI findings and degree of exposure or IGRA status.ConclusionPET-based imaging may provide important insights into the natural history following exposure to TB that may not be available from traditional tests of TB immune response or imaging. The clinical significance of the abnormalities is uncertain and merits further investigation in longitudinal studies.
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