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Objectives: High-level microsatellite instability (MSI-high) is generally associated with higher F-18 fluorodeoxyglucose ([ 18 F]FDG) uptake than stable microsatellite (MSI-stable) tumors. However, MSI-high tumors have better prognosis, which is in contrast with general understanding that high [ 18 F]FDG uptake correlates with poor prognosis. This study evaluated metastasis incidence with MSI status and [ 18 F]FDG uptake., Methods: We retrospectively reviewed 108 right-side colon cancer patients who underwent preoperative [ 18 F]FDG PET/CT and postoperative MSI evaluations using a standard polymerase chain reaction at five Bethesda guidelines panel loci. The maximum standard uptake value (SUVmax), SUVmax tumor-to-liver ratio (TLR), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary tumor were measured using SUV 2.5 cut-off threshold. Student's t-test or Mann-Whitney U test was performed for continuous variables, and χ 2 test or Fisher's exact test was performed for categorical variables (p value of  < 0.05 for statistical significance). Medical records were reviewed for metastasis incidence., Results: Our study population had 66 MSI-stable and 42 MSI-high tumors. [ 18 F]FDG uptake was higher in MSI-high tumors than MSI-stable tumors (TLR, median (Q1, Q3): 7.95 (6.06, 10.54) vs. 6.08 (4.09, 8.82), p = 0.021). Multivariable subgroup analysis demonstrated that higher [ 18 F]FDG uptake was associated with higher risks of distant metastasis in MSI-stable tumors (SUVmax: p = 0.025, MTV: p = 0.008, TLG: p = 0.019) but not in MSI-high tumors., Conclusion: MSI-high colon cancer is associated with high [ 18 F]FDG uptake, but unlike MSI-stable tumors, the degree of [ 18 F]FDG uptake does not correlate with the rate of distant metastasis., Clinical Relevance Statement: MSI status should be considered during PET/CT assessment of colon cancer patients, as the degree of [ 18 F]FDG uptake might not reflect metastatic potential in MSI-high tumors., Key Points: • High-level microsatellite instability (MSI-high) tumor is a prognostic factor for distant metastasis. • MSI-high colon cancers had a tendency of demonstrating higher [ 18 F]FDG uptake compared to MSI-stable tumors. • Although higher [ 18 F]FDG uptake is known to represent higher risks of distant metastasis, the degree of [ 18 F]FDG uptake in MSI-high tumors did not correlate with the rate at which distant metastasis occurred., (© 2023. The Author(s), under exclusive licence to European Society of Radiology.)

Objectives: To evaluate the clinical implications of lymph node (LN) density on 18 F-FDG PET/CT for mediastinal LN characterization in non-small cell lung cancer (NSCLC)., Methods: One hundred and fifty-two patients with 271 mediastinal LNs who underwent PET/CT and endobronchial ultrasound-guided transbronchial needle aspiration for staging were enrolled. Maximum standardized uptake value (SUVmax), short axis diameter, LN-to-primary cancer ratio of SUVmax, and median Hounsfield unit (HU) based on CT histogram were correlated to histopathology., Results: Of 271 nodes, 162 (59.8 %) were malignant. SUVmax, short axis diameter, and LPR of malignant LNs were higher than those of benign nodes. Among malignant LNs, 71.0 % had median HU between 25 and 45, while 78.9 % of benign LNs had values <25 HU or >45 HU. Using a cutoff value of 4.0, SUVmax showed the highest diagnostic ability for detecting malignant LNs with a specificity of 94.5 %, but showing a sensitivity of 70.4 %. Using additional density criteria (median HU 25-45) in LNs with 2.0< SUVmax ≤4.0, the sensitivity increased to 88.3 % with the specificity of 82.6 %., Conclusions: LN density is useful for the characterization of LNs with mild 18 F-FDG uptake. The risk of mediastinal LN metastasis in NSCLC patients could be further stratified using both 18 F-FDG uptake and LN density., Key Points: • SUVmax showed the highest diagnostic ability for detecting malignant LNs. • LN density was useful in characterization of LNs with mild FDG uptake. • SUVmax and LN density together could stratify the risk of LN metastasis.

Objectives: To retrospectively evaluate concordance rates and predictive values in concordant cases among multiparametric MR techniques and FDG-PET to grade cerebral gliomas., Methods: Multiparametric MR imaging and FDG-PET were performed in 60 consecutive patients with cerebral gliomas (12 low-grade and 48 high-grade gliomas). As the dichotomic variables, conventional MRI, minimum apparent diffusion coefficient in diffusion-weighted imaging, maximum relative cerebral blood volume ratio in perfusion-weighted imaging, choline/creatine ratio and (lipid and lactate)/creatine ratio in MR spectroscopy, and maximum standardised uptake value ratio in FDG-PET in low- and high-grade gliomas were compared. Their concordance rates and positive/negative predictive values (PPV/NPV) in concordant cases were obtained for the various combinations of multiparametric MR techniques and FDG-PET., Results: There were significant differences between low- and high-grade gliomas in all techniques. Combinations of two, three, four, and five out of the five techniques showed concordance rates of 77.0 ± 4.8%, 65.5 ± 4.0%, 58.3 ± 2.6% and 53.3%, PPV in high-grade concordant cases of 97.3 ± 1.7%, 99.1 ± 1.4%, 100.0 ± 0% and 100.0% and NPV in low-grade concordant cases of 70.2 ± 7.5%, 78.0 ± 6.0%, 80.3 ± 3.4% and 80.0%, respectively., Conclusion: Multiparametric MR techniques and FDG-PET have a concordant tendency in a two-tiered classification for the grading of cerebral glioma. If at least two examinations concordantly indicated high-grade gliomas, the PPV was about 95%., Key Points: • Modern imaging techniques can help predict the aggressiveness of cerebral gliomas. • Multiparametric MRI and FDG-PET have a concordant tendency to grade cerebral gliomas. • Their high-grade concordant cases revealed at least 95 % positive predictive values. • Their low-grade concordant cases revealed about 70–80% negative predictive values.

Objective: To evaluate the usefulness of FDG PET/CT to differentiate malignant endobronchial lesions with distal atelectasis from benign bronchial stenosis., Methods: This retrospective study reviewed 84 patients who underwent contrast-enhanced chest CT and then PET/CT and had histological (n = 81) or follow-up imaging (n = 3) confirmation. Two chest radiologists reviewed initial chest CT and determined endobronchial lesions to be malignant or benign. Two nuclear medicine physicians reviewed PET/CT for FDG uptake at the obstruction site and measured SUV. Malignancy was considered when increased FDG uptake was seen in the obstruction site, regardless of FDG within the atelectatic lung., Results: The sensitivity, specificity and accuracy of chest CT was 95%, 48% and 84%, compared with 95%, 91% and 94% for PET/CT. Benign obstructive lesions showed statistically lower FDG uptake than malignant obstructions (benign SUV 2.5 ± 0.84; malignant SUV 11.8 ± 5.95, p < 0.001). ROC analysis showed an SUV cut-off value of 3.4 with highest sensitivity of 94% and specificity of 91%., Conclusion: Increased FDG PET/CT uptake at the obstruction site indicates a high probability of malignancy, while benign lesions show low FDG uptake. Careful evaluation of FDG uptake pattern at the obstruction site is helpful in the differentiation between benign and malignant endobronchial lesions.

Purpose: To review the 2-deoxy-2-fluoro-[F-18]-D: -glucose (FDG) positron emission tomography (PET) findings of focal eosinophilic liver disease (FELD) and to correlate them with radiologic and pathologic findings., Materials and Methods: Fourteen patients, who were clinically or pathologically diagnosed as FELD and underwent CT and/or MR and PET, were enrolled. Two radiologists analyzed CT and MRI regarding size, shape, margin, attenuation, signal intensity (SI), and enhancement patterns of the lesion, both qualitatively and quantitatively. One pathologist determined whether the lesion is eosinophilic abscess (EA) or infiltration. One nuclear medicine physician reviewed the PET images and calculated the peak standardized uptake value (SUV) of the lesion. PET findings were then correlated with CT or MRI, and pathologic findings., Results: Eighty-five lesions were detected on CT (n = 85) and MRI (n = 10). Only four of the lesions showed FDG uptake and their mean SUV was 4.0. The size of the lesions with FDG uptake (26.5 mm) was significantly larger than those without uptake (11.8 mm). Mean attenuation and SI differences between the lesion and adjacent liver on CT and T2-weighted MRI tended to be larger in the uptake group (64.3 and 124.5) than the group without uptake (28.5 and 43.5). Among the four histologically confirmed lesions, two EAs and one of the two EIs showed FDG uptake., Conclusion: Most FELD do not show FDG uptake on PET. However, larger nodules with greater attenuation or SI differences from the background liver on CT or T2-weighted MRI or those with EA on pathology tend to show FDG uptake on PET.

Background: To investigate the utility of CT volumetry for primary gastric lesions in the prediction of pathologic response to neoadjuvant chemotherapy in patients with resectable advanced gastric cancer (AGC)., Materials and Methods: Thirty-three consecutive patients with resectable AGC stage >or=T2 and N1), who had been treated with neoadjuvant chemotherapy and radical gastric resection, were prospectively enrolled in this study. There were 30 men and 3 women with a mean age of 53.8 years. Contrast-enhanced CT was obtained after gastric distention with air before and after chemotherapy using a MDCT scanner. Pre- and post-chemotherapy thickness or short diameter and volume of the primary gastric tumor and largest lymph node (LN), were measured using a dedicated 3D software by two radiologists in consensus. PET/CT was also performed and the peak standardized uptake value (SUV) of primary gastric tumor and largest LN before and after chemotherapy was measured. The percentage diameter, volume, and SUV reduction rates for both the primary gastric tumor and the LN, were calculated and correlated with the histopathologic grades of regression using the Spearman correlation test. Differentiation between pathologic responders and nonresponders was assessed using receiver operating characteristic (ROC) analysis., Results: Among the three CT parameters which showed significant correlation with the histopathologic grades of regression, the correlation factor was highest in the percentage volume reduction rate of primary gastric tumor (rho = 0.484, P = 0.004) followed by percentage volume reduction of the index node (rho = 0.397, P = 0.022), and percentage diameter reduction of the index node (rho = 0.359, P = 0.04). However, the percentage thickness decrease rate (P = 0.208) and the percentage SUV reduction rate (P = 0.619) of primary gastric tumor were not significantly correlated with the histopathologic grades of regression. When the optimal cutoff value of the percentage volume reduction rate of primary gastric tumor was determined to be 35.6%, a sensitivity of 100% (16/16) and a specificity of 58.8% (10/17) were achieved., Conclusion: CT volumetry for primary gastric tumor may be the most accurate tool in the prediction of pathologic response following neoadjuvant chemotherapy in patients with resectable AGC.

The aim of this study is to retrospectively evaluate intrapancreatic accessory spleen (IPAS) with mutidetector computed tomography (MDCT) and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) with emphasis on the role of SPIO-MRI for the diagnosis of IPAS. Seven patients (four men and three women; mean age, 50.7 years) with IPAS underwent quadriphasic MDCT and SPIO-enhanced MRI. IPAS was diagnosed histopathologically (n = 2) or by scintigraphy (n = 5). Two radiologists evaluated CT and MRI in consensus for the location and size of each lesion and compared its attenuation on CT and signal intensity (SI) on MRI with those of the pancreas and spleen. For quantitative analysis, another radiologist calculated the mean lesional, pancreatic, and splenic attenuations or SIs on MDCT or MRI in each patient. All lesions were located in the pancreatic tail. The average lesion size was 1.5 +/- 0.5 cm. All IPASs except one appeared high-attenuating to the pancreas and were isoattenuating to the spleen on all dynamic CT phases. The IPASs were hypointense and hyperintense compared with the pancreas on unenhanced T1- and T2-weighted images, respectively, and their SI was similar to that of the spleen. On SPIO-enhanced, T2-weighted images, a similar degree of signal drop to that of the spleen was noted in all lesions. The results of the quantitative analysis were compatible with those of the subjective analysis. In most IPASs, the attenuation on CT and SI on MRI were identical to those of the spleen, and on SPIO-enhanced MRI, the degree of the signal drop in all lesions was similar to that of the spleen.