Distinguishing thymic cysts from low-risk thymomas via [18F]FDG PET/CT.

BACKGROUND: Thymic cysts are a rare benign disease that needs to be distinguished from low-risk thymoma. [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is a non-invasive imaging technique used in the differential diagnosis of thymic epithelial tumours, but its usefulness for thymic cysts remains unclear. Our study evaluated the utility of visual findings and quantitative parameters of [18F]FDG PET/CT for differentiating between thymic cysts and low-risk thymomas. METHODS: Patients who underwent preoperative [18F]FDG PET/CT followed by thymectomy for a thymic mass were retrospectively analyzed. The visual [18F]FDG PET/CT findings evaluated were PET visual grade, PET central metabolic defect, and CT shape. The quantitative [18F]FDG PET/CT parameters evaluated were PET maximum standardized uptake value (SUVmax), CT diameter (cm), and CT attenuation in Hounsfield units (HU). Findings and parameters for differentiating thymic cysts from low-risk thymomas were assessed using Pearson's chi-square test, the Mann-Whitney U-test, and receiver operating characteristics (ROC) curve analysis. RESULTS: Seventy patients (18 thymic cysts and 52 low-risk thymomas) were finally included. Visual findings of PET visual grade (P < 0.001) and PET central metabolic defect (P < 0.001) showed significant differences between thymic cysts and low-risk thymomas, but CT shape did not. Among the quantitative parameters, PET SUVmax (P < 0.001), CT diameter (P < 0.001), and CT HU (P = 0.004) showed significant differences. In ROC analysis, PET SUVmax demonstrated the highest area under the curve (AUC) of 0.996 (P < 0.001), with a cut-off of equal to or less than 2.1 having a sensitivity of 100.0% and specificity of 94.2%. The AUC of PET SUVmax was significantly larger than that of CT diameter (P = 0.009) and CT HU (P = 0.004). CONCLUSIONS: Among the [18F]FDG PET/CT parameters examined, low FDG uptake (SUVmax ≤ 2.1, equal to or less than the mediastinum) is a strong diagnostic marker for a thymic cyst. PET visual grade and central metabolic defect are easily accessible findings.

Characterization of sacral chordoma and differential diagnosis from other sacral malignancy using [18F]FDG PET/CT.

2-Deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography (PET)/computed tomography (CT) is known to be a helpful imaging modality for sacral chordoma, but its detailed characteristics have not been fully described. The purpose of our study was to identify the [18F]FDG PET/CT imaging characteristics of sacral chordoma and compare them with other sacral malignancy. This retrospective study included patients who underwent [18F]FDG PET/CT because of a mass involving the sacrum. Investigated visual findings included visual score and distribution, and semiquantitative parameters measured included standardized uptake values (SUVmax, SUVpeak, SUVmean), tumor-to-liver ratio (TLR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and tumor size. Comparison studies and receiver operating characteristics (ROC) curve analysis were performed to differentiate between sacral chordoma and other sacral malignancy. Ten patients with sacral chordoma were finally included (M:F = 6:4, median age = 67 yr). On [18F]FDG PET/CT, sacral chordomas presented as a mass with minimal-moderate uptake with a usually heterogenous distribution. Compared with 12 patients with other sacral malignancies (M:F = 4:8, median age 42 yr), sacral chordoma showed a significantly lower TLR (median value 2.1 vs 6.3, P = .021). In ROC curve analysis, TLR showed the largest area under the curve (AUC) of 0.79 (cutoff ≤ 4.0; sensitivity 100.0%, specificity 58.3%; P = .004), and SUVmax showed the second largest AUC of 0.73 (cutoff ≤ 6.9; sensitivity 80.0%, specificity 66.7%; P = .034). [18F]FDG PET/CT of sacral chordoma showed minimal-moderate uptake. The TLR of [18F]FDG PET/CT was significantly lower than that of other sacral malignancy and was the most useful parameter for differentiating sacral chordoma, with the largest AUC. SUVmax could be another helpful semiquantitative parameter.

Diagnostic Performance of Perfusion-Only SPECT/CT for Chronic Thromboembolic Pulmonary Hypertension in Comparison With Ventilation-Perfusion Planar, SPECT, and SPECT/CT Imaging.

PURPOSE: The aim of this study was to assess the diagnostic performance of perfusion-only SPECT/CT (Q SPECT/CT) in comparison with that of ventilation/perfusion planar scintigraphy (V/Q planar), perfusion SPECT with ventilation scan (V/Q SPECT), and perfusion SPECT/CT with ventilation scan (V/Q SPECT/CT) in chronic thromboembolic pulmonary hypertension (CTEPH). PATIENTS AND METHODS: Patients with pulmonary hypertension who underwent ventilation-perfusion planar and SPECT/CT were retrospectively recruited. Two nuclear medicine physicians interpreted V/Q planar, V/Q SPECT, V/Q SPECT/CT, and Q SPECT/CT according to the European Association of Nuclear Medicine criteria. The diagnostic accuracy of these modalities for CTEPH was compared using a composite reference standard of pulmonary angiography, imaging test, cardiorespiratory assessment, and follow-up. RESULTS: A total of 192 patients were enrolled, including 85 with CTEPH. The sensitivity of Q SPECT/CT was 98.8%, which similar to that of V/Q planar (97.6%), V/Q SPECT (96.5%), or V/Q SPECT/CT (100.0%). In contrast, Q SPECT/CT exhibited significantly lower specificity (73.8%) compared with V/Q planar (86.9%, P = 0.001), V/Q SPECT (87.9%, P < 0.001), and V/Q SPECT/CT (88.8%, P < 0.001). The significantly lower specificity of Q SPECT/CT, compared with the 3 others, was observed in the subgroup aged ≥50 years ( P < 0.001 for all), but not in those <50 years. CONCLUSIONS: Q SPECT/CT exhibited lower specificity compared with V/Q planar, V/Q SPECT, and V/Q SPECT/CT in diagnosing CTEPH. It might underscore the essential role of a ventilation scan in patients with PH, even with the introduction of SPECT/CT.

Somatostatin receptor 2 (SSTR2) expression is associated with better clinical outcome and prognosis in rectal neuroendocrine tumors.

Somatostatin analogues have recently been used as therapeutic targets for metastatic or surgically unresectable gastroenteropancreatic (GEP) neuroendocrine tumors (NETs), and associated somatostatin receptor (SSTR) expression has been well demonstrated in most GEP NETs, with the exception of rectal NETs. SSTR2 immunohistochemical expressions were evaluated in 350 surgically or endoscopically resected rectal NETs and compared to clinicopathologic factors. SSTR2 expression was observed in 234 (66.9%) rectal NET cases and associated tumors with smaller size (p = 0.001), low pT classification (p = 0.030), low AJCC tumor stage (p = 0.012), and absence of chromogranin expression (p = 0.009). Patients with rectal NET and SSTR2 expression had significantly better overall survival than those without SSTR2 expression both by univariable (p = 0.006) and multivariable (p = 0.014) analyses. In summary, approximately two-thirds of rectal NETs expressed SSTR2. SSTR2 expression was significantly associated with favorable behavior and good overall survival in patients with rectal NETs. Furthermore, SSTR2 expression can be used as prognostic factors. When metastatic disease occurs, SSTR2 expression can be used a possible target for somatostatin analogues.

Direct and Indirect Chimeric Antigen Receptor T-Cell Imaging with PET/MRI in a Tumor Xenograft Model.

Background Chimeric antigen receptor (CAR) T cells are a promising cancer therapy; however, reliable and repeatable methods for tracking and monitoring CAR T cells in vivo remain underexplored. Purpose To investigate direct and indirect imaging strategies for tracking the biodistribution of CAR T cells and monitoring their therapeutic effect in target tumors. Materials and Methods CAR T cells co-expressing a tumor-targeting gene (anti-CD19 CAR) and a human somatostatin receptor subtype 2 (hSSTr2) reporter gene were generated from human peripheral blood mononuclear cells. After direct labeling with zirconium 89 (89Zr)-p-isothiocyanatobenzyl-desferrioxamine (DFO), CAR T cells were intravenously injected into immunodeficient mice with a CD19-positive and CD19-negative human tumor xenograft on the left and right flank, respectively. PET/MRI was used for direct in vivo imaging of 89Zr-DFO-labeled CAR T cells on days 0, 1, 3, and 7 and for indirect cell imaging with the radiolabeled somatostatin receptor-targeted ligand gallium 68 (68Ga)-DOTA-Tyr3-octreotide (DOTATOC) on days 6, 9, and 13. On day 13, mice were euthanized, and tissues and tumors were excised. Results The 89Zr-DFO-labeled CAR T cells were observed on PET/MRI scans in the liver and lungs of mice (n = 4) at all time points assessed. However, they were not visualized in CD19-positive or CD19-negative tumors, even on day 7. Serial 68Ga-DOTATOC PET/MRI showed CAR T cell accumulation in CD19-positive tumors but not in CD19-negative tumors from days 6 to 13. Notably, 68Ga-DOTATOC accumulation in CD19-positive tumors was highest on day 9 (mean percentage injected dose [%ID], 3.7% ± 1.0 [SD]) and decreased on day 13 (mean %ID, 2.6% ± 0.7) in parallel with a decrease in tumor volume (day 9: mean, 195 mm3 ± 27; day 13: mean, 127 mm3 ± 43) in the group with tumor growth inhibition. Enhanced immunohistochemistry staining of cluster of differentiation 3 (CD3) and hSSTr2 was also observed in excised CD19-positive tumor tissues. Conclusion Direct and indirect cell imaging with PET/MRI enabled in vivo tracking and monitoring of CAR T cells in an animal model. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Bulte in this issue.

Prediction of [177Lu]Lu-DOTA-TATE therapy response using the absorbed dose estimated from [177Lu]Lu-DOTA-TATE SPECT/CT in patients with metastatic neuroendocrine tumour.

BACKGROUND: Peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA-TATE has shown efficacy in patients with metastatic neuroendocrine tumours (NETs). Personalised dosimetry is crucial to optimise treatment outcomes and minimise adverse events. In this study, we investigated the correlation between the tumour-absorbed dose (TAD) estimated from [177Lu]Lu-DOTA-TATE SPECT/CT and the therapeutic response. METHOD: A retrospective analysis was conducted on patients with advanced well-differentiated NETs grades 1-3 who underwent PRRT and exhibited greater uptake than liver on pre-therapeutic [68Ga]Ga-DOTA-TOC PET/CT. Target lesions were selected based on the RECIST 1.1 and PERCIST 1.0 criteria using [177Lu]Lu-DOTA-TATE SPECT/CT and pre-therapeutic contrast-enhanced CT scans. For anatomical image analysis, the sum of the longest diameter (SLD) of the target lesions was measured using the RECIST 1.1 criteria for patient-based analysis and the longest diameter (LD) of the target lesion using the RECIST-L criteria for lesion-based analysis. Standardised uptake values (SUVs) were measured on SPECT/CT images, and TADs were calculated based on the SUVs. Dosimetry was performed using a single SPECT/CT imaging time point at day 4-5 post-therapy. Statistical analyses were conducted to investigate correlations and determine the target lesion responses. RESULTS: Twenty patients with primary tumour sites and hepatic metastases were included. Fifty-five target lesions, predominantly located in the pancreas and liver, were analysed. The cumulative TAD (lesion-based analysis: r = 0.299-0.301, p = 0.025-0.027), but not the cycle 1 SUV (lesion-based analysis: r = 0.198-0.206, p = 0.131-0.147) or cycle 1 TAD (lesion-based analysis: r = 0.209-0.217, p = 0.112-0.126), exhibited a significant correlation with the change in LD of the target lesion. Binary logistic regression analysis identified the significance of the cumulative TAD in predicting disease control according to the RECIST-L criteria (odds ratio = 1.031-1.051, p = 0.024-0.026). CONCLUSIONS: The cumulative TAD estimated from [177Lu]Lu-DOTA-TATE SPECT/CT revealed a significant correlation with change in LD, which was significantly higher for the cumulative TAD than for the cycle 1 SUV or TAD. A higher cumulative TAD was associated with disease control in the target lesion. However, considering the limitations inherent to a confined sample size, careful interpretation of these findings is required. Estimation of the cumulative TAD of [177Lu]Lu-DOTA-TATE therapy could guide the platform towards personalised therapy.

18F-ASEM PET/MRI targeting alpha7-nicotinic acetylcholine receptor can reveal skeletal muscle denervation.

BACKGROUND: The increased expression of the nicotinic acetylcholine receptor (nAChR) in muscle denervation is thought to be associated with electrophysiological acetylcholine supersensitivity after nerve injury. Hence, we investigated the utility of the 18F-ASEM alpha7-nAChR targeting radiotracer as a new diagnostic method by visualizing skeletal muscle denervation in mouse models of sciatic nerve injury. METHODS: Ten-week-old C57BL/6 male mice were utilized. The mice were anesthetized, and the left sciatic nerve was resected after splitting the gluteal muscle. One week (n = 11) and three weeks (n = 6) after the denervation, 18F-ASEM positron emission tomography/magnetic resonance imaging (PET/MRI) was acquired. Maximum standardized uptake values (SUVmax) of the tibialis anterior muscle were measured for the denervated side and the control side. Autoradiographic evaluation was performed to measure the mean counts of the denervated and control tibialis anterior muscles at one week. In addition, immunohistochemistry was used to identify alpha7-nAChR-positive areas in denervated and control tibialis anterior muscles at one week (n = 6). Furthermore, a blocking study was conducted with methyllycaconitine (MLA, n = 5). RESULTS: 18F-ASEM PET/MRI showed significantly increased 18F-ASEM uptake in the denervated tibialis anterior muscle relative to the control side one week and three weeks post-denervation. SUVmax of the denervated muscles at one week and three weeks showed significantly higher uptake than the control (P = 0.0033 and 0.0277, respectively). The relative uptake by autoradiography for the denervated muscle was significantly higher than in the control, and immunohistochemistry revealed significantly greater alpha7-nAChR expression in the denervated muscle (P = 0.0277). In addition, the blocking study showed no significant 18F-ASEM uptake in the denervated side when compared to the control (P = 0.0796). CONCLUSIONS: Our results suggest that nAChR imaging with 18F-ASEM has potential as a noninvasive diagnostic method for peripheral nervous system disorders.

Efficacy and Safety of Lu-177 DOTATATE Peptide Receptor Radionuclide Therapy in Patients with Unresectable or Metastatic Neuroendocrine Tumors in Korea.

BACKGROUND: Lutetium (Lu)-177 peptide receptor radionuclide therapy (PRRT) is one of the standard treatments for somatostatin receptor-positive well-differentiated neuroendocrine tumors (NETs). However, limited Asian representation in the pivotal NETTER-1 trial and a lack of real-world data for Lu-177 PRRT from Asian regions exist. OBJECTIVE: This retrospective study aimed to evaluate the efficacy and safety of Lu-177 PRRT in Korean patients with advanced NETs. PATIENTS AND METHODS: This study analyzed 64 patients treated with Lu-177 DOTATATE PRRT at the Asan Medical Center, Seoul, Korea, between November 2019 and December 2022. The primary endpoint was progression-free survival (PFS), and the secondary endpoints included overall survival (OS), objective response rate (ORR), and safety profile. RESULTS: The median age of patients was 55 years. Prior to PRRT, patients received a median of two lines (range 0-6) of systemic therapy. Fifty (78%) patients received the planned four cycles of Lu-177 DOTATATE PRRT. The median PFS was 21.7 months (95% confidence interval 16.7-not available) and the ORR was 20%. With a median follow-up of 15.7 months (range 1.0-39.3), the median OS was not reached and the 1-year OS rate was 88%. The median PFS was better in patients with grade 1-2 NETs than in those with grade 3 NET (not reached vs. 14.2 months; hazard ratio 3.15; p = 0.0058). Hematological toxicities were the common adverse events, including grade ≥ 3 anemia (7.8%), neutropenia (10.9%), and thrombocytopenia (9.4%). CONCLUSIONS: In Korean patients with advanced NETs, Lu-177 DOTATATE PRRT showed efficacy and safety outcomes, consistent with those in the NETTER-1 trial and previous Western real-world studies.

A Prospective Comparative Study of 18 F-FDOPA PET/CT Versus 123 I-MIBG Scintigraphy With SPECT/CT for the Diagnosis of Pheochromocytoma and Paraganglioma.

PURPOSE: This study aimed to compare the diagnostic performances of 18 F-FDOPA PET/CT and 123 I-MIBG scintigraphy with SPECT/CT for detection of pheochromocytoma and paraganglioma (PPGL). PATIENTS AND METHODS: We conducted a prospective, single-institution comparative study. Patients suspected of having PPGL or those showing recurrence and/or distant metastasis of PPGL were enrolled. The primary objective was to affirm the noninferiority of 18 F-FDOPA PET/CT for diagnostic sensitivity. Both 123 I-MIBG scintigraphy with SPECT/CT (at 4 and 24 hours) and 18 F-FDOPA PET/CT (at 5 and 60 minutes after radiotracer administration) were performed. The final diagnosis was established either pathologically or via clinical follow-up. Nuclear physicians, unaware of the clinical data, undertook image analysis. RESULTS: Thirty-two patients were evaluated: 14 of 21 with an initial diagnosis and 9 of 11 with recurrence/metastasis had PPGLs in their final diagnoses. In patient-based analyses, 18 F-FDOPA PET/CT (95.7%) exhibited noninferior sensitivity compared with 123 I-MIBG SPECT/CT (91.3%), within the predetermined noninferiority margin of -12% by a 95% confidence interval lower limit of -10%. Both modalities showed no significant difference in specificity (88.9% vs 88.9%). In the region-based analysis for the recurrence/metastasis group, 18 F-FDOPA PET/CT demonstrated significantly higher sensitivity compared with 123 I-MIBG SPECT/CT (86.2% vs 65.5%, P = 0.031) and superior interobserver agreement (κ = 0.94 vs 0.85). The inclusion of an early phase in dual-phase 18 F-FDOPA PET/CT slightly improved diagnostic performance, albeit not to a statistically significant degree. CONCLUSIONS: 18 F-FDOPA PET/CT demonstrated noninferior sensitivity and comparable specificity to 123 I-MIBG SPECT/CT in the diagnosing PPGL. Notably, in the assessment of PPGL recurrence and metastasis, 18 F-FDOPA PET/CT outperformed 123 I-MIBG SPECT/CT in terms of both sensitivity and interobserver agreement.

[18F]fluorodeoxyglucose positron emission tomography/computed tomography characteristics of primary mediastinal germ cell tumors.

Primary mediastinal germ cell tumor (MGCT) is an uncommon tumor. Although it has histology similar to that of gonadal germ cell tumor (GCT), the prognosis for MGCT is generally worse than that for gonadal GCT. We performed visual assessment and quantitative analysis of [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) for MGCTs. A total of 35 MGCT patients (age = 33.1 ± 16.8 years, F:M = 16:19) who underwent preoperative PET/CT were retrospectively reviewed. The pathologic diagnosis of MGCTs identified 24 mature teratomas, 4 seminomas, 5 yolk sac tumors, and 2 mixed germ cell tumors. Visual assessment was performed by categorizing the uptake intensity, distribution, and contour of primary MGCTs. Quantitative parameters including the maximum standardized uptake value (SUVmax), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and maximum diameter were compared between benign and malignant MGCTs. On visual assessment, the uptake intensity was the only significant parameter for differentiating between benign and malignant MGCTs (p = 0.040). In quantitative analysis, the SUVmax (p < 0.001), TBR (p < 0.001), MTV (p = 0.033), and TLG (p < 0.001) showed significantly higher values for malignant MGCTs compared with benign MGCTs. In receiver operating characteristic (ROC) curve analysis of these quantitative parameters, the SUVmax had the highest area under the curve (AUC) (AUC = 0.947, p < 0.001). Furthermore, the SUVmax could differentiate between seminomas and nonseminomatous germ cell tumors (p = 0.042) and reflect serum alpha fetoprotein (AFP) levels (p = 0.012). The visual uptake intensity and SUVmax on [18F]FDG PET/CT showed discriminative ability for benign and malignant MGCTs. Moreover, the SUVmax may associate with AFP levels.

Prognostic significance of 25-hydroxyvitamin D levels in patients with peripheral T-cell lymphoma.

Vitamin D insufficiency has been linked to unfavourable outcomes in diverse malignancies. However, the prognostic significance of vitamin D levels in peripheral T-cell lymphoma (PTCL) remains unclear. In this study, we thus aimed to assess the prognostic relevance of 25-hydroxyvitamin D [25(OH)D] levels in patients newly diagnosed with PTCL. The analysis included 144 patients with PTCL treated from March 2015 to May 2020. The median 25(OH)D level was 12.2 (1.7-48.8) ng/mL, and 59 (41%) patients had vitamin D deficiency. Patients with vitamin D deficiency demonstrated significantly worse event-free survival (EFS) and overall survival (OS). In the multivariate analysis, vitamin D was independently associated with OS, with a hazard ratio of 1.66 (95% confidence interval, 1.05-2.63, p = 0.030). These findings suggest that vitamin D deficiency significantly correlates with poor survival outcomes in patients with PTCL.

A New Prognostic Index for Extranodal Natural Killer/T-Cell Lymphoma:Incorporation of Serum ß-2 Microglobulin to PINK.

PURPOSE: Prognostic Index for Natural Killer Lymphoma (PINK) is the most widely accepted prognostic model for patients withextranodal natural killer/T-cell lymphoma (ENKTL) treated with non-anthracycline-based therapy. We aimed to evaluate the prognostic implications of serum ß-2 microglobulin (ß2M) in the context of PINK and proposed a new prognostic model. MATERIALS AND METHODS: A total of 138 patients who were newly diagnosed with ENKTL and treated with non-anthracycline-based chemotherapy were identified. The cut-off value of high serum ß2M was calculated by maximal-chi square methods (4.1 mg/L). A new prognostic model incorporating serum ß2M into PINK was proposed and validated in an independent validation cohort (n=88). RESULTS: The patients' median age was 53.5 years (range, 19 to 80 years). Patients with high serum ß2M levels had significantly worse overall survival (OS) and progression-free survival (PFS). In multivariate analysis, high serum ß2M was an independent adverse prognostic factor for OS. A new PINK-B (Prognostic Index for Natural Killer Lymphoma-serum ß-2 microglobulin) model stratifiedpatients into three groups with distinct OS and PFS in the training cohort (3-year OS, 84.1% [95% confidence interval, 75.1 to 94.2], 46.8% [36.1 to 60.8] and 17.6% [6.3 to 49.2] for the low-, intermediate, and high-risk groups, respectively; 3-year PFS, 70.6% [59.4 to 83.8], 35.9% [25.9 to 49.8], and 7.35% [1.1 to 46.7] for the low-, intermediate-, and high-risk groups, respectively). The PINK-B model was further validated in an independent cohort. CONCLUSION: Serum ß2M is an independent prognostic factor for ENKTL patients. The new serum ß2M-based prognostic model may be useful for identifying ultra-high-risk patients, and it can easily be adopted into daily clinical practice.

Clinicopathologic Impact of Peptide Hormonal Expression in Rectal Neuroendocrine Tumors.

CONTEXT.­: Although several neuroendocrine cell types constitute gastroenteropancreatic neuroendocrine tumors (NETs), the clinical and prognostic implications of the expression of multiple peptide hormones have not been comprehensively evaluated in rectal NETs. OBJECTIVE.­: To identify the clinicopathologic characteristics and prognostic impact of peptide hormone expression. DESIGN.­: We evaluated the expression of peptide YY (PYY), glucagon, somatostatin, serotonin, insulin, and gastrin using immunolabeling in 446 endoscopically or surgically resected rectal NETs. RESULTS.­: PYY, glucagon, serotonin, somatostatin, insulin, and gastrin were expressed in 261 of 389 (67.1%), 205 of 446 (46.0%), 36 of 446 (8.1%), 33 of 446 (7.4%), 2 of 446 (0.4%), and 1 of 446 cases (0.2%), respectively. Immunoreactivity to any peptide hormone was present in 345 of 446 cases (77.4%). Tumors expressing serotonin or somatostatin were associated with lymphovascular invasion, chromogranin A expression, and shorter disease-free survival (DFS). Rectal NETs were classified as L-cell, enterochromaffin-cell, D-cell, null-expression, or mixed-expression type based on peptide hormonal expression status. Patients with D-cell NET had the shortest DFS (10-year DFS, 54.5%), followed by those with enterochromaffin-cell NET (89.5%), null expression (97.0%), L-cell NET (99.6%), and mixed-expression NET (100%; P < .001). Multivariable analyses revealed that somatostatin expression was an independent indicator of poor prognosis with respect to DFS in rectal NETs (P = .001). CONCLUSIONS.­: Somatostatin expression is a poor prognostic indicator in patients with rectal NETs. Therefore, additional peptide hormonal immunolabeling, including somatostatin, serotonin, and PYY, in rectal NETs can provide more information regarding DFS.

Preliminary Study for Quantitative Assessment of Sacroiliitis Activity Using Bone SPECT/CT: Comparison of Diagnostic Performance of Quantitative Parameters.

Purpose: We compared the feasibility of quantitative analysis methods using bone SPECT/CT with those using planar bone scans to assess active sacroiliitis. Methods: We retrospectively reviewed whole-body bone scans and pelvic bone SPECT/CTs of 8 patients who had clinically confirmed sacroiliitis and enrolled 24 patients without sacroiliitis as references. The volume of interest of each sacroiliac joint, including both the ilium and sacrum, was drawn. Active arthritis zone (AAZ) was defined as the zone of voxels with higher SUV than sacral mean SUV within the VOI of SI joint. Then, the following SPECT/CT quantitative parameters, SUVmax (maximum SUV), SUV50% (mean SUV in highest 50% of SUV), and SUV-AAZ, and the ratio of those values to sacral mean SUV (SUVmax/S, SUV50%/S, SUV-AAZ/S) were calculated. For the planar bone scan, the mean count ratio of SI joint/sacrum (SI/S) was conventionally measured. Results: Most of the SPECT/CT parameters of the sacroiliitis group were significantly higher than the normal group, whereas SI/S of the planar bone scan was not significantly different between the two groups. In receiver operating characteristic curve analysis, SUV-AAZ/S showed the highest AUC of 0.992, followed by SUV50%/S and SUVmax/S. All ratio parameters of the SPECT/CT showed higher AUC values than the SUV parameters of SI joint or SI/S of the planar scan. Conclusions: The quantitative analyses of bone SPECT/CT showed better performance in assessing active sacroiliitis than the planar bone scan. SPECT/CT parameters using the ratio of the SI joint to sacrum showed more favorable results than SUV parameters such as SUVmax, SUV50%, and SUV-AAZ.

Automated extraction of information of lung cancer staging from unstructured reports of PET-CT interpretation: natural language processing with deep-learning.

BACKGROUND: Extracting metastatic information from previous radiologic-text reports is important, however, laborious annotations have limited the usability of these texts. We developed a deep-learning model for extracting primary lung cancer sites and metastatic lymph nodes and distant metastasis information from PET-CT reports for determining lung cancer stages. METHODS: PET-CT reports, fully written in English, were acquired from two cohorts of patients with lung cancer who were diagnosed at a tertiary hospital between January 2004 and March 2020. One cohort of 20,466 PET-CT reports was used for training and the validation set, and the other cohort of 4190 PET-CT reports was used for an additional-test set. A pre-processing model (Lung Cancer Spell Checker) was applied to correct the typographical errors, and pseudo-labelling was used for training the model. The deep-learning model was constructed using the Convolutional-Recurrent Neural Network. The performance metrics for the prediction model were accuracy, precision, sensitivity, micro-AUROC, and AUPRC. RESULTS: For the extraction of primary lung cancer location, the model showed a micro-AUROC of 0.913 and 0.946 in the validation set and the additional-test set, respectively. For metastatic lymph nodes, the model showed a sensitivity of 0.827 and a specificity of 0.960. In predicting distant metastasis, the model showed a micro-AUROC of 0.944 and 0.950 in the validation and the additional-test set, respectively. CONCLUSION: Our deep-learning method could be used for extracting lung cancer stage information from PET-CT reports and may facilitate lung cancer studies by alleviating laborious annotation by clinicians.

Diagnostic value of 18F-FDG PET/CT in discriminating between benign and malignant lesions of the ribs.

PURPOSE: Imaging biomarkers for rib mass are needed to optimize treatment plan. We investigated the diagnostic value of metabolic and volumetric parameters from 18F-fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT) in discriminating between benign and malignant lesions of the ribs. PATIENTS AND METHODS: Fifty-seven patients with pathologically proven diagnosis of rib lesions were retrospectively enrolled. The size of rib lesions, the maximum, mean, and peak standardized uptake value (SUVmax, SUVmean, SUVpeak), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), and total lesions glycolysis (TLG) were measured. The FDG uptake patterns (segmental and discrete) and CT findings (soft tissue involvement and fracture) were also reviewed. RESULTS: Among the multiple parameters extracted from PET/CT, the MTV of malignant lesions was significantly higher than that of benign lesions (median; 4.7 vs 0.2, respectively, P = .041). In receiver operating characteristics curve analysis, MTV had the largest area under curve of 0.672 for differentiating malignant from benign lesions. For identifying malignant lesions, an MTV threshold of 0.5 had a sensitivity of 85.0%, specificity of 47.1%, positive predictive value of 79.1%, negative predictive value of 57.1%, and accuracy of 73.7%. The presence of adjacent soft tissue involvement around rib lesions showed a significant association with malignancy (odds ratio = 6.750; 95% CI, 1.837-24.802, P = .003). CONCLUSIONS: The MTV is a useful PET/CT parameter for assisting in the differential diagnosis of suspected malignant lesions of the ribs. CT finding of adjacent soft tissue involvement around rib was significantly associated with malignant lesions of the ribs.

Modified Stage Grouping of Diffuse Large B-Cell Lymphoma Involving the Same Side of the Diaphragm in the Rituximab Era.

Among patients with diffuse large B-cell lymphoma (DLBCL) involving the same side of the diaphragm, the prognostic implications of extranodal disease or its contiguity with the nodal lesion remain unclear. In this study, patients with DLBCL treated with R-CHOP whose disease was limited to the same side of the diaphragm were included. Survival was assessed by the presence, contiguity, and number of extranodal lesions. Among the 508 patients included, overall survival (OS) and progression-free survival (PFS) did not differ according to the presence of single extranodal involvement or its anatomical contiguity with the nodal lesion. However, patients with ≥2 extranodal involvement showed significantly inferior OS and PFS. We re-classified these patients into two groups: modified stage IIEe (≥2 extranodal involvement, n=92) and modified stage II (nodal or single extranodal involvement irrespective of anatomical contiguity, n=416). This modified staging showed improved prognostic performance based on the time-dependent ROC curve compared with Ann Arbor staging. In conclusion, the survival outcomes of patients with DLBCL on the same side of the diaphragm were associated with the number of extranodal lesions, but not with the contiguity of the lesions or presence of a single extranodal involvement. Based on these results, we propose a modified staging system (modified stage IIEe and II) for these patients.

Fully Automatic Quantitative Measurement of 18F-FDG PET/CT in Thymic Epithelial Tumors Using a Convolutional Neural Network.

OBJECTIVES: The aim of this study was to develop a deep learning (DL)-based segmentation algorithm for automatic measurement of metabolic parameters of 18F-FDG PET/CT in thymic epithelial tumors (TETs), comparable performance to manual volumes of interest. PATIENTS AND METHODS: A total of 186 consecutive patients with resectable TETs and preoperative 18F-FDG PET/CT were retrospectively enrolled (145 thymomas, 41 thymic carcinomas). A quasi-3D U-net architecture was trained to resemble ground-truth volumes of interest. Segmentation performance was assessed using the Dice similarity coefficient. Agreements between manual and DL-based automated extraction of SUVmax, metabolic tumor volume (MTV), total lesion glycolysis (TLG), and 63 radiomics features were evaluated via concordance correlation coefficients (CCCs) and linear regression slopes. Diagnostic and prognostic values were compared in terms of area under the receiver operating characteristics curve (AUC) for thymic carcinoma and hazards ratios (HRs) for freedom from recurrence. RESULTS: The mean Dice similarity coefficient was 0.83 ± 0.34. Automatically measured SUVmax (slope, 0.97; CCC, 0.92), MTV (slope, 0.94; CCC, 0.96), and TLG (slope, 0.96; CCC, 0.96) were in good agreement with manual measurements. The mean CCC and slopes were 0.88 ± 0.06 and 0.89 ± 0.05, respectively, for the radiomics parameters. Automatically measured SUVmax, MTV, and TLG showed good diagnostic accuracy for thymic carcinoma (AUCs: SUVmax, 0.95; MTV, 0.85; TLG, 0.87) and significant prognostic value (HRs: SUVmax, 1.31 [95% confidence interval, 1.16-1.48]; MTV, 2.11 [1.09-4.06]; TLG, 1.90 [1.12-3.23]). No significant differences in the AUCs or HRs were found between automatic and manual measurements for any of the metabolic parameters. CONCLUSIONS: Our DL-based model provides comparable segmentation performance and metabolic parameter values to manual measurements in TETs.

KSNM 60 in General Nuclear Medicine: the Old Dream Comes True.

Since the establishment of the Korean Society of Nuclear Medicine (KSNM) in 1961 by Professor Munho Lee, the KSNM has been progressing in various medical fields. Many papers have been published in the Korean Journal of Nuclear Medicine (KJNM), the official journal of KSNM, since 1967 and other domestic/international journals. Here, we tried to highlight the academic activities of KSNM members from the perspective of general nuclear medicine. After the introduction of the 99Mo/99mTc generator, general nuclear medicine has widened the field of clinical application with the advancement of imaging technology and emerging new radiopharmaceuticals; however, there have been many ups and downs. Treatment, as well as diagnosis, was a major concern in Korean nuclear medicine. With the recent advent of single-photon emission computed tomography/computed tomography, we hope that our old dream (diagnosis and treatment under the same principle of nuclear medicine) comes true.