Molecular Imaging with PET-CT and PET-MRI in Pediatric Musculoskeletal Diseases.

Molecular imaging has emerged as an integral part of oncologic imaging. Given the physiologic changes that precede anatomic changes, molecular imaging can enable early detection of disease and monitoring of response. [18F] Fluorodeoxyglucose (FDG) Positron emission tomography (PET) is the predominant molecular imaging modality used in oncologic assessment and can be performed using PET/CT or PET/MR. In pediatric patients, PET/MRI imaging is generally preferred due to low radiation exposure and PET/MRI is particularly advantageous for imaging musculoskeletal (MSK) diseases, as MRI provides superior characterization of tissue changes as compared to CT. In this article, we provide an overview of the typical role of PET CT/MRI in assessment of some common pediatric malignancies and benign MSK diseases with case examples. We also discuss the relative advantages of PET/MRI compared to PET/CT, and review published data with a primary focus on the use of PET/MR.

Conventional and novel [18F]FDG PET/CT features as predictors of CAR-T cell therapy outcome in large B-cell lymphoma.

Relapse and toxicity limit the effectiveness of chimeric antigen receptor T-cell (CAR-T) therapy for large B-cell lymphoma (LBCL), yet biomarkers that predict outcomes and toxicity are lacking. We examined radiomic features extracted from pre-CAR-T 18F-fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) scans (n = 341) of 180 patients (121 male; median age, 66 years). Three conventional (maximum standardized uptake value [SUVmax], metabolic tumor volume [MTV], total lesion glycolysis [TLG]) and 116 novel radiomic features were assessed, along with inflammatory markers, toxicities, and outcomes. At both pre-apheresis and pre-infusion time points, conventional PET features of disease correlated with elevated inflammatory markers. At pre-infusion, MTV was associated with grade ≥ 2 cytokine release syndrome (odds ratio [OR] for 100 mL increase: 1.08 [95% confidence interval (CI), 1.01-1.20], P = 0.031), and SUVmax was associated with failure to achieve complete response (CR) (OR 1.72 [95% CI, 1.24-2.43], P < 0.001). Higher pre-apheresis and pre-infusion MTV values were associated with shorter progression-free survival (PFS) (HR for 10-unit increase: 1.11 [95% CI, 1.05-1.17], P < 0.001; 1.04 [95% CI, 1.02-1.07], P < 0.001) and shorter overall survival (HR for 100-unit increase: 1.14 [95% CI, 1.07-1.21], P < 0.001; 1.04 [95% CI, 1.02-1.06], P < 0.001). A combined MTV and LDH measure stratified patients into high and low PFS risk groups. Multiple pre-infusion novel radiomic features were associated with CR. These quantitative conventional [18F]FDG PET/CT features obtained before CAR-T cell infusion, which were correlated with inflammation markers, may provide prognostic biomarkers for CAR-T therapy efficacy and toxicity. The use of conventional and novel radiomic features may thus help identify high-risk patients for earlier interventions.

Diagnostic performance of F-18 FDG PET/CT in recurrent adenocarcinoma gallbladder and its impact on post-recurrence survival.

PURPOSE: To analyze diagnostic performance of F-18 FDG PET/CT in recurrent adenocarcinoma gallbladder (GBC) and to establish its possible impact on post-recurrence survival. METHOD: FDG PET/CT studies of suspected recurrent GBC were retrospectively analyzed alongside tumor markers serum CEA and CA 19-9. Abnormal FDG-avid lesions and abnormal morphological lesions were considered positive for recurrence, and were categorized as isolated abdominal wall recurrence, loco-regional recurrence, and distant metastatic disease. Histopathology, definite progression on imaging and positive response to treatment was considered as reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were used as diagnostic performance parameters. Post-recurrence survival was calculated whenever appropriate follow-up was available, based on the abovementioned categories of sites of recurrence using survival curves and log-rank test. RESULTS: Out of 117 PET/CT studies, 93 (79.5%) were positive and 24 (20.5%) were negative for recurrence. 86 out of 93 were true positive and 23 of 24 were true negative. PET/CT demonstrated sensitivity, specificity, PPV, NPV and accuracy of 98.8%, 76.7%, 92.5%, 95.8% and 93.1%, respectively. Diagnostic performance of PET/CT was significantly better than combination tumor markers. Of 66 cases with available follow-up, isolated abdominal wall (port/scar site) recurrence and loco-regional recurrence demonstrated significantly higher post-recurrence survival as compared to distant metastasis; median survival being 39, 25 and 12 months, respectively. CONCLUSION: F-18 FDG PET/CT has better diagnostic performance than tumor markers combination. Isolated abdominal wall (port/scar site) recurrence and loco-regional recurrence on PET/CT demonstrated better survival than non-regional metastatic disease. These results suggest a possible role of PET/CT as a surveillance modality, as well as a guide to therapeutic decision-making in cases of recurrent GBC.

FDG PETCT for assessing marrow involvement at staging pediatric nonhematological round cell malignancies.

BACKGROUND AND HYPOTHESIS: Bone and lung are the common sites of metastasis in pediatric round cell tumors and its presence indicates poor outcomes. Staging workup for these malignancies thus includes bone marrow biopsy (BMB) along with evaluation of thorax, and tissue analysis for N MYCN status in neuroblastoma. BMB is an invasive procedure requiring general anesthesia with known disadvantages.With an aim of avoiding an invasive BMB a study was taken up to evaluate efficacy of FDG PET CT in detecting marrow involvement in neuroblastoma and rhabdomyosarcoma at staging. MATERIALS AND METHOD: Prospective observational study evaluated 83 newly diagnosed treatment naïve patients of neuroblastoma (n = 43) and rhabdomyosarcoma (n = 42) who underwent conventional imaging of PETCT with CECT of local region along with a CT thorax and BMB (both iliac crest) done within 1 week. Findings of FDG PETCT were compared with bone marrow histology and accuracy parameters were calculated. RESULT: The overall sensitivity, specificity, accuracy, positive-predictive value (PPV), negative-predictive value (NPV) of FDG PETCT for detection of marrow disease was 100%, 86.1%, 89.4%. 68.9% and 100%, respectively. Subset analysis showed sensitivity, specificity, PPV and NPV of 100%, 66%, 71.4% and 100%, respectively, for neuroblastoma, with rhabdomyosarcoma patients having few events NPV of 100% accuracy of 97.6%. CONCLUSION: FDG PETCT with sensitivity and NPV of 100% can be considered as a first stop imaging and biopsy can be avoided in patients with a negative scan.

FDG PET/CT of Primary Ewing Sarcoma of IVC.

Secondary involvement of inferior vena cava is a common presentation in aggressive solid malignancies, especially arising from kidneys, adrenals, and hepatobiliary system, mostly resulting from local infiltration. Rarely, primary tumors are seen arising from vascular tissue. The Ewing family of tumors commonly arises from bone, but there is a high propensity of these tumors to originate from nonosseous sites of mesenchymal cell origin. We would herewith demonstrate a rare presentation of Ewing sarcoma, seen originating from inferior vena cava, presenting as extensive intravascular tumor thrombosis, evaluated on FDG PET/CT imaging in a 12-year-old girl.

Metabolic Imaging as a Novel Strategy in Evaluation of Mycotic Abdominal Aortic Aneurysm: A Case Report and Brief Clinical Review.

Abdominal aortic aneurysm (AAA) is an uncommon entity with high mortality. Etiologically, they are classified as inflammatory and infective (mycotic), the latter being less common. Clinical presentation, laboratory investigations, and treatment for these may considerably overlap. However, choice of management and the need for surgical intervention depends on factors such as size and progression of aneurysm, persistent symptoms, and presence or absence of distant pathology. Although computed tomography (CT) is the gold standard for AAA, in selected cases, especially in infected AAA, fluorodeoxyglucose positron emission tomography-CT can provide valuable information.

18F-fludeoxyglucose positron emission tomography computed tomography-guided diagnosis of prostatic and leptomeningeal tuberculosis.

Genitourinary tuberculosis contributes to 10%-14% of extrapulmonary TB. Prostate tuberculosis is rare and usually found incidentally following transurethral resection of the prostate for benign prostatic hyperplasia. We report a case of an immunocompetent patient with pyrexia of unknown origin, on evaluation with whole-body 18F-fludeoxyglucose positron emission tomography computed tomography scan found to have suspicious prostatic primary, with hypermetabolic abnormalities involving the brain. Histopathological diagnosis was established as multifocal tuberculosis involving prostate, meninges, and intracranial tuberculomas.

Unusual case of infantile fibrosarcoma evaluated on F-18 fluorodeoxyglucose positron emission tomography-computed tomography.

Infantile fibrosarcoma (IFS) is a rare soft-tissue sarcoma originating from extremities and occasionally from axial soft tissue. The prognosis is good with favorable long-term survival. It is rarely metastasizing tumor, the chances being lesser with IFS originating from extremities. Use of neoadjuvant chemotherapy (NACT) as a treatment regime further reduces the chances of local relapse and distant metastasis. The organs commonly affected in metastatic IFS are lungs and lymph nodes. We report an unusual case of an IFS originating from extremity, which received NACT, yet presented with an early metastatic disease involving soft tissues and sparing lungs and lymph nodes, as demonstrated on fluorodeoxyglucose positron emission tomography-computed tomography.