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Recognition of patterns has always been extremely important in cross-sectional imaging. Peritoneal involvement, both primary and as dissemination from abdominopelvic malignancies, is manifested in different forms, purely because of anatomical complexity. We studied series of peritoneal involvement by (18)F-fluorodeoxyglucose positron-emission tomography/computed tomography fusion imaging and derived patterns of tracer uptake on maximum intensity projection and cross-sectional fusion images.

Aims and Objectives: The aim of the study was to estimate the incremental value of fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) in aiding treatment decisions in a specific cohort of patients with lower esophageal and gastroesophageal junction adenocarcinoma who were considered for potentially curative treatment on the basis of conventional imaging., Materials and Methods: The study included patients referred for a staging F-FDG PET/CT who were considered for potentially curative treatment (neoadjuvant therapy followed by surgery or definitive chemoradiotherapy) by a multidisciplinary tumor board. The proportion of patients with M1b disease (American Joint Committee on Cancer, 6th ed.) detected on F-FDG PET/CT was calculated. The sensitivity, specificity, positive and negative predictive values, and accuracy of F-FDG PET/CT for M1b disease were calculated. PET/CT findings were verified with histopathological analysis; when it was not possible to obtain pathological confirmation, correlative imaging or follow-up imaging studies were used for validation., Results: A total of 156 patients who fulfilled the inclusion criteria were analyzed. F-FDG PET/CT detected M1b disease in 25 patients (16%), changing the intent of treatment from potentially curative to palliative. In five patients, PET/CT failed to detect distant metastases. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of F-FDG PET/CT for detecting M1b disease were 83.3, 98.4, 92.5, 96.1, and 95.3%, respectively. Additional surgical procedures (hemicolectomy and polypectomy) were performed in three patients because of the detection of a second primary cancer in the colon in two patients and a colonic dysplastic polyp in one patient., Conclusion: In patients who are considered to be potentially curable after conventional imaging, F-FDG PET/CT can detect unsuspected sites of distant metastases (M1b) in a significant number of cases and thus contribute to the clinical decision-making process. PET/CT should be an integral part of the staging workup of patients with esophageal adenocarcinoma.

Primary carcinoma of gall bladder is a highly aggressive malignancy, most often detected in late stage in majority of the affected patients. It commonly spreads to the adjacent liver parenchyma and, via lymphatics, to mesenteric nodes. Extra-abdominal metastatic sites are extremely rare, with lung being the commonest site. We report a rare occurrence of isolated asymptomatic bone marrow metastases from gall bladder cancer, in the absence of locoregional adenopathy, detected on whole-body F-FDG PET/CT at initial staging.

Mesenteric lymphomas are commonly seen as bulky hypermetabolic nodal masses on F-FDG PET/CT. Very rarely, these are seen as mesenteric haziness due to localized hyperattenuation of fat, known as "misty mesentery", which morphological imaging-wise has other differentials as well. We report a unique imaging finding of segmental misty mesentery with hypermetabolic mesenteric nodes on FDG PET/CT in a patient who was kept on observation due to inconclusive biopsy, which on follow-up imaging progressed to extensive lymphomatous involvement. Thus, in retrospect, this imaging feature on baseline PET/CT was diagnostic for mesenteric lymphoma.

Von Hippel-Lindau (VHL) disease is a rare, inherited, multisystem disorder that is characterized by development of a variety of benign and malignant tumors. We report an incidental detection of clinically occult pancreatic malignancy on FDG PET/CT in a patient of VHL who underwent restaging for a previously treated endolymphatic sac tumor.

Purpose: To study whether the metabolic information provided by a prior PET/computed tomography (CT) scan can add valuable information and an incremental benefit while performing image-guided biopsies., Methods: Fluorine-18 fluorodeoxyglucose (F-FDG) PET/CT findings of 112 patients were available before biopsy and were considered for analysis. Biopsies were performed using standard techniques only after the needle tip was confirmed to be in the portion of the lesion corresponding to the hypermetabolic area seen on PET. This was achieved by visual coregistration and also by software registration algorithms that registered the intraprocedural CT images with the preselected PET/CT data. Only those biopsies for which a definitive histopathological diagnosis could be made were considered 'diagnostic'. Cases in which PET/CT added an incremental value were divided into three categories., Results: A total of 112 patients (66 male and 46 female, age range 16-74 years) underwent a biopsy based on PET findings. The biopsy sites were as follows: lung, 54; lymph nodes, 27; bone, 12; and soft-tissue masses/deposits, 19. Out of the 112 biopsies, an incremental benefit was seen overall in 53 patients (47.3%): in 40.7% (22/54) of patients who underwent lung biopsies, 44.4% (12/27) of those who underwent lymph node biopsies, 66.6% (8/12) of those who underwent bone biopsies and 57.8% (11/19) of those who underwent soft-tissue biopsies. Out of the cases that showed an incremental benefit, the highest number (30) belonged to the category in which the biopsy sample was obtained from the focal hypermetabolic portion of the apparently larger morphological lesion seen on CT., Conclusion: PET/CT data coregistered with intraprocedural CT images can guide needle placement in the viable portion of the lesion, thus increasing the chances of achieving a definitive diagnosis. This approach can offer a significant incremental benefit while performing image-guided biopsies.

Purpose: To study the impact of multiparametric MRI and (18)F-FDG-PET on the outcome of children with diffuse intrinsic pontine gliomas (DIPG)., Materials and Methods: Imaging data from a phase-II prospective therapeutic study in children with newly diagnosed DIPG were considered for evaluation. They included baseline MRI with contrast enhancement before treatment. Functional imaging included MR spectroscopy, MR perfusion and FDG-PET studies. All patients (n = 20) had baseline MRI and 11 patients had FDG-PET. Response was assessed by MRI and PET 4 weeks after therapy. Baseline imaging findings were correlated with survival. Presence or absence of adverse parameters on MRI (heterogeneous contrast enhancement, hyperperfusion or increased choline:NAA ratio) was used to develop a cumulative radiological prognostic index (RPI). Sensitivity and specificity of each imaging modality in tumour grading was estimated., Results: The cumulative RPI was able to classify the patients into different grades and was predictive of overall survival (p = 0.02). MR perfusion also predicted survival (p = 0.039). Sensitivity and specificity of MRI and FDG-PET to detect low-grade gliomas were low to moderate (33-66%), but moderate to high in detecting high-grade gliomas (50-100%). Baseline FDG uptake on PET scan did not correlate with survival (p = 0.7)., Conclusions: Cumulative RPI was able to classify tumours into different grades and predicted clinical outcome. At baseline, MR hyperperfusion indicated a shorter survival for DIPG patients. Sensitivity and specificity of imaging modalities to detect low-grade gliomas were poor.

One of the main limitations of 18F-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (FDG PET/CT) is false-positive tracer uptake by physiological and inflammatory conditions. Continuing FDG accumulation occurs in tumors, but not in inflammatory lesions, and dual time-point FDG PET can be useful for differentiating benign from malignant conditions. Experience is rather limited, and its application in the assessment of tumors inside peritoneal cavity has been rarely reported. We present 2 cases where dual time-point FDG PET imaging proved essential in differentiating intense physiological tracer uptake from peritoneal deposits in patients with intestinal obstruction.

Extramedullary hematopoiesis refers to the presence of hematopoietic elements in locations other than the bone marrow medullary space. It occurs as a compensatory mechanism to impaired hematopoiesis resulting from a variety of pathological conditions. Because of the hazards of biopsy of a highly vascular hematopoietic mass, it is desirable to establish the diagnosis noninvasively. We report a case where 18F-fluoro-3'deoxy-L-thymidine PET/CT and 99mTc-SC scintigraphy were used as a noninvasive modality to diagnose extramedullary hematopoiesis.

We report the imaging findings in extra-articular chondrocalcinosis in a 53-year-old man with swelling and pain in right scapular area for 1 year. Plain radiography showed a right scapular area calcific mass. The clinical suspicion was of a soft tissue sarcoma. As a part of diagnostic workup, a bone scan and a PET/CT scan were done. Bone scan revealed intense MDP uptake in the right scapular area. FDG PET/CT revealed intense FDG uptake in the mass. The biopsy revealed chondrocalcinosis. This is an addition to our long list of causes of extraosseous uptake of MDP.

Purpose: Our objective was to conduct a systematic review and meta-analysis of studies assessing the diagnostic performance of (18)F-fluorodeoxyglucose positron emission tomography (FDG PET) with or without computed tomography (CT) in post-treatment response assessment and/or surveillance imaging of head and neck squamous cell carcinoma (HNSCC)., Methods: A systematic search of the indexed medical literature was done using appropriate keywords to identify relevant studies. Metrics of diagnostic test accuracy, viz. sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were extracted from individual studies and combined using a random effects model to yield weighted mean pooled estimates with 95% confidence intervals (95% CI). The impact of timing of post-treatment scan, study quality and advancements in PET technology was explored through meta-regression., Results: A total of 51 studies involving 2,335 patients were included in the meta-analysis. The weighted mean (95% CI) pooled sensitivity, specificity, PPV and NPV of post-treatment FDG PET(CT) for the primary site was 79.9% (73.7-85.2%), 87.5% (85.2-89.5%), 58.6% (52.6-64.5%) and 95.1% (93.5-96.5%), respectively. Similar estimates for the neck were 72.7% (66.6-78.2%), 87.6% (85.7-89.3%), 52.1% (46.6-57.6%) and 94.5% (93.1-95.7%), respectively. Scans done ≥ 12 weeks after completion of definitive therapy had moderately higher diagnostic accuracy on meta-regression analysis using time as a covariate., Conclusion: The overall diagnostic performance of post-treatment FDG PET(CT) for response assessment and surveillance imaging of HNSCC is good, but its PPV is somewhat suboptimal. Its NPV remains exceptionally high and a negative post-treatment scan is highly suggestive of absence of viable disease that can guide therapeutic decision-making. Timing of post-treatment imaging has a significant, though moderate impact on diagnostic accuracy.