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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.

Mucocele of the appendix is an uncommon condition characterized by luminal distension and accumulation of a mucoid material. Occasionally, it can be caused due to malignancy like cystadenocarcinoma, and the preoperative diagnosis of which is very rare. We report a case of a 64-year-old lady presenting with intermittent abdominal pain diagnosed on ultrasonography as a mucocele where preoperative (18)F-flurodeoxyglucose positron emission tomography/computerized tomography (FDG PET/CT) findings raised a strong suspicion of malignancy. FDG PET/CT findings brought about a change in therapeutic plan, and the patient was considered for a more extensive surgical resection. The final histopathology revealed cystadenocarcinoma as the cause of appendicular mucocele, a finding hitherto undescribed on FDG PET/CT.

Background: Transarterial radioembolization using Y microspheres is a novel therapeutic option for inoperable hepatic malignancies. As these spheres are radiolucent, real-time assessment of their distribution during the infusion process under fluoroscopic guidance is not possible. Bremsstrahlung radiations arising from 90Y have conventionally been used for imaging its biodistribution. Recent studies have proved that sources of 90Y also emit positrons, which can further be used for PET/computed tomography (CT) imaging. This study aimed to assess the feasibility of 90Y PET/CT imaging in evaluating microsphere distributions and to compare its findings with those of Bremsstrahlung imaging., Materials and Methods: Thirty-five sessions of 90Y microsphere transarterial radioembolization were performed on 30 patients with hepatic malignancies. 90Y PET/CT imaging was performed within 3 h of therapy. Bremsstrahlung imaging was also performed for each patient. The imaging findings were compared for concordance in the distribution of microspheres., Results: Exact one-to-one correspondence between 90Y PET/CT imaging and 90Y Bremsstrahlung imaging was observed in 97.14% of cases (i.e. in 34/35 cases). Discordance was observed only in one case in which 90Y PET/CT imaging resolved the microsphere uptake in the inferior vena cava tumor thrombus, which was, however, not visualized on Bremsstrahlung imaging., Conclusion: There is good concordance in the imaging findings of 90Y PET/CT and 90Y Bremsstrahlung imaging. 90Y PET/CT imaging scores over the conventionally used Bremsstrahlung imaging in terms of better resolution, ease of technique, and comparable image acquisition time. This makes it a preferred imaging modality for assessment of the distribution of 90Y microspheres.

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.

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.

Secondary sarcomas arising on the background of a bone infarct are extremely uncommon. Based on the knowledge of classic imaging patterns, however, lesions like bone infarcts can be recognized during positron emission tomography/computed tomography studies, which are now being performed increasingly in cancer patients. We demonstrate the detection of this rare entity on positron emission tomography/computed tomography and its correlation on magnetic resonance imaging in a 56-year-old man with asymptomatic multifocal osteonecrosis secondary to steroid treatment for polymyositis.

Ablation of neoplastic lesions by using radiofrequency energy is gaining popularity in clinical practice because of the minimally invasive nature of radiofrequency ablation (RFA). Primary and secondary tumors of the liver and lung are treated with RFA when surgery is precluded because of comorbidity. Benign bone tumors are also treated with RFA to relieve pain and prevent further tumor growth. Differentiation between postablation tissue changes and residual disease is difficult with morphologic imaging modalities such as ultrasonography, computed tomography (CT), and magnetic resonance (MR) imaging, thus limiting the use of these modalities to detection of residual disease early after RFA. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is a functional imaging modality that can be used to study the effects and efficacy of RFA. Lesions that show increased FDG uptake at PET become completely photopenic immediately after RFA, a finding that is suggestive of the completeness of ablation. Focal areas of increased FDG uptake within the ablated zone are suggestive of residual disease. Reactive tissue changes such as inflammation are depicted in the periphery of the ablated lesion and show a uniform low-grade FDG uptake, which can be differentiated from the focal, nodular intense uptake in areas of residual disease. Use of combined FDG PET/CT to detect residual disease early after RFA allows ablation to be repeated, if necessary, to obtain the maximum therapeutic benefit. Note that FDG uptake in the complications sometimes associated with RFA can be a cause of potential false-positive PET results., (RSNA, 2011)

Non-neoplastic lesions have been known to mimic malignancies and metastases on positron emission tomography/computed tomography. We report the rare occurrence of multiple fluorodeoxyglucose-concentrating sclerosing hemangiomas in a patient with soft tissue sarcoma mimicking lung metastases.

Intracranial meningeal hemangiopericytomas are rare tumors that can mimic meningioma on imaging and on histopathology. However, these tumors are more aggressive with a tendency for local and metastatic recurrence, sometimes after a prolonged symptom-free interval. We report an unusual metastatic recurrence of an intracranial hemangiopericytoma, 8 years after surgery for the primary tumor and discuss the role of positron emission tomography/computed tomography in the follow-up of these patients.

Aim: To study the role of PET-CT in evaluating sarcomatous transformation in osteochondromas., Materials and Methods: This was a retrospective analysis of a prospective data base of 12 patients from 2005 to 2007 with a clinical diagnosis of an osteocartilaginous lesion who were referred for a FDG PET-CT study to evaluate for possible malignant transformation. Imaging was performed on a GE Discovery ST PET-CT system after intravenous injection of 370 MBq (10 mCi) of F-18 FDG., Results: Seven patients with histopathological evidence of a sarcomatous transformation to grade II chondrosarcoma showed moderate to high FDG uptake (SUV 3.3-6.9), whereas 1 patient with a dedifferentiated chondrosarcoma showed a focus of very intense uptake (SUV 11.4). Four patients with histopathological and/or clinical or follow-up diagnosis of a benign osteocartilaginous lesion showed low grade FDG uptake (SUV 0.8-1.3). FDG uptake was also noted in an asymptomatic osteochondroma which on histopathology revealed a grade II chondrosarcoma., Conclusions: Whole body FDG PET-CT is an important adjunct to conventional morphologic imaging in evaluating suspected malignant transformation in osteochondromas. Increased glucose metabolism can help diagnose sarcomatous transformation at the suspected sites as well as detect early malignant change at clinically unsuspected sites. Moreover, its ability to detect a focus of dedifferentiation can be useful for prognostication and to plan adjuvant treatment. A small cohort limits statistically sound conclusions to be drawn from this study, however further prospective trials based on these findings can help explore the potential application of FDG PET-CT in this clinical condition.

Purpose: To retrospectively evaluate the utility of positron emission tomography-computed tomography (PETCT) in the diagnosis of percutaneous endoscopic gastroscopy (PEG) site metastases in head and neck cancer., Materials and Methods: From the database of 250 patients of head and neck cancer who were referred for PET-CT over 2 years (from January 2005 to January 2007), 6 patients who had PEG tube placement were considered for the study. Imaging was performed on a GE Discovery ST PET-CT system after intravenous injection of 370 MBq (10 mCi) of < sup > 18 < /sup > F-fluorodeoxyglucose (FDG)., Results: Intense FDG uptake with an associated soft tissue mass was seen at the PEG site in 3 patients and mild uptake was seen in 2 patients. Biopsy revealed PEG site metastases in 2 patients, abscess in 1 patient, and granulation tissue in 1 patient. Intense uptake with an associated soft tissue mass suggested the diagnosis of metastasis. Stranding of the peristomal fat seen on the CT component of the PET-CT indicated an infective/inflammatory pathology. PET-CT findings showed local recurrence in 3 patients and disseminated metastases (excluding the PEG site) in 1 patient., Conclusion: The functional information provided by PET combined with the morphologic detail of CT can improve characterizing of the stoma site abnormality and help in distinguishing recurrence from infective/inflammatory changes. Whole body combined PET-CT is a useful modality for evaluating gastrostomy site metastases and for detecting coexisting local recurrences and distant metastases in head and neck cancer patients. In addition it can detect early asymptomatic recurrences at the gastrostomy site.