Use of 18 F-PSMA PET to Distinguish Cerebral Radiation Necrosis From Tumor Recurrence.

ABSTRACT: Brain metastasis in prostate adenocarcinoma is extremely rare and usually arises in the setting of widespread osseous and visceral metastases. Surgical resection and radiation therapy, including stereotactic radiosurgery, are the mainstays of treatment for brain metastasis. Radiation necrosis is a common complication of radiotherapy for brain metastasis, and distinguishing it from tumor recurrence by MRI is difficult because of overlapping findings. We present a 73-year-old man with prostate cancer with a solitary brain metastasis where PET with 18 F-piflufolostat helped detect disease recurrence in the setting of ambiguous MRI findings.

Muscle Infiltrative Adult Multisystem Langerhans Cell Histiocytosis Detected on Fluorodeoxyglucose Positron Emission Tomography/ Computed Tomography - A Rare Case.

Langerhans cell histiocytosis (LCH) is a disease of unknown pathogenesis characterized by the accumulation of Langerhans cells which show immunopositivity for S-100 and CD1a. LCH with skeletal muscle involvement has been rarely described in literature. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is an important tool in identifying the sites of involvement in LCH. We present a rare case of muscle invasive LCH where 18F-FDG PET/CT showed involvement of multiple other sites such as the liver, bones, bone marrow, and possibly the thyroid gland in our case. Further, the current case also shows that liver involvement by LCH (possibly fibrotic phase) can be negative on PET but show lesions on CT.

Tumor-induced osteomalacia - Current imaging modalities and a systematic approach for tumor localization.

Paraneoplastic syndromes are symptom complexes that cannot be readily explained by local or distant spread of the tumor. They can occur due to hormone production, autoimmunity or other biologically active products produced by the tumor, etc. Tumor induced osteomalacia is a rare paraneoplastic syndrome in which the manifestation is mainly musculoskeletal such as bone pain, fractures and muscle weakness as a consequence of elaboration of fibroblast growth factor 23 (FGF23) by the tumor. Most of these tumors are solitary and small and hence localization of these tumors is often challenging. This review summarizes the various anatomic imaging modalities such as plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) and nuclear medicine imaging techniques in the evaluation of these tumors.

Unsuspected Active Ulcerative Colitis in a Patient With Dermatomyositis: A Rare Association Detected on 18F-FDG PET/CT During the Search for an Occult Malignancy.

Dermatomyositis is an inflammatory myopathy with the characteristic features of skin rash and myopathy. We here present a known case of dermatomyositis evaluated with 18F-FDG PET/CT for the presence of any occult malignancy. The scan was negative for the presence of any malignancy. However, it revealed multiple intensely FDG avid colonic strictures that were later proven on colonoscopic biopsy to be ulcerative colitis. Also, a well-known association of bilateral sacroilitis was simultaneously demonstrated on the scan. The present case demonstrates that 18F-FDG PET/CT imaging can serve as a one-stop shop imaging modality in dermatomyositis by facilitating detection of occult primary if any and by providing insight into other rare systemic associations.

Cross sectional and nuclear medicine imaging of pancreatic insulinomas.

Insulinomas are rare neuroendocrine tumors which occur predominantly in the pancreas. Although majority of the insulinomas are benign, over-secretion of insulin by the tumor leads to debilitating hypoglycemic symptoms. The diagnosis is based on clinical and biochemical findings. After the diagnosis is made, the principal challenge lies in locating the tumor because most tumors are solitary and small in size. Locating the tumor is of paramount importance as complete surgical excision is the only curative treatment, and incomplete resection leads to persistence of symptoms. Different preoperative and intraoperative imaging techniques have been used with varying success rates for the insulinoma imaging. Besides localizing the tumor, imaging also helps to guide biopsy, detect metastatic lesions, and perform image-guided therapeutic procedures. This review will discuss the role of different Cross sectional and nuclear medicine imaging modalities in insulinomas.

Disseminated Skeletal Muscle and Cardiac Metastasis from Squamous Cell Carcinoma of the Lung Detected with FDG and FLT PET/CT.

Lung cancer is one of the leading cancers all over the world. Positron emission tomography (PET) using 18F fluorodeoxyglucose (18F FDG) is useful for staging of the disease and decide the appropriate management. 3'-deoxy-3'-18 F-fluorothymidine (18F FLT) is a tracer being extensively evaluated currently and is said to represent tumor proliferation. Common sites of metastases from lung cancer include adrenal glands, bone, and brain. Muscle metastasis and cardiac metastasis are uncommon findings. We report a case of squamous cell carcinoma of the lung with metastases to multiple skeletal muscles and myocardium detected with both FDG and FLT PET/computed tomography (CT).

Role of serial F-18 FDG PET/CT scans in assessing treatment response and predicting relapses in patients with symptomatic sarcoidosis.

ackground: Monitoring disease activity in sarcoidosis remains a clinical challenge as there is no gold standard. Positron emission tomography (PET) imaging is a novel tool to assess the metabolic activity. There is limited data on the role of serial PET scans in monitoring the disease activity. METHODS: This is a prospective study of 27 sarcoidosis patients treated with systemic corticosteroids. Patients underwent two serial PET/CT scans: one before initiating therapy and the follow up scan at end of therapy. The metabolic response on PET scan was classified as: (a) complete metabolic response (CMR); (b) partial metabolic response (PMR); (c) stable metabolic disease (SMD); and, (d) progressive metabolic disease (PMD). Patients with either CMR or PMR were classified as PET responders while those with SMD or PMD were considered as PET non-responders. All patients were followed at 3, 6 and 12 months after completion of therapy. Relapse rates and relapse-free survival was compared between the various groups. RESULTS: There was significant decline in the median SUVmax of the mediastinal lymph nodes, peripheral lymph nodes and the lung parenchyma in the follow up PET scan. Eight patients achieved CMR, 6 patients achieved PMR while 13 patients were PET non-responders. There was no difference in the clinical remission rates between the responders and non-responders. However, the relapse rate was significantly higher in non-responders vs. responders (61.5% vs. 14.2%, p=0.018). None of the patients who achieved a CMR relapsed during the study period. CONCLUSIONS: Patients with metabolic response on PET scan have significantly fewer relapses as compared to those with no response on PET scan.

(18)F-FDG and (18)F-FLT PET/CT imaging in the characterization of mediastinal lymph nodes.

PURPOSE: There is currently no single modality for accurate characterization of enlarged mediastinal lymph nodes into benign or malignant. Recently (18)F-fluorothymidine (FLT) has been used as a proliferation marker. In this prospective study, we examined the role of (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) and (18)F-FLT PET/CT in categorizing mediastinal lymph nodes as benign or malignant. MATERIALS AND METHODS: A total of 70 consecutive patients with mediastinal lymphadenopathy detected on computed tomography (CT) or chest radiograph underwent whole body (18)F-FLT PET/CT and (18)F-FDG PET/CT (within 1 week of each other). Lymph nodal tracer uptake was determined by calculation of standardized uptake value (SUV) with both the tracers. Results of PET/CT were compared with histopathology of the lymph nodes. RESULTS: Histopathology results showed thirty-seven patients with sarcoidosis, seven patients with tuberculosis, nine patients with non-small cell lung cancer, five patients with Hodgkin's lymphoma and twelve patients with non-Hodgkin's lymphoma. The mean FDG SUVmax of sarcoidosis, tuberculosis, Hodgkin's and non-Hodgkin's lymphoma was 12.7, 13.4, 8.2, and 8.8, respectively, and the mean FLT SUVmax was 6.0, 5.4, 4.4, and 3.8, respectively. It was not possible to characterize mediastinal lymphadenopathy as benign or malignant solely based on FDG SUVmax values (p > 0.05) or FLT SUVmax values (p > 0.05). There was no significant difference in FDG uptake (p > 0.9) or FLT uptake (p > 0.9) between sarcoidosis and tuberculosis. In lung cancer patients, the FDG SUVmax and FLT SUVmax of those lymph nodes with tumor infiltration on biopsy was 6.7 and 3.9, respectively, and those without nodal infiltration was 6.4 and 3.7, respectively, and both the tracers were not able to characterize the nodal status as malignant or benign (p > 0.05). CONCLUSION: Though (18)F-FLT PET/CT and (18)F-FDG PET/CT reflect different aspects of biology, i.e., proliferation and metabolism, respectively, neither tracer could provide satisfactory categorization of benign and malignant lymph nodes. The results of this study clearly suggest that differentiation of mediastinal nodes into benign and malignant solely based on SUVmax values cannot be relied upon, especially in settings where tuberculosis and sarcoidosis are common.

Recurrent Urinary Bladder Paraganglioma Detected on 68Ga DOTANOC PET/CT.

Urinary bladder paraganglioma constitute only a small fraction of urinary bladder tumors. These rare tumors are well known for recurrences even after many years of surgery. Functional imaging with different radiotracers has been found to be useful to evaluate the extent, metastasis, and recurrence of paragangliomas. We report a case where Ga DOTANOC PET/CT successfully detected recurrence of a paraganglioma in the urinary bladder along with pelvic lymph nodal metastasis.