18 F-FDG PET and MRI Evaluation of Paraneoplastic Limbic Encephalitis.

ABSTRACT: Autoimmune limbic encephalitis (paraneoplastic or nonparaneoplastic) is a rare condition involving autoantibodies against intracellular or cell-surface proteins of neurons. Patients typically present with acute and progressive neuropsychiatric symptoms. Although the criterion standard for diagnosis remains detection of autoantibodies in cerebrospinal fluid, there are characteristic imaging features that can aid in diagnosis, notably abnormalities in the bilateral medial temporal lobes on imaging, particularly with nuclear imaging. Here, we present 18 F-FDG PET findings of paraneoplastic limbic encephalitis in a 65-year-old man.

Incidental Uptake of 18F-Fluciclovine by Type AB Thymoma.

ABSTRACT: Biochemical recurrence of prostate cancer, detected by a rising PSA, may reflect intraprostatic or extraprostatic recurrence. 18F-Fluciclovine (Axumin), a synthetic amino acid substrate in tumor metabolism, has frequently been used for to localize recurrent prostate cancers. We present a 71-year-old man with biochemical recurrence of prostate cancer but no convincing imaging findings on 18F-fluciclovine PET/CT. Of note, however, was an incidental uptake within the anterior mediastinum, which was found on biopsy to be a type AB thymoma. With this, we stress that awareness of false-positive uptake patterns is crucial for accurate diagnosis of recurrent prostate cancer.

Laparoscopic Port-Site Metastasis From Prostate Cancer on 18F-Fluciclovine PET/CT.

ABSTRACT: Laparoscopic port-site metastasis from prostate cancer is a rare complication after radical prostatectomy and pelvic lymph node dissection. We report a case of port-site metastasis from prostate cancer identified on 18F-fluciclovine PET/CT for a patient with evidence of biochemical recurrence. Final pathology after targeted ultrasound and biopsy of the mass in the right abdominal wall revealed prostatic adenocarcinoma.

Extracranial metastases of anaplastic meningioma.

Anaplastic meningioma is a World Health Organization (WHO) Class III lesion representing 2-3% of all meningiomas, with more aggressive spread, increased mortality and increased likelihood of recurrence. Metastases outside the blood-brain barrier are uncommon but can occur to the lungs, liver, bone and skin.Definitive diagnosis is obtained with pathological analysis. The World Health Organization classifies meningiomas into benign (Grade I), atypical (Grade II) and anaplastic/malignant (Grade III) based on histological findings including number of mitoses, cellularity, nucleus to cytoplasm etc. This case presents a 58-year-old female with history of treated anaplastic meningioma with new onset headache, nausea and vomiting. Workup demonstrated multiple new bilateral pulmonary nodules, which subsequent biopsy proved to be metastasis from recurrent anaplastic meningioma, with extensive intrathoracic involvement.

18-FDG Uptake in Pulmonary Dirofilariasis.

Solitary pulmonary nodules are a common finding on chest radiography and CT. We present the case of an asymptomatic 59-year-old male found to have a 13 mm left upper lobe nodule on CT scan. The patient was asymptomatic and the CT was performed to follow up mediastinal and hilar lymphadenopathy that had been stable on several previous CT scans. He had a history of emphysema and reported a 15 pack-year smoking history. PET-CT was performed which demonstrated mild 18-FDG uptake within the nodule. Given his age and smoking history, malignancy was a consideration and he underwent a wedge resection. Pathological examination revealed a necrobiotic granulomatous nodule with a central thrombosed artery containing a parasitic worm with internal longitudinal ridges and abundant somatic muscle, consistent with pulmonary dirofilariasis. Dirofilaria immitis, commonly known as the canine heartworm, rarely affects humans. On occasion it can be transmitted to a human host by a mosquito bite. There are two major clinical syndromes in humans: pulmonary dirofilariasis and subcutaneous dirofilariasis. In the pulmonary form, the injected larvae die before becoming fully mature and become lodged in the pulmonary arteries.

Detection of pulmonary embolism during pregnancy: comparing radiation doses of CTPA and pulmonary scintigraphy.

OBJECTIVE: In pregnant patients pulmonary embolism is a common occurrence with potentially devastating outcomes, necessitating timely imaging diagnosis. In every patient, especially in pregnant patients, radiation exposure is an important consideration while selecting the best imaging modality. MATERIALS AND METHODS: We performed a retrospective analysis comparing radiation doses of computed tomography pulmonary angiography (CTPA), perfusion scintigraphy, and perfusion/ventilation scintigraphy for suspected pulmonary embolism in 53 pregnant patients at our hospital between 2006 and 2012. Effective dose and breast-absorbed and uterus-absorbed doses for CTPA as well as effective dose and breast and fetus-absorbed doses for pulmonary scintigraphy were estimated using International Commission on Radiological Protection 103 weighting factors. RESULTS: For CTPA and perfusion scintigraphy, average doses were estimated as effective doses of 21 and 1.04 mSv, breast-absorbed doses of 44 and 0.28 mGy, and uterus-absorbed dose of 0.46 mGy and fetal-absorbed dose of 0.25 mGy, respectively. With inclusion of the ventilation component of pulmonary scintigraphy, doses increased to an effective dose of 1.29 mSv, a breast-absorbed dose of 0.37 mGy, and a fetal-absorbed dose of 0.40 mGy. CONCLUSION: Perfusion nuclear medicine study has a statistically significantly lower effective and breast-absorbed dose (P<0.0001) when compared with CTPA. Similarly, the fetal-absorbed dose for pulmonary scintigraphy has a statistically lower dose (P=0.0010) when compared with CTPA, even if the ventilation component of pulmonary scintigraphy is performed, although these values are so small that they are unlikely to be clinically significant.

Epigenetic modifications of GABAergic interneurons are associated with the schizophrenia-like phenotype induced by prenatal stress in mice.

Human studies suggest that a variety of prenatal stressors are related to high risk for cognitive and behavioral abnormalities associated with psychiatric illness (Markham and Koenig, 2011). Recently, a downregulation in the expression of GABAergic genes (i.e., glutamic acid decarboxylase 67 and reelin) associated with DNA methyltransferase (DNMT) overexpression in GABAergic neurons has been regarded as a characteristic phenotypic component of the neuropathology of psychotic disorders (Guidotti et al., 2011). Here, we characterized mice exposed to prenatal restraint stress (PRS) in order to study neurochemical and behavioral abnormalities related to development of schizophrenia in the adult. Offspring born from non-stressed mothers (control mice) showed high levels of DNMT1 and 3a mRNA expression in the frontal cortex at birth, but these levels progressively decreased at post-natal days (PND) 7, 14, and 60. Offspring born from stressed mothers (PRS mice) showed increased levels of DNMTs compared to controls at all time-points studied including at birth and at PND 60. Using GAD67-GFP transgenic mice, we established that, in both control and PRS mice, high levels of DNMT1 and 3a were preferentially expressed in GABAergic neurons of frontal cortex and hippocampus. Importantly, the overexpression of DNMT in GABAergic neurons was associated with a decrease in reelin and GAD67 expression in PRS mice in early and adult life. PRS mice also showed an increased binding of DNMT1 and MeCP2, and an increase in 5-methylcytosine and 5-hydroxymethylcytosine in specific CpG-rich regions of the reelin and GAD67 promoters. Thus, the epigenetic changes in PRS mice are similar to changes observed in the post-mortem brains of psychiatric patients. Behaviorally, adult PRS mice showed hyperactivity and deficits in social interaction, prepulse inhibition, and fear conditioning that were corrected by administration of valproic acid (a histone deacetylase inhibitor) or clozapine (an atypical antipsychotic with DNA-demethylation activity). Taken together, these data show that prenatal stress in mice induces abnormalities in the DNA methylation network and in behaviors indicative of a schizophrenia-like phenotype. Thus, PRS mice may be a valid model for the investigation of new drugs for schizophrenia treatment targeting DNA methylation. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Time sensitivity: a parameter reflecting tumor metabolic kinetics by variable dual-time F-18 FDG PET imaging.

OBJECTIVES: The aim of this study was to define and investigate the time sensitivity of tumors by variable dual-time fluorodeoxyglucose positron emission tomography (FDG PET). METHODS: Variable dual-time (t) protocol (P) FDG PET-computed tomography (CT) scans from 40 patients with pathologically proven head and neck tumors without brain metastasis were analyzed. The first protocol (P.I) consisted of 26 patients with early (E) and delayed (D) PET-CT obtained at 106 +/- 15 and 135 +/- 16 min after injection of 16.3 +/- 1.9 mCi FDG. The second protocol (P.II) recruited 14 patients with E- and D-PET performed at 54 +/- 13 and 151 +/- 28 min after injection of 9.6 +/- 1.7 mCi FDG. The maximum standardized uptake values (SUVs) were measured in the primary tumor (CA1) and the cerebellum (CBL). The time sensitivity (S) was defined as d{ln(SUV)}/d{ln(t)} and its value was obtained by linear regression of ln(D-SUV/E-SUV) vs ln(t (D)/t (E)). Patients with cerebellar variations greater than 30% in SUV between E- and D-PET was excluded from the analysis. RESULTS: Two patients from P.I were excluded due to wide cerebellar SUV variations. D-SUV were significantly higher than E-SUV in CA1 for both P.I (18.9 +/- 6.9 vs 14.8 +/- 5.6, p < 0.0005) and P.II (11.5 +/- 7.9 vs 9.7 +/- 6.9, p = 0.013). The S values for CA1 in P.I and P.II were 0.67 and 0.17, respectively. The D-SUV were also higher than E-SUV in CBL for both P.I (12.5 +/- 1.6 vs 11.6 +/- 1.6, p < 0.0005) and P.II (7.6 +/- 1.6 vs 7.0 +/- 1.6, p = 0.008). The S values for CBL in P.I and P.II were 0.47 and 0.04, respectively, which were over 1.4-fold smaller than that of CA1, suggesting fundamental kinetic differences between CA1 and CBL. CONCLUSIONS: The time sensitivity factor reflects another kinetic parameter of tumor metabolism besides SUV when using variable dual-time FDG PET. It offers another useful diagnostic tool in optimizing choices of dual-time protocols for oncologic PET-CT and in reducing SUV variations due to time interval differences with corrections using S.