The role of 18F-FDG PET/CT in management of paraneoplastic limbic encephalitis combined with small cell lung cancer: A case report.

RATIONALE: Limbic encephalitis is one of the most common paraneoplastic neurological disorders (PND). The role of brain Fluorine-18-fluorodeoxyglucose position emission tomography/computed tomography (CT) in paraneoplastic limbic encephalitis (PLE) and of the whole body 18F-FDG PET/CT in this setting, remains still not well defined. PATIENT CONCERNS: We report a case of a patient with chronic inflammatory rheumatism, psoriasis and Hashimoto thyroiditis and subsequent appearance of static and dynamic ataxia and episodic memory deficit who was diagnosed as PLE combined with small cell lung cancer (SCLC). DIAGNOSES: The diagnosis of SCLC was made with EBUS-TBNA of a mediastinal lymph node. INTERVENTIONS: Whole-body 18F-FDG PET/CT was performed for the initial staging of SCLC, in the planning of radiotherapy treatment, to evaluate therapeutic response and in the follow-up. A dedicated brain scan was included to the same PET session. Whole-body contrast enhanced computed tomography (CT) and contrast enhanced whole-brain MRI were also performed. OUTCOMES: She was administered neoadjuvant chemioterapy with Cisplatin and Etoposide with concomitant radiotherapy treatment. Whole body 18F-FDG PET/CT showed a complete metabolic response already after 3 cycles of chemioterapy. Brain functional study showed a metabolic pattern characterized by the migration of hypermetabolism in the bilateral hippocampal areas during the therapeutic treatment, which correlated with the persistence of clinical symptoms. LESSONS: In the era of personalized medicine and targeted therapy, this case highlights the importance of the 18F-FDG PET/CT study as an accurate tool to identify PLE and to guide the diagnostic work-up of the underlying tumor. Considering that most of these are 18F-FDG avid tumors and that the 18F-FDG PET/CT scan is often added to the diagnostic work-up when screening patients for malignancy, this functional imaging can play a decisive role.

Role of quantitative myocardial positron emission tomography for risk stratification in patients with hypertrophic cardiomyopathy: a 2016 reappraisal.

AIMS: Myocardial blood flow <1.1 mL/min/g following dipyridamole (Dip-MBF) assessed by positron emission tomography (PET) was identified in 2003 as an important outcome predictor in hypertrophic cardiomyopathy (HCM), based on scans performed in the 90s. However, such extreme Dip-MBF impairment is rarely observed in contemporary cohorts. We, therefore, reassessed the Dip-MBF threshold defining high-risk HCM patients. METHODS: Dip-MBF was measured using 13N-ammonia in 100 HCM consecutive patients, prospectively enrolled and followed for 4.0 ± 2.2 years. Outcome was assessed based on tertiles of Dip-MBF. The study end-point was a combination of cardiovascular death, progression to severe functional limitation, cardioembolic stroke, life-threatening ventricular arrhythmias. RESULTS: Global Dip-MBF was 1.95 ± 0.85, ranging from 0.7 to 5.9 mL/min/g. Dip-MBF tertile cut-off values were: 0.73 to 1.53 mL/min/g (lowest), 1.54 to 2.13 mL/min/g (middle), and 2.14 to 5.89 mL/min/g (highest). During follow-up, lowest tertile Dip-MBF was associated with sevenfold independent risk of unfavorable outcome compared to the other two tertiles. Dip-MBF 1.35 mL/min/g was identified as the best threshold for outcome prediction. Regional perfusion analysis showed that all cardiac deaths (n = 4) occurred in patients in the lowest tertile of lateral wall Dip-MBF (≤1.72 mL/min/g); septal Dip-MBF was not predictive. CONCLUSIONS: Dip-MBF confirms its role as potent predictor of outcome in HCM. However, the threshold for prediction in a contemporary cohort is higher than that reported in earlier studies. Dip-MBF impairment in the lateral wall, possibly reflecting diffuse disease extending to non-hypertrophic regions, is a sensitive predictor of mortality in HCM.

Validation of pixel-wise parametric mapping of myocardial blood flow with ¹³NH3 PET in patients with hypertrophic cardiomyopathy.

PURPOSE: Transmural abnormalities in myocardial blood flow (MBF) are important causes of ischaemia in patients with left ventricular (LV) hypertrophy. The study aimed to test whether pixel-wise parametric mapping of (13)NH3 MBF can reveal transmural abnormalities in patients with hypertrophic cardiomyopathy (HCM). METHODS: We submitted 11 HCM patients and 9 age-matched controls with physiological LV hypertrophy to rest and stress (dipyridamole) (13)NH3 PET. We measured MBF using a compartmental model, and obtained rest and stress parametric maps. Pixel MBF values were reorganized to obtain subendocardial and subepicardial MBF of LV segments. RESULTS: MBF at rest was higher in the subendocardial than in the subepicardial layer: 0.78 ± 0.19 vs. 0.60 ± 0.18 mL/min/g in HCM patients; 0.92 ± 0.24 vs. 0.75 ± 0.24 mL/min/g in controls (both p < 0.0001). Transmural perfusion gradient (TPG = subendocardial MBF/subepicardial MBF) at rest was similar: 1.35 ± 0.31 in HCM patients; 1.28 ± 0.27 in controls (NS). During stress, controls maintained higher subendocardial MBF: 2.44 ± 0.54 vs. 1.96 ± 0.67 mL/min/g tissue (p < 0.0001), with a TPG of 1.33 ± 0.35 (NS vs. rest). In HCM patients, the difference between subendocardial and subepicardial MBF was reduced (1.46 ± 0.48 vs. 1.36 ± 0.48 mL/min/g tissue, p < 0.01) and TPG decreased to 1.11 ± 0.34 (p < 0.0001 vs. rest and vs. controls). In HCM patients 8 of 176 segments had subendocardial MBF less than -2 × SD of the mean, versus none of 144 segments in controls (p < 0.01). CONCLUSION: Pixel-wise parametric mapping of (13)NH3 MBF enables the identification of transmural abnormalities in patients with HCM.