Accuracy of 18F-FDG PET/CT in patients with the suspicion of cardiac implantable electronic device infections.

BACKGROUND: Utility of 18F-FDG PET/CT in diagnosing infective endocarditis (IE) associated with cardiac implantable electronic devices (CIEDs) is not well established. Current ESC guidelines recommend the use of FDG-PET imaging in patients with CIEDs and positive blood cultures, but the number of studies evaluating the diagnostic performance of FDG-PET imaging in these patients remain limited. Our objective was to assess the diagnostic yield of 18F-FDG PET/CT in patients with suspected CIED infections, differentiating between pocket infection (PI) and lead infection (CIED-IE). METHODS AND RESULTS: From 2013 to 2018, all patients (n = 63) admitted to a hospital with suspected CIED infection were prospectively recruited, undergoing a diagnostic work-up including a PET/CT. Explanted devices and material from the pocket were cultured. 14 cases corresponded to isolated PI and 13 were categorized as CIED-IE. Considering radionuclide uptake in the intracardiac portion of the lead, sensitivity and specificity of PET/CT for CIED-IE were 38.5% and 98.0%, respectively. Positive (19.2) and negative (0.6) likelihood ratio values, suggest that a positive PET/CT is much more probable to correspond to a patient with CIED-IE, whereas it is not possible to exclude this diagnosis when negative. For PI, sensitivity and specificity were 72.2% and 95.6%, respectively. CONCLUSIONS: The yield of 18F-FDG PET/CT for suspected CIED infections differs depending on the site of infection. Due to very high specificity but poor sensitivity, negative studies must be interpreted with caution if the suspicion of CIED-IE is high.

Not All Heart Uptakes on 99mTc-DPD Scintigraphy Are Amyloidosis: Chloroquine-Induced Cardiomyopathy.

ABSTRACT: This was the case of a 61-year-old woman with a medical history significant for hypertension and rheumatoid arthritis treated with chloroquine for the last 10 years. She was admitted to our hospital for heart failure symptoms. Echocardiography revealed severe concentric left ventricular hypertrophy. Serum and urine immunofixation electrophoresis and serum light chain assay were negative. No late gadolinium enhancement was observed on cardiovascular magnetic resonance. 99mTc-99mTc-DPD (3,3-diphosphono-1,2-propanodicarboxylic acid) scintigraphy showed myocardial uptake (Perugini score 2/3). Genetic testing excluded hereditary transthyretin cardiac amyloidosis. Endomyocardial biopsy analysis did not show findings suggestive of amyloidosis but consistent with chloroquine toxicity. Chloroquine-mediated cardiotoxicity is rare, and there are very few reports about bone scintigraphy imaging features.

Usefulness of positron emission tomography/computed tomography in patients with valve-tube graft infection.

OBJECTIVE: Infection of valved aortic grafts is a rare entity whose diagnosis remains challenging. Positron emission tomography (PET)/CT has become a criterion for the diagnosis of infective endocarditis (IE) in prosthetic valves, but its role on ascending aortic graft infections remains unclear. This study aims to assess the diagnostic value of PET/CT in patients with valved aortic graft infection. METHODS: 12 episodes with a valved aortic graft who had undergone a PET/CT due to suspicion of IE were prospectively included (group I) and compared with five controls free of infection who underwent PET/CT for other reasons (group II). Pathological uptake of 18F-fluorodeoxyglucose (FDG) and its pattern at the prosthetic valve and aortic graft were studied. RESULTS: Diagnosis of IE was confirmed in 9 out of 12 episodes of group I. 18F-FDG uptake was detectable in eight out of nine cases with a final diagnosis of IE. The most repeated pattern of uptake was homogeneous around the valve and heterogeneous around the tube. There was one false-negative study. Of the three patients in which IE was ruled out, there were two false positives and one true negative. In group II, there were three patients with a positive PET/CT study, two of them had active aortitis and the third was considered false positive. CONCLUSIONS: 18F-FDG PET/CT shows high sensitivity in the detection of infected aortic grafts. Thus, this technique should be considered in the diagnostic work-up of patients with suspicion of aortic graft infection. However, further validation of this approach is needed.

Assessment of the diagnostic accuracy of 18F-FDG PET/CT in prosthetic infective endocarditis and cardiac implantable electronic device infection: comparison of different interpretation criteria.

PURPOSE: The diagnosis of prosthetic valve (PV) infective endocarditis (IE) and infection of cardiac implantable electronic devices (CIEDs) remains challenging. The aim of this study was to assess the usefulness of 18F-FDG PET/CT in these patients and analyse the interpretation criteria. METHODS: We included 41 patients suspected of having IE by the Duke criteria who underwent 18F-FDG PET/CT. The criteria applied for classifying the findings as positive/negative for IE were: (a) visual analysis of only PET images with attenuation-correction (AC PET images); (b) visual analysis of both AC PET images and PET images without AC (NAC PET images); (c) qualitative analysis of NAC PET images; and (d) semiquantitative analysis of AC PET images. 18F-FDG PET/CT was considered positive for IE independently of the intensity and distribution of FDG uptake. The gold standard was the Duke pathological criteria (if tissue was available) or the decision of an endocarditis expert team after a minimum 4 months follow-up. RESULTS: We studied 62 areas with suspicion of IE, 28 areas (45 %) showing definite IE and 34 (55 %) showing possible IE. Visual analysis of only AC PET images showed poor diagnostic accuracy (sensitivity 20 %, specificity 57 %). Visual analysis of both AC PET and NAC PET images showed excellent sensitivity (100 %) and intermediate specificity (73 %), focal uptake being more frequently associated with IE. The accuracy of qualitative analysis of NAC PET images depended on the threshold: the maximum sensitivity, specificity and accuracy achieved were 88 %, 80 %, 84 %, respectively. In the semiquantitative analysis of AC PET images, SUVmax was higher in areas of confirmed IE than in those without IE (∆SUVmax 2.2, p < 0.001). When FDG uptake was twice that in the liver, IE was always confirmed, and SUVmax 5.5 was the optimal threshold for IE diagnosis using ROC curve analysis (area under the curve 0.71). CONCLUSION: The value of 18F-FDG PET/CT in the diagnosis of suspected IE of PVs and CIEDs is highly dependent on patient preparation and the method used for image interpretation. Based on our results, the best method is to consider a study positive for IE when FDG uptake is present in both AC PET and NAC PET images.

Visual and statistical analysis of ¹8F-FDG PET in primary progressive aphasia.

PURPOSE: Diagnosing progressive primary aphasia (PPA) and its variants is of great clinical importance, and fluorodeoxyglucose (FDG) positron emission tomography (PET) may be a useful diagnostic technique. The purpose of this study was to evaluate interobserver variability in the interpretation of FDG PET images in PPA as well as the diagnostic sensitivity and specificity of the technique. We also aimed to compare visual and statistical analyses of these images. METHODS: There were 10 raters who analysed 44 FDG PET scans from 33 PPA patients and 11 controls. Five raters analysed the images visually, while the other five used maps created using Statistical Parametric Mapping software. Two spatial normalization procedures were performed: global mean normalization and cerebellar normalization. Clinical diagnosis was considered the gold standard. RESULTS: Inter-rater concordance was moderate for visual analysis (Fleiss' kappa 0.568) and substantial for statistical analysis (kappa 0.756-0.881). Agreement was good for all three variants of PPA except for the nonfluent/agrammatic variant studied with visual analysis. The sensitivity and specificity of each rater's diagnosis of PPA was high, averaging 87.8 and 89.9% for visual analysis and 96.9 and 90.9% for statistical analysis using global mean normalization, respectively. In cerebellar normalization, sensitivity was 88.9% and specificity 100%. CONCLUSION: FDG PET demonstrated high diagnostic accuracy for the diagnosis of PPA and its variants. Inter-rater concordance was higher for statistical analysis, especially for the nonfluent/agrammatic variant. These data support the use of FDG PET to evaluate patients with PPA and show that statistical analysis methods are particularly useful for identifying the nonfluent/agrammatic variant of PPA.

Impacto de la tomografía por emisión de positrones en el tratamiento de pacientes con sospecha de enfermedad residual o recurrente de cáncer diferenciado de tiroides / Impact of positron emission tomography on therapeutic decisions in patients with suspected residual or recurrent differentiated thyroid cancer

Objetivo: Valorar las modificaciones en el tratamiento inducidas por la tomografía por emisión de positrones con 18F-desoxiglucosa (PET-FDG) en pacientes con sospecha de enfermedad residual o recurrente de cáncer diferenciado de tiroides (CDT) con tiroglobulina (Tg) elevada y rastreo corporal total (RCT) con 131I negativo. Pacientes y método: Se analizó de forma retrospectiva a un grupo de 50 pacientes (35 mujeres y 15 varones) tratados de CDT, a los que se hizo estudio PET-FDG (51 exploraciones) por elevación de Tg con RCT con 131I negativo. La comprobación de resultados se hizo según la anatomía patológica, respuesta al tratamiento o seguimiento clínico. Valoraron el impacto los médicos, que indicaron cómo influyó esta técnica en las decisiones terapéuticas, y se clasificó como alto, moderado, bajo o sin impacto, según los criterios de Hicks modificados. Resultados: La PET-FDG tuvo alto impacto en 18 (35,3%) pacientes, en los que se modificó la estrategia terapéutica; en 2 (3,9%) el impacto fue moderado, ya que no se aplicó tratamiento pero el resultado negativo de la PET-FDG evitó la realización de otros métodos diagnósticos; en 18 (35,3%), el impacto fue bajo, ya que no modificó el tratamiento; en 13 (25,5%) no tuvo impacto, pues no se tuvo en cuenta a la hora de decidir el tratamiento. Conclusiones: La PET-FDG resulta una técnica diagnóstica útil para la toma de decisiones terapéuticas en pacientes con sospecha de enfermedad residual o recurrente de CDT que presentan Tg elevada y RCT con 131I negativo (AU)

Objective: To assess FDG-PET-induced treatment modifications in patients with suspected recurrent or residual differentiated thyroid cancer (DTC) with elevated thyroglobulin (Tg) and negative 131I whole body scan (WBS). Patients and method: Fifty-one FDG-PET studies due to elevated Tg with negative WBS were retrospectively analyzed in 50 patients treated for DTC (35 women and 15 men). The results were verified by pathological analysis, treatment response or clinical follow-up. The impact of FDG-PET was assessed by asking the physicians to indicate how this technique had affected their therapeutic decisions and the influence was classified as high, moderate, low or nil according to Hicks' modified criteria. Results: The impact of FDG-PET was high in 18 patients (35.3%), in whom the therapeutic strategy was modified. A moderate impact was found in 2 patients (3.9%) since no treatment was applied; however, in these patients, negative FDG-PET results obviated the need for other diagnostic methods. Impact was low in 18 patients (35.3%) as treatment was not modified, and was null in 13 (25.5%) since this technique was not considered when therapeutic decisions were made. Conclusions: FDG-PET is a useful diagnostic technique for therapeutic decision-making in patients with suspected residual or recurrent DTC, elevated Tg and negative 131I-WBS (AU)