The more you look, the more you find: challenging results on FDG-PET CT in a patient with neurofibromatosis type I

Evaluation of the most commonly used (semi-)quantitative parameters of 18F-FDG PET/CT to detect malignant transformation of neurofibromas in neurofibromatosis type 1

In patients with neurofibromatosis type 1, transformation of neurofibromas into a malignant peripheral nerve sheath tumor (MPNST) is a severe complication of the disease. Fluorine-18-fluorodeoxyglucose PET/computed tomography (PET/CT) is a viable option for detecting malignant tumors in neurofibromatosis type 1 patients. The aim of this review was to assess the diagnostic performance of the most frequently used parameters of PET/CT in detecting MPNST. An extensive computer search was performed using the Cochrane Library, Pubmed, and Medline/Embase databases. Two reviewers independently extracted data of relevant studies and assessed the methodological quality (QUADAS-2). The diagnostic performance of PET/CT parameters in individual studies was determined by calculating a diagnostic odds ratio (DOR) using the absolute numbers of true-positive, true-negative, false-positive, and false-negative test results. A total of eight studies were included, of which three evaluated the standardized uptake value as a diagnostic parameter, two assessed the tumor-to-liver (T/L) ratio, and three articles described both parameters. The cut-off values for maximum standardized uptake value (SUVmax) ranged from 3.2 to 4.5; for the T/L ratio, the cut-off values were between 1.0 and 4.3. The sensitivity and specificity ranged from 90 to 100% and from 80 to 100%, respectively (SUVmax). T/L ratios were associated with 92-100% sensitivity and 72-94% specificity. The corresponding DORs ranged from 57 to 145 (SUVmax) and 35 to 655 (T/L ratio). Both the SUV and the T/L ratio are associated with high sensitivity combined with acceptable specificity in detecting MPNST. There is a tendency toward higher DORs using the T/L ratio, but the number of studies is limited.

Usefulness of Positron Emission Tomography in Patients with Syphilis: A Systematic Review of Observational Studies

Background:

Diagnosis of syphilis is difficult. Follow-up and therapy evaluation of syphilitic patients are poor. Little is known about positron emission tomography (PET) in syphilis. This review was to systematically review usefulness of PET for diagnosis, disease extent evaluation, follow-up, and treatment response assessment in patients with syphilis.

Methods:

We searched PubMed, EMBASE, SCOPUS, Cochrane Library, Web of Science, ClinicalTrials.gov, and three Chinese databases (SinoMed, Wanfang, and CNKI) for English and Chinese language articles from inception to September 2016. We also collected potentially relevant studies and reviews using a manual search. The search keywords included the combined text and MeSH terms “syphilis” and “positron emission tomography”. We included studies that reporting syphilis with a PET scan before and/or after antibiotic treatment. The diagnosis of syphilis was based on serological criteria or dark field microscopy. Outcomes include pre- and post-treatment PET scan, pre- and post-treatment computed tomography, and pre- and post-treatment magnetic resonance imaging. We excluded the articles not published in English or Chinese or not involving humans.

Results:

Of 258 identified articles, 34 observational studies were included. Thirty-three studies were single-patient case reports and one study was a small case series. All patients were adults. The mean age of patients was 48.3 ± 12.1 years. In primary syphilis, increased fluorodeoxyglucose (FDG) accumulation could be seen at the site of inoculation or in the regional lymph nodes. In secondary syphilis with lung, bone, gastrointestinal involvement, or generalized lymphadenopathy, increased FDG uptake was the most commonly detected changes. In tertiary syphilis, increased glucose metabolic activity, hypometabolic lesions, or normal glucose uptake might be seen on PET. There were five types of PET scans in neurosyphilis. A repeated PET scan after treatment revealed apparent or complete resolution of the asymmetry of radiotracer uptake.

Conclusion:

PET is helpful in targeting diagnostic interventions, characterizing disease extent, assessing nodal involvement, and treatment efficacy for syphilis.