title: Utility of FDG-PETCT and magnetic resonance spectroscopy in differentiating between cerebral lymphoma and non-malignant CNS lesions in HIV-infected patients.
abstract: OBJECTIVE
  In HIV infected patients, MRI cannot reliably differentiate between central nervous system (CNS) lymphoma and non-malignant CNS lesions, particularly cerebral toxoplasmosis (CTOX). This study prospectively investigates the utility of FDG PET-CT and magnetic resonance spectroscopy (MRS) in discriminating CNS lymphoma from non-malignant CNS lesions in HIV infected patients, and assesses the ability of FDG PET-CT to guide the use of early brain biopsy.
  
  
  METHODS
  10 HIV patients with neurological symptoms and contrast enhancing lesions on MRI were commenced on anti-toxoplasmosis therapy before undergoing FDG PET-CT and MRS. Brain biopsies were sought in those with FDG PET-CT suggestive of CNS lymphoma, and in those with a negative FDG PET-CT scan who failed to respond to therapy. Final diagnosis was based on histology or treatment response.
  
  
  RESULTS
  Two patients were confirmed to have CNS lymphoma and FDG PET-CT was consistent with this diagnosis in both. Six patients had cerebral toxoplasmosis in all of whom FDG PET-CT was consistent with non-malignant disease. One patient had progressive multifocal leukoencephalopathy (PML), FDG PET-CT was equivocal. One patient had a haemorrhagic brain metastasis and FDG PET-CT wrongly suggested non-malignant disease. MRS was performed successfully in eight subjects: three results were suggestive of CNS lymphoma (one true positive, two false positive), four suggested CTOX (two false negative, two true negative), one scan was equivocal.
  
  
  CONCLUSIONS
  FDG PET-CT correctly identified all cases of CNS lymphoma and CTOX, supporting its use in this situation. MRS was unhelpful in our cohort.
authors.affiliation: Department of Radiology, The Christie NHS Foundation Trust, Wilmslow Road, Manchester, United Kingdom. tdwestwood@googlemail.com
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Westwood
authors.forename: Celia
authors.initials: C
authors.lastname: Hogan
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Julyan
authors.forename: Glyn
authors.initials: G
authors.lastname: Coutts
authors.forename: Suzie
authors.initials: S
authors.lastname: Bonington
authors.forename: Bernadette
authors.initials: B
authors.lastname: Carrington
authors.forename: Ben
authors.initials: B
authors.lastname: Taylor
authors.forename: Saye
authors.initials: S
authors.lastname: Khoo
authors.forename: Alec
authors.initials: A
authors.lastname: Bonington
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis; D001927:Brain Diseases / Q000175:diagnosis* / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D015658:HIV Infections / Q000175:diagnosis* / Q000378:metabolism; D006801:Humans; D016483:Lymphoma, AIDS-Related / Q000175:diagnosis* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D064847:Multimodal Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D006113:United Kingdom
chemical_list: D015415:Biomarkers; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18