title: Optimal differentiation of high- and low-grade glioma and metastasis: a meta-analysis of perfusion, diffusion, and spectroscopy metrics.
abstract: BACKGROUND
  To perform a meta-analysis of advanced magnetic resonance imaging (MRI) metrics, including relative cerebral blood volume (rCBV), normalized apparent diffusion coefficient (nADC), and spectroscopy ratios choline/creatine (Cho/Cr) and choline/N-acetyl aspartate (Cho/NAA), for the differentiation of high- and low-grade gliomas (HGG, LGG) and metastases (MTS).
  
  
  METHODS
  For systematic review, 83 articles (dated 2000-2013) were selected from the NCBI database. Twenty-four, twenty-two, and eight articles were included respectively for spectroscopy, rCBV, and nADC meta-analysis. In the meta-analysis, we calculated overall means for rCBV, nADC, Cho/Cr (short TE-from 20 to 35 ms, medium-from 135 to 144 ms), and Cho/NAA for the HGG, LGG, and MTS groups. We used random effects model to obtain weighted averages and select thresholds.
  
  
  RESULTS
  Overall means (with 95% CI) for rCBV, nADC, Cho/Cr (short and medium echo time, TE), and Cho/NAA were: for HGG 5.47 (4.78-6.15), 1.38 (1.16-1.60), 2.40 (1.67-3.13), 3.27 (2.78-3.77), and 4.71 (3.24-6.19); for LGG 2.00 (1.71-2.28), 1.61 (1.36-1.87), 1.46 (1.20-1.72), 1.71 (1.49-1.93), and 2.36 (1.50-3.23); for MTS 5.06 (3.85-6.27), 1.35 (1.06-1.64), 1.89 (1.72-2.06), 3.14 (1.57-4.72), (Cho/NAA was not available). LGG had significantly lower rCBV, Cho/Cr, and Cho/NAA values than HGG or MTS. No significant differences were found for nADC.
  
  
  CONCLUSIONS
  Best differentiation between HGG and LGG is obtained from rCBV, Cho/Cr, and Cho/NAA metrics. MTS could not be reliably distinguished from HGG by the methods investigated.
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania. jurgita.usinskiene@gmail.com.
authors.forename: Jurgita
authors.initials: J
authors.lastname: Usinskiene
authors.affiliation: Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Agne
authors.initials: A
authors.lastname: Ulyte
authors.affiliation: Department of Physics, Oslo University Hospital, Oslo, Norway.|The Intervention Centre, Oslo University Hospital, Oslo, Norway.
authors.forename: Atle
authors.initials: A
authors.lastname: Bjørnerud
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania.
authors.forename: Jonas
authors.initials: J
authors.lastname: Venius
authors.affiliation: General Anti-Cancer and Oncological Hospital "St. Savvas", Athens, Greece.
authors.forename: Vasileios K
authors.initials: VK
authors.lastname: Katsaros
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania.
authors.forename: Ryte
authors.initials: R
authors.lastname: Rynkeviciene
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania.|Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Simona
authors.initials: S
authors.lastname: Letautiene
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania.
authors.forename: Darius
authors.initials: D
authors.lastname: Norkus
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania.
authors.forename: Kestutis
authors.initials: K
authors.lastname: Suziedelis
authors.affiliation: Faculty of Medicine, Vilnius University, Vilnius, Lithuania.|Neuroangiosurgery Center, Faculty of Medicine Vilnius University, Vilnius, Lithuania.
authors.forename: Saulius
authors.initials: S
authors.lastname: Rocka
authors.affiliation: Department of Electronic Systems, Vilnius Gedimino Technical University, Vilnius, Lithuania.
authors.forename: Andrius
authors.initials: A
authors.lastname: Usinskas
authors.affiliation: National Cancer Institute, Radiology Center, Santariskiu 1, LT-08660, Vilnius, Lithuania.|Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
authors.forename: Eduardas
authors.initials: E
authors.lastname: Aleknavicius
mesh_terms: D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005910:Glioma / Q000000981:diagnostic imaging* / Q000556:secondary; D006801:Humans; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D060787:Neoplasm Grading
keywords: Brain tumor; Diffusion magnetic resonance imaging; Magnetic resonance spectroscopy; Meta-analysis; Perfusion magnetic resonance imaging