Optimal differentiation of high- and low-grade glioma and metastasis: a meta-analysis of perfusion, diffusion, and spectroscopy metrics

Introduction 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.