Table 2.
Characteristics of the included studies. Domain-level risk of bias findings is shown in Fig. 2
| Study | N | Location | Age | Population | Design | Magnet | Sequences | Contrast | Assessor | Risk of bias |
|---|---|---|---|---|---|---|---|---|---|---|
| Serag and Ragab, 2020 [68] | 753 | Egypt | 49.8 ± 18.7 | Healthy volunteers | R-NRS | 1.5 T | T1W1, T2W1, FLAIR | Y | Radiologist | High |
| Wang et al., 2021 [76] | 579 | China | 67.6 ± 7.6 | Healthy volunteers | P-NRS | 3 T | T1W1, T2W1, FLAIR | N | Radiologist | Low |
| Hanna et al., 2020 [28] | 125 | USA | 43.9 ± 15.2 | Healthy volunteers | P-NRS | 3 T | T1W1 | N | Neuroradiologist | High |
| Vázquez-Justes et al., 2020 [71] | 514 | Spain | 57 | Type 2 diabetics | R-NRS | 1.5 T | T1W1, T2W1, FLAIR | Y | Neuroradiologist | High |
| Keuss et al., 2019 [42] | 471 | UK | 70.7 | Healthy volunteers | P-NRS | 3 T | T1W1 T2W1, FLAIR | N | Neuroradiologist | Low |
| Glasmacher et al., 2020 [22] | 514 | UK | 60 | Early-onset cognitive disorders | R-NRS | 1.5 T | T1W, T2W, DWI, FLAIR | NR | NR | High |
| Li et al., 2019 [48] | 562 | China | 59.3 ± 2.8 | Healthy volunteers | R-NRS | 3 T | T1, T2, T2-GRE, FLAIR, PDW1, PW1, DTI, TOF 3D angio | N | Neurologist | Low |
| Bos et al., 2016 [9]a | 5800 | Netherlands | 64.9 ± 10.9 | Healthy volunteers | P-NRS | 1.5 T | T1W, T2W | N | Researchers w/medical degrees or training in neuropsychology | Low |
| Vernooij et al., 2007 [72]a | 2000 | Netherlands | 63.3 | Healthy volunteers | P-NRS | 1.5 T | T1W1, T2W1, T2W-GRE, FLAIR | N | Neuroradiologist | Low |
| Li et al., 2021 [49] | 11,679 | USA | 9.9 ± 0.62 | Healthy volunteers | R-NRS | 3 T | T1W1, T2W1 | N | Neuroradiologist | Low |
| Weber and Knopf, 2006 [77] | 2536 | Germany | 20.5 | Healthy volunteers | 1 T | T1W1, T2W1, T2W-GRE, FLAIR | Y | Radiologist | Low | |
| Cohrs et al., 2018 [15] | 569 | Germany | 9.5 ± 4.4 | Mild TBI | R-NRS | 1.5 T, 3 T | DW1, T2W, FLAIR | Y | Neuroradiologist | High |
| Alturkustani et al., 2020 [3] | 275 | USA | 38 (IQR 30–52) | Headache | P-NRS | 3 T | T1 spin-echo, T2 spin-echo, FLAIR | Y | Neuroradiologist | High |
| Yilmaz et al., 2014 [81] | 449 | Turkey | 11.2 ± 3.2 | Headache | P-NRS | 1.5 T | T1W, T2W, FLAIR | Y | Radiologist | Low |
| Kim et al., 2002 [43] | 225 | USA | 11.2 | Healthy volunteers | R-NRS | NR | T1 spin-echo, T2 spin-echo | N | Neuroradiologist | High |
| Katzman et al., 1999 [41] | 1000 | USA | 30.6 | Healthy volunteers | R-NRS | NR | T1W, T2W | N | Radiologist | High |
| Onizuka et al., 2001 [57] | 4000 | Japan | 56 | Healthy volunteers | P-NRS | 1 T | FLAIR | Y | NR | High |
| Koncz et al., 2018 [44] | 400 | Australia | 70.4 | Healthy twins | P-NRS | 1.5 T | 3D T1W, T2W, FLAIR | N | Neuropsychiatrist | High |
| Lee 2008 [64] | 2164 | Taiwan | 51.8 ± 10.6 | Healthy volunteers | P-NRS | 1.5 T | NR | NR | NR | High |
| Brugulat-Serrat et al., 2017 [12] | 575 | Spain |
58.2 (males) 57.5 (females) |
Healthy volunteers w/FHx of Alzheimer’s | R-NRS | 3 T | T1W, T2W, FLAIR, fast spin-echo, gradient-recalled echo | N | Neuroradiologist | Low |
| Hoggard et al., 2009 [31] | 525 | UK | 35 | Healthy volunteers | P-NRS | 1.5 T, 3 T | T1W, T2W | N | Neuroradiologist | High |
| Boutet et al., 2017 [11] | 503 | France | 75.3 ± 0.9 | Healthy volunteers | P-NRS | 1.5 T | T1W, T2W, FLAIR | N | Neuroradiologist | Low |
| Haberg et al., 2016 [26] | 1006 | Norway | 59.2 ± 4.2 | Healthy volunteers | P-NRS | 1.5 T | T1W, ADNI, T2W, FLAIR | Y | Neuroradiologist | Low |
| Kaiser et al., 2015 [40] | 114 | USA | 8.3 | Healthy volunteers | R-NRS | 3 T | T1W, T2W, FLAIR | N | Neuroradiologist | High |
| Cieszanowski et al., 2014 [14] | 666 | Poland | 46.4 (20–77) | Healthy volunteers | R-NRS | 1.5 T | T1W, T2W, STIR, FLAIR, GRE | Y | Radiologist | High |
| Gur et al., 2013 [25] | 1400 | USA |
No findings: 14.7 ± 3.6 Incidental finding: 14.9 ± 3.9 |
Healthy volunteers | P-NRS | 3 T | T1W, GRE | N | Neuroradiologist | Low |
| Mar et al., 2013 [52] | 926 | USA | 12.4 | Headache | R-NRS | 1.5 T, 3 T | T1W, T2W, FLAIR | N | Neuroradiologist | High |
| Sandeman et al., 2013 [65] | 700 | UK | 72.5 | Healthy volunteers | P-NRS | 1.5 T | T2W, FLAIR | Y | Neuroradiologist | Low |
| Potchen et al., 2013 [60] | 96 | USA | 11.9 ± 1.5 | Healthy volunteers | R-NRS | 0.35 T | T1W, T2W, DWI | N | Radiologist | Low |
| Reneman et al., 2012 [62] | 203 | Netherlands | 21.9 ± 3.2 | Healthy volunteers | R-NRS | 1.5 T, 3 T | 3D T1W, T2W | Y | Head/neck radiologist or neuroradiologist | Low |
| Hartwigsen et al., 2010 [29] | 206 | Germany | 25.7 ± 5.7 | Healthy volunteers | P-NRS | 3 T | NR | NR | Neuroradiologist | High |
| Lubman et al., 2002 [51] | 98 | Australia | 27 | Healthy volunteers | P-NRS | 1.5 T | NR | NR | Neuroradiologist | High |
| Illes et al., 2004 [35] | 151 | USA | 47.1 | Healthy volunteers | R-NRS | NR | NR | NR | Neuroradiologist | High |
| Tsushima et al., 2005 [70] | 1113 | Japan | 52.6 ± 8.5 | Healthy volunteers | R-NRS | 1 T | T1W, T2W, TOF-MRA | N | Neuroradiologist | Low |
| Alphs et al., 2006 [2] | 656 | USA | 61 | Lead-exposed | P-NRS | NR | T1W, T2W | NR | NR | High |
aReports of the same study. Data were amalgamated to maximise detail
R-NRS retrospective non-randomised study, P-NRS prospective non-randomised study, NR not reported, TBI traumatic brain injury