Table 1. Characteristics of the included studies.

Study	Year	Nation	N	Tumor	Age	Design	Field	Index	b valuea	rb
Sugahara [26]	1999	Japan	20	brain	Adult	prospective	1.5 T	minADC	1200	−0.75
Gupta [20]	2000	USA	18	brain	Adult	prospective	1.5 T	meanADC	940	−0.65c
Gauvain [19]	2001	USA	12	brain	Children	retrospective	1.5 T	meanADC	1012	−0.67
Kono [25]	2001	Japan	17	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.75
	2001	Japan	18	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.65
Guo A [32]	2002	USA	28	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.46
Guo Y [14]	2002	China	47	breast	Adult	retrospective	1.5 T	meanADC	1000	−0.51
Chen [10]	2005	China	34	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.52
Hayashida [22]	2006	Japan	13	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.68
Plank [30]	2007	Austria	8	spinal	Adult	retrospective	1.5 T	meanADC	700	−0.64d
Matoba [27]	2007	Japan	9	lung	Adult	prospective	1.5 T	meanADC	577	−0.75
Humphries [28]	2007	USA	19	various	Children	prospective	1.5 T	meanADC	1000	−0.72c
Zelhof [15]	2008	UK	38	prostate	Adult	prospective	3.0 T	meanADC	500	−0.48
Hatakenaka [30]	2008	Japan	124	breast	Adult	prospective	1.5 T	meanADC	1000	−0.65c
Manenti [21]	2008	Italy	27	renal	Adult	retrospective	3.0 T	meanADC	500	−0.71
Yoshikawa [33]	2008	Japan	27	breast	Adult	retrospective	1.5 T	meanADC	800	0.05
Woodhams [13]	2009	Japan	15	breast	Adult	retrospective	1.5 T	meanADC	1500	−0.74
Wang [16]	2009	China	38	prostate	Adult	retrospective	1.5 T	meanADC	500	−0.63
Yamashita [31]	2009	Japan	26	brain	Adult	retrospective	1.5 T	minADC	1000	−0.69
Gibbs [9]	2009	UK	20	prostate	Adult	prospective	3.0 T	meanADC	500	−0.68
Kikuchi [11]	2009	Japan	10	brain	Adult	retrospective	1.5 T	minADC	1000	−0.66
Jenkinson [32]	2010	UK	17	brain	Adult	retrospective	1.5 T	both	1000	0.04
Ellingson [18]	2010	USA	17	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.88c
Barajas [23]	2010	USA	18	brain	Adult	retrospective	1.5 T	meanADC	1000	−0.52
Kyriazi [24]	2010	UK	8	ovarian	Adult	retrospective	1.5 T	meanADC	1050	−0.77
	2010	UK	7	omental	Adult	retrospective	1.5 T	meanADC	1050	−0.72
Wang [31]	2011	USA	18	pancreas	Adult	retrospective	1.5 T	meanADC	600	−0.35
Goyal [12]	2012	India	36	renal	Adult	retrospective	1.5 T	meanADC	500	−0.31
Doskaliyev [17]	2012	Japan	24	brain	Adult	retrospective	3.0 T	meanADC	1000	−0.58
Ginat [29]	2012	USA	18	skull	Adult	retrospective	1.5 T	meanADC	1000	−0.58

minADC = measurement of minimum ADC value, meanADC = measurement of average ADC value.

^aThe unit of the b value is s/m².

^br = Spearman correlation coefficient.

^cr values were calculated based on r² values.

^dThe r value was calculated indirectly from the scatter diagram.