Table 1 Intramodality and intermodality agreements of single erosion and total erosion volume in RA MCP-joints, measured on CT and MRI. Values on intermodality agreement are comparisons between CT and MRI erosions volumes.
Reading A (mm3), mean (median; range)Reading B (mm3), mean (median; range)Mean reading A and B (mm3), mean (median; range)Spearman’s rhoAbsolute difference (mm3),* mean (median; range)Absolute numerical difference (mm3),† mean (median; range)Relative difference (%) mean (median; range)Coefficient of variation, mean (median; range)
Intramodality agreement (CT (A) vs. CT (B) and MRI (A) vs. MRI (B))
Volume per erosion
CT (n = 77)27 (10; 0 to 272;)24 (11; 0 to 224)26 (10; 0 to 248)0.96‡3 (0; ÷71 to 56)6 (2; 0 to 71)22 (15; 0 to 93)0.11 (0.08; 0 to 0.47)
MRI (n = 62)29 (18; 1 to 159)30 (20; 1 to 166)30 (18; 1 to 163)0.95‡0 (0; ÷62 to 43)7 (3; 0 to 62)26 (20; 0 to 82)0.13 (0.10; 0 to 0.41)
Volume per patient (n = 17)
CT127 (35; 5 to 510)113 (35; 6 to 460)120 (33; 6 to 485)0.99‡13 (0; ÷56 to 144)24 (5; 0 to 144)19 (13; 0 to 75)0.09 (0.07; 0 to 0.38)
MRI112 (52; 5 to 391)111 (57; 6 to 397)111 (58; 6 to 389)0.97‡2 (÷3; ÷33 to 110)16 (9; 1 to 110)18 (18; 2 to 67)0.09 (0.09; 0.01 to 0.33)
Intermodality agreement (CT vs. MRI)**
Volume per erosion of all concordant erosions (n = 51)
CT36 (13; 2 to 272)33 (12; 2 to 224)35 (12; 2 to 248)0.64‡÷1 (÷6; ÷47 to 113)18 (11; 0 to 113)68 (61; 0 to 164)0.34 (0.30; 0 to 0.82)
MRI36 (25; 1 to 159)36 (24; 1 to 166)36 (25; 1 to 163)
Total volume per patient of all concordant erosions (n = 17)
CT109 (22; 4 to 507)98 (19; 3 to 457)104 (21; 4 to 482)0.89‡÷4 (÷15; ÷102 to 117)37 (24; 2 to 117)67 (67; 1 to 147)0.33 (0.36; 0.01 to 0.73)
MRI109 (52; 5 to 380)107 (57; 6 to 397)108 (54; 6 to 389)
Total volume per person of all erosions (n = 21)
CT102 (27; 0 to 510)92 ( 30; 0 to 460)97 (29; 0 to 485)0.89‡10 (0; ÷39 to 113)21 (8; 0 to 113)50 (43; 0 to 142)0.25 (0.21; 0 to 071)
MRI91 (44; 0 to 391)90 (46; 0 to 389)90 (46; 0 to 389)
  • CT, Computed tomography; MCP, Metacarpophalangeal; MRI, Magnetic resonance imaging; RA, Rheumatoid arthritis.

  • *Intramodality agreement: reading A minus reading B; intermodality agreement: CT erosion volume minus MRI erosion volume; **For intermodality agreement values in the five right columns refer to the relation between erosion volumes on CT and erosion volumes on MRI; †For intermodality agreement: CT erosion volume minus MRI erosion volume; ‡p<0.01.

  • Reading A and reading B denote volumes obtained at the first (A) and second (B) volume measurements, done by the same observer 1 week apart. The mean value of volumes obtained at reading A and B was used for the comparison of CT and MRI volumes.