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Table 2 Intramodality and intermodality agreements of single and total erosion volume, measured on computed tomography (CT) and magnetic resonance imaging (MRI)

From: Detection of bone erosions in rheumatoid arthritis wrist joints with magnetic resonance imaging, computed tomography and radiography

  Reading A (mm3) Reading B (mm3) Mean of readings A and B (mm3) Spearman ρ Absolute difference (mm3)a Absolute numerical difference (mm3) Relative difference (%)b Relative numerical difference (%) Coefficient of variation
Intramodality agreement: CT (reading A) vs CT (reading B) and MRI (reading A) vs MRI (reading B)
Volume per erosion          
CT (n = 135) 13 (4; 1–245) 14 (4; 1–264) 13 (4; 1–255) 0.92* -1 (0; -28 to 12) 2 (1; 0–28) -7 (0; -120 to 100) 29 (22; 0–120) 0.15 (0.11; 0–0.60)
MRI (n = 90) 17 (10; 1–132) 17 (11; 1–138) 17 (11; 1–133) 0.90* 0 (0; -23 to 18) 4 (3; 0–23) 0 (0; -100 to 86) 28 (25; 0–100) 0.14 (0.13 0–0.50)
Volume per person with erosions          
CT (n = 17) 102 (49; 2–519) 108 (56; 3–535) 105 (55; 3–527) 0.99* -6 (-2; -54 to 19) 12 (7; 1–54) -10 (-6; -43 to 15) 16 (15; 3–43) 0.08 (0.07; 0.02–0.21)
MRI (n = 15) 101 (80; 5–409) 100 (78; 5–409) 100 (76; 5–409) 0.95* 1 (0; -23 to 18) 7 (5; 0–23) 2 (0; -22 to 25) 8 (6; 0–25) 0.04 (0.03; 0–0.13)
Intermodality agreement (CT vs MRI) c
Volume per erosion of all concordant erosions (n = 64)          
CT 21 (5; 1–245) 22 (5; 1–255) 21 (5; 1–255)       
     0.55* 2 (-5; -55 to 132) 17 (9; 0–131) -54 (-59; -174 to 167) 90 (92; 0–174) 0.46 (0.45; 0–0.87)
MRI 20 (13; 1–132) 19 (13; 1–138) 19 (13; 1–133)       
Total volume per person of all concordant erosions (n = 15)          
CT 88 (18; 1–514) 93 (23; 1–528) 91 (21; 1–521)       
     0.89* 8 (-7; -56 to 147) 40 (16; 4–147) -48 (-63; -139 to 64) 72 (64; 6–139) 0.36 (0.32; 0.03–0.70)
MRI 83 (78; 5–374) 83 (62; 5–375) 83 (71; 5–375)       
Total volume per person of all erosions (n = 19)          
CT 91 (36; 0–519) 100 (49, 0–535) 94 (38; 0–527)       
     0.82* 15 (2; -60 to 118) 41 (31; 0–118) 13 (6; -129 to 200) 68 (52; 0–200) 0.34 (0.26; 0–1.0)
MRI 79 (67; 0–409) 79 (67; 0–409) 79 (63; 0–409)       
  1. Data presented as the mean (median; range). Reading A and reading B, volumes obtained at the first (reading A) and second (reading 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. *P < 0.01. aIntramodality agreement, reading A minus reading B; intermodality agreement, CT erosion volume minus MRI erosion volume. bIntramodality agreement, positive values refer to larger erosion volume at reading A than reading B, and vice versa; intermodality agreement, positive values refer to larger erosion volume on CT than MRI, and vice versa. cValues on intermodality agreement are comparisons between CT and MRI erosions volumes.