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Table 1 Table summarizing performance over different substitute CT approaches

From: A review of substitute CT generation for MRI-only radiation therapy

Approach category

MRI sequence/contrast

Number

Site

Performance metric

Note

References

main

sub 1

sub 2

sub 3

   

ΔDose [%]

MAE [HU]

DSC bone

Other

  

Voxel

Semi-automatic

T1w

 

20

brain

   

1

ΔROI

[61]

Threshold

dUTE

 

1

phantom

2

 

0.81

87

Cbone

[6264]

dUTE

 

5-19

brain

0.5

230

0.49-0.65

90

Ctissue

[22, 35, 65]

Dixon

 

2

brain

   

94/77

SSbone

[66]

dUTE

Dixon

6-98

brain

  

0.75

88/88,81

SSbone, Ctissue

[6769]

Probabilistic

Clustering

Fuzzy c-means

T2w

Dixon

2-5

brain

   

97-98/75-94

SSbone

[70, 71]

T2w

T1w

10

brain

   

98/74

SSair

[52]

  

dUTE

Dixon

9

brain

 

130

   

[72]

Bayesian

Markow RF

dUTE

 

5

brain

1

204-247

0.53-0.59

  

[22]

Regression

Discriminant

dUTE

T2w

3

phantom

2.3

88

   

[73]

dUTE

T2w

3

brain

1.2

153

   

[74]

Gaussian

dUTE

T2w

5-9

brain

0.9-1.5

137-140

0.85

68-94,98

γ11, γ33

[23, 7577]

dUTE

 

5

brain

1

136-148

0.67-0.72

  

[22, 48]

Random F

dUTE

 

5

brain

1

128

0.74

  

[22]

Semi-automatic

Dual

T1w

T2w

9

prostate

0.7

75

0.91

99.9

a, γ22

[78]

T1w

T2*w

10-15

prostate

0.3-2

135

 

93

γ11

[21, 79, 80]

PCA

T1w

 

10

torso

   

5

Δbone

[81]

Sinogram

T1w

 

10

brain

  

0.85

 

b

[82]

Neural network

T1w

 

3

brain

  

0.78

  

[83]

dUTE

 

4

brain

  

0.83

  

[84]

Pattern recognition

dUTE

Dixon

10

brain

   

76

Cair

[85]

Hybrid

Neural Network

Template

dUTE

 

4

brain

  

0.77

  

[86]

Gaussian

Spatial info

dUTE

T2w

9

brain

 

130

   

[75]

Random F

Spatial info

T1w

 

9-10

brain

  

0.92-0.98

 

c

[87, 88]

Atlas

Pattern recognition

Patch

Patch Probabilistic

T1w

 

5

40

brain

0.5

85

0.84

0.75

  

[48]

[89]

Deformable

T1w

 

28

whole body

   

0.88

DSCbrain

[90]

T1w

T2w

5-17

brain

1-2.5

97-114

0.63-0.83

1.7

ΔROI

[24, 48, 9194]

T2w

 

37

prostate

1.5

 

0.79

  

[25]

 

T2w

 

10

cervix

0.3

    

[95]

Hybrid

Deformable

Patch

T1w

 

17

brain

 

101

   

[96]

    

T2w

 

39

Prostate

0.3

40.5

0.91

100

γ22

[97]

Hybrid

Deformable

Probabilistic

 

T1w

 

9-27

brain

 

126

0.86

86/90

SSbone

[26, 98]

  

T2w

 

10

prostate

0.2

36.5

 

99.9

γ21

[27]

Regression

Random F

T2w

 

20

prostate

   

0.83

DSCprostate

[99]

  

Threshold

 

dUTE

 

154

brain

  

0.81

  

[100]

  1. Column 1: Overall approach: Voxel, atlas or hybrid. Column 2: Sub categories within each main approach. Column 3: MRI sequences/contrasts applied in the studies. Column 4: Number of subjects included in the studies (patients, volunteers, phantoms). Column 5: Anatomical site investigated. Column 6: Performance metrics. Column 7: Specification of “Other” metric and comments. Column 8: References to included studies. SSx = % specificity @ % sensitivity for tissue x, Cx = % correctly classified voxel for tissue x, Δx = mm distance bt. CT and sCT for tissue x, γxy = % of points with γx %ymm < 1 where x and y are the dosimetric and geometric deviations, respectively, aMAE of whole FOV and DSC based on 2D DRR, b Overlap ratio similar to DSCbone. c Bone > 600 HU. Method abbreviations: Bayesian Bayesian statistics, Markow RF Markow Random Fields, Discriminant Discriminant analysis, Random F Random Forest, PCA Principal Component Analysis, Patch = cluster/collection of MRI voxels, Deformable = deformable registration