Comparison of Measurement Techniques and Response Criteria for MR Imaging Follow-up in Adult Primary Central Nervous System Lymphoma

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FIG 1.
3D measurement example on postcontrast 3D T1 MPRAGE. The blue line represents the longest 1D. The orange line is the longest length perpendicular to the blue line; their product represents 2D. The green line is the longest length perpendicular to the blue and orange lines; those 3 measures are used to calculate the volume for 3D.
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FIG 2.
Postcontrast 3D T1 MPRAGE in a 56-year-old woman treated for a left temporal PCNSL. Comparison of the 3D measurements performed by the 2 readers (reader 1, A and B; reader 2, C and D).
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FIG 3.
Correlation of raw measurements calculated with the Spearman correlation after we applied cubic root on volume calculated with the 3D method and square root on surface area calculated with the 2D methods (exclusion of zero values). Rec indicates RECIST; Ax, axial.

Table 1:

Included patient characteristics (N = 40)

Patient Characteristics	Value (SD)
Mean age (yr)	61.5 (11.1)
Age range (yr)	29–81
Male/female ratio	23:17
Pathology
Primary CNS large B-cell lymphoma	40
Prior WBRT	5
Median follow-up (yr)^{^a}	3.01
Total baseline MR imaging	33
Total baseline CT	7
Total follow-up MR imaging	254
Total follow-up CT	10
Mean number of MR images per patient	7.60 (3.49)
Mean number of lesions on baseline MR image	2.33 (1.14)
Disease location
Superficial	16
Deep	15
Mixed	9
Particular disease distribution
Midline crossing lesion	10
Multifocal, bilateral lesions	16
Induction response^{^a}	22
Relapse after induction^{^a}	12

Note:—WBRT indicates whole brain radiotherapy; SD, standard deviation.
↵a One patient was lost to follow-up, and 5 stopped their treatment for palliative care and were not included in this analysis.

Table 2:

Intraobserver and interobserver correlations calculated with the ICC for each measurement method in raw units (95% CI)

Measurement Method	Intraobserver Correlation (95% CI)	Interobserver Correlation (95% CI)
Longest 1D	0.993 (0.985–0.997)	0.967 (0.947–0.979)
2D	0.997 (0.994–0.998)	0.982 (0.969–0.989)
3D	0.993 (0.985–0.997)	0.992 (0.986–0.995)

Table 3:

Correlation between raw measurements with the Spearman rank correlation coefficient

Measurement Method	Spearman Rank Correlation Coefficient (95% CI)
Longest 1D vs axial 1D	0.977
Longest 1D vs RECIST	0.930
Longest 1D vs 2D	0.965
Longest 1D vs 3D	0.935
Axial 1D vs RECIST	0.915
Axial 1D vs 2D	0.963
Axial 1D vs 3D	0.942
RECIST vs 2D	0.924
RECIST vs 3D	0.898
2D vs 3D	0.990

Table 4:

Spearman rank correlation coefficients of the lesion variation in size compared with baseline MR images^{^a}

Measurement Method	Spearman Correlation Coefficient (95% CI)
Longest 1D vs axial 1D	0.890
Longest 1D vs RECIST	0.898
Longest 1D vs 2D	0.962
Longest 1D vs 3D	0.918
Axial 1D vs RECIST	0.796
Axial 1D vs 2D	0.872
Axial 1D vs 3D	0.831
RECIST vs 2D	0.847
RECIST vs 3D	0.794
2D vs 3D	0.980