Colour map recommendations for MR relaxometry
Author Block: B. D. Wichtmann1, M. Fuderer2, N. Desouza3, F. Crameri4, V. Gulani5, N. Sollmann6, S. Weingärtner7, S. Mandija2, X. Golay3; 1Bonn/DE, 2Utrecht/NL, 3London/UK, 4Bern/CH, 5Ann Arbor, MI/US, 6Ulm/DE, 7Delft/NL
Purpose: Quantitative imaging data may be colour coded and represented as a colour-map. However, commonly used schemes (e.g. rainbow, jet) lack perceptual uniformity, have the brightest colour mid-range and are not usable by colour-blind individuals. Furthermore, lack of standardization of colour-maps, makes comparisons across studies and institutions difficult and misleading. This work describes recently published recommendations for standardisation of MR relaxometry colour-maps (Fuderer, MRM 2024) in order to promote their adoption and drive the process for other biomarkers.
Methods or Background: Recommendations were generated in 4 Delphi rounds. A multidisciplinary committee devised questions on key colour-map features, including the colour choice for T1/T2 maps, even colour gradient contrast, high overall colour and lightness contrast, intuitive and constant gradient magnitude, and recognizability. Questions were circulated to the ISMRM quantitative imaging group and European subspecialist society representatives. Respondents received feedback after each round to aid consensus. Responses on a 9-point Likert scale were summarised to Agree, Neutral, Disagree categories. 75% consensus was the threshold for items reaching recommendation.
The proposed colour maps were based on previous proposals (Griswold, ISMRM 2018) but modified for perceptual linearity and readability by colour-blind people.
Results or Findings: 58 experts responded to Round 1; 48 (45% medical, 47% physicists) completed all 4 rounds. There was consensus that the logarithm-processed Lipari colour-map for T1 and the logarithm-processed Navia colour-map for T2 were suitable. Colour bars were deemed mandatory as was a specific value indicating “invalidity”. There was no consensus on whether to fix ranges by anatomy.
Conclusion: The logarithm-processed Lipari colour map for displaying T1 and R1 values and the logarithm-processed Navia colour-map for displaying T2, R2 , T2* and R2* are recommended for use in scientific reports.
Limitations: Future work will focus on range recommendations.
Funding for this study: No funding was provided for this study.
Has your study been approved by an ethics committee? Not applicable
Ethics committee - additional information: No patient-sensitive data were processed in this study.