Prompting with the human-touch: evaluating model-sensitivity of foundation models for musculoskeletal CT segmentation

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Main Authors: Magg, Caroline, ter Wee, Maaike A., Dobbe, Johannes G. G., Streekstra, Geert J., Blankevoort, Leendert, Sánchez, Clara I., Kervadec, Hoel
Format: Preprint
Published: 2026
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author Magg, Caroline
ter Wee, Maaike A.
Dobbe, Johannes G. G.
Streekstra, Geert J.
Blankevoort, Leendert
Sánchez, Clara I.
Kervadec, Hoel
author_facet Magg, Caroline
ter Wee, Maaike A.
Dobbe, Johannes G. G.
Streekstra, Geert J.
Blankevoort, Leendert
Sánchez, Clara I.
Kervadec, Hoel
contents Promptable Foundation Models (FMs), initially introduced for natural image segmentation, have also revolutionized medical image segmentation. The increasing number of models, along with evaluations varying in datasets, metrics, and compared models, makes direct performance comparison between models difficult and complicates the selection of the most suitable model for specific clinical tasks. In our study, 11 promptable FMs are tested using non-iterative 2D and 3D prompting strategies on a private and public dataset focusing on bone and implant segmentation in four anatomical regions (wrist, shoulder, hip and lower leg). The Pareto-optimal models are identified and further analyzed using human prompts collected through a dedicated observer study. Our findings are: 1) The segmentation performance varies a lot between FMs and prompting strategies; 2) The Pareto-optimal models in 2D are SAM and SAM2.1, in 3D nnInteractive and Med-SAM2; 3) Localization accuracy and rater consistency vary with anatomical structures, with higher consistency for simple structures (wrist bones) and lower consistency for complex structures (pelvis, tibia, implants); 4) The segmentation performance drops using human prompts, suggesting that performance reported on "ideal" prompts extracted from reference labels might overestimate the performance in a human-driven setting; 5) All models were sensitive to prompt variations. While two models demonstrated intra-rater robustness, it did not scale to inter-rater settings. We conclude that the selection of the most optimal FM for a human-driven setting remains challenging, with even high-performing FMs being sensitive to variations in human input prompts. Our code base for prompt extraction and model inference is available: https://github.com/CarolineMagg/segmentation-FM-benchmark/
format Preprint
id arxiv_https___arxiv_org_abs_2603_10541
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Prompting with the human-touch: evaluating model-sensitivity of foundation models for musculoskeletal CT segmentation
Magg, Caroline
ter Wee, Maaike A.
Dobbe, Johannes G. G.
Streekstra, Geert J.
Blankevoort, Leendert
Sánchez, Clara I.
Kervadec, Hoel
Computer Vision and Pattern Recognition
Artificial Intelligence
Promptable Foundation Models (FMs), initially introduced for natural image segmentation, have also revolutionized medical image segmentation. The increasing number of models, along with evaluations varying in datasets, metrics, and compared models, makes direct performance comparison between models difficult and complicates the selection of the most suitable model for specific clinical tasks. In our study, 11 promptable FMs are tested using non-iterative 2D and 3D prompting strategies on a private and public dataset focusing on bone and implant segmentation in four anatomical regions (wrist, shoulder, hip and lower leg). The Pareto-optimal models are identified and further analyzed using human prompts collected through a dedicated observer study. Our findings are: 1) The segmentation performance varies a lot between FMs and prompting strategies; 2) The Pareto-optimal models in 2D are SAM and SAM2.1, in 3D nnInteractive and Med-SAM2; 3) Localization accuracy and rater consistency vary with anatomical structures, with higher consistency for simple structures (wrist bones) and lower consistency for complex structures (pelvis, tibia, implants); 4) The segmentation performance drops using human prompts, suggesting that performance reported on "ideal" prompts extracted from reference labels might overestimate the performance in a human-driven setting; 5) All models were sensitive to prompt variations. While two models demonstrated intra-rater robustness, it did not scale to inter-rater settings. We conclude that the selection of the most optimal FM for a human-driven setting remains challenging, with even high-performing FMs being sensitive to variations in human input prompts. Our code base for prompt extraction and model inference is available: https://github.com/CarolineMagg/segmentation-FM-benchmark/
title Prompting with the human-touch: evaluating model-sensitivity of foundation models for musculoskeletal CT segmentation
topic Computer Vision and Pattern Recognition
Artificial Intelligence
url https://arxiv.org/abs/2603.10541