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Abstract

We present Segment Anything for Microscopy, a tool for interactive and automatic segmentation and tracking of objects in multi-dimensional microscopy data. Our method is based on Segment Anything, a vision foundation model for image segmentation. We extend it by training specialized models for microscopy data that significantly improve segmentation quality for a wide range of imaging conditions. We also implement annotation tools for interactive (volumetric) segmentation and tracking, that speed up data annotation significantly compared to established tools. Our work constitutes the first application of vision foundation models to microscopy, laying the groundwork for solving image analysis problems in these domains with a small set of powerful deep learning architectures.

In-depth summary

Claude Opus 5.5 · xhigh effort · 8 Nov 2026 · from the full text of version 1 (26 Aug 2023) · CC BY 4.0

micro_sam finetunes Segment Anything into a light microscopy generalist and a cell/neurite-focused electron microscopy model, plus napari tools for interactive 2d, volumetric and tracking annotation.

Pretrained deep learning segmentation and tracking models for microscopy lose quality on data unlike their training sets, and retraining requires slow pixel-level annotation, even with CellPose 2's in-the-loop correction. Earlier biomedical uses of Segment Anything (SAM) kept the default weights; this work adds a finetuning scheme, microscopy-specific models and multidimensional interactive annotation spanning light (LM) and electron microscopy (EM).

Key results

  1. ShownFinetuning the full SAM ViT-H model on LiveCELL improved point-prompted, box-prompted and automatic instance segmentation over the default weights. Prompted results surpassed CellPose, but automatic segmentation did not, and most of the gain came from small training subsets.

    LiveCELL test split, mean segmentation accuracy over matching thresholds 0.5 to 0.95 (step 0.05), baseline CellPose trained on LiveCELL. ViT-B ablation: image encoder updates matter most, full-model finetuning is best. Training fractions of 2, 4 and 5 % already capture most of the improvement. Scores are shown only in Figure 2, not in the text. · Finetuning Segment Anything significantly…; Inference and evaluation; Figure legends

  2. ShownA light microscopy generalist trained on pooled public datasets nearly matched dataset-specific specialists and outperformed default SAM on all five held-out imaging settings. Comparisons with the CellPose cyto model were mixed across datasets and prompt types.

    Training data: LiveCELL, TissueNet, DeepBacs, Neurips Cell Segmentation, Nucleus DSB, PlantSeg; specialists were slightly better, mostly on DeepBacs (smallest set). Held-out: CovidIF, HPA, Lizard, mouse-embryo, plantseg-ovules. Against CellPose, sometimes only box prompts won and sometimes every SAM mode won, including automatic. ViT-H; scores only in Figure 3. · Light microscopy model trained on diverse data…; Figure legends

  3. ShownAn electron microscopy model trained on CREMI, MitoEM, AxonDeepSeg and PlatyEM improved cell and neurite segmentation but degraded mitochondria. The authors therefore conclude that one EM generalist is not feasible with the current SAM architecture and training.

    In-domain test splits: gains for cells, neurites and nuclei, loss for mitochondria. Held-out Lucchi (FIBSEM mitochondria), NucMM-Z (low-resolution SEM nuclei), SNEMI (SEM neurites), SpongeEM (FIBSEM cells, organelles): neurites up, mitochondria down, others mixed. Finetuned model often segments the surrounding cell instead of the mitochondrion. No baseline method compared. · Electron microscopy model improves segmentation…; Figure legends

  4. SuggestedIn brightfield organoid annotation, every semi-automatic approach beat manual labeling. Starting from automatic instance segmentation, micro_sam was faster than CellPose 2 before finetuning, and the two performed comparably after in-the-loop finetuning.

    Internal dataset with 20 ground-truth images; per-object time for manual, CellPose (cyto, three images annotated then finetuned twice) and micro_sam (default ViT-H, with/without automatic segmentation, then finetuned for 10 thousand iterations). Finetuning gave a significant gain for single-point prompts, which drive automatic segmentation. Times only in Figure 5. · Interactive annotation tools based on Segment…; Training; Figure legends

  5. SuggestedAnnotating nuclei in 3d fruit fly larva EM was almost twice as fast with micro_sam as with ilastik carving, and the masks fit better. For HeLa tracking, micro_sam was slightly faster than Trackmate with CellPose and gave clearly better tracking quality.

    3d: internal volume EM blocks; carving masks misfit some nuclei because its superpixels cannot be corrected; user-data finetuning improved scores in most settings. Tracking: Cell Tracking Challenge HeLa label-free data with added full segmentation ground truth, time per track and challenge metric; Trackmate is fast and accurate only from ground-truth masks. · Interactive annotation tools based on Segment…; Figure legends

Methods, data and reproducibility

Iterative prompt-based finetuning of SAM (Dice mask loss plus L2 loss on predicted intersection-over-union, with corrective positive and negative points sampled from errors over repeated steps), evaluated with ground-truth-derived prompts; extended with cached and tiled embeddings and slice- or frame-wise mask projection inside napari annotation tools.

  • LiveCELL cell segmentation dataset (train/test splits; finetuning, strategy ablation and data-fraction experiments)
  • LM generalist training sets: TissueNet, DeepBacs, Neurips Cell Segmentation, Nucleus DSB and PlantSeg (pooled with LiveCELL)
  • Held-out LM test sets: CovidIF (immunofluorescence), HPA (fluorescence), Lizard (histopathology), mouse-embryo (light-sheet nuclei), plantseg-ovules (confocal) · human (HPA cells), mouse (mouse-embryo); others not stated
  • EM generalist training sets: CREMI, MitoEM, AxonDeepSeg, PlatyEM (cells, cilia, mitochondria, myelinated axons, neurites, nuclei)
  • Held-out EM test sets: Lucchi (FIBSEM mitochondria), NucMM-Z (low-resolution SEM nuclei), SNEMI (SEM neurites), SpongeEM (FIBSEM cells and organelles)
  • Internal brightfield organoid images for the 2d annotation user study · n = 20 images with ground-truth masks
  • Internal volume EM of a fruit fly larva for the 3d nucleus annotation study · fruit fly (larva) · n = several small ground-truth blocks
  • Cell Tracking Challenge HeLa label-free time series, extended by the authors with full segmentation ground truth · human (HeLa cell line)
Methods & tools
Segment Anything (SAM; ViT-B and ViT-H encoders), napari, magicgui, PyTorch, torch-em, CellPose / CellPose 2 (cyto and LiveCELL models), ilastik carving (seeded graph watershed), Trackmate, Adam optimizer with ReduceLROnPlateau, Mean segmentation accuracy (0.5 to 0.95 matching thresholds), Cell Tracking Challenge tracking metric
Software & environment
micro_sam software version 0.2.2 at submission; Python library built on PyTorch, torch-em, napari and magicgui, finetuning the default SAM weights; released on GitHub under a permissive open source license.
Assay conditions & compute
Training on an A100 GPU with 80 GB VRAM; 100 thousand iterations took about two days. Laptop without GPU: about a minute per image for embeddings, under a second per interactive segmentation.
Reproducibility gaps
Internal datasets for the 2d and 3d user studies are only available upon request; public dataset sources are listed in Supp. Tables 1 and 2, not in the text; in-the-loop finetuning updates full weights and needs a GPU.
Limitations (6)
  • The EM model performs worse on mitochondria both in and out of domain. The authors expect the original SAM weights to do better on targets other than whole cells, neurites or compartments, and organelle-specific models have not been released yet. · stated by the authors
  • Finetuning updates all model weights, so it needs a GPU and considerable time. That limits in-the-loop finetuning to users with strong hardware or with cluster or cloud GPU access. · stated by the authors
  • Automatic instance segmentation remained the weaker mode: on LiveCELL it was not on par with CellPose even after finetuning, and the authors name it as an area to improve, for example with ideas from embedding-based segmentation. · stated by the authors
  • In the volumetric EM study, the authors did not test whether in-the-loop finetuning further speeds annotation; they assessed only its effect on segmentation scores. · stated by the authors
  • Each user study used one dataset, with an unreported number of annotators and no stated statistical test on annotation times, so the size and generality of the speed-ups are uncertain. · noted in this summary
  • Claims of significant improvement appear only in figures. The text gives no numeric scores, confidence intervals or test statistics, which makes independent comparison harder. · noted in this summary

Read this if you segment or track cells, nuclei or neurites in light or electron microscopy and want to finetune Segment Anything or annotate 2d, 3d and time-lapse data interactively in napari.

Citations
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