Limbus Contour

by Limbus AI  · Based in Canada → — Software solutions for cancer radiation therapy, improving efficiency and clinical workflows in cancer radiation treatment planning.
Oncology Radiology
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Regulatory Status Disclosed

Overview

Limbus Contour (by Limbus AI, acquired by Radformation) is an AI-driven, automated contouring software designed for radiation oncology. The platform utilizes clinically validated deep learning algorithms to perform segmentation of organs at risk (OARs) and clinical target volumes (CTVs) for radiation therapy planning.

The software is built for radiation oncologists, medical physicists, and dosimetrists in cancer centers and clinical practices. It features an extensive library of over 260 pre-trained anatomical structures across multiple treatment sites, including the head and neck, thorax, abdomen, and pelvis. This allows clinical teams to generate contours immediately without the need for manual atlas creation or local data curation.

Limbus Contour integrates directly into existing clinical workflows. Upon receiving a patient scan, the system automatically detects the correct treatment site, applies the appropriate clinical template, and performs the segmentation. The generated contours are exported as compliant DICOM RT-Structure files and sent directly to the treatment planning system (TPS) for manual clinician review. The software operates entirely on local clinical workstations without requiring cloud data transfers or specialized GPU hardware, keeping patient data secure within the local network.

Reviewed by Pouyan Golshani, MD — Interventional Radiologist

Key Features

  • Automatic AI autocontouring for radiation therapy
  • Extensive library of clinically validated anatomical structures (over 110 OARs and CTVs)
  • Local deployment on existing clinical workstations (no cloud data sharing)
  • Fast contouring (1-3 minutes on CPU, seconds with GPU acceleration)
  • Clinically validated deep learning segmentation
  • Vendor-neutral, exports DICOM compliant RT-Structure files
  • Supports CT and MRI modalities
  • Expanded anatomical coverage (e.g., gynecological brachytherapy, ESTRO breast lymph nodes, cardiac substructuring, prostate CBCT)
  • Automated detection and application of correct clinical templates
  • Reduces contouring time by up to 80%

Use Cases

  • Improving efficiency and clinical workflows in cancer radiation treatment planning
  • Delineating tumor targets and organs at risk (OARs)
  • Reducing contouring time in radiotherapy planning
  • Aiding adaptive therapy
  • Archiving contours for patient follow-up
  • Prostate, nodal, CNS, head and neck, breast, gynecological, cardiac, and prostate CBCT radiotherapy planning

What Physicians Need to Know

Key Capabilities
Limbus Contour provides completely automatic AI autocontouring for radiation therapy, generating clinical-grade Organs at Risk (OARs) and Clinical Target Volume (CTV) contours. It features a large selection of pre-trained organ contours for various treatment sites (e.g., Head & Neck, CNS, Thorax, Breast, Prostate, Pelvis, Abdomen) and supports both CT and MR image modalities. The system is fully automated, detecting and applying correct clinical templates and exporting contours to treatment planning systems for review. Recent updates (v1.8) expanded anatomical coverage with over 100 new models, including those for gynecological brachytherapy, ESTRO breast lymph node volumes, cardiac substructuring, and prostate CBCT.
Clinical Utility
The tool significantly reduces contouring time, with reported savings of up to 80% and specific reductions of 13-26 minutes for prostate cases, thereby streamlining clinical workflows and improving efficiency in cancer radiation treatment planning. It aims to reduce human error and inter-observer variability in contouring, ensuring more precise radiation delivery to target areas while avoiding OARs. By providing a consistent starting point for contouring, it frees up clinician time for other critical tasks or more complex patient cases.
Integration Options
Limbus Contour is vendor-neutral, exporting DICOM compliant RT-Structure files that are compatible with any treatment planning systems (TPS) without requiring plug-ins or extensions. It operates in conjunction with existing radiation treatment planning systems or DICOM viewing systems. The software is designed for seamless integration into current clinical workflows and has been integrated into systems like the RefleXion X1 radiotherapy treatment planning system. It is now unified with Radformation's AutoContour v2.7, which works seamlessly with Eclipseu2122 and other DICOM-compatible systems.
Compliance Status
The software is GDPR compliant and operates entirely on local networks or existing workstations, ensuring patient data privacy by avoiding cloud transfers. Limbus Contour has received FDA 510(k) clearance (K230575 on April 7, 2023, and K241837 on October 9, 2024). It adheres to the DICOM standard to facilitate interoperability with other DICOM products. Availability in some markets may be pending local regulatory body clearance.
Pricing Model
Limbus AI offers a tiered pricing model, including a 'Clinical Standard' license for individual centers and an 'Enterprise Pro' tier for larger hospital networks. A 30-day full-feature trial is available for institutional validation.
User Experience
Limbus Contour is designed for ease of use, with quick setup and integration into existing TPS workflows. It is a turnkey solution with an extensive library of clinically validated anatomical structures ready for immediate use. The system is fully automated, requiring minimal user input for initial contour generation and running in the background. While it provides a strong starting point, clinician review and editing of contours are considered essential. User feedback actively guides the development of new structures and model improvements.
Support Quality
Limbus AI emphasizes user feedback in its continuous development, frequently adding new structures and improving models based on clinical input. The company has a dedicated clinical data team with extensive experience in dosimetry, contouring, and quality assurance. Now part of Radformation, it benefits from an organization known for good customer service.
Implementation Complexity
Implementation is straightforward, with the software being easy to set up and running in minutes on existing clinical workstations. It has low hardware requirements and can operate as a local stand-alone client, which simplifies IT implementation and addresses security concerns often associated with cloud-based systems. The solution is designed to cause minimal workflow disruption.
Evidence Base
Limbus Contour is backed by comprehensive, peer-reviewed research and extensive clinical validation, demonstrating clinically validated deep learning segmentation for radiotherapy. Studies highlight significant time savings and good geometric similarity (Dice Similarity Coefficient generally >0.7) between AI-generated and expert contours. Dosimetric studies underscore the importance of expert review, as unmodified AI structures may occasionally compromise PTV coverage. The models are continuously fine-tuned through routine clinical evaluation and retraining, with ongoing research and publications supporting new features like HDR brachytherapy and CBCT models.
Physician Tip

Limbus Contour offers substantial time savings and consistency in radiation therapy planning, particularly for OARs and CTVs. While highly accurate, always perform a thorough clinical review and make necessary edits to AI-generated contours, especially for complex cases or structures like bowel and pelvic lymph nodes, to ensure optimal patient safety and treatment plan quality. The software's local operation enhances data security, and its vendor-neutral DICOM output facilitates integration into existing workflows. Leverage the extensive library of structures and provide feedback to contribute to ongoing model improvements.

Limbus Contour is designed for seamless integration into existing radiotherapy treatment planning ecosystems. It exports DICOM RT-Structure files, ensuring compatibility with virtually any TPS without the need for proprietary plugins. Direct integrations, such as with the RefleXion X1 system, streamline the workflow further. Now unified under Radformation's AutoContour, it offers enhanced compatibility with systems like Varian Eclipseu2122 and other DICOM-compatible platforms, providing flexibility for diverse clinical environments. The local installation minimizes IT overhead and security concerns often associated with cloud-based solutions.

Details

Category Oncology AI, Radiology & Imaging AI
Pricing Contact for pricing
  • Tiered model: Clinical Standard (for individual centers); Enterprise Pro (for large hospital networks)
DeploymentLocal installation on existing clinical workstations
Compliance
BAA AvailableUnknown AI-estimated
HIPAA CompliantUnknown AI-estimated
FDA Status 1 AI-estimated

Limbus Contour received 510(k) clearance (K241837 on 10/09/2024) from the U.S. Food and Drug Administration. It is a software-only medical device intended for use by trained radiation oncologists, dosimetrists, and physicists to derive optimal contours for input to radiation treatment planning.
Integrations
EHR Not specified
Specialties Oncology, Radiology

What the Web Says

Limbus Contour is an AI-driven auto-contouring software primarily used in radiotherapy treatment planning. It aims to reduce the time clinicians spend manually outlining organs at risk (OARs) and target volumes on medical images. Physicians and medical physicists generally find that Limbus Contour significantly streamlines the contouring process, leading to substantial time savings and improved workflow efficiency, though expert review and occasional modifications remain crucial for optimal patient outcomes.

Overall: Positive

Strengths

  • Significant time savings in contouring, reducing planning time by up to 80% for some cases.
  • Improved workflow efficiency and standardization across clinics.
  • High accuracy in contouring, with good agreement with expert contours.
  • Lightweight, effective, and hands-off product that lends itself well to automation.
  • Supports a wide range of anatomical structures (over 260) and various imaging modalities (CT, MRI).
  • Local processing option appeals to privacy-focused departments.

Limitations

  • Requires expert review and potential modification of AI-generated contours, as unmodified contours can sometimes compromise treatment plans.
  • May miss parts of organs when adjacent to other structures.
  • Recent acquisition by Radformation creates some uncertainty among users regarding future product direction and integration.
  • Limited cloud options and fewer integration or hybrid deployment options compared to some competitors.
  • Some users prefer the workflow of competing products like MIM due to existing clinic infrastructure.

Based on reviews from: Clinical evaluation of the efficacy of limbus artificial intelligence software to augment contouring for prostate and nodes radiotherapy - PMC, AI contouring? : r/MedicalPhysics - Reddit, Icon Oncology: Using Limbus AI Contouring Software - Quicker, simpler and safer., RefleXion, Limbus AI to Integrate Treatment Planning Workflow Technologies, Change My Mind - RIP LimbusAI : r/MedicalPhysics - Reddit, Clinical evaluation of the efficacy of limbus artificial intelligence software to augment contouring for prostate and nodes radiotherapy - ResearchGate, Clinical evaluation of the efficacy of limbus artificial intelligence software to augment contouring for prostate and nodes radiotherapy - PubMed, Limbus AI Inc. August 13, 2020 Ms. Mary Vater 510(k) Consultant Medical Device Academy 245 Lincoln Hill Road SHREWSBURY VT - accessdata.fda.gov, Radformation acquires LimbusAi : r/MedicalPhysics - Reddit, Review of the game by a gacha gamer not brainrotted like us ! : r/limbuscompany - Reddit, Artificial intelligence-based autosegmentation for radiotherapy in: IMAGING Volume 17 Issue 1 (2025), AI Contouring Software for Radiotherapy: Platform Comparison - Wellbeing Magazine, Anyone have a solid comparison of auto segmentation tools to share? : r/MedicalPhysics, Limbus Contour v1.8 Highlights - Radformation Blog, What are y'all opinion on Limbus company : r/libraryofruina - Reddit, Limb AI Chatbot Reviews 2026: Details, Pricing, & Features - G2, Review: Even Realities G2 smart glasses add a simplistic yet engaging floating display for your face - 9to5Google

Last updated: 2026-07-18

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Press & Coverage

Limbus AI
Radformation to Accelerate AI-Based Solutions with Limbus AI Acquisition
Radformation, Inc. acquired Limbus AI in April 2024, signifying a commitment to expanding AI-driven capabilities in cancer care and improving the radiation therapy process. This acquisition aims to accelerate innovation and enhance patient outcomes globally.
2024-04
Radformation Blog
Limbus Contour v1.8 Highlights - Radformation Blog
Limbus Contour version 1.8, released in June 2024, introduces over 100 new anatomical models, including those for gynecological brachytherapy, ESTRO breast lymph node volumes, cardiac substructuring, and prostate CBCT, along with enhanced model performance and software improvements.
2024-06
RefleXion Medical Inc.
RefleXion, Limbus AI to Integrate Treatment Planning Workflow Technologies
RefleXion Medical Inc. and Limbus AI announced a licensing agreement in March 2024 to integrate Limbus Contour into the RefleXion X1 radiotherapy treatment planning system, aiming to reduce contouring time by up to 80%. This integration addresses a significant bottleneck in patient treatment planning.
2024-03
PR Newswire (via Accuray)
Accuray and Limbus AI Unveil Online Adaptive Therapy Solution for the Radixactu00ae System at American Society for Radiation Oncology (ASTRO) Annual Meeting
Accuray and Limbus AI partnered to unveil Cenosu2122, an online adaptive therapy option for the Radixactu00ae System, at the 2023 ASTRO Annual Meeting. This solution, which has a 510(k) pending, integrates Limbus Contour to provide accurate and fast contouring for adaptive treatment.
2023-10
pharmaphorum
AI can be used to speed up radiotherapy planning, says NICE
NICE (National Institute for Health and Care Excellence) guidance from August 2023 suggests that AI, including Limbus Contour, can significantly reduce the time for radiotherapy treatment planning, potentially saving between three and 80 minutes per plan.
2023-08
PMC
Clinical evaluation of the efficacy of limbus artificial intelligence software to augment contouring for prostate and nodes radiotherapy
A clinical study published in 2023 demonstrated that Limbus Contour reduced the time to produce clinically acceptable contours for prostate and nodes patients by 13 to 26 minutes, respectively, while maintaining good initial agreement with expert contours.
2023-12
Limbus AI
Limbus AI Receives ANVISA Marketing Authorization for Limbus Contouru2122 in Brazil
Limbus AI announced in August 2023 that it received full Marketing Authorization (MA) from ANVISA, Brazil's National Health Surveillance Agency, for its AI auto-contouring software, Limbus Contouru2122.
2023-08
ResearchGate
Using an Artificial Intelligence System “Limbus AIu201d for Automatic Segmentation of OAR's in Radiotherapy: Evaluation of Effectiveness and Dosimetric Impact
A study evaluating Limbus Contour (version 1.5.0) in radiotherapy workflow for head-neck, left breast, and prostate cancer found an average Dice Index of 84% and significant time savings, particularly 80 minutes for head-neck tumors.
2026-05

Videos

Product demos, reviews, and walkthroughs for Limbus Contour.

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Frequently Asked Questions

Limbus Contour is designed to integrate seamlessly with existing treatment planning systems, typically through DICOM import/export, and can be installed on local networks. Its primary application is to automate or semi-automate the contouring of organs-at-risk (OARs) and target volumes, aiming to significantly reduce manual contouring time and improve consistency in radiation therapy planning.
Limbus Contour holds FDA 510(k) clearance, indicating its safety and efficacy as a software-only medical device for its intended use in radiation treatment planning. It ensures patient data privacy by operating entirely on local networks, avoiding cloud storage of patient data, and employing robust data anonymization and encryption protocols to comply with regulations like GDPR.
While Limbus Contour offers high accuracy and significant time savings, particularly for common OARs, complex anatomies, cases with significant imaging artifacts, or rare pathologies may still require physician review and manual adjustment. The software is not intended to automatically contour tumors or tumor clinical target volumes, and its performance can vary across different anatomical sites and image modalities.
Limbus Contour differentiates itself through its clinically validated deep-learning segmentation algorithms, speed, and ability to be installed on existing local networks, addressing patient data privacy concerns by avoiding cloud usage. Compared to manual contouring, it offers substantial time savings, potentially up to 80%, and improved inter-observer consistency, while other AI tools may differ in their specific algorithms, validation data, and integration capabilities.
Limbus AI typically offers a tiered pricing model for Limbus Contour, such as a 'Clinical Standard' license for individual centers and an 'Enterprise Pro' tier for larger hospital networks, often subscription-based. Associated costs can include initial integration fees, ongoing maintenance, and potential training, with a 30-day full-feature trial often available for institutional validation.
Limbus Contour is supported by peer-reviewed clinical validation studies demonstrating its accuracy against expert manual contouring, with reported Dice Similarity Coefficient (DSC) values often greater than 0.7 for various structures. These studies highlight significant time savings, such as reducing contouring time by 13-26 minutes for prostate and nodal patients, while maintaining geometric accuracy and dosimetric plan quality after physician review.

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Suggest an Edit → | Last Verified: 2026-04-18 | First Added: 2026-04-18
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