影像导引放射线治疗市场－全球产业规模、份额、趋势、机会、预测：按产品、流程、应用、地区和竞争格局划分，2021-2031年

全球影像导航放射治疗市场预计将从 2025 年的 20.2 亿美元成长到 2031 年的 27.8 亿美元，复合年增长率为 5.45%。

这种先进的治疗方法将磁振造影(MRI) 和电脑断层扫描 (CT) 等常用影像通讯协定直接整合到放射治疗过程中，最大限度地提高肿瘤靶向精度，同时保护周围健康组织。市场成长的主要驱动力是全球癌症患者数量的增加，以及人们对安全性更高、疗效更佳的非侵入性治疗方法的偏好转变。核能2024 年的数据证实了这一紧迫性，数据显示，全球约 50% 至 70% 的癌症患者将需要接受放射治疗，这推动了对能够优化这些关键治疗的高精度技术的需求。

然而，由于实施和营运这些先进系统需要巨额资本投入，该市场面临许多障碍。除了购置设备的高昂成本外，建造专用基础设施和持续维护的财务负担也是主要的进入门槛。这些财务限制严重限制了科技的普及率，尤其对中低收入地区的医疗机构影响尤其显着，因为这些地区的医疗机构往往缺乏资金筹措来购买高成本的医疗技术。

市场驱动因素

全球癌症发生率的不断上升是影像导航放射治疗市场成长的主要驱动力，因此迫切需要可扩充性的解决方案来应对日益增长的患者数量。随着疾病负担的加重，医疗机构不得不部署高通量系统，以确保有效控制局部疾病并最大限度地减少副作用。问题的严重性凸显了这项迫切需求。世界卫生组织（WHO）下属的国际癌症研究机构（IARC）在2024年2月发布的一份关于全球癌症负担的新闻稿中指出，2022年全球新增癌症病例估计达2000万例。因此，病例数量的不断增加直接加速了放射治疗设备的采购，医院正在扩大肿瘤科以满足不断增长的患者群体的基本医疗需求。

同时，科技的快速发展，特别是人工智慧（AI）的融合，正在透过变革治疗方式推动市场发展。现代影像导引放射治疗（IGRT）平台采用自适应演算法，能够即时校正放射束，显着提高标靶区精度。产业向这些自适应系统的转型已从强劲的商业业绩中得到印证。例如，Accuray在2024年8月发布的「2024财年第四季及全年业绩」中报告了3.421亿美元的订单总额，显示市场对精密仪器的需求旺盛。西门子医疗等行业领导者也进一步支撑了该领域的财务规模。西门子医疗旗下的瓦里安部门在2024年实现了41.4亿美元的总收入，主要得益于先进放射治疗解决方案的持续应用。

市场挑战

影像导航放射治疗（IGRT）系统的引进和安装需要大量资本投入，这严重阻碍了其在全球市场的扩张。这些先进的治疗平台不仅需要购买昂贵的硬件，还需要在专用设施基础设施（例如辐射屏蔽掩体）以及严格的持续维护通讯协定投入巨资。沉重的经济负担提高了进入门槛，限制了医疗机构（尤其是资源匮乏地区的医疗机构）取得必要设备的能力。这有效地限制了潜在基本客群，并减缓了整体普及速度。

这种经济壁垒加剧了医疗服务取得的不平等，并直接阻碍了发展中地区（这些地区临床需求最为迫切）的市场渗透。根据全球放射治疗联盟2024年的报告，全球约有58个国家无法提供放射治疗服务，这主要是由于当地医疗系统无法负担相关技术的初始资本和营运成本。众多国家基础设施的匮乏使得製造商无法进入新兴市场，从而限制了全球放射治疗产业的成长。

市场趋势

生物导引放射治疗平台的出现代表着市场的一次变革性演进，它将治疗重点从解剖成像转向利用肿瘤生物学进行即时标靶治疗。与仅依赖结构差异的传统系统不同，这些先进平台能够透过侦测肿瘤直接发射的正子断层扫描（PET）讯号，在单次治疗中精准治疗多个转移病灶。这项创新技术满足了晚期恶性肿瘤治疗的关键需求，而传统的聚焦疗法往往难以有效治疗这些肿瘤。监管方面的进展标誌着这项技术的快速普及。正如RefleXion Medical在2025年1月发布的新闻稿「RefleXion启动关键临床试验」中所述，更新后的报销代码预计将使SCINTIX疗法的适用人群扩大到约40万名患者，这表明生物驱动的工作流程已全面融入临床实践。

同时，基于云端的治疗计画和数据分析的整合，正透过集中式数位生态系统优化复杂的肿瘤工作流程。医疗机构正在加速从孤立的现场工作站向互联的软体平台转型，这些平台支援远端计画审查、跨中心资料交换，并提升营运效率。这种数位资源的整合使他们能够在不相应扩充实体基础设施的情况下，有效应对不断增长的患者数量。这一趋势的商业性成功已体现在近期的财务指标中。在2025年5月发布的2024/25财年财报中，Elekta宣布其软体部门实现了两位数的成长。这是其调整后息税前利润率达到16.3%的关键因素，也清楚显示医疗服务模式正向软体转型。

目录

第一章概述

第二章：调查方法

第三章执行摘要

第四章：客户心声

第五章：全球影像导引放射线治疗市场展望

• 市场规模及预测
  • 按金额
• 市占率及预测
  • 产品特定资讯（4D放射治疗、直线加速器、MRI导引放射治疗、门控CT影像）
  • 依治疗方法（IMRT、立体定位放射治疗、粒子束治疗）
  • 依应用领域（子宫颈癌、摄护腺癌、乳癌）
  • 按地区
  • 按公司（2025 年）
• 市场地图

第六章：北美影像导引放射线治疗市场展望

• 市场规模及预测
• 市占率及预测
• 北美洲：国别分析
  • 我们
  • 加拿大
  • 墨西哥

第七章：欧洲影像导引放射线治疗市场展望

• 市场规模及预测
• 市占率及预测
• 欧洲：国别分析
  • 德国
  • 法国
  • 英国
  • 义大利
  • 西班牙

第八章：亚太地区影像导引放射线治疗市场展望

• 市场规模及预测
• 市占率及预测
• 亚太地区：国别分析
  • 中国
  • 印度
  • 日本
  • 韩国
  • 澳洲

第九章：中东和非洲影像导引放射线治疗市场展望

• 市场规模及预测
• 市占率及预测
• 中东与非洲：国别分析
  • 沙乌地阿拉伯
  • 阿拉伯聯合大公国
  • 南非

第十章：南美洲影像导引放射线治疗市场展望

• 市场规模及预测
• 市占率及预测
• 南美洲：国别分析
  • 巴西
  • 哥伦比亚
  • 阿根廷

第十一章 市场动态

• 促进因素
• 任务

第十二章 市场趋势与发展

• 併购
• 产品发布
• 近期趋势

第十三章：全球影像导引放射放射线治疗市场：SWOT分析

第十四章：波特五力分析

• 产业竞争
• 新进入者的潜力
• 供应商的议价能力
• 顾客权力
• 替代品的威胁

第十五章 竞争格局

• Siemens Healthineers AG
• ViewRay, Inc.
• Varian Medical Systems, Inc.
• Toshiba Corporation
• GE HealthCare Technologies, Inc.
• Accuray Inc.
• Becton, Dickinson, and Company
• Vision RT Ltd.

第十六章 策略建议

第十七章：关于研究公司及免责声明

The Global Image-Guided Radiation Therapy Market is projected to expand from USD 2.02 Billion in 2025 to USD 2.78 Billion by 2031, registering a compound annual growth rate of 5.45%. This advanced treatment modality integrates frequent imaging protocols, such as magnetic resonance imaging or computed tomography, directly into the radiation delivery process to maximize tumor targeting precision while preserving surrounding healthy tissue. The market's upward trajectory is primarily fueled by the escalating global prevalence of cancer and a shifting preference toward non-invasive therapeutic options that ensure higher safety standards and treatment effectiveness. Data from the International Atomic Energy Agency in 2024 underscores this urgency, revealing that approximately 50 to 70 percent of cancer patients worldwide require radiotherapy, thereby driving the demand for high-precision technologies capable of optimizing these critical interventions.

However, the market confronts substantial hurdles stemming from the immense capital expenditures necessary to procure and deploy these advanced systems. The prohibitive costs related to purchasing equipment, combined with the financial demands of specialized infrastructure construction and continuous maintenance, establish significant barriers to entry. These financial constraints severely limit adoption rates, particularly affecting healthcare institutions within low- and middle-income regions where funding for high-cost medical technologies is often restricted.

Market Driver

The escalating global incidence of cancer serves as the principal engine for growth within the Image-Guided Radiation Therapy market, creating an urgent imperative for scalable solutions capable of managing increasing patient volumes. As the burden of disease intensifies, healthcare providers are compelled to implement high-throughput systems that ensure effective localized disease control while minimizing adverse effects. This critical demand is highlighted by the scale of the issue; the World Health Organization's International Agency for Research on Cancer reported in a February 2024 press release regarding the 'Global Cancer Burden' that there were an estimated 20 million new cancer cases worldwide in 2022. Consequently, this rising caseload is directly accelerating the procurement of radiation therapy machinery as hospitals expand their oncology departments to address the essential care requirements of a growing patient demographic.

Concurrently, rapid technological evolution, specifically the incorporation of artificial intelligence, is propelling market development by transforming how treatments are delivered. Contemporary IGRT platforms now utilize adaptive algorithms capable of modifying radiation beams in real-time, which significantly refines targeting accuracy. The industry's pivot toward these adaptive systems is evidenced by strong commercial results; for instance, Accuray Incorporated reported gross orders totaling $342.1 million in its 'Fourth Quarter and Fiscal 2024 Financial Results' released in August 2024, demonstrating solid demand for precision tools. The financial magnitude of the sector is further exemplified by industry leaders like Siemens Healthineers, whose Varian segment achieved a total revenue of $4.14 billion in 2024, a figure driven by the persistent uptake of advanced radiotherapy solutions.

Market Challenge

The significant capital investment necessary for the acquisition and installation of Image-Guided Radiation Therapy (IGRT) systems presents a major impediment to the market's global expansion. These sophisticated treatment platforms require not only the procurement of costly hardware but also substantial outlays for specialized facility infrastructure, such as radiation-shielded bunkers, along with rigorous ongoing maintenance protocols. This heavy financial load establishes a steep barrier to entry that limits the capacity of healthcare institutions, especially those in resource-constrained environments, to obtain essential equipment, thereby effectively restricting the potential customer base and decelerating overall adoption rates.

This economic barrier precipitates a severe disparity in accessibility, directly hindering market penetration in developing regions where the clinical necessity is often most acute. According to the Global Coalition for Radiotherapy in 2024, approximately 58 nations worldwide lacked any radiotherapy services entirely, a deficit largely attributed to local healthcare systems' inability to finance the initial capitalization and operational expenses associated with these technologies. The lack of infrastructure in such a significant number of countries prevents manufacturers from accessing potential revenue streams in emerging markets, ultimately constraining the global industry's growth trajectory.

Market Trends

The emergence of Biologically Guided Radiation Therapy platforms marks a transformative evolution in the market, shifting focus from anatomical imaging to the utilization of tumor biology for real-time targeting. In contrast to traditional systems that depend solely on structural variations, these advanced platforms detect positron emission tomography signals released directly by the tumor, enabling the precise treatment of multiple metastatic locations in a single session. This innovation meets a critical need for managing late-stage malignancies where conventional focal therapies often prove inadequate. The rapid adoption of this technology is highlighted by regulatory advancements; as noted by RefleXion Medical in its 'RefleXion Launches Pivotal Study' press release from January 2025, updated reimbursement codes are set to expand access to SCINTIX therapy to approximately 400,000 additional patients, signaling the substantial clinical integration of biologically driven workflows.

In parallel, the integration of cloud-based treatment planning and data analytics is optimizing complex oncology workflows through centralized digital ecosystems. Healthcare institutions are increasingly moving away from isolated, on-site workstations toward interconnected software platforms that support remote plan reviews, multi-site data exchange, and improved operational productivity. This consolidation of digital resources enables clinics to effectively handle growing patient volumes without necessitating a proportional expansion of physical infrastructure. The commercial success of this trend is reflected in recent financial metrics; Elekta, in its 'Year-end report May 2024/25' released in May 2025, announced double-digit growth within its software division, a critical contributor to an adjusted EBIT margin of 16.3 percent, indicating a definitive industry shift toward software-centric models of care delivery.

Key Market Players

• Siemens Healthineers AG
• ViewRay, Inc.
• Varian Medical Systems, Inc.
• Toshiba Corporation
• GE HealthCare Technologies, Inc.
• Accuray Inc.
• Becton, Dickinson, and Company
• Vision RT Ltd.

Report Scope

In this report, the Global Image-Guided Radiation Therapy Market has been segmented into the following categories, in addition to the industry trends which have also been detailed below:

Image-Guided Radiation Therapy Market, By Product

• 4D RT
• LINAC
• MRI-guided radiotherapy
• Portal CT Imaging

Image-Guided Radiation Therapy Market, By Procedure

• IMRT
• Stereotactic
• Particle

Image-Guided Radiation Therapy Market, By Application

• Neck
• Prostate
• Breast cancer

Image-Guided Radiation Therapy Market, By Region

• North America
  • United States
  • Canada
  • Mexico
• Europe
  • France
  • United Kingdom
  • Italy
  • Germany
  • Spain
• Asia Pacific
  • China
  • India
  • Japan
  • Australia
  • South Korea
• South America
  • Brazil
  • Argentina
  • Colombia
• Middle East & Africa
  • South Africa
  • Saudi Arabia
  • UAE

Competitive Landscape

Company Profiles: Detailed analysis of the major companies present in the Global Image-Guided Radiation Therapy Market.

Available Customizations:

Global Image-Guided Radiation Therapy Market report with the given market data, TechSci Research offers customizations according to a company's specific needs. The following customization options are available for the report:

Company Information

• Detailed analysis and profiling of additional market players (up to five).

Table of Contents

1. Product Overview

• 1.1. Market Definition
• 1.2. Scope of the Market
  • 1.2.1. Markets Covered
  • 1.2.2. Years Considered for Study
  • 1.2.3. Key Market Segmentations

2. Research Methodology

• 2.1. Objective of the Study
• 2.2. Baseline Methodology
• 2.3. Key Industry Partners
• 2.4. Major Association and Secondary Sources
• 2.5. Forecasting Methodology
• 2.6. Data Triangulation & Validation
• 2.7. Assumptions and Limitations

3. Executive Summary

• 3.1. Overview of the Market
• 3.2. Overview of Key Market Segmentations
• 3.3. Overview of Key Market Players
• 3.4. Overview of Key Regions/Countries
• 3.5. Overview of Market Drivers, Challenges, Trends

4. Voice of Customer

5. Global Image-Guided Radiation Therapy Market Outlook

• 5.1. Market Size & Forecast
  • 5.1.1. By Value
• 5.2. Market Share & Forecast
  • 5.2.1. By Product (4D RT, LINAC, MRI-guided radiotherapy, Portal CT Imaging)
  • 5.2.2. By Procedure (IMRT, Stereotactic, Particle)
  • 5.2.3. By Application (Neck, Prostate, Breast cancer)
  • 5.2.4. By Region
  • 5.2.5. By Company (2025)
• 5.3. Market Map

6. North America Image-Guided Radiation Therapy Market Outlook

• 6.1. Market Size & Forecast
  • 6.1.1. By Value
• 6.2. Market Share & Forecast
  • 6.2.1. By Product
  • 6.2.2. By Procedure
  • 6.2.3. By Application
  • 6.2.4. By Country
• 6.3. North America: Country Analysis
  • 6.3.1. United States Image-Guided Radiation Therapy Market Outlook
    • 6.3.1.1. Market Size & Forecast
      • 6.3.1.1.1. By Value
    • 6.3.1.2. Market Share & Forecast
      • 6.3.1.2.1. By Product
      • 6.3.1.2.2. By Procedure
      • 6.3.1.2.3. By Application
  • 6.3.2. Canada Image-Guided Radiation Therapy Market Outlook
    • 6.3.2.1. Market Size & Forecast
      • 6.3.2.1.1. By Value
    • 6.3.2.2. Market Share & Forecast
      • 6.3.2.2.1. By Product
      • 6.3.2.2.2. By Procedure
      • 6.3.2.2.3. By Application
  • 6.3.3. Mexico Image-Guided Radiation Therapy Market Outlook
    • 6.3.3.1. Market Size & Forecast
      • 6.3.3.1.1. By Value
    • 6.3.3.2. Market Share & Forecast
      • 6.3.3.2.1. By Product
      • 6.3.3.2.2. By Procedure
      • 6.3.3.2.3. By Application

7. Europe Image-Guided Radiation Therapy Market Outlook

• 7.1. Market Size & Forecast
  • 7.1.1. By Value
• 7.2. Market Share & Forecast
  • 7.2.1. By Product
  • 7.2.2. By Procedure
  • 7.2.3. By Application
  • 7.2.4. By Country
• 7.3. Europe: Country Analysis
  • 7.3.1. Germany Image-Guided Radiation Therapy Market Outlook
    • 7.3.1.1. Market Size & Forecast
      • 7.3.1.1.1. By Value
    • 7.3.1.2. Market Share & Forecast
      • 7.3.1.2.1. By Product
      • 7.3.1.2.2. By Procedure
      • 7.3.1.2.3. By Application
  • 7.3.2. France Image-Guided Radiation Therapy Market Outlook
    • 7.3.2.1. Market Size & Forecast
      • 7.3.2.1.1. By Value
    • 7.3.2.2. Market Share & Forecast
      • 7.3.2.2.1. By Product
      • 7.3.2.2.2. By Procedure
      • 7.3.2.2.3. By Application
  • 7.3.3. United Kingdom Image-Guided Radiation Therapy Market Outlook
    • 7.3.3.1. Market Size & Forecast
      • 7.3.3.1.1. By Value
    • 7.3.3.2. Market Share & Forecast
      • 7.3.3.2.1. By Product
      • 7.3.3.2.2. By Procedure
      • 7.3.3.2.3. By Application
  • 7.3.4. Italy Image-Guided Radiation Therapy Market Outlook
    • 7.3.4.1. Market Size & Forecast
      • 7.3.4.1.1. By Value
    • 7.3.4.2. Market Share & Forecast
      • 7.3.4.2.1. By Product
      • 7.3.4.2.2. By Procedure
      • 7.3.4.2.3. By Application
  • 7.3.5. Spain Image-Guided Radiation Therapy Market Outlook
    • 7.3.5.1. Market Size & Forecast
      • 7.3.5.1.1. By Value
    • 7.3.5.2. Market Share & Forecast
      • 7.3.5.2.1. By Product
      • 7.3.5.2.2. By Procedure
      • 7.3.5.2.3. By Application

8. Asia Pacific Image-Guided Radiation Therapy Market Outlook

• 8.1. Market Size & Forecast
  • 8.1.1. By Value
• 8.2. Market Share & Forecast
  • 8.2.1. By Product
  • 8.2.2. By Procedure
  • 8.2.3. By Application
  • 8.2.4. By Country
• 8.3. Asia Pacific: Country Analysis
  • 8.3.1. China Image-Guided Radiation Therapy Market Outlook
    • 8.3.1.1. Market Size & Forecast
      • 8.3.1.1.1. By Value
    • 8.3.1.2. Market Share & Forecast
      • 8.3.1.2.1. By Product
      • 8.3.1.2.2. By Procedure
      • 8.3.1.2.3. By Application
  • 8.3.2. India Image-Guided Radiation Therapy Market Outlook
    • 8.3.2.1. Market Size & Forecast
      • 8.3.2.1.1. By Value
    • 8.3.2.2. Market Share & Forecast
      • 8.3.2.2.1. By Product
      • 8.3.2.2.2. By Procedure
      • 8.3.2.2.3. By Application
  • 8.3.3. Japan Image-Guided Radiation Therapy Market Outlook
    • 8.3.3.1. Market Size & Forecast
      • 8.3.3.1.1. By Value
    • 8.3.3.2. Market Share & Forecast
      • 8.3.3.2.1. By Product
      • 8.3.3.2.2. By Procedure
      • 8.3.3.2.3. By Application
  • 8.3.4. South Korea Image-Guided Radiation Therapy Market Outlook
    • 8.3.4.1. Market Size & Forecast
      • 8.3.4.1.1. By Value
    • 8.3.4.2. Market Share & Forecast
      • 8.3.4.2.1. By Product
      • 8.3.4.2.2. By Procedure
      • 8.3.4.2.3. By Application
  • 8.3.5. Australia Image-Guided Radiation Therapy Market Outlook
    • 8.3.5.1. Market Size & Forecast
      • 8.3.5.1.1. By Value
    • 8.3.5.2. Market Share & Forecast
      • 8.3.5.2.1. By Product
      • 8.3.5.2.2. By Procedure
      • 8.3.5.2.3. By Application

9. Middle East & Africa Image-Guided Radiation Therapy Market Outlook

• 9.1. Market Size & Forecast
  • 9.1.1. By Value
• 9.2. Market Share & Forecast
  • 9.2.1. By Product
  • 9.2.2. By Procedure
  • 9.2.3. By Application
  • 9.2.4. By Country
• 9.3. Middle East & Africa: Country Analysis
  • 9.3.1. Saudi Arabia Image-Guided Radiation Therapy Market Outlook
    • 9.3.1.1. Market Size & Forecast
      • 9.3.1.1.1. By Value
    • 9.3.1.2. Market Share & Forecast
      • 9.3.1.2.1. By Product
      • 9.3.1.2.2. By Procedure
      • 9.3.1.2.3. By Application
  • 9.3.2. UAE Image-Guided Radiation Therapy Market Outlook
    • 9.3.2.1. Market Size & Forecast
      • 9.3.2.1.1. By Value
    • 9.3.2.2. Market Share & Forecast
      • 9.3.2.2.1. By Product
      • 9.3.2.2.2. By Procedure
      • 9.3.2.2.3. By Application
  • 9.3.3. South Africa Image-Guided Radiation Therapy Market Outlook
    • 9.3.3.1. Market Size & Forecast
      • 9.3.3.1.1. By Value
    • 9.3.3.2. Market Share & Forecast
      • 9.3.3.2.1. By Product
      • 9.3.3.2.2. By Procedure
      • 9.3.3.2.3. By Application

10. South America Image-Guided Radiation Therapy Market Outlook

• 10.1. Market Size & Forecast
  • 10.1.1. By Value
• 10.2. Market Share & Forecast
  • 10.2.1. By Product
  • 10.2.2. By Procedure
  • 10.2.3. By Application
  • 10.2.4. By Country
• 10.3. South America: Country Analysis
  • 10.3.1. Brazil Image-Guided Radiation Therapy Market Outlook
    • 10.3.1.1. Market Size & Forecast
      • 10.3.1.1.1. By Value
    • 10.3.1.2. Market Share & Forecast
      • 10.3.1.2.1. By Product
      • 10.3.1.2.2. By Procedure
      • 10.3.1.2.3. By Application
  • 10.3.2. Colombia Image-Guided Radiation Therapy Market Outlook
    • 10.3.2.1. Market Size & Forecast
      • 10.3.2.1.1. By Value
    • 10.3.2.2. Market Share & Forecast
      • 10.3.2.2.1. By Product
      • 10.3.2.2.2. By Procedure
      • 10.3.2.2.3. By Application
  • 10.3.3. Argentina Image-Guided Radiation Therapy Market Outlook
    • 10.3.3.1. Market Size & Forecast
      • 10.3.3.1.1. By Value
    • 10.3.3.2. Market Share & Forecast
      • 10.3.3.2.1. By Product
      • 10.3.3.2.2. By Procedure
      • 10.3.3.2.3. By Application

11. Market Dynamics

• 11.1. Drivers
• 11.2. Challenges

12. Market Trends & Developments

• 12.1. Merger & Acquisition (If Any)
• 12.2. Product Launches (If Any)
• 12.3. Recent Developments

13. Global Image-Guided Radiation Therapy Market: SWOT Analysis

14. Porter's Five Forces Analysis

• 14.1. Competition in the Industry
• 14.2. Potential of New Entrants
• 14.3. Power of Suppliers
• 14.4. Power of Customers
• 14.5. Threat of Substitute Products

15. Competitive Landscape

• 15.1. Siemens Healthineers AG
  • 15.1.1. Business Overview
  • 15.1.2. Products & Services
  • 15.1.3. Recent Developments
  • 15.1.4. Key Personnel
  • 15.1.5. SWOT Analysis
• 15.2. ViewRay, Inc.
• 15.3. Varian Medical Systems, Inc.
• 15.4. Toshiba Corporation
• 15.5. GE HealthCare Technologies, Inc.
• 15.6. Accuray Inc.
• 15.7. Becton, Dickinson, and Company
• 15.8. Vision RT Ltd.

16. Strategic Recommendations

17. About Us & Disclaimer