KV Imaging Systems for Linear Accelerators

In modern radiation therapy, imaging plays a critical role in delivering safe, accurate, and effective treatment. Over the years, kilovoltage (kV) imaging systems have become central to this effort, offering a balance of precision, patient safety, and support for advanced clinical workflows.

When we first explored this topic in our 2015 blog, kV imaging was still gaining traction as a standard in image-guided radiation therapy (IGRT). Since then, the field has evolved significantly with the introduction of advanced platforms like Varian TrueBeam, Halcyon, and other systems that have cemented kV imaging as a cornerstone of today’s radiation therapy.

Understanding KV Imaging: What It Is and How It Works

KV imaging uses low-energy X-rays to produce high-quality images before and during radiation treatment. These images help ensure that patients are positioned correctly, so the radiation dose is delivered exactly where it’s needed.

Compared to older EPID (MV) systems, kV imaging offers several key advantages:

• Better soft tissue visibility
• Lower imaging dose to the patient
• 3D imaging through cone beam CT (CBCT)

This combination of clarity and safety has made kV imaging the standard for image-guided radiation therapy (IGRT) in 2025.

How KV Imaging Supports Modern Radiation Therapy

KV imaging systems have become an essential component of modern radiation therapy, playing a critical role in delivering precise, efficient, and safe treatments. Here’s why they’re indispensable:

Leading KV Imaging Systems

Varian OBI (On-Board Imager)

• Integrated with Varian TrueBeam and Ethos systems
• Provides high-resolution 2D radiographs and 3D CBCT
• Supports image-guided and adaptive therapy workflows
• Enables precise patient positioning before and during treatment

Varian Halcyon Imaging

• Uses an integrated kV CBCT system rather than the OBI detector used on TrueBeam
• Provides high-quality 3D imaging tailored to Halcyon’s workflow
• Designed for efficient image acquisition and patient setup
• Supports daily imaging for accurate positioning within a simplified system design

Elekta XVI (X-ray Volume Imaging)

• Fully integrated with Elekta Versa HD and Unity systems.
• Offers fast, high-resolution 3D CBCT imaging for precise patient positioning.
• Enables multi-modality image fusion and supports adaptive radiotherapy strategies.
• Optimized for MR-LINAC hybrid workflows with superior soft tissue visualization.

Accuray ClearRT KVCT Imaging

• Embedded in the Radixact system for helical KVCT imaging.
• Delivers enhanced soft tissue contrast for improved tumor delineation.
• Facilitates real-time adaptive radiotherapy with integrated imaging and treatment delivery.
• Designed to support biology-guided and image-guided treatment protocols.

Established KV Systems for Budget-Conscious Facilities

While innovative platforms like Varian HyperSight™, Elekta ImagingRing, and RefleXion SCINTIX are advancing image-guided radiotherapy with cutting-edge features and AI integration, established KV imaging systems remain a reliable and cost-effective choice.

These systems are a practical option for clinics with tighter budgets or lower patient volumes, delivering essential imaging functionality without the high cost of newer technologies.

Key Considerations When Selecting a kV Imaging System

When evaluating kV imaging systems, facilities should weigh their technology needs against budget realities. Established systems like Varian OBI, Elekta XVI, and Accuray ClearRT remain reliable, cost-effective options that deliver precise image guidance. At the same time, newer platforms that incorporate AI and adaptive therapy capabilities such as Varian HyperSight™, Elekta ImagingRing, or RefleXion SCINTIX represent the next wave of innovation.

Compatibility with adaptive workflows may be an important factor for clinics planning to expand into adaptive therapy in the future. The right choice depends on whether a clinic prioritizes proven reliability at a lower cost or is ready to invest in advanced features that support adaptive care.

Frequently Asked Questions About kV Imaging in Radiation Therapy

What is the main advantage of kV imaging compared to MV imaging?

kV imaging uses lower-energy X-rays, which provide better soft tissue visibility and a lower imaging dose for patients. This makes it more effective than older MV (EPID) systems for accurate positioning and treatment verification.

How does cone beam CT (CBCT) enhance kV imaging?

CBCT allows clinicians to capture 3D images of the patient directly on the treatment machine. This improves accuracy by confirming tumor and organ positioning in three dimensions before and during therapy.

Which linear accelerator systems use kV imaging today?

Several leading platforms include Varian TrueBeam and Halcyon with OBI or integrated CBCT, Elekta Versa HD and Unity with the XVI system, and Accuray Radixact with ClearRT. Each offers unique strengths depending on the clinical workflow.

Are newer kV imaging systems worth the higher investment?

For clinics planning to adopt adaptive therapy or AI-driven workflows, newer platforms like Varian HyperSight™, Elekta ImagingRing, or RefleXion SCINTIX may be worth the investment. For facilities focused on proven reliability and lower upfront costs, established systems like Varian OBI, Elekta XVI, and Accuray ClearRT remain excellent choices.

Is kV imaging now considered the standard for IGRT?

Yes. With its combination of clear visualization, lower imaging dose, and support for advanced workflows, kV imaging has become the standard for image-guided radiation therapy (IGRT) in 2025.