Commissioning of a precision preclinical 200 kV x‐ray irradiator based on modular adaptations
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-03-26 |
| Journal | Medical Physics |
| Authors | Lorenz Wolf, Peter Kuess, Sabine Leitner, Dietmar Georg, Barbara Knäusl |
| Institutions | Medical University of Vienna, Fachhochschule Wiener Neustadt |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Precision Preclinical X-ray Irradiator Commissioning
Section titled “Technical Documentation & Analysis: Precision Preclinical X-ray Irradiator Commissioning”Executive Summary
Section titled “Executive Summary”This research details the successful commissioning and validation of a cost-effective, high-precision preclinical 200 kV x-ray irradiation system, achieved through modular adaptations of an industrial unit.
- High-Precision Preclinical Platform: A modified industrial kilovoltage x-ray unit was commissioned to replicate horizontal particle beam geometry, enabling high-precision irradiation of small animals and in vitro samples.
- Modular Adaptations: Custom-designed components, including a dual brass collimation system (5 mm to 30 mm apertures), a multimodal mouse bedding unit, and dedicated dosimetric and QA phantoms, were developed and validated.
- Diamond Detector Validation: Dosimetry relied heavily on a microDiamond (mD) detector, confirming the suitability of synthetic diamond for high-resolution beam characterization in small kilovoltage x-ray fields.
- Exceptional Accuracy: The resulting beam model in the commercial Treatment Planning System (TPS) was validated with a maximum dose deviation of 1.7%.
- Sharp Field Definition: The system achieved a sharp penumbra of 0.6 mm for the smallest 5 mm aperture, crucial for sparing surrounding healthy tissue in small animal models.
- Robust QA: Subject-specific QA measurements yielded a median gamma passing rate of 100% (using a strict 1%/1 mm acceptance criterion), confirming the system’s suitability for reproducible preclinical research.
- Cost-Effective Solution: The modular framework provides an accessible and cost-effective upgrade path for existing kilovoltage x-ray systems, enhancing accessibility to high-quality preclinical irradiation research.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the commissioning and validation results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| X-ray Tube Voltage | 200 | kV | Operating setting for measurements. |
| X-ray Tube Current | 20 | mA | Operating setting for measurements. |
| Filtration | 3 mm Be, 3 mm Al, 0.5 mm Cu | - | Used to harden the beam spectrum. |
| Focal Spot Size | 5.5 | mm | Tungsten target angle 20°. |
| Source-to-Surface Distance (SSD) | 331 | mm | Used for PDD measurements. |
| Secondary Collimator Apertures | 5 to 30 | mm | Interchangeable brass SCs manufactured. |
| Penumbra (Smallest Field) | 0.6 | mm | For 5 mm aperture at 20 mm depth in RW3. |
| Dose Rate (Mean) | 1.722 ± 0.002 | Gy min-1 | At 10 mm depth (30-330 s irradiation time). |
| Beam Model Validation (Max Deviation) | 1.7 | % | Relative dose deviation (measurement vs. calculation). |
| QA Gamma Passing Rate (Median) | 100 | % | Using 1% dose difference / 1 mm distance to agreement. |
| Homogeneity Index (HI) | 9.9 ± 0.7 | % | For 5 mm target diameter (in silico mouse brain). |
| Total Standard Uncertainty (1-σ) | 2.4 to 4.7 | % | Combined uncertainty budget (small to large field sizes). |
Key Methodologies
Section titled “Key Methodologies”The experimental framework involved precise mechanical adaptation, advanced dosimetry, and Monte Carlo beam modeling:
- X-ray Unit Adaptation: An industrial YXLON Maxishot kilovoltage x-ray unit was modified, mounting the tube horizontally to mimic the geometry of a particle therapy beam line for comparative radiobiological studies.
- Dual Collimation System: A brass dual collimation system was designed and manufactured, featuring a fixed primary collimator and interchangeable secondary collimators (SCs) ranging from 5 mm to 30 mm in diameter.
- Modular Phantoms: Custom 3D-printed (ABS) modular devices were developed, including a mouse bedding unit (compatible with CT/MR/PET imaging), a Small Field Dosimetry Phantom (SFDP) using RW3 slabs, and a Solid Water HE QA phantom.
- Dosimetry Detectors: Beam data acquisition utilized a PTW microDiamond (mD) detector (shown suitable for small kilovoltage beams) and Gafchromic EBT3 films for lateral dose profiles (LDPs).
- Absolute Calibration: Air kerma calibration using a Farmer ionization chamber was converted to absorbed dose to water, following IAEA TRS-398 recommendations, despite geometric constraints (SSD 331 mm).
- Beam Modeling: Percentage Depth Dose (PDD) curves and relative LDPs were used as input for the commercial µ-RayStation 8B TPS, which employs a GPU-based Monte Carlo dose engine (0.2 mm dose grid resolution).
- Validation: The beam model was validated against measurements across various depths and apertures. Subject-specific QA was performed using the mD and EBT3 films in the QA phantom, analyzed via 2D gamma analysis (1%/1 mm criterion).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The successful commissioning of this high-precision preclinical irradiator relies on detectors capable of accurate, high-resolution dosimetry in small fields (down to 5 mm). The microDiamond detector (mD) used in this study is based on synthetic Single Crystal Diamond (SCD). 6CCVD is an expert manufacturer of MPCVD diamond materials, perfectly positioned to supply and customize the core components required to replicate or advance this research.
| Research Requirement | 6CCVD Solution & Value Proposition | Applicable Material |
|---|---|---|
| Ultra-Small Field Dosimetry | The study confirms the necessity of synthetic diamond for high-resolution PDD and LDP measurements in fields < 10 mm. 6CCVD provides the highest purity SCD substrates for next-generation, ultra-miniature detector fabrication. | Electronic Grade Single Crystal Diamond (SCD): Available in thicknesses from 0.1 µm to 500 µm, ideal for creating thin, high-sensitivity active layers required for sub-5 mm field characterization. |
| Custom Detector Geometry | The QA phantom required precise detector inserts (7 mm diameter). 6CCVD offers advanced laser cutting and shaping services to produce custom diamond geometries with sub-millimetric accuracy. | Custom Dimensions & Polishing: Plates/wafers up to 125 mm, with SCD polished to Ra < 1 nm and PCD to Ra < 5 nm, ensuring seamless integration into custom phantoms and collimator systems. |
| Optimizing Energy Response | The paper notes that synthetic diamond response can vary for low-energy photons. 6CCVD can tailor the material properties to optimize detector performance for specific kilovoltage spectrums. | Boron-Doped Diamond (BDD): Customizable doping levels for optimizing conductivity and charge collection efficiency, crucial for developing detectors with minimized energy dependence in kV beams. |
| Advanced Detector Prototyping | Future work requires investigating alternative detectors (e.g., scintillators) and smaller field sizes (< 5 mm). 6CCVD supports full detector prototyping, including electrical contact deposition. | Advanced Metalization: Internal capability for depositing high-purity metal contacts (Au, Pt, Pd, Ti, W, Cu) directly onto diamond substrates, essential for creating robust, reliable electrical connections for detector prototypes. |
| Global Research Support | The modular design is intended for global adoption by other research groups. 6CCVD supports global shipping (DDU default, DDP available) and provides expert consultation. | Engineering Support: Our in-house PhD team specializes in material selection and optimization for radiation dosimetry and high-power optics, ready to assist with similar preclinical x-ray or particle beam projects. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Background Preclinical research in radiation oncology encompasses a range of methodologies, including in vitro cell studies and in vivo small animal experiments, as well as in silico studies to evaluate radiation‐induced side effects and tumor responses. Purpose This study addresses the need for high‐precision x‐ray irradiation solutions as reference for preclinical research. Modifications of an industrial kilovoltage x‐ray unit, along with the commissioning of a commercial treatment planning system (TPS), aimed to enable reliable irradiation of small animals in a horizontal beam geometry. All advancements enhancing the irradiation framework are made available, offering cost‐effective upgrades for existing systems. Methods An industrial kilovoltage x‐ray unit was equipped with a dual collimation system, featuring a fixed primary and variable secondary collimators with aperture diameters of 5 to 30 mm. Additional modular adaptations were designed and manufactured, including a multimodal mouse bedding unit, a dedicated dosimetry phantom and a quality assurance (QA) phantom. Output factors, percentage depth dose curves and lateral dose profiles were acquired to generate a beam model in the ‐RayStation 8B (RaySearch Laboratories, Stockholm, Sweden), using a diamond detector and radiochromic films. Treatment plans for 10 mice were created, evaluated via dose‐volume metrics and the homogeneity index and subsequently dosimetrically compared to QA measurements through a gamma analysis with a 1%/ acceptance criterion. Results The resulting beam model was validated within a maximum dose deviation of 1.7%. Aperture diameters close to potential target diameters were found to be effective for achieving sufficient target coverage in silico, as demonstrated for a 5 mm target with a homogeneity index of (9.9 0.7)%. Dedicated QA measurements revealed a maximum dose deviation of 1.9% from the TPS and a median gamma passing rate of 100%, confirming the suitability of the proposed solution. Conclusions Cost‐effective adaptations for an kilovoltage x‐ray irradiation framework were designed, manufactured and commissioned, and contribute to the accessibility of preclinical irradiation research. These components are integrated into a comprehensive preclinical particle beam platform.