HDR Brachytherapy with Fricke Gel Dosimetry

Precision in Cancer Treatment: 3D Dose Measurement Breakthrough

Theo Raines in Health & Wellness December 2025 • 5 min read.

"New method uses Fricke gel dosimeters and optical computed tomography to enhance HDR brachytherapy, improving accuracy and reducing side effects."

High-dose-rate (HDR) brachytherapy is a precise cancer treatment that places radioactive sources directly inside or next to tumors. This method allows doctors to deliver high doses of radiation to cancer cells while minimizing damage to surrounding healthy tissue. The key to its effectiveness lies in the accuracy of the dose delivery, which ensures that the tumor receives the intended radiation while sparing critical organs.

Measuring radiation dose distribution accurately, especially around HDR brachytherapy sources, is challenging. Traditional dosimetry systems often lack the necessary spatial resolution and sensitivity to capture the sharp dose gradients near the radiation source. This limitation has spurred the development of advanced techniques to visualize and verify the dose distribution in three dimensions.

A promising solution involves Fricke gel dosimeters combined with optical computed tomography (CT). Fricke gels react to radiation by changing color, and optical CT scans can then create detailed 3D images of these color changes, revealing the dose distribution. This method offers high spatial resolution and is nearly water-equivalent, meaning it doesn't significantly alter the radiation field. Recent research has refined this technique to overcome challenges, paving the way for more accurate and reliable HDR brachytherapy treatments.

How Fricke Gel Dosimeters and Optical CT Scanning Work Together

HDR Brachytherapy with Fricke Gel Dosimetry

The recent study published in 'Australasian Physical & Engineering Sciences in Medicine' details a new method for enhancing the precision of HDR brachytherapy using Fricke gel dosimeters and optical CT. The researchers aimed to create an accurate, high-resolution technique for measuring 3D dose distributions, addressing limitations of previous methods.

To achieve this, they developed a multi-needle brachytherapy gel phantom containing four stainless-steel brachytherapy needles and a Fricke Xylenol gel sample. A Paris-style HDR brachytherapy treatment was planned and delivered to the gel. The gel was then scanned using a novel optical CT method.

Phantom Creation: A custom phantom was 3D-printed to hold brachytherapy needles in a precise arrangement.
Gel Preparation: Fricke Xylenol gel was carefully prepared and poured into the phantom, encasing the needles.
Treatment Planning: The HDR brachytherapy treatment was planned using specialized software to deliver a specific dose distribution.
Irradiation: The gel phantom was irradiated with the planned treatment, causing chemical changes in the gel proportional to the radiation dose.
Optical CT Scanning: After irradiation, the needles were removed and replaced with a refractive index-matched fluid to minimize artifacts during scanning. The gel was then scanned using optical CT to create a 3D image of the dose distribution.
Data Analysis: The CT images were processed to subtract background noise and convert optical density changes into dose values. These measured dose values were then compared to the planned dose distribution.

A crucial step in their method was removing the stainless-steel needles before scanning and replacing them with a refractive index-matched fluid. This minimized artifacts caused by missing ray-sum data, which can distort the accuracy of optical CT reconstructions. The results demonstrated excellent agreement between measured and calculated doses, with differences of less than 1% at distances greater than 0.1 cm from each needle. This confirms that 3D Fricke gel phantoms are valuable tools for verifying HDR brachytherapy treatments.

The Future of HDR Brachytherapy

The phantom construction and optical CT scanning method offer the potential for routine quality assurance measurements of complex HDR brachytherapy treatment deliveries. By adapting this technique, clinicians can ensure that radiation is delivered precisely as planned, optimizing treatment outcomes and minimizing side effects. This innovation opens new avenues for personalized cancer therapy, where treatment plans are verified with unprecedented accuracy.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1007/s13246-018-0715-y, Alternate LINK

Title: A Method For Obtaining Three-Dimensional Measurements Of Hdr Brachytherapy Dose Distributions Using Fricke Gel Dosimeters And Optical Computed Tomography

Subject: Radiology, Nuclear Medicine and imaging

Journal: Australasian Physical & Engineering Sciences in Medicine

Publisher: Springer Science and Business Media LLC

Authors: Andre Asena, Sanna Nilsson, Shaun T. Smith, Tanya Kairn, Scott B. Crowe, Jamie V. Trapp

Published: 2018-11-20

Everything You Need To Know

What is HDR brachytherapy, and why is precision so important?

High-dose-rate (HDR) brachytherapy is a cancer treatment where radioactive sources are placed directly inside or next to tumors. This allows for a high dose of radiation to be delivered to the cancer cells while reducing the impact on surrounding healthy tissue. The precision of HDR brachytherapy is critical to ensure the tumor receives the intended radiation dose, sparing nearby critical organs. Any inaccuracies in dose delivery can lead to ineffective treatment or increased side effects, highlighting the importance of precise dose measurement and delivery techniques.

What are Fricke gel dosimeters, and how do they work with optical CT in radiation measurement?

Fricke gel dosimeters are radiation-sensitive materials that change color when exposed to radiation. The intensity of the color change is proportional to the radiation dose received. When combined with optical computed tomography (CT), Fricke gels enable the creation of detailed 3D images of radiation dose distribution. This method allows for high spatial resolution and accurate dose measurement, as the gel is nearly water-equivalent and minimally alters the radiation field. The use of Fricke gel dosimeters and optical CT is crucial for verifying the accuracy of complex cancer therapies like HDR brachytherapy.

How does optical CT scanning contribute to measuring radiation dose, and what steps are taken to ensure accuracy?

Optical CT scanning is used to create 3D images of the radiation dose distribution within Fricke gel dosimeters. After the gel has been exposed to radiation, it undergoes color changes proportional to the dose. Optical CT scans capture these color changes and reconstruct them into a 3D image, revealing the spatial distribution of the radiation dose. Removing the stainless-steel needles used in brachytherapy and replacing them with a refractive index-matched fluid is a critical step in this process to minimize artifacts and ensure accurate reconstruction of the dose distribution.

How does the use of 3D Fricke gel dosimeters and optical CT scanning improve the quality assurance process in HDR brachytherapy?

The integration of 3D Fricke gel dosimeters and optical CT scanning enhances the quality assurance of HDR brachytherapy by providing a highly accurate method for verifying dose distributions. This technique helps clinicians ensure that radiation is delivered precisely as planned, optimizing treatment outcomes and minimizing side effects. This approach is particularly important for complex treatments where precise dose delivery is essential to target the tumor while sparing surrounding healthy tissues. Without this level of precision, there is a risk of underdosing the tumor or overdosing healthy tissue.

In what ways does this new method contribute to more personalized cancer therapy?

This method improves personalized cancer therapy by allowing for the verification of treatment plans with unprecedented accuracy. By ensuring that radiation is delivered precisely as planned, clinicians can tailor treatments to each patient's specific needs, optimizing treatment outcomes and minimizing side effects. The ability to verify dose distributions in 3D enables more informed decision-making and allows for adaptive planning, where treatment plans can be adjusted based on real-time measurements. This level of precision is essential for delivering effective and safe cancer treatments.