Novel Detection Techniques for Ion Beams

About Us

Ion beam radiotherapy & its challenges

Ion beam radiotherapy is a highly precise treatment modality for tumors close to critical organs like brainstem or eye nerves. Unlike in conventional radiotherapy with photons, in ion radiotherapy even minor geometrical changes in the patient's anatomy (e.g. tissue swelling, different kinds of movement or incorrect patient positioning) can lead to severe changes of the radiation dose distribution in the patient. Consequently, quantitative imaging of the internal patient structures and the radiation field inside of the patient during therapy are crucial for the success of ion-beam treatments.

Timepix detectors:

In all our projects Timepix detectors are used for the experimental measurements. The generations of Timepix radiation detector technology were developed at CERN. These finely pixelated semiconductor detectors enable noise-free detection of individual ionizing particles and their properties, as well as ion tracking.

Current research projects

A diagram shows a mannequin lying on a table, positioned for a medical examination. An imaging device is positioned near the mannequin's head, with lines indicating the direction of light or radiation. The focus is on the layout for a medical procedure.

InViMo project: Non-contact assessment of the dose distribution in the patient

Secondary radiation is used in this project for in-vivo monitoring of the dose distribution in the patient. As secondary radiation is escaping the patient instantaneously during the irradiation as a by-product, no additional dose to the patient is required for this kind of imaging.

While a wide spectrum of radiation is created in the patient, we focus on measuring the tracks of charged nuclear fragments. By analysing their distribution we draw conclusions about internal changes in the patient's tissue along the beam path (e.g. filling of the nose cavity).

Following year-long research on patient models, we started a clinical study at the Heidelberg Ion Beam Therapy Center.

Funding: National Center for Tumor Diseases (NCT), Funding Program "Proof-of-Concept Clinical Trials", Project: In-vivo monitoring of carbon ion radiotherapy delivery (InViMo)

Related publications:

1. L. Kelleter, L. Marek, G. Echner, P. Ochoa-Parra, M. Winter, S. Harrabi, J. Jakubek, O. Jäkel, J. Debus, M. Martisikova. An in-vivo treatment monitoring system for ion-beam radiotherapy based on 28 Timepix3 detectors. Scientific Reports 14 (2024) 15452

2. L. Schweins, R. Kirchgässner, P. Ochoa-Parra, M. Winter, S. Harrabi, A. Mairani, O. Jäkel, J. Debus, M. Martišíková, L. Kelleter. Detection of an internal density change in an anthropomorphic head phantom via tracking of charged nuclear fragments in carbon-ion radiotherapy. Medical Physics 52: 2399–2411 (2025).

3. L. Ghesquière-Diérickx, R. Félix-Bautista, A. Schlechter, L. Kelleter, M. Reimold, G. Echner, P. Soukup, O. Jäkel, T. Gehrke and M. Martišíková. Detecting perturbations of a radiation field inside a head-sized phantom exposed to therapeutic carbon-ion beams through charged-fragment tracking. Medical Physics 29 (2022) 1776-1792 Editor's Choice

The image displays an X-ray of a bone structure with a red rectangle indicating a focus area. Below, a color gradient map shows varying measurements labeled "WET (mm)," highlighting differences in water content in the highlighted region.

He-ion radiography: Imaging of the patient with helium ion beams

To precisely identify possible changes within the patient directly before the treatment, when the patient is already positioned on the couch, we develop an imaging method with helium ions instead of conventionally used photons. These ions must have sufficient energy to cross the entire patient, since the residual energy of the ions leaving the patient is needed. Bulky calorimeters are used to measure it. Our approach is to use thin (< 1 mm) Timepix detectors, in combination with an adjustable energy of the incoming helium-ion beam. This unique approach we named "energy painting".

Funding: German Research Society (DFG), Project:Ion radiography for motion detection (Grant ID: MA 4437/3-1) and Project: Ion radiography with adaptive energy choice for a precise radiotherapy

Related publications:

1. C. Knobloch, M. Metzner, F. Kehrein, C. Schömers, S. Scheloske, S. Brons, R. Hermann, A. Peters, O. Jäkel, M. Martišíková and T. Gehrke. Experimental helium-beam radiography with a high-energy beam: Water-equivalent thickness calibration and first image-quality results. Medical Physics 49 (2022) 5347-5362 Editor's Choice

2. M. Metzner, F. K. Longarino, B. Ackermann, A. Schlechter, M. Saphörster, Y. Xu, J. Schlecker, P. Wohlfahrt, C. Richter, S. Brons, J. Debus, O. Jäkel, M. Martišíková, T. Gehrke. Accuracy of a helium-beam radiography system based on thin pixel detectors for an anthropomorphic head phantom. Medical Physics 52: 4757–4768 (2025).

3. M. Martišíková, T. Gehrke, S. Berke, G.Aricò and O. Jäkel. Helium ion beam imaging for image guided ion radiotherapy. Radiation Oncology 13(1) (2018) 109