A liquid fiducial marker for image-guided proton beam therapy of abdominal tumors
In brief
Liquid fiducials produced smaller CT artifacts than solid markers in phantom tests
In an abdominal phantom, liquid markers were more visible on X-ray and produced smaller CT artifacts than solid markers, with artifact areas up to 30.5 mm3 versus 279.4 mm3. They also disturbed proton dose less, and their chemical composition remained stable after irradiation. Whether these advantages hold in patients remains untested.
- Journal
- Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) (Q2)
- Published
- 21 October 2026
- Study design
- Unclassified
- Evidence level
- Level 5, Expert Opinion (CEBM 5)
- Authors
- Sarah Stefanowicz, Jonas R Henriksen, Rasmus Jølck, Stefan Menkel, Michael W Mortensen, Esther G C Troost
- PMID
- 42906269
- DOI
- 10.1016/j.ejmp.2026.107203
Why clinicians should know about it
- Picked for Medical Physics (top studies of the week, 25 October 2026): Phantom-tested proton fiducial visibility, artifacts, and dose perturbation
Abstract
PURPOSE: This study compared a liquid to solid fiducial markers regarding visibility, artifact characteristics on X-ray imaging and dose perturbation for image-guided proton therapy (IGPT) of abdominal tumors. Additionally, the radio-opaque composition of the liquid fiducial marker was optimized, and the chemical stability after proton beam irradiation was analyzed. MATERIAL AND METHODS: The fiducial markers inserted into an anthropomorphic abdominal phantom were exposed to X-ray, single-energy computed tomography (SECT), dual-energy CT (DECT) and cone-beam CT (CBCT) to determine contrast-to-noise ratios (CNR) and artifacts. Proton dose perturbation estimations were performed using a Monte Carlo dose algorithm. Chemical stability following proton beam irradiation was assessed with biophysical and optical methods. RESULTS: The CNR of the liquid marker with a volume ≥ 100 μl (CNR ≤ 2.69) on 2D X-ray images was superior to the solid markers (CNR ≤ 1.72). The artifact areas (A) and severity in the CT modalities were more pronounced for the solid (e.g. , SECT: A ≤ 279.4 mm3) than for the liquid fiducial marker (A ≤ 30.5 mm3). Dose mitigation of ≥ 50% in a proton beam was calculated for solid fiducial markers, while the liquid marker less influenced the dose distribution. Increasing radio-opaque content in the liquid prototypes improved visibility (CNR ≤ 2.97) without significantly increasing artifact volume (SECT: A ≤ 40.5 mm3) or dose perturbation. No degradation of the liquid fiducial marker's chemical composition was observed. CONCLUSION: The liquid fiducial marker demonstrated comparable visibility and chemical stability with reduced artifact generation and dose perturbation compared to solid markers, indicating superiority for IGPT of abdominal tumors. Optimization of the liquid marker composition may be considered.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.