ArticleJournal of applied clinical medical physics2026
Identification and mitigation of unexplained dose attenuation caused by sub-table water accumulation in an MR-Linac (Elekta Unity).
Article in Journal of applied clinical medical physics, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
1 citing paper in PubMed.
- Identification and mitigation of unexplained dose attenuation caused by sub-table water accumulation in an MR-Linac (Elekta Unity).Journal of applied clinical medical physics · 2026Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
4 authors.
Funding
Abstract
purposeTo report and investigate a case of significant dose attenuation observed during quality assurance (QA) of an Elekta Unity MR-Linac system, and to elucidate its root cause and solution.
methodsDuring a period of abnormal environmental conditions (elevated temperature and humidity), a >20% dose output reduction was detected at a gantry angle of 180°. A comprehensive investigation was undertaken, including dose output measurements at multiple gantry angles, beam quality assessment, mechanical accuracy checks, EPID image analysis, and gamma pass rate analysis using ArcCheck-MR. The source of the attenuation was localized through a process of elimination.
resultsThe investigation revealed severe dose attenuation specifically at angles traversing beneath the treatment couch, with a gamma pass rate (3%/3 mm) dropping to 39.1% at 180°. All other system parameters, including MRI quality and mechanical alignments, were within tolerance. Visual inspection after disassembly confirmed the presence of a substantial pool of water beneath the table, estimated to be at least 3.5 cm deep, which acted as an unintended attenuator. The water was attributed to condensation and drainage issues exacerbated by the failed air-conditioning system. Mitigation strategies, including hardware sealing, enhanced drainage, revised maintenance protocols, and the addition of a 180° dose check to daily QA, successfully resolved the issue.
conclusionThis case highlights a previously unreported and critical failure mode for MR-Linac systems. It underscores the profound impact of environmental control on machine performance and patient safety. Robust HVAC maintenance, proactive monitoring of sub-table areas, and the inclusion of oblique-angle dosimetry in QA routines are essential for all Elekta Unity and similar high-precision radiotherapy systems.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.