Free-breathing GRASP MRI Shows Limited Ability to Represent Full Respiratory Motion in Liver Cancer Radiotherapy
A study of 54 liver cancer patients found that free-breathing GRASP MRI can accurately represent organ motion only during mid-respiratory phases (30%-60%), not across the full breathing cycle. The research compared GRASP MRI fusion with 4D-CT, the current gold standard for assessing tumor motion during stereotactic body radiation therapy. The findings suggest GRASP MRI should be combined with 4D-CT rather than used alone for treatment planning to ensure complete motion assessment.
Researchers conducted a retrospective analysis of 54 patients undergoing liver stereotactic body radiation therapy (SBRT) to evaluate whether free-breathing GRASP MRI could independently represent respiratory-induced organ motion. Using 4D-CT as the reference standard, they performed image fusion between GRASP MRI and each respiratory phase of 4D-CT, measuring fusion quality with maximum cross-correlation coefficients and validation by two blinded radiation oncologists. Results showed that the 50% respiratory phase achieved optimal fusion quality with GRASP MRI, with acceptable performance across the mid-respiratory window (30%-70%), but significantly degraded fusion quality at extreme respiratory phases (0%, 10%, 20%, 80%, 90%). The study concludes that while GRASP MRI performs well during mid-breathing phases, it cannot independently represent the full range of organ motion and should be combined with 4D-CT or other dynamic imaging for comprehensive motion assessment in liver SBRT treatment planning.
What's missing
The study does not discuss potential clinical implications of the mid-respiratory phase limitation (e.g., whether this affects treatment outcomes or safety margins), nor does it address the cost-effectiveness or practical workflow advantages/disadvantages of combining GRASP MRI with 4D-CT compared to using 4D-CT alone. The generalizability of findings to other tumor sites or patient populations is not addressed.
What different sources said
- arXiv physicsCenter
The Role of Free-breathing GRASP MRI in Accurate Phase Matching with 4D-CT for Motion Representation in Liver Cancer Radiotherapy
Related
Gut Bacteria Enzyme Found to Break Down Heat-Processed Food Compounds, Producing Novel Biogenic Amines
Researchers have discovered that an enzyme in common gut bacteria can degrade N-epsilon-carboxymethyllysine (CML), a compound formed during thermal food processing, producing previously unknown biogenic amines. The enzyme, ornithine decarboxylase SpeC from enterobacteria, acts on CML and related modified lysine derivatives through a low-level 'underground' catalytic activity. This finding suggests a previously unrecognized communication axis between thermally processed dietary compounds and gut microbial physiology, with potential implications for host health.
Full-Length Gene Sequencing Reveals Two Distinct Bacterial Communities in Black-Legged Ticks Expanding Into Canada
Researchers used Oxford Nanopore full-length 16S rRNA gene sequencing to characterize the microbiome of Ixodes scapularis black-legged ticks collected in Nova Scotia, Canada, distinguishing between tick-adapted bacteria and environmentally acquired bacteria. The study comes as I. scapularis — the primary vector of Lyme disease — is rapidly expanding northward into Canada due to climate change. The findings suggest that environmentally derived bacteria in tick microbiomes are not mere contamination, which has implications for how tick microbiome data is collected and interpreted across surveillance studies.
Study Identifies Metabolic Link Between Cell Envelope Stress and Biofilm Formation in Bacteria
Researchers have discovered that the metabolite acetyl-CoA directly inhibits enzymes that degrade the bacterial signaling molecule c-di-GMP, connecting cell envelope biosynthesis stress to biofilm formation in Pseudomonas aeruginosa. The study found that sub-inhibitory concentrations of antibiotics targeting early peptidoglycan biosynthesis — but not other antibiotic classes — elevate c-di-GMP levels by reducing phosphodiesterase activity, with acetyl-CoA competing for the enzyme active site. Because the relevant enzyme domain is broadly conserved across bacterial species, this checkpoint mechanism may be widespread and could have implications for understanding antibiotic-induced biofilm responses.