Technical development and implementation of 3D-QALAS on a 1.5T MR-Linac for the brain: A prospective R-IDEAL stage 0/1 technology development report.
4 affiliations
- 1UT MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, Houston, Texas, USA.
- 2Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
- 3Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
- 4Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
Abstract
Background
Quantitative relaxometry of the brain on the integrated MRI / linear accelerator (MR-Linac) at high isotropic reconstructed resolution is currently limited due to prohibitively long scan times and limited field-of-views.Purpose
The purpose of this study was to assess the technical feasibility of the 3D-QALAS technique on the 1.5T MR-Linac which can acquire whole-brain 1 mm isotropic quantitative T1, T2, and PD maps along with multiple synthetic images in a 7-minute acquisition time.Methods
A 1 mm isotropic 3D-QALAS acquisition was scanned in both phantoms and five healthy volunteers on the 1.5T Elekta Unity MR-Linac device with scan times around seven minutes. A test-retest protocol across five independent sessions for the phantom was conducted. The Lin's Concordance Correlation Coefficient (LCCC), repeatability, and reproducibility between measured and reference quantitative T1, T2, and PD values were determined in the phantom. Distortion was also studied. Vendor-provided reconstruction through SyMRI was performed to extract synthetic images and brain volume metric assessments in the healthy volunteers.Results
The slope and LCCC between the measured and phantom reference values was 1.02 (1.00), 1.09 (0.90), and 0.99 (1.00) for T1, T2, and PD, respectively. Median distortion across the phantom remained below 2 mm. The repeatability and reproducibility coefficient-of-variation (CoV) was under 8% for all measured values. The measured brain volumes in the healthy volunteer was within expected age-adjusted reference values.Conclusions
The technical feasibility of using 3D-QALAS on the integrated 1.5T MR-Linac was confirmed. Applying this technique to the adaptive radiation therapy workflow of the brain will provide new opportunities to integrate quantitative imaging relaxometry biomarkers at 1 mm isotropic reconstructed resolution.
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BibTeX
@article{mccullum2026technical,
title = {{Technical development and implementation of 3D-QALAS on a 1.5T MR-Linac for the brain: A prospective R-IDEAL stage 0/1 technology development report.}},
author = {Lucas McCullum and Ashley Harrington and Natalie West and Grace Nehring and Ziyu Fu and Ergys Subashi and Brian A Taylor and Ken-Pin Hwang and Clifton D Fuller},
journal = {Journal of applied clinical medical physics},
year = {2026},
month = oct,
doi = {10.1002/acm2.70886},
url = {https://europepmc.org/article/MED/42949424},
note = {CC BY},
}
RIS
TY - JOUR
TI - Technical development and implementation of 3D-QALAS on a 1.5T MR-Linac for the brain: A prospective R-IDEAL stage 0/1 technology development report.
AU - Lucas McCullum
AU - Ashley Harrington
AU - Natalie West
AU - Grace Nehring
AU - Ziyu Fu
AU - Ergys Subashi
AU - Brian A Taylor
AU - Ken-Pin Hwang
AU - Clifton D Fuller
PY - 2026
DA - 2026/10/28
JO - Journal of applied clinical medical physics
DO - 10.1002/acm2.70886
UR - https://europepmc.org/article/MED/42949424
AB - Background Quantitative relaxometry of the brain on the integrated MRI / linear accelerator (MR-Linac) at high isotropic reconstructed resolution is currently limited due to prohibitively long scan times and limited field-of-views.Purpose The purpose of this study was to assess the technical feasibility of the 3D-QALAS technique on the 1.5T MR-Linac which can acquire whole-brain 1 mm isotropic quantitative T1, T2, and PD maps along with multiple synthetic images in a 7-minute acquisition time.Methods A 1 mm isotropic 3D-QALAS acquisition was scanned in both phantoms and five healthy volunteers on the 1.5T Elekta Unity MR-Linac device with scan times around seven minutes. A test-retest protocol across five independent sessions for the phantom was conducted. The Lin's Concordance Correlation Coefficient (LCCC), repeatability, and reproducibility between measured and reference quantitative T1, T2, and PD values were determined in the phantom. Distortion was also studied. Vendor-provided reconstruction through SyMRI was performed to extract synthetic images and brain volume metric assessments in the healthy volunteers.Results The slope and LCCC between the measured and phantom reference values was 1.02 (1.00), 1.09 (0.90), and 0.99 (1.00) for T1, T2, and PD, respectively. Median distortion across the phantom remained below 2 mm. The repeatability and reproducibility coefficient-of-variation (CoV) was under 8% for all measured values. The measured brain volumes in the healthy volunteer was within expected age-adjusted reference values.Conclusions The technical feasibility of using 3D-QALAS on the integrated 1.5T MR-Linac was confirmed. Applying this technique to the adaptive radiation therapy workflow of the brain will provide new opportunities to integrate quantitative imaging relaxometry biomarkers at 1 mm isotropic reconstructed resolution.
SN - 1526-9914
ER -