Evaluation of optimized breath‐hold and free‐breathing 3D ultrashort echo time contrast agent‐free MRI of the human lung

Abstract

Purpose To evaluate an optimized stack of radials ultrashort echo time (UTE) three-dimensional MRI sequence for breath-hold and free breathing imaging of the human lung. Methods A 3D stack of ultrashort echo time radials trajectory was optimized for coronal and axial lower resolution breath-hold and higher resolution free breathing scans using Bloch simulations. The sequence was evaluated in ten volunteers, without the use contrast agents. SNR mean and 95% confidence interval were determined from separate signal and noise images in a semi-automated fashion. The four scanning schemes were evaluated for significant differences in image quality using the Student’s t-test. Ten clinical patients were scanned with the sequence and findings were compared with concomitant CT in nine patients. Breath-hold 3D spokes images were compared with 3D stack of radials in five volunteers. Mann-Whitney U test was performed to test significance in both cases. Results Breath-hold imaging of the entire lung in volunteers was performed with SNR (mean = 42.5 [CI]: 35.5 – 49.5; mean = 34.3 [CI]: 28.6 – 40) in lung parenchyma for coronal and axial scans respectively, which can be used as a quick scout scan. Longer respiratory triggered free breathing scan enabled high resolution UTE scanning with mean SNR of 14.2 ([CI]: 12.9 – 15.5) and 9.2 ([CI]: 8.2 – 10.2) for coronal and axial scans, respectively. Axial free breathing scans showed significantly higher image quality (P = 0.008) than the three other scanning schemes. The mean score for comparison with CT was 1.67 (score 0: N = 0; 1: N = 3; 2: N = 6). There was no significant difference between CT and MRI (P = 0.25). 3D stack of radials images were significantly better than 3D spokes images (P < 0.001). Conclusion The optimized 3D stack of radials trajectory was shown to provide high quality MR images of the lung parenchyma without the use of MRI contrast agents. The sequence may offer the possibility of breath-hold imaging and provides greater flexibility in trading off slice thickness and parallel imaging for scan time.

Ultra‐short echo time images quantify high liver iron

“…The demonstrated robustness of the free‐breathing protocol will immediately improve LIC estimates for participants who cannot complete a breath‐hold of over 10 s. Patient comfort is improved through the negation of breath‐holds and the reduction in scan time due to decreased protocol duration and reduction in repeated series. SNR improvement relative to breath‐holding has been demonstrated with triggered, free‐breathing UTE imaging and improved estimation in iron overloaded liver . In constrast, slice‐selective UTE has demonstrated robustness in LIC up to ≈1150 Hz .…”

Hyperpolarized 129Xe for investigation of mild cystic fibrosis lung disease in pediatric patients

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Value of PET/MRI for assessing tumor resectability in NSCLC—intra-individual comparison with PET/CT

“…ultra-short time to echo and zero time to echo-so called UTE-and ZTE-sequences). Recently, Ohno et al demonstrated improved pulmonary nodule detection rates of thin-section MRI with UTE and further described the usefulness of UTE for evaluation of nodule type as at least as efficacious as standard-dose thin-section CT. 33 Other studies using UTE-sequences have shown a good visualization of the lung parenchyma and mediastinum in adult patients 34,35 as well as a good visibility of the airways including the trachea and main bronchi in infants. 36 There are several limitations that have to be considered in the present study.…”