Abstract
The zero echo time (ZTE) technique has improved the detection of lung nodules in PET/MRI but respiratory motion remains a challenge in lung scan. We investigated the feasibility and performance of fractionated deep-inspiration breath-hold (FDIBH) three-dimensional (3D) ZTE FDG PET/MRI for assessing lung nodules in patients with proved malignancy. Sixty patients who had undergone ZTE FDG PET/MRI and chest CT within a three-day interval were retrospectively included. Lung nodules less than 2 mm were excluded for analysis. Two physicians checked the adequacy of FDIBH ZTE and compared the lung nodule detection rates of FDIBH 3D ZTE and free-breathing (FB) four-dimensional (4D) ZTE, with chest CT as the reference standard. FDIBH resolved the effect of respiratory motion in 49 patients. The mean number and size of the pulmonary nodules identified in CT were 15 ± 31.3 per patient and 5.9 ± 4.6 mm in diameter. The overall nodule detection rate was 71% for FDIBH 3D ZTE and 70% for FB 4D ZTE (p = 0.73). FDIBH 3D ZTE significantly outperformed FB 4DZTE in detecting lung base nodules (72% and 68%; p = 0.03), especially for detecting those less than 6 mm (61% and 55%; p = 0.03). High inter-rater reliability for FDIBH 3D ZTE and FB 4D ZTE (k = 0.9 and 0.92) was noted. In conclusion, the capability of FDIBH 3D ZTE in respiratory motion resolution was limited with a technical failure rate of 18%. However, it could provide full expansion of the lung in a shorter scan time which enabled better detection of nodules (< 6 mm) in basal lungs, compared to FB 4D ZTE.
Highlights
The zero echo time (ZTE) technique has improved the detection of lung nodules in PET/MRI but respiratory motion remains a challenge in lung scan
This study aimed to investigate the feasibility of fractionated Deep-inspiration breath-hold (DIBH) (FDIBH) 3D ZTE imaging for the evaluation of lung nodules in patients with proven malignancy using a hybrid PET/MRI system and to compare the nodule detecting efficacy with that of the FB 4D ZTE images
Our preliminary result showed that fractionated deep-inspiration breath-hold (FDIBH) was feasible and resolved the effect of respiratory motion in 82% of the patients
Summary
The zero echo time (ZTE) technique has improved the detection of lung nodules in PET/MRI but respiratory motion remains a challenge in lung scan. The capability of FDIBH 3D ZTE in respiratory motion resolution was limited with a technical failure rate of 18% It could provide full expansion of the lung in a shorter scan time which enabled better detection of nodules (< 6 mm) in basal lungs, compared to FB 4D ZTE. In addition to continued efforts to shorten the TE to enhance small nodule detection, another problem for MRI to detect lung nodule is the respiratory m otion[10] Several clinical techniques such as respiratory triggering, prospective gating, and single-breath hold have been described to deal with the respiratory motion during the MRI evaluation of lung n odules[8,11,12]. The detection of lung base nodules may be difficult due to a lack of full expansion of the lung
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