Quiet Submillimeter MR Imaging of the Lung Is Feasible with a PETRA Sequence at 1.5 T
Quiet submillimeter MR imaging of the lung is feasible with the pointwise encoding time reduction with radial acquisition, or PETRA, sequence at 1.5 T.
To assess lung magnetic resonance (MR) imaging with a respiratory-gated pointwise encoding time reduction with radial acquisition (PETRA) sequence at 1.5 T and compare it with imaging with a standard volumetric interpolated breath-hold examination (VIBE) sequence, with extra focus on the visibility of bronchi and the signal intensity of lung parenchyma.
Materials and Methods
The study was approved by the local ethics committee, and all subjects gave written informed consent. Twelve healthy volunteers were imaged with PETRA and VIBE sequences. Image quality was evaluated by using visual scoring, numbering of visible bronchi, and quantitative measurement of the apparent contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). For preliminary clinical assessment, three young patients with cystic fibrosis underwent both MR imaging and computed tomography (CT). Comparisons were made by using the Wilcoxon signed-rank test for means and the McNemar test for ratios. Agreement between CT and MR imaging disease scores was assessed by using the κ test.
PETRA imaging was performed with a voxel size of 0.86 mm3. Overall image quality was good, with little motion artifact. Bronchi were visible consistently up to the fourth generation and in some cases up to the sixth generation. Mean CNR and SNR with PETRA were 32.4% ± 7.6 (standard deviation) and 322.2% ± 37.9, respectively, higher than those with VIBE (P < .001). Good agreement was found between CT and PETRA cystic fibrosis scores (κ = 1.0).
PETRA enables silent, free-breathing, isotropic, and submillimeter imaging of the bronchi and lung parenchyma with high CNR and SNR and may be an alternative to CT for patients with cystic fibrosis.
© RSNA, 2015
- 1. . Cancer risks from CT scans: now we have data, what next? Radiology 2012;265(2):330–331. Link, Google Scholar
- 2. . The role of advanced imaging techniques in cystic fibrosis follow-up: is there a place for MRI? Pediatr Radiol 2010;40(6):844–849. Crossref, Medline, Google Scholar
- 3. . Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Lancet 2012;380(9840):499–505. Crossref, Medline, Google Scholar
- 4. . Pulmonary 3 T MRI with ultrashort TEs: influence of ultrashort echo time interval on pulmonary functional and clinical stage assessments of smokers. J Magn Reson Imaging 2014;39(4):988–997. Crossref, Medline, Google Scholar
- 5. . Quiet T1-weighted imaging using PETRA: initial clinical evaluation in intracranial tumor patients. J Magn Reson Imaging 2014;41(2):447–453. Crossref, Medline, Google Scholar
- 6. . Sequence-based acoustic noise reduction of clinical MRI scans. Magn Reson Med 2014 May 29. [Epub ahead of print] Google Scholar
- 7. . Ultrashort echo time imaging using pointwise encoding time reduction with radial acquisition (PETRA). Magn Reson Med 2012;67(2):510–518. Crossref, Medline, Google Scholar
- 8. . Magnetic resonance imaging detects changes in structure and perfusion, and response to therapy in early cystic fibrosis lung disease. Am J Respir Crit Care Med 2014;189(8):956–965. Crossref, Medline, Google Scholar
- 9. . Computed tomography and magnetic resonance imaging in cystic fibrosis lung disease. J Magn Reson Imaging 2010;32(6):1370–1378. Crossref, Medline, Google Scholar
- 10. , Ducou Le Pointe H. HRCT and MRI of the lung in children with cystic fibrosis: comparison of different scoring systems. J Cyst Fibros 2014;13(2):198–204. Crossref, Medline, Google Scholar
- 11. . Visualization of morphological parenchymal changes in emphysema: comparison of different MRI sequences to 3D-HRCT. Eur J Radiol 2010;73(1):43–49. Crossref, Medline, Google Scholar
- 12. . Proton MRI in the evaluation of pulmonary sarcoidosis: comparison to chest CT. Eur J Radiol 2013;82(12):2378–2385. Crossref, Medline, Google Scholar
- 13. . 3 Tesla proton MRI for the diagnosis of pneumonia/lung infiltrates in neutropenic patients with acute myeloid leukemia: initial results in comparison to HRCT. Eur J Radiol 2014;83(1):e61–e66. Crossref, Medline, Google Scholar
- 14. . Magnetic resonance imaging of the lung in cystic fibrosis. Proc Am Thorac Soc 2007;4(4):321–327. Crossref, Medline, Google Scholar
- 15. . Lung morphology: fast MR imaging assessment with a volumetric interpolated breath-hold technique: initial experience with patients. Radiology 2003;226(1):242–249. Link, Google Scholar
- 16. . Sampling density compensation in MRI: rationale and an iterative numerical solution. Magn Reson Med 1999;41(1):179–186. Crossref, Medline, Google Scholar
- 17. . Selection of a convolution function for Fourier inversion using gridding [computerised tomography application]. IEEE Trans Med Imaging 1991;10(3):473–478. Crossref, Medline, Google Scholar
- 18. . Reconstructing MR images from undersampled data: data-weighting considerations. Magn Reson Med 2000;43(6):867–875. Crossref, Medline, Google Scholar
- 19. . Lateral views of the segmental bronchi and related pulmonary vessels in an injected preparation of the lungs. Radiology 1953;61(2):183–188. Link, Google Scholar
- 20. . Optimized 3D ultrashort echo time pulmonary MRI. Magn Reson Med 2013;70(5):1241–1250. Crossref, Medline, Google Scholar
- 21. . Ultra-short echo-time pulmonary MRI: evaluation and reproducibility in COPD subjects with and without bronchiectasis. J Magn Reson Imaging 2014 Jun 26. [Epub ahead of print] Google Scholar
- 22. . Cystic fibrosis: scoring system with thin-section CT. Radiology 1991;179(3):783–788. Link, Google Scholar
- 23. . Individual comparisons of grouped data by ranking methods. J Econ Entomol 1946;39(2):269. Crossref, Medline, Google Scholar
- 24. . Measuring diagnostic agreement. J Consult Clin Psychol 1996;64(6):1285–1289. Crossref, Medline, Google Scholar
- 25. . Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1(8476):307–310. Crossref, Medline, Google Scholar
- 26. . Correcting slice selectivity in hard pulse sequences. J Magn Reson 2012;214(1):61–67. Crossref, Medline, Google Scholar
- 27. . Pulmonary nodules in patients with primary malignancy: comparison of hybrid PET/MR and PET/CT imaging. Radiology 2013;268(3):874–881. Link, Google Scholar
Article HistoryReceived August 14, 2014; revision requested October 1; revision received November 3; accepted November 16; final version accepted December 23.
Published online: Mar 13 2015
Published in print: July 2015