Design and evaluation of a 32‐channel phased‐array coil for lung imaging with hyperpolarized 3‐helium
ABSTRACT Imaging with hyperpolarized 3-helium is becoming an increasingly important technique for MRI diagnostics of the lung but is hampered by long breath holds (>20 sec), which are not always applicable in patients with severe lung disease like chronic obstructive pulmonary disease (COPD) or α-1-anti-trypsin deficiency. Additionally, oxygen-induced depolarization decay during the long breath holds complicates interpretation of functional data such as apparent diffusion coefficients. To address these issues, we describe and validate a 1.5-T, 32-channel array coil for accelerated 3He lung imaging and demonstrate its ability to speed up imaging 3He. A signal-to-noise ratio increase of up to a factor of 17 was observed compared to a conventional double-resonant birdcage for unaccelerated imaging, potentially allowing increased image resolution or decreased gas production requirements. Accelerated imaging of the whole lung with one-dimensional and two-dimensional acceleration factors of 4 and 4 × 2, respectively, was achieved while still retaining excellent image quality. Finally, the potential of highly parallel detection in lung imaging is demonstrated with high-resolution morphologic and functional images. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.
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ABSTRACT: Inhalation of hyperpolarized (3)He allows magnetic resonance imaging (MRI) of ventilated airspaces. (3)He hyperpolarization decays more rapidly when interacting with paramagnetic O(2). We describe a method for in vivo determination of intrapulmonary O(2) concentrations ([O(2)]) based on MRI analysis of the fate of measured amounts of inhaled hyperpolarized (3)He in imaged regions of the lung. Anesthetized pigs underwent controlled normoventilation in a 1.5-T MRI unit. The inspired O(2) fraction was varied to achieve different end-tidal [O(2)] fractions (FET(O(2))). With the use of a specifically designed applicator, (3)He (100 ml, 35-45% polarized) was administered at a predefined time within single tidal volumes. During subsequent inspiratory apnea, serial two-dimensional images of airways and lungs were acquired. At least once in each animal studied, the radio-frequency excitation used for imaging was doubled at constant FET(O(2)). Signal intensity measurements in regions of interest of the animals' lungs (volume range, 54-294 cm(3)), taken at two different radio-frequency excitations, permitted calculation of [O(2)] in these regions of interest. The [O(2)] fractions in the regions of interest correlated closely with FET(O(2)) (R = 0.879; P < 0.0001). O(2)-sensitive (3)He-MRI may allow noninvasive study of regional distribution of ventilation and alveolar PO(2) in the lung.Journal of Applied Physiology 12/1999; 87(6):2043-52. · 3.48 Impact Factor
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ABSTRACT: The pulse sequences for hyperpolarized (3)He lung MRI that have made the most clinical impact to date are 1) those that supply regional apparent diffusion coefficient (ADC) measurements, which provide insight into early emphysematous destruction of the alveoli in the lungs, and 2) high-resolution ventilation images that provide regional indicators of airway obstruction in obstructive airway disease, such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease (COPD). In this work a hybrid 2D ADC-ventilation sequence was used with low flip angles to acquire both sets of data in the same breath-hold. The performance of the sequence was investigated in vivo in a healthy subject and a subject with mild emphysema, and compared with conventional 2D gradient-echo (GRE) (3)He ventilation and ADC imaging sequences. Acquisition of the ADC and ventilation images in one breath-hold provides ventilation images with equal or better SNR (approximately 20) and the same spatial resolution (3.75 mm x 3.3 mm in plane) with simultaneous accurate, high-resolution ADC images. The hybrid sequence offers a means of conserving gas by using two-thirds of the (3)He gas needed for separate ADC and ventilation exams, and saves the subject from having to perform an extra breath-hold. The data are inherently spatially and temporally registered, allowing quantitative cross-correlation between high-spatial-resolution ADC and ventilation data.Magnetic Resonance in Medicine 07/2007; 57(6):1185-9. · 3.27 Impact Factor
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ABSTRACT: A radial projection sliding-window sequence has been developed for imaging the rapid flow of (3)He gas in human lungs. The short echo time (TE) of the radial sequence lends itself to fast repetition times, and thus allows a rapid update in the image when it is reconstructed with a sliding window. Oversampling in the radial direction combined with angular undersampling can further reduce the time needed to acquire a complete image data set, without significantly compromising spatial resolution. Controlled flow phantom experiments using hyperpolarized (3)He gas exemplify the temporal resolution of the method. In vivo studies on three healthy volunteers, one patient with chronic obstructive pulmonary disease (COPD), and one patient with hemiparalysis of the right diaphragm demonstrate that it is possible to accurately resolve the passage of gas down the trachea and bronchi and into the peripheral lung.Magnetic Resonance in Medicine 07/2003; 49(6):991-7. · 3.27 Impact Factor