Imaging of the lungs using 3he MRI: Preliminary clinical experience in 18 patients with and without lung disease

Abstract

The purpose of this study was to describe the 3He MRI findings of normal pulmonary ventilation in healthy volunteers and to evaluate abnormalities in patients with different lung diseases. Hyperpolarized 3He gas (300 ml, 3 x 10(5) Pa, polarized to 35-45% by optical pumping, provided in special glass cells) was inhaled by 8 healthy volunteers and 10 patients with different lung diseases. Imaging was performed with a three-dimensional fast low-angle shot (FLASH) sequence (TR = 11.8 msec; TE = 5 msec; transmitter amplitude, 5-8 V; corresponding flip angle, < 5 degrees) in a single breath-hold (22-42 seconds). Clinical and radiological examinations were available for correlation. The studies were performed successfully in eight of eight volunteers and in 8 of 10 patients. The lung parenchyma of volunteers with normal ventilatory function exhibited rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease or bronchiectasis presented with severe signal inhomogeneities with patchy or wedge-shaped defects. The mass effect of bronchogenic carcinoma, chronic empyema, lymphadenopathy, or pleural effusion caused large signal defects, representing the lesion and adjacent hypoventilation, the extent of which had not been presumed from chest x-ray or CT. 3He MRI is a promising new modality for the assessment of pulmonary ventilation and its abnormalities. Additional studies are needed to determine its potential clinical role.

Assessment of a single‐acquisition imaging sequence for oxygen‐sensitive 3He‐MRI

“…A previously-described coil (12) was used for signal transmission and detection. A spoiled gradient-echo pulse sequence with centric k-space acquisition order and TR ϭ 11 ms, TE ϭ 4.2 ms, field of view ϭ (320 mm) 2 , and raw data matrix ϭ 81 ϫ 128 was applied. The raw data were zero-filled to 256 ϫ 256 before image reconstruction.…”

“…A comparison of Eqs. [2] and [9] shows that the y n give the searched-for time course of p O2 at mean times t n . The A n or A m values can then be used to calculate the flip angle ␣ via Eq.…”

“…The first encompasses studies of overt or subclinical lung disease, e.g., in chronic obstructive pulmonary disease (COPD) and emphysema patients (1,2), asthma patients (3), and smokers (4). The latter includes the use of fast imaging sequences (5-7), diffusion studies (8 -10), and the determination of intrapulmonary oxygen partial pressures (11)(12)(13).…”

Functional lung imaging using hyperpolarized gas MRI

“…More recently, functional lung imaging has been performed using positron emission tomography (PET) (7,9 -11), and hyperpolarized gas MRI (HP MRI) (12)(13)(14)(15); techniques capable of providing three dimensional (3D) regional information and quantitative or semiquantitative measures of ventilation and perfusion. These new techniques are rapidly expanding the field of functional lung imaging for improved diagnosis and noninvasive monitoring of disease progression-in some cases with the necessary sensitivity to track an individual patient's response to therapy.…”

An open-access, very-low-field MRI system for posture-dependent 3He human lung imaging

“…This technique has been used with conventional, clinical MRI instruments to make quantitative images of human ventilation [5,6], to acquire 3 He diffusion maps that yield images of lung gas-space dimensions [7,8], and to map the spatial variation of 3 He T 1 relaxation to provide images of alveolar O 2 concentration [9,10], which has recently been directly linked to the physiologically relevant ventilation/perfusion ratio (V/Q) [10]. Imaging of hyperpolarized 3 He has also found wide applications in the study of many lung diseases, including emphysema [11,12], cystic fibrosis [13] and asthma [14,15]. In all these clinical studies, subjects have been imaged while horizontal, generally supine, due to the design of clinical MRI systems based on a solenoid magnet with narrow inner diameter.…”