Effect of Lung Inflation Level on Hyperpolarized³He Apparent Diffusion Coefficient Measurements in Never-Smokers

Abstract

Purpose:To evaluate the effects of lung volume differences on apparent diffusion coefficient (ADC) measurements on a regional basis, with breath holds at volumes adjusted for differences in lung size across individuals according to the subject's vital capacity (VC). Materials and Methods:This study was approved by the local institutional review board and was compliant with HIPAA. Informed consent was obtained from all subjects. Imaging was performed under a physician's Investigational New Drug application from the Food and Drug Administration. ADC changes as a function of inflation levels were evaluated in 24 healthy never-smokers across three lung volumes (20%, 60%, and 100% VC) on the basis of the spirometric data collected from each subject. Response variables based on lung volume and anatomic position were assessed with multifactorial analysis of variance followed by posthoc pair-wise testing. Imaging was performed with a 1.5-T magnetic resonance (MR) unit with use of a two-dimensional gradient-echo fast low-angle shot sequence. Results:Significant differences in ADCs between lung volumes were observed for all inflation levels (20%, 60%, and 100% VC; P , .001), along with significant dependentnondependent vertical gradients at 20% VC (P , .0001) and 60% VC (P , .0001, left lung only). In addition, significant differences between mean values in the left and right lungs with respect to those in the whole lung were observed at the lower lung inflation levels (20% and 60% VC, P , .01), reaching more uniform expansion at 100% VC. Conclusion:The results confirm known anatomic differences in patterns of regional inflation and ventilation with corresponding lung volume changes, emphasizing the need for tight control over lung volume when performing hyperpolarized helium 3 ( He MR imaging is to be used to follow up small longitudinal changes in lung abnormalities.q RSNA, 2013

Assessment of Regional Lung Function with Multivolume1H MR Imaging in Health and Obstructive Lung Disease: Comparison with3He MR Imaging

“…As no ionizing radiation is associated with MR imaging, the method would be particularly attractive for examinations in children and pregnant women and when repetitive examinations are required. To introduce the method into clinical practice, the methodology of volume control becomes pivotal and would require standardization, as significant differences in lung microstructure with lung inflation level have been observed (41).…”

Magnetic resonance imaging with hyperpolarized agents: methods and applications

“…ADC is regarded as a surrogate for localized airway or acinar dimensions, and can be calculated for each voxel to construct a semi-quantitative ADC map (Figure 5). Regional ADC changes have been observed in response to increases in lung volume [162, 163], gravity dependence [162, 164, 165], age [166], and emphysema in chronic obstructive pulmonary disease (COPD) or α-1-antitrypsin deficiency [121, 164, 167, 168]. ADC values for 129 Xe are lower than those of 3 He by an order of magnitude due to the higher density of 129 Xe gas (Table 1).…”

Regional anisotropy of airspace orientation in the lung as assessed with hyperpolarized helium‐3 diffusion MRI

“…Previous studies using diffusion‐sensitization gradients applied in one direction demonstrated heterogeneity of ADC values in healthy lungs, most notably a gradual increase in ADC in the craniocaudal and (subject posture‐dependent) anteroposterior directions, likely reflecting gravity‐dependent variations in alveolar size. Nonetheless, Halaweish et al demonstrated that the anteroposterior ADC gradient essentially disappears at total lung capacity, as used for all images collected in our study.…”