Simultaneous measurement of pulmonary partial pressure of oxygen and apparent diffusion coefficient by hyperpolarized ³He MRI

Abstract

Hyperpolarized 3 He (HP 3 He) MRI shows promise to assess structural and functional pulmonary parameters in a sensitive, regional, and noninvasive way. Structural HP 3 He MRI has applied the apparent diffusion coefficient (ADC) for the detection of disease-induced lung microstructure changes at the alveolar level, and HP 3 He pulmonary partial pressure of oxygen (pO 2 ) imaging measures the oxygen transfer efficiency between the lung and blood stream. Although both parameters are affected in chronic obstructive pulmonary disease (COPD), a quantitative assessment of the regional correlation of the two parameters has not been reported in the literature. In this work, a single acquisition technique for the simultaneous measurement of ADC and pO 2 is presented. This technique is based on the multiple regression method, in which a general linear estimator is used to retrieve the values of ADC and pO 2 from a series of measurements. The measurement uncertainties are also analytically derived and used to find an optimal measurement scheme. The technique was first tested on a phantom model, and then on an in vivo normal pig experiment. A case study was performed on a COPD patient, which showed that in a region of interest ADC was 29% higher while oxygen depletion rate was 61% lower than the corresponding global average values. Magn Reson Med 61:1015-1021, 2009.

Quantitative Assessment of Lung Ventilation and Microstructure in an Animal Model of Idiopathic Pulmonary Fibrosis Using Hyperpolarized Gas MRI

“…Threshold analysis of ADC indicated a greater difference between the bleomycin and the control animals than did the difference between the mean values of the ADC. ADC has been measured in humans [32, 33] and animal models of emphysema and asthma [34, 35]. This study however presents the first utilization of this radiologic measure of lung microstructure to interstitial lung disease.…”

3He pO2 mapping is limited by delayed‐ventilation and diffusion in chronic obstructive pulmonary disease

“…For free 3 He diffusion in air D ¼ 0.86 cm 2 /s (7), whereas smaller apparent diffusion coefficients (ADCs) are characteristic of longer diffusion times in healthy acinar tissue when measured with longitudinal diffusion weighted magnetization pulse sequences (8-11). Similarly, any other change in signal decay, which is not related to oxygen concentration or RF depolarization, such as a delayed in-flow of gas into the region of interest (ROI), could cause errors in the pO 2 values calculated with the technique.3 He pO 2 mapping has been used to image patients with bronchiolitis obliterans (12) and lung transplant (12,13), and several studies have performed pO 2 mapping in patients with chronic obstructive pulmonary disease (COPD) (13)(14)(15)(16)(17). COPD is characterized by abnormalities of air-flow and elevation in regional gas ADC related to emphysema in the alveolar spaces (18).…”

“…3 He pO 2 mapping has been used to image patients with bronchiolitis obliterans (12) and lung transplant (12,13), and several studies have performed pO 2 mapping in patients with chronic obstructive pulmonary disease (COPD) (13)(14)(15)(16)(17). COPD is characterized by abnormalities of air-flow and elevation in regional gas ADC related to emphysema in the alveolar spaces (18).…”

A multislice single breath‐hold scheme for imaging alveolar oxygen tension in humans

“…HP 3 He, specifically, with an attractive safety profile and negligible blood uptake, has demonstrated unique potential to probe functional and structural aspects of the lung at the acinar level, including ventilation (7), diffusion (8), and most notably oxygen tension (9). Several p A O 2 imaging schemes have been implemented in animals and humans (10)(11)(12).…”