Measurement of Pulmonary Partial Pressure of Oxygen and Oxygen Depletion Rate with Hyperpolarized Helium-3 MRI: A Preliminary Reproducibility Study on Pig Model

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Reliable, noninvasive, and high-resolution imaging of alveolar partial pressure of oxygen (p A O 2 ) is a potentially valuable tool in the early diagnosis of pulmonary diseases. Several techniques have been proposed for regional measurement of p A O 2 based on the increased depolarization rate of hyperpolarized 3 He. In this study, we explore one such technique by applying a multislice p A O 2 -imaging scheme that uses interleaved-slice ordering to utilize interslice time-delays more efficiently. This approach addresses the low spatial resolution and long breath-hold requirements of earlier techniques, allowing p A O 2 measurements to be made over the entire human lung in 10-15 s with a typical resolution of 8.3 3 8.3 3 15.6 mm 3 . PO 2 measurements in a glass syringe phantom were in agreement with independent gas analysis within 4.7 6 4.1% (R 5 0.9993). The technique is demonstrated in four human subjects (healthy nonsmoker, healthy former smoker, healthy smoker, and patient with COPD), each imaged six times on 3 different days during a 2-week span. Two independent measurements were performed in each session, consisting of 12 coronal slices. The overall p A O 2 mean across all subjects was 95.9 6 12.2 Torr and correlated well with end-tidal O 2 (R 5 0.805, P < 0.0001). The alveolar O 2 uptake rate was consistent with the expected range of 1-2 Torr/s. Repeatable visual features were observed in p A O 2 maps over different days, as were characteristic differences among the subjects and gravity-dependent effects. Magn Reson Med 67:1332-1345, 2012. V C 2011 Wiley Periodicals, Inc.

Section: Accuracy Of Measurementsmentioning

confidence: 65%

Section: He Spin-relaxation Dynamics In Vivomentioning

confidence: 99%

“…1b,c). (9,11); (e) the interleaved scheme used in this study. The arrows indicate the acquisition timing pattern of the first slice.…”

Section: Technique Comparisonmentioning

confidence: 99%

Section: He Spin-relaxation Dynamics In Vivomentioning

confidence: 99%

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confidence: 99%

See 3 more Smart Citations

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

Hamedani

Kadlecek

Emami

et al. 2011

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A short‐breath‐hold technique for lung pO₂ mapping with ³He MRI

Miller

Mugler

Altes

et al. 2009

A pulse-sequence strategy was developed for generating regional maps of alveolar pO2 in a single six-second breath hold, for use in human subjects with impaired lung function. Like previously described methods, pO2 values are obtained by measuring the oxygen-induced T1 relaxation of inhaled hyperpolarized 3He. Unlike other methods, only two 3He images are acquired: one with reverse-centric and the other with centric phase-encoding order. This phase-encoding arrangement minimizes the effects of regional flip-angle variations, so that an accurate map of instantaneous pO2 can be calculated from two images acquired a few seconds apart. By combining this phase-encoding strategy with variable flip angles, the vast majority of the hyperpolarized magnetization goes directly into the T1 measurement, minimizing noise in the resulting pO2 map. The short-breath-hold pulse sequence was tested in phantoms containing known O2 concentrations. The mean difference between measured and prepared pO2 values was 1 mm Hg. The method was also tested in four healthy volunteers and three lung-transplant patients. Maps of healthy subjects were largely uniform, whereas focal regions of abnormal pO2 were observed in diseased subjects. Mean pO2 values varied with inhaled O2 concentration. Mean pO2 was consistent with normal steady-state values in subjects that inhaled 3He diluted only with room air.

A variability study of regional alveolar oxygen tension measurement in humans using hyperpolarized ³He MRI

Hamedani

Kadlecek

Ishii

et al. 2013

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To presents the first systematic reproducibility measurement of alveolar partial pressure of oxygen (pAO2) in the human lung, regional variability is defined in terms of an intraclass correlation coefficient (ICC) between co-localized, same-subject measurements separated by one-week or couple of minutes (short-term). In addition, the repeatability of the average lung pAO2 is compared to that of the standard pulmonary function tests (PFT). PFT and pAO2 imaging were performed on eight subjects: 4 nonsmokers (1 man, 3 women; 56 ± 1.7 years), 4 smokers (1 woman, 3 men; 52 ± 7.5 years) in three visits during two weeks. Regional variability was assessed based on a mixed-effects model and an ICC. The coefficient of variation (CV) of mean and standard deviation of pAO2 in three days was also compared to CV of PFT results. Short-term regional reproducibility based on ICC was 0.71 and 0.63 for nonsmokers and smokers; respectively. The one-week variability was lower (ICC=0.59 and 0.47; respectively). The CV of whole-lung average pAO2 was significantly higher than that of FVC(forced vital capacity; P=0.02) but not from DLCO (diffusing capacity). The smoker group shows more variability in pAO2 measurements both between experiments and in each individual pAO2 maps. pAO2 had a similar repeatability to DLCO.