Quantitative regional oxygen transfer Imaging of the human lung

Purpose: To demonstrate that the use of nonquantitative methods in oxygen-enhanced (OE) lung imaging can be problematic and to present a new approach for quantitative OE lung imaging, which fulfills the requirements for easy application in clinical practice. Materials and Methods: A total of 10 healthy volunteers and three non-small-cell lung cancer (NSCLC) patients were examined using a 1.5T scanner. OE imaging was performed using a snapshot fast low-angle shot (FLASH) T-1-mapping technique (TE = 1.4 msec, TR = 3.5 msec) as well as a series of T-1-weighted inversion recovery (IR) half-Fourier acquisition single-shot turbo spin-echo (HASTE) (TEeffective = 43 msec, TEinter= 4.2 msec, and inversion time [TI] = 1200 msec) images. Semiquantitative relative signal enhancement ratios (RER) of T-1-weighted images before and after inhalation of oxygen-enriched gas were compared to the quantitative change in T-1. A hybrid method is proposed that combines the advantages of T-1-weighted imaging with the quantification provided by T-1-mapping. To this end, the IR-HASTE images were transformed into quantitative parameter maps. To prevent mismatching and incorrect parameter maps, retrospective image selection was performed using a postprocessing navigator technique. Results: The PER was dependent on the intrinsic values of T-1 in the lung. Quantitative parameters, such as the decrease of T-1 after switching the breathing gas, were more suited to oxygen transfer quantification than to relative signal enhancement. The mean T-1 value during inhalation of room air (T-1,T-room) for the volunteers was 1260 msec. This value decreased by about 10% after switching the breathing gas to carbogen. For the patients, the mean T-1,T-room value was 1182 msec, which decreased by about 7% when breathing carbogen. The parameter Conclusion: For the purpose of intersubject comparison, OE lung imaging should be performed quantitatively. The proposed hybrid technique produced reliable quantitative results in a short amount of time and, therefore, is suited for clinical use.