Despite a myriad of technical advances in medical imaging, as well as the growing need to address the global impact of pulmonary diseases, such as asthma and chronic obstructive pulmonary disease, on health and quality of life, it remains challenging to obtain in vivo regional depiction and quantification of the most basic physiological functions of the lung-gas delivery to the airspaces and gas uptake by the lung parenchyma and blood-in a manner suitable for routine application in humans. We report a method based on MRI of hyperpolarized xenon-129 that permits simultaneous observation of the 3D distributions of ventilation (gas delivery) and gas uptake, as well as quantification of regional gas uptake based on the associated ventilation. Subjects with lung disease showed variations in gas uptake that differed from those in ventilation in many regions, suggesting that gas uptake as measured by this technique reflects such features as underlying pathological alterations of lung tissue or of local blood flow. Furthermore, the ratio of the signal associated with gas uptake to that associated with ventilation was substantially altered in subjects with lung disease compared with healthy subjects. This MRI-based method provides a way to quantify relationships among gas delivery, exchange, and transport, and appears to have significant potential to provide more insight into lung disease.gas exchange | pulmonary function | pulmonary ventilation

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Learning Objectives: On successful completion of this activity, participants should be able to describe (1) advantages and shortcomings of hybrid PET/MR scanners with respect to cardiovascular applications (e.g. myocardial perfusion imaging and viability imaging), (2) additional value of the MR component in cardiac imaging, and (3) technical challenges and workflow considerations regarding hybrid PET/MR scanners in the field of cardiology (e.g. attenuation correction and cardiac/respiratory/patient motion).Financial Disclosure: Dr. Schwaiger is an investigator, meeting participant, and lecturer for Siemens Medical. The authors of this article have indicated no other relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, participants can access this activity through the SNMMI Web site (http:// www.snmmi.org/ce_online) through March 2016.PET/CT and other combined scanners have in the past decade rapidly emerged as important research tools and are proving to be invaluable for improved diagnostics in routine nuclear medicine. The design of hybrid PET/MR scanners presented a formidable technical challenge, and only recently were these instruments introduced to the market. Initial expectations of the performance of these scanners have been high, notably because of the potential for superior tissue contrast inherent in the MR modality, as well as the potential for multiparametric functional imaging in conjunction with PET. However, the additional value and potential clinical role that these new systems might bring to the cardiac field have yet to be documented. This review presents a comparative summary of the existing applications for PET and MR in the field of cardiology and suggests potential cardiac applications exploiting unique properties of the newly introduced combined instrumentation. The diverse range of imaging modalities for cardiology includes echocardiography, CT, MR imaging, SPECT, and PET, each of which offers distinct properties and advantages. The demand for combined PET/CT instrumentation in clinical nuclear medicine has grown remarkably, because of the notable advantages presented by hybrid imaging with respect to anatomic localization of lesions. Although these advantages were initially driven by the demands of oncology imaging, the resultant broader availability of PET/CT has provided the opportunity to use these scanners for indications beyond oncology, such as in the field of cardiac imaging (1). Furthermore, CT images are necessary for rapid attenuation correction, which is of particular importance for quantification in myocardial perfusion imaging. Through the use of suitable CT components a...