The recent development of quinoline-based PET tracers that act as fibroblast-activation-protein inhibitors (FAPIs) demonstrated promising preclinical and clinical results. FAP is overexpressed by cancer-associated fibroblasts of several tumor entities. Here, we quantify the tumor uptake on 68 Ga-FAPI PET/CT of various primary and metastatic tumors to identify the most promising indications for future application. Methods: 68 Ga-FAPI PET/CT scans were requested by various referring physicians according to individual clinical indications that were considered insufficiently covered by 18 F-FDG PET/CT or other imaging modalities. All PET/CT was performed 1 h after injection of 122-312 MBq of 68 Ga-FAPI-04. We retrospectively identified 80 patients with histopathologically proven primary tumors or metastases or radiologically unequivocal metastatic lesions of histologically proven primary tumors. Tumor uptake was quantified by SUV max and SUV mean (60% isocontour). Results: Eighty patients with 28 different tumor entities (54 primary tumors and 229 metastases) were evaluated. The highest average SUV max (.12) was found in sarcoma, esophageal, breast, cholangiocarcinoma, and lung cancer. The lowest 68 Ga-FAPI uptake (average SUV max , 6) was observed in pheochromocytoma, renal cell, differentiated thyroid, adenoid cystic, and gastric cancer. The average SUV max of hepatocellular, colorectal, head-neck, ovarian, pancreatic, and prostate cancer was intermediate . SUV varied across and within all tumor entities. Because of low background in muscle and blood pool (SUV max , 2), the tumor-to-background contrast ratios were more than 3-fold in the intermediate and more than 6fold in the high-intensity uptake group. Conclusion: Several highly prevalent cancers presented with remarkably high uptake and image contrast on 68 Ga-FAPI PET/CT. The high and rather selective tumor uptake may open up new applications for noninvasive tumor characterization, staging examinations, or radioligand therapy. ://jnm.snmjournals.org/content/60/6/801 This article and updated information are available at: http://jnm.snmjournals.org/site/subscriptions/online.xhtml Information about subscriptions to JNM can be found at: http://jnm.snmjournals.org/site/misc/permission.xhtml

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The nuclear spin polarization of the noble gas isotopes 3 He and 129 Xe can be increased using optical pumping methods by four to five orders of magnitude. This extraordinary gain in polarization translates directly into a gain in signal strength for MRI. The new technology of hyperpolarized (HP) gas MRI holds enormous potential for enhancing sensitivity and contrast in pulmonary imaging. This review outlines the physics underlying the optical pumping process, imaging strategies coping with the nonequilibrium polarization, and effects of the alveolar microstructure on relaxation and diffusion of the noble gases. It presents recent progress in HP gas MRI and applications ranging from MR microscopy of airspaces to imaging pulmonary function in patients and suggests potential directions for future developments. MRI has been extremely successful at diagnosing soft tissue disease since its discovery in 1972 (1). However, MRI is not as sensitive in comparison with other biomedical imaging techniques, such as CT, positron-emission tomography, or single-photon emission computed tomography. This is a consequence of a very small signal from a small population difference between nuclear energy states. For a spin-1/2 system, the "nuclear spin polarization", P N , is defined as:where N ϩ and N Ϫ denote populations with magnetic spin quantum numbers ϩ1/2 and Ϫ1/2, respectively. Typically, the thermal energy of the sample at temperature T exceeds the energy difference between the nuclear spin states in a magnetic field B 0 by several orders of magnitude ("hightemperature approximation") and the equilibrium polarization can be written as:where ␥ is the magnetogyric ratio, ប is Planck's constant divided by 2 , and k B is Boltzmann's constant. As an example, P N,0 Ϸ 5 ppm is predicted with Eq.[2] for protons ( 1 H) at body temperature (T ϭ 37°C) and B 0 ϭ 1.5T. In view of the inherent sensitivity problem, increasing the signalto-noise ratio (SNR) has been a field of continuous research since the discovery of NMR. Recently, the use of optically polarized noble gas isotopes 3 He and 129 Xe has attracted increasing interest for use in a variety of promising MR applications. These systems exhibit polarizations exceeding the thermal levels by several orders of magnitude. While the use of such "hyperpolarized" (HP) gases for MRI is a recent development, it is based on a solid foundation of work in atomic physics. The groundwork was laid by Kastler (2) more than 50 years ago by demonstrating transfer of angular momentum from circularly polarized light to the electron and nuclear spins of atoms, a process called "optical pumping" (OP). Since 1991, exploitation of OP as a means of enhancing signal initiated the development of a novel field in NMR (3,4). Research involving HP noble gases has been exceptionally fruitful in biomedical MRI as well as providing applications for investigation of materials (5-8).In the context of proton MRI, the lung is a particularly challenging area to study (9). Even at end expiration, the overall density is ...

With more than 900,000 confirmed cases worldwide and nearly 50,000 deaths during the first 3 months of 2020, the coronavirus disease 2019 (COVID-19) pandemic has emerged as an unprecedented health care crisis. The spread of COVID-19 has been heterogeneous, resulting in some regions having sporadic transmission and relatively few hospitalized patients with COVID-19 and others having community transmission that has led to overwhelming numbers of severe