Phase-Contrast MRI: Physics, Techniques, and Clinical Applications.

With phase-contrast imaging, the MRI signal is used to visualize and quantify velocity. This imaging modality relies on phase data, which are intrinsic to all MRI signals. With use of bipolar gradients, degrees of phase shift are encoded and in turn correlated directly with the velocity of protons. The acquisition of diagnostic-quality images requires selection of the correct imaging plane to ensure accurate measurement and selection of the encoding velocity and thus prevent aliasing and achieve the highest signal-to-noise ratio. Multiple applications of phase-contrast imaging are actively used in clinical practice. One of the most common clinical uses is in cardiac valvular flow imaging, at which the data are used to assess the severity of valvular disease and quantify the shunt fraction. In neurologic imaging, phase-contrast imaging can be used to measure the flow of cerebrospinal fluid. This measurement can aid in the diagnosis and direct management of normal pressure hydrocephalus or be used to evaluate the severity of stenosis, such as that in Chiari I malformations. At vascular analysis, phase-contrast imaging can be used to visualize arterial and venous flow, and this application is used most commonly in the brain. Three-dimensional imaging can yield highly detailed flow data in a technique referred to as four-dimensional flow. A more recently identified application is in MR elastography. Shear waves created by using an impulse device can be velocity encoded, and this velocity is directly proportional to the stiffness of the organ, or the shear modulus. This imaging modality is most commonly used in the liver for evaluation of cirrhosis and steatosis, although research on the assessment of other organs is being performed. Phase-contrast imaging is an important tool in the arsenal of MRI examinations and has many applications. Proper use of phase-contrast imaging requires an understanding of the many practical and technical factors and unique physics principles underlying the technique.©RSNA, 2020.

Recurrent metastatic breast cancer manifesting as pulmonary tumor thrombotic microangiopathy with interstitial pulmonary fibrosis and infarcts: A clinicopathological correlation.

Pulmonary Tumor Thrombotic Microangiopathy (PTTM) is a fatal complication of malignancy characterized by embolization of tumor cells to the pulmonary vasculature leading to a vascular reaction resulting in stenosis and pulmonary hypertension. Because the clinical manifestations of PTTM overlap with those of other entities, premortem diagnosis is challenging. We describe an unusual case of PTTM as the only clinical manifestation of recurrent metastatic breast cancer. A 50 year-old woman presented with hypoxemia and echocardiographic findings consistent with pulmonary hypertension and cor pulmonale. Correlation of premortem pulmonary imaging with autopsy histopathologic findings revealed that ill-defined ground-glass opacities identified on CT angiogram corresponded to areas of cellular interstitial fibrosis and widespread intrapulmonary tumor emboli involving predominantly small-sized arteries with associated florid intimal fibrosis. The radiologic nodularities and scattered peripheral wedge-shaped consolidations corresponded to evolving pulmonary infarcts on histopathology. Although retrospectively, the imaging findings were concordant with a spectrum of increasing severity of tumor embolization and vascular remodeling, the diagnosis of PTTM was not made premortem. PTTM is a rare entity that must be considered in cancer patients with unexplained hypoxemia, pulmonary hypertension and lung opacities on imaging.

Coating of an anti-Fas antibody on silicone: first in vivo results.

BACKGROUND: Although the etiology of capsular contracture after breast augmentation has not yet been definitively clarified, the literature contains numerous reports placing the blame on a foreign body reaction. We have developed a procedure for covalently activating a silicone surface with an anti-Fas antibody, which might suppress the foreign body reaction on the silicone surface. OBJECTIVES: The authors evaluate whether surrounding tissue might be influenced by anti-Fas antibody coating on silicone disks in comparison to untreated silicone disks in an in vivo model. METHODS: During this study, 4-mm anti-Fas-coated silicone disks were implanted subcutaneously in the paravertebral region of mice (C57/BL6). Silicone disks passing the activation coating process without anti-Fas antibody incubation were defined as the control group. Twelve weeks after implantation, the disks were removed and the surrounding tissue examined. RESULTS: The tissue surrounding the silicone disks in the experimental group showed significantly increased levels of collagen type 3, elevated levels of matrix metalloproteinase 9, markedly decreased levels of transforming growth factor ß2, and a reduced CD68 expression in the pericapsular tissue. CONCLUSIONS: The first in vivo data reveal that the tissue surrounding a silicone surface can be influenced by the vectored binding of an anti-Fas antibody.