Seminars in respiratory and critical care medicine
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Beyond being a substitute for X-ray, computed tomography, and scintigraphy, magnetic resonance imaging (MRI) inherently combines morphologic and functional information more than any other technology. Lung perfusion: The most established method is first-pass contrast-enhanced imaging with bolus injection of gadolinium chelates and time-resolved gradient-echo (GRE) sequences covering the whole lung (1 volume/s). Images are evaluated visually or semiquantitatively, while absolute quantification remains challenging due to the nonlinear relation of T1-shortening and contrast material concentration. ⋯ Respiratory mechanics: Time-resolved series with high background signal such as GRE or steady-state free precession visualize the movement of chest wall, diaphragm, mediastinum, lung tissue, tracheal wall, and tumor. The assessment of volume changes allows drawing conclusions on regional ventilation. With this arsenal of functional imaging capabilities at high spatial and temporal resolution but without radiation burden, MRI will find its role in regional functional lung analysis and will therefore overcome the sensitivity of global lung function analysis for repeated short-term treatment monitoring.
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Pulmonary hypertension is defined as a resting mean pulmonary arterial pressure of 25 mm Hg or more determined at right heart catheterization. The challenges for imaging in patients with suspected PH are fivefold: the imaging modality should have a high diagnostic accuracy with regard to the presence of PH; it should be able to characterize the underlying disease, and allow for quantification of its extent by measuring pulmonary hemodynamics. Finally, it should provide prognostic information, and can be used for monitoring of therapy. ⋯ MR imaging is the reference standard for assessment of cardiac structure and function and allows for physiologic assessment of the pulmonary vasculature. New developments show that with MR techniques, an estimation of hemodynamic parameters such as mean pulmonary arterial pressure and pulmonary vascular resistance will be possible. Actually, CT and MR imaging should be considered as complementary investigations providing comprehensive information in patients with pulmonary hypertension.
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Semin Respir Crit Care Med · Feb 2014
Risks, Benefits, and Risk Reduction Strategies in Thoracic CT Imaging.
Chest computed tomography (CT) is a useful tool for diagnosing various thoracic conditions and has become the diagnostic imaging modality of choice for many diseases. Recent discussions about the radiation dose from CT have attracted the attention of medical professionals and the general public. ⋯ Four techniques are discussed in detail, including tube current modulation, automatic exposure control, automatic tube voltage selection, and iterative image reconstruction. Adopting these techniques in routine clinical practice can dramatically reduce radiation dose levels.
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Lung cancer is the leading cause of cancer death worldwide and accounts for more deaths than breast, prostate, colon, and pancreatic cancers combined. A distinct minority (15%) of lung cancers are diagnosed at an early stage; 5-year survival (all lung cancers) approximates 15%. Randomized, controlled trials in the 1960s and 1970s found that chest radiographic screening did not confer a survival benefit for high-risk patients. ⋯ Who should be screened and how often? What is the appropriate workup when lesions are noted in asymptomatic individuals? What is the risk of cumulative radiation exposure from repetitive low-dose CT scans? What is the responsibility of health care personnel to evaluate nonpulmonary issues detected by CT (e.g., coronary calcifications). In this review, we address these and other questions that arise. Further, implementation of screening programs may be logistically difficult, require additional personnel and computer software, and will incur significant health care costs.
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Semin Respir Crit Care Med · Feb 2014
ReviewIntegrated cardiothoracic imaging with computed tomography.
The respiratory and the cardiovascular systems are intimately connected. Because of the high degree of morphological and functional interaction, pathophysiological processes in one compartment are likely to induce adaptive changes in the other. ⋯ Up-to-date advanced imaging strategies allow for a combined assessment of the cardiopulmonary unit. Besides improved techniques of electrocardiogram (ECG)-synchronization for obtaining both morphological and functional information, latest advances of dual-source CT (DSCT) have shown great promise for even more comprehensive integrated cardiothoracic imaging.