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Introduction to medical imaging
Published in David A Lisle, Imaging for Students, 2012
MDCT therefore provides many varied applications including: CT angiography: coronary, cerebral, carotid, pulmonary, renal, visceral, peripheralCardiac CT, including CT coronary angiography and coronary artery calcium scoringCT colography (virtual colonoscopy)CT cholangiographyCT enterographyBrain perfusion scanningPlanning of fracture repair in complex areas: acetabulum, foot and ankle, distal radius and carpusDisplay of complex anatomy for planning of cranial and facial reconstruction surgery (Fig. 1.9).
Clinical Perspectives of Spectral Photon-Counting CT
Published in Katsuyuki Taguchi, Ira Blevis, Krzysztof Iniewski, Spectral, Photon Counting Computed Tomography, 2020
Salim Si-Mohamed, Loic Boussel, Philippe Douek
PET shaped the concepts underlying modern acute stroke imaging and remains the gold standard. Based on validated thresholds, affected tissue can be classified as core, penumbra, oligemia. However, this method is not available in emergency practice for acute stroke management. Multiparametric MRI combining diffusion weighted imaging (DWI) with perfusion weighted imaging (PWI) has changed the management of acute stroke. DWI and PWI have revolutionized the diagnostic sensitivity of imaging ischemia. Expansion of the initial lesion within the area at risk occurs almost exclusively in those patients, who initially have a perfusion defect larger than the DWI lesion. However, one of the main limitations of MRI is the lack of absolute quantification of perfusion parameters and therefore the accurate distinction between penumbra and oligemia. In contrast, investigations of dynamic CT perfusion scanning have shown the feasibility and promise of this method for the rapid assessment of patients with acute stroke. Compared with other methods of cerebral perfusion imaging, CT perfusion imaging with intravenous infusion of iodinated contrast material offers a number of practical advantages. Dynamic CT perfusion scanning can provide better quantitative information about multiple hemodynamic parameters (e.g., cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak enhancement, or mean transit time (MTT)) from one examination. Matched perfusion abnormalities on CBV and MTT maps correspond to areas of non-salvageable brain tissue and neuronal death, also known as core infarct. Mismatched areas of abnormal perfusion namely, areas of prolonged MTT and diminished CBF where CBV is relatively preserved correspond to areas of salvageable tissue. However, CT quantification needs to be improved for a better assessment of ischemic tissue viability. Furthermore, hyperdense lesions can frequently be observed on the CT obtained immediately after endovascular intervention, and it is sometimes difficult to differentiate intraparenchymal hemorrhage from contrast agent extravasation. DECT should already provide more accurate perfusion assessment of heterogeneous tissues than conventional CT perfusion but K-edge imaging should be more specific and accurate as previously explained. Spectral CT may further provide more accurate pattern of hemodynamic status, by direct and precise quantification of contrast agent concentrations in the different brain areas instead of current attenuation measurements with superposition of the contrast agent attenuation with inhomogeneous tissues densities.
Review of pulmonary emboli and techniques for their mechanical removal to inform device design
Published in Journal of Medical Engineering & Technology, 2020
Jessica Brand, Roger McGowan, Amit Nimunkar
A third, less common PE detection technique is ventilation-perfusion scanning. During the ventilation scan, patients inhale radioisotopes that provide visualisation of airflow into the lungs. During the perfusion scan, patients are injected with radioisotopes that provide visualisation of blood flow through the arteries [11]. Though effective, it cannot be performed on critically ill patients or patients with cardiopulmonary disease. Further, it typically requires follow-up x-ray imaging [1,11].