Measurement of Pulmonary Vascular Structure and Pulmonary Blood Distribution by Multidetector-Row Computed Tomography and Magnetic Resonance Imaging Techniques

Abstract

Pulmonary-based X-ray computed tomography (CT) and magnetic resonance (MR) imaging techniques have been developed for structural and functional assessment of the lungs. CT methods, taking advantage of newer multidetector-row CT (MDCT) technology, provide a means of quantitatively studying regional pulmonary perfusion (via iodine-based contrast agents) in conjunction with the acquisition of highly detailed information regarding the lung parenchyma and vasculature structure. Additional scanning protocols also allow for regional assessment of ventilation via the use of xenon gas, which is radiodense. Simultaneous to advances in imaging and imaging protocols, software has emerged which provides reliable quantitative tools for automated assessment of structure and function. Texture measures provide information at levels beyond the ability to resolve anatomic structures. CT-based pulmonary vascular structure and assessment for acute and chronic pulmonary embolism (PE) is now common clinical practice, and new functional perfusion techniques are being applied in research studies focusing on pathological changes and the causes of COPD and pulmonary hypertension (PH). Advances in technology have also dramatically improved the image quality and diversity of pulse sequences used for the lung in MR imaging, providing for another powerful imaging technique for the assessment of lung function. This diverse array of MR pulse sequences can be performed back to back to obtain a comprehensive assessment of the lung vasculature with MR angiography (MRA), perfusion imaging, and assessment of the right side of the heart. New functional measures including hyperpolarized noble gas imaging provide new measures of lung function, including ventilation and regional partial oxygen measurements.