HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vidal Melo, M. F. Articles by Venegas, J. G. Search for Related Content PubMed PubMed Citation Articles by Vidal Melo, M. F. Articles by Venegas, J. G.

Quantification of Regional Ventilation-Perfusion Ratios with PET

¹ Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
² School of Engineering, Massachusetts Institute of Technology, Boston, Massachusetts
³ Pulmonary and Critical Care Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
⁴ Clinic of Anesthesiology and Intensive Care Medicine, University Clinic Carl Gustav Carus, Dresden University of Technology, Dresden, Germany
⁵ Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts

View larger version (30K): [in a new window]   FIGURE 1. (A) Semilogarithmic plot of voxel 13NN activity vs. time in voxel exhibiting uniform (1 compartment) behavior. Initial activity A0 is proportional to regional perfusion 0. Washout time constant corresponds to inverse of regional specific ventilation (sr). Thus, area under curve is given by A0· = k·0/sr—that is, proportional to ratio of perfusion to specific ventilation. (B) Semilogarithmic plot of voxel 13NN activity vs. time for voxel exhibiting 2-compartment behavior. Tracer washout shows fast compartment with initial activity A0f proportional to its respective initial perfusion fast and slow compartment with initial activity A0s proportional to its initial perfusion slow. Hatched and dotted areas indicate values of k·/sr corresponding to each of those compartments.

View larger version (61K): [in a new window]   FIGURE 2. Regional perfusion and end-of-washout lung images, tracer kinetics of whole-lung field, and PET-derived A/ distributions for single examples of normal sheep and sheep after pulmonary embolism, saline lung lavage, and bronchoconstriction. Images are tomographic sections viewed in craniocaudal direction from top to bottom. Animals were prone for normal, bronchoconstriction, and pulmonary embolism studies and supine for lung lavage study. In supine position, left side in image corresponds to left side in animal. Note different scales for images. Regions of unperfused lung are seen after embolism. After lung lavage, there is redistribution of perfusion and increase in residual tracer at end of washout. Early peak and fast drop to plateau in lung lavage tracer kinetics indicates presence of intrapulmonary shunt. There is significant retention of tracer in large areas after bronchoconstriction.

View larger version (29K): [in a new window]   FIGURE 3. 13NN washout curves in single examples of individual voxels for experimental data. (A) Normal, single-compartment region. (B) Intraregional heterogeneity suggesting 2-compartment washout. (C) Limit of heterogeneous condition when slow compartment essentially does not eliminate portion of tracer, corresponding to partial intraregional air trapping. (D) Region of virtually complete trapping where A 0. Since regional perfusion is finite, A/ 0.

View larger version (18K): [in a new window]   FIGURE 4. Measured vs. estimated global PaO2 derived from PET-based A/ distributions. Points correspond to values before () and after () pulmonary embolism, after saline lung lavage (), and before () and after (•) bronchoconstriction. Line of identity is shown for comparison.

View larger version (18K): [in a new window]   FIGURE 5. Measured vs. estimated global PaCO2 derived from PET-based A/ distributions. Points correspond to values before () and after () pulmonary embolism, after saline lung lavage (), and before () and after (•) bronchoconstriction. Line of identity is shown for comparison.

View larger version (38K): [in a new window]   FIGURE 6. Maps of regional SecO2 and PecCO2 before (Control) and after bronchoconstriction (BC). Images are tomographic sections in craniocaudal direction from top to bottom. There is marked regional SecO2 (SO2) and PecCO2 (PCO2) heterogeneity after BC. Regional PecCO2 after BC shows larger degree of heterogeneity than SecO2. Note different color scales for SecO2 and PecCO2 to best depict regional changes.