Related Experiment Video
Updated: Aug 14, 2026

Magnetic Resonance Imaging Quantification of Pulmonary Perfusion using Calibrated Arterial Spin Labeling
Published on: May 30, 2011
Effect of posture on inter-regional distribution of pulmonary perfusion and VA/Q ratios in man
Abstract:
Using a gamma camera regional pulmonary perfusion per unit alveolar volume (Q/VA) and ventilation-perfusion ratios (VA/Q) were measured in fourteen normal male volunteers in upright, supine, lateral decubitus, prone and prone suspended postures with inhalation and intravenous infusion of radioactive 81Krm (half-life 13 sec) and inhalation of radioactive 85Krm (half-life 4.4 h). In the vertical axis, Q/VA increased from upper to lower lung regions in upright, lateral decubitus, prone and prone suspended postures but was uniform in supine and within the dependent lung in decubitus postures. Horizontally, Q/VA decreased from cranial to caudal in lateral decubitus, prone suspended, and near the diaphragm in supine. Vertically, VA/Q decreased from upper to lower in all postures except in supine and within the dependent decubitus lung where it increased. VA/Q tended to increase from cranial to caudal in horizontal postures. The effects of gravity on Q/VA and VA/Q vertical distributions are modified when FRC is low (supine, lower decubitus lung) because perfusion is more uniformly distributed. Horizontal gradients of Q/VA and VA/Q are more pronounced under conditions of high local lung volume but also occur in postures where FRC is low.
More Related Videos
Related Concept Videos
Assessment of Ventilation I: Respiratory Rate
A Ventilation assessment is critical for monitoring a patient's health status. Respiration, one of the most accessible vital signs, provides insights into the function of numerous body systems and can indicate serious health issues, such as brainstem injuries from head trauma.
Critical Guidelines for Assessing Ventilation:
Assessment of Diffusion and Perfusion
The Role of Diffusion in Respiration
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the respiratory system, this principle...
Respiratory Volumes
Tidal Volume (TV) Tidal volume (TV) is the air inhaled or exhaled in a...
Pressure Relationships in Thoracic Cavity
Breathing Mechanisms
Both intra-alveolar and intrapleural pressures rely on specific lung properties. The ability to breathe—allowing air to enter the lungs during...
Factors Affecting Pulmonary Ventilation
Alveolar Surface Tension
The alveolar fluid lines the luminal surface of the alveoli and exerts a force called surface tension. This force is caused by the polar water molecules in the liquid being more strongly attracted to each...
Radiological Investigation II: MRI and Ventilation Perfusion Scan
Magnetic Resonance Imaging (MRI) and Ventilation Perfusion Scans are two radiological investigations that offer detailed diagnostic images of the body, particularly lung structures.
MRI
MRI uses magnetic fields and radiofrequency signals to distinguish between normal and abnormal tissues. This technology provides a more detailed diagnostic image than CT scans, enabling it to characterize pulmonary nodules, stage bronchogenic carcinoma, and evaluate inflammatory activity in...

