Development of a method to measure regional perfusion of the lung in anesthetized ponies using computed tomography angiography and the maximum slope model.

The research article presents a prototype method for measuring regional lung perfusion in anesthetized ponies utilising CT angiography and the Maximum Slope Model. The method was tested and compared with standard techniques, revealing promising results for its potential to monitor lung health and the impact of therapeutic interventions.

Methodology

• To develop the method, six ponies were anesthetized and positioned in dorsal recumbency in the CT gantry. The positioning means that the animals were placed lying on their backs inside the CT scanner.
• Contrast was injected in order to highlight the pulmonary vasculature and the lungs were imaged both during spontaneous breathing and while mechanically ventilated. These images provided data on the state of the lungs under different conditions.
• Two observers outlined the areas of interest in aerated and atelectatic (collapsed) lung areas. The perfusion or blood flow throughout these regions was calculated with the Maximum Slope Model (MSM).
• The measurements gained using this computerized method were contrasted with manual measurements, and compared with values previously obtained using the microsphere technique.

Results

• The perfusion measurements gained using the MSM correlated well with those previously reported using the microsphere method. This implies the new method delivers accurate and reliable results.
• While the ponies were spontaneously breathing, the average blood flow through aerated and atelectatic lung regions were measured. Similar measurements were taken while the ponies were under mechanical ventilation, at both peak inspiration and end expiration states.
• The study found good intraobserver agreement while interobserver agreement was slightly lower. This means the measurements are fairly consistent when performed by the same individual but varied more between different individuals.
• The computerised measurements of the new method correlated well with the results of manual measurements.

Conclusion

• The study concluded that CT angiography and the Maximum Slope Model could be reliably used to measure regional lung perfusion in anesthetized ponies positioned in dorsal recumbency.
• The method proved to be repeatable, suggesting its applicability for determining the effectiveness of therapeutic interventions aiming to improve ventilation-perfusion matching.
• Additionally, it could potentially be used for other studies where measurement of regional lung perfusion is necessary.