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Pulmonary Perfusion Patterns and Pulmonary Arterial Pressure¹

¹ From the Division of Nuclear Medicine, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, 55 Fruit St, Boston, MA 02114. Received August 9, 2001; revision requested September 7; revision received October 22; accepted December 11. Address correspondence to the author.

View larger version (22K): [in a new window]   Figure 1. Example of fractal dimension calculation in (top row) a patient with pulmonary hypertension (predicted pressure, 75 mm Hg; measured PA systolic [sys] pressure, 80 mm Hg) and (bottom row) a normotensive patient (predicted pressure, 16 mm Hg; actual PA systolic pressure, 18 mm Hg). In the top and bottom rows, the left image is the original posterior perfusion image of the right lung, the middle image shows the lung contour after subtracting 20% of the lowest count pixels, and the right image shows the lung contour after subtracting 33% of the lowest count pixels. Fractal dimension (FD) is shown beneath each subtracted image. The fractal dimension is higher in the patient with pulmonary hypertension and increases as more low-count density pixels are subtracted from the original image.

View larger version (23K): [in a new window]   Figure 2. Graph shows correlation of each input parameter with the measured PA systolic pressure. These individual correlation coefficients, ranging from 0.070 to 0.432, are small compared with the correlation coefficient of the ANN prediction (0.846). LP = left lung posterior view, RP = right lung posterior view, RA = right lung anterior view, LA = left lung anterior view; 33%, 25%, 20%, and 17% refer to the percentages of low-count density pixels that were subtracted from the original image. R-Mean and L-Mean are the mean pixel densities in the posterior view of the right and left lungs, respectively. R-SD and L-SD are the standard deviations of pixel density in the posterior view of the right and left lungs, respectively.

View larger version (28K): [in a new window]   Figure 3. Scatterplot of ANN-predicted PA systolic pressures versus those measured at angiography in patients with and in those without pulmonary embolism (r = 0.846, P < .001).