The invention relates to an inexpensive and easy to use method of visualizing an arterial circulation, using biodegradable microspheres which are permeated with an imaging energy absorbent contrast material, such as an X-ray absorbent material, which enables the diagnosis of pulmonary embolism. The microspheres may be comprised of a variety of materials, including human albumin, and may be dyed with a number of X-ray absorbent materials, or other imaging energy absorbent materials. The microspheres are injected into the bloodstream at a particular location such that they travel through the desired circulation, e.g. an arterial circulation and ultimately become lodged in the capillaries of a tissue of interest. Upon exposure of the arterial circulation to X-rays, blood vessels therein containing the microspheres will absorb the X-rays, causing them to show on a developed X-ray film in contrast to other blood vessels and body tissue which do not contain the microspheres that transmit the X-rays. The microspheres are designed to dissolve into the bloodstream within fifteen to thirty minutes after their introduction, the X-ray dye or other contrast material being ultimately excreted from the body via the urine or metabolized by the liver.