Soon doctors will be able to virtually "fly through" regions of your body. Already, the first applications of 3-D anatomical modeling -- computerized images of the body from all angles -- hold promise for helping rule out major surgery. In the next five years a large percent of chest surgery will be performed using minimally invasive endoscopy systems. (An endoscope is an instrument that can visualize the interior of a hollow organ). A big problem for the surgeon, though, is how to determine the feasibility of endoscopic procedures.

The CT Marketing department of Siemens Medical Systems, Inc of Islin, NJ, has FDA clearance to introduce a virtual endoscopy system called "fly through." This program will help surgeons determine whether they can perform the less traumatic technique, or whether the problem is to big or complex to undertake with the slender instrument and requires the knife. With the Siemens technology physicians can virtually travel through a patient's chest to "see" if he is a candidate for endoscopy, for instance, to remove a tumor. Another system "flys through" the abdomen.

One step in creating a model of a trachea, bronchi, and lungs -- is to make a cat scan or magnetic resonance images (soft tissue pictures) of the patient's thorax. The cross-sectional slices are then "stacked" and formatted using 3-D computer graphics techniques similar to computer aided design and mechanics (CAD/CAM). The result is a 3-D picture of the patient's chest area. Then a model of the tumor is superimposed within the 3-D model, followed by a model of the real endoscope superimposed on all the others.

Circle shows what virtual endoscope "sees" at this location in the lungs

Using a mouse the physician can then endoscopically journey down the model trachea, into the bronchi and into the lung to the site of the tumor. If the doctor can maneuver the endoscope within a few millimeters of- the tumor, then an actual endoscopy will be okay. The doctor can also measure how far the tumor is from the bronchial wall, and determine whether it can be biopsied or whether other treatments should be considered.

Dr. Ali Bani-Hashemi, a project manager in the imaging and visualization department of Siemens corporate research, and his team designed the "fly through" technology. They are now developing further applications to automate complex visual processes for the physician in his or her office. Bani-Hashemi explains how the physician can build up a virtual version of a patient's coronary arteries: An initial model is created from a textbook or atlas of the human body. Then the CT scan data of the individual's arteries are entered into the program's software. "Then we let the model deform before our eyes," says Bani-Hashemi, "until it fits the patient's data. Once the model begins to conform with the patient's data, the physician can go back and forth from the model to the patient's data until the model is just right." The "fly through" applications, adds Bani-Hashemi, may be used in many ways including medical training.

-- Leah Gandler