UPMC Horizon hospitals will soon offer a new alternative in detecting cancerous tumors in the body.

Starting in January, UPMC Horizon expects to have a mobile Positron Emission Tomography, or PET, unit available for two days a month. The PET scanning service will be offered in collaboration with Vantage Healthcare Network Inc., Meadville, and NEO PET, an Ohio-based mobile PET service provider.

NEO PET will provide the equipment and technical support for the program while UPMC Horizon will provide a part-time nurse coordinator for the project.

Radiologists at the hospital will read the PET scan results.

Until recently, Horizon patients could only receive PET scans in Pittsburgh, said Dr. Edgardo R. Lob, a Greenville hematologist and medical oncologist.

PET, a nuclear medicine test, is used as a compliment to, but not in place of, CAT scans, ultrasounds and MRIs.

The PET scanner is similar in a appearance to a CAT scanner, but doesn't take pictures like an X-ray, said Dr. Scott Pickering, radiologist at UPMC Horizon. PET works by scanning radioactive sugar dye injected into the patient's bloodstream.

"The theory is the tumor will have a higher metabolic rate," Pickering said. An active tumor will metabolize sugar faster than inactive tissue, he said.

"Most tumors are more active than normal tissue," Lob said.

The scan takes about an hour to an hour and 15 minutes, Pickering said.

First, the patient is injected with the dye and then is slid into the tube-like scanner after the dye has time to get into the patient's cells, which takes about an hour. The PET scan detects "hot spots" -- places where the glucose metabolizes faster.

"It's an activity test, not a structure test," said Lob, explaining that a CAT scan shows a three dimensional image of structures in a patient's body, while the PET scan measures the metabolic rates.

A PET scan can detect small tumors or enlarged lymph nodes that won't show up on a CAT scan, making it easier for doctors to catch cancer in its earliest stages.

Because the PET scan shows the whole body, doctors can determine if the cancer has spread.

Pickering said a PET scan can also be used in place of a biopsy to determine if a tumor is benign or malignant.

Malignant tumors have a higher metabolism than benign ones, he said.

So far, Medicare has only approved five diagnoses for a PET scan, including single pulmonary nodules, non-small cell lung cancer, lymphoma, colorectal cancer and melanoma.

Lob said more diagnoses may be included as PET scans become more common.