Spokane-based Inland Imaging LLC has installed a piece of imaging equipment that it expects will improve outcomes for breast cancer patients here. The device, a positron emission mammography (PEM) scanner, is one of only two such devices in Washington state and one of only about 25 in use around the country, the big radiology services provider claims.


Inland Imaging breast specialist Dr. Robert Arnett says using PEM scans will improve doctors ability to determine how advanced breast cancer is after diagnosis and to locate diseased breast tissue that isnt easily seen with some other types of imaging. Arnett says he believes the technique will be shown to have a positive effect on breast cancer outcomes over the long term.


PEM harnesses positron emission tomography (PET) scanning technology in a mammogram-like machine, imaging a breast at closer range than is possible with a conventional PET scanner, improving the ability to identify areas of breast disease with greater accuracy. The machine, made by Naviscan PET Systems Inc., of San Diego, was approved by the U.S. Food and Drug Administration in 2003, and the equipment is beginning to catch on as a diagnostic tool at imaging centers around the country, Arnett says.


PEM technology, like its PET counterpart, captures images of areas of increased metabolism caused by the growth of abnormal cells. It detects a radioactive substance mixed with glucose that has been injected into the patient prior to the scan and that accumulates in abnormal cells. The PEM unit is an upright machine, similar to a conventional mammography machine. The patient sits in a chair facing the machine and the breast is positioned between two plates that contain the scanners.


The PEM also can be used to scan other small body parts, such as wrists, and a PEM-guided biopsy system used to obtain cells for testing, currently being reviewed the FDA, should be available near the end of the year, Arnett says.


Inland Imaging bought the scanner for $525,000 and began using it last month, Arnett says. It normally would cost about $700,000, but Inland Imaging got a price break because it agreed to participate in clinical research with the equipment, he says.


So far, roughly a dozen patients have had PEM scans here at Inland Imagings radiology facility in the Sacred Heart Doctors Building, Arnett says. Inland Imaging has been increasing its focus on breast health, hiring five new breast imaging specialists over the past year, for a total of 12 such specialists.


Arnett says that the use of PEM scans likely will lead to more, rather than fewer, mastectomies, but also to increased survival rates and fewer recurring breast cancers, since it will help doctors discover additional disease in breast tissue instead of focusing on one specific lump.


Cancer cells consume glucose at a higher rate than normal cells, and patients who are to be scanned are injected with a special glucose that contains low levels of a radioactive marker. The fluorine-infused glucose accumulates quickly in the diseased cells rather than metabolizing, and the radioactive marker shows up clearly in PET scans.


In addition to breast-related uses, the scanner can be used to evaluate tissue samples that are removed in a biopsy, to ensure that the correct tissue was sampled, Arnett says.


Typically, a PEM scan is done as a follow-up study if a woman is diagnosed with breast cancer by conventional X-ray mammogram or magnetic resonance imaging (MRI). Its used to evaluate the size and extent of the breast cancer, Arnett says. Because the images show diseased cells clearly, the scanner helps determine the tumors size and whether there is additional disease in either breast or if it has spread to nearby lymph nodes.


Though PEM wont replace other imaging studies, it adds another level of clarity for diagnosis and determining the stage of breast disease, he says, adding, Its another tool in the arsenal.


Arnett says PEM also can be used as an alternative if a patient has a suspicious mass, but prefers to avoid having a biopsy. He says that, though diabetic patients must have their blood sugar monitored carefully when injected with the glucose solution used for PEM scans, they can have the scans.


PET scans have been used for years, but PEM has several advantages over traditional PET scans and over other types of imaging such as MRI, ultrasound, and conventional X-ray mammography, Arnett says. In a traditional PET scan, the patient lies prone on a table and the table is passed through a large cylindrical scanner. The resulting images are taken from a number of inches away. Since the plates of a PEM scanner are positioned right against the breast in the same way that mammography plates are, a much higher resolution image is captured. With a PEM scanner, a tumor as small as 1.5 millimeters to 2 millimeters across, about the size of a grain of rice, can be seen clearly, whereas with a conventional PET scanner, only tumors between about 6 millimeters and 8 millimeters can be seen, Arnett says.


Most patients are referred for more imaging studies, such as PET or MRI images following an abnormal mammogram. The conventional mammogram uses X-ray technology to take images of the breast. Inland Imaging uses digital mammography, which produces a slightly higher resolution image than film mammography, but if a woman has dense breasts, masses arent easy to see on a mammogram. Unless its evident from the location, its impossible to tell a benign mass from a cancerous tumor on a mammogram, Arnett says.


With PEM, specifically cancerous or pre-cancerous cells that take up more glucose are visible, while most benign conditions are not.


In MRI imaging, the patient must lay on her stomach on a special table designed to allow breast imaging. Arnett says that the advantage of an MRI is that a larger area can be imaged, including a cross section of the shoulder and lymph nodes.


MRI images are extremely sensitive, so they show all sorts of little bumps and fibrous tissues that may or may not be benign, so it can be difficult to decide what to biopsy, Arnett says.


For a breast MRI, a patient must be between day seven and 14 of her menstrual cycle because the effects of hormones on breast tissue change how it reacts to the contrast used for MRIs, Arnett says. Some women with newly diagnosed breast cancer have had to wait up to a month for additional imaging studies, he says. The fluorine-glucose solution used with the PEM scanner, however, is not affected the same way.


In addition to adding accuracy to pinpointing the size and location of a cancer, PEM is more comfortable and less costly than some of the other common imaging techniques, Arnett says.


He says patients who have back problems or are claustrophobic often cant tolerate an MRI, and at a cost of about $2,700, MRI scans cost about twice as much as PEM scans.


The large number of MRI images, which are viewed in sequence via a computer, can be both an advantage and a disadvantage, he says. With the PEM scan, the radiologist looks at sequences that each show four images, from side view or top view of the breast, whereas an MRI sequence can contain about 1,600 images.


As word spreads about the new equipment, some oncologists here are beginning to request that Inland Imaging do a PEM scan also when a patient is scheduled for a conventional PET scan for something else, Arnett says. For example, if a patient is getting a PET scan for a uterine cancer diagnosis, the doctor might request that the center do a PEM scan of her breasts at the same time. Since the patient already has the fluorine glucose injection on board, Inland Imaging will perform the PEM scan at no additional charge, Arnett says.


Contact Jeanne Gustafson at (509) 344-1264 or via e-mail at jeanneg@spokanejournal.com.