Taking MRI a Step Beyond

A new diagnostic system developed at the Weizmann Institute enables a scan to detect a tumor and also to tell whether it's benign or malignant

A new system for identifying and diagnosing tumors, developed at the Weizmann Institute, has received approval from the U.S. Food and Drug Administration and is already being used in diagnosing breast and testicular cancer. The system is expected to change the process of biopsy testing, obviate the need for invasive procedures, save resources and reduce the stressful period of waiting for answers.

The method was developed by a research team headed by Prof. Hadassa Degani of the Weizmann Institute's Department of Biological Regulation, based on magnetic resonance imaging (MRI), but with much more sophisticated results than previously known.

MRI testing bounces radio waves off hydrogen atoms in the water molecules of the body, via a very powerful magnetic field, to create a visual image. The same instrument is also used for MRS testing, in which radioactive contrast material injected into the patient penetrates the intercellular layers and permits a clearer identification of tissues with especially high cellular density - thereby enabling the identification of cancerous growths.

The research group headed by Dr. Degani used existing MRS technology but the form of the test was altered. The existing method can identify whether there is a tumor or not, but cannot show whether it is benign or malignant; for that, a biopsy has to be sent for examination and the patient had to wait anxiously for several days for the crucially important results.

Dr. Degani's team found that the speed and manner in which the contrast substance enters the body and leaves it can reveal a lot about the nature of the tumor. Prof. Degani explains that malignant tumors are not visually uniform; if the growth is benign, however, the contrast material will make it visible very quickly and in a uniform color. When the area of the suspected tumor is viewed, if the contrast injection is spreading unevenly, it may be cancer.

The outflow reveals a lot

The group also found that the injected material disappears differently from benign as opposed to malignant tumors, hence the way the material flows out of the tissues is telling. In healthy tissue, the material hardly spreads beyond the confines of the tumor, whereas if the growth is cancerous, the higher cell density will force rapid leakage. Since the contrast material circulates in the blood vessels, around a cancerous growth there will be a typical augmentation of microscopic blood vessels visible.

Aside from the innovative monitoring of how the contrast injection circulates, the researchers also send a special type of tissue sample for examination. The system is called 3TP (for "3 time points"). To get more detailed results and a higher resolution of the images, they take a sample at each of three specific points in time, set in advance, enabling the equipment to put more power into providing a short but much more precise image. Subsequent interpretation is aided by mathematical formulas.

In clinical trials done in recent years, when the results of using this system were compared with results of biopsies done on the same patients, the new system identified nearly 100 percent of the cancerous growths with a diameter of five millimeters or greater. In trials that included women with DCIS (ductal carcinoma in situ), a cancer of the milk ducts in the breast, that had not spread nor formed lumps, the diagnosis was accurate about 90 percent of the time.

Prof. Degani, a breast cancer expert, says that the new system has many advantages over existing diagnostic approaches to this common disease. Degani believes that, in future, MRI and ultrasound systems will replace X-ray testing, which is currently still the cheapest but also has risks associated with ionizing radiation.

Of tissue samples sent for biopsy, two-thirds or more (65-80 percent) are found to be benign. The new system does away with the need for the invasive biopsy procedure and the long wait for results for most women in whom a growth has been discovered. There will still be some situations in which the results will be borderline and the 3TP system will be unable to offer a conclusive diagnosis, Degani cautions, and then a biopsy will be required. "But there will be a fairly large group of women to whom we'll be able to say immediately, `Your tumor is benign.'"

Following the breast cancer study, which lasted more than 10 years, the team began investigating testicular cancer, where the tissue involved is very similar to that of breast tissue. Next will come lung cancer, which is currently the most lethal in the world and is generally discovered late. "It's a difficult subject," says Degani. "The tissue itself is not an obstacle, but the patient's strong breathing and heart movements create a technical problem." The new system is already in use in the United States, but not yet in Israel. n