Aug. 10, 2005 Johns Hopkins researchers have, for what is believed to be the first time, used a magnetic resonance imaging (MRI) technique called diffusion-weighted MRI (DWI), a technique that images the movement, or diffusion, of water molecules in tissues, to successfully determine the effectiveness of high-intensity focused ultrasound for treating uterine fibroids. Uterine fibroids are noncancerous tumors that line the uterine wall and can cause intense pain and bleeding. The study appears in the July edition of Radiology.
Ultrasound treatment works by directing focused ultrasound energy that heats the targeted tissue to induce cell damage or death without damaging the surrounding tissue. Because it's noninvasive, the treatment provides a desirable alternative to conventional surgery and was undergoing clinical trials nationally and was recently given FDA approval.
When fibroids or other tissues are damaged or destroyed by ultrasound treatment, water molecules are trapped within the tissue because the cellular pumps that control the movement of water into or out of cells no longer function properly. By measuring the movement of this water using DWI, the researchers hoped to better gauge the impact of treatment on the fibroids by using a quantitative biophysical parameter called the apparent diffusion coefficient (ADC).
Currently, treatment success is determined using regular MRI with a contrast agent (a dye injected into the patient to enhance the resulting image). However, the image produced during this procedure does not precisely show functional information on the degree of fibroid destruction. Therefore, physicians also rely on questionnaires administered to patients after their fibroid treatment, which often are very subjective and unreliable.
In the study, 14 patients with uterine fibroids received ultrasound treatment and subsequent MR imaging using three different MR techniques: conventional MRI, MRI with contrast material, and DWI MRI. Results showed significantly greater signal intensity on DWI of ultrasound treated fibroids than on the images of untreated fibroids or treated fibroids obtained with the other MR methods. These results were confirmed in the 12 patients who took part in the six-month follow up study. Also observed were differences in the ADC. The DWI technique was able to map the ADC in fibroids, showing lower ADC values in treated fibroids than in surrounding tissue, a measure of restricted cellular water flow due to the ultrasound treatment.
"While these results are preliminary and more research is needed, they strongly suggest that the diffusion-weighted MR technique provides images that show functional changes and the extent of fibroid damage from treatment. DWI may be useful for monitoring the effects of ultrasound treatment on uterine fibroids," says Michael Jacobs, Ph.D., assistant professor of radiology and oncology at the Russell H. Morgan Department of Radiology and Radiological Science at Johns Hopkins. "The results also suggest that this imaging technique may be useful for monitoring other focused ultrasound treatments for lesions in the prostate, and breast, when available." The other co-authors of the study were Hyun "Kevin" Kim, M.D. and Edward Herskovits, M.D., Ph.D. This study was supported in part by grants from the National Institutes of Health.
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