Johns Hopkins researchers have, for what is believed to be the firsttime, used a magnetic resonance imaging (MRI) technique calleddiffusion-weighted MRI (DWI), a technique that images the movement, ordiffusion, of water molecules in tissues, to successfully determine theeffectiveness of high-intensity focused ultrasound for treating uterinefibroids. Uterine fibroids are noncancerous tumors that line theuterine wall and can cause intense pain and bleeding. The study appearsin the July edition of Radiology.
Ultrasound treatment works by directing focused ultrasound energythat heats the targeted tissue to induce cell damage or death withoutdamaging the surrounding tissue. Because it's noninvasive, thetreatment provides a desirable alternative to conventional surgery andwas undergoing clinical trials nationally and was recently given FDAapproval.
When fibroids or other tissues are damaged or destroyed by ultrasoundtreatment, water molecules are trapped within the tissue because thecellular pumps that control the movement of water into or out of cellsno longer function properly. By measuring the movement of this waterusing DWI, the researchers hoped to better gauge the impact oftreatment on the fibroids by using a quantitative biophysical parametercalled the apparent diffusion coefficient (ADC).
Currently, treatment success is determined using regular MRIwith a contrast agent (a dye injected into the patient to enhance theresulting image). However, the image produced during this proceduredoes not precisely show functional information on the degree of fibroiddestruction. Therefore, physicians also rely on questionnairesadministered to patients after their fibroid treatment, which often arevery subjective and unreliable.
In the study, 14 patients with uterine fibroids received ultrasoundtreatment and subsequent MR imaging using three different MRtechniques: conventional MRI, MRI with contrast material, and DWI MRI.Results showed significantly greater signal intensity on DWI ofultrasound treated fibroids than on the images of untreated fibroids ortreated fibroids obtained with the other MR methods. These results wereconfirmed in the 12 patients who took part in the six-month follow upstudy. Also observed were differences in the ADC. The DWI technique wasable to map the ADC in fibroids, showing lower ADC values in treatedfibroids than in surrounding tissue, a measure of restricted cellularwater flow due to the ultrasound treatment.
"While these results are preliminary and more research is needed, theystrongly suggest that the diffusion-weighted MR technique providesimages that show functional changes and the extent of fibroid damagefrom treatment. DWI may be useful for monitoring the effects ofultrasound treatment on uterine fibroids," says Michael Jacobs, Ph.D.,assistant professor of radiology and oncology at the Russell H. MorganDepartment of Radiology and Radiological Science at Johns Hopkins. "Theresults also suggest that this imaging technique may be useful formonitoring other focused ultrasound treatments for lesions in theprostate, and breast, when available." The other co-authors of thestudy were Hyun "Kevin" Kim, M.D. and Edward Herskovits, M.D., Ph.D.This study was supported in part by grants from the National Institutesof Health.
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