E4 Health&Science

Space tourism craft makes its virgin flight

A suborbital spaceship owned by aspiring space tourism opera- tor Virgin Galactic was airlifted into the skies over California’s Mojave Desert last week for its first flight. The six-passenger ship, VSS Enterprise, remained attached to the center of its carri- er aircraft throughout the flight. Virgin Galactic, an offshoot of London-based Virgin Group, has collected about $45 million in de- posits and fares from more than 330 amateur astronauts, each of whom will be charged $200,000 to experience a few minutes of suborbital spaceflight. Enterprise is closely modeled on a prototype named SpaceShipOne, which is now in the Smithsonian National Air and Space Museum. Test flights are scheduled through 2011, with commercial operations targeted to begin in 2012.

— Reuters

MARK GREENBERG/ASSOCIATED PRESS

KLMNO

TUESDAY, MARCH 30, 2010

Elastography may help treat internal-organ tumors

biopsies continued from E1

protocols, ultrasound images are heavily dependent on the talents of the administering doctor or technician. A judicious twist of the transducer or a subtle in- crease in finger pressure can turn a blurry, inconclusive image into a definitive diagnosis. Perform- ing an ultrasound scan is much like playing a musical instru- ment.

RADIOLOGICAL SOCIETY OF NORTH AMERICA

Figure A shows an ultrasound image of a potentially cancerous solid mass. When elastography was applied, in Figure B, the suspect area was noticeably larger. A biopsy proved this to be invasive cancer.

Better pictures

Elastography provides two ba- sic add-ons to basic ultrasound: It uses software that produces

pictures that enhance the edges and texture of a tumor; and, in advanced elastography systems, it uses sophisticated transducers that further improve the visibility of the tumor and provide data to measure tissue stiffness. With first-generation elastog-

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raphy machines, dating to around 2000, diagnosticians could measure tumor stiffness by applying hand pressure to the transducer to compress the or- gan. (In a standard ultrasound exam, there is no application of pressure.) This resulted in signifi- cantly variable results from ex- aminer to examiner. In recent months, second-generation sys- tems have been developed in which the sound waves rather than the human hand compress the organ, thereby minimizing the human factor. This second- generation technique is known as ARFI (acoustic radiation force impulse). Elastograms of the suspected tumor are compared with images taken via standard ultrasound. When malignant tissue is pre- sent, it will appear larger in the elastogram than in the standard image. (This is because elastog- raphy can detect and project the dense, fibrous tissue that grows around malignant tumors, mak- ing the tumor appear larger.) Tumor shapes are irregular and hard to measure; second- generation elastography provides tools to make more accurate com- putations than human estimates can provide.

Aiming for accuracy

Since organs at or near the

body’s surface are easier to image with ultrasound, most research using elastography has focused on the skin, breast and thyroid. Stamatia V. Destounis, a radiol-

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ogist at Elizabeth Wende Breast Care, an imaging center in Roch- ester, N.Y., estimates that breast radiologists will be able to begin

passing up biopsies based on elastography within four to five years. Her ongoing research shows 98 percent accuracy (58 of 59 cases) in predicting malignant breast tumors, but only 78 percent accu- racy (54 of 69 cases) in predicting non-malignant tumors. All of these cases were confirmed by bi- opsy. Thus, had elastography findings alone been used to de- termine which patients would re- ceive biopsies, 15 would have re- ceived biopsies unnecessarily and one patient who had breast cancer would have gone untreat- ed. For elastography to become widely accepted as the final arbi- ter of which patients will receive

Performing an ultrasound scan is much like playing a musical

instrument.

biopsies, such false negatives must approach zero.

At the Radiological Society of

North America meeting in De- cember, Bahar Dasgeb, a Wayne State University dermatologist who is also board-certified in ra- diology, and Eliot Siegel, a Uni- versity of Maryland radiologist, presented a paper reporting an ability to differentiate with al- most 100 percent accuracy be- tween malignant skin cancers and benign conditions of the skin. But because skin is so easy to biopsy and few dermatology practices have ultrasound exper- tise, elastography is unlikely to reduce the number of skin biop- sies.

Where elastography is likely to be most useful in skin therapy,

Dasgeb said in her presentation is in streamlining Mohs surgery, a common procedure that re- moves successive amounts of skin until abnormal tissue is no longer visible under the micro- scope. Mohs surgery for a simple tumor can take up a good part of a patient’s day, with most of the time spent waiting for lab results. With elastography, the surgeon can get an immediate view of how much skin to remove, short- ening the procedure and avoid- ing disfiguring results that re- quire complicated reconstructive surgery. The thyroid gland, a common site for cancer, illustrates some of the pitfalls in elastography. Al- though easily accessible from the patient’s neck, the thyroid sits ad- jacent to the trachea and the common carotid artery. Because both of these are harder than a thyroid tumor, false negatives of- ten result when the gland is im- aged using elastography. This same limitation arises when a tu- mor is located next to bone. Doctors say second-generation elastography will prove partic- ularly useful in treating such in- ternal organs as the liver, lungs, prostate and kidneys. Duan Li, an ultrasound specialist and inter- ventional radiologist at Memorial Sloan-Kettering Cancer Center in New York, noted that, in addition to avoiding biopsies of the deep organs, elastography can guide the surgeon to be more precise in removing cancerous tissue. Li said that elastography can also be helpful in determining how much cancerous tissue re- mains after tumor ablation. A problem with ablation — a pro- cedure in which heat or extreme cold are administered to the tu- mor to kill it — is that the doctor often is not sure how much of the tumor has been killed. “Elastog- raphy can provide immediate an- swers,” Li said.

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