A multi vendor effort to standardize and cross-calibrate dual-energyx-ray absorptiometry (DEXA) measurements has been under way forover a year. Dr. Willi Kalendar of Siemens spearheaded the effort,according to Joel B. Weinstein, vice president of
A multi vendor effort to standardize and cross-calibrate dual-energyx-ray absorptiometry (DEXA) measurements has been under way forover a year. Dr. Willi Kalendar of Siemens spearheaded the effort,according to Joel B. Weinstein, vice president of marketing forHologic of Waltham, MA.
Kalendar is head of a densitometry task force of COMAC, a standardsbody of the European Economic Community. In that position, hewas able to bring DEXA and quantitative computed tomography vendorstogether with clinical researchers at the last two RSNA meetings,Weinstein said.
The objective of those meetings was to obtain technical supportand hammer out a consensus on the development of a phantom forcross-calibration of DEXA equipment and, possibly, comparisonof DEXA and QCT results. The COMAC group developed specificationsfor a standard anthropomorphic phantom last July, Weinstein toldSCAN.
The COMAC phantom was to be presented last week at a workshopon bone densitometry in Bad Reichenhall, Germany. While the abilityof the phantom to cross-calibrate DEXA systems still needs testing,there is a good chance that the vendors will support this effort,he said.
A previous bone mineral density standardization effort supportedby the American Association of Physicists in Medicine and theAmerican College of Radiology broke down in 1987 when Lunar rejecteda recommendation by the two groups to use a spine phantom developedby Hologic, Weinstein said.
Lunar indicated that Hologic had vetoed another attempt touse a phantom built by Radiation Measurements, a third-party calibrationcompany (SCAN 4/24/91). The four DEXA vendors are Lunar, Hologic,Norland and Sopha of France.
"I am optimistic we will be more successful this time,"Weinstein said. "The COMAC phantom may be built by a thirdparty or licensed to the manufacturers," he said.
There has already been cooperation between DEXA vendors onan individual basis. Norland's DEXA system was originally calibratedagainst a Hologic spine phantom, and Hologic is considering usinga Norland phantom for whole-body bone and soft tissue measurementcross-calibration, Weinstein said.
"Preliminary results look good," he said. "Itlooks like the two (Norland and Hologic) instruments read valuesof soft tissue as well as bone identically on that (Norland) phantom,"he said.
Measurements of the fat and lean mass of soft tissue are obtainedas a by-product of bone mineral density studies. This soft tissueinformation may prove useful in exercise physiology and nutritionapplications, Weinstein said.