MR spectroscopy advocates hope

Medicare payments may focus attention on technique

MR spectroscopy may finally be ready to shed its image as a research tool with limited clinical application thanks to the Health Care Financing Administration's decision to approve Medicare and Medicaid payments for the technique. While much remains to be done before the technology can achieve widespread clinical use, HCFA's move is a huge step forward, according to spectroscopy advocates.

HCFA issued reimbursement codes for MR spectroscopy in December, and made the decision retroactive to Jan. 1 (SCAN 2/4/98). The reimbursement level will vary by region, but in one state the reimbursement has been set at $537. The CPT code for spectroscopy is 76390.

Spectroscopy is the foundation on which modern MR was built, with early research conducted in the 1940s and '50s. Unlike MRI's basis in displaying anatomy, spectroscopy measures metabolism, or changes in the chemical composition of tissue, and is based on the principle that different nuclei locked into different chemical bonds will have varying resonance frequencies. The technique typically produces waveforms that measure the spectra of chemicals in the body.

The most basic level of spectroscopy is single-voxel spectroscopy, in which the chemical composition of a volume from 1 to 3 cc is examined. More advanced techniques include chemical shift imaging (CSI), in which spectra from multiple voxels are collected and merged into an image that resembles a nuclear medicine or PET exam, according to Linda Eastwood, MR marketing manager for Picker International of Cleveland. Such images can be overlaid on conventional MR scans to create an image that provides both anatomical and metabolic data.

Clinical areas where spectroscopy has carved out niches generally involve the brain. One such technique is tumor therapy monitoring, where spectroscopy can help clinicians confirm that all of a tumor has been destroyed or excised, according to Yuri Wedmid, high-field MR product manager for Siemens Medical Systems in Iselin, NJ. Imaging techniques often fall short in this application because scar tissue or healing tissue can distort images. With spectroscopy, however, malignant tissue is clearly differentiated from benign due to the different chemical metabolism rates.

Other applications include focal and nonfocal brain lesions. With nonfocal lesions, in which a conventional MR image may appear normal, spectroscopy can help radiologists identify areas of abnormal chemical metabolism. Spectroscopy packages targeted for detecting phosphor can be useful for body applications, such as heart and muscle tissue, according to James Meng, manager of clinical science for Philips Medical Systems North America of Shelton, CT.

Spectroscopy's early influence. Despite its research-oriented nature, the potential of spectroscopy framed much of the early debate over MRI technology in the mid- and early '80s. GE Medical Systems of Milwaukee cited spectroscopy's promise in promoting 1.5-tesla superconducting magnets over the lower field systems that its competitors were selling at the time. GE was hoping to develop what it called the integrated exam, which would merge spectroscopy and imaging data into a single procedure, according to Morry Blumenfeld, general manager for advanced development at GE.

Due to its complexity, long scan times, and the difficulty in interpreting exam results, spectroscopy took much longer to develop than first expected, however, and was soon overshadowed by rapid advancements in MR image quality. Indeed, improvements in MR's ability to display anatomical detail have made some spectroscopy applications obsolete due to the shorter exam times and higher sensitivity of imaging, according to Wedmid.

"Spectroscopy is technologically challenging, and if you can do it an easier way, you'd rather do so," Wedmid said. "But if you can't do it any other way, spectroscopy does have advantages."

Most of the major MRI vendors have clinical spectroscopy packages under development or on the market. Some aim to make spectroscopy more user-friendly to radiologists and clinicians by automating the chemical analysis process. Spectroscopy upgrade packages tend to cost between $40,000 and $50,000 and are usually limited to 1.5-tesla scanners.

Whether HCFA's decision will spur demand for these packages remains to be seen. Prior to HCFA's ruling, clinical spectroscopy was so rarely used that a high-volume site was considered one that did one or two studies a day. One site, at the University of Pennsylvania Medical Center in Philadelphia, reports that interest in the technique has been rising sharply, and the center is doing two or three studies a day, according to Robert Lenkinski, a professor of radiology.

HCFA's ruling is an important psychological milestone that will prompt radiologists to look at spectroscopy in a new light, according to Blumenfeld. Radiologists must still be trained in the technique, however, before widespread usage occurs.

"There is going to be a huge requirement for training, fueled by people who will be saying, 'Now I can get reimbursed for this, what does it really mean, and where do I go to learn it?'" Blumenfeld said. "We are going to encourage the academic centers and potentially the societies to work as hard as possible on the education problem."

One prominent spectroscopy advocate, Dr. Victor Haughton, a professor of radiology and director of neuroradiology at the Medical College of Wisconsin in Milwaukee, believes that spectroscopy has a bright future, regardless of HCFA reimbursement.

"It will achieve wider clinical use no matter what," Haughton said. "It is a clinically useful technology, and it is a cost-saving technology. It can obviate more expensive procedures."