Fusion Imaging: Where Form Meets Function

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With the sum being greater than it parts, fusion imaging - largely of PET-CT images - is having a growing impact on cancer diagnosis, staging, re-staging and therapy follow-up. And the technology is beginning to stretch its wings into assessing oncology drug therapy, cardiovascular and neurological imaging and targeted radiotherapy.

Multimodality or fusion imaging is making its mark in diagnosis and therapy of cancer thanks to boosts in physician confidence and improvements in patient care. And it is beginning to earn believers in cardiac and neurology imaging applications.

The leading hybrid modality today is PET-CT. A positron emission tomography scanner uses small concentrations of radioactive material injected into the blood to show concentrations of cancer cells in color spectrum, while computed tomography scanners produce cross sectional x-rays of the body. By combining the two modalities, radiologists and nuclear medicine physicians possess images that combine metabolic function and anatomic form. Tumors can be located more accurately and physicians can determine whether or not it has invaded other nearby structures or spread elsewhere in the body.

"This is a rapidly moving and evolving field," says Richard Wahl, MD, director of nuclear medicine/PET and vice chair of technology and business development at Johns Hopkins Medicine. "Virtually any study that has been looked at with PET-CT is at least as accurate as and generally more accurate than PET and CT done alone."

Embraced as a better diagnostic tool in the spectrum of cancer care, PET-CT has fueled market numbers, too. In 2002, Frost & Sullivan estimated that PET-CT garnered 45 percent of the overall PET market and within one to two years could surpass standalone PET systems in total sales. According to the American Society of Radiologic Technologists (ASRT), an estimated 150 PET-CT units were in operation in 2002 and 225 units by 2003. By the end of 2004, more than 400 units will have been sold to hospital-based nuclear medicine, CT or radiation therapy departments as well as outpatient center-based radiology and oncology departments.

AN EVOLVING TECHNOLOGY

PET-CT was developed jointly by David Townsend, PhD, senior PET physicist and professor of radiology at the University of Pittsburgh School of Medicine and Ronald Nutt, PhD, president of CPS Innovations, Knoxville, Tenn. The first prototype was tested at University Pittsburgh Medical Center (UPMC) from 1998 to 2001 and results from the trials led to the FDA approval of PET-CT as a diagnostic tool for cancer in October 2000.

Since 1998, UPMC has performed 8,000 PET-CT scans. The facility uses two Reveal-RTs (CPS Innovations), a dual-slice Lutetium oxyorthosilicate (LSO) PET-CT scanner and a Bismuth sermante (BGO) single slice PET-CT scanner. The systems, located in the PET center of the facility separate from both nuclear medicine and radiology, are used for the diagnosis, restaging and therapy planning for cancer. "Since 1998, many studies that we do have changed patient management solely because of the fusion scanner," says Todd Blodgett, MD, radiology resident at UPMC.

To date, fusion imaging is only reimbursed by insurance companies for a number of malignancies. The Centers for Medicare & Medicaid Services (CMS) offer Medicare coverage for non-small cell lung cancer, lymphoma, colorectal cancer, melanoma, head/neck cancer, esophageal cancer, breast cancer and thyroid cancer. Malignancies that will most likely benefit from hybrid imaging but are not yet covered by Medicare include small cell lung cancer, ovarian cancer, cervical cancer, testicular cancer, pancreatic cancer, multiple myeloma and soft-tissue sarcoma.

Reimbursement is hindering private practices and imaging centers from purchasing the expensive modality, with PET-CT systems ranging in cost from $1.5 million to $3 million. A 16-slice CT with high-resolution PET scanner is significantly more expensive than a dual-slice scanner and a regular PET system. No fixed CPT codes exist for PET-CT. "Basically, you have two options," explains Blodgett. "You can either charge for PET only or you can charge for PET and CT. At UPMC, we bill for both the CT and PET portion of the exam and that's because we are using contrast [agents]."

BLENDING SPECIALTIES

Many academic medicine centers administer contrast agents (oral or intravenous) for the CT portion of the PET-CT exam because they have a credentialed radiologist on board to interpret the diagnostic