In a session on fusion imaging Tuesday morning at the 93rd annual meeting of the Radiological Society of North America (RSNA), David Gilmore, MS, CNMT, NCT, RT, Beth Israel Deaconess Hospital in Boston, Mass., discussed the future of the fusion imaging for molecular medicine. Nuclear cardiology is not going away, he said, and “we have to figure out how to embrace it.”
The first chapter was when there was only one radioisotope—thallium, only static images, it took 30 to 45 minutes per study, and the test only could determine the existence of coronary artery disease (CAD).
Chapter 2 was when SPECT was created and nuclear cardiology became its own modality, Gilmore said. That introduced gating and attenuation correction and a study could determine the patient’s prognosis of CAD. SPECT offers lots of advantages and is continuing to become the true gold standard. Lots of studies have been published showing the cost-effectiveness of SPECT. Disadvantages, however, include the fact that it’s still prone to artifacts and is a length study. It takes about two to two-and-a-half hours for a complete stress/rest test.
Chapter 3 brought PET for improved efficiency, lower radiation exposure, fixed pricing, less attenuation, improved resolution, increased accuracy and the ability to measure coronary blood flow.
“We have to be careful about radiation dosage,” Gilmore said, particularly cumulative radiation exposure as more and more patients are having multiple studies so their cumulative exposure is getting outside a safe dose.
Chapter 4 is now. The field is determining the value of PET-CT which offers high spatial resolution, high contrast, lower patient and staff radiation exposure, and superior sensitivity and specificity.
“PET-CT is here to stay,” Gilmore said.
Meanwhile, fusion imaging and hybrid imaging are often used interchangeably, but mean different things. Fusion imaging indicates the use of software to create a composite picture from scans taken on separate systems. Hybrid imaging is two procedures performed in one scan.
Hybrid imaging has a lot of value in patient satisfaction, Gilmore said, because they don’t have to schedule and take the time for two different procedures.
The next chapter is still a question, he said. One problem is the challenge of keeping up with training for the newest systems. “We have to figure out how to plan to get technologists ready to operate these systems.” In many parts of the world, CT technologists can’t perform nuclear medicine exams and vice versa, but those silos need to be addressed by the various organizations that oversee licensing.
Other types of hybrid imaging on the horizon include MR/CT, PET/MR and PET/mammo. The studies are becoming a commodity, Gilmore said. “We need to be prepared and make sure we’re offering the highest quality imaging. We’re trying to move from anatomy-based imaging to biology-based medicine to justify the expense of imaging studies.”
Cumulative dose is more important than ever, Gilmore said. “We have to be conscious of it and make sure we’re not causing more damage to our patients.” He said that 62 percent of overall radiation exposure comes from medical imaging. The radiation exposure of one abdomen CT is equal to the amount of natural exposure over three years.
“Hybrid and fusion imaging is not going away,” Gilmore said. “We’re continuing to find the true utilization while working to improve accuracy and patient throughput.”