Diagnostics & Imaging Week Washington Editor

WASHINGTON — Hospital administrators must face down a hoard of requests for the latest and greatest technology, and supporters of CT scanning as a replacement for conventional angiography were in plentiful supply on the second day at the 2006 edition of Transcatheter Cardiovascular Therapeutics conference here in DC.

Unfortunately for the budget-conscious administrator, the attempt to contain costs will tend to be overwhelmed by drive toward the "minimally invasive" paradigm of modern medicine. But this will boost the prospects for manufacturers to get their machines installed in hospitals across the world's largest market for medical equipment — the U.S.

Despite all the apparent momentum, proponents of multi-slice CT equipment had a competitor on the dais who argued that the buck is better spent on MRI equipment, making a further case that the return on investment is less a gamble with the latter technology because of the range of applications that are reimbursable — reimbursement being the keystone for advancing the newest and most expensive.

Among those highlighting the strengths of multi-detector computed tomographic angiography, or MDCTA, was Robert Schwartz, MD, a cardiologist at the Minneapolis Heart Institute (Minneapolis, Minnesota), who said that MDCTA is comparable to conventional angiography in terms of the accuracy of its depiction of coronary anatomy. But he pointed out that the per-procedure cost is roughly $5,000 for the former and only about $800 for MDCTA. He described the risks of standard angiography only as "present" and that of MDCTA as "tiny."

The time required for the patient at a hospital or other facility also diverges sharply, with a patient needing most or all of a day for the traditional angiogram versus roughly an hour for the newcomer. MDCTA also scored favorably on the amount of time necessary for the procedure, said to run typically for 12 minutes versus an hour or more for the stand-by angiogram.

Schwartz reminded the audience that he was discussing a 16-slice CT scanner rather than one with fewer projection points, and that data from older studies indicated rates of accurate diagnosis of 90%, but he said that this number was now surely a low estimate. "With greater experience, it's very easy to get in the high 90s," he said, insisting that the accuracy "seems to be comparable" between the two approaches.

One of the drawbacks to MDCTA is that it is contraindicated with high levels of calcification. However, Schwartz said that of 3,200 patients, less than one-tenth of one percent [were rejected] due to extreme calcification." He also noted that this medium "does have some false positives" that to some extent are generated by defensive scoring.

W. Guy Weigold, MD, director of cardiac CT imaging at the Washington Hospital Center (WHC; Washington), discussed the requirements for a functioning coronary CT imaging practice, based on his work at WHC.

Some of this advice seemed plain-Jane enough, such as obtaining dedicated phone and fax lines, but Weigold also urged anyone interested in assembling such a practice to make sure that "your scheduler is aware of exclusion criteria," such as obesity.

"Patient selection is really the key" to a successful practice, Weigold said, adding that "you can't just take any body and expect to get a good quality image" from CT technology.

Patients with arrhythmias also are not candidates for MDCTA, and those with body-mass indices of greater than 45 are poor candidates as well, a threshold that he said "has crept up" of late from the previous metric of 40.

Weigold said that for patients with serum calcium scores of higher than 1,500 "you might want to back off and not perform a CTA" because this level or higher usually indicates substantial calcification in the heart and most such patients will end up "doing the angiogram anyway."

"Data storage is an issue you'll want to think about" with regard to CT angiography, Weigold said, because these machines generate rather large volumes of data. Some 16-slice CT systems are said to generate files as large as a gigabyte per scanning session, leaving a busy clinic with a need for a hefty picture archiving system, or PACS.

And one cannot assume that such storage needs can be calculated merely by adding up the number of scans the facility is expected to perform over the timeframe in question because backup data files will double that requirement immediately. However, backup files can be recorded in a different medium and are often stored offsite to avoid their loss by a disaster that claims the primary files.

Edward Martin, MD, a non-invasive cardiologist at the Oklahoma Heart Institute (Tulsa), pushed another idea into the debate, commencing with the remark that "CT is a very good device, but I don't think you want to forget about MRI." He said that he and his associates "do about 200 or so cardiovascular MRs a month."

MRI for angiography, Martin noted, has almost the same spatial resolution as CT, but that "it's an order of magnitude or better in temporal resolution than CT," describing the temporal resolution of MR as between 10 and 20 milliseconds (ms) versus the 120-160 ms of CT cardiography.

"We also have excellent contrast resolution and are not constrained to an axial view," Martin noted, and that the contrast agents for MRI procedures are typically not as toxic to the kidneys.

"I want a versatile machine in my office," Martin said, adding that given the vagaries of reimbursement in the modern world, a single application-machine that loses its reimbursement potential "shuts down your office."

One of the downsides of MR vs. axial X-ray scanning is the training demand upon operators.

Martin acknowledged that "everyone says that CT is much easier" to get the hang of, noting that "you have to understand the physics more" to make effective use of this technology.

However, he insisted that MRI machines "will stand the test of time and will weather the changes in reimbursement," thanks to their versatility.

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