JACR: CTA spikes, while conventional angio use plunges
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| Cardiac CT with Somatom Definition Image source: Siemens Healthcare |
"In the past two decades, there has been a steady increase in the utilization of high-cost, advanced imaging studies such as CT and MRI in the U.S.," cited David P. Friedman, MD, and co-authors from the department of radiology at Jefferson Medical College and Thomas Jefferson University Hospital in Philadelphia. "The escalating cost of diagnostic imaging has made national headlines, as has concern related to increasing radiation exposure to the general population of the U.S."
Friedman and colleagues used the Physician Supplier Procedure Summary Master Files to measure imaging volumes for approximately 35 million fee-for-service Medicare beneficiaries between 2002 and 2007. The population of Medicare enrollees increased by 436,907 over the study period, an increase of just one percent, leaving percent changes in total volume of procedures and rates of usage per 100,000 beneficiaries approximately equivalent.
The researchers compared rates for head and neck CTA and head and neck MR angiography (MRA) with and without contrast. Duplex ultrasound of carotid arteries, cranial carotid angiography, cervical carotid angiography and vertebral angiography were also compared as references for trends in imaging over the five-year period.
The total number of head CTAs increased 827 percent from 8,987 in 2002 to 83,297 in 2007. All head MRA also grew over the period, though at a markedly slower pace, from 272,387 in 2002 to 377,820 in 2007, an increase of 39 percent.
The volume of neck CTAs grew even more rapidly than head, increasing 1074 percent from 9,796 procedures in 2002 to 115,021 in 2007. All techniques of MRA grew in the aggregate by 31 percent, from 192,653 to 253,170 cases.
Together, CTA of the head and neck increased by 956 percent. "During the study interval, the rate of growth of head and neck CTA was dramatically higher than for head and neck MRA, and there was minimal change in the overall MRA volume from 2005 to 2007," the authors noted. "These data suggest that head and neck CTA is replacing head and neck MRA for many patients."
Both head MRA with contrast and neck MRA without contrast decreased over the study period, dropping by 7 percent and 18 percent, respectively, to 2007 volumes.
The authors observed an increase in the volume of carotid artery ultrasound of 20 percent during the study period, while all forms of conventional angiography decreased from 2002 to 2007. Specifically:
- Cranial carotid angiography dropped 36 percent;
- Cervical carotid angiography decreased by 37 percent; and
- Craniocervical vertebral angiography fell by 19 percent.
Overall catheter angiography fell by 32 percent over the study period.
"Technical advancements in multidetector CT scanners have undoubtedly contributed to the dramatic growth in CTA of the head and neck and the decline in the volume of conventional craniocervical carotid and vertebral angiography; there were 75,154 fewer conventional angiographic studies performed in 2007 compared with 2002," the authors claimed.
"[F]or many indications, clinicians and radiologists now regard CTA as a surrogate for conventional angiography; from the perspective of patient safety and comfort, this represents a tremendous improvement."
The authors cautioned that the increase in CTA means that the "Medicare population is now receiving more contrast material and radiation to noninvasively assess the arterial vasculature of the head and neck." Although ionizing radiation is less of a concern in elderly Medicare patients than in the general population, the authors argued that the increasing trends are likely applicable to most age groups in the U.S.
Moreover, increases in the number of MRA orders with contrast may have negative consequences in elderly patients, 11 percent of whom have chronic kidney disease. "Clearly, the elderly Medicare population is now receiving markedly more contrast material to noninvasively assess the arterial vasculature of the head and neck. ... Although serum creatinine levels are now routinely checked in elderly patients before the administration of contrast (representing an additional, indirect cost per imaging study), this contrast burden (and potential for nephrotoxicity or theoretically nephrogenic systemic fibrosis) cannot be viewed as desirable."
Friedman and colleagues also discussed the cost implications of this growth in CTA, noting that the 71 percent growth in the volume of all CTA and MRA was accompanied by "a commensurate 72 percent increase in cost, which amounted to a cost increase of $181 million in just 6 years for interrogating only neurovascular anatomy with these modalities in the Medicare population."
"These data do not provide answers to many important questions," the authors noted, including whether the increase in advanced neurovascular imaging has resulted in improved quality of care; the number of avoided complications resulting from the decrease in angiography; and whether the growth in less invasive CTA and MRA resulted in costly and unnecessary imaging orders.
"The answers to many of these questions fall into the realm of evidence-based medicine, and they are extremely important. In the current economic and health care climate, insurers and politicians will certainly want to know what gains are being achieved for any increase in cost," Friedman and colleagues concluded.