Peripheral arterial occlusive disease (PAOD) remains a significant health care problem in the United States today, affecting approximately 8 million Americans, especially those aged >65 years . There is an increased prevalence in patients with tobacco use, African American ethnicity, diabetes, hypercholesterolemia, and impaired renal function . PAOD is a strong predictor of systemic atherosclerosis, and patients with PAOD have a threefold higher risk for all-cause death and a sixfold higher risk for cardiovascular-related death compared with patients without PAOD . Various noninvasive diagnostic tests for evaluating PAOD have been developed, including the simple, but critically important, ankle-brachial index, pulse volume recording measurements, and ultrasound examinations with color flow duplex imaging.
In the conservative management of patients with intermittent claudication associated with significant functional impairment, or with acute or critical limb ischemia, in whom surgical intervention is appropriate, arterial imaging becomes necessary and justified . Contrast angiography, especially digital subtraction angiography, is usually considered the “gold standard” for arterial imaging. However, during the past two decades, techniques for vascular imaging have been developed using computed tomography and magnetic resonance. Computed tomographic (CT) angiography (CTA) and magnetic resonance angiography of the extremities may be used to diagnose the anatomic locations and presence of significant stenoses in patients with lower-extremity PAOD, to select patients with lower-extremity PAOD as candidates for endovascular intervention or surgical bypass, and to select the sites of surgical anastomosis. Magnetic resonance angiography, CTA, and color flow duplex imaging may also be used in advance of invasive imaging to develop an individualized diagnostic strategic plan, including assistance in the selection of access sites, the identification of significant lesions, and the determination of the need for invasive evaluation .
Each of these techniques has specific strengths and limitations. Contrast angiography, in addition to being invasive in nature, has specific limitations, including difficulties with the timing of both legs in instances of asymmetric obstruction, overlapping of vessels, and limited visualization of the vessels immediately distal to a complete obstruction. Each of these limitations can result in the need for additional injections and imaging with modified timing requirements. As the techniques of CTA are refined, the status of contrast angiography as the gold standard has been questioned. It has been documented that multidetector CTA (MDCTA) is cost effective and has specificity, sensitivity, and accuracy that rival those of digital subtraction angiography . This highlights the continued need for improving and refining the techniques involved in the acquisition, postprocessing, and display phases of MDCTA.
The article by Roos et al at Stanford University Medical Center in this month’s Academic Radiology gives us the opportunity to review the latest developments in MDCTA. Specifically, certain limitations in the technology surrounding curved planar reconstruction (CPR) of the arteries are addressed, and a promising new technique is offered to overcome these limitations.
This paper is of interest to academic radiologists on two levels. First, it presents a step forward in the work done on automating CPR for CTA. Second, it describes a form of patient-specific modeling used to provide medical imaging information that is not directly derived from a CT scan itself.
Advances in curved planar reconstruction
MDCTA for PAOD is a technique of vascular imaging that uses multislice CT imaging to acquire images of the abdominal aorta and the pelvic and lower-extremity arteries. Optimal imaging requires understanding and the proper application of CT technical factors and proper timing of contrast administration and scanning. The reader is referred to an excellent review of the available techniques by Fleischman et al . The data generated by CTA are processed and are generally presented to radiologists in the form of cross-sectional images, maximum-intensity projection images, and three-dimensional volume-rendered images. The number of images presented for interpretation is on the order of 1000 and can be overwhelming to radiologists. Cross-sectional images are required to evaluate areas of stenosis and occlusion, especially in areas of dense calcifications and stents, for which maximum-intensity projection and surface-rendering volume-rendered techniques are ill-equipped to display the status of the inner lumen. This approach, which requires the viewing and assessment of the cross-sectional images, is generally considered inefficient and inadequate.
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Partial vector space projection and patient-specific modeling
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References
1. Arain F.A., Cooper L.T.: Peripheral arterial disease: diagnosis and management. Concise review for clinicians. Mayo Clin Proc 2008; 83: pp. 944-950.
2. Hirsch A.T., Haskal Z.J., Hertzer N.R., et. al.: ACC/AHA guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society for Vascular Medicine and Biology, and the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Peripheral Arterial Disease). Summary of recommendations. J Vasc Interv Radiol 2006; 17: pp. 1383-1398.
3. Sun Z.: Diagnostic accuracy of multislice CT angiography in peripheral arterial disease. J Vasc Interv Radiol 2006; 17: pp. 1915-1921.
4. Visser K., Kock M.C.J.M., Kuntz K.M., Donaldson M.C., Gazelle G.S., Hunink M.G.M.: Cost-effectiveness targets for multi-detector row CT angiography in the work-up of patients with intermittent claudication. Radiology 2003; 227: pp. 647-656.
5. Roos J.E., Rakshe T., Tran D.N., et. al.: Lower extremity CT angiography (CTA): initial evaluation of a knowledge-based centerline estimation algorithm for femoro-popliteal artery (FPA) occlusions. Acad Radiol 2009; 16: pp. 646-653.
6. Fleischmann D., Hallett R.L., Rubin G.D.: CT angiography of peripheral arterial disease. J Vasc Interv Radiol 2006; 17: pp. 3-26.
7. Raman R., Napel S., Beaulieu C.F., Bain E.S., Jeffrey R.B., Rubin G.D.: Automated generation of curved planar reformations from volume data: method and evaluation. Radiology 2002; 223: pp. 275-280.
8. Roos J.E., Fleischmann D., Koechl A., et. al.: Multipath curved planar reformation of the peripheral arterial tree in CT angiography. Radiology 2007; 244: pp. 281-290.
9. Rakshe T., Fleischmann D., Rosenberg J., Roos J.E., Napel S.: Knowledge-based interpolation of curves: application to femoropopliteal arterial centerline restoration. Med Image Anal 2007; 11: pp. 157-168.
10. Stewart W.F., Shah N.R., Selna M.J., Paulus R.A., Walker J.M.: Bridging the inferential gap: the electronic health record and clinical evidence. Health Aff (Millwood) 2007; 26: pp. w181-w191.
11. Lemke HU. Berliner L. Model-based patient care with a therapy imaging and model management system. In: Golubnitschaja O, ed. Predictive diagnostics and personalized treatment: dream or reality? New York: Nova Science. In press.