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Letters to the Editor |
* Department of Radiology, Hennepin County and University of Minnesota Medical Centers, 701 Park Avenue, Minneapolis, MN 55415 e-mail: mckinrad{at}umn.edu
Department of Radiology, Baskent University Medical School, Ankara, Turkey
In the August 2007 issue of Radiology, Dr Papke and colleagues (1) have presented highly relevant information regarding the detection rate of noninvasive multidetector computed tomographic (CT) angiography for intracranial aneurysms and the advantages of multidetector CT angiography in determining aneurysm coilability. As multidetector CT evolves, the information provided by multidetector CT angiography is likely to be relied on further by neuroradiologists, neurointerventionalists, and neurosurgeons alike.
We briefly submit an additional point that we feel is substantial. Three-dimensional (3D) rotational angiography, performed during conventional diagnostic angiography, has been shown to be at least as sensitive as digital subtraction angiography (DSA) in the detection of ruptured and unruptured intracranial aneurysms and may decrease the overall radiation dose of DSA by decreasing the number of acquisitions necessary (2–7). The information offered by 3D rotational angiography regarding the aneurysm neck, configuration (including lobulation and a "teatlike" bleeding site), aneurysm direction and/or orientation, and dynamic aneurysm filling can be obtained by reviewing the subtracted maximum intensity projection, surface-shaded display, and source images from the rotational angiogram; these characteristics on 3D rotational angiograms have been shown to correlate well with the surgical findings (2–6).
With 3D rotational angiography, the angiographic data obtained can be manipulated in a near-infinite number of planes in a fashion similar to multidetector CT angiography. Although 3D rotational angiography does not demonstrate the aneurysm's relationship to adjacent brain parenchyma, bones, or veins as well as does multidetector CT angiography, in some cases this phenomenon is preferred in order to demonstrate the vessel contour minus structures that can be potentially problematic for multidetector CT angiography, such as with bony structures adjacent to tiny aneurysms of the cavernous or proximal supraclinoid internal carotid segments (5,8–11).
Potentially, the combination of bone subtraction (by means of double scanning or dual-source multidetector CT) and the use of an increasing number of detectors for multidetector CT angiography could lead to an accuracy of diagnosing aneurysms that is equivalent to the combination of DSA and 3D rotational angiography (12). However, before we as radiologists unequivocally state that a noninvasive technique is equal to DSA in the detection of aneurysms (inherently suggesting that preoperative conventional angiography may not be necessary), we should compare the best noninvasive technique (potentially multidetector CT angiography) with what may be the best nonsurgical invasive technique (potentially 3D rotational angiography).
A.M.M. and C.L.T. serve on the medical advisory board of Vitrea (Vital Images, Minnetonka, Minn).
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,
Martin Fruth, MD *,
Cornel Haupt, MD *,
Martin Schlunz-Hendann, MD *,
Dieter Sauner, MD *,
Martin Fiebich, PhD 
,
Alan Bani, MD 
, and
Friedhelm Brassel, MD *
* Department of Radiology and Neuroradiology , Klinikum Duisburg, Zu den Rehwiesen 9, D-47055 Duisburg, Germany
e-mail: karsten.papke{at}klinikum-duisburg.de
Department of Neurosurgery, Klinikum Duisburg, Zu den Rehwiesen 9, D-47055 Duisburg, Germany
Department of Radiology, Rheinische Friedrich-Wilhelms-University of Bonn, Bonn, Germany
University of Applied Sciences Giessen-Friedberg, Giessen, Germany
We are grateful to Dr McKinney and colleagues for adding an aspect we have not discussed in our article on the role of multidetector CT angiography in the diagnosis of intracranial aneurysms (1).
We agree with the authors that 3D rotational angiography is highly accurate and can improve both detection rate (2,3) and the anatomic depiction of intracranial aneurysms (2,4). It may decrease radiation by reducing the number of two-dimensional DSA exposures necessary (5,6), facilitate treatment decisions (2,4), and provide useful information for both surgical (7) and endovascular treatment (2,4,5).
However, these advantages of 3D rotational angiography have also been described for CT angiography: CT angiography has been shown to depict aneurysms that were not revealed at DSA (8), owing to the possibility of visualization from any viewpoint (9). Treatment decisions in ruptured aneurysms have also been based on findings at CT angiography (10), and meanwhile, large series of aneurysms have been treated with clip placement by using CT angiography alone (8). Concerning endovascular treatment, measurements for coil sizing and selection of a working projection can also be based on findings at multidetector CT angiography (11,12).
Without a direct comparison between 3D rotational angiography and multidetector CT angiography, we cannot exclude that 3D rotational angiography might be better than multidetector CT angiography in some aspects. However, potential benefits of 3D rotational angiography are outweighed by practical disadvantages. Multidetector CT angiography requires only approximately 2 minutes additional time following a conventional head CT and demonstrates all intracranial vessels in a single data set. Data reconstruction and image interpretation (10–15 minutes) may take place while the patient is prepared for aneurysm therapy.
For 3D rotational angiography, 3–15 minutes have been reported for the creation of 3D images (2,5,7), not including image interpretation. If 3D rotational angiography is used for the detection of aneurysms in all vascular territories, at least three rotational exposures are necessary, with a considerable prolongation of the angiographic procedure.
In our own clinical practice, we initially used both 3D rotational angiography and multidetector CT angiography. However, in direct comparison, we found that 3D rotational angiography does not provide relevant information in addition to multidetector CT angiography for both endovascular (ie, neck assessment and working projection) and surgical (aneurysm morphology and location) treatment decisions. Therefore, we have meanwhile stopped the routine use of 3D rotational angiography.
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