[CT angiography to determine the size of intracranial aneurysms before GDC therapy].

OBJECTIVE

To examine in a model and in clinical practice whether CT angiography (CTA) is suitable to determine the size of intracranial aneurysms.

METHODS

For an aneurysm model the contrast medium-filled balloon of an occlusion catheter was used. At different levels of filling images were obtained by both CTA and digital subtraction angiography (DSA). In the CT image the size of the simulated aneurysm was calculated from the CTA data at the workstation while from the DSA images it was performed by the DSA system with the use of both an external reference structure (two-ring method) and a stereotactic system (ANGIOLOG). In 7 patients, the size of the aneurysm was determined by CTA and DSA prior to aneurysm occlusion by means of guglielmi detachable coils (GDC therapy).

RESULTS

On the basis of 2 D reconstructions of the CT average size deviations in the XY plane of 1.6% and on the Z axis of 3.2% were determined. These errors increased to 3.4% (XY plane) and 5.6% (Z axis) with 3 D reconstructions. By use of the two-ring model, DSA gave an average size deviation of 3% while with the stereotactic system (ANGIOLOG) it was as high as 11%. In 6 of the 7 patients, the appropriate spiral size was chosen primarily after CTA measurements.

CONCLUSIONS

CTA enables the reliable determination of the size of an intracranial arterial aneurysm and in individual cases can give a better representation of an anatomic situation at the base of an aneurysm than DSA. Thus, CTA imaging of an aneurysm prior to GDC therapy is useful.