The speed and resolution of 64-slice CT have resulted in new applications for CT angiography (CTA) owing to rapid data acquisition during the arterial phase, improved visualization of small vessels, and lengthened anatomic coverage. Extremity CT angiography is one such region. This case report shows the utility of multislice CTA for the evaluation of hemodialysis graft dysfunction.
Although the introduction of helical CT dramatically improved the quality of CT angiography (CTA), the acquisition speed and spatial resolution of single- or four-detector helical CT scanners limited angiographic applications. Specifically, the resolution was not adequate for very small vessels such as the upper extremity vessels, and the speed was insufficient for long anatomic regions, like the peripheral vasculature. However, recently introduced 64-slice CT scanners enable gantry rotation speeds of 0.4 seconds or less and acquisition collimation of 0.6 mm with spatial resolution of under 0.4 mm, such that CTA has become not only practical but advantageous compared with other modalities.
The most recent 64-slice scanners allow the same spatial resolution in x, y, and z directions, improving three-dimensional (3D) reconstructions. Thus, CTA currently has nearly similar spatial resolution and much better 3D capabilities compared with conventional angiography. Furthermore, it still retains the benefits of the conventional CT scanning as a noninvasive modality with excellent capability for detecting anatomic abnormalities. CTA has better spatial resolution and shorter acquisition time compared with MR angiography (MRA). Other advantages of CTA compared with both MRA and conventional angiography are much wider accessibility, 24-hour availability in most hospitals, and significantly lower cost.
Currently, many institutions routinely perform CTA of the brain, chest, abdomen, and pelvis. Lower extremity CTA has only recently become feasible with the implementation of multislice CT. With respect to the upper extremity, many referring physicians may not be aware of the utility of CT angiography. However, indications for evaluation of upper extremity vessels by CT include vasculitis, musculoskeletal masses,12 traumatic injuries, vascular complications of osteomyelitis, congenital anomalies, assessment of vascularized bone grafts before and after reconstructive surgery,1 evaluation of arteriovenous (AV) fistula, evaluation of previously placed graft, and evaluation of arm swelling of unclear etiology. The unsurpassed resolution afforded by 64-slice CT opens a range of new possibilities for imaging the vasculature of the upper extremity, as shown in this case report.