Biomedical Engineering Reference
In-Depth Information
disease [3]. CE-MRA with automated table movement (MoBI-trak) using a 1.5
T superconducting magnet (Philips Gyroscan ACS NT) was equipped with a
Power Trak 6000 gradient. Contrast medium (Gd-DTPA) was administered in
two sequential boluses-20 cm
3
at 0.6 cm
3
/sec (starting phase) and 20 cm
3
at
0.3 cm
3
/sec (maintenance phase), using a MedRad Spectris automatic injector.
DSA was the gold standard and was performed using a Philips Integris 3000,
with a brilliance intensifier of 38 sec. DSA and MRA were evaluated on printed
films. DSA provided more than 200 diagnostic assessments including stenosis
<
50-99% occlusions. CE-MRA MoBI-trak exhibited good sensitivity, specificity,
positive and negative predictive values and high diagnostic accuracy. Using this
technique MoBI-trak has been shown to be a reliable technique for the detec-
tion of peripheral vascular disease up to the trifurcation, although it under-
lines the necessity for more diagnostic investigation and improvements in the
technique.
3.4.4 Magnetic Resonance Angiography with
Diffusion-Weighted Imaging
This approach was used for intraoperative magnetic resonance imaging, in-
cluding magnetic resonance angiography and diffusion-weighted imaging [4].
This integrated approach was used to monitor the surgical treatment of a
patient with an intracranial aneurysm. Intraoperative imaging was performed
with a ceiling-mounted, mobile, 1.5-T magnet (developed in collaboration
with Innovative Magnetic Resonance Imaging Systems, Inc., Winnipeg, MB,
Canada) that included high-performance 20-mT/m gradients. Pre- and postclip-
ping, intraoperative, T1-weighted, angiographic, and diffusion-weighted mag-
netic resonance images were obtained from a patient with an incidental, 8-
mm, anterior communicating artery aneurysm. T1-weighted images demon-
strated brain anatomic features, with visible shifts induced by surgery. Mag-
netic resonance angiography demonstrated the aneurysm and indicated that,
after clipping, the A1 and A2 anterior cerebral artery branches were patent.
Diffusion-weighted studies demonstrated no evidence of brain ischemia. For
the first time, intraoperative magnetic resonance imaging was reported to mon-
itor the surgical treatment of a patient with an intracranial aneurysm (see
Fig. 3.29).
