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4D-TRAK combines high speed and spatial resolution for MRA

Best Practice
Dr. Tombach, Bernd, M.D. Münster, University Hospital Münster Germany

4D-TRAK combines high speed and spatial resolution for vascular studies

Imaging studies designed to help radiologists distinguish the degree of stenosis in cerebral vessels need to be both fast and capable of resolving details in the smallest vessels.Traditional MRA techniques can provide high speed and high resolution but not enough of both to reliably depict certain challenging cerebrovascular pathologies, says Bernd Tombach, M.D., radiologist at University Hospital Münster. Doctors at Münster have been using a prototype of Philips' 4D-TRAK technique for over two years in diverse vascular imaging applications, including their most recent clinical use in cerebrovascular studies. 4D-TRAK combines the speed of SENSE and CENTRA keyhole methods to deliver the all important high spatial and temporal resolution to resolve cerebrovascular anatomy and pathology. Dr. Bernd Tombach.
 Dr. Bernd Tombach University Hospital Münster
Dr. Bernd Tombach
University Hospital Münster

Münster radiologists use 4D-TRAK for run-off studies

In 2003, radiologists at University Hospital Münster began using the 4D-TRAK technique to avoid venous overlay in the run-off (peripheral) vascular system. In a three-FOV study (i.e., aortoiliac system, femoral system, lower leg system), venous overlay often occurs due to disparate flow velocity and arterial filling times between right and left legs, a common observation in peripheral arterial occlusive disease (PAOD). Using conventional MRA exclusively for the run-off system could provide the speed to overcome venous contamination, but at the cost of unacceptably low spatial resolution.


"We adopted a hybrid approach that started with a 4D-TRAK study of the run-off system, consisting of eight dynamics of the lower leg vasculature in the coronal orientation and using a PV coil, followed by the bolus chase method for the aortoiliac and femoral system," Dr. Tombach says. "In the peripheral system, we typically obtained a voxel size of 1.22 mm in each direction, with a reconstructed voxel size of 0.88 x 0.88 x 0.61 mm. The total scan duration was 2:05 minutes, with 10.2 seconds for each dynamic 4D-TRAK acquisition. We simply look at the MIPs of each dynamic acquisition to determine which original data set to examine to enable the diagnosis."


1.5T 4D-TRAK peripheral MRA study demonstrating high spatial and temporal resolution.



Subsequently, Münster clinicians combined 4D-TRAK with whole body MRA in a preliminary unified approach for four FOVs. "This study used a bolus chase technique for the aortic arch with the carotid arteries, the aortoiliac region, the femoral arteries and the run-off system documenting the feasibility," he says.

Versatile 4D-TRAK enhances cerebrovascular studies

In 2005, Münster radiologists began applying 4D-TRAK to the cerebrovasculature. Cerebrovascular pathology may be either arterial or venous in nature, often making MRA technique selection difficult if presenting symptoms are ambiguous. "If you use a time-of-flight technique for the arterial system and a phase contrast technique for the venous system, it takes up to 10 minutes acquisition time to achieve an appropriate image quality," Dr. Tombach observes.


"Since arteriovenous shunting time is just two to four seconds, regular CE-MRA - even with a short acquisition of, say, 15 seconds - isn't fast enough to avoid venous overlay. We envisioned combining the two MRA techniques to image the arterial and venous systems in one rapid approach using a single contrast agent injection."


4D-TRAK study of cerebral vasculature, done at 1.5T.
Temporal resolution is 7 seconds.



Implementing 4D-TRAK on their 1.5T system, Münster radiologists are able to obtain a measured voxel size of 0.78 x 0.78 x 1.4 mm and a reconstruction voxel size of 0.39 x 0.39 x 0.7 mm, with a dynamic 4D-TRAK scan acquisition time of just 7.3 seconds per 3D volume and a total scan time of 1:03 minutes for all dynamics. On the center's Intera 3.0T system, maintaining the same spatial resolution, clinicians can even further reduce the temporal resolution to 3.5 seconds.


4D-TRAK at 3.0T, two consecutive arterial phases.

Dynamic keyhole scan duration: 3.5 sec



14 sec 21 sec
14 sec
21 sec

Patient with a sinus cavernosus fistula.

Total volume MIP's of dynamics of a 4D-TRAK scan at 1.5T



"If you want to match DSA's ability to help distinguish the grade of stenosis then you have to be below one millimeter in voxel size and 4D-TRAK accomplishes this easily," Dr. Tombach says. "Furthermore, using MR and 4D-TRAK avoids several DSA disadvantages, including an arterial puncture, risk of dislodging a thrombus, contraindications regarding renal impairment and radiation dosages, and a longer time slot. For run-off studies, in fact, after 150 patient examinations we use 4D-TRAK exclusively instead of DSA. "Our clinical colleagues are impressed with this technique and with the image quality in run-off studies," he adds. "For intracranial studies, we are changing more minds everyday. Our neuroradiologist increasingly asks for this technique as a planning scan for percutaneous interventions, 4D-TRAK actually leads to a shorter interventional procedure."


1.5T 4D-TRAK study.




For an explanation of 4D-TRAK, see

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Oct 19, 2006

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Best Practice
Achieva 1.5T, Achieva 3.0T
Release 1, Release 2
Nova, Nova Dual, Pulsar, Quasar Dual
Brain, Peripheral MRA, Total Body MRA, Vascular

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