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3.0T spine imaging at General Hospital St. Jan

Best Practice
Casselman, Jan, M.D., Ph.D. Brugge, AZ St. Jan AV Belgium

New SENSE NeuroVascular and Spine coils enhance 3.0T spine MRI

Although spine MRI at 3.0T has a reputation of being difficult, all this is being consigned to the past with the new SENSE NeuroVascular and SENSE Spine coils for the Achieva 3.0T X-series. Radiologist Dr. Jan Casselman and his colleagues at General Hospital St. Jan (Brugge, Belgium), evaluated the performance of their 3.0T Achieva X-series system in imaging the spine with the new coils, and compared this performance with spine MRI at 1.5T. The results according to Dr. Casselman were conclusive - with the new coils, spine MRI at 3.0T routinely provides excellent results.


Excellent cervical spine imaging

The radiologists at General Hospital St. Jan already had considerable experience in spine MRI with their Intera 1.5T and were curious to see how their new Achieva 3.0T X-series would perform in this area. MRI studies of the spine at 3.0T have been difficult in the past and sometimes disappointing owing to a higher level of artifacts related to high field imaging.


"On our 3.0T system we use the new SENSE NeuroVascular 16 coil for imaging the cervical spine and I must say that the quality of this coil is excellent, producing images of the cervical spine far superior to what we were used to at 1.5T," says Jan Casselman, M.D., Ph.D., Clinical Director of MR and Head and Neck Imaging and Chairman of St. Jan's Department of Radiology. "Signals from the anterior and posterior coil elements provide deep penetration into the neck, which was a problem at 1.5T." However, Dr. Casselman does not always use all the elements together but chooses to sometimes exclude the head elements to limit the amount of data generated.


"On top of that, when using the Neuro- Vascular coil to image the cervical spine, which we now routinely do, the larger FOV of the Achieva 3.0T X-series means we can have a complete view from the back of the brain - including the brain stem - right down to T5 or T6. The large coverage of this coil together with high SNR provided by 3.0T also enables the study of more difficult patients."

New coil boosts performance in thoracic and lumbar spine

But when it came to the dorsal and lumbar spine, images acquired with the previous spine coil were less convincing and sensitive to artifacts," said Dr. Casselman. However, it became quite a different story once he received the new SENSE Spine 15 coil. In comparison to the earlier coil, which had elements aligned along the vertebra, the new coil has its elements arranged in five rows of three coils, one on the mid-line and two to each side. This results in a really wide and homogeneous signal area.


"With this new coil, we can really take advantage of the higher signal strength without artifacts. We get signal from very far anteriorly, which means we see through all abdominal organs and can even see if a patient puts a hand on his belly during a scan," he says. "This is quite a contrast to 1.5T. For example, in obese patients, the relatively large distance between the spine and the coil may result in low signal-to-noise ratio at 1.5T and make it difficult to see instances of myelomalacia and to observe the roots in the neuroforamina in cases of degenerative disease of the spinal canal. None of this is a problem at 3.0T because of the much higher signal intensity. This is especially important when looking at the medulla where low SNR in 1.5T images can make it quite a challenge to determine whether or not myelomalacia is present."

Sagittal T2-weighted TSE image through the thoracic

spine in a patient who has undergone cardiac surgery

and sternotomy. The signal provided by the 15-element

SENSE Spine coil enables good visualization even of the

anterior thoracic and abdominal wall. The metal

materials used to close the sternotomy and the heart

do not cause any artifacts at the level of the spine and

hence an anterior saturation slab is not necessary.

Diffusion imaging also important in the spine

Dr. Casselman finds that the 3.0T's higher SNR also pays big dividends when performing diffusion weighted imaging of the spine. For example, high resolution DWI (1.4 x 1.4 x 3 mm in 2.06 minutes) of the cervical medulla can help to evaluate acute infarction and distinguish recent and old changes due to medulla compression.


"If you discover a lesion in the medulla, a spinal canal stenosis, for example, it's important to know if it's a long-standing condition or a new condition requiring immediate treatment. Using diffusion imaging at 3.0T with the SENSE Spine 15 coil, we can clearly see the signal changes inside the medulla without any artifacts. Since doing this at 3.0T, we have also tried it at 1.5T and I can tell you it is far more difficult and sometimes not possible at 1.5T due to the lower signal intensity."

Total spine, total neuro with SENSE Head Spine coil

The SENSE NeuroVascular 16 coil and the SENSE Spine 15 coil can also be combined to work as one coil (33-element SENSE Head Spine coil combination) for total spine or total neuro imaging. For this, Dr. Casselman and his colleagues at St. Jan also see significant advantages of the large FOV provided by the short-bore magnet of the new Achieva 3.0T X-series. "With the large field of view of the 3.0T system, we can now do total spine imaging - all the vertebrae from C1 down to the sacrum - in just two stages. This dramatically cuts imaging time, which is very important, for instance, when imaging suspicous lesions," he says. Furthermore, St. Jan's radiologists find that the combined coils work very well in total neuro imaging. The complete neuro axis can be scanned in just three stages.

New techniques add to performance

Dr. Casselman and his colleagues also applied the new feature asymmetric TSE (a-TSE). "The use of this asymmetric k-space sampling results in shorter time and/or higher signal. We found that we can get significant reductions in acquisition times with no loss of resolution," Dr. Casselman explains. "This technique only works in scans with an echo train but in spine imaging we use TSE a lot. By making incremental changes to the repetition time of the echo trains just by toggling, we found that the acquisition time would suddenly drop by 30 to 40% without any loss of signal. Of course, if the echo train becomes too long or too short, the time increases again. Almost everything is a trade-off in MR but this is one of the few examples where you get a real gain without paying a penalty somewhere else. You get significant scan time reduction nearly for free." Another new technique is m-FFE. "Multi-echo FFE is a fantastic sequence if you want to see the differentiation between grey and white matter inside the medulla.


m-FFE yields three images at different echo times plus a summation of the three images, which shows very good contrast. It works very well both in the cervical and thoracic spine," Dr. Casselman explains.

Evaluating SmartExam for spine

Philips introduced its SmartExam automated planning, scanning and processing technology based on ExamCards at RSNA 2005. The most recent extension to SmartExam is spine imaging, and the St. Jan radiologists have been evaluating a prototype of SmartExam Spine.


"The major benefit of SmartExam for spine is the time it saves on examinations," points out Dr. Casselman. "It doesn't influence the way you work, but with SmartExam you automatically correct for angulations in the sagittal and coronal planes. After a dedicated 3D scan, in just 47 seconds, the system provides a survey of the patient's spine with all the vertebrae numbered for you. We now use SmartExam Spine in virtually all our cervical and lumbar spine examinations."


SmartExam for cervical spine (also available for lumbar spine). This software automatically recognizes and indicates the different vertebrae (left). Note that T6 is routinely visualized when the 16-element SENSE NeuroVascular coil is used for cervical spine imaging. Once the software has identified the different levels, it also automatically positions and angulates the slices in the coronal and sagittal plane (middle image).


The future of 3.0T

Dr. Casselman's experience with the new SENSE NeuroVascular and Spine coils has caused him to revise his view of 3.0T as an all-round system. "The most frequently performed MR examinations are brain, musculoskeletal and spine exams. The 3.0T system had already conclusively shown us during the first two weeks that its performance for the first two applications is far superior to 1.5T. Now, our experience with the new coils has shown us that the Achieva 3.0T X-series is capable of challenging 1.5T in the spine and even outperforming 1.5T when it comes to spine diffusion, DTI, etc. And while 1.5T is probably sufficient for most examinations, the availability of high quality 3.0T spine imaging will ensure that the popularity of 3.0T will continue to grow in the years ahead."

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Sep 4, 2008

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Best Practice
Achieva 3.0T X-series
Release 2, Release 2.5
Quasar, Quasar Dual
3T, Cervical spine, Lumbar spine, Neuro, Thoracic spine

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