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Intera 1.5T head, neck applications abound at General Hospital St. Jan, Brugge, Belgium

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

Intera 1.5T head, neck applications abound at General Hospital St. Jan

 

In the human body, a lot can go wrong above the shoulders, but General Hospital St. Jan (Brugge, Belgium) is attacking these problems head-on with its Intera 1.5T and Philips MR tools, including SENSE, Explorer gradients and CENTRA.The Intera 1.5T has replaced other imaging modalities for head and neck indications and facilitated many advanced imaging studies, particularly those for cranial nerves, inner ear, stroke and carotids, according to Jan Casselman, M.D., Ph.D., Clinical Director of MR and Head and Neck Imaging. For head and neck studies, Intera brings a unique combination of high-resolution scanning and speed, to maximize image contrast while reducing scan time and artifacts.

The MR team Jan Casselman, M.D., Ph.D. is on the right.General Hospital St. Jan Brugge, Belgium
The MR team
General Hospital St. Jan
Jan Casselman, M.D., Ph.D. is on the right.
Brugge, Belgium

Explorer gradients, SENSE and Synergy coils have dramatic impact on many studies

At General Hospital St. Jan, CT's speed and mobility are appreciated for trauma and routine sinus imaging and in examinations of the mandible and middle ear. However, MR is now preferred in virtually all other soft tissue head and neck indications. St. Jan solidified MR's hold on head and neck imaging after the acquisition of its Intera 1.5T in October 2001 and an upgrade to Explorer gradients (60 mT/m) a year later. Before October 2001, clinicians had been using a Siemens 1.5T system, now five-years-old. With Intera, clinicians here are setting new standards for evaluating acute stroke and visualizing cranial nerves, inner ear structures and many other head and neck indications.

Explorer gradients make big impact in acute stroke

Susceptibility artifacts in diffusionweighted imaging (DWI) of patients suffering acute stroke virtually disappeared when St. Jan clinicians began using the Explorer gradients.

 

"The Explorer gradients provide beautiful diffusion images," Dr. Casselman notes. "We achieve maximum detail - even in the brain stem. We use SENSE to further minimize susceptibility artifacts and that really gives you excellent images."

 

The Intera 1.5T also brought unparalleled vascular imaging capabilities to the stroke workup. Using the Synergy Head/Neck coil and a recently perfected vascular protocol, St. Jan physicians are achieving exceptional detail in the cerebrovasculature.

 

"This sequence gives us 320 images through the brain vessels, using 0.5 mm slices, 512 matrix. The vessel resolution is unbelievable," Dr. Casselman says. "And, we don't see just the circle of Willis, we also visualize the external carotid and even the vessels on the skull surface. It's a very beautiful overview of all the vessels, covering the complete brain."
Combining the Explorer gradients and SENSE in DWI, and using SENSE for MRA have significantly benefited the imaging of premature infants, a St. Jan specialty. This application uses the SENSE Flex-S coil in a survey for infarctions or perinatal problems. "The combination with SENSE makes it so fast, you can also use high resolution and still have enough SNR - it's fantastic," he observes.

Many techniques required for tracking one cranial nerve course

Cranial nerves can travel through and/ or alongside bone, vessels and fluid depending on the nerve. For even very small lengths, a single sequence won't suffice.

 

"For example, for tracking the sixth nerve from the brain stem to the orbit - although it's only about four centimeters long - you have to change technique four times," Dr. Casselman notes. "Because every segment is different, you have to adapt your technique to the surrounding tissue. If there is fluid around it, you can only see the nerve on a T2-weighted image. If there are veins around it, you have to inject contrast and do time-offlight imaging. If there are soft tissues around it, then you have to use a T1-weighted sequence to see the fat and enhance to make the veins white, see the images at the top of this page."

 

At St. Jan and many other sites, the trigeminal (5th) cranial nerve is imaged most frequently, in the differential diagnosis of neuropathy and neuralgia. The starting point for examining the trigeminal nerve (and others) is the brain stem, using T2-weighted and proton density sequences to find an infarction or MS lesion that would confirm a diagnosis of neuropathy.

 

Next is the prepontine cistern in the CSF area. Philips' DRIVE or Balanced FFE technique is used to aid in the detection of abnormal lesions or schwannoma growing back along the nerve. In the nerve's peripheral branches in the parasellar and facial areas, high-resolution coronal T1-weighted images with contrast agent and a 512 matrix are used to assist in lesion detection.

 

If these initial sequences detect no neuropathic lesions, St. Jan clinicians add a high-resolution (5122), submillimeter slice thickness time-of-flight sequence - with and without contrast agent - to visualize vessels that may be involved in the neurovascular conflict of trigeminal neuralgia.

 

For nerves with courses through the temporal bone (7th, 8th) and jugular foramen (9th-12th), the protocols start out the same (T2-weighted, proton density), but techniques shift to account for differences in surrounding tissue.

 

"Techniques change depending on the nerve course and this is imperative in cranial nerve imaging," he says. "Using the right technique is everything - otherwise you won't even see the nerve."

 

Balanced FFE image ... ... through the cisternal segment of the left trigeminal nerve (black arrow), showing a conflict with the superior cerebellar artery (black arrowhead), displacing the nerve slightly medially.Time-of-flight CE-MRA ... ... 512 matrix, 1 mm slices.The basilar venous plexus is enhancing behind the clivus (white arrowheads), resulting in visualization of the abducent or sixth cranial nerves inside this venous plexus on both sides, seen as black lines or spots inside the plexus (white arrows).High resolution image: Contrast-enhanced T1-weighted image through the cavernous sinus, showing
cranial nerves III, IV,V-1,VI and V-2, see arrows. Made with Synergy Head/Neck coil.
Balanced FFE image ...
Time-of-flight CE-MRA ...
High resolution image:
... through the cisternal segment of the left trigeminal nerve (black arrow), showing a conflict with the superior cerebellar artery (black arrowhead), displacing the nerve slightly medially.
... 512 matrix, 1 mm slices.The basilar venous plexus is enhancing behind the clivus (white arrowheads), resulting in visualization of the abducent or sixth cranial nerves inside this venous plexus on both sides, seen as black lines or spots inside the plexus (white arrows).
Contrast-enhanced T1-weighted image through the cavernous sinus, showing cranial nerves III, IV,V-1,VI and V-2, see arrows. Made with Synergy Head/Neck coil.

CE-MRAs now preferred by vascular surgeons

In the past, St. Jan's vascular surgeons weren't interested in CE-MRAs of the supraaortic arteries. The 1.5T system they were using couldn't scan fast enough to produce high-resolution images in a short arterial window, so images acquired with a 256 matrix were all radiologists could offer. "Our surgeons said the images couldn't compare with regular x-ray angios," Dr. Casselman recalls.

 

The Intera 1.5T system brought three powerful tools for CE-MRA: the neurovascular Synergy Head/Neck coil, SENSE and CENTRA. CENTRA, an innovative Philips method for high-resolution, high-contrast, timing-robust MRA, enabled St. Jan clinicians to extend MRA data acquisition to 70 seconds (40 seconds previously) without having venous return visualized on the images. SENSE's speed (factor 2) is traded for higher resolution and thinner slices, enabling St. Jan to boost resolution to 512 and even 670 at a voxel size of 0.5 x 0.5 x 0.5 mm3 .

 

"We put the Synergy Head/Neck coil, SENSE and CENTRA together and suddenly surgeons prefer these magnificent CE-MRA images over x-ray angio," he says.

 

High resolution CE-MRA ... ... of the neck vessels from the aortic arch to the circle of Willis with Synergy Head/Neck coil. Minor changes are seen at the carotid bifurcation, however an unexpected thrombus or stenosis was found in the left middle cerebral artery, see arrow.
High resolution CE-MRA ...
... of the neck vessels from the aortic arch to the circle of Willis with Synergy Head/Neck coil. Minor changes are seen at the carotid bifurcation, however an unexpected thrombus or stenosis was found in the left middle cerebral artery, see arrow.

Intera reveals anatomy and pathology of inner ear

Patients with sensorineural hearing loss - deafness associated with the structures of the inner ear and their connections to the brain - come to St. Jan for MR examinations. The cochlea, which contains the main hearing receptor, is particularly important in attempts to restore hearing. Therefore, imaging the cochlea's status is crucial, as is that of the brain stem and nerves in the IAC.

 

"We want to see inside the cochlea, especially the scala tympani and scala vestibuli, the spiral passageways that make two-and-half turns parallel to one another within the cochlea (see images below)," Dr. Casselman says.

 

"These compartments become very important in decisions regarding cochlear implant surgery, because surgeons need to determine which one is open and hence is the best to use. So, you have to visualize both compartments and the fluid in them."

 

MRI of the cochlea using St. Jan's other 1.5T system had produced ambiguous results. "I could always see the separation of the scala, but not on every turn of the cochlea, and there were some troubling artifacts," he recalls. "The resolution Intera affords is higher, so we can now more reliably see the compartments on every turn, artifact free."

 

In addition to the cochlea, Dr. Casselman is interested in visualizing the four nerves in the internal auditory canal. If the Intera shows that the cochlear nerve is missing, the cochlear implant procedure will not work.

 

Often, an acoustic schwannoma impinges on one or more of the nerves in the IAC. "Surgeons want to know on which nerve is the schwannoma," he says. "In addition, they want to know if they can treat the lesion while preserving hearing. Therefore, we have to determine if there is still fluid between the schwannoma and the base of the cochlea. Plus, we have to appreciate the signal intensity of the fluid in the cochlea with the opposite side. If the fluid signal goes down, you probably can't save hearing. There are many subtle things you can only see with high resolution T2 and contrast-enhanced T1 images that today help the surgeon tremendously."

 

The MR technique St. Jan radiologists use is DRIVE with SENSE and a 1024x1024 matrix. The small SENSE Flex-S coil is used, which can be placed close to the ear for more SNR.

 

High resolution DRIVE image... ... through the right temporal bone, 0.7 mm slices, made every 0.35 mm with, 1024 matrix, Synergy Flex-S coil. Note the large vestibular aqueduct (arrow). The scala vestibuli and scala tympani can be distinguished (arrowheads) and the different nerve branches can be depicted inside the internal auditory canal.MIP of inner ear DRIVE images Maximum Intensity Projection (MIP) image made using all DRIVE images of an inner ear
study. The parallel spiral passageways of the scala tympani and scala vestibuli can be
distinguished on this 3D reconstruction.Surface reconstruction ... ... made from the DRIVE images.The semicircular canals and cochlea can be seen in detail. Note the large endolymphatic sac and duct (arrow).
High resolution DRIVE image...
MIP of inner ear DRIVE images
Surface reconstruction ...
... through the right temporal bone, 0.7 mm slices, made every 0.35 mm with, 1024 matrix, Synergy Flex-S coil. Note the large vestibular aqueduct (arrow). The scala vestibuli and scala tympani can be distinguished (arrowheads) and the different nerve branches can be depicted inside the internal auditory canal.
Maximum Intensity Projection (MIP) image made using all DRIVE images of an inner ear study. The parallel spiral passageways of the scala tympani and scala vestibuli can be distinguished on this 3D reconstruction.
... made from the DRIVE images.The semicircular canals and cochlea can be seen in detail. Note the large endolymphatic sac and duct (arrow).
T1-FFE through inner ear Contrast-enhanced T1-weighted FFE image through the inner ear, 1 mm slices made every 0.5 mm. Acute labyrinthitis with enhancement in the cochlea and vestibule (arrowheads). The cochlear branch (white arrow) and inferior vestibular branch (black arrow) of the vestibulocochlear nerve can be distinguished on these images. Also, observe the enhancing vascular loop (AICA) near the porus.T1-FFE through larynx. Contrast-enhanced T1-weighted image through the larynx. Note tumoral invasion of the left
thyroid cartilage (arrow). Even the vocal cords and arytenoids cartilage can be evaluated in
detail. Synergy Flex-S coils, 3mm slices, scan time 3:38 min.T1-FFE through the neck. Contrast-enhanced T1-weighted image through the neck in a patient with a branchial cleft
cyst.The image is 4 mm thick, and all images were acquired in four minutes using the
Synergy Head/Neck coil.
T1-FFE through inner ear
T1-FFE through larynx.
T1-FFE through the neck.
Contrast-enhanced T1-weighted FFE image through the inner ear, 1 mm slices made every 0.5 mm. Acute labyrinthitis with enhancement in the cochlea and vestibule (arrowheads). The cochlear branch (white arrow) and inferior vestibular branch (black arrow) of the vestibulocochlear nerve can be distinguished on these images. Also, observe the enhancing vascular loop (AICA) near the porus.
Contrast-enhanced T1-weighted image through the larynx. Note tumoral invasion of the left thyroid cartilage (arrow). Even the vocal cords and arytenoids cartilage can be evaluated in detail. Synergy Flex-S coils, 3mm slices, scan time 3:38 min.
Contrast-enhanced T1-weighted image through the neck in a patient with a branchial cleft cyst.The image is 4 mm thick, and all images were acquired in four minutes using the Synergy Head/Neck coil.

Many other head and neck applications

St. Jan employs its Intera 1.5T for many other head and neck indications, including evaluations of patients suffering from vertigo and tinnitus - two additional inner ear-related disorders. In addition, the Intera has proved invaluable in routine neck examinations, especially in tumor surveys of the larynx, and in standard and spectroscopic imaging of brain tumors. The Intera 1.5T is also used extensively in studies of the cervical spine to help differentiate disk pathology from bone and CSF. A growing application at St. Jan is diffusion tensor imaging, used to preoperatively visualize the trajectory of white matter fiber tracts near tumors.

"The Intera is a fantastic machine," Dr. Casselman says. "I'm really fond of it."

 

 

Scan protocols Head and Neck - General Hospital St. Jan, Brugge

 

Intera 1.5T, Explorer gradients, Release 10

ClVw: Intera 1.5 T head neck application
ClVw: Intera 1.5 T head neck application
ClVw: Intera 1.5 T head neck application
ClVw: Intera 1.5 T head neck application


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Best Practice
Intera 1.5T
Release 10
Explorer / Nova Dual
Brain, Brain stem, IAC, Neck, Neuro, Pituitary, Vascular
 

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