Field Strength. Achieva 3.0T excels in wide range of applications. Fletcher Allen Health Care finds many uses for versatile system

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1 Field Strength Publication for the Philips MRI Community Achieva 3.0T excels in wide range of applications Fletcher Allen Health Care finds many uses for versatile system This article is part of Field Strength Issue 29 July 2006

2 Achieva 3.0T excels in wide range of applications Fletcher Allen Health Care finds many uses for versatile system Steven P. Braff, M.D. Christopher Filippi, M.D. In 2004, Fletcher Allen Health Care (Burlington,Vt., USA) clinicians anticipated that their new Philips 3.0T system would stand out in their majority applications of brain and CNS imaging. The Achieva 3.0T system met their expectations for neuro MRI, fmri and MRA applications and further impressed Fletcher Allen radiologists in abdominal, musculoskeletal and cardiac studies, in addition to directed examinations, such as MR spectroscopy. The tremendous SNR boost at 3.0T, the clinical capabilities of the Philips 3.0T system and Philips strategies for managing SAR at this field strength, have brought MRI scanning to a new level at Fletcher Allen. Fletcher Allen Health Care "It quickly became obvious that breathhold and fatsuppressed abdominal and pelvic studies are exquisite at 3.0T." Until April 2004, Fletcher Allen Health Care operated only 1.5T scanners two fixed systems and one mobile unit were Fletcher Allen s workhorses, performing 14,000 examinations annually. However, with an expanding list of advanced MRI techniques that benefit immensely from higher signal, the addition of a higher field strength system became a necessity, says Fletcher Allen Interim Chairman of Radiology, Steven P. Braff, M.D. A 3.0T system has twice the SNR of a 1.5T system, so for the advanced applications we re interested in here spectroscopy, neurofunctional imaging, cartilage imaging and advanced cardiac imaging 3.0T is the future, he says. Although Fletcher Allen had never previously owned a Philips MRI system, it selected the Philips 3.0T after comparing several commercial systems. We chose Philips because we believe the company has the most advanced, complete clinical 3.0T product on the market, particularly regarding how SAR is managed, Dr. Braff remarks. We ve never had problems with SAR on the Philips 3.0T scanners. My friends and professional colleagues who have competitive 3.0T systems have had scans shut down in mid-examination due to SAR limits. Philips RF management solution, RF-SMART, makes this 3.0T system a clinically friendlier unit. Routine and advanced neuro As Fletcher Allen clinicians expected, all routine CNS and brain MRI and MRA exams have benefited from the higher SNR that 3.0T provides; Fletcher Allen doctors consider the 3.0T system their instrument of choice over 1.5T systems for these applications. Since the institution began scanning at 3.0T, however, brain imaging has become infinitely more refined with BOLD fmri and diffusion tensor imaging (DTI) techniques that excel with extra SNR, enabling the addition of advanced examinations, such as pre-surgical localization of eloquent cortex. Fletcher Allen neuroradiologists use an fmri paradigm device to present sophisticated stimuli to patients, enabling clinicians to pre-surgically map areas of eloquent cortex, such as the motor strip and Broca s and Wernicke s areas. Together with fmri and all 3.0T brain scans for that matter clinicians also acquire DTI data sets to obtain fractional anisotropy maps that can help doctors determine the course of white matter fiber tracts, thus helping neurosurgeons avoid them during surgery. 12 Field Strength Issue 29 - July 2006

3 Neuro imaging Post contrast GRASE DWI 22-year-old with optic neuritis. Left image shows mildly enlarged right optic nerve. Post-contrast image demonstrates optic nerve enhancement. The diagnosis was multiple sclerosis. Middle-aged woman with ataxia and cranial neuropathies. Left image shows a heterogeneous lesion within pons showing striking hypointensity and marked edema tracking into cerebellum and brain stem. On the diffusion-weighted image, a central hypointensity is seen within the lesion. On both pre-biopsy images marked enhancement is present with central areas of non-enhancement. On the coronal image, note the enlargement of the temporal horns due to obstructive hydrocephalus. This patient underwent biopsy, which confirmed a tuberculoma. Tuberous sclerosis. The image shows multifocal areas of hyperintense signal abnormality in the subcortical white matter and corresponding cortical signal abnormality. In the coronal image, a nodule lining ependymal surface of the lateral ventricle is noted. With the doubled SNR and improved contrast we get at 3.0T, fmri studies have really benefited, says Christopher Filippi, M.D., Fletcher Allen s director of MRI. On a 1.5T magnet, we re looking for differences in oxygenation of hemoglobin of only 1% to 5%. At 3.0T, we ve found it s more like 10% to 15% a tenfold difference. That allows us to localize eloquent cortex much more reliably. We also can use faster gradients and pulse sequences than we can at 1.5T. In addition, the higher SNR provides greater sensitivity for DTI, enabling acquisition of as many diffusion directions as we want to improve our anisotropy measurements and fiber tracking. In addition to combining fmri and DTI data for the one to two pre-operative mapping cases that the center performs weekly, clinicians also use DTI routinely to help them diagnose Lou Gehrig s disease (ALS). Fletcher Allen research studies that are profiting from the power of Achieva 3.0T include fmri studies of language lateralization and hemispheric dominance, and working memory in post-menopausal women. Outstanding abdominal and musculoskeletal imaging Soon after Fletcher Allen s 3.0T unit became operational, radiologists discovered the system also provided exceptional abdominal and orthopedic imaging. It quickly became obvious that breathhold and fat-suppressed abdominal and pelvic studies are exquisite at 3.0T far better than those acquired on our 1.5T system, even over large fields-of-view, Dr. Braff observes. We do nearly all of our MRCPs and abdominal and pelvic exams preferentially on Achieva 3.0T. The higher SNR enables us to use very short breath-holds, which freezes peristaltic and respiratory motion. The 3.0T abdominal images are just spectacular. In musculoskeletal imaging, cartilage imaging in particular has benefited, Dr. Filippi adds. Orthopedic department researchers are using volumetric analysis of cartilage to document cartilage loss, he says. This segmentation ability is available only on the Achieva 3.0T scanner. The emerging 3.0T cardiac study Clearly, increased SNR helps any study, Issue 29 - July 2006 Field Strength 13

4 Pediatric imaging T2-weighted TSE TSE A 2-month-old following prolonged cardiac arrest. In the left image, hypointense signal abnormality is noted in caudate, basal ganglia and thalami, in addition to posterior limb of internal capsule. These areas are abnormally hyperintense on the image. The diagnosis was hypoxic ischemic encephalopathy. T2-weighted TSE Post contrast DWI 5-year-old female presented with chronic right hip pain. Initial x-rays showed faint sclerosis of the iliac crest.the image shows complete marrow replacement of iliac crest with large soft tissue mass. In the coronal image, diffuse abnormal marrow signal and large soft tissue mass and areas of spiculated hypointensity perpendicular to cortex, which suggests sunbursttype periosteal new bone formation. The third image shows marked periosteal new bone formation. The axial image demonstrates the large soft tissue mass and invasion into the gluteal musculature. Diagnosis after biopsy of mass was osteosarcoma. GRASE 12-year-old patient presented with a hard lump on the frontal bone. In the T2-weighted image, hyperintense lesion within diploic compartment of frontal bone is visualized. In the image, the lesion is isointense with respect to marrow. In the postcontrast image, mild enhancement is noted. The lesion is markedly hyperintense on the diffusion-weighted image, which is consistent with an epidermoid. Note excellent lesion conspicuity despite its location. 13-year-old with new onset of seizure. A cortical/subcortical susceptibility lesion is seen on the GRASE image. The image shows multifocal areas of hyperintense signal abnormality in the subcortical white matter. 14 Field Strength Issue 29 - July 2006

5 SPAIR SPAIR An example of non-tropical chyluria. Note the dilated lymphatic channels nicely delineated on these fatsuppressed, long TR images. but the challenge in 3.0T cardiac imaging is to compensate for the increased susceptibility, which has hampered 3.0T s ability to surpass 1.5T in cardiac imaging. Some of the work I ve seen at European and U.S.-based Philips sites, however, indicates a relatively short time 18 months perhaps before 3.0T equals or surpasses 1.5T for a full cardiac exam, Dr. Braff maintains. We need to use adiabatic pulse sequences and optimize them to address susceptibility when imaging the heart, which is composed of both fat and muscle, is constantly moving, and has blood continuously flowing through it. None of these challenges is trivial, but we are doing far better cardiac imaging now than we were even six months ago. Dr. Braff predicts that dynamic Philips techniques such as k-t BLAST or, alternatively, multi-channel cardiac coils which will realize their full potential with Achieva system s multi-channel FreeWave RF architecture are two possible avenues to the routine 3.0T cardiac examination. SmartExam streamlines Achieva 3.0T workflow for brain scans Fletcher Allen is the first clinical USA site to use SmartExam, which includes Philipsexclusive technology to enable a completely automatic examination of the head. With SmartExam, all head studies can be performed with reproducible scan quality with any patient position, any operator, any day. SmartExam adapts its planning according to the way an operator plans studies. Additionally, SmartExam seamlessly integrates with an imaging center s ExamCards, facilitating automatic planning, scanning and processing of complete patient studies with a single mouse-click. SmartExam can increase operational efficiency by as much as 30%. "With five minutes of instruction, SmartExam allows a person with limited training to position a patient and obtain a brain exam that is completely reproducible when the patient returns for follow-up examinations, Dr. Braff observes. And SmartExam enables consistent imaging between different patients having the same type of MR study. An example of SmartExam inter-patient consistency at Fletcher Allen would be pituitary studies, MR technologist Gretchen White says. The coverage will be precisely the same between different patients, regardless of which technologist is implementing the study, she notes. SmartExam also is very easy to use and it frees up more of the technologist s time to perform postprocessing. A 3.0T scanner may be a very complex system, but Philips philosophy is that just because a technology increases in complexity doesn t mean the user interface has to, Dr. Braff adds. The winner in the battle for 3.0T supremacy will be the company that makes 3.0T scanning the easiest, and Philips seems to be leading in this category with SmartExam and ExamCards. We re using SmartExam for brain studies presently and will for spines in the near future. Imagine a year or 18 months from now when the whole body is mapped out in such a way that, by using SmartExam, you can simply position the patient and the machine does most of the work for you. It will be an incredible step forward. "SmartExam enables consistent imaging between different patients having the same type of MR study." Net Forum Visit the MRI NetForum Community to view or download Achieva 3.0T ExamCards contributed by Fletcher Allen Health Care. Issue 29 - July 2006 Field Strength 15