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3T_Tim_2006 MRI Hot Topics Enabling Clinical 3T—MAGNETOM Trio Powered by Tim s medical !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 2 Enabling Clinical 3T—MAGNETOM Trio Powered by Tim Milind D. Dhamankar, MD; Christopher Boyea, MBA, RT (R)(MR); Abraham P...

3T_Tim_2006
MRI Hot Topics Enabling Clinical 3T—MAGNETOM Trio Powered by Tim s medical !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 2 Enabling Clinical 3T—MAGNETOM Trio Powered by Tim Milind D. Dhamankar, MD; Christopher Boyea, MBA, RT (R)(MR); Abraham Padua, RT (R)(MR); Siemens Medical Solutions USA, Inc. Introduction “Tim proves it” is a message from Siemens and Siemens users alike, as Tim systems have been shipping since 2003. However, 2005 saw Tim capabilities first introduced to Ultra High Field at ISMRM in Miami. The value provided at 3T has created a significant amount of awareness within the world of Ultra High Field users as well as clinical users currently operating high field equipment. Consistently the question is asked, “is 3T ready for prime time?” Extended Coverage—Realized Clinical Benefit Tim allows flexible coil combinations and extended FoV imaging; after all, pathology doesn’t always end at the edges of a coil. The elimination of the need to reposition patients or coils allows greater flexibility for extended coverage or multiple studies, providing immeasurable benefits when imaging critically ill patients. With the ability to leave the Spine Matrix coil on the table at all times, Tim enables improved patient workflow, efficiently enhancing patient care. The following case is just one illustration of the impact that extended coverage without patient and coil repositioning has on the daily clinical routine and results in improvement of care. A 37-year-old male with medulloblastoma presents for MR follow-up post-surgical treatment (see Figure 1). To provide excellent quality of care it is important to know the exact level and extent of spread of metastatic disease for post-operative radiation therapy. In order to look for skip metastases, a brain and whole spine examination was performed in 20 minutes. This extended exam was performed in this short duration because of a combination of capabilities made possible by Tim technology including the employment of GRAPPA (made possible by Matrix coils) and the elimination of the need to repositioning the patient or coils. The examination showed a fourth ventricular mass with high vertex metastases (normally missed by CT due to partial volume effect if not careful), enhancement in the brain and several leptomeningeal metastases down at the T12-L1 levels. Spine composing software stitches the anatomy seamlessly for referring clinicians to better understand the clinical picture and plan therapy. It is also particularly helpful for the neuroradiologist to ensure each level is completely covered, to verify each of the levels carefully on a composed whole spine image and to confirm the level of the pathology. Essentials to delivering this quality examination in the short duration include large homogenous FoVs, use of GRAPPA, and reduced patient set up and transition between anatomical coverage. 3T + GRAPPA Allows Orthopedic Imaging to Excel MAGNETOM Trio with Tim is the first 3T system to support parallel imaging for the spine, wrist, and peripheral angiography. The flexibility of Tim technology allows the implementation of parallel imaging in almost any clinical application. This flexibility directly translates to faster scans, increased patient throughput and/or higher resolution, better image quality, improved patient comfort due to shorter acquisition times, 3D isotropic acquisitions acquired in just a few minutes, and much more. 1 Figure 1: Courtesy NYU Medical Center. !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 3 Notes Figure 22: This 3D VIBE example was acquired post contrast 36 slices in 19:52 seconds with a PAT factor of 2, and FoV 350mm and 5mm effective thickness. Courtesy Siker Medical Imaging, USA. Figure 21: Large FoV RF-Fat saturation VIBE breathhold acquired with Body Matrix coils. Courtesy UCLA. 8 !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 4 aggressive resolution acquisition, with a 1.7mm slice and a 14cm FoV, where 18cm may by typical on other scanners and field strengths. The selection of the 3D SPACE sequence, a variable flip angle 3D Turbo Spin Echo, permits isotropic acquisitions in T1, T2, or proton density weighting. This proton density with fat-saturation was acquired with isotropic resolution and employed an iPAT factor of 2. The red and green lines on the images in Figure 5, through the femoral neck, provide the axis for surgical evaluation. In this clinical case the surgical evaluation through radial MPR provided depiction of a labral tear that otherwise may have been difficult to visualize. SWI—Susceptibility Weighted Imaging SWI, a technique unique to Siemens, reveals blood products and venous structures with greater clarity than methods currently available, thanks to superior sensitivity to deoxyhemoglobin and other blood products. The SWI example shown in Figure 6 demonstrates the advantage of this new capability compared to conventional T2* imaging methods. A 52-year-old male trauma patient was imaged with the conventional T2* image on the right and the SWI method on the left. Improved visualization of the hemorrhagic condition resulted from the SWI acquisition. BLADE Motion correction is an important implementation across field strengths, and the robustness of the motion corrections available on Siemens products are beyond any other systems available today. With 1D PACE, 2D PACE, 3D PACE and 3D ART (both for fMRI), and now BLADE, clinical studies can be achieved with the most difficult patients. The implementation of BLADE allows for correction in any of the acquired orientations. The scenario illustrated in Figure 7 is of a 34-year-old, post-operative patient, presented to MR from ICU for tumor evaluation. This case presented a challenge for routine T2 imaging as demonstrated in the image on the left. The implementation of BLADE, with an acquisition time of less than 3 minutes, provided a motion-free 26 slice, T2 FSE, acquired in the sagittal plane. The value of this method is clearly demonstrated in this example. Optimizing T1 Contrast at 3T Throughout years of optimization, T1 Dark Fluid has been found to have significant advantages in the suppression of CSF for spinal applications. At higher field strengths the T1 Dark Fluid over T1 Spin Echo and Turbo Spin Echo methods have demonstrated improvement in visualization of the cord, and in post-contrast studies improved visualization of metastatic disease and other subtle enhancements (see Figure 8). The comparison image of a 2-year-old pediatric spine demonstrates the differences in contrast of T1 Spin Echo and T1 Dark Fluid at 3.0T (see Figure 9). This example demonstrates the conus and the cauda equina, neither of Figure 6: An example of Susceptibility Weighted Imaging. Courtesy Duke University. Figure 7: An example of the implementation of BLADE. Courtesy Duke University. Figure 8: Optimizing T1 Contrast at 3T. The 4mm thick T1 Dark Fluid image acquired at a 512 matrix, interpolated to 1024. Courtesy Duke University. 3 !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 5 Optimizing Parameters for IAC Imaging The selection of a 3D TSE sequence with a Restore pulse minimizes pulsatility artifacts, and provides the desired heavy T2 weighting for visualization of intracranial nerves. The 12-channel Head Matrix coil coupled with the signal provided by the field strength of 3T permitted a 0.8mm slice thickness, with an acquired 14cm FoV (see Figure 13). An iPAT factor of 2 was used on the 3D TSE sequence enabling nearly 40mm of coverage in less than 5 minutes. Matrix Spectroscopy Another innovative Siemens technology currently not available on other systems is Matrix Spectroscopy. The SNR of 3T coupled with Matrix Spectroscopy (using a 12-channel Head Matrix coil), provides improved spectral quality with respect to SNR and resolution compared to other methods. Figure 14 shows a 16 x 16 matrix that was acquired using a weighted acquisition method; an automated combination of weighted and phase-corrected signals from the twelve individual coil elements provides a significantly reduced acquisition time of 7:34 minutes (see Figures 14–15). MAGNETOM Trio with Tim With the introduction of Tim technology on the MAGNETOM Trio, there are now up to 102 seamlessly integrated Matrix coil elements and up to 32 RF channels. Flexible combination of the ultra light weight Tim Matrix coil elements encourages creativity in building an anatomically- and patient-customized coil. This reduces the need for a large number of dedicated coils and at the same time covers different applications. Clinical Challenge: Brachial Plexus Imaging In this case, acquired at NYU Medical Center, a surface coil for Brachial Plexus imaging was created by utilizing the Neck Matrix, Spine Matrix, and a Body Matrix coil (see Figure 16). The signal delivered as a result of this creative coil combination provided a resolution opportunity that was maximized through a 512 squared matrix, interpolated to 1024, 2mm thickness, and a FoV of 20cm. Sequence duration was 3 minutes for this coronal T2 FSE. Figure 14: A 16 x 16 matrix acquired using a weighted acquisition method. Courtesy University of Tubingen. Figure 15: The Cho/Cr-map shows the active tumor region of this left temporal Glioblastoma. Courtesy University of Tubingen. Figure 13: Optimizing Parameters for IAC Imaging. Courtesy Duke University. 5 !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 6 Figure 16: Combining the Neck, Spine, and Body Matrix coil provides opportunity for optimal Brachial Plexus imaging. Courtesy NYU Medical Center. Figure 17: Off-center fatsat shoulder—2D TSE fatsat with PAT 2, 3mm slices, 140mm FoV, TA 2:15 minutes, Shoulder coil. Courtesy Siker Medical Imaging, USA. Magnet One of the essential ingredients to building a system that meets both research and clinical needs at 3T is homogeneity. The Siemens 3T magnet offers 1 ppm VRMS at 50cm DSV which is 3 times better then any other product offering. A three-fold improvement in homogeneity directly impacts the quality of spectroscopy, fMRI, EPI and chemical-shift fat suppression. MAGNETOM Trio with Tim is the only system that offers 50cm FoV in one acquisition, essential for coronal and sagittal spine imaging, MR colonography and head-to-neck four vessel ce-MRA just to name a few. The offset FoV RF fatsat coronal in Figure 17 implemented GRAPPA, with an acceleration of 2, resulted in an acquisition time of just greater than two minutes. Gradients Gradients are commonly referenced as the horse power of the MR system. As a leader in the design of gradient coils and amplifiers, Siemens designed the TQ-engine (45mT/m @ 200mT/m/ms per axis at full 50 x 50 x 50cm FoV), providing state-of-the art gradient power, unsurpassed linearity and the least possible eddy currents. All of this technology does not lose sight of practicality; there is still the advantage of being able to utilize the full slew rate across any FoV and through Siemens unique technology delivering Audio Comfort with a 90% reduction in acoustic noise, without performance trade-off, compared to conventional 3T systems. High-grade Stenosis in the Right Carotid Artery Right After the Bifurcation Implementation of GRAPPA with iPAT 4 enables an acquired 576 matrix, resulting in a 0.7mm isotropic voxel in only 20 seconds (see Figure 19). These acquisition parameters enable the ability to magnify to the carotid bifurcation and the circle of willis for further evaluation without the loss of detail. This provides an excellent stroke evaluation protocol all in one sequence (see Figure 18). Figure 18: Head and Neck Matrix coil combination providing extended coverage for this iPAT factor 4 carotid study demonstrating high grade stenosis. Courtesy UCLA. 6 !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 7 which are visualized clearly on the TSE T1 Spin Echo. The SNR of the 24-element Spine Matrix coil allowed resolution optimization of a 3mm thick slice at a 20cm FoV. Siemens is the only vendor that provides a dedicated coil for cervical spine imaging. The Neck Matrix coil eliminates the need for users to make the tradeoff of coverage for optimized signal. By employing the 3D VIBE sequence with the Neck Matrix coil, the full signal potential of 3T can be harnessed enabling the pursuit of higher resolution than what is achievable at lower field strengths. This axial 3D T1 VIBE was acquired at 2.0mm and a 13 FoV (see Figure 10). The 256 acquired matrix, resulting in a submillimeter pixel resolution of 0.6mm, was further improved in visual resolution by employing a reconstruction matrix of 512. The nerve roots coming off of the cord provide visualization through the foramina and improve the conspicuity for potential visualization of MS lesions within the spinal cord. Optimization of T1 contrast at 3T includes employment of 2D FLASH-based sequences as a result of the ability to achieve shorter TE’s and TR’s. Compared to Spin Echo methods that at 1.5T may have employed flow compensation and pushed TE’s slightly higher, trading off flow compensation for the Figure 9: Optimizing T1 Contrast at 3T. Comparison image of a 2-year-old pediatric spine. Courtesy Duke University. Figure 11: Post contrast T1 weighted 2D FLASH. Acquired in 2:39 minutes. Courtesy Duke University. Figure 10: Optimizing T1 Contrast at 3T. Axial 3D T1 VIBE. Courtesy Scott and White Hospital. shorter TE’s offered by FLASH have been found to significantly minimize pulsatility artifacts while the reduced flip angle and short TR provide improved grey white matter delineation. In the 2D FLASH sequence shown in Figure 11, a TE of 2.6ms and TR of 380 provide the desired contrast, while the signal of 3T afforded a 3mm slice thickness, acquired in 2:39 minutes. Figure 12: Large FoV, with a 1024 reconstruction matrix with Dark Fluid for cord visualization. Courtesy NYU Medical Center. 4 !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 8 Figure 19: iPAT factor of 4 for this 112 slice 576 matrix and submillimeter slice thickness was acquired in 20 seconds. Courtesy UCLA. Faster rise times are used to reduce echo times and shorten inter-echo spacing to decrease the dephasing associated with susceptibility-induced field variations. Higher gradient strengths allow thinner slices that help improve diagnostic capability due to higher resolution. When high gradient strength is coupled with Parallel Acquisition Techniques (PAT), extreme speed for shorter breathhold exams or higher resolution in the same acquisition time becomes possible. Increased coverage via more slices in both 2D and 3D imaging with reduced acquisition times improve the diagnostic confidence of breathhold imaging methods as a result of increased patient acceptance. The excellent linearity for a 50cm FoV (1.7% VRMS) enables powerful advanced applications like EPI, ce-MRA and cardiac to image with large FoVs. Conclusion For prospective MRI buyers, the MAGNETOM Trio with Tim makes a well-calculated choice, particularly if a 1.5T MRI is already present. Siemens takes pride in its leadership in MRI and continually delivers unsurpassed innovations. With increased performance by means of a greater application range, with higher throughput by means of increased procedure volumes and with better differentiation by means of satisfying increasing clinical demands in the tough competitive environment, the MAGNETOM Trio with Tim has moved 3T from research to clinical. The MAGNETOM Family heritage, including syngo MR, Inline technology, Phoenix and iPAT, contribute to the distinct advantages of the MAGNETOM Trio with Tim. Figure 20: High temporal resolution enabled by GRAPPA factor of 4. Courtesy UCLA. 7 !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 9 The Proton Density Turbo Spin Echo image shown in Figure 4, demonstrating an anterior miniscal tear, was acquired with a 1.7mm slice thickness and a 512 matrix in only 2:31 minutes as a result of the implementation of GRAPPA. Body Matrix Coils and iPAT Deliver Improved Isotropic Imaging The Body Matrix coil may be used for a number of examinations beyond routine cardiac and body applications. The coil may be combined with the Spine Matrix and Neck Matrix coil for improved upper torso and contrast enhanced imaging, or wrapped around an anatomy in the case of a unilateral hip. Resolution and acquisition time can be optimized further with the employment of GRAPPA, which by the nature of the method does not require opposed coil elements, as is the case for image-based parallel imaging. In this example of unilateral hip imaging, a 6-element Body Matrix coil was wrapped around the patient’s anatomy (see Figure 5). The signal of 3T permitted an By offering both image-based (mSENSE) and raw data-based (GRAPPA) parallel imaging methods, users are able to employ the benefits offered by parallel imaging in a greater number of clinical situations. The Siemens exclusive GRAPPA is found beneficial in small FoV imaging. The orthopedic imaging example in Figure 2 demonstrates the everyday value acceleration capabilities can deliver in routine clinical imaging. GRAPPA allows parallel imaging to be employed in smaller anatomies without the artifacts associated with SENSE-based techniques. Both images were acquired with identical resolution parameters including a 6cm FoV, 2mm slice thickness, and a 320 matrix (interpolated to 640). The resultant resolution based on acquisition resolution is 2 microns. Acquisition time of the left image was 7:07 minutes; however, employing GRAPPA with an acceleration factor of 3 resulted in greater than a 50% reduction in scan time at 2:57 minutes. 2 Figure 5: Isotropic unilateral hip imaging with iPAT factor of 2. Courtesy Duke University. Figure 2: 6cm FoV wrist, at 2 micron resolution, left image 7:07 minutes, with GRAPPA right image 2:57 minutes. Courtesy NYU Medical Center. Figure 3: 5cm FoV finger acquired with a 1mm slice thickness, demonstrating the signal benefits of 3T. Courtesy 3T Imaging of Morton Grove. Figure 4: GRAPPA enabled 51 slices in 2:31 minutes. Courtesy 3T Imaging of Morton Grove. !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 10 On account of certain regional limitations of sales rights and service availability, we cannot guarantee that all products included in this brochure are available through the Siemens sales organization worldwide. Availability and packaging may vary by country and is subject to change without prior notice. Some/All of the features and products described herein may not be available in the United States. The information in this document contains general technical descriptions of specifications and options as well as standard and optional features which do not always have to be present in individual cases. Siemens reserves the right to modify the design, packaging, specifications and options described herein without prior notice. Please contact your local Siemens sales representative for the most current information. Note: Any technical data contained in this document may vary within defined tolerances. Original images always lose a certain amount of detail when reproduced. Siemens Medical Solutions USA, Inc. Magnetic Resonance Division 51 Valley Stream Parkway Malvern, PA 19355-1406 USA Telephone: 1-888-826-9702 www.usa.siemens.com/medical © 2006 Siemens Medical Solutions Order No. A9119-6391-1C-4A00 Printed in USA Siemens Medical Solutions that help !152805_3T_HT_revised_final.qxd 1/23/06 11:37 AM Page 1
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