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Excellent breast imaging at FAHC with MultiTransmit and SmartExam

Best Practice
Herschorn, Sally, M.D. Burlington, Fletcher Allen Health Care USA

The high spatial resolution enabled by 3.0T is a clear benefit in breast imaging, but obtaining uniform fat saturation can be more challenging at this field strength. MultiTransmit and SmartExam Breast innovations in the new Achieva 3.0T TX are designed to neutralize inhomogeneities - resulting in higher image quality and consistent fat saturation - and make scan planning much easier and faster. Fletcher Allen's Dr. Sally Herschorn and her colleagues have been evaluating both solutions in an Achieva 3.0T X-series system and recently on their Achieva 3.0T TX.
 Sally Herschorn, MD Fletcher Allen Health Care is Vermont's academic medical center, based in Burlington.
Sally Herschorn, MD
Fletcher Allen Health Care is Vermont's academic medical center, based in Burlington.

Transfer to 3.0T made impact, but challenges remained

Fletcher Allen clinicians employ MRI mostly when examining high-risk patients and patients with a new diagnosis. MRI also is used in occasional problem-solving cases, such as evaluating for disease recurrence at a lumpectomy site and resolving one-view mammographic densities. Frontline diagnostic modalities include digital mammography and ultrasound - 30,000 studies per year and 4,000 studies per year, respectively.

Fletcher Allen shifted its breast studies from an old 1.5T system to the Achieva 3.0T in October 2005, enabling clinicians to obtain bilateral axial images with much higher SNR and resolution. Dr. Herschorn and her colleagues have been using an advanced ExamCard consisting of a T1-weighted non-fat saturated sequence, a T2-weighted sequence with SPAIR fat saturation, followed by a dynamic fat saturated THRIVE series. A high resolution THRIVE is positioned between the second and third dynamic series.

In the beginning, results were inconsistent, Dr. Herschorn observes. "In some patients, we obtained excellent images, while in others there was poor or inhomogeneous fat saturation and every degree in between."

This variability was due to a wide range of patient factors, and to a lesser extent, technologist skill and experience, Dr. Herschorn notes. At 3.0T, inhomogeneities of the main magnetic field (B0) are likely to occur in patients with large breasts, asymmetric breasts, extensive breast folding and those who have had prior surgery and have one or two implants. If these inhomogeneities are not compensated for - either by manual or automatic shimming or by repositioning the patient - the result will be poor fat suppression and image quality.

Manual placement of shim boxes can be fairly tricky and time-consuming, though, she says. Patients undergoing MRI are anxious about a new cancer or about their risk for cancer to begin with. It is critical for technologists to be confident that the sequences they program will work right the first time. Technologist frustration and insecurity are easily transmitted to patients, making them more anxious. Therefore, it is vital that technologists work quickly and expertly.

SmartExam Breast improves workflow and image quality

"Workflow without SmartExam Breast was not ideal," Dr. Herschorn observes. "It was time-consuming to plan the volume shim box and check the offset frequencies needed. This required trial-and-error. Often manual central frequency determination was also needed to improve fat suppression quality. And even after these steps, outcomes were inconsistent. SmartExam Breast completely eliminates this problem and has made achieving acceptable fat saturation a non-issue."

SmartExam Breast is the newest SmartExam application. It provides intelligent assistance in planning, scanning and processing. It automatically detects the breasts and chest wall to efficiently plan the scan. Perhaps more importantly, it automatically optimizes localized shimming. The automatic image-based higher order shim results in better image quality and better fat suppression. With SmartExam Breast, workflow is tremendously simplified. And the result is excellent, reproducible image quality.

According to Supervisor of MRI, Gretchen White, one of every two 3.0T breast MRI examinations present shimming challenges. "There are so few women whose breasts are exactly alike," White observes. "Even a little asymmetry can cause problems, particularly in achieving good fat saturation at 3.0T, so manual shimming was a monumental task. With SmartExam Breast, it was as if someone had sprinkled magic dust on our magnet. Shimming was automated and homogeneity was optimized for every patient. SmartExam Breast is absolutely wonderful."

"SmartExam Breast has made technologists feel confident that they can get a good image on the first try. Patients can easily sense stress or confidence in their technologist and feel more comfortable in their exam when the technologist is confident. This leads to less patient motion and better quality exams - not to mention happier patients and in turn, happier referring physicians," says Dr. Herschorn.

In 2008, Dr. Herschorn's team used SmartExam Breast in 3.0T breast MRI exams on nearly 400 patients (1-2 patients per day). Previously, in difficult cases, the manual shimming step would add an average of 15 minutes or more to each breast MRI examination, which takes 30 minutes under optimal conditions. In especially difficult cases, as the length of time it took to obtain decent fat saturation increased, technologist and patient anxiety increased. The longer it took, the worse fat saturation would get. Often, these cases resulted in images of unacceptable quality. "SmartExam Breast has eliminated delays in implementing fat saturation, resulting in better workflow and increased patient comfort," Dr. Herschorn says.

 Standard THRIVE MultiTransmit and SmartExam
Standard THRIVE
MultiTransmit and SmartExam

47-year-old patient. Fat suppression with SmartExam Breast image-based shimming and MultiTransmit is significantly better than in standard THRIVE (arrows).

Patient-adaptive MultiTransmit achieves consistent image uniformity at 3.0T

The dielectric effect causes RF field (B1) non-uniformity and is exacerbated at 3.0T due to a larger RF wavelength at this field strength. The result is non-uniform signal - or shading - in the image, which can obscure anatomy and pathology. MultiTransmit solves this problem by adding an extra RF transmit source to provide simultaneous parallel RF transmission. The dielectric effect and shading are nullified, resulting in enhanced signal uniformity and consistency.

Dr. Herschorn and FAHC-based Philips clinical scientist Trevor Andrews, PhD, have used MultiTransmit on about 20 women so far. They currently are beginning a project to assess the impact of both MultiTransmit and SmartExam Breast on image quality.

"We are seeing a significant uniformity improvement in the nonfat saturated images," she reports. "Not all patients present these shading issues, but for the ones who do, the signal uniformity is enhanced through MultiTransmit. Fat saturation also is more uniform, which enables improved visualization of the axilla. This is particularly important in patients with cancer."

Dr. Herschorn says with 3.0T imaging, there often is a right breast/left breast shading difference. "However," she continues, "MultiTransmit will automatically adapt the RF signal to each patient's unique anatomy. The result in every case so far has been neutralized shading. This is where the true benefit of MultiTransmit lies: it helps us achieve a high level of image quality and image uniformity in all of our patients, which in turn makes image interpretation easier."

T1W TSE MultiTransmit and SmartExam
Standard T1W TSE
MultiTransmit and SmartExam
 THRIVE MultiTransmit and SmartExam
MultiTransmit and SmartExam

42-year-old high-risk patient. Signal inhomogeneities are noted in standard T1W TSE (red arrows). Using MultiTransmit the image is significantly more uniform. While fat suppression is inhomogeneous in standard THRIVE (arrows), it is excellent with MultiTransmit and SmartExam Breast.

 Standard MultiTransmit and SmartExam
MultiTransmit and SmartExam

50-year-old patient with DCIS and family history of breast cancer. The standard THRIVE images shows non-uniform fat suppression (yellow arrows) and parenchymal tissue signal is inhomogeneous comparing right to left breast (red arrows). In the THRIVE image with MultiTransmit and SmartExam Breast, fat suppression is uniform throughout the entire field of view.

Achieva 3.0T TX: premium breast imaging system

With its high spatial resolution enabled by the 3.0T field strength and its powerful tools for enhanced workflow and consistently optimized image uniformity, Achieva 3.0T TX with the Elite Breast Clinical Solution seems destined to become the option of choice for breast MRI imaging.

"We have only just started breast imaging on Achieva 3.0T TX," Dr. Herschorn says. "But the nice thing is that SmartExam Breast solves B0 inhomogeneities and MultiTransmit solves RF shading, so you're able to address both issues, enabling us to fully leverage the benefits of 3.0T breast imaging."

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Jun 17, 2010

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Best Practice
Achieva 3.0T, Achieva 3.0T TX, Achieva 3.0T X-series
Release 2.5, Release 2.6, Release 3.2
Quasar, Quasar Dual
Body, Breast, MultiTransmit, SmartExam, Women's health

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