Quality Abdominal MRI with High Field Open

Size: px

Start display at page:

Download "Quality Abdominal MRI with High Field Open"

Lizbeth Fisher
5 years ago
Views:

1 WHITEPAPER Quality Abdominal MRI with High Field Open By Dr. Smita Sharma and Dr. Devaraju Kanmaniraja Authors Bios: Smita Sharma, M.D., specializes in abdominal and women s imaging. Dr. Sharma, an assistant professor in the Department of Radiology at the University of Florida Jacksonville, completed a fellowship in abdominal imaging at the University of Pittsburgh in Pittsburgh, PA, and is board certified in Diagnostic Radiology. Devaraju Kanmaniraja, M.D., was chief of the Division of Abdominal Imaging and assistant professor in the Department of Radiology at the University of Florida - Jacksonville. In early 2018, Dr. Kanmaniraja assumed a faculty position in radiology at the Montefiore Medical Center in Bronx, NY. He completed a fellowship in abdominal imaging at the Cleveland Clinic in Cleveland, OH and is board certified in Diagnostic Radiology.

2 Executive Summary Oasis produces demonstrably excellent results in the abdomen. We have been very happy with image quality. The Oasis 1.2T High-Field Open MRI delivers abdominal imaging quality comparable to that of 1.5T cylindrical systems; yet does so without imposing the feelings of anxiety associated with cylindrical systems. Consequently, scans using this high-field open (HFO) are better tolerated by patients, particularly those who are anxious, as well as those who have difficulty being scanned, namely the very young, very sick and elderly. Its open design allows MRI abdominal scans of patients who might not otherwise be able to tolerate or complete these examinations. We have been using the Oasis 1.2T open scanner since 2015, first only for outpatients referred from Jacksonville and the surrounding area, then from expanding services in the University of Florida (UF) medical complex where Oasis is sited. Recently our patient population has expanded to include inpatients from a UF hospital opened in a tower adjacent to where the scanner is located. We routinely use the Oasis to perform exams of the female pelvis, as well as MR cholangiopancreatography (MRCP). In MRCP, interactive visualization of the bile or pancreatic ducts is accomplished using 3D primefse acquisition by heavily weighting T2. 2D radial slice stack positioning can be used to achieve fast and repeatable slice planning. In enterography, breath-hold acquisitions using single-shot primefse or high-resolution fat separation studies can be used to visualize the small bowels. Visualization can also be achieved using free-breathing motility studies with cine playback. Congenital and uterine anomalies in the female pelvis are visualized with Oasis TIGRE, a fast gradient echo fat saturation scan. Also applied is RADAR, which minimizes motion artifacts. RADAR compensates for patient movement as well as more subtle motion resulting from respiration, for example, and the flow of cerebrospinal fluid or blood. Its use improves image quality and, consequently, reduces the need for rescans and patient call backs. RADAR is especially helpful for patients who have difficulty holding their breath, such as those who are elderly, very ill or pediatric. High-power gradients and a homogenous magnetic field routinely deliver high-quality MR images comparable to those of 1.5T scanners. We also use techniques that increase the efficiency of exams. Among them is a fat separation technique that allows us to obtain several different images in a single scan. Oasis produces demonstrably excellent results in the abdomen. We have been very happy with image quality. 2 Quality Abdominal MRI with High Field Open

The Need for Abdominal MRI We routinely use MRI of the abdomen to find and evaluate abdominal issues, including problems that underlie abdominal pain or swelling as well as cause abnormal blood

Figure 1: High resolution MR angiography. MRI may be used as a follow-up when blood work, radiography, ultrasound or CT scans have uncovered abnormal results.

3 The Need for Abdominal MRI We routinely use MRI of the abdomen to find and evaluate abdominal issues, including problems that underlie abdominal pain or swelling as well as cause abnormal blood tests, for example affecting liver or kidney function. The modality may be used to assess lymph nodes in the abdomen in addition to masses in the liver, kidneys, adrenals, pancreas or spleen. Figure 1: High resolution MR angiography. MRI may be used as a follow-up when blood work, radiography, ultrasound or CT scans have uncovered abnormal results. MRI can help us identify abnormal changes in the structures of organs or other tissues. It can also help us distinguish malignant and benign tumors from normal tissues. Details about the size and spread of malignant tumors provide information we use to determine the stage of the cancer. We routinely use MRI to check the lower abdominal and pelvic organs for tumors, bleeding and congenital abnormalities. Scans may indicate, for example, blockages in the bile duct through which bile is carried from the liver to the gallbladder. Figure 2: Fast 3D Dynamic TIGRE breath-hold. MRI is also performed in the abdomen to uncover vascular problems, as well as check organs and vasculature prior to organ transplant or surgery. MR angiography avoids risk associated with radiation exposure encountered in CT and allergic reactions to iodinated contrast media. 3

4 The Value of Oasis...providing a patient friendly open atmosphere, along with routinely producing high quality images of the abdomen. Many published studies of abdominal MRI have documented the value of high-field cylindrical MRI scanners. These systems, however, can intimidate patients, particularly if they are fearful of tight spaces. Cylindrical scanners may also be impossibly small for large patients. We have demonstrated in our practice, however, that an open MRI scanner can markedly reduce or eliminate these issues by providing a patient friendly open atmosphere, along with routinely producing high quality images of the abdomen. The University of Florida in Jacksonville has been using the 1.2T Oasis (Figure 3) to scan the abdomen and female pelvis since Many of these scans have been for diagnosis, but we also regularly field requests from referring physicians for follow-up scans, as well as scans to assess or adjust therapies. Figure 3: High-Field Open 1.2T Oasis Scanner For example, we have demonstrated the utility of Oasis abdominal scanning with patients undergoing locoregional therapy for HCC (hepatocellular carcinoma). In such cases, treatment response is better evaluated with MRI than CT. The reason is that these lesions are very small, often less than a centimeter in diameter. 4 Quality Abdominal MRI with High Field Open

5 The HFO has greater lesion sensitivity than multidetector CT. Also chronic liver disease, which is often present in these patients, makes lesions easier to detect with MRI than CT. Efficiency. Oasis scans are as fast as those performed with 1.5T systems. On average we scan 13 patients per day with the Oasis. On our busiest days, we have scanned 17. The HFO was first sited as an outpatient scanner in a state-of-theart medical complex at our UF North location. With the opening in June 2017 of a 92-bed hospital in a separate tower of UF North, Oasis has become the go-to MRI scanner for hospital inpatients, as well. The HFO was first sited in 2015 at our UF North location to handle outpatients. Demand for Oasis scans expanded with the establishment of emergency services, outpatient surgery and ancillary services, which have been added in recent years to the UF North medical complex. This expansion continued when, in June 2017, we began scanning inpatients from a 92-bed hospital established in UF North. Speed. We believe that patients demand fast exams. MRI exams must be quick, accurate and consistent. Hospital inpatients and patients from the emergency department are typically scanned during the day. When serving only outpatients, the MRI scanner operates until about 6pm; however, at times, we perform scans as late as 11 p.m. Patients are typically scheduled during 45-minute slots from 7:15 a.m. to 5:30 p.m. (This includes the scan and getting the patient onto and off the table.) We build flexibility into our schedule so we can meet the needs of patients. High throughput naturally translates into financial benefits through increased revenue. Oasis automation allows us to make the most of our time with each patient. We use automation to reduce setup time. The AutoPose feature automatically performs slice positioning to set up scans efficiently. Its use saves us at least two or three minutes per exam. These time savings can add up. 5

6 By automatically determining and locating slice acquisitions, AutoPose increases reproducibility and consistency. Consequently, it (Oasis) is used like a typical high-field system, scanning any and all patients. Two other tools available on Oasis boost workflow and improve accuracy. Built into the Oasis graphical user interface, these tools -- Intelligent Parameter Guidance and Real-time Image Quality Calculator -- help the technologist consider parameters affecting the quality of the scan. For example, a technologist might consider adjusting the TR to obtain more slices. Doing so, however, may affect image resolution, signal to noise ratio, contrast to noise and scan time. Oasis automatically considers the effects of scan parameters before the technologist starts the scan. If the chosen parameters are likely to affect scan quality, a pop-up window will appear with options indicating the trade-offs, in this case, between the number of slices and length of the TR. This allows quick resolution of any conflicts that may affect the selection of parameters. Open Design. The open design of the scanner has been essential when serving patients who have difficulty fitting into or completing conventional MRI scans. Large, claustrophobic or otherwise anxious inpatients are selectively assigned to Oasis. Similarly, outpatients who are anxious or large are selectively assigned for scanning with the Oasis. Flexibility. It is important to note, however, that we do not reserve the use of Oasis just for these challenging patients. Oasis is the only MRI scanner near the UF North Hospital. Consequently, it is used like a typical high-field system, scanning any and all patients. These include bariatric, elderly and infant patients, as well as routine cases. With Oasis, we consistently deliver high-quality, diagnostic MRI studies regardless of the patient type. Our use of the Oasis HFO does not require us to compromise on either throughput or image quality. 6 Quality Abdominal MRI with High Field Open

Delivering Clinical Quality Our experience with the Hitachi Oasis 1.2T HFO contradicts decades of early open MRI use. Early open systems typically operated at or below 0.

7 Delivering Clinical Quality Our experience with the Hitachi Oasis 1.2T HFO contradicts decades of early open MRI use. Early open systems typically operated at or below 0.3T and lacked the power to deliver highquality images. Our Oasis HFO consistently delivers image quality equivalent to that of cylindrical 1.5T scanners. High-resolution MR angiography of the abdomen is routinely accomplished with the Oasis. Oasis also routinely delivers highquality images in the most challenging patients. For example, we regularly use MR cholangiopancreatography (MRCP) to visualize biliary and pancreatic ducts. We have found MRCP with the Oasis to be a simple means for non-invasive hepatobiliary evaluations. In the case of a 32-year-old female who presented with a Müllerian duct anomaly and absent right kidney on ultrasound, MR images obtained from an Oasis scan confirmed the ultrasound findings of unicornuate uterus with absent rudimentary horn and a left pelvic kidney. Axial and sagittal RADAR T2 FSE images (Figure 4) show the unicornuate uterus (yellow arrow) along the right pelvic sidewall with absent rudimentary horn. The left pelvic kidney (green arrow) is also shown in the presacral region. Figure 4: Axial and sagittal views of the uterus taken at 1.2T on the Oasis high-field MR scanner. 7

In the case of a 61-year-old male patient, MRCP performed with Oasis characterized a cystic lesion in the pancreas. The lesion was initially identified on CT.

Axial TIGRE pre- and post-contrast images show non-enhancement of the cystic pancreatic lesion (green arrows) and the absence of septations or enhancing nodular components within it.

8 In the case of a 61-year-old male patient, MRCP performed with Oasis characterized a cystic lesion in the pancreas. The lesion was initially identified on CT. An MRCP radial sequence demonstrated (Figure 5) the cystic pancreatic lesion (green arrow) and communication to the normal caliber main pancreatic duct (yellow arrow). Axial TIGRE pre- and post-contrast images show non-enhancement of the cystic pancreatic lesion (green arrows) and the absence of septations or enhancing nodular components within it. This is compatible with branch duct type IPMN (Intraductal Papillary Mucinous Neoplasm). Figure 5: An MRCP radial sequence demonstrates a cystic pancreatic lesion and communication to the normal caliber main pancreatic duct. In a 45-year-old female with history of fibroids, we used Oasis to determine the underlying cause of uterine bleeding. The scan also helped characterize an indeterminate right adnexal mass seen on ultrasound. Sagittal, coronal and axial RADAR T2 FSE in the plane of the uterus demonstrated (Figure 6) a broad-based 4 cm hypointense submucosal fibroid (green arrows) protruding into the endometrial canal. Also seen was a lobulated hypointense lesion in the right adnexa with signal characteristics and enhancement compatible with a broad ligament fibroid (yellow arrows). Figure 6: Sagittal coronal and axial views of the uterus, visualized with Oasis, demonstrate a fibroid protruding into the endometrial canal. 8 Quality Abdominal MRI with High Field Open

9 Patients - Our Top Priority The Oasis HFO at UF-Jacksonville has proven effective at managing all patients. Providers often say that patient welfare is their top priority. Truly putting patients interests ahead of everything else requires that exams are not only diagnostic but safe and comfortable. Unquestionably, cylindrical MRI scanners deliver high-quality images, but their inherently closed design can cause patient anxiety and discomfort. The imaging community has long recognized the concerns that claustrophobics have about tight spaces. Only in recent years, however, has it been widely accepted that many patients who do not fit the criteria of clinical claustrophobia are still anxious about tight spaces. This anxiety can be very disturbing to the patient and can impact both the quality of the exam and the scheduling of an MRI scanner. Very ill patients, as well as elderly and very young patients, may have trouble tolerating the tight spaces in conventional scanners. Consequently, they are prone to moving, which can cause image artifacts. Bariatric, as well as large but not obese patients, pose a different challenge, as they may not easily or comfortably fit into the bore of a closed MRI scanner. Unfinished or interrupted exams can throw off schedules. Call backs impact patients directly. In a worst case scenario, the patient who needs an MRI does not return to get one. Therefore, if MRI scans can only be performed using cylindrical magnets, a range of negative consequences may result. In contrast, the Oasis HFO at UF-Jacksonville has proven effective at managing all patients. This includes some of the most challenging patients. Oasis technologists report that a lot of patients, who otherwise would have to be sedated to undergo MRI, do so without sedation in the HFO. This is important in 9

abdominal scanning because breath holds are necessary and, therefore, patients cannot be sedated. In Oasis scans, knowing their parents are nearby naturally reduces motion during the scan.

10 abdominal scanning because breath holds are necessary and, therefore, patients cannot be sedated. In Oasis scans, knowing their parents are nearby naturally reduces motion during the scan. One patient who had severe claustrophobia told our technologists that he never had an MRI exam without sedation. Yet, he was able to complete an Oasis abdominal study from which we obtained very good images. By turning his head to the side and looking at pictures on the wall, the patient was able to control his anxiety. Oasis also has proven useful when imaging infants and toddlers. One example stands out -- a 5-year-old trauma patient. During the scan, the mother laid to the side of the Oasis, reaching in regularly to comfort the child. We effortlessly completed the whole study without sedation and obtained motionless images, as seen in this sagittal cervical spine image. (Figure 7) Figure 7: Pediatric sagittal cervical spine The Oasis open MRI scanner allows eye contact between these youngsters and their parents. In Oasis scans, knowing their parents are nearby naturally reduces motion during the scan. This decreases the occurrence of motion-related artifacts in images and makes MRI exams more comfortable for patients and parents. 10 Quality Abdominal MRI with High Field Open

Delivering Quality and Comfort The vertical 1.2T magnetic field produces high signalto-noise. This allows the Oasis HFO to deliver abdominal images comparable in quality to those of 1.

11 Delivering Quality and Comfort The vertical 1.2T magnetic field produces high signalto-noise. This allows the Oasis HFO to deliver abdominal images comparable in quality to those of 1.5T cylindrical systems. The Oasis HFO offers safe and comfortable access for even large patients. (Figure 8) Its 82 cm-wide table supports up to 660 pounds. (We have scanned patients weighing nearly 600 pounds.) Figure 8: The Oasis HFO 82 cm-wide table supports up to 660 pounds. The vertical 1.2T magnetic field produces high signal-to-noise. This allows the Oasis HFO to deliver abdominal images comparable in quality to those of 1.5T cylindrical systems. Oasis multidirectional HOAST (Higher Order Active Shimming Technology) delivers consistent uniformity of the magnetic field after the patient enters the magnet. HOAST delivers large field-of-view fat suppression. With Oasis large field-of-view and HOAST, we can visualize the entire urinary tract in a single breath hold. 3D isofse (isotropic fast spin echo) acquires isotropic data in any plane while maintaining high resolution. After data acquisitions are performed, images can be reformatted in any plane. We use 3D isofse to produce high-field, quality images of the cervical spine, as well as to evaluate patients suspected of having perianal fistulas. Preoperative MRI to map these complex fistulous tracts can help in the appropriate management of patients and help minimize the recurrence of infection. 11

12 We use Oasis fat and water separation technique, known as FatSep, to optimize abdominal scan times. FatSep Imaging. We use Oasis fat and water separation technique, known as FatSep, to optimize abdominal scan times. These techniques can reduce scan times by as much as 40 percent. Sequences are based on the Dixon method of fat suppression, a chemical shift imaging method by which signals are selectively acquired from fat and water. The concept goes back to the mid-1980s. It was not practically applied, however, until 1998, when Hitachi released the Airis II. We routinely use in- and out-of-phase scans to image the kidney and other abdominal organs. For FatSep Dixon imaging, typically multi-echo gradient echo or fast spin echo sequences are leveraged. In these sequences, one echo is acquired when fat and water signals are in-phase; another is acquired when the signals are opposed. These signals can be subtracted or added to create images. The resulting images may show only fat, only water, or a mixture of the two. This mixture can vary depending on the level of fat suppression. Levels can be set by the user to light, medium or heavy fat suppression. In-Phase and Out-of-Phase Imaging. Multi-echo Gradient Echo allows us to obtain different images in a single scan. In abdominal imaging during a single short breath-hold, we typically reconstruct data into two image contrasts: one in-phase, the other out-ofphase. When fat is present, the out-of-phase image (Figure 9) is characterized by a dark border (India Ink artifact) between fatty and non-fatty tissues. Figure 9: When fat is present, the out-of-phase image is characterized by a dark border (India Ink artifact) between fatty and non-fatty tissues. 12 Quality Abdominal MRI with High Field Open

13 We have found that abdominal lesions exhibiting this drop in signal (as visualized with out-of-phase images) likely contain microscopic fat. Identifying microscopic fat in these sequences can help in the diagnosis of lesions such as hepatocellular adenomas and hepatocellular carcinoma. In-phase and out-of-phase images can be especially helpful in the diagnosis of abdominal lesions. Out-of-phase images may exhibit a dark border between fatty and non-fatty tissues in the abdomen. When we image angiomyolipomas, this border is very helpful in making the diagnosis. In- and out-of-phase images can be especially helpful when evaluating patients with clear cell (renal cell) carcinoma. Because this carcinoma contains intra-cytoplasmic fat, the out-of-phase images demonstrate a drop in signal. Therefore, when imaging a renal mass, this signal drop is very suggestive of a clear cell carcinoma. Also, in cases of suspected focal fatty infiltration of the liver, we can use in-phase and out-of-phase images to differentiate a liver mass from focal fat. This is often very difficult to do on CT. On the Oasis, however, a drop in signal seen in the out-of-phase images indicates focal fatty infiltration. When this happens, we can differentiate between liver metastases and other liver tumors. 13

We have found TIGRE particularly useful when visualizing the liver and kidneys. Reducing Motion Artifact. RADAR allows robust motion compensation.

We use RADAR routinely to suppress motion for spin echo and fast spin echo, inversion recovery, and gradient echo scanning.

This radial motion compensation technique allows us to use motion compensation routinely. It may be applied in a broad range of sequences.

14 We have found TIGRE particularly useful when visualizing the liver and kidneys. Reducing Motion Artifact. RADAR allows robust motion compensation. It eliminates artifacts due to patient movement as well as subtle motion, for example, due to breathing and the flow of cerebrospinal fluid or blood. We use RADAR routinely to suppress motion for spin echo and fast spin echo, inversion recovery, and gradient echo scanning. (Figure 10) Figure 10: RADAR is used routinely to suppress motion for spin echo and fast spin echo, inversion recovery, and gradient echo scanning. This radial motion compensation technique allows us to use motion compensation routinely. It may be applied in a broad range of sequences. Single Shot Fast Spin Echo (ssfse) and steady state gradient echo sequences that use BASG or TIGRE support quick data acquisition so breath holds are comfortable. Yet Oasis still produces high resolution images in a large field-of-view. TIGRE is used for fast dynamic T1-weighted contrast enhanced imaging. We have found TIGRE particularly useful when visualizing the liver and kidneys. We use it on all of our dynamic contrastenhanced imaging and fat saturation scans as demonstrated in these pre- (Figure 11 - left) and post-contrast (Figure 11 - right) TIGRE images of the liver. How Oasis Helps Us Meet Challenges Figure 11: Dynamic contrast-enhanced imaging and fat saturation scans as demonstrated in these pre- (left) and post-contrast (right) TIGRE images of the liver. 14 Quality Abdominal MRI with High Field Open

15 How Oasis Helps Us Meet Challenges Value-driven medicine is propelling radiology beyond diagnostic medicine into patient management. Increasingly we are being asked to assess patients throughout the care cycle. And we are being asked to do so with fewer resources. Falling reimbursements and rising patient expectations require that we make the best use of the resources we have. Flexibility is critically important. Oasis provides the scan quality we have needed to expand our services. Conclusion The future of medical practice depends on our ability to deliver value. Oasis helps us do that by consistently delivering high-quality images while maintaining an environment that is comfortable to the patient. We have found that high-field open MRI on the Oasis produces demonstrably excellent results in the abdomen. We are very happy with Oasis performance and the quality of its images. 15

16 Hitachi Healthcare Americas 1959 Summit Commerce Park Twinsburg, Ohio USA Tel: Fax: /1000/DM# Hitachi Healthcare Americas

Echelon Oval provides a robust suite of leading musculoskeletal imaging capabilities for detailed assessment of all anatomy for your most challenging

Echelon Oval provides a robust suite of leading musculoskeletal imaging capabilities for detailed assessment of all anatomy for your most challenging cases. Hitachi Medical Systems America, Inc. 1959 Summit