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by Cat Vasko
· Surprise Negative Oral Contrast Agent: Blueberry Juice
· Siemens Demonstrates Prototype MRI-PET System
· MRE Allows Physicians to Diagnose Liver Disease Noninvasively
Surprise Negative Oral Contrast Agent: Blueberry Juice
MR cholangiopancreatography (MRCP) imaging is constantly challenged by gastric secretions in the stomach and duodenum, which create high fluid signals that can obscure the bile ducts behind them. Research going back more than a decade has shown that this high signal can be eliminated by certain manganese-rich drinkable liquids, however, including blueberry juice, pine-apple juice, Kaopectate, and green tea.
As a 1995 study in Radiology noted, “T1 and T2 relaxation curves for blueberry juice and manganese chloride showed similar signal intensity profiles as a function of manganese concentration. … At appropriate concentrations, blueberry juice has the potential to be an effective oral contrast agent for MR imaging.”
Wayne Patola, MRI technologist and supervisor at St. Paul’s Hospital, Vancouver, British Columbia, turned this potential into reality after he happened to notice a poster at a conference about the use of blueberry juice in MRCP. He had already heard of using Kaopectate the same way: “I was at a center in Windsor and had seen them use Kaopectate,” he recalled. “They had very good results with it, but I watched the patients drink it, and they certainly didn’t seem to enjoy it very much.”
The problem of high signals from gastric fluid cannot necessarily be solved by the traditional method of instructing the patient not to eat or drink for a few hours before the exam, Patola explained. “That’s supposed to reduce the amount of fluid in the bowel, but unfortunately, we still see fluid because of normal gastric secretions over that 3- or 4-hour period. It’s hit and miss.” When signals from gastric secretions interfere with imaging of the bile duct, time and money are lost?sometimes patients even return to be imaged again, “hopefully in a condition where they have less fluid in their bowel, or you have to resort to using a negative contrast material,” Patola noted.
So Patola returned to St. Paul’s determined to try the technique with a much tastier alternative?blueberry juice. “It worked very well,” he said. “We’ve been doing it for around 6 months. The manganese causes an alteration in the magnetic field nearby, like when you stick a piece of iron in a magnetic field and all the field lines move toward it. By causing that alteration, we then change the signal intensity we receive from any fluid that’s in the direct vicinity of those manganese molecules, and that allows us to remove the brightness of the fluid from the stomach and duodenum.”
A 2004 study in The British Journal of Radiology found that pineapple juice?which is more commercially available overseas than blueberry juice?achieves similar results. “Pineapple juice has been proposed as an alternative naturally occurring manganese containing agent that has desirable effects as an oral contrast agent for abdominal MR imaging in patients with inflammatory bowel disease,” the study said. “Our study demonstrates that PJ may be used as a negative oral contrast agent that significantly improves the quality of MRCP imaging. Visualization of the pancreatic duct, in whole and part, is significantly improved following PJ if imaged at 15 minutes or 30 minutes post- ingestion.”
Because blueberry juice is so well tolerated by patients, administration is refreshingly easy?not to mention cost-effective. “We give it to them right before the exam,” Patola said. “Five or 10 minutes is ample to get the juice into the stomach and duodenum. You don’t need to fill the whole small bowel or anything. And we often continue to scan for 30 to 45 minutes and still see the same effect.”
The Radiology study on blueberry juice notes, “Although further clinical trials are needed to determine the most effective manganese concentration (to minimize dilution effects and to maximize delineation of the more distal bowels), we found in our preliminary clinical study that a manganese concentration of 3.0 mg/dL was optimal.”
According to Patola, the technique is finally starting to catch on. “It’s getting out there,” he said. “I’ve received phone calls from other sites across Canada asking about it. I think people just aren’t aware that blueberry juice can be used in this way.”
Siemens Demonstrates Prototype MRI-PET System
The first in vivo simultaneous MR-PET images of the human brain have been acquired by a new prototype system from Siemens Medical Solutions, Malvern, Pa. MRI-PET imaging?which brings the soft tissue contrast and high specificity of MR together with the physiological and metabolic data of PET?shows tremendous potential for diagnosis and therapy of neurological diseases, stroke, and cancer.
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| Image courtesy University Hospital, Tennessee, and University Hospital, Tuebingen, Germany |
“At Siemens, we have identified a number of ‘mega trends,’ and one of these is the merging of technologies to deliver solutions across the health care continuum,” said Walter Maerzendorfer, president of Siemens’ MR division. “Fusing existing technologies, in this case, goes far beyond the simple fusion of images.”
The Siemens MR-PET prototype is dedicated to imaging of the brain; the PET scanner uses a next-generation Avalanche Photodiode Detector (APD), which immunizes the scanner against magnetic fields and provides excellent PET results. The prototype has been developed for the Magnetom Trio system in order to fully leverage the research and clinical advantages of 3T field strength.
Many hybrid imaging devices such as PET-CT and SPECT-CT combine both modalities into one machine, but take scans sequentially; the Siemens MR-PET prototype, on the other hand, can image simultaneously.
The two modalities complement each other ideally, especially when it comes to assessing neurological problems. For example, when diagnosing Alzheimer’s, PET can detect mild cognitive impairment at an early stage, but only MR can determine whether the volume of the brain has been reduced by atrophy. For stroke patients, the technology could allow physicians to assess which brain tissues might be salvageable following a stroke; in the case of traumatic head injury, patients would be scanned only once instead of requiring a separate scan for each modality.
MR-PET imaging also shows potential for research in therapeutics, including stem cell therapy; because MR-PET enables simultaneous measurement of anatomy, functionality, and biochemistry, it may allow researchers to better track stem cell migration to damaged areas of the brain, determine whether cells are still alive, and identify how cells are integrated into the body’s neurological network.
“From biomarker development to imaging equipment, to clinical applications, to information technology solutions, Siemens is well positioned to continue to advance the molecular imaging of biological processes,” said Siemens president and CEO Erich Reinhardt.
“The ability to determine in great detail the loss of neurological function puts us on the path to better care,” said Maerzendorfer.
MRE Allows Physicians to Diagnose Liver Disease Noninvasively
A noninvasive technique developed by imaging researchers at the Mayo Clinic, Rochester, Minn, provides an accurate tool for diagnosing liver disease, according to two recent studies performed by the group. MR elastography (MRE)?which uses a modification of MR imaging to map the mechanical properties of tissue?could help physicians detect and treat liver disease in its early stages.
Through imaging, MRE simulates palpation, a detection method used by physicians to literally feel for abnormalities in accessible tissue, such as the thyroid, breast, or prostate. MRE applies vibrations to the liver through a drum-like device to measure the stiffness or elasticity of the organ. The processed wave images map the mechanical properties of the liver, such as tissue stiffness, which often indicates fibrosis.
“Healthy liver tissue is very soft, while a liver with fibrosis is firmer, and a liver with cirrhosis is almost rock-hard,” said Richard Ehman, MD, lead researcher on the MRE project.
Collaborating with Mayo Clinic gastroenterologists, Ehman’s imaging research team used MRE to examine 20 healthy volunteers and 57 patients with chronic liver disease. The study showed that MRE accurately detects fibrosis with high sensitivity and specificity, and that the presence of steatosis?fatty acids or triglycerides in liver cells?did not interfere with MRE’s fibrosis detection.
In a second study, researchers set out to determine whether MRE can accurately detect portal hypertension, a condition that often indicates cirrhosis of the liver. After looking at the MRE examinations of 12 healthy volunteers and 35 patients with varying degrees of chronic liver disease, the research team found a significant correlation between liver and spleen stiffness in patients with portal hypertension. However, determining the validity of spleen stiffness as a noninvasive measure of portal venous pressure will require further study.
Encouraging results like these could mean that MRE will be an appropriate diagnostic tool for other tissue as well. According to Ehman, the Mayo Clinic team is exploring the use of MRE to detect breast cancer and Alzheimer’s disease.
In the meantime, MRE examinations will continue to help physicians diagnose liver disease. Traditionally, patients undergo a needle biopsy to confirm the presence of fibrosis, but MRE could help physicians decide when a liver biopsy is warranted.
“Based on this research, we are now using MRE examinations in select patients to determine liver stiffness and assess the need for liver biopsies,” said Jayant Talwalkar, MD, a Mayo Clinic gastroenterologist and an investigator on the MRE studies.
?Ann H. Carlson
