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Vancouver! Editor’s note: This article was produced from research on MRI applications presented at the recent meeting of the American Roentgen Ray Society (ARRS). It was prepared from materials produced by the ARRS staff and edited by Radiology Today staff.
For the study, the researchers studied 26 patients with NAFLD who underwent CCE MRI. Using a five-point scale, the researchers found that the staging of the NAFLD on CCE MRI closely matched the staging of NAFLD using conventional pathology. The definitive method of diagnosis and staging NAFLD is liver biopsy, but it has several limitations, the researchers say. It is invasive, costly, has risks, and only samples about 1/50,000th of the liver. “This sampling issue is important because the pathological processes that affect the NAFLD liver are not evenly distributed throughout, so that tiny changes in needle placement will result in potentially large changes in biopsy interpretation. Because of these limitations, alternative methods such as CCE MR, need to be developed,” said Claude Sirlin, MD, lead author of the study, who presented results at the annual meeting of the ARRS in Vancouver in April. “Except for CCE MR, all other experimental techniques rely on surrogate or indirect markers of fibrosis,” Sirlin said. “CCE MR attempts to directly visualize fibrosis by using two contrast agents with complementary mechanisms, iron particles to darken the background liver, and gadolinium to brighten the fibrosis. Gadolinium alone and iron particles alone are not adequate for visualization of fibrosis, unless the fibrosis is extremely advanced. However, when given together, the agents show fibrosis with high clarity.” The combined use of two or more complementary contrast agents is uncommon in radiology, according to the researchers. “Partly, this is because of the prevailing radiology paradigm and partly, this is because most third-party insurers refuse to pay for two contrast agents,” said Sirlin. Other potential advantages of CCE MRI, say the researchers, include that CCE MRI can directly visualize the fibrosis, has a higher safety profile than biopsy, can detect liver cancers simultaneously, the procedure is repeatable, and the possibility that CCE MRI may be more accurate than any other noninvasive method for assessing liver fibrosis.
Researchers at Shantou University Medical College in China and the University of Toronto analyzed the MRIs of 24 patients with ischemic stroke within five hours of symptom onset. Ten of the patients developed hemorrhaging within the skull. The parenchymal enhancement, in which certain cells appear brighter than usual on MRI, was found in six of those patients, and the hyperintense MCA sign, a special anomaly detected on MRI, was found in five of the 10. The 14 patients who did not develop hemorrhaging had no parenchymal enhancement or hyperintense MCA sign. Intravenous tissue plasminogen activator (tPA) remains the only drug approved in North America and Europe for acute ischemic stroke treatment, but one of the most significant problems with this therapy is the risk of hemorrhaging within the skull, according to researchers. Approximately one half of all stroke patients experience some forms of this bleeding within the first week. “The risk of life-threatening hemorrhaging increases tenfold after intravenous tPA, so the ability to identify patients at increased risk for secondary bleeding after acute stroke could potentially be helpful in increasing the effectiveness and safety of the therapy,” said Gang Guo, MD, lead author of the study. “This study suggests that patients with the presence of these signs on their MRIs may be at a higher risk for developing hemorrhagic complications following tPA treatment. This could lead to an extension of the treatment window beyond current time constraints [three hours after symptoms onset] in those patients who have a stable brain blood barrier. “We recommend that acute stroke imaging protocols that usually include gadolinium administration be followed with T1-weighted spin-echo MRI to screen for parenchymal enhancement and the hyperintense MCA sign,” Guo added.
The physicians reviewed the shoulder MRIs of 100 consecutive patients, 67 of whom also underwent arthroscopy to detect shoulder cartilage tears. Of those 67 patients, 46 were diagnosed with some type of torn cartilage. The researchers found that 3T MRI was able to detect the tears in 42 of those 46 patients. “The results of our study show that MRI has a high correlation with what is found at surgery,” said Thomas Magee, MD, lead author of the study done at Neuroskeletal Imaging Institute in Merritt Island, Fla. Results from the study were presented at the annual meeting of the ARRS in April in Vancouver. The benefit of using MRI to diagnose shoulder cartilage tears is significant, say the researchers. “Some doctors advocate using arthroscopy on every patient, but with MRI, we can diagnose tears without the need for arthroscopy, so many patients won’t have to undergo surgery,” Magee said.
The researchers analyzed the results of 14 women with symptomatic fibroids who were treated with the rapid interleaved MRgFUS. The researchers found that interleaved MRgFUS permitted up to 127 sonications—sound wave pulses that break up the fibroid—in a three-hour treatment. That’s nearly twice as many as the 60 to 70 sonications with the conventional technique in the same time span. The procedure had no serious adverse side effects at six months follow up. The treatment was effective in markedly reducing symptoms in 12 of 14 patients. “Using this technique, women with fibroids can be treated faster and women [who] would not be considered for the treatment because of the size of their fibroid can now also be treated,” said George A. Holland, MD, lead author of the study, who presented results at annual meeting of the ARRS in Vancouver in April.
In a healthy person, urine is excreted by the kidney and flows down the ureter into the bladder. In patients with VUR, there is an abnormal reverse passage of urine from the bladder back up into the kidney. According to the researchers, this may cause urinary tract infections and kidney damage, often in young children. “The incidence of VUR is under 1% in healthy children, but is 20% to 50% in children with urinary tract infections,” said Hui-Seong Teh, MD, of Changi General Hospital in Singapore, lead author of the study. For the study, five patients who had VUR detected by conventional x-ray cystography underwent MR cystography. For both conventional and MR cystography, contrast material is put into the bladder using a small tube and the ureters are imaged repeatedly using x-rays or MRI, respectively, to look for reverse flow of contrast into the ureters. The researchers found that the two methods were concordant for 80% of the ureters in these patients. The other 20% was split, with MR cystography detecting VUR in one ureter and x-ray cystography detecting it in the other. The researchers also found that MRI could show scarring of the kidneys and loss of kidney tissue, which is related to the extent of kidney damage from VUR, better than conventional x-ray cystography. The current radiological tests for assessing VUR involve significant radiation to the patients, say the researchers. Patients with this condition often require repeated examinations to monitor disease progression and assess treatment effectiveness. Minimizing radiation exposure to the patient is of great concern, particularly for children. “For a child 5 to 10 years of age, it has been
estimated that the radiation exposure from a single conventional x-ray
cystogram is equivalent to that of 20 chest radiographs or six months
of natural background radiation,” Teh said. “MR cystography
is accurate and, perhaps, more importantly, doesn’t expose patients
to ionizing radiation.” |
June
19, 2006
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