News from the American Society of Neuroradiology
Applied Radiology — Vol. 32 , Issue 6 , pp. 22 -23
DOI: 10.37549/AR1195
Published: June 1, 2003
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The latest advances in neuroradiology were presented at the 41st Annual Meeting of the American Society of Neuroradiology (ASNR), held in Washington, DC, April 28th through May 2, 2003. This column presents a few of the innovative studies presented.
MR contrast agent for imaging brain, head, and neck tumors
Two studies evaluated MRI and the investigative lymph node imaging agent, ferumoxtran-10 (Combidex, Advanced Magnetics, Inc., Cambridge, MA), examining its potential in assessing primary and residual brain, head, and neck tumors.
The first study, presented by Yoshimi Anzai, MD, Associate Professor of Radiology at the University of Washington, Seattle, assessed the efficacy of ferumoxtran-10 in imaging primary tumors of the head and neck. A total of 29 patients with head and neck cancer underwent MRI and then repeat MRI 24 hours following a 2.6 mg/kg intravenous (IV) dose of ferumoxtran-10. A primary head or neck tumor was identified by MRI in 15 of the 29 patients, these 15 comprised the study population.
The results showed significant increase in T1 signal intensity and decrease in T2 intensity in the primary tumor following ferumoxtran-10 administration. The enhancement was more intense at the periphery of the tumor than at the center. A dark rim of iron deposition was clearly seen at the tumor margin in 7 of the 15 patients. Histologic examination in these cases found the presence of iron deposition within macrophages or other inflammatory cells, predominantly at the periphery of tumor.
The researchers concluded that ferumoxtran- 10 may be a valuable contrast agent for demonstrating true tumor margins in primary head and neck cancers. They noted that these findings may have significant implications for clinical management and that further large clinical studies should be undertaken.
A second study, presented by Peter Varallyay, MD, Visiting Fellow, Neuroradiology Section, Department of Radiology at Oregon Health and Sciences University, Portland, examined the value of both gadolinium (Gd)- and Combidexenhanced MRI in pre- and postoperative assessment of malignant brain tumors.
In this trial, 7 patients with malignant brain tumors underwent pre- and postoperative MRI with Gd and ferumoxtran. Following the Gd-enhanced study, patients received an IV infusion of 2.6 mg/kg ferumoxtran-10 and underwent a second imaging study at least 24 hours later. Patients underwent craniotomy the same day and MRI was repeated before and after Gd administration an average of 18 hours postsurgery.
All malignant tumors showed ferumoxtran accumulation with T1 and T2 signal changes. In 5 patients, there were areas of enhancement seen with ferumoxtran-10 that were not seen using Gd. In 1 case, Gd enhancement developed and progressed in these areas. In 5 of the 7 cases, comparison of the pre- and postoperative ferumoxtran- enhanced MRI revealed residual ferumoxtran-enhancing areas, which had shown persistent increased T1 signal intensity.
Dr. Varallyay concluded that ferumoxtran- 10 may show areas in malignant tumors that do not enhance with Gd. Persistent increased T1 signal intensity was clearly seen in postoperative residual ferumoxtran-enhancing lesions, avoiding repeat Gd-enhanced postoperative MRI studies. Histologic examinations showed iron uptake in reactive cells.
Pediatric neuroimaging studies
Two separate studies evaluated the use of magnetic resonance spectroscopy (MRS) to identify chemical differences in the brains of pediatric patients, particularly in those with mood disorders and those with closed traumatic brain injuries (TBI).
Brain metabolite changes and mood disorder
One study used MRS to evaluate brain chemistry in children with a mood disorder who have at least one parent with bipolar disorder compared with healthy children whose parents do not have such a disorder.
“Few studies have examined the neurochemical abnormalities that underlie pediatric bipolar disorder,” noted presenter Kim Cecil, MD, of the Cincinnati Children’s Hospital. “Until recently, it was believed that the condition did not present until adolescence. We hypothesized that these children would exhibit neurochemical differences compared with healthy children.”
In this study, 9 children with a mood disorder and at least 1 parent with bipolar disorder were matched to 10 healthy children for age, race, sex, education, and Tanner stage. They then underwent MRS using 8-mL volumes within the frontal cortex, frontal white matter, and the cerebellar vermis. Metabolite ratios and concentrations were calculated and compared between groups.
The researchers found that the concentration of N-acetylasparate (NAA) and creatine in the cerebellar vermis were lower and the myoinositol levels were elevated in children with mood disorders compared with the control subjects.
The researchers concluded that neurochemical abnormalities within the frontal cortex and the cerebellar vermis are present in children with a mood disorder and a familiar risk for bipolar disorder, similar to that found in adults with bipolar disorder. The researchers are replicating this study with a larger patient population.
Traumatic brain injury
The second study looked at the cognitive and emotional changes often seen in children following moderate to severe TBI. “Cognitive defects and emotional disturbance following traumatic brain injury in children have been implicated in declines in academic achievement, psychosocial adjustment, and adaptive functioning,” explained Jill Hunter, MD, of Texas Children’s Hospital, Houston. “However, none of the currently available testing methods is adequate to predict outcomes for varied levels of injury. We believe that further research will lead to the development of an algorithm— one that combines a multimedia testing approach together with imaging—that will give better prognostication and treatment options for each child.”
In this study, 5 children (4 girls and 1 boy) with a mean age of 9.1 years at the time of TBI and 3 uninjured controls (2 girls and 1 boy) underwent imaging using a 1.5-T Gyroscan Intera scanner (Philips Medical Systems; Best, The Netherlands) using conventional twodimensional chemical shift imaging techniques. Data were collected for the left and right frontoparietal white matter Creatine, NAA, and choline phantoms were prepared, scanned, and used for data analysis.
The study found that only NAA was lower in the TBI group than in the control group. Group x side interactions were seen for choline and creatine with higher left than right hemisphere values in the controls, but not in those with TBI.
The researchers concluded that the lower NAA in the study group suggests frontoparietal neuronal and axonal injury, as previous research has shown. This study also found, however, the apparent loss of asymmetry in creatine and choline in the frontal white matter in those with TBI, which might reflect myelination differences in the dominant hemisphere of normal right-handed children that may be lost after frontal lobe injury.
“Neuroradiology is assuming an increasingly significant role in the clinical care of patients,” concluded Dr. Hunter. “Through rapidly developing technologies, we are able to narrow differential diagnoses, direct specific therapies, and analyze the patient noninvasively during and after treatment.”
Functional MRI: The new lie detector?
Another study suggested that functional MRI (fMRI) may one day be able to serve as a new form of lie-detector test.
Scott Faro, MD, Associate Professor of Radiology, and Director of the MRI Research Laboratory at Drexel University Medical Center, Philadelphia, presented the results of a very small preliminary study that showed that when subjects were lying different regions of the brain were activated than when they were telling the truth.
“The purpose of this study,” he said, “was to investigate the regions of brain activation during truth-telling or deception with fMRI using blood-oxygenation-level–dependent (BOLD) contrast, while simultaneously recording physiologic signals with a standard polygraph machine.”
Four healthy volunteers were scanned (1.5-T Vision scanner, Siemens Medical Solutions, Iselin, NJ) using a standard head coil. During questioning, physiologic responses were measured. Contiguous oblique axial images were positioned and aligned parallel to the anterior-posterior commissure line covering the brain. Functional images were acquired with an echoplanar imaging, free-induction decay pulse sequence.
Subjects were asked to either lie or to tell the truth in response to 13 relevant and control questions. The questions were randomized and repeated four times. The data were used to create statistical parametric maps to show areas of the brain in which statistically significant differences were seen in BOLD contrast during truth telling and deception.
The results showed that during truth telling, activation occurred mainly in the temporal lobe and superior temporal gyrus. When subjects lied, activation occurred in areas of the frontal lobe, temporal lobe, sublobar, extra nuclear, and inferior frontal gyrus. The polygraph results correlated well with truth telling but were inclusive during deception.
“These results suggest that there may be unique patterns of brain activation involved in truth telling or deception that can be measured using fMRI,” said Faro. “It makes sense, theoretically, that the regions we discovered to be activated during the deception process were the same brain regions involved with judgment, fear, and anxiety.” The study also found that it was possible to simultaneously use the polygraph machine to measure the physiologic signals inside the MR scanner without producing noticeable artifacts. AR
Citation
. News from the American Society of Neuroradiology. Applied Radiology. 2003;32(6):22-23. doi:10.37549/AR1195.