Differential Riagnosis of the Brain Tumor and Brain Abscess: the Usefulness of Dynamic MR Imaging

PURPOSE: To evaluate the usefulness of dynamic MR imaging in the differential diagnosis of intracranial tumorand abscess. MATERIALS AND METHODS: Dynamic MR images of 36 patients with surgically or clinically provenintracranial enhancing lesions were retrospectively reviewed. These lesions comprised 15 metastases, 14 gliomas,and seven abscesses. Images were sequentially obtained every 30 seconds for 3-5 minutes using the spin-echotechnique(TR/TE : 200 msec/15 msec) after bolus injection of gadolinium dimeglumine(2-3cc/sec). The dynamics ofcontrast enhancement of the lesions was analyzed visually and by calculating the sequential contrast-enhancementratio(CER). RESULTS: CER during the 30-second early dynamic phase was 93.16 in metastases, 67.78 in gliomas, and48.3 in abscesses(ANOVA, p<0.005). The contrast enhancement pattern of metastases showed rapidly increased signalintensity(SI) up to 30 seconds, followed by a relatively rapid decrease; less time was then required to reach theCER peak. In gliomas, SI increased gradually up to 180 seconds and then took a longer time to reach the CER peak.The SI of abscesses was similar to that of gliomas, with a more gradual increase for 30-60 seconds and a longertime for the CER peak to be reached. CONCLUSION: The contrast enhancement pattern and CER parameters seen ondynamic MRI can help differentiate intracranial tumor and abscess.

Brain MRI Findings of Spontaneous Intracranial Hypotension

PURPOSE: To evaluate brain MRI findings of spontaneous intracranial hypotension. MATERIALS AND METHODS: A retrospective review of MRI findings was conducted on six patients with clinically proven spontaneous intracranial hypotension ; no patient had history of previous spinal puncture. Follow-up MRI was available in two patients, and to detect CSF leakage, radionuclide cisternography (n=5), myelography (n=1), and MR myelography (n=1) were performed. RESULTS: On contrast-enhanced T1WI, diffuse dural enhancement was seen in all cases, subdural hematoma or hygroma was seen in four cases, pituitary gland prominence in four, dural sinus dilatation in four, downward displacement of cerebellar tonsil in two, downward displacement of iter in one, and suprasellar and prepontine cistern effacement in two. In no patient was abnormal CSF leakage found. CONCLUSION: Although dural enhancement, as seen on MRI, is not specific, diffuse enhancement of dura matter accompanying by subdural hematoma, hygroma, pituitary gland prominence, dural sinus dilatation, downward displacement of the cerebellar tonsil, or suprasellar and prepontine cistern effacement can strongly suggest intracranial hypotension.

MR findings of Dysembryoplastic Neuroepithelial Tumor

PURPOSE: Dysembryoplastic neuroepithelial tumor (DNET) is a newly described, pathologically benign tumor arising within the supratentorial cortex. We reviewed the MR appearance of five patients with DNET, emphasizing the clinical and radiologic features. MATERIALS AND METHODS: MR images in the five patients (three male and two female) with a history of epileptic seizure and pathologically-proven DNET were retrospectively reviewed. We analyzed the location, configuration, signal intensity, contrast enhancement, vasogenic edema and calcifications of these tomors. RESULTS: The tumors were located mainly in the cortical to subcortical area with very little perifocal mass effect on MR imaging. They were essentially hypointense on T1-weighted imaging, and showed a hyperintense well circumscribed mass on T2-weighted imaging and a thick gyrus-like configuration was retained within the lesions. On contrast enhanced study, focal nodular enhancement was seen in one patient, and multifocal nodular enhancement in two. CONCLUSION: DNET is rare benign tumor resulting in often medically intractable epileptic seizure and shows a characteristic gyriform configuration, well-described lobular tumor margins and sometimes multifocal nodular enhancement. These radiologic features may aid in differentiating DNET from ganglioglioma and other gliomas.

Usefulness of Dynamic Magnetic Resonance Imaging in Pituitary Microadenomas

PURPOSE: To investigate the usefulness of dynamic MR imaging in the diagnosis of pituitary microadenomas. MATERIALS AND METHODS: Dynamic MR imaging was performed in 31 patients with suspicious pituitary microadenoma. The MR examination was performed on a 2.0T or 1.5T superconductive MR unit using spin echo(SE) technique with arepetition time of 200m sec, echo time of 15 m sec, 128 x 256 matrix and one excitation. Actual sampling time perimage was 26 seconds. The field of view was 25cm and a section thickness of 3mm with 2mm gap was chosen. After arapid hand injection(2-3ml/sec) of Gd-DTPA(0.1 mmol/kg of body weight), dynamic coronal plane MR images were obtained every 20-30 seconds for 3-5 minutes. Between never and ten serial images were usually obtained. After dynamic MR imaging, routine SE T1-weighted images(T1WI) were obtained in the same plane as dynamic images, and detection rates of pituitary microadenoma using dynamic MR imaging and using routine enhanced T1WI, were retrospectively compared. RESULTS: On early dynamic images(30|90 seconds), 23 of 31 adenomas(74.2%) were well visualized, with a clear border ; of particular note is the fact that 11 of the 31 were well visualized at 30-second dynamic image. On late dynamic images(120-180 seconds), six microadeomas(19.4%) were well-visualized and; two(6.5%) were well-visualized throughout on all dynamic images. Meanwhile, 12 of 31 microadenomas(38.7%) were well-visualized on routine Gd-DTPA enhanced T1WI. CONCLUSION: Dynamic MR imaging with Gd-DTPA bolus injection was the most useful technique for the detection of pituitary microadenomas, especially on early-phase dynamic images.

MR Imaging of Proximal Femur: Age-related Changes

PURPOSE: The purpose of this study is to illustrate MR patterns of signal intensity of proximal femur in normal subjects according to the age distribution. METHOD AND MATERIAL: Tl-weighted MR images of the proximal femur in 125 subjects, aged 13 days to 25 years, were retrospectively analyzed. Age distribution was classified to 4 groups;below 4 months, 5 months to 4 years, 5 years to 14 years, and 15 years to 25 years. RESULTS: By the age of 4 months, the non-ossified femoral epiphysis was seen as intermediate-signal-intensity cartilage. At 5 months-4 years, the ossified fernoral capital epiphysis was seen within intermediate-signal-intensity cartilage and appeared as decreased or increased signal-intensity red or yellow marrow surrounded by a rim of low-signal-intensity cortical bone. At 5-14 years, the ossified femoral capital and greater trochanteric epiphysis were seen within the intermediate-signal-intensity cartilage and appeared as decreased or increased signal-intensity red or yellow marrow. At 15-25 years, the proximal metaphyseal marrow showed increased signal intensity. Four patterns of the metaphyseal marrow were recognized by Ricci et al. The frequency of pattern la progressively decreased with age. Pattern 2 and 3 were visible in the 15-25 years age group. CONCLUSION: An understanding of the spectrum of normal age-related change of the proximal femoral cartilage and marrow patterns serves as the foundation for interpretation of proximal femur pathologies.

MR Patterns of Bone Marrow of Calvarium and Vertebral Body in Normal Subjects; Pattern Analysis According to Age Distribution

PURPOSE: The purpose of this study is to illustrate MR patterns of bone marrow of calvarium and vertebral body in normal subjects according the age distribution and to understand the course of the fatty replacement from red marrow. METHODS AND MATERIAL: We retrospectively evaluated MR examinations of the calvaria(n=71), cervical spine(n=71), thoracic spine(n=65), Imbar spine(n =68) in subjects without bone marrow abnormality whose age ranged 3 weeks to 74 years. Three distinctive patterns were categorized on Tl-weighted images of the skull. In pattern 1, uniformly low signal intensity with or without very small areas of high intensity in frontal and occipital bones is noted. In pattern 2, frontal and occipital bones have uniformly high signal intensity, and patchy area of high intensity appears in parietal bone. In pattern 3, the entire skull has uniformly high signal intensity. In the spine, four patterns were categorized on Tl-weighted MR images. In pattern 1, the vertebral body has uniformly low signal intensity except for linear areas of high intensity superior and inferior to basivertebral vein. In pattern 2, bandlike and triangular areas of high signal intensity are found in the periphery. Pattern 3 and 4 have diffusely distributed areas of high signal intensity; pattern 3 consist of numerous indistinct dots measuring a few millimeter or less, and pattern 4 consist of fairly well marginated areas ranging in size from 5 to 1.5cm. RESULT:In the calvaria, 73% of pattern 1 were younger than 20 years, pattern 2 were evenly distributed, and 86% of pattern 3 were older than 40 years. In the spine, 87% of pattern 1 were younger than 40 years, 72% of pattern 3 were in 40 to 50 years, and 87% of pattern 4 were older than 50 years. Pattern 2 were evenly distributed in the cervical and thoracic spine, but in the thoracic spine 62% were younger than 30 years. CONCLUSION:It is concluded that younger age group shows mainly pattern 1, whereas elderly group has pattern 3 or 4 in the calvarial and vertebral body marrow. This suggests that conversion to fatty marrow begin locally and progress diffusely with age.

Usefulness of Dynamic Magnetic Resonance Imaging in Brain Tumors

PURPOSE: To investigate the usefulness of dynamic MR imaging in the differential diagnosis of brain tumors. MATERIALS AND METHODS: Dynamic MR imaging was performed in 43 patients with histopathologically proved brain tumrs. Serial images were sequentially obtained every 30 seconds for 3--5 minutes with use of spin-echo technique(TR 200msec/TE 15msec) after rapid injection of Gd-DTPA in a dose of 0.1mmol/kg body weight. Dynamics of contrast enhancement of the brain tumors were analyzed visually and by the sequential contrast enhancement ratio(CER). RESULTS: On the dynamic MR imaging, contrast enhancement pattern of the gliomas showed gradual increase in signal intensity(SI) till 180 seconds and usually had a longer time to peak of the CER. The SI of metastatic brain tumors increased steeply till 30 seconds and then rapidly or gradually decreased and the tumors had a shorter time to peak of the CER. Meningiomas showed a rapid ascent in SI till 30 to 60 seconds and then made a plateau or slight descent of the CER. Lymphomas and germinomas showed relatively rapid increase of Sl till 30 seconds and usually had a longer time peak of the CER. CONCLUSION: Dynamic MR imaging with Gd-DTPA may lead to further information about the brain tumors as the sequential contrast enhancement pattern and CER parameters seem to be helpful in discriminating among the brain tumors.

Role of MR in Diagnosis of Uterine Leiomyoma

PURPOSE: Uterine myoma is the most common benign uterine neoplasm, and assosiated with gynecologic and obsteric complications. Preoperative acurrate analysis of the number, location and type of the myoma is important, especially in reproductive women. We analyze the MR findings of uterine myoma for evaluation of the role of MR in diagnosis of uterine myoma. MATERIALS AND METHODS: We analyze MR findings of 76 myomas in 40 patients, and 34 myomas in 17 patients of them were confirmed by surgery. With 2. 0T Spectro-20000(Gold-star, Korea), TlWl axial images and T2Wl axial and sagittal images were obtained. Locations were classified into fundus, anterior body, posterior body, right body, left body, and cervix. Types were classified into submucosal, intramural, and subserosal. Associated findings were analiyed also. RESULTS: The most common location and type wre posterior body and intramural type, respectively. Ten myomas were confirmed on surgery only, and the causes were as follows:first, all 10 myomas were less than 2 cm in size;second, 1 subserosal myoma was abutted to a large ovarian mass;third, small myomas were abutted to each other, or small one was adjacent to larger one and considered as one large myoma. Degenerative change was noted in 50% of histologically confirmed cases. High signal halo on T2Wl was noted in 14%. CONCLUSION: MR is excellent in detection and localization of uterine leiomyoma larger than 2cm, and may be a preoperative diagnostic method of choice in patient who need myomectomy for preservation of childbearing function.

MRI of the diffuse axonal injury

CT has facilitated early recognition and treatment of focal brain injuries in patients with head trauma. However. CT shows relatively low sensitivity in identifying nonhemorrhagic contusion and injuries of white matter. MR is known to be superior to CT in detection of which matter injuries, such as diffuse axonal injury. MR imaging in 14 cases of diffuse axonal injury on 2.0T was studied. The corpus callosum, especially the body portion, was the most commonly involved site. The lesions ranged from 5 to 20 mm in size with ovoid to elliptical shape. T2WI was the most sensitive pulse sequence in detecting lesions such as white matter degeneration, hemorrhagic and nonhemorrhagic contusion. The lesions were nonspecific as high and low signal intensities on T2WI and T1WI respectively. CT showed white matter abnormality in only 1 case of 14 cases. We propose MR imaging as the primary imaging procedure for the detection of diffuse axonal injury because of its multiplanar capabilities and higher sensitivity.