Reproducibility Analysis of Brain Volumetry Measured from Inter MR Scanner of Multi-Institute

PURPOSE: The aim of this study was to evaluate the variations of brain volumetry between the different MR scanners or the different institutes. MATERIALS AND METHODS: Ten normal subjects were scanned at four different MR scanners, two of them were the same models, to measure inter-MR scanner variations using intraclass correlation coefficient (ICC), coefficient of variation (CV) and percent volume difference (PVD) and to calculate minimal thresholds to detect the significant volumetric changes in gray matter and subcortical regions. RESULTS: Averaged statistical reliability (ICC = 0.837) and volumetric variation (CV = 4.310%) in all segmented regions were observed on overall MR scanners. Comparing the segmented volumes with PVD between two MR scanners, volumetric differences on same models were the lowest (PVD = 3.611%) and volume thresholds were calculated with 7.168%. PVD results and thresholds values on systemically different MR scanners were evaluated with 5.785% and 11.340% respectively. CONCLUSION: Authors conclude that the reliability of brain volumetry is not so high. Calibration studies of MRI system and image processing are essential to reduce the volumetric variability. Additionally, frameworks comprised of database and algorithms with high-speed image processing are also required for the efficient image data management.

A Comparison Study on Human Brain Volume of White Matter, Gray Matter and Hippocampus Depending on Magnetic Resonance Imaging Conditions and Applied Brain Template

PURPOSE: The aim of this study was to examine the volume differences of human brain 3-D MR images obtained by automatic segmentation methods depending on brain templates and image acquisition conditions, respectively. MATERIALS AND METHODS: 3D T1-weighted MR images oriented in coronal and sagittal plane were acquired from eight healthy subjects (29.5+/-5.66 years) using two identical 3T MR scanners at different sites. Caucasian brain template and Korean elderly brain template were applied for the same subject to segment brain structural region. Volumetric differences and variation of gray matter, white matter and hippocampus depending on scan orientations and brain template types were statistically evaluated. RESULTS: Volumetric measurements have some different results for the same subject images depending on scan orientation in identical MR scanners but not significantly. However, all segmented volumes relied upon brain templates were significantly different (p<0.05). Small variation of the volume in gray matter, white matter (coefficient of variation, CV< or =1%) and hippocampus (CV< or =3%) were obtained. Comparing the mean CV in all segmented regions, variation of scan orientation was not significantly different with inter scanner variation but variation relied upon brain templates were significantly different (p<0.001). CONCLUSION: Authors found that brain template regarding the specific properties of the subjects is required to reduce the errors of brain volumetry.

Ultrasound-Guided Fine-Needle Aspiration Biopsy in Infracentimetric Thyroid Nodules

PURPOSE: The aim of this study is to determine the efficacy of ultrasound-guided fine-needle aspiration biopsy (US-FNAB) of thyroid nodules that are equal to or less than 1 cm at the maximum diameter. MATERIALS AND METHODS: The US-FNABs performed on thyroid nodules from March to August 2009 were included in this study. We retrospectively evaluated the cytopathologic results as well as any complications associated with the procedure. RESULTS: Of the 241 thyroid nodules (range: 0.1 - 1.0 cm, mean size: 5.8 mm) in 184 patients (female: male = 164:20, mean age: 49.0 years, age range: 18 - 77 years old), the incidence of an inadequate sample was 14.1% (34/241) for the US-FNABs. Eighty six nodules were surgically removed in 62 patients, of which 15 were confirmed to be benign nodules and 71 were confirmed to be malignant nodules. The number of true positive, false positive, true negative and false negative results for US-FNAB were 59, 0, 10 and 3%, respectively, and the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 95.2%, 100%, 100%, 76.9% and 95.8%, respectively. All the false negative cases were less than 3 mm at the maximal diameter. There were no serious complications in all the patients. CONCLUSION: US-FNAB was effective for the cases of thyroid nodule under 1 cm at the maximal diameter. However, a false negative result of US-FNAB should be considered for the cases of very small nodules that are less than 3 mm at the maximal diameter.

Size and Location of Ruptured Intracranial Aneurysms

OBJECTIVE: The aim of study was to review our patient population to determine whether there is a critical aneurysm size at which the incidence of rupture increases and whether there is a correlation between aneurysm size and location. METHODS: We reviewed charts and radiological findings (computed tomography (CT) scans, angiograms, CT angiography, magnetic resonance angiography) for all patients operated on for intracranial aneurysms in our hospital between September 2002 and May 2004. Of the 336 aneurysms that were reviewed, measurements were obtained from angiograms for 239 ruptured aneurysms by a neuroradiologist at the time of diagnosis in our hospital. RESULTS: There were 115 male and 221 female patients assessed in this study. The locations of aneurysms were the middle cerebral artery (MCA, 61), anterior communicating artery (ACoA, 66), posterior communicating artery (PCoA, 52), the top of the basilar artery (15), internal carotid artery (ICA) including the cavernous portion (13), anterior choroidal artery (AChA, 7), A1 segment of the anterior cerebral artery (3), A2 segment of the anterior cerebral artery (11), posterior inferior cerebellar artery (PICA, 8), superior cerebellar artery (SCA, 2), P2 segment of the posterior cerebral artery (1), and the vertebral artery (2). The mean diameter of aneurysms was 5.47+/-2.536 mm in anterior cerebral artery (ACA), 6.84+/-3.941 mm in ICA, 7.09+/-3.652 mm in MCA and 6.21+/-3.697 mm in vertebrobasilar artery. The ACA aneurysms were smaller than the MCA aneurysms. Aneurysms less than 6 mm in diameter included 37 (60.65%) in patients with aneurysms in the MCA, 43 (65.15%) in patients with aneurysms in the ACoA and 29 (55.76%) in patients with aneurysms in the PCoA. CONCLUSION: Ruptured aneurysms in the ACA were smaller than those in the MCA. The most prevalent aneurysm size was 3-6 mm in the MCA (55.73%), 3-6 mm in the ACoA (57.57%) and 4-6 mm in the PCoA (42.30%). The more prevalent size of the aneurysm to treat may differ in accordance with the location of the aneurysm.

Radiologic Features of Fibrous Hamartoma of Infancy Involving the Buttocks

Fibrous hamartoma of infancy (FHI) is a rare benign subcutaneous tumor that presents in children younger than two years. The tumor mostly affects the trunk, axilla and upper extremities. Imaging findings of FHI that involve the buttocks have not been reported in the clinical literature. We reported the imaging features of a lesion in a 9-month-old infant who presented with a palpable mass on the buttocks. The imaging findings were evaluated after a review of previous studies.

Time Resolution Improvement of MRI Temperature Monitoring Using Keyhole Method

PURPOSE: This study proposes the keyhole method in order to improve the time resolution of the proton resonance frequency(PRF) MR temperature monitoring technique. The values of Root Mean Square (RMS) error of measured temperature value and Signal-to-Noise Ratio(SNR) obtained from the keyhole and full phase encoded temperature images were compared. MATERIALS AND METHODS: The PRF method combined with GRE sequence was used to get MR temperature images using a clinical 1.5T MR scanner. It was conducted on the tissue-mimic 2% agarose gel phantom and swine's hock tissue. A MR compatible coaxial slot antenna driven by microwave power generator at 2.45GHz was used to heat the object in the magnetic bore for 5 minutes followed by a sequential acquisition of MR raw data during 10 minutes of cooling period. The acquired raw data were transferred to PC after then the keyhole images were reconstructed by taking the central part of K-space data with 128, 64, 32 and 16 phase encoding lines while the remaining peripheral parts were taken from the 1st reference raw data. The RMS errors were compared with the 256 full encoded self-reference temperature image while the SNR values were compared with the zero filling images. RESULTS: As phase encoding number at the center part on the keyhole temperature images decreased to 128, 64, 32 and 16, the RMS errors of the measured temperature increased to 0.538, 0.712, 0.768 and 0.845degrees C, meanwhile SNR values were maintained as the phase encoding number of keyhole part is reduced. CONCLUSION: This study shows that the keyhole technique is successfully applied to temperature monitoring procedure to increases the temporal resolution by standardizing the matrix size, thus maintained the SNR values. In future, it is expected to implement the MR real time thermal imaging using keyhole method which is able to reduce the scan time with minimal thermal variations.

Long-term Follow-up Sonography of Benign Cystic Thyroid Nodules after a Percutaneous Ethanol Injection: The Incidence of Malignancy-mimicking Nodules

PURPOSE: To evaluate the incidence of malignancy-mimicking sclerosed thyroid nodules, from long-term follow-up ultrasonography (US) after an US-guided percutaneous ethanol injection (PEI). MATERIALS AND METHODS: We examined 86 benign cystic thyroid nodules from 80 patients. The nodules were classified into two groups based on whether an aspiration (Group A, n=26) or non-aspiration (Group B, n=60) of infused ethanol was performed. The final follow-up US over 12 months was performed in all patients. RESULTS: Of the 86 nodules, the cystic portion of 82 (95.3%) cases, from 76 patients, completely disappeared subsequent to the first follow-up US (Group A, n=24, Group B, n=58) (Chi-square test, p>0.05). Moreover, 46 sclerosed thyroid nodules showed two or more of the 'five sonographic criteria' upon a follow-up US (Group A, n=13, 50.0%, Group B, n=32, 53.3%). A higher ratio of the cystic portion of the nodules was associated with a higher incidence of the 'five sonographic criteria' for malignancies detected via a follow-up US (p<0.01; Student's t-test). CONCLUSION: For the long-term follow-up US, the 'five sonographic criteria' were observed in half the patients who received US-guided PEI. Also, by acknowledging the possibility that sonographic findings mimic a malignancy, since the sclerosed thyroid nodule, patients may avoid an unnecessary biopsy.

Preliminary Study on the MR Temperature Mapping using Center Array-Sequencing Phase Unwrapping Algorithm

PURPOSE: To investigate the feasibility and accuracy of Proton Resonance Frequency (PRF) shift based magnetic resonance (MR) temperature mapping utilizing the selfdeveloped center array-sequencing phase unwrapping (PU) method for non-invasive temperature monitoring. MATERIALS AND METHODS: The computer simulation was done on the PU algorithm for performance evaluation before further application to MR thermometry. The MR experiments were conducted in two approaches namely PU experiment, and temperature mapping experiment based on the PU technique with all the image postprocessing implemented in MATLAB. A 1.5T MR scanner employing a knee coil with T2* GRE (Gradient Recalled Echo) pulse sequence were used throughout the experiments. Various subjects such as water phantom, orange, and agarose gel phantom were used for the assessment of the self-developed PU algorithm. The MR temperature mapping experiment was initially attempted on the agarose gel phantom only with the application of a custom-made thermoregulating water pump as the heating source. Heat was generated to the phantom via hot water circulation whilst temperature variation was observed with T-type thermocouple. The PU program was implemented on the reconstructed wrapped phase images prior to map the temperature distribution of subjects. As the temperature change is directly proportional to the phase difference map, the absolute temperature could be estimated from the summation of the computed temperature difference with the measured ambient temperature of subjects. RESULTS: The PU technique successfully recovered and removed the phase wrapping artifacts on MR phase images with various subjects by producing a smooth and continuous phase map thus producing a more reliable temperature map. CONCLUSION: This work presented a rapid, and robust self-developed center arraysequencing PU algorithm feasible for the application of MR temperature mapping according to the PRF phase shift property.

The Steroid Effect on the Blood-Ocular Barrier Change Induced by Triolein Emulsion as seen on Contrast-Enhanced MR Images

OBJECTIVE: The purpose of this study is to evaluate the effect of dexamethasone on the damaged blood-ocular barrier caused by triolein emulsion, using contrast-enhanced MR imaging. MATERIALS AND METHODS: An emulsion of 0.1-mL triolein in 20 mL of saline was infused into the carotid arteries of 32 cats, 12 cats were placed in the treatment group and 18 cats were placed in the Control group. Thirty minutes after the infusion of triolein emulsion, a set of orbital pre- and post-contrast T1-weighted MR images (T1WIs) were obtained. Infusion of 10 mg/kg dexamethasone into the ipsilateral carotid artery of each of the cats in the treatment group cats and 20 mL saline in each of the cats in the control group was given. A second set of pre- and post-contrast orbital T1WIs were obtained three hours following triolein emulsion infusion. Qualitative analysis was performed for the the anterior chamber (AC), the posterior chamber (PC), and in the vitreous humor of the ipsilateral and contralateral eyes. The signal intensity ratios of the ipsilateral eye over the contralateral eye were quantitatively evaluated in the three ocular chambers on the first and second set of T1WIs, and were then statistically compared. RESULTS: Qualitatively, the AC, the PC or the vitreous did not show immediate contrast enhancement on the first and the second set of post-contrast T1WIs. However, the AC and the PC showed delayed contrast enhancement for both groups of cats on the second pre-contrast T1WIs. No enhancement or minimally delayed enhancement was seen for the vitreous humor. Quantitatively, the signal intensity ratios in the PC of the treatment group of cats were statistically lower than the ratios of the control group of cats for the second set of T1WIs (p = 0.037). The AC and vitreous showed no statistically significant difference between the feline treatment group and control group (p > 0.05). CONCLUSION: Contrast-enhanced MR images revealed increased vascular permeability in the PC of the eye after infusion of triolein emulsion. Dexamethasone seems to decrease the breakdown of the blood-aqueous barrier in the PC.

Metastatic Spinal Epidural Leiomyoma: A Case Report

We report here on a case of a spinal extradural leiomyoma in a 67-year-old woman, and this tumor was in a very unusual location for a leiomyoma. Because the patient underwent hysterectomy for a uterine leiomyoma 20 years ago, we can speculate that the spinal lesion was a metastatic leiomyoma.

Gd(DTPA)2--enhanced, and Quantitative MR Imaging in Articular Cartilage

PURPOSE: Early degeneration of articular cartilage is accompanied by a loss of glycosaminoglycan (GAG) and the consequent change of the integrity. The purpose of this study was to biochemically quantify the loss of GAG, and to evaluate the Gd(DTPA)2--enhanced, and T1, T2, rho relaxation map for detection of the early degeneration of cartilage. MATERIALS AND METHODS: A cartilage-bone block in size of 8mmx10 mm was acquired from the patella in each of three pigs. Quantitative analysis of GAG of cartilage was performed at spectrophotometry by use of dimethylmethylene blue. Each of cartilage blocks was cultured in one of three different media: two different culture media (0.2 mg/ml trypsin solution, 1mM Gd (DTPA)2- mixed trypsin solution) and the control media (phosphate buffered saline (PBS)). The cartilage blocks were cultured for 5 hrs, during which MR images of the blocks were obtained at one hour interval (0 hr, 1 hr, 2 hr, 3 hr, 4 hr, 5 hr). And then, additional culture was done for 24 hrs and 48 hrs. Both T1-weighted image (TR/TE, 450/22 ms), and mixed-echo sequence (TR/TE, 760/21-168ms; 8 echoes) were obtained at all times using field of view 50 mm, slice thickness 2 mm, and matrix 256x512. The MRI data were analyzed with pixel-by-pixel comparisons. The cultured cartilage-bone blocks were microscopically observed using hematoxylin & eosin, toluidine blue, alcian blue, and trichrome stains. RESULTS: At quantitation analysis, GAG concentration in the culture solutions was proportional to the culture durations. The T1-signal of the cartilage-bone block cultured in the Gd(DTPA)2- mixed solution was significantly higher (42% in average, p0.05). However the focal increase in T1 relaxation time at superficial and transitional layers of cartilage was seen in Gd(DTPA)2- mixed culture. Toluidine blue and alcian blue stains revealed multiple defects in whole thickness of the cartilage cultured in trypsin media. CONCLUSION: The quantitative analysis showed gradual loss of GAG proportional to the culture duration. Microimagings of cartilage with Gd(DTPA)2--enhancement, relaxation maps were available by pixel size of 97.9x195 micrometer. Loss of GAG over time better demonstrated with Gd(DTPA)2--enhanced images than with T1, T2, rho relaxation maps. Therefore Gd(DTPA)2--enhanced T1-weighted image is superior for detection of early degeneration of cartilage.

Ex Vivo 1H MR Spectroscopy: Normal gastric and cancer tissue

PURPOSE: In this study, we attempted to ascertain the proton magnetic resonance spectroscopy (1H MRS) peak characteristics of human gastric tissue layers and finally to use the metabolic peaks of MRS to distinguish between normal and abnormal gastric specimens. MATENRIALS AND METHODS: Ex-vivo 1H MRS examinations of thirty-five gastric specimens were performed to distinguish abnormal gastric tissues invaded by carcinoma cells from normal stomach-wall tissues. High-resolution 400-MHz (9.4-T) 1H nuclear magnetic resonance (NMR) spectra of two gastric layers, a proper muscle layer, and a composite mucosa- submucosa layer were compared with those of clinical 64- MHz (1.5-T) MR spectra. Three-dimensional spoiled gradient recalled (SPGR) images were used to determine the size and the position of a voxel for MRS data collection. RESULTS: For normal gastric tissue layers, the metabolite peaks of 400-MHz 1H MRS were primarily found to be as follows: lipids at 0.9 ppm and 1.3 ppm; alanine at 1.58 ppm; N-acetyl neuraminic acid (sialic acid) at 2.03 ppm; and glutathione at 2.25 ppm in common. The broad and feature-less spectral peaks of the 64-MHz MRS were bunched near 0.9, 1.3, and 2.0, and 2.2 ppm in human specimens without respect to layers. In a specimen (Borrmmann type III) with a tubular adenocarcinoma, the resonance peaks were measured at 1.26, 1.36 and 3.22 ppm. All the peak intensities of the spectrum of the normal gastric tissue were reduced, but for gastric tumor tissue layers, the lactate peak split into 1.26 and 1.39 ppm, and the peak intensity of choline at 3.21 ppm was increased. CONCLUSION: We found that decreasing lipids, an increasing lactate peak that split into two peaks, 1.26 ppm and 1.36 ppm, and an increasing choline peak at 3.22 ppm were markers of tumor invasion into the gastric tissue layers. This study implies that MR spectroscopy can be a useful diagnostic tool for gastric cancer.

Ex Vivo 1H MR Spectroscopy: Normal gastric and cancer tissue

PURPOSE: In this study, we attempted to ascertain the proton magnetic resonance spectroscopy (1H MRS) peak characteristics of human gastric tissue layers and finally to use the metabolic peaks of MRS to distinguish between normal and abnormal gastric specimens. MATENRIALS AND METHODS: Ex-vivo 1H MRS examinations of thirty-five gastric specimens were performed to distinguish abnormal gastric tissues invaded by carcinoma cells from normal stomach-wall tissues. High-resolution 400-MHz (9.4-T) 1H nuclear magnetic resonance (NMR) spectra of two gastric layers, a proper muscle layer, and a composite mucosa- submucosa layer were compared with those of clinical 64- MHz (1.5-T) MR spectra. Three-dimensional spoiled gradient recalled (SPGR) images were used to determine the size and the position of a voxel for MRS data collection. RESULTS: For normal gastric tissue layers, the metabolite peaks of 400-MHz 1H MRS were primarily found to be as follows: lipids at 0.9 ppm and 1.3 ppm; alanine at 1.58 ppm; N-acetyl neuraminic acid (sialic acid) at 2.03 ppm; and glutathione at 2.25 ppm in common. The broad and feature-less spectral peaks of the 64-MHz MRS were bunched near 0.9, 1.3, and 2.0, and 2.2 ppm in human specimens without respect to layers. In a specimen (Borrmmann type III) with a tubular adenocarcinoma, the resonance peaks were measured at 1.26, 1.36 and 3.22 ppm. All the peak intensities of the spectrum of the normal gastric tissue were reduced, but for gastric tumor tissue layers, the lactate peak split into 1.26 and 1.39 ppm, and the peak intensity of choline at 3.21 ppm was increased. CONCLUSION: We found that decreasing lipids, an increasing lactate peak that split into two peaks, 1.26 ppm and 1.36 ppm, and an increasing choline peak at 3.22 ppm were markers of tumor invasion into the gastric tissue layers. This study implies that MR spectroscopy can be a useful diagnostic tool for gastric cancer.

The Influence of Changes in Cervical Lordosis on Bulging Disk and Spinal Stenosis: Functional MR Imaging

PURPOSE: To assess the effect of lordotic curve change of the cervical spine on disk bulging and spinal stenosis by means of functional cervical MR imaging at the flexion and extension position. MATERIALS AND METHODS: Using a 1.5T imager, kinematic MR examinations of 25 patients with degenerative spondylosis (average age, 41 years) were performed at the neutral, flexed and extended position of the cervical spine. Sagittal T2-weighted turbo spin-echo images were obtained during each of the three phases. Lordotic an-gle, bulging thickness of the disk, AP diameter of the spinal canal, and distance between the disk and spinal cord were measured on the workstation at each disk level. After qualitative independent observation of disk bulging, one of four grades(0, normal; 1, mild; 2, moderate; 3, marked) was assigned at each phase, and after further comparative observation, one of five scores (-2, prominent decrease; -1, mild decrease; 0, no change; 1, notable increase; 2 prominent increase) was also assigned. In addition, bulging thickness of the disk was measured and compared at the neutral, flexed, and extended positions. RESULTS: Average angles of the cervical spine were 160.5+/-5.9 degrees (neutral position, lordotic angle); 185.4+/-8.5 degrees (flexion, kyphotic angle); and 143.7+/-6.7 degrees (extension, lordotic angle). Average grades of disk bulging were 0.55 at the neutral position, 0.16 at flexion, and 0.7 at extension. Comparative observation showed that average scores of disk bulging were -0.39 at flexion and 0.31 at extension. The bulging thickness of the disk decreased by 24.2% at flexion and increased by 30.3% at extension, while the diameter of the spinal canal increased by 4.5% at flexion and decreased by 3.6% at extension. The distance from the posterior margin of the disk to the anterior margin of the spinal cord decreased at both flexion(6.6%) and extension(19.1%). CONCLUSION: Functional MRI showed that compared with the neutral position, disk bulging and spinal stenosis are less prominent at flexion and accentuated at extension. The results demonstrate the need to consider the extent to which changes in the cervical lordotic curve affect the degree of disk bulging and spinal stenosis.

MR Findings of Calvarial Eosinophilic Granuloma

PURPOSE: The purpose of this study was to evaluate the MR findings of calvarial eosinophilic granuloma. MATERIALS AND METHODS: We reviewed the MR imaging studies of nine patients [M:F=3:6, aged 6 -35 (mean, 20.5) years] with pathologically proven eosinophilic granuloma in the calvaria. The findings were evaluated for involvement of the diploic space, changes in adjacent bone marrow, distinction of the transitional zone, pattern of bone destruction, signal intensity and contrast enhancement of the tumor, and contrast enhancement of the adjacent dura. RESULTS: All lesions involved the diploic space, showed no change in adjacent bone marrow, and had a distinct transitional zone. In most (8/9) cases there was asymmetric bony destruction. On T1-weighted images, signal intensities of the tumors varied, while on T2-weighted images, hyperintensity was observed in seven cases, isointensity in one, and hypointensity in one. After the administration of contrast material, enhancement was homogeneous in four cases and inhomogeneous in five. Enhancement of the adjacent dura was demonstrated in all nine cases. CONCLUSION: The characteristic MR findings of calvarial eosinophilic granuloma are variable signal intensity on T1WI, high signal intensity on T2WI, and marked contrast enhancement; in addition, there is a distinct transitional zone, asymmetrical bony destruction, and associated dural enhancement.

Usefulness of Combined Fat- and Fluid-Suppressed SPIR-FLAIR Images in Optic Neuritis: Comparison with Fat-Suppressed SPIR or STIR Images or STIR images

PURPOSE: To compare the usefulness of combined fat- and fluid-suppressed selective partial inversion recovery-fluid attenuated inversion recovery(SPIR-FLAIR) images in the detection of high signal intensity of the optic nerve in optic neuritis with that of fat-suppressed selective partial inversion recovery(SPIR) or short inversion time inversion recovery(STIR) images. MATERIALS AND METHODS: Two radiologists independently analyzed randomly mixed MR images of 16 lesions in 14 patients (M:F=7:7; mean age, 40years) in whom optic neuritis had been clinically diagnosed. All subjects underwent both SPIR-FLAIR and fat-suppressed SPIR or STIR imaging, in a blind fashion. In order to evaluate the optic nerve, coronal images perpendicular to its long axis were obtained. The detection rate of high signal intensity of the optic nerve, the radiologists' preferred imaging sequences, and intersubject consistency of detection were evaluated. 'High signal intensity' was defined as the subjective visual evaluation of increased signal intensity compared with that of the contralateral optic nerve or that of white matter. RESULTS: The mean detection rate of high signal intensity of the optic nerve was 90% for combined fat- and fluid-suppressed SPIR-FLAIR images, and 59% for fat-suppressed SPIR or STIR images. In all cases in which the signal intensity observed on SPIR-FLAIR images was normal, that on fat-suppressed SPIR or STIR images was also normal. The radiologists preferred the contrast properties of SPIR-FLAIR to those of fat-suppressed SPIR or STIR images. CONCLUSION: In the diagnosis of optic neuritis using MRI, combined fat- and fluid-suppressed SPIR-FLAIR images were more useful for the detection of high signal intensity of the optic nerve than fat-suppressed SPIR or STIR images. For the evaluation of optic neuritis, combined fat- and fluid-suppressed SPIR-FLAIR imaging is superior to fat-suppressed SPIR or STIR imaging.

Serial MRI Findings in a Clinically Diagnosed Adult Onset Leigh Syndrome

Adult onset Leigh syndrome is a very rare neurodegenerative disorder of unknown cause. We report the evolution of the lesions on serial MRIs in a 38-year-old man with clinically diagnosed Leigh syndrome. We emphasize that the mammillary bodies can be involved during the disease course and that premortem diagnosis of Leigh syndrome is pos-sible, if a characteristic distribution of lesions can be demonstrated on MRI.

Evaluation of Therapeutic Effect of Acoustic Schwannoma After Gamma-Knife Radiosurgery using Follow-up MRI

PURPOSE: To evaluate, using short-term follow-up MR imagings, the usefulness of gamma-knife radiosurgery in patients with acoustic schwannoma. MATERIALS AND METHODS: In 34 patients (M:F=11:23, aged 11 -69 years) with acoustic schwannoma, eleven of whom had undergone microsurgical resection prior to gamma-knife radiosurgery, we retrospectively reviewed the serial MR imaging findings obtained before and after this procedure. Analysis focused on post-surgical changes in tumor volume and intratumoral enhancement, and the follow-up period ranged from 3 to 44 months. RESULTS: Follow-up imaging revealed that after radiosurgery, tumor size had decreased in 17 cases (50%), was unchanged in 14 (41.2%), and had increased in three (8.8%). Local tumor control was achieved in 31 of 34 cases (91.2%). Objectively defined tumor shrinkage was seen within 3 to 24 (median, 12) months of treatment, the rate of shrinkage increasing with longer follow-up. Three to 16 (median, 6) months after treatment, loss of central tumor enhancement was evident in 28 cases(82.4%). In 25 of 28 patients with intratumoral necrosis (89.3%), tumors were either smaller of their size was unchanged. Three to six (mean, 3.6) months after treatment, five cases demonstrated a transient size increase. CONCLUSION: Gamma-knife radiosurgery effectively controlled the growth of acoustic schwannoma, and intra-tumoral necrosis appears to be a predictable sign for decreased tumor size.

Evaluation of Therapeutic Effect of Acoustic Schwannoma After Gamma-Knife Radiosurgery using Follow-up MRI

PURPOSE: To evaluate, using short-term follow-up MR imagings, the usefulness of gamma-knife radiosurgery in patients with acoustic schwannoma. MATERIALS AND METHODS: In 34 patients (M:F=11:23, aged 11 -69 years) with acoustic schwannoma, eleven of whom had undergone microsurgical resection prior to gamma-knife radiosurgery, we retrospectively reviewed the serial MR imaging findings obtained before and after this procedure. Analysis focused on post-surgical changes in tumor volume and intratumoral enhancement, and the follow-up period ranged from 3 to 44 months. RESULTS: Follow-up imaging revealed that after radiosurgery, tumor size had decreased in 17 cases (50%), was unchanged in 14 (41.2%), and had increased in three (8.8%). Local tumor control was achieved in 31 of 34 cases (91.2%). Objectively defined tumor shrinkage was seen within 3 to 24 (median, 12) months of treatment, the rate of shrinkage increasing with longer follow-up. Three to 16 (median, 6) months after treatment, loss of central tumor enhancement was evident in 28 cases(82.4%). In 25 of 28 patients with intratumoral necrosis (89.3%), tumors were either smaller of their size was unchanged. Three to six (mean, 3.6) months after treatment, five cases demonstrated a transient size increase. CONCLUSION: Gamma-knife radiosurgery effectively controlled the growth of acoustic schwannoma, and intra-tumoral necrosis appears to be a predictable sign for decreased tumor size.

Malignant Rhabdoid Tumor

Primary CNS rhabdoid tumor is an extremely rare malignant tumor affecting children. Clinical, radiological, and histopathological features of malignant rhabdoid tumor are presented. Following the complete extirpation of a large tumor at the frontoparietal region, a 16-year-old male patient suffered from several local recurrences. The neoplasm is, defined by its histopathological and ultrastructural characteristics and by the pattern of its antigenicity as a malignant rhabdoid tumor(MRT).