Generating Motion- and Distortion-Free Local Field Map Using 3D Ultrashort TE MRI: Comparison with T₂* Mapping

PURPOSE: To generate phase images with free of motion-induced artifact and susceptibility-induced distortion using 3D radial ultrashort TE (UTE) MRI.MATERIALS AND METHODS: The field map was theoretically derived by solving Laplace's equation with appropriate boundary conditions, and used to simulate the image distortion in conventional spin-warp MRI. Manufacturer's 3D radial imaging sequence was modified to acquire maximum number of radial spokes in a given time, by removing the spoiler gradient and sampling during both rampup and rampdown gradient. Spoke direction randomly jumps so that a readout gradient acts as a spoiling gradient for the previous spoke. The custom raw data was reconstructed using a homemade image reconstruction software, which is programmed using Python language. The method was applied to a phantom and in-vivo human brain and abdomen. The performance of UTE was compared with 3D GRE for phase mapping. Local phase mapping was compared with T₂* mapping using UTE.RESULTS: The phase map using UTE mimics true field-map, which was theoretically calculated, while that using 3D GRE revealed both motion-induced artifact and geometric distortion. Motion-free imaging is particularly crucial for application of phase mapping for abdomen MRI, which typically requires multiple breathold acquisitions. The air pockets, which are caught within the digestive pathway, induce spatially varying and large background field. T₂* map, that was calculated using UTE data, suffers from non-uniform T₂* value due to this background field, while does not appear in the local phase map of UTE data.CONCLUSION: Phase map generated using UTE mimicked the true field map even when non-zero susceptibility objects were present. Phase map generated by 3D GRE did not accurately mimic the true field map when non-zero susceptibility objects were present due to the significant field distortion as theoretically calculated. Nonetheless, UTE allows for phase maps to be free of susceptibility-induced distortion without the use of any post-processing protocols.

Quantitative Evaluation of the First Order Creatine-Kinase Reaction Rate Constant in in vivo Shunted Ovine Heart Treated with Oxandrolone Using Magnetization Transfer 31P Magnetic Resonance Spectroscopy (MT-31P-MRS) and 1H/31P Double-Tuned Surface Coil: a Preliminary Study

PURPOSE: Children born with single ventricle physiology demonstrate poor growth rate and suffer from malnutrition, which lead to increased morbidity and mortality in this population. We assume that an anabolic steroid, oxandrolone, will promote growth in these infants by improving myocardial energy utilization. The purpose of this paper is to study the efficacy of oxandrolone on myocardial energy consumption in these infants. MATERIALS AND METHODS: We modeled single ventricle physiology in a lamb by prenatally shunting the aorta to the pulmonary artery and then postnatally, we monitored cardiac energy utilization by quantitatively measuring the first order reaction rate constant, kf of the creatine-kinase reaction in the heart using magnetization transfer 31P magnetic resonance spectroscopy, home built 1H/31P transmit/receive double tuned coil, and transmit/receive switch. We also performed cine MRI to study the structure and dynamic function of the myocardium and the left ventricular chamber. The spectroscopy data were processed using home-developed python software, while cine data were analyzed using Argus software. RESULTS: We quantitatively measured both the first order reaction rate constant and ejection fraction in the control, shunted, and the oxandrolone-treated lambs. Both kf and ejection fraction were found to be more significantly reduced in the shunted lambs compared to the control lambs, and they are increased in oxandrolone-treated lambs. CONCLUSION: Some improvement was observed in both the first order reaction rate constant and ejection fraction for the lamb treated with oxandrolone in our preliminary study.

Accuracy of Diffusion Tensor Imaging for Diagnosing Cervical Spondylotic Myelopathy in Patients Showing Spinal Cord Compression

OBJECTIVE: To assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings. MATERIALS AND METHODS: A total of 33 patients who underwent MRI of the cervical spine including DTI using two-dimensional single-shot interleaved multi-section inner volume diffusion-weighted echo-planar imaging and whose spinal cords were deformed but showed no signal changes on conventional MRI were the subjects of this study. Mean diffusivity (MD), longitudinal diffusivity (LD), radial diffusivity (RD), and fractional anisotropy (FA) were measured at the most stenotic level. The calculated performance of MD, FA, MD∩FA (considered positive when both the MD and FA results were positive), LD∩FA (considered positive when both the LD and FA results were positive), and RD∩FA (considered positive when both the RD and FA results were positive) in diagnosing CSM were compared with each other based on the estimated cut-off values of MD, LD, RD, and FA from receiver operating characteristic curve analysis with the clinical diagnosis of CSM from medical records as the reference standard. RESULTS: The MD, LD, and RD cut-off values were 1.079 × 10⁻³, 1.719 × 10⁻³, and 0.749 × 10⁻³ mm²/sec, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD∩FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD∩FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD∩FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD∩FA (p = 0.003), FA and LD∩FA (p < 0.001), FA and RD∩FA (p < 0.001), MD and LD∩FA (p = 0.024) and MD and RD∩FA (p = 0.024). CONCLUSION: Fractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.

Reversal of Apparent Diffusion Coefficient (ADC) Following Transient Focal Cerebral Ischemia in Cats

PURPOSE: To determine the minimal threshold ADC ratio suggesting reversible ischemia in a temporary model of MCAO. MATERIALS AND METHODS: Seven Korean cats weighing 3-3.5 kg were used as a temporary model of MCAO. The MCA was occluded for 1 hour, and diffusion-weighted images (DWI), and ADC and regional cerebral blood volume (rCBV) maps, were obtained at 1, 3, 6 and 24 hours after reperfusion using a 1.5T MR unit. The Cats were sacrificed 24 hours after imaging. Triphenyl tetrazolium chloride (TTC) staining of brain slices was performed, and DWI images and TTC-stained brain slices were compared with the naked eye. Reversible ischemia was defined as the area of high signal intensity at 1-hour DWI that normalized at follow-up DWI and in which TTC staining was normal. Using the ADC image obtained at 1 hour after reperfusion, 60 ADC ratios were obtained in the periphery of the infarct and reversible ischemia. Tissue survival showing normal TTC staining was used for final determination. The sensitivity and specificity of each ADC ratio was obtained and an ROC curve was plotted. RESULTS: Five of seven cats showed the reversible ischemia. An area of high signal intensity was seen on DWI images obtained 1 hour after reperfusion, and this improved at follow-up imaging. The distribution of the ADC ratio in the periphery of the infarct core was 0.71-0.81, and in the periphery of reversible ischemia it was 0.79-0.93. The ADC ratio of 0.80 obtained 1 hr after reperfusion predicted the survival of the ischemic tissue with 93% sensitivity and 90% specificity. The ADC ratio of the reversible ischemia was 0.82+/-0.03 at 1 hour after reperfusion, and this was higher than that of the infarct, which was 0.74+/-0.03. CONCLUSION: The minimal threshold ADC ratio suggesting reversible ischemia in this temporary model of MCAO was 0.80.

Significance of 99mTc-ECD SPECT in Acute and Subacute Ischemic Stroke: Comparison with MR Images Including Diffusion and Perfusion Weighted Images

99mTc-ECD SPECT is valuable for the evaluation of cell viability and function. The purpose of the present study was to evaluate the significance of 99mTc-ECD brain SPECT in ischemic stroke. We compared 99mTc-ECD brain SPECT with perfusion and diffusion weighted images (PWI, DWI). Ten patients with acute and early subacute ischemic stroke were included in this prospective study. T2-weighted images (T2WI), DWI, PWI and 99mTc-ECD SPECT were obtained during both the acute/early subacute and late subacute stages. In the case of PWI, time to peak (TTP) and regional cerebral blood volume (rCBV) maps were obtained. The rCBV map and 99mTc-ECD SPECT images were compared in 8 lesions using delta AI. The asymmetry index (AI) was calculated as (Ci - Cc) X 200 / (Ci + Cc); where Ci is the mean number of pixel counts of an ipsilateral lesion and Cc is the mean number of pixel counts of the normal contralateral hemisphere. delta AI was defined as AIacute - AIsubacute in the ischemic core and periphery. PWI and 99mTc-ECD SPECT detected new lesions of the hyperacute stage or of evolving stroke more accurately than T2WI and DWI. 99mTc-ECD SPECT was able to localize the infarct core and peri-infarct ischemia in all lesions in both the acute and the subacute stages. delta AI was higher in the rCBV map than in the 99mTc-ECD SPECT images in the ischemic core (p = 0.063) and in the periphery (p = 0.091). In the 99mTc-ECD SPECT images, delta AI was higher in the ischemic core than in the periphery (p = 0.028). During the subacute stage, 99mTc-ECD SPECT detected all the lesions without the pseudonormalization seen in the MR images of 5/11 lesions. Based on this study, 99mTc-ECD SPECT is comparable to PWI in terms of its ability to detect acute stroke and is more useful than PWI in the case of subacute infarction.

Comparison of Surface and Saddle Endoanal Coil to Evaluate anal Sphincter in Infants and Young Children: Experimental Study Using Phantom and Cats

PURPOSE: We designed an inside-out-type endoanal surface and saddle coil to evaluate the anal sphincter of young children who have difficulty in controlling defecation after the correction of anorectal malformation, and compared two coils using an imaging phantom and cats. MATERIALS AND METHODS: Using two coils, T1- and T2-weighted axial and coronal images of the phantom and of the anorectal region of cats were obtained, and the results were compared in terms of changes in signal intensity and SNR according to the distance from the coil's surface. We also compared the capability of the coils to delineate the internal and external anal sphincter of cat anorectum, both of which are important in the control of defecation. RESULTS: The saddle coil was slightly superior to the surface coil in terms of SNR, but inferior in terms of the signal intensity of the region of interest of the cat's anorectum. Moreover, artifacts of low signal intensity appeared in an azimuthal direction on axial images acquired using the saddle coil and prohibited delineation of the whole of the anal sphincter. In terms of image quality, the surface coil was therefore superior to the saddle coil. CONCLUSION: Our findings suggest that among inside-out-type endoanal coils, the surface coil may be superior to the saddle coil in MR imaging to evaluate the anal sphincter of young children.

Diffusion-weighted image and MR spectroscopic analysis of a case of MELAS with repeated attacks

We report the clinical and MR manifestations of an 18 year-old girl with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. Recurrent status epilepticus caused reversible cytotoxic edema on diffusion-weighted images (DWI). Initial and one month follow-up MR spectroscopy, after seizure control, showed some discrepancies in the ratio of metabolites. N-acetylaspartate (NAA) partially recovered (NAA/creatine (Cr) ratio: 1.27-->1.84). This was because of a normalization of decreased NAA due to cellular dysfunction as a result of status epilepticus. A low ratio of NAA/Cr due to abnormal mitochondria remained in the decreased state. Reversible NAA/Cr ratios in the acute lesion suggested that NAA reflects the neuronal function as well as the level of neuronal structural damage. The altered NAA/Cr ratio better correlated with the abnormal signal intensity area of T2-weighted images (T2WI) and DWI than the lactate (Lac)/Cr ratio. With conservative treatment with anti-epileptics not accompanied by coenzyme Q or sodium dichloroacetate, lactate persistently increased (Lac/Cr ratio: 1.01-->1.21) because of the continued production of lactate in cells with respiratory deficiency, which is the main pathology of MELAS.

Correlation of Laminated MR Appearance of Artcular Cartilage with Histology

PURPOSE: To determine the correlation of laminae of different signal intensities (SI) of articular cartilage,as seen on magnetic resonance (MR) imaging with histologic layes, using artificially constructed landmarks. MATERIALS AND METHODS: For a landmark that can exactly correlate the cartilage specimen with the MR image, five'V'-shaped markings of different depths were made on the surface of bovine patella. Both T1-weighted (TR/TE :300/14) and FSE T2-weighted images (TR/TE : 2000/53) were obtained on a 1.5T system with high gradient echostrength (25mT/m) and a voxel size of 78x78x2000 micrometer. Images were obtained with 1) changed frequency-encodingdirections on T1-weighted study, and 2) changed readout gradient strength (x2, x1/2) on T2-weighted sequence.Raw image data were transferred to a workstation and signal intensity profile was generated for each image. 1 : 1correlation of histologic specimens and MR images was performed. RESULTS: Line Profile through the cartilageshowed few peaks, suggesting changes in signal intensity profile in the cartilage. On the basis of artificiallandmarks, the histologic zone was accurately identified. The histologic tangential and transitional zonescorrelated with superficial high SI on T1WI, as well as high and low SII on T2WI. On T1WI, the radial zonecorrelated with a lamina of intermediate SI, and on T2WI, with a lamina for which SI gradually decreased from highto low. Additional well-defined low and intermediate SI bands were noted on bovine T1WI in the lower radial zone.In both T1 and T2 studies, calcified cartilage layers were of low SI. On T1-weighted study, changes in thedirection of frequency gradient did not lead to changes in the laminae. The alteration of readout gradientstrengths did not result in an inversely proportional difference in the thickness of the laminae. These becamemore distinct thus ruling out chemical shift and susceptibility artifacts. CONCLUSION: The laminated appearanceof articular cartilage, as seen on spin echo and fast spin-echo MR images, correlated with histologic layersrather than susceptibility or chemical shift artifacts.

MR Imaging of Experimental Focal Cerebral Ischemia in Cats: Temporal Evolution of Hyperacute Stroke

PURPOSE: To evaluate the temporal evolution of the ischemic area and trace ratio, and to define ischemic penumbra within the hyperacute experimental focal cerebral ischemia model. MATERIALS AND METHODS: A focal cerebral ischemia model of middle cerebral artery occlusion (MCAO) was constructed in twelve Korean cats weighing 2 -3 Kg. T2-weighted images (T2WI) and diffusion-weighted images(DWI) were obtained using a 1.5T MR imager. Trace images were reconstructed after post-image processing with IDL 5.0. The trace ratio (ipsilateral trace value/contralateral trace value) was calculated in the ischemic core and periphery, and MR images were obtained at 1, 3, 6, and 24 hrs after MCAO. The twelve cats were divided into three groups, and 4, 5, and 3 cats were sacrified after obtaining MR images at 3, 6, and 24 hrs after MCAO, respectively. After 2% triphenyl tetrazolium chloride (TTC) solution and formalin preparation, the infarction area of the brain slice and T2WI and DWI trace images of the same slice were compared. The trace ratio was calculated at the peripheral portion of the ischemic core, which was the presumed ischemic penumbra in images obtained 1hr after MCAO. Changes in trace ratio in the ischemic core and infarction territory were also evaluated according to time. RESULTS: The trace ratio in the peripheral portion of the ischemic core was 0.71 +/- 0.03. The region where the trace ratio was 0.83 +/- 0.06 in images obtained 1 hour after MCAO was presumed to be ischemic penumbra; the region progressed to infarction in images taken during the next time period. In all cases the abnormal area of trace images was larger than that seen on DWI. The trace ratio was lower, by 6.2 %, 3 -6hrs after MCAO than at any other time. In cat number 3, the trace radio decreased rapidly and progressively, by 21%, during the first six hours. For 3 -6hrs after MCAO, the area of infarction showed progressive enlargement. CONCLUSION: Within six hours of MCAO, ischemic penumbra is progressively incorporated into the ischemic core. In the experimental focal cerebral ischemia model, an area of trace ratio larger than 0.71 and less than 1may be defined as ischemic penumbra.

Osteosarcoma: Correlation of T1 Map and Histology Map

PURPOSE: To determine whether T1 mapping shows regional differences between viable and necrotic regions of osteosarcomas after anticancer chemotherapy and to assess whether this mapping is able to express the characteristics of various intramural tissue components. MATERIALS AND METHODS: Eleven of 20 osteosarcomas were included in this study, while the remaining nine were excluded because the tumor site was inappropriate for comparison of T1 map and tumor macrosection. All patients underwent MR imaging for the purpose of T1 mapping, followed by pre-operative chemotherapy and subsequentl limb-salvage surgery. Spin echo pulse sequencing was used with varying TR (100, 200, 400, 800, 1600, and 2400 msec) and a constant TE of 20 msec. Using a C-language software program, T1 relaxation time was calculated on a pixel-by-pixel basis and then a T1 map was generated by using a post-processing program, NIH Image. We attempted correlation of the T1 map and histologic findings, particularly in regions of interest(ROI) if certain areas were different from other regions on either the T1 or histologic map. Value was expressed as an average of the ratio of T1 of ROI and T1 of fat tissue, and this was used as an internal reference for normalization of the measurement. RESULTS: Tumor necrosis was 100%(Grade IV) in six specimens, and over 90 % (Grade III) in five. Viable tumor cells were found mostly in regions with chondroid matrix and seldom in regions with osteoid matrix. Regardless of cell viability, values ranged from 0.9 to 9.87(mean, 4.02) in tumor necrotic area with osteoid matrices, and from 3.04 to 3.9(mean, 3.55) in areas with chondroid matrices. Other regions with fibrous tissue proliferation, hemorrhage, and fatty necrosis showed values of 2.92-9.83(mean, 7.20), 2.65 -5.96(mean, 3.59), and 1.43 -3.11(mean, 2.68) respectively. The values of various tissues overlapped. No statistically significant difference was found between regions in which tumors were viable and those with tumor necrosis. CONCLUSION: Although we hypothesized that areas of necrotic tumor would show an increased water component(proton number) and would have a longer T1 value than viable tumor tissues, our results were otherwise. Necrotic osteosarcoma tissves showed a wide range of T1 values according to the prevailing tissue components.

The Value of True FISP Sequence as a Fast T2-Weighted MR Imaging of Liver: Comparison with Breath-hold Turbo Spin Echo and HASTE Sequence

PURPOSE: To document the relative usefulness of true Fast-imaging steady-state precession(FISP) comparing to breath-hold turbo spin-echo(TSE), and half-Fourier single-shot turbo spin-echo(HASTE) as a fast T2-weighted sequence during hepatic MR imaging. MATERIALS AND METHODS: For 46 patients with 87 focal hepatic lesions(hepatocellular carcinoma, n=26; metastasis. n=5; cavernous hemangioma, n=37; cyst, n=19), we obtained MR imaging of the liver at 1.5T. True FISP, TSE with and without fat-suppresion(FS), and HASTE with and without FS images were obtained during one breath-hold. Images were compared on the basis of tumor detectability and lesion-to-liver contrast-to-noise ratio(CNR). Qualitative analysis of each imaging sequence was also performed in terms of hepatic contour, visibility of vascular landmarks and imaging artifacts. RESULTS: TSE-FS depicted more focal lesions(78/87, 90%) than other sequences(TSE, 75/87=86%;HASTE, 74/87=85%; HASTE-FS, 75/87=86%;true FISP,73/87=84%). However, there was no statistical significance between each sequence(p> .05). Using true FISP or HASTE, there was a statistically significant difference(p< .01) between the CNRs of solid tumors, crystal and hemangiomas. Additionally, true FISP sequence showed better hepatic contour, vascular landmarks and less artifacts comparing with TSE or HASTE regardless of FS(p< .001). CONCLUSION: True FISP sequence allows differentiation between solid tumors, hemangiomas and cystic lesions in terms of CNR, and provides better imaging quality than other fast T2-weighted MR sequences.

Effect of Angulation between Aorta and Renal Artery on Signal Void of Proximal Renal Artery on MR Angiography:Phantom Study

PURPOSE: To determine the effect of anglulation between aorta the and renal artery on signal loss in theproximal renal artery, as seen on magnetic resonance angiography by phantom study using a pulsatile flow model. MATERIALS AND METHODS: Three phantoms of aorta and renal artery with angulation of 90 degree, 60 degree, and 30 degree wereobtained. Pulsatile recirculating flow (44%W/W glycerin, 60bpm) was used for MR angiography. First, axial 3D-TOFimages were obtained and reconstructed. MIP images were analyzed for the presence, area, and location of signalloss. 2D-PC images were obtained perpendicularly to the renal artery at a distance of 0, 4, 8 and 12mm from theostium. To calculate mean signal intensity of the renal artery, a ROI was drawn on 2D-PC images. To correlatesignal loss in 3D-TOF images with signal decrease in 2D-PC, we analyzed changes in signal intensity during onepulse cycle according to change of angulation and distance from the ostium of the renal artery by the calculatedvalues of relative signal decrease and ratio of signal decrease. RESULTS: A signal loss was observed up to 4mmfrom the ostium of the renal artery only in the case of the 90 degree phantom. Because the signal intensity measured inthe 2D-PC image of the 90 degree phantom was higher than that of the 60 degree phantom the signal loss observed in the3D-TOF images of the 90 degree phantom could not be explained by the magnitude of measured signal intensity alone.Relative signal decrease only at a distance of 0 and 4mm in the 90 degree phantom was evenly increased through a pulsecycle and the ratio of signal decrease at the same location was more than 50%. In contrast to the results of the90 degree phantom, those of 60 degree and 30 degree showed decreased of signal intensity mainly during the diastolic phase.CONCLUSION: Signal loss should become apparent at a certain angle between 60 degree and 90 degree. Decreased signalintensity causing signal loss in 3D-TOF was maintained throughout the systolic and diastolic phase of a pulsatilecycle and correlated with the ratio of signal decrease.

Benign and Malignant Musculoskeletal Tumors Evaluated with the Aid of Pa rametric Maximum Slope and Blood Volume Images

PURPOSE: To assess the values of parametric "maximum slope(MS) and blood volume(BV)" images as indicators of tissue vascularization and perfusion in distinguishing benign from malignant musculoskeletal tumors. MATERIAL AND METHODS: Dynamic inversion recovery spin-echo echo-planar imaging (TR/TE/TI/NEX: 1 5 0 0 / 2 4 / 5 00 ms/1; matrix 128 x 128; slice thickeness 5 mm, interleaved) at 1.5-second intervals(200 phases) was performed after intravenous bolus injection of Gd-DTPA. A total of 32 pathologically proven muscu-loskeletal masses(benign 9, malignant 23) were included in this study. MS was derived by fitting a time-intensity curve using a polynomial model. BV was determined by integration until maximum slope was reached. On a pixel-by-pixel basis, MS and BV images were generated and displayed by gray-scale. We selected a region of interest(ROI, more than 6 x 6 pixels) including the highest value of the tumors and calculated mean values of MS and BV. Wilcoxon's signed rank test was used to compare benign tumors with malignant pre- and postchemotherapy tumors. RESULT: The mean values of ROIs selected on MS images were significantly different (p=.008) between benign (mean 3.33, range 0.01 -16.47 ) and prechemotherapy malignant(mean 8.54, range 1.61 -16.90) tumors, as were the mean values of ROIs on BV images(p=.005; benign tumors: mean 162.17, range 91.17 -2 8 3 . 7 ; prechemotherapy malignant tumors: mean 330.18, range 117.5 -845.1). MS and BV values of benign and malignant tumors overlapped but tended to be separated. CONCLUSION: BV and MS images may help distinguish benign from malignant musculoskeletal tumors.

Benign and Malignant Musculoskeletal Tumors Evaluated with the Aid of Pa rametric Maximum Slope and Blood Volume Images

PURPOSE: To assess the values of parametric "maximum slope(MS) and blood volume(BV)" images as indicators of tissue vascularization and perfusion in distinguishing benign from malignant musculoskeletal tumors. MATERIAL AND METHODS: Dynamic inversion recovery spin-echo echo-planar imaging (TR/TE/TI/NEX: 1 5 0 0 / 2 4 / 5 00 ms/1; matrix 128 x 128; slice thickeness 5 mm, interleaved) at 1.5-second intervals(200 phases) was performed after intravenous bolus injection of Gd-DTPA. A total of 32 pathologically proven muscu-loskeletal masses(benign 9, malignant 23) were included in this study. MS was derived by fitting a time-intensity curve using a polynomial model. BV was determined by integration until maximum slope was reached. On a pixel-by-pixel basis, MS and BV images were generated and displayed by gray-scale. We selected a region of interest(ROI, more than 6 x 6 pixels) including the highest value of the tumors and calculated mean values of MS and BV. Wilcoxon's signed rank test was used to compare benign tumors with malignant pre- and postchemotherapy tumors. RESULT: The mean values of ROIs selected on MS images were significantly different (p=.008) between benign (mean 3.33, range 0.01 -16.47 ) and prechemotherapy malignant(mean 8.54, range 1.61 -16.90) tumors, as were the mean values of ROIs on BV images(p=.005; benign tumors: mean 162.17, range 91.17 -2 8 3 . 7 ; prechemotherapy malignant tumors: mean 330.18, range 117.5 -845.1). MS and BV values of benign and malignant tumors overlapped but tended to be separated. CONCLUSION: BV and MS images may help distinguish benign from malignant musculoskeletal tumors.

Comparison of ADC Map with Trace Map in the Normal and Infarct Areas of the Brains of Stro ke Patients

PURPOSE: To compare ADC mapping with trace mapping in normal and infarct areas of the brains of strokepatients. MATERIALS AND METHODS: Eighteen patients diagnosed on the basis of clinical and brain MRI examinationsas suffering from brain infarction were included in this study (hyperacute-1, acute-4, subacute-12, chronic-1).Diffusion weighted images of three orthogonal directions of a patient's brain were obtained by means of a singleshot EPI pulse sequence, using a diffusion gradient with four serial b-factors. Three ADC maps were thenreconstructed by post-image processing and were summed pixel by pixel to yield a trace map. ROIs were selected inthe normal areas of white matter, gray matter and CSF of one hemisphere, and other ROIs of the same size wereselected at the same site of the contralateral hemisphere. ADC and trace values were measured and right/leftratios of ADC and trace values were calculated. Using these values, we then compared the ADC map with the tracemap, and compared the degree of anisotropic diffusion between white matter, gray matter and CSF. Except for three,whose infarct lesions were small and lay over white and gray matter, patients were divided into two groups. Thosewith infarct in the white matter (n=10)were assigned to one group, and those with in-farct in the gray matter(n=5) to the other. ROIs were selected in the infarct area and other ROIs of the same size were selected at thesame site of the contralateral hemisphere. ADC and trace values were measured and infarct/contralateral ratioswere calculated. We then compared ADC ratio with trace ratio in white matter and gray matter infarct. RESULTS: Innormal white matter, the Dxx ratio was 0.980 +/-0.098, the Dyy ratio 1.019 +/-0.086, the Dzz ratio 0.999 +/-0.111,and the trace ratio 0.995 +/-0.031. In normal gray matter, the Dxx ratio was 1.001 +/-0 . 0 5 8 , the Dyy ratio0.996 +/-0.063, Dzz ratio 1.005 +/-0.070, and the trace ratio 1.001 +/-0.028. In CSF, the Dxx ratio was 1.002+/-0.064, the Dyy ratio 1.023 +/-0.055, the Dzz ratio 0.999 +/-0.060 and the trace ratio 1.007 +/-0 . 0 2 1. Becausethe standard deviation of trace ratios (0.05), the trace ratio is moreaccurate representative value. The standard deviation of white matter is greater than that of gray matter or CSF(p<0.05), the degree of anisotropic diffusion in white matter is therefore more severe than in gray matter andCSF. The difference between the ADC ratios and trace ratio is greater in an infarct involving white matter than inone involving gray matter (p<0.05). CONCLUSION: Because a trace map overcomes the anisotropic diffusions of ADCmaps, the former offers better post-image processing. The deviation of ADC ratios owing to the direction ofdiffusion gradient is greater in white matter than in gray matter, and the trace map is thus superior forevaluation of an infarct involving white matter.

Cerebral Blood Volume and Relative Perfusion Rate Mapping with Contrast Enhanced Gradient Echo Echo PlanarImaging

PURPOSE: To assess regional cerebral blood volume and perfusion rate by MR imaging. MATERIALS AND METHODS:Eight normal volunteers and one patient underwent MR imaging after bolus injection of a double dose ofgadoinium(0.2mMol/kg). Gradient-echo EPI pulse sequencing was used, with TR/TE 1500/40msec, flip angle 90o, matrixsize 256X128. One hundred sequential images at the same level were obtained. The time-signal intensity curve wasplotted and converted to a time-concentration ( R2) curve. Relative cerebral blood volume was determined, withintegration of time-concentration curve pixel by pixel. Perfusion rate was determined by calculating maximal slopeof the R2 curve and the time taken to attain this. RESULTS: On volume maps, clear differentiation of gray matter,white matter and major vessels was established. The mean gray and white matter ratio of blood volume was2.78+/-0.43. Slope and volume maps were similar, but in one patient perfusion was apparently greater on the ratemap than on the volume map. CONCLUSION: Cerebral blood volvme and slope map images reflect changes in cerebralhemodynamics. It is thought that these findings can be clinically applied to the determination of vascularity inbrain tumors and acute cerebral ischemia

: 1H-MR spectroscopic and SPECT findings in a patient with MELAS syndrome confirmed by molecular genetic analysis

An eighteen-year-old girl presented recurrent partial and generalized seizures associated with the T-2 high signal intensities of MR brain imaging. Serum and CSF lactate levels were elevated. Muscle biopsy revealed "ragged red fiber" . The diagnosis of MELAS was confirmed by molecular genetic analysis showing 3,243 mtDNA point mutation. Localized proton MR spectroscopy was performed on a GE 1.5 T SIGNA MRI/MRS system and analyzed by STEAM (Stimulated Echo Acquisition Method). 1H-MR spectrocopy demonstrated elevation of lactate contents and decrease of N-acetyl aspartate contents in the involed area. The Tc99m-ECD SPECT revealed multifocal decrease of perfusion in bilateral parietal, temporal and occipital lobe, especially right temporal and left occipital lobe. These features suggest that the pathology of brain lesions of MELAS syndrome may be sub-necrotic incomplete ischemic changes caused by metabolic derangement.

Volumetric measurement of the inflamed synovium of rheumatoid wrist joint for the evaluation of synovitis and remission

PURPOSE: To evaluate the changes and remission of disease activity with changes in inflamed synivial volumes of rheumatoid joints after therapy. MATERIALS AND METHODS: Seven rheumatoid arthritis patients who had been treated with antiinflammatory drugs were followed up. Using NIH imaging and a segmentation technique, pre- and post-enhanced images were measured in subtracted images. Intra- and interobserver variation were evaluated by two radiologists(A and B), using two independent measurements. For comparison, the cases were assigned to one of two groups : remission and non-remission. Changes in ESR and total joint counts(TJC) after therapy were compared with inflamed synovial volumes. RESULTS: Intraobserver variations were 3.2% and 2.7% in A and B, respectively, interobserver variation between A and B was 7.1%. Changes in inflamed synovial volumes correlated well with those in ESR (r=0.88, p<0.009) and TJC (r=0.78, p<0.037) after therapy. Changes between the remission and non-remission group were insignificant, however. CONCLUSION: Changes in inflamed synovial volumes reflect those in the activity of rheumatoid arthritis between pre- and post- treatment. This technique may be used as a tool for predicting therapeutic response in rheumatoid arthritis cases. Changes in inflamed synovial volumes are of limited value, however, in predicting the remission of rheumatoid arthritis after therapy.

Volumetric measurement of the inflamed synovium of rheumatoid wrist joint for the evaluation of synovitis and remission

PURPOSE: To evaluate the changes and remission of disease activity with changes in inflamed synivial volumes of rheumatoid joints after therapy. MATERIALS AND METHODS: Seven rheumatoid arthritis patients who had been treated with antiinflammatory drugs were followed up. Using NIH imaging and a segmentation technique, pre- and post-enhanced images were measured in subtracted images. Intra- and interobserver variation were evaluated by two radiologists(A and B), using two independent measurements. For comparison, the cases were assigned to one of two groups : remission and non-remission. Changes in ESR and total joint counts(TJC) after therapy were compared with inflamed synovial volumes. RESULTS: Intraobserver variations were 3.2% and 2.7% in A and B, respectively, interobserver variation between A and B was 7.1%. Changes in inflamed synovial volumes correlated well with those in ESR (r=0.88, p<0.009) and TJC (r=0.78, p<0.037) after therapy. Changes between the remission and non-remission group were insignificant, however. CONCLUSION: Changes in inflamed synovial volumes reflect those in the activity of rheumatoid arthritis between pre- and post- treatment. This technique may be used as a tool for predicting therapeutic response in rheumatoid arthritis cases. Changes in inflamed synovial volumes are of limited value, however, in predicting the remission of rheumatoid arthritis after therapy.

Knee MRI Study of Normal Cruciate Ligaments Comparing the Flexion Images with the Extension Images: Preliminary study

PURPOSE: As a baseline study for clinical application, we investigated MRI findings of normal cruciate ligaments in the knee being flexed as compared to those in the knee being extended. MATERIALS AND METHODS: Seven asymptomatic volunteers were studied. Knee MRI was performed with a 1.5 Tesla unit using a dual 3 inch coil. Inthe decubitus position, sagittal scanning was performed with the knee in extension, and subsequently, in flexion. We observed the shape and signal intensity of both cruciate ligaments, and measured the angles between the longaxis of the femur and ligaments, and the ligament dimensions in extension and flexion images. RESULTS: As flexionand extension images were compared, cruciate ligaments differed both in their appearance and dimensions. With flexion, joint space was widened, PCL became straightened and the signal intensity of ACL became homogeneously low; both cruciate ligaments became longer and thinner. These MRI findings were statistically significant except forthinning of PCL. CONCLUSION: MRI appearance and the dimensions of cruciate ligaments were different in the flexed knee as compared to those in the extended knee.