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Objective To investigate the accuracy and reproducibility of multi echo data imagine combination (MEDIC) sequence with water excitation at 3. 0 T in swine knee cartilage. Methods Sagittal MEDIC sequences (0.6 mm slice thickness, isotropic) were acquired twice at 3. 0 T MRI in 30 swine knees. The knee cartilage was then removed and the volume was directly measured with water substitution method. The cartilage volume was also determined with a validated open source image software OsiriX by two observers ( A and B). The cartilage volumes obtained by two methods were compared. The reproducibility of MEDIC for quantitative measurement was accessed by the root-mean-square (RMS) of variation coefficient. Interobserver and intraobserver precision errors were compared using a paired students t-test. The accuracy of MEDIC for quantitative measurement was determined by the random pairwise differences, systematic pairwise differences and the Pearson correlation coefficients. Time of semiautomatic and manual segmentation were recorded. Results Time was saved about 75% by using semiautomatic segmentation methods [(4.0 ±1.5) min] versus manual segmentation [(16.0 ±0.9) min]. Interobserver precision errors (RMS CV%for paired analysis) between A and B for cartilage volume measurement were (2. 66 ±0. 82) ml and(2. 61 ±0.81) ml, t=0.24, P=0. 81 (patella); (2.40 ±0.69) ml and(2.49 ±0. 85) ml, t= -0.45,P =0. 65 (medial femoral condyle) ;(2. 28 ±0.74) ml and(2.41 ±0. 78) ml, t = -0. 66, P = 0. 51 (lateral femoral condyle);(3.43±1.28) ml and(3. 51 ±1. 08) ml, t= -0.26, P=0.79 (femora trochlea) with sagittal MEDIC. Intraobserver precision errors ( RMS CV% for paired analysis) of observer A for the first and second cartilage volume measurement were(2. 64 ±0. 62) ml and(2. 67 ±0. 60) ml, t = -0.19, P =0. 85(patella); (2.43 ±0.60) ml and(2. 39 ±0.59) ml, t =0.26, P = 0. 80 (medial femoral condyle);(2. 26 ±0. 56) ml and (2. 30 ±0. 57) ml, t = - 0.27, P = 0. 78 (lateral femoral condyle); (3.40 ±1.20) ml and(3.47 ±1. 11) ml, t = -0.23, P = 0. 82 (femora trochlea) with sagittal MEDIC. The cartilage volume of direct measurement were (2.73 ±0.97 ) ml ( patella ) , (2. 28 ±0. 66 ) ml ( medial femoral condyle) ,(2. 18 ±0. 55) ml (lateral femoral condyle) and (3. 39 ±1.31) ml (femora trochlea).Correlation coefficients between MEDIC and direct measurement for cartilage volume measurement were high [r = 0.95, t = 16. 10, P<0.05 ( patella); r=0.92, t = 12.42, P<0.05 (medial femoral condyle); r =0.94, t = 14.58, P < 0.05 (lateral femoral condyle) and r = 0.98, t = 26.06, P < 0. 05 (femora trochlea) ]. Conclusion Using image software OsiriX, sagittal MEDIC sequence permits accurate and precise measurement of cartilage volume at reasonable acquisition and segmentation time at 3.0 T MRI in swine knee.
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Objective To study the capability in detection and qualitative analysis of carotid atherosclerotic plaque with 3.0T MR scanner.Methods Bilateral carotid arteriae in thirty-two patients with arterosclerosis which detected by Doppler ultrasound were examined with a 3.0T MR scanner.The pulse sequences included 3D time of flight,FLASH-3D,TSE-DIR T_1WI,TSE-DIR PDWI-FS,DIR TSE-T_2WI-FS and TSE-T_2WI.According to AHA modified criteria of atherosclerosis typing,the signal characteristics of plaques were analysed.Results Carotid plaques were homogeneous signal intensity on all sequences in 30/49,heterogeneous signal intensity on at least one sequence in 15/49,among them,7 with lipid core,3/49 plaques contained calcification ,2/49 appeared as thrombosis and resulting in vessel occulusion,28/49 plaques presented the character of thick fibrous cap,13/49 plaques showed character of thin fibrous cap,the surfaces of 5/49 plaques were rough.Conclusion High resolution multiple sequences imaging with 3.0T MR scanner can be used for detection and qualitative analysis of the carotid atherosclerotic plaque in a certain degree.
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Objective To evaluate the repeatability and accuracy of semi-automated software OsiriX in the assessment of cartilage volume in normal knees on 3.0T MR. Methods Thirty right knees of healthy subjects were scanned twice with 3.0T MR using 3D-FLASH sequence with selective water excitation. Cartilage volume of the patellar compartment was determined with a validated open-source software OsiriX and manual segmentation separately by 3 observers using MRI data sets. After calculating the cartilage volumes, the segmentation processing times, the repeatability and volume results were compared between two segmentations. Results ①Compared with the manual segmentation, a time saving of at least 50% for cartilage volume measurement was achieved with OsiriX software segmentation. ②The interobserver repeatability error was 4.88% and 9.82% with OsiriX software segmentation and manual segmentation, respectively;the intraobserver repeatability error of high experienced observer was 0.77% and 1.29%, the interindividual repeatability range were 0.14%-1.11% and 0.52%-1.61%, respectively. The repeatability error of OsiriX software segmentaion was proved to be significantly smaller than manual segmentation (P＜0.05). ③System difference between results obtained with OsiriX software measurement and manual measurement was (-3.80±3.93)% and absolute pairwise difference was (4.68±2.70)%. There was no statistical difference between the volume results measured using two techniques (t=0.92, P=0.36). Conclusion Compared to manual segmentation, cartilage volume measurement with OsiriX semi-automated segmentation is faster and has higher inter- and intraobserver repeatability with relatively fixed standard. This technique may therefore be used for clinical and multi-center trials of large sample.
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Objective To compare HASTE-MRCP single-slice acquisition technique with ordinary MR cholangiopancreatography (OMRCP) and to assess the clinical application value of HASTE-MRCP single-slice acquisition technique.Methods 48 cases with biliary obstructive diseases and 30 cases without obstructive jaundice were studied with a 3. 0T super conductive unit(Magnetom Trio;Siemens,Germany) that used a body coil. Two acquisition techniques of MRCP were used for all patients . The accuracy of the two kinds of technique were compared. Results OMRCP , single-slice HASTE-MRCP had the same sensitivity and specificity in showing the site and feature of the diseases , the proximal dilated biliarys and distant normal cholangiopancreatic ducts .The diameter of dilated bile ducts at the same level was compared and no significant difference in them. Single-slice HASTE-MRCP had a high spatial resolution ,and shot aquisition time ,but more vessel artifact. OMRCP had high density resoultion ,but more motion artifacts.Conclusion The single-slice acquisition of HASTE-MRCP is an excellent technique in the diagnosis of biliary tract diseases.