An experimental study on rabbit liver by 3.0 Tesla magnetic resonance diffusion-weighted imaging / 中国医学科学院学报

<p><b>OBJECTIVE</b>To explore the methodology as well as the features, quantificational index, and reference standard of 3.0 Tesla magnetic resonance (MR) diffusion-weighted imaging (DWI) on the normal rabbit's liver.</p><p><b>METHODS</b>Twenty New Zealand white rabbits were enrolled and DWI was performed after anesthetics with multi-b values at 3.0 T MR scanner. Apparent diffusion coefficient (ADC) values as well as the difference between maximum and minimum ADC values, signal strength (SH), noise signal (SD), signal to noise ratio (SNR), and quality index (QI) were recorded and analyzed.</p><p><b>RESULTS</b>With b value increased, the ADC values decreased accordingly (P < 0.001). The difference between maximum and minimum ADC values with b = 1000 s/mm2 was the least (good stability), b = 600 s/mm2 was the second least, and b = 300 s/mm2 was greatest (bad stability). The SH decreased at the same time (P < 0.001), but the difference among DWI with b =600, 800, and 1000 s/mm2 was not statistically significant (P > 0.05). The SD decreased at the same time (P < 0.001), but the difference between DWI with b = 800 s/mm2 and b = 1000 s/mm2 was not statistically significant (P > 0.05). The SNR decreased at the same time (P < 0.001), but there were no significant differences between DWI with b = 600 s/mm2 and b = 800 s/mm2 or b = 600 s/mm2 and b = 1000 s/mm2 (P > 0.05). The SNR of DWI with b = 800 s/mm2 and b = 1000 s/mm2 was lower. The QI decreased at the same time (P < 0. 001) , but the difference between DWI with b = 800 s/mm2 and b = 1000 s/mm was not statistically significant (P > 0.05).</p><p><b>CONCLUSION</b>When 3.0 T MR DWI is applied for rabbit liver, it is better to use b = 600 s/mm2 for reducing scanning time and assuring better diffusion weights, quantity of images, and stability of ADC measurement.</p>

Quantitative study of dynamic magnetic resonance perfusion-weighted imaging in rabbit models of implanted hepatic VX2 tumor / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the possibility of dynamic magnetic resonance (MR) perfusion-weighted imaging (PWI) in rabbit models of implanted hepatic VX2 tumor.</p><p><b>METHODS</b>MRI and PWI images were obtained from 16 rabbit models of implanted hepatic VX2 tumor and 4 normal rabbits at 14, 18, 22, and 26 days after tumor implantation, respectively, and the mean time to enhancement (MTE) and maximum slope of increase (MSI) were estimated and compared with pathological changes.</p><p><b>RESULTS</b>In the rabbit models of implanted hepatic tumor the MTE tended to increase and MSI to descend 14, 18, 22, and 26 days after tumor implantation, showing significant differences from the control group. Coagulation necrosis and fibrous hyperplasia in the tumors appeared to progress with time as found pathologically.</p><p><b>CONCLUSION</b>Dynamic MR PWI quantitative analysis of rabbit models of implanted hepatic VX2 tumor provides valuable means for observing the growth behaviors of VX2 tumor and may be clinically applicable in the evaluation of hepatic diseases.</p>

Modification of the method for preparing rabbit liver VX2 tumor model and its MRI findings / 南方医科大学学报

<p><b>OBJECTIVE</b>To improve the method for preparing rabbit VX2 liver tumor model and observe the magnetic resonance imaging (MRI) features of the implanted tumors.</p><p><b>METHODS</b>Sixteen adult New Zealand white rabbits were assigned randomly into 4 equal groups, and VX2 tumor tissues were implanted into the right and left liver lobes with spiral CT guidance. Plain and contrast-enhanced MR scan and pathological analysis were performed in different stages (14, 18, 22 and 26 days) after tumor implantation.</p><p><b>RESULTS</b>Tumor implantation was successful in all the rabbits, and 18 to 22 days after tumor implantation, the diameters of the tumor ranged from 1 to 2 cm, which allowed observation and study. In plain MR scans, lower or equivalent tumor signal in comparison with hepatic parenchyma was observed, and contrast-enhanced scans produced obvious enhancement of the tumor edges. At 22 days after tumor implantation, obvious necrosis was observed in the center of the tumor.</p><p><b>CONCLUSION</b>This method of preparing rabbit VX2 liver tumor model with spiral CT guidance is simple and convenient, and the tumors can be observed effectively with dynamic plain and contrast-enhanced MR scans.</p>

Preliminary quantitative study of dynamic magnetic resonance diffusion tensor imaging in rabbit models implanted with hepatic tumor grafts from VX2 / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the feasibility of dynamic magnetic resonance diffusion tensor imaging (DTI) in rabbit models with implanted VX2 hepatic tumor grafts.</p><p><b>METHODS</b>MRI and DTI images were obtained from 16 rabbit models with implanted VX2 hepatic tumor grafts (14, 18, 22, and 26 days after tumor implantation, respectively) and 4 normal rabbits. The average diffusion coefficient (ADC) and exponential ADC (eADC) were estimated and compared against pathological findings.</p><p><b>RESULTS</b>The ADC values increased after tumor implantation but then decreased in the rabbit models, whereas eADC exhibited a pattern of reverse changes. These changes significantly differed from those in the control group. Coagulation necrosis and fibrous hyperplasia showed obvious increase as found by pathological examination.</p><p><b>CONCLUSION</b>Dynamic MR DTI quantitative analysis of rabbit models of implanted VX2 hepatic tumor can partially describe the growth behaviors of implanted liver cancer.</p>

Quantitative study of diffusion weighted imaging on magnetic resonance imaging in focal hepatic lesions less than 3 cm / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To evaluate the characteristics of MR imaging of hepatic lesions using measurement of apparent diffusion coefficient (ADC) value of hepatic lesions on diffusion weighted imaging.</p><p><b>METHODS</b>MR diffusion weighted images were obtained in patients with 97 hepatic lesions (22 hepatocellular carcinomas, 21 metastatic tumors, 28 hemangiomas, 26 cysts). ADC values were evaluated with different sequences. The ADC ratio of lesion/liver was estimated.</p><p><b>RESULTS</b>Average ADC values of hepatic lesions were as follows: carcinomas (0.91 +/- 0.07) x 10(-3) mm(2)/s, metastatic tumors (1.13 +/- 0.27) x 10(-3) mm(2)/s, cavernous hemangiomas (1.94 +/- 0.37) x 10(-3) mm(2)/s, cysts (3.26 +/- 0.30) x 10(-3) mm(2)/s. The ADC ratio of lesion/liver was significantly different between primary carcinomas and metastatic tumors (P < 0.05).</p><p><b>CONCLUSION</b>Quantitative study in hepatic lesions using ADC values and the ADC ratio of lesion/liver, would improve the accuracy in diagnosing hepatic lesions.</p>