Dynamic magnetic resonance imaging of femoral head perfusion in femoral neck fracture.

A prospective followup study of 36 femoral neck fractures according to the assessment of femoral head perfusion using dynamic magnetic resonance imaging is reported. Patients were divided into three groups based on the dynamic magnetic resonance imaging findings (dynamic curve pattern and relative enhancement ratio) that were conducted within 48 hours of the injury. Traction was used to achieve anatomic reduction and to prevent additional damage to vascularity until minimally invasive internal fixation could be done. The fractures of all 17 patients whose femoral head perfusion was normal (Type A; n = 11) or was impaired but not totally absent (Type B; n = 6) healed without complications. Among the 19 patients whose femoral head perfusion was absent (Type C), 15 had complications (osteonecrosis, n = 10; nonunion, n = 5). Assuming that fractures with a Type A or Type B curve pattern would unite successfully and that those with a Type C curve pattern would not, the sensitivity, specificity, and accuracy of the predictions of successful osteosynthesis of the femoral neck fractures using this method were 81%, 100%, and 89%, respectively. The current classification of femoral neck fractures using dynamic magnetic resonance imaging may be useful in selecting an appropriate treatment method for the fractures.     

Prediction of osteonecrosis by magnetic resonance imaging after femoral neck fractures

Thirty-one patients undergoing internal fixation for femoral neck fractures who were examined by magnetic resonance imaging at 2, 6, and 12 months after surgery and who could be followed up more than 2 years were enrolled in the current study. The items investigated were timing of the appearance of the band image on T1 weighted images, magnetic resonance imaging classification, and plain radiographs. Band images were observed 2 months after surgery in eight patients and 6 months in 12 patients (39% of all patients). According to the location and extent of the band image on magnetic resonance imaging, one patient was classified in the B1 Group (lateral type), four patients in the B2 Group (surface type), three patients in the B3 Group (intermediate type), and four patients in the B4 Group (extended type). Band images appeared in all patients in the B4 Group 6 months after surgery. Femoral heads of the patients in the B3 and B4 Groups by magnetic resonance imaging classification all were collapsed. On plain radiographs, osteonecrosis of the femoral head could be diagnosed in eight patients between 11 and 24 months after injury. The interval giving the greatest sensitivity, specificity, and accuracy of the diagnosis of osteonecrosis of the femoral head by magnetic resonance imaging was 6 months after surgery.     

Histologic correlation in magnetic resonance imaging of femoral head osteonecrosis

The present study was undertaken to determine whether a correlation exists between localized magnetic resonance image (MRI) signal behavior and specific histopathologic features of femoral head osteonecrosis. Contiguous, 5-mm coronal MRI sections were compared with corresponding histologic sections from six surgically excised femoral heads. After identifying specific areas of interest on the images, signal intensity was evaluated, both subjectively and objectively, and T1 and T2 relaxation times were calculated. Mean values for these data were compared among the following histologic categories: normal bone, unrepaired dead bone and marrow, unrepaired dead bone with marrow replaced by amorphous debris, and zones of repair. For each type of tissue, MRI signal intensity on T1- and intermediately T2-weighted images behaved in a distinctive fashion. Active repair tissue could be differentiated from both necrotic bone and normal bone by a tendency for the signal to increase in intensity on intermediately T2-weighted images. These findings suggest that MRI may provide a noninvasive means of quantitatively analyzing the volume and spacial distribution of repair tissue in osteonecrotic femoral heads. In clinical practice, such analysis may lead to improvements in disease staging and treatment planning.     

Signal variability in magnetic resonance imaging of femoral head osteonecrosis

The present study was designed to document the pattern and extent of magnetic resonance imaging (MRI) changes in femoral head osteonecrosis and also to correlate MRI findings with technetium bone scans and computed tomograms. Over a three-year period, MRI was performed on 26 patients who had clinical and roentgenographic evidence of femoral head necrosis in one or both hips. MRI abnormalities were present in all 41 hips with osteonecrosis, even when symptoms were absent and roentgenographic findings were nonspecific or not yet apparent. A single possible false-positive MRI was noted in a hip with mild degenerative change. There was considerable variation in the pattern and extent of MRI abnormalities. The most common findings were irregularity of the subchondral cortical outline (82.9%), an inhomogeneous pattern of signal loss (50%), focal increases in signal intensity with T2 weighting (35.5%), and effusion (33.3%). Regions of dense cancellous bone on computed tomograms correlated with bands of low-intensity MRI signal. In the diagnosis of asymptomatic hips, MRI was clearly more sensitive than technetium bone imaging. The role of MRI in defining prognosis and treatment selection remains to be established.     

Prosthetic heart valve evaluation by magnetic resonance imaging.

OBJECTIVE: To evaluate the potential of magnetic resonance imaging (MRI) for evaluation of velocity fields downstream of prosthetic aortic valves. Furthermore, to provide comparative data from bileaflet aortic valve prostheses in vitro and in patients. METHODS: A pulsatile flow loop was set up in a 7.0 Tesla MRI scanner to study fluid velocity data downstream of a 25 mm aortic bileaflet heart valve prosthesis. Three dimensional surface plots of velocity fields were displayed. In six NYHA class I patients blood velocity profiles were studied downstream of their St. Jude Medical aortic valves using a 1.5 Tesla MRI whole-body scanner. Blood velocity data were displayed as mentioned above. RESULTS: Fluid velocity profiles obtained from in vitro studies 0.25 valve diameter downstream of the valve exhibited significant details about the cross sectional distribution of fluid velocities. This distribution completely reflected the valve design. Blood velocity profiles in humans were considerably smoother and in some cases skewed with the highest velocities toward the anterior-right ascending aortic wall. CONCLUSION: Display and interpretation of fluid and blood velocity data obtained downstream of prosthetic valves is feasible both in vitro and in vivo using the MRI technique. An in vitro model with a straight tube and the test valve oriented orthogonally to the long axis of the test tube does not entail fluid velocity profiles which are compatible to those obtained from humans, probably due to the much more complex human geometry, and variable alignment of the valve with the ascending aorta. With the steadily improving quality of MRI scanners this technique has significant potential for comparative in vitro and in vivo hemodynamic evaluation of heart valves.     

股骨颈骨折病人的股骨头样本结构的Micro-CT评估

[目的]利用Micro-CT（Micro-computed Tomography）对正常人和老年股骨颈骨折病人的股骨头松质骨样本进行三维评价和比较。[方法]对6位正常人（正常组，27～36岁）和9位老年股骨颈骨折病人（骨折组，70～78岁）的股骨头松质骨样本进行DEXA检查，获取骨矿物密度数据。行Micro-CT扫描，得到松质骨小梁空间结构的计算机三维图形，并进行三维计量。[结果]与正常组相比，股骨颈骨折病人股骨头负重区样本的骨小梁结构在骨体积分数BV／TV、骨表面积体积比BS／TV、骨小梁厚度Tb.Th、骨小梁间隙Tb．Sp存在显著差异（P〈0．01），而骨小梁数目Tb．N、结构模型指数SMI和骨小梁模型因子Tb．Pf之间无统计学差别。骨密度检测两组没有显著性差异（P〉0．05）。[结论]股骨头松质骨的空间结构会因年龄增大而发生改变。     

Study of the anatomical position of the femoral nerve by magnetic resonance imaging in patients with fractured neck of femur: relevance to femoral nerve block

Study ObjectiveTo determine the anatomical location of the femoral nerve in patients who have sustained fracture of the neck of femur, and its relevance to femoral nerve block technique.DesignProspective, observational clinical study.SettingOrthopedic and Radiology departments of a regional hospital.Subjects10 consecutive adult ASA physical status II and III patients (mean age, 78.5 yrs) and 4 adult healthy volunteers.InterventionsA T1 magnetic resonance imaging scan was performed of both upper thighs in patients and healthy volunteers successfully.MeasurementsThe distance (mm) between the midpoint of the femoral artery and the midpoint of the femoral nerve, and the distance of the femoral nerve from the skin was measured at the mid-inguinal ligament, the pubic tubercle, and at the mid-inguinal crease. Data are shown as means (SD). Differences between both sides were compared using paired Student's t-tests. P < 0.05 was significant.Main ResultsIn patients the mean distance (mm) between the midpoint of the femoral nerve from the midpoint of femoral artery at the mid-inguinal crease on the fractured and non-fractured sides was 10.7 and 11.0, respectively (P = 0.87). The mean distance (mm) between the midpoint of the femoral nerve from the midpoint of the femoral artery at the mid-inguinal ligament on the fractured and non-fractured sides was 9.64 and 12.5, respectively (P = 0.03). The mean distance (mm) between the midpoint of the femoral nerve from the midpoint of the femoral artery at the pubic tubercle on the fractured and non-fractured sides was 8.74 and 10.49, respectively (P = 0.18).ConclusionsBlockade of the femoral nerve may be easier to perform at the mid-inguinal crease in patients with fractured neck of femur.     

Magnetic resonance imaging of the femoral head after acute intracapsular fracture of the femoral neck

In fifteen patients who had a subcapital fracture of the femoral neck (twelve displaced fractures and three non-displaced fractures), magnetic resonance imaging of the femoral head was done with two-dimensional Fourier transform spin-echo technique within forty-eight hours of injury. The magnetic resonance image did not show avascular necrosis of the femoral head in any of the patients. In eleven patients, there was a decreased signal at the base of the femoral head, immediately adjacent to the fracture. This decreased signal corresponded to a recognized band of necrosis and hemorrhage next to the site of the fracture and was not related to the viability of the femoral head. No other changes were seen on the images. We concluded that this type of magnetic resonance imaging is inadequate to determine the viability of the femoral head within forty-eight hours after a patient sustains an acute intracapsular fracture of the femoral neck.     

MRI在乳腺癌综合治疗中的应用价值及评价

随着乳腺癌个体化、规范化综合治疗理念的推广,乳腺MRI在综合治疗中的作用日益受到重视。伴随乳腺MRI临床应用开展和研究的深入,其在乳腺癌的诊断、保乳治疗、新辅助化疗(NAC)以及随访监测中的应用价值得到评估。乳腺MRI对肿瘤范围的精确显示为多种治疗方式的合理应用、评估及监测治疗效果等方面具有重要价值,对乳腺癌综合治疗起着不可替代的作用。     

磁共振检查在评估微波消融治疗肝癌中的应用

目的 探讨MRI检查在评估微波消融治疗肝癌中的价值.方法 回顾性分析2005年11月至2009年6月解放军总医院经肝穿刺活组织检查证实为肝癌行微波消融治疗的51例患者的临床资料,分析65个肿瘤灶微波消融治疗前后的MRI表现.结合血清学检查和肝穿刺活组织检查评估MRI检查结果.结果 消融后1个月内复查MRI,49例患者共63个肿瘤灶表现为T_1 WI高信号、T_2WI低信号的无强化区,周边伴有均匀的环状强化带,诊断为凝固坏死.患者同期的血清AFP水平由术前的333.83μg/L下降到37.68μg/L.其余2例患者共2个肿瘤灶表现为T_1WI低信号、T_2WI高信号,与T_1WI高信号、T_2WI低信号的消融区形成鲜明对比,诊断为肿瘤局部残留,肝穿刺活组织榆查证实为肝癌.51例患者微波消融治疗1个月后定期随访,5例患者肿瘤灶消融区周边新出现强化的T_1WI低信号、T_2WI高信号结节影,表现与肿瘤局部残留相似,结合肝穿刺活组织检查和AFP诊断为肿瘤局部复发.23例患者肝内出现新肿瘤灶,1例患者出现腹壁转移,这24例患者同期血清AFP水平均不同程度升高,平均为120.16μg/L.结论 MRI检查能够准确评估微波消融治疗肝癌的效果.     

Single imaging modality evaluation of living donors in liver transplantation: magnetic resonance imaging.

BACKGROUND: Liver graft size, anatomy of the bile duct and the vascular inflow and outflow are essential for living related liver transplantation (LRLT). Preoperative delineation of those variations that would change the operative procedure to achieve a successful result especially in an emergency condition. PURPOSE: Our aim was to develop a rapid and noninvasive imaging diagnostic method for the detection of anatomical variants that is mandatory for a safe operation when selecting potential liver transplant living donors. We used a different magnetic resonance (MR) imaging technique, which enabled to us to exploit the anatomical landmark of the liver, signal enhancement of blood flow in the abdomen, and the intrahepatic biliary routes inside the liver. Then, with the help of Advantage Window workstation reconstruction, the reconstructed single vascular or biliary systems were displaced in a three-dimensional fashion and the whole examination finished within 30 min. METHODS: Modification of the standard MR technique was performed on a superconductive 1.5T whole body image scanner, MR arteriogaphy, venography, and cholangiography with three-dimensional reconstruction in evaluating the anatomy of the hepatic arteries, hepatic veins, portal venous system, bile ducts, and liver size in potential liver transplant living donors. These anatomical structures were compared with traditional imaging methods. RESULTS: In all 38 cases, as well as delineation of the portal vein detail to the segmental level was satisfactorily obtained in this MR study. The images were well displayed in a three-dimensional fashion, which had good correlation with images from traditional imaging modalities and operative findings. In 86.8% cases, the MR arteriography was well matched with the celiac angiography. Of those 17 operative cases, estimation of liver volume was well correlated with the liver graft within 3.9-12.5% variation. In the major hepatic vein, we obtained 100% accuracy and 88.2% in the minor branches. Of 12 donors received intraoperative cholangiography during liver donation, good correlation of biliary anatomy was achieved. One donor was excluded from graft donation due to the complicated arterial supply to the left liver. According to the anatomical variation, surgical procedures in graft harvesting and anastomosis were readjusted and no major complications were found in those donors and all recipients survived after liver transplantation. CONCLUSION: MR volumetry, venography, angiography, and cholangiography with three-dimensional reconstruction is sufficient for all major imaging evaluation. It may replace the traditional conventional catheter angiography, computed tomography, sonography and endoscopic retrograde cholangiography as a single investigation in the evaluation of the potential liver transplant donors. Angiography is only valuable in suboptimal cases and intraoperative cholangiography is only performed in biliary ductile variants.     

Bladder pheochromocytoma: evaluation with magnetic resonance imaging

A 17-year-old black woman with a large vesical pheochromocytoma was managed successfully by hemicystectomy and ureteroneocystotomy. Preoperatively, in addition to the routine diagnostic evaluation, magnetic resonance imaging was performed. Magnetic resonance imaging proved to be an extremely useful modality to assess the integrity of the bladder wall and extent of extravesical involvement.     

Center of the femoral head: a magnetic resonance imaging study

Determination of the center of the femoral head (CFH) may be difficult because of incomplete epiphyseal ossification of the femoral head in children younger than 8 years. The purpose of this study is to find a practical method for determining the center of the femoral head in normal hips of children younger than 8 years. Twenty-seven children who had magnetic resonance imaging (MRI) examinations of their hips (N = 54) were reviewed retrospectively. The average age of the subjects was 4.7 years (range, 1.2-8 years). Measurements were performed on the closest section to the midcoronal plane of the femoral head (the widest spherical femoral head seen on the MRI section). The CFH on the MRI section was found using a constructed circular frame by using a computer program. The medial and lateral edges of the proximal femoral ossific nucleus were marked, and the midpoint of the ossific nucleus adjacent to the growth plate (MPON) was determined. The distance between the MPON and the CFH was calculated. The average distance was 1.5 mm (range, 0-5 mm). The distance between these 2 points was less than or equal to 2 mm in 40 hips (74%). In conclusion, this study shows that the MPON can be used as a landmark to determine the center of the femoral head in normal hips of children younger than 8 years and can be used to measure the lower extremity mechanical axis.     

A comparison of magnetic resonance imaging to bone scintigraphy in early traumatic ischemia of the femoral head.

In adult rabbits, a unilateral subcapital osteotomy of the femoral neck was performed to induce avascularity. One half of the osteotomy sites were fixed with a magnetic resonance imaging (MRI) compatible absorbable pin and the other osteotomies had no fixation. The femoral heads were studied at three, five, and 12 days with roentgenographs, bone scintigraphy, and MRI, and MRI only at four weeks and six weeks after osteotomy. Histologic studies were performed after imaging to evaluate the viability of the femoral heads. At three, five, and 12 days after osteotomy, bone scintigraphy showed a decrease in uptake of radioisotope in the region of the femoral head on the operated side relative to the acetabulum and greater trochanter in 17 of 18 rabbits. A comparison of the surgically treated hip to the normal hip in fixed and unfixed osteotomies showed no change in the signal behavior of T1- or T2-weighted images in all rabbits Days 3, 5, and 12 (n = 18) after operation. The rabbit femoral heads with fixation of the osteotomy 28 days after operation showed a decrease in signal intensity in the subcapital region of the femoral head. Six weeks after operation, the fixed femoral head shows a loss of signal in a portion of the femoral head near the osteotomy. The MRI signal intensity appears to increase in the unfixed femoral heads six weeks after operation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lower femoral neck bone mineral density in prepubertal former preterm girls.

The purpose of this case-control study was to determine bone mineral content and areal bone mineral density at various skeletal sites in former preterm girls, aged 7-9 years, and to compare these data with age-matched term controls. Subjects included 25 white, prepubertal, former preterm girls (gestational age 30.8 +/- 0.3 weeks, birthweight 1461 +/- 56 g [mean +/- SEM]). Controls included 50 healthy, white, prepubertal girls born at term and matched for age (two controls per case). Measurements included anthropometric variables, calcium intake according to a food-frequency questionnaire, bone mineral content (BMC; grams), and areal bone mineral density (aBMD; grams per square centimeter), using dual-energy X-ray absorptiometry (DXA) at six skeletal sites. Thirteen preterm girls and 13 age-matched term controls were reassessed 1 year after the first DXA measurement. The former preterm girls were similar to controls in terms of age and height, but were lighter (24.6 +/- 0.6 vs. 27.0 +/- 0.6 kg, p = 0.02). They also reported a higher median calcium intake (1058 vs. 759 mg/day, p = 0.004). aBMD was lower in former preterms compared with controls at the level of the radial metaphysis (0.283 +/- 0.006 vs. 0.298 +/- 0.004, p = 0.04), femoral neck (0.593 +/- 0.011 vs. 0.638 +/- 0.010, p = 0.007), and total hip (0.596 +/- 0.012 vs. 0.640 +/- 0.010, p = 0.007), but was similar between the two groups at the radial diaphysis (0.437 +/- 0.004 vs. 0.436 +/- 0.004) and femoral diaphysis (1.026 +/- 0.015 vs. 1.030 +/- 0.011). Femoral neck aBMD remained lower compared with controls in the subgroup of preterm girls reassessed after 1 year (0.608 +/- 0.017 vs. 0.672 +/- 0.020, p = 0.02). In random effects models for longitudinal data, taking into account the effects of age, weight, and height on aBMD (dependent variable), femoral neck aBMD remained lower in former preterms (p < 0.001). Prepubertal former preterm girls showed growth recovery, but had lower aBMD at the hip and radial metaphysis than age-matched term controls, despite spontaneously higher calcium intake. Preterm girls had similar aBMD results compared with controls at sites with predominantly cortical bone (radial and femoral diaphysis), which are known to be more sensitive to calcium intake.     

Application of magnetic resonance imaging to ischemic necrosis of the lunate

Twenty patients (22 wrists), in whom ischemic necrosis of the lunate was suspected clinically, were studied prospectively by physical examination, conventional radiography, radionuclide bone scintigraphy, and magnetic resonance imaging. Magnetic resonance imaging showed more specificity than radiography or radionuclide bone imaging in making the diagnosis of ischemic necrosis of the lunate. Two patterns of lunate signal defect were seen on magnetic resonance imaging with focal or generalized signal loss on T1-weighted and T2-weighted images. Generalized loss of lunate signal on T1-weighted images was diagnostic for ischemic necrosis of the lunate. Focal signal loss on the radial one half of the lunate suggested early involvement. Normal or increased signal on the corresponding T2-weighted image implied an earlier stage and a better prognosis. Magnetic resonance imaging evaluation of the lunate may be useful for subclassification of Lichtman's radiographic stage 2 and can be employed to follow lunate revascularization after treatment. Magnetic resonance imaging is a low risk, noninvasive diagnostic technique, which can modify diagnosis, staging, treatment and prognosis of ischemic necrosis of the lunate.     

磁共振成像在骨小梁结构研究中的应用

近来的各项研究都表明,骨小梁的强度和易骨折性不仅由骨密度决定,更与骨微结构有关.磁共振成像(MRI)作为一项新兴的非侵人性技术,也证实骨结构决定骨强度.由于MRI图像中骨小梁为低信号而骨髓为高信号,因此对显示骨结构尤为适合.MRI可以深入反映骨小梁内部的三维结构.MRI图像中的各项参数也与骨的生物力学特性和脆性有关.此外,MRI还可在动物或人体研究为疗效的评估提供帮助.本文对MRI的主要特点、技术方法、操作步骤、图像分析及其不足和应用前景作了回顾.