Correlation between baseline femoral neck marrow status and the development of femoral head osteonecrosis in corticosteroid-treated patients: a longitudinal study by MR imaging

OBJECTIVE: To test the hypothesis that the development of corticosteroid (CS)-associated femoral head osteonecrosis (ON) is influenced by baseline femoral neck marrow status. PATIENTS AND METHODS: The population consisted of 20 untreated patients with a newly diagnosed rheumatic disease in whom a standardized CS regimen was planned. Before CS treatment, baseline femoral neck marrow status was determined by magnetic resonance (MR) imaging on T1-weighted images (proportion of surface area of femoral neck and intertrochanteric area occupied by fatty marrow; index of marrow conversion [IMC]) and on a quantitative MR sequence (bulk T1 values of femoral head and neck). The presence of ON was assessed by coronal T1-weighted MR images of the hips at 6 and 12 months. RESULTS: None of the patients suffered from ON at baseline. Four patients (20%) developed bilateral femoral head ON at 6 months. The mean percentage of fat marrow in the femoral neck before treatment was significantly higher in ON-positive than in ON-negative patients (p=0.0025). The mean baseline femoral neck IMC value, which parallels the degree of red to yellow marrow conversion, was higher in ON-positive than in ON-negative patients (p=0.089). The mean baseline bulk T1 value of the femoral neck (but not of the femoral head), which inversely correlates with the amount of fat marrow, was significantly shorter in ON-positive than in ON-negative patients (p=0.0298). CONCLUSION: The development of CS-associated femoral head ON is correlated with a high fat content in the proximal femur before CS therapy.     

Red and yellow marrow in the femur: age-related changes in appearance at MR imaging

T1-weighted magnetic resonance (MR) images of the femur in 77 subjects, aged 1 month to 24 years, were retrospectively analyzed for the distribution and appearance of red and yellow marrow. The subjects were divided into six age groups, and the signal intensity and degree of mottling of marrow in the proximal epiphysis, proximal metaphysis, diaphysis, distal metaphysis, and distal epiphysis were observed and assigned a grade. Bone marrow with low or intermediate to slightly increased signal intensity was considered red marrow, while bone marrow with increased signal intensity was considered fatty marrow. An orderly progression of red to yellow marrow conversion in the femur was appreciated first in the diaphysis (ages 1-10 years) and then in the distal metaphysis (ages 10-20 years), with an adult pattern seen by age 24 years. The MR spectrum of red and yellow marrow differs from the existing macroscopic anatomical data because MR imaging is apparently more sensitive to the presence of microscopic fat in bone marrow.     

Osteonecrosis of hip and knee in patients with severe acute respiratory syndrome treated with steroids

PURPOSE: To evaluate whether there is a relationship between steroid treatment and risk for osteonecrosis of the hip and knee in patients with severe acute respiratory syndrome (SARS). MATERIALS AND METHODS: The hospital ethics committee approved the study, and all patients provided written informed consent. A total of 254 patients with confirmed SARS treated with steroids underwent evaluation with magnetic resonance (MR) imaging for osteonecrosis. Clinical profiles, joint symptoms, relevant past medical and drug history, steroid dose, and radiographic and MR imaging evidence of osteonecrosis and other bone abnormalities were evaluated. Mann-Whitney, Kruskal-Wallis, and Pearson exact chi(2) tests were performed, and univariate and multivariate logistic regression analyses were applied. RESULTS: One hundred thirty-four (53%) of 254 patients had recent onset of large joint pain, but 211 (80%) of 264 painful joints were not associated with abnormality on MR images. MR images in 12 (5%) of 254 patients showed evidence of subchondral osteonecrosis in the proximal femur (n = 9), distal femur (n = 2), and proximal and distal femora and proximal tibiae (n = 1). Additional nonspecific subchondral and intramedullary bone marrow abnormalities were present in 77 (30%) of 254 patients. Results of multiple logistic regression analysis confirmed cumulative prednisolone-equivalent dose to be the most important risk factor for osteonecrosis. The risk of osteonecrosis was 0.6% for patients receiving less than 3 g and 13% for patients receiving more than 3 g prednisolone-equivalent dose. No relationship was found between additional nonspecific bone marrow abnormalities and steroid dose. CONCLUSION: An appreciable dose-related risk was found for osteonecrosis in patients receiving steroid therapy for SARS. Additional nonspecific bone marrow abnormalities were frequent. Joint pain was common after SARS infection and was not a useful clinical indicator of osteonecrosis.     

激素治疗风湿病患者股骨头骨坏死风险评估的MRI研究

目的 观察激素治疗风湿病患者髋部骨及骨髓的MRI表现,分析MRI在股骨头坏死风险评估中的意义.资料与方法 激素治疗的50例风湿病患者行髋关节X线平片及冠状位MRI检查,MRI检查序列包括自旋回波T1WI、脂肪抑制序列(STIR)、动态增强扫描(DCE-MRI).采用股骨骨髓转化系数(MCI)值及DCE-MRI时间-信号强度曲线定量分析激素治疗未发生骨坏死患者股骨骨髓的信号强度及血流灌注;并选取同期年龄相匹配的20例正常志愿者作为正常对照组.结果 50例患者中,5例(6髋)发生股骨头坏死,其中1例为双髋.20例未发生骨坏死的激素治疗患者与正常对照组( 79.51±6.58)相比,股骨MCI明显增高(90.41±5.23),差异有统计学意义(t=4.10,P＜0.01);两组干骺端及股骨头的血流灌注差异有统计学意义(t=4.47,P＜0.05;t=5.12,P＜ 0.05).结论 MRI股骨骨髓转化系数及DCE-MRI是评估股骨头骨坏死风险的有效手段,可为股骨头坏死的临床研究提供影像学依据.     

Patterns of premature physeal arrest: MR imaging of 111 children

OBJECTIVE: The purpose of this study was to use MR imaging, especially fat-suppressed three-dimensional (3D) spoiled gradient-recalled echo sequences, to identify patterns of growth arrest after physeal insult in children. MATERIALS AND METHODS: We evaluated 111 children with physeal bone bridges (median age, 11.4 years) using MR imaging to analyze bridge size, location in physis, signal intensity, growth recovery lines, avascular necrosis, and metaphyseal cartilage tongues. Fifty-eight patients underwent fat-suppressed 3D spoiled gradient-recalled echo imaging with physeal mapping. The cause, bone involved, radiographic appearance, and surgical interventions (60/111) were also correlated. Data were analyzed with the two-tailed Fisher's exact test. RESULTS: Posttraumatic bridges, accounting for 70% (78/111) of patients, were most often distal, especially of the tibia (n = 43) and femur (n = 14), whereas those due to the other miscellaneous causes were more frequently proximal (p < 0.0001). The position of the bridge in the physis was related to the bone involved (p < 0.0001). Sixty-five percent of distal tibial bridges involved the anteromedial physis, whereas 60% of the distal femoral arrests were central. Larger bridges had higher T1 signal intensity (p < 0.008). Oblique growth recovery lines were seen exclusively with bridges involving the peripheral physis (p = 0.002) and smaller, more potentially resectable bridges. Metaphyseal cartilaginous tongues were seen with all causes, but avascular necrosis was exclusively posttraumatic (p = 0.03). Signal characteristics and bridge size did not vary with the cause. CONCLUSION: Premature physeal bony bridging in children is most often posttraumatic and disproportionately involves the distal tibia and femur where bridges tend to develop at the sites of earliest physiologic closure, namely anteromedially and centrally, respectively. MR imaging, especially with the use of fat-suppressed 3D spoiled gradient-recalled echo imaging, exquisitely shows the growth disturbance and associated abnormalities that may follow physeal injury and guides surgical management.     

Normal age-related patterns of cellular and fatty bone marrow distribution in the axial skeleton: MR imaging study

Knowledge of age-related distribution patterns of cellular and fatty marrow is critical to the interpretation of magnetic resonance (MR) imaging studies. To determine such patterns, the authors retrospectively evaluated 70 examinations each of the skull, cervical spine, thoracic spine, lumbar spine, pelvis, and proximal femur (420 examinations) in patients without known bone marrow abnormality who ranged in age from 6 months to older than 70 years. Two to four distinct patterns were identified in each anatomic area on spin-echo images obtained with a short repetition time and a short echo time. The relative frequency of the patterns for different age groups is consistent with the known physiologic conversion from cellular to fatty marrow with advancing age. Knowledge of these patterns should help in the interpretation of MR images of the axial skeleton.     

Hematopoietic bone marrow hyperplasia: high prevalence on MR images of the knee in asymptomatic marathon runners.

In a prior study of marathon runners, we noticed that MR scans of the knee frequently showed hyperplasia of red (i.e., hematopoietic) bone marrow. Because the frequency of this finding in various populations is unknown, the purpose of this study was to determine the relative prevalences of hematopoietic bone marrow hyperplasia on MR examinations of the knees of healthy volunteers (n = 74), patients with symptoms of knee disorders (n = 54), and asymptomatic marathon runners (n = 23). The prevalence of hematopoietic bone marrow hyperplasia was 3% (2/74) for the healthy volunteers, 15% (8/54) for the patients, and 43% (10/23) for the marathon runners. The difference in prevalence between each of the three groups was statistically significant at p less than .05 in each case with hematopoietic bone marrow hyperplasia, the distal femur was the only area affected, while the epiphysis and proximal tibia were uninvolved. This pattern of affected bone marrow with hyperplasia of the hematopoietic marrow may be useful for the differential diagnosis. We postulate that the high prevalence of hematopoietic bone marrow hyperplasia in marathon runners may develop as a response to "sports anemia", which is commonly found in highly conditioned, aerobically trained athletes. Furthermore, this is considered to be a normal variant when found in the pattern described here.     

Chronic lymphocytic leukemia: Changes in bone marrow composition and distribution assessed with quantitative MRI

The purposes of this study were (α) to determine the prevalence of bone marrow abnormalities in patients with chronic lymphocytic leukemia (CLL) using quantitative MR assessment of axial marrow composition and peripheral marrow distribution; (b) to assess the agreement between both quantitative MR methods and compare their sensitivities to detect marrow alterations; and (c) to correlate MR findings with clinical and laboratory parameters. Twenty-nine consecutive patients with biopsy-proven CLL were investigated on a .5-T MR imager to determine bulk T1 relaxation times of the vertebral bone marrow and proportion of proximal femur surface area occupied by nonfatty marrow on coronal T1-weighted MR images of one hip. Of the 29 patients, 12 (41%) had abnormal increase in lumbar marrow T1 values (>600 msec) and 16 (55%) had increased proportion of surface area occupied by non-fatty marrow in the proximal femur (>+1 SD compared to normal values determined in sex- and age-matched healthy subjects). The results of both quantitative MR methods were normal in 12 patients and abnormal in 11 patients (agreement, 79%). Patients with alterations in peripheral marrow distribution had significantly higher T1 relaxation times (P = .001) than those with normal peripheral marrow. Patients with abnormal marrow composition or distribution at MRI had significantly higher blood and marrow lymphocytosis than patients without these features. In conclusion, the agreement between both quantitative MR methods suggests a parallelism between changes in axial marrow composition and in peripheral marrow distribution in patients with CLL. The limits of quantitative MRI in CLL must be kept in mind, because quantitative MR methods failed to detect leukemic marrow infiltration in 41% of patients.     

MR assessment of red marrow distribution and composition in the proximal femur: correlation with clinical and laboratory parameters

 Objective. To correlate the MR appearance of the proximal femur marrow with clinical and blood parameters. Design and patients. The proportion of the femoral neck surface area occupied by red marrow was determined on T1-weighted magnetic resonance (MR) images of the hip in a series of 120 subjects, aged from 15 to 75 years, with ten females and ten males per decade, and correlated with clinical data. This parameter and the bulk T1 values of femoral red marrow were determined in 30 other subjects 25–46 years of age and correlated with their blood parameters. Results. In the series of 120 subjects, the proportion of red marrow surface area decreased with age (P<10^–4) and was higher in female than male subjects (P<10^–4). Within each decade, the proportion of red marrow surface area was higher in females than in males between 25 and 65 years but neither before 25 nor after 65 years. In the series of 30 subjects, the proportion of red marrow surface area and bulk T1 values of femoral red marrow were significantly negatively correlated with hemoglobin blood levels but not with blood cell counts. Conclusion. The MR appearance of proximal femur red marrow is influenced by age and sex. A relationship with hemoglobin blood level is demonstrated.     

Bone marrow: ultrasmall superparamagnetic iron oxide for MR imaging

An ultrasmall superparamagnetic iron oxide (USPIO) preparation was evaluated as a potential intravenous contrast agent for magnetic resonance (MR) imaging of bone marrow. One hour after administration of USPIO (40, 80, and 160 mumols of iron per kilogram body weight) in rats and rabbits, T1 and T2 relaxation times were, respectively, approximately 30%, 50%, and 65% lower than precontrast relaxation times. Maximum decrease in relaxation times of marrow occurred within 1-24 hours after intravenous administration; thereafter, relaxation times slowly returned to normal within 7 days. In vivo MR imaging of rabbits and rats confirmed that USPIO decreases signal intensity of red and yellow marrow. The decrease was most marked with gradient echo pulse sequences. An animal model of intramedullary tumor demonstrated the potential of USPIO to enable differentiation between tumor and normal red marrow. USPIO-enhanced MR imaging improves detection of smaller tumors and allows differentiation of tumor deposits from islands of hyperplastic or normal red marrow.     

Femoral capital osteonecrosis: MR finding of diffuse marrow abnormalities without focal lesions

Six painful hips in five patients were examined with magnetic resonance (MR) imaging and were found to have diffuse signal abnormalities in the marrow of the femoral head and neck, which extended into the intertrochanteric area in five cases. The abnormal regions were low in signal intensity on images obtained with a short repetition time (TR) and a short echo time (TE) and were isointense or hyperintense on long TR/TE images--findings that have been attributed by others to bone marrow edema. Edema was also seen in marrow just above the acetabulum in two cases. No focal abnormalities characteristic of osteonecrosis were seen. Osteonecrosis was subsequently shown to be present in all six femoral heads at core biopsy (three cases) or by subsequent development of focal MR abnormalities reported to be highly specific for osteonecrosis (three cases). The affected hips had been radiographically normal or subtly osteopenic and had shown intense radionuclide uptake in the femoral head at scintigraphy, with lesser abnormality in the neck and intertrochanteric region. Follow-up MR examinations of five of the six femoral heads showed the diffuse abnormalities to have been transient. Although diffuse MR abnormalities in the proximal femur are not specific, they may indicate the presence of osteonecrosis of the femoral head.     

Magnetic resonance imaging findings of osteoid osteoma of the proximal femur

Osteoid osteoma (OO) is a benign bone tumor whose main radiological finding is nidus. OO of the proximal femur can also result in non-specific findings such as hip joint effusion, perinidal bone marrow edema and soft tissue mass. Since the nidus may be difficult to identify with MR, these non-specific findings can lead to erroneous diagnosis. Therefore, MR imaging technique should be optimized in order to identify nidus. Since MR imaging has assumed increasing importance in the evaluation of disorders of the hip, radiologists must be aware of the spectrum of findings of OO of the proximal femur. The aim of this pictorial review is to show the MR imaging findings of intra-articular and extra-articular OO of the proximal femur.     

Magnetic resonance perfusion and diffusion imaging characteristics of transient bone marrow edema,avascular necrosis and subchondral insufficiency fractures of the proximal femur

Purpose

To evaluate magnetic resonance (MR) perfusion and diffusion imaging characteristics in patients with transient bone marrow edema (TBME), avascular necrosis (AVN), or subchondral insufficiency fractures (SIF) of the proximal femur.

Materials and methods

29 patients with painful hip and bone marrow edema pattern of the proximal femur on non-contrast MR imaging were examined using diffusion-weighted and dynamic gadolinium-enhanced sequences. Apparent diffusion coefficients (ADCs) and perfusion parameters were calculated for different regions of the proximal femur. Regional distribution and differences in ADC values and perfusion parameters were evaluated.

Results

Seven patients presented with TBME, 15 with AVN and seven with SIF of the proximal femur. Perfusion imaging showed significant differences for maximum enhancement values (E_max), slope (E_slope) and time to peak (TTP) between the three patient groups (p < 0.05). In contrast, no significant differences for ADC values were calculated when comparing TBME, AVN, and SIF patients.

Conclusion

Diffusion weighted imaging of bone marrow of the proximal femur did not show significant differences between patients with TBME, AVN or SIF. In contrast, MR perfusion imaging demonstrated significant differences for the different patient groups and may as a complementary imaging technique add information to the understanding of the pathophysiology of diseases associated with bone marrow edema.     

Detection and quantification of recent myocardial infarction: diagnostic value of multiecho multislice spin echo imaging

Thirty-four patients with documented transmural MI were studied with gated three echo, multislice MR imaging. In 12 patients MRI MI size was compared with CK release measurement, Tl-201 SPECT defect, and with Tc-99m LVEF. Infarct was visualised in 29/34 patients on 3rd echo images (18/34 on 2nd and 6/34 on 1st echo images). Mean MR infarct size (planimetered from 3rd echo images): 33.1 +/- 9% overestimated the SPECT defect (mean value of 23.8 +/- 15%). However, the overall correlation between MRI and Tl-201 sizing was significant: r = 0.82; p less than 0.001; SEE = 5.5%. The correlation with LVEF also appeared significant: r = -0.61; p less than 0.038.     

Pelvic phased-array MR imaging of anal carcinoma before and after chemoradiation

The aim of this study was to evaluate the MR findings of anal carcinoma using an external pelvic phased-array coil before and after chemoradiation treatment. 15 patients with carcinoma of the anal canal underwent T(2) weighted and short-tau inversion recovery (STIR) imaging before and after chemoradiation. Images were reviewed in consensus by two radiologists. At pre-treatment imaging, the tumour size and stage, signal intensity and infiltration of adjacent structures were recorded. MR imaging was repeated immediately after chemoradiation, every 6 months for the first year and then yearly. Tumour response was assessed by recording change in tumour size and signal intensity. Prior to treatment, the mean tumour size was 3.9 cm (range, 1.8-6.4 cm). Tumours appeared mildly hyperintense at T(2) weighted and STIR imaging. There was good agreement in T staging between clinical examination and MR imaging (kappa = 0.68). In 12 responders with long disease remission, a greater percentage reduction in the size of MR signal abnormality in the tumour area was observed at 6 months (mean 54.7%; 46-62%) than immediately after treatment (mean 38.6%; 30-46%) (p = 0.002, t-test). 7/12 showed stabilization of T(2) signal reduction in the tumour area after 1 year, and 5/12 showed complete resolution of signal alterations at 2 years. Pelvic phased-array MR imaging is useful for local staging of anal carcinoma and assessing treatment response. After treatment, a decrease in tumour size accompanied by reduction and stability of the MR T(2) signal characteristics at 1 year after chemoradiation treatment was associated with favourable outcome.     

Mid-term follow-up after percutaneous hydrodynamic thrombectomy in lower limb ischemia: initial experience with two-dimensional MR imaging and three-dimensional MR angiography

PURPOSE: To assess noninvasively mid-term patency, reocclusion, and mid-term changes of the arterial wall after percutaneous hydrodynamic thrombectomy in patients with acute lower limb ischemia using magnetic resonance (MR) imaging/MR angiography (MRA). MATERIALS AND METHODS: Arterial wall and luminal changes were evaluated in 16 patients (10 men, six women; mean age, 70 years), with a minimum follow-up of 12 months after percutaneous thrombectomy with a hydrodynamic catheter for acute lower limb ischemia (embolic, n = 5; thrombotic, n = 11). Adjunctive PTA was performed in 44%. The mean follow-up was 23 months +/- 7.6 (range, 12-33 months). MR imaging and MRA were performed on a 1.0 T system using an extremity coil and two-dimensional (2D) time-of-flight, turbo spin echo, 2D gradient echo, and contrast enhanced three-dimensional (3D) gradient echo sequences. RESULTS: In one patient, a complete reocclusion was noted and, in two patients, a hemodynamically insignificant restenosis (< or = 50%) was identified with MR imaging. This was in accordance with color flow duplex sonography, physical examination, ankle/brachial index measurements, and the treadmill test. The MR morphometry documented an increase of the entire vessel area from 48.9 mm2 +/- 3.3 (control segments) to 55.5 mm2 +/- 2.8 at the treated segments (+13.3%; P < .05). The vessel wall area increased from 31.7 mm2 +/- 1.8 to 39.4 mm2 +/- 2.3 (+24.4%; P < .05). The mean area stenosis grade was 12%. CONCLUSION: MR imaging with use of morphometric analysis is a possible tool to noninvasively determine the mid-term patency and restenosis/reocclusion and remodeling process after percutaneous thrombectomy and other interventional procedures.     

Bone marrow perfusion evaluated with gadolinium-enhanced dynamic fast MR imaging in a dog model

The authors studied, in a dog model, the feasibility of using gadolinium-enhanced dynamic magnetic resonance (MR) imaging to noninvasively monitor bone marrow perfusion of the proximal femur. With a gradient-recalled acquisition, sequential images of 10 hips in five healthy dogs were obtained for 14 minutes after an intravenous bolus injection of 0.2 mmol of gadopentetate dimeglumine per kilogram. The study was repeated after unilateral arterial embolization of major femoral vessels. Radiolabeled microspheres were injected before and after vessel occlusion. After unilateral embolization, statistically significant differences in enhancement were observed between embolized and control sides (eg, 31% vs 83% average peak enhancement in the femoral neck). There was a high correlation (r = .81 [average]) between the MR data and the microsphere blood flow measurements. The postembolization data indicate that contrast-enhanced fast MR imaging may allow early detection of abnormal bone marrow flow. This technique may be valuable in evaluating patients at risk for avascular necrosis of the femoral head, especially in posttraumatic cases.     

Deferoxamine-induced bone dysplasia in the distal femur and patella of pediatric patients and young adults: MR imaging appearance

OBJECTIVE: We investigated the MR imaging appearance of deferoxamine-induced bone dysplasia in the distal femur and patella in patients with thalassemia major. MATERIALS AND METHODS: Thirty-five patients with homozygous ss-thalassemia major who were undergoing regular transfusions and chelation therapy underwent coronal T1-weighted MR imaging of the femur, including the femoral head and the distal femoral epiphysis. Additional coronal fat-saturated dual-echo and sagittal T1-weighted images of the distal femur and patella were obtained in 11 patients who were suspected of having distal femoral lesions on the basis of the coronal T1-weighted images of the entire femur. RESULTS: No dysplastic change was detected in the proximal femur on coronal T1-weighted images. In 22 distal femurs of 11 patients, the following abnormalities were detected on MR imaging: blurred physeal-metaphyseal junction (n = 22), distal metaphyseal areas of hyperintensity (n = 21), physeal widening (n = 18), metadiaphyseal lesions (n = 11), epiphyseal lesions (n = 10), and patellar lesions (n = 2). Physeal widening and distal metaphyseal hyperintense areas were all more pronounced peripherally. Of the 21 distal metaphyseal hyperintensities, lateral abnormalities were larger than medial abnormalities in 16. Of the 18 distal femurs in which physeal widening was detected, the lateral widening was more marked than the medial widening in 12. Patients with MR imaging evidence of bone dysplasia have a significantly (p = 0.003) greater height reduction than patients without such evidence of bone dysplasia. CONCLUSION: Deferoxamine-induced bone dysplasia in the distal femur and patella is represented by a spectrum of morphologic changes in the epiphysis, physis, metaphysis, and metadiaphysis on MR imaging.     

Initial experience with dynamic MR imaging in evaluation of normal bone marrow versus malignant bone marrow infiltrations in humans

The purpose of this study was (a) evaluation of dynamic contrast-enhanced MR imaging of normal bone marrow versus malignant bone marrow infiltrations in patients with proven B-cell-type chronic lymphocytic leukemia (B-CLL) and (b) correlation with the clinical stage according to Binet (stages A, B, C) and response to therapy. Bone marrow imaging of the lumbar spine, pelvis, and proximal femurs was performed at 1.5 T in 45 patients without known malignancy and in 30 patients with B-CLL. The differences between opposed-phase and in-phase dynamic gradient-echo sequences before and up to 10 minutes after intravenous application of .1 mmol/kg body weight of gadolinium-diethylenetriamine penta-acetic acid (Gd-DTPA) were evaluated in normal bone marrow. The contrast-enhancement patterns of normal and malignant bone marrow were compared using the opposed-phase dynamic gradient-echo sequence. Ten of the patients with bone marrow infiltrations (Binet stage C) additionally underwent MR imaging follow-up during therapy. Opposed-phase gradient echo sequences demonstrated a signal decrease of normal bone marrow, and in-phase gradient echo sequences demonstrated a signal increase of normal bone marrow after administration of Gd-DTPA. The dynamic signal intensity time courses differed significantly (P < .05) between Binet stages B and C and controls as well as among the three Binet stages of B-CLL. In the 10 patients followed during therapy, MR imaging sensitively demonstrated response (n = 6), nonresponse (n = 2), or relapse after initial response (n = 2). In out-of-phase imaging, both normal bone marrow and initial bone marrow infiltration in CLL stage Binet A show signal decrease after administration of contrast agent, whereas there is increase in signal intensity in higher-grade bone marrow infiltration in Binet stage B or C disease. The signal loss of normal bone marrow in out-of-phase imaging is a phase effect rather than a T2* effect. The differentiation of initial from higher-grade bone marrow infiltration on out-of-phase images relies solely on a shift in the fat/water ratio.     

Method for cortical bone structural analysis from magnetic resonance images

RATIONALE AND OBJECTIVES: Quantitative evaluation of cortical bone architecture as a means to assess bone strength typically is accomplished on the basis of images obtained by means of dual-energy X-ray absorptiometry (DXA) or computed tomography. Magnetic resonance (MR) imaging has potential advantages for this task in that it allows imaging in arbitrary scan planes at high spatial resolution. However, several hurdles have to be overcome to make this approach practical, including resolution of issues related to nonlinear receive coil sensitivity, variations in marrow composition, and the presence of periosteal isointense tissues, which all complicate segmentation. The aim of this study is to develop MR acquisition and analysis methods optimized for the detection of cortical boundaries in such complex geometries as the femoral neck. MATERIALS AND METHODS: Cortical boundary detection is achieved by radially tracing intensity profiles that intersect the periosteal and endosteal boundaries of bone. Profiles subsequently are normalized to the intensity of the marrow signal, processed with morphologic image operators, and binarized. The resulting boundaries are mapped back onto the spatial image, and erroneous boundary points are removed. From the detected cortical boundaries, cortical cross-sectional area and thickness are computed. The method was evaluated on cortical bone specimens and human volunteers on the basis of high-resolution images acquired at a 1.5-Tesla field strength. To assess whether the method is sensitive to detect the expected dependencies of cortical parameters in weight-bearing bone on overall habitus, 10 women aged 46-73 years (mean age, 56 years) underwent the cortical imaging protocol in the proximal femur, and results were compared with DXA bone mineral density parameters of the hip and spine. RESULTS: Reproducibility was approximately 2%. Double oblique images of the femoral neck in the 10 women studied showed that cortical cross-sectional area correlated strongly with height (r = 0.88; p = .0008), whereas cortical diameter versus age approached significance (r = 0.61; p = .06). Measurements in specimens of some cortical parameters indicated resolution dependence. However, note that specimen ranking within each parameter remained constant across all resolutions studied. CONCLUSION: Data suggest the new method to be robust and applicable on standard clinical MR scanners at arbitrary anatomic locations to yield clinically meaningful quantitative results.