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

Methods to predict osteonecrosis of femoral head after femoral neck fracture: a systematic review of the literature

BACKGROUND

Femoral neck fracture (FNF) is a very common traumatic disorder and a major cause of blood supply disruption to the femoral head, which may lead to a severe long-term complication, osteonecrosis of femoral head (ONFH). Early prediction and evaluation of ONFH after FNF could facilitate early treatment and may prevent or reverse the development of ONFH. In this review paper, we will review all the prediction methods reported in the previous literature.

METHODS

Studies on the prediction of ONFH after FNF were included in PubMed and MEDLINE databases with articles published before October 2022. Further screening criteria were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. This study highlights all the advantages and disadvantages of the prediction methods.

RESULTS

There were a total of 36 studies included, involving 11 methods to predict ONFH after FNF. Among radiographic imaging, superselective angiography could directly visualize the blood supply of the femoral head, but it is an invasive examination. As noninvasive detection methods, dynamic enhanced magnetic resonance imaging (MRI) and SPECT/CT are easy to operate, have a high sensitivity, and increase specificity. Though still at the early stage of development in clinical studies, micro-CT is a method of highly accurate quantification that can visualize femoral head intraosseous arteries. The prediction model relates to artificial intelligence and is easy to operate, but there is no consensus on the risk factors of ONFH. For the intraoperative methods, most of them are single studies and lack clinical evidence.

CONCLUSION

After reviewing all the prediction methods, we recommend using dynamic enhanced MRI or single photon emission computed tomography/computed tomography in combination with the intraoperative observation of bleeding from the holes of proximal cannulated screws to predict ONFH after FNF. Moreover, micro-CT is a promising imaging technique in clinical practice.

Quantitative dynamic contrast-enhanced MRI of bone marrow perfusion at the proximal femur: influence of femoral head osteonecrosis risk factor and overt osteonecrosis

OBJECTIVE

To evaluate the MRI perfusion changes in patients with risk factors for osteonecrosis and normally appearing femoral heads prior to overt femoral head osteonecrosis.

METHODS

Fifty-eight patients (105 hips) were prospectively included in this ethics committee-approved study. There were 46 hips with no image anomalies and no risk factors for osteonecrosis of the femoral head (ONFH) risk factors, 38 with ONFH risk factors and no image abnormalities, and 21 with overt ONFH. All patients underwent DCE-MRI. Semi-quantitative (peak enhancement [PE], area under the curve [AUC], time to maximum enhancement [TME]) and quantitative perfusion parameters (volume plasma, KTRANS, and KEP) were calculated. Excessive alcohol consumption, corticosteroid use, and trauma were considered major risk factors for osteonecrosis of the femoral head.

RESULTS

Measured at the femoral neck and compared to the healthy hips without OFNH risk factors, PE was significantly lower in the hips of patients with OFNH risk factors. Moreover, the difference was greater in females with risk factors, who presented significantly lower PE values (p = 0.0096). A PE threshold of 1.4% yielded a 92% sensitivity and 54% specificity for the presence of associated ONFH risk factors. The hips with overt OFNH compared to those with normally appearing showed an increase of PE of 45% in the neck (p < 0.014). Various epiphyseal femoral head perfusion parameters (PE, TME, AUC, and K_trans) presented statistically significant differences in hips with ONFH and those without (p < 0.0001).

CONCLUSION

DCE-MRI can identify perfusion marrow changes related to the presence of ONFH risk factors and adjacent to osteonecrosis areas.

KEY POINTS

• Bone marrow perfusion changes may occur prior to overt ONFH and extend beyond the osteonecrosis area to the entire femoral head and neck. • Peak enhancement values were significantly reduced in patients with ONFH risk factors, compared to those without. • The presence of ONFH led to a significant increase in marrow perfusion adjacent to the osteonecrosis area.

Quantitative contrast enhanced dual energy CT to predict avascular necrosis: a feasibility study of proximal humerus fractures

BACKGROUND

Avascular necrosis is a delayed complication of proximal humerus fractures that increases the likelihood of poor clinical outcomes. CT scans are routinely performed to guide proximal humerus fracture management. We hypothesized iodine concentration on post-contrast dual energy CT scans identifies subjects who develop avascular necrosis and ischemia due to compromised blood flow.

MATERIALS AND METHODS

55 patients with proximal humerus fractures enrolled between 2014 and 2017 underwent clinical, radiographic and contrast enhanced dual energy CT assessment. Iodine densities of the humeral head and the glenoid (control) were measured on CT. Subjects managed with open reduction internal fixation or conservatively (non-surgical) were followed for up to two years for radiographic evidence of avascular necrosis. Arthroplasty subjects underwent histopathologic evaluation for ischemia of the resected humeral head.

RESULTS

17 of 55 subjects (30.9%) were treated conservatively, 21 (38.2%) underwent open reduction internal fixation and 17 of 55 (30.9%) underwent arthroplasty. Of the 38 subjects treated conservatively or with ORIF, 20 (52.6%) completed 12 months of follow up and 14 (36.8%) 24 months of follow up. At 12 months follow up, two of 20 subjects (10%) and at 24 months 3 of 14 subjects (21.4%) developed avascular necrosis. At 12 months, the mean humerus/glenoid iodine ratio was 1.05 (standard deviation 0.24) in subjects with AVN compared to 0.91 (0.24) in those who did not. At 24 months, subjects with avascular necrosis had a mean humerus/glenoid iodine concentration ratio of 1.06 (0.17) compared to 0.924 (0.21) in those who did not. Of 17 arthroplasty subjects, 2 had severe ischemia and an iodine ratio of 1.08 (0.30); 5 had focal ischemia and a ratio of 1.00 (0.36); and 8 no ischemia and a ratio of 0.83 (0.08).

CONCLUSIONS

Quantifying iodine using dual energy CT in subjects with proximal humerus fractures is technically feasible. Preliminary data suggest higher humeral head iodine concentration may increase risk of avascular necrosis; however, future studies must enroll and follow enough subjects managed with open reduction internal fixation or conservatively for two or more years to provide statistically significant results. Trial Registrations NCT02170545 registered June 23, 2014, ClinicalTrials.gov.

Edema-like marrow signal intensity: a narrative review with a pictorial essay

The term edema-like marrow signal intensity (ELMSI) represents a general term describing an area of abnormal signal intensity at MRI. Its appearance includes absence of clear margins and the possibility of exceeding well-defined anatomical borders (for example, physeal scars). We can define "ELMSI with unknown cause" an entity where the characteristic MR appearance is associated with the absence of specific signs of an underlying condition. However, it is more often an important finding indicating the presence of an underlying disease, and we describe this case as "ELMSI with known cause." It presents a dynamic behavior and its evolution can largely vary. It initially corresponds to an acute inflammatory response with edema, before being variably replaced by more permanent marrow remodeling changes such as fibrosis or myxomatous connective tissue that can occur over time. It is important to study ELMSI variations over time in order to evaluate the activity state and therapeutic response of an inflammatory chronic joint disease, the resolution of a trauma, and the severity of an osteoarthritis. We propose a narrative review of the literature dealing with various subjects about this challenging topic that is imaging, temporal evolution, etiology, differential diagnoses, and possible organization, together with a pictorial essay.

Quantifying lumbar vertebral perfusion by a Tofts model on DCE-MRI using segmental versus aortic arterial input function

The purpose of this study was to investigate the influence of arterial input function (AIF) selection on the quantification of vertebral perfusion using axial dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). In this study, axial DCE-MRI was performed on 2 vertebrae in each of eight healthy volunteers (mean age, 36.9 years; 5 men) using a 1.5-T scanner. The pharmacokinetic parameters K^trans, v_e, and v_p, derived using a Tofts model on axial DCE-MRI of the lumbar vertebrae, were evaluated using various AIFs: the population-based aortic AIF (AIF_PA), a patient-specific aortic AIF (AIF_A) and a patient-specific segmental arterial AIF (AIF_SA). Additionally, peaks and delay times were changed to simulate the effects of various AIFs on the calculation of perfusion parameters. Nonparametric analyses including the Wilcoxon signed rank test and the Kruskal–Wallis test with a Dunn–Bonferroni post hoc analysis were performed. In simulation, K^trans and v_e increased as the peak in the AIF decreased, but v_p increased when delay time in the AIF increased. In humans, the estimated K^trans and v_e were significantly smaller using AIF_A compared to AIF_SA no matter the computation style (pixel-wise or region-of-interest based). Both these perfusion parameters were significantly greater using AIF_SA compared to AIF_A.

Transient Bone Marrow Edema Syndrome versus Osteonecrosis: Perfusion Patterns at Dynamic Contrast-enhanced MR Imaging with High Temporal Resolution Can Allow Differentiation

Purpose To prospectively evaluate the perfusion patterns at quantitative dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging of transient bone marrow edema syndrome (TBMES) and avascular osteonecrosis. Materials and Methods Institutional review board approval and written informed consent were obtained. Thirty-two patients (21 men, 11 women; mean age, 48 years; 26 hips, 10 knees) underwent conventional MR imaging and a dynamic contrast-enhanced three-dimensional spoiled gradient-echo sequence at 3 T. Parameter maps for mean transit time (MTT) and plasma flow (PF) were evaluated qualitatively and quantitatively. Differences in perfusion patterns were analyzed by using the Fisher exact test. Regions of interest were drawn in areas of high PF and long MTT on each parametric map. Mean, median, standard deviation, minimum, and maximum values were determined. TBMES and osteonecrosis were compared statistically by using the Mann-Whitney U and Wilcoxon signed-rank tests, with a P value of less than .05 considered indicative of a significant difference. Results Nineteen joints with TBMES and 17 joints with osteonecrosis were evaluated. TBMES joints showed a subchondral elongated area of high PF and low MTT that was surrounded by an area of long MTT and low PF. Osteonecrosis joints showed a subchondral area with low or no detectable PF and MTT adjacent to the joint surface, which was surrounded by a rim of high PF and intermediate MTT. Patterns for TBMES and osteonecrosis did not overlap. A significant difference (P < .001) in PF in the immediate subchondral area was found between TBMES and osteonecrosis; in joints with osteonecrosis, this was comparable to background noise, and therefore, could not be quantified. In the circumscribed rim of high PF and intermediate MTT, which was only found in joints with osteonecrosis, mean ± standard deviation PF was 18.9 mL/100 mL per minute ± 11.0 and mean MTT was 213.3 seconds ± 56.8. No significant difference between TBMES and osteonecrosis was found for MTT (P = .09) and PF (P = .75) in the surrounding area. Conclusion Parameter maps derived at dynamic contrast-enhanced MR imaging with high temporal resolution can allow differentiation of osteonecrosis from TBMES in hip and knee joints. ^© RSNA, 2016 Online supplemental material is available for this article.

Static, Dynamic and First-Pass MR Imaging of Musculoskeletal Lesions Using Gadodiamide Injection

Forty-five patients with known or suspected musculoskeletal tumors were examined with static and dynamic MR imaging to evaluate the safety, tolerability and diagnostic utility of gadodiamide injection and to assess the diagnostic value of dynamic MR imaging and parametric “first-pass” (FP) images. The proportion of patients presenting more diagnostic information on the contrast-enhanced compared to the precontrast spin-echo examinations was determined. The dynamic enhancement characteristics were evaluated with time-intensity curves and parametric images of the FP enhancement rate. The tolerance of gadodiamide injection was good. Contrast enhancement was useful for delineating tumor from muscle, and differentiating viable from necrotic tissue and cystic from solid lesions. Malignant tumors showed a significantly higher slope value, earlier onset of enhancement, and higher maximum enhancement than benign lesions. However, slope values could not be used to predict the malignant potential of a lesion, due to overlap between highly vascular benign and low vascular malignant lesions. By displaying highly vascular areas, parametric FP images provided useful information on the most active part in a tumor before biopsy and for assessing the incorporation of bone-chip allografts. Static, dynamic and FP MR imaging using gadodiamide injection appears safe and provides useful information for diagnosis, biopsy and follow-up of musculoskeletal lesions.

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 (Emax), slope (Eslope) 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.

Dynamic contrast-enhanced magnetic resonance perfusion compared with digital subtraction angiography for the evaluation of extradural spinal metastases: a pilot study

STUDY DESIGN

This was a retrospective study comparing dynamic contrast-enhanced magnetic resonance (DCE-MR) perfusion with digital subtraction angiography (DSA) in determining the vascularity of spinal tumors.

OBJECTIVE

To report on the efficacy of DCE-MR perfusion as a potential noninvasive surrogate for measuring vascularity and thus determine the need for preoperative embolization.

SUMMARY OF BACKGROUND DATA

Although primary spinal tumors are rare, spine metastases are relatively common and symptomatic in approximately 14% of patients. Symptomatic patients require palliation with radiotherapy and/or surgery, with possible preoperative endovascular embolization of the tumor.

METHODS

A retrospective review revealed 10 patients with 11 diseased vertebral bodies who had received spine DCE-MR perfusion studies and subsequently underwent spinal DSA. Processed MR data were used to calculate a blood flow ratio comparing blood flow with a diseased and an adjacent normal vertebral body. Spinal tumor vascularity was graded on the basis of angiographic tumor blush from 0 (decreased enhancement compared with a normal vertebral body) to 4 (marked tumor blush with early arteriovenous shunting).

RESULTS

Eight vertebral bodies demonstrated increased vascularity on DSA with blood flow ratios of greater than 1.8, 2 vertebral bodies demonstrated normal enhancement on DSA with cerebral blood flow (CBF) ratio of 0.55 to 1.14, and 1 vertebral body level had decreased enhancement on DSA, with a CBF ratio of 0.43. There was a strong correlation between CBF ratio and DSA score, with Spearman ρ = 0.87 (P = 0.00012).

CONCLUSION

These data show a statistically significant correlation between CBF ratio and DSA and suggest that DCE-MR perfusion can serve as a surrogate to DSA for determining tumor vascularity in patients with extramedullary spinal metastases.

Measurement of blood perfusion in spinal metastases with dynamic contrast-enhanced magnetic resonance imaging: evaluation of tumor response to radiation therapy

STUDY DESIGN

This was a retrospective study focusing on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to assess treatment response in patients with spinal metastases.

OBJECTIVE

To demonstrate DCE-MRI changes before and after radiation treatment and correlating with other imaging and clinical findings.

SUMMARY OF BACKGROUND DATA

Currently, conventional imaging is limited in evaluating early treatment success or failure, which impacts patient care.

METHODS

Consecutive patients with known spinal metastases underwent DCE-MRI before and after radiotherapy. Perfusion data on 19 lesions were analyzed. Radiotherapy was classified as success (n = 17) or failure (n = 2) on the basis of evidence of tumor contraction (n = 4), negative positron emission tomography (n = 2), or stability for more than 11 months (n = 11). Perfusion parameters blood plasma volume (Vp), time-dependent leakage (Ktrans), area under the curve, and peak enhancement were derived from the signal intensity-time curves and changes in parameter values from pre- to post-treatment were calculated. Curve morphologies were also qualitatively assessed in 13 pre- and 13 post-treatment scans.

RESULTS

Vp was the strongest predictor of treatment response (false-positive rate = 9.38 × 10 and false-negative rate = 0.055). All successfully treated lesions showed decreases in Vp, and the 2 treatment failures showed drastic increases in Vp. Changes in area under the curve and peak enhancement demonstrated similar relationships to the observed treatment response, whereas changes in Ktrans showed no significant relationship. Signal intensity curve morphologies also demonstrated specificity for active disease (11 of 13) and treated disease (8 of 13).

CONCLUSION

Changes in perfusion, particularly Vp, reflect tumor responses to radiotherapy in spinal bone metastases. These changes were able to predict positive outcomes earlier than 6 months after treatment in 16 of 17 tumors. The ability of DCE-MRI to detect early treatment response has the potential to improve patient care and outcome.

Is dynamic contrast-enhanced MRI useful for assessing proximal fragment vascularity in scaphoid fracture delayed and non-union?

OBJECTIVE

To assess dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) as a measure of vascularity in scaphoid delayed-union or non-union.

MATERIALS AND METHODS

Thirty-five patients (34 male, one female; mean age, 27.4 ± 9.4 years; range, 16-51 years) with scaphoid delayed-union and non-union who underwent DCE MRI of the scaphoid between September 2002 and October 2012 were retrospectively reviewed. Proximal fragment vascularity was classified as good, fair, or poor on unenhanced MRI, contrast-enhanced MRI, and DCE MRI. For DCE MRI, enhancement slope, Eslope comparison of proximal and distal fragments was used to classify the proximal fragment as good, fair, or poor vascularity. Proximal fragment vascularity was similarly graded at surgery in all patients. Paired t test and McNemar test were used for data comparison. Kappa value was used to assess level of agreement between MRI findings and surgical findings.

RESULTS

Twenty-five (71 %) of 35 patients had good vascularity, four (11 %) had fair vascularity, and six (17 %) had poor vascularity of the proximal scaphoid fragment at surgery. DCE MRI parameters had the highest correlation with surgical findings (kappa = 0.57). Proximal scaphoid fragments with surgical poor vascularity had a significantly lower Emax and Eslope than those with good vascularity (p = 0.0043 and 0.027). The sensitivity, specificity, positive and negative predictive value and accuracy of DCE MRI in predicting impaired vascularity was 67, 86, 67, 86, and 80 %, respectively, which was better than that seen with unenhanced and post-contrast MRI. Flattened time intensity curves in both proximal and distal fragments were a feature of protracted non-union with a mean time interval of 101.6 ± 95.5 months between injury and MRI.

CONCLUSIONS

DCE MRI has a higher diagnostic accuracy than either non-enhanced MRI or contrast enhanced MRI for assessing proximal fragment vascularity in scaphoid delayed-union and non-union. For proper interpretation of contrast-enhanced studies in scaphoid vascularity, one needs to incorporate the time frame between injury and MRI.

Quantitative evaluation of the tibial tunnel after anterior cruciate ligament reconstruction using diffusion weighted and dynamic contrast enhanced MRI: a follow-up feasibility study

OBJECTIVE

The aim of the study was to evaluate the feasibility of two quantitative MRI methods: diffusion weighted imaging (DWI) and dynamic contrast enhanced imaging (DCEI), for follow-up assessment of the tibial tunnel after reconstruction of the anterior cruciate ligament (ACL).

MATERIALS AND METHODS

Twenty-three patients were examined by MRI at 1 and 6 months following ACL reconstruction. DWI and DCEI were utilized for evaluating the region of interest (ROI) within the proximal part of the tibial tunnel. From the resulting apparent diffusion coefficient (ADC) maps, ADC values were calculated. DCEI data were used to extract the enhancement factor (f(enh)) and the enhancement gradient (g(enh)) for the same ROI.

RESULTS

Calculated ADC as well as the f(enh) and g(enh) had diminished to a statistically significant extent by 6 months after ACL reconstruction. The average ADC value diminished from 1.48 (10(-3) mm(2)/s) at 1 month to 1.30 (10(-3) mm(2)/s) at 6 months after reconstruction. The average f(enh) value decreased from 1.21 at 1 month to 0.50 at 6 months and the average g(enh) value decreased from 2.01%/s to 1.15%/s at 6 months, respectively.

CONCLUSION

The study proved feasibility of DWI and DCEI for quantitative assessment of the tibial tunnel at 1 and 6 months after ACL reconstruction. Both methods have the potential for use as an additional tool in the evaluation of new methods of ACL reconstruction. To our knowledge, this is the first time quantitative MRI has been used in the follow-up to the ACL graft healing process.

Perfusion parameters analysis of the vertebral bone marrow in patients with Ph¹⁻ chronic myeloproliferative neoplasms (Ph(neg) MPN): a dynamic contrast-enhanced MRI (DCE-MRI) study

PURPOSE

To evaluate perfusion parameters of the vertebral bone marrow in patients with Philadelphia negative chronic myeloproliferative neoplasms (Ph(neg) MPN) using dynamic contrast-enhanced MRI (DCE-MRI).

MATERIALS AND METHODS

The study enrolled 24 patients with Ph(neg) MPN: 12 patients with myelofibrosis (Group A), 6 with essential thrombocythemia (ET), and 6 with polycythemia vera (PV) (Group B) who underwent DCE-MRI of the lumbosacral spine. Twelve normal individuals served as control group (Group C). Wash-in (WIN), wash-out (WOUT), maximum contrast-enhancement (CE  max), time-to-peak (TTPK), time-to-maximum slope (TMSP), and the WIN/TMSP ratio (WTSP) were calculated.

RESULTS

WIN, CE(max) , and WTSP parameters were higher in Group A than in Group C (P < 0.05). These parameters were significant (P < 0.0001) in discriminating patients with myelofibrosis from normal individuals with sensitivities 74.14%, 87.93%, 74.14%, and specificities 91.07%, 83.93%, 91.07%, respectively. WIN, WOUT, CE(max) , and WTSP parameters were higher in Group A than in Group B (P < 0.05). Group B exhibited no differences in perfusion parameters as compared with Group C with the exception of WOUT.

CONCLUSION

Patients with myelofibrosis exhibited increased perfusion parameters in vertebral bone marrow, which could be consisted with increased vascularity, probably related to neoangiogenesis as opposed to ET or PV patients showing no increased perfusion. DCE-MRI may be of value in discriminating subgroups of Ph(neg) MPN patients and in indicating those progressing to myelofibrosis.

Recovery of the blood flow around the femoral head during early corticosteroid therapy: dynamic magnetic resonance imaging in systemic lupus erythematosus patients

Disturbance of blood supply to the femoral head is a risk factor for corticosteroid-associated osteonecrosis. The aim was to measure blood supply of the proximal femur during corticosteroid therapy in systemic lupus erythematosus (SLE) patients. We repeatedly performed 78 dynamic MRIs of 19 hip joints in 19 SLE patients after initiation of corticosteroid administration for one year. Blood supply of the femoral head (epiphysis, growth plate, and metaphysis), the femoral neck, and the medial circumflex femoral artery were measured in terms of peak percent enhancement. At the first month, blood supply of the growth plate was significantly higher in the pediatric group (<15 years old) than in the adolescent and adult group (>15 years old). At the fourth month, blood supply in every part of the femoral head (epiphysis, growth plate, and metaphysis) was significantly higher in the pediatric group than in the adolescent and adult group. Multiple regression analysis revealed that blood supply to the femoral head depended on the number of days after initiation of corticosteroid administration and the age at the time of dynamic MRI. Blood supply to the femoral head is abundant in pediatric patients and is a function of the number of days after initiation of corticosteroid administration.

Dynamic contrast-enhanced magnetic resonance imaging for evaluating intraosseous cleft formation in patients with osteoporotic vertebral compression fractures before vertebroplasty

STUDY DESIGN

A prospective trial of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in patients with osteoporotic vertebral compression fracture (VCF).

OBJECTIVE

To investigate the relationship between intraosseous clefts and bone marrow perfusion using DCE-MRI in patients with osteoporotic VCF before vertebroplasty.

SUMMARY OF BACKGROUND DATA

The nonhealing cleft may be responsible for persistent pain and progressive vertebral collapse after acute injury. If localized kyphosis increased, there is risk of neuropathy appearing as a complication. Even after receiving vertebroplasty, it was reported to be at increased risk for subsequent cemented vertebral refracture and new adjacent vertebral fractures. DCE -MRI has been used for the evaluation of bone marrow perfusion. However, there are few reports on the evaluation of osteoporotic VCF and intraosseous cleft formation.

MATERIALS

Forty subjects referred for evaluation of VCF underwent DCE-MRI. Bone marrow perfusion, as measured using the DCE-MRI time-intensity curve from a noninjured vertebrae was developed using two distinct parameters including peak enhancement ratio and enhancement slope. The ratio of the well-enhanced and the poorly enhanced zone of each injured vertebra were calculated. Multiple logistic regression analysis was used to evaluate the relationships between baseline clinical factors, parameters of DCE-MRI and presence or absence of intraosseous clefts.

RESULTS

Twenty-nine injured vertebrae (72%) had intraosseous clefts. Lower PER of the noninjured vertebrae was associated with higher poorly enhanced zone ratio of the injured vertebrae (γ = -0.362, P = 0.017). Multivariate logistic regression analysis identified only lower PER (hazard ratio, 0.000; 95% confidence interval, 0.000-0.096; P = 0.009) was associated with the presence of intraosseous clefts. A peak enhancement ratio value less than 0.57 had a sensitivity of 80% and specificity of 90% for predicting intraosseous clefts.

CONCLUSION

In patients with osteoporotic VCF before vertebroplasty, decreased bone marrow perfusion, as measured by DCE-MRI, was associated with intraosseous cleft formation.

Relationship of idiopathic osteonecrosis of the femoral head to perfusion changes in the proximal femur by dynamic contrast-enhanced MRI

OBJECTIVE

The purpose of this article is to relate intramedullary perfusion of the proximal femur to severity of osteonecrosis of the femoral head by using dynamic contrast-enhanced MRI (DCE-MRI).

SUBJECTS AND METHODS

Twelve patients (14 symptomatic hips) who underwent DCE-MRI and had subsequent core decompression of the femoral head were examined. Hips were graded for severity according to MRI findings and were assigned scores of 0 (negative findings), 1 (focal marrow abnormalities), and 2 (subchondral collapse). Thirteen asymptomatic hips acted as controls. The DCE-MRI data were analyzed by use of a pharmacokinetic two-compartment model.

RESULTS

Compared with control hips, there was significantly greater peak enhancement in the femoral head in hips of all grades (p < 0.001) and in the femoral neck (p = 0.001) and intertrochanteric area (p = 0.001) in grade 2 hips. The time to peak was significantly delayed in the femoral head in grade 0 hips (p = 0.02) and in the intertrochanteric area in grade 2 hips (p = 0.003) compared with the controls.

CONCLUSION

As evaluated by DCE-MRI, intramedullary peak enhancement in the femoral head increased with progression of idiopathic osteonecrosis of the femoral head, whereas there was delayed peak enhancement in the femoral head in hips with negative findings and intertrochanteric stasis in advanced osteonecrosis of the femoral head. Such perfusion changes as shown on MRI can occur with early osteonecrosis in the absence of other MRI abnormalities.

Early prediction of femoral head avascular necrosis following neck fracture

Femoral neck fracture puts at risk functional prognosis in young patients and can be life-threatening in the elderly. The present study reviews methods of femoral head vascularity assessment following neck fracture, to address the following issues: what is the risk of osteonecrosis? And what, in the light of this risk, is the best-adapted treatment to avoid iterative surgery? Femoral head vascularity depends on retinacular vessels and especially the lateral epiphyseal artery, which contributes from 70 to 80% of the femoral head vascular supply. Fracture causes vascular lesions, which are in turn the prime cause of necrosis. Other factors combine with this: hematoma tamponade effect, reduced joint space and increased pressure due to lower extremity positioning in extension/internal rotation/abduction during surgery. Head deformity is not due to direct cell death but to the repair process originating from the surrounding living bone. In post-traumatic necrosis, proliferation rapidly invades the head, with significant osteogenesis. Pathologic fractures occur at the boundary between the new and dead bone. Many techniques have been reported to help assess residual hemodynamics and risk of necrosis. Some are invasive: superselective angiography, intra-osseous oxygen pressure measurement, or Doppler-laser hemodynamic measurement; others involve imaging: scintigraphy, conventionnal or dynamic MRI. The future seems to lie with dynamic MRI, which allows a new classification of femoral neck fractures, based on a non-invasive assessment of femoral head vascularity.

Proximal femur bone marrow blood perfusion indices are reduced in hypertensive rats: a dynamic contrast-enhanced MRI study

PURPOSE

To investigate the differences in proximal femoral bone marrow blood perfusion indices between hypertensive and normotensive rats using perfusion magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Six-month-old male spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were used (12 of each). Dynamic contrast-enhanced MRI of the right hip was performed after bolus injection of Gd-DOTA administered through a tail vein cannula. In all, 800 images were acquired at 0.6 sec/image. Regions of interest (ROIs) were drawn comprising the medullary component of proximal femoral shaft and femoral head. MRI maximum enhancement (E(max)) and enhancement slope (E(slope)) were analyzed.

RESULTS

The E(max) and E(slope) of proximal femoral shaft and femoral head of SHR were significantly lower than those of WKY (E(max): 107.4 +/- 18.2% vs. 130.6 +/- 21.5%, P = 0.009, and 76.0 +/- 12.5% vs. 97.9 +/- 6.9%, P < 0.001, respectively; E(slope): 3.01 +/- 0.63%/sec vs. 3.75 +/- 0.74%/sec, P = 0.016, and 1.95 +/- 0.33%/sec vs. 2.28 +/- 0.28%/sec, P = 0.012, respectively). The E(max) and E(slope) of femoral head were significantly lower than those of proximal femoral shaft in both SHR and WKY (P < 0.001). In both SHR and WKY, proximal femoral shaft and femoral head had a rather different contrast enhancement pattern.

CONCLUSION

Proximal femoral shaft and femoral head bone marrow blood perfusion indices were significantly lower in hypertensive rats than in normotensive rats. Femoral head bone marrow was less perfused than proximal femoral shaft in both rats.

Subchondral fluid dynamics in a model of osteoarthritis: use of dynamic contrast-enhanced magnetic resonance imaging

OBJECTIVE

The hypothesis of this study is that changes in fluid dynamics in subchondral bone bear a functional relationship to bone remodeling and cartilage breakdown in osteoarthritis (OA). We have utilized dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) to extract kinetic parameters of bone perfusion at various stages in the development of OA in the Dunkin-Hartley guinea pig.

DESIGN

Animals of four different ages (6, 9, 12 and 15 months), representing various stages in the development of OA, were studied. All animals underwent DCE MRI and perfusion data were analyzed based on the Brix two-compartment pharmacokinetic model. Regions of interest were studied at the medial and lateral tibial plateaus and compared to histological-histochemical scores of articular cartilage and subchondral bone plate thickness.

RESULTS

A decrease in perfusion as well as outflow obstruction was observed in animals between 6 and 9 months of age, only in the medial tibial plateau subchondral bone. The eventual cartilage and bone lesions of OA occurred also in the medial tibia. Changes in perfusion occurred in the lateral tibia but not until OA lesions were established. Kinetic parameters of inflow were unchanged in both the medial and lateral plateaus.

CONCLUSIONS

DCE MRI can be used to extract kinetic information on bone perfusion in an animal model of OA. The signal enhancement in subchondral bone temporally precedes and spatially localizes at the same site of the eventual bone and cartilage lesions. Time-intensity curves suggest outflow obstruction as an underlying mechanism.

Diffusion-weighted MR imaging in musculoskeletal radiology: applications in trauma, tumors, and inflammation

Diffusion-weighted imaging is a noninvasive magnetic resonance technique that is capable of measuring icroscopic movement of water molecules (ie, random or Brownian motion) within biologic tissues. Diffusion weighting is achieved with a pulsed-field gradient that leaves "static" spins unaffected but causes dephasing of spin ensembles that experience different motion histories according to their diffusion paths, with respect to the direction of the gradient. This article focuses on the interesting opportunities of the use of diffusion weighted imaging in the diagnosis of musculoskeletal diseases, including trauma, tumor, and inflammation.

Reproducibility of MR perfusion and (1)H spectroscopy of bone marrow

PURPOSE

To determine the reproducibility of proton ((1)H) magnetic resonance (MR) spectroscopy and dynamic contrast-enhanced MR imaging in a clinical setting for the assessment of marrow fat fraction and marrow perfusion in longitudinal studies.

MATERIALS AND METHODS

In all, 36 subjects (17 females, 19 males, mean age 72.9 +/- 2.9 years) who underwent MR spectroscopy and/or dynamic contrast-enhanced perfusion imaging of the proximal femur were asked to return after 1 week for a repeat MR examination.

RESULTS

Reproducibility of (1)H MR spectroscopy in all bone areas tested was high, ranging from 0.78-0.85, with the highest reproducibility being in the femoral head and lowest in the femoral neck. Reproducibility of paired perfusion measurements ranged from 0.59 (enhancement slope femoral head) to 0.98 (enhancement maximum acetabulum). Overall reproducibility of (1)H MR spectroscopy and dynamic contrast-enhanced imaging tended to be best in areas with the highest inherent fat fraction or perfusion.

CONCLUSION

Reproducibility of (1)H MR spectroscopy or perfusion imaging is sufficiently high to warrant these techniques being applied to the longitudinal study of bone diseases.

Functional perfusion MRI predicts later occurrence of steroid-associated osteonecrosis: an experimental study in rabbits

Ischemia is the defined pathway leading to steroid-associated osteonecrosis (ON). Early detection of ischemic condition may help predict later ON occurrence. Bone marrow perfusion function evaluation by perfusion magnetic resonance imaging (MRI) may be a unique modality for this application. Twenty-five adult male New Zealand white rabbits were used in this study. Lipopolysaccharide (LPS) and methylprednisolone (MPS) were administrated for ON induction based on a published protocol. T1-weighted and fat suppression T2-weighted MR imaging (conventional MRI) were performed for ON lesion detection based on the abnormal signal in the proximal femora at week 0 as the baseline (before LPS injection), and week 1 and week 2 after MPS injection. At the same time, the blood perfusion function in the proximal femora was measured by perfusion MRI. Maximum enhancement (ME)--an index of MRI perfusion function was analyzed. After MRI scanning, the proximal femora were prepared histopathologically for ON lesion analysis. The rabbit with bilateral histopathological ON lesions was defined as an ON+ rabbit and included in the ON+ group evaluated at week 1 and week 2, respectively, and the rabbit without ON lesions in bilateral femora was classified into the ON- group. For the underlying mechanism of perfusion change, the extravascular marrow fat cells were measured and the intravascular endothelium inflammation injury indicator of tissue factor (TF) expression and thrombus formation were detected. In ON+ group, ME in perfusion MRI showed a significant decrease at week 1 and week 2 as compared with the baseline (p < 0.01). There was a more than 50% decrease in ME at week 1 in ON+ group; whereas there were no detectable ON lesions by conventional MRI at week 1, though 93% (14/15) rabbits could be detected at week 2 in ON+ group. In ON- group, ME showed a slight decrease at week 1 (less than 30%), and nearly recovered to normal at week 2 as compared with the baseline. Histological results showed a much larger average marrow fat area and more severe marrow blood sinusoids compression from surrounding crowded fat cells, and stronger positive TF expression in marrow endothelium and more thrombus formation in ON+ rabbits than ON- rabbits. This study demonstrated that functional perfusion MRI could predict development of steroid-associated ON. Our experimental data suggested that perfusion MRI might be a sensitive noninvasive modality for monitoring steroid-associated ON in patients.

Intervertebral disk degeneration related to reduced vertebral marrow perfusion at dynamic contrast-enhanced MRI

OBJECTIVE

The purpose of this study was to use dynamic contrast-enhanced MRI to ascertain the relation between intervertebral disk degeneration and lumbar vertebral marrow blood perfusion.

SUBJECTS AND METHODS

We recruited 25 patients (50 vertebral bodies) who underwent dynamic contrast-enhanced MRI of the lumbar spine. The peak signal enhancement of each vertebral body was calculated from the time signal after curve fitting of a pharmacokinetic model. We controlled for other variables that might have affected blood perfusion by assessing two vertebral bodies in each patient. The 25 patients were divided into three groups. In group 1, one of the vertebral bodies (L1 or L3) evaluated was between two adjacent normal disks and the other was between two adjacent degenerated disks. In group 2, each of the two vertebral bodies evaluated was between two normal disks. In group 3 each of the two vertebral bodies evaluated was between two degenerated disks.

RESULTS

Without normalization by minimization of other variables, there were no statistically significant differences in original peak enhancement values among groups 1, 2, and 3 (p = 0.179). After normalization, the peak enhancement in group 1 (0.846 +/- 0.060) was significantly lower than that in group 2 (0.988 +/- 0.047) (p = 0.003) or group 3 (0.973 +/- 0.081) (p = 0.008).

CONCLUSION

After normalization, lumbar vertebral marrow perfusion correlated well with intervertebral disk degeneration evaluated with dynamic contrast-enhanced MRI. Blood perfusion was 14% less in the vertebral body marrow between two degenerated disks than in vertebral marrow between two normal disks.

Outcome measures for evaluation of treatments for osteonecrosis

With the advent of cell-based therapies, biologics, and pharmaceuticals for the potential treatment of osteonecrosis, it is important to conduct evaluations using scientifically accepted outcomes measures. For the treatment of osteonecrosis, most studies have focused on pain relief, surgery, or the need for surgery, disease progression (advancing stage), and change in lesion size. Quantification of imaging techniques continue to gain in sophistication but have not yet been validated for use in clinical trials. Despite recent interest in using biomarkers or genetic markers in the diagnosis and analysis of disease progression, more research is needed to determine the sensitivity and specificity of these techniques with respect to osteonecrosis.

Compromised bone marrow perfusion in osteoporosis

A link between bone blood flow and osteoporosis may exist. Outside of the spine, the proximal femur is the most common site of osteoporotic fracture and is also an area prone to avascular necrosis and fracture nonunion. This study of the proximal femur investigates the relationship between BMD, bone marrow fat content, bone perfusion, and muscle perfusion. One hundred twenty healthy female subjects (mean age, 74 yr; age range, 67-89 yr) underwent DXA examination of the hip, proton MR spectroscopy, and dynamic contrast-enhanced MR imaging of the right proximal femur, acetabulum, and adductor thigh muscle. In all bone areas examined (femoral head, femoral neck, femoral shaft, acetabulum), perfusion indices (maximum enhancement, enhancement slope) were significantly reduced in subjects with osteoporosis compared with subjects with osteopenia or normal BMD. Adductor muscle perfusion was not affected by change in BMD. As marrow perfusion decreased in the proximal femur, marrow fat increased (r = 0.827). This increase in fat content seemed to account for the decrease in marrow perfusion more than a reduction in BMD. For normal BMD subjects, perfusion parameters in the femoral head were one third of those in the femoral neck or shaft and one fifth of those in the acetabulum. Perfusion throughout the proximal femur is reduced in osteoporotic subjects compared with osteopenic and normal subjects. This reduction in perfusion only affects bone and not those tissues outside of bone with the same blood supply. As bone perfusion decreased, there was a corresponding increase in marrow fat.

Monitoring ankylosing spondylitis therapy by dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging

OBJECTIVE

The effects of different therapies on enthesitis/osteitis in active ankylosing spondylitis (AS) were evaluated by magnetic resonance imaging (MRI). The aim was to assess the role of quantitative MRI in the evaluation of AS treatment efficacy.

MATERIALS AND METHODS

Thirty patients with active spondylitis or bilateral sacroiliitis were selected and followed up for 1 year. Ten of the patients were treated only with non-steroidal anti-inflammatory drugs, 10 patients additionally received at baseline an intravenous pulse of glucocorticoids and 10 patients were treated with regular infusions of infliximab. Disease activity was measured according to clinical instruments and laboratory tests. For each patient, one selected inflamed lesion was followed from baseline through control visits quantitatively by diffusion-weighted imaging (DWI) measuring the apparent diffusion coefficient (ADC) and by dynamic contrast-enhanced imaging (DCEI) with evaluation of the enhancement factor (f(enh)) and enhancement gradient (g(enh)).

RESULTS

Clinical and quantitative MRI parameters diminished significantly with regression of the inflammatory activity. The improvement in AS was most pronounced in patients treated with infliximab; after 12 months the ADC diminished from an average of 1.31 to 0.88 x 10(-3) mm(2)/s, f(enh) from 1.85 to 0.60, and g(enh) from 3.09 to 1.40 %/s.

CONCLUSION

Diffusion-weighted imaging and DCEI were shown to be effective in quantifying changes in inflammation in skeletal lesions during the treatment of AS, and could therefore be convenient for assessing treatment efficacy. To the best of our knowledge this is the first time DWI was used to evaluate the activity of skeletal inflammation in rheumatic diseases such as AS.

Vertebral marrow fat content and diffusion and perfusion indexes in women with varying bone density: MR evaluation

PURPOSE

To prospectively study the relationship among vertebral marrow fat content, marrow diffusion indexes, and marrow and erector spinae muscle perfusion indexes in female subjects with varying bone mineral density.

MATERIALS AND METHODS

Institutional study approval and informed consent were obtained. Dual x-ray absorptiometry, proton magnetic resonance (MR) spectroscopy, diffusion-weighted MR imaging, and dynamic contrast material-enhanced MR imaging of the lumbar spine and erector spinae muscle were performed in 110 women (mean age, 73 years; range, 67-84 years). Marrow fat content, marrow apparent diffusion coefficient (ADC), and perfusion indexes (maximum enhancement and enhancement slope) of marrow and erector spinae muscle were compared among three bone density groups (normal, osteopenic, and osteoporotic). The t test comparisons and Pearson correlations were applied.

RESULTS

Seven subjects were excluded, which yielded a final cohort of 103 subjects: 18 with normal bone density, 30 with osteopenia, and 55 with osteoporosis. Vertebral marrow fat content was significantly increased in the osteoporotic group (67.8% +/- 8.5 [standard deviation]) when compared with that of the normal bone density group (59.2% +/- 10.0, P = .002). Vertebral marrow perfusion indexes were significantly decreased in the osteoporotic group (enhancement slope, 1.10%/sec +/- 0.51) compared with those of the osteopenic group (1.45%/sec +/- 0.51, P = .01) and normal bone density group (1.70%/sec +/- 0.52, P < .001). Erector spinae muscle perfusion indexes did not decrease as bone density decreased. The ADC of vertebral marrow did not change with bone density.

CONCLUSION

The subjects experienced a decrease in vertebral marrow maximum enhancement and enhancement slope and an increase in marrow fat content as bone density decreased. The reduction in perfusion indexes occurred only within the vertebral body and not in the paravertebral tissues supplied by the same artery.

Rapid improvement in rheumatoid arthritis patients on combination of methotrexate and infliximab: clinical and magnetic resonance imaging evaluation

The objectives of this study was to assess, using clinical and magnetic resonance imaging (MRI) criteria, the efficacy of combination infliximab therapy in patients with active rheumatoid arthritis (RA) refractory to methotrexate (MTX) treatment and to ascertain whether the changes in MRI parameters correlate with the clinical response. Four infusions of infliximab (3 mg/kg) at weeks 0, 2, 6, and 14 were added to a stable background dose of MTX in 19 patients with active disease. Clinical parameters were assessed before each infusion and at week 14. Dynamic contrast-enhanced MRI examination of the most severely affected wrist was performed at baseline and week 14. Synovitis severity, volume of synovitis, and synovial perfusion indices were evaluated. Significant improvement in all clinical disease activity parameters was seen at week 14 with reduction in C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and DAS28. Sixty-eight percent of patients achieved ACR20. MRI disease activity parameters also significantly decreased after treatment with reduction in grading of synovitis, volume of active synovitis, and perfusion enhancement slope. Significant positive correlations were seen between the baseline volume of synovitis and the pain score (r=0.65), patient global score (r=0.68), and health assessment questionnaire (HAQ) score (r=0.46). In conclusion, addition of infliximab to methotrexate rapidly reduces inflammation in longstanding patients with RA. Assessment of enhancing synovial volume and perfusion indices on serial MRI examination was helpful in documenting the effect of treatment over this short period.

Correlation between the bone marrow blood perfusion and lipid water content on the lumbar spine in female subjects

PURPOSE

To assess the marrow lipid water ratio (LWR) and spectral line width (LW) of lumbar vertebra by proton MR spectroscopy ((1)H MRS) and correlate with the marrow blood perfusion (MBP) by contrast-enhanced dynamic MRI (dMRI) in female subjects.

MATERIALS AND METHODS

A total of 50 female subjects were included. Single-voxel (1)H MRS was measured at the L3 vertebrae. In the dMRI study, the maximum enhancement percentage (E(max)) and enhancement slope were calculated from time-intensity curves. Pearson's correlation was calculated to explore the association of (1)H MRS, age, and perfusion parameters. Partial correlation was then used to control confounder effect.

RESULTS

LWR was negatively correlated with E(max) (r = -0.72; P < 0.0001), but positively correlated with age (r = 0.63; P < 0.0001). Lipid LW was negatively correlated with age (r = -0.33; P <0.05), but positively correlated with E(max) (r = 0.4; P < 0.05). After adjusting for the age effect by partial correlation, marrow LWR still negatively correlated with E(max) (r = -0.63; P < 0.0001). After adjusting for the E(max) effect, marrow LWR still positively correlated with age (r = 0.37; P < 0.05).

CONCLUSION

After controlling the age factor, the LWR and water LW has significant negative correlation with vertebral BMP. Further investigation is needed to explore the relationship between bone marrow fat metabolism and angiogenesis.

Dynamic contrast-enhanced perfusion MR imaging of diseased vertebrae: analysis of three parameters and the distribution of the time-intensity curve patterns

OBJECTIVE

To assess the diagnostic value of perfusion MR imaging of diseased vertebrae by analysis of three parameters and the distribution of the time-intensity curve (TIC) patterns.

DESIGN AND PATIENTS

Dynamic MR imaging was performed on 34 patients with 48 lesions. All lesions were assigned to one of four groups: osteoporotic compression fracture, benign lesion without compression fracture, pathologic compression fracture, or metastatic lesion without fracture. Peak enhancement, steepest slope, and slope value were calculated from the TIC of diseased vertebrae. TICs were classified into five types. Comparisons were made among groups by analysis of the three parameters and the distributions of the TICs pattern.

RESULT

All parameters of pathologic compression fracture were significantly higher than those of osteoporotic compression fracture (P<0.05). The steepest slopes of metastatic lesions with and without pathologic compression fracture were significantly higher than those of benign lesions without compression fracture (P<0.05). No characteristic distribution of the TIC pattern helpful for the differentiation of benign and metastatic lesions was found.

CONCLUSION

In distinguishing osteoporotic from pathologic compression fractures, semiquantitative analysis of the perfusion MR imaging may be useful. However, the analysis of the TIC patterns can not significantly contribute to the differential diagnosis.

Vertebral bone mineral density, marrow perfusion, and fat content in healthy men and men with osteoporosis: dynamic contrast-enhanced MR imaging and MR spectroscopy

PURPOSE

To prospectively use hydrogen 1 (1H) magnetic resonance (MR) spectroscopy and dynamic contrast material-enhanced MR imaging to measure vertebral body marrow fat content and bone marrow perfusion in older men with varying bone mineral densities as documented with dual x-ray absorptiometry (DXA).

MATERIALS AND METHODS

This study had institutional review board approval, and all participants provided informed consent. DXA, 1H MR spectroscopy, and dynamic contrast-enhanced MR imaging of the lumbar spine were performed in 90 men (mean age, 73 years; range, 67-101 years). Vertebral marrow fat content and perfusion (maximum enhancement and enhancement slope) were compared for subject groups with differing bone densities (normal, osteopenic, and osteoporotic). The t test was used for comparisons between groups, and the Pearson test was used to determine correlation between marrow fat content and perfusion indexes.

RESULTS

Eight subjects were excluded, yielding a final cohort of 82 subjects (mean age, 73 years; range, 67-101 years) that included 42 subjects with normal bone density (mean T score, 0.8 +/- 1.1 [standard deviation]), 23 subjects with osteopenia (mean T score, -1.6 +/- 0.4), and 17 subjects with osteoporosis (mean T score, -3.2 +/- 0.5). Vertebral marrow fat content was significantly increased in subjects with osteoporosis (mean fat content, 58.23% +/- 7.8) (P = .002) or osteopenia (mean fat content, 55.68% +/- 10.2) (P = .034) compared with that in subjects with normal bone density (50.45% +/- 8.7). Vertebral marrow perfusion indexes were significantly decreased in osteoporotic subjects (mean enhancement slope, 0.78%/sec +/- 0.3) compared with those in osteopenic subjects (mean enhancement slope, 1.15%/sec +/- 0.6) (P = .007) and those in subjects with normal bone density (mean enhancement slope, 1.48%/sec +/- 0.7) (P < .001).

CONCLUSION

Subjects with osteoporosis have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with osteopenia. Similarly, subjects with osteopenia have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with normal bone density.

Correlation of MR lumbar spine bone marrow perfusion with bone mineral density in female subjects

PURPOSE

To prospectively assess lumbar spine bone marrow perfusion at dynamic magnetic resonance (MR) imaging and correlate perfusion with bone mineral density (BMD) in female subjects.

MATERIALS AND METHODS

BMD measurement and dynamic MR imaging of the lumbar spine were performed in 69 female subjects (mean age +/- standard deviation, 57 years +/- 11). Subjects were stratified into premenopausal (n = 19) and postmenopausal (n = 50) groups, with the latter group including both women who were (n = 13) and women who were not (n = 37) receiving hormone replacement therapy. BMD (in grams per square centimeter) was measured with dual energy absorptiometry in the lumbar spine. Peak enhancement ratio, measured with time-signal intensity curves calculated from dynamic MR image data, represented bone marrow perfusion. Peak enhancement ratio was compared with age and BMD by using linear regression analysis and Pearson correlation.

RESULTS

A significant positive correlation was found for BMD with peak enhancement ratio of lumbar vertebrae among all subjects (n = 69, r = 0.63, P <.001), all postmenopausal women (n = 50, r = 0.50, P <.001), and postmenopausal women without hormone replacement therapy (n = 37, r = 0.61, P <.001). However, the correlation between BMD and peak enhancement ratio was not significant (P >.05) in premenopausal women (n = 19) or postmenopausal women receiving hormone therapy (n = 13). Both BMD and peak enhancement ratio were inversely correlated with age (P <.001, Pearson correlation). Pearson partial correlation coefficient for peak enhancement ratio and mean in all subjects, with control for inverse correlation with age, was significant (r = 0.63, P <.001).

CONCLUSION

Significant correlation was found between the peak enhancement ratio of vertebral bone marrow and BMD in postmenopausal female subjects. This result may suggest a vascular component in the pathogenesis of osteoporosis.

Effect of calcium channel blockers on vertebral bone marrow perfusion of the lumbar spine

PURPOSE

To investigate the effect of calcium channel blockers on blood perfusion of vertebral bone marrow in the lumbar spine.

MATERIALS AND METHODS

Sixteen healthy volunteers (eight men and eight women) underwent dynamic contrast material-enhanced magnetic resonance (MR) imaging of the lumbar spine. One hundred twenty minutes after the first MR examination, each subject ingested 10 mg sublingual nifedipine before undergoing a second MR examination 20-25 minutes later. Semiquantitative (peak enhancement ratio and enhancement slope) and quantitative (amplitude and rate constant of the exchange [K(out)]) parameters were analyzed with the time-intensity curve. Data obtained before and after administration of nifedipine were compared. The Wilcoxon signed rank test and Spearman rank correlation test were used.

RESULTS

Median peak enhancement ratio of vertebral bodies decreased from 0.60 (mean +/- SD, 0.68 +/- 0.29) to 0.51 (mean, 0.56 +/- 0.24) after administration of nifedipine. Median and mean decreases were 0.11 and 0.12 +/- 0.15, respectively, and the percentage difference was 17% (P =.005). A P value of less than.05 was considered to indicate a statistically significant difference. Median enhancement slope changed from 0.45 (mean, 0.45 +/- 0.13) to 0.41 (mean, 0.40 +/- 0.24). Median and mean changes were 0.05 and 0.04 +/- 0.23, respectively, and the percentage difference was 9% (P =.334). Median amplitude changed from 0.059 (mean, 0.059 +/- 0.028) to 0.045 (mean, 0.048 +/- 0.023). Median and mean changes were 0.008 and 0.011 +/- 0.025, respectively, and the percentage difference was 18% (P =.072). Median K(out) changed from 0.068 (mean, 0.063 +/- 0.018) to 0.067 (mean, 0.066 +/- 0.028). Median and mean changes were 0.011 and 0.004 +/- 0.028, respectively (P =.404). Nifedipine affected peak enhancement ratio significantly but did not affect enhancement slope, amplitude, or K(out). Data before and after administration of nifedipine showed no differences between men and women. Spearman rank correlation coefficients suggest no significance between the differences in heart rate and blood pressure and the differences in peak enhancement ratio, enhancement slope, amplitude, or K(out).

CONCLUSION

After sublingual administration of nifedipine, the peak enhancement ratio of vertebral bone marrow decreased.

Relationship between vertebral bone marrow blood perfusion and common carotid intima-media thickness in aging adults

PURPOSE

To evaluate the relationship between vertebral marrow blood perfusion and common carotid intima-media thickness (IMT) in aging adults.

MATERIALS AND METHODS

An age- and sex-matched case control study was conducted. Subjects were contacted and enrolled voluntarily according to a database containing 2,258 cases that received carotid ultrasonography examination at our hospital in the previous two years. Forty-three pairs of subjects (56 male, 30 female; aged 44-85 years, average 63 years) underwent dynamic contrast-enhanced magnetic resonance (MR) study of the lumbar spine. The average peak enhancement percentage of the second to fourth lumbar vertebrae was used to represent the vertebral marrow perfusion status for each subject. The common carotid IMT, presence of plaque, peak enhancement percentage, body mass index (BMI), systolic and diastolic blood pressure, serum total cholesterol, high-density lipoprotein (HDL), and triglycerol levels were acquired for statistical analysis.

RESULTS

The average peak enhancement percentage was significantly lower in thickened IMT group compared to the normal IMT group (73 +/- 23 vs. 90 +/- 27, P=0.0023). The carotid IMT inversely correlated with vertebral peak enhancement percentage (r=-0.33, P=0.0018). The vertebral peak enhancement percentage was significantly lower in subjects with presence of any carotid plaque (P=0.032). Common carotid IMT was the only significant variable that was negatively associated with vertebral marrow perfusion after adjusting for the effect of sex, age, blood pressure, BMI, total cholesterol, HDL, and triglycerol level in linear regression model (P=0.008).

CONCLUSION

Our data demonstrate the negative association between vertebral marrow blood perfusion and common carotid IMT. These results suggest that common carotid IMT may provide the information of tissue perfusion status of the vertebral bone marrow.

Dynamic contrast-enhanced magnetic resonance imaging of osteoporotic vertebral fracture

STUDY DESIGN

This was a retrospective study of the relation between the blood perfusion of bone marrow in injured vertebrae and the degree of subsequent vertebral collapse in patients with osteoporotic vertebral fractures.

OBJECTIVE

The objective was to evaluate blood perfusion of bone marrow in injured vertebrae using dynamic magnetic resonance imaging and study the possibility of predicting the progression of vertebral collapse.

SUMMARY OF BACKGROUND DATA

Avascular necrosis of the vertebra is considered to be a cause of delayed vertebral collapse following osteoporotic vertebral fractures, but studies on the relation with the degree of progression of vertebral collapse by evaluation of vertebral blood perfusion have not been reported.

METHODS

The subjects were 15 vertebrae in 14 patients with osteoporotic vertebral fractures, including 11 women and three men with a median age of 79 years. All patients underwent dynamic magnetic resonance imaging soon after the fracture and the area rate of the noncontrast region of the injured vertebrae in dynamic magnetic resonance imaging was measured. The correlation with the degree of progression of vertebral collapse obtained from plain radiograph imaging was studied.

RESULTS

The vertebral collapse rate (percentage loss in vertebral body height) on initial examination was 17 +/- 10% (mean +/- SD) and that at the final examination was 33 +/- 19%, showing a progression of 16 +/- 11%. The noncontrast area rate in dynamic magnetic resonance imaging was 18 +/- 12%. A significant correlation was found between the degree of progression of vertebral collapse and the noncontrast area rate (Spearman r = 0.97, P < 0.001).

CONCLUSIONS

The subsequent progression of vertebral collapse tended to increase the greater the noncontrast area in the injured vertebrae in dynamic magnetic resonance imaging. Dynamic magnetic resonance imaging appears to be useful in predicting the progression of collapse of fractured vertebrae.

Evaluation of femoral perfusion in a non-traumatic rabbit osteonecrosis model with T2*-weighted dynamic MRI

We evaluated femoral perfusion in a non-traumatic rabbit serum sickness osteonecrosis (ON) model, using serial repetitive T2*-weighted (T2*W) dynamic magnetic resonance imaging (MRI) and investigated prediction of ON occurrence in early stages, comparing T2*W dynamic MRI with non-enhanced (T2-, T1- and fat suppression T1-weighted) and contrast-enhanced MRI. Early microcirculatory injury or necrotic lesion was detected in 0% of femora (extravasation, 0/6) at 72 h, 33% (necrotic, 4/12) at 1 week and 100% (necrotic, 14/14) at 3 weeks using non-enhanced MRI, and in 67% of femora (extravasation, 4/6) at 72 h, 58% (necrotic, 7/12) at 1 week and 100% (necrotic, 14/14) at 3 weeks using contrast-enhanced MRI. In contrast, microcirculatory injury or necrotic lesion was detected in 83% of femora (extravasation, 5/6) at 72 h, 92% (necrotic, 11/12) at 1 week and 100% (necrotic, 14/14) at 3 weeks using T2*W dynamic MRI as no transient decrease or less marked transient decrease in signal intensity of regions of interest (ROIs), compared to normal femora, which showed a clear transient decrease in signal intensity of ROIs. These results indicate that T2*W dynamic MRI with optimal imaging parameters and a dose of contrast agent is the most sensitive of these three MRI methods and may be clinically useful for evaluating femoral perfusion in artery phase and predicting ON occurrence.

Dynamic magnetic resonance guided treatment of developmental dysplasia of the hip

This study demonstrates the feasibility and advantages of near real-time, multiplanar, dynamic magnetic resonance image-assisted treatment of patients with developmental dysplasia of the hip. Pathoanatomy and dynamic blocks to reduction are visualized with anatomic clarity not otherwise possible. Continuous imaging allows accurate assessment and maintenance of optimum positioning throughout the casting procedure. Patient charges for this new technique are less than standard methods of treatment, and the child receives no ionizing radiation.

Dynamic contrast-enhanced mr imaging and histopathology in chronic achilles tendinosis. A longitudinal MR study of 15 patients

PURPOSE

To evaluate the value of dynamic contrast-enhanced MR imaging (DEMRI) and its correlation to symptoms and histopathology in chronic Achilles tendinosis.

MATERIAL AND METHODS

Fifteen patients with severe symptoms underwent DEMRI preoperatively and 2 years postoperatively. US-guided core biopsies of tendinosis tissue were obtained preoperatively and the specimens were analyzed using a semiquantitative protocol. DEMRI was evaluated by calculating the area under curve (AUC) of signal alteration and the static MR by a semiquantitative grading scale. A questionnaire and clinical examination evaluated the clinical outcome.

RESULTS

Early contrast enhancement (first 72 s) was seen in DEMRI at tendon lesions of the symptomatic Achilles tendons with a significant difference to asymptomatic contralateral tendon that revealed no or mild enhancement. Increased severity of tendon pathology (including fiber structure abnormality, increased vascularity, rounding of nuclei and increased amount of glycosaminoglycans) was correlated to both dynamic and static signal enhancement. Two years following surgical treatment, the signal alterations showed regression of early contrast enhancement (AUC decreased from 9 preoperatively to 2 postoperatively). The clinical outcome was as follows: 8 patients excellent, 4 good, 2 fair and 1 poor.

CONCLUSION

Patients with chronic painful achillodynia showed an early contrast-agent enhancement corresponding to the tendon lesion. Increased enhancement correlated to increased severity of tendon histopathology and patient symptoms. Two years after surgical treatment the contrast-agent enhancement decreased.

The relationship between proximal pole blood flow and the subjective assessment of increased density of the proximal pole in acute scaphoid fractures

The cause and importance of increased density of the proximal pole of the scaphoid seen in radiographs after an acute fracture were investigated. Blood flow to the proximal poles of 32 nonsurgically treated scaphoid fractures were assessed 1 to 2 weeks after injury by measuring their uptake of gadopentetate dimeglumine with dynamic magnetic resonance imaging and calculating its steepest slope and percentage of enhancement values. Initial (week 0) and week 8 scaphoid series radiographs were independently assessed by 2 observers for increased proximal pole density; both agreed that the density had increased during treatment in 9 fractures. All 9 fractures united, suggesting that increased proximal pole density is not a major determinant of fracture outcome. Increased density of the proximal pole was associated with low proximal pole blood flow, but this relationship was not absolute, suggesting that other factors contribute to the appearance of increased density.

Blood perfusion of vertebral lesions evaluated with gadolinium-enhanced dynamic MRI: in comparison with compression fracture and metastasis

PURPOSE

To investigate blood perfusion of vertebral lesions using dynamic Gd-DTPA-enhanced MRI.

MATERIALS AND METHODS

Dynamic MR studies were performed for cases of acute compression fracture, chronic compression fracture, metastatic vertebral lesions with or without compression fracture. A total of 42 patients (71 vertebral segments) were included. Five types of time-intensity curves (TICs) were defined as: nearly no enhancement (type A), slow enhancement (type B), a rapid contrast wash-in followed by an equilibrium phase (type C), a rapid contrast wash-in followed by early wash-out (type D), and a rapid contrast wash-in with a second slower-rising slope (type E).

RESULTS

Metastatic vertebral lesions with or without fracture had a higher peak enhancement percentage and steeper enhancement slope than those of chronic compression fracture, but had no difference as compared to those of acute compression fracture. The type D curve had high positive predictive value for metastatic group (100%), and the type E curve had high positive predictive value for benign compression fracture (85.7%).

CONCLUSION

Type D and E curves are valuable in the differentiation of benign and malignant vertebral lesions.

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.

Vertebral bone marrow perfusion evaluated with dynamic contrast-enhanced MR imaging: significance of aging and sex

PURPOSE

To investigate blood perfusion of nonfractured, normal-appearing vertebral bodies with regard to age and sex.

MATERIALS AND METHODS

Dynamic magnetic resonance imaging (160 images obtained in 80 seconds) was performed from T10 to L5 in 66 patients. Patients were assigned to three groups: group 1, those 50 years or younger without compression fracture; group 2, those older than 50 years without compression fracture; or group 3, those older than 50 years with compression fracture. Peak enhancement percentage and enhancement slope were determined from the time-intensity curve of normal (nonfractured) vertebral body. Comparisons were made between groups, and the effect of age and sex interaction was analyzed.

RESULTS

Higher peak enhancement percentage was demonstrated for group 1 compared with group 2 (58.21 +/- 44.65 [SD] vs 21.88 +/- 14.77, P <.005). Group 1 women revealed a higher enhancement percentage compared with group 1 men (87.17 +/- 54.13 vs 38.16 +/- 21.69, P <.05), which significantly decreased in those older than 50 years (from 87.17 +/- 54.13 to 17.98 +/- 13.80, P <.005). For men, this decrease in those older than 50 years was not as pronounced (from 38.16 +/- 21.69 to 25.38 +/- 15.43, P >.05). Presence of compression fracture at other levels of the spine (group 3) was not associated with a different enhancement percentage for normal vertebrae.

CONCLUSION

Rate of vertebral bone marrow perfusion revealed a significant decrease in subjects older than 50 years. Women demonstrated a higher marrow perfusion rate than men younger than 50 years and a more marked decrease than men older than 50 years.

Serial magnetic resonance imaging in a non-traumatic rabbit osteonecrosis model: an experimental longitudinal study

We investigated the time-dependent natural course of experimental osteonecrosis (ON), including initial changes in ON and the reparative process, using in vivo serial repetitive magnetic resonance imaging (MRI) in a non-traumatic rabbit serum sickness ON model. Some necrotic lesions were detected at 1 week (3 of 16 femora with necrotic lesions) and some in the metaphysis were detected by 12 weeks (2 of 6 femora with lesions) on T(1)-weighted, T(2)-weighted, and fat suppression T(1)-weighted images. On contrast-enhanced MRI, extravasation of the erythrocytes was detected at 72 h (7 of 26 femora with lesions) as a small, focal enhanced area. Necrotic lesions were detected in all abnormal femora by 6 weeks (16 of 16 femora with lesions) as focal, homogeneously or inhomogeneously enhanced areas. Reparative tissue replaced with new vascular and trabecular formation in necrotic areas was detected as an extended marginal enhanced area at 12 weeks. These results suggest that the enhancement patterns on contrast-enhanced MRI may provide helpful information about the developmental and reparative process of clinical ON.

Nontraumatic osteonecrosis: MR perfusion imaging evaluation in an experimental model

RATIONALE AND OBJECTIVES

Because the nature and time course of changes in early, nontraumatic osteonecrosis at perfusion and magnetic resonance (MR) imaging are unknown, the authors evaluated this technique in the assessment of early osteonecrosis with a nontraumatic model.

MATERIALS AND METHODS

Five rabbits underwent intravenous injection of lipopolysaccharide endotoxin followed by intramuscular injection of methylprednisolone. MR imaging of the femora was performed before and at weekly intervals after endotoxin injection. Histologic findings from the areas of osteonecrosis were correlated with the findings of MR imaging and MR perfusion studies.

RESULTS

Histologic evaluation showed osteonecrosis in six femora of four animals 2-4 weeks after endotoxin injection. Findings on T1-weighted images of the femur were normal in all animals; T2-weighted images of one femur showed equivocal changes. On MR perfusion images, the baseline mean peak percentage of enhancement was 52.7% +/- 12.6. In the six areas without osteonecrosis, the mean percentage of enhancement was similar to the baseline percentage of enhancement at 1 week (62.2% +/- 31.2). In the four areas with diffuse osteonecrosis, there was essentially no contrast enhancement 1-4 weeks after endotoxin injection.

CONCLUSION

T1- and T2-weighted MR imaging is insensitive to the presence of early nontraumatic osteonecrosis. MR perfusion imaging might be useful to detect early nontraumatic osteonecrosis.

Assessing permeability alterations of the blood-bone marrow barrier due to total body irradiation: in vivo quantification with contrast enhanced magnetic resonance imaging

Our aim was to quantify irradiation-induced permeability alterations of the blood-bone marrow barrier (BMB) with dynamic contrast enhanced magnetic resonance imaging (MRI). The standard small molecular contrast agent, gadoterate meglumine, and a new macromolecular contrast agent, carboxymethyldextran-Gd-DOTA (CMD-Gd-DOTA), were compared. Twenty New Zealand white rabbits underwent MRI of the bone marrow before and 1-2 days after total body irradiation (TBI). Dynamic, repetitive T1-weighted MRI was performed before and after injection of either 0.05 mmol/kg BW CMD-Gd-DOTA (n = 10) or 0.5 mmol/kg BW gadoterate (n = 10). Bone marrow contrast enhancement was quantified as delta signal intensity: DeltaSI = |(SIpost - SIpre) / SIpre| * 100%. All MRI data were compared with the histopathologic BMB ultrastructure. Dynamic bone marrow DeltaSI data steadily increased after CMD-Gd-DOTA injection, while blood DeltaSI data slightly decreased. This bone marrow contrast enhancement, indicative of contrast agent extravasation, was significantly higher and prolonged in the irradiated group as compared to non-irradiated controls (P < 0.05) and corresponded to irradiation-induced alterations of the BMB ultrastructure seen on electron microscopy. By contrast, DeltaSI data of non-irradiated and irradiated marrow were not significantly different following gadoterate injection (P > 0.05). We conclude that irradiation-induced alterations in BMB permeability could be reliably assessed with dynamic MRI, using the new macromolecular contrast agent CMD-Gd-DOTA. Bone Marrow Transplantation (2000) 25, 71-78.