Differentiation of osteoporotic and neoplastic vertebral fractures by chemical shift {in-phase and out-of phase} MR imaging

Differentiation between focal malignant marrow-replacing lesions and benign red marrow deposition of the spine with T2*-corrected fat-signal fraction map using a three-echo volume interpolated breath-hold gradient echo Dixon sequence

Objective

To assess the feasibility of T2^*-corrected fat-signal fraction (FF) map by using the three-echo volume interpolated breath-hold gradient echo (VIBE) Dixon sequence to differentiate between malignant marrow-replacing lesions and benign red marrow deposition of vertebrae.

Materials and Methods

We assessed 32 lesions from 32 patients who underwent magnetic resonance imaging after being referred for assessment of a known or possible vertebral marrow abnormality. The lesions were divided into 21 malignant marrow-replacing lesions and 11 benign red marrow depositions. Three sequences for the parameter measurements were obtained by using a 1.5-T MR imaging scanner as follows: three-echo VIBE Dixon sequence for FF; conventional T1-weighted imaging for the lesion-disc ratio (LDR); pre- and post-gadolinium enhanced fat-suppressed T1-weighted images for the contrast-enhancement ratio (CER). A region of interest was drawn for each lesion for parameter measurements. The areas under the curve (AUC) of the parameters and their sensitivities and specificities at the most ideal cutoff values from receiver operating characteristic curve analysis were obtained. AUC, sensitivity, and specificity were respectively compared between FF and CER.

Results

The AUCs of FF, LDR, and CER were 0.96, 0.80, and 0.72, respectively. In the comparison of diagnostic performance between the FF and CER, the FF showed a significantly larger AUC as compared to the CER (p = 0.030), although the difference of sensitivity (p = 0.157) and specificity (p = 0.157) were not significant.

Conclusion

Fat-signal fraction measurement using T2^*-corrected three-echo VIBE Dixon sequence is feasible and has a more accurate diagnostic performance, than the CER, in distinguishing benign red marrow deposition from malignant bone marrow-replacing lesions.

Imaging of primary bone tumors: determination of tumor extent by non-contrast sequences

Magnetic resonance imaging (MRI) is the modality of choice for determining the extent of a primary bone tumor. This article will discuss the MRI techniques needed to accurately define the intramedullary extent of a bone sarcoma, emphasizing the need for non-contrast T1-weighted sequences and highlighting the role of chemical shift imaging.

Osteoporotic vertebral compression fractures: a rare complication of radiotherapy in a patient with lung cancer

The development of bone fractures after radiotherapy is a rare event which mainly concerns the pelvis or the long bones. This complication is unusual in the vertebrae. We describe the case of a 66-year-old male patient with lung cancer who was treated with combined radio-chemotherapy and developed dorsal pain secondary to vertebral compression 4 months after the end of radiotherapy. Investigations led to a diagnosis of post-radiotherapy vertebral osteonecrosis. It is important to differentiate metastatic lesions from radiological complications. It is not possible to differentiate a metastasis from a recent osteoporotic compression fracture by imaging. A bone biopsy may therefore be necessary. Metastatic bone involvement is common in patients with lung cancer. When images are not typical of secondary progression, however, and there is no change in the general state of the patient, evidence of thoracic progression of the tumour or distal progression other than bone, vertebral osteoporotic complications should be considered. It is important that a wrong diagnosis is not made without histological proof of metastasis which has a poor prognosis.

Advances in magnetic resonance imaging of musculoskeletal tumours

Functional magnetic resonance imaging (MRI) improves tissue characterisation and staging of bone and soft-tissue tumours compared to the information usually supplied by structural imaging. Perfusion MRI, diffusion MRI, and in-phase/opposed-phase MRI can be performed in everyday practice. Nuclear magnetic resonance (NMR) spectroscopic imaging is a challenging technique that is available only in specialised centres. Tumour characterisation can benefit from perfusion MRI with dynamic gadolinium injection and enhancement time-intensity curve analysis or from diffusion MRI. Highly cellular malignant tumours restrict diffusion and consequently decrease the apparent diffusion coefficient (ADC). With some tumours, tissue heterogeneity or the presence of a myxoid component can hinder this evaluation. Chronic hematoma can be distinguished from haemorrhagic sarcoma. Perfusion and diffusion MRI contribute to the evaluation of tumour spread, in particular by differentiating oedema from tumour tissue. Another advantage of perfusion MRI and ADC mapping is the early identification of good responders to chemotherapy. The use of NMR spectroscopy remains limited. Evaluation of the choline peak can help to differentiate benign and malignant tumours. All available functional MRI techniques have limitations and leave some overlap between benign and malignant tumours. Functional MRI can be used only as an adjunctive imaging modality to complement morphological imaging.

Musculoskeletal tumors: how to use anatomic, functional, and metabolic MR techniques

Although the function of magnetic resonance (MR) imaging in the evaluation of musculoskeletal tumors has traditionally been to help identify the extent of disease prior to treatment, its role continues to evolve as new techniques emerge. Conventional pulse sequences remain heavily used and useful, but with the advent of chemical shift imaging, diffusion-weighted imaging, perfusion imaging and MR spectroscopy, additional quantitative metrics have become available that may help expand the role of MR imaging to include detection, characterization, and reliable assessment of treatment response. This review discusses a multiparametric approach to the evaluation of musculoskeletal tumors, with a focus on the utility and potential added value of various pulse sequences in helping establish a diagnosis, assess pretreatment extent, and evaluate a tumor in the posttreatment setting for recurrence and treatment response.

Imaging of stress fractures of the spine

Back pain caused by stress fractures, fatigue, or insufficiency, affects varied patient populations based on the level of physical activity and bone mineral density. Stress fractures may involve the vertebral body, pars interarticularis, and the pedicle; often overlooked are stress fractures of the sacrum or bony pelvis, which can mimic pain of spinal origin and delay diagnosis. The choice of optimal imaging (radiographs, nuclear medicine, magnetic resonance imaging, and computed tomography) also depends on the patient population under study and the clinically suspected diagnosis. The diagnosis typically determines which imaging modality is best to follow healing or progression.

Research synthesis: what is the diagnostic performance of magnetic resonance imaging to discriminate benign from malignant vertebral compression fractures? Systematic review and meta-analysis

STUDY DESIGN

This study is a research synthesis of the published literature evaluating the performance of magnetic resonance imaging (MRI) for differentiation of malignant from benign vertebral compression fractures (VCFs).

OBJECTIVE

Perform a systematic review and meta-analysis to summarize and combine the published data on MRI for discriminating malignant from benign VCFs.

SUMMARY OF BACKGROUND DATA

The differentiation between benign and malignant VCFs in the spine is a challenging problem confronting spine practitioners.

METHODS

MEDLINE, EMBASE, and other databases were searched by 2 independent reviewers to identify studies that reported the performance of MRI for discriminating malignant from benign VCF. Included studies were assessed for described MRI features and study quality. The sensitivity, specificity, and diagnostic odds ratio (OR) of each feature were pooled with a random-effects model weighted by the inverse of the variance of each individual estimate.

RESULTS

A total of 31 studies with 1685 subjects met the selection criteria. All the studies focused on describing specific features rather than overall diagnostic performance. Signal intensity ratio on opposed phase (chemical shift) imaging 0.8 or more (OR = 164), apparent diffusion coefficient on echo planar diffusion-weighted images 1.5 × 10(-3) mm2/s or less with b value 500 s/mm2 (OR = 130), presence of other noncharacteristic vertebral lesions (OR = 55), presence of paraspinal mass (OR = 33), involvement of posterior element (OR = 28), involvement of pedicle (OR = 24), complete replacement of normal bone marrow in VCF (OR = 19), presence of epidural mass (OR = 13), and diffuse convexity of posterior vertebral border (OR = 10) were associated with malignant VCFs, whereas coexisting healed benign VCF (OR = 0.006), presence of "fluid sign" (OR = 0.08), presence of focal posterior vertebral border convexity/retropulsion (OR = 0.08), and band-like shape of abnormal signal (OR = 0.07) were associated with benign VCFs.

CONCLUSION

Several specific MRI features using signal intensity characteristics, morphological characteristics, quantitative techniques, and findings at other levels can be useful for distinguishing benign from malignant VCFs and can serve as inputs for a prediction model. Observer performance reliability has not been adequately assessed.

MRI of spinal bone marrow: part I, techniques and normal age-related appearances

OBJECTIVE

This article reviews MRI protocols, including routine and nonroutine pulse sequences as well as the normal MRI appearance of spinal marrow and expected age-related changes.

CONCLUSION

Routine MRI of the spine provides useful evaluation of the spinal bone marrow, but nonroutine MRI pulse sequences are increasingly being used to evaluate bone marrow pathology. An understanding of MRI pulse sequences and the normal and age-related appearances of bone marrow is important for the practicing radiologist.

Bone marrow fat quantification of osteoporotic vertebral compression fractures: comparison of multi-voxel proton MR spectroscopy and chemical-shift gradient-echo MR imaging

BACKGROUND

Only a few studies have used in/opposed phase method for a quantitative evaluation of fat fraction in the spine.

PURPOSE

To compare multivoxel proton MR spectroscopy and chemical-shift gradient-echo MR imaging for bone marrow fat quantification in vertebral compression fractures (VCF).

MATERIAL AND METHODS

Vertebral marrow fat quantification in fifteen patients was measured at 3.0-T. Multi-voxel proton spectroscopy (MRS) and in/opposed-phase MR imaging using a fat map build with a triple-echo gradient-echo sequence was used. All the patients had benign vertebral collapse. Bone marrow fat content was evaluated by both techniques in compressed (acute or chronic) and in non-compressed vertebrae.

RESULTS

The percentage of fat fraction measured by the triple-echo sequence was well correlated with those calculated by MRS (r(2) = 0.85; P < 10(-4)). There was a significant decrease of fat fraction in acute VCF versus both chronic VCF (P < 10(-9)) and non-fractured vertebrae (P < 10(-7)). There was no significant difference in fat fraction evaluated by both techniques between non-fractured vertebrae and chronic VCF.

CONCLUSION

We have validated the in/opposed phase method compared with MRS for vertebral bone marrow fat quantification. The fat mapping using a triple-echo gradient-echo sequence allows distinguishing acute and chronic benign VCF.

Evaluation of vertebral bone marrow fat content by chemical-shift MRI in osteoporosis

OBJECTIVE

To quantitatively evaluate vertebral bone marrow fat content and investigate its association with osteoporosis with chemical-shift magnetic resonance imaging (CS-MRI).

MATERIALS AND METHODS

Fifty-six female patients (age range 50-65 years) with varying bone mineral densities as documented with dual x-ray absorptiometry (DXA) were prospectively included in the study. According to the DXA results, the patients were grouped as normal bone density, osteopenic, or osteoporotic. In order to calculate fat content, the lumbar region was visualized in the sagittal plane by CS-MRI sequence. "Region of interest" (ROI)s were placed within L3 vertebral bodies and air (our reference point) at different time points by different radiologists. Fat content was calculated through "signal intensity (SI) suppression rate" and "SI Index". The quantitative values were compared statistically with those obtained from DXA examinations. Kruskal-Wallis, and Mann-Whitney U tests were used for comparisons between groups. The reliability of the measurements performed by two radiologists was evaluated with the "intraclass correlation coefficient". This study was approved by an institutional review board and all participants provided informed consent to participate in the study.

RESULTS

Eighteen subjects with normal bone density (mean T score, 0.39 ± 1.3 [standard deviation]), 20 subjects with osteopenia (mean T score, -1.79 ± 0.38), and 18 subjects with osteoporosis (mean T score, -3 ± 0.5) were determined according to DXA results. The median age was 55.9 (age range 50-64 years) in the normal group, 55.5 (age range 50-64 years) in the osteopenic group, and 55.1 (age range 50-65 years) in the osteoporotic group (p = 0.872). In the CS-MRI examination, the values of "SI suppression ratio" and "SI Index" (median [min:max]) were calculated by the first and second reader, independently. There was no statistically significant difference between the groups with regard to vertebral bone marrow fat content (p > 0.05). According to the "intraclass correlation coefficient", the measurements were reliable (0.55 and 0.60).

CONCLUSIONS

Vertebral bone marrow fat content calculated with CS-MRI is not a reliable parameter for predicting bone mineral density in female patients aged between 50 and 65 years.

Vertebral fracture

Vertebral fractures are usually the first to occur in osteoporosis, provide indisputable evidence of reduced bone strength, and are frequently a harbinger of further vertebral and nonvertebral fracture. Radiologists are best placed to draw attention to the presence of vertebral fractures, most of which are clinically silent. Magnetic resonance imaging supplemented if necessary by computed tomography is usually sufficient to enable distinction between osteoporotic and non-osteoporotic vertebral fracture, without a need for percutaneous biopsy.