Differentiation of acute osteoporotic and malignant compression fractures of the spine: use of additive qualitative and quantitative axial diffusion-weighted MR imaging to conventional MR imaging at 3.0 T

Quantitative imaging methods in osteoporosis

Osteoporosis is characterized by a decreased bone mass and quality resulting in an increased fracture risk. Quantitative imaging methods are critical in the diagnosis and follow-up of treatment effects in osteoporosis. Prior radiographic vertebral fractures and bone mineral density (BMD) as a quantitative parameter derived from dual-energy X-ray absorptiometry (DXA) are among the strongest known predictors of future osteoporotic fractures. Therefore, current clinical decision making relies heavily on accurate assessment of these imaging features. Further, novel quantitative techniques are being developed to appraise additional characteristics of osteoporosis including three-dimensional bone architecture with quantitative computed tomography (QCT). Dedicated high-resolution (HR) CT equipment is available to enhance image quality. At the other end of the spectrum, by utilizing post-processing techniques such as the trabecular bone score (TBS) information on three-dimensional architecture can be derived from DXA images. Further developments in magnetic resonance imaging (MRI) seem promising to not only capture bone micro-architecture but also characterize processes at the molecular level. This review provides an overview of various quantitative imaging techniques based on different radiological modalities utilized in clinical osteoporosis care and research.

Acute benign vertebral compression fractures: "see-through sign" on contrast-enhanced MR images

PURPOSE

To retrospectively evaluate the diagnostic role of the contrast-enhanced MRI (CE-MRI) for differentiation between benign VCFs and malignant VCFs focusing on the internal transparent trabecular bone on CE-MRI (the "see-through sign").

MATERIALS AND METHODS

The institutional review board approved this study and informed consent was waived due to the retrospective nature of the study. From January 2012 to December 2013, all 149 consecutive benign or malignant VCF patients were enrolled for consideration in this study from a CE-MRI database. In the first analysis, four radiologists independently evaluated the presence or absence of the see-through sign. The see-through sign was defined as internal transparent trabecular bone morphology on CE-MRI. The intraclass correlation coefficient (ICC), percentage agreement, and Fleiss's kappa statistics were obtained.

RESULTS

Fifty-seven patients (M:F = 27:30; mean age, 63 years; age range, 20-88 years) who diagnosed as acute benign (n = 24) and malignant (n = 33) VCFs were finally included for the analysis. The results of all readers showed that the see-through sign was associated with acute benign VCFs (p < 0.05). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of the see-through sign ranged from 75-96, 70-88, 66-85, 81-97 %, respectively. The inter-observer reliability of the see-through sign was sufficient with ICC = 0.847, percentage agreement = 78.9, and κ = 0.578.

CONCLUSION

The see-through sign on CE-MRI is featured in acute benign VCFs, and it can be a useful finding to differentiate between benign and malignant VCFs.

Diffusion weighted imaging: Technique and applications

Diffusion weighted imaging (DWI) is a method of signal contrast generation based on the differences in Brownian motion. DWI is a method to evaluate the molecular function and micro-architecture of the human body. DWI signal contrast can be quantified by apparent diffusion coefficient maps and it acts as a tool for treatment response evaluation and assessment of disease progression. Ability to detect and quantify the anisotropy of diffusion leads to a new paradigm called diffusion tensor imaging (DTI). DTI is a tool for assessment of the organs with highly organised fibre structure. DWI forms an integral part of modern state-of-art magnetic resonance imaging and is indispensable in neuroimaging and oncology. DWI is a field that has been undergoing rapid technical evolution and its applications are increasing every day. This review article provides insights in to the evolution of DWI as a new imaging paradigm and provides a summary of current role of DWI in various disease processes.

Usefulness of diffusion-weighted MR imaging for differentiating between benign and malignant superficial soft tissue tumours and tumour-like lesions

OBJECTIVE

To evaluate the usefulness of adding diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping to conventional 3.0-T MRI to differentiate between benign and malignant superficial soft-tissue masses (SSTMs).

METHODS

The institutional review board approved this study and informed consent was waived. The authors retrospectively analyzed conventional MR images including diffusion-weighted images (b-values: 0, 400, 800 s mm(-2)) in 60 histologically proven SSTMs (35 benign and 25 malignant) excluding lipomas. Two radiologists independently evaluated the conventional MRI alone and again with the additional DWI for the evaluation of malignant masses. The mean ADC values measured within an entire mass and the contrast-enhancing solid portion were used for quantitative analysis. Diagnostic performances were compared using receiver-operating characteristic analysis.

RESULTS

For an inexperienced reader, using only conventional MRI, the sensitivity, specificity and accuracy were 84%, 80% and 81.6%, respectively. When combining conventional MRI and DWI, the sensitivity, specificity and accuracy were 96%, 85.7% and 90%, respectively. Additional DWI influenced the improvement of the rate of correct diagnosis by 8.3% (5/60). For an experienced reader, additional DWI revealed the same accuracy of 86.7% without added value on the correct diagnosis. The group mean ADCs of malignant SSTMs were significantly lower than that of benign SSTMs (p < 0.001). The best diagnostic performance with respect to differentiation of SSTMs could be obtained when conventional MRI was assessed in combination with DWI.

CONCLUSION

Adding qualitative and quantitative DWI to conventional MRI can improve the diagnostic performance for the differentiation between benign and malignant SSTMs.

ADVANCES IN KNOWLEDGE

Because the imaging characteristics of many malignant superficial soft-tissue lesions overlap with those of benign ones, inadequate surgical resection due to misinterpretation of MRI often occurs. Adding DWI to conventional MRI yields greater diagnostic performances [area under the receiver-operating characteristic curve (AUC), 0.83-0.99] than does the use of conventional MRI alone (AUC, 0.71-0.93) in the evaluation of malignant superficial masses by inexperienced readers.

Computed Tomography and Magnetic Resonance Imaging in the Differentiation of Osteoporotic Fractures From Neoplastic Metastatic Fractures

Determining whether a low-intensity vertebral fracture in an older person, particularly one with a history of cancer, is due to osteoporosis (OP) or is the result of a metastasis, is a not infrequent clinical problem that has important prognostic and therapeutic implications. The 2 types of fracture are usually indistinguishable on plain radiographs and require higher order imaging for diagnosis. Magnetic resonance imaging is the modality of choice because of its unique ability to depict the bone marrow, which becomes transiently edematous in an acute OP fracture. Preservation of at least part of the normal marrow signal, the visualization of a fracture line parallel to the end plates, the presence of an intravertebral cleft, lack of pedicle involvement, and no extra-osseous mass all favor a benign OP fracture. Absence of the preceding signs, particularly if there is complete replacement of the normal bone marrow and a convex posterior contour of the vertebral body, favors a fracture of malignant origin. Non-routine magnetic resonance sequences using diffusion-weighted imaging and/or chemical shift imaging may be helpful in difficult cases.

Whole body diffusion weighted MRI--a new view of myeloma

The recent consensus statement from the International Myeloma Working Group has introduced the role of whole body (WB) magnetic resonance imaging (MRI) into the management pathway for patients with multiple myeloma. The speed, coverage and high sensitivity of WB diffusion weighted (DW)-MRI and the unique capability to quantify both burden of disease and response to treatment has led to increasing implementation at leading centres worldwide for imaging malignant marrow disease, both primary and metastatic. WB DW-MRI is likely to have a significant impact on management decisions and pathways for patients with multiple myeloma. This review will introduce the basic principles of DW-MRI, present current evidence for patients with myeloma and will discuss practicalities and exciting future applications.

Differentiation of malignant from benign soft tissue tumours: use of additive qualitative and quantitative diffusion-weighted MR imaging to standard MR imaging at 3.0 T

OBJECTIVES

To determine the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) to differentiate malignant from benign soft tissue tumours at 3.0 T.

METHODS

3.0 T MR images including DWI in 63 patients who underwent surgery for soft tissue tumours were retrospectively analyzed. Two readers independently interpreted MRI for the presence of malignancy in two steps: standard MRI alone, standard MRI and DWI with qualitative and quantitative analysis combined.

RESULTS

There were 34 malignant and 29 non-malignant soft tissue tumours. In qualitative analysis, hyperintensity relative to skeletal muscle was more frequent in malignant than benign tumours on DWI (P=0.003). In quantitative analysis, ADCs of malignant tumours were significantly lower than those of non-malignant tumours (P≤0.002): 759±385 vs. 1188±423 μm(2)/sec minimum ADC value, 941±440 vs. 1310±440 μm(2)/sec average ADC value. The mean sensitivity, specificity and accuracy of both readers were 96%, 72%, and 85% on standard MRI alone and 97%, 90%, and 94% on standard MRI with DWI.

CONCLUSIONS

The addition of DWI to standard MRI improves the diagnostic accuracy for differentiation of malignant from benign soft tissue tumours at 3.0 T.

KEY POINTS

DWI has added value for differentiating malignant from benign soft tissue tumours. Addition of DWI to standard MRI at 3.0 T improves the diagnostic accuracy. Measurements of both ADC min within solid portion and ADC av are helpful.

Differentiating benign from malignant vertebral fractures using T1 -weighted dynamic contrast-enhanced MRI

PURPOSE

To differentiate pathologic from benign vertebral fractures, which can be challenging. We hypothesized that dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can aid in the noninvasive distinction between pathologic and benign fractures.

MATERIALS AND METHODS

Consecutive patients with vertebral fractures who underwent DCE-MRI, biopsy, and kyphoplasty were reviewed. Forty-seven fractures were separated into pathologic and benign fractures. Benign fractures were in turn separated into acute and chronic fractures for further comparison. Regions of interest (ROIs) were placed over fractured vertebral bodies. Perfusion parameters: plasma volume (Vp ), K(trans) , wash-in slope, peak enhancement, and area under the curve (AUC) were measured and compared between the three different groups of fractures. A Mann-Whitney U-test was conducted to assess the difference between the groups.

RESULTS

Pathologic fractures had significantly higher (P < 0.01) perfusion parameters (Vp , K(trans) , wash-in slope, peak enhancement, and AUC) compared with benign fractures. We also found significant differences (P < 0.001) in all parameters between chronic and acute fractures. Vp and K(trans) were able to differentiate between pathologic and acute fractures (P < 0.01). No significant differences were found with peak enhancement (P = 0.21) and AUC (P = 0.4) between pathologic and acute fractures.

CONCLUSION

Our data demonstrate that T1 -weighted DCE-MRI has potential to differentiate between pathologic vs. benign, acute vs. chronic, and most important, benign acute vs. pathologic vertebral fractures.