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

Diagnosing osteomyelitis in diabetic foot by diffusion-weighted imaging and dynamic contrast material-enhanced magnetic resonance imaging: a systematic review and meta-analysis

AIM

To evaluate the diagnostic performance of diffusion-weighted imaging (DWI) and dynamic contrast enhanced (DCE), for diagnosing osteomyelitis in the diabetic foot.

MATERIALS AND METHODS

A thorough search was carried out to identify suitable studies published up to September 2023. The quality of the studies involved was evaluated using Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). The diagnostic sensitivity and specificity of each imaging modality/method for each specific cut point were summarized. The summary receiver operating characteristic (SROC) curve was calculated using bivariate mixed effects models.

RESULTS

Five studies investigating 187 patients and 234 bone lesions with 110 diagnosed osteomyelitis were enrolled. Four studies used DWI (172 lesions), three studies used DCE techniques (140 lesions) and two studies presented results of conventional MRI (66 lesions). The sensitivity ranges using conventional MRI, DWI and DCE were 65%-100%, 65%-100% and 64%-100%, respectively. The specificity ranges were 50%-61%, 56%-95%, and 66%-93%, respectively. The SROC curve of DWI and DCE was 0.89 (95% CI, 0.86-0.92) and 0.90 (95% CI, 0.87-0.92), respectively.

CONCLUSION

Combining DWI and DCE methods, alongside conventional MRI, can improve the reliability and accuracy of diabetic foot osteomyelitis diagnosis. However, the study recognizes result variability due to varying protocols and emphasizes the need for well-designed studies with standardized approaches. To optimize diagnostic performance, the study recommends considering low ADC values, Ktrans or rapid wash-in rate from DCE such as iAUC60, along with using large ROIs that cover the entire lesion while excluding normal bone marrow.

Dynamic Contrast Enhanced MR Perfusion and Diffusion-Weighted Imaging of Marrow-Replacing Disorders of the Spine: A Comprehensive Review

Significant advancements in cancer treatment have led to improved survival rates for patients, particularly in the context of spinal metastases. However, early detection and monitoring of treatment response remain crucial for optimizing patient outcomes. Although conventional imaging methods such as bone scan, PET, MR imaging, and computed tomography are commonly used for diagnosing and monitoring treatment, they present challenges in differential diagnoses and treatment response monitoring. This review article provides a comprehensive overview of the principles, applications, and practical uses of dynamic contrast-enhanced MR imaging and diffusion-weighted imaging in the assessment and monitoring of marrow-replacing disorders of the spine.

Dynamic Contrast-Enhanced MR Perfusion: Role in Diagnosis and Treatment Follow-Up in Patients with Vertebral Body Tumors

Recent therapeutic advances have led to increased survival times for patients with metastatic disease. Key to survival is early diagnosis and subsequent treatment as well as early detection of treatment failure allowing for therapy modifications. Conventional MR imaging techniques of the spine can be at times suboptimal for identifying viable tumor, as structural changes and imaging characteristics may not differ pretreatment and posttreatment. Advanced imaging techniques such as DCE-MRI can allow earlier and more accurate noninvasive assessment of viable disease by characterizing physiologic changes and tumor microvasculature.

Delay of Aortic Arterial Input Function Time Improves Detection of Malignant Vertebral Body Lesions on Dynamic Contrast-Enhanced MRI Perfusion

Dynamic contrast-enhanced MRI (DCE) is an emerging modality in the study of vertebral body malignancies. DCE-MRI analysis relies on a pharmacokinetic model, which assumes that contrast uptake is simultaneous in the feeding of arteries and tissues of interest. While true in the highly vascularized brain, the perfusion of the spine is delayed. This delay of contrast reaching vertebral body lesions can affect DCE-MRI analyses, leading to misdiagnosis for the presence of active malignancy in the bone marrow. To overcome the limitation of delayed contrast arrival to vertebral body lesions, we shifted the arterial input function (AIF) curve over a series of phases and recalculated the plasma volume values (V_p) for each phase shift. We hypothesized that shifting the AIF tracer curve would better reflect actual contrast perfusion, thereby improving the accuracy of V_p maps in metastases. We evaluated 18 biopsy-proven vertebral body metastases in which standard DCE-MRI analysis failed to demonstrate the expected increase in V_p. We manually delayed the AIF curve for multiple phases, defined as the scan-specific phase temporal resolution, and analyzed DCE-MRI parameters with the new AIF curves. All patients were found to require at least one phase-shift delay in the calculated AIF to better visualize metastatic spinal lesions and improve quantitation of V_p. Average normalized V_p values were 1.78 ± 1.88 for zero phase shifts (P0), 4.72 ± 4.31 for one phase shift (P1), and 5.59 ± 4.41 for two phase shifts (P2). Mann-Whitney U tests obtained p-values = 0.003 between P0 and P1, and 0.0004 between P0 and P2. This study demonstrates that image processing analysis for DCE-MRI in patients with spinal metastases requires a careful review of signal intensity curve, as well as a possible adjustment of the phase of aortic AIF to increase the accuracy of V_p.

Early diagnosis of spinal tuberculosis by magnetic resonance: perfusion weighted imaging in a rabbit model

BACKGROUND

This study aimed to analyze the application value of magnetic resonance (MR)-perfusion weighted imaging (PWI) in the early imaging diagnosis of rabbit spinal tuberculosis.

METHODS

Spinal tuberculosis model was established using ATCC25177 Mycobacterium tuberculosis strain in the lumbar spine of rabbits. Forty rabbits were divided into 2 groups: rabbits in the experiment group were injected with 0.2 ml of 5.0 mg/ml tuberculosis suspension (n = 30) and those in the control group were injected with 0.2 ml of normal saline (n = 10) after vertebrae drilling surgery. Routine MRI and MR-PWI were performed at 4, 6, and 8 weeks after surgery. The statistical difference in terms of perfusion parameter values in the early MR-PWI scan of spinal tuberculosis between two groups was analyzed. The receiver operating characteristic (ROC) curve analysis was conducted for the accuracy of MR-PWI parameters in the early diagnosis of spinal tuberculosis.

RESULTS

Except time to peak, the other perfusion parameters in the experiment group were all increased with time. In addition, the difference between the two groups, as well as the differences at each time point was statistically significant (all P < 0.05). First-pass enhancement rate (Efirst), early enhancement rate (Ee), peak height (PH), maximum slope of increase (MSI), maximum signal enhancement rate (Emax) and signal enhancement rate (SER) showed high values in early diagnosing spinal tuberculosis.

CONCLUSION

The parameters including Efirst, Ee, PH, MSI, Emax and SER may provide valuable imaging evidence for the early diagnosis of spinal tuberculosis in clinical application.

State-of-the-Art Imaging Techniques in Metastatic Spinal Cord Compression

Metastatic Spinal Cord Compression (MSCC) is a debilitating complication in oncology patients. This narrative review discusses the strengths and limitations of various imaging modalities in diagnosing MSCC, the role of imaging in stereotactic body radiotherapy (SBRT) for MSCC treatment, and recent advances in deep learning (DL) tools for MSCC diagnosis. PubMed and Google Scholar databases were searched using targeted keywords. Studies were reviewed in consensus among the co-authors for their suitability before inclusion. MRI is the gold standard of imaging to diagnose MSCC with reported sensitivity and specificity of 93% and 97% respectively. CT Myelogram appears to have comparable sensitivity and specificity to contrast-enhanced MRI. Conventional CT has a lower diagnostic accuracy than MRI in MSCC diagnosis, but is helpful in emergent situations with limited access to MRI. Metal artifact reduction techniques for MRI and CT are continually being researched for patients with spinal implants. Imaging is crucial for SBRT treatment planning and three-dimensional positional verification of the treatment isocentre prior to SBRT delivery. Structural and functional MRI may be helpful in post-treatment surveillance. DL tools may improve detection of vertebral metastasis and reduce time to MSCC diagnosis. This enables earlier institution of definitive therapy for better outcomes.

Diffusion-weighted magnetic resonance imaging of mandibular bone marrow: do apparent diffusion coefficient values of the cervical vertebrae and mandible correlate with age?

OBJECTIVES

The objective of this investigation was to assess the correlation between the mandible and cervical vertebrae bone marrow apparent diffusion coefficient (ADC), obtained by diffusion-weighted magnetic resonance imaging (DWI), with age; to verify the correlation between ADC values from the mandible and the cervical vertebrae; to describe and assess the differences between ADC values obtained from DWI examinations of distinct mandible areas as well as cervical vertebrae.

METHODS

Thirty imaging examinations with DWI for that included the mandible and C1, C2, C3, and C4 vertebrae in the same examination were included. ADC values were collected from 7 distinct areas in the mandible and the cervical vertebrae. Differences between ADC values and non-parametric correlations were performed.

RESULTS

A total of 270 regions were assessed. No significant difference was found between ADC values of all areas tested. An inverse correlation was found between C2, C3, and C4 vertebrae ADC values and age. The significant correlation of anatomic area ADC values and age were presented as graphics to verify if the linear trend of ADC values and age are in accordance with the literature CONCLUSIONS: The mandible area that most correlates with the cervical vertebrae, using ADC values, is the posterior trabecular area, below the inferior molars. Also, C2, C3, and C4 vertebrae ADC values inversely correlate with age, which demonstrates the bone qualitative changes in bone composition. ADC values may be useful for the qualitative assessment of bone quality to screen patients at osteoporosis risk.

Diffusion MRI for Assessment of Bone Quality; A Review of Findings in Healthy Aging and Osteoporosis

Diffusion MRI (dMRI) is a growing imaging technique with the potential to provide biomarkers of tissue variation, such as cellular density, tissue anisotropy, and microvascular perfusion. However, the role of dMRI in characterizing different aspects of bone quality, especially in aging and osteoporosis, has not yet been fully established, particularly in clinical applications. The reason lies in the complications accompanied with implementation of dMRI in assessment of human bone structure, in terms of acquisition and quantification. Bone is a composite tissue comprising different elements, each contributing to the overall quality and functional competence of bone. As diffusion is a critical biophysical process in biological tissues, early changes of tissue microstructure and function can affect diffusive properties of the tissue. While there are multiple MRI methods to detect variations of individual properties of bone quality due to aging and osteoporosis, dMRI has potential to serve as a superior method for characterizing different aspects of bone quality within the same framework but with higher sensitivity to early alterations. This is mainly because several properties of the tissue including directionality and anisotropy of trabecular bone and cell density can be collected using only dMRI. In this review article, we first describe components of human bone that can be potentially detected by their diffusivity properties and contribute to variations in bone quality during aging and osteoporosis. Then we discuss considerations and challenges of dMRI in bone imaging, current status, and suggestions for development of dMRI in research studies and clinics to segregate different contributing components of bone quality in an integrated acquisition. Level of Evidence: 5 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:975-992.

Dual energy CT can aid in the emergent differentiation of acute traumatic and pathologic fractures of the pelvis and long bones

PURPOSE

To determine whether dual energy CT (DECT) scanning can aid in the differentiation between acute traumatic and pathologic fractures of the pelvis and long bones.

METHODS

Retrospective review of 11 patients with 15 pathologic fractures proven by biopsy and/or other advanced imaging modalities. Age- and sex-matched patients with non-pathologic traumatic fractures were used as controls. Studies were reviewed by two readers on syngo.via software before and after the creation of virtual bone marrow color maps. Hounsfield units (HU) of the marrow space at the level of the fracture were recorded on both reviews. Differences between the HU of the bone marrow of traumatic and pathologic fractures were compared using two-tailed unpaired t-test.

RESULTS

A statistically significant difference was found in the HU of the affected bone marrow on DECT virtual noncalcium bone marrow color maps between the pathologic group (mean HU:4.89) and the non-pathologic group (mean HU: - 286.2) (p = 0.0177). HU measurements on the mixed kVp images were 150.4 for the pathologic and 94.1 for the non-pathologic fracture groups, respectively, with no statistical significance (p = 0.272).

CONCLUSIONS

DECT scanning can aid in the differentiation between hematoma at acute traumatic fracture sites and neoplasm at pathologic fracture sites. HU of the bone marrow is higher for pathologic fractures, and the difference in bone marrow attenuation is more evident on the virtual bone marrow color maps.

Differential diagnosis of benign and malignant vertebral compression fractures using conventional and advanced MRI techniques

Atraumatic vertebral compression fractures (VCFs) are commonly encountered in clinical practice and often represent a diagnostic challenge. MRI plays a major role in the differential diagnosis of benign and malignant VCFs, due to its high contrast resolution and the possibility to obtain quantitative and functional data with the employment of advanced sequences. Computer-aided diagnosis systems are also applied on MRI images for this purpose, showing promising results. In this setting, aim of this pictorial review is to elucidate the role of MRI in the differential diagnosis of VCFs with a specific focus on advanced and post-processing imaging techniques.

Neuroimaging and Stereotactic Body Radiation Therapy (SBRT) for Spine Metastasis

Historically, management options for spinal metastases include surgery for stabilization and decompression and/or external beam radiation therapy (EBRT). EBRT is palliative in nature, as it lacks accurate targeting such that the prescribed radiation doses must be limited in order to maintain safety. Modern advancement in imaging and radiotherapy technology have facilitated the development of stereotactic body radiation therapy (SBRT), which provides increased targeted precision for radiation delivery to tumors resulting in lower overall toxicity, particularly to regional structures such as the spinal cord and esophagus, while delivering higher, more effective, and radically ablative radiation doses.Over the past decade, SBRT has been increasingly utilized as a method of treating spinal metastases either as the primary modality or following surgical intervention in both de novo and reirradiation setting. Numerous studies suggest that SBRT is associated with an 80% to 90% rate of 1-year local control across clinical scenarios. For example, studies of SBRT as the primary treatment modality suggest long-term local control rate of 80% to 95% for spinal metastases. Similarly, SBRT in the adjuvant setting following surgery is associated with local control rates ranging from 70% to 100%. Furthermore, because SBRT allows for lower dose to the spinal cord, it has also been used in patients who have had prior radiation therapy, with studies showing 66% to 93% local control in this scenario.

Malignant Metastasis Misdiagnosed as Osteoporotic Compression Fracture: A Case Report

In cases of vertebral collapse after a trivial injury in elderly patients with severe osteoporosis, it can be a diagnostic challenge to determine whether the cause is a benign compression fracture or malignant metastasis. A 78-year-old male patient was referred to the emergency department for the evaluation of weakness of the left lower limb. He had undergone percutaneous vertebroplasty four months earlier after being diagnosed with L3 osteoporotic compression fracture. He was treated with foraminotomy at the L3-4 level after being diagnosed with foraminal stenosis two months earlier at a spine clinic. Magnetic resonance (MR) images showed significant signal change from the vertebral body to the posterior element, and widely spreading extraspinal extension of soft tissue at L3. Computed tomography scan revealed osteolytic changes in regions including the ventral body and pedicle. Emergent decompressive laminectomy and bone biopsy were performed, and the histologic evaluation showed metastatic squamous cell carcinoma. A retrospective review of previous MR images showed obvious pedicle and facet involvement, and paraspinal extension of soft tissue, which are highly suggestive of malignant metastasis.

Differentiating Atypical Hemangiomas and Metastatic Vertebral Lesions: The Role of T1-Weighted Dynamic Contrast-Enhanced MRI

BACKGROUND AND PURPOSE

Vertebral hemangiomas are benign vascular lesions that are almost always incidentally found in the spine. Their classic typical hyperintense appearance on T1- and T2-weighted MR images is diagnostic. Unfortunately, not all hemangiomas have the typical appearance, and they can mimic metastases on routine MR imaging. These are generally referred to as atypical hemangiomas and can result in misdiagnosis and ultimately additional imaging, biopsy, and unnecessary costs. Our objective was to assess the utility of dynamic contrast-enhanced MR imaging perfusion in distinguishing vertebral atypical hemangiomas and malignant vertebral metastases. We hypothesized that permeability and vascular density will be increased in metastases compared with atypical hemangiomas.

MATERIALS AND METHODS

Consecutive patients from 2011 to 2015 with confirmed diagnoses of atypical hemangiomas and spinal metastases from breast and lung carcinomas with available dynamic contrast-enhanced MR imaging were analyzed. Time-intensity curves were qualitatively compared among the groups. Perfusion parameters, plasma volume, and permeability constant were quantified using an extended Tofts 2-compartment pharmacokinetic model. Statistical significance was tested using the Mann-Whitney U test.

RESULTS

Qualitative inspection of dynamic contrast-enhanced MR imaging time-intensity curves demonstrated differences in signal intensity and morphology between metastases and atypical hemangiomas. Quantitative analysis of plasma volume and permeability constant perfusion parameters showed significantly higher values in metastatic lesions compared with atypical hemangiomas (P < .001).

CONCLUSIONS

Our data demonstrate that plasma volume and permeability constant perfusion parameters and qualitative inspection of contrast-enhancement curves can be used to differentiate atypical hemangiomas from vertebral metastatic lesions. This work highlights the benefits of adding perfusion maps to conventional sequences to improve diagnostic accuracy.

Dynamic fluorescent imaging with the activatable probe, γ-glutamyl hydroxymethyl rhodamine green in the detection of peritoneal cancer metastases: Overcoming the problem of dilution when using a sprayable optical probe

Optical fluorescence-guided imaging is increasingly used to guide surgery and endoscopic procedures. Activatable probes are particularly useful because of high target-to-background ratios that increase sensitivity for tiny cancer foci. However, green fluorescent activatable probes suffer from interference from autofluorescence found in biological tissue. The purpose of this study was to determine if dynamic imaging can be used to differentiate specific fluorescence arising from an activated probe in a tumor from autofluorescence in background tissues especially when low concentrations of the dye are applied. Serial fluorescence imaging was performed using various concentrations of γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) which was sprayed on the peritoneal surface with tiny implants of SHIN3-DsRed ovarian cancer tumors. Temporal differences in signal between specific green fluorescence in cancer foci and non-specific autofluorescence in background tissue were measured at 5, 10, 20 and 30 min after application of gGlu-HMRG and were processed into three kinetic maps reflecting maximum fluorescence signal (MF), wash-in rate (WIR), and area under the curve (AUC), respectively. Using concentrations up to 10 μM of gGlu-HMRG, the fluorescence intensity of cancer foci was significantly higher than that of small intestine but only at 30 min. However, on kinetic maps derived from dynamic fluorescence imaging, the signal of cancer foci was significantly higher than that of small intestine after only 5 min even at concentrations as low as 2.5 μM of gGlu-HMRG (p < 0.01). At lower concentrations, kinetic maps derived from dynamic fluorescence imaging were superior to unprocessed images for cancer detection.

Review of the Imaging Features of Benign Osteoporotic and Malignant Vertebral Compression Fractures

Vertebral compression fractures are very common, especially in the elderly. Benign osteoporotic and malignant vertebral compression fractures have extremely different management and prognostic implications. Although there is an overlap in appearances, characteristic imaging features can aid in the distinction between these 2 types of compression fractures. The aim of this review is to characterize the imaging features of benign and malignant vertebral compression fractures seen with CT, PET, SPECT, and MR imaging.

Sildenafil improves blood perfusion in steroid-induced avascular necrosis of femoral head in rabbits via a protein kinase G-dependent mechanism

Objective

The aim of the study were to evaluate the effect of sildenafil against avascular necrosis of femoral head (ANFH) in a rabbit model, and to study the role of protein kinase G (PKG) pathway and vascular endothelial growth factor (VEGF) in ANFH.

Methods

Three weeks after inducing ANFH with methylprednisolone injection, 45 female adult New Zealand white rabbits were divided into three groups and treated as follows: group SI received daily intraperitoneal sildenafil with a dose of 10 mg/kg per day; group SD received daily sildenafil identically to group SI plus auricular vein injection DT3 (a specific PKG inhibitor); group NS received only normal saline. The blood perfusion function in the femoral head was measured by perfusion MRI and ink artery infusion. Bilateral femora heads were examined histopathologically for the presence of osteonecrosis; VEGF of tissue was examined by Western blot analysis; cGMP level and PKG activity were also measured.

Results

The incidence of ANFH in SI group was significantly lower than that observed in NS and SD groups (p < 0.05). VEGF in SI group was increased compared to NS group. cGMP level and PKG activity were also significantly different between NS and SI group (p < 0.05). However, these effects of sildenafil in SD group were all markedly inhibited by the administration of DT3 compared to SI group.

Conclusion

Sildenafil appear to increase the perfusion of femoral head by up-regulating VEGF through PKG pathway. The increased perfusion of femoral head could prevent ANFH.

MRI protocol optimization for quantitative DCE-MRI of the spine

PURPOSE

In this study we systematically investigated different Dynamic Contrast Enhancement (DCE)-MRI protocols in the spine, with the goal of finding an optimal protocol that provides data suitable for quantitative pharmacokinetic modelling (PKM).

MATERIALS AND METHODS

In 13 patients referred for MRI of the spine, DCE-MRI of the spine was performed with 2D and 3D MRI protocols on a 3T Philips Ingenuity MR system. A standard bolus of contrast agent (Dotarem - 0.2ml/kg body weight) was injected intravenously at a speed of 3ml/s. Different techniques for acceleration and motion compensation were tested: parallel imaging, partial-Fourier imaging and flow compensation. The quality of the DCE MRI images was scored on the basis of SNR, motion artefacts due to flow and respiration, signal enhancement, quality of the T₁ map and of the arterial input function, and quality of pharmacokinetic model fitting to the extended Tofts model.

RESULTS

Sagittal 3D sequences are to be preferred for PKM of the spine. Acceleration techniques were unsuccessful due to increased flow or motion artefacts. Motion compensating gradients failed to improve the DCE scans due to the longer echo time and the T₂* decay which becomes more dominant and leads to signal loss, especially in the aorta. The quality scoring revealed that the best method was a conventional 3D gradient-echo acquisition without any acceleration or motion compensation technique. The priority in the choice of sequence parameters should be given to reducing echo time and keeping the dynamic temporal resolution below 5s. Increasing the number of acquisition, when possible, helps towards reducing flow artefacts. In our setting we achieved this with a sagittal 3D slab with 5 slices with a thickness of 4.5mm and two acquisitions.

CONCLUSION

The proposed DCE protocol, encompassing the spine and the descending aorta, produces a realistic arterial input function and dynamic data suitable for PKM.

Spinal metastases: multimodality imaging in diagnosis and stereotactic body radiation therapy planning

Due to increased effectiveness of cancer treatments and increasing survival rates, metastatic disease has become more frequent compared to the past, with the spine being the most common site of bony metastases. Diagnostic imaging is an integral part of screening, diagnosis and follow-up of spinal metastases. In this article, we review the principles of multimodality imaging for tumor detection with respect to their value for diagnosis and stereotactic body radiation therapy planning for spinal metastases. We will also review the current international consensus agreement for stereotactic body radiation therapy planning, and the role of imaging in achieving the best possible treatment plan.

CT Perfusion in Spinal Disease: An Adjunct Tool to Vertebral Body Biopsy

Routine diagnostic techniques are inadequate for diagnosis of spinal diseases. The purpose of this study was to determine whether CT perfusion can differentiate inflammatory diseases like tuberculosis from neoplastic diseases of spine. Thirty-two patients with vertebral body lesions associated with paraspinal mass underwent CT guided bone biopsy and histopathological evaluation. CT perfusion was done in all patients before doing biopsy. Perfusion parameters like blood volume (BV), blood flow (BF) and time to peak (TTP) were calculated and correlated with histopathology. Statistical analysis was done using Mann-Whitney test. p value <0.05 was considered significant. Of 32 cases, 20 had tuberculous osteomyelitis and 12 neoplastic disease (seven metastasis, three plasmacytoma, one each lymphoma and chordoma). Mean rBF was [inflammatory lesions, 1.459 and neoplastic lesions, 18.080 (p<0.000). Mean rBV was (inflammatory disease, 2.8589 and neoplastic lesions, 12.2133 (p<0 .000)). Mean rTTP was [inflammatory pathology, 1.041 and neoplastic pathology, 0.703(p<0.079)]. This shows the deconvolution-based CTP technique's potential for noninvasive diagnosis of at least all inflammatory lesions affecting the spine that are associated with paraspinal mass. Validation of the use of deconvolution CTP parameters for differentiation of inflammatory from neoplastic pathology may permit this technique to be used as an adjunct tool when biopsy when routine imaging findings are inconclusive.

Intravital Microscopy Imaging Approaches for Image-Guided Drug Delivery Systems

Rapid technical advances in the field of non-linear microscopy have made intravital microscopy a vital pre-clinical tool for research and development of imaging-guided drug delivery systems. The ability to dynamically monitor the fate of macromolecules in live animals provides invaluable information regarding properties of drug carriers (size, charge, and surface coating), physiological, and pathological processes that exist between point-of-injection and the projected of site of delivery, all of which influence delivery and effectiveness of drug delivery systems. In this Review, we highlight how integrating intravital microscopy imaging with experimental designs (in vitro analyses and mathematical modeling) can provide unique information critical in the design of novel disease-relevant drug delivery platforms with improved diagnostic and therapeutic indexes. The Review will provide the reader an overview of the various applications for which intravital microscopy has been used to monitor the delivery of diagnostic and therapeutic agents and discuss some of their potential clinical applications.

Bone Metastases of Hepatocellular Carcinoma: Appearance on MRI Using a Standard Abdominal Protocol

OBJECTIVE

The purpose of this study is to describe the MRI features of hepatocellular carcinoma (HCC) bone metastases.

MATERIALS AND METHODS

Thirty-three consecutive patients were included. Two radiologists performed qualitative and quantitative analysis. The coordinator searched for clinical and epidemiologic features related to patients and their primary liver tumors. Earlier MRI studies were also reviewed to determine whether bone metastases were already present and prospectively identified. Descriptive statistics and the Lin concordance correlation coefficient were used.

RESULTS

Chronic hepatitis C virus infection was the most common cause of liver disease (20/32; 62.5%), and diffuse and multifocal HCC were the most frequent types of liver HCCs (28/33; 84.8%). Most lesions were located at the spine (109/155; 70.3%), with high signal intensity on fat-suppressed T1-weighted (54/62; 87.1%) and T2-weighted (53/62; 85.5%) images. Bone metastases were predominantly nodular (48/62; 77.4%), confined to the vertebral body (40/60; 66.7%), and best visualized at the arterial phase (40/62; 64.5%). The ring pattern of enhancement was present in 23 of 62 lesions, and the remaining lesions showed diffuse enhancement. Thirty-five of 62 (56.4%) bone metastases showed arterial peak of enhancement. In 13 of 33 (39.9%) patients, bone metastases were not prospectively reported.

CONCLUSION

Most patients with bone metastases had chronic hepatitis C virus infection and diffuse or multifocal HCC. Metastases are most commonly appreciated as hypervascular focal moderately intensely enhancing nodular masses on the hepatic arterial dominant phase images, with concomitant moderately high signal intensity on fat-suppressed T1- and T2-weighted images.

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.

Blockage of Src by Specific siRNA as a Novel Therapeutic Strategy to Prevent Destructive Repair in Steroid-Associated Osteonecrosis in Rabbits

Vascular hyperpermeability and highly upregulated bone resorption in the destructive repair progress of steroid-associated osteonecrosis (SAON) are associated with a high expression of VEGF and high Src activity (Src is encoded by the cellular sarcoma [c-src] gene). This study was designed to prove our hypothesis that blocking the VEGF-Src signaling pathway by specific Src siRNA is able to prevent destructive repair in a SAON rabbit model. Destructive repair in SAON was induced in rabbits. At 2, 4, and 6 weeks after SAON induction, VEGF, anti-VEGF, Src siRNA, Src siRNA+VEGF, control siRNA, and saline were introduced via intramedullary injection into proximal femora for each group, respectively. Vascularization and permeability were quantified by dynamic contrast-enhanced (DCE) MRI. At week 6 after SAON induction, proximal femurs were dissected for micro-computed tomography (μCT)-based trabecular architecture with finite element analysis (FEA), μCT-based angiography, and histological analysis. Histological evaluation revealed that VEGF enhanced destructive repair, whereas anti-VEGF prevented destructive repair and Src siRNA and Src siRNA+VEGF prevented destructive repair and enhanced reparative osteogenesis. Findings of angiography and histomorphometry were consistent with those determined by DCE MRI. Src siRNA inhibited VEGF-mediated vascular hyperpermeability but preserved VEGF-induced neovascularization. Bone resorption was enhanced in the VEGF group and inhibited in the anti-VEGF, Src siRNA, Src siRNA+VEGF groups as determined by both 3D μCT and 2D histomorphometry. FEA showed higher estimated failure load in the Src siRNA and Src siRNA+VEGF groups when compared to the vehicle control group. Blockage of VEGF-Src signaling pathway by specific Src siRNA was able to prevent steroid-associated destructive repair while improving reconstructive repair in SAON, which might become a novel therapeutic strategy.

Pharmacokinetic modeling of multislice dynamic contrast-enhanced MRI in normal-healing radial fractures: A pilot study

PURPOSE

To define the range of quantitative pharmacokinetic parameters in normal-healing bone with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). DCE-MRI is an established technique for characterizing abnormal tissue microvasculature within solid tumors, but has also shown promise for assessing bone and bone marrow.

MATERIALS AND METHODS

In this study ethical approval for eight patients was obtained. Inclusion criteria were an extra-articular distal radial fracture in patients aged 20-50 years which had united by 6 weeks in plaster cast. This was assessed by an experienced orthopedic surgeon. DCE-MRI was performed at 1.5T 6 weeks after initial injury. The transfer constant (K(trans) ), transfer rate (Kep ), and initial area under the curve (IAUC) values for the fracture site and adjacent marrow were obtained for each patient.

RESULTS

The mean T1 , K(trans) , Kep , and IAUC at the fracture site were 1713 (standard deviation [SD] 645), 0.09 (SD 0.07), 0.17 (SD 0.17) and 4.9 (SD 4.4). The relative standard deviation (RSD) for the fracture site ranged from 0.38 to 0.97 and for the adjacent marrow ranged from 0.95-3.88. Within each patient the range of RSDs was 0.04-0.42 for T1 , 0.26-0.91 for K(trans) , 0.14-1.06 for Kep , and 0.35-0.96 for the IAUC.

CONCLUSION

Pharmacokinetic measures of perfusion can be obtained from healing fractures using DCE-MRI with "excellent" intraclass correlation coefficients for inter- and intrarater reliability. The use of these perfusion parameters is limited by wide patient-to-patient variation and slice-to-slice variation within patients.

Anisotropic field-of-view support for golden angle radial imaging

PURPOSE

To provide anisotropic field-of-view (FOV) support for golden angle radial imaging.

THEORY AND METHODS

In radial imaging, uniform spoke density leads to a circular FOV, which is excessive for objects with anisotropic dimensions. Larson et al previously showed that the angular k-space spoke density can be determined by the desired anisotropic FOV. We show that conventional golden angle sampling can be deployed in an angle-normalized space and transformed back to k-space such that the desired nonuniform spoke density is preserved for arbitrary temporal window length. Elliptical FOVs were used to illustrate this generalized mapping approach. Point-spread-function and spoke density analysis was performed. Phantom and in vivo cardiac images were acquired.

RESULTS

Simulations, phantom, and in vivo experiments confirmed that the proposed method is able to achieve anisotropic FOV while still maintaining the benefits of golden angle sampling. This approach requires 50% less spokes for elliptical FOV with major-to-minor-axis ratio of 1:0.3, when compared with isotropic FOV with the same undersampling factor.

CONCLUSION

We demonstrate a simple method for applying golden angle view ordering to anisotropic FOV radial imaging. This can reduce imaging time for objects with anisotropic dimensions while still allowing arbitrary temporal window selection. Magn Reson Med 76:229-236, 2016. © 2015 Wiley Periodicals, Inc.

[Differentiation between acute osteoporotic and metastatic vertebral body fractures by imaging]

OBJECTIVES

This article discusses the morphological criteria for the differentiation between acute osteoporotic and metastatic vertebral body fractures and new imaging methods, such as diffusion-weighted and chemical shift magnetic resonance imaging (MRI) are presented.

BACKGROUND

The differential diagnostics of osteoporotic and metastatic vertebral body fractures can be difficult in some cases. Both entities normally occur without adequate trauma and predominantly in elderly patients.

IMAGING

Conventional X-ray examination is the initial imaging method of choice but is not able to reliably differentiate between the osteoporotic or metastatic etiology of a fracture. Computed tomography (CT) clearly depicts osseous destruction in metastatic fractures but lacks specificity. Magnetic resonance imaging (MRI) shows a higher sensitivity and specificity in differentiating osteoporotic and metastatic fractures.

DIFFERENTIAL DIAGNOSTICS

The combination CT and MRI allows an accurate diagnosis with respect to an osteoprorotic or metastatic etiology in most of cases but bone marrow edema in acute fractures sometimes leads to ambiguous results and differential diagnostic problems.

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.

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.

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.

How to image patients with spine pain

Different radiological methods play an important role in the work-up of patients complaining of spine pain. Depending on the symptoms and the suspected underlying etiology different methods are selected. In the following presentation we briefly present the different radiological and magnetic resonance tomography methods that are at hand, give some guidance in which method to use, and present the typical imaging findings in some of the most common conditions that presents with spine pain.

Therapy monitoring of skeletal metastases with whole-body diffusion MRI

Current methods of assessing tumor response at skeletal sites with metastatic disease use a combination of imaging tests, serum and urine biochemical markers, and symptoms assessment. These methods do not always enable the positive assessment of therapeutic benefit to be made but instead provide an evaluation of progression, which then guides therapy decisions in the clinic. Functional imaging techniques such as whole-body diffusion magnetic resonance imaging (MRI) when combined with anatomic imaging and other emerging "wet" biomarkers can improve the classification of therapy response in patients with metastatic bone disease. A range of imaging findings can be seen in the clinic depending on the type of therapy and duration of treatment. Successful response to systemic therapy is usually depicted by reductions in signal intensity accompanied by apparent diffusion coefficient (ADC) increases. Rarer patterns of successful treatment include no changes in signal intensity accompanying increases in ADC values (T2 shine-through pattern) or reductions in signal intensity without ADC value changes. Progressive disease results in increases in extent/intensity of disease on high b-value images with variable ADC changes. Diffusion MRI therapy response criteria need to be developed and tested in prospective studies in order to address current, unmet clinical and pharmaceutical needs for reliable measures of tumor response in metastatic bone disease.

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.

Atraumatic vertebral compression fractures: differential diagnosis between benign osteoporotic and malignant fractures by MRI

Atraumatic vertebral compression fractures are a common clinical problem, especially in elderly population. Metastases are the most frequent source of bone tumors, and the spine is a common site of metastatic disease; in case of cortical involvement or osteolysis, they may result in pathological compression fractures. Atraumatic compression fractures may result from other primary neoplasms of vertebrae and also from osteomyelitis, Paget's disease, hyperparathyroidism and other metabolic processes. Osteoporosis is a common source of vertebral compression fractures in elderly population, which may be indistinguishable from those of metastatic origin. The differentiation between osteoporotic compression fractures and malignant fracture is necessary to establish an appropriate staging and a therapeutic planning, especially in the acute and subacute stages. Anamnestic data about preexisting disease can be useful to individuate the potential cause of vertebral collapse. Plain radiography shows some difficulties in distinguishing whether the fracture represents a consequence of osteoporosis, a metastatic lesion or some other primary bone neoplasm. Computed tomography is one of the most suitable imaging techniques for the evaluation of bone structure and fragments and to establish the degree of cortical bone destruction; MR imaging (MRI) is the most helpful radiological investigation in order to provide the basis for the distinction between metastatic and acute osteoporotic compression fractures. The most relevant MRI findings to establish a differential diagnosis are described.

Quantitative analysis of acute benign and malignant vertebral body fractures using dynamic contrast-enhanced MRI

OBJECTIVE

The objective of our study was to evaluate quantitative dynamic contrast-enhanced MRI (DCE-MRI) based on tracer kinetic modeling of perfusion in the differentiation of benign from malignant vertebral fractures.

SUBJECTS AND METHODS

Patients with 26 osteoporotic vertebral fractures (18 women, eight men; mean age, 69 years) and patients with 20 malignant vertebral fractures (nine women, 11 men; mean age, 63.4 years) underwent dynamic contrast-enhanced MRI. T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. Dynamic contrast-enhanced image sets were acquired with a 2D saturation-recovery spoiled gradient-echo sequence. Regions of interest in parameter maps of mean transit time (MTT) and plasma flow in the fractured vertebral bodies were analyzed with a two-compartment tracer kinetic model. Plasma flow, plasma volume (PV), extraction flow, and interstitial volume were calculated. The forward volume transfer constant (K(trans)) and the extracellular volume (ECV) were derived. A two-tailed Fisher exact test, Mann-Whitney U test, and receiver operating characteristic analysis were performed.

RESULTS

Forty-four vertebral fractures in 44 patients could be evaluated. In spots of increased plasma flow, interstitial volume (p = 0.0003), ECV (p = 0.002), and extraction flow (p = 0.03) for osteoporotic and malignant vertebral fractures were significantly different. The mean interstitial volume was 28.62 mL/100 mL for osteoporotic fractures and 11.73 mL/100 mL for malignant fractures, and the area under the curve (AUC) was 0.819 for a cutoff of 11.72 mL/100 mL or less indicating malignancy (sensitivity, 63.2%; specificity, 96.0%). The mean ECV was 52.68 mL/100 mL for osteoporotic fractures and 36.71 mL/100 mL for malignant fractures, and the AUC was 0.802 for a cutoff of 35.83 mL/100 mL or less indicating malignancy (sensitivity, 63.2%; specificity, 92.0%). The mean extraction flow was 15.19 mL/100 mL/min for osteoporotic fractures and 23.67 mL/100 mL/min for malignant fractures, and the AUC was 0.693 for a cutoff of 6.52 mL/100 mL/min or less indicating malignancy (sensitivity, 57.9%; specificity, 92.0%). K(trans), plasma flow, and PV in the spots of increased plasma flow and all quantitative perfusion parameters in the regions of increased MTT did not show any significant differences between benign and malignant fractures.

CONCLUSION

In spots of high plasma flow, which can be determined with a deconvolution analysis, the quantitative perfusion parameters of interstitial volume, ECV, and extraction flow are significantly different between acute osteoporotic and malignant vertebral fractures and can aid in the distinction between the two entities.

Assessing the relation between bone marrow signal intensity and apparent diffusion coefficient in diffusion-weighted MRI

OBJECTIVE

The purposes of this study were to observe the relation between signal intensity (SI) on MR images with a high b value and the apparent diffusion coefficient (ADC) of bone marrow on body diffusion-weighted MR images, to determine cutoff values that enable separation of malignant and normal bone marrow, and to identify the upper ADC values of untreated multiple myeloma lesions and bone metastatic lesions of breast cancer.

MATERIALS AND METHODS

Retrospective evaluations of 16 patients without bone disease, 21 patients with untreated metastases of breast cancer, and 12 patients with myeloma undergoing body diffusion-weighted MRI were performed (b values, 50 s/mm(2) and 800 or 900 s/mm(2)). Normal yellow and red bone marrow regions were compared with metastatic breast and myeloma bone marrow lesions (one to five regions of interest per patient). SI values were normalized to kidney, muscle, and spinal cord SI. Signal-to-noise ratio and ADC for each lesion were recorded. Nonparametric, receiver operating characteristic, and nonlinear regression analyses were performed.

RESULTS

Yellow bone marrow and red bone marrow ADC values were lower than the tumor values (p < 0.001; area under the curve, 0.94; cutoff, 774 μm(2)/s). Tissue-normalized SI and the signal-to-noise ratio of normal bone marrow were also lower than those in tumor regions (p < 0.001; area under the curve, 0.86-0.88). Second-order polynomial curve fitting between SI and ADC was observed (muscle normalized SI, R(2) = 0.4). The 95th percentile and maximum values for mean tumor ADC distribution were 1209 μm(2)/s and 1433 μm(2)/s.

CONCLUSION

Both tissue-normalized SI and ADC measurements allow differentiation between normal bone marrow and tumors of myeloma and breast cancer. The presence of a nonlinear relation between bone marrow SI and ADC values enables definition of an upper limit of ADC value for untreated myeloma lesions and metastatic lesions of breast cancer.

Characterizing hypervascular and hypovascular metastases and normal bone marrow of the spine using dynamic contrast-enhanced MR imaging

BACKGROUND AND PURPOSE

The role of DCE-MR imaging in the study of bone marrow perfusion is only partially developed, though potential applications for routine use in the clinical setting are beginning to be described. We hypothesize that DCE-MR imaging can be used to discriminate between hypervascular and hypovascular metastases based on measured perfusion variables.

MATERIALS AND METHODS

We conducted a retrospective study of 26 patients using conventional MR imaging and DCE-MR imaging. Patients were assigned to a hypervascular or hypovascular group based on tumor pathology. ROIs were drawn around normal-appearing bone marrow (internal controls) and enhancing tumor areas. Average wash-in enhancement slope, average peak enhancement signal percentage change, and average peak enhancement signal percentage change in areas of highest wash-in enhancement slope were calculated. Indices were compared among control, hypervascular, and hypovascular groups. Conventional imaging was assessed by calculating pre- to postgadolinium signal percentage changes in hypervascular and hypovascular lesions.

RESULTS

Hypervascular and hypovascular tumors differed significantly with regard to wash-in enhancement slope (P < .01; hypervascular 95% CI, 22.5-26.5 AU/s; hypovascular 95% CI, 14.1-20.9 AU/s) and peak enhancement signal percentage change in areas of highest wash-in enhancement slope (P < .01; hypervascular 95% CI, 174.1-323.3%; hypovascular 95% CI, 39.5-150.5%). Peak enhancement signal percentage change over all voxels was not significant (P = .62). Areas of normal-appearing marrow showed no appreciable contrast enhancement. Conventional contrast-enhanced MR imaging was unable to differentiate between hypervascular and hypovascular tumors (P = .58).

CONCLUSIONS

Our data demonstrate that, unlike conventional MR imaging sequences, DCE-MR imaging may be a more accurate technique in discriminating hypervascular from hypovascular spinal metastases.

Differential diagnosis of vertebral compression fracture using in-phase/opposed-phase and short TI inversion recovery imaging

BACKGROUND

Magnetic resonance imaging (MRI) is highly useful for detecting diseases of the bone marrow. The sensitivity for detecting compression fracture is very high, but specificity is low for differential diagnosis between malignant and benign cases.

PURPOSE

To evaluate the usefulness of in-phase/opposed-phase and short TI inversion recovery (STIR) magnetic resonance imaging (MRI) of bone marrow for differentiation between benign and malignant vertebral compression fractures.

MATERIAL AND METHODS

A retrospective review of 66 patients with 70 vertebral compression fractures was performed. The signal intensity ratio (SIR) defined as SIR (opposed/in) was calculated from in-phase/opposed-phase MR images, and the signal intensity ratio as SIR (STIR) was calculated from STIR MR images. The relationships between values of SIR (opposed/in) and SIR (STIR) and the differential diagnosis of malignant vs. benign fractures were considered.

RESULTS

When SIR (opposed/in) was less than 1.0, bone marrow was benign. The bone marrow was malignant when both SIR (opposed/in) was greater than 1.0 and SIR (STIR) was less than 2.0.

CONCLUSION

In cases of acute compression fracture, malignant bone marrow showed SIR(STIR) values less than 2.0 and SIR (in/opposed) greater than 1.0. In contrast, benign bone marrow showed SIR (STIR) values greater than 2.5. For chronic compression fracture, malignant bone marrow showed SIR (in/opposed) greater than 1.0. Bone marrow was benign in all cases with SIR (in/opposed) less than 1.0.

Whole-body diffusion-weighted MR imaging in cancer: current status and research directions

Diffusion-weighted (DW) magnetic resonance (MR) imaging is emerging as a powerful clinical tool for directing the care of patients with cancer. Whole-body DW imaging is almost at the stage where it can enter widespread clinical investigations, because the technology is stable and protocols can be implemented for the majority of modern MR imaging systems. There is a continued need for further improvements in data acquisition and analysis and in display technologies. Priority areas for clinical research include clarification of histologic relationships between tissues of interest and DW MR imaging biomarkers at diagnosis and during therapy response. Because whole-body DW imaging excels at bone marrow assessments at diagnosis and for therapy response, it can potentially address a number of unmet clinical and pharmaceutical requirements. There are compelling needs to document and understand how common and novel treatments affect whole-body DW imaging results and to establish response criteria that can be tested in prospective clinical studies that incorporate measures of patient benefit.

Hematopoietic tumors and metastases involving bone

This review explores in depth the most common malignant process involving the bone, namely metastatic disease, as well as some of the more common proliferative forms of hematopoietic disease of bone marrow. These are commonly encountered pathologic processes that often have vague nonspecific symptoms. Imaging findings are frequently subtle on initial radiographs; however, advanced imaging techniques, including CT, MR, and positron emission tomography, allow for accurate diagnosis, staging, and follow-up in most cases.

Dynamic contrast-enhanced MR imaging findings of bone metastasis in patients with prostate cancer

AIM: To evaluate the dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) findings of bone metastasis in prostate cancer patients.

METHODS: Sixteen men with a diagnosis of metastatic prostate cancer to bones were examined with DCE-MRI at 1.5 Tesla. The mean contrast agent concentration vs time curves for bone metastasis and normal bone were calculated and K^trans and ve values were estimated and compared.

RESULTS: An early significant enhancement (wash-out: n = 6, plateau: n = 8 and persistent: n = 2) was detected in all bone metastases (n = 16). Bone metastasis from prostate cancer showed significant enhancement and high K^trans and ve values compared to normal bone which does not enhance in the elderly population. The mean K^trans was 0.101/min and 0.0051/min (P < 0.001), the mean ve was 0.141 and 0.0038 (P < 0.001), for bone metastases and normal bone, respectively.

CONCLUSION: DCE-MRI and its quantitative perfusion parameters may have a role in improving the detection of skeletal metastasis in prostate cancer patients.

Bony metastases: assessing response to therapy with whole-body diffusion MRI

There are no universally accepted methods for assessing tumour response in skeletal sites with metastatic disease; response is assessed by a combination of imaging tests, serum and urine biochemical markers and symptoms assessments. Whole-body diffusion magnetic resonance imaging excels at bone marrow assessments at diagnosis and for therapy evaluations. It can potentially address unmet clinical and pharmaceutical needs for a reliable measure of tumour response. Signal intensity on high b-value images and apparent diffusion coefficient values can be related to underlying biophysical properties of skeletal metastases. Four patterns of change in response to therapy are described this review. Therapy response criteria need to be tested in prospective clinical studies that incorporate conventional measures of patient benefit.