Reactive bone marrow changes in infectious spondylitis: quantitative assessment with MR imaging

Hematopoietic islands mimicking osteoblastic metastases within the axial skeleton

BACKGROUND

Hyperplasia of the hematopoietic bone marrow in the appendicular skeleton is common. In contrast, focal hematopoietic islands within the axial skeleton are a rare entity and can confuse with osteoblastic metastases. This study aimed to characterize typical MRI and CT findings of hematopoietic islands in distinction from osteoblastic metastases to help both radiologists and clinicians, on the one hand, not to overdiagnose this entity and, on the other hand, to decide on a reasonable work-up.

METHODS

We retrospectively analyzed the imaging findings of 14 hematopoietic islands of the axial skeleton in ten patients (nine females, median age = 65.5 years [range, 49-74]) who received both MRI and CT at initial diagnosis between 2006 and 2020. CT-guided biopsy was performed in five cases to confirm the diagnosis, while the other five patients received long-term MRI follow-up (median follow-up = 28 months [range, 6-96 months]). Diffusion-weighted imaging was available in three, chemical shift imaging respectively ¹⁸F- fluorodeoxyglucose PET/CT in two, and Technetium 99 m skeletal scintigraphy in one of the patients.

RESULTS

All lesions were small (mean size = 1.72 cm²) and showed moderate hypointense signals on T1- and T2-weighted MRI sequences. They appeared isointense to slightly hyperintense on STIR images and slightly enhanced after gadolinium administration. To differentiate this entity from osteoblastic metastases, CT provides important additional information, as hematopoietic islands do not show sclerosis.

CONCLUSIONS

Hematopoietic islands within the axial skeleton can occur and mimic osteoblastic metastases. However, the combination of MRI and CT allows for making the correct diagnosis in most cases.

Diffuse vertebral marrow changes at MRI: Multiple myeloma or normal?

Five MRI patterns of marrow involvement (diffuse, focal, combined diffuse and focal, variegated, and normal) are observed in patients with a marrow proliferative disorder including MM. The wide range of marrow involvement patterns in monoclonal plasma cell proliferative disorders mirrors that of their natural histories that can vary from indolent to rapidly lethal. MRI of the axial bone marrow contributes to stage these disorders, but it should not be obtained for disease detection and characterization because of its limited specificity and sensitivity. At MRI, diffuse benign hematopoietic marrow hyperplasia and marrow heterogeneities in elderly patients mimic the diffuse and variegated patterns observed in MM patients. Careful analysis of fat- and fluid-sensitive MR images and quantitative marrow assessment by using MRI and FDG-PET can contribute in differentiating these changes from those associated with neoplastic marrow infiltration, with some residual overlapping findings.

Fat fraction estimation of morphologically normal lumbar vertebrae using the two-point mDixon turbo spin-echo MRI with flexible echo times and multipeak spectral model of fat: Comparison between cancer and non-cancer patients

PURPOSE

This study aims to compare fat fraction of lumbar vertebrae between cancer and non-cancer patients, using the two-point modified Dixon (mDixon) turbo spin-echo (TSE) MRI with flexible echo times and multipeak fat spectral model.

MATERIALS AND METHODS

Fat fraction was calculated from fat and water images reconstructed by the mDixon TSE technique. Fat fraction of fat-water phantoms measured with the mDixon TSE method was compared with actual fat percentages. Patients who had undergone mDixon spine MRI and dual-energy X-ray absorptiometry within one year and had no bone metastasis were divided into cancer (n=7) and non-cancer (n=23) groups. Fat fraction and bone mineral density (BMD) were compared between the two groups.

RESULTS

Fat fraction of phantoms measured with mDixon MRI was highly correlated with their actual fat percentages (P<0.01, R(2)=0.93). Fat fraction of lumbar vertebrae was significantly lower in cancer patients (58.27±3.16%) than in non-cancer patients (70.48±1.83%) (P<0.01). BMD was not different between cancer (0.912±0.057g/cm(2)) and non-cancer patients (0.876±0.032g/cm(2)) (P=0.58). Fat fraction and BMD showed no significant correlation (P=0.95, R=0.006).

CONCLUSIONS

A two-point mDixon TSE method for assessing fat fraction was reliable. Fat fraction of morphologically normal lumbar vertebrae was significantly lower in cancer patients compared to non-cancer patients, using the two-point mDixon TSE technique.

Magnetic resonance imaging of the spinal marrow: Basic understanding of the normal marrow pattern and its variant

For now, magnetic resonance (MR) is the best noninvasive imaging modality to evaluate vertebral bone marrow thanks to its inherent soft-tissue contrast and non-ionizing nature. A daily challenging scenario for every radiologist interpreting MR of the vertebral column is discerning the diseased from normal marrow. This requires the radiologist to be acquainted with the used MR techniques to judge the spinal marrow as well as its normal MR variants. Conventional sequences used basically to image marrow include T1W, fat-suppressed T2W and short tau inversion recovery (STIR) imaging provides gross morphological data. Interestingly, using non-routine MR sequences; such as opposed phase, diffusion weighted, MR spectroscopy and contrasted-enhanced imaging; may elucidate the nature of bone marrow heterogeneities; by inferring cellular and chemical composition; and adding new functional prospects. Recalling the normal composition of bone marrow elements and the physiologic processes of spinal marrow conversion and reconversion eases basic understanding of spinal marrow imaging. Additionally, orientation with some common variants seen during spinal marrow MR imaging as hemangiomas and bone islands is a must. Moreover, awareness of the age-associated bone marrow changes as well as changes accompanying different variations of the subject’s health state is essential for radiologists to avoid overrating normal MR marrow patterns as pathologic states and metigate unnecessary further work-up.

Diffusion-weighted imaging in musculoskeletal radiology-clinical applications and future directions

Diffusion-weighted imaging (DWI) is an established diagnostic tool with regards to the central nervous system (CNS) and research into its application in the musculoskeletal system has been growing. It has been shown that DWI has utility in differentiating vertebral compression fractures from malignant ones, assessing partial and complete tears of the anterior cruciate ligament (ACL), monitoring tumor response to therapy, and characterization of soft-tissue and bone tumors. DWI is however less useful in differentiating malignant vs. infectious processes. As of yet, no definitive qualitative or quantitative properties have been established due to reasons ranging from variability in acquisition protocols to overlapping imaging characteristics. Even with these limitations, DWI can still provide clinically useful information, increasing diagnostic accuracy and improving patient management when magnetic resonance imaging (MRI) findings are inconclusive. The purpose of this article is to summarize recent research into DWI applications in the musculoskeletal system.

MRI of spinal bone marrow: part 2, T1-weighted imaging-based differential diagnosis

OBJECTIVE

The purpose of this article is to review the structure of bone marrow and the differential diagnosis of bone marrow pathology on the basis of T1-weighted MRI patterns.

CONCLUSION

Bone marrow is an organ that is evaluated routinely during MRI of the spine, particularly lumbar spine evaluation. Thus, it is one of the most commonly performed MRI examinations. T1-weighted MRI is a fundamental sequence in evaluating spinal marrow, and an understanding of T1-weighted MR signal abnormalities is important for the practicing radiologist.

Magnetic resonance imaging evaluation of mandibular condyle bone marrow and temporomandibular joint disc signal intensity in anaemia patients

OBJECTIVES

To compare the signal intensity (SI) of mandibular condyle bone marrow (MCBM) and the temporomandibular joint (TMJ) disc in patients with chronic anaemia and healthy subjects, and to investigate the relationships between bone marrow changes, age, types of anaemia and severity of anaemia.

METHODS

MRIs of 18 patients with chronic anaemia were compared with those of 12 healthy subjects. The SI of MCBM and the TMJ disc were quantitatively evaluated. The SI of the grey matter (GM), white matter (WM) and the lateral pterygoid muscle were also investigated. Relationships between age, MCBM and TMJ disc signal-intensities and anaemia severity, and correlations between the groups, were analysed.

RESULTS

The mean MCBM SI was lower in anaemia patients (including both subgroups and also separately) than in healthy subjects (P < 0.05). No statistical significance was found for GM, WM and the muscle SI between the anaemia patients and healthy patient group (P > 0.05). No statistical significance was found between the groups with respect to the anterior band, whereas the mean SI value of the posterior band in the study group was significantly lower than in healthy subjects (P < 0.05). There were no correlations between age and MCBM SI, or between anaemia severity and MCBM SI.

CONCLUSIONS

Anaemia may cause bone marrow alterations without any internal derangement. Patients with chronic anaemia exhibit lower mandibular condyle bone marrow and posterior band SI than healthy subjects.

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.

Magnetic resonance imaging of bone marrow in oncology, Part 1

Magnetic resonance imaging plays an integral role in the detection and characterization of marrow lesions, planning for biopsy or surgery, and post-treatment follow-up. To evaluate findings in bone marrow on MR imaging, it is essential to understand the normal composition and distribution of bone marrow and the changes in marrow that occur with age, as well as the basis for the MR signals from marrow and the factors that affect those signals. The normal distribution of red and yellow marrow in the skeleton changes with age in a predictable sequence. Important factors that affect MR signals and allow detection of marrow lesions include alterations in fat-water distribution, destruction of bony trabeculae, and contrast enhancement. This two-part article reviews and illustrates these issues, with an emphasis on the practical application of MR imaging to facilitate differentiation of normal marrow, tumor, and treatment-related marrow changes in oncology patients.

MR Imaging Evaluation of the Bone Marrow and Marrow Infiltrative Disorders of the Lumbar Spine

The use of MR imaging in assessing lumbar bone marrow first requires an understanding of the bone marrow's normal composition and the various imaging sequences available for use. One of the most useful sequences is the T1-weighted spin-echo sequence. This sequence may be combined with other sequences such as T2-weighted or diffusion-weighted sequences; techniques such as fat suppression, chemical shift imaging, and contrast-enhanced imaging are discussed. The varying features of normal lumbar marrow related to the normal physiologic changes that occur with aging and with changes in hematopoietic demand are important to understand and are described. The appearances of infiltrative marrow disease are explained on the basis of marrow composition and whether disease causes proliferation, replacement, or depletion of normal marrow components.

[Klippel-Trenaunay syndrome and bone scintigraphy. A case report]

A 34-year-old man with Klippel-Trenaunay syndrome (KTS) was performed three bone scintigraphies. The first one to evaluate the possibility of avascular necrosis of the femoral head. Secondly, to dismiss a reflex sympathetic dystrophy in the affected lower limb and finally, due to knee pain. Magnetic resonance of pelvis and knee and biopsy of iliac spine were performed too.

Normal variants and frequent marrow alterations that simulate bone marrow lesions at MR imaging

MR imaging of the spine is routinely performed for the assessment of patients with spine-related symptoms and of patients with cancer. This article addresses normal variants and frequent alterations of the vertebral bone marrow that are encountered on MR imaging studies and can simulate lesions.

MRI evaluation of cranial bone marrow signal intensity and thickness in chronic anemia

BACKGROUND AND PURPOSE

The aim is to assess the magnetic resonance imaging (MRI) findings for cranial bone marrow (CBM) signal intensity and thickness in patients with chronic anemia and compared these with findings in healthy subjects. We also investigated the relationships between CBM changes and age, type of anemia (hemolytic versus non-hemolytic), and severity of anemia.

METHODS

We quantitatively evaluated CBM signal intensity and thickness on images from 40 patients with chronic anemia (20 with congenital hemolytic anemia (HA) and 20 with acquired anemia) and compared these to findings in 28 healthy subjects. The intensity of CBM relative to scalp, white matter (WM), gray matter (GM), and muscle intensity was also investigated in patients and subjects in the control group. The sensitivity and specificity of CBM hypointense to GM and CBM hypointense to WM as markers of anemia were evaluated. Relationships between age and CBM thickness/intensity, and between anemia severity (hemoglobin (Hb) level) and CBM thickness/intensity were evaluated.

RESULTS

Cranial bone marrow signal intensity was lower in the chronic anemia patients than in the controls (P<0.001). In the control group, CBM intensity was higher than GM intensity, whereas the opposite was true in the patient group. The finding of CBM hypointense to GM was 85% sensitive and 67% specific as a marker of anemia. The corresponding statistics for CBM hypointense to WM were 90 and 46%. The patients had thicker CBM than the controls (temporal, P<0.05; parietal, P<0.005). The subgroup with hemolytic anemia had thicker parietal CBM than the subgroup with non-hemolytic anemia (NHA) (P<0.05) and exhibited thicker temporal and parietal CBM than the controls (temporal, P<0.05; parietal, P<0.001). The CBM thicknesses in the non-hemolytic anemia subgroup were similar to control values (P>0.05 for both). There were no correlations between age and CBM intensity or thickness, or between anemia severity and CBM intensity or thickness.

CONCLUSION

Patients with chronic anemia exhibit lower CBM signal intensity on MRI than healthy subjects. Patients with hemolytic anemia have thicker CBM than patients with non-hemolytic anemia or healthy individuals. Decreased CBM intensity may indicate that the patient has anemia, and increased CBM thickness may specifically point to hemolytic anemia. These MRI findings may signal the need for further evaluation for the clinician.

Magnetic resonance imaging of the axial skeleton in rheumatoid disease

The axial skeleton is a target for both spondyloarthritis and rheumatoid arthritis. While conventional radiography allows the clear documentation of the late stages of inflammatory changes, magnetic resonance imaging (MRI) is sensitive enough to depict early inflammatory lesions. It is, therefore, of particular importance for radiologists and clinicians to know the MRI appearances of inflammatory changes of the axial skeleton in rheumatoid diseases. Typical lesions in ankylosing spondylitis and related conditions comprise spondylitis (Romanus lesion), spondylodiscitis (Andersson lesion), arthritis of the apophyseal joints, the costovertebral and costotransverse joints, and insufficiency fractures of the ankylosed vertebral spine (non-inflammatory type of Andersson lesion). Sacroiliitis is associated with chronic changes such as sclerosis, erosions, transarticular bone bridges, periarticular accumulation of fatty tissue and ankylosis. In addition, acute findings include capsulitis, juxta-articular osteitis and the enhancement of the joint space after contrast medium administration. Another important sign of spondyloarthritis is enthesitis, which affects the interspinal and supraspinal ligaments of the vertebral spine and the interosseous ligaments in the retroarticular space of the sacroiliac joints. The main site of manifestation of spinal involvement in rheumatoid arthritis is the cervical spine. Typical changes are the destruction of the atlantoaxial complex by pannus tissue with subsequent atlantoaxial subluxation, basilar impression and erosion of the dens axis. Changes in the lower segments of the cervical spine are destruction of the apophyseal joints resulting in the so-called stepladder phenomenon. Because of the uniform response of the discovertebral complex to different noxae, a number of different conditions must be distinguished on the basis of the patient's clinical findings and history in combination with their imaging appearance. These conditions comprise degenerative disc disease, septic spondylodiscitis, Scheuermann's disease, Paget's disease and diffuse idiopathic skeletal hyperostosis (DISH).

Imaging of spinal infection

MR imaging is the modality of choice for the detection, staging, and differential diagnosis of inflammatory disorders of the spine. Infectious spondylitis is characterized by the involvement of two adjacent vertebrae and the intervening disk with severe BME and early destruction of the end plates. The disk space is narrowed and typically exhibits water-equivalent signal intensity on T2-weighted or STIR images. Prevertebral and epidural extensions, abscess formation, enhancement of the BME, the disk space, and the surrounding granulation tissue are well demonstrated by gadolinium-enhanced images. Cervical spondylitis frequently involves more than one level. Bone marrow abnormalities may be subtle at this level and increased signal intensity of the disk space on T2-weighted or STIR images is an important finding. The risk for neurologic complications is increased. Granulomatous infections caused by tuberculosis, brucellosis, fungi, and parasites, including hydatid disease (Echinococcus), are frequently associated with imaging findings different from those seen with nonspecific bacterial infection. In patients with chronic infectious spondylitis, diffuse reactive bone marrow changes with decreased signal intensity on T1-weighted images, increased signal intensity on T2-weighted and STIR images, and increased uptake after gadolinium administration may occur. This phenomenon is probably caused by reactive bone marrow stimulation, simulating diffuse hematologic neoplastic disease. Erosive intervertebral osteochondrosis with bandlike disk gadolinium enhancement and BME, which is commonly associated with local pain, is the most important differential diagnosis of bacterial spondylitis.