Normal age-related patterns of cellular and fatty bone marrow distribution in the axial skeleton: MR imaging study

The Spinal Bone Marrow in Health and Disease

Radiologists play a key role in identifying, characterizing, sampling, and, in some cases, treating abnormalities of the spinal bone marrow. This article discusses the composition and dynamic nature of the bone marrow, and how these changes directly correlate with the imaging appearance. Examples of entities that are diffuse, infiltrative, solitary, and multifocal are shown and diagnostic dilemmas and mimics are described The radiologist must be aware of the expected appearance and variability of the bone marrow in order to provide timely, accurate diagnoses.

Vertebral osteomyelitis in patients with infective endocarditis: prevalence, risk factors and mortality

PURPOSE

Infective endocarditis (IE) can be complicated by vertebral osteomyelitis (VO). This study investigates risk factors associated with VO in patients with infective endocarditis, and 6-month mortality and relapse rates in patients with IE and concomitant VO.

METHODS

We performed a observational study in two hospitals between September 2016 and October 2022. Patients with possible or definite IE according European Society of Cardiology (2015) modified criteria were retrieved from the local endocarditis team registries. The VO diagnosis was based on radiological signs, irrespective of clinical symptoms. Multivariable logistic regression analysis was performed to identify risk factors for vertebral osteomyelitis.

RESULTS

We included 633 consecutive patients with IE. A total of 229 (36.2%) patients had prosthetic valves and 127 (20.1%) had cardiac implantable electronic devices. The most frequent causative micro-organism was Streptococcus species (217, 34.3%), followed by Staphylococcus aureus (167, 26.4%). VO was diagnosed in 73 patients (11.5%, 95% CI 9.0%-14.0%). Enterococcus spp.(OR 2.48, 95% CI 1.31-4.52) and age (OR 1.04 per year, 95% CI 1.02-1.06) were independently associated with concomitant VO. The 6-month mortality risk did not differ between patients with (16/73, 21.9%) or without (110/560, 19.6%) VO (HR 1.13, 95% CI 0.67-1.91). Relapse rate was higher in patients with VO but the difference was not statistically significant (16.1 vs. 7.5%, OR 3.62, 95% CI 0.94-13.34).

CONCLUSIONS

Twelve percent of patients with IE also had VO. Among older patients and patients with IE caused by enterococci, there should be a higher index of suspicion for vertebral infection.

Imaging paediatric bone marrow in immunocompromised patients

The bone marrow of immunocompromised patients may exhibit abnormalities due to the underlying disease, adverse treatment effects, and/or complications arising from either source. Such complexity poses a significant diagnostic challenge, particularly in children. Magnetic resonance imaging (MRI) is the modality of choice when evaluating bone marrow in these patients. The high soft tissue contrast of MRI studies allows for detailed evaluation of bone marrow composition, including fat content, cellularity, and vascularisation. During the early years of life, bone marrow undergoes physiological maturation manifesting as a wide range of MRI findings. Understanding the most common MRI features during this phase of development is essential. However, it is equally critical to recognise physiological variations that can mimic pathological changes, as distinguishing between variations and truly pathological abnormalities is crucial for accurate diagnosis and management. This article reviews normal bone marrow and its variations during childhood, as well as the most common alterations presenting in immunocompromised patients.

The Never Ending Story-What Are the Differentiable Magnetic Resonance Imaging Characteristics Between Pyogenic and Mycobacterial Thoracolumbar Infections?

Background/Objectives: This study aimed to determine if MRI features can distinguish between spinal infections caused by pyogenic bacteria and Mycobacterium tuberculosis. Methods: Patients underwent an MRI of the thoracolumbar spine with and without contrast. Three blinded observers assessed the images, using statistical tests for analysis. Results: Demographic characteristics and symptom duration were similar between patients with tuberculous and pyogenic spinal infections. In 36 cases of pyogenic infections, the MRI showed weakly delineated paravertebral tissue enhancement (76%), a hyperintense signal in the T2 TIRM sequences (89%), and homogeneous vertebral body enhancement (89%). In 32 cases of Mycobacterium infections, the MRI revealed well-delineated paravertebral changes, mixed vertebral body signals, and variable enhancement. Pyogenic infections were more often found in the lumbar spine (67%) and typically involved two vertebrae, while tuberculous infections preferred the thoracic spine (75%) and often involved two vertebrae, with 25% affecting three or more vertebrae. Conclusions: The MRI features can help differentiate between pyogenic and tuberculous spine infections, though none are definitive. The study suggests that MRI can be used for initial differentiation or as a diagnostic tool when biopsy or surgical exploration is not possible.

Clinical challenges in prostate cancer management: Metastatic bone-tropism and the role of circulating tumor cells

Prostate cancer (PCa) metastasis is one of the leading causes of cancer-related mortality in men worldwide, primarily due to its tendency to metastasize, with bones of axial skeleton being the favored target-site. PCa bone-metastasis (PCa-BM) presents significant clinical challenges, especially by the weakening of bone architecture, majorly due to the formation of osteoblastic lesions, leading to severe bone fractures. Another complication is that the disease predominantly affects elderly men. Further exploration is required to understand how the circulating tumor cells (CTCs) adapt to varying microenvironments and other biomechanical stresses encountered during the sequential steps in metastasis, finally resulting in colonization specifically in the bone niche, in PCa-BM. Deciphering how CTCs encounter and adapt to different biochemical, biomechanical and microenvironmental factors may improve the prospects of PCa diagnosis, development of novel therapeutics and prognosis. Moreover, the knowledge developed is expected to have broader implications for cancer research, paving the way for better therapeutic strategies and targeted therapies in the realm of metastatic cancer progression across different types of cancers. Our review begins with analyzing the challenges in PCa diagnosis, treatment and management, and delves into the formation and dynamics of CTCs, highlighting their role in PCa metastasis and bone-tropism. We further explore the pivotal role of individual factors in dictating the predisposition of tumors to metastasize to specific secondary sites, such as the noteworthy tendency of PCa bone-metastasis. Finally, we highlight the unresolved questions and potential avenues for further exploration.

The effects of spondylodiscitis on the inflammation burden in infective endocarditis

BACKGROUND

This study investigates the effects of spondylodiscitis on the inflammation burden in infective endocarditis patients.

METHODS

A prospective, observational study was conducted between September 2018 and October 2022 in a non-surgical teaching hospital. Patients with a definite or possible and treated as infective endocarditis were recruited from the Alkmaar Endocarditis Team meetings. Spondylodiscitis was diagnosed based on symptoms and radiological findings. The inflammation burden was defined as the area under the C‑reactive protein (CRP) curve.

RESULTS

174 consecutive patients with infective endocarditis were included (mean age 73 years, 34.5% female). Concomitant spondylodiscitis was present in 32 patients (18%), frequently associated with Streptococcus species (38%). At admission, the mean level of CRP was significantly higher in patients with concomitant spondylodiscitis (p = 0.004). The median CRP area under the curve was significantly higher in spondylodiscitis patients (4.2 × 106 min.mg/l [1.2 × 105 - 1.6 × 107 min.mg/l] vs 2.0 × 106 min.mg/l [8.7 × 104 - 1.6 × 107 min.mg/l], p < 0.001). This difference remained during the whole treatment period. At 6 months of follow-up, rates of mortality and relapse of infective endocarditis were not significantly different.

CONCLUSION

The prevalence of spondylodiscitis in non-referred patients with infective endocarditis was 18%. Endocarditis patients with spondylodiscitis had an increased inflammation burden at and during admission. This difference in normalisation of CRP levels was particularly apparent in the final phase of antibiotic treatment but not related to infectious complications. Despite an augmented inflammation burden, spondylodiscitis was not associated with mortality, cardiac surgery or infectious relapse.

Musculoskeletal perturbations of deep space radiation: Assessment using a Gateway MRI

Human space exploration expansion from Low-Earth Orbit to deep space is accelerating the need to monitor and address the known health concerns related to deep space radiation. The human musculoskeletal system is vulnerable to these risks (alongside microgravity) and its health reflects the well-being of other body systems. Multiparametric magnetic resonance imaging (MRI) is an important approach for assessing temporal physiological changes in the musculoskeletal system. We propose that ultra-low-field MRI provides an optimal low Size Weight and Power (SwaP) solution for non-invasively monitoring muscle and bone changes on the planned Gateway lunar space station. Our proposed ultra-low-field Gateway MRI meets low SWaP design specifications mandated by limited room in the lunar space station. This review summarizes the current state of our knowledge on musculoskeletal consequences of spaceflight, especially with respect to radiation, and then elaborates how MRI can be used to monitor the deleterious effects of space travel and the efficacy of putative countermeasures. We argue that an ultra-low-field MRI in cis-lunar space on the Gateway can provide valuable research and medical insights into the effects of deep space radiation exposure on astronauts. Such an MRI would also allow the development of imaging protocols that would facilitate Earth-bound teams to monitor space personnel musculoskeletal changes during future interplanetary spaceflight. It will especially have a role in monitoring countermeasures, such as the use of melanin, in protecting space explorers.

Compliant substrates mitigate the senescence associated phenotype of stress induced mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are a promising cell population for musculoskeletal cell-based therapies due to their multipotent differentiation capacity and complex secretome. Cells from younger donors are mechanosensitive, evidenced by changes in cell morphology, adhesivity, and differentiation as a function of substrate stiffness in both two- and three-dimensional culture. However, MSCs from older individuals exhibit reduced differentiation potential and increased senescence, limiting their potential for autologous use. While substrate stiffness is known to modulate cell phenotype, the influence of the mechanical environment on senescent MSCs is poorly described. To address this question, we cultured irradiation induced premature senescent MSCs on polyacrylamide hydrogels and assessed expression of senescent markers, cell morphology, and secretion of inflammatory cytokines. Compared to cells on tissue culture plastic, senescent MSCs exhibited decreased markers of the senescence associated secretory phenotype (SASP) when cultured on 50 kPa gels, yet common markers of senescence (e.g., p21, CDKN2A, CDKN1A) were unaffected. These effects were muted in a physiologically relevant heterotypic mix of healthy and senescent MSCs. Conditioned media from senescent MSCs on compliant substrates increased osteoblast mineralization compared to conditioned media from cells on TCP. Mixed populations of senescent and healthy cells induced similar levels of osteoblast mineralization compared to healthy MSCs, further indicating an attenuation of the senescent phenotype in heterotypic populations. These data indicate that senescent MSCs exhibit a decrease in senescent phenotype when cultured on compliant substrates, which may be leveraged to improve autologous cell therapies for older donors.

Adipose tissue as a linchpin of organismal ageing

Ageing is a conserved biological process, modulated by intrinsic and extrinsic factors, that leads to changes in life expectancy. In humans, ageing is characterized by greatly increased prevalence of cardiometabolic disease, type 2 diabetes and disorders associated with impaired immune surveillance. Adipose tissue displays species-conserved, temporal changes with ageing, including redistribution from peripheral to central depots, loss of thermogenic capacity and expansion within the bone marrow. Adipose tissue is localized to discrete depots, and also diffusely distributed within multiple organs and tissues in direct proximity to specialized cells. Thus, through their potent endocrine properties, adipocytes are capable of modulating tissue and organ function throughout the body. In addition to adipocytes, multipotent progenitor/stem cells in adipose tissue play a crucial role in maintenance and repair of tissues throughout the lifetime. Adipose tissue may therefore be a central driver for organismal ageing and age-associated diseases. Here we review the features of adipose tissue during ageing, and discuss potential mechanisms by which these changes affect whole-body metabolism, immunity and longevity. We also explore the potential of adipose tissue-targeted therapies to ameliorate age-associated disease burdens.

Perspectives on anemia: Factors confounding understanding of past occurrence

OBJECTIVE

This paper reviews factors confounding the understanding of the past occurrence of anemia. Using the evidence gathered, a framework is presented of ways forward to enable greater confidence in diagnosing acquired anemia in paleopathology, facilitating insights into longer-term perspectives on this globally relevant condition.

RESULTS

To date, porotic lesions have been central to paleopathological investigations of anemia. The fact that porotic bone lesions are omnipresent and have multiple causes but are likely to have a relatively low, age-related frequency in individuals with anemia, a condition that will have been common in past communities, is confounding.

METHODS

Establishing frameworks that move away from porotic lesions is proposed to facilitate higher levels of more accurate anemia diagnoses in paleopathology.

SIGNIFICANCE

Acceptance of the fundamental principle that anemia may be better considered as a condition requiring metric evaluation of bone structures, supplemented by careful consideration of lesions, will advance understanding of acquired anemia in past communities. Such an approach would provide a clear basis for further consideration of congenital conditions causing anemia, such as sickle-cell disease and thalassemia.

LIMITATIONS

This paper simply opens the conversation on the better diagnosis of anemia in paleopathology; it starts the iterative process of achieving some consensus and progress on diagnosing anemia in paleopathology.

SUGGESTIONS FOR FURTHER RESEARCH

Engagement with ideas presented, sharing data and development of metric parameters will assist in identifying the effects of marrow hyperplasia on bone, enabling more robust work on the important topic of anemia.

Perfusion Imaging of the Musculoskeletal System

Perfusion imaging is the aspect of functional imaging, which is most applicable to the musculoskeletal system. In this review, the anatomy and physiology of bone perfusion is briefly outlined as are the methods of acquiring perfusion data on MR imaging. The current clinical indications of perfusion related to the assessment of soft tissue and bone tumors, synovitis, osteoarthritis, avascular necrosis, Keinbock's disease, diabetic foot, osteochondritis dissecans, and Paget's disease of bone are reviewed. Challenges and opportunities related to perfusion imaging of the musculoskeletal system are also briefly addressed.

[Imaging Findings of Spinal Metastases with Differential Diagnosis: Focusing on Solitary Spinal Lesion in Older Patients]

If a solitary spinal lesion is found in an older patient, bone metastasis can be primarily considered as the diagnosis. Bone metastasis can occur anywhere, but it mostly occurs in the vertebral body and may sometimes show typical imaging findings, presenting as a single lesion. Therefore, differentiating it from other lesions that mimic bone metastases can be challenging, potentially leading to delayed diagnosis and initiation of primary cancer treatment. This review provides an overview of imaging findings and clinical guidelines for bone metastases and discusses its differences from other diseases that can occur as solitary spinal lesions in older patients.

The total mass, number, and distribution of immune cells in the human body

The immune system is a complex network of cells with critical functions in health and disease. However, a comprehensive census of the cells comprising the immune system is lacking. Here, we estimated the abundance of the primary immune cell types throughout all tissues in the human body. We conducted a literature survey and integrated data from multiplexed imaging and methylome-based deconvolution. We also considered cellular mass to determine the distribution of immune cells in terms of both number and total mass. Our results indicate that the immune system of a reference 73 kg man consists of 1.8 × 1012 cells (95% CI 1.5-2.3 × 1012), weighing 1.2 kg (95% CI 0.8-1.9). Lymphocytes constitute 40% of the total number of immune cells and 15% of the mass and are mainly located in the lymph nodes and spleen. Neutrophils account for similar proportions of both the number and total mass of immune cells, with most neutrophils residing in the bone marrow. Macrophages, present in most tissues, account for 10% of immune cells but contribute nearly 50% of the total cellular mass due to their large size. The quantification of immune cells within the human body presented here can serve to understand the immune function better and facilitate quantitative modeling of this vital system.

Recommendations for the Management of Incidental Musculoskeletal Findings on MRI and CT

The Canadian Association of Radiologists (CAR) Incidental Findings Working Group consists of both academic subspeciality and general radiologists tasked with either adapting American College of Radiology (ACR) guidelines to meet the needs of Canadian radiologists or authoring new guidelines where appropriate. In this case, entirely new guidelines to deal with incidental musculoskeletal findings that may be encountered on thoracoabdominal computed tomography or magnetic resonance imaging were drafted, focussing on which findings should prompt recommendations for further workup. These recommendations discuss how to deal with incidental marrow changes, focal bone lesions, abnormalities of the pubic symphysis and sacroiliac joints, fatty soft tissue masses, manifestations of renal osteodystrophy and finally discuss opportunistic osteoporosis evaluation.

Energy Balance and Bone Health: a Nutrient Availability Perspective

PURPOSE OF REVIEW

Obesity is highly prevalent and is associated with bone fragility and fracture. The changing nutrient availability to bone in obesity is an important facet of bone health. The goal of this article is to summarize current knowledge on the effects of carbohydrate and dietary fat availability on bone, particularly in the context of other tissues.

RECENT FINDINGS

The skeleton is a primary site for fatty acid and glucose uptake. The trafficking of carbohydrates and fats into tissues changes with weight loss and periods of weight gain. Exercise acutely influences nutrient uptake into bone and may affect nutrient partitioning to bone. Bone cells secrete hormones that signal to the brain and other tissues information about its energetic state, which may alter whole-body nutrient trafficking. There is a critical need for studies to address the changes that metabolic perturbations have on nutrient availability in bone.

MR Imaging of the Developing Pediatric Marrow: An Overview of Pearls and Pitfalls

The dynamic and developing pediatric skeleton is a well-elucidated process that occurs in a stepwise faction. Normal development has been reliably tracked and described with Magnetic Resonance (MR) imaging. The recognition of the normal patterns of skeletal development is essential, as normal development may mimic pathology and vice versa. The authors review normal skeleton maturation and the corollary imaging findings while highlighting common marrow imaging pitfalls and pathology.

Magnetic Resonance Imaging of Accelerated Bone Remodeling

A regional acceleration of bone remodeling may possibly follow biomechanical insults to the bone. This review assesses the literature and clinical arguments supporting the hypothetical association between accelerated bone remodeling and bone marrow edema (BME)-like signal intensity on magnetic resonance imaging. BME-like signal is defined as a confluent ill-delimited area of bone marrow with a moderate decrease in signal intensity on fat-sensitive sequences and a high signal intensity on fat-suppressed fluid-sensitive sequences. In addition to this confluent pattern, a linear subcortical pattern and a patchy disseminated pattern have also been recognized on fat-suppressed fluid-sensitive sequences. These particular BME-like patterns may remain occult on T1-weighted spin-echo images. We hypothesize that these BME-like patterns, with particular characteristics in terms of distribution and signal, are associated with accelerated bone remodeling. Limitations in recognizing these BME-like patterns are also discussed.

Normal Bone Marrow and Non-neoplastic Systemic Hematopoietic Disorders in the Adult

This article provides an overview of the imaging appearances of normal adult bone marrow with an emphasis on magnetic resonance imaging. We also review the cellular processes and imaging features of normal developmental yellow-to-red marrow conversion and compensatory physiologic or pathologic red marrow reconversion. Key imaging features that differentiate between normal adult marrow, normal variants, non-neoplastic hematopoietic disorders, and malignant marrow disease are discussed, as well as posttreatment changes.

[Clinical Application and Limitations of Myeloma Response Assessment and Diagnosis System (MY-RADS)]

Multiple myeloma, which is a proliferative disease of plasma cells that originate from a single clone, is the second most common hematologic malignancy following non-Hodgkin lymphoma. In the past, its diagnosis was made based on clinical findings (so-called "CRAB") and a skeletal survey using radiographs. However, since the implementation of the International Myeloma Working Group's revised guideline regarding the radiologic diagnosis of multiple myeloma, whole-body (WB) MRI has emerged to play a central role in the early diagnosis of multiple myeloma. Diffusion-weighted imaging and fat quantification using Dixon methods enable treatment response assessment by MRI. In keeping with the trend, a multi-institutional and multidisciplinary consensus for standardized image acquisition and reporting known as the Myeloma Response Assessment and Diagnostic System (MY-RADS) has recently been proposed. This review aims to describe the clinical application of WB-MRI based on MY-RADS in multiple myeloma, discuss its limitations, and suggest future directions for improvement.

Postsurgical Evaluation of the Pediatric Foot and Ankle

This article reviews situations in which surgical treatment is required in the context of different types of pathology in the foot and ankle of children, focusing on the role of imaging in surgical planning and postsurgical assessment. The types of pathology analyzed from this perspective are congenital pathology, neuromuscular disorders, osteochondral lesions, fractures and infection, ligament injuries, and tumors.We address the most common pitfalls of postsurgical imaging of the ankle and foot in children. With some exceptions, postsurgical follow-up focuses on clinical assessment, with imaging follow-up only needed in patients where complications are suspected or symptoms recur. Postoperative assessment of the foot and ankle in children and adolescents requires knowing the indications for surgery and the most common types of interventions, along with their imaging characteristics. The radiologist needs to be aware of the normal sequence of development of structures and how to select adequate imaging techniques to assess anatomy at various stages or in different postsurgical scenarios.

Immune and stem cell compartments of acetabular and femoral bone marrow in hip osteoarthritis patients

OBJECTIVE

Hip osteoarthritis (OA) affects all components of the osteochondral unit, leading to bone marrow (BM) lesions, and unknown consequences on BM cell functionality. We analyzed the cellular composition in OA-affected acetabula compared to proximal femur shafts obtained of hip OA patients to reveal yet not explored immune and stem cell compartments.

DESIGN

Combining flow cytometry, cellular assays and transcription analyses, we performed extensive ex vivo phenotyping of acetabular BM cells from 18 hip OA patients, comparing them with their counterparts from patient-matched femoral shaft BM samples. Findings were related to differences in skeletal sites and age.

RESULTS

Acetabular BM had a greater frequency of T-lymphocytes, non-hematopoietic cells and colony-forming units fibroblastic potential than femoral BM. The incidence of acetabular CD45⁺CD3⁺ T-lymphocytes increased (95% CI: 0.1770 to 0.0.8416), while clonogenic hematopoietic progenitors declined (95% CI: -0.9023 to -0.2399) with age of patients. On the other side, in femoral BM, we observed higher B-lymphocyte, myeloid and erythroid cell frequencies. Acetabular mesenchymal stromal cells (MSCs) showed a senescent profile associated with the expression of survival and inflammation-related genes. Efficient osteogenic and chondrogenic differentiation was detected in acetabular MSCs, while adipogenesis was more pronounced in their femoral counterparts.

CONCLUSION

Our results suggest that distinctions in BM cellular compartments and MSCs may be due to the influence of the OA-stressed microenvironment, but also acetabular vs femoral shaft-specific peculiarities cannot be excluded. These results bring new knowledge on acetabular BM cell populations and may be addressed as novel pathogenic mechanisms and therapeutic targets in OA.

Imaging of Bone Marrow: From Science to Practice

The study of the bone marrow may pose important challenges, due to its changing features over the life span, metabolic stress, and in cases of disease or treatment. Bone marrow adipocytes serve as storage tissue, but they also have endocrine and paracrine functions, contributing to local and systemic metabolism.Among different techniques, magnetic resonance (MR) has the benefit of imaging bone marrow directly. The use of advanced MR techniques for bone marrow study has rapidly found clinical applications. Beyond the clinical uses, it has opened up pathways to assess and quantify bone marrow components, establishing the groundwork for further study of its implications in physiologic and pathologic conditions.We summarize the features of the bone marrow as an organ, address the different modalities available for its study, with a special focus on MR advanced techniques and their addition to analysis in recent years, and review some of the challenges in interpreting the appearance of bone marrow.

Dual-Energy Computed Tomography-Based Quantitative Bone Marrow Imaging in Non-Hematooncological Subjects: Associations with Age, Gender and Other Variables

Background: Our aim is to assess the utility and associations of quantitative bone marrow attenuation (BMA) values measured on clinical dual-energy computed tomography (DECT) exams in non-hematooncologic subjects with skeletal regions, patient age, gender, and other clinical variables. Methods: Our local ethics committee approved this retrospective image data analysis. Between July 2019 and July 2021, 332 eligible patients (mean age, 64 ± 18 years; female, 135) were identified. Inclusion criteria were the availability of a standardized abdominopelvic DECT data set acquired on the same scanner with identical protocol. Eleven regions-of-interest were placed in the T11-L5 vertebral bodies, dorsal iliac crests, and femur necks. Patient age, gender, weight, clinical, habitual variables, inflammation markers, and anemia were documented in all cases. Results: Multi-regression analyses (all, p < 0.05) identified age as the strongest predictor of lumbar BMA (standardized coefficient: β = −0.74), followed by CRP (β = 0.11), LDH (β = 0.11), and gender (β = −0.10). In the lower thoracic spine, age was the strongest predictor (β = −0.58) of BMA, followed by gender (β = −0.09) and LDH (β = 0.12). In femoral bones, age was negatively predictive of BMA (β = −0.12), whereas LDH and anemia were positively predictive (β = 0.16 both). Heart insufficiency significantly decreased (β = 0.12, p = 0.034) a BMA value gradient from higher to lower HU values along the vertebrae T11 and L5, whereas age significantly increased this gradient (β = −0.2, p ≤ 0.001). Conclusions: DECT-based BMA measurements can be obtained from clinical CT exams. BMA values are negatively associated with patient age and influenced by gender, anemia, and inflammatory markers.

Magnetic resonance imaging study of normal cranial bone marrow conversion at high altitude

BACKGROUND

To use conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) to investigate the effects of long-term hypoxia on cranial bone marrow conversion in healthy people at high altitudes.

METHODS

A total of 1,130 individuals were selected from altitudinal areas of 2,000-3,000, 3,100-4,000, and >4,100 m. Each altitude range was divided into 5 age groups: 0-5, 6-14, 15-29, 30-49, and ≥50 years. Firstly, cranial bone marrow typing of the participants in each altitude range was performed on sagittal T1-weighted images (T1WI) according to the average diploe thickness and signal intensity of the normal skull, and the relationship between bone marrow conversion and age was analyzed. Secondly, the apparent diffusion coefficient (ADC) values of the frontal bone, parietal bone, occipital bone, and temporal bone were measured in the DWI post-processing workstation and statistical methods were used to analyze whether different altitudinal gradients and long-term hypoxic environment had any effect on cranial bone marrow conversion.

RESULTS

There was a positive correlation between bone marrow type and age in the healthy populations at all 3 levels of altitude (P<0.05). The average thickness of the cranial diploe also positively correlated with age (P<0.05); in the age ranges of 30-49 and ≥50 years, the ADC values of the occipital and temporal bone marrow positively correlated with increasing altitude (P<0.05).

CONCLUSIONS

The cranial bone marrow of normal people at high altitudes changes from Type I to Type IV with increasing age and under the influence of long-term chronic hypoxia. The bone marrow of the occipital and temporal bones of healthy people aged 30-49 and ≥50 years showed erythromedularization during the process of Type III and IV bone marrow conversion.

A biological approach to adult sex differences in skeletal indicators of childhood stress

OBJECTIVES

In previous work examining the etiology of cribra orbitalia (CO) and porotic hyperostosis (PH) in a contemporary juvenile mortality sample, we noted that males had higher odds of having CO lesions than females. Here, we examine potential reasons for this pattern in greater detail. Four non-mutually exclusive mechanisms could explain the observed sex differences: (1) sex-biased mortality; (2) sexual dimorphism in immune responses; (3) sexual dimorphism in bone turnover; or (4) sexual dimorphism in marrow conversion.

SUBJECTS AND METHODS

The sample consists of postmortem computed tomography scans and autopsy reports, field reports, and limited medical records of 488 individuals from New Mexico (203 females; 285 males) aged between 0.5 and 15 years. We used Kaplan-Meier survival analysis, predicted probabilities, and odds ratios to test each mechanism.

RESULTS

Males do not have lower survival probabilities than females, and we find no indications of sex differences in immune response. Overall, males have a higher probability of having CO or PH lesions than females.

CONCLUSIONS

All results indicate that lesion formation in juveniles is influenced by some combination of sex differences in the pace of red-yellow conversion of the bone marrow and bone turnover. The preponderance of males with CO and PH likely speaks to the potential for heightened osteoblastic activity in males. We find no support for the hypotheses that sex biases in mortality or immune responses impacted lesion frequency in this sample. Sex differences in biological processes experienced by children may affect lesion formation and lesion expression in later life.

Study of bone marrow microstructure in healthy young adults using intravoxel incoherent motion diffusion-weighted MRI

Bone marrow is one of the most important organs in the human body. The evaluation of bone marrow microstructure and gender-related cellular and capillary networks in healthy young adults can help to better understand the process of bone metabolism. Intravoxel incoherent motion (IVIM) provides both diffusion and perfusion quantifications without requiring intravenous contrast agent injection. In this prospective study, 60 healthy young age-matched volunteers (30 men and 30 women) underwent MRI scans at 1.5 T using multi-b-value diffusion-weighted imaging on sagittal planes covering the lumbar bone marrow. The apparent diffusion coefficient (ADC), true ADC (D), pseudo-ADC (D*), and perfusion fraction (f) were calculated from the diffusion-weighted images using the mono- and bi-exponential models. Lumbar cancellous bone (L2-L4) was selected as the region of interest. An independent t-test was used to detect significant differences in ADC values and IVIM parameters between men and women. The differences in IVIM parameters among the L2, L3, and L4 groups were compared with analysis of variance. The D and f values in women were significantly higher than that in men (p = 0.001, 0.026). However, D* was significantly lower in women than that in men (p = 0.001). Furthermore, there was no significant gender difference for the conventional ADC value (p = 0.186). Moreover, there were no significant differences in the D, f, and D* values among the L2, L3, and L4 vertebras of women or men. IVIM parameters can show differences in bone marrow between young women and men. As a non-invasive method, it can assess bone marrow microstructure, such as cellularity and perfusion.

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.

Intracranial Transthecal Fat Migration After a Sacral Fracture: 2 Case Reports

BACKGROUND The presence of fat droplets within the subarachnoid space is an uncommon finding, which is almost exclusively associated with a ruptured dermoid cyst. In a trauma setting, transthecal migration of fat droplets is an extremely rare occurrence. We present 2 case reports of intracranial transthecal migration of fatty bone marrow after sacral fractures. CASE REPORT Both patients presented to the Emergency Department (ED) after falls from a standing height. The first patient, an 84-year-old woman, suffered a stable sacral fracture extending into a large meningeal cyst within the right S2 foramen. Her initial neurological assessment and computed tomography (CT) of the head were unremarkable. As the fracture did not require surgical treatment, she was discharged home and prescribed bed rest, analgesics, and venous thromboembolism prophylaxis. Three days after the injury, she was readmitted to the ED with a mild headache, dizziness, and an episode of nausea and vomiting. A follow-up head CT revealed fat droplets in the subarachnoid space and lateral ventricles. After successful symptomatic treatment, she was discharged home in good general condition. The second patient, a 60-year-old man, underwent a head CT for a scalp hematoma, which revealed fat droplets in the 3rd ventricle and right lateral ventricle. The pelvic CT revealed a large sacral meningeal cyst with microfractures in its wall. He was discharged home on the same day and prescribed bed rest and analgesics. CONCLUSIONS The detection of intracranial intrathecal fat droplets in association with a specific trauma mechanism should initiate the search for a sacral fracture.

Whole-body magnetic resonance imaging for the diagnosis of metastasis in children and adolescents: a systematic review and meta-analysis

Whole-body magnetic resonance imaging (WB-MRI) is a noninvasive imaging method that can be used to diagnose and stage tumors, as well as to assess therapeutic responses in oncology. The objective of this meta-analysis was to evaluate the accuracy of WB-MRI for the diagnosis of metastases in pediatric patients. The following electronic databases were searched: Medline, Embase, Cochrane Central Register of Controlled Trials, Scientific Electronic Library Online, Latin-American and Caribbean Health Sciences Literature, Cumulative Index to Nursing and Allied Health Literature, Web of Science, and ClinicalTrials.gov. All of the selected studies included children and adolescents with histopathological confirmation of a primary tumor. Collectively, the studies included 118 patients ranging in age from 7 months to 19 years. The pooled sensitivity and specificity of WB-MRI were, respectively, 0.964 (95% CI: 0.944-0.978; I² = 0%) and 0.902 (95% CI: 0.882-0.919; I² = 98.4%), with an area under the curve (AUC) of 0.991. We found that WB-MRI had good accuracy for the diagnosis of metastases in pediatric patients and could therefore provide an alternative to complete the staging of tumors in such patients, being a safer option because it does not involve the use of ionizing radiation.

Differentiation of Diffuse Infiltration Pattern in Multiple Myeloma From Hyperplastic Hematopoietic Bone Marrow: Qualitative and Quantitative Analysis Using Whole-Body MRI

BACKGROUND

The visual assessment used for diffuse infiltration of multiple myeloma (MM) is inadequate. It can be difficult to differentiate MM from hyperplastic hematopoietic bone marrow (HHBM) because the MRI signal characteristics overlap.

PURPOSE

To analyze the bone marrow diffuse signal changes on whole-body MRI caused by MM and HHBM.

STUDY TYPE

Retrospective.

SUBJECTS

Thirty Four patients with MM (21 men and 13 women), 22 patients with HHBM (9 men and 13 women), and 15 healthy controls (9 men and 6 women).

FIELD STRENGTH/SEQUENCE

A 3.0 T MRI; diffusion-weighted whole-body imaging with background body signal suppression (DWIBS), modified Dixon T1 fast field echo, and T2 STIR.

ASSESSMENT

Three radiologists analyzed the whole-body MRI alone and in combination with apparent diffusion coefficient (ADC) and fat fraction (FF) with qualitative and quantitative analysis. Normalized T1 and T2 signal intensities (nT1 and nT2) and signal-to-noise ratio (SNR) were obtained.

STATISTICAL TESTS

Kruskal-Wallis and chi-square tests.

RESULTS

The MM group had significantly higher ADC and significantly lower FF than HHBM and control groups. There was no significant difference in nT1, nT2 or SNR between MM and HHBM (P = 0.932, P = 0.097, and P = 0.110, respectively). Receiver operating characteristic (ROC) analysis using ADC and FF cut-off values of 0.47 × 10^-3  mm² /sec and 20.63%, respectively. The AUC was 0.866 for ADC and 0.886 for FF. The quantitative analysis yielded better specificity (observer 1: 81.8% vs. 27.3%; observer 2: 68.2% vs. 22.7%; and observer 3: 72.7% vs. 18.2%) and a higher diagnostic accuracy (observer 1: 82.1% vs. 51.8%; observer 2: 80.4% vs. 50.0%; observer 3: 76.8% vs. 44.6%) than the qualitative analysis.

DATA CONCLUSION

Whole-body MRI combined with DWIBS and mDIXON could be used to differentiate between MM and HHBM. Combining the quantitative ADC and FF with the whole-body MRI improved the specificity and accuracy in differentiating these conditions.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Prevalence and Clinical Significance of Residual or Reconverted Red Bone Marrow on Knee MRI

BACKGROUND

Residual/reconverted red bone marrow (RBM) in adult knees is occasionally observed on routine knee magnetic resonance imaging (MRI). We aimed to identify its prevalence, distribution, and associations with lifestyle factors, knee structural abnormalities, and knee symptoms in young adults.

METHODS

Participants (n = 327; aged = 31-41 years) were selected from the Childhood Determinants of Adult Health (CDAH) knee study. They underwent T1-weighted and proton-density-weighted fat-suppressed MRI scans of knees. Residual/reconverted RBM in distal femur and proximal tibia were graded semi-quantitatively (grades: 0-3) based on the percentage area occupied. Knee structural abnormalities were graded semi-quantitatively using previously published MRI scoring systems. Knee symptoms (pain, stiffness, and dysfunction) were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale during CDAH knee study (year: 2008-2010) and at 6-9-year follow-up during the CDAH-3 study (year: 2014-2019). Associations between definite RBM (grade ≥ 2) and lifestyle factors, knee symptoms, and structural abnormalities were described using log-binomial regressions.

RESULTS

Definite RBM was seen in females only, in 29 out of 154 cases (18.8%), with femoral involvement preceding tibial involvement. Definite RBM was associated with increased BMI (PR = 1.09/kg/m2; 95% CI: 1.03, 1.16), overweight status (PR = 2.19; 95% CI: 1.07, 4.51), and WOMAC knee pain (PR = 1.75; 95% CI: 1.11, 2.74) in cross-section analysis. However, there was no association between RBM and knee-pain after seven years (PR = 1.15; 95% CI: 0.66, 2.00). There were no associations between RBM and knee structural abnormalities.

CONCLUSION

Presence of definite RBM in young adult knees was observed in females only. Definite RBM was associated with overweight measures, and the modest association with knee pain may not be causally related.

Marrow failure and aging: The role of "Inflammaging"

Despite aging and the enormous cellular output required of the marrow every day of the lifespan, most aged patients do not suffer significant marrow failure or cytopenias, an attestation to the proliferative capacity of this system. However, as marrow and its hematopoietic stem cells age, a reduction in ability to maintain homeostasis after stress or with exposure to prolonged chronic inflammation, so-called "inflammaging," may contribute to cytopenias, inadequate immune responses, and dysplasia/leukemia. In some instances, these changes may be intrinsic to the stem cell but in others, there may be extrinsic environmental influences. In this review, the role of aging as it relates to stem cell changes, immune function, and anemia are reviewed.

Pediatric skeletal diffusion-weighted magnetic resonance imaging: part 1 - technical considerations and optimization strategies

Diffusion-weighted MRI, or DWI, is a fast, quantitative technique that is easily integrated into a morphological MR acquisition. The ability of DWI to aid in detecting multifocal skeletal pathology and in characterizing tissue cellularity to a level beyond that possible with other techniques makes it a niche component of multiparametric MR imaging of the skeleton. Besides its role in disease detection and establishing cellularity and character of osseous lesions, DWI continues to be examined as a surrogate biomarker for therapeutic response of several childhood bone tumors. There is increasing interest in harnessing DWI as a potential substitute to alternative modes of imaging evaluation that involve radiation or administration of intravenous contrast agent or radiopharmaceuticals, for example in early detection and diagnosis of capital femoral epiphyseal ischemia in cases of Legg-Calvé-Perthes disease, or diagnosis and staging of lymphoma. The expected evolution of skeletal diffusivity characteristics with maturation and the unique disease processes that affect the pediatric skeleton necessitate a pediatric-specific discussion. In this article, the author examines the developmentally appropriate normal appearances, technique, artifacts and pitfalls of pediatric skeletal DWI.

Clinical imaging of marrow adiposity

Research examining bone marrow adipose tissue (BMAT) has rapidly expanded during the last two decades, leading to advances in knowledge on the role of BMAT in the pathogenesis of bone loss and endocrine disorders. Clinical imaging has played a crucial role for the in vivo assessment of BMAT, allowing non-invasive quantification and evaluation of BMAT composition. In the present work, we review different imaging methods for assessing properties of BMAT. Our aim is to review conventional magnetic resonance imaging (MRI), water-fat imaging, and single-voxel proton magnetic resonance spectroscopy (¹H-MRS), as well as computed tomography (CT)-based techniques, including single energy and dual energy CT. We will also discuss the clinical applications of these methods in type 2 diabetes mellitus, obesity and anorexia nervosa.

Imaging features of the aging spine

Among many degenerative abnormalities commonly found in spine imaging, not all are associated with the patient's symptoms. We aimed to assess features of the standard, asymptomatic aging process of the spine. In this narrative review, we emphasize studies that describe imaging features of the spine in asymptomatic populations of different age groups. Degeneration of the intervertebral discs, bulging, and facet joint arthropathy have been documented in almost 90% of asymptomatic patients over 60 years of age. After the age of 40 years, nearly all patients have anterior and lateral vertebral osteophytes, whereas posterior osteophytes are found in a minority of them. There is a gradual increase in vertebral bone marrow fat composition with age with the acceleration of this process in women after menopause. The prevalence of these findings is common in asymptomatic populations and varies depending on the patient's age. It is essential to differentiate likely natural and age-related findings from pathological abnormalities to make an accurate diagnosis.

Aging and Options to Halt Declining Immunity to Virus Infections

Immunosenescence is a process associated with aging that leads to dysregulation of cells of innate and adaptive immunity, which may become dysfunctional. Consequently, older adults show increased severity of viral and bacterial infections and impaired responses to vaccinations. A better understanding of the process of immunosenescence will aid the development of novel strategies to boost the immune system in older adults. In this review, we focus on major alterations of the immune system triggered by aging, and address the effect of chronic viral infections, effectiveness of vaccination of older adults and strategies to improve immune function in this vulnerable age group.

Axial Spondyloarthritis: Mimics and Pitfalls of Imaging Assessment

Axial spondyloarthritis (axSpA) is a chronic inflammatory disorder that predominantly involves the axial skeleton. Imaging findings of axSpA can be divided into active changes, which include bone marrow edema, synovitis, enthesitis, capsulitis, and intra-articular effusion, and structural changes, which include erosions, sclerosis, bone fatty infiltration, fat deposition in an erosion cavity, and bone bridging or ankylosis. The ability to distinguish between imaging lesions suggestive of axSpA and artifacts or lesions suggestive of other disorders is critical for the accurate diagnosis of axSpA. Diagnosis may be challenging, particularly in early-stage disease and magnetic resonance imaging (MRI) plays a key role in the detection of subtle or inflammatory changes. MRI also allows the detection of structural changes in the subchondral bone marrow that are not visible on conventional radiography and is of prognostic and monitoring value. However, bone structural changes are more accurately depicted using computed tomography. Conventional radiography, on the other hand, has limitations, but it is easily accessible and may provide insight on gross changes as well as rule out other pathological features of the axial skeleton. This review outlines the imaging evaluation of axSpA with a focus on imaging mimics and potential pitfalls when assessing the axial skeleton.

Quantitative assessment of age-related changes in the mandibular bone marrow using apparent coefficient value

PURPOSE

The purpose of this study was to investigate the age-related changes in apparent diffusion coefficient (ADC) values of the mandibular bone marrow using diffusion-weighted imaging (DWI).

MATERIALS AND METHODS

This retrospective cohort study comprised all patients who underwent pantomography and magnetic resonance imaging (MRI) between April 2018 and November 2020 at our institution. A total of 351 participants (140 men, 211 women), aged 15-89 years (mean age 46.01 years), were included in the study. Spearman's correlation coefficients were calculated using age groups as the criterion variable and the ADC values as the explanatory variables. P < 0.05 was considered statistically significant.

RESULTS

The mean ADC value for all age groups was 0.91 ± 0.18 in men and 0.86 ± 0.16 in women (p = 0.016). There was a significant negative correlation between age and the ADC values in each sex group (p < 0.001).

CONCLUSION

This study demonstrates that the normal ADC values of the mandibular bone marrow show significant negative correlation with increasing age. These findings will be useful in the diagnosis of bone marrow diseases.

Infectious Osteomyelitis: Marrying Bone Biology and Microbiology to Shed New Light on a Persistent Clinical Challenge

Infections of bone occur in a variety of clinical settings, ranging from spontaneous isolated infections arising from presumed hematogenous spread to those associated with skin and soft tissue wounds or medical implants. The majority are caused by the ubiquitous bacterium Staphyloccocus (S.) aureus, which can exist as a commensal organism on human skin as well as an invasive pathogen, but a multitude of other microbes are also capable of establishing bone infections. While studies of clinical isolates and small animal models have advanced our understanding of the role of various pathogen and host factors in infectious osteomyelitis (iOM), many questions remain unaddressed. Thus, there are many opportunities to elucidate host-pathogen interactions that may be leveraged toward treatment or prevention of this troublesome problem. Herein, we combine perspectives from bone biology and microbiology and suggest that interdisciplinary approaches will bring new insights to the field. © 2021 American Society for Bone and Mineral Research (ASBMR).

DXA and pQCT derived parameters in Indian children with beta thalassemia major - A case controlled study

Children with beta thalassemia major (BTM) are known to have reduced bone mass which increases incidence of non-traumatic fractures. Few studies have assessed prevalence of fractures and bone health in underprivileged children with BTM. Our objectives were to 1) determine prevalence of fractures in underprivileged Indian children with BTM, 2) assess size corrected bone density and bone geometry using Dual x-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (pQCT) in these children and healthy controls 3) determine predictors of fractures in children with BTM 4) compare differences in bone density between children with BMT with and without fractures. Bone mineral content and areal bone mineral density (aBMD) of lumbar spine and whole body and vertebral fracture assessment (VFA) was performed by DXA in 334 children (3-18 years, 167 BTM + 167 controls). Volumetric BMD (vBMD) and bone geometry were assessed by pQCT (subset, 70 BTM, 70 healthy) at distal radius. Children with BTM had higher prevalence of vertebral and long bone fractures (p < 0.05). DXA aBMD was lower in children with BTM (p < 0.05), whereas, lumbar spine bone mineral apparent density (LSBMAD) was higher (p > 0.05). Children with BTM had lower total distal radial vBMD, cortical vBMD and strength strain index (SSI) at 66% site whereas, distal radial trabecular vBMD at 4% was higher (p < 0.05). On height adjustment, children with BTM had lower muscle area and cortical thickness and higher marrow area (p < 0.05) at 66% site. Age, body size, total body less head (TBLH) aBMD and strength strain index (SSI) were important predictors of fractures in children with BTM. Thus, children with BTM had higher prevalence of non-traumatic fractures. Despite lower areal and volumetric densities, they had higher LSBMAD and trabecular densities which may be attributed to erythroid hyperplasia and iron deposition due to inadequate transfusion and chelation. As LSBMAD is raised in these children, it is unlikely to identify BTM subjects at risk of fracture; VFA thus maybe useful in identifying asymptomatic vertebral fractures.

Quantification and Qualification of Stem Cells From Blood After Mobilization With Filgrastim, and Concentration Using a Platelet-Rich Plasma System

PURPOSE

To determine the cellular composition of a product created with peripheral blood harvested after systemic mobilization with filgrastim and processed with one point-of-care blood concentrating system, i.e., a platelet-rich plasma (PRP) system. The second purpose was to compare mobilized platelet-rich plasma (M-PRP) with a concentrated bone marrow aspirate (cBMA) and a PRP created from the same subjects with the same PRP system.

METHODS

Ten healthy volunteer subjects were recruited for collection and analysis of 3 tissue sources: non-treated peripheral blood, bone marrow aspirate, and filgrastim-mobilized peripheral blood, involving 4 doses of weight-based filgrastim. One point-of-care blood and bone marrow concentrating system was used to create 3 products: PRP, cBMA, and M-PRP. Automated hematologic analysis was performed on all products to quantify total red blood cells, white blood cells (WBCs), monocyte, platelet, and hematopoietic progenitor cell (HPC) concentrations. Flow cytometry was used to determine hematopoietic and mesenchymal progenitor cell populations. Lastly, concentrates were cultured and fibroblast colony-forming units (CFU-F) and morphology of adherent cells were evaluated.

RESULTS

M-PRP contained a greater concentration of WBC (mean difference = 53.2 k/μL; P < .0001), monocytes (mean difference = 8.3 k/μL; P = .002), and a trend toward a greater concentration of HPC (mean difference = 200.5 /μL; P = .060) when compared with PRP. M-PRP contained a greater concentration of monocytes (mean difference = 5.5 k/μL; P = .017) and a trend toward a greater concentration of platelets (mean difference = 348 k/μL; P = .051) and HPC (mean difference = 193.4 /μL; P = .068) when compared with cBMA. M-PRP had a similar concentration of platelets to PRP (mean difference = 110 k/μL; P = .051) and PRP had a greater concentration than cBMA (mean difference = 458 k/μL; P = .003). cBMA remained the only product capable of producing CFU-Fs (446 ± 247 /mL) as neither the M-PRP nor PRP produced CFU-Fs. M-PRP produced colonies consistent with WBC.

CONCLUSIONS

M-PRP, produced with filgrastim mobilized blood and a proprietary PRP system, contained more total WBCs, monocytes, platelets, and HPCs than cBMA and more WBCs, monocytes, and HPCs than PRP.

CLINICAL RELEVANCE

Filgrastim mobilized PRP may be an alternative to cBMA for use as a point-of-care product for orthopaedic treatments.

Intervertebral disc degeneration associated with vertebral marrow fat, assessed using quantitative magnetic resonance imaging

OBJECTIVE

To investigate the potential clinical application of quantitative MRI in assessing the correlation between lumbar vertebrae bone marrow fat deposition and intervertebral disc degeneration.

MATERIALS AND METHODS

A total of 104 chronic lower-back pain volunteers underwent 3.0-T MRI with T2-weighted imaging, T2 mapping, and iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL-IQ) between August 2018 and June 2019. Each disc was assessed with T2 value by T2 mapping, and the L1-S1 vertebral bone marrow fat fraction was assessed by IDEAL-IQ. The differences and relationship between T2 value and the adjacent vertebral bone marrow fat fraction values within the five Pfirrmann groups, five age groups, and five lumbar levels were statistically analyzed.

RESULTS

The vertebral bone marrow fat fraction had a significant negative correlation with T2 values of nucleus pulposus' T2 values (p < 0.001). However, the significant negative correlation was only found between T2 values of nucleus pulposus and adjacent vertebral bone marrow fat in Pfirrmann II-III, L1/2-L5/S1 level, and 40-49 years' age groups. Pfirrmann grades of the intervertebral disc were positively correlated with adjacent vertebrae bone marrow fat fraction (p < 0.05).

CONCLUSION

Lumbar bone marrow fat deposition significantly increases during the early stages of intervertebral disc degeneration. Quantitative measurements of bone marrow fat deposition and water content of intervertebral discs have a predictive value and are an important supplement to the qualitative traditional classification strategies for the early stages of intervertebral disc degeneration.

Confounding factors in multi-parametric q-MRI protocol: A study of bone marrow biomarkers at 1.5 T

OBJECT

The MRI tissue characterization of vertebral bone marrow includes the measurement of proton density fat fraction (PDFF), T₁ and T₂* relaxation times of the water and fat components (T_1W, T_1F, T₂*_W, T₂*_F), IVIM diffusion D, perfusion fraction f and pseudo-diffusion coefficient D*. However, the measurement of these vertebral bone marrow biomarkers (VBMBs) is affected with several confounding factors. In the current study, we investigated these confounding factors including the regional variation taking the example of variation between the anterior and posterior area in lumbar vertebrae, B₁ inhomogeneity and the effect of fat suppression on f.

MATERIALS AND METHODS

A fat suppressed diffusion-weighted sequence and two 3D gradient multi-echo sequences were used for the measurements of the seven VBMBs. A turbo flash B₁ map sequence was used to estimate B₁ inhomogeneities and thus, to correct flip angle for T₁ quantification. We introduced a correction to perfusion fraction f measured with fat suppression, namely f_PDFF.

RESULTS

A significant difference in the values of PDFF, f and f_PDFF, T_1F, T₂*_W and D was observed between the anterior and posterior region. Although, little variations of flip angle were observed in this anterior-posterior direction in one vertebra but larger variations were observed in head-feet direction from L1 to L5 vertebrae.

DISCUSSION

The regional difference in PDFF, f_PDFF and T₂*_W can be ascribed to differences in the trabecular bone density and vascular network within vertebrae. The regional variation of VBMBs shows that care should be taken in reproducing the same region-of-interest location along a longitudinal study. The same attention should be taken while measuring f in fatty environment, and measuring T₁. Furthermore, the MRI-protocol presented here allows for measurements of seven VBMBs in less than 6 min and is of interest for longitudinal studies of bone marrow diseases.

Hyperplasia and accelerated hypertrophy of marrow adipocytes with knee immobilization were sustained despite remobilization

Skeletal disuse can cause an accumulation of bone marrow adipose tissue (MAT) characterized by a combination of marrow adipocyte hyperplasia and/or hypertrophy. The malleability of MAT accumulation and of the hyperplasia and hypertrophy upon remobilization is unknown. In this study, we showed extensive hyperplasia and accelerated hypertrophy of bone marrow adipocytes in the proximal tibia epiphysis of rat knees immobilized for durations between 1 and 32 wk. Similar histomorphometric measures of adipocytes carried out in unoperated controls allowed distinguishing the effects of immobilization from the effects of aging. Although both knee immobilization and aging led to adipocyte hypertrophy, adipocyte hyperplasia was the hallmark signature effect of immobilization on MAT. Both bone marrow adipocyte hyperplasia and hypertrophy were sustained despite knee remobilization for durations up to four times the duration of immobilization. These results suggest that adipocyte hyperplasia is the predominant mechanism explaining MAT accumulation in skeletal disuse. In this model, the changes were unremitting for the investigated time points. Investigating the cellular and molecular mechanisms of marrow adipocyte mechanoregulation will be important to better understand how adipocytes adapt to changes in mechanical environments.NEW & NOTEWORTHY This longitudinal study elucidates the response of marrow adipose tissue adipocytes in weight-bearing joints to changes in different mechanical environments, and we provide insight on the malleability of the changes over time. In a rat animal model, knee immobilization induced hyperplasia and accelerated the age-dependent hypertrophy of adipocytes. Changes in adipocyte number and size were sustained despite unassisted remobilization. Multimodal distributions of cell size were characteristic of bone marrow adipocytes.

Bone marrow magnetic resonance imaging: physiologic and pathologic findings that radiologist should know

Magnetic resonance imaging (MRI) plays a leading role in the non-invasive evaluation of bone marrow (BM). Normal BM pattern depends on the ratio and distribution of yellow and red marrow, which are subject to changes with age, pathologies, and treatments. Neonates show almost entirely red marrow. Over time, yellow marrow conversion takes place with a characteristic sequence leading to a red marrow persistence in proximal metaphyses of long bones. In adults, normal BM is composed of both red (40% water, 40% fat) and yellow marrow (15% water, 80% fat). Due to the higher content of fat, yellow marrow normally appears hyperintense on T1-weighted (T1w) fast spin echo (FSE) sequences and hypo-/iso-intense in short tau inversion recovery (STIR) T2-weighted (T2w); red marrow appears slightly hyperintense in T1w FSE and hyper-/iso-intense in STIR T2w. Pathologic BM has reduced fat and increased water percentages, resulting hypointense in T1w FSE and hyperintense in STIR T2w. In oncologic patients, BM MRI signal largely depends on the treatment (irradiation and/or chemotherapy) and its timing. BM fat and water amount and location in normal red/yellow and pathologic marrow are responsible for different signals in MRI sequences whose knowledge by radiologists may help to differentiate between normal and pathologic findings. Our aim was to discuss and illustrate the MRI of BM physiologic conversion and pathologic reconversion occurring in malignancies and after treatments in cancer patients.

Assessing the effects of body weight on subchondral bone formation with quantitative 18F-sodium fluoride PET

OBJECTIVES

The aim of this study was to quantify subchondral bone remodeling in the elbows, hands, knees, and feet using volumetric and metabolic parameters derived from ¹⁸F-sodium fluoride positron emission tomography (NaF-PET) and to assess the convergent validity of these parameters as an index of joint degeneration and preclinical osteoarthritis.

METHODS

A retrospective analysis was conducted in 34 subjects (32 males, 2 females) with metastatic bone disease who underwent full-body NaF-PET/CT scans. An adaptive contrast-oriented thresholding algorithm was applied to segment NaF-avid regions in the bilateral elbows, hands, knees, and feet of each subject, and metabolically active volume (MAV), maximum standardized uptake value (SUVmax), mean metabolic volumetric product (MVPmean), and partial volume-corrected MVPmean (cMVPmean) of the segmented regions were calculated. Global parameters for MAV, SUVmax, MVPmean, and cMVPmean were defined as the sum of the corresponding values in all the joints of a subject. Inter-rater reliability was determined with Lin's concordance correlation, and associations of global values with subject body weight and age were assessed with Pearson correlation and Spearman correlation analyses.

RESULTS

Inter-rater reliability was observed to be the highest in SUVmax (ρc = 0.99), followed by MVPmean (ρc = 0.96), cMVPmean (ρc = 0.93), and MAV (ρc = 0.93). MAV, MVPmean, and cMVPmean were observed to significantly increase with weight (all p < 0.0001) determined by Pearson correlation. In addition, Spearman rank-order analysis demonstrated a significant correlation between SUVmax and weight in addition to MAV, MVPmean, and cMVPmean and weight (all p < 0.01). No significant association between age and any PET parameter was observed.

CONCLUSIONS

These preliminary data demonstrate the feasibility and reliability of assessing bone turnover at the joints using quantitative NaF-PET. Our findings corroborate the fact that biomechanical factors including mechanical loading and weight-bearing are contributors to osteoarthritis disease progression.

Bone marrow fat change in pediatric patients with non-alcoholic fatty liver disease

OBJECTIVES

To investigate changes of fat in bone marrow (BM) and paraspinal muscle (PSM) associated with the degree of fatty liver in pediatric patients with non-alcoholic fatty liver disease (NAFLD) in consideration of age and body mass index (BMI).

METHODS

Hepatic fat, BM fat, and PSM fat from proton density fat fraction of liver MRI between June 2015 and April 2019 were quantitatively evaluated on axial images of the fat map at the mid-level of T11-L2 vertebral bodies for BM fat and at the mid-level of L2 for PSM fat. Age, height, and weight at the time of MRI were recorded and BMI was calculated. Correlation analysis was performed.

RESULTS

A total of 147 patients (114 male) were included with a mean age of 13.3 ± 2.9 years (range 7-18 years). The mean fat fractions were 24.3 ± 13.0% (2-53%) in liver, 37.4 ± 8.6% (17.3-56%) in vertebral BM, and 2.7 ± 1.1% (1.0-6.9%) in PSM. Age, height, weight, and BMI were not correlated with liver fat or BM fat. However, weight (ρ = 0.174, p = 0.035) and BMI (ρ = 0.247, p = 0.003) were positively correlated with PSM fat. Liver fat showed positive correlation with BM fat when adjusting age and BMI (ρ = 0.309, p<0.001), but not with PSM fat.

CONCLUSIONS

BM fat positively correlates with liver fat, but not with age or BMI in pediatric NAFLD patients.

Bone Marrow Senescence and the Microenvironment of Hematological Malignancies

Senescence is the irreversible arrest of cell proliferation that has now been shown to play an important role in both health and disease. With increasing age senescent cells accumulate throughout the body, including the bone marrow and this has been associated with a number of age-related pathologies including malignancies. It has been shown that the senescence associated secretory phenotype (SASP) creates a pro-tumoural environment that supports proliferation and survival of malignant cells. Understanding the role of senescent cells in tumor development better may help us to identify new treatment targets to impair tumor survival and reduce treatment resistance. In this review, we will specifically discuss the role of senescence in the aging bone marrow (BM) microenvironment. Many BM disorders are age-related diseases and highly dependent on the BM microenvironment. Despite advances in drug development the prognosis particularly for older patients remains poor and new treatment approaches are needed to improve outcomes for patients. In this review, we will focus on the relationship of senescence and hematological malignancies, how senescence promotes cancer development and how malignant cells induce senescence.