Correlation between the bone marrow blood perfusion and lipid water content on the lumbar spine in female subjects

In vivo Measurement of Intraosseous Vascular Haemodynamic Markers in Human Bone Tissue Utilising Near Infrared Spectroscopy

Objective: Poor vascular health is associated with reduced bone strength and increased risk of fragility fracture. However, direct measurement of intraosseous vascular health is difficult due to the density and mineral content of bone. We investigated the feasibility of using a commercially available continuous wave near infrared spectroscopy (NIRS) system for the investigation of vascular haemodynamics in human bone in vivo.

Approach: An arterial occlusion (AO) protocol was developed for obtaining haemodynamic measurements of the proximal tibia and lateral calf, including assessment of the protocol’s intra operator reproducibility. For 36 participants, intraosseous haemodynamics derived by NIRS were compared to alternative tests of bone health based on dual x-ray absorptiometry (DXA) testing and MRI.

Main Results: Near infrared spectroscopy markers of haemodynamics of the proximal tibia demonstrated acceptable reproducibility, comparable with reproducibility assessments of alternative modalities measuring intraosseous haemodynamics, and the use of NIRS for measuring muscle. Novel associations have been demonstrated between haemodynamic markers of bone measured with NIRS and body composition and bone mineral density (BMD) measurements obtained with both DXA and MRI.

Significance: Near infrared spectroscopy provides inexpensive, non-invasive, safe, and real time data on changes in oxygenated and deoxygenated haemoglobin concentration in bone at the proximal tibia. This study has demonstrated the potential for NIRS to contribute to research investigating the pathophysiological role of vascular dysfunction within bone tissue, but also the limitations and need for further development of NIRS technology.

Validation of diffuse reflectance spectroscopy with magnetic resonance imaging for accurate vertebral bone fat fraction quantification

Safe and accurate placement of pedicle screws remains a critical step in open and minimally invasive spine surgery. The diffuse reflectance spectroscopy (DRS) technique may offer the possibility of intra-operative guidance for pedicle screw placement. Currently, Magnetic Resonance Imaging (MRI) is one of the most accurate techniques used to measure fat concentration in tissues. Therefore, the purpose of this study is to compare the accuracy of fat content measured invasively in vertebrae using DRS and validate it against the Proton density fat fraction (PDFF) derived via MRI. Chemical shift-encoding-based water-fat imaging of the spine was first performed on six cadavers. PDFF images were computed and manually segmented. 23 insertions using a custom-made screw probe with integrated optical fibers were then performed under cone beam computer tomography (CBCT). DR spectra were recorded at several positions along the trajectory as the optical screw probe was inserted turn by turn into the vertebral body. Fat fractions determined via DRS and MRI techniques were compared by spatially correlating the optical screw probe position within the vertebrae on CBCT images with respect to the PDFF images. The fat fraction determined by DRS was found to have a high correlation with those determined by MRI, with a Pearson coefficient of 0.950 (P< 0.001) as compared with PDFF measurements calculated from the MRI technique. Additionally, the two techniques were found to be comparable for fat fraction quantification within vertebral bodies (R² = 0.905).

Evaluation of DCE-MRI postprocessing techniques to assess metastatic bone marrow in patients with prostate cancer

Dynamic contrast-enhanced magnetic resonance imaging was performed in control patients with normal bone marrow and patients with untreated bone metastases of prostate cancer (PCa). Perfusion data were assessed using region of interest-based and pixel-wise current standard postprocessing techniques (signal intensity pattern, increase in signal intensity, upslope, time to peak, extended Kety model, k-means clustering). Bone marrow perfusion is significantly increased in bone metastases of PCa compared to normal bone marrow. Pixel-wise kinetic modeling should be recommended to assess tumoral processes affecting bone marrow microcirculation.

Degenerative endplate changes of the lumbosacral spine: dynamic contrast-enhanced MRI profiles related to age, sex, and spinal level

PURPOSE

To investigate differences in perfusion profiles between degenerative endplate marrow changes and normal vertebral marrow in relation to spinal level, age, and sex with dynamic contrast-enhanced magnetic resonance imaging (DCE MRI).

MATERIALS AND METHODS

Ninety-two consecutive patients referred for evaluation of low back pain or sciatica, without history of malignant or chronic disease, underwent conventional and DCE MRI of the lumbosacral spine. Fifty-two of them demonstrated degenerative endplate marrow changes. Regions of interest were placed on sites of normal marrow (group A) and degenerative changes (group B) on subtracted images. Fitted time-intensity curves (fTICs) were generated and evaluated for curve pattern. Both groups were stratified into upper (L1-L2) and lower (L3-I1) levels, males and females younger or older than 50 years. Perfusion parameters were calculated and statistically compared for both groups and subgroups. Receiver operator curve (ROC) analysis was also performed.

RESULTS

Two fTIC patterns were identified. Perfusion parameters of degenerative changes and normal marrow differed significantly, even when groups were stratified for spinal level, age, and sex (P < 0.05). A time to peak value >108 seconds was characteristic for degenerative changes with sensitivity 69.5% and specificity 84.6%.

CONCLUSION

DCE MRI profiles of degenerative endplate marrow changes of the lumbosacral spine differ significantly from normal marrow regardless of spinal level, age, or sex.

Age, gender, and skeletal variation in bone marrow composition: a preliminary study at 3.0 Tesla

PURPOSE

To evaluate the efficacy of MR Spectroscopy (MRS) at 3.0 Tesla for the assessment of normal bone marrow composition and assess the variation in terms of age, gender, and skeletal site.

MATERIALS AND METHODS

A total of 16 normal subjects (aged between eight and 57 years) were investigated on a 3.0 Tesla GE Signa system. To investigate axial and peripheral skeleton differences, non-water-suppressed spectra were acquired from single voxels in the calcaneus and lumbar spine. In addition, spectra were acquired at multiple vertebral bodies to assess variation within the lumbar spine. Data was also correlated with bone mineral density (BMD) measured in six subjects using dual-energy X-ray absorptiometry (DXA).

RESULTS

Fat content was an order of magnitude greater in the heel compared to the spine. An age-related increase was demonstrated in the spine with values greater in men compared to female subjects. Significant trends in vertebral bodies within the same subjects were also shown, with fat content increasing L5 > L1. Population coefficient of variation (CV) was greater for fat fraction (FF) compared to BMD.

CONCLUSION

Significant normal variations of marrow composition have been demonstrated, which provide important data for the future interpretation of patient investigations.