MRI Measurement of Bone Marrow Cellularity for Radiation Dosimetry

Abstract

The current gold standard for measuring marrow cellularity is the bone marrow (BM) biopsy of the iliac crest. This measure is not predictive of total marrow cellularity, because the biopsy volume is typically small and fat fraction varies across the skeleton. MRI and localized MR spectroscopy have been demonstrated as noninvasive means for measuring BM cellularity in patients. The accuracy of these methods has been well established in phantom studies and in the determination of in vivo hepatic fat fractions but not for in vivo measurement of BM cellularity. Methods: Spoiled gradient-echo in vivo images of the femur, humerus, upper spine, and lower spine were acquired for 2 dogs using a clinical 3-T MRI scanner. Single-peak iterative decomposition of water and fat with echo asymmetry and least squares (SP-IDEAL) was used to derive BM fat fractions. Stimulated-echo acquisition mode spectra were acquired in order to perform multipeak IDEAL with precalibration (MP-IDEAL). In vivo accuracy was validated by comparison with histology measurements. Histologic fat fractions were derived from adipocyte segmentation. Results: Bland-Altman plots demonstrated excellent agreement between SP-IDEAL and histology, with a mean difference of 20.52% cellularity and most differences within 62% cellularity, but agreement between MP-IDEAL and histology was not as good (mean difference, 27% cellularity, and differences between 5% and 220%). Conclusion: Adipocyte segmentation of histology slides provides a measure of volumetric fat fraction (i.e., adipocyte volume fraction [AVF]) and not chemical fat fraction, because fat fraction measured from histology is invariant to the relative abundances of lipid chemical species. In contrast, MP-IDEAL provides a measure of chemical fat fraction, thus explaining the poor agreement of this method with histology. SP-IDEAL measures the relative abundance of methylene lipids, and this measure is shown to be equivalent to AVF. AVF provides the appropriate parameter to account for patient-specific cellularity in BM mass predictive equations and is consistent with current micro-CTbased models of skeletal dosimetry.

Evaluation of green pepper (Capsicum annuum L.) juice on the weight gain and changes in lipid profile in C57BL/6 mice fed a high-fat diet

“…From the results obtained in this study, we presumed that it shows a similar trend among fat image volume from a 4.7 T MRI, histology from adipocytes, and fat mass gain from mice. Some recent studies showed that MRI and localised MR spectroscopy are used to confirm the amount of body fat in obese mice or for phantom studies and the determination of in vivo hepatic fat fractions . In this study, by using staining techniques, we observed that treatments with green pepper juice tended to reduce the amount of adipose tissue; and by using non‐invasive MRI in a mouse model receiving a high‐fat diet with green pepper juice we showed a decrease in abdominal fat mass.…”

Quantitative MRI and spectroscopy of bone marrow

“…Insufficiency fractures and hematologic toxicity are clinically important complications of radiation therapy . Bone marrow water/fat quantification has been proposed for measuring the patient‐specific bone marrow cellularity distribution in radiation therapy planning . The quantitative evaluation of radiation therapy‐associated changes has only been performed in a limited number of studies.…”

“…155 Bone marrow water/fat quantification has been proposed for measuring the patient-specific bone marrow cellularity distribution in radiation therapy planning. 156 The quantitative evaluation of radiation therapy-associated changes has only been performed in a limited number of studies. Changes of irradiated bone marrow reflecting fatty replacement are traditionally recognized by prolonged T 1 relaxation times.…”

Bone marrow fat is increased in chronic kidney disease by magnetic resonance spectroscopy

“…Bone marrow fat can be quantified by magnetic resonance spectroscopy (MRS), which utilizes the resonance frequency of protons to differentiate fat from water; the ratio provides an assessment of chemical composition of bone marrow [14]. In animal studies, the volume of bone marrow fat by biopsy strongly correlates ( r =0.9) with fat volume assessed by MRS [15]. MRS is currently used for quantifying the bone marrow fat in the normal population, with lumbar spine being the most studied site [16].…”