Monitoring of Cellular Changes in the Bone Marrow following PTH(1-34) Treatment of OVX Rats Using a Portable Stray-Field NMR Scanner.

Osteoporosis is characterized by reduction in trabecular bone in conjunction with increased marrow cell adiposity. While these changes occur within weeks, monitoring of treatment efficacy as performed by DEXA is sensitive only to long-term changes. MRI is sensitive to bone marrow changes but is less affordable. In a recent study, we have shown that a stray-field NMR can monitor bone marrow cellular changes that are related to osteoporosis. Objectives. To demonstrate sensitivity of a low-field tabletop NMR scanner to bone marrow dynamics following hormonal treatment in rats. Methods. Two-month-old female rats (n = 36) were ovariectomized (OVX) and dosed for the ensuing 3 or 5 weeks with 20 mg/kg of PTH(1-34). Hind limbs femurs and tibiae were isolated and underwent ex vivo microradiography and histology and NMR relaxometry at 6 weeks (preventive experiment) and 11 weeks (therapeutic treatment experiment) after OVX. Results. OVX rats developed osteoporotic changes including adipogenic marrow compared to Sham and PTH treated rats. T2 and ADC NMR relaxation coefficients were found to correlate with marrow composition. Conclusions. This study suggests that stray-field NMR, an affordable method that is sensitive to the rapid cellular changes in bone marrow, may have a clinical value in monitoring hormonal treatment for osteoporosis.

Detection of bone marrow changes related to estrogen withdrawal in rats with a tabletop stray-field NMR scanner.

PURPOSE: Osteoporosis is characterized by a decrease in bone mineral density (BMD). A preliminary stage of the disease is progressive bone marrow adiposity, caused by imbalance between osteogenesis and adipogenesis in the marrow. Detection of osteoporosis relies on the quantification of BMD with techniques such as dual-energy X-ray absorptiometry. This work aimed to detect bone marrow changes in an experimental model of osteopenia using a low-field tabletop NMR scanner. METHODS: An experiment was performed on 32 female rats, 3 months old, 16 of which were ovariectomized (OVX) and 16 were sham-operated (sham). The femur and tibia from both hind limbs were isolated and underwent ex vivo NMR scans at four time points after the OVX and sham operations. NMR scans were complemented by BMD measurements and histology. RESULTS: Significant changes in the bone marrow of ovariectomized rats, relative to sham operated rats, were observed after 3.5 and 4.5 months. Bone marrow adiposity was detected by significant changes in T1 and T2 relaxation times, and in the diffusion coefficient. CONCLUSIONS: This study suggests a potential detection of changes to the bone marrow using a tabletop NMR device. Clinical translation may facilitate screening, early detection of bone weakening as a result of estrogen withdrawal, and monitoring of treatment efficacy. Magn Reson Med 78:860-870, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

In vivo assessment of aged human skin with a unilateral NMR scanner.

Human skin undergoes morphological and biochemical changes as a result of chronological aging and exposure to solar ultraviolet irradiation (photoaging). Noninvasive detection of these changes may aid in the prevention and treatment of both types of aging. This article presents a noninvasive method for the evaluation of aging skin with a unilateral stray field NMR scanner. These portable and inexpensive scanners may be suitable for in-depth skin characterization. In vivo profiles of sun-protected and sun-exposed skin from the forearms of female subjects of different ages (n = 9) were measured. Skin biopsies for histopathological examination were used as reference. T2 analysis with a bi-exponential decay model was applied and the extracted parameters were examined as markers for dermal aging. In the upper reticular dermis, a significant increase in the fraction of the slow T2 component and in the T2 value itself was found to correlate with chronological aging. For most subjects, there was an additional increase in the values of the slow T2 component and the T2 values from the sun-exposed forearm, superimposed on that measured for the sun-protected forearm. These results are in agreement with the decline in collagen content and the increase in free water content with aging. The results suggest that such a technique can be used as a tool for the assessment of aging, and that bi-exponential fitting can produce sensitive fingerprint parameters for the dermal alterations that occur during aging.

Faster imaging with a portable unilateral NMR device.

Unilateral NMR devices are important tools in various applications such as non-destructive testing and well logging, but are not applied routinely for imaging, primarily because B0 inhomogeneity in these scanners leads to a relatively low signal and requires use of the slow single point imaging scan scheme. Enabling high quality, fast imaging could make this affordable and portable technology practical for various imaging applications as well as for new applications that are not yet feasible with MRI technology. The goal of this work was to improve imaging times in a portable unilateral NMR scanner. Both Compressed Sensing and Fast Spin Echo were modified and applied to fit the unique characteristics of a unilateral device. Two printed phantoms, allowing high resolution images, were scanned with both methods and compared to a standard scan and to a low pass scan to evaluate performance. Both methods were found to be feasible with a unilateral device, proving ways to accelerate single point imaging in such scanners. This outcome encourages us to explore how to further accelerate imaging times in unilateral NMR devices so that this technology might become clinically applicable in the future.