Radiographic assessment of acute vs chronic vertebral compression fractures.

PURPOSE: Distinguishing between acute and chronic vertebral compression fractures typically requires advanced imaging techniques such as magnetic resonance imaging (MRI). Recognizing specific radiographic findings associated with fracture acuity may improve the accuracy of radiographic assessment. METHODS: Patients with compression fractures that had both radiographic and MRI studies of the lumbar spine within a 30-day time frame were retrospectively reviewed. MRI studies were used to determine compression fracture acuity. Radiographs were interpreted by a separate group of radiologists blinded to the MRI results. Radiographic findings of endplate osteophyte, subendplate density, subendplate cleft, and subendplate cyst were recorded as was the overall impression of fracture acuity. RESULTS: Sensitivity and specificity for radiographic reporting of acute fracture were 0.52 (95% CI: 0.42, 0.61) and 0.95 (95% CI: 0.93, 0.97) respectively. For chronic fractures, the sensitivity and specificity were 0.52 (95% CI: 0.41, 0.63) and 0.94 (95% CI: 0.92, 0.96). The radiographic presence of a subendplate cleft increased the odds of a fracture being acute by a factor of 1.75 (95% CI: 1.09, 2.81; P = 0.0202). The radiographic presence of subendplate density increased the odds of a fracture being acute by a factor of 1.78 (95% CI: 1.21, 2.63; P = 0.0037). The presence of an endplate osteophyte or subendplate cyst was not significantly associated with fracture acuity. CONCLUSION: Radiographs are relatively insensitive in distinguishing between acute and chronic lumbar compression fractures but the presence of a subendplate cleft or subendplate density increases the likelihood that a given fracture is acute.

Mass-Like Fat at the Medial Midfoot: A Common Pseudolesion.

Background Fatty masses are common and may be encountered in the foot and ankle. In some cases, normal subcutaneous fat may be mistaken for a discrete mass. Aims The aim of this study was to evaluate the common finding of prominent subcutaneous fat at the medial midfoot resembling a lipoma and to determine the prevalence of this pseudolesion by applying a series of potential size cutoff criteria. Materials and Methods Three musculoskeletal radiologists retrospectively evaluated 91 sequentially performed magnetic resonance imaging examinations of the ankle to measure fat resembling a discrete lipoma at the medial midfoot. Each blinded reader measured the largest area of continuous subcutaneous fat in orthogonal axial, coronal craniocaudal, and coronal transverse dimensions. Patient age, sex, and study indications were also recorded. Statistical analysis was performed with R and SAS 9.4 software Results A discrete fatty pseudolesion as defined by measuring at least 1 cm in all planes by measurements of at least two of three readers was present in 87% of cases (79 of 91). When a size criterion of 1.5 cm was used, a pseudolesion was documented in 14% of cases (13 of 91). There was a significant correlation between larger pseudolesion size and female sex in the axial plane; however, there was no correlation in the coronal craniocaudal and coronal transverse dimensions. Conclusions Subcutaneous fat at the medial midfoot often has a mass-like appearance that could be mistaken for a lipoma. It is important to recognize this pseudolesion variant and not to confuse the imaging appearance for a discrete mass.

Remote Focusing in a Temporal Focusing Microscope.

In a temporal focusing microscope, dispersion can remotely shift the temporal focal plane axially, but only a single depth can be in focus at a time on a fixed camera. In this paper, we demonstrate remote focusing in a temporal focusing microscope. Dispersion tuning with an electrically tunable lens (ETL) in a 4 f pulse shaper scans the excitation plane axially, and another ETL in the detection path keeps the shifted excitation plane in focus on the camera. Image stacks formed using two ETLs versus a traditional stage scan are equivalent.

Dispersion compensation by a liquid lens (DisCoBALL).

We present dispersion compensation by a liquid lens (DisCoBALL), which provides tunable group-delay dispersion (GDD) that is high speed, has a large tuning range, and uses off-the-shelf components. GDD compensation is crucial for experiments with ultrashort pulses. With an electrically tunable lens (ETL) at the Fourier plane of a 4f grating pair pulse shaper, the ETL applies a parabolic phase shift in space and therefore a parabolic phase shift to the laser spectrum, i.e., GDD. The GDD can be tuned with a range greater than 2×105 fs2 at a rate of 100 Hz while maintaining stable coupling into a single-mode fiber.

High speed multiphoton axial scanning through an optical fiber in a remotely scanned temporal focusing setup.

Simultaneous spatial and temporal focusing is used to acquire high speed (200Hz), chemically specific axial scans of mouse skin through a single-mode fiber. The temporal focus is remotely scanned by modulating the group delay dispersion (GDD) at the proximal end of the fiber. No moving parts or electronics are required at the distal end. A novel GDD modulation technique is implemented using a piezo bimorph mirror in a folded grating pair to achieve a large GDD tuning range at high speed.

Deep tissue multiphoton microscopy using longer wavelength excitation.

We compare the maximal two-photon fluorescence microscopy (TPM) imaging depth achieved with 775-nm excitation to that achieved with 1280-nm excitation through in vivo and ex vivo TPM of fluorescently-labeled blood vessels in mouse brain. We achieved high contrast imaging of blood vessels at approximately twice the depth with 1280-nm excitation as with 775-nm excitation. An imaging depth of 1 mm can be achieved in in vivo imaging of adult mouse brains at 1280 nm with approximately 1-nJ pulse energy at the sample surface. Blood flow speed measurements at a depth of 900 mum are performed.

Enhanced axial confinement of sum-frequency generation in a temporal focusing setup.

We demonstrate enhanced axial confinement in a temporal focusing setup with a shaped spectrum and a narrow emission filter, achieving a reduction of 1 order of magnitude of the out-of-focus background when compared with conventional point-scanning two-photon microscopy. By rejecting the background in the optical domain, our technique circumvents the noise problems common in other background subtraction techniques.

Tunable dispersion compensation by a rotating cylindrical lens.

We present a technique for tunable dispersion compensation that is low cost, high speed, and has a large tuning range. By rotating a cylindrical lens at the Fourier plane of a folded 4f grating pair system, the group-velocity dispersion can be tuned over a range greater than 10(5) fs(2), sufficient for compensating the dispersion of several meters of optical fiber.

Simultaneous spatial and temporal focusing for axial scanning.

We show theoretically and experimentally that simultaneous spatial and temporal focusing can scan the temporal focal plane axially by adjusting the group velocity dispersion in the excitation beam path. When the group velocity dispersion is small, the pulse width at the temporal focal plane is transform-limited, and the amount of shift depends linearly upon the dispersion. By adding a meter of large mode area fiber into the system, we demonstrate this axial scanning capability in a fiber delivery configuration. Because a transform-limited pulse width is automatically recovered at the temporal focal plane, simultaneous spatial and temporal focusing negates the need for any dispersion pre-compensation, further facilitating its integration into a fiber delivery system. A highly promising application for simultaneous spatial and temporal focusing is an axial scanning multiphoton fluorescence fiber probe without any moving parts at the distal end and without dispersion pre-compensation.

Simultaneous spatial and temporal focusing of femtosecond pulses.

We study and demonstrate the technique of simultaneous spatial and temporal focusing of femtosecond pulses, with the aim to improve the signal-to-background ratio in multiphoton imaging. This concept is realized by spatially separating spectral components of pulses into a "rainbow beam" and recombining these components only at the spatial focus of the objective lens. Thus, temporal pulse width becomes a function of distance, with the shortest pulse width confined to the spatial focus. We developed analytical expressions to describe this method and experimentally demonstrated the feasibility. The concept of simultaneous spatial and temporal focusing of femtosecond pulses has the great potential to significantly reduce the background excitation in multiphoton microscopy, which fundamentally limits the imaging depth in highly scattering biological specimens.

The expression of the t-SNARE AtSNAP33 is induced by pathogens and mechanical stimulation.

The fusion of vesicles in the secretory pathway involves the interaction of t-soluble N-ethylmaleimide-sensitive factor attachment protein receptors (t-SNAREs) on the target membrane and v-SNAREs on the vesicle membrane. AtSNAP33 is an Arabidopsis homolog of the neuronal t-SNARE SNAP-25 involved in exocytosis and is localized at the cell plate and at the plasma membrane. In this paper, the expression of AtSNAP33 was analyzed after different biotic and abiotic stresses. The expression of AtSNAP33 increased after inoculation with the pathogens Plectosporium tabacinum and virulent and avirulent forms of Peronospora parasitica and Pseudomonas syringae pv tomato. The expression of PR1 transcripts encoding the secreted pathogenesis-related protein 1 also increased after inoculation with these pathogens and the expression of AtSNAP33 preceded or occurred at the same time as the expression of PR1. AtSNAP33 was also expressed in npr1 plants that do not express PR1 after pathogen inoculation as well as in cpr1 plants that overexpress PR1 in the absence of a pathogen. The level of AtSNAP33 decreased slightly in leaves inoculated with P. parasitica in the NahG plants, and eds5 and sid2 mutants that are unable to accumulate salicylic acid (SA) after pathogen inoculation, indicating a partial dependence on SA. AtSNAP33 was also expressed in systemic noninoculated leaves of plants inoculated with P. syringae. In contrast to the situation in infected leaves, the expression of AtSNAP33 in systemic leaves was fully SA dependent. Thus, the expression of AtSNAP33 after pathogen attack is regulated by SA-dependent and SA-independent pathways. Mechanical stimulation also led to an increase of AtSNAP33 transcripts.