Citations

We validate a technique for model-free measurement of shear wave velocity and attenuation. A mechanical shaker was used to excite harmonic plane and cylindrical waves in phantoms and excised tissue. Radiation force was used to excite impulsive cylindrical waves. 2D FFT of the displacement yielded the k-space whose coordinates are frequency and the wave number. The shear wave velocity at each frequency was obtained by finding the maximum at the given frequency in k-space and dividing the frequency coordinate by the wave number coordinate. The attenuation (α) at a given frequency was calculated using α = FWHM × π/√3, where FWHM is the full width at half maximum of the k-space peak along the given frequency. This method was applied to measure shear wave velocity and attenuation of transplanted kidneys and livers, and in the thyroid tumor, and compare it to the healthy tissues. The velocities and attenuations at each frequency for various excitation methods agree within one standard deviation. The k-space estimates of velocity and attenuation agreed with those obtained using the phase gradient (velocity) and amplitude decay (attenuation). The transplanted organs and the thyroid tumor had higher velocity and lower attenuation than healthy tissues.

Introduction: Ultrasound radiation force-based methods can quantitatively evaluate tissue viscoelastic material properties. A limitation of current methods includes neglecting the inherent anisotropy nature of tissue. To explore this phenomenon, we created a phantom incorporating fibrous material that has preferential orientations. Methods: Two phantoms were made in a cube-shaped mold using a fibrous material arranged in multiple layers and embedded in porcine gelatin using two different concentrations of the gelatin (8%, 14%). Shear wave measurements were made in the phantoms at different angles by rotating the phantom, where 0° and 180° were defined along the fibers, and 90° and 270° across the fibers. Measurements were performed using a Verasonics ultrasound system equipped with a linear array transducer. Results/Discussion: The mean shear wave speeds and mean standard deviations for 8% and 14% gelatin along the fibers (0°) were (3.60 ± 0.03 and 4.10 ± 0.11 m/s) and across the fibers (90°) were (3.18 ± 0.12 and 3.90 ± 0.02 m/s), respectively. Conclusion: The fibrous gelatin-based phantoms exhibited anisotropy that could be measured using quantitative shear waves speed measurements. Increasing the gelatin percentage increases the shear wave speed and anisotropic moduli. [This study was supported by NIH grant DK092255.]

Diastolic dysfunction is the impaired ability of the left ventricle (LV) to passively fill during diastole and maintain its stroke volume at physiologic filling pressures and is associated with impaired relaxation and reduced compliance of LV. Knowledge of the quantitative values of the myocardial viscoelastic properties would improve the clinician’s ability to evaluate diastolic dysfunction in patients. To gain better understanding of the viscoelastic properties of the LV as a function of geometry, we studied Lamb wave propagation in different directions in excised porcine free-wall myocardium. The phantom consisting of a dissected porcine LV free-wall embedded in gelatin was fixed in a water tank. A mechanical shaker was used for harmonic excitation over a range of 40–500 Hz and a 7.5 MHz ultrasound transducer was used for motion measurements. Motion amplitude and phase at different depths of the sample were analyzed to obtain dispersion curves in four orthogonal directions. The data were fitted to the Lamb wave equations and shear elasticity and viscosity coefficients were estimated. The values of μ1 and μ2 were 13.75 ± 0.96 and 5.86 ± 0.75 Pa s. Our results suggest that the viscoelastic characteristics of the porcine LV free-wall in orthogonal directions were similar.

Synovial cysts of the temporomandibular joint are rare, and to our knowledge, only 14 cases have been reported. The most common presentation is local pain and swelling. We present a case of a synovial cyst presenting with neuralgia in the distribution of the auriculotemporal nerve, initially misdiagnosed as trigeminal neuralgia.

Key Points miR-155 levels are significantly and increasingly overexpressed as normal B cells progress to MBL and to CLL. Plasma levels of miR-155 before treatment were significantly lower in patients with CLL who experienced complete response than in all others.

Background Isolated neuralgic pain in the deep ear may arise from either nervus intermedius (NIN) or glossopharyngeal (GPN) neuralgias. Current International Headache Society (IHS) International Classification of Headache Disorders, second edition (ICHD-2) criteria for these cranial neuralgias require the presence of a characteristic trigger. Aim The aim of this article is to report cases of triggerless neuralgic otalgia to better understand a subset of patients for whom there may be diagnostic uncertainty. Methods Methods included an observational cohort series and systematic literature review. Results We identified five female patients with a median age at symptom onset of 58 (range: 47 to 73). Our patients generally experienced an excellent clinical response to carbamazepine. Patients were contacted by telephone at a median follow-up duration of seven years (range: four to 32) from symptom onset, at which time carbamazepine-free remissions were reported by five of five (100%) of the patients. A systematic review of the literature on neuralgic otalgia led us to conclude that NIN was most common among young women (age < 50), and GPN across a wider range of ages of either gender. Among surgically validated cases reported in the literature, triggers were frequently absent in NIN, and variably noted in GPN. Conclusions We conclude that the presence of a trigger is not fundamental, and may be impractical, to the diagnosis of neuralgic otalgia, but remains important for specificity between NIN and GPN.

Genomewide association studies (GWAS) and candidate‐gene studies have implicated single‐nucleotide polymorphisms (SNPs) in at least 45 different genes as putative glioma risk factors. Attempts to validate these associations have yielded variable results and few genetic risk factors have been consistently replicated. We conducted a case‐control study of Caucasian glioma cases and controls from the University of California San Francisco (810 cases, 512 controls) and the Mayo Clinic (852 cases, 789 controls) in an attempt to replicate previously reported genetic risk factors for glioma. Sixty SNPs selected from the literature (eight from GWAS and 52 from candidate‐gene studies) were successfully genotyped on an Illumina custom genotyping panel. Eight SNPs in/near seven different genes (TERT, EGFR, CCDC26, CDKN2A, PHLDB1, RTEL1, TP53) were significantly associated with glioma risk in the combined dataset (P < 0.05), with all associations in the same direction as in previous reports. Several SNP associations showed considerable differences across histologic subtype. All eight successfully replicated associations were first identified by GWAS, although none of the putative risk SNPs from candidate‐gene studies was associated in the full case‐control sample (all P values > 0.05). Although several confirmed associations are located near genes long known to be involved in gliomagenesis (e.g., EGFR, CDKN2A, TP53), these associations were first discovered by the GWAS approach and are in noncoding regions. These results highlight that the deficiencies of the candidate‐gene approach lay in selecting both appropriate genes and relevant SNPs within these genes.

The cardiovascular diseases such as atherosclerosis, coronary artery disease, hypertension and diastolic dysfunction have been associated with arterial stiffening and decreased ventricular compliance. Noninvasive techniques capable of quantifying elasticity and viscosity of cardiovascular tissues could facilitate early diagnosis and improve treatment. Here, we present a technique that uses focused ultrasound radiation force to excite mechanical waves in the tissue of interest and pulse echo to track the tissue deformation. Analysis of tissue deformation as a function of time using Fourier transforms allows calculation of the phase wave velocity dispersion (change of velocity as a function of frequency) of various modes of deformation. Continuum mechanics equations governing the motion of a viscoelastic plate and a tube are used to model the myocardial wall and arteries, respectively. Dispersion equations are derived for the two geometries and fit to the measured velocity dispersion to estimate tissue elasticity and viscosity. ECG-gated in vivo measurements of porcine myocardial and arterial elasticity and viscosity through a heart cycle are reported. The results show that both elasticity and viscosity increase during systole and decrease during diastole in the myocardium and arteries, consistent with underlying physiology.