Tissue Imaging Techniques Research Articles

Endovascular impedance spectroscopy: A new technique for tissue imaging

Endovascular impedance spectroscopy: A new technique for tissue imaging

22]In Vivo andex Vivo tissue applications of two-photon microscopy

Publisher Summary This chapter describes in vivo and ex vivo tissue applications of two-photon microscopy (TPM) and reviews key areas—such as neurobiology—in which TPM has already made a major impact. TPM is one of the emerging optical tissue imaging techniques, and it is constructive to compare two-photon imaging with other in vivo optical tissue imaging techniques. TPM is a powerful technique for tissue imaging because of its inherent 3D resolution and long penetration depth. This technique also provides biochemical information about tissues and causes minimal photodamage. TPM is based on a nonlinear fluorescence excitation process. The simultaneous absorption of two infrared photons promotes the transition of a fluorophore to the excited state. Because of the nonlinear excitation process, there is only sufficient photon density very near the focal region to produce appreciable excitation, which results in an inherent 3D sectioning effect. The unique advantages of TPM for deep tissue imaging have been recognized nearly since its inception. TPM tissue imaging applications are proliferating rapidly.

Evaluation of healthy and diseased muscle with magnetic resonance elastography

Basford JR, Jenkyn TR, An K-N, Ehman RL, Heers G, Kaufman KR. Evaluation of healthy and diseased muscle with magnetic resonance elastography. Arch Phys Med Rehabil 2002;83:1530-6. Objective: To investigate whether a new tissue-imaging technique, magnetic resonance elastography (MRE), offers a viable, noninvasive way to study healthy and diseased muscle. Design: Convenience sample. Setting: A magnetic resonance imaging (MRI) laboratory. Participants: Eight control subjects (4 men, 4 women), between the ages of 24 and 41 years, with normal neuromuscular examinations and histories, and 6 subjects (3 men, 3 women), ages 17 to 63 years, with lower-extremity neuromuscular dysfunction (1 with childhood poliomyelitis, 2 with flaccid, 3 with spastic paraplegia). Interventions: Subjects lay supine with their legs within the coils of a 1.5T MRI machine, with their feet strapped to a footplate positioned so that the axes of rotation of their ankles coincided with the apparatus. All subjects were tested in a no-load (0 torque) condition. Control subjects were also evaluated as they isometrically resisted ankle dorsi- (20.2Nm, 40.5Nm) and plantar- (8.2Nm, 16.4Nm) flexion moments. Subjects with neuromuscular dysfunction were evaluated in the same manner, except 1 individual with residual lower-extremity strength who could only be tested in the resting and passive ankle dorsiflexion modes. Shear waves were induced with a 150-Hz electromechanic transducer located over the belly tibialis anterior. MRE images were collected with a gradient-echo technique gated to the transducer's motion. Wave-phase propagation was visualized with 8 equally offset images across 1 vibration-cycle. Main Outcome Measures: Changes in shear-wave wavelength (λ) and muscle stiffness (as expressed by the shear modulus [G]) in the tibialis anterior and gastrocnemius muscles. Results: Wavelength and G differed between the groups in all the muscles studied, and increased as the load increased. Moreover, λ and G in the neuromuscular disease group at rest (eg, 3.88±0.48cm; range, 2.87–4.91cm; 38.40±00.77kPa; range, 22.35–59.67kPa) and in the lateral gastrocnemius were, respectively, more than 1.5 and 2.4 times larger than they were in the same muscle in the control group (2.56±0.28cm, 16.16±00.19kPa; P=.0002) (1Pa=1N/m2). Conclusions: Shear-wave wavelength and muscle stiffness increased with load in healthy muscle. In addition, at least for our sample, these quantities differed significantly between muscles with and without neuromuscular disease. In summary, MRE appears to provide in vivo physiologic information about the mechanical properties of muscle at rest and during contraction that is not otherwise available. The potential of this technique for monitoring the effects of treatment and exercise on both healthy and diseased muscle merits further research. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Longitudinal magnetic resonance imaging quantitation of rat liver regeneration after partial hepatectomy.

This report demonstrates the advantages of using a noninvasive soft tissue imaging technique--magnetic resonance imaging (MRI)--to monitor liver regeneration after 70% partial hepatectomy in the rat in a longitudinal manner. Six animals were scanned prior to and on 6 subsequent occasions up to 9 days after surgical removal of the median and left lateral lobes. Within the observed time frame liver volumes were restored to approximately 88% of presurgery values. Final liver volumes correlated well with postmortem liver weights (R = 0.93). Regeneration is well-quantified empirically by a 4 parameter logistic equation: % Regeneration = 84 - (84/(1 + (Days/2.31)(2.34))) The rate of regeneration was maximal at 1.5 days, which coincided with the maximum increase of Mitotic Index--a measure of cell proliferation, determined in a subsequent study. Pre- and postpartial hepatectomy measurements remove two potentially confounding unknowns--the presurgery liver volume, and the amount of liver actually excised. 3D reconstructions of the liver effectively illustrate the morphological changes associated with the procedure, and the regrowth of liver tissue.

Enhanced echocardiographic techniques for imaging tissue

There are more technologic advances in ultrasonic imaging today than at any time in the past 30–40 years. Among these many developments is enhanced ultrasonic imaging of tissue. Table Ishows some of the new tissue imaging techniques that have become commercially available. The first of the major advances is the introduction of digital ultrasonic instruments with broadband transducer technology. These transducers transmit and receive multiple frequencies. Thus, they enhance the penetration and resolution of the ultrasonic examination. In recent years, there has been great interest in using Doppler to image tissue in addition to its usual visualization of blood. A modification of the Doppler technique utilizes a moving-target indicator approach to highlight those objects that move and suppress those that do not. Harmonic imaging of tissue has become an extremely important tool for enhancing myocardial visualization. Finally, parallel processing, whereby 1 ultrasonic signal is sampled multiple times, has become a principle means of increasing the rate of image acquisition.

Doppler tisular del anillo mitral en pacientes con disfunción sistólica ventricular izquierda. Análisis de la función diastólica

We assessed the Doppler tissue imaging technique in the left mitral annulus of patients with left ventricular systolic dysfunction since the technique has been used to evaluate diastolic function of the left ventricle and the values obtained have been considered to be relatively independent of the preload. Patients (n = 46) with an ejection fraction < 40% in sinus rhythm without mitral regurgitation underwent pulsed wave Doppler analyses of mitral inflow (E and A waves), pulmonary venous flow (S, D and Ar waves) and Doppler tissue imaging of the mitral annulus (Ea and Aa waves). Overall, the linear correlations between the different Doppler measurements were poor. When sub-grouped with respect to E/A < 1 and E/A >= 1 (Groups 1 and 2, respectively), the Ea value did not significantly differ between the two groups: 5.0 cm/s (4.2/6.0) vs 6.2 cm/s (5.5/8. 2) respectively; p = 0.129 and neither did the E/Ea quotient: 10.2 (8.2/14.5) vs 12.9 (9.1/17.4) respectively; p = 0.160. Atrial size was significantly greater in Group 2: 20.0 cm2 (18.0/22.0) vs 25.0 cm2 (20.0/29.0) respectively; p = 0.000. The Ea/Aa quotient was pseudo-normalized in Group 2: 0.65 (0.48/0.83) vs 1.15 (0.75/1.71) respectively; p = 0.001. In patients with left ventricular systolic dysfunction the Ea/Aa value tends towards pseudo-normalization when the preload is increased. This does not apply to the values of Ea, E/Ea or to size of the left atrium. Therefore, Doppler tissue imaging of the left mitral annulus is valuable in the assessment of left ventricular dysfunction and the problem of pseudo-normalization due to preloading.

Future directions in innovative minimally invasive surgery

Future directions in innovative minimally invasive surgery

0-100. Preliminary in vitro studies of electrical impedance mammography (EIM): a future technique for non-invasive breast tissue imaging?

0-100. Preliminary in vitro studies of electrical impedance mammography (EIM): a future technique for non-invasive breast tissue imaging?

Dynamic 3-dimensional echocardiographic reconstruction of the left ventricle using color doppler myocardial tissue imaging technique. In vivo experimental and clinical study

Dynamic 3-dimensional echocardiographic reconstruction of the left ventricle using color doppler myocardial tissue imaging technique. In vivo experimental and clinical study

Determination of ultrasonic velocity in human enamel and dentine

Acoustic velocity data have been obtained preparatory to investigation of high frequency ultrasound as a non-invasive imaging technique for dental hard tissues and their pathology. In vitro studies were conducted on extracted human permanent teeth. Pulse-echo ultrasound of 18 MHz centre frequency and approx. 150 ns pulse duration successfully detected the front and back surfaces of 0.45 – 1.07 mm thick sections of enamel and of dentine. Water was used as the coupling agent. The oscilloscope traces of the echoes from pure enamel and pure dentine were similar. The longitudinal ultrasonic velocities for pure enamel and dentine were experimentally determined for a number of teeth in different planes of section. For enamel in longitudinal and transverse sections, the mean ultrasonic velocities were 6150 ± 140 and 6500 ± 190m/s respectively. For dentine in longitudinal section, the mean ultrasonic velocity was 4050 ± 30m/s.