3D Elastography Research Articles

In vivo high-resolution magnetic resonance elastography of the uterine corpus and cervix.

To apply 3D multifrequency MR elastography (3DMMRE) to the uterus and analyse the viscoelasticity of the uterine tissue in healthy volunteers considering individual variations and variations over the menstrual cycle. Sixteen healthy volunteers participated in the study, one of whom was examined 12 times over two menstrual cycles. Pelvic 3DMMRE was performed on a 1.5-T scanner with seven vibration frequencies (30-60 Hz) using a piezoelectric driver. Two mechanical parameter maps were obtained corresponding to the magnitude (|G (*) |) and the phase angle (φ) of the complex shear modulus. On average, the uterine corpus had higher elasticity, but similar viscosity compared with the cervix, reflected by |G (*) |uterine corpus = 2.58 ± 0.52 kPa vs. |G (*) |cervix = 2.00 ± 0.34 kPa (p < 0.0001) and φ uterine corpus = 0.54 ± 0.08, φ cervix = 0.57 ± 0.12 (p = 0.428). With 2.23 ± 0.26 kPa, |G (*) | of the myometrium was lower in the secretory phase (SP) compared with that of the proliferative phase (PP, |G (*) | = 3.01 ± 0.26 kPa). For the endometrium, the value of |G (*) | in SP was 68% lower than during PP (PP, |G (*) | = 3.34 ± 0.42 kPa; SP, |G (*) | = 1.97 ± 0.34 kPa; p = 0.0061). 3DMMRE produces high-resolution mechanical parameter maps of the uterus and cervix and shows sensitivity to structural and functional changes of the endometrium and myometrium during the menstrual cycle. MR elastography provided for the first time spatially resolved viscoelasticity maps of uterus. Uterine corpus had a higher elasticity, but similar viscosity compared with cervix. The stiffness of both endometrium and myometrium decreases during the menstrual cycle.

Feasibility of using 3D MR elastography to determine pancreatic stiffness in healthy volunteers

To evaluate the feasibility of using three-dimensional (3D) MR elastography (MRE) to determine the stiffness of the pancreas in healthy volunteers. Twenty healthy volunteers underwent 1.5 Tesla MRE exams using an accelerated echo planar imaging (EPI) pulse sequence with low-frequency vibrations (40 and 60 Hz). Stiffness was calculated with a 3D direct inversion algorithm. The mean shear stiffness in five pancreatic subregions (uncinate, head, neck, body, and tail) and the corresponding liver stiffness were calculated. The intrasubject coefficient of variation (CV) was calculated as a measure of the reproducibility for each volunteer. The mean shear stiffness (average of values obtained in different pancreatic subregions) was (1.15 ± 0.17) kPa at 40 Hz, and (2.09 ± 0.33) kPa at 60 Hz. The corresponding liver stiffness was higher than the pancreas stiffness at 40 Hz ([1.60 ± 0.21] kPa, mean pancreas-to-liver stiffness ratio: 0.72), but similar at 60Hz ([2.12 ± 0.23) kPa, mean ratio: 0.95). The mean intrasubject CV for each pancreatic subregion was lower at 40 Hz than 60 Hz (P < 0.05 for all subregions, range: 11.9-15.7% at 40 Hz and 16.5-19.6% at 60 Hz). The 3D pancreatic MRE can provide promising and reproducible stiffness measurements throughout the pancreas, with more consistent data acquired at 40 Hz.

2D ultrasonic elastography with lateral displacement estimation using statistics.

Ultrasound elastography is the method of obtaining relative stiffness information of biological tissue, which plays an important role in early diagnosis. Generally, a gradient-based strain imaging algorithm assumes that motion only occurs in an axial direction. However, because tissue has different relative stiffness, the scatter presents lateral motion under high freehand compression. Therefore, errors occur in estimating the cross-correlation phase in the calculation window. A 2D elastography algorithm with lateral displacement estimation using statistics was proposed to reduce errors. The new method was investigated through simulation, and the experiment confirmed that errors introduced by lateral tissue movement have been greatly reduced with no sacrifice of real-time ultrasonic imaging quality.

Multiparametric ultrasonography of the pediatric scrotum and in boys with undescended testes.

Due to its noninvasiveness and high resolving power, ultrasound examination is the examination of choice for the imaging of the structures of the pediatric scrotum. It allows to reveal changes impossible to find in the course of a clinical examination. Its significance has increased over the past few years due to the technological developments. The introduction of transducers with frequency of 10–17 MHz has improved the resolution of pediatric testes images as well as the resolution of the inguinal canals images, which has been of particular importance for the evaluation of undescended, retractile and abdominal testes. New diagnostic tools have also been introduced, such as 3D imaging or elastography, whose application has helped provide valuable additional information for the evaluation of pediatric testes, for treatment monitoring, and for post-surgical follow-up examinations. 3D imaging facilitates a more accurate evaluation of the location of an undescended testicle, testicular volume, and vascularization. Elastography may be used for the evaluation of focal lesions, post-ischemic lesions, unclear fluid spaces, undescended testes, and following orchiopexy.

3D static elastography at the micrometer scale using Full Field OCT

Full-Field OCT (FF-OCT) is able to image biological tissues in 3D with micrometer resolution. In this study we add elastographic contrast to the FF-OCT modality. By combining FF-OCT with elastography, we create a virtual palpation map at the micrometer scale. We present here a proof of concept on multi-layer phantoms and preliminary results on ex vivo biological samples such as porcine cornea, human breast tissues and rat heart. The 3D digital volume correlation that is used in connection with the 3D stack of images allows to access to the full 3D strain tensor and to reveal stiffness anisotropy.

Three Dimentional Elastography of Breast Tumor

Brief Description of the Purpose of the StudyReal Time Tissue Elastography is capable to differenｔiate breast tumor whether it is malignant or benign. Authors tried to construct three dimensional elastography of breast tumors and studied whether it is possible to differentiate the tumor is benign or malignant.MethodsThree dimensional elastography was ;performed for 70 cases of breast tumor, including 51 benign and 19 malignant tumors. Ultrasonic equipment HIVISION Ascendus with automatic linear probe EUP-LV74 was used. The probe moves electric linear transducer mechanically for obtain three dimensional elastography. 3D Elastography image is superimposed on 3D B-mode image. Hard tissue is colored blue and soft tissue is read. 3D image is displayed as volume rendering.Main ResultsBenign tumors, 40 out of 51 (78.5%) were shown as less blue or hard parts and while malignant tumors, 16 out of 19 (84.2%) were displayed as irregular shaped solid mas by 3D elastography.Importance of the ConclusionsAuthors could construct 3D images of breast tumors. 3D Elastography is able to differentiate breast tumors whether it is benign or malignant. Brief Description of the Purpose of the StudyReal Time Tissue Elastography is capable to differenｔiate breast tumor whether it is malignant or benign. Authors tried to construct three dimensional elastography of breast tumors and studied whether it is possible to differentiate the tumor is benign or malignant. Real Time Tissue Elastography is capable to differenｔiate breast tumor whether it is malignant or benign. Authors tried to construct three dimensional elastography of breast tumors and studied whether it is possible to differentiate the tumor is benign or malignant. MethodsThree dimensional elastography was ;performed for 70 cases of breast tumor, including 51 benign and 19 malignant tumors. Ultrasonic equipment HIVISION Ascendus with automatic linear probe EUP-LV74 was used. The probe moves electric linear transducer mechanically for obtain three dimensional elastography. 3D Elastography image is superimposed on 3D B-mode image. Hard tissue is colored blue and soft tissue is read. 3D image is displayed as volume rendering. Three dimensional elastography was ;performed for 70 cases of breast tumor, including 51 benign and 19 malignant tumors. Ultrasonic equipment HIVISION Ascendus with automatic linear probe EUP-LV74 was used. The probe moves electric linear transducer mechanically for obtain three dimensional elastography. 3D Elastography image is superimposed on 3D B-mode image. Hard tissue is colored blue and soft tissue is read. 3D image is displayed as volume rendering. Main ResultsBenign tumors, 40 out of 51 (78.5%) were shown as less blue or hard parts and while malignant tumors, 16 out of 19 (84.2%) were displayed as irregular shaped solid mas by 3D elastography. Benign tumors, 40 out of 51 (78.5%) were shown as less blue or hard parts and while malignant tumors, 16 out of 19 (84.2%) were displayed as irregular shaped solid mas by 3D elastography. Importance of the ConclusionsAuthors could construct 3D images of breast tumors. 3D Elastography is able to differentiate breast tumors whether it is benign or malignant. Authors could construct 3D images of breast tumors. 3D Elastography is able to differentiate breast tumors whether it is benign or malignant.

Testicular adrenal rest tumors in boys with congenital adrenal hyperplasia: 3D US and elastography – Do we get more information for diagnosis and monitoring?

BackgroundTesticular adrenal rest tumors (TART) are the nodular testicular lesions deriving from the adrenal remnant tissue reported in boys and men with congenital adrenal hyperplasia. Until now, the diagnostics of TART have been based on a combination of clinical features, imaging methods (primarily two dimensional ultrasound – 2D US), response of the foci to glycocorticosteroid (GCS) therapy and exclusion of the neoplastic process. Application of 2D US supplies however a limited range of information about the volume, demarcation, structure and vascularization of the lesions. ObjectiveTo define whether the use of 3D US, power Doppler and elastography changes the algorithm of the diagnostics and monitoring or treatment of TART. Material and methodsIn this study, modern ultrasound techniques such as 3D US and elastography were introduced in two boys with TART. ResultsThe 3D power Doppler option gives the opportunity for accurate assessment of the volume of testes and adrenal tissue foci and their vascularization. Sonographic elastography allows the assessment of stiffness of adrenal tissue areas compared to normal testis parenchyma. ConclusionThe use of these modern techniques enables more adequate and advanced diagnostics, and more precise monitoring of the effects of treatment in patients with TART.

Nonlinear characterization of breast cancer using multi-compression 3D ultrasound elastography in vivo

The main objective of this article is to introduce a new nonlinear elastography based classification method for human breast masses. Multi-compression elastography imaging is elucidated in this study to differentiate malignant from benign lesions, based on their nonlinear mechanical behavior under compression. Three classification parameters were used and compared in this work: a new nonlinear parameter based on a power-law behavior of the strain difference between breast masses and healthy tissues, mass-soft tissue strain ratio and the mass relative volume between B-mode and elastography imaging. Using 3D elastography, these parameters were tested in vivo. A pilot study on 10 patients was performed, and results were compared with biopsy diagnosis as a gold standard. Initial elastography results showed a good agreement with biopsy outcomes. The new estimated nonlinear parameter had an average value of 0.163±0.063 and 1.642±0.261 for benign and malignant masses, respectively. Strain ratio values for the benign and malignant masses had an average value of 2.135±0.707 and 4.21±2.108, respectively. Relative mass volume was 0.848±0.237 and 2.18±0.522 for benign and malignant masses. In addition to the traditional normal axial strain, new strain types were used for elastography and constructed in 3D, including the first principal, maximum shear and Von Mises strains. The new strains provided an enhanced distinction of the stiff lesion from the soft tissue. In summary, the proposed elastographic techniques can be used as a noninvasive quantitative characterization tool for breast cancer, with the capability of visualizing and separating the masses in a three dimensional space. This may reduce the number of unnecessary painful breast biopsies.

Current Status and New Developments in Breast Cancer Diagnosis and Detection

Despite extensive research into new ways of imaging the breast x-ray mammography and breast ultrasound, supplemented where necessary by magnetic resonance imaging, remain the techniques used for the vast majority of breast imaging for screening and the assessment of symptomatic breast problems. Recent advances in these technologies mean that these three techniques are highly effective for both detecting disease and for confirming normality. X-ray based imaging of the breast has been around now for 100 years but it is only in the last 10 years or so that digital technology developments have allowed for major advances in the efficacy of this technique. Digital breast tomosynthesis is currently the most promising technology as it has the potential to both improve detection of breast cancer and greatly reduce the numbers of false positive events. Technological advances in grey scale high frequency ultrasound imaging mean that it is now universally used in both symptomatic diagnosis and breast screening. Newer ultrasound techniques such as 3D imaging, Doppler analyses and elastography add some additional value but so far none of these has achieved their hoped for additional potential. Magnetic resonance imaging is currently the most sensitive imaging technique for the detection and characterisation of breast disease, but its cost remains a barrier to its more widespread use. Nuclear medicine techniques have a role is special circumstances but are yet to show that they should be used in routine practice. There are a large number of potential alternative new imaging techniques for the breast, but, as yet, none of these have shown any significant benefits over the current techniques. Dedicated breast computed tomography has perhaps the best promise but clinically effective breast imaging at present remains in the application and refinement of recent developments in digital mammography, ultrasound and magnetic resonance imaging.

Fast optimization-based elasticity parameter estimation using reduced models

Elasticity parameters are central to physically-based animation and medical image analysis. We present an accelerated method to automatically estimate these parameters for a deformation simulator using an iterative optimization framework, given the desired (target) output surface/shape. During the optimization, the input model is deformed by the simulator, and the distance between the deformed surface and the target surface is minimized numerically. To accelerate the optimization process, we introduce a dimension reduction technique to allow a trade-off between the computational efficiency and desired accuracy. The reduced model is constructed using statistical training with a set of example deformations. To demonstrate this approach, we apply the computational framework to 2D animations of elastic bodies simulated with a linear finite element method. We also present a 3D elastography example, which is simulated with a reduced-dimension finite element model to improve the performance of the optimizer.

A novel breast software phantom for biomechanical modeling of elastography

In developing breast imaging technologies, testing is done with phantoms. Physical phantoms are normally used but their size, shape, composition, and detail cannot be modified readily. These difficulties can be avoided by creating a software breast phantom. Researchers have created software breast phantoms using geometric and/or mathematical methods for applications like image fusion. The authors report a 3D software breast phantom that was built using a mechanical design tool, to investigate the biomechanics of elastography using finite element modeling (FEM). The authors propose this phantom as an intermediate assessment tool for elastography simulation; for use after testing with commonly used phantoms and before clinical testing. The authors design the phantom to be flexible in both, the breast geometry and biomechanical parameters, to make it a useful tool for elastography simulation. The authors develop the 3D software phantom using a mechanical design tool based on illustrations of normal breast anatomy. The software phantom does not use geometric primitives or imaging data. The authors discuss how to create this phantom and how to modify it. The authors demonstrate a typical elastography experiment of applying a static stress to the top surface of the breast just above a simulated tumor and calculate normal strains in 3D and in 2D with plane strain approximations with linear solvers. In particular, they investigate contrast transfer efficiency (CTE) by designing a parametric study based on location, shape, and stiffness of simulated tumors. The authors also compare their findings to a commonly used elastography phantom. The 3D breast software phantom is flexible in shape, size, and location of tumors, glandular to fatty content, and the ductal structure. Residual modulus, maps, and profiles, served as a guide to optimize meshing of this geometrically nonlinear phantom for biomechanical modeling of elastography. At best, low residues (around 1-5 KPa) were found within the phantom while errors were elevated (around 10-30 KPa) at tumor and lobule boundaries. From our FEM analysis, the breast phantom generated a superior CTE in both 2D and in 3D over the block phantom. It also showed differences in CTE values and strain contrast for deep and shallow tumors and showed significant change in CTE when 3D modeling was used. These changes were not significant in the block phantom. Both phantoms, however, showed worsened CTE values for increased input tumor-background modulus contrast. Block phantoms serve as a starting tool but a next level phantom, like the proposed breast phantom, will serve as a valuable intermediate for elastography simulation before clinical testing. Further, given the CTE metrics for the breast phantom are superior to the block phantom, and vary for tumor shape, location, and stiffness, these phantoms would enhance the study of elastography contrast. Further, the use of 2D phantoms with plane strain approximations overestimates the CTE value when compared to the true CTE achieved with 3D models. Thus, the use of 3D phantoms, like the breast phantom, with no approximations, will assist in more accurate estimation of modulus, especially valuable for 3D elastography systems.

An octahedral shear strain-based measure of SNR for 3D MR elastography

A signal-to-noise ratio (SNR) measure based on the octahedral shear strain (the maximum shear strain in any plane for a 3D state of strain) is presented for magnetic resonance elastography (MRE), where motion-based SNR measures are commonly used. The shear strain, γ, is directly related to the shear modulus, μ, through the definition of shear stress, τ = μγ. Therefore, noise in the strain is the important factor in determining the quality of motion data, rather than the noise in the motion. Motion and strain SNR measures were found to be correlated for MRE of gelatin phantoms and the human breast. Analysis of the stiffness distributions of phantoms reconstructed from the measured motion data revealed a threshold for both strain and motion SNR where MRE stiffness estimates match independent mechanical testing. MRE of the feline brain showed significantly less correlation between the two SNR measures. The strain SNR measure had a threshold above which the reconstructed stiffness values were consistent between cases, whereas the motion SNR measure did not provide a useful threshold, primarily due to rigid body motion effects.

Characterization of Cysts Using Differential Correlation Coefficient Values from Two Dimensional Breast Elastography: Preliminary Study

Although simple cysts are easily identified using sonography, description and management of nonsimple cysts remains uncertain. This study evaluated whether the correlation coefficient differences between breast tissue and lesions, obtained from 2D breast elastography, could potentially distinguish nonsimple cysts from cancers and fibroadenomas. We hypothesized that correlation coefficients in cysts would be dramatically lower than surrounding tissue because noise, imaging artifacts, and particulate matter move randomly and decorrelate quickly under compression, compared with solid tissue. For this preliminary study, 18 breast lesions (7 nonsimple cysts, 4 cancers, and 7 fibroadenomas) underwent imaging with 2D elastography at 7.5 MHz through a TPX (a polymethyl pentene copolymer) 2.5 mm mammographic paddle. Breasts were compressed similar to mammographic positioning and then further compressed for elastography by 1 to 7%. Images were correlated using 2D phase-sensitive speckle tracking algorithms and displacement estimates were accumulated. Correlation coefficient means and standard deviations were measured in the lesion and adjacent tissue, and the differential correlation coefficient (DCC) was introduced as the difference between these values normalized to the correlation coefficient of adjacent tissue. Mean DCC values in nonsimple cysts were 24.2 ± 11.6%, 5.7 ± 6.3% for fibroadenomas, and 3.8 ± 2.9 % for cancers ( p < 0.05). Some of the cysts appeared smaller in DCC images than gray-scale images. These encouraging results demonstrate that characterization of nonsimple breast cysts may be improved by using DCC values from 2D elastography, which could potentially change management options of these cysts from intervention to imaging follow-up. A dedicated clinical trial to fully assess the efficacy of this technique is recommended. (E-mail: jrubin@med.umich.edu)

Diagnosing Cysts With Correlation Coefficient Images From 2-Dimensional Freehand Elastography

We compared the diagnostic potential of using correlation coefficient images versus elastograms from 2-dimensional (2D) freehand elastography to characterize breast cysts. In this preliminary study, which was approved by the Institutional Review Board and compliant with the Health Insurance Portability and Accountability Act, we imaged 4 consecutive human subjects (4 cysts, 1 biopsy-verified benign breast parenchyma) with freehand 2D elastography. Data were processed offline with conventional 2D phase-sensitive speckle-tracking algorithms. The correlation coefficient in the cyst and surrounding tissue was calculated, and appearances of the cysts in the correlation coefficient images and elastograms were compared. The correlation coefficient in the cysts was considerably lower (14%-37%) than in the surrounding tissue because of the lack of sufficient speckle in the cysts, as well as the prominence of random noise, reverberations, and clutter, which decorrelated quickly. Thus, the cysts were visible in all correlation coefficient images. In contrast, the elastograms associated with these cysts each had different elastographic patterns. The solid mass in this study did not have the same high decorrelation rate as the cysts, having a correlation coefficient only 2.1% lower than that of surrounding tissue. Correlation coefficient images may produce a more direct, reliable, and consistent method for characterizing cysts than elastograms.

3D prostate elastography: algorithm, simulations and experiments

A multi-resolution hybrid strain estimator is presented. The estimator is locally initialized by the B-mode tracking stage. Nonlinear and linear stretching regimes are applied in successive RF tracking stages for refining the estimated axial and lateral displacements. A staggering operator is used to derive the strain images from the reconstructed axial displacements. Simulations and experiments, conducted at a center frequency of 12 MHz, 40% fractional bandwidth, on a 128 element transducer with 0.2 mm pitch, with elastographic window length of 2 mm and overlap of 90%, demonstrate a 3–6 dB improvement in the elastographic contrast-to-noise ratio over the results obtained using conventional multi-stage stretching based strain estimators. The average image cross-correlation coefficient obtained using the proposed algorithm was improved by 6–8%. 3D elastographic simulations conducted to study the performance of a 3D elastographic imaging framework predict achievable axial and lateral resolutions of approximately five and ten wavelengths, respectively. A close correspondence between inclusions reconstructed from experimental elastograms and the known physical shape of actual 3D inclusions demonstrates the potential application of 3D elastography for identifying and classifying the detected lesions (invisible in sonograms) on the basis of their shape.