Magnetic resonance elastography of uterine leiomyomas: a feasibility study

Feasibility study of the application of magnetic resonance elastography to diagnose uterine adenomyosis

OBJECTIVE

Magnetic resonance elastography (MRE), a novel imaging technique that allows in vivo measurement of tissue mechanical properties, was used to test the prediction that the stiffness of the uterus may be increased due to fibrotic changes in patients with adenomyosis.

DESIGN

A feasibility study in which a 3-dimensional (3D) MRE imaging protocol was developed to measure the stiffness of the tissues of the uterus.

SUBJECTS

Four patients with suspected adenomyosis and heavy menstrual bleeding diagnosed via transvaginal ultrasound and clinical history and 1 healthy control were recruited. Two patients underwent hysterectomy, and histologic analysis of the tissue samples was performed.

MAIN OUTCOME MEASURES

The stiffness of the whole uterus was obtained by region of interest analysis of the 3D MRE images for the 4 patients and 1 healthy control. In addition, for the 2 patients who underwent hysterectomy, the uterine tissue samples were assessed to determine histologic presence of adenomyosis via hematoxylin and eosin staining, cellular/molecular measures of tissue stiffness (collagen [picrosirius red], α-smooth muscle actin, and e-cadherin), and whether a relationship existed between in vivo assessment of the uterus via 3D MRE and in vitro uterine tissue histology.

RESULTS

3D MRE was successfully used to acquire elastograms for 4 patients with adenomyosis (diffuse, n = 3; focal, n = 1) and 1 healthy control. Calculated global uterine stiffness was higher in women with adenomyosis (2.93 kPa; range, 2.34-3.39 kPa) than in the healthy control (2.04 kPa). Regions of high stiffness on the 3D elastograms reflected adenomyotic changes visualized via conventional magnetic resonance imaging and were correlated with histologic and immunohistochemical markers of tissue stiffness.

CONCLUSION

3D MRE has the potential to provide non-invasive characterization of changes in the mechanical properties of uterine tissue that is not possible using conventional magnetic resonance imaging or transvaginal ultrasound. Further studies are needed to confirm the efficacy of the 3D MRE protocol for diagnosing adenomyosis.

3D vector MR elastography applications in small organs

BACKGROUND

Magnetic resonance elastography (MRE) is a rapidly developing medical imaging technique that allows for quantitative assessment of the biomechanical properties of the tissue. MRE is now regarded as the most accurate noninvasive test for detecting and staging liver fibrosis. A two-dimensional (2D MRE) acquisition version is currently deployed at >2000 locations worldwide. 2D MRE allows for the evaluation of the magnitude of the complex shear modulus, also referred to as stiffness. The development of 3D vector MRE has enabled researchers to assess the biomechanical properties of small organs where wave propagation cannot be adequately analyzed with the 2D MRE imaging approach used in the liver. In 3D vector MRE, the shear waves are imaged and processed throughout a 3D volume and processed with an algorithm that accounts for wave propagation in any direction. Additionally, the motion is also imaged in x, y, and z directions at each voxel, allowing for more advanced processing to be applied.

PURPOSE

This review describes the technical principles of 3D vector MRE, surveys its clinical applications in small organs, and discusses potential clinical significance of 3D vector MRE.

CONCLUSION

3D vector MRE is a promising tool for characterizing the biomechanical properties of small organs such as the uterus, pancreas, thyroid, prostate, and salivary glands. However, its potential has not yet been fully explored.

Multiparametric quantitative magnetic resonance imaging of uterine fibroids for prediction of growth rate-a pilot study

Background

Uterine fibroid (UF) growth rate and future morbidity cannot be predicted. This can lead to sub-optimal clinical management, with women being lost to follow-up and later presenting with severe disease that may require hospitalization, transfusions, and urgent surgical interventions. Multi-parametric quantitative magnetic resonance imaging (MRI) could provide a biomarker to predict growth rate facilitating better-informed disease management and better clinical outcomes. We assessed the ability of putative quantitative and qualitative MRI predictive factors to predict UF growth rate.

Methods

Twenty women with UFs were recruited and completed baseline and follow-up MRI exams, 1-2.5 years apart. The subjects filled out symptom severity and health-related quality of life questionnaires at each visit. A standard clinical pelvic MRI non-contrast exam was performed at each visit, followed by a contrast-enhanced multi-parametric quantitative MRI (mp-qMRI) exam with T2, T2*, and apparent diffusion coefficient (ADC) mapping and dynamic contrast-enhanced MRI. Up to 3 largest fibroids were identified and outlined on the T2-weighted sequence. Fibroid morphology and enhancement patterns were qualitatively assessed on dynamic contrast-enhanced MRI. The UFs' volumes and average T2, T2*, and ADC values were calculated. Pearson correlation coefficients were calculated between UF growth rate and T2, T2*, ADC, and baseline volume. Multiple logistic regression and receiver operating characteristic (ROC) analysis were performed to predict fast-growing UFs using combinations of up to 2 significant predictors. A significance level of alpha =0.05 was used.

Results

Forty-four fibroids in 20 women had growth rate measurement available, and 36 fibroids in 16 women had follow-up quantitative MRI available. The distribution of fibroid growth rate was skewed, with approximately 20% of the fibroids exhibiting fast growth (>10 cc/year). However, there were no significant changes in median baseline and follow-up values of symptom severity and health-related quality of life scores. There was no change in average T2, T2*, and ADC at follow-up exams and there was a moderate to strong correlation to the fibroid growth rate in baseline volume and average T2 and ADC in slow-growing fibroids (<10 cc/year). A multiple logistic regression to identify fast growing UFs (>10 cc/year) achieved an area under the curve (AUC) of 0.80 with specificity of 69% at 100% sensitivity.

Conclusions

The mp-qMRI parameters T2, ADC, and UF volume obtained at the time of initial fibroid diagnosis may be able to predict UF growth rate. Mp-qMRI could be integrated into the management of UFs, for individualized care and improved clinical outcomes.

Histological findings in resected leiomyomas following MR-HIFU treatment, single-institution data from seven patients with unfavorable focal therapy

PURPOSE

Magnetic resonance - high-intensity focused ultrasound (MR-HIFU) is a noninvasive treatment option for symptomatic uterine leiomyomas. Currently, pretreatment MRI is used to assess tissue characteristics and predict the most likely therapeutic response for individual patients. However, these predictions still entail significant uncertainties. The impact of tissue properties on therapeutic outcomes remains poorly understood and detailed knowledge of the histological effects of ultrasound ablation is lacking. Investigating these aspects could aid in optimizing patient selection, enhancing treatment effects and improving treatment outcomes.

METHODS AND MATERIALS

We present seven patients who underwent MR-HIFU treatment for leiomyoma followed by second-line surgical treatment. Tissue samples obtained during the surgery were stained with hematoxylin and eosin, Masson's trichrome and Herovici to evaluate general morphology, fibrosis and collagen deposition of leiomyomas. Immunohistochemical CD31, Ki-67 and MMP-2 stainings were performed to study vascularization, proliferation and matrix metalloproteinase-2 protein expression in leiomyomas, respectively.

RESULTS

The clinical characteristics and radiological findings of the leiomyomas prior to treatment as well as qualitative histological findings after the treatment are presented and discussed in the context of current literature. A tentative model for volume reduction is presented.

CONCLUSION

These findings provide insights into potential factors contributing to suboptimal therapeutic outcomes and the variability in histological changes following treatment.

Tumor stiffness measured by 3D magnetic resonance elastography can help predict the aggressiveness of endometrial carcinoma: preliminary findings

BACKGROUND

Preoperative evaluation of aggressiveness, including tumor histological subtype, grade of differentiation, Federation International of Gynecology and Obstetrics (FIGO) stage, and depth of myometrial invasion, is significant for treatment planning and prognosis in endometrial carcinoma (EC). The purpose of this study was to evaluate whether three-dimensional (3D) magnetic resonance elastography (MRE) can help predict the aggressiveness of EC.

METHODS

From August 2015 to January 2019, 82 consecutive patients with suspected uterine tumors underwent pelvic MRI and MRE scans, and 15 patients with confirmed EC after surgical resection were enrolled. According to pathological results (tumor grade, histological subtype, FIGO stage, and myometrial invasiveness), the patients were divided into two subgroups. The independent-samples t-test or Mann-Whitney U test was used to compare the stiffness between different groups. The diagnostic performance was determined with receiver operating characteristic (ROC) curve analysis.

RESULTS

The stiffness of EC with ≥ 50 % (n = 6) myometrial invasion was significantly higher than that with < 50 % (n = 9) myometrial invasion (3.68 ± 0.59 kPa vs. 2.61 ± 0.72 kPa, p = 0.009). Using a stiffness of 3.04 kPa as a cutoff value resulted in 100 % sensitivity and 77.8 % specificity for differentiating ≥ 50 % myometrial invasion from < 50 % myometrial invasion of EC. The stiffness of poorly differentiated EC (n = 8) was significantly higher than that of well/moderately differentiated EC (n = 7) (3.47 ± 0.64 kPa vs. 2.55 ± 0.82 kPa, p = 0.028). Using a stiffness of 3.04 kPa as a cutoff value resulted in 75 % sensitivity and 71.4 % specificity for differentiating poorly differentiated from well/moderately differentiated EC. The stiffness of FIGO stage II/III EC was significantly higher than that of FIGO stage I EC (3.69 ± 0.65 kPa vs. 2.72 ± 0.76 kPa, p = 0.030). Using a stiffness of 3.04 kPa as a cutoff value resulted in 100 % sensitivity and 70 % specificity for differentiating FIGO stage I EC from FIGO stage II/III EC. The tumor stiffness value in type II (n = 3) EC was higher than that in type I (n = 12) EC (3.67 ± 0.59 kPa vs. 2.88 ± 0.85 kPa), but the difference was not significant (p = 0.136).

CONCLUSIONS

Tumor stiffness measured by 3D MRE may be potentially useful for predicting tumor grade, FIGO stage and myometrial invasion of EC and can aid in the preoperative risk stratification of EC.

Uterine leiomyomas: correlation between histologic composition and stiffness via magnetic resonance elastography - a Pilot Study

OBJECTIVES

To evaluate magnetic resonance elastography as a tool for characterizing uterine leimyomas.

MATERIAL AND METHODS

At total of 12 women with symptomatic leiomyomas diagnosed in physical and ultrasound examinations were enrolled in this pilot study. Before surgery, all patients underwent magnetic resonance elastography of the uterus using a 1.5 T MR whole-body scanner (Optima, GE Healthcare, Milwaukee, WI, USA). Surgical specimens were forwarded for histological examination. The findings were allocated into 3 categories depending on the percentage content of connective tissue: below 15%, from 15 to 30% and more than 30%. The median stiffness of leiomyomas for each of the group was calculated. The U-Mann Whitney test was used for statistical analysis.

RESULTS

The stiffness of the leiomyomas ranged between 3.7-6.9 kPa (median value 4.9 kPa). The concentration of extracellular components in the leiomyomas did not exceed 40%. An increasing trend of the stiffness with the growing percentage of extracellular component was observed. Stiffness of the leiomyomas obtained by MRE varies depending on microscopic composition.

CONCLUSIONS

The value of stiffness shows a trend of increasing with the percentage of extracellular component of the leiomyoma. Further studies are required to assess the usefulness of MRE in diagnostics of uterine leiomyomas.

MR-guided Focused Ultrasound for Uterine Fibroids: A Preliminary Study of Relationship between the Treatment Outcomes and Factors of MR Images Including Elastography

We evaluated the value of magnetic resonance elastography (MRE) for the prediction of response to magnetic resonance-guided focused ultrasound (MRgFUS) for uterine fibroids. Eleven patients were enrolled. A fractional change of >30% in Symptoms Severity Score (SSS) was defined as a ‘substantial symptomatic improvement’ at 12 months after treatment. The fractional stiffness value reduction in the patients with a substantial improvement in SSS was significantly higher than that in those without (P = 0.0446).

New and Emerging Applications of Magnetic Resonance Elastography of Other Abdominal Organs

Increasing clinical experience and ongoing research in the field of magnetic resonance elastography (MRE) is leading to exploration of its applications in other abdominal organs. In this review, the current research progress of MRE in prostate, uterus, pancreas, spleen, and kidney will be discussed. The article will describe patient preparation, modified technical approach including development of passive drivers, modification of sequences, and inversion. The potential clinical application of MRE in the evaluation of several disease processes affecting these organs will be discussed. In an era of increasing adoption of multiparametric magnetic resonance imaging approaches for solving complex abdominal problems, abdominal MRE as a biomarker may be seamlessly incorporated into a standard magnetic resonance imaging examination to provide a rapid, reliable, and comprehensive imaging evaluation at a single patient appointment in the future.

Soft tissue elastography via shearing interferometry

Early detection of cancer can significantly increase the survival chances of patients. Palpation is a traditional method in order to detect cancer; however, in minimally invasive surgery the surgeon is deprived of the sense of touch. We demonstrate how shearing elastography can recover elastic parameters and furthermore can be used to localize stiffness imhomogenities even if hidden underneath the surface. Furthermore, the influence of size and depth of the stiffness imhomogenities on the detection accuracy and localization is investigated.

Uterine Leiomyosarcoma: Can MRI Differentiate Leiomyosarcoma From Benign Leiomyoma Before Treatment?

OBJECTIVE

The purpose of this article is to provide background on the epidemiologic, clinical, and economic impact of uterine leiomyomas, summarize the concerns associated with treating women with potential occult leiomyosarcomas (LMSs), and review the known and emerging imaging features of typical and atypical leiomyomas and explain how to differentiate them from LMSs.

CONCLUSION

Surgical management of presumed benign uterine leiomyomas received popular media attention when a case of disseminated LMS occurred after laparoscopic power morcellator-assisted hysterectomy. A subsequent U.S. Food and Drug Administration review found a higher prevalence of unsuspected uterine sarcoma and LMS among patients undergoing myomectomy or hysterectomy for presumed benign leiomyomas than was previously reported. This heightened concern has led to increased pressure on radiologists to distinguish LMSs from leiomyomas.

Uterine fibroids: correlations between MRI appearance and stiffness via magnetic resonance elastography

RATIONALE AND OBJECTIVES

Magnetic resonance elastography has proven to be a valuable tool in the diagnosis of liver fibrosis, breast and cervical cancer, but its application in uterine fibroids requires further characterization. The aim of the present study was to examine the relationship between uterine fibroid stiffness by MRE and MR imaging characteristics.

MATERIALS AND METHODS

An IRB-approved, HIPAA compliant review was performed of prospectively collected pelvic MRI and 2D-MRE data in patients with symptomatic uterine fibroids (N = 102). T1 and T2 weighted pelvic MRI with gadolinium enhancement were performed. In a small patient subset, fibroid stiffness was assessed by both 2D and 3D MRE. Fibroid stiffness by modality or imaging characteristics was analyzed using one-way analysis of variance followed by Student t test.

RESULTS

Four fibroid groups were identified based on T2 appearance: Isointense (N = 7), bright (N = 6), dark with minimal heterogeneity (N = 69), and dark with substantial heterogeneity (N = 20). Mean fibroid stiffness was 4.81 ± 2.12 kPa. Comparison of fibroid stiffness by T2 signal intensity showed that T2 bright fibroids were significantly less stiff than fibroids appearing T2 dark with minimal heterogeneity (mean stiffness difference = 2.38 kPa; p < 0.05) and T2 dark fibroids with substantial heterogeneity were significantly less stiff than T2 dark fibroids with minimal heterogeneity (mean difference = 1.25 kPa; p < 0.05). There was no significant association between fibroid stiffness and T1 signal characteristics or gadolinium enhancement. There was no significant difference in stiffness values obtained by either 2D vs. 3D MRE.

CONCLUSIONS

These data suggest differences in fibroid stiffness are associated with different T2 imaging characteristics with less stiff fibroids being T2 bright and more stiff fibroids being T2 dark. Further studies are needed to determine if fibroid stiffness by MRE may serve as an imaging biomarker to help predict MR-guided treatment response.

Large-field-of-view optical elastography using digital image correlation for biological soft tissue investigation

In minimally invasive surgery the haptic feedback, which represents an important tool for the localization of abnormalities, is no longer available. Elastography is an imaging technique that results in quantitative elastic parameters. It can hence be used to replace the lost sense of touch, as to enable tissue localization and discrimination. Digital image correlation is the chosen elastographic imaging technique. The implementation discussed here is clinically sound, based on a spectrally engineered illumination source that enables imaging of biological surface markers (blood vessels) with high contrast. Mechanical loading and deformation of the sample is performed using a rolling indenter, which enables the investigation of large organs (size of kidney) with reduced measurement time compared to a scanning approach. Furthermore, the rolling indentation results in strain contrast improvement and an increase in detection accuracy. The successful application of digital image correlation is first demonstrated on a silicone phantom and later on biological samples. Elasticity parameters and their corresponding four-dimensional distribution are generated via solving the inverse problem (only two-dimensional displacement field and strain map experimentally available) using a well-matched hyperelastic finite element model.

Loss of stiffness in collagen-rich uterine fibroids after digestion with purified collagenase Clostridium histolyticum

BACKGROUND

Uterine fibroids are a significant health problem. These common benign tumors occur in 70-80% of women before age 50 years and often cause bleeding and pain and can interfere considerably with daily life. Current treatment options are limited. Fibroids contain substantial amounts of altered and disordered collagens, which contribute to their bulk. Targeting these collagens directly presents a novel treatment approach.

OBJECTIVES

We sought to test the hypothesis that a highly purified collagenase Clostridium histolyticum will digest interstitial collagen in uterine fibroids and reduce their stiffness and thereby evaluate the feasibility that this collagenase C histolyticum can be developed into an alternative treatment for fibroids. A secondary objective was to describe the collagen content of the fibroid tissue.

STUDY DESIGN

Fibroid tissue cubes (1 cm³; n = 154) were cut from 17 uterine fibroids that were obtained from 7 consented subjects undergoing scheduled hysterectomies. Tissue cubes were injected with diluent, placebo, or highly purified collagenase C histolyticum (0.05, 0.1, or 0.2 mg/cube) and incubated at 37°C for 24, 48, 72, or 96 hours. At each time point, 6 noninjected control cubes were also evaluated. Tissue cubes were photographed before and after incubation. Myometrial samples (n = 21) were also evaluated. Stiffness was quantified through rheometry by measuring complex shear moduli of the tissues. Percent fibrosis was determined by computerized analysis of Masson-trichrome-stained slides. Digestion of collagen fibrils was confirmed by transmission electron microscopy.

RESULTS

Fibrosis in untreated fibroids ranged from 37% to 77%, reflecting the collagen-rich nature of these tumors. After treatment with collagenase for 96 hours, fibrosis ranged from 5.3% to 2.4%. Transmission electron microscopy confirmed complete digestion of collagen fibrils. Tissue stiffness was reduced with all 3 doses of collagenase treatment and at all 4 time points. Longer incubation times with collagenase caused greater reduction in stiffness, and treated cubes lost their cuboidal shape and had gelatinous/liquefied centers. At 96 hours the stiffness in tissues treated with the lowest dose was reduced to 966 ± 106 Pascal compared with the diluent-treated control at the same time (5323 ± 903 Pascal; P < .0001; by analysis of variance with Tukey-Kramer).

CONCLUSION

Uterine fibroids have a high content of collagen that can be effectively digested by highly purified collagenase C histolyticum, resulting in reduced tissue stiffness. Loss of stiffness may decrease bulk symptoms in vivo and possibly lead to shrinkage of fibroids through changed mechanotransduction, leading ultimately to reduced fibroid symptoms of pain and bleeding. Clinical trials are necessary to evaluate the safety and efficacy of collagenase C histolyticum including the rate of regrowth of fibroids. The data of this study provide a strong rationale for using this purified collagenase in clinical trials as a local treatment for women with fibroids.

Magnetic resonance elastography (MRE) in cancer: Technique, analysis, and applications

Tissue mechanical properties are significantly altered with the development of cancer. Magnetic resonance elastography (MRE) is a noninvasive technique capable of quantifying tissue mechanical properties in vivo. This review describes the basic principles of MRE and introduces some of the many promising MRE methods that have been developed for the detection and characterization of cancer, evaluation of response to therapy, and investigation of the underlying mechanical mechanisms associated with malignancy.

Magnetic resonance elastography of abdomen

Many diseases cause substantial changes in the mechanical properties of tissue, and this provides motivation for developing methods to noninvasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate noninvasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed.

Leiomyoma cells in 3-dimensional cultures demonstrate an attenuated response to fasudil, a rho-kinase inhibitor, when compared to 2-dimensional cultures

Uterine leiomyomata are common benign tumors in women of reproductive age and demonstrate an attenuated response to mechanical signaling that involves Rho and integrins. To further characterize the impairment in Rho signaling, we studied the effect of Rho-kinase inhibitor, fasudil, on extracellular matrix production, in 2-dimensional (2D) and 3-dimensional (3D) cultures of leiomyoma and myometrial cells. Leiomyoma 2D cultures demonstrated a rapid decrease in gene transcripts and protein for fibronectin, procollagen 1A, and versican. In 3D cultures, fibronectin and procollagen 1A proteins demonstrated increased levels at lower concentrations of fasudil, followed by a concentration-dependent decrease. Versican protein increased up to 3-fold, whereas fibromodulin demonstrated a significant decrease of 1.92-fold. Myometrial 2D or 3D cultures demonstrated a decrease in all proteins after 72 hours of treatment. The 3D leiomyoma cultures demonstrated a significant increase in active RhoA, followed by a concentration-dependent decrease at higher concentrations. A concentration-dependent increase in phospho-extracellular regulated signal kinase and proapoptotic protein Bax was observed in 3D leiomyoma cultures. Fasudil relaxed the contraction of the 3D collagen gels caused by myometrium and leiomyoma cell growth. These findings indicate that the altered state of Rho signaling in leiomyoma was more clearly observed in 3D cultures. The results also suggest that fasudil may have clinical applicability for treatment of uterine leiomyoma.

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

OBJECTIVES

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

KEY POINTS

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.

The extracellular matrix contributes to mechanotransduction in uterine fibroids

The role of the extracellular matrix (ECM) and mechanotransduction as an important signaling factor in the human uterus is just beginning to be appreciated. The ECM is not only the substance that surrounds cells, but ECM stiffness will either compress cells or stretch them resulting in signals converted into chemical changes within the cell, depending on the amount of collagen, cross-linking, and hydration, as well as other ECM components. In this review we present evidence that the stiffness of fibroid tissue has a direct effect on the growth of the tumor through the induction of fibrosis. Fibrosis has two characteristics: (1) resistance to apoptosis leading to the persistence of cells and (2) secretion of collagen and other components of the ECM such a proteoglycans by those cells leading to abundant disposition of highly cross-linked, disoriented, and often widely dispersed collagen fibrils. Fibrosis affects cell growth by mechanotransduction, the dynamic signaling system whereby mechanical forces initiate chemical signaling in cells. Data indicate that the structurally disordered and abnormally formed ECM of uterine fibroids contributes to fibroid formation and growth. An appreciation of the critical role of ECM stiffness to fibroid growth may lead to new strategies for treatment of this common disease.

Acoustic waves in medical imaging and diagnostics

Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term ultrasonography, or its abbreviated version sonography, meant an imaging modality based on the use of ultrasonic compressional bulk waves. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a different mode of acoustic wave: shear waves. Imaging with these waves was shown to provide very useful and very different information about the biological tissue being examined. We discuss the physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities and frequencies that have been used in different imaging applications is presented. We discuss the potential for future shear wave imaging applications.

Is fibroid heterogeneity a significant issue for clinicians and researchers?

The clinical and scientific literature overwhelmingly deals with fibroids as a single entity or disease. This convenient assumption of homogeneity may be an important oversight given that substantial evidence exists for heterogeneity between fibroids at many levels. Failure to recognize and accommodate fibroid heterogeneity can have significant ramifications for both clinical treatment decisions and research protocol design. The aim of this article is to review the current knowledge of fibroid heterogeneity and to identify key areas where fibroid heterogeneity should be taken into consideration both clinically and when designing research protocols. Uterine leiomyomata display significant and well-documented heterogeneity in symptoms, diagnostic imaging appearance, pathology, genetic background and therapeutic requirements. Additional research is needed to better understand fibroid heterogeneity as it relates to pathogenesis, molecular targets for potential new therapies, patient symptoms and, ultimately, treatment. To this list should also be added heterogeneity of genetics, lifestyle and individual clinical characteristics of the fibroid. Increasingly, an understanding of uterine leiomyoma heterogeneity will be of importance for clinicians who see patients with this common and costly disease.

A novel saline infusion sonohysterography-based strain imaging approach for evaluation of uterine abnormalities in vivo: preliminary results

In this article, we demonstrate the feasibility of saline infusion sonohysterography-based strain imaging for the determination of stiffness variations in uterine masses in vivo. Strain images are estimated using a 2-dimensional multilevel hybrid algorithm developed for sector array ultrasound transducers. Coarse displacements are initially estimated using envelope echo signals, followed by a guided finer displacement estimation using window lengths on the order of 6 wavelengths and 7 A-lines on radiofrequency data. Strain images are obtained by estimating displacement slopes using least squares estimation. In this prospective study, we show that stiffer masses such as fibroids appear darker or as regions with low strain on strain images and are thus clearly differentiated when compared to normal uterine tissue. A high strain boundary around stiffer masses referred to as a "halo" due to increased slipping or sliding of the mass during the applied deformation is also visualized. Uterine polyps, on the other hand, are visualized as masses that are brighter or regions with high strain when compared to the background myometrium, indicating the presence of a softer mass. Axial strain images provide additional new information that may supplement current clinical B-mode imaging used for the diagnosis of uterine abnormalities. Our results show the feasibility of improving clinical diagnosis based on strain imaging.

Characterization of tissue biomechanics and mechanical signaling in uterine leiomyoma

Leiomyoma are common tumors arising within the uterus that feature excessive deposition of a stiff, disordered extracellular matrix (ECM). Mechanical stress is a critical determinant of excessive ECM deposition and increased mechanical stress has been shown to be involved in tumorigenesis. Here we tested the viscoelastic properties of leiomyoma and characterized dynamic and static mechanical signaling in leiomyoma cells using three approaches, including measurement of active RhoA. We found that the peak strain and pseudo-dynamic modulus of leiomyoma tissue was significantly increased relative to matched myometrium. In addition, leiomyoma cells demonstrated an attenuated response to applied cyclic uniaxial strain and to variation in substrate stiffness, relative to myometrial cells. However, on a flexible pronectin-coated silicone substrate, basal levels and lysophosphatidic acid-stimulated levels of activated RhoA were similar between leiomyoma and myometrial cells. In contrast, leiomyoma cells plated on a rigid polystyrene substrate had elevated levels of active RhoA, compared to myometrial cells. The results indicate that viscoelastic properties of the ECM of leiomyoma contribute significantly to the tumor's inherent stiffness and that leiomyoma cells have an attenuated sensitivity to mechanical cues. The findings suggest there may be a fundamental alteration in the communication between the external mechanical environment (extracellular forces) and reorganization of the actin cytoskeleton mediated by RhoA in leiomyoma cells. Additional research will be needed to elucidate the mechanism(s) responsible for the attenuated mechanical signaling in leiomyoma cells.