Differentiation of prostate cancer from benign lesions using strain index of transrectal real-time tissue elastography

Novel non-MRI imaging techniques for primary diagnosis of prostate cancer: micro-ultrasound, contrast-enhanced ultrasound, elastography, multiparametric ultrasound, and PSMA PET/CT

BACKGROUND

Multiparametric magnetic resonance imaging (mpMRI) provides enhanced diagnostic accuracy in the detection of prostate cancer, but is not devoid of limitations. Given the recent evolution of non-MRI imaging techniques, this critical review of the literature aimed at summarizing the available evidence on ultrasound-based and nuclear medicine imaging technologies in the initial diagnosis of PCa.

METHODS

Three databases (PubMed®, Web of Science™, and Scopus®) were queried for studies examining their diagnostic performance in the primary diagnosis of PCa, weighted against a histological confirmation of PCa diagnosis, using a free-text protocol. Retrospective and prospective studies, both comparative and non-comparative, systematic reviews (SR) and meta-analysis (MA) were included. Based on authors' expert opinion, studies were selected, data extracted, and results qualitatively described.

RESULTS

Micro-ultrasound (micro-US) appears as an appealing diagnostic strategy given its high accuracy in detection of PCa, apparently non-inferior to mpMRI. The use of multiparametric US (mpUS) likely gives an advantage in terms of effectiveness coming from the combination of different modalities, especially when certain modalities are combined. Prostate-specific membrane antigen (PSMA) PET/CT may represent a whole-body, one-step approach for appropriate diagnosis and staging of PCa. The direct relationship between lesions avidity of radiotracers and histopathologic and prognostic features, and its valid diagnostic performance represents appealing characteristics. However, intrinsic limits of each of these techniques exist and further research is needed before definitively considering them reliable tools for accurate PCa diagnosis. Other novel technologies, such as elastography and multiparametric US, currently relies on a limited number of studies, and therefore evidence about them remains preliminary.

CONCLUSION

Evidence on the role of non-MRI imaging options in the primary diagnosis of PCa is steadily building up. This testifies a growing interest towards novel technologies that might allow overcoming some of the limitations of current gold standard MRI imaging.

Advanced strain elastography is a reliable approach for prostate cancer detection in patients with elevated PSA levels

This study aimed to examine the validity and reproducibility of strain elastography (SE) for detecting prostate cancer (PCa) in patients with elevated prostate-specific antigen (PSA) levels. The study included 107 patients with elevated PSA levels. All eligible patients underwent transrectal ultrasound (TRUS) with real-time elastography (RTE) to detect suspicious lesions. Two readers independently evaluated the lesions and assigned a strain ratio and elastography score to each lesion. Histopathology was used as a reference standard to estimate the validity of RTE in predicting malignant lesions. An intraclass correlation (ICC) was performed to detect reliability of the strain ratios and elastography scores. TRUS-guided biopsy detected malignancies in 64 (59.8%) patients. TRUS with RTE revealed 122 lesions. The strain ratio index (SRI) cut-off values to diagnose malignancy were 4.05 and 4.35, with sensitivity, specificity, and accuracy of 94.7%, 91.3%, and 93.4%, respectively. An elastography score > 3 was the best cut-off value for detecting malignancy. According to readers, the sensitivity, specificity, and accuracy were 91.3-94.7%, 89.5-93.4%, and 91.3-90.9%, respectively. Excellent inter-reader agreement was recorded for SRI and elastography scores, with ICC of 0.937 and 0.800, respectively. SE proves to be an efficient tool for detecting PCa with high accuracy in patients with elevated PSA levels.

Role of the elastography strain ratio using transrectal ultrasonography in the diagnosis of prostate cancer and clinically significant prostate cancer

This study investigated the efficacy of the elastography strain ratio (ESR) as a predictor of prostate cancer (PCa) in targeted prostate biopsy. In total, 257 patients who underwent magnetic resonance imaging-targeted biopsy were enrolled. Before biopsy, we placed regions of interest (zone A and B) in the lesion and levator ani. The ESR was measured as zone A/zone B. Multivariate analyses were performed to predict PCa and clinically significant PCa. There were 206 (71.5%) positive cancer lesions. No difference in digit rectal examination findings was found between patients with and without PCa. For predicting clinically significant PCa, an ESR ≥ 6.8 was significantly higher in the PCa (+) group than in the PCa (-) group (p < 0.001). The area under the receiver operating characteristic curve (AUC) for the conventional variables (model 1) plus the ESR was 0.845, which was significantly higher than that for model 1 (p = 0.001). In prostate imaging reporting and data system score 3 lesions, an ESR ≥ 4.6 was a significant predictor of PCa (p = 0.002). The AUC in model 1 plus the ESR was 0.856, which was significantly higher than that in model 1 alone (p = 0.017). The ESR is useful for predicting clinically significant PCa.

Assessment of elastographic Q-analysis score combined with Prostate Imaging-Reporting and Data System (PI-RADS) based on transrectal ultrasound (TRUS)/multi-parameter magnetic resonance imaging (MP-MRI) fusion-guided biopsy in differentiating benign and malignant prostate

BACKGROUND

Magnetic resonance imaging (MRI) has advantages in the diagnosis of prostate diseases, but there is also overdiagnosis. We compensate for this with fusion imaging and elastography. In this study, we want to evaluate Elastographic Q-analysis score (EQS) combined with Prostate Imaging Reporting and Data System (PI-RADS), based on transrectal ultrasound (TRUS)/multi-parameter magnetic resonance imaging (MP-MRI) fusion biopsy in differentiating benign and malignant prostate lesions.

METHODS

A total of 296 patients with 318 prostate lesions who underwent TRUS/MP-MRI fusion biopsy between October 2017 and October 2019 were retrospectively analysed. The performance of the EQS was evaluated on the sites of the suspicious areas of MP-MRI. The cut-off value of EQS was obtained according to receiver operating characteristic (ROC) curve, which was used to upgrade and downgrade the PI-RADS scores. The area under the curve (AUC), integrated discrimination improvement, and decision curve analysis were used to assess the new PI-RADS performance.

RESULTS

In total, 318 MP-MRI suspicious prostate lesions (94 malignant vs. 224 benign lesions). The EQS optimal threshold was 1.85, and the AUC was 0.816. All cases were constructed three models by using 1.85 as the cut-off value: upgrade-PI-RADS, downgrade-PI-RADS and complex-PI-RADS. The AUC of PI-RADS, upgrade-PI-RADS, downgrade-PI-RADS and complex-PI-RADS were 0.869, 0.867, 0.872 and 0.873 respectively. The diagnostic coincidence rate of PI-RADS was increased from 0.667 to 0.874 by using strain elastography, among which the diagnostic rate of prostate cancer was increased from 0.557 to 0.806, and the diagnostic rate of non-prostate cancer was increased from 0.775 to 0.967. The integrated discrimination improvement indicated that downgrade-PI-RADS had a better diagnostic capability (P<0.05). The net benefit of all models, which downgrade-PI-RADS can maximize the net benefit value of patients by decision curve analysis.

CONCLUSIONS

The combination of PI-RADS and EQS with TRUS/MP-MRI fusion, particularly downgrade-PI-RADS, can reduce unnecessary biopsy procedures and prevent overdiagnosis.

Recent advances of multi-modal ultrasound in image-guided prostate-targeted biopsy

Prostate-targeted biopsy is usually the preferred method over systematic biopsy because it can effectively detect prostate cancer using only a few puncture cores with fewer complications. With the development of ultrasound, it has gained multimodal technological upgrades, such as the emergence of contrast-enhanced ultrasound, ultrasound elastography, and three-dimensional ultrasonography. Moreover, multimodal ultrasound has played an increasingly significant role in prostate-targeted biopsies.

Multiparametric ultrasound and micro-ultrasound in prostate cancer: a comprehensive review

Prostate cancer (PCa) is the most common non-cutaneous cancer diagnosed in males. Traditional tools for screening and diagnosis, such as prostate-specific antigen, digital rectal examination and conventional transrectal ultrasound (TRUS), present low accuracy for PCa detection. Multiparametric MRI has become a game changer in the PCa diagnosis pathway and MRI-targeted biopsies are currently recommended for males at risk of clinically significant PCa, even in biopsy-naïve patients. Recent advances in ultrasound have also emerged with the goal to provide a readily accessible and cost-effective tool for detection of PCa. These newer techniques include elastography and contrast-enhanced ultrasound, as well as improved B-mode and Doppler techniques. These modalities can be combined to define a novel ultrasound approach, multiparametric ultrasound. High frequency Micro-ultrasound has emerged as a promising imaging technology for PCa diagnosis. Initial results have shown high sensitivity of Micro-ultrasound in detecting PCa in addition to its potential in improving the accuracy of targeted biopsies, based on targeting under real-time visualization, rather than relying on cognitive/fusion software MRI-transrectal ultrasound-guided biopsy.

Sonoelastography in the Diagnosis of Carpal Tunnel Syndrome: A Systematic Review of Diagnostic Values Compared With the Normative Population

BACKGROUND

Sonoelastography (SEL) is widely used for assessing tissue stiffness and pathophysiology. It has also been used to diagnose carpal tunnel syndrome (CTS). However, the current criteria to diagnose CTS in SEL are diverse. The aim of this study was to systematically review the literature and assess the diagnostic value of SEL for CTS.

METHODS

A literature review was performed using MEDLINE (PubMed), EMBASE, and the Cochrane Collaboration Library for primary research articles using the keywords sonoelastography and carpal tunnel syndrome. Data related to diagnostic and cutoff value were extracted. Bias assessment was performed.

RESULTS

A total of 121 publications were reviewed. Nineteen primary case series met the inclusion criteria and were selected for full analysis. Different diagnostic approaches were identified, with units/expressions including kilopascals, conduct velocity, and strain ratio. The kilopascals and conduct velocity were measured using shear wave elastography, whereas strain ratio was calculated by relative compression quantification. A mean shear modulus cutoff value from 38.25 to 86 kPa and an acoustic radiation force impulse cutoff value of 3.0 to 3.23 m/s were used to diagnose CTS. Eight articles reported strain ratio between the median nerve and nearby tissues with diverse results due to different reference points. The other 3 additional diagnostic values were reported.

CONCLUSIONS

Sonoelastography is a useful noninvasive and promising modality to diagnose CTS. It may reflect both the condition of soft tissue scarring and quantitative values for CTS and median nerve stiffness. A diversity of examination values was found in different modalities. A high level of evidence was absent.

Ultrasound elastography in characterization of prostatic lesions: correlation with histopathological findings

OBJECTIVE

Ultrasound elastography is increasingly used in the diagnosis of prostate cancer, however results are heterogeneous. We correlate in a large sample-size prospective study the accuracy of elastography, aiming to settle an accurate cut-off point for diagnosis and possibility of use as a screening tool.

METHODS

Prospective study that included 120 patients with mean age 59.5 ± 9.8 years, showing enlarged prostate by clinical examination with prostate-specific antigen >4 ng ml-1.The study was done using high frequency high resolution endorectal probe with real time tissue elastography.Grayscale ultrasound examination was done first with Doppler followed by elastography color-coded map and strain ratio measurement. Then, transrectal ultrasound-guided core biopsy was done from suspicious areas detected by elastography (totally or partly stiff by color-coded map or with relative increased strain ratio), besides standard six-quadrant core biopsy samples.

RESULTS

There was statistically significant difference (p < 0.001) regarding strain ratio in benign and malignant lesions. Strain ratio showed significant proportionate correlation with prostate-specific antigen level and Gleason pathological score, while no significant correlation noted with the age or the prostatic volume. A strain ratio with a cut-off value of 1.9 showed a sensitivity of 100%, specificity 93.8%, positive predictive value of 79.3%, negative predictive value 100 and 95% accuracy in differentiating between malignant and benign lesions.

CONCLUSION

Strain ratio improves the detection of prostatic cancer with high sensitivity (100%) and high negative predictive value (100%).

ADVANCES IN KNOWLEDGE

Different prostatic lesions are mostly similar in grayscale ultrasound.Imaging plays an important role in differentiation of prostatic nodules.Ultrasound elastography may play an important role in distinguishing benign from malignant nodules.

Assessing Low Skeletal Mass in Patients Undergoing Hip Surgery: The Role of Sonoelastography

Purpose

To analyze the utility of sonoelastography—a radiation-free procedure to characterize muscle properties—as an instrument to qualitatively and quantitatively assess the rectus femoris muscle.

Materials and Methods

Fifty-one consecutive patients who underwent a pelvic computed tomography (CT) exam were enrolled prospectively. The final analysis was conducted using data from 39 patients after 12 were removed due to exclusion criteria (muscle strength could not be measured due to poor cognition [n=11]; too young [n=1]). The potential correlation between average Hounsfield unit (HFU) at the rectus femoris muscle (measured by CT) and muscle quality grade (determined by sonoelastography) was assessed along with a retrospective analysis of the relationship between hand grip strength, knee extensor power, history of intensive care unit stay, length of hospital day and sonoelastographic grade.

Results

There was a significant correlation between sonoelastographic grade and the average HFU (P<0.001). Furthermore, hand grip strength (P<0.001) and knee extensor power (P<0.001) decreased significantly as the sonoelastographic grade increased. The likelihood of an intensive care unit stay and prevalence of low skeletal mass increased significantly with an increase in sonoelastography grade (P=0.037, P<0.001, respectively). The sensitivity, specificity, and accuracy of sonoelastographic images for predicting low skeletal mass were 77.3%, 100%, and 87.5%, respectively.

Conclusion

Sonoelastography advantages, including the lack of radiation and greater accessibility, may make it a valuable alternative to qualitatively and quantitatively identify sarcopenia and low skeletal mass.

Relationship between Lower Urinary Tract Symptoms and Prostatic Urethral Stiffness Using Strain Elastography: Initial Experiences

We attempted to visualize the periurethral stiffness of prostatic urethras using strain elastography in the midsagittal plane of transrectal ultrasonography (TRUS) and to evaluate periurethral stiffness patterns in relation to lower urinary tract symptoms (LUTS). A total of 250 men were enrolled. The stiffness patterns of the entire prostate and individual zones were evaluated using strain elastography during a TRUS examination. After excluding 69 men with inappropriate elastography images, subjects were divided according to periurethral stiffness into either group A (low periurethral stiffness, N = 80) or group B (high periurethral stiffness, N = 101). There were significant differences in patient age (p = 0.022), transitional zone volume (p = 0.001), transitional zone index (p = 0.33), total international prostate symptom score (IPSS) (p < 0.001), IPSS-voiding subscore (p < 0.001), IPSS-storage subscore (p < 0.001), and quality of life (QoL) score (p = 0.002) between groups A and B. After adjusting for relevant variables, significant differences in total IPSS, IPSS-voiding subscore, and QoL score were maintained. Men with high periurethral stiffness were associated with worse urinary symptoms than those with low periurethral stiffness, suggesting that periurethral stiffness might play an important role in the development of LUTS.

Evaluation of the Performance of the Ultrasound (US) Elastographic Q-Analysis Score Combined With the Prostate Imaging Reporting and Data System for Malignancy Risk Stratification in Prostate Nodules Based on Transrectal US-Magnetic Resonance Imaging Fusion Imaging

OBJECTIVES

This study retrospectively evaluated the prognostic performance of the ultrasound elastographic Q-analysis score (EQS) combined with the Prostate Imaging Reporting and Data System (PI-RADS) for malignancy risk stratification in prostate nodules based on transrectal ultrasound-magnetic resonance imaging fusion imaging.

METHODS

Sixty-two patients who were suspected to have PCa between October 2017 and May 2018 in our hospital were retrospectively evaluated. The performance of the EQS and PI-RADS was evaluated by patients' receiver operating characteristic curves in differentiating malignant and benign prostate nodules. The combination of the EQS and PI-RADS methods for prostate imaging was evaluated.

RESULTS

Sixty-two prostate nodules in 62 patients were included. All of the patients underwent biopsy; 29 cases were prostate cancer, and the rest were benign prostate lesions. Both the EQS and PI-RADS were significantly higher in malignant nodules than in benign nodules. The sensitivity, specificity, area under the curve, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value, and Youden index of an EQS cutoff of 2.05 were 86.2%, 81.8%, 85.9%, 4.73, 0.169, 80.6%, 87.1%, and 68%, respectively. The corresponding numbers for a PI-RADS cutoff of 4 were 82.7%, 69.7%, 84.2%, 2.72, 0.25, 70.6%, 82.1%, and 52.4%. The "tandem" method had a higher diagnostic specificity (87.9%), positive likelihood ratio (6.55), and positive predictive value (85.1%). The "parallel" method had a higher diagnostic sensitivity (96.5%), negative likelihood ratio (0.06), and negative predictive value (95.2%).

CONCLUSIONS

both the EQS and PI-RADS had good diagnostic performance in differentiating between malignant and benign prostate lesions. The combination of the EQS and PI-RADS improved the diagnostic performance to a certain degree.

Strain elastography as an early predictor of long-term prognosis in patients with locally advanced cervical cancers treated with concurrent chemoradiotherapy

OBJECTIVE

To explore the value of strain elastography as an early predictor of long-term prognosis in patients with locally advanced cervical cancers treated with concurrent chemoradiotherapy (CCRT).

METHODS

Strain elastography examinations were performed on 45 patients with locally advanced cervical cancers at 3 time points: prior to CCRT, and at 1 and 2 weeks after the start of CCRT. The maximum tumor diameter (D_max), strain ratio (SR), and their percentage changes (ΔD_max and ΔSR) were calculated to predict long-term prognosis. Based on the results of physical examinations, Papanicolaou test, and pelvic magnetic resonance imaging, we classified patients into two groups: responders (complete remission) and non-responders (sustained disease, recurrence, or death).

RESULTS

After a median follow-up of 30 months (range, 12-36 months), 36 of 45 (80%) patients were disease free. The D_max as well as ΔD_max at 2 weeks during CCRT was able to predict the responder outcomes, with an area-under-the-curve (AUC) of 0.733 and 0.731, respectively. Furthermore, significant differences in SR and ΔSR at 1 and 2 weeks during therapy were shown between the responder and non-responder groups (all p < 0.05), and ΔSR at 2 weeks during CCRT presented with the highest AUC (0.91), yielding 88.9% sensitivity and 88.9% specificity with a selected cutoff value.

CONCLUSIONS

Strain elastography may be useful as an early predictor of long-term outcomes after CCRT for patients with cervical cancer.

KEY POINTS

• The D _maxas well as ΔD _maxat 2 weeks during CCRT can predict the responder outcomes. • The elastography parameters (SR and ΔSR) exhibited predictive values of favorable response after therapy initiation. • ΔSR at 2 weeks during CCRT held the best predictive value for the responder outcomes.

Comparison of median nerve stiffness with and without rheumatoid arthritis by ultrasound real-time tissue elastography: A propensity score matching study

Objectives: This study aimed to compare median nerve stiffness measured by ultrasound real-time tissue elastography in patients with and without rheumatoid arthritis (RA and non-RA groups, respectively).Methods: Altogether, 402 hands of 201 RA group and 222 hands of 111 non-RA group were included in the study. Ultrasonography was performed to evaluate the circumference, cross-sectional area (CSA) and strain ratio as an elasticity of the median nerve at the inlet level of the carpal tunnel and the proximal portion of the carpal tunnel inlet. Using propensity score matching, the difference between RA and non-RA group were analyzed.Results: After propensity score matching, 135 hands in 104 RA group and 70 non-RA group were finally analyzed. There were no significant differences in the circumference and CSA of the median nerve between the two groups. The strain ratio of the median nerve was significantly higher in RA group than in non-RA group only at the inlet of the carpal tunnel level.Conclusions: The nerve stiffness in patients with RA measured by ultrasound real-time tissue elastography was higher than without RA. Inflammatory condition of the flexor tendon and wrist joint in patients with RA may generate fibrotic changes in the median nerve.Trial registration: University Hospital Medical Information Network Clinical Trials Registry: UMIN000015314.

Elastography as a diagnostic tool in the prostate tumour detection in Labrador retriever

Prostate tumours are hard to detect in dogs. Early diagnosis is a key to maintain fertility and to protect against metastasis and death. Elastography is a diagnostic tool to obtain very detailed results of changes in tissue stiffness of this organ. There are no studies about the application of elastography to diagnose the prostate tumours in dogs. In our case, in male Labrador retriever there was state a prostate lesion by both scanning-grey ultrasonogram and elastography. Fine needle aspiration biopsy (FNA) confirmed the adenocarcinoma only in elastography-changed area. Thus, this method is helpful to diagnose prostate tumours and should be the first additional survey in routine examination of the prostate in the dog.

Strain Ratio as a Quantification Tool in Strain Imaging

Ultrasound-based strain imaging is available in several ultrasound (US) scanners. Strain ratio (SR) can be used to quantify the strain recorded simultaneously in two different user-selected areas, ideally exposed to the same amount of stress. The aim of this study was to evaluate SR variability when assessed in an in-vitro setup with a tissue-mimicking phantom on resected tissue samples and in live tissue scanning with endoscopic applications. We performed an in vivo retrospective analysis of SR variability used for quantification of elastic contrasts in a tissue-mimicking phantom containing four homogenous inclusion in 38 resected bowel wall lesions and 48 focal pancreatic lesions. Median SR and the inter-quartile range (IQR) were calculated for all external and endoscopic ultrasound (EUS) applications. The IQR and median provide a measure of SR variability focusing on the two percentiles of the data closest to the median value. The overall SR variability was lowest in a tissue-mimicking phantom (mean QR/median SR: 0.07). In resected bowel wall lesions representing adenomas, adenocarcinomas, or Crohn lesions, the variability increased (mean IQR/Median: 0.62). During an in vivo endoscopic examination of focal pancreatic lesions, the variability increased further (mean IQR/Median: 2.04). SR variability increased when assessed for different targets with growing heterogeneity and biological variability from homogeneous media to live tissues and endoscopic application. This may indicate a limitation for the accuracy of SR evaluation in some clinical applications.

Renal Allograft Dysfunction: Evaluation with Shear-wave Sonoelastography

Purpose To evaluate whether shear-wave sonoelastography can help differentiate stable renal allograft from acute allograft dysfunction and chronic allograft dysfunction and to correlate shear-wave sonoelastography measurements with resistive index (RI), serum creatinine level, estimated glomerular filtration rate (eGFR) obtained with the Nankivell equation, and biopsy findings. Materials and Methods A prospective study of 60 patients who had undergone renal transplantation was conducted between October 2014 and March 2016. Patients were classified as having stable allograft, acute allograft dysfunction, or chronic allograft dysfunction on the basis of clinical parameters. Mean parenchymal stiffness was compared. The Banff score was used wherever applicable. Receiver operating characteristic curves were drawn to evaluate the feasibility of differentiation. Results Thirty patients had graft dysfunction (acute in 19 patients and chronic in 11). Mean parenchymal stiffness values in stable allograft, acute allograft dysfunction, and chronic allograft dysfunction were 8.51 kPa ± 2.44, 11.06 kPa ± 2.91, and 24.50 kPa ± 4.49, respectively (stable vs acute dysfunction, P = .010; stable vs chronic dysfunction, P < .001; acute sysfunction vs chronic dysfunction, P < .001). The allograft parenchymal stiffness values for patients with Banff grade I (mild interstitial fibrosis and tubular atrophy) differed significantly from those with Banff grade II (moderate interstitial fibrosis and tubular atrophy) (P = .02). Parenchymal stiffness showed a negative correlation with eGFR (r = -0.725; P < .001) and a positive correlation with RI (r = 0.562; P < .001) and serum creatinine level (r = 0.714; P < .001). The sensitivity was 73.68% and specificity was 80% in the differentiation of stable graft from acute graft dysfunction (threshold value, 10.11 kPa). Conclusion Shear-wave sonoelastographic evaluation of renal parenchymal stiffness may help differentiate stable allograft from acute and chronic allograft dysfunction. The inverse correlation of parenchymal stiffness with eGFR and positive correlation with RI and serum creatinine level show that shear-wave sonoelastography may reflect functional status of the renal allograft.

Evaluation of Pancreas with Strain Elastography in Children with Type 1 Diabetes Mellitus

Background

To investigate changes in pancreatic elasticity in children with type 1 diabetes mellitus (T1DM).

Material/Methods

The study group consisted of 60 children with T1DM, and the control group was comprised of 60 healthy children. Strain ratios were obtained for the pancreas using ultrasound strain elastography (Toshiba Applio 500 device). Baseline descriptive data, hemoglobin A1c (%) level, time since diagnosis of T1DM (months), and strain ratio values were noted and compared between the 2 groups. Furthermore, correlation between strain ratio values and other variables was investigated.

Results

ROC analysis yielded an optimal cut-off value of 2.245 (AUC=0.999, p<0.001, sensitivity=0.983, specificity=1.00) for the strain ratio. Strain ratio values greater than 2.245 were likely to be pathological, which could be attributed to increased tissue stiffness in T1DM. The strain ratio was significantly higher in T1DM patients than in the control group (3.38±0.66 vs. 1.32±0.35; p<0.001). The strain ratio correlated positively with age and duration of T1DM (p<0.001 for both), and there was a correlation between the strain ratio and age in the control group (p=0.011).

Conclusions

Strain elastography is a promising, safe, non-invasive, and practical method for early detection, long-term screening, and follow-up in children with T1DM.

Prostate Cancer Detection with a Tactile Resonance Sensor-Measurement Considerations and Clinical Setup

Tumors in the human prostate are usually stiffer compared to surrounding non-malignant glandular tissue, and tactile resonance sensors measuring stiffness can be used to detect prostate cancer. To explore this further, we used a tactile resonance sensor system combined with a rotatable sample holder where whole surgically removed prostates could be attached to detect tumors on, and beneath, the surface ex vivo. Model studies on tissue phantoms made of silicone and porcine tissue were performed. Finally, two resected human prostate glands were studied. Embedded stiff silicone inclusions placed 4 mm under the surface could be detected in both the silicone and biological tissue models, with a sensor indentation of 0.6 mm. Areas with different amounts of prostate cancer (PCa) could be distinguished from normal tissue (p < 0.05), when the tumor was located in the anterior part, whereas small tumors located in the dorsal aspect were undetected. The study indicates that PCa may be detected in a whole resected prostate with an uneven surface and through its capsule. This is promising for the development of a clinically useful instrument to detect prostate cancer during surgery.

Performances and Limitations of Several Ultrasound-Based Elastography Techniques: A Phantom Study

The objective of this study is to assess strain and shear wave (SW) elastography performance in terms of accuracy by performing in vitro measurements on a calibrated elastography phantom. Acquisitions were done on a phantom containing 4 inclusions (12-74 kPa) embedded in a homogeneous background material (30 kPa). We performed qualitative assessment on elastograms, semiquantitative assessment with strain or elasticity ratios between each inclusion and the background and quantitative evaluation with SW acquisitions. Ratio and elasticity estimations were compared with expected values. Biases, relative errors and 95% confidence intervals (95% CI) were calculated. All techniques adequately classified inclusions as harder or softer than the background. For stiffness ratio estimation, SW methods were more precise than strain methods and had significantly higher percentages of correctly classified measurements (p = 0.008). Quantitative stiffness measurements were reproducible despite constant biases. SW elastography methods provide more reproducible estimations of tissue stiffness ratio than strain methods, as well as reproducible quantitative tissue stiffness despite constant biases.

Transrectal real-time tissue elastography targeted biopsy coupled with peak strain index improves the detection of clinically important prostate cancer

The focus of the present study was to evaluate transrectal real-time tissue elastography (RTE)-targeted two-core biopsy coupled with peak strain index for the detection of prostate cancer (PCa) and to compare this method with 10-core systematic biopsy. A total of 141 patients were enrolled for evaluation. The diagnostic value of peak strain index was assessed using a receiver operating characteristic curve. The cancer detection rates of the two approaches and corresponding positive cores and Gleason score were compared. The cancer detection rate per core in the RTE-targeted biopsy (44%) was higher compared with that in systematic biopsy (30%). The peak strain index value of PCa was higher compared with that of the benign lesion. PCa was detected with the highest sensitivity (87.5%) and specificity (85.5%) using the threshold value of a peak strain index of ≥5.97 with an area under the curve value of 0.95. When the Gleason score was ≥7, RTE-targeted biopsy coupled with peak strain index detected 95.6% of PCa cases, but 84.4% were detected using systematic biopsy. Peak strain index as a quantitative parameter may improve the differentiation of PCa from benign lesions in the prostate peripheral zone. Transrectal RTE-targeted biopsy coupled with peak strain index may enhance the detection of clinically significant PCa, particularly when combined with systematic biopsy.

Real-time ultrasound elastography of the Achilles tendon in patients with cerebral palsy: is there a correlation between strain ratio and biomechanical indicators?

PURPOSE

Our aim was to comparatively investigate the strain ratio and thickness of the Achilles tendon in children with cerebral palsy (CP), and to elucidate whether there is a correlation between biomechanical features of the Achilles tendon and strain ratio.

METHODS

A total of 155 participants (72 CP patients and 83 healthy controls) who underwent real-time elastography of both Achilles tendons were studied. A linear transducer (4.8-11.0 MHz) was used to obtain the images. Correlation analysis between age, length, and thickness of the Achilles tendon, and strain ratio (SR) was performed by means of Pearson correlation and Spearman's rho tests.

RESULTS

Comparison of results obtained from CP patients and controls showed that the length of the Achilles tendon was shorter (p < 0.001) and SR was higher (p < 0.001) in CP patients. In CP patients, there was a positive correlation between SR and age and between SR and the thickness and length of the Achilles tendon (p < 0.001 for all). Furthermore, the length of the tendon and age were positively associated (p < 0.001). ROC analysis revealed that the cut-off value for SR was 1.89.

CONCLUSION

The results of the present study demonstrated that real-time elastography can constitute a simple, practical, and noninvasive method for evaluation of the elasticity of the Achilles tendon in children with CP.

WFUMB Guidelines and Recommendations on the Clinical Use of Ultrasound Elastography: Part 5. Prostate

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced guidelines for the use of elastography techniques, including basic science, breast, liver and thyroid elastography. Here we present elastography in prostate diseases. For each available technique, procedure, reproducibility, results and limitations are analyzed and recommendations are given. Finally, recommendations are given based on the level of evidence of the published literature and on the WFUMB expert group's consensus. This document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of prostate diseases.

Identifying Clinically Significant Prostate Cancers using 3-D In Vivo Acoustic Radiation Force Impulse Imaging with Whole-Mount Histology Validation

Overly aggressive prostate cancer (PCa) treatment adversely affects patients and places an unnecessary burden on our health care system. The inability to identify and grade clinically significant PCa lesions is a factor contributing to excessively aggressive PCa treatment, such as radical prostatectomy, instead of more focal, prostate-sparing procedures such as cryotherapy and high-dose radiation therapy. We have performed 3-D in vivo B-mode and acoustic radiation force impulse (ARFI) imaging using a mechanically rotated, side-fire endorectal imaging array to identify regions suspicious for PCa in 29 patients being treated with radical prostatectomies for biopsy-confirmed PCa. Whole-mount histopathology analyses were performed to identify regions of clinically significant/insignificant PCa lesions, atrophy and benign prostatic hyperplasia. Regions of suspicion for PCa were reader-identified in ARFI images based on boundary delineation, contrast, texture and location. These regions of suspicion were compared with histopathology identified lesions using a nearest-neighbor regional localization approach. Of all clinically significant lesions identified on histopathology, 71.4% were also identified using ARFI imaging, including 79.3% of posterior and 33.3% of anterior lesions. Among the ARFI-identified lesions, 79.3% corresponded to clinically significant PCa lesions, with these lesions having higher indices of suspicion than clinically insignificant PCa. ARFI imaging had greater sensitivity for posterior versus anterior lesions because of greater displacement signal-to-noise ratio and finer spatial sampling. Atrophy and benign prostatic hyperplasia can cause appreciable prostate anatomy distortion and heterogeneity that confounds ARFI PCa lesion identification; however, in general, ARFI regions of suspicion did not coincide with these benign pathologies.

Elastographic Strain Index in the Evaluation of Focal Lesions Detected With Transrectal Sonography of the Prostate Gland

OBJECTIVES

The purpose of this study was to evaluate the value of elastography in evaluating focal lesions detected by transrectal sonography and to suggest a reference strain index.

METHODS

Sixty-nine patients with focal lesions on transrectal sonography were referred to our department for prostate biopsy. Focal lesions were classified as either highly or less suspicious lesions by our criteria. A strain index from elastography was calculated for the focal lesions. Systematic 12-core randomized biopsies plus 2 targeted biopsies were performed. The mean strain indices for malignant and benign focal lesions were compared, and a cutoff strain index was attained to maximize the sensitivity and specificity for prostate cancer. Strain indices were correlated with Gleason scores.

RESULTS

The mean strain index ± SD for malignant focal lesions (3.26 ± 1.77) was significantly higher than that for benign focal lesions (2.16 ± 1.52; P = .008). The sensitivity, specificity, and area under the receiver operating characteristic curve for diagnosing cancer were 66.7%, 71.1%, and 0.701, respectively, at a strain index cutoff value of greater than 2.4. The strain index showed a moderate linear correlation with the Gleason score (r = 0.441; P = .013).

CONCLUSIONS

Any focal lesion on transrectal sonography with a strain index of greater than 2.4 is at risk for prostate cancer.

Grey-scale sonography and sonoelastography for diagnosing carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is a common peripheral entrapment neuropathy of the median nerve at wrist level, and is thought to be caused by compression of the median nerve in the carpal tunnel. There is no standard quantitative reference for the diagnosis of CTS. Grey-scale sonography and sonoelastography (SEL) have been used as diagnostic tools. The most commonly agreed findings in grey-scale sonography for the diagnosis of CTS is enlargement of the median nerve cross-sectional area (CSA). Several authors have assessed additional parameters. “Delta CSA” is the difference between the proximal median nerve CSA at the pronator quadratus and the maximal CSA within the carpal tunnel. The “CSA ratio” is the ratio of CSA in the carpal tunnel to the CSA at the mid forearm. These additional parameters showed better diagnostic accuracy than CSA measurement alone. Recently, a number of studies have investigated the elasticity of the median nerve using SEL, and have shown that this also has diagnostic value, as it was significantly stiffer in CTS patients compared to healthy volunteers. In this review, we summarize the usefulness of grey-scale sonography and SEL in diagnosing CTS.

Elastography: history, principles, and technique comparison

Elastography is a relatively new imaging technology that creates images of tissue stiffness. It can be thought of an extension of the ancient technique of palpation but it gives better spatial localization information and is less subjective. Two main types of elastography are currently in use, strain elastography where the tissue displacement in response to gentle pressure is used to compute and image tissue strain, and shear wave elastography where the speed of shear waves traversing tissue is measured and used to create an image of tissue stiffness. Each method has advantages and disadvantages but generally strain imaging is excellent for focal lesions and shear wave imaging, being more quantitative, is best for diffuse organ diseases. Strain imaging requires additional training in acquisition technique to obtain high quality images. Pitfalls to avoid and tips for good images are provided. Improvements in strain imaging are focused on better quality indicators and better methods for quantification. Improvements in shear wave imaging will be higher frame rates, greater accuracy in focal lesions, and making results more comparable between different ultrasound systems. Both methods will continue to improve and will provide ever more powerful new tools for diagnosis of diffuse and focal diseases.

Comparison of meta-analyses among elastosonography (ES) and positron emission tomography/computed tomography (PET/CT) imaging techniques in the application of prostate cancer diagnosis

The early diagnosis of prostate cancer (PCa) appears to be of vital significance for the provision of appropriate treatment programs. Even though several sophisticated imaging techniques such as positron emission tomography/computed tomography (PET/CT) and elastosonography (ES) have already been developed for PCa diagnosis, the diagnostic accuracy of these imaging techniques is still controversial to some extent. Therefore, a comprehensive meta-analysis in this study was performed to compare the accuracy of various diagnostic imaging methods for PCa, including 11C-choline PET/CT, 11C-acetate PET/CT, 18F-fluorocholine PET/CT, 18F-fluoroglucose PET/CT, transrectal real-time elastosonography (TRTE), and shear-wave elastosonography (SWE). The eligible studies were identified through systematical searching for the literature in electronic databases including PubMed, Cochrane, and Web of Science. On the basis of the fixed-effects model, the pooled sensitivity (SEN), specificity (SPE), and area under the receiver operating characteristics curve (AUC) were calculated to estimate the diagnostic accuracy of 11C-choline PET/CT, 11C-acetate PET/CT, 18F-fluorocholine (FCH) PET/CT, 18F-fluoroglucose (FDG) PET/CT, TRTE, and SWE. All the statistical analyses were conducted with R language Software. The present meta-analysis incorporating a total of 82 studies demonstrated that the pooled sensitivity of the six imaging techniques were sorted as follows: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 11C-acetate PET/CT > 18F-FDG PET/CT; the pooled specificity were also compared: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 18F-FDG PET/CT > 11C-acetate PET/CT; finally, the pooled diagnostic accuracy of the six imaging techniques based on AUC were ranked as below: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 11C-acetate PET/CT > 18F-FDG PET/CT. SWE and 18F-FCH PET/CT imaging could offer more assistance in the early diagnosis of PCa than any other studied imaging techniques. However, the diagnostic ranking of the six imaging techniques might not be applicable to the clinical phase due to the shortage of stratified analysis.

Strain elastography in the characterization of renal cell carcinoma and angiomyolipoma

INTRODUCTION

We evaluate the diagnostic performance of strain elastography to differentiate renal cell carcinoma (RCC) from angiomyolipoma (AML).

METHODS

Strain elastography was performed in 65 patients (mean age 55.5 years; range: 32-81) who had renal lesions (24 AMLs and 41 RCCs) prospectively. Lesions were classified according to lesion size and histological subtypes. The strain ratios of the RCCs and AMLs were evaluated by a radiologist. The area under the curve and the cut-off point were used to assess diagnostic performance. Sensitivity, specificity, and positive and negative predictive values were obtained.

RESULTS

In assessing the mean strain ratio, we divided the groups in 3 according to size: (1) <20-mm lesions; (2) 20- to 40-mm lesions; and (3) >40-mm lesions; the respective mean strain ratios were: 1.5 ± 0.5 (range: 0.06-5.92), 2.8 ± 0.4 (range: 0.17-9.92), 2.7 ± 0.3 (range: 0.08-6.15). When RCCs and AMLs were compared, there was a statistically significant difference in the strain ratio among the 3 groups divided per lesion size (p < 0.01). For the strain ratio, the mean ± standard deviation was 1.1 ± 0.1 for AMLs and 3.4 ± 0.3 for RCCs (p < 0.01). When lesion subtypes were compared, there was a statistically significant difference in the strain ratio between the AML and clear cell RCC (p < 0.01).

CONCLUSIONS

For assessing renal lesions, strain elastography and strain ratio values may be useful in differentiating RCCs from AMLs.

Hepatocellular carcinoma: stiffness value and ratio to discriminate malignant from benign focal liver lesions

PURPOSE

To investigate the use of stiffness value and stiffness ratio (ratio of lesion to background liver parenchyma values) to discriminate malignant from benign focal liver lesions by using histologic results as the reference standard.

MATERIALS AND METHODS

This study was approved by the institutional review board, and written informed consent was obtained. Three hundred seventy-three patients with focal liver lesions proven at histologic examination underwent measurement of liver stiffness with elastography point quantification. First, stiffness values in two regions of the background liver parenchyma (at 0.5-2 cm and >2 cm from the lesion periphery) near 163 hepatocellular carcinomas were analyzed to determine a reference background liver for calculating the stiffness ratio. Second, the use of the lesion stiffness value and the stiffness ratio for prediction of liver malignancy was investigated in a cohort of patients with 58 benign and 201 malignant lesions. Results were validated in another independent cohort of patients with 25 benign and 89 malignant lesions by using analysis of the area under the receiver operating characteristic (AUC) curve.

RESULTS

The coefficient of variation for the background liver at 0.5-2 cm from the lesion was higher (196%) than that at greater than 2 cm from the lesion (66%). In the development phase, diagnostic accuracy with use of the stiffness value was significantly higher than that with use of the stiffness ratio for discrimination of malignant from benign lesions (AUC, 0.86 vs 0.66, respectively; P < .001). Diagnostic performance with the stiffness value was lower than that with the stiffness ratio (AUC, 0.53 vs 0.86, respectively; P < .001) for discrimination of cirrhotic nodules from other benign lesions. Diagnostic performance with the stiffness value was significantly lower than that with the stiffness ratio (AUC, 0.58 vs 0.71 respectively; P = .007) for discrimination of metastasis from primary liver cancers. In the validation phase, similar findings were revealed for the discrimination of malignant from benign lesions (AUC, 0.87 vs 0.67; P < .001) and discrimination between metastasis and primary liver cancers (AUC, 0.49 vs 0.73; P < .001).

CONCLUSION

Use of stiffness values measured in the liver parenchyma at more than 2 cm from the lesion allowed better diagnostic performance than did values measured in a region closer to the tumor. Stiffness value was more accurate than stiffness ratio for differentiation of malignant from benign focal liver lesions, but the stiffness ratio might be useful for subclassification of benign and malignant lesions. Online supplemental material is available for this article.

Diagnostic performance of axial-strain sonoelastography in confirming clinically diagnosed Achilles tendinopathy: comparison with B-mode ultrasound and color Doppler imaging

This primary aim of this study was to evaluate the diagnostic performance of axial-strain sonoelastography (ASE), B-mode ultrasound (US) and color Doppler US in confirming clinically symptomatic Achilles tendinopathy. The secondary aim was to establish the relationship between the strain ratio during sonoelastography and Victorian Institute of Sport Assessment-Achilles (VISA-A) scores. The VISA-A questionnaire is a validated clinical rating scale that evaluates the symptoms and dysfunction of the Achilles tendon. One hundred twenty Achilles tendons of 120 consecutively registered patients with clinical symptoms of Achilles tendinopathy and another 120 gender- and age-matched, asymptomatic Achilles tendons of 120 healthy volunteers were assessed with B-mode US, ASE and color Doppler US. Symptomatic patients had significantly higher strain ratio scores and softer Achilles tendon properties compared with controls (p < 0.001). The strain ratio was moderately correlated with VISA-A scores (r = -0.62, p < 0.001). The diagnostic accuracy of B-mode US, ASE and color Doppler US in confirming clinically symptomatic Achilles tendinopathy was 94.7%, 97.8% and 82.5% respectively. There was excellent correlation between the clinical reference standard and the grade of tendon quality on ASE (κ = 0.91, p < 0.05), compared with B-mode US (κ = 0.74, p < 0.05) and color Doppler imaging (κ = 0.49, p < 0.05). ASE is an accurate clinical tool in the evaluation of Achilles tendinopathy, with results comparable to those of B-mode US and excellent correlation with clinical findings. The strain ratio may offer promise as a supplementary tool for the objective evaluation of Achilles tendon properties.

Detection and characterisation of biopsy tissue using quantitative optical coherence elastography (OCE) in men with suspected prostate cancer

We present first quantitative three-dimensional (3D) data sets recorded using optical coherence elastography (OCE) for the diagnosis and detection of prostate cancer (PCa). 120 transrectal ultrasound guided prostate biopsy specimens from 10 men suspected with prostate cancer were imaged using OCE. 3D quantitative mechanical assessment of biopsy specimens obtained in kilopascals (kPa) at an interval of 40 µm was compared with histopathology. Sensitivity, specificity, and positive and negative predictive values were calculated for OCE in comparison to histopathology. The results show OCE imaging could reliably differentiate between benign prostate tissue, acinar atypical hyperplasia, prostatic intraepithelial neoplasia and malignant PCa. The sensitivity and specificity of OCE for the detection of prostate cancer was 0.98 and 0.91 with AUC > 0.99. Quantitative 3D OCE based on the assessment of mechanical properties of tissues can reliably differentiate prostate tissue specimen in an ex-vivo setting. This is a promising imaging modality for characterising different grades of cancers.

Transrectal real-time tissue elastography - an effective way to distinguish benign and malignant prostate tumors

BACKGROUND

To investigate the relationship between extracellular matrix parameters and texture of prostatic lesions evaluated by transrectal real-time tissue elastography (TRTE).

METHODS

120 patients suspicious for prostate cancer underwent TRTE. Targeted biopsies were carried out after 12-core systematic biopsy. Epithelia were stained with hematoxylin-eosin, and Victoria blue and Ponceau S were used to stain elastic-collagen fibers, and picric acid-sirius red for visualization of collagen type I (Col1) and III (Col3). Smooth muscles were visualized by immunohistochemistry. All image analyses were performed in a blind manner using Image Pro Plus 6.0, and the area ratios of epithelium, elastic fibers, collagen fibers and Col1/Col3 were determined.

RESULTS

42 patients with typical elastograms were included in the final data analysis. Significant differences were detected between the benign and malignant groups in the area ratios of epithelium (P = 0.01), smooth muscles and Col1/Col3 (P = 0.04, P = 0.02, respectively). There were no significant differences in the area ratios of epithelium, smooth muscle and elastic fibers between the stiff and soft lesion groups. The area ratio of Col1 was (0.05 ± 0.03) in the stiff group, and (0.02 ± 0.01) in the soft group (P= 0.00). However, the area ratio of Col3 was (0.03 ± 0.02) in the stiff group, and (0.05 ± 0.04) in the soft group (P = 0.16). Col1/Col3 in the stiff group (1.99 ± 1.59) was greater than in the soft group (0.71 ± 0.64) (P = 0.01).

CONCLUSIONS

Tissue hardness of prostatic tumors was mainly dependent on the Col1 content, Col1/Col3 being higher in malignant than in benign lesions, so the prostate tissue texture can be used as a target for distinguishing between the two with TRTE.

Sonoelastography: musculoskeletal applications

All participants for image samplings provided written informed consent. Conventional B-mode ultrasonography (US) has been widely utilized for musculoskeletal problems as a first-line approach because of the advantages of real-time access and the relatively low cost. The biomechanical properties of soft tissues reflect to some degree the pathophysiology of the musculoskeletal disorder. Sonoelastography is an in situ method that can be used to assess the mechanical properties of soft tissue qualitatively and quantitatively through US imaging techniques. Sonoelastography has demonstrated feasibility in the diagnosis of cancers of the breast and liver, and in some preliminary work, in several musculoskeletal disorders. The main types of sonoelastography are compression elastography, shear-wave elastography, and transient elastography. In this article, the current knowledge of sonoelastographic techniques and their use in musculoskeletal imaging will be reviewed.

The future perspectives in transrectal prostate ultrasound guided biopsy

Prostate cancer is one of the most common neoplasms in men. Transrectal ultrasound (TRUS)-guided systematic biopsy has a crucial role in the diagnosis of prostate cancer. However, it shows limited value with gray-scale ultrasound alone because only a small number of malignancies are visible on TRUS. Recently, new emerging technologies in TRUS-guided prostate biopsy were introduced and showed high potential in the diagnosis of prostate cancer. High echogenicity of ultrasound contrast agent reflect the increased status of angiogenesis in tumor. Molecular imaging for targeting specific biomarker can be also used using ultrasound contrast agent for detecting angiogenesis or surface biomarker of prostate cancer. The combination of TRUS-guided prostate biopsy and ultrasound contrast agents can increase the accuracy of prostate cancer diagnosis. Elastography is an emerging ultrasound technique that can provide the information regarding tissue elasticity and stiffness. Tumors are usually stiffer than the surrounding soft tissue. In two types of elastography techniques, shearwave elastography has many potential in that it can provide quantitative information on tissue elasticity. Multiparametric magnetic resonance imaging (MRI) from high resolution morphologic and functional magnetic resonance (MR) technique enables to detect more prostate cancers. The combination of functional techniques including apparent diffusion coefficient map from diffusion weighted imaging, dynamic contrast enhanced MR and MR spectroscopy are helpful in the localization of the prostate cancer. MR-ultrasound (US) fusion image can enhance the advantages of both two modalities. With MR-US fusion image, targeted biopsy of suspicious areas on MRI is possible and fusion image guided biopsy can provide improved detection rate. In conclusion, with recent advances in multiparametric-MRI, and introduction of new US techniques such as contrast-enhanced US and elastography, TRUS-guided biopsy may evolve toward targeted biopsies rather than systematic biopsy for getting information reflecting the exact status of the prostate.

Elastic modulus of the prostate: a new non-invasive feature to diagnose bladder outlet obstruction in patients with benign prostatic hyperplasia

The purpose of our study was to develop a reliable method for the non-invasive evaluation of bladder outlet obstruction (BOO) caused by benign prostate hyperplasia (BPH). In our study, the International Prostate Symptom Score was assessed in, and trans-rectal ultrasound (TRUS) and shear wave sonoelastography (SWE) were performed on, 55 patients with BPH who had undergone urodynamic evaluation (the gold standard diagnostic procedure for BOO). The results indicated that the elastic modulus of the transitional zone was the indicator most strongly correlated with BOO stage (r = 0.666, p < 0.001), and had the largest area under the receiver operating characteristic curve, 0.826 (95% confidence interval: 0.717-0.934, p = 0.001). An elastic modulus of the transitional zone ≥ 32.4 kPa or a total prostate volume ≥ 54.4 mL was diagnostic of BOO, with a sensitivity, specificity, positive predictive value, negative predictive value and accuracy for BOO of 97.2%, 62.5%, 85.4%, 90.9% and 86.5%, respectively. The elastic modulus of the transitional zone is a promising indicator in the assessment of the severity of BOO. In addition, the combination of elastic modulus and total prostate volume was the most accurate indicator in the non-invasive diagnosis of BOO in patients with BPH.

Real-time elastography of the prostate

Palpation of organs is one of the oldest clinical examination techniques, for instance, if you think of the palpation of the breast or the digital rectal examination of the prostate, where hard palpable regions are suspicious for cancer. This is the basic principle of real-time elastography, an ultrasound technique, which is able to visualise tissue elasticity. Since prostate cancer features an increased stiffness due to the higher cell and vessel density than the normal surrounding tissue, real-time elastography has been used for several years for prostate cancer detection. This review introduces the different techniques of ultrasound elastography and furthermore summarises its limitations and potentials.

Ultrasound elastography in the differential diagnosis of benign and malignant cervical lesions

OBJECTIVES

This study aimed to evaluate the clinical value of ultrasound elastography in the differential diagnosis of benign and malignant cervical lesions and to compare the accuracy of the elasticity score and strain ratio in differentiating cervical lesions.

METHODS

B-mode sonography and ultrasound elastography were performed on 84 cervical lesions (40 benign and 44 malignant) in 84 patients. All of the images were obtained transvaginally. The elasticity score was determined by a 5-point scoring method. Calculation of the strain ratio was based on a comparison of the average strain measured in the lesion with the adjacent tissue of the same depth, size, and shape. The findings were compared with histopathologic results. With the use of receiver operating characteristic curves, the diagnostic value of the elasticity score and strain ratio methods was determined.

RESULTS

The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the elasticity score in the differential diagnosis of cervical lesions were 81.8%, 85.0%, 83.3%, 85.7%, and 81.0%, respectively, whereas those of the strain ratio were 90.9%, 90.0%, 90.5%, 90.9%, and 90.0%. A strain ratio cutoff value of 4.525 was used as a standard to distinguish benign from malignant lesions. The strain ratio values of malignant lesions were much higher than those of benign lesions (range, 4.85-8.91 versus 0.62-4.50). The differences were statistically significant (P < .01).

CONCLUSIONS

Ultrasound elastography is a promising technique that is easy and rapid to perform and can help identify cervical lesions that are likely to be malignant. It is obvious that the strain ratio yielded better results than the elasticity score. Both methods are semiquantitative, but quantification of the strain ratio is finer than that of the elasticity score.

Accuracy of visual scoring and semi-quantification of ultrasound strain elastography--a phantom study

Purpose

The aim of this study was to evaluate the performance of strain elastography in an elasticity phantom and to assess which factors influenced visual scoring, strain histograms and strain ratios. Furthermore this study aimed to evaluate the effect of observer experience on visual scorings.

Materials and Methods

Two operators examined 20 targets of various stiffness and size (16.7 to 2.5 mm) in an elasticity phantom at a depth of 3.5 cm with a 5–18 MHz transducer. Two pre-settings were used yielding 80 scans. Eight evaluators, four experienced, four inexperienced, performed visual scorings. Cut-offs for semi-quantitative methods were established for prediction of target stiffness. Data was pooled in two categories allowing calculations of sensitivity and specificity. Statistical tests chi-square test and linear regression as relevant.

Results

Strain ratios and strain histograms were superior to visual scorings of both experienced and inexperienced observers (p = 0.025, strain histograms vs. experienced observers, p<0.001, strain histograms vs. inexperienced observers, p = 0.044 strain ratios vs. experienced observers and p = 0.002 strain ratios vs. inexperienced observers). No significant difference in predicting target stiffness between strain ratios and strain histograms (p = 0.83) nor between experienced and inexperienced observers (p = 0.054) was shown when using four categories. When pooling data in two groups (80 kPa/45 kPa vs. 14/8 kPa) the difference between the observers became significant (p<0.001). Target size had a significant influence on strain ratios measurements (p = 0.017) and on visual scorings (p<0.001) but not on the strain histograms(p = 0.358). Observer experience had significant effect on visual scorings(p = 0.003).

Conclusion

Strain ratios and strain histograms are superior to visual scoring in assessing target stiffness in a phantom. Target size had a significant impact on strain ratios and visual scoring, but not on strain histograms. Experience influenced visual scorings but the difference between experienced and inexperienced observers was only significant when looking at two classes of target stiffness.

Effects of compression force on elasticity index and elasticity ratio in ultrasound elastography

OBJECTIVES

The purpose of this study was to investigate the relationship between compression force and hardness values in ultrasound elastography.

METHODS

Ultrasound elastography was performed using an elastography phantom, comprising inclusions with different elasticities and echogenicities. The compression force was set to approximately 100 gw (light force) and approximately 500 gw (heavy force). The elasticity index (EI) of the inclusion was measured. The EI was a relative hardness value of a structure within an elastographic image. Similarly, the EI of the background was measured as a reference. The elasticity ratio (ER) was calculated as the EI of the inclusion divided by the EI of the reference.

RESULTS

The hardness of the phantom could be discerned with both the EI and ER, regardless of the compression force. The EI and ER with heavy force tended to be higher than those with light force, but the difference was not significant. A strong correlation was observed between the EI and ER of soft structures, whereas the correlation between the EI and ER of hard structures was weak, and the ER values varied widely.

CONCLUSIONS

The EI offers potential as a good indicator for assessing the hardness.

Alterations in mechanical properties are associated with prostate cancer progression

Cancer progression and metastasis have been shown to be accompanied by alterations in the mechanical properties of tissues, but the relationship between the mechanical properties and malignant behavior in prostate cancer (Pca) is less clear. The aims of this study were to detect the mechanical properties of benign prostatic hyperplasia (BPH) and Pca tissues on both the macro- and micro-scales, to explore the relationships between mechanical properties and malignant behavior and, finally, to identify the important molecules in the mechanotransduction signaling pathway. We demonstrated that the strain index of Pca tissue was significantly higher than that of BPH tissue on the macro-scale but the Young's modulus of the Pca tissues, especially in advanced Pca, was lower than that of BPH tissues on the micro-scale. These two seemingly contradictory results can be explained by the excessive proliferation of tumor cells (Ki-67) and the degradation of scaffold proteins (collagens). These data indicate that alterations of the macro- and micro-mechanical properties of Pca tissues with malignant behavior are contradictory. The mechanical properties of tissues might be useful as a new risk factor for malignancy and metastasis in Pca. Furthermore, collagens, matrix metalloproteinase, fibronectin, and integrins might be the important molecules in the mechanotransduction signaling pathway.

Carpal tunnel syndrome: diagnosis by means of median nerve elasticity--improved diagnostic accuracy of US with sonoelastography

PURPOSE

To compare the elasticity of the median nerve (MN) between healthy volunteers and patients with carpal tunnel syndrome (CTS) and to evaluate the diagnostic utility of sonoelastographic measurements of the elasticity of the MN.

MATERIALS AND METHODS

This study was performed with institutional review board approval and written informed consent from all participants. Hands in 22 healthy volunteers and in 31 patients with symptomatic CTS were studied. The cross-sectional area (CSA) and the elasticity of the MN, which was measured as the acoustic coupler (AC)/MN strain ratio, were evaluated.

RESULTS

Both hands in 22 healthy volunteers (three men [mean age, 52.7 years; age range, 41-65 years]; 19 women [mean age, 62.2 years; age range, 40-88 years]) and 43 hands in 31 patients with symptomatic CTS (three men [mean age, 69.0 years; age range, 46-88 years]; 28 women [mean age, 61.2 years; age range, 39-92 years]) were studied. Both the AC/MN strain ratio and the CSA in the patients with CTS were significantly higher than those in the healthy volunteers (P < .001). The presence of CTS was predicted by means of AC/MN strain ratio and CSA cutoff values, respectively, of 4.3 and 11 mm(2), with areas under the receiver operating characteristic curves (AUCs) of 0.78 (95% confidence interval [CI]: 0.69, 0.88) and 0.85 (95% CI: 0.78, 0.93). A logistic model that combined the AC/MN strain ratio and the CSA improved diagnostic accuracy for CTS, with an AUC of 0.91 (95% CI: 0.85, 0.97; P < .001).

CONCLUSION

Sonoelastography provides significant improvement in the diagnostic accuracy of the ultrasonographic assessment of CTS.

Prostatic elasticity: a new non-invasive parameter to assess bladder outlet obstruction caused by benign prostatic hyperplasia (a canine experiment)

OBJECTIVE

To evaluate the change of prostatic elasticity during the development of benign prostatic hyperplasia (BPH) and its correlation with the degree of bladder outlet obstruction (BOO) in the canine model of BOO caused by BPH.

MATERIALS AND METHODS

Ten male beagle dogs were selected in this study. To establish canine model of BOO caused by BPH, each beagle underwent castration surgery followed by encapsulating the prostate with a double layer of nylon mesh and then treating the beagles with a combination of steroids for 12 weeks. Transrectal ultrasound (TRUS) examination and urodynamic evaluation were performed before and at 4, 8, and 12 weeks of hormone administration. Prostatic volume, Young modulus of prostatic tissue, and urodynamic parameters were compared at each time instance, and the correlation between the Young modulus of the prostatic tissue and urodynamic parameters were evaluated.

RESULTS

All beagles developed BOO caused by BPH over the time period of the study. Prostatic volume, Young modulus of prostatic tissue, and urodynamic parameters had statistically significant differences before and after 4, 8, and 12 weeks of hormone administration (P <.05). Young modulus of prostatic tissue showed a very significant correlation with urodynamic parameters, including maximum urine flow (Qmax) (r = -0.802, P <.01), Qave (r = -0.711, P <.01), Pves@open (r = 0.638, P <.01), Pves@Qmax (r = 0.699, P <.01), Pdet@Qmax (r = 0.757, P <.01), and Pdetmax (r = 0.739, P <.01).

CONCLUSION

Young modulus of prostatic tissue increased during the development of the BPH. There was a significant correlation between Young modulus of prostatic tissue and the degree of BOO.

Potential role of strain elastography for detection of the extent of large-scar endometriosis

OBJECTIVES

The purpose of this study was to evaluate the clinical value of strain elastography for detection of the lesion extent of large-scar endometriosis and compare it to conventional sonography and magnetic resonance imaging (MRI).

METHODS

Eight patients suspected of having large-scar endometriosis underwent transabdominal sonography, strain elastography, and MRI. The mass was located and assessed for its size, imaging appearance, and, especially, widest boundary and vertical extent. After wide surgical excision and pathologic diagnosis, lesions in the central area shown on conventional sonography and the extended area shown on strain elastography underwent immunohistochemical examination.

RESULTS

Nodules were always deep in the subcutaneous plane, in contact with the fascia or muscle. Horizontally, the mean lesion size shown on conventional sonography was mainly consistent with the size on MRI in all cases, but it was obviously smaller on sonography than on strain elastography in 7 cases. Vertically, the lesion depth was mainly consistent with the depth on MRI in 7 cases, but it was more infiltrative on strain elastography in 6 cases. The vertical and horizontal infiltration scales of the postoperative specimens were consistent with strain elastography in all cases. All 8 patients showed strong collagen type I expression in the central area of the lesions; 6 patients showed strong collagen type I expression and the other 2 showed moderate expression in the extended area.

CONCLUSIONS

Strain elastography can elevate the diagnostic accuracy of large-scar endometriosis, the extent of which may be evaluated insufficiently by transabdominal sonography and MRI.

Ultrasound elastography of the prostate: state of the art

Prostate cancer is the cancer exhibiting the highest incidence rate and it appears as the second cause of cancer death in men, after lung cancer. Prostate cancer is difficult to detect, and the treatment efficacy remains limited despite the increase use of biological tests (prostate-specific antigen [PSA] dosage), the development of new imaging modalities, and the use of invasive procedures such as biopsy. Ultrasound elastography is a novel imaging technique capable of mapping tissue stiffness of the prostate. It is known that prostatic cancer tissue is often harder than healthy tissue (information used by digital rectal examination [DRE]). Two elastography techniques have been developed based on different principles: first, quasi-static (or strain) technique, and second, shear wave technique. The tissue stiffness information provided by US elastography should improve the detection of prostate cancer and provide guidance for biopsy. Prostate elastography provides high sensitivity for detecting prostate cancer and shows high negative predictive values, ensuring that few cancers will be missed. US elastography should become an additional method of imaging the prostate, complementing the conventional transrectal ultrasound and MRI. This technique requires significant training (especially for quasi-static elastography) to become familiar with acquisition process, acquisition technique, characteristics and limitations, and to achieve correct diagnoses.