Color Doppler USG of the scrotum has been demonstrated to be useful in the diagnosis of scrotal lesions. Gray-scale USG characterizes the lesions as testicular or extratesticular and, with color Doppler and power Doppler, flow and perfusion can also be assessed. Color Doppler is particularly helpful in acute painful conditions, where it can differentiate testicular ischemia from inflammatory conditions and thus prevent unnecessary surgical explorations. With color Doppler, useful information can be gained about vascularity in testicular malignancies. Color Doppler also has high sensitivity and high specificity in the diagnosis of lesions like varicoceles.
Color Doppler; testicular torsion; epididymo-orchitis; varicoceles
In the early 2000s, the main stream of endoscopic ultrasonography (EUS) changed from a mechanical scanning method to electronic radial or linear scanning methods. Subsequently, useful applications in trans-abdominal ultrasonography came within reach of EUS. In particular, contrast-enhanced EUS (CE-EUS) and EUS-elastography became cutting-edge diagnostic modalities for pancreatic disorders. Each type of pancreatic disorder has characteristic hemodynamics. CE-EUS uses color Doppler flow imaging and harmonic imaging to classify pancreatic lesions. EUS-elastography can assess tissue hardness by measuring its elasticity. This parameter appears to correlate with the malignant potential of the lesions. Tissue elasticity studies can provide information on both its pattern and distribution. The former is the conventional method of morphological diagnosis, but it is restricted to observations made in a region of interest (ROI). The latter is an unbiased analysis that can be performed by image analysis software and is theoretically constant, regardless of the ROI. Though EUS-fine needle aspiration (FNA) is also a very useful diagnostic tool, there are several limitations. Diagnostic EUS-FNA of pancreatic cystic lesions has marginal utility mainly due to low sensitivity. Therefore, in particular, endoscopists should keep this limitation in mind.
Contrast-enhanced endoscopic ultrasonography; Endoscopic ultrasonography-elastography; Endoscopic ultrasonography-fine needle aspiration; Pancreatic cystic lesions; Dissemination; Track seeding; Marginal utility for pancreatic cystic lesions of endoscopic ultrasonography-fine needle aspiration
Although elastography can enhance the differential diagnosis of thyroid nodules, its diagnostic performance is not ideal at present. Further improvements in the technique and creation of robust diagnostic criteria are necessary. The purpose of this study was to compare the usefulness of strain elastography and a new generation of elasticity imaging called supersonic shear wave elastography (SSWE) in differential evaluation of thyroid nodules. Six thyroid nodules in 4 patients were studied. SSWE yielded 1 true-positive and 5 true-negative results. Strain elastography yielded 5 false-positive results and 1 false-negative result. A novel finding appreciated with SSWE, were punctate foci of increased stiffness corresponding to microcalcifications in 4 nodules, some not visible on B-mode ultrasound, as opposed to soft, colloid-inspissated areas visible on B-mode ultrasound in 2 nodules. This preliminary paper indicates that SSWE may outperform strain elastography in differentiation of thyroid nodules with regard to their stiffness. SSWE showed the possibility of differentiation of high echogenic foci into microcalcifications and inspissated colloid, adding a new dimension to thyroid elastography. Further multicenter large-scale studies of thyroid nodules evaluating different elastographic methods are warranted.
The aim of this publication is to give an answer to the question whether 2D, 3D and 4D sonography of the breast can be replaced by elastography or whether elastography is an adjunct tool to B-mode imaging. The Breast Imaging and Reporting Data System (BI-RADS) ultrasound (US) descriptors of a lesion besides vascularity are based on B-mode imaging. US elastography displays the mechanical tissue properties. This information can be obtained by freehand compression and decompression. Acoustic radiation force impulse imaging (ARFI) produces stress with low-frequency push pulses. Manual compression by the transducer is not necessary. Shear wave elastography (SWE) is the combination of ARFI and the measurement of the consecutive shear wave propagations in the tissue. A quantification of the elasticity in kilopascal (kPa) is offered. Discussing B-mode imaging and elastography combined with the literature, elastography is seen as an addition to B-mode imaging with the potential to increase the specificity of the B-mode imaging-based BI-RADS assessment. In spite of additional elasticity information, the sensitivity remains high. A time-saving diagnostic algorithm for 2D, 3D US and elastography is described. In conclusion, it must be said that elasticity is not a stand-alone US modality able to replace 2D and 3D sonography.
Breast; Ultrasound; Three-dimensional imaging; Elastography; Breast Diseases
Breast elastography is a new sonographic imaging technique which provides information on breast lesions in addition to conventional ultrasonography (US) and mammography. Elastography provides a noninvasive evaluation of the stiffness of a lesion. Today, two technical solutions are available for clinical use: strain elastography and shear wave elastography. Initial evaluations of these techniques in clinical trials suggest that they may substantially improve the possibility of differentiating benign from malignant breast lesions thereby limiting recourse to biopsy and considerably reducing the number of benign breast biopsy diagnoses. This article reviews the basics of this technique, how to perform the examination, image interpretation and the results of major clinical studies. Although elastography is easy to perform, training and technical knowledge are required in order to obtain images permitting a correct interpretation. This paper will highlight the technique and point out common pitfalls.
Sonoelastography; Breast elastography; Breast lesions
Segmental (partial) testicular infarction is a very rare condition of unknown cause in more than 70% of cases. Several predisposing conditions have been described, but to our knowledge, this is the first documented case and often overlooked complication occurring as a result of cysto-prostatectomy. It usually presents in an acute manner resembling testicular torsion or epididymo-orchitis and is confirmed using ultrasonography. In some cases, it may present insidiously with no pain and may be confused with a testicular tumor due to the hypo-echoic features on imaging. In unclear situations, Doppler sonography shows vascularity and a magnetic resonance scan can be useful to distinguish between the two conditions.
Cysto-prostatectomy; infarction; segmental; testicular
Elastography is emerging as an imaging modality that can distinguish normal versus diseased tissues via their biomechanical properties. This article reviews current approaches to elastography in three areas — quasi-static, harmonic, and transient — and describes inversion schemes for each elastographic imaging approach. Approaches include: first-order approximation methods; direct and iterative inversion schemes for linear elastic; isotropic materials; and advanced reconstruction methods for recovering parameters that characterize complex mechanical behavior. The paper’s objective is to document efforts to develop elastography within the framework of solving an inverse problem, so that elastography may provide reliable estimates of shear modulus and other mechanical parameters. We discuss issues that must be addressed if model-based elastography is to become the prevailing approach to quasi-static, harmonic, and transient elastography: (1) developing practical techniques to transform the ill-posed problem with a well-posed one; (2) devising better forward models to capture the transient behavior of soft tissue; and (3) developing better test procedures to evaluate the performance of modulus elastograms.
Intratesticular arteriovenous malformations (AVMs) are extremely rare benign incidental lesions of the testis. Ultrasonography (US) generally reveals a hypoechoic solid mass within the testicular parenchyma. We describe a patient with intratesticular AVM which was found incidentally during workup for infertility. The gray-scale and Doppler US appearance of an intratesticular AVM and the differential diagnosis have been presented. Based on the gray-scale, US appearance differentiation from malignant testicular tumors is difficult. Doppler US examination aids in the diagnosis by demonstrating the vascular nature of the tumor.
Testicular ischemia is a rare complication of inguinal hernia repair. It results from the injury to the vessels that course along the inguinal canal. Typically it is painful at the beginning and asymptomatic later. Ultrasonographic appearance and aspects of testicular ischemia result in diffusely hypoechoic and disomogeneous testis, with complete lack of intratesticular vascular signal on color-Doppler and cremasteric vessels hypertrophy in chronic cases.
This report describes a testicular ischemia seen in a patient referred to because of hernia recurrence, without any sign or symptom of acute scrotum. Ultrasound examination showed the most frequent complications after inguinal hernia repair: both hernia recurrence and testicular ischemia.
Testicular ischemia; Ultrasonography; Color-Doppler; Inguinal hernia repair
Myofascial taut bands are central to diagnosis of myofascial pain. Despite their importance, we still lack either a laboratory test or imaging technique capable of objectively confirming either their nature or location. This study explores the ability of magnetic resonance elastography to localize and investigate the mechanical properties of myofascial taut bands on the basis of their effects on shear wave propagation.
This study was conducted in three phases. The first involved the imaging of taut bands in gel phantoms, the second a finite element modeling of the phantom experiment, and the third a preliminary evaluation involving eight human subjects-four of whom had, and four of whom did not have myofascial pain. Experiments were performed with a 1.5 Tesla magnetic resonance imaging scanner. Shear wave propagation was imaged and shear stiffness was reconstructed using matched filtering stiffness inversion algorithms.
The gel phantom imaging and finite element calculation experiments supported our hypothesis that taut bands can be imaged based on its outstanding shear stiffness. The preliminary human study showed a statistically significant 50-100% (p=0.01) increase of shear stiffness in the taut band regions of the involved subjects relative to that of the controls or in nearby uninvolved muscle.
This study suggests that magnetic resonance elastography may have a potential for objectively characterizing myofascial taut bands that have been up to now detectable only by the clinician's fingers.
Magnetic Resonance Elastography; Myofascial Pain; Wave Propagation; Finite Element Modeling
Transverse testicular ectopia, an extremely rare anomaly, is a deviation of testicular descent resulting in unilateral location of both testes, usually associated with an inguinal hernia, with the spermatic cord of the ectopic testes originating from the appropriate side. In most reported cases, the correct diagnosis was not made preoperatively. But we made a diagnosis of transverse testicular ectopia preoperatively by using the ultrasonography in patient with right-side inguinal hernia and left-side cryptorchism. Left testis was found on the right inguinal area and right testis was found in the right scrotum by ultrasonography, so we could make a diagnosis of transverse testicular ectopia. After right inguinal hemiorraphy, both testes were easily brought down sequentially through the right groin into the scrotum. Left testis was placed in the left hemoscrotum through transceptal incision to the scrotal subdartous pouch.
Protein S deficiency is an inherited cause of thrombophilia. We present the second reported case in the literature of a man developing testicular infarction secondary to protein S deficiency.
A 63 year old man presented with sudden onset of pain in his left hemi-scrotum. Despite oral warfarin therapy the plasma INR was only 1.4 at presentation. Doppler ultrasound scan of the scrotum confirmed absent blood flow to the left testis with increased echogenicity. Orchidectomy was performed to remove the necrotic testis. Post-operatively the patient did well and was referred to the Regional Haemophilia and Thrombosis Centre for further management.
The case highlights a rare but potential complication of protein S deficiency and demonstrates the importance of adequate anticoagulation in these patients.
Shear wave elastography is a new method of obtaining quantitative tissue elasticity data during breast ultrasound examinations. The aims of this study were (1) to determine the reproducibility of shear wave elastography (2) to correlate the elasticity values of a series of solid breast masses with histological findings and (3) to compare shear wave elastography with greyscale ultrasound for benign/malignant classification.
Using the Aixplorer® ultrasound system (SuperSonic Imagine, Aix en Provence, France), 53 solid breast lesions were identified in 52 consecutive patients. Two orthogonal elastography images were obtained of each lesion. Observers noted the mean elasticity values in regions of interest (ROI) placed over the stiffest areas on the two elastography images and a mean value was calculated for each lesion. A sub-set of 15 patients had two elastography images obtained by an additional operator. Reproducibility of observations was assessed between (1) two observers analysing the same pair of images and (2) findings from two pairs of images of the same lesion taken by two different operators. All lesions were subjected to percutaneous biopsy. Elastography measurements were correlated with histology results. After preliminary experience with 10 patients a mean elasticity cut off value of 50 kilopascals (kPa) was selected for benign/malignant differentiation. Greyscale images were classified according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS). BI-RADS categories 1-3 were taken as benign while BI-RADS categories 4 and 5 were classified as malignant.
Twenty-three benign lesions and 30 cancers were diagnosed on histology. Measurement of mean elasticity yielded an intraclass correlation coefficient of 0.99 for two observers assessing the same pairs of elastography images. Analysis of images taken by two independent operators gave an intraclass correlation coefficient of 0.80. Shear wave elastography versus greyscale BI-RADS performance figures were sensitivity: 97% vs 87%, specificity: 83% vs 78%, positive predictive value (PPV): 88% vs 84%, negative predictive value (NPV): 95% vs 82% and accuracy: 91% vs 83% respectively. These differences were not statistically significant.
Shear wave elastography gives quantitative and reproducible information on solid breast lesions with diagnostic accuracy at least as good as greyscale ultrasound with BI-RADS classification.
The increasing quality of diagnostic ultrasound has resulted in the detection of greater numbers of potentially benign hepatic lesions. Current radiological practice requires contrast enhanced ultrasound, CT or MRI to confirm the diagnosis. Acoustic radiation force impulse (ARFI) elastography is an imaging technique measuring the elasticity of biological tissues. Recent technical advances in ultrasound have made it possible to generate shear waves, whose velocity in the liver is proportional to the degree of hepatic elasticity.
This shear wave velocity (SWV) may be used as a marker for both focal and diffuse liver pathology.We used this technique to examine patients with normal livers and those with haemangiomata and metastases.
Patients with normal ultrasound examinations and normal liver enzymes, n = 99, had SWVs of 1.24±0.23 m s−1 (mean ± standard deviation) independent of site of measurement, age or gender. Results of SWV measurements in haemangiomata, n = 35, produced values of the same order, 1.35±0.48 m s−1. In contrast, patients with metastases, n = 10, had SWVs of 4.23±0.59 m s−1. With a cut-off value of 2.5 m s−1, the sensitivity and specificity for haemangiomata were 97.1% and 100%, respectively, with an area under the curve of 0.999.
ARFI elastography with SWV measurements is a promising new technique which could replace invasive investigations for benign hepatic lesions.
To provide the reader with the background knowledge to ensure a prompt and proper initial evaluation of the athlete with acute scrotal pain.
A MEDLINE search was conducted using the key words “scrotum” and “pain” for the years 1980 to 1999.
The 4 most common causes of acute scrotal pain in athletes are trauma, testicular torsion, torsion of a testicular appendage, and epididymitis. Although all can appear clinically similar, subtle features in the history and physical examination may lead the examiner to the correct diagnosis. However, physician evaluation is essential, and diagnostic imaging or surgery may be required for a definitive diagnosis and to avoid loss of the testicle.
Conclusions and Recommendations:
Although acute scrotal pain is a rare occurrence, it is important for the athletic trainer to recognize the common causes of the condition. An understanding of normal scrotal anatomy and the pathology of scrotal trauma, testicular torsion, torsion of a testicular appendage, and epididymitis are essential to provide a prompt initial evaluation and appropriate referral.
testicular appendage; testicular torsion; epididymitis; testicular trauma; groin injury
A 19 year old man presented with unilateral testicular swelling and pain. An initial diagnosis of epididymo-orchitis was modified to a presumed testicular neoplasm following ultrasonography. The final diagnosis of isolated testicular vasculitis was established following histological examination of the orchidectomy specimen. Staining for antineutrophil cytoplasmic antibodies was negative. Despite immunosuppressive treatment, the patient developed further symptoms affecting the remaining testis one year later. He responded well to an increase in immunosuppressive therapy and has remained asymptomatic 18 months from diagnosis. Symptomatic vasculitis confined to the testis is extremely rare, but must be considered in the differential diagnosis of testicular swelling and may be the presenting feature of a systemic vasculitis such as polyarteritis nodosa. The risk of progression to systemic disease in such cases is unknown. Immunosuppressive therapy must be considered carefully and long term follow up is important.
Traumatic ectopic dislocation of testis is a rare occurrence and usually occurs following a motorcycle collision, in what is referred to as “fuel tank injury”. Early identification and subsequent surgical management is of utmost importance to maintain normal spermatogenesis in the dislocated testis. In appropriate clinical setting, scrotal ultrasound examination with gray-scale and color flow Doppler imaging is the method of choice for diagnosis. Computed tomography of the abdomen is a useful adjunct procedure. We report a case of traumatic testicular dislocation with partial testicular torsion following a motorcycle collision, diagnosed with imaging, and subsequently confirmed on surgery.
Ectopic testis; fuel tank injury; traumatic dislocation of testis
Magnetic Resonance Elastography (MRE) is a rapidly developing technology for quantitatively assessing the mechanical properties of tissue. The technology can be considered to be an imaging-based counterpart to palpation, commonly used by physicians to diagnose and characterize diseases. The success of palpation as a diagnostic method is based on the fact that the mechanical properties of tissues are often dramatically affected by the presence of disease processes such as cancer, inflammation, and fibrosis. MRE obtains information about the stiffness of tissue by assessing the propagation of mechanical waves through the tissue with a special magnetic resonance imaging (MRI) technique. The technique essentially involves three steps:
generating shear waves in the tissue,acquiring MR images depicting the propagation of the induced shear waves andprocessing the images of the shear waves to generate quantitative maps of tissue stiffness, called elastograms.
MRE is already being used clinically for the assessment of patients with chronic liver diseases and is emerging as a safe, reliable and noninvasive alternative to liver biopsy for staging hepatic fibrosis. MRE is also being investigated for application to pathologies of other organs including the brain, breast, blood vessels, heart, kidneys, lungs and skeletal muscle. The purpose of this review article is to introduce this technology to clinical anatomists and to summarize some of the current clinical applications that are being pursued.
elasticity imaging; palpation; mechanical properties; shear stiffness
We report a case of a 50-year-old male who presented to the Emergency Department and was diagnosed with epididymo-orchitis. Sonographic evaluation of the testicle initially showed a normal, low resistance color Doppler waveform. The patient was admitted to the hospital. A follow up sonogram two days later demonstrated reversal of diastolic arterial flow on Pulse-Wave color Doppler imaging. Reversal of diastolic blood flow in testicular color Doppler sonography is a sign of impending infarction. On hospital day 6, the patient had a follow up ultrasound which demonstrated infarction of the testicle. Pathology confirmed the diagnosis and the tissue culture grew E. coli and Candida Albicans. This case documents the rapid progression of epididymo-orchitis with a normal spectral waveform to testicular infarction with reversal of diastolic blood flow on color Doppler imaging as a sign of impending infarction.
Testicular infarction; epididymo-orchitis; reversal of diastolic flow
We describe the vasculature of the camelid testis using plastic casting. We also use color pulsed-wave Doppler ultrasonography to measure testicular blood flow and compare the differences between testicular blood flow in fertile and infertile camelids. The testicular artery originates from the ventral surface of the aorta, gives rise to an epididymal branch, and becomes very tortuous as it approaches the testis. Within the supratesticular arteries, peak systolic velocity (PSV) was higher in fertile males compared to infertile males (P = 0.0004). In addition, end diastolic velocity (EDV) within the supratesticular arteries was higher for fertile males when compared to infertile males (P = 0.0325). Within the marginal arteries, PSV was also higher in fertile males compared to infertile males (P = 0.0104). However, EDV within the marginal arteries was not significantly different between fertile and infertile males (P = 0.121). In addition, the resistance index was not significantly different between fertile and infertile males within the supratesticular (P = 0.486) and marginal arteries (P = 0.144). The significance of this research is that in addition to information obtained from a complete reproductive evaluation, a male camelid's fertility can be determined using testicular blood flow measured by Doppler ultrasonography.
Viscoelastic properties of mouse brain tissue were estimated non-invasively, in vivo, using magnetic resonance elastography (MRE) at 4.7 T to measure the dispersive properties of induced shear waves. Key features of this study include: (i) the development and application of a novel MR-compatible actuation system which transmits vibratory motion into the brain through an incisor bar; and (ii) the investigation of the mechanical properties of brain tissue over a 1200 Hz bandwidth from 600 Hz –1800 Hz. Displacement fields due to propagating shear waves were measured during continuous, harmonic excitation of the skull. This protocol enabled characterization of the true steady-state patterns of shear wave propagation. Analysis of displacement fields obtained at different frequencies indicates that the viscoelastic properties of mouse brain tissue depend strongly on frequency. The average storage modulus (G') increased from approximately 1.6 kPa to 8 kPa over this range; average loss modulus (G”) increased from approximately 1 kPa to 3 kPa. Both moduli were well-approximated by a power-law relationship over this frequency range. MRE may be a valuable addition to studies of disease in murine models, and to pre-clinical evaluations of therapies. Quantitative measurements of the viscoelastic parameters of brain tissue at high frequencies are also valuable for modeling and simulation of traumatic brain injury (TBI).
magnetic resonance elastography; viscoelasticity; brain; dispersion; shear modulus; traumatic brain injury; TBI; MRE; MRI
Early diagnosis of testicular torsion is absolutely mandatory for salvage of a viable organ. The classical clinical presentation is a boy in the second decade with sudden onset of testicular pain accompanied by testicular tenderness and swelling as well as scrotal erythema and edema. The management is emergency exploration of the testicle with either orchiopexy or orchidectomy, depending upon the viability of the testis. In this series of 20 cases 90% had exploration with a salvage rate of 72%. Torsion of the testicle is in most cases due to a congenital abnormality; therefore contralateral orchiopexy is always done at the time of the exploration of the scrotum. The critical time interval from onset to exploration of the torsion is approximately 10 hours. In addition to the acute clinical entity, chronic torsion of the testis should be considered in all patients with unexplained orchalgia.
Acute scrotal conditions are a common clinical setting that present with pain and swelling of the hemiscrotum. The aim of our study has been to evaluate the findings in boys operated on acute scrotum.
A descriptive study was conducted on 100 patients with acute scrotum admitted to Mofid Children's Hospital from March 1993 to March 2007. Data included history, age, primary symptoms, definite diagnosis, side involvement, paraclinical tests, imaging modalities, medical or surgical management and type of the surgery.
Diagnosis was made mainly by clinical signs and symptoms and surgical exploration. Torsion of testis (n=31) was the most common cause of acute scrotum followed by incarcerated inguinal hernia (n=30), torsion of testicular appendage (n=27), epididymo-orchitis (n=7), idiopathic scrotal edema (n=4) and hematocele (n=1). Most (34%) of the patients were in the first year of life and the mean age was 5.4 years. The commonest signs were pain and swelling (62%) followed by pain, swelling and redness (21%) and pain alone (16%). 83 patients consisting of 31 with torsion of testis, 14 with torsion of testicular appendage, 30 with incarcerated hernia and 7 with epididymo–orchitis underwent surgical exploration after careful physical examination. 10 of 31 patients with torsion of testis had orchiectomy and orchiopexy of contra–lateral testis and the rest had detorsion and bilateral orchiopexy. 80% of patients were referred to the hospital after 12 hours of clinical onset of symptoms.
Early exploration of scrotum based on careful physical examination excludes the risk of misdiagnosis by diagnostic procedures and unnecessary delay by diagnostic techniques. Exploration of scrotum is a relatively safe and simple procedure with good cosmetic results, it also allows an accurate diagnosis to be made.
Scrotum; Testicular Torsion; Scrotal Swelling; Epididymitis; Orchitis
Formation of a capsule is a natural inflammatory response to a foreign body such as a breast implant. Breast capsular contracture is the most severe complication of implant surgery.
To evaluate breast tissues and the periprosthetic reaction with sonoelastography.
Material and methods
Nineteen patients aged 20-41 underwent breast augmentation with silicone-filled implants. Their 38 breasts were evaluated before surgery, and 7 and 14 days after surgery. Whole breast stiffness was measured by applanation tonometry. Patients underwent shear wave elastography and Young's moduli of breast tissues and the periprosthetic capsule were estimated. During surgery patients underwent standard anaesthesia and were released home 2 days later after removal of drainage. Each day, patients completed the pain visual analogue scale questionnaire separately for left and right breasts.
Applanation tonometry did not correlate with any parameter. In shear wave elastography we observed statistically significant changes in elasticity of all breast tissues with the highest values on day 7 after surgery and decreasing on day 14. The correlations between pain and capsule elasticity in lower quadrants measured were significant between days 4 and 10, whereas correlations of pain with applanation tonometry were insignificant. Glandular tissue elasticity in lower quadrants did not correlate with pain, whereas in upper quadrants there was a significant correlation on days 6-10. Fatty tissue, muscle and thoracic fascia elasticity did not correlate with breast pain. Breast implant volume correlated with pain only shortly after surgery, but did not correlate with any sonoelastographic parameters.
Breast pain correlates strongly with periprosthetic stiffness in elastography 4 to 10 days after breast augmentation, suggesting the possible role of an inflammatory reaction.
breast augmentation; implant; ultrasound; elastography; capsular contracture
This paper presents a new shear wave velocity imaging technique to monitor radio-frequency and microwave ablation procedures, coined electrode vibration elastography. A piezoelectric actuator attached to an ablation needle is transiently vibrated to generate shear waves that are tracked at high frame rates. The time-to-peak algorithm is used to reconstruct the shear wave velocity and thereby the shear modulus variations. The feasibility of electrode vibration elastography is demonstrated using finite element models and ultrasound simulations, tissue-mimicking phantoms simulating fully (phantom 1) and partially ablated (phantom 2) regions, and an ex vivo bovine liver ablation experiment. In phantom experiments, good boundary delineation was observed. Shear wave velocity estimates were within 7% of mechanical measurements in phantom 1 and within 17% in phantom 2. Good boundary delineation was also demonstrated in the ex vivo experiment. The shear wave velocity estimates inside the ablated region were higher than mechanical testing estimates, but estimates in the untreated tissue were within 20% of mechanical measurements. A comparison of electrode vibration elastography and electrode displacement elastography showed the complementary information that they can provide. Electrode vibration elastography shows promise as an imaging modality that provides ablation boundary delineation and quantitative information during ablation procedures.
Electrode vibration elastography; radio-frequency (RF) ablation; shear wave tracking; time-to-peak; ultrasound