Prostate cancer diagnosis: value of real-time elastography

Evaluation of prostate cancer detection using micro-ultrasound versus MRI through co-registration to whole-mount pathology

Micro-ultrasound has recently been introduced as a low-cost alternative to multi-parametric MRI for imaging prostate cancer. Early clinical studies have demonstrated promising results; however, robust validation via comparison with whole-mount pathology has yet to be achieved. Due to micro-ultrasound probe design and tissue deformation during scanning, it is difficult to accurately correlate micro-ultrasound imaging planes with ground truth whole-mount pathology slides. In this study, we developed a multi-step methodology to co-register micro-ultrasound and MRI to whole-mount pathology. The three-step process had a registration error of 3.90 ± 0.11 mm and consists of: (1) micro-ultrasound image reconstruction, (2) 3D landmark registration of micro-ultrasound to MRI, and (3) 2D capsule registration of MRI to whole-mount pathology. This process was then used in a preliminary reader study to compare the diagnostic accuracy of micro-ultrasound and MRI in 15 patients who underwent radical prostatectomy for prostate cancer. Micro-ultrasound was found to have equivalent performance to retrospective MRI review for index lesion detection (91.7% vs. 80%), while demonstrating an increased detection of tumor extent (52.5% vs. 36.7%) with similar false positive regions-of-interest (38.3% vs. 40.8%). Prospective MRI review had reduced detection of index lesions (73.3%) and tumor extent (18.9%) but improved false positive regions-of-interest (22.7%) relative to micro-ultrasound and retrospective MRI. Further evaluation is needed with a larger sample size.

Diagnostic accuracy of sonoelastography in different diseases

The objective of this study was to evaluate the diagnostic accuracy of sonoelastography in patients of primary and secondary health care settings. Google scholar, PubMed, Medline, Medscape, Wikipedia and NCBI were searched in October 2017 for all original studies and review articles to identify the relevant material. Two reviewers independently selected articles for evaluation of the diagnostic accuracy of sonoelastography in different diseases based on titles and abstracts retrieved by the literature search. The accuracy of sonoelastography in different diseases was used as the index text, while B-mode sonography, micro pure imaging, surgery and histological findings were used as reference texts. Superficial lymph nodes, neck nodules, malignancy in thyroid nodules, benign and malignant cervical lymph nodes, thyroid nodules, prostate carcinoma, benign and malignant breast abnormalities, liver diseases, parotid and salivary gland masses, pancreatic masses, musculoskeletal diseases and renal disorders were target conditions. The data extracted by the two reviewers concerning selected study characteristics and results were presented in tables and figures. In total, 46 studies were found for breast masses, lymph nodes, prostate carcinoma, liver diseases, salivary and parotid gland diseases, pancreatic masses, musculoskeletal diseases and renal diseases, and the overall sensitivity of sonoelastography in diagnosing all these diseases was 83.14% while specificity was 81.41%. This literature review demonstrates that sonoelastography is characterized by high sensitivity and specificity in diagnosing different disorders of the body.

Strain Elastography - How To Do It?

Tissue stiffness assessed by palpation for diagnosing pathology has been used for thousands of years. Ultrasound elastography has been developed more recently to display similar information on tissue stiffness as an image. There are two main types of ultrasound elastography, strain and shear wave. Strain elastography is a qualitative technique and provides information on the relative stiffness between one tissue and another. Shear wave elastography is a quantitative method and provides an estimated value of the tissue stiffness that can be expressed in either the shear wave speed through the tissues in meters/second, or converted to the Young's modulus making some assumptions and expressed in kPa. Each technique has its advantages and disadvantages and they are often complimentary to each other in clinical practice. This article reviews the principles, technique, and interpretation of strain elastography in various organs. It describes how to optimize technique, while pitfalls and artifacts are also discussed.

Accuracy of shear wave elastography for the diagnosis of prostate cancer: A meta-analysis

Many studies have established the high diagnostic accuracy of shear wave elastography (SWE) for the detection of prostate cancer (PCa); however, its utility remains a subject of debate. This meta-analysis sought to appraise the overall accuracy of SWE for the detection of PCa. A literature search of the PubMed, Embase, Cochrane Library, Web of Science and CNKI (China National Knowledge Infrastructure) databases was conducted. In all of the included studies, the diagnostic accuracy of SWE was compared with that of histopathology, which was used as a standard. Data were pooled, and the sensitivity, specificity, area under the curve (AUC), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated to estimate the accuracy of SWE. The pooled sensitivity and specificity for the diagnosis of PCa by SWE were 0.844 (95% confidence interval: 0.696–0.927) and 0.860 (0.792–0.908), respectively. The AUC was 0.91 (0.89–0.94), the PLR was 6.017 (3.674–9.853), and the NLR was 0.182 (0.085–0.389). The DOR was 33.069 (10.222–106.982). Thus, SWE exhibited high accuracy for the detection of PCa using histopathology as a diagnostic standard. Moreover, SWE may reduce the number of core biopsies needed.

Lymphangiogenesis in Breast Cancer Correlates with Matrix Stiffness on Shear-Wave Elastography

PURPOSE

To correlate tumor stiffness and lymphangiogenesis in breast cancer and to find its clinical implications.

MATERIALS AND METHODS

A total of 140 breast cancer patients were evaluated. Tumor stiffness was quantitatively measured by shear-wave elastography in preoperative ultrasound examination, calculated as mean elasticity value (kPa). Slides of resected breast cancer specimens were reviewed for most fibrotic area associated with tumor. D2-40 immunohistochemical staining was applied for fibrotic areas to detect the lymphatic spaces. Microlymphatic density, tumor stiffness, and clinicopathologic data were analyzed.

RESULTS

Higher elasticity value was associated with invasive size of tumor, microlymphatic density, histologic grade 3, absence of extensive intraductal component, presence of axillary lymph node metastasis, and Ki-67 labeling index (LI) in univariate regression analysis, and associated with Ki-67 LI and axillary lymph node metastasis in multivariate regression analysis. Microlymphatic density was associated histologic grade 3, mean elasticity value, and Ki-67 LI in univariate regression analysis. In multivariate regression analysis, microlymphatic density was correlated with mean elasticity value.

CONCLUSION

In breast cancer, tumor stiffness correlates with lymphangiogenesis and poor prognostic factors.

4-D spatiotemporal analysis of ultrasound contrast agent dispersion for prostate cancer localization: a feasibility study

Currently, nonradical treatment for prostate cancer is hampered by the lack of reliable diagnostics. Contrastultrasound dispersion imaging (CUDI) has recently shown great potential as a prostate cancer imaging technique. CUDI estimates the local dispersion of intravenously injected contrast agents, imaged by transrectal dynamic contrast-enhanced ultrasound (DCE-US), to detect angiogenic processes related to tumor growth. The best CUDI results have so far been obtained by similarity analysis of the contrast kinetics in neighboring pixels. To date, CUDI has been investigated in 2-D only. In this paper, an implementation of 3-D CUDI based on spatiotemporal similarity analysis of 4-D DCE-US is described. Different from 2-D methods, 3-D CUDI permits analysis of the entire prostate using a single injection of contrast agent. To perform 3-D CUDI, a new strategy was designed to estimate the similarity in the contrast kinetics at each voxel, and data processing steps were adjusted to the characteristics of 4-D DCE-US images. The technical feasibility of 4-D DCE-US in 3-D CUDI was assessed and confirmed. Additionally, in a preliminary validation in two patients, dispersion maps by 3-D CUDI were quantitatively compared with those by 2-D CUDI and with 12-core systematic biopsies with promising results.

Usefulness of real-time elastography strain ratio in the assessment of bile duct ligation-induced liver injury and the hepatoprotective effect of chitosan: an experimental animal study

The purpose of the study described here was to evaluate the usefulness of the elastographic strain ratio in the assessment of liver changes in an experimental animal setting and the hepatoprotective effects of chitosan. Ultrasonography and Strain Ratio calculation were performed before and after bile duct ligation (BDL) in three groups of Wistar albino rats (n = 10 animals per group): (i) rats subjected to bile duct ligation only; (ii) rats subjected to bile duct ligation and administered chitosan for 14 d; (iii) rats subjected to bile duct ligation and administered chitosan for 7 d. The results were compared with the laboratory data and pathologic findings. Strain ratios revealed an increase in liver stiffness after bile duct ligation (p < 0.05), except in the group with chitosan administered for 7 d, and agreed with laboratory and pathology data. In conclusion, strain ratio can be used as an experimental research instrument in the assessment of liver response to injury. To the best of our knowledge, this is the first study reporting on the usefulness of the sonoelastographic liver-to-kidney strain ratio in assessing the effects of experimentally induced liver lesions.

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.

Novel trends in transrectal ultrasound imaging of prostate gland carcinoma

Carcinoma of the prostate gland is the most common neoplasm in men. Its treatment depends on multiple factors among which local staging plays a significant role. The basic method is transrectal ultrasound imaging. This examination enables imaging of the prostate gland and its abnormalities, but it also allows ultrasound-guided biopsies to be conducted. A conventional gray-scale ultrasound examination enables assessment of the size, echostructure and outlines of the anatomic capsule, but in many cases, neoplastic lesions cannot be observed. For this reason, new sonographic techniques are implemented in order to facilitate detectability of cancer. The usage of contrast agents during transrectal ultrasound examination must be emphasized since, in combination with color Doppler, it facilitates detection of cancerous lesions by visualizing flow which is not observable without contrast enhancement. Elastography, in turn, is a different solution. It uses the differences in tissue elasticity between a neoplastic region and normal prostatic parenchyma that surrounds it. This technique facilitates detection of lesions irrespective of their echogenicity and thereby supplements conventional transrectal examinations. However, the size of the prostate gland and its relatively far location from the transducer may constitute limitations to the effectiveness of elastography. Moreover, the manner of conducting such an examination depends on the examiner and his or her subjective assessment. Another method, which falls within the novel, popular trend of combining imaging methods, is fusion of magnetic resonance imaging and transrectal sonography. The application of multidimensional magnetic resonance imaging, which is currently believed to be the best method for prostate cancer staging, in combination with the availability of a TRUS examination and the possibility of monitoring biopsies in real-time sonography is a promising alternative, but it is associated with higher costs and longer duration of the examination. This paper presents the most important novel trends in transrectal imaging in prostate cancer diagnosis based on the review of the articles available in the PubMed base and published after 2010.

Application of vibro-acoustography in prostate tissue imaging

PURPOSE

To evaluate the potential of the imaging modality vibro-acoustography (VA) for imaging of the prostate.

METHODS

Excised cadaver prostate specimens were embedded in tissue mimicking gel to simulate the properties of surrounding soft tissues. The samples were imaged at various depths using a laboratory prototyped VA imaging system. The recorded signals were used for offline processing and image reconstruction. In a selected subgroup of tissue samples, conventional ultrasound (B-mode) and x-ray imaging were performed for further analysis, evaluation, and validation of the VA images.

RESULTS

The imaging results of prostate tissue samples indicate the capability of VA imaging to detect prostatic nodules and lesions. In the prostate sample with an adenocarcinoma, the lesion appears with a clear contrast with respect to its surrounding tissue. The VA images could also identify the presence of calcifications deep inside the prostate tissue. Further, quantifications of the imaging results demonstrate that VA imaging has higher sensitivity to detect the calcifications compared to conventional ultrasound imaging. VA is also capable of visualizing prostatic tissue structures and in some cases can identify the anatomical zones. More specifically, the observed higher texture level in peripheral zones demonstrates the ability of VA to differentiate between prostatic anatomical zones.

CONCLUSIONS

Imaging results of ex vivo prostate tissues, reveals the potency of VA as a promising tool to detect abnormalities, delineate tissue structures and anatomical zones, and locate calcifications. The results of this pilot study suggest that in vivo VA imaging of the prostate may be of clinical utility.

Indentation loading response of a resonance sensor--discriminating prostate cancer and normal tissue

Prostate cancer is the most common type of cancer among men worldwide. Mechanical properties of prostate tissue are promising for distinguishing prostate cancer from healthy prostate tissue. The aim was to investigate the indentation loading response of a resonance sensor for discriminating prostate cancer tissue from normal tissue. Indentation measurements were done on prostate tissue specimens ex vivo from 10 patients from radical prostatectomy. The measurement areas were analysed using standard histological methods. The stiffness parameter was linearly dependent on the loading force (average R(2 )= 0.90) and an increased loading force caused a greater stiffness contrast of prostate cancer vs normal tissue. The accuracy of the stiffness contrast was assessed by the ROC curve with the area under the curve being 0.941 for a loading force of 12.8 mN. The results are promising for the development of a resonance sensor instrument for detecting prostate cancer.

Irreversible electroporation ablation of the liver can be detected with ultrasound B-mode and elastography

BACKGROUND

Irreversible electroporation (IRE) is a novel ablation technique that induces permanent membrane permeability and cell death. We are interested in ultrasound B-mode and elastography to monitor IRE ablation in the liver.

METHODS

Yorkshire pigs underwent IRE ablation of the liver and were imaged with ultrasound B-mode and elastography. Histologic evaluation of cell death by triphenyltetrazolium chloride and hematoxylin and eosin staining was performed.

RESULTS

Elastography showed that liver ablated by IRE exhibited increased tissue stiffness with a peak strain ratio of 2.22. The IRE lesion had a discrete border without bubble artifact, and the lesion size significantly correlated with area of cell death on histology. IRE ablation was unaffected by presence of large blood vessels or bile ducts.

CONCLUSION

IRE ablation led to increased tissue stiffness that was detectable by elastography and indicative of cell death. Elastography may complement B-mode ultrasonography to monitor IRE ablation of the liver.

Incorporating endorectal MR elastography into multi-parametric MRI for prostate cancer imaging: Initial feasibility in volunteers

PURPOSE

To investigate the tolerability and technical feasibility of performing endorectal MR elastography (eMRE) in human volunteers within the representative age group commonly affected by prostate cancer.

MATERIALS AND METHODS

Endorectal MRE was conducted on seven volunteers in a 1.5 Tesla (T) MR imager using a rigid endorectal coil. Another five volunteers were imaged on a 3T MR imager using an inflatable balloon type endorectal coil. Tolerability was accessed for vibration amplitudes of ±1-50 μm and for frequencies of 100-300 Hz.

RESULTS

All 12 volunteers tolerated the displacements necessary to successfully perform eMRE. Shear waves with frequencies up to 300 Hz could propagate across the entire prostate using both coil designs.

CONCLUSION

The results of this study motivate further investigation of eMRE in prostate cancer patients to help determine if there is an added value of integrating eMRE into existing multi-parametric prostate MRI exams.

Impact of Real-Time Elastography versus Systematic Prostate Biopsy Method on Cancer Detection Rate in Men with a Serum Prostate-Specific Antigen between 2.5 and 10 ng/mL

The actual gold standard for the diagnosis of prostate cancer includes the serum prostate-specific antigen, the digital rectal examination, and the ultrasound-guided systematic prostate biopsy sampling. In the last years, the real-time elastography has been introduced as an imaging technique to increase the detection rate of prostate cancer and simultaneously reduce the number of biopsies sampled for a single patient. Here, we evaluated a consecutive series of 102 patients with negative digital-rectal examination and transrectal ultrasound, and prostate-specific antigen value ranging between 2.5 ng/mL and 10 ng/mL, in order to assess the impact of real-time elastography versus the systematic biopsy on the detection of prostate cancer. We found that only 1 out of 102 patients resulted true positive for prostate cancer when analysed with real-time elastography. In the other 6 cases, real-time elastography evidenced areas positive for prostate cancer, although additional neoplastic foci were found using systematic biopsy sampling in areas evidenced by real-time elastography as negative. Although additional studies are necessary for evaluating the effectiveness of this imaging technique, the present study indicates that the limited accuracy, sensitivity, and specificity do not justify the routine application of real-time elastography in prostate cancer detection.

[The impact of ultrasound in urology]

Ultrasound is of great importance in the diagnosis of acute and chronic diseases in urology, such as kidney colic, testicular torsion, low-grade kidney trauma or for follow-up of vesicoureteral reflux, evaluation of infertility, measurement of residual urinary volume and the detection of cancer. An ultrasound examination is time and cost-effective without exposure to ionizing radiation and is routinely performed by practitioners as well as in the clinical daily routine. With technical innovations, such as contrast-enhanced ultrasound or real time elastography, it would for instance be possible to extend the application field of ultrasound. However, in some fields of investigation ultrasound still lacks accuracy and despite its many advantages the validity of ultrasound findings sometimes has to be verified with computed tomography (CT) or magnetic resonance imaging (MRI).

Diagnostic accuracy of transrectal elastosonography (TRES) imaging for the diagnosis of prostate cancer: a systematic review and meta-analysis

To assess the diagnostic performance of transrectal elastosonography (TRES) for the detection of prostate cancer. Two reviewers independently extracted the data from each study. Quality was assessed with a validated quality assessment tool for diagnostic accuracy studies. Diagnostic accuracy of TRES in relation to current standard references (transrectal ultrasonography [TRUS] biopsies and histopathology of radical prostatectomy [RP] specimens) was estimated. A bivariate random effects model was used to obtain sensitivity and specificity values. Hierarchical summary receiver operating characteristic (HSROC) were calculated. In all, 16 studies (2278 patients) were included in the review. Using histopathology of the RP specimen as reference standard, the pooled data of four studies showed that the sensitivity of TRES ranged between 0.71 to 0.82 and the specificity ranged between 0.60 to 0.95 (pooled diagnostic odds ratio [DOR] 19.6; 95% confidence interval [CI] 7.7-50.03). The sensitivity varied from 0.26 to 0.87 and specificity varied from 0.17 to 0.76 (pooled DOR 2.141; 95% CI 0.525 to -8.737) using TRUS biopsies (minimum of 10) as a reference standard. The quality of most studies was modest. SROC estimated 0.8653 area under the curve predicting high chances of detecting prostate cancer. There were no health economics or health-related quality of life of the participants reported in the studies and all the studies used compressional technique with no reported standardisation. The TRES technique appears to improve the detection of prostate cancer compared with systematic biopsy and shows a good accuracy in comparison with histopathology of the RP specimen. However, studies lacked standardisation of the technique, had poor quality of reporting and a large variation in the outcomes based on the reference standards and techniques used.

Stiffness mapping prostate biopsy samples using a tactile sensor

Previous studies have demonstrated that the stiffness of cancerous cells reflects their pathological stage and progression rates, with increased cancerous cell stiffness associated with increased aggressiveness. Therefore, the elasticity of the cancerous cells has the potential to be used as an indicator of the cancer's aggressiveness. However, the sensitivity and resolution of current palpation and imaging techniques are not sufficient to detect small cancerous tissues. In previous studies, we developed a tactile-based device to map with high resolution the stiffness of a tissue section. The purpose of this study is to evaluate this device using different tissues (BPH, Cancer and PZ) collected from human prostates. The preliminary results show that the tactile device is sensitive enough to tell the differences of the stiffness of different tissues. The results also disclosed the factors (humidity, temperature and tissue degradation) which could dramatically affect the results of stiffness mapping. The tactile technology described in this paper has the potential to help disclose the underlying mechanical mechanisms that lead to increased stiffness in prostate tumors.

Acoustic radiation force impulse imaging of human prostates: initial in vivo demonstration

Reliably detecting prostate cancer (PCa) has been a challenge for current imaging modalities. Acoustic radiation force impulse (ARFI) imaging is an elasticity imaging method that uses remotely generated, focused acoustic beams to probe tissue stiffness. A previous study on excised human prostates demonstrated ARFI images portray various prostatic structures and has the potential to guide prostate needle biopsy with improved sampling accuracy. The goal of this study is to demonstrate the feasibility of ARFI imaging to portray internal structures and PCa in the human prostate in vivo. Custom ARFI imaging sequences were designed and implemented using a modified Siemens Antares™ scanner with a three-dimensional (3-D) wobbler, end-firing, trans-cavity transducer, EV9F4. Nineteen patients were consented and imaged immediately preceding surgical prostatectomy. Pathologies and anatomic structures were identified in histologic slides by a pathologist blinded to ARFI data and were then registered with structures found in ARFI images. The results demonstrated that when PCa is visible, it generally appears as bilaterally asymmetric stiff structures; benign prostatic hyperplasia (BPH) appears heterogeneous with a nodular texture; the verumontanum and ejaculatory ducts appears softer compared with surrounding tissue, which form a unique 'V' shape; and the boundary of the transitional zone (TZ) forms a stiff rim separating the TZ from the peripheral zone (PZ). These characteristic appearances of prostatic structures are consistent with those found in our previous study of prostate ARFI imaging on excised human prostates. Compared with the matched B-mode images, ARFI images, in general, portray prostate structures with higher contrast. With the end-firing transducer used for this study, ARFI depth penetration was limited to 22 mm. Image contrast and resolution were decreased as compared with the previous ex vivo study due to the small transducer aperture. Even with these limitations, this study suggests ARFI imaging holds promise for guidance of targeted prostate needle biopsy and focal therapy, as well as aiding assessment of changes during watchful waiting/active surveillance.

Elastography: the next step

In the past few decades, various tools have emerged that claim to enhance detection of oral cancer. The most important prognostic factor in patients with oral cancer is lymph node status: the presence of nodal spread decreases the 5-year survival rate by approximately 50%. Differentiation between reactive and metastatic lymphadenopathy is thus vital, and one differentiating criterion is hardness (elasticity) of the lymph node. The purpose of this review is to highlight a promising new ultrasound technique, known as elastography, which measures the characteristics of tissue compliance. The principles underlying elastography are that tissue compression produces strain (displacement) within the tissue - which is lower in harder tissues than in softer tissues - and that malignant tissues are generally harder than normal surrounding tissue. Therefore, elastography might yield clinical information useful in diagnosing cervical metastasis and improving prognosis in oral cancer. It has long been used for cancers of the breast, pancreas, and thyroid, and its use in cervical lymphadenopathy is now being explored, which could lead to great advancements in the diagnosis and prognosis of oral cancer.

Transrectal real-time elastography of the prostate: Normal patterns

INTRODUCTION

Given the growing importance in clinical practice of transrectal real-time sonoelastography of the prostate, it is important to define normal patterns correlated to volume growth and reconsider the technical problems.

MATERIALS AND METHODS

We selected a sample of 100 men aged 30 to 87 with prostate volumes ranging from 20 to 100 cc. Strain images were obtained using an end-fire convex probe. The elasticity patterns of the various anatomical zones of the prostate were compared with the volume.

RESULTS

The peripheral zone showed intermediate elasticity in 100% of cases regardless of the volume. We found some rare small areas of more limited elasticity in 23% of cases, among patients over 40. The posterior side of the central zone exhibited intermediate elasticity, and relative inelasticity was observed on the lateral side and at the base in 79% of cases. The entire central zone appeared compliant in 15% of cases and inelastic in 6%. The transition zone findings were stratified according to gland volume. When the volume was less than 45 cc, the transition zone was elastic in 67% of cases, inhomogeneously inelastic in 22%, and uniformly inelastic in 11%. In glands larger than 45 cc, the appearance was mainly elastic in 31% of cases, inhomogeneously inelastic in 57%, and uniformly inelastic in 12%.

CONCLUSIONS

Real-time elastography can distinguish the elastic properties of the prostate and define the normal patterns associated with increases in gland volume.

Focal laser ablation of prostate cancer: numerical simulation of temperature and damage distribution

Background

The use of minimally invasive ablative techniques in the management of patients with low grade and localized prostate tumours could represent a treatment option between active surveillance and radical therapy. Focal laser ablation (FLA) could be one of these treatment modalities. Dosimetry planning and conformation of the treated area to the tumor remain major issues, especially when, several fibers are required. An effective method to perform pre-treatment planning of this therapy is computer simulation. In this study we present an in vivo validation of a mathematical model.

Methods

The simulation model is based on finite elements method (FEM) to solve the bio-heat and the thermal damage equations. Laser irradiation was performed with a 980 nm laser diode system (5 W, 75 s). Light was transmitted using a cylindrical diffusing fiber inserted inside a preclinical animal prostate cancer model induced in Copenhagen rats. Non-enhanced T2-weighted and dynamic gadolinium-enhanced T1-weighted MR imaging examinations were performed at baseline and 48 hours after the procedure. The model was validated by comparing the simulated necrosis volume to the results obtained in vivo on (MRI) and by histological analysis. 3 iso-damage temperatures were considered 43° C, 45° C and 50° C.

Results

The mean volume of the tissue necrosis, estimated from the histological analyses was 0.974 ± 0.059 cc and 0.98 ± 0.052 cc on the 48 h MR images. For the simulation model, volumes were: 1.38 cc when T = 43° C, 1.1 cc for T = 45°C and 0.99 cc when T = 50 C°.

Conclusions

In this study, a clear correlation was established between simulation and in vivo experiments of FLA for prostate cancer.

Simulation is a promising planning technique for this therapy. It needs further more evaluation to allow to FLA to become a widely applied surgical method.

An abdominal and thyroid status with Acoustic Radiation Force Impulse Elastometry--a feasibility study: Acoustic Radiation Force Impulse Elastometry of human organs

PURPOSE

Acoustic Radiation Force Impulse (ARFI) is a new method for the quantification of tissue elasticity. To date, ARFI technology has not been applied systematically to establish an abdominal and thyroid status. The aim of this prospective feasibility study was to evaluate ARFI elastometry performed on various healthy abdominal organs and the thyroid gland.

MATERIAL AND METHODS

94 patients (43 females, 51 males) with a mean age of 54 years and 20 healthy controls were enrolled in the study. A routine ultrasound examination of the abdomen was scheduled in 72, and of the thyroid in 25. ARFI elastometry was performed in liver, spleen, pancreas, prostate, kidneys and thyroid gland with the ultrasound system Acuson S2000. ARFI values are proportional to tissue elasticity. Patients with ultrasonic or anamnestic evidence of diseased organs were excluded from the analysis. ARFI measurements were compared with the aid of the t-test and correlated using Spearman's correlation coefficient.

RESULTS

ARFI elastometry proved feasible and the measurements obtained in the various organs differed significantly. Among healthy organs the spleen showed the highest mean ARFI velocities, followed by the kidney, thyroid, pancreas and the prostate. The lowest ARFI values were regularly found in healthy liver. Measurements in the kidneys and the spleen showed high standard deviation.

CONCLUSIONS

ARFI elastometry may describe parenchymal stiffness of various abdominal organs and the thyroid gland. Further investigations are needed to compare these baseline findings in healthy organs with those of various tumours or diseases affecting the individual organs.

Value of real-time elastography targeted biopsy for prostate cancer detection in men with prostate specific antigen 1.25 ng/ml or greater and 4.00 ng/ml or less

PURPOSE

We assessed the prostate cancer detection rate of real-time elastography targeted biopsy in men with total prostate specific antigen 1.25 ng/ml or greater and 4.00 ng/ml or less.

MATERIALS AND METHODS

Real-time elastography using an EUB 8500 Hitachi ultrasound system (Hitachi Medical, Tokyo, Japan) was done in 94 men with a mean age of 57.4 years (range 35 to 77) with increased prostate specific antigen between 1.25 ng/ml or greater and 4.00 ng/ml or less (mean 3.20, range 1.30 to 4.00) and a free-to-total prostate specific antigen ratio of less than 18%. Real-time elastography was done to evaluate peripheral zone tissue elasticity and hard areas were defined as suspicious. Targeted biopsies with a maximum of 5 cores were done in suspicious areas, followed by 10-core systematic biopsy. We analyzed the cancer detection rate of real-time elastography and systematic biopsy.

RESULTS

Cancer was found in 27 of 94 patients (28.7%). Real-time elastography detected cancer in 20 patients (21.3%) and systematic biopsy detected it in 18 (19.1%). Positive cancer cores were found in real-time elastography targeted cores in 38 of 158 cases (24%) and in systematic cores in 38 of 752 (5.1%) (chi-square test p <0.0001). The cancer detection rate per core was 4.7-fold greater for targeted than for systematic biopsy.

CONCLUSIONS

Real-time elastography targeted biopsy allows prostate cancer detection in men with prostate specific antigen 1.25 ng/ml or greater and 4 ng/ml or less with a decreased number of cores compared with that of systematic biopsy.

Effect of injection site on in situ implant formation and drug release in vivo

In situ forming drug delivery implants offer an attractive alternative to pre-formed implant devices for local drug delivery due to their ability to deliver fragile drugs, simple manufacturing process, and less invasive placement. However, the clinical translation of these systems has been hampered, in part, by poor correlation between in vitro and in vivo drug release profiles. To better understand this effect, the behavior of poly(D,l-lactide-co-glycolide) (PLGA) in situ forming implants was examined in vitro and in vivo after subcutaneous injection as well as injection into necrotic, non-necrotic, and ablated tumor. Implant formation was quantified noninvasively using an ultrasound imaging technique. Drug release of a model drug agent, fluorescein, was correlated with phase inversion in different environments. Results demonstrated that burst drug release in vivo was greater than in vitro for all implant formulations. Drug release from implants in varying in vivo environments was fastest in ablated tumor followed by implants in non-necrotic tumor, in subcutaneous tissue, and finally in necrotic tumor tissue with 50% of the loading drug mass released in 0.7, 0.9, 9.7, and 12.7h respectively. Implants in stiffer ablated and non-necrotic tumor tissue showed much faster drug release than implants in more compliant subcutaneous and necrotic tumor environments. Finally, implant formation examined using ultrasound confirmed that in vivo the process of precipitation (phase inversion) was directly proportional to drug release. These findings suggest that not only is drug release dependent on implant formation but that external environmental effects, such as tissue mechanical properties, may explain the differences seen between in vivo and in vitro drug release from in situ forming implants.

Acoustic radiation force impulse imaging of human prostates ex vivo

It has been challenging for clinicians using current imaging modalities to visualize internal structures and detect lesions inside human prostates. Lack of contrast among prostatic tissues and high false positive or negative detection rates of prostate lesions have limited the use of current imaging modalities in the diagnosis of prostate cancer. In this study, acoustic radiation force impulse (ARFI) imaging is introduced to visualize the anatomical and abnormal structures in freshly excised human prostates. A modified Siemens Antares ultrasound scanner (Siemens Medical Solutions USA Inc., Malvern, PA) and a Siemens VF10-5 linear array were used to acquire ARFI images. The transducer was attached to a three-dimensional (3-D) translation stage, which was programmed to automate volumetric data acquisition. A depth dependent gain (DDG) method was developed and applied to 3-D ARFI datasets to compensate for the displacement gradients associated with spatially varying radiation force magnitudes as a function of depth. Nine human prostate specimens were collected and imaged immediately after surgical excision. Prostate anatomical structures such as seminal vesicles, ejaculatory ducts, peripheral zone, central zone, transition zone and verumontanum were visualized with high spatial resolution and in good agreement with McNeal's zonal anatomy. The characteristic appearance of prostate pathologies, such as prostate cancerous lesions, benign prostatic hyperplasia, calcified tissues and atrophy were identified in ARFI images based upon correlation with the corresponding histologic slides. This study demonstrates that ARFI imaging can be used to visualize internal structures and detecting suspicious lesions in the prostate and appears promising for image guidance of prostate biopsy.

Ultrasound of the prostate

Ultrasound is a widely used imaging modality for evaluation of the prostate. The main topic of diagnostic imaging is an improvement of prostate cancer diagnosis. The current available systematic prostate biopsy is performed only under ultrasound guidance, but new imaging techniques allow prostate cancer visualization and therefore improved detection. Evolving methods such as contrast-enhanced colour Doppler imaging, contrast-specific ultrasound techniques and elastography may dramatically change the role of ultrasound for prostate cancer diagnosis. The purpose of this review is to provide an overview of ultrasound and its different techniques for imaging of the prostate and to discuss current trends and future directions.

Is focal therapy the future for prostate cancer?

Focal therapy aims to find a middle ground between surveillance and radical therapies by treating the cancer alone, with a margin, and preserving as much tissue as is practical. Early feasibility studies have demonstrated an absence of rectal toxicity and preservation of genitourinary function in 80–90% of men. The incidence of low- to intermediate-risk prostate cancer is rising owing to informal and formal prostate-specific antigen screening practices. The treatment burden from radical therapies is high with over 50% of men suffering genitourinary or rectal toxicity. Active surveillance, on the other hand, carries surveillance and psychological burden with risk of progression. A research strategy to evaluate focal therapy should be embedded within pragmatic designs using a broad patient group, using the available ablative technologies (cryotherapy, high-intensity focused ultrasound, brachytherapy and photodynamic therapy) with end points derived from biochemical, biopsy and imaging. Within this framework there exists a unique opportunity to undertake landmark diagnostic studies incorporating imaging techniques and biomarkers in addition to studies directed at the biology of prostate cancer over time.

A new algorithm in patients with elevated and/or rising prostate-specific antigen level, minor lower urinary tract symptoms, and negative multisite prostate biopsies

Patients with elevated and/or rising prostate-specific antigen (PSA), minor lower urinary tract symptoms (LUTS), and no evidence for prostate cancer on (multiple) extended prostate biopsies are a regularly encountered problem in urological practice. Even now, patients are seen with no objective explanation of this persistent elevated and/or rising PSA. So far, many strategic proposals have been elaborated and published to deal with this specific population including the use of different PSA derivates; applying different biopsy schemes—strategies—biopsy target imaging; diagnostic use of prostate cancer genes; and many more. In this review, we propose a new algorithm in which an urodynamic evaluation should be included since bladder outlet obstruction (BOO) can be expected. Once BOO is confirmed, a transurethral resection of the prostate (TURP) can be offered to these patients. This procedure will result in subjective and biochemical improvement and allows extensive histological examination. Current literature was reviewed with regard to this specific population. This research was performed using the commercially available Medline online search tools and applying the following search terms: “diagnostic TURP”; “elevated PSA”; and “prostate biopsy”. Furthermore, subsequent reference search was executed on retrieved articles.