Synthetic Elastography Using B-Mode Ultrasound Through a Deep Fully Convolutional Neural Network

Shear-wave elastography (SWE) permits local estimation of tissue elasticity, an important imaging marker in biomedicine. This recently developed, advanced technique assesses the speed of a laterally traveling shear wave after an acoustic radiation force "push" to estimate local Young's moduli in an operator-independent fashion. In this work, we show how synthetic SWE (sSWE) images can be generated based on conventional B-mode imaging through deep learning. Using side-by-side-view B-mode/SWE images collected in 50 patients with prostate cancer, we show that sSWE images with a pixel-wise mean absolute error of 4.5 ± 0.96 kPa with regard to the original SWE can be generated. Visualization of high-level feature levels through t -distributed stochastic neighbor embedding reveals substantial overlap between data from two different scanners. Qualitatively, we examined the use of the sSWE methodology for B-mode images obtained with a scanner without SWE functionality. We also examined the use of this type of network in elasticity imaging in the thyroid. Limitations of the technique reside in the fact that networks have to be retrained for different organs, and that the method requires standardization of the imaging settings and procedure. Future research will be aimed at the development of sSWE as an elasticity-related tissue typing strategy that is solely based on B-mode ultrasound acquisition, and the examination of its clinical utility.

Blind Source Separation for Clutter and Noise Suppression in Ultrasound Imaging: Review for Different Applications

Blind source separation (BSS) refers to a number of signal processing techniques that decompose a signal into several "source" signals. In recent years, BSS is increasingly employed for the suppression of clutter and noise in ultrasonic imaging. In particular, its ability to separate sources based on measures of independence rather than their temporal or spatial frequency content makes BSS a powerful filtering tool for data in which the desired and undesired signals overlap in the spectral domain. The purpose of this work was to review the existing BSS methods and their potential in ultrasound imaging. Furthermore, we tested and compared the effectiveness of these techniques in the field of contrast-ultrasound super-resolution, contrast quantification, and speckle tracking. For all applications, this was done in silico, in vitro, and in vivo. We found that the critical step in BSS filtering is the identification of components containing the desired signal and highlighted the value of a priori domain knowledge to define effective criteria for signal component selection.

Convective-Dispersion Modeling in 3D Contrast-Ultrasound Imaging for the Localization of Prostate Cancer

Despite being the solid tumor with the highest incidence in western men, prostate cancer (PCa) still lacks reliable imaging solutions that can overcome the need for systematic biopsies. Dynamic contrast-enhanced ultrasound imaging (DCE-US) allows us to quantitatively characterize the vascular bed in the prostate, due to its ability to visualize an intravenously administered bolus of contrast agents. Previous research has demonstrated that DCE-US parameters related to the vascular architecture are useful markers for the localization of PCa lesions. In this paper, we propose a novel method to assess the convective dispersion (D) and velocity (v) of the contrast bolus spreading through the prostate from three-dimensional (3D) DCE-US recordings. By assuming that D and v are locally constant, we solve the convective-dispersion equation by minimizing the corresponding regularized least-squares problem. 3D multiparametric maps of D and v were compared with 3D histopathology retrieved from the radical prostatectomy specimens of six patients. With a pixel-wise area under the receiver operating characteristic curve of 0.72 and 0.80, respectively, the method shows diagnostic value for the localization of PCa.

Semi-automated Database Design by the End-user

An information system was developed to manage the data for a large number of research projects simultaneously. The system, called URIS, has facilitated the management of research data in an academic urological department. It enables end-users, who are not necessarily skilled computer scientists, to design their own databases semi-automatically, by supporting data entry screen design and the specification of research items. The system creates the database tables automatically after these activities. The specification of research items is the most important but also most difficult part in this process.

The prostate cancer detection rates of CEUS-targeted versus MRI-targeted versus systematic TRUS-guided biopsies in biopsy-naïve men: a prospective, comparative clinical trial using the same patients

BACKGROUND

The current standard for Prostate Cancer (PCa) detection in biopsy-naïve men consists of 10-12 systematic biopsies under ultrasound guidance. This approach leads to underdiagnosis and undergrading of significant PCa while insignificant PCa may be overdiagnosed. The recent developments in MRI and Contrast Enhanced Ultrasound (CEUS) imaging have sparked an increasing interest in PCa imaging with the ultimate goal of replacing these "blind" systematic biopsies with reliable imaging-based targeted biopsies.

METHODS/DESIGN

In this trial, we evaluate and compare the PCa detection rates of multiparametric (mp)MRI-targeted biopsies, CEUS-targeted biopsies and systematic biopsies under ultrasound guidance in the same patients. After informed consent, 299 biopsy-naïve men will undergo mpMRI scanning and CEUS imaging 1 week prior to the prostate biopsy procedure. During the biopsy procedure, a systematic transrectal 12-core biopsy will be performed by one operator blinded for the imaging results and targeted biopsy procedure. Subsequently a maximum of 4 CEUS-targeted biopsies and/or 4 mpMRI-targeted biopsies of predefined locations determined by an expert CEUS reader using quantification techniques and an expert radiologist, respectively, will be taken by a second operator using an MRI-US fusion device. The primary outcome is the detection rate of PCa (all grades) and clinically significant PCa (defined as Gleason score ≥7) compared between the three biopsy protocols.

DISCUSSION

This trial compares the detection rate of (clinically significant) PCa, between both traditional systematic biopsies and targeted biopsies based on predefined regions of interest identified by two promising imaging technologies. It follows published recommendations on study design for the evaluation of imaging guided prostate biopsy techniques, minimizing bias and allowing data pooling. It is the first trial to combine mpMRI imaging and advanced CEUS imaging with quantification.

TRIAL REGISTRATION

The Dutch Central Committee on Research Involving Human Subjects registration number NL52851.018.15, registered on 3 Nov 2015. Clinicaltrials.gov database registration number NCT02831920 , retrospectively registered on 5 July 2016.

MRI and contrast-enhanced ultrasound imaging for evaluation of focal irreversible electroporation treatment: results from a phase I-II study in patients undergoing IRE followed by radical prostatectomy

OBJECTIVES

Irreversible electroporation (IRE) is an ablative therapy with a low side-effect profile in prostate cancer. The objective was: 1) To compare the volumetric IRE ablation zone on grey-scale transrectal ultrasound (TRUS), contrast-enhanced ultrasound (CEUS) and multiparametric MRI (mpMRI) with histopathology findings; 2) To determine a reliable imaging modality to visualize the IRE ablation effects accurately.

METHODS

A prospective phase I-II study was performed in 16 patients scheduled for radical prostatectomy (RP). IRE of the prostate was performed 4 weeks before RP. Prior to, and 4 weeks after the IRE treatment, imaging was performed by TRUS, CEUS, and mpMRI. 3D-analysis of the ablation volumes on imaging and on H&E-stained whole-mount sections was performed. The volumes were compared and the correlation was calculated.

RESULTS

Evaluation of the imaging demonstrated that with T2-weighted MRI, dynamic contrast enhanced (DCE) MRI, and CEUS, effects of IRE are visible. T2MRI and CEUS closely match the volumes on histopathology (Pearson correlation r = 0.88 resp. 0.80). However, IRE is not visible with TRUS.

CONCLUSIONS

mpMRI and CEUS are appropriate for assessing IRE effects and are the most feasible imaging modalities to visualize IRE ablation zone. The imaging is concordant with results of histopathological examination.

KEY POINTS

• mpMRI and contrast-enhanced ultrasound are appropriate imaging modalities for assessing IRE effects • mpMRI and CEUS are the most feasible imaging modalities to visualize IRE ablation zone • The imaging is concordant with results of histopathological examination after IRE • Grey-scale US is insufficient for assessing IRE ablations.

Imaging modalities in Focal Therapy: Multiparametric Ultrasound

OBJECTIVES

Prostate cancer (PCa) is the most common form of cancer among men in the US and the second most common cause of death. It has been observed that an increasing number of newly diagnosed patients exhibit low-risk features and that over-treatment with radical prostatectomy is a growing problem. The feasibility of focal therapy as an organsparing alternative, however, depends on the reliability of imaging techniques to identify, localize and monitor clinically relevant PCa lesions. The aim of this review is to investigate the potential of multiparametric ultrasound (mpUS) for focal therapy.

METHODS

We briefly introduce the most common focal therapies and thoroughly discuss the ability of available ultrasound modalities to localize PCa and reflect tissue properties. The imaging requirements of the focal therapies are studied to put the performance of the US techniques into perspective.

RESULTS

We found that transrectal greyscale echography, Doppler sonography, elastography, contrast-enhanced ultrasonography and computerized ultrasound have been studied for the purpose of prostate imaging. Several of these modalities are already frequently used in current clinical practice; to add to the diagnostic process of PCa, to guide and monitor the application of focal therapy or to perform follow-up after treatment. Despite their capability to detect a large fraction of the PCa lesions, none of these modalities is currently considered sufficiently accurate for stand-alone tumour detection and localization. However, although there are only few studies reporting on a combined use of different ultrasound modalities, the results of an mpUS approach seem promising.

CONCLUSION

Several US modalities have been successfully applied as a viable alternative to monitor tissue destruction during and after treatment. In view of the advantages of US and the promising results of a multiparametric approach in PCa detection and localization, researchers are urged to further investigate mpUS for therapeutic purposes.

The correlation between the electrode configuration and histopathology of irreversible electroporation ablations in prostate cancer patients

PURPOSE

Irreversible electroporation (IRE) is a novel minimally invasive therapy for prostate cancer using short electric pulses to ablate prostate tissue. The purpose of this study is to determine the IRE effects in prostate tissue and correlate electrode configuration with the histology of radical prostatectomy (RP) specimens. We hypothesize that the area within the electrode configuration is completely ablated and that the area within the electrode configuration is predictive for the ablated area after treatment.

METHODS

A prospective phase I/II study was conducted in 16 consecutive patients with histopathologically confirmed prostate cancer scheduled for RP. Focal or extended IRE treatment of the prostate was performed 4 weeks prior to RP. The locations of the electrodes were used to calculate the planned ablation zone. Following RP, the specimens were processed into whole-mount sections, histopathology (PA) was assessed and ablation zones were delineated. The area of the tissue alteration was determined by measuring the surface. The planned and the histological ablation zones were compared, analysed per individual patient and per protocol (focal vs. extended).

RESULTS

All cells within the electrode configuration were completely ablated and consisted only of necrotic and fibrotic tissue without leaving any viable cells. The histological ablation zone was always larger than the electrodes configuration (2.9 times larger for the 3 electrodes configuration and 2.5 times larger for the ≥4 electrode configuration). These ablation effects extended beyond the prostatic capsule in the neurovascular bundle in 13 out of 15 cases.

CONCLUSIONS

IRE in prostate cancer results in completely ablated, sharply demarcated lesions with a histological ablation zone beyond the electrode configuration. No skip lesions were observed within the electrode configuration.

CLINICAL TRIALS

ClinicalTrials.gov Identifier: NCT01790451 https://clinicaltrials.gov/ct2/show/NCT01790451.

[Advances in ultrasound techniques for the diagnosis and staging of prostate cancer. Elastography, Doppler ultrasound, ultrasound contrast media, ultrasound quantification media and MRI fusion]

OBJECTIVES

Transrectal ultrasound-guided prostate biopsy remains the gold standard in the diagnosis of prostate cancer. Various Ultrasound modalities have been proposed to increase the cancer detection rate. Our purpose is to evaluate each of these methods , and to present its current literature and clinical utility.

METHOD

A non structured review of the current literature was conducted over these different various ultrasound modalities used during the transrectal ultrasound-guided prostate biopsied in the diagnosis of prostate cancer.

RESULTS

The data investigation of the various modalities associated sonographic features exhibits great heterogeneity and highly variable results. Some new techniques sampling present promising results with high sensitivity and specificity, thus increasing the diagnostic yield of transrectal biopsy. It seems that elastography shows encouraging figures, especially given the recent introduction of the "shearvawe" elastography that decreases the user-dependent factor.

CONCLUSIONS

The ultrasound-guided prostate biopsy has an acceptable sensitivity in the diagnosis of prostate cancer, but its specificity is still low. Various modalities associated with ultrasound are available in clinical practice in order to increase cancer detection rate. Although some promising data have been published for some of the modalities, we believe the combination of these includes validated ultrasound guided biopsy protocols to accurately target and diagnose prostate cancer.

Closed-form solution of the convolution integral in the magnetic resonance dispersion model for quantitative assessment of angiogenesis

Prostate cancer (PCa) diagnosis and treatment is still limited due to the lack of reliable imaging methods for cancer localization. Based on the fundamental role played by angiogenesis in cancer growth and development, several dynamic contrast enhanced (DCE) imaging methods have been developed to probe tumor angiogenic vasculature. In DCE magnetic resonance imaging (MRI), pharmacokinetic modeling allows estimating quantitative parameters related to the physiology underlying tumor angiogenesis. In particular, novel magnetic resonance dispersion imaging (MRDI) enables quantitative assessment of the microvascular architecture and leakage, by describing the intravascular dispersion kinetics of an extravascular contrast agent with a dispersion model. According to this model, the tissue contrast concentration at each voxel is given by the convolution between the intravascular concentration, described as a Brownian motion process according to the convective-dispersion equation, with the interstitium impulse response, represented by a mono-exponential decay, and describing the contrast leakage in the extravascular space. In this work, an improved formulation of the MRDI method is obtained by providing an analytical solution for the convolution integral present in the dispersion model. The performance of the proposed method was evaluated by means of dedicated simulations in terms of estimation accuracy, precision, and computation time. Moreover, a preliminary clinical validation was carried out in five patients with proven PCa. The proposed method allows for a reduction by about 40% of computation time without any significant change in estimation accuracy and precision, and in the clinical performance.

The safety and efficacy of irreversible electroporation for the ablation of prostate cancer: a multicentre prospective human in vivo pilot study protocol

INTRODUCTION

Current surgical and ablative treatment options for prostate cancer have a relatively high incidence of side effects, which may diminish the quality of life. The side effects are a consequence of procedure-related damage of the blood vessels, bowel, urethra or neurovascular bundle. Ablation with irreversible electroporation (IRE) has shown to be effective in destroying tumour cells and harbours the advantage of sparing surrounding tissue and vital structures. The aim of the study is to evaluate the safety and efficacy and to acquire data on patient experience of minimally invasive, transperineally image-guided IRE for the focal ablation of prostate cancer.

METHODS AND ANALYSIS

In this multicentre pilot study, 16 patients with prostate cancer who are scheduled for a radical prostatectomy will undergo an IRE procedure, approximately 30 days prior to the radical prostatectomy. Data as adverse events, side effects, functional outcomes, pain and quality of life will be collected and patients will be controlled at 1 and 2 weeks post-IRE, 1 day preprostatectomy and postprostatectomy. Prior to the IRE procedure and the radical prostatectomy, all patients will undergo a multiparametric MRI and contrast-enhanced ultrasound of the prostate. The efficacy of ablation will be determined by whole mount histopathological examination, which will be correlated with the imaging of the ablation zone.

ETHICS AND DISSEMINATION

The protocol is approved by the ethics committee at the coordinating centre (Academic Medical Center (AMC) Amsterdam) and by the local Institutional Review Board at the participating centres. Data will be presented at international conferences and published in peer-reviewed journals.

CONCLUSIONS

This pilot study will determine the safety and efficacy of IRE in the prostate. It will show the radiological and histopathological effects of IRE ablations and it will provide data to construct an accurate treatment planning tool for IRE in prostate tissue.

TRIAL REGISTRATION NUMBER

Clinicaltrials.gov database: NCT01790451.

[Imaging of the prostate]

Recently several new technologies for prostate imaging have been developed. The aim of these technologies was to improve the diagnosis of prostate cancer. Especially the transrectal ultrasound (TRUS) has been refined to the so-called enhanced ultrasound, as regular grey scale TRUS has limited ability to identify cancer lesions in the prostate. In several studies elastography has shown good capability to identify cancer lesions in the prostate as well as to absolutely increase the detection rate of randomized biopsies by up to 10 %.. Contrast-enhanced ultrasound shows varying results in the published literature with increased detection rates on the one hand and unchanged detection rates relative to randomized biopsy on the other hand. The online available ANNA/C-TRUS system shows detection rates with six targeted biopsies that are comparable to the published detection rates of randomized saturation biopsies. Direct systematic comparison to randomized biopsies is missing. The Histoscanning system currently provides the poorest data as no biopsy studies are available. Multicenter trials are mandatory for all new imaging technologies in order to implement them as standard into clinical practice.

Prostate cancer localization by novel magnetic resonance dispersion imaging

Diagnosis and focal treatment of prostate cancer, the most prevalent form of cancer in men, is hampered by the limits of current clinical imaging. Angiogenesis imaging is a promising option for detection and localization of prostate cancer. It can be imaged by dynamic contrast-enhanced (DCE) MRI, assessing microvascular permeability as an indicator for angiogenesis. However, information on microvascular architecture changes associated with angiogenesis is not available. This paper presents a new model enabling the combined assessment of microvascular permeability and architecture. After the intravenous injection of a gadolinium-chelate bolus, time-concentration curves (TCCs) are measured by DCE-MRI at each voxel. According to the convective dispersion equation, the microvascular architecture is reflected in the dispersion coefficient. A solution of this equation is therefore proposed to represent the intravascular blood plasma compartment in the Tofts model. Fitting the resulting model to TCCs measured at each voxel leads to the simultaneous generation of a dispersion and a permeability map. Measurement of an arterial input function is no longer required. Preliminary validation was performed by spatial comparison with the histological results in seven patients referred for radical prostatectomy. Cancer localization by the obtained dispersion maps provided an area under the receiver operating characteristic curve equal to 0.91. None of the standard DCE-MRI parametric maps could outperform this result, motivating towards an extended validation of the method, also aimed at investigating other forms of cancer with pronounced angiogenic development.

Contrast-ultrasound dispersion imaging for prostate cancer localization by improved spatiotemporal similarity analysis

Angiogenesis plays a major role in prostate cancer growth. Despite extensive research on blood perfusion imaging aimed at angiogenesis detection, the diagnosis of prostate cancer still requires systematic biopsies. This may be due to the complex relationship between angiogenesis and microvascular perfusion. Analysis of ultrasound-contrast-agent dispersion kinetics, determined by multipath trajectories in the microcirculation, may provide better characterization of the microvascular architecture. We propose the physical rationale for dispersion estimation by an existing spatiotemporal similarity analysis. After an intravenous ultrasound-contrast-agent bolus injection, dispersion is estimated by coherence analysis among time-intensity curves measured at neighbor pixels. The accuracy of the method is increased by time-domain windowing and anisotropic spatial filtering for speckle regularization. The results in 12 patient data sets indicated superior agreement with histology (receiver operating characteristic curve area = 0.88) compared with those obtained by reported perfusion and dispersion analyses, providing a valuable contribution to prostate cancer localization.

Evaluation of renal masses with contrast-enhanced ultrasound

The clinical need for characterising small renal masses (SRMs) is increasing due to their rising incidental detection. This increase is especially seen in younger and older generations and concerns mainly SRMs. Diagnostics is mainly made by contrast-enhanced CT or MRI. However, these imaging methods fail to accurately distinguishing benign from malignant SRMs. Other disadvantages of CT or MRI are high costs, the use of ionizing radiation, nephrotoxicity induced by iodine contrast agents or nephrogenic systemic fibrosis (NSF) induced by gadolinium contrast agents. Contrast-enhanced ultrasound (CEUS) is based on ultrasonography and microbubbles to real-time visualize the renal blood flow without the use of nephrotoxic agents or ionizing radiation. This comprehensive review evaluates the capabilities of CEUS in the diagnostics of benign (angiomyolipomas, cysts, oncocytomas, pseudotumors) and malignant masses (renal cell carcinomas), and focuses on possible future treatment.

Focal therapy in prostate cancer-report from a consensus panel

PURPOSE

To establish a consensus in relation to case selection, conduct of therapy, and outcomes that are associated with focal therapy for men with localized prostate cancer.

MATERIAL AND METHODS

Urologic surgeons, radiation oncologists, radiologists, and histopathologists from North America and Europe participated in a consensus workshop on focal therapy for prostate cancer. The consensus process was face to face within a structured meeting, in which pertinent clinical issues were raised, discussed, and agreement sought. Where no agreement was possible, this was acknowledged, and the nature of the disagreement noted.

RESULTS

Candidates for focal treatment should have unilateral low- to intermediate-risk disease with clinical stage <or=cT(2a). Prostate size and both tumor volume and tumor topography are important case selection criteria that depend on the ablative technology used. Currently, the best method to ascertain the key characteristics for men who are considering focal therapy is exposure to transperineal template mapping biopsies. MRI of the prostate using novel techniques such as dynamic contrast enhancement and diffusion weighed imaging are increasingly being used to diagnose and stage primary prostate cancer with excellent results. For general use, however, these new techniques require validation in prospective clinical trials. Until such are performed, MRI will, in most centers, continue to be an investigative tool in assessing eligibility of patients for focal therapy.

CONCLUSIONS

Consensus was derived for most of the key aspects of case selection, conduct of treatment, and outcome measures for men who are undergoing focal therapy for localized prostate cancer. The level of agreement achieved will pave the way for future collaborative trials.

Speckle-initialized dynamic segmentation of the prostate

Echography is a commonly used modality for prostate imaging. Prostate segmentation is the first step in analyzing echographic prostate images. Because of the nature of these images, traditional local image processing operators are inadequate for finding the prostate boundary. Most automated segmentations described in literature require user interaction for contour initializing or editing. Also shape templates are applied as prior knowledge. In this paper, an automatic segmentation method is presented, based on prostate specific image granulation and image intensity. First, a granulation detector is used to extract granulation. Subsequently, the Hessian is adopted to evaluate granulation shape and intensity for the extraction of the prostate-specific dot pattern. This dot pattern is used to construct the contour initialization. A smooth contour model (discrete dynamic contour; DDC) is evolved from this initialization to the final contour. The guiding vector field for the DDC deformation is the gradient vector flow field calculated from an edge map of the original image. The scale of the relevant edges (large compared to granulation) is estimated from the prostate-specific dot pattern. Comparison of automated segmentations with clinical expert manual segmentations reveals a mean sensitivity and accuracy of 0.90 and 0.93, respectively.

Transrectal contrast enhanced ultrasound for diagnosis of prostate cancer

The diagnosis of prostate cancer is based on histology. Prostate biopsies are obtained based on the triad of prostate specific antigen (PSA), digital rectal examination (DRE) and transrectal ultrasound. Because prostate biopsies still have a large percentage of negative outcomes, patient selection and biopsy direction need improvement. This paper describes the recent improvements in prostate cancer imaging, especially contrast-enhanced transrectal ultrasound.

[Advances in the ultrasound diagnosis of prostate cancer]

OBJECTIVES

Ultrasound guided biopsies are the mainstay in the diagnosis of prostate cancer. With the aim of improving diagnostic performances different protocols of prostate biopsy have been designed. The addition of vascular contrasts to the ultrasound allows for identification of hypervascular regions more likely to be cancer. The new ultrasound modalities enhance contrast signal and specifically differentiate its signal from the tissue reflections.

METHOD

A non structured review of the literature was conducted on the utility of the different ultrasound modalities and types in targeting the biopsies of the prostate.

RESULTS

There are four types of ultrasound guided biopsies of the prostate: ultrasound guided biopsy of hypoechoic nodes, systematic biopsy protocols, Doppler guided biopsy and Contrast Enhanced Doppler guided biopsy. In spite of the broad literature only few series possess a methodologically correct design related to the use of reference standards. The diagnostic performance of each one of the different types of biopsy varies widely. Sensitivity and specificity of ultrasound guided biopsy of hypoechoic nodes depends on the type of population included in the study but in general its positive predictive value is low. The protocols of systematic biopsy increase the sensitivity of the prostate biopsy but still specificity is low. The Doppler techniques offer a marginal benefit. Contrast Enhanced Doppler guided biopsies series have reported only a slightly increase in sensitivity and a significant improvement of the odds risk for diagnostic of prostate cancer. New arising ultrasound modalities present with promising preliminary results.

CONCLUSIONS

Ultrasound guided biopsy have an acceptable sensitivity in the diagnosis of prostate cancer, however specificity is overall low. Among the different ultrasound techniques only Contrast Enhanced Ultrasound improves significantly the diagnostic risk of the biopsy although the sensitivity remains quite stable. New specific contrast ultrasound techniques are currently under investigation.

Cryotherapy for renal-cell cancer: diagnosis, treatment, and contrast-enhanced ultrasonography for follow-up

Cryotherapy is a curative treatment option for patients with small (<4 cm) renal-cell cancers. For the followup of ablated lesions, imaging is the only available method, but the best tool has not yet been determined. The method selected should be able to determine the presence or absence of perfusion in the area and measure the lesion. Usually, contrast-enhanced CT or MRI is used. The accompanying video shows cryotherapy treatment along with contrast-enhanced ultrasound investigations before and afterward. We used a Siemens Acuson Sequoia device with contrast pulse sequence imaging and Sonovue (Bracco) as the contrast agent. The lesion could be identified and measured easily. Because this method enables selective detection of contrast, the presence and absence of perfusion can be determined objectively.

The Bell-Shaped Nitinol Prostatic Stent in the Treatment of Lower Urinary Tract Symptoms: Experience in 108 Patients

OBJECTIVES

To assess the efficacy, safety, and durability of the bell-shaped nitinol prostatic stent in the treatment of moderate to severe lower urinary tract symptoms caused by benign prostatic enlargement in otherwise healthy patients.

METHODS

Stents were inserted in an outpatient setting under local anaesthesia. Assessments included maximum urinary flow (Qmax), postvoid residual (PVR) urine volume, International Prostate Symptom Score (IPSS), including quality of life (QoL) item, at baseline and follow-up visits.

RESULTS

108 men were enrolled in the trial. Stents were successfully inserted in 97% of the patients. Spontaneous voiding was achieved in all patients. After one month Qmax (+3.7 ml/s), PVR (-99 ml), IPSS (-12) and QoL (-1.7) all showed statistically significant improvements compared to baseline. Substantial improvements, however, were maintained for only one to two months. The main complications were haematuria (19%), urge incontinence (22%), and migration (15%). The median indwelling time was 105 days. The main reason for removal of stents was worsening of symptoms, which might be attributable to the tilting of stents within the prostatic urethra, found upon removal.

CONCLUSIONS

Insertion of the bell-shaped nitinol prostatic stent temporarily improves voiding parameters and symptom scores. Because of the limited durability, however, the bell-shaped prostatic stent is not suitable for clinical practice.

[Laparoscopic assisted cryoablation of small renal masses]

AIMS

To review the current status of cryoablation of small renal masses and to preliminary report our experience at the AMC.

MATERIAL AND METHODS

A bibliographic search was conducted (PubMed/Medline/Embase) and the most important series were analyzed. Our series includes 13 patients with a solitary small renal mass treated by Laparoscopic assisted Cryoblation with fine cryoprobes (1,5 cm diameter). Postoperative follow-up was done by means of CT and/or MRI every three months during the first year and every 6 months during the second year.

RESULTS

There are no randomized trials comparing Cryoblation of renal masses (<4 cm diameter) with either radical surgery or partial nephrectomy but only case series. Complication rate is low as it is the recurrence or persistence rate in most of the series but one referring to radiologically guided Cryoablation (8%). The maximal diameter of the masses treated in our series were 3,2 cm. Tumors were approached retro or transperitoneally depending on their localization in the kidney. Average surgical time were 208 minutes (108-379) and average time of exposition to temperatures lower than -20 degrees C in the tumor periphery was 10 minutes. AT a mean follow-up of 8 months no tumoral recurrence were objectivated.

CONCLUSIONS

Cryoablation of small renal masses may be an acceptable alternative of treatment although mean follow-up is still short in all the series.

LONG-TERM FUNCTIONAL AND URODYNAMIC RESULTS OF 50 PATIENTS RECEIVING A MODIFIED SIGMOID NEOBLADDER CREATED WITH A SHORT DISTAL SEGMENT

PURPOSE

We assessed the long-term functional and urodynamic outcomes of a modified sigmoid neobladder.

MATERIALS AND METHODS

A total of 50 patients received a sigmoid neobladder with a short distal segment after radical cystoprostatectomy. Patients were followed at 3-month intervals the first year and every 6 months thereafter. Continence and voiding patterns were assessed using questionnaires and interview. The International Continence Society classification was used after 1996. Urodynamic assessment was performed 3 times during followup.

RESULTS

Mean sigmoid segment length +/- SD was 18 cm (+/- 2.8). Mean followup was 38 months (+/- 24.8). Ureter stricture and reflux were present in 8% and 17% of the reimplanted units, respectively. Mean creatinine serum levels did not change after surgery and remained stable during followup. At 2 years 89% of the patients were continent in the daytime and 90% had good or satisfactory daytime continence according to the International Continence Society classification. At 3 years 77% of the patients voided every 3 or 4 hours during the day. Nighttime continence was poor. Only 10% of the patients complied with an alarm program. Mean maximal capacity of the reservoir was 300 ml and remained stable during followup. Mean intrareservoir pressure at maximal capacity decreased from 61 to 51 cm H2O from the first to the third urodynamic evaluation. No patient required clean intermittent catheterization.

CONCLUSIONS

This modified sigmoid neobladder offers good daytime continence with low post-void residual and adequate daytime micturition frequency. Nighttime continence is poor. The presence of high intrareservoir pressures did not impair renal function.

The methodology of corpus cavernosum electromyography revisited

OBJECTIVE

The methodology of corpus cavernosum electromyography (CC-EMG) was revisited, in order to overcome current methodological difficulties that hinder its clinical application.

MATERIALS AND METHODS

Using an 8-channel device, CC-EMG was performed in 12 healthy volunteers. Surface electrodes were placed bilaterally on the penile shaft and the kneecap (reference electrode), the pubis region and the anterior superior iliac spine (ASIS). A band pass filter with cut-off frequencies of 0.1 and 20 Hz was used. At least 2 sessions of recordings were performed in each subject.

RESULTS

Thirty-five of 46 recordings were interpretable. Significant time delays between potentials recorded from different sites of the CC were detected. Clear spatial voltage gradients related to CC-potentials were observed on the pubis region. No voltage changes related to CC-potentials, but electrical activity from other sources were recorded from the ASIS. In contrast to frequency, a clear correlation could be demonstrated between amplitude, duration and polyphasity of CC-potentials recorded in 2 different sessions in the same individual.

CONCLUSIONS

Multichannel monopolar recording of CC-EMG with surface electrodes is practical and has several advantages compared with bipolar recording. The results provide evidence that the recorded signals indeed reflect electrical activity of the CC and therefore offer a basis to pursue further clinical validation studies.

The value of corpus cavernosum electromyography in erectile dysfunction: current status and future prospect

In the last decade, several investigators have tried to develop corpus cavernosum electromyography (CC-EMG) as a direct clinical method to evaluate the state of the penile autonomic innervation and the cavernous smooth muscle. Both basic and clinical studies have shown promising results. However, its application as a diagnostic tool with clinical relevance was hindered by insufficient knowledge of cavernous smooth muscle electrophysiology, lack of standardization, technical and practical difficulties and problems in the interpretation of the results. Recently, the European Commission created the so-called COST Action B18 (corpus cavernosum EMG in erectile dysfunction), aiming to strengthen the coordination of the European research groups and give the development of CC-EMG a new impetus. This review presents an overview of the physiological background, the current status of CC-EMG, and discusses possibilities for further developments.

Penile duplex pharmaco-ultrasonography revisited: revalidation of the parameters of the cavernous arterial response

PURPOSE

We revalidate parameters of the cavernous arterial response (peak systolic blood flow velocity) and acceleration time using penile duplex pharmaco-ultrasonography.

MATERIALS AND METHODS

Blood flow velocity in the cavernous artery following pharmaco-stimulation was determined with duplex ultrasonography in 106 patients with erectile dysfunction. Intima media thickness of the common carotid artery, a valid index for atherosclerosis and clinical diagnosis based on a comprehensive evaluation were used as references. The clinical diagnosis was used to determine cutoff values. For the statistical analysis, Pearson correlation and ROC curves were used.

RESULTS

When correlating peak systolic velocity and acceleration time to intima media thickness, acceleration time (r = 0.51, p <0.01) was the most valid parameter to detect cavernous atherosclerotic pathology (peak systolic velocity r = -0.18, p = 0.12). This finding was confirmed by a comparison of both parameters to the clinical diagnosis. AUC was 0.59, 95% CI 0.49-0.69 for peak systolic velocity and 0.72 (95% CI 0.62-0.80 for acceleration time). The cutoff point for acceleration time to discriminate between atherosclerotic and nonatherosclerotic erectile dysfunction was determined at acceleration time 100 milliseconds or greater. Sensitivity was 66% and specificity was 71%.

CONCLUSIONS

The results of this study show that acceleration time has more power than peak systolic velocity to diagnose atherosclerotic erectile dysfunction.

Penile duplex pharmaco-ultrasonography revisited: revalidation of the parameters of the cavernous arterial response

PURPOSE

We revalidate parameters of the cavernous arterial response (peak systolic blood flow velocity) and acceleration time using penile duplex pharmaco-ultrasonography.

MATERIALS AND METHODS

Blood flow velocity in the cavernous artery following pharmaco-stimulation was determined with duplex ultrasonography in 106 patients with erectile dysfunction. Intima media thickness of the common carotid artery, a valid index for atherosclerosis and clinical diagnosis based on a comprehensive evaluation were used as references. The clinical diagnosis was used to determine cutoff values. For the statistical analysis, Pearson correlation and ROC curves were used.

RESULTS

When correlating peak systolic velocity and acceleration time to intima media thickness, acceleration time (r = 0.51, p <0.01) was the most valid parameter to detect cavernous atherosclerotic pathology (peak systolic velocity r = -0.18, p = 0.12). This finding was confirmed by a comparison of both parameters to the clinical diagnosis. AUC was 0.59, 95% CI 0.49-0.69 for peak systolic velocity and 0.72 (95% CI 0.62-0.80 for acceleration time). The cutoff point for acceleration time to discriminate between atherosclerotic and nonatherosclerotic erectile dysfunction was determined at acceleration time 100 milliseconds or greater. Sensitivity was 66% and specificity was 71%.

CONCLUSIONS

The results of this study show that acceleration time has more power than peak systolic velocity to diagnose atherosclerotic erectile dysfunction.

Correlation of transrectal ultrasound, computer analysis of transrectal ultrasound and histopathology of radical prostatectomy specimen

A system for computerised analysis of ultrasonographic prostate images (AUDEX=Automated Urologic Diagnostic EXpert system) for the detection of prostate carcinoma was developed. The ultimate goal is to develop a system that is reliable and non-observer dependent. Results of an earlier study with a small group were encouraging and this study describes the results of the computerised analysis in a larger group. Sixty-two patients who were scheduled to undergo a radical prostatectomy were prospectively analysed. The radical prostatectomy specimens were step-sectioned in the transverse plane, corresponding to the ultrasound pictures. Malignant regions identified by each study were quantified and compared by computer calculation. No correlation was observed between ultrasound analysis and pathology result. For the AUDEX analysis an overall sensitivity of 85% and a specificity of 18% with only a diagnostic accuracy of 57% was noticed when presence or absence of malignancy was evaluated by octant (total 496). When applying a cut-off value of 0.5 ml the numbers were 71%, 33% and 55%, respectively. Correlation was significantly better for the ventral octants. In this study the earlier results of our AUDEX system could not be confirmed. Although sensitivity was good, specificity and especially diagnostic accuracy were lower than expected. We have to conclude that the current settings are inappropriate for routine clinical use. Prostate Cancer and Prostatic Diseases (2001) 4, 56-62

Value of contrast ultrasonography in the detection of significant prostate cancer: correlation with radical prostatectomy specimens

BACKGROUND

The presented study has investigated a possible improvement of imaging prostate cancer: three-dimensional contrast-enhanced power Doppler ultrasonography (3D-CE-PDU).

METHODS

Seventy patients with biopsy proven prostate cancer and scheduled for radical retropubic prostatectomy received a 3D-CE-PDU investigation before surgery. Two experts analyzed the ultrasound images. The ultrasound images were correlated to the whole-mount sections of the prostate specimen. The correlation protocol consisted of three evaluation steps.

RESULTS

In total, 153 prostate tumors were found in the 70 prostate specimens: 61 tumors <5 mm, 93 tumors >or=5 mm. The diagnosis of clinical significant and insignificant prostate cancer was made in 85 and 88% of the patients for expert I and II, respectively. Diagnosis by imaging improved from 61% (43 of 70 of the prostate cancers) for standard detection tools to an average 86% (60 of 70 prostate cancers) for 3D-CE-PDU.

CONCLUSION

3D-CE-PDU improves the detection of prostate cancer in this group of prostate cancer patients. The use of 3D-CE-PDU in the clinic is questionable as indications are still unclear.

Microvessel density: correlation between contrast ultrasonography and histology of prostate cancer

OBJECTIVE

Increased microvessel density (MVD) of prostate cancer seems to be associated with poor prognosis and higher stage. Assessment of MVD using noninvasive methods could be of use in the work-up of patients with prostate cancer. The aim of the present study was to correlate three-dimensional contrast-enhanced power Doppler ultrasound (3D-CE-PDU) findings with MVD characteristics of radical prostatectomy specimens.

METHODS

Seven patients with biopsy-proven prostate cancer had 3D-CE-PDU investigations 2-3 weeks after prostate biopsies were taken and prior to radical prostatectomy. The investigations were performed using Levovist contrast agent (Schering AG, Berlin, Germany) in combination with a Voluson 530D ultrasound scanner (Kretz AG, Zipf, Austria). The 7 patients were selected because of lateralization of the contrast enhancement. Histology slides were made of the side with 'contrast enhancement' and of the contralateral 'unenhanced' side and stained according to the catalyzed reporter deposition (CARD) amplification procedure, and MVD parameters were obtained.

RESULTS

In all patients the MVD count of the 'enhanced' side was higher than the MVD count of the 'unenhanced' side, averaging 1.93 times higher. On histology all enhanced lesions proved to contain prostate cancer tissue (average maximum diameter 25 mm (range 17-31)). Two patients had a small bilateral tumor lesion (4 and 5 mm respectively) and in total 5 patients had even smaller satellite lesions (1-2 mm). The smaller lesions were not identified using 3D-CE-PDU.

CONCLUSIONS

The present study shows that 3D power Doppler contrast ultrasonography is a minimally invasive imaging modality, which has the potential to visualize lesions with increased MVD. This property of 3D-CE-PDU could be used in the detection of prostate cancer.

The value of sildenafil as mode of stimulation in pharmaco-penile duplex ultrasonography

The purpose of this work was to assess whether a single intracavernous injection (ICI) of a low dose of the combination of papaverine-phentolamine is replaceable by a high dose of the oral erectogenic agent sildenafil as mode of stimulation during pharmaco-penile duplex ultrasonography (PPDU). Eleven patients with complaints of erectile dysfunction were included in a crossover study. With an interval of two weeks the patients were exposed to ICI with papaverine/phentolamine (3.75 mg/0.125 mg) and oral administration with sildenafil (100 mg) preceding PPDU. Five patients started with ICI. Six patients started with sildenafil. In the sildenafil stimulation mode, visual erotic stimulation (VES) was used to initiate erection. VES was applied by personal LCD monitor. Cut-off values to define sufficient arterial response were: peak flow velocity (PSV) >25 cm/s and acceleration time (AT) <72 ms. Cut-off value to define sufficient veno-occlusion was a resistance index > or =1.00. Statistical analysis of PPDU parameters shows no significant difference between the two modes of stimulation for arterial response (PSV, AT), whereas the resistance index, as a parameter of veno-occlusive response was significantly higher in the sildenafil mode. This finding is confirmed in the clinical translation of the results: two patients with an insufficient arterial response to ICI had a sufficient arterial response to sildenafil and only one patient showed an insufficient arterial response following sildenafil, whereas the response following ICI was sufficient. Analysis of veno-occlusive responses shows remarkable differences between both modes of stimulation. Whereas following the administration of sildenafil all veno-occlusive responses were classified as sufficient, seven patients showed an insufficient veno-occlusive response following ICI. As mode of stimulation in PPDU, high dose sildenafil yields significantly less false positive diagnoses of 'veno-occlusive dysfunction' than intracavernous injection of the combination papaverine/phentolamine. No difference was found in the quality of the arterial response. Based on this study we conclude that sildenafil may replace ICI as mode of stimulation during PPDU.

Three-dimensional grayscale ultrasound: evaluation of prostate cancer compared with benign prostatic hyperplasia

OBJECTIVES

To compare the accuracy of the detection, localization, and staging of prostate cancer using transrectal three-dimensional (3D) grayscale ultrasonography (3D-US) with conventional transrectal two-dimensional grayscale ultrasonography (2D-US).

METHODS

Fifty patients with clinical localized prostate cancer scheduled to undergo radical retropubic prostatectomy and 50 patients with clinical benign prostatic hyperplasia underwent transrectal ultrasound investigations (2D and 3D). The prostate images were retrospectively analyzed by two ultrasound experts unaware of the clinical findings. The images of the prostate cancer group were correlated with the whole-mount histologic specimens of the prostate.

RESULTS

All percentages are given for experts 1 and 2. The sensitivity, specificity, and accuracy for the detection of prostate cancer without considering the definitive localization of the tumor for 2D-US was 72% and 76%, 50% and 54%, and 63% and 64%, respectively; for 3D-US, the rates were 82% and 88%, 40% and 42%, and 61% and 65%. The sensitivity, specificity, and accuracy of the combination of 2D-US with 3D-US was 88% and 90%, 36% and 38%, and 62% and 64%, respectively. The sensitivity, specificity, and accuracy for the exact localization of the prostate tumor for 2D-US was 44% and 46%, 50% and 54%, and 47% and 50%, respectively; for 3D-US, they were 52% and 62%, 40% and 42%, and 46% and 52%. The staging of prostate cancer using 3D-US was correct in 49% (expert 1) and in 57% (expert 2) of patients. No difference was observed between 2D-US and 3D-US for accurate staging. Both experts judged the interpretation of 3D-US images as superior to that of 2D-US images.

CONCLUSIONS

Although 3D-US had statistically significant increased sensitivity in the detection of lesions and decreased specificity compared with 2D-US, 3D-US did not result in significant clinical improvement in the detection and staging of prostate cancer.

Reproducibility of contrast-enhanced transrectal ultrasound of the prostate

Transrectal three-dimensional (3-D) contrast-enhanced power Doppler ultrasound (US) is a novel technique for studying possible prostate malignancy. Before studies can be performed to investigate the clinical validity of the technique, reproducibility of the contrast US studies must be proven. Reproducibility of contrast US was studied in 10 patients with biopsy-proven prostate cancer. The studies performed included static investigations and dynamic investigations of the prostate vasculature. All studies were double performed. The assessment of reproducibility was done objectively using a computer program and, subjectively, by visual assessment. The results indicate high reproducibility of static contrast investigations, for both the objective and subjective assessment. The subjective assessment of the dynamic studies was also highly reproducible. The objective assessment of the dynamic contrast studies, however, was less reproducible, mainly due to motion artefact. We concluded that, especially static 3-D contrast-enhanced, power Doppler investigations of the prostate are highly reproducible.

Intra-prostatic vasculature studies: can they predict the outcome of transurethral microwave thermotherapy for the management of bladder outflow obstruction?

BACKGROUND

Blood perfusion regulates intraprostatic temperatures during transurethral microwave thermotherapy (TUMT). We evaluated baseline intraprostatic vasculature, as a predictor of efficacy of TUMT.

METHODS

Twenty-two patients, with lower urinary tract symptoms (LUTS) suggestive of bladder outflow obstruction, were treated with TUMT (Prostatron). At baseline, three-dimensional contrast-enhanced power-flow-Doppler prostate ultrasonography (3D-CE-PFD) was performed. Assuming that the percentage of perfused area (PPA) is a realistic measure of blood flow, it was used to quantify intraprostatic vasculature.

RESULTS

The median (range) age, prostate size, and energy delivered were 66 years (48-80), 47 cm(3) (30-121), 110 kJ (29-136), respectively. The response was 77% (5 failures). The median (range) PPA was 2.76% (0.7-11.3). No difference in PPA among good and poor responders was detected nor was any correlation between PPA and baseline parameters.

CONCLUSIONS

The baseline intraprostatic vascularization, documented by CE-PFD studies, has no predictive value for the efficacy of TUMT. It seems that "static" baseline blood flow does not reflect the "dynamic" thermoregulatory role of blood flow during treatment.

alpha-Blockade improves symptoms suggestive of bladder outlet obstruction but fails to relieve it

PURPOSE

We investigated the effect of the alpha-blockers alfuzosin, terazosin and tamsulosin on urodynamic parameters after 6 months of therapy.

MATERIALS AND METHODS

Between February 1992 and June 1998, 163 patients with lower urinary tract symptoms suggestive of bladder outlet obstruction were treated with alfuzosin (60), terazosin (66) and tamsulosin (37). Patients were evaluated with urodynamic studies, including pressure flow analysis, before treatment and after 6 months of therapy. Initially, all patients were also assessed by the International Prostate Symptom Score questionnaire and measurement of urinary flow rate.

RESULTS

The majority of patients had no clear improvement in obstructive parameters, regardless of the alpha-blocker used, as urethral resistance factor and detrusor pressure maximum flow rate decreased by only 4 cm. H2O. There was a clear subjective and statistically significant decrease in International Prostate Symptom Score and quality of life scores of 6 and 2 points, respectively. No relevant statistical difference was noted among the effects of the 3 alpha-blockers on relieving symptoms or improving urodynamic parameters of obstruction.

CONCLUSIONS

The alpha-blockers are effective for treating symptoms suggestive of bladder outlet obstruction in patients presenting with lower urinary tract symptoms but not for treating the obstruction.

Computerized artifact detection and correction of uroflow curves: towards a more consistent quantitative assessment of maximum flow

OBJECTIVES

To evaluate a computerized method of artifact detection and correction of uroflow and compare the quantitative assessment of maximum flow obtained by the computer with visual correction by experts.

METHODS

A total of 90 randomly chosen flows was scanned into the computer whereafter automated artifact detection and correction was performed according to pre-established rules implemented in the software. Three experts visually corrected the flows using the same artifact detection and correction specifications as the computer. Measuring agreement between different methods of assessment of maximum flow was evaluated by calculating the difference and the standard deviation (SD) of the differences. The repeatability of assessing the maximum flow value by the computer and by expert 1 was assessed by calculating the difference between 2 readings and the coefficient of repeatability.

RESULTS

The coefficient of repeatability of maximum flow after detection and correction of artifacts by the computer (0.38 ml/s) was slightly better when compared with the coefficient of repeatability between 2 observations by 1 expert (1.12 ml/s). The interobserver variation for the quantitative assessment of maximum flow appeared to be great. A total of 51% of the maximum flow values assessed by expert 2 was 1 ml/s or more greater than those assessed by expert 1. When comparing the results of the computer with those of the experts, the mean value of maximum flow from expert 1 was 0.71 ml/s smaller than the computer value (p < 0.01), the mean value from expert 2 was 0.53 ml/s greater (p < 0.01) and the mean value from expert 3 was not significantly different (0.25 ml/s greater). The SD of maximum flow after correction by the computer was 0.3 ml/s smaller than the SD of the raw data from the flowmeter and the corrected values by 2 experts.

CONCLUSIONS

Computerized artifact detection and correction eliminates an important fraction of the variability of manually corrected maximum flow values. This may lead to smaller sample size requirements, especially in studies where the primary objective is to assess a small (+/- 1 ml/s) difference in mean maximum flow between groups.

Intraprostatic temperature monitoring during transurethral microwave thermotherapy: status and future developments

Transurethral microwave thermotherapy is being applied as a minimally invasive treatment for alleviating the symptoms of urinary outlet obstruction associated with benign prostatic hyperplasia. Treatment progress has traditionally been guided in its effective power by rectally and urethrally measured temperatures, whereas intraprostatic temperatures would be preferred for feedback purposes. A critical evaluation is presented of intraprostatic thermometry techniques that have been suggested, the techniques currently being used and investigated, and the problems that remain to be solved. Techniques for noninvasive temperature measurement and detecting tissue response during thermal therapy are discussed in more detail. Results presented in the literature have shown magnetic resonance imaging and ultrasonic imaging to be adequate thermometry modalities. For treatment monitoring of transurethral microwave thermotherapy, ultrasonic imaging is especially promising. Future research will indicate whether the promise evolves into a sound clinical technique.