Evaluation of visualization of the prostate gland in vibro-elastography images

In this paper, vibro-elastography (VE), an ultrasound-based method that creates images of tissue viscoelasticity contrast, is evaluated as an imaging modality to visualize and segment the prostate. We report a clinical study to characterize the visibility of the prostate in VE images and the ability to detect the boundary of the gland. Measures for contrast, edge strength characterized by gradient and statistical intensity change at the edge, and the continuity of the edges are proposed and computed for VE and B-mode ultrasound images. Furthermore, using MRI as the gold standard, we compare the error in the computation of the volume of the gland from VE and B-mode images. The results demonstrate that VE images are superior to B-mode images in terms of contrast, with an approximately six fold improvement in contrast-to-noise ratio, and in terms of edge strength, with an approximately two fold improvement in the gradient in the direction normal to the edge. The computed volumes show that the VE images provide an accurate 3D visualization of the prostate with volume errors that are slightly lower than errors computed based on B-mode images. The total gland volume error is 8.8±2.5% for VE vs. MRI and 10.3±4.6% for B-mode vs. MRI, and the total gland volume difference is -4.6±11.1% for VE vs. MRI and -4.1±17.1% for B-mode vs. MRI, averaged over nine patients and three observers. Our results show that viscoelastic mapping of the prostate region using VE images can play an important role in improving the anatomic visualization of the prostate and has the potential of becoming an integral component of interventional procedures such as brachytherapy.     

Contrast-Specific Spherical Lesion Phantoms and Ancillary Analysis Software for the Objective Evaluation of Transrectal Ultrasound System Contrast Detectability

Brachytherapy is an efficacious treatment option because of its benefits for patient recovery, dose localization and conformity, but these favorable outcomes can be ensured only if the transrectal ultrasound (TRUS) system is optimized for the specific application of ultrasound-guided prostate brachytherapy. The ability to delineate the prostate from surrounding tissue during TRUS-guided prostate brachytherapy is vital for treatment planning, and consequently, so is the contrast resolution. This study describes the development of task-specific contrast-detail phantoms with clinically relevant contrast and spherical target sizes for contrast-detail performance evaluation of TRUS systems used in the brachytherapy procedure. The procedure for objective assessment of the contrast detectability of the TRUS systems is also described; a program was developed in MATLAB (R2017a, The MathWorks, Natick, MA, USA) to quantitatively analyze image quality in terms of the lesion signal-to-noise ratio (LSNR) and validated with representative control test images. The LSNR of the Hitachi EUB-7500A (2013, Hitachi, Ltd, Tokyo, Japan) TRUS system was measured on sagittal and transverse TRUS images of the contrast-detail phantoms described in this work. Results revealed the efficacy of the device as an image quality evaluation tool and the impact of the size, depth and relative contrast of the targets to the surrounding tissue on the contrast detectability of a TRUS system for both transducer arrays. The MATLAB program objectively measured the contrast detectability of the TRUS system and has the potential to determine optimized imaging parameters that could be designed as part of standardization of the imaging protocol used in TRUS-guided prostate brachytherapy for prostate cancer.     

Tumour-Targeted Treatment Intensification for Prostate Cancer Using Magnetic Resonance Imaging Guidance

IntroductionLocal control in prostate cancer may be improved with targeted dose escalation to regions with high tumour burden. Multiparametric magnetic resonance imaging (mpMRI) combined with MRI-guided biopsies may aid in defining tumour-dense regions before radiation therapy. Deformable registration techniques may be used to map these tumour regions onto the radiotherapy planning MRI. Radiation therapy delivery techniques such as volumetric modulated arc therapy and high-dose-rate brachytherapy may allow for highly conformal dose escalation, and when coupled with image-guided radiation delivery (ie, cone beam computed technology and fiducial markers), may allow high-precision dose-escalated treatment.MethodsEligible prostate cancer patients were enrolled on a prospective trial of tumour dose escalation. Two strategies were investigated: (1) an integrated boost to external beam radiation for a total tumour dose of 95 Gy in 38 fractions or (2) a focal high-dose-rate boost of 10 Gy before 76 Gy in 38 fractions external beam radiation. Patients underwent MRI-guided biopsy with fiducial marker placement before therapy. mpMRI was acquired and used in conjunction with a non-endorectal coil T2 MRI and computed technology simulation images to define the gross tumour volume via a deformable registration approach for intraprostatic tumour dose escalation.ResultsA case example for each dose escalation strategy illustrates the tumour-targeted approach using MRI guidance.ConclusionsCombining mpMRI sequences with a deformable registration approach may aid in more accurate and reproducible definition of tumour-dense regions. This novel process coupled with daily image guidance may allow high-precision dose-escalated tumour-targeted radiotherapy for prostate cancer.     

Recent developments in tissue-type imaging (TTI) for planning and monitoring treatment of prostate cancer

Because current methods of imaging prostate cancer are inadequate, biopsies cannot be effectively guided and treatment cannot be effectively planned and targeted. Therefore, our research is aimed at ultrasonically characterizing cancerous prostate tissue so that we can image it more effectively and thereby provide improved means of detecting, treating and monitoring prostate cancer. We base our characterization methods on spectrum analysis of radiofrequency (rf) echo signals combined with clinical variables such as prostate-specific antigen (PSA). Tissue typing using these parameters is performed by artificial neural networks. We employed and evaluated different approaches to data partitioning into training, validation, and test sets and different neural network configuration options. In this manner, we sought to determine what neural network configuration is optimal for these data and also to assess possible bias that might exist due to correlations among different data entries among the data for a given patient. The classification efficacy of each neural network configuration and data-partitioning method was measured using relative-operating-characteristic (ROC) methods. Neural network classification based on spectral parameters combined with clinical data generally produced ROC-curve areas of 0.80 compared to curve areas of 0.64 for conventional transrectal ultrasound imaging combined with clinical data. We then used the optimal neural network configuration to generate lookup tables that translate local spectral parameter values and global clinical-variable values into pixel values in tissue-type images (TTIs). TTIs continue to show cancerous regions successfully, and may prove to be particularly useful clinically in combination with other ultrasonic and nonultrasonic methods, e.g., magnetic-resonance spectroscopy.     

Multiparametric Ultrasound for Targeting Prostate Cancer: Combining ARFI,SWEI, QUS and B-Mode

Diagnosing prostate cancer through standard transrectal ultrasound (TRUS)-guided biopsy is challenging because of the sensitivity and specificity limitations of B-mode imaging. We used a linear support vector machine (SVM) to combine standard TRUS imaging data with acoustic radiation force impulse (ARFI) imaging data, shear wave elasticity imaging (SWEI) data and quantitative ultrasound (QUS) midband fit data to enhance lesion contrast into a synthesized multiparametric ultrasound volume. This SVM was trained and validated using a subset of 20 patients and tested on a second subset of 10 patients. Multiparametric US led to a statistically significant improvements in contrast, contrast-to-noise ratio (CNR) and generalized CNR (gCNR) when compared with standard TRUS B-mode and SWEI; in contrast and CNR when compared with MF; and in CNR when compared with ARFI. ARFI, MF and SWEI also outperformed TRUS B-mode in contrast, with MF outperforming B-mode in CNR and gCNR as well. ARFI, although only yielding statistically significant differences in contrast compared with TRUS B-mode, captured critical qualitative features for lesion identification. Multiparametric US enhanced lesion visibility metrics and is a promising technique for targeted TRUS-guided prostate biopsy in the future.     

Imaging of prostate cancer

Prostate cancer diagnosis and treatment is fast emerging as a major health care issue in the United States. However, there are great uncertainties about the value of specific tests and therapies. Imaging modalities play a major role in the current management of patients with prostate cancer and this role is likely to expand in the future. Transrectal ultrasound is used to identify non-palpable lesions, direct systematic biopsies, determine gland volume and stage prostate cancers. For staging skeletal metastases, the bone scan is acknowledged as the best method, however controversy surrounds its routine use in patients with low prostate specific antigen (PSA) values. Computed tomography (CT) and transrectal ultrasound have limited value in detecting extracapsular disease but CT can be used in conjunction with percutaneous biopsy to identify nodal metastases. The role of Endorectal coil MRI is currently evolving in the wake of a disappointing multiinstitutional trial but MRI still holds the most promise for accurately detecting local extent of prostate cancer. New radiolabeled techniques with monoclonal antibodies and peptide imaging are also having early but promising results. The role of imaging in prostate cancer is continuing to evolve as technology and knowledge about prostate cancer biology improves and health care economics force a more judicious use of imaging resources.     

MR-guided interventions for prostate cancer

MR imaging is currently the most effective diagnostic imaging tool for visualizing the anatomy and pathology of the prostate gland. Currently, the practicality and cost effectiveness of transrectal ultrasound dominates image guidance for needle-based prostate interventions. Challenges to the integration of diagnostic and interventional MR imaging have included the lack of real-time feed-back, the complexity of the imaging technique, and limited access to the perineum within the geometric constraints of the MR imaging scanner. Two basic strategies have been explored and clinically demonstrated in the literature: (1) coregistration of previously acquired diagnostic MR imaging to interventional TRUS or open scanner MR images, and (2) stereotactic needle interventions within conventional diagnostic scanners using careful patient positioning or the aid of simple manipulators. Currently, researchers are developing techniques that render MR imaging the method of choice for the direct guidance of many procedures. This article focuses on needle-based interventions for prostate cancer, including biopsy, brachytherapy, and thermal therapy With rapid progress in biologic imaging of the prostate gland, the authors believe that MR imaging guidance will play an increasing role in the diagnosis and treatment of prostate cancer.     

MR-guided interventions of the prostate gland.

In recent years MR imaging has played an increasingly important role in the diagnosis and treatment of prostate cancer. MR imaging of the prostate allows a clear delineation of the anatomic structures and prostate tumors when performing interventions such as biopsies, brachytherapy or thermal therapy of the prostate gland. MRI robotic assistance will improve the accuracy of the interventions. Due to the advantages of MR imaging MR-guided prostate interventions will play an increasing role in future.     

Planning,simulation and assistance with intraoperative MRI

This paper introduces some of the authors' recent attempts to enhance image-guided treatment in intraoperative magnetic resonance imaging (MRI). These include the deformable registration of preoperative images obtained by 1.5 Tesla MRI to the intraoperative images, and a needle-holding robotic system that is MR-compatible and optimized to work with intraoperative MRI. The role of deformable registration is to enhance intraoperative planning and simulation, and the robotic system is to systematically link the result of such planning and simulation to active surgical assistance. The former was retrospectively examined in prostate cancer biopsy cases and statistically suggested that deformable registration significantly improved the quality of registration. The latter, which is planned to be applied to prostate brachytherapy, was found to have good MR compatibility and its maneuvering had no adverse effect on the imaging and vice versa.     

超声引导下125Ⅰ放射性粒子植入治疗前列腺癌疗效观察

目的 探讨超声引导下经会阴穿刺植入125Ⅰ放射性粒子治疗前列腺癌的疗效.方法 40例前列昧癌患者在直肠超声引导下行经会阴125Ⅰ粒子植入术.其中29例行单纯粒子治疗.11例术后加外放疗.首先对前列腺进行超声扫描,将图像传送到计算机制定种植治疗计划,并在种植前计算放射线对前列腺体积的有效覆盖,以患者血前列腺特异性抗原(prostate-specific antigen,PSA)作为疗效评价标准.结果 粒子植入术前和术后各时期PSA值相比明显下降(差异均有显著统计学意义.P≤0.01),其中10人14次出现PSA反弹,而单纯粒子组与联合治疗患者组PsA反弹发生率差异无统计学意义(22.2％vs 27.3％).结论 超声引导经会阴125Ⅰ放射性粒子植入治疗前列腺癌具有安全、微创、并发症发生率低等优点.     

Ultrasonic multifeature tissue characterization for prostate diagnostics

A new system for prostate diagnostics based on multifeature tissue characterization is proposed. Radiofrequency (RF) ultrasonic echo data are acquired during the standard transrectal ultrasound (US) imaging examination. Nine spectral, texture, first order and morphologic parameters are calculated and fed into two adaptive neuro-fuzzy inference systems (FIS) working in parallel. The outputs of the FISs are fed into a postprocessing procedure evaluating contextual information before being combined to form a malignancy map in which areas of high cancer probability are marked in red. The malignancy map is presented to the physician during the examination to improve the early detection of prostate cancer. The system has been evaluated on 100 patients undergoing radical prostatectomy. The ROC curve area using leave-one-out cross-validation over patients is A(Z) = 0.86 when distinguishing between hyperechoic and hypoechoic tumors and normal tissue and A(Z) = 0.84 when distinguishing between isoechoic tumors and healthy tissue, respectively. Tumors that are not visible in the conventional B-mode image can be located. Diagnosis of the prostate carcinoma using multifeature tissue characterization in combination with US imaging allows the detection of tumors at an early stage. Also, biopsy guidance and therapy planning can be improved.     

前列腺癌分子影像学诊断与治疗进展

前列腺癌严重威胁着男性健康,近年来我国前列腺癌的发病率也迅速增加,早期发现前列腺癌对于提高生存率具有十分积极的意义。目前各前列腺癌指南中仍需通过超声引导下的前列腺活检确诊,再通过主动监测、根治性切除术、放疗及局部放疗等手段进行治疗。但前列腺活检增加了尿潴留、血尿等不必要的风险,还会遗漏多达1/3的癌组织,且目前的治疗方法因缺乏特异性而对患者进行过度或不足的治疗。近年来,对前列腺癌的诊断和治疗已经迈入分子水平,通过分子影像学进行无创精准的诊断和治疗展现出巨大的发展前景。本文将从核医学分子成像、MR分子成像、光学分子成像、超声分子成像4种常见分子影像学技术在前列腺癌的应用进展进行回顾并作一综述。      

超声引导下~(125)I放射性粒子植入治疗前列腺癌疗效观察

目的探讨超声引导下经会阴穿刺植入125I放射性粒子治疗前列腺癌的疗效。方法 40例前列腺癌患者在直肠超声引导下行经会阴125I粒子植入术。其中29例行单纯粒子治疗,11例术后加外放疗。首先对前列腺进行超声扫描,将图像传送到计算机制定种植治疗计划,并在种植前计算放射线对前列腺体积的有效覆盖,以患者血前列腺特异性抗原(prostate-specific antigen,PSA)作为疗效评价标准。结果粒子植入术前和术后各时期PSA值相比明显下降(差异均有显著统计学意义,P≤0.01),其中10人14次出现PSA反弹,而单纯粒子组与联合治疗患者组PSA反弹发生率差异无统计学意义(22.2%vs 27.3%)。结论超声引导经会阴125I放射性粒子植入治疗前列腺癌具有安全、微创、并发症发生率低等优点。     

Prostate boundary detection and volume estimation using TRUS images for brachytherapy applications

Objective: Authors propose a semi-automatic segmentation algorithm for three-dimensional prostate boundary detection from trans-rectal ultrasound images. As a part of brachytherapy treatment with seeds for early stage prostate cancer, a patient’s prostate is scanned using a trans-rectal ultrasound probe, its boundary is manually outlined, and its volume is estimated for dosimetry purposes. Proposed algorithm requires a reduced amount of radiologist’s input, and thus speeds up the surgical procedure. Methods: The proposed segmentation algorithm utilizes texture differences between ultrasound images of the prostate and the surrounding tissues. It is carried out in the polar coordinate system and uses three-dimensional data correlation to improve the smoothness and reliability of the segmentation. The algorithm is applied to axial trans-rectal ultrasound images and the results are compared to the “ground truth” set by manual prostate boundary outlining (by experienced radiologist). Method is validated on six patients. Results: In our tests, the proposed algorithm estimated prostate volume within 95% of the original radiologist’s estimate. Conclusions: The boundary segmentation obtained from the algorithm can reduce manual input by a factor of 3, without significantly affecting the accuracy of the segmentation. The reduction in the manual input reduces the overall brachytherapy procedure time.     

The efficacy of transrectal ultrasound and prostate cancer

An increased interest in the diagnosis and treatment of prostate cancer, particularly in the last few years, is reflected in the literature. Numerous articles have been published since 1980 on the subject of imaging of the prostate gland. This article is a review of transrectal ultrasound and its efficacy in the diagnosis and treatment of prostate cancer. Included is a review of the normal prostate anatomy, typical and atypical sonographic features, clinical and radiographic staging of prostate cancer, efficacy of the digital rectal examination, role of ultrasound in prostate cancer screening, surgical treatment, and radiotherapy of prostate cancer.     

125I微粒子植入术联合内分泌治疗局部晚期前列腺癌(附14例报告)

目的探讨放射性微粒子植入术联合内分泌治疗局部晚期前列腺癌。方法回顾14例局部晚期前列腺癌患者,术前经直肠超声(TRUS)确定前列腺体积,描绘前列腺的轮廓和横断面,运用三维治疗计划系统制定放射治疗方案,在TRUS引导下,植入放射性粒子125I。结果14例患者随访18～24月,治疗后PSA值、前列腺体积、IPSS评分均较术前有明显改善(P<0.05),一例出现放射性直肠炎并发症,经中药保留灌肠治疗后好转。结论TRUS引导下125I粒子植入联合内分泌治疗是治疗晚期局部前列腺癌的一种可行的方法,有较好的疗效。     

实时双平面立体成像超声引导经直肠前列腺穿刺活检术临床评价

目的探讨实时双平面立体成像超声引导经直肠前列腺多点穿刺活检的临床价值。方法回顾分析255例实时双平面立体成像超声引导下经直肠前列腺多点穿刺活检患者的临床资料。结果本组255例中确诊为前列腺癌90例，良性前列腺增生142例，慢性前列腺炎21例，正常前列腺组织2例。所有接受穿刺的患者无1例出现严重的并发症。结论实时双平面立体成像超声引导经直肠前列腺多点穿刺活检是一种安全，有效的方法，有助于提高前列腺癌的早期诊断率，极具临床应用价值。     

Short-lag spatial coherence beamforming of photoacoustic images for enhanced visualization of prostate brachytherapy seeds

Prostate brachytherapy, administered by implanting tiny radioactive seeds to treat prostate cancer, currently relies on transrectal ultrasound imaging for intraoperative visualization of the metallic seeds. Photoacoustic (PA) imaging has been suggested as a feasible alternative to ultrasound imaging due to its superior sensitivity to metal surrounded by tissue. However, PA images suffer from poor contrast when seeds are distant from the light source. We propose a transperineal light delivery method and investigate the application of a short-lag spatial coherence (SLSC) beamformer to enhance low-contrast photoacoustic signals that are distant from this type of light source. Performance is compared to a conventional delay-and-sum beamformer. A pure gelatin phantom was implanted with black ink-coated brachytherapy seeds and the mean contrast was improved by 3–25 dB with the SLSC beamformer for fiber-seed distances ranging 0.6–6.3 cm, when approximately 10% of the receive aperture elements were included in the short-lag sum. For fiber-seed distances greater than 3–4 cm, the mean contrast-to-noise ratio (CNR) was approximately doubled with the SLSC beamformer, while mean signal-to-noise ratios (SNR) were mostly similar with both beamformers. Lateral resolution was decreased by 2 mm, but improved with larger short-lag values at the expense of poorer CNR and SNR. Similar contrast and CNR improvements were achieved with an uncoated brachytherapy seed implanted in ex vivo tissue. Results indicate that the SLSC beamformer has potential to enhance the visualization of prostate brachytherapy seeds that are distant from the light source.OCIS codes: (170.5120) Photoacoustic imaging, (100.0100) Image processing, (100.3010) Image reconstruction techniques, (030.1640) Coherence, (170.1650) Coherence imaging, (170.7230) Urology