Automated prostate recognition: a key process for clinically effective robotic prostatectomy

Clinical trials of PROBOT, a robotic system for prostate surgery, have shown that robotic surgery of soft tissue can be successful. Monitoring of the progress of the resection has shown to be a necessary feature of an effective robotic system for prostate surgery. It should provide the surgeon with a reliable method of assessing the cavity during resection. An automatic system for intraoperative monitoring of the progress of the resection during robotic prostatectomy consists of two subsystems: real-time intraoperative imaging of the prostate and automatic identification of the contour of the gland on each image. The development of a fully automatic scheme for prostate recognition on transurethral ultrasound scans is reported. A genetic algorithm has been developed to automatically adjust a model of the prostate boundary until an optimum fit to the prostate in a given image is obtained. An analysis of its performance on 22 different ultrasound images showed an average error of 6.21 mm. Use of a genetic algorithm and a constrained prostate model have shown to be a robust way to automatically identify the prostate in ultrasound images. The scheme is able to produce approximate prostate boundaries, without any human intervention, on ultrasound scans of varying quality. In addition to soft tissue robotic surgery, the genetic algorithm technique is also applicable to a wide range of computer assisted surgical techniques.     

Automated prostate recognition: a key process for clinically effective robotic prostatectomy

Clinical trials of PROBOT, a robotic system for prostate surgery, have shown that robotic surgery of soft tissue can be successful. Monitoring of the progress of the resection has shown to be a necessary feature of an effective robotic system for prostate surgery. It should provide the surgeon with a reliable method of assessing the cavity during resection. An automatic system for intraoperative monitoring of the progress of the resection during robotic prostatectomy consists of two subsystems: real-time intraoperative imaging of the prostate and automatic identification of the contour of the gland on each image. The development of a fully automatic scheme for prostate recognition on transurethral ultrasound scans is reported. A genetic algorithm has been developed to automatically adjust a model of the prostate boundary until an optimum fit to the prostate in a given image is obtained. An analysis of its performance on 22 different ultrasound images showed an average error of 6.21 mm. Use of a genetic algorithm and a constrained prostate model have shown to be a robust way to automatically identify the prostate in ultrasound images. The scheme is able to produce approximate prostate boundaries, without any human intervention, on ultrasound scans of varying quality. In addition to soft tissue robotic surgery, the genetic algorithm technique is also applicable to a wide range of computer assisted surgical techniques.     

Application of reinforcement learning for segmentation of transrectal ultrasound images

Background  

Among different medical image modalities, ultrasound imaging has a very widespread clinical use. But, due to some factors, such as poor image contrast, noise and missing or diffuse boundaries, the ultrasound images are inherently difficult to segment. An important application is estimation of the location and volume of the prostate in transrectal ultrasound (TRUS) images. For this purpose, manual segmentation is a tedious and time consuming procedure.     

MRI-compatible transurethral ultrasound system for the treatment of localized prostate cancer using rotational control

Magnetic resonance imaging (MRI)-guided transurethral ultrasound therapy is a potential minimally invasive treatment for localized prostate cancer offering precise targeting of tissue within the gland, short treatment times, and the capability to quantify the spatial heating pattern delivered during therapy. A significant challenge in MRI-guided ultrasound therapy is the design and construction of MRI-compatible equipment capable of operation in a closed-bore MR imager. We describe a prototype system developed for MRI-guided transurethral ultrasound therapy and characterize the performance of the different components including the heating applicator design, rotational motor, and radio frequency electronics. The ultrasound heating applicator described in this study incorporates a planar transducer and is capable of producing high intensity ultrasound energy in a localized region of tissue. Results demonstrated that the heating applicator exhibits excellent MRI-compatibility, enabling precise MR temperature measurements to be acquired as close as 6 mm from the device. Simultaneous imaging and rotational motion was also possible during treatment using a motor based on piezoelectric actuators. Heating experiments performed in both phantoms and in a canine model with the prototype system verified the capability to perform simultaneous MR imaging and therapy delivery with this system. Real-time control over therapy using MR temperature measurements acquired during heating can be implemented to achieve precise patterns of thermal damage within the prostate gland. The technical feasibility of using the system developed in this study for MRI-guided transurethral ultrasound therapy in a closed-bore MR imager has been demonstrated.     

Experimental study of transurethral robotic laser resection of the prostate using the LaserTrode lightguide

A longer operating time and steeper learning curve in mastering the techniques for transurethral laser resection of the prostate are the main problems faced by surgeons in addition to the existing ones in standard transurethral resection of the prostate (TURP). However, these disadvantages can be alleviated with the introduction of a treatment procedure designed and developed based on an integrated system of computer, robotics and laser technology. In vitro experiments were carried out to determine variables affecting the vaporization and coagulation lesions, in order to study the effectiveness and feasibility of robotics for this procedure. Human cadaveric prostates and fresh tauted chicken breast tissues were irradiated with different parameters using the LaserTrode lightguide in contact with the tissue. The effects of irrigant flow rate, fiber/tissue angle of inclination, number of passes, direction, speed and power of lase on the volume of tissue vaporized and coagulated, were assessed. The final phase of the experiments includes executing the robotic motion plan for the laser resection procedure on the human cadaveric prostate tissue embedded in an anatomically alike prostate phantom. It was concluded from our study that power and speed of lase are the most significant parameters influencing the volume of the vaporized and coagulated lesion. Comparison of removal rate using the new treatment procedure of robotic laser resection of the prostate with TURP and HoLRP evinced equivalent results.     

Motorised resection device for transurethral resection of the prostate: A laboratory evaluation

Transurethral resection of the prostate is the most common method of relieving urinary outflow obstruction secondary to prostatic enlargement. However, this procedure can be responsible for various complications, including irrigant-fluid absorption and blood loss, both of which are strongly dependent on operation duration time. To reduce the latter, a new resection device has been designed for transurethral prostatectomy. The device basically consists of a rotating cutting loop controlled externally, with three degrees of freedom, to fit the adenoma shape. Its performance is assessed in vitro by drilling conical and semi-ellipsoidal cavities in agar gel models. The mean difference between the calculated and obtained cavity volumes is 3% (SD=0.9%). The volume cutting rate, found to be independent of the type of cavity drilled, is equal to 2.9±0.3 cm³ min⁻¹. The advantages of this motorised resection device prototype are reduction in operation duration and accuracy of the resected volume. In vivo resection of a 20 cm³ adenoma in less than 15 min can be expected.     

Design and evaluation of a 3D transrectal ultrasound prostate biopsy system

Biopsy of the prostate using ultrasound guidance is the clinical gold standard for diagnosis of prostate adenocarcinoma. The current prostate biopsy procedure is limited to using 2D transrectal ultrasound (TRUS) images to target biopsy sites and record biopsy core locations for postbiopsy confirmation. Localization of the 2D image in its actual 3D position is ambiguous and limits procedural accuracy and reproducibility. We have developed a 3D TRUS prostate biopsy system that provides 3D intrabiopsy information for needle guidance and biopsy location recording. The system conforms to the workflow and imaging technology of the current biopsy procedure, making it easier for clinical integration. In this paper, we describe the system design and validate the system accuracy by performing mock biopsies on US/CT multimodal patient-specific prostate phantoms. Our biopsy system generated 3D patient-specific models of the prostate with volume errors less than 3.5% and mean boundary errors of less than 1 mm. Using the 3D biopsy system, needles were guided to within 2.3 +/- 1.0 mm of 3D targets and with a high probability of biopsying clinically significant tumors. The positions of the actual biopsy sites were accurately localized to within 1.5 +/- 0.8 mm.     

Prostate segmentation by feature enhancement using domain knowledge and adaptive region based operations

Estimation of prostate location and volume is essential in determining a dose plan for ultrasound-guided brachytherapy, a common prostate cancer treatment. However, manual segmentation is difficult, time consuming and prone to variability. In this paper, we present a semi-automatic discrete dynamic contour (DDC) model based image segmentation algorithm, which effectively combines a multi-resolution model refinement procedure together with the domain knowledge of the image class. The segmentation begins on a low-resolution image by defining a closed DDC model by the user. This contour model is then deformed progressively towards higher resolution images. We use a combination of a domain knowledge based fuzzy inference system (FIS) and a set of adaptive region based operators to enhance the edges of interest and to govern the model refinement using a DDC model. The automatic vertex relocation process, embedded into the algorithm, relocates deviated contour points back onto the actual prostate boundary, eliminating the need of user interaction after initialization. The accuracy of the prostate boundary produced by the proposed algorithm was evaluated by comparing it with a manually outlined contour by an expert observer. We used this algorithm to segment the prostate boundary in 114 2D transrectal ultrasound (TRUS) images of six patients scheduled for brachytherapy. The mean distance between the contours produced by the proposed algorithm and the manual outlines was 2.70 +/- 0.51 pixels (0.54 +/- 0.10 mm). We also showed that the algorithm is insensitive to variations of the initial model and parameter values, thus increasing the accuracy and reproducibility of the resulting boundaries in the presence of noise and artefacts.     

Method for MRI-guided conformal thermal therapy of prostate with planar transurethral ultrasound heating applicators

A method for conformal prostate thermal therapy using transurethral ultrasound heating applicators incorporating planar transducers is described. The capability to shape heating patterns to the geometry of the prostate gland from a single element in a multi-element heating applicator was evaluated using Bioheat transfer modelling. Eleven prostate geometries were obtained from patients who underwent MR imaging of the prostate gland prior to radical prostatectomy. Results indicate that ultrasound heating applicators incorporating multi-frequency planar transducers (4 x 20 mm, f = 4.7 MHz, 9.7 MHz) are capable of shaping thermal damage patterns to the geometry of individual prostates. A temperature feedback control algorithm has been developed to control the frequency, rotation rate and applied power level from transurethral heating applicators based on measurements of the boundary temperature during heating. The discrepancy between the thermal damage boundary and the target boundary was less than 5 mm, and the transition distance between coagulation and normal tissue was less than 1 cm. Treatment times for large prostate volumes were less than 50 min, and perfusion did not have significant impact on the control algorithm. Rectal cooling will play an important role in reducing undesired heating near the rectal wall. Experimental validation of the simulations in a tissue-mimicking gel phantom demonstrated good agreement between the predicted and generated patterns of thermal damage.     

Correlation of digital rectal examination, prostate specific antigen, and transrectal ultrasound in prostate carcinoma in African Americans.

Since there is general agreement that screening for prostate cancer should be carried out, at least for high-risk individuals, there should be little debate that African-American men should be screened. Current screening guidelines include the two most cost-effective methods of early detection, digital rectal examination and prostate specific antigen. The use of transrectal ultrasound and guided biopsy improves the yield. This article reports on the findings of 50 African-American patients with prostatic carcinoma diagnosed by sonographically guided biopsy in a single, community urology practice. Overall, prostate specific antigen was elevated in 94%, digital rectal examination was positive in 60%, and transrectal ultrasound was positive in 78%. A focal hypoechoic lesion was demonstrated in 58%. When the site of tumor, as specified in the pathology report, was correlated with the findings on digital rectal examination and transrectal ultrasound, both digital rectal examination and transrectal ultrasound were positive in 45%. Transrectal ultrasound was positive when digital rectal examination was negative in 30%. Digital rectal examination was positive when ultrasound was not in 14%. Random biopsy revealed areas of carcinoma that were not detected by digital rectal examination nor ultrasound in 40%. We conclude that even though random biopsy significantly improves the detection of prostate carcinoma, sonographic guidance is beneficial to systematically biopsy the gland and to avoid omission of characteristic lesions during random samplings.     

The continuing role of fine-needle aspiration of the prostate gland into the 21st century: a tribute to Torsten Löwhagen

A brief review of the history of transrectal fine-needle aspiration (FNA) of the prostate gland is reported in this article; the authors'experience of FNA during the last 20 yr is described also. Despite the worldwide acceptance of the thin-needle core approach, the use of transrectal FNA of palpable abnormalities of the prostate still is advocated because it is cheaper, faster, easier to perform, and results in lower morbidity than any other technique so far developed. High sensitivity, specificity, and efficacy account for its reliability. Appropriate training in performing transrectal FNA of the prostate and in interpreting the smears is, of course, essential. Transrectal FNA should be the initial diagnostic procedure for suspected prostatic cancer and will continue to be a useful diagnostic tool in the 21st century.     

3D conformal MRI-controlled transurethral ultrasound prostate therapy: validation of numerical simulations and demonstration in tissue-mimicking gel phantoms

MRI-controlled transurethral ultrasound therapy uses a linear array of transducer elements and active temperature feedback to create volumes of thermal coagulation shaped to predefined prostate geometries in 3D. The specific aims of this work were to demonstrate the accuracy and repeatability of producing large volumes of thermal coagulation (>10 cc) that conform to 3D human prostate shapes in a tissue-mimicking gel phantom, and to evaluate quantitatively the accuracy with which numerical simulations predict these 3D heating volumes under carefully controlled conditions. Eleven conformal 3D experiments were performed in a tissue-mimicking phantom within a 1.5T MR imager to obtain non-invasive temperature measurements during heating. Temperature feedback was used to control the rotation rate and ultrasound power of transurethral devices with up to five 3.5 × 5 mm active transducer elements. Heating patterns shaped to human prostate geometries were generated using devices operating at 4.7 or 8.0 MHz with surface acoustic intensities of up to 10 W cm(-2). Simulations were informed by transducer surface velocity measurements acquired with a scanning laser vibrometer enabling improved calculations of the acoustic pressure distribution in a gel phantom. Temperature dynamics were determined according to a FDTD solution to Pennes' BHTE. The 3D heating patterns produced in vitro were shaped very accurately to the prostate target volumes, within the spatial resolution of the MRI thermometry images. The volume of the treatment difference falling outside ± 1 mm of the target boundary was, on average, 0.21 cc or 1.5% of the prostate volume. The numerical simulations predicted the extent and shape of the coagulation boundary produced in gel to within (mean ± stdev [min, max]): 0.5 ± 0.4 [-1.0, 2.1] and -0.05 ± 0.4 [-1.2, 1.4] mm for the treatments at 4.7 and 8.0 MHz, respectively. The temperatures across all MRI thermometry images were predicted within -0.3 ± 1.6 °C and 0.1 ± 0.6 °C, inside and outside the prostate respectively, and the treatment time to within 6.8 min. The simulations also showed excellent agreement in regions of sharp temperature gradients near the transurethral and endorectal cooling devices. Conformal 3D volumes of thermal coagulation can be precisely matched to prostate shapes with transurethral ultrasound devices and active MRI temperature feedback. The accuracy of numerical simulations for MRI-controlled transurethral ultrasound prostate therapy was validated experimentally, reinforcing their utility as an effective treatment planning tool.     

The impact of transrectal ultrasound on stage migration in a predominantly African-American population.

An important question left unanswered is whether transrectal ultrasound will result in earlier diagnosis in African Americans. Tumor registry data for 1985 and 1990 for a predominantly African-American population were reviewed to determine whether transrectal ultrasound influenced the stage at diagnosis of prostate cancer. Diagnosis by ultrasound increased from 0% to 60% of cases in those 5 years. Curable diseases (stages A and B) increased from 38% to 57% of cases. It is concluded that transrectal ultrasound can increase the diagnostic yield of potentially curable disease in a predominantly African-American population.     

Is The Ability to Perform Transurethral Resection of the Prostate Influenced by the Surgeon’s Previous Experience?

PURPOSE: To evaluate the influence of the urologist's experience on the surgical results and complications of transurethral resection of the prostate (TURP). PATIENTS AND METHODS: Sixty-seven patients undergoing transurethral resection of the prostate without the use of a video camera were randomly allocated into three groups according to the urologist's experience: a urologist having done 25 transurethral resections of the prostate (Group I - 24 patients); a urologist having done 50 transurethral resections of the prostate (Group II - 24 patients); a senior urologist with vast transurethral resection of the prostate experience (Group III - 19 patients). The following were recorded: the weight of resected tissue, the duration of the resection procedure, the volume of irrigation used, the amount of irrigation absorbed and the hemoglobin and sodium levels in the serum during the procedure. RESULTS: There were no differences between the groups in the amount of irrigation fluid used per operation, the amount of irrigation fluid absorbed or hematocrit and hemoglobin variation during the procedure. The weight of resected tissue per minute was approximately four times higher in group III than in groups I and II. The mean absorbed irrigation fluid was similar between the groups, with no statistical difference between them (p=0.24). Four patients (6%) presented with TUR syndrome, without a significant difference between the groups. CONCLUSION: The senior urologist was capable of resecting four times more tissue per time unit than the more inexperienced surgeons. Therefore, a surgeon's experience may be important to reduce the risk of secondary TURP due to recurring adenomas or adenomas that were incompletely resected. However, the incidence of complications was the same between the three groups.     

超声引导下经直肠前列腺穿刺诊断前列腺癌的价值研究

目的 研究与分析超声引导下经直肠前列腺穿刺诊断前列腺癌的价值。方法 选取2015年1月~2017年1月我院收治的疑似前列腺癌患者100例,其中经超声引导下行会阴法穿刺诊断者50例为对照组,经超声引导下行直肠前列腺12点穿刺诊断者50例为观察组。比较分析两组诊断结果以及并发症情况。结果 观察组确诊率为72.00%,高于对照组的42.00%,差异具有统计学意义（P＜0.05）。观察组并发症发生率为8.00%,低于对照组的22.00%,差异具有统计学意义（P＜0.05）。结论 超声引导下经直肠前列腺穿刺诊断前列腺癌具有较高的确诊率,且能有效减少患者各种并发症,并为临床诊断前列腺疾病提供一定依据,值得应用推广。     

Processing of Dynamic Images during Transurethral Resection of the Prostate Gland

An analytical model of dynamic imaging of the prostate gland during prostate transurethral resection is described. The structure of a system of dynamic image processing for guiding resectoscope motion inside the prostate was developed. A trajectory processing technique for dynamic imaging is suggested and analyzed.     

Solitary fibrous tumor of the prostate: a report of two cases

We here report two cases of solitary fibrous tumor (SFT) arising in the prostate. Two men, 66 and 69 years old, with urinary tract symptoms were diagnosed with SFT on transrectal needle biopsy and transurethral resection of the prostate, respectively. The tumors were removed by a low anterior resection including tumor, prostate and rectum en bloc and cystoprostatectomy, respectively. Both tumors were well-circumscribed but also showed some infiltration of the prostate glands. They were composed of storiform bundles of bland spindle cells that stained strongly for CD34 and vimentin but negative for muscle markers. Although rare, SFT should be considered as differential diagnosis of spindle cell lesions on prostate biopsies.     

Computer-aided detection of prostate cancer

BACKGROUND: Prostate cancer is one of the most frequent cancers in men and is a major cause of mortality in developed countries. Detection of prostate carcinoma at an early stage is crucial for successful treatment. MATERIAL AND METHODS: A method for the analysis of transrectal ultrasound images aimed at computer-aided diagnosis of prostate cancer is tested in this paper. First, two classifiers based on k-nearest neighbors and Hidden Markov models are compared. Second, the diagnostic capacity of our system is tested by means of a set of experiments where humans with varying degrees of experience classified a set of ultrasound images with and without the aid of the computer-aided system. The corpus used in this study was specifically acquired for this purpose. It consists of 4944 ultrasound images corresponding to 303 patients, and is publicly available for non-commercial use upon request. RESULTS: The best classification results achieve an area under the receiver operating characteristic curve of 61.6%. However, the diagnostic capacity of an expert urologist using the computer-aided system improves only slightly compared with his/her capacity without the aid of the system. CONCLUSIONS: Despite the difficulty of this task, the obtained results indicate that discrimination between cancerous and non-cancerous tissue is possible to a certain degree. The computer-aided system helps an inexperienced user to make a better diagnosis, however it must be able to perform better in order to be useful in a real-world clinical context.     

Detection of fluoroquinolone-resistant organisms from rectal swabs by use of selective media prior to a transrectal prostate biopsy

Sepsis caused by fluoroquinolone-resistant Escherichia coli is a risk for patients undergoing an ultrasound-guided, transrectal prostate biopsy. A method incorporating selective broth and media was evaluated using rectal swabs obtained from 136 patients prior to a biopsy procedure. Fluoroquinolone-resistant organisms were isolated from 22% of the patients included in this study.