The significance of isoechoic prostatic carcinoma

How to Improve TRUS-Guided Target Biopsy following Prostate MRI

TRUS is a basic imaging modality when radiologists or urologists perform cognitive fusion or image fusion biopsy. This modality plays the role of the background images to add to an operator's cognitive function or MRI images. Operators need to know how to make TRUS protocols for lesion detection or targeting. Tumor location, size, and shape on TRUS are different from those on MRI because the scan axis is different. TRUS findings of peripheral or transition tumors are not well known to radiologists and urologists. Moreover, it remains unclear if systematic biopsy is necessary after a tumor is targeted. The purpose of this review is to introduce new TRUS protocols, new imaging features, new biopsy techniques, and to assess the necessity of systematic biopsy for improving biopsy outcomes.

Clinical factors for predicting malignancy in patients with PSA < 10 ng/mL and PI-RADS 3 lesions

AIM

To determine clinical risk factors in patients with PI-RADS 3 lesions and prostate-specific antigen (PSA) < 10 ng/mL.

METHODS

In this prospective study, all patients underwent multiparametric magnetic resonance imaging. Following the 2-5 core fusion-targeted biopsy, standard 12-core prostate biopsy was performed in each patient (combined biopsy). The cutoff values were calculated with receiver-operating characteristic analysis. First, univariate logistic regression analysis was used to evaluate the relationship between total eight parameters and prostate cancer. Subsequently, multiple logistic regression analysis was performed to the parameters associated with prostate cancer.

RESULTS

Two hundred and eighty-eight patients were included in the study. Some clinical parameters are determined to be significant in univariate and multiple logistic regression analyses, including PSA, free/total PSA ratio, PSA density (PSA/total prostate volume), positive family history of PCa, and PI-RADS 3 lesion diameter. Patients were classified between 0 and 5 according to the number of risk factors. While the risk of cancer was 7.1% in patients with one or less risk factors, the PCA rate was 45.2% among patients with all risk factors.

CONCLUSION

In patients with PI-RADS 3 lesion and PSA < 10 ng/mL, histopathological results of biopsy can be estimated with higher accuracy using some clinical parameters.

Multiparametric MRI fusion-guided prostate biopsy in biopsy naive patients: Preliminary results from 80 patients

OBJECTIVE

The aim of this prospective study was to evaluate the early results of transrectal prostate biopsies performed under the guidance of multiparametric prostate magnetic resonance imaging (mpMRI) in biopsy naive patients.

MATERIAL AND METHODS

Biopsy naive patients who had prostate-specific antigen level 4-10 ng/mL and/or abnormal digital rectal examination findings and provided informed consent were examined using mpMRI. The study included 80 patients with an MRI-defined lesion with a Prostate Imaging and Reporting and Data System (PIRADS) score of ≥3. All mpMRIs were reported by the same uro-radiologist according to PIRADS version 2. An MRI-targeted biopsy was performed by an ultrasonography system with rigid fusion registration software. The first two to five core biopsies per MRI-defined lesions were obtained, and then a standard random 12-core biopsy was performed. Transrectal biopsies were performed under local anesthesia or sedoanalgesia.

RESULTS

Of the 80 patients, 29 (36.3%) were found to have cancer using the conventional 12-core biopsy, but only 20 (25%) were found to have prostate cancer using the MRI-targeted prostate biopsy. Combining the two biopsy methods (conventional+MRI-targeted), cancer detection rate increased to 43.8% (35/80 patients). The cancer detection rate using the combined method was statistically higher than that using the conventional biopsy method (p=0.03). Using the conventional biopsy method, 960 core biopsies were collected from 80 patients. Of the 960 core biopsies, 111 (11.6%) were found to be cancer. Further, 101 suspected lesions were detected using mpMRI in 80 patients. In addition, 397 core biopsies were obtained from these lesions. Of the 397 core biopsies, 62 (15.6%) were reported as prostate cancer. The core positivity rate of MR-targeted biopsy was statistically higher than that of conventional biopsy (p=0.04).

CONCLUSION

The preliminary results of MRI-targeted prostate biopsy combined with conventional biopsy suggested that the combined biopsy method was crucial in prostate cancer diagnosis especially in patients with prostate cancer suspicion and no biopsy history. However, larger sample prospective studies are needed to validate the effectiveness of MRI-targeted biopsy and combined biopsy methods.

The predictive efficacy of hypoechoic lesion in ultrasound for prostate cancer in Chinese people: five-year experience in a moderated 10-core transperineal prostate biopsy procedure

We aim to investigate the predictive efficacy of hypoechoic lesion for prostate cancer at different levels of serum PSA in the procedure of transrectal ultrasound guided 10-core trans-perineal prostate biopsy (TP-PBx). In this study, we collected clinical parameters involving age, digital rectal examination (DRE), PSA, prostate volume, pathological diagnosis, Gleason score, novel Gleason group, and numbers of positive cores from 856 patients who had elevated level of PSA above 4 ng/ml or susceptible nodule of prostate gland in DRE received the moderated 10-core TP-PBx procedure. There were 481 cases (56.2%) with no visible lesion of hypoechoic nodule in transrectal ultrasound (TRUS) and 375 cases (43.8%) with the hypoechoic lesion. The total cancer detection rate is 45.56%. The predictive efficacy of hypoechoic lesion for prostate cancer varies among different PSA intervals. For PSA groups of 0-4, 4-10, 10-20, 20-100, > 100 ng/ml, the Youden's indexes are 0.3483, 0.3506, 0.3941, 0.2795 and 0.8667, respectively. Besides, the visible lesions are inclined to be detected in patients with higher Gleason score. We concluded that the hypoechoic lesions in TRUS could improve the predictive accuracy for diagnosing prostate cancer and present different predictive efficacy in the respective PSA intervals. Besides, it was probably associated with more aggressive clinical significance.

The value of magnetic resonance imaging and ultrasonography (MRI/US)-fusion biopsy platforms in prostate cancer detection: a systematic review

Despite limitations considering the presence, staging and aggressiveness of prostate cancer, ultrasonography (US)-guided systematic biopsies (SBs) are still the 'gold standard' for the diagnosis of prostate cancer. Recently, promising results have been published for targeted prostate biopsies (TBs) using magnetic resonance imaging (MRI) and ultrasonography (MRI/US)-fusion platforms. Different platforms are USA Food and Drug Administration registered and have, mostly subjective, strengths and weaknesses. To our knowledge, no systematic review exists that objectively compares prostate cancer detection rates between the different platforms available. To assess the value of the different MRI/US-fusion platforms in prostate cancer detection, we compared platform-guided TB with SB, and other ways of MRI TB (cognitive fusion or in-bore MR fusion). We performed a systematic review of well-designed prospective randomised and non-randomised trials in the English language published between 1 January 2004 and 17 February 2015, using PubMed, Embase and Cochrane Library databases. Search terms included: 'prostate cancer', 'MR/ultrasound(US) fusion' and 'targeted biopsies'. Extraction of articles was performed by two authors (M.G. and A.A.) and were evaluated by the other authors. Randomised and non-randomised prospective clinical trials comparing TB using MRI/US-fusion platforms and SB, or other ways of TB (cognitive fusion or MR in-bore fusion) were included. In all, 11 of 1865 studies met the inclusion criteria, involving seven different fusion platforms and 2626 patients: 1119 biopsy naïve, 1433 with prior negative biopsy, 50 not mentioned (either biopsy naïve or with prior negative biopsy) and 24 on active surveillance (who were disregarded). The Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to assess the quality of included articles. No clear advantage of MRI/US fusion-guided TBs was seen for cancer detection rates (CDRs) of all prostate cancers. However, MRI/US fusion-guided TBs tended to give higher CDRs for clinically significant prostate cancers in our analysis. Important limitations of the present systematic review include: the limited number of included studies, lack of a general definition of 'clinically significant' prostate cancer, the heterogeneous study population, and a reference test with low sensitivity and specificity. Today, a limited number of prospective studies have reported the CDRs of fusion platforms. Although MRI/US-fusion TB has proved its value in men with prior negative biopsies, general use of this technique in diagnosing prostate cancer should only be performed after critical consideration. Before bringing MRI/US fusion-guided TB in to general practice, there is a need for more prospective studies on prostate cancer diagnosis.

Prostate cancer detection and diagnosis: the role of MR and its comparison with other diagnostic modalities--a radiologist's perspective

It is now universally recognized that many prostate cancers are over-diagnosed and over-treated. The European Randomized Study of Screening for Prostate Cancer from 2009 evidenced that, to save one man from death from prostate cancer, over 1400 men need to be screened, and 48 need to undergo treatment. The detection of prostate cancer is traditionally based on digital rectal examination (DRE) and the measurement of serum prostate-specific antigen (PSA), followed by ultrasound-guided biopsy. The primary role of imaging for the detection and diagnosis of prostate cancer has been transrectal ultrasound (TRUS) guidance during biopsy. Traditionally, MRI has been used primarily for the staging of disease in men with biopsy-proven cancer. It has a well-established role in the detection of T3 disease, planning of radiation therapy, especially three-dimensional conformal or intensity-modulated external beam radiation therapy, and planning and guiding of interstitial seed implant or brachytherapy. New advances have now established that prostate MRI can accurately characterize focal lesions within the gland, an ability that has led to new opportunities for improved cancer detection and guidance for biopsy. Two new approaches to prostate biopsy are under investigation. Both use pre-biopsy MRI to define potential targets for sampling, and the biopsy is performed either with direct real-time MR guidance (in-bore) or MR fusion/registration with TRUS images (out-of-bore). In-bore and out-of-bore MRI-guided prostate biopsies have the advantage of using the MR target definition for the accurate localization and sampling of targets or suspicious lesions. The out-of-bore method uses combined MRI/TRUS with fusion software that provides target localization and increases the sampling accuracy of TRUS-guided biopsies by integrating prostate MRI information with TRUS. Newer parameters for each imaging modality, such as sonoelastography or shear wave elastography, contrast-enhanced ultrasound and MRI elastography, show promise to further enrich datasets.

State-of-the-art uroradiologic imaging in the diagnosis of prostate cancer

In the diagnostic process of prostate cancer, several radiologic imaging modalities significantly contribute to the detection and localization of the disease. These range from transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) to positron emission tomography (PET). Within this review, after evaluation of the literature, we will discuss the advantages and disadvantages of these imaging modalities in clarifying the patient's clinical status as to whether he has prostate cancer or not and if so, where it is located, so that therapy appropriate to the patient's disease may be administered. TRUS, specifically with the usage of intravenous contrast agents, provides an excellent way of directing biopsy towards suspicious areas within the prostate in the general (screening) population. MRI using functional imaging techniques allows for highly accurate detection and localization, particularly in patients with prior negative ultrasound guided biopsies. A promising new development is the performance of biopsy within the magnetic resonance scanner. Subsequently, a proposal for optimal use of radiologic imaging is presented and compared with the European and American urological guidelines on prostate cancer.

[Prostate carcinoma]

Prostate cancer is the most common malignancy in men in Europe, North America, and in some African states. Early diagnosis in an asymptomatic stage is possible through the combination of digitorectal examination, PSA serum testing, and systematic biopsy. However, general screening is so far not recommended by the Urologic Societies, because the efficiency is not yet proved. Imaging is also not recommended for first-line screening. Novel functional methods of transrectal ultrasound (TRUS) and endorectal MRI can improve accuracy of tumor detection to more than 90% and can be used for TRUS- and now also MRI-guided biopsy leading to two- to threefold higher tumor detection rates. There is general agreement that all men over 50 years of age should be informed about the possibilities, benefits, and risks of the available methods for early tumor detection.

Adaptation of a 3D prostate cancer atlas for transrectal ultrasound guided target-specific biopsy

Due to lack of imaging modalities to identify prostate cancer in vivo, current TRUS guided prostate biopsies are taken randomly. Consequently, many important cancers are missed during initial biopsies. The purpose of this study was to determine the potential clinical utility of a high-speed registration algorithm for a 3D prostate cancer atlas. This 3D prostate cancer atlas provides voxel-level likelihood of cancer and optimized biopsy locations on a template space (Zhan et al 2007). The atlas was constructed from 158 expert annotated, 3D reconstructed radical prostatectomy specimens outlined for cancers (Shen et al 2004). For successful clinical implementation, the prostate atlas needs to be registered to each patient's TRUS image with high registration accuracy in a time-efficient manner. This is implemented in a two-step procedure, the segmentation of the prostate gland from a patient's TRUS image followed by the registration of the prostate atlas. We have developed a fast registration algorithm suitable for clinical applications of this prostate cancer atlas. The registration algorithm was implemented on a graphical processing unit (GPU) to meet the critical processing speed requirements for atlas guided biopsy. A color overlay of the atlas superposed on the TRUS image was presented to help pick statistically likely regions known to harbor cancer. We validated our fast registration algorithm using computer simulations of two optimized 7- and 12-core biopsy protocols to maximize the overall detection rate. Using a GPU, patient's TRUS image segmentation and atlas registration took less than 12 s. The prostate cancer atlas guided 7- and 12-core biopsy protocols had cancer detection rates of 84.81% and 89.87% respectively when validated on the same set of data. Whereas the sextant biopsy approach without the utility of 3D cancer atlas detected only 70.5% of the cancers using the same histology data. We estimate 10-20% increase in prostate cancer detection rates when TRUS guided biopsies are assisted by the 3D prostate cancer atlas compared to the current standard of care. The fast registration algorithm we have developed can easily be adapted for clinical applications for the improved diagnosis of prostate cancer.

Transrectal ultrasound in detecting prostate cancer compared with serum total prostate-specific antigen levels

We carried out a retrospective study to review the efficiency of grey-scale transrectal ultrasonography (TRUS) in detecting prostate cancer compared with the data in recent published work, including alternative imaging methods of the prostate gland. Our study group consisted of 830 patients who underwent TRUS-guided biopsy of the prostate between May 2000 and June 2004. The relation between abnormal TRUS findings and serum total prostate-specific antigen (tPSA) levels was evaluated in patients with prostate cancer who were divided into three different groups according to serum tPSA levels. Group I included patients with tPSA levels of 4-9.9 ng/mL, group II included tPSA levels of 10-19.9 ng/mL and group III included patients with tPSA levels of 20 ng/mL or more. In general, TRUS detected 185 (64%) of 291 cancers with a specificity of 89%, a PPV of 76% and an accuracy of 80%. TRUS findings enabled the correct identification of 22 (56%) of the 39 cancers in group I, 28 (30%) of the 93 cancers in group II and 135 (85%) of the 159 cancers in group III. In conclusion, TRUS alone has a limited potential to identify prostate cancer, especially in patients with tPSA levels lower than 20 ng/mL. Therefore, increased numbers of systematically placed biopsy cores must be taken or alternative imaging methods are required to direct TRUS-guided biopsy for improving prostate cancer detection.

The incidence of hyperechoic prostate cancer in transrectal ultrasound-guided biopsy specimens

OBJECTIVES

To estimate the incidence of transrectal ultrasound (TRUS) hyperechoic lesions and of hyperechoic prostate cancer in TRUS-guided biopsy specimens.

METHODS

We prospectively studied 200 patients with total prostate-specific antigen values less than 20 ng/mL and/or positive results on digital rectal examination who had undergone TRUS-guided prostate biopsy. Each patient underwent laterally directed systemic six-core biopsy plus cores from abnormal TRUS lesions and rectally palpable lesions. Six to 10 biopsy cores were obtained from each patient.

RESULTS

Hyperechoic lesions were found in 19 patients (9.5%), hypoechoic in 83 (41.5%), and isoechoic in 98 (49.0%). Prostate cancer was diagnosed in 33.0% of study patients. Isoechoic findings on TRUS were recorded in 31.8% of patients diagnosed with prostate cancer, whereas 60.6% of cancers had hypoechoic and 7.6% hyperechoic lesions. There was no significant difference in the mean Gleason score between isoechoic cancers (mean 5.4) and hypoechoic cancers (mean 5.6). However, hyperechoic cancers had a mean Gleason score of 7.0, which was higher when compared with isoechoic and hypoechoic cancers.

CONCLUSIONS

Biopsy of hyperechoic lesions was positive for prostate cancer in a higher percentage of patients than previously reported in the literature, and Gleason score of these cancers was higher when compared with isoechoic and hypoechoic cancers.

Computerized transrectal ultrasound (C-TRUS) of the prostate: detection of cancer in patients with multiple negative systematic random biopsies

This study was designed to compare the diagnostic yield of computerized transrectal ultrasound (C-TRUS) guided biopsies in the detection of prostate cancer in a group of men with a history of multiple systematic random biopsies with no prior evidence of prostate cancer. The question was asked: Can we detect cancer by C-TRUS that has been overlooked by multiple systematic biopsies? The entrance criteria for this study were prior negative systematic random biopsies regardless of number of biopsy sessions or number of individual biopsy cores. Serial static TRUS images were evaluated by C-TRUS, which assessed signal information independent of visual gray scale. Five C-TRUS algorithms were utilized to evaluate the information of the ultrasound signal. Interpretation of the results were documented and the most suspicious regions marked by C-TRUS were biopsied by guiding the needle to the marked location. Five hundred and forty men were biopsied because of an elevated PSA or abnormal digital rectal exam. 132 had a history of prior negative systematic random biopsies (1-7 sessions, median: 2 and between 6 and 72 individual prostate biopsies, median: 12 cores). Additionally, a diagnostic TUR-P of the prostate with benign result was performed in four patients. The PSA ranged from 3.1-36 ng/ml with a median of 9.01 ng/ml. The prostate volume ranged from 6-203 ml with a median of 42 ml. Of the 132 patients with prior negative systematic random biopsies, cancer was found in 66 (50%) by C-TRUS targeted biopsies. In this group the median number of negative biopsy sessions was two and a median of 12 biopsy cores were performed. From literature we would expect a cancer detection rate in this group with systematic biopsies of approximately 7%. We only found five carcinomas with a Gleason Score (GS) of 5, 25 with GS 6, 22 with GS 7, 8 with GS 8 and even 7 with GS 9. The results of this prospective clinical trail indicates that the additional use of the C-TRUS identifies clinical significant cancerous lesions that could not been visualized or detected by systematic random biopsies in a very high percentage. In addition, the results of the study support the efforts to search for strategies that utilize expertise and refinement of imaging modalities rather than elevating the number of random biopsies (f.e. 141 cores in one session) in the detection of prostate cancer.

Prostate Cancer Screening

Prostate cancer incurs a substantial incidence and mortality burden, similarly to breast cancer, and it ranks among the top ten specific causes of death in the United States. It is inherent as we maximize the detection of early prostate cancer that we increase the detection of both nonaggressive (slow growing) and aggressive (faster growing) prostate cancers. The evidence clearly supports the use of PSA screening in conjunction with DRE as a means of early detection of prostate cancer. Widespread implementation of prostate cancer screening in the United States has led to the phenomenon of stage migration with more cancers being detected at a lower stage. Such a trend has decreased the incidence of metastatic disease at diagnosis and paralleled the decrease of the mortality rate from prostate cancer. Our understanding of the natural history of prostate cancer is progressing over time, but the question of its length is unanswerable. The relatively long doubling time (on average) of early prostate cancer of 3 to 4 years or more indicates a relatively good prognosis for many men with this disease, even without early detection and treatment. Unfortunately, the poor specificity of the PSA test in men with benign prostatic hyperplasia (BPH) leads to high rates of prostate biopsy and attendant illnesses and costs. Early detection is more apt to detect a slow-growing prostate cancer than a faster growing cancer that is associated with a more rapid course of progression to metastatic disease. Hence, the launching of mass screening programs for the early detection of prostate cancer is premature. However, in the absence of solid evidence of benefit, one reasonable approach to screening at the individual level is to involve the patient in decisions about whether or not to perform a PSA test. Thus, "offering" PSA testing must be accompanied by informed discussion within the context of an ongoing patient-physician relationship. This is to be distinguished from the use of PSA testing for the purpose of "mass screening." Concepts that must be explored with the patient include: 1. The long-term ramifications of screening 2. The relatively high probability of further evaluation and biopsy with positive results 3. Potentially difficult decisions that may arise about using treatments that are associated with considerable morbidity and uncertain benefits (at the time) if cancer is discovered We should identify a future path that is evidence-based, focused on the issues that make a difference to patients, and results in better and longer lives of those with the disease and those who are at risk of getting it. If that path leads to treating fewer patients in the future, even if sometimes more aggressively, we should pursue it definitely and consequently.

3D prostate elastography: algorithm, simulations and experiments

A multi-resolution hybrid strain estimator is presented. The estimator is locally initialized by the B-mode tracking stage. Nonlinear and linear stretching regimes are applied in successive RF tracking stages for refining the estimated axial and lateral displacements. A staggering operator is used to derive the strain images from the reconstructed axial displacements. Simulations and experiments, conducted at a center frequency of 12 MHz, 40% fractional bandwidth, on a 128 element transducer with 0.2 mm pitch, with elastographic window length of 2 mm and overlap of 90%, demonstrate a 3-6 dB improvement in the elastographic contrast-to-noise ratio over the results obtained using conventional multi-stage stretching based strain estimators. The average image cross-correlation coefficient obtained using the proposed algorithm was improved by 6-8%. 3D elastographic simulations conducted to study the performance of a 3D elastographic imaging framework predict achievable axial and lateral resolutions of approximately five and ten wavelengths, respectively. A close correspondence between inclusions reconstructed from experimental elastograms and the known physical shape of actual 3D inclusions demonstrates the potential application of 3D elastography for identifying and classifying the detected lesions (invisible in sonograms) on the basis of their shape.

Transrectal ultrasound guided biopsy for detecting prostate cancer: can random biopsies be reduced using the 4-dimensional technique?

We present our experience with a new technique of real time 3-dimensional sonography -- "4-dimensional Transrectal ultrasound (TRUS)" guided prostate biopsy. A total of 64 patients suspected of having prostate cancer based on an elevated prostate-specific antigen (greater than 4 ng/ml) formed the study group. A voluson (General Electric Vivid 3) ultrasound machine equipped with a transrectal 5-8 MHz curvilinear transducer was used. Sonography-guided prostate biopsy was performed following prostate imaging and volume calculation using 3D and 4D imaging. Biopsies of tumor suspicious areas, if present, as well as random biopsies were done. Histopathology showed prostate cancer in 15 (23.4%) and benign prostatic conditions in 49 (76.6%). TRUS examination in the 15 detected prostatic cancers showed that 6(40%) were hypoechoic, 4 (26.7%) were of mixed hypo and hyper echogenicity, 1 (6.7%) was hyperechoic, and 4 (26.7%) were isoechoic. TRUS finding of a hypoechoic lesion was significantly associated with malignancy. Other TRUS findings such as texture, calcification, and cysts did not show any association with malignancy. Mortality was zero after ultrasound-guided prostate biopsy. TRUS is the diagnostic test of choice in detection of prostate cancer. With advances in the technique of TRUS, effort is being made to identify more subtle lesions in order to reduce random biopsies. 4-Dimensional TRUS does improve the diagnostic accuracy but there is still a group of patients with "invisible" cancers. Therefore, the policy of random biopsies has to be continued till this incidence can be eliminated.

MR-compatible assistance system for punction in a high-field system: device and feasibility of transgluteal biopsies of the prostate gland

We present the first cadavic study results concerning the feasibility of the use of an MR-guided assistance system, Innomotion (Innomedic, Herxheim, Germany), for accurate and consistent placement of percutaneous needles in the prostate gland. The MR-compatible assistance system consists of a C-arch, guiding arm and application module (AMO). T1-weighted fast low angle shot (FLASH) 2-D-GRE sequence (TR/TE=110/4 ms) and T2-weighted turbo spin-echo (TSE)-sequences (TR/TE=3200/97 ms) in transversal orientation were used for the monitoring of the punction of the prostate gland. Planning and control of the intervention is to be made outside the scanner room on a desktop computer that receives DICOM images from the scanner. Servopneumatic drives move the AMO to the insertion point. The physician has to introduce the punction needle manually. The mean deviation of the needle tip to the target in a gel phantom was 0.35 mm. An accurate punction of the prostate gland can easily be performed using this system with a transgluteal access. The T2-weighted images are superior for the evaluation of the prostate anatomy and the needle position during the interventions. In conclusion, our preliminary results indicate that this MR-guided assistance system is suitable for an accurate transgluteal needle placement in the prostate.

Prostate cancer localization with dynamic contrast-enhanced MR imaging and proton MR spectroscopic imaging

PURPOSE

To prospectively determine the accuracies of T2-weighted magnetic resonance (MR) imaging, dynamic contrast material-enhanced MR imaging, and quantitative three-dimensional (3D) proton MR spectroscopic imaging of the entire prostate for prostate cancer localization, with whole-mount histopathologic section findings as the reference standard.

MATERIALS AND METHODS

This study was approved by the institutional review board, and informed consent was obtained from all patients. Thirty-four consecutive men with a mean age of 60 years and a mean prostate-specific antigen level of 8 ng/mL were examined. The median biopsy Gleason score was 6. T2-weighted MR imaging, dynamic contrast-enhanced MR imaging, and 3D MR spectroscopic imaging were performed, and on the basis of the image data, two readers with different levels of experience recorded the location of the suspicious peripheral zone and central gland tumor nodules on each of 14 standardized regions of interest (ROIs) in the prostate. The degree of diagnostic confidence for each ROI was recorded on a five-point scale. Localization accuracy and ROI-based receiver operating characteristic (ROC) curves were calculated.

RESULTS

For both readers, areas under the ROC curve for T2-weighted MR, dynamic contrast-enhanced MR, and 3D MR spectroscopic imaging were 0.68, 0.91, and 0.80, respectively. Reader accuracy in tumor localization with dynamic contrast-enhanced imaging was significantly better than that with quantitative spectroscopic imaging (P < .01). Reader accuracy in tumor localization with both dynamic contrast-enhanced imaging and spectroscopic imaging was significantly better than that with T2-weighted imaging (P < .01).

CONCLUSION

Compared with use of T2-weighted MR imaging, use of dynamic contrast-enhanced MR imaging and 3D MR spectroscopic imaging facilitated significantly improved accuracy in prostate cancer localization.

Prostate cancer: three-dimensional sonoelastography for in vitro detection

PURPOSE

To prospectively evaluate the accuracy of three-dimensional (3D) sonoelastographic imaging, relative to that of gray-scale ultrasonography (US), in the in vitro detection of prostate cancer.

MATERIALS AND METHODS

The study was approved by the institutional review board and was HIPAA compliant. Informed consent was obtained from all patients. Nineteen prostatectomy specimens from patients aged 46-70 years with biopsy-proved prostate cancer were scanned in three dimensions by using conventional B-mode US and sonoelastography with vibrations of more than 100 Hz. Step-sectioned whole-mount histologic specimens were used to create a 3D volume of the prostate and the tumors within it. B-mode US scans and regions of low vibration on the sonoelastographic images (hard regions) were formatted in three dimensions. The lesions in the 19 cases were classified into two groups, as follows: G1 lesions were pathologically confirmed tumors with a volume of at least 1.0 cm3, and G2 lesions were pathologically confirmed tumors smaller than 1.0 cm3. G1 lesions were evaluated with B-mode US and sonoelastography and classified as true-positive, false-positive, true-negative, or false-negative; G2 lesions were evaluated only with sonoelastography. Findings at histologic examination were used as the reference standard. True-positive findings necessitated 3D lesion correlation between pathologic and imaging data. Conventional definitions of accuracy and sensitivity were used for statistical analysis.

RESULTS

For G1 lesions (seven lesions with a volume of at least 1.0 cm3), sonoelastography had an accuracy of 55% and a sensitivity of 71% and B-mode US had an accuracy of 17% and a sensitivity of 29%. The mean tumor volume was 3.1 cm3 +/- 2.1 (standard deviation). For G2 lesions (22 lesions with a volume of less than 1.0 cm3), the mean tumor volume was 0.32 cm3 +/- 0.21. Sonoelastography had an accuracy of 34% and a sensitivity of 41%; there were six false-positive findings.

CONCLUSION

Sonoelastography performed considerably better than did gray-scale US in the depiction of prostate cancer for tumors with volumes of more than 1 cm3.

Transrectal ultrasound guided biopsy of the prostate: random sextant versus biopsies of sono-morphologically suspicious lesions

Transrectal ultrasound (TRUS) guided multiple systematic random biopsies are presently the method of choice for determining the presence or absence of prostate cancer. TRUS image information is only used to guide the biopsy needle into the prostate, but not to localize and target cancerous lesions. Our aim in this study was to evaluated the possible predictive value of tumor suspicious endosonographic lesions of the prostate for prostate biopsies. We prospectively compared six systematic biopsies with lesion guided biopsies in a consecutive series of 217 patients. All patients had a prostate specific antigen (PSA) level of >4 ng/ml without a history of prostate disease. In a subgroup of 145 men with sonomorphologic lesions suggestive for prostate cancer (hypoechoic areas or asymmetries predominantly in the peripheral zone), lesion-guided biopsies were taken in addition to the systematic biopsies. We evaluated the number of tumors which were diagnosed or missed by both of the biopsy strategies. Of the 217 evaluated patients, 64 (29%) had histology confirmed cancer. Four patients with negative sextant biopsies had a positive TRUS guided biopsy. Out of 145 patients with a normal TRUS, three were cancer positive by sextant biopsy. A total of 1,387 individual biopsy cores were evaluated. Of the 1,304 systematic biopsy cores, 182 (14%) were positive and 1,122 (86%) negative. Of the 329 TRUS lesion guided biopsy cores 139 (42%) were positive and 190 (58%) negative. Patients with tumor suggestive TRUS lesions have a considerably higher risk of being diagnosed with prostate cancer compared to patients without such lesions. Both systematic sextant and TRUS lesion guided biopsies missed detectable prostate cancer in a minority of patients. Taking the endosonographic morphology of the prostate gland into consideration for biopsy strategies may improve the quality of the biopsy and avoid unnecessary invasive procedures in selected cases.

Three dimensional ultrasound and prostate cancer

Three-dimensional ultrasound (3-D US) is a non-invasive method of producing whole volume images of solid structures. Early work on prostate imaging identified several advantages over 2-D imaging with a good ability to detect intraprostatic lesions. Several 3-D transrectal ultrasound (3-D TRUS) systems are now available for prostate imaging. Initial work using gray scale ultrasound appears promising with reported overall staging accuracies of up to 94%. These results were favourable when compared to other modalities for local staging of prostate cancer. Several adjuncts to 3-D gray scale TRUS have been investigated. A greater sensitivity for cancer detection has been achieved with the addition of power colour Doppler and contrast agents. Further clinical applications for 3-D TRUS include assessing placement of brachytherapy seeds and for cyroablation techniques. Computer enhancement with image registration has shown that 3-D US images can be manipulated to derive more information. Although the results of gray scale imaging alone or with adjuncts and post processing appear promising, these techniques remain largely experimental.

Computergest�tzter transrektaler Ultraschall (C-TRUS) in der Diagnostik des Prostatakarzinoms

In the diagnosis of prostate cancer digital rectal examination and transrectal ultrasound (TRUS) are the most utilized methods for clinical evaluation. However, both methods are not able to differentiate between benign and malignant findings with a high amount of certainty. Nevertheless, TRUS is an excellent tool to guide biopsies in practically any region of the prostate. The most significant problem of visual TRUS interpretation is the lack of specificity, especially being an inexperienced user. In order to enhance the diagnostic capabilities of TRUS we developed a computerized analysis of the TRUS signal information (C-TRUS/ANNA), which was validated by the pathohistologic findings of radical prostatectomies. The question was asked: Can C-TRUS detect cancer that has been missed by even multiple systematic biopsies? The entrance criteria was prior negative systematic random biopsies regardless of number of biopsy sessions or number of individual biopsy cores. Five C-TRUS subvisual algorithms were utilized to evaluate the information of the ultrasound signal. The most suspicious regions were marked by C-TRUS and biopsied by guiding a needle into that specific location. In this study 132 with a history of 6-72 negative systematic random biopsies (median: 12 cores) were evaluated by C-TRUS. The PSA ranged from 3.1-36 ng/ml with a median of 9.01 ng/ml. C-TRUS detected in 66 (50%) of these 132 patients cancer by targeted biopsies. In thes 66 men the median number of negative biopsy sessions were two and a median of 12 biopsy cores had been taken. From the literature, we would expect a cancer detection rate in this group with systematic sextant biopsies of about 7%. Only five of the detected carcinomas showed a Gleason Score (GS) of 5, were as 25 had a GS of 6, 22 a GS of 7 and 15 a GS above 7. The results of this prospective clinical trail indicate that C-TRUS is able to identify clinically significant cancers that were missed by even multiple systematic random biopsies. In addition, the concept of searching for strategies that utilize expertise and refinement of imaging modalities is supported rather than just elevating the number of random biopsies (i.e. 141 cores in one session).

Contemporary impact of transrectal ultrasound lesions for prostate cancer detection

PURPOSE

Transrectal ultrasound (TRUS) guided systematic biopsy of the prostate is the gold standard diagnostic modality for prostate cancer. Consequently, the value of discrete hypoechoic lesions on TRUS lesions considered suspicious for cancer deserves meticulous reevaluation, specifically in the prostate specific antigen era when the majority of tumors diagnosed are nonpalpable. We studied whether the predictability of a biopsy core changes if the tissue comes from an isoechoic vs hypoechoic lesion.

MATERIALS AND METHODS

Prospective data were collected on 3,912 consecutive patients referred to our medical center between 1993 and 1999 for biopsy of the prostate. A sextant technique (apex, mid gland and base) with an additional core biopsy from the transitional zone was used. If a hypoechoic lesion was identified, the biopsy was taken from the lesion. Correlation between hypoechoic lesions, isoechoic areas and cancer detection for each core was performed.

RESULTS

A total of 31,296 cores were obtained from the cohort. Overall 2,642 (68%) cores had at least 1 hypoechoic lesion ultrasonographically. Cancer was detected in 675 (25.5%) and 323 (25.4%) patients with or without hypoechoic lesions (p = 0.97). The per core cancer detection was fairly uniform and averaged 9.3% and 10.4% for hypoechoic and isoechoic areas, respectively. The difference was not statistically significant (p = 0.3). Gleason scores were less than 7, 7 and greater than 7 in 46%, 34% and 20% of cases, respectively.

CONCLUSIONS

Despite the higher prevalence of cancers discovered in prostates with hypoechoic areas, the hypoechoic lesion itself was not associated with increased cancer prevalence compared with biopsy cores from isoechoic areas. For impalpable tumors TRUS findings are not contributory for staging.

Prognostic significance of visible lesions on transrectal ultrasound in impalpable prostate cancers: implications for staging

PURPOSE

The current tumor-node metastasis (TNM) staging system classifies impalpable prostate cancers identified by needle biopsy and invisible by imaging as T1c and those visible as T2. Palpable cancers are classified as at least T2. However, most urologists consider impalpable prostate cancers T1c tumors, irrespective of findings on transrectal ultrasound (TRUS). The aim of this article is to provide a differentiated view of the significance of TRUS findings for staging purposes in impalpable prostate cancers.

PATIENTS AND METHODS

A consecutive series of 1670 patients with impalpable tumors and palpable T2 cancers after radical prostatectomy were evaluated. Tumor characteristics and 5-year biochemical cure rates of cancers invisible and visible on TRUS were compared, as well as the rates of impalpable but visible and palpable T2 cancers.

RESULTS

Impalpable cancers invisible on TRUS presented significantly more favorable pathologic stages and lower cancer volumes than those visible on TRUS (P =.002, P =.010). In the latter, these clinical features were more favorable compared with T2 cancers (P <.001, P <.001). Progression-free probability of impalpable cancers invisible on TRUS was 86.8%; progression-free probability for impalpable cancers visible on TRUS was 85.4% (log-rank test P =.2060). The corresponding rate for T2 tumors was 73.9%, significantly lower when compared to those of visible and impalpable cancers (log-rank test P =.0001).

CONCLUSION

Impalpable prostate cancers invisible on TRUS present more favorable cancer features than those that are visible on TRUS. However, these differences are not as pronounced as those between impalpable but visible cancers and palpable T2 tumors. Thus, based on our data, it seems inappropriate to classify impalpable prostate cancers visible on TRUS as T2 cancers.

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.

Ultrasonic tissue characterization for prostate diagnostics: spectral parameters vs. texture parameters

An ultrasonic multi-feature tissue characterizing system for the detection of prostate cancer is presented. The system is based on the processing of radio frequency (RF) ultrasonic echo data. Data from 100 patients was acquired in a clinical study. Parameters are extracted from the RF echo data and classified using two adaptive network-based fuzzy inference systems (FIS) working in parallel as a nonlinear classifier. Next to spectral parameters, conventional texture parameters are calculated using demodulated and log-compressed echo data. In the first approach, the classifier is trained on both, spectral and texture parameters. In the second approach, the classifier is only trained on texture parameters. Classification results of both approaches are compared and it is demonstrated, that only the use of spectral parameters yields satisfying classification results. Results of a minimum distance classifier (MDC) are presented for comparison with the fuzzy inference system. For the final fuzzy inference systems used in this approach, the area under the ROC curve is between 84% and 86% for the combined approach and between 70% and 74% for the approach based on texture parameters only.

Phased-array MRI of canine prostate using endorectal and endourethral coils

A four-channel phased array consisting of one surface coil, two endorectal coils, and one flexible endourethral loop coil was designed for MRI of the canine prostate. The endorectal coils provide high signal in the posterior region of the prostate, while the endourethral and surface coils are sensitive to the central and anterior regions of the prostate. Gel phantom experiments indicate that the proposed phased-array configuration generates 15 times more signal-to-noise ratio (SNR) than a combination of two surface coils and one endorectal coil within the posterior region of the prostate; the performance of the two configurations is comparable near the anterior prostate surface. Ultimate intrinsic SNR (UISNR) analysis was used to compare the proposed phased array's performance to the best possible SNR for external coils. This analysis showed that the proposed phased array outperforms the best-case external coil within the posterior and central regions of the prostate by up to 20 times. In canine experiments in vivo, high-resolution fast spin-echo (FSE) images of the prostate were obtained with a pixel size of 230 microm obtained in 3 min 12 s. The proposed phased-array design potentially can be used to increase the accuracy of prostate cancer staging and the feasibility of MR-guided prostate interventions.

[Transrectal ultrasound of the prostate. Current status and prospects]

In recent years the role of ultrasound in the diagnosis of prostate carcinoma has increased in importance. In view of the increasing incidence of prostate cancer, which is the most frequent malignant neoplasm in men, TRUS (transrectal ultrasound) is an important imaging method in the diagnosis of various prostate diseases. This paper provides a basic overview of physical and technical bases of TRUS investigation of the prostate. It concerns technical developments and modern techniques designed to improve its value in diagnosis. Impressive innovations in ultrasound equipment, particularly in the area of colour-coded Doppler sonography in association with microbubble-enhanced colour Doppler ultrasound, have given rise to justifiable hope of improvements in the early diagnosis of prostate cancer.

Real time MRI-ultrasound image guided stereotactic prostate biopsy

To report a technique for target directed transperineal ultrasound guided biopsy using high resolution endorectal MRI images Ultrasound fusion. Two patients presented after external beam irradiation for prostate cancer with a rising PSA. An Endorectal MRI using a 1.5 Tesla scanner was obtained. Subsequently a Transrectal Ultrasound guided biopsy was performed. The Ultrasound probe was fixed to a stepper-stabilizer to provide a reference coordinate system for stereotaxic needle biopsy needle placement. The MRI image set was fused to the Ultrasound images in real time. Abnormal areas determined in the MR images were targeted for biopsy. Recurrent prostate carcinoma was detected pathologically in 3 of 4 stereotactic biopsies. Abnormal areas suspicious for cancer detected on T1 weighted images obtained in a strong field Endorectal MRI scan can be targeted for stereotactic biopsy using Transrectal Ultrasound. This image guide technique may be very useful in directing biopsies.

Should ultrasound criteria of the prostate be redefined to better evaluate when and where to biopsy

During the past 10 years, it has been suggested, and accepted by some, that transrectal ultrasound (TRUS) of the prostate should be used to identify a hypoechoic lesion or, if needed, guide biopsy into nonspecific areas. Retrospectively, the authors attempted to evaluate the need to identify areas that were on pathologic analysis, prostate cancer, but were not hypoechoic, but would require random/systematic biopsy to exclude prostate cancer. Six-hundred fifteen consecutive men were referred to the authors because of a concern found on digital rectal examination or because of increase in prostate-specific antigen. All patients underwent TRUS-guided biopsy of the prostate using either the four-quadrant or sextant biopsy technique. Each area undergoing biopsy was characterized as: 1) normal-appearing; 2) hypoechoic; 3) mixed echogenic (containing both hypoechoic and hyperechoic elements); 4) subtly hyperechoic (containing no calculi); or 5) isoechoic (lesion was seen because of distortion of the normal architecture). A diagnosis of carcinoma was made in 197 patients (32%). Of these, 99 (50.2%) patients had a hypoechoic lesion as the primary site, corresponding to their highest Gleason grade. Twenty-five (12.7%) had mixed echogenicity, nine (4.6%) had hyperechoic foci, and 23 (11.7%) had isoechoic biopsy-proven foci of prostate cancer. Forty-one (20.8%) patients with adenocarcinoma had normal ultrasound findings. The median Gleason grade for cancer in visible mixed echogenic and hyperechoic areas were generally higher than that for cancer in hypoechoic sites. Hypoechoic cancer sites had a Gleason grade range of 2 to 10 (median 5); mixed echogenic foci had a Gleason range of 2 to 10 (median 6); hyperechogenic cancers had a Gleason range of 2 to 8 (median 6); isoechoic cancers had a Gleason range of 2 to 7 (median 5); normal foci had a Gleason range of 2 to 8 (median 5). Results of this study suggest that 50% of clinically significant prostate cancers are not purely hypoechoic, and 37% of all diagnosed cancers contain no hypoechoic elements.

Predictors of prostate carcinoma: accuracy of gray-scale and color Doppler US and serum markers

PURPOSE

To determine the accuracy of detecting prostate cancer by using (a) gray-scale and color Doppler transrectal ultrasonography (US), (b) serum and excess prostate-specific antigen (PSA) levels, and (c) targeted and sextant transrectal US-guided biopsy. The relationship between US-detected neovascularity and tumor biologic activity was also evaluated.

MATERIALS AND METHODS

Between 1995 and 1999, 544 patients with elevated PSA levels and/or abnormal digital rectal examination underwent transrectal US-guided sextant biopsy and targeted biopsy of US abnormalities. Sensitivity, specificity, and accuracy of gray-scale US, color Doppler US, targeted biopsy, and PSA and excess PSA were calculated.

RESULTS

Gray-scale US depicted 78 (41.1%) of 190 cancers, whereas color Doppler US depicted 30 (15.8%) additional cancers. Targeted biopsy was used to detect 108 (56.8%) cancers, whereas sextant biopsy was used to detect 82 (43.2%) additional cancers. Although US-visible cancers had a higher Gleason grade than did cancers discovered at sextant biopsy (P <.05), 25 of the 66 cancers identified with sextant biopsy alone were Gleason grade 6 or higher. Color Doppler US-depicted hypervascularity correlated with biologically aggressive tumors. Excess PSA was normal in 58 (30.5%) cancers, with an accuracy of 67.3%, resulting in better prediction of prostate tumors than with serum PSA level alone.

CONCLUSION

Gray-scale transrectal US, even coupled with color Doppler US, is inadequate for prostate carcinoma screening; therefore, targeted biopsy should always be accompanied by complete sextant biopsy sampling.

Transrectal ultrasound and biopsy in the early diagnosis of prostate cancer

BACKGROUND

Historically, the prostate was evaluated for cancer by simple digital rectal examination, and biopsy to obtain a tissue diagnosis of cancer was performed blindly. The advent of ultrasound technology offered a new way to evaluate the prostate, and biopsy techniques were soon developed to incorporate ultrasound guidance.

METHODS

The authors review the role of transrectal ultrasound (TRUS) of the prostate and ultrasound-guided biopsy of the prostate in the diagnosis of prostate cancer. These techniques are traced from their origins to the current standards of care, with attention paid to developments and controversies in recent literature.

RESULTS

Early experience with TRUS led to the description of "classic" sonographic findings of prostate cancer. To obtain a tissue diagnosis of cancer, these regions were initially targeted in ultrasound-guided biopsies. Concomitant with the development of TRUS, though, was the development of the prostate-specific antigen (PSA) assay. Over the past decade, there has been a profound stage migration due to earlier detection of prostate cancer. Most patients now diagnosed with prostate cancer have no palpable abnormality or specific sonographic findings. In response, ultrasound-guided biopsies have become more systematic, rather than lesion-specific, in nature.

CONCLUSIONS

TRUS continues to play an important role in the evaluation of the prostate when malignancy is suspected. Although the optimal method of prostate biopsy is controversial, ultrasound is critical in ensuring accurate sampling of the gland.

The role of colour Doppler ultrasonography in detecting prostate cancer

OBJECTIVE

To determine the usefulness of colour Doppler ultrasonography (CDUS) in detecting prostate cancer, by comparing CDUS with grey-scale transrectal ultrasonography (TRUS) and magnetic resonance imaging (MRI).

PATIENTS AND METHODS

In all, 278 patients who underwent prostate biopsies because of an abnormal digital rectal examination, elevated prostate specific antigen levels, and/or abnormal TRUS between May 1998 and November 1999 were evaluated. The diagnostic accuracies of TRUS, CDUS, MRI and combinations of these imaging techniques in detecting prostate cancer were compared, based on the biopsy results.

RESULTS

Carcinoma was detected in 233 of 1696 specimens, and 87 patients were diagnosed with prostate cancer. For each detected cancer site, the sensitivity of CDUS was lower than those of other imaging techniques, but CDUS had high a specificity and positive predictive value. The combination of grey-scale TRUS and CDUS or MRI improved the sensitivity and negative predictive value. The specificity and positive predictive value of the combination of grey-scale TRUS and MRI were less than those for grey-scale TRUS alone, while those for the combination of grey-scale TRUS and CDUS were higher than those for grey-scale TRUS alone. Five tumours were isoechoic but seen as hypervascular lesions with CDUS.

CONCLUSION

CDUS provides information useful for detecting prostate cancer when used in combination with grey-scale TRUS, and should be included in the routine examination for prostate cancer.

Twelve prostate biopsies detect significant cancer volumes (> 0.5 mL)

OBJECTIVES

To compare, in a retrospective study, pathological specimens of prostate cancer detected in additional areas of a 12-core biopsy with tumours detected using traditional sextant biopsy.

PATIENTS AND METHODS

The study included 27 patients who had undergone radical prostatectomy (RP) for prostate cancer. Prostatectomy specimens of cancers detected using standard sextant biopsies were compared with those detected using six additional core biopsies. The RP specimens were analysed for cancer volume, Gleason score, tumour grade (Mostofi) and pathological stage.

RESULTS

Of the 27 patients, six (29%) had cancer detected in the extra six biopsy cores which would have otherwise have been undetected using sextant biopsy. Only two insignificant cancers were detected. The mean Gleason score was 6.1 for cancer detected by the sextant or 12-core method (P = 0.907); the mean grade (Mostofi) was 2.1 and 2. 33, respectively (P = 0.29). The final tumour stage in the 21 patients undergoing sextant biopsy was pT2 in 13 and pT3 in eight, compared with six pT2 tumours in the six patients diagnosed using extra biopsies. The mean (median, range) tumour volume was 5.7 (3.5, 0.312-23.75) mL for cancers detected on sextant biopsy and 1.99 (1. 85, 0.4-3.6) mL in the six cancers detected using extra cores (P = 0. 0138).

CONCLUSION

The detection of prostate cancer was increased using extra biopsy cores. There was a significant difference in tumour volume but not in Gleason score, Mostofi grade or final pathological tumour stage between tumours diagnosed using 12 cores and those detected on sextant biopsy.

Imaging prostate cancer

In the detection of prostate cancer, the most important role of imaging is ultrasound-guided prostatic biopsy. In the staging evaluation of prostate cancer, each presently used modality--transrectal US (TRUS), MR imaging, CT, nuclear medicine, and positron emission tomography--has advantages and disadvantages. Evidence-based guidelines on the use of CT and nuclear medicine bone scan, in assessing the risk of distant spread of prostate cancer, are available. There is no consensus and there are no guidelines, however, for the use of imaging in the evaluation of prostate cancer local tumor extent. Results on the value of TRUS vary widely, and prospective multicenter studies suggest that TRUS is no better than digital rectal examination in predicting extracapsular extension. MR imaging offers the most promise for local staging of prostate cancer, but it must resolve problems of reproducible image quality and interobserver variability, and it should prove its efficacy in multicenter trials before it can be recommended for general clinical use. The introduction of MR spectroscopic imaging further expands the value of MR imaging, offering anatomic and metabolic evaluation of prostate cancer.

Artificial neural network analysis (ANNA) of prostatic transrectal ultrasound

BACKGROUND

Our purpose was to determine the diagnostic potential of a new, computerized method of interpreting transrectal ultrasound (TRUS) information by artificial neural network analysis (ANNA). This method was developed to resolve the current dilemma of visual differentiation between benign and malignant tissue on TRUS. To train and objectively evaluate ANNA, a new precise method of computerized virtual correlation of preoperative ultrasound findings and radical prostatectomy histopathology was devised. After training with this pathologically confirmed digitized TRUS information, ANNA was tested in a blinded study.

METHODS

Following radical prostatectomy, 289 pathology whole-mount sections of 61 patients were correlated digitally with the corresponding TRUS slices. Specific selection of TRUS areas unequivocally identified on the correlated digitized pathohistology resulted in 553 pathology-confirmed representations (samples). Of these, 53 were used for training and 500 were subjected to blind analysis by ANNA.

RESULTS

ANNA classified 378 (99%) of the 381 benign pathology-confirmed samples correctly as benign. The false-positive rate was 1% (n = 3). Of the 119 pathology-confirmed malignant samples, 94 (79%) were classified correctly; 25 (21%) were falsely classified as normal. Out of all 119 cancers, ANNA classified 60 (71%) of the hypoechoic cancers as malignant and 24 (29%) as benign. Surprisingly, 34 (97%) of the isoechoic cancers were correctly classified by ANNA, missing only one sample.

CONCLUSIONS

The introduction of ANNA enhanced the accuracy of TRUS prostate cancer identification. Although not all malignant areas were detected, cancer was detected in each patient. The ability to detect isoechoic cancerous lesions appears to be the essential innovation over conventional TRUS interpretation.