Contrast-enhanced gray-scale transrectal ultrasound-guided prostate biopsy in men with elevated serum prostate-specific antigen levels

Low frequency 3D transmission ultrasound tomography: technical details and clinical implications

A novel 3D ultrasound tomographic (3D UT) method (called volography) that creates a speed of sound (SOS) map and a reflection modality that is co-registered are reviewed and shown to be artifact free even in the presence of high contrast and thus shown to be applicable for breast, orthopedic and pediatric clinical use cases. The 3D UT images are almost isotropic with mm resolution and the reflection image is compounded over 360 degrees to create sub-mm resolution in plane.

METHODS

The physics of ultrasound scattering requires 3D modeling and the concomitant high computational cost is ameliorated with a bespoke algorithm (paraxial approximation - discussed here) and Nvidia GPUs. The resulting reconstruction times are tabulated for clinical relevance. The resulting SOS map is used to create a refraction corrected reflection image at ∼3.6 MHz center frequency. The transmission data are highly redundant, collected over 360 degrees and at 2 mm levels by true matrix receiver arrays yielding 3D data. The high resolution SOS and attenuation maps and reflection images are used in a segmentation algorithm that optimally utilizes this information to segment out glandular, ductal, connective tissue, fat and skin. These volumes are used to estimate breast density, an important correlate to cancer.

RESULTS

Multiple SOS images of breast, knee and segmentations of breast glandular and ductal tissue are shown. Spearman rho is calculated between our volumetric breast density estimates and Volpara™ from mammograms, as 0.9332. Multiple timing results are shown and indicate the variability of the reconstruction times with breast size and type but are ∼30 minutes for average size breast. The timing results with the 3D algorithm indicate ∼60 minute reconstruction times for pediatrics with two Nvidia GPUs. Characteristic variations of the glandular and ductal volumes over time are shown. The SOS from QT images are compared with literature values. The results of a multi-reader multi-case (MRMC) study are shown that compares the 3D UT with full field digital mammography and resulted in an average increase in ROC AUC of 10%. Orthopedic (knee) 3D UT images compared with MRI indicate regions of zero signal in the MRI are clearly displayed in the QT image. Explicit representation of the acoustic field is shown, indicating its 3D nature. An image of in vivo breast with the chest muscle is shown and speed of sound agreement with literature values are tabulated. Reference is made to a recently published paper validating pediatric imaging.

CONCLUSIONS

The high Spearman rho indicates a monotonic (not necessarily linear) relation between our method and industry gold standard Volpara™ density. The acoustic field verifies the need for 3D modeling. The MRMC study, the orthopedic images, breast density study, and references, all indicate the clinical utility of the SOS and reflection images. The QT image of the knee shows its ability to monitor tissue the MRI cannot. The included references and images herein indicate the proof of concept for 3D UT as a viable and valuable clinical adjunct in pediatric and orthopedic situations in addition to the breast imaging.

Application of Multiple Ultrasonic Techniques in the Diagnosis of Prostate Cancer

Methods for diagnosing prostate cancer (PCa) are developing in the direction of imaging. Advanced ultrasound examination modes include micro-Doppler, computerized-transrectal ultrasound, elastography, contrast-enhanced ultrasound and microultrasound. When two or more of these modes are used in PCa diagnosis, the combined technique is called multiparameter ultrasound (mp-US). Mp-US provides complementary information to multiparameter magnetic resonance imaging (mp-MRI) for diagnosing PCa. At present, no study has attempted to combine the characteristics of different ultrasound modes with advanced classification systems similar to the PIRADS system in mpMRI for the diagnosis of PCa. As an imaging method, mp-US has great potential in the diagnosis of PCa.

[Sonography of the prostate : Relevance for urologists in daily clinical routine]

Despite the continuous technical progress regarding the transrectal ultrasonography of the prostate (TRUS) and its successful use in combination with magnetic resonance imaging (MRI) in MRI-targeted biopsy, there is no radiologic modality being able to rule out clinically significant prostate cancer without the need of systematic biopsy. In the past few years, TRUS regained more attention due to the development of high frequency ultrasound as well as the combination of different ultrasonic modalities like shear wave elastography and contrast-enhanced sonography (CEUS). Currently, multiparametric MRI (mpMRI)-targeted biopsy shows the best results concerning detection rates, sensitivity and specificity of clinically significant prostate cancer compared to systematic biopsy. In the future, transperineal biopsy is probably going to increasingly replace the transrectal biopsy approach. For both approaches, transrectal ultrasonography is necessary to display the prostate and to detect suspicious lesions. Therefore future improvements in transrectal ultrasonography can be expected.

The Value of Contrast-Enhanced Ultrasonography Combined with Real-Time Strain Elastography in the Early Diagnosis of Prostate Cancer

To evaluate the performance of a combination of real-time strain elastography (RTSE) and contrast-enhanced transrectal ultrasound (CETRUS) for prostate cancer detection. Patients with serum prostate-specific antigen (PSA) levels of ≥4.0 ng/ml were prospectively enrolled between June 2014 and December 2016. 153 prostate nodules diagnosed by conventional ultrasound were prospectively enrolled and examined by CETRUS and RTSE before a biopsy. Multivariate logistic regression models were established for CETRUS, and CETRUS combined with RTSE to diagnose prostate malignancy. The diagnostic performances of CETRUS, RTSE, and their combined use were evaluated with the receiver operating characteristic (ROC) curve. The multivariate logistic regression for CETRUS combined with RTSE showed that enhanced strength, enhanced uniformity, and elasticity scores were the independent predictors of prostate malignancy. The area under the ROC curve of CETRUS combined with RTSE (0.921±0.023) was higher than that of CETRUS and RTSE (0.88±0.029 and 0.80±0.038, respectively; both p<0.05). Moreover, the sensitivity, accuracy and negative predictive value of CETRUS combined with RTSE were 92.1%, 86.2%, and 84.6%, respectively. The omission diagnostic rate of CETRUS combined with RTSE (7.9%) was reduced. And the diagnostic accuracy of CETRUS combined with RTSE was significantly higher than that of CETRUS and RTSE (p<0.05). While the diagnostic accuracy of CETRUS was close to the RTSE, the difference was not statistically significant (p>0.05). The combined RTSE with CETRUS approach significantly improved the sensitivity and overall accuracy for correctly identifying prostate cancer.

Diagnostic performance of contrast enhanced ultrasound in patients with prostate cancer: a meta-analysis

RATIONALE AND OBJECTIVES

We aimed to do a meta-analysis of the existing literature to assess the accuracy of prostate cancer (PCa) studies that use contrast-enhanced ultrasound (CEUS) as a diagnostic tool.

MATERIALS AND METHODS

The MEDLINE, EMBASE, and Cochrane Library databases were searched for relevant original articles published up to August 2012. Characteristics of Included studies were recorded. Methodological quality was assessed by using the quality assessment of diagnostic studies tool. Pooled weighted estimates of diagnostic odds ratio (DOR), sensitivity, specificity, and positive and negative likelihood ratio (LR) were calculated. A summary receiver operator characteristic (SROC) curve was constructed to calculate the area under the curve (AUC). Publication bias analysis was also performed.

RESULTS

Sixteen studies (2624 patients) were included in the meta-analysis. Various contrast agents and imaging modes were applied. The independent random-effects summary showed a variation in diagnostic values. The summary estimates of sensitivity, specificity, and DOR were 0.70, 0.74, and 9.09, respectively. The weighted positive and negative LR were 2.81 and 0.35, with statistically significant between-study heterogeneity (P < .001). Sensitivity was better in positive patient studies than positive biopsy cores ones (0.78 vs. 0.64). SROC plot displayed value for AUC (0.82). Begg's test (P = .822) and Egger's test (P = .198) did not show evidence of publication bias.

CONCLUSION

CEUS is a promising tool in the detection of PCa, but it cannot completely replace systematic biopsy under the present circumstances. It is necessary to standardize imaging techniques, contrast agents and diagnostic criteria. Large samples, multi-center studies and high-quality prospective trials are necessary to assess its clinical value.

The contribution of strain patterns in characterization of prostate peripheral zone lesions at transrectal ultrasonography

BACKGROUND

Elasticity is an important characteristic of tissue. During an elastography examination, various strain images of lesions are observed, and a suitable classification of strain patterns (SP) may provide vital diagnostic information about lesions. Numerous studies have shown that ultrasound elastography can improve the detection of prostate cancer, but the diagnostic value of SP classification has not yet been fully evaluated.

PURPOSE

To investigate the contribution of SP on the characterization of prostate peripheral zone lesions by transrectal real-time tissue elastography (TRTE) in combination with conventional transrectal ultrasonography (TRUS).

MATERIAL AND METHODS

One hundred and seventy-one patients with suspected prostate cancer underwent TRUS and TRTE examinations. The SPs of the suspicious lesions were classified into five scores by TRTE according to the degree and distribution of strain. All findings were confirmed by transrectal systematic 12-core biopsies and targeted biopsies for suspicious areas detecting by TRUS and/or TRTE.

RESULTS

One hundred and forty-eight of 171 patients had high-quality TRTE imaging and were included into the study. When a cut-off point of SP score III was used, the area under the receiver-operating characteristic curve (AUC) was, respectively, 0.75 (95% CI: 0.67-0.83), 0.85 (95% CI: 0.78-0.91) and 0.84 (95% CI: 0.77-0.91) for the diagnosis of prostate cancer by TRUS, TRTE and TRTE + TRUS. A linear tendency of SP and Gleason scores was observed in scores III-V. The detection rate of prostate cancer using TRTE-targeted biopsy (75.8%) was significantly higher than that of systematic 12-core biopsy plus TRUS-targeted biopsy (14.5%) (P = 0.00).

CONCLUSION

This study suggests the significant contribution of SP on characterization of prostate peripheral zone lesions and the improvement of TRTE-targeted biopsy on detection of prostate cancer.

Differentiation of prostate cancer from benign lesions using strain index of transrectal real-time tissue elastography

OBJECTIVE

This study was to assess the diagnostic value of strain index (SI) for transrectal real-time tissue elastography (TRTE) on differentiating malignant from benign lesions in the prostate peripheral zone.

METHODS

83 patients suspected of having prostate cancer (PCa) underwent transrectal ultrasonography (TRUS) and TRTE examinations. The lesions in the prostate peripheral zone detected by TRTE were set as the regions of interest (ROI) for strain ratio (SR) measurement (SRA). The moderate texture tissues without lesion were set as the reference ROI for SR measurement (SRB). Then, SI (SRB/SRA) of total lesions (ASI) and local lesion (PSI) were calculated, and the diagnostic values of ASI and PSI on differentiating benign from malignant lesions were assessed respectively.

RESULTS

The range of PSI was 2.23-67.21 (29.97 ± 15.58) in malignant tumors and 0. 4-43.6 (7.79 ± 8.75) in benign lesions (AUC=0.90), while the range of ASI was 2.84-47.9 (8.38 ± 12.20) in malignant tumors and 0.4 -2.79 (5.85 ± 7.29) in benign lesions (AUC=0.62). There was significant difference of PSI values between the benign and malignant lesions (P<0.01). At the cutoff value of 17.44, PSI yielded the highest sensitivity (74.5%) and specificity (83.3%) for discriminating PCa from benign lesions. The capability of PSI in the diagnosis of PCa improved with the increase of Gleason scores.

CONCLUSION

PSI is one of the elasticity parameters obtained easily by TRTE, it can provide more information in the differentiation of prostate peripheral zone lesions.

MR to ultrasound registration for image-guided prostate interventions

A deformable registration method is described that enables automatic alignment of magnetic resonance (MR) and 3D transrectal ultrasound (TRUS) images of the prostate gland. The method employs a novel "model-to-image" registration approach in which a deformable model of the gland surface, derived from an MR image, is registered automatically to a TRUS volume by maximising the likelihood of a particular model shape given a voxel-intensity-based feature that represents an estimate of surface normal vectors at the boundary of the gland. The deformation of the surface model is constrained by a patient-specific statistical model of gland deformation, which is trained using data provided by biomechanical simulations. Each simulation predicts the motion of a volumetric finite element mesh due to the random placement of a TRUS probe in the rectum. The use of biomechanical modelling in this way also allows a dense displacement field to be calculated within the prostate, which is then used to non-rigidly warp the MR image to match the TRUS image. Using data acquired from eight patients, and anatomical landmarks to quantify the registration accuracy, the median final RMS target registration error after performing 100 MR-TRUS registrations for each patient was 2.40 mm.

Technologies for localization and diagnosis of prostate cancer

The gold standard for detecting prostate cancer (PCa), systematic biopsy, lacks sensitivity as well as grading accuracy. PSA screening leads to over-treatment of many men, and it is unclear whether screening reduces PCa mortality. This review provides an understanding of the difficulties of localizing and diagnosing PCa. It summarizes recent developments of ultrasound (including elastography) and MRI, and discusses some alternative experimental techniques, such as resonance sensor technology and vibrational spectroscopy. A comparison between the different methods is presented. It is concluded that new ultrasound techniques are promising for targeted biopsy procedures, in order to detect more clinically significant cancers while reducing the number of cores. MRI advances are very promising, but MRI remains expensive and MR-guided biopsy is complex. Resonance sensor technology and vibrational spectroscopy have shown promising results in vitro. There is a need for large prospective multicentre trials that unambiguously prove the clinical benefits of these new techniques.

Imaging techniques for prostate cancer: implications for focal therapy

The multifocal nature of prostate cancer has necessitated whole-gland therapy in the past; however, since the widespread use of PSA screening, patients frequently present with less-advanced disease. Many men with localized disease wish to avoid the adverse effects of whole-gland therapy; therefore, focal therapy for prostate cancer is being considered as a treatment option. For focal treatment to be viable, accurate imaging is required for diagnosis, staging, and monitoring of treatment. Developments in MRI and PET have brought more attention to prostate imaging and the possibility of improving the accuracy of focal therapy. In this Review, we discuss the advantages and disadvantages of conventional methods for imaging the prostate, new developments for targeted imaging, and the possible role of image-guided biopsy and therapy for localized prostate cancer.