Initial clinical experience with real-time transrectal ultrasonography-magnetic resonance imaging fusion-guided prostate biopsy

Ultrasound-Tomographic Image Fusion - A Novel Tool for Follow up After Acute Complicated Appendicitis

BACKGROUND

Computerized tomography (CT) is an integral part of the follow-up and decision-making process in complicated acute appendicitis (AA) treated non-operatively. However, repeated CT scans are costly and cause radiation exposure. Ultrasound-tomographic image fusion is a novel tool that integrates CT images to an Ultrasound (US) machine, thus allowing accurate assessment of the healing process compared to CT on presentation. In this study, we aimed to assess the feasibility of US-CT fusion as part of the management of appendicitis.

MATERIALS AND METHODS

We retrospectively collected data of consecutive patients with complicated AA managed non-operatively and followed up with US Fusion for clinical decision-making. Patients demographics, clinical data, and follow-up outcomes were extracted and analyzed.

RESULTS

Overall, 19 patients were included. An index Fusion US was conducted in 13 patients (68.4%) during admission, while the rest were performed as part of an ambulatory follow-up. Nine patients (47.3%) had more than 1 US Fusion performed as part of their follow-up, and 3 patients underwent a third US Fusion. Eventually, 5 patients (26.3%) underwent elective interval appendectomy based on the outcomes of the US Fusion, due to a non-resolution of imaging findings and ongoing symptoms. In 10 patients (52.6%), there was no evidence of an abscess in the repeated US Fusion, while in 3 patients (15.8%), it significantly diminished to less than 1 cm in diameter.

CONCLUSION

Ultrasound-tomographic image fusion is feasible and can play a significant role in the decision-making process for the management of complicated AA.

Meta-Learning Initializations for Interactive Medical Image Registration

We present a meta-learning framework for interactive medical image registration. Our proposed framework comprises three components: a learning-based medical image registration algorithm, a form of user interaction that refines registration at inference, and a meta-learning protocol that learns a rapidly adaptable network initialization. This paper describes a specific algorithm that implements the registration, interaction and meta-learning protocol for our exemplar clinical application: registration of magnetic resonance (MR) imaging to interactively acquired, sparsely-sampled transrectal ultrasound (TRUS) images. Our approach obtains comparable registration error (4.26 mm) to the best-performing non-interactive learning-based 3D-to-3D method (3.97 mm) while requiring only a fraction of the data, and occurring in real-time during acquisition. Applying sparsely sampled data to non-interactive methods yields higher registration errors (6.26 mm), demonstrating the effectiveness of interactive MR-TRUS registration, which may be applied intraoperatively given the real-time nature of the adaptation process.

Diagnostic yield of fusion magnetic resonance-guided prostate biopsy versus cognitive-guided biopsy in biopsy-naive patients: a head-to-head randomized controlled trial

BACKGROUND

The combination of MRI-guided targeted biopsy (MRGB) with systematic biopsy (SB) provides the highest accuracy in detecting prostate cancer. There is a controversy over the superiority of fusion targeted biopsy (fus-MRGB) over cognitive targeted biopsy (cog-MRGB). The present head-to-head randomized controlled trial was performed to compare diagnostic yield of fus-MRGB in combination with SB with cog-MRGB in combination with SB.

METHODS

Biopsy-naive patients with a prostate-specific antigen level between 2 and 10 ng/dL who were candidates for prostate biopsy were included in the study. Multiparametric MRI was performed on all patients and patients with suspicious lesions with Prostate Imaging Reporting and Data System score of 3 or more were randomized into two groups. In the cog-MRGB group, a targeted cognitive biopsy was performed followed by a 12-core SB. Similarly, in the fus-MRGB group, first targeted fusion biopsy and then SBs were performed. The overall and clinically significant prostate cancer detection rates between the two study groups were compared by the Pearson χ² test. McNemar test was used to compare detection rates yielded by SB and targeted biopsy in each study group.

RESULTS

One-hundred men in the cog-MRGB group and 99 men in the fus-MRGB group were compared. The baseline characteristics of patients including age, PSA level, prostate volume, PSA density, and clinical stage were similar in the two groups (p > 0.05). Both the overall and clinically significant prostate cancer detection rates in the fus-MRGB group (44.4% and 33.3%, respectively) were significantly higher than cog-MRGB group (31.0% and 19.0%, respectively) (p = 0.035 and p = 0.016, respectively).

CONCLUSION

The accuracy of identifying overall and clinically significant prostate cancer by fus-MRGB in biopsy-naive patients with PSA levels between 2 and 10 ng/dL is significantly higher than cog-MRGB and if available, we recommend using fus-MRGB over cog-MRGB in these patients.

Biomechanically constrained non-rigid MR-TRUS prostate registration using deep learning based 3D point cloud matching

A non-rigid MR-TRUS image registration framework is proposed for prostate interventions. The registration framework consists of a convolutional neural networks (CNN) for MR prostate segmentation, a CNN for TRUS prostate segmentation and a point-cloud based network for rapid 3D point cloud matching. Volumetric prostate point clouds were generated from the segmented prostate masks using tetrahedron meshing. The point cloud matching network was trained using deformation field that was generated by finite element analysis. Therefore, the network implicitly models the underlying biomechanical constraint when performing point cloud matching. A total of 50 patients' datasets were used for the network training and testing. Alignment of prostate shapes after registration was evaluated using three metrics including Dice similarity coefficient (DSC), mean surface distance (MSD) and Hausdorff distance (HD). Internal point-to-point registration accuracy was assessed using target registration error (TRE). Jacobian determinant and strain tensors of the predicted deformation field were calculated to analyze the physical fidelity of the deformation field. On average, the mean and standard deviation were 0.94±0.02, 0.90±0.23 mm, 2.96±1.00 mm and 1.57±0.77 mm for DSC, MSD, HD and TRE, respectively. Robustness of our method to point cloud noise was evaluated by adding different levels of noise to the query point clouds. Our results demonstrated that the proposed method could rapidly perform MR-TRUS image registration with good registration accuracy and robustness.

Magnetic resonance imaging-transrectal ultrasound image fusion guidance of prostate biopsies: current status, challenges and future perspectives

The use of multiparametric magnetic resonance imaging (mpMRI) in prostate cancer (PCa) diagnosis is rapidly evolving to try to overcome the limitations of the current diagnostic pathway using systematic transrectal ultrasound-guided biopsies (TRUS_bx) for all men with clinical suspicion of PCa. Prostate mpMRI allows for high quality lesion detection and characterization and has been shown to improve detection of significant PCa with a more accurate Gleason score grading. Suspicious lesions can be stratified by suspicion and sampled by selective MRI-guided targeted biopsies (TBx) for improved diagnostic accuracy. Several TBx methods have been established and include MRI/TRUS image fusion biopsies (cognitive or software-assisted) and in-bore biopsies, but none have yet proven superior in clinical practice. However, while MRI in-bore biopsy is not routinely used due to its costs and limited availability, MRI/TRUS image fusion is rapidly embraced as it allows skilled urologists to perform TBx in an outpatient clinic. Furthermore, it gives the operator the advantage of adding TBx to the systematic standard biopsy scheme, which is the currently recommended approach. With the anticipated increased future use of prebiopsy mpMRI, a more widespread implementation of MRI/TRUS image fusion platforms is concurrently expected in clinical practice. Therefore, the objective of this review is to assess the current status, challenges and future perspectives of prostate MRI/TRUS image fusion biopsies.

Pilot study of MRI/ultrasound fusion imaging in postpartum assessment of Cesarean section scar

OBJECTIVE

To evaluate prospectively the uterine scar after Cesarean section (CS) and the corresponding uterine region after vaginal delivery (VD) at 6 weeks postpartum using transabdominal (TAS) and transvaginal (TVS) sonography with magnetic resonance imaging (MRI) fusion to investigate whether fusion imaging allows standardized and reproducible identification of the scar location and measurement of uterine wall thickness compared with high-resolution MRI alone.

METHODS

Pelvic MRI was performed 6 weeks after delivery in 30 women (10 with planned CS (PCS), 10 with emergency CS (ECS) and 10 with VD). After transfer of MRI-DICOM datasets to the ultrasound system, the scar region after CS and the corresponding uterine region after VD were examined by TAS (5 MHz) and TVS (10 MHz) using smart fusion with MRI to guide visualization of the region in the corresponding sectional planes for both modalities. Vascularization of the scar region was determined as a percentage area using power Doppler ultrasound. Anterior (AW) and posterior (PW) uterine wall thickness was measured using TAS and TVS with fusion imaging and using MRI alone.

RESULTS

TVS with fusion imaging was applied successfully for uterine assessment at the end of the postpartum period in all women. TAS failed to identify the scar area in three women. Imaging techniques were similar in the evaluation of AW and PW thickness following VD. MRI and MRI/TVS fusion showed significant differences in AW thickness or scar area, in terms of the difference relative to PW thickness, in women with PCS and ECS (MRI: PCS, 4.3 mm; ECS, 4.2 mm; VD, 0.8 mm; P = 0.034; MRI/TVS fusion: PCS, 2.0 mm; ECS, 3.3 mm; VD, 0.0 mm; P = 0.01). The degree of vascularization in the scar region measured by power Doppler ultrasound was lower after PCS (13.1 ± 9.4%/area) and ECS (17.0 ± 8.2%/area) than after VD (34.6 ± 8.5%/area; P = 0.0017).

CONCLUSION

MRI/ultrasound fusion imaging can be performed in a reproducible manner for examination of the postpartum uterus. MRI/TVS fusion enables standardized identification of the CS scar location and vascularization is reduced in this area. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

MRI-directed cognitive fusion-guided biopsy of the anterior prostate tumors

PURPOSE

We aimed to evaluate the efficacy of magnetic resonance imaging (MRI)-directed cognitive fusion transrectal ultrasonography (TRUS)-guided anterior prostate biopsy for diagnosis of anterior prostate tumors and to illustrate this technique.

METHODS

A total of 39 patients with previous negative TRUS biopsy, but high clinical suspicion of occult prostate cancer, prospectively underwent prostate MRI including diffusion-weighted imaging (DWI). Patients with a suspicious anterior lesion on MRI underwent targeted anterior gland TRUS-guided biopsy with cognitive fusion technique using sagittal probe orientation. PIRADS version 1 scores (T2, DWI, and overall), lesion size, prostate-specific antigen (PSA), PSA density, and prostate gland volume were compared between positive and negative biopsy groups and between clinically significant cancer and remaining cases. Logistic regression analysis of imaging parameters and prostate cancer diagnosis was performed.

RESULTS

Anterior gland prostate adenocarcinoma was diagnosed in 18 patients (46.2%) on targeted anterior gland TRUS-guided biopsy. Clinically significant prostate cancer was diagnosed in 13 patients (33.3%). MRI lesion size, T2, DWI, and overall PIRADS scores were significantly higher in patients with positive targeted biopsies and those with clinically significant cancer (P < 0.05). Biopsies were positive in 90%, 33%, and 29% of patients with overall PIRADS scores of 5, 4, and 3 respectively. Overall PIRADS score was an independent predictor of all prostate cancer diagnosis and of clinically significant prostate cancer diagnosis.

CONCLUSION

Targeted anterior gland TRUS-guided biopsy with MRI-directed cognitive fusion enables accurate sampling and may improve tumor detection yield of anterior prostate cancer.

Multimodal Imaging in Focal Therapy Planning and Assessment in Primary Prostate Cancer

PURPOSE

There is increasing interest in focal therapy (male lumpectomy) of localized low-intermediate risk prostate cancer. Focal therapy is typically associated with low morbidity and provides the possibility of retreatment. Imaging is pivotal in stratification of men with localized prostate cancer for active surveillance, focal therapy or radical intervention. This article provides a concise review of focal therapy and the evolving role of imaging in this clinical setting.

METHODS

We performed a narrative and critical literature review by searching PubMed/Medline database from January 1997 to January 2017 for articles in the English language and the use of search keywords "focal therapy", "prostate cancer", and "imaging".

RESULTS

Most imaging studies are based on multiparametric magnetic resonance imaging. Transrectal ultrasound is inadequate independently but multiparametric ultrasound may provide new prospects. Positron emission tomography with radiotracers targeted to various underlying tumor biological features may provide unprecedented new opportunities. Multimodal Imaging appears most useful in localization of intraprostatic dominant index lesions amenable to focal therapy, in early assessment of therapeutic efficacy and potential need for additional focal treatments or transition to whole-gland therapy, and in predicting short-term and long-term outcomes.

CONCLUSION

Multimodal imaging is anticipated to play an increasing role in the focal therapy planning and assessment of low-intermediate risk prostate cancer and thereby moving this form of treatment option forward in the clinic.

Magnetic Resonance Imaging-Ultrasound Fusion-Guided Prostate Biopsy: Review of Technology, Techniques, and Outcomes

Transrectal ultrasound (TRUS)-guided (12-14 core) systematic biopsy of the prostate is the recommended standard for patients with suspicion of prostate cancer (PCa). Advances in imaging have led to the application of magnetic resonance imaging (MRI) for the detection of PCa with subsequent development of software-based co-registration allowing for the integration of MRI with real-time TRUS during prostate biopsy. A number of fusion-guided methods and platforms are now commercially available with common elements in image and analysis and planning. Implementation of fusion-guided prostate biopsy has now been proven to improve the detection of clinically significant PCa in appropriately selected patients.

Prostate cancer detection using multiparametric 3 - tesla MRI and fusion biopsy: preliminary results

Objective:

To evaluate the diagnostic efficacy of transrectal ultrasonography (US) biopsy with imaging fusion using multiparametric (mp) magnetic resonance imaging (MRI) in patients with suspicion of prostate cancer (PCa), with an emphasis on clinically significant tumors according to histological criteria.

Materials and Methods:

A total of 189 consecutive US/MRI fusion biopsies were performed obtaining systematic and guided samples of suspicious areas on mpMRI using a 3 Tesla magnet without endorectal coil. Clinical significance for prostate cancer was established based on Epstein criteria.

Results:

In our casuistic, the average Gleason score was 7 and the average PSA was 5.0ng/mL. Of the 189 patients that received US/MRI biopsies, 110 (58.2%) were positive for PCa. Of those cases, 88 (80%) were clinically significant, accounting for 46.6% of all patients. We divided the MRI findings into 5 Likert scales of probability of having clinically significant PCa. The positivity of US/MRI biopsy for clinically significant PCa was 0%, 17.6% 23.5%, 53.4% and 84.4% for Likert scores 1, 2, 3, 4 and 5, respectively. There was a statistically significant difference in terms of biopsy results between different levels of suspicion on mpMRI and also when biopsy results were divided into groups of clinically non-significant versus clinically significant between different levels of suspicion on mpMRI (p-value <0.05 in both analyzes).

Conclusion:

We found that there is a significant difference in cancer detection using US/MRI fusion biopsy between low-probability and intermediate/high probability Likert scores using mpMRI.

MR-targeted TRUS prostate biopsy using local reference augmentation: initial experience

Purpose

To evaluate MR-targeted TRUS prostate biopsy using a novel local reference augmentation method.

Patients and methods

Tracker-based MR–TRUS fusion was applied using local reference augmentation. In contrast to conventional whole gland fusion, local reference augmentation focuses the highest registration accuracy to the region surrounding the lesion to be biopsied. Pre-acquired multi-parametric MR images (mpMRI) were evaluated using PIRADS classification. T2-weighted MR images were imported on an ultrasound machine to allow for MR–TRUS fusion. Biopsies were targeted to the most suspicious lesion area identified on mpMRI. Each target was biopsied 1–5 times. For each biopsied lesion the diameter, PIRADS and Gleason scores, visibility during fusion, and representativeness were recorded.

Results

Included were 23 consecutive patients with 25 MR suspicious lesions, of which 11 patients had a previous negative TRUS-guided biopsy and 12 were biopsy naïve. The cancer detection rate was 64 % (Gleason score ≥6). Biopsy was negative (i.e., no Gleason score) in seven patients confirmed by follow-up in all of them (up to 18 months). After MR–TRUS fusion, 88 % of the lesions could be visualized on TRUS. The cancer detection rate increases with increasing lesion size, being 73 % for lesions larger than 10 mm.

Conclusion

Tracker-based MR–TRUS fusion biopsy with local reference augmentation is feasible, especially for lesions with an MR maximum diameter of at least 10 mm or PIRADS 5 lesions. If this is not the case, we recommend in-bore MR-guided biopsy.

Biomechanical modeling constrained surface-based image registration for prostate MR guided TRUS biopsy

PURPOSE

Adding magnetic resonance (MR)-derived information to standard transrectal ultrasound (TRUS) images for guiding prostate biopsy is of substantial clinical interest. A tumor visible on MR images can be projected on ultrasound (US) by using MR-US registration. A common approach is to use surface-based registration. The authors hypothesize that biomechanical modeling will better control deformation inside the prostate than a regular nonrigid surface-based registration method. The authors developed a novel method by extending a nonrigid surface-based registration algorithm with biomechanical finite element (FE) modeling to better predict internal deformations of the prostate.

METHODS

Data were collected from ten patients and the MR and TRUS images were rigidly registered to anatomically align prostate orientations. The prostate was manually segmented in both images and corresponding surface meshes were generated. Next, a tetrahedral volume mesh was generated from the MR image. Prostate deformations due to the TRUS probe were simulated using the surface displacements as the boundary condition. A three-dimensional thin-plate spline deformation field was calculated by registering the mesh vertices. The target registration errors (TREs) of 35 reference landmarks determined by surface and volume mesh registrations were compared.

RESULTS

The median TRE of a surface-based registration with biomechanical regularization was 2.76 (0.81-7.96) mm. This was significantly different than the median TRE of 3.47 (1.05-7.80) mm for regular surface-based registration without biomechanical regularization.

CONCLUSIONS

Biomechanical FE modeling has the potential to improve the accuracy of multimodal prostate registration when comparing it to a regular nonrigid surface-based registration algorithm and can help to improve the effectiveness of MR guided TRUS biopsy procedures.

Towards Personalized Statistical Deformable Model and Hybrid Point Matching for Robust MR-TRUS Registration

Registration and fusion of magnetic resonance (MR) and 3D transrectal ultrasound (TRUS) images of the prostate gland can provide high-quality guidance for prostate interventions. However, accurate MR-TRUS registration remains a challenging task, due to the great intensity variation between two modalities, the lack of intrinsic fiducials within the prostate, the large gland deformation caused by the TRUS probe insertion, and distinctive biomechanical properties in patients and prostate zones. To address these challenges, a personalized model-to-surface registration approach is proposed in this study. The main contributions of this paper can be threefold. First, a new personalized statistical deformable model (PSDM) is proposed with the finite element analysis and the patient-specific tissue parameters measured from the ultrasound elastography. Second, a hybrid point matching method is developed by introducing the modality independent neighborhood descriptor (MIND) to weight the Euclidean distance between points to establish reliable surface point correspondence. Third, the hybrid point matching is further guided by the PSDM for more physically plausible deformation estimation. Eighteen sets of patient data are included to test the efficacy of the proposed method. The experimental results demonstrate that our approach provides more accurate and robust MR-TRUS registration than state-of-the-art methods do. The averaged target registration error is 1.44 mm, which meets the clinical requirement of 1.9 mm for the accurate tumor volume detection. It can be concluded that the presented method can effectively fuse the heterogeneous image information in the elastography, MR, and TRUS to attain satisfactory image alignment performance.

Recent advances in image-guided targeted prostate biopsy

Prostate cancer is a common malignancy in the United States that results in over 30,000 deaths per year. The current state of prostate cancer diagnosis, based on PSA screening and sextant biopsy, has been criticized for both overdiagnosis of low-grade tumors and underdiagnosis of clinically significant prostate cancers (Gleason score ≥7). Recently, image guidance has been added to perform targeted biopsies of lesions detected on multi-parametric magnetic resonance imaging (mpMRI) scans. These methods have improved the ability to detect clinically significant cancer, while reducing the diagnosis of low-grade tumors. Several approaches have been explored to improve the accuracy of image-guided targeted prostate biopsy, including in-bore MRI-guided, cognitive fusion, and MRI/transrectal ultrasound fusion-guided biopsy. This review will examine recent advances in these image-guided targeted prostate biopsy techniques.

Phase I/II prospective trial of cancer-specific imaging using ultrasound spectrum analysis tissue-type imaging to guide dose-painting prostate brachytherapy

PURPOSE

To assess the technical feasibility, toxicity, dosimetry, and preliminary efficacy of dose-painting brachytherapy guided by ultrasound spectrum analysis tissue-type imaging (TTI) in low-risk, localized prostate cancer.

METHODS AND MATERIALS

Fourteen men with prostate cancer who were candidates for brachytherapy as sole treatment were prospectively enrolled. Treatment planning goal was to escalate the tumor dose to 200% with a modest de-escalation of dose to remaining prostate compared with our standard. Primary end points included technical feasibility of TTI-guided brachytherapy and equivalent or better toxicity compared with standard brachytherapy. Secondary end points included dose escalation to tumor regions and de-escalated dose to nontumor regions on the preimplant plan, negative prostate biopsy at 2 years, and freedom from biochemical failure.

RESULTS

Thirteen of fourteen men successfully completed the TTI-guided brachytherapy procedure for a feasibility rate of 93%. A software malfunction resulted in switching one patient from TTI-guided to standard brachytherapy. An average of 2.7 foci per patient was demonstrated and treated with an escalated dose. Dosimetric goals on preplan were achieved. One patient expired from unrelated causes 65 days after brachytherapy. Toxicity was at least as low as standard brachytherapy. Two-year prostate biopsies were obtained from six men; five (83%) were definitively negative, one showed evidence of disease with treatment effect, and none were positive. No patients experienced biochemical recurrence after a median followup of 31.5 (24-52) months.

CONCLUSIONS

We have demonstrated that TTI-guided dose-painting prostate brachytherapy is technically feasible and results in clinical outcomes that are encouraging in terms of low toxicity and successful biochemical disease control.

Age-related changes of normal prostate: evaluation by MR diffusion tensor imaging

In this study, fifty healthy normal volunteers were divided into 3 groups according to age: group A (15-30 years, n=14), group B (31-50 years, n=24), group C (>51 years, n=12). The FA and ADC values in PZ and CZ were measured, and difference between the PZ and CZ were assessed. The results indicated that no significant difference were found in the FA and ADC values between the left and right of PZ (P>0.05), but significant differences were observed in the FA and ADC values between PZ and CZ within each group (P<0.05). The FA values of PZ in three groups were 0.227±0.052, 0.202±0.055, and 0.145±0.034, respectively. The ADC values were found to be 1.439±0.160×10(-3), 1.652±0.256×10(-3), and 2.001±0.266×10(-3) mm(2)/s, accordingly. The FA and ADC values in PZ were significantly (P<0.05) different between groups. The FA values of CZ in different groups were found to be 0.291±0.083, 0.287±0.045, and 0.257±0.059, respectively; while the corresponding ADC values were 1.374±0.171×10(-3), 1.382±0.178×10(-3), and 1.415±0.136×10(-3) mm(2)/s, respectively. The FA and ADC values in CZ were not statistically (P>0.05) different between groups. Pearson correlation analysis results showedthat the FA values in PZ havenegative correlation with age (r=-0.498, P<0.05), while the ADC values exhibited a positive correlation with age (r=0.682, P<0.05). No correlations between the changes of FA and ADC values and age were noted in CZ. In conclusion, the FA and ADC values in the normal prostatic PZ were age-dependent. FA decreases and ADC increases with age. In contrast, the FA and ADC values in the normal prostatic CZ were not significantly age-related.

Addressing the need for repeat prostate biopsy: new technology and approaches

No guidelines currently exist that address the need for rebiopsy in patients with a negative diagnosis of prostate cancer on initial biopsy sample analysis. Accurate diagnosis of prostate cancer in these patients is often complicated by continued elevation of serum PSA levels that are suggestive of prostate cancer, resulting in a distinct management challenge. Following negative initial findings of biopsy sample analysis, total serum PSA levels and serum PSA kinetics are ineffective indicators of a need for a repeat biopsy; therefore, patients suspected of having prostate cancer might undergo several unnecessary biopsy procedures. Several alternative strategies exist for identifying men who might be at risk of prostate cancer despite negative findings of biopsy sample analysis. Use of other serum PSA-related measurements enables more sensitive and specific diagnosis and can be combined with knowledge of clinicopathological features to improve outcomes. Other options include the FDA-approved Progensa(®) test and prostate imaging using MRI. Newer tissue-based assays that measure methylation changes in normal prostate tissue are currently being developed. A cost-effective strategy is proposed in order to address this challenging clinical scenario, and potential directions of future studies in this area are also described.

Three-dimensional nonrigid landmark-based magnetic resonance to transrectal ultrasound registration for image-guided prostate biopsy

Registration of three-dimensional (3-D) magnetic resonance (MR) to 3-D transrectal ultrasound (TRUS) prostate images is an important step in the planning and guidance of 3-D TRUS guided prostate biopsy. In order to accurately and efficiently perform the registration, a nonrigid landmark-based registration method is required to account for the different deformations of the prostate when using these two modalities. We describe a nonrigid landmark-based method for registration of 3-D TRUS to MR prostate images. The landmark-based registration method first makes use of an initial rigid registration of 3-D MR to 3-D TRUS images using six manually placed approximately corresponding landmarks in each image. Following manual initialization, the two prostate surfaces are segmented from 3-D MR and TRUS images and then nonrigidly registered using the following steps: (1) rotationally reslicing corresponding segmented prostate surfaces from both 3-D MR and TRUS images around a specified axis, (2) an approach to find point correspondences on the surfaces of the segmented surfaces, and (3) deformation of the surface of the prostate in the MR image to match the surface of the prostate in the 3-D TRUS image and the interior using a thin-plate spline algorithm. The registration accuracy was evaluated using 17 patient prostate MR and 3-D TRUS images by measuring the target registration error (TRE). Experimental results showed that the proposed method yielded an overall mean TRE of [Formula: see text] for the rigid registration and [Formula: see text] for the nonrigid registration, which is favorably comparable to a clinical requirement for an error of less than 2.5 mm. A landmark-based nonrigid 3-D MR-TRUS registration approach is proposed, which takes into account the correspondences on the prostate surface, inside the prostate, as well as the centroid of the prostate. Experimental results indicate that the proposed method yields clinically sufficient accuracy.

Three-Dimensional Nonrigid MR-TRUS Registration Using Dual Optimization

In this study, we proposed an efficient nonrigid magnetic resonance (MR) to transrectal ultrasound (TRUS) deformable registration method in order to improve the accuracy of targeting suspicious regions during a three dimensional (3-D) TRUS guided prostate biopsy. The proposed deformable registration approach employs the multi-channel modality independent neighborhood descriptor (MIND) as the local similarity feature across the two modalities of MR and TRUS, and a novel and efficient duality-based convex optimization-based algorithmic scheme was introduced to extract the deformations and align the two MIND descriptors. The registration accuracy was evaluated using 20 patient images by calculating the TRE using manually identified corresponding intrinsic fiducials in the whole gland and peripheral zone. Additional performance metrics [Dice similarity coefficient (DSC), mean absolute surface distance (MAD), and maximum absolute surface distance (MAXD)] were also calculated by comparing the MR and TRUS manually segmented prostate surfaces in the registered images. Experimental results showed that the proposed method yielded an overall median TRE of 1.76 mm. The results obtained in terms of DSC showed an average of 80.8±7.8% for the apex of the prostate, 92.0±3.4% for the mid-gland, 81.7±6.4% for the base and 85.7±4.7% for the whole gland. The surface distance calculations showed an overall average of 1.84±0.52 mm for MAD and 6.90±2.07 mm for MAXD.

Evaluation of MRI-TRUS fusion versus cognitive registration accuracy for MRI-targeted, TRUS-guided prostate biopsy

OBJECTIVE

The purpose of this article is to compare transrectal ultrasound (TRUS) biopsy accuracies of operators with different levels of prostate MRI experience using cognitive registration versus MRI-TRUS fusion to assess the preferred method of TRUS prostate biopsy for MRI-identified lesions. SUBJECTS AND METHODS; One hundred patients from a prospective prostate MRI-TRUS fusion biopsy study were reviewed to identify all patients with clinically significant prostate adenocarcinoma (PCA) detected on MRI-targeted biopsy. Twenty-five PCA tumors were incorporated into a validated TRUS prostate biopsy simulator. Three prostate biopsy experts, each with different levels of experience in prostate MRI and MRI-TRUS fusion biopsy, performed a total of 225 simulated targeted biopsies on the MRI lesions as well as regional biopsy targets. Simulated biopsies performed using cognitive registration with 2D TRUS and 3D TRUS were compared with biopsies performed under MRI-TRUS fusion.

RESULTS

Two-dimensional and 3D TRUS sampled only 48% and 45% of clinically significant PCA MRI lesions, respectively, compared with 100% with MRI-TRUS fusion. Lesion sampling accuracy did not statistically significantly vary according to operator experience or tumor volume. MRI-TRUS fusion-naïve operators showed consistent errors in targeting of the apex, midgland, and anterior targets, suggesting that there is biased error in cognitive registration. The MRI-TRUS fusion expert correctly targeted the prostate apex; however, his midgland and anterior mistargeting was similar to that of the less-experienced operators.

CONCLUSION

MRI-targeted TRUS-guided prostate biopsy using cognitive registration appears to be inferior to MRI-TRUS fusion, with fewer than 50% of clinically significant PCA lesions successfully sampled. No statistically significant difference in biopsy accuracy was seen according to operator experience with prostate MRI or MRI-TRUS fusion.

The role of transurethral resection of the prostate for patients with an elevated prostate-specific antigen

Purpose

The aim of this study was to define the clinical significance of transurethral resection of the prostate (TURP) in patients with benign prostate hyperplasia (BPH) and an elevated prostate-specific antigen (PSA) level.

Methods

We retrospectively evaluated patients with BPH, lower urinary tract symptoms (LUTS; International Prostate Symptom Score [IPSS]≥8), an elevated serum PSA level (≥4 ng/mL), and previous negative transrectal ultrasonography (TRUS) guided prostate biopsy. The PSA level after TURP was monitored by long-term follow-up. The tumor detection rate on resected prostate tissue, IPSS, maximal urinary flow rate (Qmax), and postvoid residual urine (PVR) were analyzed.

Results

One-hundred and eighty-six patients were enrolled. Histological examination of resected tissue by TURP revealed prostate cancer in 12 of these patients (6.5%). Among 174 patients without prostate cancer, the mean PSA level and the PSA normalization rate in 112 patients followed up at postoperative day (POD) 3 months were 1.26±0.13 ng/mL and 94.6%, respectively. The mean PSA level and the PSA normalization rate were 1.28±1.01 ng/mL and 95.7% in 47 patients at 1st year, 1.17±0.82 ng/mL and 97.1% in 34 patients at second years, and 1.34±1.44 ng/mL and 97.2% in 36 patients at third years of TURP. One patient showed a dramatic increase in the PSA level was diagnosed with prostate cancer at 7 years after TURP. IPSS, quality of life, Qmax, and PVR were improved significantly at POD 3 months compared to baseline (P<0.05), respectively.

Conclusions

TURP significantly reduced the serum PSA level, which was maintained for at least 3 years. This could be helpful to screen the prostate cancer using PSA value in the patient with previous negative biopsy and elevated PSA. In addition, TURP improves IPSS, Qmax, and PVR in patients with BPH, moderate LUTS, and an elevated PSA level.

Multiparametric MRI-targeted TRUS prostate biopsies using visual registration

Prebiopsy multiparametric prostate MRI (mp-MRI), followed by transrectal ultrasound-guided (TRUS-G) target biopsies (TB) of the prostate is a key combination for the diagnosis of clinically significant prostate cancers (CSPCa), to avoid prostate cancer (PCa) overtreatment. Several techniques are available for guiding TB to the suspicious mp-MRI targets, but the simplest, cheapest, and easiest to learn is “cognitive,” with visual registration of MRI and TRUS data. This review details the successive steps of the method (target detection, mp-MRI reporting, intermodality fusion, TRUS guidance to target, sampling simulation, sampling, TRUS session reporting, and quality insurance), how to optimize each, and the global indications of mp-MRI-targeted biopsies. We discuss the diagnostic yield of visually-registered TB in comparison with conventional biopsy, and TB performed using other registration methods.

Detection of significant prostate cancer with magnetic resonance targeted biopsies--should transrectal ultrasound-magnetic resonance imaging fusion guided biopsies alone be a standard of care?

PURPOSE

Magnetic resonance imaging-transrectal ultrasound fusion targeted prostate biopsies were suggested to detect significant cancer with more accuracy than systematic biopsies. In this study we evaluate the pathological characteristics of multiparametric magnetic resonance imaging detected and undetected tumor foci on radical prostatectomy specimens.

MATERIALS AND METHODS

We selected 125 consecutive patients treated with radical prostatectomy for clinically localized prostate cancer diagnosed on magnetic resonance imaging-transrectal ultrasound targeted biopsy and/or systematic biopsy. On multiparametric magnetic resonance imaging each suspicious area was graded according to the PI-RADS score. On radical prostatectomy specimen, tumor foci with a Gleason score greater than 3+3 and/or tumor volume greater than 0.5 ml were considered significant. A correlation analysis between multiparametric magnetic resonance imaging and pathological findings was performed.

RESULTS

Pathological analysis of radical prostatectomy specimens detected 230 tumor foci. Of these, 137 were considered significant (Gleason score greater than 3+3 in 112) and were observed in 111 (89%) glands. A total of 95 individual tumor foci, including 14 significant foci, were missed with multiparametric magnetic resonance imaging. All of them were located in glands where another focus was detected with multiparametric magnetic resonance imaging. An additional 9 individual tumor foci, including 7 significant, were detected on multiparametric magnetic resonance imaging but missed with targeted biopsy, resulting in 5 (4%) significant cancers undetected with magnetic resonance imaging-transrectal ultrasound fusion targeted biopsy. The magnetic resonance imaging target largest diameter was associated with high volume (greater than 0.5 cc) foci detection, while PI-RADS score and cancer involvement on targeted biopsy were associated with significant foci detection.

CONCLUSIONS

In these series of men with suspicious prostate multiparametric magnetic resonance imaging findings, magnetic resonance imaging-transrectal ultrasound fusion guided targeted biopsy alone strategy would have resulted in the under detection of only 4% significant cancers.

TRUS-MRI image registration: a paradigm shift in the diagnosis of significant prostate cancer

Accuracy of multiparametric MRI has greatly improved the ability of localizing tumor foci of prostate cancer. This property can be used to perform a TRUS-MR image registration, new technological advance, which allows for an overlay of an MRI onto a TRUS image to target a prostate biopsy toward a suspicious area Three types of registration have been developed: cognitive-based, sensor-based, and organ-based registration. Cognitive registration consists of aiming a suspicious area during biopsy with the knowledge of the lesion location identified on multiparametric MRI. Sensor-based registration consists of tracking in real time the TRUS probe with a magnetic device, achieving a global positioning system which overlays in real-time prostate image on both modalities. Its main limitation is that it does not take into account prostate and patient motion during biopsy. Two systems (Artemis and Uronav) have been developed to partially circumvent this drawback. Organ-based registration (Koelis) does not aim to track the TRUS probe, but the prostate itself to compute in a 3D acquisition the TRUS prostate shape, allowing for a registration with the corresponding 3D MRI shape. This system is not limited by prostate/patient motion and allows for a deformation of the organ during registration. Pros and cons of each technique and the rationale for a targeted biopsy only policy are discussed.

Virtual CT sonographically guided biopsy of a retroperitoneal mass in a patient with Erdheim-Chester disease

Image fusion between sonography and CT allows real-time synchronization of CT multiplanar reconstructed images with the corresponding sonographic images. This technique has mainly been used in liver imaging. We report the use of image fusion to target and successfully guide the percutaneous biopsy of a retroperitoneal a mass. This technique represents a promising tool in abdominal imaging, and it should be considered for the biopsy of lesions that are difficult to approach with conventional imaging guidance techniques.

MRI-guided biopsy for prostate cancer detection: a systematic review of current clinical results

In-bore magnetic resonance-guided biopsy (MRGB) has been increasingly used in clinical practice to detect prostate cancer (PCa). This review summarizes the current clinical results of this biopsy method. A systematic literature search was performed in the PubMed and Embase databases. Of 2,035 identified records, 49 required full review. In all, ten unique studies reporting clinical results of MRGB could be included. Reported PCa detection rates ranged from 8 to 59 % (median 42 %). The majority of tumors detected by MRGB were clinically significant (81-93 %). Most frequent complications of MRGB are transient hematuria (1-24 %) and short-term perirectal bleeding (11-17 %). Major complications are rare. Based on the reviewed literature, MRGB can be regarded an accurate and safe diagnostic tool to detect clinically significant PCa. However, as general availability is limited, this procedure should be reserved for specific patients. Appropriate indications will have to be determined.

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.

MRI-safe robot for targeted transrectal prostate biopsy: animal experiments

OBJECTIVES

To study the feasibility and safety of using a magnetic resonance imaging (MRI)-safe robot for assisting MRI-guided transrectal needle placement and biopsy in the prostate, using a canine model. To determine the accuracy and precision afforded by the use of the robot while targeting a desired location in the organ.

MATERIALS AND METHODS

In a study approved by the Institutional Animal Care and Use Committee, six healthy adult male beagles with prostates of at least 15 × 15 mm in size at the largest transverse section were chosen for the procedure. The probe portion of the robot was placed into the rectum of the dog, images were acquired and image-to-robot registration was performed. Images acquired after placement of the robot were reviewed and a radiologist selected targets for needle placement in the gland. Depending on the size of the prostate, up to a maximum of six needle placements were performed on each dog. After needle placement, robot-assisted core biopsies were performed on four dogs that had larger prostate volumes and extracted cores were analysed for potential diagnostic value.

RESULTS

Robot-assisted MRI-guided needle placements were performed to target a total of 30 locations in six dogs, achieving a targeting accuracy of 2.58 mm (mean) and precision of 1.31 mm (SD). All needle placements were successfully completed on the first attempt. The mean time required to select a desired target location in the prostate, align the needle guide to that point, insert the needle and perform the biopsy was ∼ 3 min. For this targeting accuracy study, the inserted needle was also imaged after its placement in the prostate, which took an additional 6-8 min. Signal-to-noise ratio analysis indicated that the presence of the robot within the scanner bore had minimal impact on the quality of the images acquired. Analysis of intact biopsy core samples indicated that the samples contained prostatic tissues, appropriate for making a potential diagnosis. Dogs used in the study did not experience device- or procedure-related complications.

CONCLUSIONS

Results from this preclinical pilot animal study suggest that MRI-targeted transrectal biopsies are feasible to perform and this procedure may be safely assisted by an MRI-safe robotic device.

MRI-targeted prostate biopsy: a review of technique and results

Multiparametric magnetic resonance imaging (mpMRI) is of interest for the diagnosis of clinically significant prostate cancer and mpMRI-targeted biopsies are being used increasingly in clinical practice. Target acquisition is performed using a range of magnet strengths and varying combinations of anatomical and functional sequences. Target identification at the time of biopsy can be carried out in the MRI scanner (in-bore biopsy) or, more commonly, the MRI-target is biopsied under ultrasonographic guidance. Many groups use cognitive or visual registration, whereby the biopsy target is identified on MRI and ultrasonography is subsequently used to direct the needle to the same location. Other groups use registration software to show prebiopsy MRI data on real-time ultrasonography. The reporting of histological results in MRI-targeted biopsy studies varies greatly. The most useful reports compare the detection of clinically significant disease in standard cores versus mpMRI-targeted cores in the same cohort of men, as recommended by the STAndards of Reporting for MRI-Targeted biopsy studies (START) consensus panel. Further evidence is needed before an mpMRI-targeted strategy can be recommended as the standard intervention for men at risk of prostate cancer.

Magnetic resonance spectroscopy imaging-directed transrectal ultrasound biopsy increases prostate cancer detection in men with prostate-specific antigen between 4-10 ng/mL and normal digital rectal examination

OBJECTIVES

To evaluate the ability of magnetic resonance spectroscopic imaging to improve prostate cancer detection rate.

METHODS

A retrospective analysis was carried out of 278 men with prostate-specific antigen in the range of 4-10 ng/mL and normal digital rectal examination who underwent transrectal ultrasound-guided prostate biopsy. Outcomes were compared between men who had a standard biopsy versus those who also underwent a prebiopsy magnetic resonance spectroscopic imaging. Men with an abnormal voxel on magnetic resonance spectroscopic imaging had standard transrectal ultrasound biopsies plus biopsies directed to the abnormal voxels.

RESULTS

The study group (n = 140) and control group (n = 138) were similar in baseline parameters, such as mean age, prostate size and mean prostate-specific antigen. The overall cancer detection in the magnetic resonance spectroscopic imaging positive group (24.4%) was more than double that of the control group (10.1%). On comparing the magnetic resonance spectroscopic imaging results with the transrectal ultrasound biopsy findings, magnetic resonance spectroscopic imaging had 95.6% sensitivity, 41.9% specificity, a positive predictive value of 24.4%, a negative predictive value of 98% and an accuracy of 51.4%.

CONCLUSIONS

Magnetic resonance spectroscopic imaging-directed transrectal ultrasound biopsy increases the cancer detection rate compared with standard transrectal ultrasound biopsy in patients with normal digital rectal examination and elevated prostate-specific antigen in the range of 4-10 ng/mL.

Image-directed, tissue-preserving focal therapy of prostate cancer: a feasibility study of a novel deformable magnetic resonance-ultrasound (MR-US) registration system

OBJECTIVE

To evaluate the feasibility of using computer-assisted, deformable image registration software to enable three-dimensional (3D), multi-parametric (mp) magnetic resonance imaging (MRI)-derived information on tumour location and extent, to inform the planning and conduct of focal high-intensity focused ultrasound (HIFU) therapy.

PATIENTS AND METHODS

A nested pilot study of 26 consecutive men with a visible discrete focus on mpMRI, correlating with positive histology on transperineal template mapping biopsy, who underwent focal HIFU (Sonablate 500®) within a prospective, Ethics Committee-approved multicentre trial ('INDEX'). Non-rigid image registration software developed in our institution was used to transfer data on the location and limits of the index lesion as defined by mpMRI. Manual contouring of the prostate capsule and histologically confirmed MR-visible lesion was performed preoperatively by a urologist and uro-radiologist. A deformable patient-specific computer model, which captures the location of the target lesion, was automatically generated for each patient and registered to a 3D transrectal ultrasonography (US) volume using a small number (10-20) of manually defined capsule points. During the focal HIFU, the urologist could add additional sonications after image-registration if it was felt that the original treatment plan did not cover the lesion sufficiently with a margin.

RESULTS

Prostate capsule and lesion contouring was achieved in <5 min preoperatively. The mean (range) time taken to register images was 6 (3-16) min. Additional treatment sonications were added in 13 of 26 cases leading to a mean (range) additional treatment time of 45 (9-90) s.

CONCLUSION

Non-rigid MR-US registration is feasible, efficient and can locate lesions on US. The process has potential for improved accuracy of focal treatments, and improved diagnostic sampling strategies for prostate cancer. Further work on whether deformable MR-US registration impacts on efficacy is required.

Can magnetic resonance-ultrasound fusion biopsy improve cancer detection in enlarged prostates?

PURPOSE

Patients with an enlarged prostate and suspicion of prostate cancer pose a diagnostic dilemma. The prostate cancer detection rate of systematic 12-core transrectal ultrasound guided biopsy is between 30% and 40%. For prostates greater than 40 cc this decreases to 30% or less. Magnetic resonance-ultrasound fusion biopsy has shown superior prostate cancer detection rates. We defined the detection rate of magnetic resonance-ultrasound fusion biopsy in men with an enlarged prostate gland.

MATERIALS AND METHODS

We retrospectively analyzed the records of patients who underwent multiparametric prostate magnetic resonance imaging followed by magnetic resonance-ultrasound fusion biopsy at our institution. Whole prostate volumes were calculated using magnetic resonance imaging reconstructions. Detection rates were analyzed with respect to age, prostate specific antigen and whole prostate volumes. Multivariable logistic regression was used to assess these parameters as independent predictors of prostate cancer detection.

RESULTS

We analyzed 649 patients with a mean±SD age of 61.8±7.9 years and a median prostate specific antigen of 6.65 ng/ml (IQR 4.35-11.0). Mean whole prostate volume was 58.7±34.3 cc. The overall detection rate of the magnetic resonance-ultrasound fusion platform was 55%. For prostates less than 40 cc the detection rate was 71.1% compared to 57.5%, 46.9%, 46.9% 33.3%, 36.4% and 30.4% for glands 40 to 54.9, 55 to 69.9, 70 to 84.9, 85 to 99.9, 100 to 114.9 and 115 cc or greater, respectively (p<0.0001). Multivariable logistic regression showed a significant inverse association of magnetic resonance imaging volume with prostate cancer detection, controlling for age and prostate specific antigen.

CONCLUSIONS

Transrectal ultrasound guided and fusion biopsy cancer detection rates decreased with increasing prostate volume. However, magnetic resonance-ultrasound fusion biopsy had a higher prostate cancer detection rate compared to that of transrectal ultrasound guided biopsy in the literature. Magnetic resonance-ultrasound fusion biopsy represents a promising solution for patients with suspicion of prostate cancer and an enlarged prostate.

Performance of multiparametric magnetic resonance imaging in the evaluation and management of clinically low-risk prostate cancer

OBJECTIVE

The purpose of this article is to review the multiparametric magnetic resonance imaging (mMRI) of the prostate and MR-guided prostate biopsy, and their role in the evaluation and management of men with low-risk prostate cancer.

METHODS

We performed a literature review based on the MEDLINE database search for publications on the role of mMRI (a) in detection and localization of prostate cancer, prediction of tumor aggressiveness and progression and (b) in guiding targeted prostate biopsy.

RESULTS

The mMRI, particularly diffusion-weighted imaging with T2-weighted imaging, is a useful tool for tumor localization in low-risk prostate cancer as it can detect lesions that are more likely missed on extended biopsy schemes and can identify clinically significant disease requiring definitive treatment. The MR-guided biopsy of the most suspicious lesions enables more accurate and safer approach to guide enrollment into the active surveillance program. However, the MR-guided biopsy is complex. The fusion of MRI data with transrectal ultrasound for the purpose of biopsy provides a more feasible technique with documented accurate sampling.

CONCLUSION

Although the mMRI is not routinely used for risk stratification and prognostic assessment in prostate cancer, it can provide valuable information to guide management of men with low-risk disease. Incorporation of mMRI into the workup and monitoring of patients with low-risk prostate cancer can help discriminate clinically significant disease from indolent disease. Targeted biopsy of MR-suspicious lesions enables accurate sampling of potentially aggressive tumors that may affect outcomes.

MRI-ultrasound fusion for guidance of targeted prostate biopsy

PURPOSE OF REVIEW

Prostate cancer (CaP) may be detected on MRI. Fusion of MRI with ultrasound allows urologists to progress from blind, systematic biopsies to biopsies, which are mapped, targeted and tracked. We herein review the current status of prostate biopsy via MRI/ultrasound fusion.

RECENT FINDINGS

Three methods of fusing MRI for targeted biopsy have been recently described: MRI-ultrasound fusion, MRI-MRI fusion ('in-bore' biopsy) and cognitive fusion. Supportive data are emerging for the fusion devices, two of which received US Food and Drug Administration approval in the past 5 years: Artemis (Eigen, USA) and Urostation (Koelis, France). Working with the Artemis device in more than 600 individuals, we found that targeted biopsies are two to three times more sensitive for detection of CaP than nontargeted systematic biopsies; nearly 40% of men with Gleason score of at least 7 CaP are diagnosed only by targeted biopsy; nearly 100% of men with highly suspicious MRI lesions are diagnosed with CaP; ability to return to a prior biopsy site is highly accurate (within 1.2 ± 1.1 mm); and targeted and systematic biopsies are twice as accurate as systematic biopsies alone in predicting whole-organ disease.

SUMMARY

In the future, MRI-ultrasound fusion for lesion targeting is likely to result in fewer and more accurate prostate biopsies than the present use of systematic biopsies with ultrasound guidance alone.

Real-time image fusion involving diagnostic ultrasound

OBJECTIVE

The aim of our article is to give an overview of the current and future possibilities of real-time image fusion involving ultrasound. We present a review of the existing English-language peer-reviewed literature assessing this technique, which covers technical solutions (for ultrasound and endoscopic ultrasound), image fusion in several anatomic regions, and electromagnetic needle tracking.

CONCLUSION

The recent progress of real-time ultrasound in image fusion may provide several new possibilities, including diagnosis, treatment, and follow-up of oncologic patients.

Prostate cancer diagnosis: multiparametric MR-targeted biopsy with cognitive and transrectal US-MR fusion guidance versus systematic biopsy--prospective multicenter study

PURPOSE

To compare biopsy performance of two approaches for multiparametric magnetic resonance (MR)-targeted biopsy (TB) with that of extended systematic biopsy (SB) in prostate cancer (PCa) detection.

MATERIALS AND METHODS

This institutional review board-approved multicenter prospective study (May 2009 to January 2011) included 95 patients with informed consent who were suspected of having PCa, with a suspicious abnormality (target) at prebiopsy MR. Patients underwent 12-core SB and four-core TB with transrectal ultrasonographic (US) guidance, with two cores aimed visually (cognitive TB [TB-COG]) and two cores aimed using transrectal US-MR fusion software (fusion-guided TB [TB-FUS]). SB and TB positivity for cancer and sampling quality (mean longest core cancer length, Gleason score) were compared. Clinically significant PCa was any 3 mm or greater core cancer length or any greater than 3 Gleason pattern for SB or any cancer length for TB. Statistical analysis included t test, paired χ(2) test, and κ statistic. Primary end point (core cancer length) was calculated (paired t test).

RESULTS

Among 95 patients (median age, 65 years; mean prostate-specific antigen level, 10.05 ng/mL [10.05 μg/L]), positivity rate for PCa was 59% (n = 56) for SB and 69% (n = 66) for TB (P = .033); rate for clinically significant PCa was 52% (n = 49) for SB and 67% (n = 64) for TB (P = .0011). Cancer was diagnosed through TB in 16 patients (17%) with negative SB results. Mean longest core cancer lengths were 4.6 mm for SB and 7.3 mm for TB (P < .0001). In 12 of 51 (24%) MR imaging targets with positive SB and TB results, TB led to Gleason score upgrading. In 79 MR imaging targets, positivity for cancer was 47% (n = 37) with TB-COG and 53% (n = 42) with TB-FUS (P = .16). Neither technique was superior for Gleason score assessment.

CONCLUSION

Prebiopsy MR imaging combined with transrectal US-guided TB increases biopsy performance in detecting PCa, especially clinically significant PCa. No significant difference was observed between TB-FUS and TB-COG for TB guidance.

Repeat prostate biopsy strategies after initial negative biopsy: meta-regression comparing cancer detection of transperineal, transrectal saturation and MRI guided biopsy

Introduction

There is no consensus on how to investigate men with negative transrectal ultrasound guided prostate biopsy (TRUS-B) but ongoing suspicion of cancer. Three strategies used are transperineal (TP-B), transrectal saturation (TS-B) and MRI-guided biopsy (MRI-B). We compared cancer yields of these strategies.

Methods

Papers were identified by search of Pubmed, Embase and Ovid Medline. Included studies investigated biopsy diagnostic yield in men with at least one negative TRUS-B and ongoing suspicion of prostate cancer. Data including age, PSA, number of previous biopsy episodes, number of cores at re-biopsy, cancer yield, and Gleason score of detected cancers were extracted. Meta-regression analyses were used to analyse the data.

Results

Forty-six studies were included; 12 of TS-B, 14 of TP-B, and 20 of MRI-B, representing 4,657 patients. Mean patient age, PSA and number of previous biopsy episodes were similar between the strategies. The mean number of biopsy cores obtained by TP-B and TS-B were greater than MRI-B. Cancer detection rates were 30·0%, 36·8%, and 37·6% for TS-B, TP-B, and MRI-B respectively. Meta-regression analysis showed that MRI-B had significantly higher cancer detection than TS-B. There were no significant differences however between MRI-B and TP-B, or TP-B and TS-B. In a sensitivity analysis incorporating number of previous biopsy episodes (36 studies) the difference between MRI-B and TP-B was not maintained resulting in no significant difference in cancer detection between the groups. There were no significant differences in median Gleason scores detected comparing the three strategies.

Conclusions

In the re-biopsy setting, it is unclear which strategy offers the highest cancer detection rate. MRI-B may potentially detect more prostate cancers than other modalities and can achieve this with fewer biopsy cores. However, well–designed prospective studies with standardised outcome measures are needed to accurately compare modalities and define an optimum re-biopsy approach.