Accuracy of Elastic Fusion of Prostate Magnetic Resonance and Transrectal Ultrasound Images under Routine Conditions: A Prospective Multi-Operator Study

The learning curve for robotic-assisted transperineal MRI/US fusion-guided prostate biopsy

Transperineal fusion prostate biopsy has a considerable learning curve (LC). Robotic-assisted transperineal MRI/Ultrasound fusion-guided biopsy (RA-TP-FBx) may have an easier LC due to automatization. We aimed to assess the LC of RA-TP-FBx and analyze its most difficult steps. We prospectively analyzed cases randomized to a biopsy-naïve urology resident, the chief resident, and an expert urologist in RA-TP-FBx (controls). We also analyzed consecutive cases in the LC of the expert. The LC was defined by procedure time, PCa detection rate (including stratification by PI-RADS), entrustable professional activities (EPA) assessment scores, and the NASA task load index. We collectively performed 246 RA-TP-FBx with the Mona Lisa device. Procedure time for residents decreased steeply from maximum 53 min to minimum 10 min, while the mean procedure time for the expert was 9 min (range 17-5 min). PCa detection for PI-RADS-4 lesions was 57% for the naïve resident, 61% for the chief resident and 62% for the expert. There was also no difference in Pca detection for PI-RADS-4 lesions when comparing the first and second half of the experts' biopsies (p = 0.8). Maximum EPA score was registered after 22 cases. Workload steeply declined. Proficient RA-TP-FBx performance appears feasible after 22 cases regardless of previous experience.

Significant prostate cancer risk after MRI-guided biopsy showing benign findings: Results from a cohort of 381 men

BACKGROUND

MRI-guided biopsy (MGB) contributes to the diagnosis of clinically significant Prostate Cancer (csPCa). However, there are no clear recommendations for the management of men after a negative MGB. The aim of this study was to assess the risk of csPCa after a first negative MGB.

METHODS

Between 2014 and 2020, we selected men with a PI-RADS score ≥ 3 on MRI and a negative MGB (showing benign findings) performed for suspected prostate cancer. MGB (targeted and systematic biopsies) was performed using fully integrated mobile fusion imaging (KOELIS). The primary endpoint was the rate of csPCa (defined as an ISUP grade ≥ 2) diagnosed after a first negative MGB.

RESULTS

A total of 381 men with a negative MGB and a median age of 65 (IQR: 59-69, range: 46-85) years were included. During the median follow-up of 31 months, 124 men (32.5%) had a new MRI, and 76 (19.9%) were referred for a new MGB, which revealed csPCa in 16 (4.2%) of them. We found no statistical difference in the characteristics of men diagnosed with csPCa compared with men with no csPCa after the second MGB.

CONCLUSION

We observed a risk of significant prostate cancer in 4% of men two years after a negative MRI-guided biopsy. Performing a repeat MRI could improve the selection of men who will benefit from a repeat MRI-guided biopsy, but a clear protocol is needed to follow these patients.

LEVEL OF EVIDENCE: 4

Systematic Biopsies as a Complement to Magnetic Resonance Imaging-targeted Biopsies: "To Be or Not To Be"?

In light of recent prostate cancer screening programme proposed by the European Association of Urology, there is an urgent need to optimise detection of clinically significant cancer while minimising overdiagnosis. This may be achieved by omitting systematic biopsies while ensuring quality control for diagnostic magnetic resonance imaging and targeted biopsies.

The current role of MRI for guiding active surveillance in prostate cancer

Active surveillance (AS) is the recommended treatment option for low-risk and favourable intermediate-risk prostate cancer management, preserving oncological and functional outcomes. However, active monitoring using relevant parameters in addition to the usual clinical, biological and pathological considerations is necessary to compensate for initial undergrading of the tumour or to detect early progression without missing the opportunity to provide curative therapy. Indeed, several studies have raised concerns about inadequate biopsy sampling at diagnosis. However, the implementation of baseline MRI and targeted biopsy have led to improved initial stratification of low-risk disease; baseline MRI correlates well with disease characteristics and AS outcomes. The use of follow-up MRI during the surveillance phase also raises the question of the requirement for serial biopsies in the absence of radiological progression and the possibility of using completely MRI-based surveillance, with triggers for biopsies based solely on MRI findings. This concept of a tailored-risk, imaging-based monitoring strategy is aimed at reducing invasive procedures. However, the abandonment of serial biopsies in the absence of MRI progression can probably not yet be recommended in routine practice, as the data from real-life cohorts are heterogeneous and inconclusive. Thus, the evolution towards a routine, fully MRI-guided AS pathway has to be preceded by ensuring quality programme assessment for MRI reading and by demonstrating its safety in prospective trials.

Biomechanical modelling of the pelvic system: improving the accuracy of the location of neoplasms in MRI-TRUS fusion prostate biopsy

Background

An accurate knowledge of the relocation of prostate neoplasms during biopsy is of great importance to reduce the number of false negative results. Prostate neoplasms are visible in magnetic resonance images (MRI) but it is difficult for the practitioner to locate them at the time of performing a transrectal ultrasound (TRUS) guided biopsy. In this study, we present a new methodology, based on simulation, that predicts both prostate deformation and lesion migration during the biopsy.

Methods

A three-dimensional (3-D) anatomy model of the pelvic region, based on medical images, is constructed. A finite element (FE) numerical simulation of the organs motion and deformation as a result of the pressure exerted by the TRUS probe is carried out using the Code-Aster open-source computer software. Initial positions of potential prostate lesions prior to biopsy are taken into consideration and the final location of each lesion is targeted in the FE simulation output.

Results

Our 3-D FE simulations show that the effect of the pressure exerted by the TRUS probe is twofold as the prostate experiences both a motion and a deformation of its original shape. We targeted the relocation of five small prostate lesions when the TRUS probe exerts a force of 30 N on the rectum inner wall. The distance travelled by these lesions ranged between 5.6 and 13.9 mm.

Conclusions

Our new methodology can help to predict the location of neoplasms during a prostate biopsy but further studies are needed to validate our results. Moreover, the new methodology is completely developed on open-source software, which means that its implementation would be affordable to all healthcare providers.

Comparison of Accuracies between Real-Time Nonrigid and Rigid Registration in the MRI-US Fusion Biopsy of the Prostate

Magnetic resonance imaging (MRI) is increasingly important in the detection and localization of prostate cancer. Regarding suspicious lesions on MRI, a targeted biopsy using MRI fused with ultrasound (US) is widely used. To achieve a successful targeted biopsy, a precise registration between MRI and US is essential. The purpose of our study was to show any decrease in errors using a real-time nonrigid registration technique for prostate biopsy. Nineteen patients with suspected prostate cancer were prospectively enrolled in this study. Registration accuracy was calculated by the measuring distance of corresponding points by rigid and nonrigid registration between MRI and US, and compared for rigid and nonrigid registration methods. Overall cancer detection rates were also evaluated by patient and by core. Prostate volume was measured automatically from MRI and manually from US, and compared to each other. Mean distances between the corresponding points in MRI and US were 5.32 ± 2.61 mm for rigid registration and 2.11 ± 1.37 mm for nonrigid registration (p < 0.05). Cancer was diagnosed in 11 of 19 patients (57.9%), and in 67 of 266 biopsy cores (25.2%). There was no significant difference in prostate-volume measurement between the automatic and manual methods (p = 0.89). In conclusion, nonrigid registration reduces targeting errors.

MRI-targeted prostate biopsy: the next step forward!

Aim

For decades, the gold standard technique for diagnosing prostate cancer was the 10 to 12 core systematic transrectal or transperineal biopsy, under ultrasound guidance. Over the past years, an increased rate of false negative results and detection of clinically insignificant prostate cancer has been noted, resulting into overdiagnosis and overtreatment. The purpose of the current study was to evaluate the changes in diagnosis and management of prostate cancer brought by MRI-targeted prostate biopsy.

Methods

A critical review of literature was carried out using the Medline database through a PubMed search, 37 studies meeting the inclusion criteria: prospective studies published in the past 8 years with at least 100 patients per study, which used multiparametric magnetic resonance imaging as guidance for targeted biopsies.

Results

In-Bore MRI targeted biopsy and Fusion targeted biopsy outperform standard systematic biopsy both in terms of overall and clinically significant prostate cancer detection, and ensure a lower detection rate of insignificant prostate cancer, with fewer cores needed. In-Bore MRI targeted biopsy performs better than Fusion biopsy especially in cases of apical lesions.

Conclusion

Targeted biopsy is an emerging and developing technique which offers the needed improvements in diagnosing clinically significant prostate cancer and lowers the incidence of insignificant ones, providing a more accurate selection of the patients for active surveillance and focal therapies.

Effect of lesion diameter and prostate volume on prostate cancer detection rate of magnetic resonance imaging: Transrectal-ultrasonography-guided fusion biopsies using cognitive targeting

OBJECTIVE

This study aimed to evaluate the effect of prostate volume and lesion size on the clinically significant prostate cancer (csPCa) detection rates of transrectal ultrasonography (TRUS)-guided prostate biopsies, performed by a cognitive targeting method for sampling peripheral zone lesions.

MATERIAL AND METHODS

We retrospectively enrolled 219 consecutive patients, who underwent multiparametric magnetic resonance imaging with a 3-T scanner and had peripheral zone lesions suspected for prostate cancer. All of these patients underwent combined cognitive targeted biopsy of suspicious lesions and TRUS-guided systematic biopsy. The detection rates of csPCa according to different lesion diameters (<5 mm, 5-9.9 mm, and ≥10 mm) and prostate volumes (<30 mL, 30-49.9 mL, 50-79.9 mL, and ≥80 mL) were calculated per lesion basis. In addition, subgroup analysis of csPCa detection rates was performed according to Prostate Imaging Reporting and Data System scores of lesions.

RESULTS

The csPCa detection rates according to lesion diameters <5 mm, 5-9.9 mm, and ≥10 mm were 4%, 9.8%, and 33.1%, respectively, and were significantly lower for lesions <10 mm (p<0.001). The csPCa detection rates were 61.5%, 24.1%, 16.2%, and 6.9%, respectively, for prostate volumes <30 mL, 30-49.9 mL, 50-79.9 mL, and ≥80 mL, and were significantly higher for prostate volumes <30 mL (p<0.001).

CONCLUSIONS

Clinicians should be very careful when they prefer cognitive targeted prostatic biopsy in patients with periferal zone lesions less than 10 mm and with prostate volumes greater than 30 mL, because of significantly low csPCa detection rates.

Cognitive Versus Magnetic Resonance-Ultrasound Fusion Prostate Biopsy: Which One Is Worthier to Perform?

The aim of our study is to compare 2 prostate fusion biopsy models in terms of accurate target sampling. One hundred patients who had Prostate Imaging-Reporting and Data System score 3, 4, or 5 lesions (lesion diameter, >5 mm in long axis) in multiparametric-magnetic resonance imaging and prostate-specific antigen levels between 3 and 10 ng/mL were enrolled in the study. All patients were biopsy naive. Two groups were composed with 50 patients each. Group 1 patients had cognitive fusion (CF) biopsy, and group 2 had magnetic resonance-ultrasound fusion platform biopsy. After fusion biopsy, standard biopsy was also performed. Outcomes of histopathologic and demographic data were evaluated statistically. There were no statistical differences between the 2 groups in terms of age, prostate-specific antigen levels, prostate volume, and lesion length (P > 0.05). There was no statistically significant difference in sampling targeted lesions (P > 0.05). Also, no difference was found between the 2 groups in terms of random biopsy cancer detection rates (P > 0.05). There was no statistically significant difference between CF and magnetic resonance-ultrasound fusion in terms of cancer detection rates. For the experienced operators, we recommend lesions that are longer than 5 mm can be sampled using CF, an inexpensive and faster technique.

Clinically significant prostate cancer detection and segmentation in low-risk patients using a convolutional neural network on multi-parametric MRI

Objectives

To develop an automatic method for identification and segmentation of clinically significant prostate cancer in low-risk patients and to evaluate the performance in a routine clinical setting.

Methods

A consecutive cohort (n = 292) from a prospective database of low-risk patients eligible for the active surveillance was selected. A 3-T multi-parametric MRI at 3 months after inclusion was performed. Histopathology from biopsies was used as reference standard. MRI positivity was defined as PI-RADS score ≥ 3, histopathology positivity was defined as ISUP grade ≥ 2. The selected cohort contained four patient groups: (1) MRI-positive targeted biopsy-positive (n = 116), (2) MRI-negative systematic biopsy-negative (n = 55), (3) MRI-positive targeted biopsy-negative (n = 113), (4) MRI-negative systematic biopsy-positive (n = 8). Group 1 was further divided into three sets and a 3D convolutional neural network was trained using different combinations of these sets. Two MRI sequences (T2w, b = 800 DWI) and the ADC map were used as separate input channels for the model. After training, the model was evaluated on the remaining group 1 patients together with the patients of groups 2 and 3 to identify and segment clinically significant prostate cancer.

Results

The average sensitivity achieved was 82–92% at an average specificity of 43–76% with an area under the curve (AUC) of 0.65 to 0.89 for different lesion volumes ranging from > 0.03 to > 0.5 cc.

Conclusions

The proposed deep learning computer-aided method yields promising results in identification and segmentation of clinically significant prostate cancer and in confirming low-risk cancer (ISUP grade ≤ 1) in patients on active surveillance.

Key Points

• Clinically significant prostate cancer identification and segmentation on multi-parametric MRI is feasible in low-risk patients using a deep neural network.

• The deep neural network for significant prostate cancer localization performs better for lesions with larger volumes sizes (> 0.5 cc) as compared to small lesions (> 0.03 cc).

• For the evaluation of automatic prostate cancer segmentation methods in the active surveillance cohort, the large discordance group (MRI positive, targeted biopsy negative) should be included.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07008-z) contains supplementary material, which is available to authorized users.

Cartography-based quality control of prostate cancer care: a necessary ground to targeted focal therapy

PURPOSE OF REVIEW

We summarize the evidence on accurate target definition, precise imaging, and guiding systems that are a necessary ground to targeted focal therapy.

RECENT FINDINGS

Accurate target detection is based on the ability of imaging to locate and characterize precisely the tumor burden and differentiation inside the prostate. There is a clear correlation with the multiparametric MRI (mpMRI) images and the morphologic attributes of the tumor. Limitations stem from the heterogeneity and the multifocality of prostate cancer. Some prostate cancers are MRI-negative tumors. Safety margins should also be elaborated based on the tumor grade and burden. PET prostate specific membrane antigen is another promising technology yielding same results as multiparametric MRI for primary detection of prostate cancer, but PET/MRI imaging is promising. Perfect guiding requires sophisticated software with good quality control to track the needle inside the prostate and to record the position allowing recall when second look biopsy, active surveillance, or targeted focal therapy are required.

SUMMARY

The multimodal fusion cartography model proves effective and necessary to fulfill preoperative and postoperative requirements for targeted focal therapy.

The role of a template-assisted cognitive transperineal prostate biopsy technique in patients with benign transrectal prostate biopsies: a preliminary experience

Introduction

Urologists are commonly facing the dilemma of elevating prostate-specific antigen (PSA) levels despite a series of negative prostate biopsy results. Although fusion biopsies are being used increasingly, they are not available in many centers. We evaluated the prostate cancer detection rate using transperineal magnetic resonance imaging (MRI) template-guided cognitive biopsy.

Material and methods

Twenty-two patients with a suspicious lesion on MRI were enrolled into this study and underwent a repeated biopsy. All procedures were done under anesthesia and with antibiotic prophylaxis. Brachytherapy template was applied in each case.

Results

The median age, PSA and prostate volume were 67 years, 9.2 ng/ml, and 65 ml, respectively. The average number of biopsy cores was 24. Nine patients (41%) were diagnosed with prostate cancer. The grade distribution was Gleason score 7 for 5 patients, and Gleason score 6 for 4 patients. No major complications occurred.

Conclusions

Transperineal MRI template-guided cognitive prostate biopsy appears to be a safe procedure, which helps to detect significant cancer. The biopsy-associated adverse events are negligible.

Controversies in MR targeted biopsy: alone or combined, cognitive versus software-based fusion, transrectal versus transperineal approach?

PURPOSE

To review the evidence addressing current controversies around prostate biopsy. Specific questions explored were (1) mpMRI targeted (TgBx) alone versus combined with systematic (SBx) biopsy; (2) cognitive versus software-based targeted biopsy; (3) transrectal or transperineal route (TP).

METHODS

We performed a literature search of peer-reviewed English language articles using PubMed and the words "prostate" AND "biopsy". Web search was implemented by manual search.

RESULTS

Prostate mpMRI is revolutionizing prostate cancer (PCa) diagnosis, and TgBx improves the detection of clinically significant (cs) PCa compared to SBx alone. The utility of combining SBx-TgBx is variable, but in non-expert centres the two should be combined to overcome learning curve-limitations. Whether SBx should be maintained in expert centres depends on what rate of missed cancer the urological community and patients are prone to accept; this has implications for insignificant cancer diagnosis as well. TgBx may be more precise using a software-based-approach despite cognitive TgBx proved non-inferior in some studies, and may be used for large accessible lesions. TP-biopsies are feasible in an in-office setting. Avoidance of the rectum and accessibility of virtually all prostate areas are attractive features. However, this has to be balanced with local setting and resources implications. Ongoing trials will shed light on unsolved issues.

CONCLUSION

The prostate biopsy strategy should be tailored to local expertise, needs and resources availability. Targeted biopsy enhance the ratio between cs and insignificant cancer diagnosis, although some csPCa might be missed. Software-based TgBx are likely to be more precise, especially for new users, although the additional cost might be not justified in all cases. TPBx have ideal attributes for performing TgBx and avoiding infection, although this has resources implications.

The current role of prostate multiparametric magnetic resonance imaging

Prostate multi-parametric magnetic resonance imaging (mpMRI) has shown excellent sensitivity for Gleason ≥7 cancers, especially when their volume is ≥0.5 mL. As a result, performing an mpMRI before prostate biopsy could improve the detection of clinically significant prostate cancer (csPCa) by adding targeted biopsies to systematic biopsies. Currently, there is a consensus that targeted biopsies improve the detection of csPCa in the repeat biopsy setting and at confirmatory biopsy in patients considering active surveillance. Several prospective multicentric controlled trials recently showed that targeted biopsy also improved csPCa detection in biopsy-naïve patients. The role of mpMRI and targeted biopsy during the follow-up of active surveillance remains unclear. Whether systematic biopsy could be omitted in case of negative mpMRI is also a matter of controversy. mpMRI did show excellent negative predictive values (NPV) in the literature, however, since NPV depends on the prevalence of the disease, negative mpMRI findings should be interpreted in the light of a priori risk for csPCa of the patient. Nomograms combining mpMRI findings and classical risk predictors (age, prostate-specific antigen density, digital rectal examination, etc.) will probably be developed in the future to decide whether a prostate biopsy should be obtained. mpMRI has a good specificity for detecting T3 stage cancers, but its sensitivity is low. It should therefore not be used routinely for staging purposes in low-risk patients. Nomograms combining mpMRI findings and other clinical and biochemical data will also probably be used in the future to better assess the risk of T3 stage disease.

Use of prostate systematic and targeted biopsy on the basis of multiparametric MRI in biopsy-naive patients (MRI-FIRST): a prospective, multicentre, paired diagnostic study

BACKGROUND

Whether multiparametric MRI improves the detection of clinically significant prostate cancer and avoids the need for systematic biopsy in biopsy-naive patients remains controversial. We aimed to investigate whether using this approach before biopsy would improve detection of clinically significant prostate cancer in biopsy-naive patients.

METHODS

In this prospective, multicentre, paired diagnostic study, done at 16 centres in France, we enrolled patients aged 18-75 years with prostate-specific antigen concentrations of 20 ng/mL or less, and with stage T2c or lower prostate cancer. Eligible patients had been referred for prostate multiparametric MRI before a first set of prostate biopsies, with a planned interval of less than 3 months between MRI and biopsies. An operator masked to multiparametric MRI results did a systematic biopsy by obtaining 12 systematic cores and up to two cores targeting hypoechoic lesions. In the same patient, another operator targeted up to two lesions seen on MRI with a Likert score of 3 or higher (three cores per lesion) using targeted biopsy based on multiparametric MRI findings. Patients with negative multiparametric MRI (Likert score ≤2) had systematic biopsy only. The primary outcome was the detection of clinically significant prostate cancer of International Society of Urological Pathology grade group 2 or higher (csPCa-A), analysed in all patients who received both systematic and targeted biopsies and whose results from both were available for pathological central review, including patients who had protocol deviations. This study is registered with ClinicalTrials.gov, number NCT02485379, and is closed to new participants.

FINDINGS

Between July 15, 2015, and Aug 11, 2016, we enrolled 275 patients. 24 (9%) were excluded from the analysis. 53 (21%) of 251 analysed patients had negative (Likert ≤2) multiparametric MRI. csPCa-A was detected in 94 (37%) of 251 patients. 13 (14%) of these 94 patients were diagnosed by systematic biopsy only, 19 (20%) by targeted biopsy only, and 62 (66%) by both techniques. Detection of csPCa-A by systematic biopsy (29·9%, 95% CI 24·3-36·0) and targeted biopsy (32·3%, 26·5-38·4) did not differ significantly (p=0·38). csPCa-A would have been missed in 5·2% (95% CI 2·8-8·7) of patients had systematic biopsy not been done, and in 7·6% (4·6-11·6) of patients had targeted biopsy not been done. Four grade 3 post-biopsy adverse events were reported (3 cases of prostatitis, and 1 case of urinary retention with haematuria).

INTERPRETATION

There was no difference between systematic biopsy and targeted biopsy in the detection of ISUP grade group 2 or higher prostate cancer; however, this detection was improved by combining both techniques and both techniques showed substantial added value. Thus, obtaining a multiparametric MRI before biopsy in biopsy-naive patients can improve the detection of clinically significant prostate cancer but does not seem to avoid the need for systematic biopsy.

FUNDING

French National Cancer Institute.

Accuracy of elastic fusion biopsy in daily practice: Results of a multicenter study of 2115 patients

OBJECTIVES

To assess the accuracy of Koelis fusion biopsy for the detection of prostate cancer and clinically significant prostate cancer in the everyday practice.

METHODS

We retrospectively enrolled 2115 patients from 15 institutions in four European countries undergoing transrectal Koelis fusion biopsy from 2010 to 2017. A variable number of target (usually 2-4) and random cores (usually 10-14) were carried out, depending on the clinical case and institution habits. The overall and clinically significant prostate cancer detection rates were assessed, evaluating the diagnostic role of additional random biopsies. The cancer detection rate was correlated to multiparametric magnetic resonance imaging features and clinical variables.

RESULTS

The mean number of targeted and random cores taken were 3.9 (standard deviation 2.1) and 10.5 (standard deviation 5.0), respectively. The cancer detection rate of Koelis biopsies was 58% for all cancers and 43% for clinically significant prostate cancer. The performance of additional, random cores improved the cancer detection rate of 13% for all cancers (P < 0.001) and 9% for clinically significant prostate cancer (P < 0.001). Prostate cancer was detected in 31%, 66% and 89% of patients with lesions scored as Prostate Imaging Reporting and Data System 3, 4 and 5, respectively. Clinical stage and Prostate Imaging Reporting and Data System score were predictors of prostate cancer detection in multivariate analyses. Prostate-specific antigen was associated with prostate cancer detection only for clinically significant prostate cancer.

CONCLUSIONS

Koelis fusion biopsy offers a good cancer detection rate, which is increased in patients with a high Prostate Imaging Reporting and Data System score and clinical stage. The performance of additional, random cores seems unavoidable for correct sampling. In our experience, the Prostate Imaging Reporting and Data System score and clinical stage are predictors of prostate cancer and clinically significant prostate cancer detection; prostate-specific antigen is associated only with clinically significant prostate cancer detection, and a higher number of biopsy cores are not associated with a higher cancer detection rate.

The emerging role of imaging in prostate cancer secondary screening: multiparametric magnetic resonance imaging and the incipient incorporation of molecular imaging

An increasingly robust body of evidence indicates that multiparametric MRI (mpMRI) prior to prostate biopsy can improve the detection of clinically significant prostate cancer while avoiding unnecessary biopsies. As a result, the use of mpMRI and biopsy platforms that allow for the real-time fusion of mpMRI and transrectal ultrasound images is now routinely used in clinical practice. On the horizon, molecular imaging offers the promise of improved sensitivity relative to mpMRI and early data would suggest that the combination of mpMRI and positron emission tomography using radiotracers targeting prostate-specific membrane antigen provide a more accurate assessment than either modality alone. In this review, we examine the current role of imaging to aid in the initial diagnosis of prostate cancer.

Comparison of Elastic and Rigid Registration during Magnetic Resonance Imaging/Ultrasound Fusion-Guided Prostate Biopsy: A Multi-Operator Phantom Study

PURPOSE

The relative value of rigid or elastic registration during magnetic resonance imaging/ultrasound fusion guided prostate biopsy has been poorly studied. We compared registration errors (the distance between a region of interest and fiducial markers) between rigid and elastic registration during fusion guided prostate biopsy using a prostate phantom model.

MATERIALS AND METHODS

Four gold fiducial markers visible on magnetic resonance imaging and ultrasound were placed throughout 1 phantom prostate model. The phantom underwent magnetic resonance imaging and the fiducial markers were labeled as regions of interest. An experienced user and a novice user of fusion guided prostate biopsy targeted regions of interest and then the corresponding fiducial markers on ultrasound after rigid and then elastic registration. Registration errors were compared.

RESULTS

A total of 224 registration error measurements were recorded. Overall elastic registration did not provide significantly improved registration error over rigid registration (mean ± SD 4.87 ± 3.50 vs 4.11 ± 2.09 mm, p = 0.05). However, lesions near the edge of the phantom showed increased registration errors when using elastic registration (5.70 ± 3.43 vs 3.23 ± 1.68 mm, p = 0.03). Compared to the novice user the experienced user reported decreased registration error with rigid registration (3.25 ± 1.49 vs 4.98 ± 2.10 mm, p <0.01) and elastic registration (3.94 ± 2.61 vs 6.07 ± 4.16 mm, p <0.01).

CONCLUSIONS

We found no difference in registration errors between rigid and elastic registration overall but rigid registration decreased the registration error of targets near the prostate edge. Additionally, operator experience reduced registration errors regardless of the registration method. Therefore, elastic registration algorithms cannot serve as a replacement for attention to detail during the registration process and anatomical landmarks indicating accurate registration when beginning the procedure and before targeting each region of interest.

Prostate Imaging-Reporting and Data System Steering Committee: PI-RADS v2 Status Update and Future Directions

CONTEXT

The Prostate Imaging-Reporting and Data System (PI-RADS) v2 analysis system for multiparametric magnetic resonance imaging (mpMRI) detection of prostate cancer (PCa) is based on PI-RADS v1, accumulated scientific evidence, and expert consensus opinion.

OBJECTIVE

To summarize the accuracy, strengths and weaknesses of PI-RADS v2, discuss pathway implications of its use and outline opportunities for improvements and future developments.

EVIDENCE ACQUISITION

For this consensus expert opinion from the PI-RADS steering committee, clinical studies, systematic reviews, and professional guidelines for mpMRI PCa detection were evaluated. We focused on the performance characteristics of PI-RADS v2, comparing data to systems based on clinicoradiologic Likert scales and non-PI-RADS v2 imaging only. Evidence selections were based on high-quality, prospective, histologically verified data, with minimal patient selection and verifications biases.

EVIDENCE SYNTHESIS

It has been shown that the test performance of PI-RADS v2 in research and clinical practice retains higher accuracy over systematic transrectal ultrasound (TRUS) biopsies for PCa diagnosis. PI-RADS v2 fails to detect all cancers but does detect the majority of tumors capable of causing patient harm, which should not be missed. Test performance depends on the definition and prevalence of clinically significant disease. Good performance can be attained in practice when the quality of the diagnostic process can be assured, together with joint working of robustly trained radiologists and urologists, conducting biopsy procedures within multidisciplinary teams.

CONCLUSIONS

It has been shown that the test performance of PI-RADS v2 in research and clinical practice is improved, retaining higher accuracy over systematic TRUS biopsies for PCa diagnosis.

PATIENT SUMMARY

Multiparametric magnetic resonance imaging (MRI) and MRI-directed biopsies using the Prostate Imaging-Reporting and Data System improves the detection of prostate cancers likely to cause harm, and at the same time decreases the detection of disease that does not lead to harms if left untreated. The keys to success are high-quality imaging, reporting, and biopsies by radiologists and urologists working together in multidisciplinary teams.