Evaluation of T2-weighted and dynamic contrast-enhanced MRI in localizing prostate cancer before repeat biopsy

Dynamic Contrast-Enhanced Study in the mpMRI of the Prostate-Unnecessary or Underutilised? A Narrative Review

The aim of this review is to summarise recent scientific literature regarding the clinical use of DCE-MRI as a component of multiparametric resonance imaging of the prostate. This review presents the principles of DCE-MRI acquisition and analysis, the current role of DCE-MRI in clinical practice with special regard to its role in presently available categorisation systems, and an overview of the advantages and disadvantages of DCE-MRI described in the current literature. DCE-MRI is an important functional sequence that requires intravenous administration of a gadolinium-based contrast agent and gives information regarding the vascularity and capillary permeability of the lesion. Although numerous studies have confirmed that DCE-MRI has great potential in the diagnosis and monitoring of prostate cancer, its role is still inadequate in the PI-RADS categorisation. Moreover, there have been numerous scientific discussions about abandoning the intravenous application of gadolinium-based contrast as a routine part of MRI examination of the prostate. In this review, we summarised the recent literature on the advantages and disadvantages of DCE-MRI, focusing on an overview of currently available data on bpMRI and mpMRI, as well as on studies providing information on the potential better usability of DCE-MRI in improving the sensitivity and specificity of mpMRI examinations of the prostate.

Development and validation of nomogram to improve the specificity of multiparametric MRI for clinically significant prostate cancer

OBJECTIVE

To develop and validate a nomogram to improve the specificity of prostate imaging reporting and data system (PI-RADS) on multiparametric magnetic resonance imaging (MRI) for clinically significant prostate cancer on targeted fusion biopsy.

METHODS

A retrospective review of patients who underwent fusion biopsy for PI-RADS 3-5 lesions using UroNav and Artemis systems between 2016 and 2022 was performed. Patients were divided into those with CS disease on fusion biopsy (Gleason grade group ≥2) versus those without. Multivariable analysis was used to identify variables associated with CS disease. A 100-point nomogram was constructed, and ROC curve was generated.

RESULTS

1485 lesions (1032 patients) were identified, 510 (34%) were PI-RADS 3, 586 (40%) were PI-RADS 4, and 389 (26%) were PI-RADS 5. Of these, 11% of PI-RADS 3, 39% of PI-RADS 4, and 61% of PI-RADS 5 showed CS disease. CS disease was associated with older age (OR 1.04, 95% CI 1.02-1.06, p < 0.01), previous negative biopsy (OR 0.52, 95% CI 0.36-0.74, p < 0.01), presence of multiple PI-RADS 3-5 lesions (OR 0.61, 95% CI 0.45-0.83, p < 0.01), peripheral zone location (OR 1.88, 95% CI 1.30-2.70, p < 0.01), PSA density (OR 1.48 per 0.1 unit, 95% CI 1.33-1.64, p < 0.01), PI-RADS score 4 (OR 3.28, 95% CI 2.21-4.87, p < 0.01), and PI-RADS score 5 (OR 7.65, 95% CI 4.93-11.85, p < 0.01). Area under ROC curve was 82% for nomogram compared to 75% for PI-RADS score alone.

CONCLUSION

We report a nomogram that combines PI-RADS score with other clinical parameters. The nomogram outperforms PI-RADS score for the detection of CS prostate cancer.

Design, Development, and Multi-Characterization of an Integrated Clinical Transrectal Ultrasound and Photoacoustic Device for Human Prostate Imaging

The standard diagnostic procedure for prostate cancer (PCa) is transrectal ultrasound (TRUS)-guided needle biopsy. However, due to the low sensitivity of TRUS to cancerous tissue in the prostate, small yet clinically significant tumors can be missed. Magnetic resonance imaging (MRI) with TRUS fusion biopsy has recently been introduced as a way to improve the identification of clinically significant PCa in men. However, the spatial errors in coregistering the preprocedural MRI with the real-time TRUS causes false negatives. A real-time and intraprocedural imaging modality that can sensitively detect PCa tumors and, more importantly, differentiate aggressive from nonaggressive tumors could largely improve the guidance of biopsy sampling to improve diagnostic accuracy and patient risk stratification. In this work, we seek to fill this long-standing gap in clinical diagnosis of PCa via the development of a dual-modality imaging device that integrates the emerging photoacoustic imaging (PAI) technique with the established TRUS for improved guidance of PCa needle biopsy. Unlike previously published studies on the integration of TRUS with PAI capabilities, this work introduces a novel approach for integrating a focused light delivery mechanism with a clinical-grade commercial TRUS probe, while assuring much-needed ease of operation in the transrectal space. We further present the clinical potential of our device by (i) performing rigorous characterization studies, (ii) examining the acoustic and optical safety parameters for human prostate imaging, and (iii) demonstrating the structural and functional imaging capabilities using deep-tissue-mimicking phantoms. Our TRUSPA experimental studies demonstrated a field-of-view in the range of 130 to 150 degrees and spatial resolutions in the range of 300 μm to 400 μm at a soft tissue imaging depth of 5 cm.

Usefulness of Bi-Parametric Magnetic Resonance Imaging with b=1,800 s/mm² Diffusion-Weighted Imaging for Diagnosing Clinically Significant Prostate Cancer

Purpose

This study was conducted to compare the accuracy of bi-parametric magnetic resonance imaging (bpMRI) with high b-value (b=1,000 s/mm², b1000) diffusion-weighted imaging (DWI) to that of bpMRI with ultra-high b-value (b=1,800 s/mm², b1800) DWI to detect clinically significant prostate cancer (csPCa).

Materials and Methods

A total of 408 patients with suspected PCa were evaluated by bpMRI prior to biopsy. One reader retrospectively reviewed all images for confirmation of Prostate Imaging–Reporting and Data System (PI-RADS) score. Cognitive magnetic resonance/ultrasound fusion target biopsy was done for all visible lesions (PI-RADS 3–5). Systematic biopsy was done for all cases. The csPCa detection rates were compared according to the bpMRI protocol (with/without b1800 DWI) or PI-RADS score. The accuracy of PI-RADS score was estimated using receiver operating characteristics curve. The signal intensity (SI) ratio (visible lesion/surrounding background) was evaluated.

Results

Among 164 men confirmed having PCa, 102 had csPCa (Gleason score≥7). Proportions of PI-RADS score 1–2/3/4/5 without b1800 DWI (n=133) and with b1800 DWI (n=275) were 19.5%/57.9%/15.8%/6.8% and 21.1%/48.7%/22.2%/8.0%, respectively. csPCa detection rates with/without b1800 DWI were 27.6%/19.5% (p=0.048), respectively. Areas under the curve of PI-RADS grading with/without b1800 DWI for csPCa detection were 0.885 and 0.705, respectively. The SI ratio in b1800 DWI was higher than that in b1000 DWI (p<0.001).

Conclusions

Adding b1800 DWI to bpMRI protocol improved the diagnostic accuracy and detection rate of csPCa. The higher SI ratio (lesion/background) in b1800 DWI enabled clearer identification of lesions.

Does the introduction of prostate multiparametric magnetic resonance imaging into the active surveillance protocol for localized prostate cancer improve patient re-classification?

OBJECTIVES

To determine whether replacement of protocol-driven repeat prostate biopsy (PB) with multiparametric magnetic resonance imaging (mpMRI) ± repeat targeted prostate biopsy (TB) when evaluating men on active surveillance (AS) for low-volume, low- to intermediate-risk prostate cancer (PCa) altered the likelihood of or time to treatment, or reduced the number of repeat biopsies required to trigger treatment.

PATIENTS AND METHODS

A total of 445 patients underwent AS in the period 2010-2016 at our institution, with a median (interquartile range [IQR]) follow-up of 2.4 (1.2-3.7) years. Up to 2014, patients followed a 'pre-2014' AS protocol, which incorporated PB, and subsequently, according to the 2014 National Institute for Health and Care Excellence (NICE) guidelines, patients followed a '2014-present' AS protocol that included mpMRI. We identified four groups of patients within the cohort: 'no mpMRI and no PB'; 'PB alone'; 'mpMRI ± TB'; and 'PB and mpMRI ± TB'. Kaplan-Meier plots and log-rank tests were used to compare groups.

RESULTS

Of 445 patients, 132 (30%) discontinued AS and underwent treatment intervention, with a median (IQR) time to treatment of 1.55 (0.71-2.4) years. The commonest trigger for treatment was PCa upgrading after mpMRI and TB (43/132 patients, 29%). No significant difference was observed in the time at which patients receiving a PB alone or receiving mpMRI ± TB discontinued AS to undergo treatment (median 1.9 vs 1.33 years; P = 0.747). Considering only those patients who underwent repeat biopsy, a greater proportion of patients receiving TB after mpMRI discontinued AS compared with those receiving PB alone (29/66 [44%] vs 32/87 [37%]; P = 0.003). On average, a single set of repeat biopsies was needed to trigger treatment regardless of whether this was a PB or TB.

CONCLUSIONS

Replacing a systematic PB with mpMRI ±TB as part of an AS protocol increased the likelihood of re-classifying patients on AS and identifying men with clinically significant disease requiring treatment. mpMRI ±TB as part of AS thereby represents a significant advance in the oncological safety of the AS protocol.

Predictors for the detection of prostate cancer and clinically significant prostate cancer using TRUS-guided biopsy in patients with negative initial biopsy results

PURPOSE

We aimed to determine the predictors for the detection of prostate cancer and clinically significant prostate cancer in the setting of repeat prostate biopsy using trans-rectal ultrasonography-guided biopsy.

METHODS

A total of 636 patients who underwent repeat prostate biopsy were included. The patients were divided into two groups according to the repeat biopsy results (with vs. without prostate cancer). A multivariable analysis was performed to assess the predictors for the detection of prostate cancer and clinically significant prostate cancer.

RESULTS

Prostate cancer was detected in 98 patients (15.4%). Although there was no difference in the prostate-specific antigen velocity, the prostate-specific antigen density was higher in the patients with prostate cancer at the initial (0.14 vs. 0.17 ng/mL/cc, p = 0.049) and repeat biopsies (0.17 vs. 0.26 ng/mL/cc, p < 0.001). The proportions of the patients who met the active surveillance criteria were as follows: 22.4% (Johns Hopkins), 30.6% (University of Toronto), 32.7% (University of California at San Francisco), 30.6% (Prostate Cancer Research International Active Surveillance), 27.6% (Memorial Sloan Kettering Cancer Center), and 13.3% (University of Miami). In the multivariable analysis, age, hypoechoic lesion on trans-rectal ultrasonography, and prostate-specific antigen density at the repeat biopsy were the significant predictors for prostate cancer and clinically significant prostate cancer.

CONCLUSIONS

Trans-rectal ultrasonography before repeat prostate biopsy and the prostate-specific antigen density are useful for selecting patients with a high probability for prostate cancer if repeat trans-rectal ultrasonography-guided biopsy is considered. In addition, these are also helpful for detecting clinically significant prostate cancer.

MRI in early prostate cancer detection: how to manage indeterminate or equivocal PI-RADS 3 lesions?

This review focuses on indeterminate lesions on prostate magnetic resonance imaging (MRI), assigned as PI-RADS category 3. The prevalence of PI-RADS 3 index lesion in the diagnostic work-up is significant, varying between one in three (32%) to one in five (22%) men, depending on patient cohort of first biopsies, previously negative biopsies, and active surveillance biopsies. A management strategy must be developed for this group of men with an indeterminate suspicion of having clinically significant prostate cancer (csPCa). Currently available data show that the actual prevalence of csPCa after targeted biopsy in PI-RADS 3 lesions vary between patients groups from one in five (21%) to one in six (16%), depending on previous biopsy status. Although this prevalence is lower in comparison to PI-RADS 4 and PI-RADS 5 lesions, still a considerable proportion of men harbor significant disease. Men with such a PI-RADS 3 lesion should therefore be adequately managed. In general, the clinical approach of using a threshold of PI-RADS ≥4 instead of PI-RADS ≥3 to select MRI for targeted biopsies is not supported by data from our explorative literature search using current definitions of csPCa. A possible adaptation to the threshold of PI-RADS ≥4 in combination with other clinical markers could be considered within an active surveillance protocol, where the balance between the individual risk of missing csPCa and the constant process of repeating prostate biopsies is crucial. In the future, improvements in MR imaging and interpretation, combined with molecular biomarkers and multivariate risk models will all be employed in prostate cancer detection and monitoring. These combinations will aid decision-making in challenging circumstances, such as unclear and diagnostic equivocal results for csPCa at early detection.

Automatic Detection and Quantitative DCE-MRI Scoring of Prostate Cancer Aggressiveness

Purpose

To develop a robust and clinically applicable automated method for analyzing Dynamic Contrast Enhanced (DCE-) MRI of the prostate as a guide for targeted biopsies and treatments.

Materials and methods

An unsupervised pattern recognition (PR) method was used to analyze prostate DCE-MRI from 71 sequential radiotherapy patients. Identified regions of interest (ROIs) with increased perfusion were assigned either to the peripheral (PZ) or transition zone (TZ). Six quantitative features, associated with the washin and washout part of the weighted average DCE curve from the ROI, were calculated. The associations between the assigned DCE-scores and Gleason Score (GS) were investigated. A heatmap of tumor aggressiveness covering the entire prostate was generated and validated with histopathology from MRI-ultrasound fused (MRI-US) targeted biopsies.

Results

The volumes of the PR-identified ROI’s were significantly correlated with the highest GS from the biopsy session for each patient. Following normalization (and only after normalization) with gluteus maximus muscle’s DCE signal, the quantitative features in PZ were significantly correlated with GS. These correlations straightened in subset of patients with available MRI-US biopsies when GS from the individual biopsies were used. Area under the receiver operating characteristics curve for discrimination between indolent vs aggressive cancer for the significant quantitative features reached 0.88–0.95. When DCE-scores were calculated in normal appearing tissues, the features were highly discriminative for cancer vs no cancer both in PZ and TZ. The generated heatmap of tumor aggressiveness coincided with the location and GS of the MRI-US biopsies.

Conclusion

A quantitative approach for DCE-MRI analysis was developed. The resultant map of aggressiveness correlated well with tumor location and GS and is applicable for integration in radiotherapy/radiology imaging software for clinical translation.

A systematic review on multiparametric MR imaging in prostate cancer detection

BACKGROUND

Literature data suggest that multi-parametric Magnetic Resonance Imaging (MRI), including morphologic T2-weigthed images (T2-MRI) and functional approaches such as Dynamic Contrast Enhanced-MRI (DCE-MRI), Diffusion Weighted Imaging (DWI) and Magnetic Resonance Spectroscopic Imaging (MRSI), give an added value in the prostate cancer localization and local staging.

METHODS

We performed a systematic review of literature about the role and the potentiality of morphological and functional MRI in prostate cancer, also in a multimodal / multiparametric approach, and we reported the diagnostic accuracy results for different imaging modalities and for different MR coil settings: endorectal coil (ERC) and phased array coil (PAC). Forest plots and receiver operating characteristic curves were performed. Risk of bias and the applicability at study level were calculated.

RESULTS

Thirty three papers were identified for the systematic review. Sensitivity and specificity values were, respectively, for T2-MRI of 75% and of 60%, for DCE-MRI of 80% and of 72%, for MRSI of 89% and of 69%, for combined T2-MRI and DCE-MRI of 87% and of 46%, for combined T2-MRI and MRSI of 79% and of 57%, for combined T2-MRI, DWI and DCE-MRI of 81% and of 84%, and for combined MRSI and DCE-MRI of 83% and of 83%. For MRI studies performed with ERC we obtained a pooled sensitivity and specificity of 81% and of 66% while the pooled values for MRI studies performed with PAC were of 78% and of 64%, respectively (p>0.05 at McNemar test). No studies were excluded from the analysis based on the quality assessment.

CONCLUSIONS

ERC use yielded no additional benefit in terms of prostate cancer detection accuracy compared to multi-channel PAC use (71% versus 68%) while the use of additional functional imaging techniques (DCE-MRI, DWI and MRSI) in a multiparametric MRI protocol improves the accuracy of prostate cancer detection allowing both the early cure and the guidance of biopsy.

Accuracy of dynamic contrast-enhanced magnetic resonance imaging in the diagnosis of prostate cancer: systematic review and meta-analysis

The goals of this meta-analysis were to assess the effectiveness of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in patients with prostate carcinoma (PCa) and to explore the risk profiles with the highest benefit. Systematic electronic searched were conducted in database. We used patient-based and biopsy-based pooled weighted estimates of the sensitivity, specificity, and a summary receiver operating characteristic (SROC) curve for assessing the diagnostic performance of DCE. We performed direct and indirect comparisons of DCE and other methods of imaging. A total of 26 articles met the inclusion criteria for the analysis. DCE-MRI pooled sensitivity was 0.53 (95% CI 0.39 to 0.67), with a specificity of 0.88 (95% CI 0.83 to 0.92) on whole gland. The peripheral zone pooled sensitivity was 0.70 (95% CI 0.46 to 0.86), with a specificity of 0.88 (95% CI 0.76 to 0.94). Compared with T2-weighted imaging (T2WI), DCE was statistically superior to T2. In conclusion, DCE had relatively high specificity in detecting PCa but relatively low sensitivity as a complementary functional method. DCE-MRI might help clinicians exclude cases of normal tissue and serve as an adjunct to conventional imaging when seeking to identify tumor foci in patients with PCa.

Comparison of Multiparametric and Biparametric MRI in First Round Cognitive Targeted Prostate Biopsy in Patients with PSA Levels under 10 ng/mL

PURPOSE

To determine the efficacy of cognitive targeted prostate biopsy using biparametric magnetic resonance imaging (b-MRI) for patients with prostate-specific antigen levels under 10 ng/mL.

MATERIALS AND METHODS

We reviewed data from 123 consecutive patients who underwent cognitive targeted prostate biopsy using prostate MRI. Of these patients, the first 55 underwent prostate biopsy using multiparametric MRI (mp-MRI), and the remaining 68 underwent prostate biopsy using b-MRI. For b-MRI, we generated T2 weighted axial imaging and diffusion-weighted imaging sequences. We found that 62 of the 123 men had suspicious lesions on MRI (32 of the 55 men in the mp-MRI group and 30 of the 68 men in the b-MRI group). We compared the prostate cancer detection rates and the proportions of clinically significant prostate cancer between the different MRI sequences.

RESULTS

Between the two MRI groups, there were no statistically significant differences in prostate cancer detection rate and proportions of clinically significant prostate cancer (41.8% vs. 30.9%, p=0.208 and 82.6% vs. 76.2%, p=0.598). Among the 62 men who had suspicious lesions on MRI, the prostate cancer detection rates were 62.5% and 63.3% (p=0.709) in the mp-MRI and b-MRI groups, respectively, and the proportions of clinically significant prostate cancer were 95.0% and 84.2% (p=0.267).

CONCLUSION

Prostate biopsy using b-MRI showed similar performance to that using mp-MRI for detecting prostate cancer and clinically significant prostate cancer. Considering the satisfactory performance and cost effectiveness of b-MRI, this technique could be a good option for obtaining intraprostatic information for first round prostate biopsy.

What Is the Negative Predictive Value of Multiparametric Magnetic Resonance Imaging in Excluding Prostate Cancer at Biopsy? A Systematic Review and Meta-analysis from the European Association of Urology Prostate Cancer Guidelines Panel

CONTEXT

It remains unclear whether patients with a suspicion of prostate cancer (PCa) and negative multiparametric magnetic resonance imaging (mpMRI) can safely obviate prostate biopsy.

OBJECTIVE

To systematically review the literature assessing the negative predictive value (NPV) of mpMRI in patients with a suspicion of PCa.

EVIDENCE ACQUISITION

The Embase, Medline, and Cochrane databases were searched up to February 2016. Studies reporting prebiopsy mpMRI results using transrectal or transperineal biopsy as a reference standard were included. We further selected for meta-analysis studies with at least 10-core biopsies as the reference standard, mpMRI comprising at least T2-weighted and diffusion-weighted imaging, positive mpMRI defined as a Prostate Imaging Reporting Data System/Likert score of ≥3/5 or ≥4/5, and results reported at patient level for the detection of overall PCa or clinically significant PCa (csPCa) defined as Gleason ≥7 cancer.

EVIDENCE SYNTHESIS

A total of 48 studies (9613 patients) were eligible for inclusion. At patient level, the median prevalence was 50.4% (interquartile range [IQR], 36.4-57.7%) for overall cancer and 32.9% (IQR, 28.1-37.2%) for csPCa. The median mpMRI NPV was 82.4% (IQR, 69.0-92.4%) for overall cancer and 88.1% (IQR, 85.7-92.3) for csPCa. NPV significantly decreased when cancer prevalence increased, for overall cancer (r=-0.64, p<0.0001) and csPCa (r=-0.75, p=0.032). Eight studies fulfilled the inclusion criteria for meta-analysis. Seven reported results for overall PCa. When the overall PCa prevalence increased from 30% to 60%, the combined NPV estimates decreased from 88% (95% confidence interval [95% CI], 77-99%) to 67% (95% CI, 56-79%) for a cut-off score of 3/5. Only one study selected for meta-analysis reported results for Gleason ≥7 cancers, with a positive biopsy rate of 29.3%. The corresponding NPV for a cut-off score of ≥3/5 was 87.9%.

CONCLUSIONS

The NPV of mpMRI varied greatly depending on study design, cancer prevalence, and definitions of positive mpMRI and csPCa. As cancer prevalence was highly variable among series, risk stratification of patients should be the initial step before considering prebiopsy mpMRI and defining those in whom biopsy may be omitted when the mpMRI is negative.

PATIENT SUMMARY

This systematic review examined if multiparametric magnetic resonance imaging (MRI) scan can be used to reliably predict the absence of prostate cancer in patients suspected of having prostate cancer, thereby avoiding a prostate biopsy. The results suggest that whilst it is a promising tool, it is not accurate enough to replace prostate biopsy in such patients, mainly because its accuracy is variable and influenced by the prostate cancer risk. However, its performance can be enhanced if there were more accurate ways of determining the risk of having prostate cancer. When such tools are available, it should be possible to use an MRI scan to avoid biopsy in patients at a low risk of prostate cancer.

Computed Tomography Perfusion of Prostate Cancer: Diagnostic Value of Quantitative Analysis

OBJECTIVE

The aim of the study was to assess the diagnostic value of computed tomography perfusion (CTp) of prostate in distinguishing between normal tissue and malignant lesion by using quantitative threshold values of CTp parameters.

MATERIALS AND METHODS

Sixty-one consecutive men with indication for radical prostatectomy were prospectively enrolled. All patients were intravenously injected with 80-mL bolus of nonionic iodinated contrast medium during cine-mode acquisition protocol. Perfusion data sets were analyzed by a dedicated software system and values for each of the 4 CTp parameters (blood volume, blood flow, mean transit time, and permeability surface-area product measurements) were recorded. Receiver operating characteristic curves were calculated to find which CTp parameter and which cutoff value might reveal the best diagnostic accuracy. Histopathology was used as reference standard.

RESULTS

Statistical correlation between radiological and pathological results was performed on 48 patients using 3456 segmented squares. Blood volume and permeability surface revealed the best diagnostic accuracy for differentiating between malignant and benign squares, with cutoff values of 6.1 and 16.5, respectively, and a sensitivity of 84.8% and 81.8%, respectively. All parameters showed also a high negative predictive value: 97.1% for blood volume and 95.4% for permeability surface.

CONCLUSIONS

Blood volume and permeability surface are the 2 CTp parameters with the highest diagnostic accuracy in differentiating between normal tissue and prostatic neoplasia. Due to the extremely high negative predictive value, they are particularly valuable in excluding the presence of cancer and thus resulting potentially useful in assessing cancer response to adjuvant therapy.

Prostate cancer risk stratification with magnetic resonance imaging

In recent years, multiparametric magnetic resonance imaging (mpMRI) has shown promise for prostate cancer (PCa) risk stratification. mpMRI, often followed by targeted biopsy, can be used to confirm low-grade disease before enrollment in active surveillance. In patients with intermediate or high-risk PCa, mpMRI can be used to inform surgical management. mpMRI has sensitivity of 44% to 87% for detection of clinically significant PCa and negative predictive value of 63% to 98% for exclusion of significant disease. In addition to tumor identification, mpMRI has also been shown to contribute significant incremental value to currently used clinical nomograms for predicting extraprostatic extension. In combination with conventional clinical criteria, accuracy of mpMRI for prediction of extraprostatic extension ranges from 92% to 94%, significantly higher than that achieved with clinical criteria alone. Supplemental sequences, such as diffusion-weighted imaging and dynamic contrast-enhanced imaging, allow quantitative evaluation of cancer-suspicious regions. Apparent diffusion coefficient appears to be an independent predictor of PCa aggressiveness. Addition of apparent diffusion coefficient to Epstein criteria may improve sensitivity for detection of significant PCa by as much as 16%. Limitations of mpMRI include variability in reporting, underestimation of PCa volume and failure to detect clinically significant disease in a small but significant number of cases.

Quantifying Gleason scores with photoacoustic spectral analysis: feasibility study with human tissues

Gleason score is a highly prognostic factor for prostate cancer describing the microscopic architecture of the tumor tissue. The standard procedure for evaluating Gleason scores, namely biopsy, is to remove prostate tissue for observation under microscope. Currently, biopsies are guided by transrectal ultrasound (TRUS). Due to the low sensitivity of TRUS to prostate cancer (PCa), non-guided and saturated biopsies are frequently employed, unavoidably causing pain, damage to the normal prostate tissues and other complications. More importantly, due to the limited number of biopsy cores, current procedure could either miss early stage small tumors or undersample aggressive cancers. Photoacoustic (PA) measurement has the unique capability of evaluating tissue microscopic architecture information at ultrasonic resolution. By frequency domain analysis of the broadband PA signal, namely PA spectral analysis (PASA), the microscopic architecture within the assessed tissue can be quantified. This study investigates the feasibility of evaluating Gleason scores by PASA. Simulations with the classic Gleason patterns and experiment measurements from human PCa tissues have demonstrated strong correlation between the PASA parameters and the Gleason scores.

Prostate cancer identification: quantitative analysis of T2-weighted MR images based on a back propagation artificial neural network model

Computer-aided diagnosis (CAD) systems have been proposed to assist radiologists in making diagnostic decisions by providing helpful information. As one of the most important sequences in prostate magnetic resonance imaging (MRI), image features from T2-weighted images (T2WI) were extracted and evaluated for the diagnostic performances by using CAD. We extracted 12 quantitative image features from prostate T2-weighted MR images. The importance of each feature in cancer identification was compared in the peripheral zone (PZ) and central gland (CG), respectively. The performance of the computer-aided diagnosis system supported by an artificial neural network was tested. With computer-aided analysis of T2-weighted images, many characteristic features with different diagnostic capabilities can be extracted. We discovered most of the features (10/12) had significant difference (P<0.01) between PCa and non-PCa in the PZ, while only five features (sum average, minimum value, standard deviation, 10th percentile, and entropy) had significant difference in CG. CAD prediction by features from T2w images can reach high accuracy and specificity while maintaining acceptable sensitivity. The outcome is convictive and helpful in medical diagnosis.

How accurate is multiparametric MR imaging in evaluation of prostate cancer volume?

PURPOSE

To assess the factors influencing multiparametric (MP) magnetic resonance (MR) imaging accuracy in estimating prostate cancer histologic volume (Vh).

MATERIALS AND METHODS

A prospective database of 202 patients who underwent MP MR imaging before radical prostatectomy was retrospectively used. Institutional review board approval and informed consent were obtained. Two independent radiologists delineated areas suspicious for cancer on images (T2-weighted, diffusion-weighted, dynamic contrast material-enhanced [DCE] pulse sequences) and scored their degree of suspicion of malignancy by using a five-level Likert score. One pathologist delineated cancers on whole-mount prostatectomy sections and calculated their volume by using digitized planimetry. Volumes of MR true-positive lesions were measured on T2-weighted images (VT2), on ADC maps (VADC), and on DCE images [VDCE]). VT2, VADC, VDCE and the greatest volume determined on images from any of the individual MR pulse sequences (Vmax) were compared with Vh (Bland-Altman analysis). Factors influencing MP MR imaging accuracy, or A, calculated as A = Vmax/Vh, were evaluated using generalized linear mixed models.

RESULTS

For both readers, Vh was significantly underestimated with VT2 (P < .0001, both), VADC (P < .0001, both), and VDCE (P = .02 and P = .003, readers 1 and 2, respectively), but not with Vmax (P = .13 and P = .21, readers 1 and 2, respectively). Mean, 25th percentile, and 75th percentile, respectively, for Vmax accuracy were 0.92, 0.54, and 1.85 for reader 1 and 0.95, 0.57, and 1.77 for reader 2. At generalized linear mixed (multivariate) analysis, tumor Likert score (P < .0001), Gleason score (P = .009), and Vh (P < .0001) significantly influenced Vmax accuracy (both readers). This accuracy was good in tumors with a Gleason score of 7 or higher or a Likert score of 5, with a tendency toward underestimation of Vh; accuracy was poor in small (<0.5 cc) or low-grade (Gleason score ≤6) tumors, with a tendency toward overestimation of Vh.

CONCLUSION

Vh can be estimated by using Vmax in aggressive tumors or in tumors with high Likert scores.

Prostate cancer: diagnostic performance of real-time shear-wave elastography

PURPOSE

To prospectively evaluate the performance of real-time ultrasonographic (US) shear-wave elastography (SWE) in the diagnosis of peripheral zone prostate cancer in patients with high and/or increasing prostate-specific antigen levels and/or abnormal digital rectal examination results.

MATERIALS AND METHODS

After signing an informed consent form, men referred for transrectal prostate biopsy were enrolled in this prospective HIPAA-compliant two-center study, which was conducted with institutional review board approval. Transrectal US SWE of the prostate was performed after a conventional transrectal US examination and immediately before US-guided 12-core sextant biopsy. For each sextant, the maximum SWE value was measured and matched to the pathologic results of that sextant biopsy. The diagnostic performance of SWE was assessed at both patient and sextant levels. The elasticity value maximizing the Youden index was used to derive sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

The elasticity values were matched to pathologic results for a total of 1040 peripheral zone sextants in 184 men. One hundred twenty-nine positive biopsy findings (size, ≥3 mm; Gleason score, ≥6) were identified in 68 patients. The sextant-level sensitivity, specificity, PPV, NPV, and area under the receiver operating characteristic curve for SWE with a cutoff of 35 kPa for differentiating benign from malignant lesions were 96% (95% confidence interval [CI]: 95%, 97%), 85% (95% CI: 83%, 87%), 48% (95% CI: 46%, 50%), 99% (95% CI: 98%, 100%), and 95% (95% CI: 93%, 97%), respectively.

CONCLUSION

Use of a 35-kPa threshold at SWE may provide additional information for the detection and biopsy guidance of prostate cancer, enabling a substantial reduction in the number of biopsies while ensuring that few peripheral zone adenocarcinomas are missed.

3-Tesla magnetic resonance imaging improves the prostate cancer detection rate in transrectral ultrasound-guided biopsy

The detection rate of prostate cancer (PCa) using traditional biopsy guided by transrectal ultrasound (TRUS) is not satisfactory. The aim of this study was to determine the utility of 3-Tesla (3-T) magnetic resonance imaging (MRI) prior to TRUS-guided prostate biopsy and to investigate which subgroup of patients had the most evident improvement in PCa detection rate. A total of 420 patients underwent 3-T MRI examination prior to the first prostate biopsy and the positions of suspicious areas were recorded respectively. TRUS-guided biopsy regimes included systematic 12-core biopsy and targeted biopsy identified by MRI. Patients were divided into subgroups according to their serum prostate-specific antigen (PSA) levels, PSA density (PSAD), prostate volume, TRUS findings and digital rectal examination (DRE) findings. The ability of MRI to improve the cancer detection rate was evaluated. The biopsy positive rate of PCa was 41.2% (173/420), and 41 of the 173 (23.7%) patients were detected only by targeted biopsy in the MRI-suspicious area. Compared with the systematic biopsy, the positive rate was significantly improved by the additional targeted biopsy (P=0.0033). The highest improvement of detection rate was observed in patients with a PSA level of 4–10 ng/ml, PSAD of 0.12–0.20 ng/ml², prostate volume >50 ml, negative TRUS findings and negative DRE findings (P<0.05). Therefore, it is considered that 3-T MRI examination could improve the PCa detection rate on first biopsy, particularly in patients with a PSA level of 4–10 ng/ml, PSAD of 0.12–0.20 ng/ml², prostate volume of >50 ml, negative TRUS findings and negative DRE findings.

The clinical value of dynamic contrast-enhanced magnetic resonance imaging at 3.0T to detect prostate cancer

Objective

To compare dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and T2-weighted imaging (T2WI) at 3.0T for detection of prostate cancer.

Methods

Patients with elevated prostate-specific antigen underwent T2WI and DCE-MRI prior to prostate needle biopsy. The sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of T2WI and DCE-MRI to diagnose prostate cancer were evaluated. The relationship between Gleason score and prostate cancer detection by DCE-MRI was evaluated.

Results

Prostate adenocarcinoma was histopathologically confirmed in 44/75 patients. DCE-MRI had significantly higher sensitivity, accuracy and NPV than T2WI. The detection rate of prostate cancer by DCE-MRI was significantly better for tumours with Gleason score 7–9 than for those Gleason score 4–6.

Conclusion

DCE-MRI at 3.0T can significantly improve prostate cancer detection using simple visual diagnostic criteria, compared with T2WI.

Characterization of prostate lesions as benign or malignant at multiparametric MR imaging: comparison of three scoring systems in patients treated with radical prostatectomy

PURPOSE

To compare the subjective Likert score to the Prostate Imaging Reporting and Data System (PIRADS) and morphology-location-signal intensity (MLS) scores for categorization of prostate lesions as benign or malignant at multiparametric magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Two hundred fifteen patients who underwent T2-weighted, diffusion-weighted, and dynamic contrast material-enhanced multiparametric MR imaging of the prostate before radical prostatectomy were included in a prospective database after they signed the institutional review board-approved forms. Senior readers 1 and 2 prospectively noted the location, shape, and signal intensity of lesions on MR images from individual pulse sequences and scored each for likelihood of malignancy by using a Likert scale (range, 1-5). A junior reader (reader 3) retrospectively reviewed the database and did the same analysis. The MLS score (range, 1-13) was computed by using the readers' descriptions of the lesions. Then, the three readers again scored the lesions they described by using the PIRADS score (range, 3-15). MLS and PIRADS scores were compared with the Likert score by using their areas under the receiver operating characteristic curves.

RESULTS

Areas under the receiver operating characteristic curves of the Likert, MLS, and PIRADS scores were 0.81, 0.77 (P = .03), and 0.75 (P = .01) for reader 1; 0.88, 0.74 (P < .0001), and 0.76 (P < .0001) for reader 2; and 0.81, 0.78 (P = .23), and 0.75 (P = .01) for reader 3. For diagnosing cancers with Gleason scores greater than or equal to 7, the Likert score was significantly more accurate than the others, except for the MLS score for reader 3. Weighted κ values were 0.470-0.524, 0.405-0.430, and 0.378-0.441 for the Likert, MLS, and PIRADS scores, respectively.

CONCLUSION

The Likert score allowed significantly more accurate categorization of prostate lesions on MR images than did the MLS and PIRADS scores.

Prostate focal peripheral zone lesions: characterization at multiparametric MR imaging--influence of a computer-aided diagnosis system

PURPOSE

To assess the impact of a computer-aided diagnosis (CAD) system in the characterization of focal prostate lesions at multiparametric magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Formal institutional review board approval was not required. Thirty consecutive 1.5-T multiparametric MR imaging studies (with T2-weighted, diffusion-weighted, and dynamic contrast material-enhanced imaging) obtained before radical prostatectomy in patients between September 2008 and February 2010 were reviewed. Twelve readers assessed the likelihood of malignancy of 88 predefined peripheral zone lesions by using a five-level (level, 0-4) subjective score (SS) in reading session 1. This was repeated 5 weeks later in reading session 2. The CAD results were then disclosed, and in reading session 3, the readers could amend the scores assigned during reading session 2. Diagnostic accuracy was assessed by using a receiver operating characteristic (ROC) regression model and was quantified with the area under the ROC curve (AUC).

RESULTS

Mean AUCs were significantly lower for less experienced (<1 year) readers (P < .02 for all sessions). Seven readers improved their performance between reading sessions 1 and 2, and 12 readers improved their performance between sessions 2 and 3. The mean AUCs for reading session 1 (83.0%; 95% confidence interval [CI]: 77.9%, 88.0%) and reading session 2 (84.1%; 95% CI: 78.1%, 88.7%) were not significantly different (P = .76). Although the mean AUC for reading session 3 (87.2%; 95% CI: 81.0%, 92.0%) was higher than that for session 2, the difference was not significant (P = .08). For an SS positivity threshold of 3, the specificity of reading session 2 (79.0%; 95% CI: 71.1%, 86.4%) was not significantly different from that of session 1 (78.7%; 95% CI: 70.5%, 86.8%) but was significantly lower than that of session 3 (86.2%; 95% CI: 77.1%, 93.1%; P < .03). The sensitivity of reading session 2 (68.4%; 95% CI: 57.5%, 77.7%) was significantly higher than that of session 1 (64.0%; 95% CI: 52.9%, 73.9%; P = .003) but was not significantly different from that of session 3 (71.4%; 95% CI: 58.3%, 82.7%).

CONCLUSION

A CAD system may improve the characterization of prostate lesions at multiparametric MR imaging by increasing reading specificity.

Prostate MRI: access to and current practice of prostate MRI in the United States

PURPOSE

MRI of the prostate has increasingly become more important in clinical medicine because of the risk of over-detection of low-grade, low-volume prostate cancer, as well as because of the poor sampling of transrectal ultrasound-guided prostate biopsy in high-risk patients. We sought to determine the access, imaging protocols, and indications for MRI imaging of the prostate in the United States.

METHODS

A brief survey was sent through mailing lists to members of the Society of Abdominal Radiology and Texas Radiological Society.

RESULTS

Thirty-six academic centers responded to the survey, 88.9% of which routinely perform prostate MRI. Nine centers routinely performed imaging at 1.5T with an endorectal coil (25%), 11 performed at 3.0T without an endorectal coil (31%), and 10 performed at 3.0T with an endorectal coil (28%). All institutions used T1-weighted axial and orthogonal T2-weighted sequences. Most groups used diffusion-weighted imaging (94.7%) and dynamic contrast enhancement (81.6%). Only 21.1% of groups performing prostate MRI routinely performed MR spectroscopy as part of their protocol.

CONCLUSIONS

Prostate MRI is becoming a commonly performed examination at academic institutions, with most locations performing prostate MRI at minimum standards. There is a need to educate nonacademic practices regarding the addition of functional MRI techniques to anatomic techniques, increase the number of institutions that regularly perform prostate MRI, and increase access to direct MRI-guided biopsy in institutions that perform prostate MRI on a regular basis.

The role of magnetic resonance imaging in the diagnosis and management of prostate cancer

BACKGROUND

The diagnosis of prostate cancer has long been plagued by the absence of an imaging tool that reliably detects and localises significant tumours. Recent evidence suggests that multi-parametric MRI could improve the accuracy of diagnostic assessment in prostate cancer. This review serves as a background to a recent USANZ position statement. It aims to provide an overview of MRI techniques and to critically review the published literature on the clinical application of MRI in prostate cancer.

TECHNICAL ASPECTS

The combination of anatomical (T2-weighted) MRI with at least two of the three functional MRI parameters - which include diffusion-weighted imaging, dynamic contrast-enhanced imaging and spectroscopy - will detect greater than 90% of significant (moderate to high risk) tumours; however MRI is less reliable at detecting tumours that are small (<0.5 cc), low grade (Gleason score 6) or in the transitional zone. The higher anatomical resolution provided by 3-Tesla magnets and endorectal coils may improve the accuracy, particularly in primary tumour staging.

SCREENING

The use of mpMRI to determine which men with an elevated PSA should undergo biopsy is currently the subject of two large clinical trials in Australia. MRI should be used with caution in this setting and then only in centres with established uro-radiological expertise and quality control mechanisms in place. There is sufficient evidence to justify using MRI to determine the need for repeat biopsy and to guide areas in which to focus repeat biopsy.

IMAGE-DIRECTED BIOPSY

MRI-directed biopsy is an exciting concept supported by promising early results, but none of the three proposed techniques have so far been proven superior to standard biopsy protocols. Further evidence of superior accuracy and core-efficiency over standard biopsy is required, before their costs and complexities in use can be justified.

TREATMENT SELECTION AND PLANNING

When used for primary-tumour staging (T-staging), MRI has limited sensitivity for T3 disease, but its specificity of greater than 95% may be useful in men with intermediate-high risk disease to identify those with advanced T3 disease not suitable for nerve sparing or for surgery at all. MRI appears to be of value in planning dosimetry in men undergoing radiotherapy, and in guiding selection for and monitoring on active surveillance.

Prostate MRI: can we do without DCE sequences in 2013?

Multiparametric MRI (mp-MRI) of the prostate currently provides stable and reproducible performances. The usefulness of dynamic contrast-enhanced (DCE) sequences is currently challenged, as they sometimes only confirm what has already been observed on diffusion-weighted imaging (DWI) and require the additional purchase of a contrast agent. Eliminating these sequences may help accelerate the use of MRI in addition to, or in lieu of, prostate biopsies in selected patients. However, many studies show that these sequences can detect lesions invisible on T2-weighted and diffusion-weighted images, better assess cancer extension and aggressiveness, and finally help detecting recurrence after treatment. We present the various applications of dynamic MRI and discuss the possible consequences of its omission from the current protocol.

Ultrasound elastography of the prostate: state of the art

Prostate cancer is the cancer exhibiting the highest incidence rate and it appears as the second cause of cancer death in men, after lung cancer. Prostate cancer is difficult to detect, and the treatment efficacy remains limited despite the increase use of biological tests (prostate-specific antigen [PSA] dosage), the development of new imaging modalities, and the use of invasive procedures such as biopsy. Ultrasound elastography is a novel imaging technique capable of mapping tissue stiffness of the prostate. It is known that prostatic cancer tissue is often harder than healthy tissue (information used by digital rectal examination [DRE]). Two elastography techniques have been developed based on different principles: first, quasi-static (or strain) technique, and second, shear wave technique. The tissue stiffness information provided by US elastography should improve the detection of prostate cancer and provide guidance for biopsy. Prostate elastography provides high sensitivity for detecting prostate cancer and shows high negative predictive values, ensuring that few cancers will be missed. US elastography should become an additional method of imaging the prostate, complementing the conventional transrectal ultrasound and MRI. This technique requires significant training (especially for quasi-static elastography) to become familiar with acquisition process, acquisition technique, characteristics and limitations, and to achieve correct diagnoses.

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.

[Multiparametric MRI, elastography, contrastenhanced TRUS. Are there indications with reliable diagnostic advantages before prostate biopsy?]

Prostate cancer (PCA) is the most common malignancy in men with an increasing incidence and is responsible for about 11,000 deaths per year in Germany. Fortunately, the mortality of PCA has decreased in recent years despite the rising incidence reflecting improvements in diagnostic methods. Many new innovations in imaging techniques for PCA are available and may be helpful in early detection of PCA. Contrast-enhanced sonography, computer-assisted sonography, elastography and multiparametric magnetic resonance imaging (MRI) seem to be the most promising methods to increase the detection rate of PCA during diagnostic work-up. The value of these new innovative techniques concerning improvement in PCA detection is reviewed.

Development and preliminary evaluation of a motorized needle guide template for MRI-guided targeted prostate biopsy

To overcome the problems of limited needle insertion accuracy and human error in the use of a conventional needle guide template in magnetic resonance imaging (MRI)-guided prostate intervention, we developed a motorized MRI-compatible needle guide template that resembles a transrectal ultrasound-guided prostate template. The motorized template allows automated, gapless needle guidance in a 3T MRI scanner with minimal changes in the current clinical procedure. To evaluate the impact of the motorized template on MRI, signal-to-noise ratio and distortion were measured under various system configurations. A maximum of 44% signal-to-noise ratio decrease was found when the ultrasonic motors were running, and a maximum of 0.4% image distortion was observed due to the presence of the motorized template. To measure needle insertion accuracy, we performed four sets of five random target needle insertions mimicking four biopsy procedures, which resulted in an average in-plane targeting error of 0.94 mm with a standard deviation of 0.34 mm. The evaluation studies indicated that the presence and operation of the motorized template in the MRI bore create insignificant image degradation, and provide submillimeter targeting accuracy. The automated needle guide that is directly controlled by navigation software eliminates human error so that the safety of the procedure can be improved.

Overview of dynamic contrast-enhanced MRI in prostate cancer diagnosis and management

OBJECTIVE

This article is a primer on the technical aspects of performing a high-quality dynamic contrast-enhanced MRI (DCE-MRI) examination of the prostate gland.

CONCLUSION

DCE-MRI is emerging as a useful clinical technique as part of a multi-parametric approach for evaluating the extent of primary and recurrent prostate cancer. Performing a high-quality DCE-MRI examination requires a good understanding of the technical aspects and limitations of image acquisition and postprocessing techniques.

Is it possible to model the risk of malignancy of focal abnormalities found at prostate multiparametric MRI?

OBJECTIVE

To evaluate whether focal abnormalities (FAs) depicted by prostate MRI could be characterised using simple semiological features.

METHODS

134 patients who underwent T2-weighted, diffusion-weighted and dynamic contrast-enhanced MRI at 1.5 T before prostate biopsy were prospectively included. FAs visible at MRI were characterised by their shape, the degree of signal abnormality (0 = normal to 3 = markedly abnormal) on individual MR sequences, and a subjective score (SS(1) = probably benign to SS(3) = probably malignant). FAs were then biopsied under US guidance.

RESULTS

56/233 FAs were positive at biopsy. The subjective score significantly predicted biopsy results (P < 0.01). As compared to SS(1) FAs, the odds ratios (OR) of malignancy of SS(2) and SS(3) FAs were 9.9 (1.8-55.9) and 163.8 (11.5-2331). Unlike FAs' shape, a simple combination of MR signal abnormalities (into "low-risk", "intermediate" and "high-risk" groups) significantly predicted biopsy results (P < 0.008). As compared to "low risk" FAs, the OR of malignancy of "intermediate" and "high-risk" FAs were 4.5 (1.1-18.4) and 52.7 (6.8-407) in the overall population and 5.4 (1.1-27.2) and 118.2 (6.1-2301) in PZ.

CONCLUSIONS

A simple combination of signal abnormalities of individual MR sequences can significantly stratify the risk of malignancy of FAs, holding promise of a more standardised interpretation of MRI by readers with varying experience.

KEY POINTS

• Using multiparameter(mp)-MRI, experienced uroradiologists can stratify the malignancy risk of prostatic lesions • The shape of prostatic focal abnormalities in the peripheral zone does not help predicting malignancy. • A simple combination of findings at mp-MRI can help less-experienced radiologists.

MRI of localized prostate cancer: coming of age in the PSA era

Prostate cancer is the most common cancer among American men. It varies widely in aggressiveness, ranging from completely indolent to highly aggressive. Currently, predicting the natural history of a particular tumor and deciding on the appropriate treatment, which might include active surveillance, surgery, radiation or hormonal therapies, are based on the condition and age of the patient as well as the presumed stage of the disease. Imaging plays an important role in staging localized prostate cancer. Magnetic resonance imaging (MRI) best depicts the zonal anatomy, with a superior soft tissue resolution providing better results for tumor localization, monitoring, and local staging. Previously, the major function of prostate MRI has been in staging, and this role remains important. In this article, we introduce the reader to the expanding roles that MRI plays in the management of localized prostate cancer.

Prostate cancer detection on dynamic contrast-enhanced MRI: computer-aided diagnosis versus single perfusion parameter maps

OBJECTIVE

The purpose of this article is to assess the value of computer-aided diagnosis (CAD) for prostate cancer detection on dynamic contrast-enhanced MRI (DCE-MRI).

MATERIALS AND METHODS

DCE-MRI examinations of 42 patients with prostate cancer were used to generate perfusion parameters, including baseline and peak signal intensities, initial slope, maximum slope within the initial 50 seconds after the contrast injection (slope(50)), wash-in rate, washout rate, time to peak, percentage of relative enhancement, percentage enhancement ratio, time of arrival, efflux rate constant from the extravascular extracellular space to the blood plasma (k(ep)), first-order rate constant for eliminating gadopentetate dimeglumine from the blood plasma (k(el)), and constant depending on the properties of the tissue and represented by the size of the extravascular extracellular space (A(H)). CAD for cancer detection was established by comprehensive evaluation of parameters using a support vector machine. The diagnostic accuracy of single perfusion parameters was estimated using receiver operating characteristic analysis, which determined threshold and parametric maps for cancer detection. The diagnostic performance of CAD for cancer detection was compared with those of T2-weighted imaging (T2WI) and single perfusion parameter maps, using histologic results as the reference standard.

RESULTS

The accuracy, sensitivity, and specificity of CAD were 83%, 77%, and 77%, respectively, in the entire prostate; 77%, 91%, and 64%, respectively, in the transitional zone; and 89%, 89%, and 89%, respectively, in the peripheral zone. Values for k(ep), k(el), initial slope, slope(50), wash-in rate, washout rate, and time to peak showed greater area under the curve values (0.803-0.888) than did the other parameters (0.545-0.665) (p < 0.01) and were compared with values for CAD. In the entire prostate, accuracy was greater for CAD than for all perfusion parameters or T2WI (63-77%); sensitivity was greater for CAD than for T2WI, initial slope, wash-in rate, slope(50), and washout rate (38-77%); and specificity was greater for CAD than for T2WI, k(ep), k(el), and time to peak (59-68%) (p < 0.05).

CONCLUSION

CAD can improve the diagnostic performance of DCE-MRI in prostate cancer detection, which may vary according to zonal anatomy.

Dynamic gadolinium-enhanced perfusion MRI of prostate cancer: assessment of response to hypofractionated robotic stereotactic body radiation therapy

OBJECTIVE

The purpose of this study was to evaluate the utility of dynamic gadolinium-enhanced perfusion MRI for monitoring the response to robotic stereotactic body radiation therapy for prostate cancer.

MATERIALS AND METHODS

Eighty-seven patients with prostate cancer underwent dynamic gadolinium-enhanced MRI before robotic stereotactic body radiation therapy, and prostate volume was calculated. Pharmacokinetic analysis postprocessing software was used to generate colorized parametric maps showing perfusion of enhancing tumors. The transfer constant K(trans) was calculated for identified tumors. Follow-up MRI was performed 2 months after treatment for 22 patients, 6 months for 71 patients, 12 months for 54 patients, and 24 months for 27 patients with repeated measurements of prostate volume and K(trans).

RESULTS

Perfusion MRI depicted focal enhancing prostate tumors that correlated with the biopsy results in 82 of 87 patients (94%). The median K(trans) of tumors before robotic stereotactic body radiation therapy was 1.79 minutes(-1). Follow-up MRI showed decreases in the size and degree of enhancement of tumors. The median tumor K(trans) decreased to 1.21 minutes(-1) 2 months, 0.39 minutes(-1) 6 months, 0.30 minutes(-1) 12 months, and 0.22 minutes(-1) 24 months after treatment. Prostate volume had decreased 23% 2 months, 26% 6 months, 33% 12 months, and 37% 24 months after robotic stereotactic body radiation therapy. The corresponding median prostate-specific antigen concentration before treatment was 6.45 ng/mL. After treatment, the concentration was 2.90 ng/mL at 2 months, 1.30 ng/mL at 6 months, 1.10 ng/mL at 12 months, and 0.59 ng/mL at 24 months.

CONCLUSION

Dynamic gadolinium-enhanced MRI is a useful tool for monitoring the response of prostate cancer to robotic stereotactic body radiation therapy, yielding both qualitative and quantitative data.

Usefulness of prebiopsy multifunctional and morphologic MRI combined with free-to-total prostate-specific antigen ratio in the detection of prostate cancer

OBJECTIVE

The purpose of the study was to assess the predictive value for prostate cancer of MRI using morphologic (T2-weighted imaging [T2WI]) and functional (MR spectroscopy [MRS], diffusion-weighted imaging [DWI], and dynamic contrast-enhanced [DCE] MRI) sequences and the free-to-total prostate-specific antigen (PSA) ratio, alone and combined.

MATERIALS AND METHODS

This retrospective study included 70 patients (PSA level, > 4 ng/mL; free-to-total PSA ratio, < 20%) who underwent endorectal 1.5-T MRI before biopsy. We graded the likelihood of cancer on a 5-point scale. Imaging data were compared with histologic results on biopsy or prostatectomy. Accuracies were estimated from the area under receiver operating characteristic using the hemiprostate as the unit of analysis. A p value less than 0.05 denoted statistical significance.

RESULTS

The model combining all variables was more accurate than each variable alone (95.2% vs 73.5% for T2WI, 76.0% for MRS, 81.8% for DWI, 75.6% for DCE-MRI, and 78.8% for free-to-total PSA ratio). The complete model had accuracy similar to that of combining two imaging variables with free-to-total PSA ratio, especially free-to-total PSA ratio, T2WI, and DWI (94.0%); and free-to-total PSA ratio, DWI, and MRS (93.8%); with negative predictive values of 91.0% and 89.5%, respectively. The best models combining two imaging variables (MRS and DWI, 85.8%; T2WI and DWI, 84.8%) had accuracy that was similar to that of the combination of all imaging variables (87.3%) and higher than that of the best individual imaging variable (DWI, 81.8%), but lower than that of the complete model.

CONCLUSION

The combination of at least one functional technique with free-to-total PSA ratio is more accurate than combining only imaging variables in cancer detection. The use of more than two imaging variables does not increase the detection rate. Functional MRI has the potential to help avoid a large number of negative biopsies.

Location of residual cancer after transrectal high-intensity focused ultrasound ablation for clinically localized prostate cancer

What's known on the subject ? and What does the study add? Transrectal High-Intensity Focused Ultrasound (HIFU) ablation has been used as a minimally invasive treatment for localized prostate cancer for 15 years. Five-year disease-free survival rates of 66-78% have been reported, challenging the results of external-beam radiation therapy. Usually, a 6-mm safety margin is used in the apex to preserve the urinary sphincter and potency. The influence of this 6-mm margin on the results of the treatment has never been assessed. This retrospective study of a cohort of 99 patients who underwent systematic biopsy 3-6 months after HIFU ablation for prostate cancer (with a 6-mm safety margin in the apex) shows that post-HIFU residual cancer is found more frequently in the apex. Therefore, new strategies improving the prostate destruction at the apex while preserving the urinary continence need to be found.

OBJECTIVE

• To evaluate whether the location (apex/midgland/base) of prostate cancer influences the risk of incomplete transrectal high-intensity focused ultrasonography (HIFU) ablation.

PATIENTS AND METHODS

• We retrospectively studied 99 patients who underwent prostate cancer HIFU ablation (Ablatherm; EDAP, Vaulx-en-Velin, France) with a 6-mm safety margin at the apex, and had systematic biopsies 3-6 months after treatment. • Locations of positive pre- and post-HIFU sextants were compared. • The present study included two analyses. First, sextants negative before and positive after treatment were recoded as positive/positive, hypothesizing that cancer had been missed at pretreatment biopsy. Second, patients with such sextants were excluded.

RESULTS

• Pre-HIFU biopsies found cancer in all patients and in 215/594 sextants (36.2%); 55 (25.6%) positive sextants were in the apex, 86 (40%) in the midgland and 74 (34.4%) in the base. • After treatment, residual cancer was found in 36 patients (36.4%) and 50 sextants (8.4%); 30 (60%) positive sextants were in the apex, 12 (24%) in the midgland and eight (16%) in the base. • Both statistical analyses found that the locations of the positive sextants before and after HIFU ablation were significantly different (P < 0.001), with a higher proportion of positive apical sextants after treatment. • At the first analysis, the mean (95% confidence interval) probability for a sextant to remain positive after HIFU ablation was 8.8% (3.5-20.3%) in the base, 12.7% (5.8-25.9%) in the midgland and 41.7% (27.2-57.89%) in the apex. • At the second analysis, these same probabilities were 5.9% (1.9-17%), 9.9% (3.9-23.2%) and 27.3% (13.7-47%), respectively.

CONCLUSION

• When a 6-mm apical safety margin is used, residual cancer after HIFU ablation is found significantly more frequently in the apex.