Diffusion-Weighted MRI at 3 T for the Evaluation of Prostate Cancer

Comparison and optimization of b value combinations for diffusion-weighted imaging in discriminating hepatic fibrosis

INTRODUCTION AND OBJECTIVES

Diffusion-weighted imaging (DWI) has shown potential in characterizing hepatic fibrosis. However, there are no widely accepted apparent diffusion coefficient (ADC) values for the b value combination. This study aims to determine the optimal high and low b values of DWI to assess hepatic fibrosis in patients with chronic liver disease.

MATERIALS AND METHODS

The prospective study included 81 patients with chronic liver disease and 21 healthy volunteers who underwent DWI, Magnetic resonance elastography (MRE), and liver biopsy. The ADC was calculated by twenty combinations of nine b values (0, 50, 100, 150, 200, 800, 1000, 1200, and 1500 s/mm2).

RESULTS

All ADC values of the healthy volunteers were significantly higher than those of the hepatic fibrosis group (all P < 0.01). With the progression of hepatic fibrosis, ADC values significantly decreased in b value combinations (100 and 1000 s/mm2, 150 and 1200 s/mm2, 200 and 800 s/mm2, and 200 and 1000 s/mm2). ADC values derived from b values of both 200 and 800 s/mm2 and 200 and 1000 s/mm2 were found to be more discriminative for differentiating the stages of hepatic fibrosis. An excellent correlation was between the ADC200-1000 value and MRE shear stiffness (r = - 0.750, P < 0.001).

CONCLUSION

DWI offers an alternative to MRE as a useful imaging marker for detecting and staging hepatic fibrosis. Clinically, ADC values for b values ranging from 200-800 s/mm2 to 200-1000 s/mm2 are recommended for the assessment of hepatic fibrosis.

Addressing image misalignments in multi-parametric prostate MRI for enhanced computer-aided diagnosis of prostate cancer

Prostate cancer (PCa) diagnosis on multi-parametric magnetic resonance images (MRI) requires radiologists with a high level of expertise. Misalignments between the MRI sequences can be caused by patient movement, elastic soft-tissue deformations, and imaging artifacts. They further increase the complexity of the task prompting radiologists to interpret the images. Recently, computer-aided diagnosis (CAD) tools have demonstrated potential for PCa diagnosis typically relying on complex co-registration of the input modalities. However, there is no consensus among research groups on whether CAD systems profit from using registration. Furthermore, alternative strategies to handle multi-modal misalignments have not been explored so far. Our study introduces and compares different strategies to cope with image misalignments and evaluates them regarding to their direct effect on diagnostic accuracy of PCa. In addition to established registration algorithms, we propose 'misalignment augmentation' as a concept to increase CAD robustness. As the results demonstrate, misalignment augmentations can not only compensate for a complete lack of registration, but if used in conjunction with registration, also improve the overall performance on an independent test set.

Attention-guided multi-scale learning network for automatic prostate and tumor segmentation on MRI

BACKGROUND AND OBJECTIVE

Image-guided clinical diagnosis can be achieved by automatically and accurately segmenting prostate and prostatic cancer in male pelvic magnetic resonance imaging (MRI) images. For accurate tumor removal, the location, number, and size of prostate cancer are crucial, especially in surgical patients. The morphological differences between the prostate and tumor regions are small, the size of the tumor is uncertain, the boundary between the tumor and surrounding tissue is blurred, and the classification that separates the normal region from the tumor is uneven. Therefore, segmenting prostate and tumor on MRI images is challenging.

METHODS

This study offers a new prostate and prostatic cancer segmentation network based on double branch attention driven multi-scale learning for MRI. To begin, the dual branch structure provides two input images with different scales for feature coding, as well as a multi-scale attention module that collects details from different scales. The features of the double branch structure are then entered into the built feature fusion module to get more complete context information. Finally, to give a more precise learning representation, each stage is built using a deep supervision mechanism.

RESULTS

The results of our proposed network's prostate and tumor segmentation on a variety of male pelvic MRI data sets show that it outperforms existing techniques. For prostate and prostatic cancer MRI segmentation, the dice similarity coefficient (DSC) values were 91.65% and 84.39%, respectively.

CONCLUSIONS

Our method maintains high correlation and consistency between automatic segmentation results and expert manual segmentation results. Accurate automatic segmentation of prostate and prostate cancer has important clinical significance.

Validating the accuracy of multispectral metal artifact suppressed diffusion-weighted imaging

BACKGROUND

Diffusion-weighted imaging (DWI) provides quantitative measurement of random water displacement in tissue as calculated by the apparent diffusion coefficient (ADC). While heavily utilized in stroke and oncology applications, DWI is a promising tool to map microstructural changes in musculoskeletal applications including evaluation of synovial reactions resulting from total hip arthroplasty (THA). One major challenge facing the application of DWI in THA is the significant artifacts related to the conventional echo-planar imaging (EPI) readout used. Multispectral imaging (MSI) techniques, including the multiacquisition with variable resonance image combination (MAVRIC), have been shown to effectively reduce metallic susceptibility artifacts around total joint replacements to render clinically useful images. Recently, a 2D periodically rotated overlapping parallel line with enhanced reconstruction (PROPELLER) FSE acquisition that incorporates a diffusion preparation pulse with 2D-MAVRIC has been developed to mitigate both distortion and dropout artifacts. While there have been some preliminary assessments of DWI-MAVRIC, the repeatability of DWI-MAVRIC and the effects of key parameters, such as the number of spectral bins, are unknown.

PURPOSE

To evaluate the quantitative accuracy of DWI-MAVRIC as compared to conventional diffusion sequences.

METHODS

A diffusion phantom with different reference diffusivities (ADC = 113-1123 μm2 /s) was used. Scans were performed on two 1.5T MRI scanners. DWI-EPI and DWI-MAVRIC were acquired in both the axial and coronal planes. Three spatial offsets (0 cm, 10 cm left, and 10 cm right off iso-center) were used to evaluate effects of off-isocenter positioning. To assess intraday and interday repeatability, DWI-EPI and DWI-MAVRIC acquisitions were repeated on one scanner at same-day and 9-month intervals. To assess inter-scanner repeatability, DWI-EPI and DWI-MAVRIC acquisitions were compared between two scanners. ADC maps were generated with and without gradient nonlinearity correction (GNC). Linear regression, correlation, and error statistics were determined between calculated and reference ADC values. Bland-Altman plots were generated to evaluate intraday, interday, and interscanner repeatability.

RESULTS

DWI-MAVRIC had excellent correlation to reference values but at reduced linearity (r = 1.00, slope = 0.91-0.94) as compared to DWI-EPI (r = 1.00, slope = 0.99-1.01). A greater than 5% ADC bias was observed at the lowest ADC values, predominantly in the DWI-MAVRIC scans. ADC values did not vary with DWI-MAVRIC parameters. DWI-EPI acquisitions had intraday, interday, and interscanner repeatability of 3.18 μm2 /s, 19.2 μm2 /s, and 20.2 μm2 /s, respectively. DWI-MAVRIC acquisitions had inferior intraday, interday, and interscanner repeatability of 13.3 μm2 /s, 44.7 μm2 /s, 110 μm2 /s, respectively. Lower ADC errors were found at isocenter, as compared to the left and right positions. GNC reduced the absolute error by 0.31% ± 0.89%, 3.6% ± 1.4%, 0.65% ± 2.4% for the center, left, and right positions, respectively.

CONCLUSIONS

DWI-MAVRIC provides good linearity with respect to reference values and good intra- and interday repeatability.

Detection of High-Grade Prostate Cancer With a Super High B-value (4000 s/mm2) in Diffusion-Weighted Imaging Sequences by Magnetic Resonance Imaging

Introduction: High-grade adenocarcinoma of the prostate tends to have denser glandular structures and a prominent desmoplastic reaction, which could be detected by magnetic resonance imaging (MRI) with a super-high b-value in diffusion-weighted imaging (DWI) sequence, to differentiate it from low-grade carcinomas.

Objective: To evaluate the diagnostic validity of the diffusion sequence with values ​​of b4000 s/mm2 for the diagnosis of high-grade prostate cancer (Gleason score ≥ 7).

Materials and methods: It is a retrospective analytical study of male patients who have undergone a prostate biopsy and count with a prostate MRI with a DWI sequence of a super-high b-value (4000 s/mm2).

Results: The sensitivity of the diffusion sequence with b4000 s/mm2 values ​​to classify as positive for prostate cancer was 57.14% as compared to biopsy. The specificity of the diffusion sequence with b4000 s/mm2 values ​​classifying patients with prostate carcinoma as negative was 84.62%. The probability that the diffusion sequence with b4000 s/mm2 values ​​classifies patients with prostate cancer was 80%. The probability that the diffusion sequence with b4000 s/mm2 values ​​does not classify patients with prostate cancer was 64.71%. The proportion of patients adequately classified with prostate cancer using the diffusion sequence with b4000 s/mm2 values ​​was 70.37%.

Conclusions: The study shows that using the diffusion sequence with values of b4000 s/mm2 is an optimal value that serves as a tool to be able to decant those high-risk carcinomas with those of low risk; however, it is not a definitive method of diagnosis that could replace the performance of a biopsy. Since the study sample was limited, these results cannot be interpreted as reliable for diagnosing high-grade prostate cancer and should encourage future studies on a larger scale population to obtain significant evidence for a non-invasive diagnostic tool with a better cost-benefit for the patient.

Diffusion and quantification of diffusion of prostate cancer

For assessing a cancer treatment, and for detecting and characterizing cancer, Diffusion-weighted imaging (DWI) is commonly used. The key in DWI's use extracranially has been due to the emergence of of high-gradient amplitude and multichannel coils, parallelimaging, and echo-planar imaging. The benefit has been fewer motion artefacts and high-quality prostate images.Recently, new techniques have been developed to improve the signal-to-noise ratio of DWI with fewer artefacts, allowing an increase in spatial resolution. For apparent diffusion coefficient quantification, non-Gaussian diffusion models have been proposed as additional tools for prostate cancer detection and evaluation of its aggressiveness. More recently, radiomics and machine learning for prostate magnetic resonance imaging have emerged as novel techniques for the non-invasive characterisation of prostate cancer. This review presents recent developments in prostate DWI and discusses its potential use in clinical practice.

Design of a high-performance non-linear gradient coil for diffusion weighted MRI of the breast

Diffusion-weighted imaging (DWI) in the female breast is a magnetic resonance imaging (MRI) technique that complements clinical routine protocols, and that might provide an independent diagnostic value for specific clinical tasks in breast imaging. To further improve specificity of DWI in the breast, stronger and faster diffusion weighting is advantageous. Here, a dedicated gradient coil is designed, targeted at diffusion weighting in the female breast, with the peak gradient magnitude exceeding that of the current clinical MR scanners by an order of a magnitude. Design of application-tailored gradient coils in MRI has recently attracted increased attention. With the target application in mind, the gradient coil is designed on an irregularly shaped semi-open current-carrying surface. Due to the coil former closely fitting the non-spherical target region, non-linear encoding fields become particularly advantageous for achieving locally exceptionally high gradient strengths. As breast tissue has a predominantly isotropic cellular microstructure, the direction of the diffusion-weighting gradient may be allowed to vary within the target volume. However, due to the quadratic dependency of the b-factor on the gradient strength, variation of the gradient magnitude should be carefully controlled. To achieve the above design goals the corresponding multi-objective optimization problem is reformulated as a constrained optimization, allowing for flexible and precise control of the coil properties. A novel constraint is proposed, limiting gradient magnitude variation within every slice while allowing for variations in both the direction of the gradient within the slice and the magnitude across the slices. These innovations enable the design of a unilateral coil for diffusion weighting in the female breast with local gradient strengths exceeding 1 T/m with highly homogeneous diffusion weighting for imaging in the coronal slice orientation.

Diagnostic performance of diffusion-weighted imaging combined with dynamic contrast-enhanced magnetic resonance imaging for prostate cancer: a systematic review and meta-analysis

BACKGROUND

The diagnostic performance of diffusion-weighted imaging (DWI) combined with dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) for the detection of prostate cancer (PCa) has not been studied systematically to date.

PURPOSE

To investigate the value of DWI combined with DCE-MRI quantitative analysis in the diagnosis of PCa.

MATERIAL AND METHODS

A systematic search was conducted through PubMed, MEDLINE, the Cochrane Library, and EMBASE databases without any restriction to language up to 10 December 2019. Studies that used a combination of DWI and DCE-MRI for diagnosing PCa were included.

RESULTS

Nine studies with 778 participants were included. The combination of DWI and DCE-MRI provide accurate performance in diagnosing PCa with pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratios of 0.79 (95% confidence interval [CI] = 0.76-0.81), 0.85 (95% CI = 0.83-0.86), 6.58 (95% CI = 3.93-11.00), 0.24 (95% CI = 0.17-0.34), and 36.43 (95% CI = 14.41-92.12), respectively. The pooled area under the summary receiver operating characteristic curve was 0.9268. Moreover, 1.5-T MR scanners demonstrated a slightly better performance than 3.0-T scanners.

CONCLUSION

Combined DCE-MRI and DWI could demonstrate a highly accurate area under the curve, sensitivity, and specificity for detecting PCa. More studies with large sample sizes are warranted to confirm these results.

Diagnostic accuracy of high b-value diffusion weighted imaging for patients with prostate cancer: a diagnostic comprehensive analysis

We performed a meta-analysis to assess the diagnostic accuracy of high b-value diffusion-weighted imaging for patients with prostate cancer. A comprehensive literature search of the PubMed, Excerpta Medica Database, Cochrane Library, China National Knowledge Infrastructure, China Biology Medicine disc, and Wanfang databases from January 1, 1995, to April 30, 2021, was conducted. The quality of the retrieved papers was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and their 95% confidence intervals (CIs) were evaluated using bivariate mixed effects models. A total of twenty-four articles matched the selection criteria and were finally included after screening the titles, abstracts, and full texts of 641 initial articles. The pooled sensitivity and specificity (95% CI) were 0.84 (0.80-0.87) and 0.87 (0.81-0.91), respectively. The pooled positive and negative likelihood ratios (95% CI) were 6.4 (4.4-9.3) and 0.19 (0.16-0.23), respectively. The diagnostic odds ratio was 34 (95% CI: 22-51). The area under the summary receiver operator characteristic curve was 0.91 (95% CI: 0.88-0.93). Subgroup analysis presents similar results. The diagnostic accuracy of high b-value diffusion-weighted imaging was similarly high in the qualitative and quantitative evaluation of prostate cancer.

Value of integrated PET-IVIM MRI in predicting lymphovascular space invasion in cervical cancer without lymphatic metastasis

PURPOSE

To evaluate the contributory value of positron emission tomography (PET)-intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in the prediction of lymphovascular space invasion (LVSI) in patients with cervical cancer without lymphatic metastasis.

MATERIALS AND METHODS

A total of 90 patients with cervical cancer without signs of lymph node metastasis on PET/MRI were enrolled in this study. The tumours were classified into LVSI-positive (n = 25) and LVSI-negative (n = 65) groups according to postoperative pathology. The PET-derived parameters (SUV_max, SUV_mean, metabolic tumour volume (MTV) and total lesion glycolysis (TLG)) and IVIM-derived parameters (ADC_mean, ADC_min, D_mean, D_min, f, D* and gross tumour volume (GTV)) between the two groups were evaluated using a Student's t test (Mann-Whitney U test for variables with a nonnormal distribution) and receiver operating characteristic (ROC) curves. The optimal combination of PET/MR parameters for predicting LVSI was investigated using univariate and multivariate logistic regression models and evaluated by ROC curves. The optimal cutoff threshold values corresponded to the maximal values of the Youden index. A control model was established using 1000 bootstrapped samples, for which the performance was validated using calibration curves and ROC curves.

RESULTS

PET-derived parameters (SUV_max, SUV_mean, MTV, TLG) and IVIM MRI-derived parameters (D_min, ADC_min, GTV) were significantly different between patients with and without LVSI (P < 0.05). Logistic analyses showed that a combination of TLG and D_min had the strongest predictive value for LVSI diagnosis (area under the curve (AUC), 0.861; sensitivity, 80.00; specificity, 86.15; P < 0.001). The optimal cutoff threshold values for D_min and TLG were 0.58 × 10^-3 mm²/s and 66.68 g/cm³, respectively. The verification model showed the combination of TLG and D_min had the strongest predictive value, and its ROC curve and calibration curve showed good accuracy (AUC, 0.878) and consistency.

CONCLUSIONS

The combination of TLG and D_min may be the best indicator for predicting LVSI in cervical cancer without lymphatic metastasis.

Prostate magnetic resonance imaging technique

Multiparametric magnetic resonance (MR) imaging of the prostate is an excellent tool to detect clinically significant prostate cancer, and it has widely been incorporated into clinical practice due to its excellent tissue contrast and image resolution. The aims of this article are to describe the prostate MR imaging technique for detection of clinically significant prostate cancer according to PI-RADS v2.1, as well as alternative sequences and basic aspects of patient preparation and MR imaging artifact avoidance.

Stimulated-echo diffusion-weighted imaging with moderate b values for the detection of prostate cancer

OBJECTIVES

Conventional spin-echo (SE) DWI leads to a fundamental trade-off depending on the b value: high b value provides better lesion contrast-to-noise ratio (CNR) by sacrificing signal-to-noise ratio (SNR), image quality, and quantitative reliability. A stimulated-echo (STE) DWI acquisition is evaluated for high-CNR imaging of prostate cancer while maintaining SNR and reliable apparent diffusion coefficient (ADC) mapping.

METHODS

In this prospective, IRB-approved study, 27 patients with suspected prostate cancer (PCa) were scanned with three DWI sequences (SE b = 800 s/mm², SE b = 1500 s/mm², and STE b = 800 s/mm²) after informed consent was obtained. ROIs were drawn on biopsy-confirmed cancer and non-cancerous tissue to perform quantitative SNR, CNR, and ADC measurements. Qualitative metrics (SNR, CNR, and overall image quality) were evaluated by three experienced radiologists. Metrics were compared pairwise between the three acquisitions using a t test (quantitative metrics) and Wilcoxon rank test (qualitative metrics).

RESULTS

Quantitative measurements showed that STE DWI at b = 800 s/mm² has significantly better SNR compared to SE DWI at b = 1500 s/mm² (p < 0.0001) and comparable CNR to high-b value SE DWI at b = 1500 s/mm² (p < 0.05) in the peripheral zone. Qualitative assessment showed preference to STE b = 800 s/mm² in SNR and SE b = 1500 s/mm² in CNR. The overall image quality and lesion detectability among most readers showed no significant preference between STE b = 800 s/mm² and SE b = 1500 s/mm². Further, STE DWI had similar ADC contrast between lesion and normal tissue as SE DWI at b = 800 s/mm² (p = 0.90).

CONCLUSION

STE DWI has the potential to provide high-SNR, high-CNR imaging of prostate cancer while also enabling reliable ADC mapping.

KEY POINTS

• Quantitative analysis showed that STE DWI at b = 800 s/mm²is able to achieve simultaneously high CNR, high SNR, and reliable ADC mapping, compared to SE b = 800 s/mm²and SE b = 1500 s/mm². • Qualitative assessment by three readers showed that STE DWI at b = 800 s/mm²has significantly higher SNR than SE b = 1500 s/mm². No preference between SE b = 1500 s/mm²and STE b = 800 s/mm²was determined in terms of CNR with no missed lesions were found in both acquisitions. • A single STE DWI acquisition at moderate b value (800-1000 s/mm²) may provide sufficient image quality and quantitative reliability for prostate cancer imaging within a shorter scan time, in place of two DWI acquisitions (one with moderate b value and one with high b value).

Diffusion-weighted and perfusion-weighted magnetic resonance imaging of the prostate gland of healthy adult dogs

OBJECTIVE

To describe diffusion and perfusion characteristics of the prostate gland of healthy sexually intact adult dogs as determined by use of diffusion-weighted and perfusion-weighted MRI.

ANIMALS

12 healthy sexually intact adult Beagles.

PROCEDURES

Ultrasonography of the prostate gland was performed. Subsequently, each dog was anesthetized, and morphological, diffusion-weighted, and perfusion-weighted MRI of the caudal aspect of the abdomen was performed. The apparent diffusion coefficient was calculated for the prostate gland parenchyma in diffusion-weighted MRI images in the central ventral and peripheral dorsal areas. Perfusion variables were examined in multiple regions of interest (ROIs) in the ventral and dorsal areas of the prostate gland and in the gluteal musculature. Signal intensity was determined, and a time-intensity curve was generated for each ROI.

RESULTS

Results of ultrasonographic examination of the prostate gland revealed no abnormalities for any dog. Median apparent diffusion coefficient of the prostate gland was 1.51 × 10^-3 mm²/s (range, 1.04 × 10^-3 mm²/s to 1.86 × 10^-3 mm²/s). Perfusion-weighted MRI variables for the ROIs differed between the prostate gland parenchyma and gluteal musculature.

CONCLUSIONS AND CLINICAL RELEVANCE

Results provided baseline information about diffusion and perfusion characteristics of the prostate gland in healthy sexually intact adult dogs. Additional studies with dogs of various ages and breeds, with and without abnormalities of the prostate gland, will be necessary to validate these findings and investigate clinical applications.

Intravoxel incoherent motion diffusion-weighted imaging evaluated the response to concurrent chemoradiotherapy in patients with cervical cancer

To evaluate the application of multiple b values diffusion-weighted imaging based on biexponential signal decay model to predict the response to concurrent chemoradiotherapy in cervical cancer patients.This prospective study enrolled 28 patients (mean age: 50.89 ± 10.70 years) with cervical cancer confirmed by biopsy who received concurrent chemoradiotherapy. Pelvic magnetic resonance scans were performed 2 weeks before, 7 days and 21 days after the initiation of therapy, and 1 month after the end of the treatment. Diffusion-weighted imaging with b values of 0, 50, 450, and 850 s/mm were performed, and tumor volume, means of tumor apparent diffusion coefficient (ADC)min, ADCmean, ADCslow, ADCfast, and Ffast were measured.Pretreatment ADCmin and ADCslow of good outcome group were significantly higher than those of poor outcome group (P < .05). At the 7th day of the treatment, Ffast and its change rate of good outcome group were significantly higher than those of poor outcome group (P < .05). At the 7th day and 21st day of the treatment, Ffast showed a slowly increasing tendency with no significant difference compared with pretreatment value in poor outcome group (P < .05). One month post-treatment, only ADCslow change rate was significantly higher in good outcome group than that in poor outcome group.Intravoxel incoherent motion-related ADC values could be utilized to better predict the outcome of cervical cancer chemoradiotherapy.

The Evolution of MRI of the Prostate: The Past, the Present, and the Future

OBJECTIVE. The purpose of this article is to discuss the evolution of MRI in prostate cancer from the early 1980s to the current day, providing analysis of the key studies on this topic. CONCLUSION. The rapid diffusion of MRI technology has meant that residual variability remains between centers regarding the quality of acquisition and the quality and standardization of reporting.

Effects of the addition of quantitative apparent diffusion coefficient data on the diagnostic performance of the PI-RADS v2 scoring system to detect clinically significant prostate cancer

PURPOSE

To evaluate the impact of the addition of quantitative apparent diffusion coefficient (ADC) data into the diagnostic performance of the Prostate Imaging Reporting and Data System version 2 (PI-RADSv2) scoring system to predict clinically significant prostate cancer (CSPCa).

METHODS

We retrospectively included 91 consecutive patients who underwent prostate multiparametric magnetic resonance imaging (mp-MRI) and histopathological evaluation. Mp-MRI images were reported by the PI-RADSv2 scoring system and patients were divided into groups considering the likelihood of CSPCa. ADC value and ratio were obtained. Findings were correlated with histopathological data.

RESULTS

CSPCa was found in 41.8% of cases (n = 38). PI-RADSv2 score 3-5 yielded a sensitivity of 97.4% (95% confidence intervals 86.5-99.5), a specificity of 50.9% (37.9-63.9), and AUC of 0.74 (0.67-0.81) to predict CSPCa. ADC value < 750 µm²/s and an ADC ratio < 0.62 were the most accurate thresholds for differentiation of CSPCa, with AUC of 0.81 and 0.76, respectively. Combined PI-RADSv2 score 3-5 and ADC value < 750 µm²/s yielded a specificity of 84.9 (72.9-92.2), sensitivity of 70.3 (54.2-82.5), and AUC of 0.77 (0.68-0.86). Combined PI-RADSv2 score 3-5 and ADC ratio < 0.62 yielded a specificity of 86.5 (74.7-93.3), sensitivity of was 64.9 (48.8-78.2), and AUC of 0.75 (0.66-0.84).

CONCLUSION

Quantitative ADC data might not be beneficial to be used routinely in mp-MR imaging as criteria to detect clinically significant lesions due to the reduced sensitivity. Instead, when prostate lesions present a PI-RADSv2 score ≥ 3, additional quantitative ADC criteria can be helpful to increase the PI-RADS score specificity.

PTEN Expression in Prostate Cancer: Relationship With Clinicopathologic Features and Multiparametric MRI Findings

OBJECTIVE. The objective of our study was to investigate whether phosphatase and tensin homolog (PTEN) expression is associated with clinicopathologic features and multiparametric MRI findings in prostate cancer. MATERIALS AND METHODS. Forty-three patients with prostate cancer who underwent radical prostatectomy were included. Index tumor was identified on pretreatment MRI and delineated in the area that correlated best with histopathology results. The apparent diffusion coefficient (ADC) from DWI and pharmacokinetic parameters derived from dynamic contrast-enhanced MRI (DCE-MRI) using the extended Tofts model (K^trans, k_ep, v_e, and v_p) within the tumor were estimated. The following clinicopathologic parameters were assessed: pretreatment serum levels of prostate-specific antigen, disseminated tumor cell status, age, Gleason score, tumor size, extraprostatic extension (EPE), tumor location, and lymph node metastases. Gene expression profiles were acquired in biopsies from the tumor using bead arrays, and validated using reverse transcription quantitative polymerase chain reaction (RT-qPCR) on a different part of the biopsy. RESULTS. Based on bead arrays (p = 0.006) and RT-qPCR (p = 0.03) data, a significantly lower ADC was found in tumors with low PTEN expression. Moreover, PTEN expression was negatively associated with lymph node metastases (bead arrays, p = 0.008; RT-qPCR, p < 0.001). A weak but significant association between PTEN expression, EPE (p = 0.048), and Gleason score (p = 0.028) was revealed on bead arrays. ADC was negatively correlated with Gleason score (p = 0.001) and tumor size (p = 0.023). No association among DCE parameters, PTEN expression, and clinicopathologic features was found. CONCLUSION. ADC derived from DWI may be useful in selecting patients with potentially aggressive tumor caused by PTEN deficiency.

Exploratory study of geometric distortion correction of prostate diffusion-weighted imaging using B0 map acquisition

BACKGROUND

Evaluation of prostate MRI relies on diffusion-weighted imaging (DWI), commonly distorted by susceptibility artifacts, thereby creating a need for approaches to correct such distortion.

PURPOSE

To compare geometric distortion on prostate MRI between standard DWI and a geometric distortion correction method for DWI described as static distortion correction DWI (SDC DWI).

STUDY TYPE

Retrospective case study.

POPULATION

Thirty patients (ages 31-81 years) undergoing prostate MRI.

SEQUENCE

Geometric distortions from echo planar imaging were corrected with the SDC DWI protocol, which first acquires a B₀ -field map to estimate geometric distortions.

ASSESSMENT

Contours of the prostate were placed on axial T₂ -weighted imaging (T₂ WI) as an anatomic standard. Pixel shifts and apparent diffusion coefficient (ADC) values were compared between prostate contours applied to the SDC DWI and standard DWI sequences. Detailed characterization of the impact of SDC DWI was performed in three representative patients.

STATISTICAL TESTS

One-way analysis of variance (ANOVA) test, Spearman correlation test, and Bland-Altman plots were calculated.

RESULTS

There was significantly greater overlap of the SDC DWI prostate region of interest (ROI) with T₂ WI than standard DWI with T₂ WI (10.56 cm² ± 3.14, P < 0.05). R² of ADC values from standard DWI vs. SDC DWI in the 30 patients ranged from 0.02-0.94 (mean 0.60). A patient without susceptibility artifact demonstrated minimal pixel shift ranging from 0.6-1.3 mm and high correlation of ADC values (R² = 0.89) between SDC DWI and standard DWI. A patient with rectal gas showed greater pixel shift (range: -2.5 to -0.5 mm) and less ADC value correlation (R² = 0.69). A patient with a pelvic phlebolith adjacent to the prostate showed an even greater pixel shift (range: 10-16 mm) and decreased ADC correlation (R² = 0.21).

DATA CONCLUSION

SDC DWI appears to correct for susceptibility-related pixel shifts in the prostate compared with standard DWI, which may have value for assessing prostate lesions obscured by geometric warping. Level of Evidence 4 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2019;50:1614-1619.

[Imaging for initial diagnosis of localized prostate cancer]

The initial diagnosis of prostate cancer has been traditionally performed using systematic core biopsies with the use of magnetic resonance imaging (MRI) reserved to problem-solving scenarios. There is currently an ongoing paradigm shift towards the use of MRI prior to targeted biopsy as the standard approach. Prostate cancer therefore does not remain the last solid tumor entity diagnosed by non-targeted techniques but joins other solid tumor entities for which targeted diagnostic approaches have existed for a while. However, the complexity of the background tissue signal in the prostate makes lesion detection challenging. This article will provide an overview of the components of multiparametric prostate MRI and their interpretation using structured interpretation according to the current PI-RADSv2 (Prostate Imaging Reporting and Data System version 2) guidelines and of novel ultrasound techniques for primary diagnosis.

The value of MR textural analysis in prostate cancer

Current diagnosis and treatment stratification of patients with suspected prostate cancer relies on a combination of histological and magnetic resonance imaging (MRI) findings. The aim of this article is to provide a brief overview of prostate pathological grading as well as the relevant aspects of multiparametric (MRI) mpMRI, before indicating the potential that magnetic resonance textural analysis (MRTA) offers within prostate cancer. A review of the evidence base on MRTA in prostate cancer will enable discussion of the utility of this field while also indicating recommendations to future research. Radiomic textural analysis allows the assessment of spatial inter-relationships between pixels within an image by use of mathematical methods. First-order textural analysis is better understood and may have more clinical validity than higher-order textural features. Textural features extracted from apparent diffusion coefficient maps have shown the most potential for clinical utility in MRTA of prostate cancers. Future studies should aim to integrate machine learning techniques to better represent the role of MRTA in prostate cancer clinical practice. Nomenclature should be used to reduce misidentification between first-order and second-order energy and entropy. Automated methods of segmentation should be encouraged in order to reduce problems associated with inclusion of normal tissue within regions of interest. The retrospective and small-scale nature of most published studies, make it difficult to draw meaningful conclusions. Future larger prospective studies are required to validate the textural features indicated to have potential in characterisation and/or diagnosis of prostate cancer before translation into routine clinical practice.

The diagnostic accuracy of high b-value diffusion- and T2-weighted imaging for the detection of prostate cancer: a meta-analysis

Purpose

This study aims to investigate the role of diffusion-weighted imaging (DWI) and T₂-weighted imaging (T₂WI) in combination for the detection of prostate cancer, specifically assessing the role of high b-values (> 1000 s/mm²), with a systematic review and meta-analysis of the existing published data.

Methods

The electronic databases MEDLINE, EMBASE, and OpenSIGLE were searched between inception and September 1, 2017. Eligible studies were those that reported the sensitivity and specificity of DWI and T₂WI for the diagnosis of prostate cancer by visual assessment using a histopathologic reference standard. The QUADAS-2 critical appraisal tool was used to assess the quality of included studies. A meta-analysis with pooling of sensitivity, specificity, likelihood, and diagnostic odds ratios was undertaken, and a summary receiver-operating characteristics (sROC) curve was constructed. Predetermined subgroup analysis was also performed.

Results

Thirty-three studies were included in the final analysis, evaluating 2949 patients. The pooled sensitivity and specificity were 0.69 (95% CI 0.68–0.69) and 0.84 (95% CI 0.83–0.85), respectively, and the sROC AUC was 0.84 (95% CI 0.81–0.87). Subgroup analysis showed significantly better sensitivity with high b-values (> 1000 s/mm²). There was high statistical heterogeneity between studies.

Conclusion

The diagnostic accuracy of combined DWI and T₂WI is good with high b-values (> 1000 s/mm²) seeming to improve overall sensitivity while maintaining specificity. However, further large-scale studies specifically looking at b-value choice are required before a categorical recommendation can be made.

Electronic supplementary material

The online version of this article (10.1007/s00261-017-1400-4) contains supplementary material, which is available to authorized users.

Multiparametric Magnetic Resonance Imaging for Active Surveillance of Prostate Cancer

Active surveillance has gained popularity as an acceptable management option for men with low-risk prostate cancer. Successful utilization of this strategy can delay or prevent unnecessary interventions - thereby reducing morbidity associated with overtreatment. The usefulness of active surveillance primarily depends on correct identification of patients with low-risk disease. However, current population-wide algorithms and tools do not adequately exclude high-risk disease, thereby limiting the confidence of clinicians and patients to go on active surveillance. Novel imaging tools such as mpMRI provide information about the size and location of potential cancers enabling more informed treatment decisions. The term “multiparametric” in prostate mpMRI refers to the summation of several MRI series into one examination whose initial goal is to identify potential clinically-significant lesions suitable for targeted biopsy. The main advantages of MRI are its superior anatomic resolution and the lack of ionizing radiation. Recently, the Prostate Imaging-Reporting and Data System has been instituted as an international standard for unifying mpMRI results. The imaging sequences in mpMRI defined by Prostate Imaging Reporting and Data System version 2 includes: T2-weighted MRI, diffusion-weighted MRI, derived apparent-diffusion coefficient from diffusion-weighted MRI, and dynamic contrast-enhanced MRI. The use of mpMRI prior to starting active surveillance could prevent those with missed, high-grade lesions from going on active surveillance, and reassure those with minimal disease who may be hesitant to take part in active surveillance. Although larger validation studies are still necessary, preliminary results suggest mpMRI has a role in selecting patients for active surveillance. Less certain is the role of mpMRI in monitoring patients on active surveillance, as data on this will take a long time to mature. The biggest obstacles to routine use of prostate MRI are quality control, cost, reproducibility, and access. Nevertheless, there is great a potential for mpMRI to improve outcomes and quality of treatment. The major roles of MRI will continue to expand and its emerging use in standard of care approaches becomes more clearly defined and supported by increasing levels of data.

Accuracy of high b-value diffusion-weighted MRI for prostate cancer detection: a meta-analysis

Background The diagnostic accuracy of diffusion-weighted imaging (DWI) to detect prostate cancer is well-established. DWI provides visual as well as quantitative means of detecting tumor, the apparent diffusion coefficient (ADC). Recently higher b-values have been used to improve DWI's diagnostic performance. Purpose To determine the diagnostic performance of high b-value DWI at detecting prostate cancer and whether quantifying ADC improves accuracy. Material and Methods A comprehensive literature search of published and unpublished databases was performed. Eligible studies had histopathologically proven prostate cancer, DWI sequences using b-values ≥ 1000 s/mm², less than ten patients, and data for creating a 2 × 2 table. Study quality was assessed with QUADAS-2 (Quality Assessment of diagnostic Accuracy Studies). Sensitivity and specificity were calculated and tests for statistical heterogeneity and threshold effect performed. Results were plotted on a summary receiver operating characteristic curve (sROC) and the area under the curve (AUC) determined the diagnostic performance of high b-value DWI. Results Ten studies met eligibility criteria with 13 subsets of data available for analysis, including 522 patients. Pooled sensitivity and specificity were 0.59 (95% confidence interval [CI], 0.57-0.61) and 0.92 (95% CI, 0.91-0.92), respectively, and the sROC AUC was 0.92. Subgroup analysis showed a statistically significant ( P = 0.03) improvement in accuracy when using tumor visual assessment rather than ADC. Conclusion High b-value DWI gives good diagnostic performance for prostate cancer detection and visual assessment of tumor diffusion is significantly more accurate than ROI measurements of ADC.

PI-RADS version 2: evaluation of diffusion-weighted imaging interpretation between b = 1000 and b = 1500 s mm-2

OBJECTIVE

To investigate the variability of diffusion-weighted imaging (DWI) interpretation of Prostate Imaging Reporting and Data System (PI-RADS) version 2 (v2) in evaluating prostate cancer (PCa).

METHODS

154 patients with PCa underwent multiparametric 3T MRI, followed by radical prostatectomy. DWI with different b values (b = 0, 100, 1000 and 1500 s mm^-2) was obtained. Using the PI-RADS v2, two radiologists independently scored suspicious lesions in each patient and compared DWI of b = 1000 (DWI₁₀₀₀) with 1500 (DWI₁₅₀₀) s mm^-2.

RESULTS

On DWI₁₀₀₀ and DWI₁₅₀₀, the intermethod and interobserver agreements of DWI scores were excellent in all patients (κ ≥ 0.873). In each peripheral zone and transition zone DWI scores, both observers showed excellent intermethod agreement between DWI₁₀₀₀ and DWI₁₅₀₀ (κ ≥ 0.897), and interobserver agreement for DWI₁₀₀₀ and DWI₁₅₀₀ was good to excellent (κ ≥ 0.796). For estimating clinically significant cancer, the area under receiver operating characteristics curves of DWI₁₀₀₀ and DWI₁₅₀₀ were 0.710 and 0.724 for observer 1 (p = 0.11), and 0.649 and 0.656 for observer 2 (p = 0.12), respectively.

CONCLUSION

The PI-RADS v2 scoring at 3T shows excellent agreement between DWI₁₀₀₀ and DWI₁₅₀₀ in evaluating PCa, with excellent inter-observer agreement. Advance in knowledge: DWI using b = 1000 s mm^-2 instead of b = 1500 s mm^-2 reduces examination time or image distortion, with improved the signal-to-noise ratio.

Discrimination of local recurrence after radical prostatectomy: value of diffusion-weighted magnetic resonance imaging

Background

Multiparametric magnetic resonance is the most accurate imaging technique for prostate cancer detection, staging, localization, and aggressiveness evaluation. We assessed accuracy of diffusion-weighted imaging in local recurrence diagnosis after radical prostatectomy.

Materials and methods

A retrospective study was conducted in 118 patients with findings suggestive of local recurrence in dynamic contrast-enhanced-magnetic resonance imaging. Local recurrence was defined clinically as a rising prostate-specific antigen level (biochemical recurrence) without radiographic evidence of distant metastasis over 6 months after surgery. Eighty-four patients (71.2%) had local recurrence (group 1) and 34 (28.8%) showed no recurrence (group 2). The diagnostic accuracy of diffusion-weighted imaging was assessed, and factors associated with local recurrence were evaluated using multivariate logistic regression analysis. Additional accuracy analysis was carried out according to the size of the nodule.

Results

In post-operative findings, group 1 patients had significantly higher serum prostate-specific antigen (P = 0.001), larger enhancing nodules (P = 0.005), and more positive findings in diffusion-weighted imaging (P = 0.001) than group 2 patients. The sensitivity of diffusion-weighted imaging was significantly higher for nodules ≥1 cm than for all nodules (96.6 vs. 80.9%, P = 0.001), whereas the specificities were equivalent (100.0 vs. 97.1, P = 0.529). In multivariate analysis, a positive finding in diffusion-weighted imaging was the independent predictor of local recurrence (P = 0.005), along with pathologic T stage (P = 0.018).

Conclusions

Diffusion-weighted imaging is accurate in distinguishing recurrence from enhancing nodule on dynamic contrast-enhanced-magnetic resonance. Nodules showing decreased diffusion suggest local recurrence, especially if sized ≥1 cm.

Trends in targeted prostate brachytherapy: from multiparametric MRI to nanomolecular radiosensitizers

The treatment of localized prostate cancer is expected to become a significant problem in the next decade as an increasingly aging population becomes prone to developing the disease. Recent research into the biological nature of prostate cancer has shown that large localized doses of radiation to the cancer offer excellent long-term disease control. Brachytherapy, a form of localized radiation therapy, has been shown to be one of the most effective methods for delivering high radiation doses to the cancer; however, recent evidence suggests that increasing the localized radiation dose without bound may cause unacceptable increases in long-term side effects. This review focuses on methods that have been proposed, or are already in clinical use, to safely escalate the dose of radiation within the prostate. The advent of multiparametric magnetic resonance imaging (mpMRI) to better identify and localize intraprostatic tumors, and nanomolecular radiosensitizers such as gold nanoparticles (GNPs), may be used synergistically to increase doses to cancerous tissue without the requisite hazard of increased side effects.

Segmented diffusion-weighted imaging of the prostate: Application to transperineal in-bore 3T MR image-guided targeted biopsy

OBJECTIVE

This study aims to evaluate the applicability of using single-shot and multi-shot segmented diffusion-weighted imaging (DWI) techniques to support biopsy target localization in a cohort of targeted MRI-guided prostate biopsy patients.

MATERIALS AND METHODS

Single-shot echo-planar diffusion-weighted imaging (SS-DWI) and multi-shot segmented (MS-DWI) were performed intra-procedurally on a 3Tesla system in a total of 35 men, who underwent in-bore prostate biopsy inside the scanner bore. Comparisons between SS-DWI and MS-DWI were performed with (in 16 men) and without (in 19 men) parallel coil acceleration (iPAT) for SS-DWI. Overall image quality and artifacts were scored by a radiologist and scores were compared with the Wilcoxon-Mann-Whitney rank test. Correlation between the presence of air and image quality scores was evaluated with Spearman statistics. To quantify distortion, the anteroposterior prostate dimension was measured in SS and MS b=0 diffusion- and T2-weighted images. Signal-to-noise ratio was estimated in a phantom experiment. Agreement and accuracy of targeting based on retrospective localization of restricted diffusion areas in DWI was evaluated with respect to the targets identified using multi-parametric MRI (mpMRI).

RESULTS

Compared to SS-DWI without iPAT, the average image quality score in MS-DWI improved from 2.0 to 3.3 (p<0.005) and the artifact score improved from 2.3 to 1.4 (p<0.005). When iPAT was used in SS-DWI, the average image quality score in MS-DWI improved from 2.6 to 3.3 (p<0.05) and the artifact score improved from 2.1 to 1.4 (p<0.01). Image quality (ρ=-0.74, p<0.0005) and artifact scores (ρ=0.77, p<0.0005) both showed strong correlation with the presence of air in the rectum for the SS-DWI sequence without iPAT. These correlations remained significant when iPAT was enabled (ρ=-0.52, p<0.05 and ρ=0.64, p<0.01). For the comparison MS-DWI vs SS-DWI without iPAT, median differences between diffusion- and T2-weighted image gland measurements were 1.1(0.03-10.4)mm and 4.4(0.5-22.7)mm, respectively. In the SS-DWI-iPAT cohort, median gland dimension differences were 2.7(0.4-5.9)mm and 4.2(0.7-8.9)mm, respectively. Out of the total of 89 targets identified in mpMRI, 20 had corresponding restricted diffusion areas in SS-DWI and 28 in MS-DWI. No statistically significant difference was observed between the distances for the targets in the target-concordant SS- and MS-DWI restricted diffusion areas (5.5mm in SS-DWI vs 4.5mm in MS-DWI, p>0.05).

CONCLUSIONS

MS-DWI applied to prostate imaging leads to a significant reduction of image distortion in comparison with SS-DWI. There is no sufficient evidence however to suggest that intra-procedural DWI can serve as a replacement for tracking of the targets identified in mpMRI for the purposes of targeted MRI-guided prostate biopsy.

Role of multiparametric MRI in the diagnosis of prostate cancer: update

Prostate cancer is the most common malignancy of the male gender. The role of magnetic resonance imaging has evolved very rapidly over the years to be currently recognized as a fundamental tool in the diagnosis, treatment and follow-up of prostate cancer.

Poor standard mp-MRI and routine biopsy fail to precisely predict intraprostatic tumor localization

PURPOSE

To evaluate the localization accuracy of routinely performed preoperative multiparametric MRI (mp-MRI), not being assessed according to PI-RADS criteria.

METHODS

One hundred and six patients underwent radical retropubic prostatectomy (January 2011-June 2012) with preoperative MRI. Intraprostatic tumor localization suggested by mp-MRI was correlated to both biopsy and histopathology results.

RESULTS

Sensitivity and specificity were as low as 25-62 and 60-94 %, respectively. Neither higher field force nor the use of an endorectal coil could enhance accuracy. There was no statistically significant concordance in any sextant. The mean number of correctly identified sextants was between 3.11 and 4.00 and, thus, insignificantly above the value of 3 that one would obtain by tossing the coin. For transrectal biopsies, sensitivity and specificity of tumor localization were 52-63 and 46-80 %, respectively.

CONCLUSIONS

Neither routinely performed "non-PI-RADS" MRI nor transrectal biopsy can accurately localize prostate cancer. Focal therapy concepts rely on a precise intraprostatic tumor detection and therefore inevitably require PI-RADS assessment by radiologists with genitourinary specialization. Regarding patient discomfort and costs, "non-PI-RADS" MRIs of the prostate are not justified.

Prostate diffusion-weighted imaging at 3T: effect of intravenous gadobutrol administration

OBJECTIVE

To investigate whether gadolinium-based contrast agent (GBCA) administration significantly affects diffusion-weighted imaging (DWI) at 3 T in the evaluation of prostate cancer and benign tissue.

METHOD

Thirty-four consecutive patients with surgically proven prostate cancer underwent preoperative DWI at 3 T before and after GBCA administration. Exponential apparent diffusion coefficient (EADC) and ADC maps were developed from DWI data. The ADC and EADC values pre- and post-contrast were measured in the cancer and benign tissue, respectively. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated on pre- and post-contrast DWI.

RESULTS

The ADC and EADC values of the cancer and benign transition zone were not significantly different between pre- and post-contrast, respectively (P > 0.05), while those in the benign peripheral zone were significantly different (P = 0.030 and 0.037, respectively). In all tissues, the SNRs and CNRs of the DWI, ADC map and EADC map were not significantly different between pre- and post-contrast (P > 0.05). Between pre- and post-contrast, ADC and EADC values showed excellent agreement (intraclass correlation coefficient ≥ 0.894) and variability of ≤3.2 %.

CONCLUSION

Prostate 3 T-DWI after GBCA administration may be used without a significant difference in SNR or CNR, with minimal variability of the cancer ADC and EADC values.

KEY POINTS

• ADCs and EADCs have excellent agreement before and after gadobutrol administration. • SNRs of prostate DWI are similar before and after gadobutrol administration. • CNRs of cancers are similar between pre- and post-contrast DWI.

Oncological outcomes following robotic-assisted radical prostatectomy in a multiracial Asian population

This study evaluates the oncological outcomes of RARP in a multiracial Asian population from a single institution. All suitable patients from 1st January 2003-30th June 2013 were identified from a prospectively maintained cancer registry. Peri-operative and oncological outcomes were analysed. Significance was defined as p < 0.05. There were n = 725 patients identified with a mean follow-up duration 28 months. The mean operative time, EBL and LOS were 186 min, 215 ml and 3 days, respectively. The pathological stage was pT2 in 68.6% (n = 497/725), pT3 in 31.3% (n = 227/725) and n = 1 patient with pT4 disease. The pathological Gleason scores (GS) were 6 in 27.9% (n = 202/725), GS 7 in 63.6% (n = 461/725) and GS ≥ 8 in 8.0 % (n = 58/725). The node positivity rate was 5.8% (n = 21/360). The positive margin rates were 31.0% (n = 154/497) and 70.9% (n = 161/227) for pT2 and pT3, respectively, and decreasing PSM rates are observed with surgical maturity. The biochemical recurrence rates were 9.7% (n = 48/497) and 34.2% (n = 78/228) for pT2 and pT3/T4, respectively. On multivariate analysis, independent predictors of BCR were pathological T stage and pathological Gleason score. Post-operatively, 78.5% (n = 569/725) of patients had no complications and 17.7% (n = 128/725) had minor (Clavien grade I-II) complications. This series, representing the largest from Southeast Asia, suggests that RARP can be a safe and oncologically feasible treatment for localised prostate cancer in an institution with moderate workload.

Triexponential function analysis of diffusion-weighted MRI for diagnosing prostate cancer

BACKGROUND

To evaluate more detailed information noninvasively through on diffusion and perfusion in prostate cancer (PCa) using triexponential analysis of diffusion-weighted imaging (DWI).

METHODS

Sixty-three prostate cancer patients underwent preoperative 3.0 Tesla MRI including eight b-values DWI. Triexponential analysis was performed to obtain three diffusion coefficients (Dp , Df , Ds ), as well as fractions (Fp , Ff , Fs ). Each diffusion parameter for cancerous lesions and normal tissues was compared and the relationship between diffusion parameters and Gleason score (GS) was assessed. K(trans) , Ve , and the ratios of intracellular components measured in histopathological specimens were compared with diffusion parameters.

RESULTS

Dp was significantly greater for cancerous lesions than normal peripheral zone (PZ) (P < 0.001), whereas Dp in transition zone (TZ) showed no significant difference (P = 0.74, 95% confidence interval (CI) = -4.69-6.48). Ds was significantly smaller for each cancerous lesions in PZ and TZ (P < 0.001, respectively). There was no significant difference in Df between cancerous lesions and normal tissues in PZ and TZ (P = 0.07, 95% CI = -0.29-0.12 and P = 0.53, 95% CI = -3.51-2.29, respectively). D obtained with biexponential analysis were significantly smaller in cancerous lesions than in normal tissue in PZ and TZ (P < 0.001 for both), while D* in PZ and TZ showed no significant difference (P = 0.14, 95% CI = -1.60-0.24 and P = 0.31, 95% CI = -3.43-1.16, respectively). Dp in PZ and TZ showed significant correlation with K(trans) (R = 0.85, P < 0.001; R = 0.81, P < 0.001, respectively), while D(*) in PZ obtained with biexponential analysis showed no such correlation (P = 0.08, 95% CI = -0.14-0.30). Fs was significantly correlated with intracellular space fraction evaluated in histopathological specimens in PZ and TZ cancer (R = 0.41, P < 0.05; R = 0.59, P < 0.001, respectively). Ff and Fs correlated significantly with GS in PZ and TZ cancer (PZ: R = -0.44, P < 0.05; R = 0.37, P < 0.05, TZ: R = -0.59, P < 0.05; R = 0.57, P < 0.05, respectively).

CONCLUSION

Triexponential analysis is a noninvasive approach that can provide more detailed information regarding diffusion and perfusion of PCa than biexponential analysis.

Uroncor consensus statement: Management of biochemical recurrence after radical radiotherapy for prostate cancer: From biochemical failure to castration resistance

Management of patients who experience biochemical failure after radical radiotherapy with or without hormonal therapy is highly challenging. The clinician must not only choose the type of treatment, but also the timing and optimal sequence of treatment administration. When biochemical failure occurs, numerous treatment scenarios are possible, thus making it more difficult to select the optimal approach. Moreover, rapid and ongoing advances in treatment options require that physicians make decisions that could impact both survival and quality of life. The aim of the present consensus statement, developed by the Urological Tumour Working Group (URONCOR) of the Spanish Society of Radiation Oncology (SEOR), is to provide cancer specialists with the latest, evidence-based information needed to make the best decisions for the patient under all possible treatment scenarios. The structure of this consensus statement follows the typical development of disease progression after biochemical failure, with the most appropriate treatment recommendations given for each stage. The consensus statement is organized into three separate chapters, as follows: biochemical failure with or without local recurrence and/or metastasis; progression after salvage therapy; and treatment of castration-resistant patients.

Apparent diffusion coefficient values of normal testis and variations with age

The usefulness of diffusion-weighted magnetic resonance imaging (DWI) in the evaluation of scrotal pathology has recently been reported. A standard reference of normal testicular apparent diffusion coefficient (ADC) values and their variations with age is necessary when interpreting normal testicular anatomy and pathology. We evaluated 147 normal testes using DWI, including 71 testes from 53 men aged 20-39 years (group 1), 67 testes from 42 men aged 40-69 years (group 2) and nine testes from six men older than 70 years (group 3). DWI was performed along the axial plane, using a single shot, multislice spin-echo planar diffusion pulse sequence and b-values of 0 and 900 s mm-2 . The mean and standard deviation of the ADC values of normal testicular parenchyma were calculated for each age group separately. Analysis of variance (ANOVA) followed by post hoc analysis (Dunnett T3) was used for statistical purposes. The ADC values (× 10-3 mm 2 s-1 ) of normal testicular tissue were different among age groups (group 1: 1.08 ± 0.13; group 2: 1.15 ± 0.15 and group 3: 1.31 ± 0.22). ANOVA revealed differences in mean ADC among age groups (F = 11.391, P < 0.001). Post hoc analysis showed differences between groups 1 and 2 (P = 0.008) and between groups 1 and 3 (P = 0.043), but not between groups 2 and 3 (P = 0.197). Our findings suggest that ADC values of normal testicular tissue increase with advancing age.

Evaluation of suspected soft tissue lesion in the prostate bed after radical prostatectomy using 3T multiparametric magnetic resonance imaging

PURPOSE

To investigate the usefulness of multiparametric MR imaging (mp-MRI) at 3T for evaluating suspected soft tissue lesion in the prostate bed after radical prostatectomy (RP).

MATERIALS AND METHODS

Forty-three patients with biochemical recurrence (BCR) who received RP underwent mp-MRI at 3T with a phased-array coil, including T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI) and dynamic contrast-enhanced imaging (DCE-MRI) and were enrolled in this study. All patients with BCR had a suspected soft tissue lesion in the prostate bed, followed by transrectal ultrasound-guided biopsy. As a control group, 14 consecutive patients without BCR who received RP were also enrolled. Two experienced radiologists independently analyzed four different imaging datasets.

RESULTS

For predicting local recurrence, the specificity, accuracy and area under the curve for both readers were significantly greater on all combined imaging datasets than on T2WI alone (P<0.05). The sensitivity of all combined imaging datasets in both readers was not statistically different with T2WI alone (P>0.05), except for combined T2WI and DWI. Inter-reader agreements for the four different imaging datasets were moderate.

CONCLUSION

DCE-MRI or DWI in combination with T2WI at 3T with a phased-array coil appears to be more useful than T2WI alone in evaluating suspected soft tissue lesion of the prostate bed after RP.

The optimal timing of post-prostate biopsy magnetic resonance imaging to guide nerve-sparing surgery

The goal of our study was to evaluate the impact of the interval between prostate biopsy and magnetic resonance imaging (MRI) on the accuracy of simple tumor localization, which is essential information that enables nerve-sparing surgery. We also sought to determine the optimal timing of a post-biopsy MRI. A total of 184 patients who had undergone MRI before radical prostatectomy at an institution without a predetermined schedule for MRI after a prostate biopsy were enrolled. The mean interval from the biopsy to the MRI was 30.8 ± 18.6 days. The accuracy of the MRI for simplified tumor location (right, left, bilateral and none) was 44.6%. In the group with discordant pathologic and MRI findings, the most common reason recorded was ‘MRI predicted a unilateral lesion, but pathology revealed bilateral lesions’ (58.3%), followed by ‘MRI predicted no lesion, but pathology revealed the presence of a lesion’ (32.0%). Multivariable analysis showed that the discordant group had a shorter interval (25.0 ± 14.3 vs 38.1 ± 20.6 days, P < 0.01) preceding the MRI and a higher rate of hemorrhage as observed by MRI (80.4% vs 54.8%, P < 0.01) in comparison with the accordant group. In receiver operating characteristics analysis, the area under the curve of the MRI interval in accurate prediction of the tumor location was 0.707 (P < 0.001). At the MRI interval's cutoff of 28.5 days, the sensitivity was 73.2% and the specificity was 63.7%. When the MRI was performed within 28 days, the accumulated accuracy was only 26.1% (23/88); however, when it was performed after 28 days, the reversely accumulated accuracy was 61.5% (59/96). These data support a waiting period of at least 4 weeks after a biopsy before performing an MRI for the purposes of surgical refinement.

High-resolution diffusion-weighted imaging of the prostate

OBJECTIVE

The purpose of this study was to evaluate the effect of increasing the spatial resolution of the prostate DWI protocol on image quality and lesion conspicuity.

SUBJECTS AND METHODS

Twenty-nine patients with biopsy-proven prostate cancer undergoing MRI examinations were imaged with two diffusion-weighted imaging (DWI) protocols: current standard clinical protocol (6.7 mm(3) voxels) and a new high-resolution protocol (3.1 mm(3) voxels). Diffusion-weighted images were independently and subjectively scored on lesion conspicuity, internal architecture definition, and overall image quality by two radiologists. Average apparent diffusion coefficient (ADC) values were measured in normal tissue and cancerous lesions on both sequences. Reader scores and ADC and contrast values were compared between the two protocols. Cancer ADC values were correlated with Gleason scores.

RESULTS

The signal-to-noise ratio of the new high-resolution DWI protocol was 40% lower than that of the standard protocol. The reader scores were higher by 0.73 (range, 0.29-1.16) grades, or 19% (range, 7-32%), on average, for the new protocol, indicating better image quality. The average ADC values were 8% higher with the new protocol, with ADC contrast values between cancer and normal prostate unchanged. There was marginally significant correlation of cancer ADC values with Gleason scores (p = 0.05, r ≈ -0.36).

CONCLUSION

We showed that for DWI of the prostate at 3-7 mm(3) voxel sizes the benefits of higher spatial resolution outweigh the effects of reduced signal-to-noise and contrast-to-noise ratios, potentially improving the sensitivity to small or sparse prostate cancers. Radiologists can consider using higher-spatial-resolution DWI sequences in their practices.

Quantitative evaluation of computed high B value diffusion-weighted magnetic resonance imaging of the prostate

OBJECTIVES

Computed diffusion-weighted magnetic resonance imaging (cDWI) refers to the synthesizing of arbitrary b value diffusion-weighted images (DWI) from a set of measured b value images by voxelwise fitting. The objectives of this study were to quantitatively analyze the noise and the contrast-to-noise ratio (CNR) in cDWI as a function of b value by numerical simulations and by measurements in patients with prostate cancer and to compare cDWI to directly measured DWI at a b value of 1400 s/mm2.

MATERIALS AND METHODS

Numerical simulations were performed to assess image noise and CNR in both cDWI and regular DWI. Forty-two patients with prostate cancer (age, 51-73 years; prostate specific antigen level, 0.5-30 ng/mL; and biopsy Gleason score, 6-9) received 2 DWI examinations at 3.0 T (one with b values of 100, 500, and 1400 s/mm2 and another with b values of 0, 100, 400, and 800 s/mm2) to create cDWI images at arbitrary b values, both with and without incorporating a b value of 0 s/mm2 in their calculation. Regions of interest were drawn to compare the scan time adjusted CNR (CNR eff) between cDWI and directly measured DWI at b = 1400 s/mm2 on tumor-suspicious lesions and normal-appearing regions.

RESULTS

In the numerical simulations, noise depended strongly on the b value, the diffusion coefficient, and the signal intensity at a b value of 0 s/mm2 in cDWI but not in regular DWI. The CNR between simulated tumor and normal regions showed a continuous increase with increasing b value. Both these findings were also observed in tumor-suspicious and normal-appearing regions in in vivo data. In vivo prostate DWI at a b value of 1400 s/mm2 showed a similar CNR eff between the tumor-suspicious regions and the normal-appearing tissue in cDWI as in the directly measured DWI (P = 0.395).

CONCLUSIONS

The CNR eff between tumor-suspicious and normal-appearing prostate tissue in DWI images at a b value of 1400 s/mm2 is comparable in cDWI and directly measured DWI. Computed DWI at even higher b values, calculated from measured images with b values between 0 and 800 s/mm2, yields higher CNR eff than measured DWI, which may be of clinical aid in the management of prostate cancer.

Imaging in prostate carcinoma

Imaging plays a central role in the detection, diagnosis, staging, and follow-up of prostate carcinoma. This article discusses the role of multiple imaging modalities in the diagnosis and staging of prostate cancer, with attention to imaging features of localized and metastatic disease, imaging adjuncts to improve prostate biopsy, and potential imaging biomarkers. In addition, the role of imaging in the management of prostate cancer, with emphasis on surveillance, evaluation of response to new therapies, and detection of recurrent disease is described. Lastly, future directions in prostate cancer imaging are presented.

High b value (2,000 s/mm2) diffusion-weighted magnetic resonance imaging in prostate cancer at 3 Tesla: comparison with 1,000 s/mm2 for tumor conspicuity and discrimination of aggressiveness

Objective

The objective of our study was to investigate tumor conspicuity and the discrimination potential for tumor aggressiveness on diffusion-weighted magnetic resonance imaging (DW-MRI) with high b value at 3-T.

Materials and Methods

The institutional review board approved this study and waived the requirement for informed consent. A total of 50 patients with prostate cancer (69 cancer foci; 48 in the PZ, 20 in the TZ, and one in whole prostate) who underwent multiparametric prostate MRI including DW-MRI (b values: 0, 1000 s/mm² and 0, 2000 s/mm²) on a 3-T system were included. Lesion conspicuity score (LCS) using visual assessment (1 = invisible for surrounding normal site; 2 = slightly high intensity; 3 = moderately high; and 4 = very high) and tumor-normal signal intensity ratio (TNR) were assessed, and apparent diffusion coefficient (ADC, ×10⁻³ mm²/s) of the tumor regions and normal regions were measured.

Results

Mean LCS and TNR at 0, 2000 s/mm² was significantly higher than those at 0, 1000 s/mm² (p<0.001 for both). In addition, ADC at both 0, 1000 and 0, 2000 s/mm² was found to distinguish intermediate or high risk cancer with Gleason score ≥7 from low risk cancer with Gleason score ≤6 (p<0.001 for both). Furthermore, ADC of tumor regions correlated with Gleason score at both 0, 1000 s/mm² (ρ = −0.602; p<0.001) and 0, 2000 s/mm² (ρ = −0.645; p<0.001).

Conclusions

For tumor conspicuity and characterization of prostate cancer on DW-MRI of 3-T MRI, b = 0, 2000 s/mm² is more useful than b = 0, 1000 s/mm².