Diffusion-weighted endorectal MR imaging at 3 T for prostate cancer: tumor detection and assessment of aggressiveness

Restriction spectrum imaging: An evolving imaging biomarker in prostate MRI

Restriction spectrum imaging (RSI) is a novel diffusion-weighted MRI technique that uses the mathematically distinct behavior of water diffusion in separable microscopic tissue compartments to highlight key aspects of the tissue microarchitecture with high conspicuity. RSI can be acquired in less than 5 min on modern scanners using a surface coil. Multiple field gradients and high b-values in combination with postprocessing techniques allow the simultaneous resolution of length-scale and geometric information, as well as compartmental and nuclear volume fraction filtering. RSI also uses a distortion correction technique and can thus be fused to high resolution T2-weighted images for detailed localization, which improves delineation of disease extension into critical anatomic structures. In this review, we discuss the acquisition, postprocessing, and interpretation of RSI for prostate MRI. We also summarize existing data demonstrating the applicability of RSI for prostate cancer detection, in vivo characterization, localization, and targeting.

LEVEL OF EVIDENCE

5 J. Magn. Reson. Imaging 2017;45:323-336.

Evaluating Prostate Cancer Using Fractional Tissue Composition of Radical Prostatectomy Specimens and Pre-Operative Diffusional Kurtosis Magnetic Resonance Imaging

BACKGROUND

Evaluating tissue heterogeneity using non-invasive imaging could potentially improve prostate cancer assessment and treatment.

METHODS

20 patients with intermediate/high-risk prostate cancer underwent diffusion kurtosis imaging, including calculation of apparent diffusion (Dapp) and kurtosis (Kapp), prior to radical prostatectomy. Whole-mount tissue composition was quantified into: cellularity, luminal space, and fibromuscular stroma. Peripheral zone tumors were subdivided according to Gleason score.

RESULTS

Peripheral zone tumors had increased cellularity (p<0.0001), decreased fibromuscular stroma (p<0.05) and decreased luminal space (p<0.0001). Gleason score ≥4+3 tumors had significantly increased cellularity and decreased fibromuscular stroma compared to Gleason score ≤3+4 (p<0.05). In tumors, there was a significant positive correlation between median Kapp and cellularity (ρ = 0.50; p<0.05), and a negative correlation with fibromuscular stroma (ρ = -0.45; p<0.05). In normal tissue, median Dapp had a significant positive correlation with luminal space (ρ = 0.65; p<0.05) and a negative correlation with cellularity (ρ = -0.49; p<0.05). Median Kapp and Dapp varied significantly between tumor and normal tissue (p<0.0001), but only median Kapp was significantly different between Gleason score ≥4+3 and ≤3+4 (p<0.05).

CONCLUSIONS

Peripheral zone tumors have increased cellular heterogeneity which is reflected in mean Kapp, while normal prostate has a more homogeneous luminal space and cellularity better represented by Dapp.

A model describing diffusion in prostate cancer

PURPOSE

Quantitative diffusion MRI has frequently been studied as a means of grading prostate cancer. Interpretation of results is complicated by the nature of prostate tissue, which consists of four distinct compartments: vascular, ductal lumen, epithelium, and stroma. Current diffusion measurements are an ill-defined weighted average of these compartments. In this study, prostate diffusion is analyzed in terms of a model that takes explicit account of tissue compartmentalization, exchange effects, and the non-Gaussian behavior of tissue diffusion.

METHOD

The model assumes that exchange between the cellular (ie, stromal plus epithelial) and the vascular and ductal compartments is slow. Ductal and cellular diffusion characteristics are estimated by Monte Carlo simulation and a two-compartment exchange model, respectively. Vascular pseudodiffusion is represented by an additional signal at b = 0. Most model parameters are obtained either from published data or by comparing model predictions with the published results from 41 studies. Model prediction error is estimated using 10-fold cross-validation.

RESULTS

Agreement between model predictions and published results is good. The model satisfactorily explains the variability of ADC estimates found in the literature.

CONCLUSION

A reliable model that predicts the diffusion behavior of benign and cancerous prostate tissue of different Gleason scores has been developed. Magn Reson Med 78:316-326, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Optimal high b-value for diffusion weighted MRI in diagnosing high risk prostate cancers in the peripheral zone

PURPOSE

To retrospectively determine the optimal b-value(s) of diffusion-weighted imaging (DWI) associated with intermediate-high risk cancer in the peripheral zone (PZ) of the prostate.

MATERIALS AND METHODS

Forty-two consecutive patients underwent multi b-value (16 evenly spaced b-values between 0 and 2000 s/mm² ) DWI along with multi-parametric MRI (MP-MRI) of the prostate at 3 Tesla followed by trans-rectal ultrasound/MRI fusion guided targeted biopsy of suspicious lesions detected at MP-MRI. Computed DWI images up to a simulated b-value of 4000 s/mm² were also obtained using a pair of b-values (b = 133 and 400 or 667 or 933 s/mm² ) from the multi b-value DWI. The contrast ratio of average intensity of the targeted lesions and the background PZ was determined. Receiver operator characteristic curves and the area under the curve (AUCs) were obtained for separating patients eligible for active surveillance with low risk prostate cancers from intermediate-high risk prostate cancers as per the cancer of the prostate risk assessment (CAPRA) scoring system.

RESULTS

The AUC first increased then decreased with the increase in b-values reaching maximum at b = 1600 s/mm² (0.74) with no statistically significant different AUC of DWI with b-values 1067-2000 s/mm² . The AUC of computed DWI increased then decreased with the increase in b-values reaching a maximum of 0.75 around b = 2000 s/mm² . There was no statistically significant difference between the AUC of optimal acquired DWI and either of optimal computed DWI.

CONCLUSION

The optimal b-value for acquired DWI in differentiating intermediate-high from low risk prostate cancers in the PZ is b = 1600 s/mm² . The computed DWI has similar performance as that of acquired DWI with the optimal performance around b = 2000 s/mm² .

LEVEL OF EVIDENCE

4 J. Magn. Reson. Imaging 2017;45:125-131.

Multiparametric prostate magnetic resonance imaging in the evaluation of prostate cancer

Imaging has traditionally played a minor role in the diagnosis and staging of prostate cancer. However, recent controversies generated by the use of prostate-specific antigen (PSA) screening followed by random biopsy have encouraged the development of new imaging methods for prostate cancer. Multiparametric magnetic resonance imaging (mpMRI) has emerged as the imaging method best able to detect clinically significant prostate cancers and to guide biopsies. Here, the authors explain what mpMRI is and how it is used clinically, especially with regard to high-risk populations, and we discuss the impact of mpMRI on treatment decisions for men with prostate cancer. CA Cancer J Clin 2016;66:326-336. © 2015 American Cancer Society.

Pilot Study of the Use of Hybrid Multidimensional T2-Weighted Imaging-DWI for the Diagnosis of Prostate Cancer and Evaluation of Gleason Score

OBJECTIVE

The objective of our study was to evaluate the role of a hybrid T2-weighted imaging-DWI sequence for prostate cancer diagnosis and differentiation of aggressive prostate cancer from nonaggressive prostate cancer.

MATERIALS AND METHODS

Twenty-one patients with prostate cancer who underwent preoperative 3-T MRI and prostatectomy were included in this study. Patients underwent a hybrid T2-weighted imaging-DWI examination consisting of DW images acquired with TEs of 47, 75, and 100 ms and b values of 0 and 750 s/mm(2). The apparent diffusion coefficient (ADC) and T2 were calculated for cancer and normal prostate ROIs at each TE and b value. Changes in ADC and T2 as a function of increasing the TE and b value, respectively, were analyzed. A new metric termed "PQ4" was defined as the percentage of voxels within an ROI that has increasing T2 with increasing b value and has decreasing ADC with increasing TE.

RESULTS

ADC values were significantly higher in normal ROIs than in cancer ROIs at all TEs (p < 0.0001). With increasing TE, the mean ADC increased 3% in cancer ROIs and increased 12% in normal ROIs. T2 was significantly higher in normal ROIs than in cancer ROIs at both b values (p ≤ 0.0002). The mean T2 decreased with increasing b value in cancer ROIs (ΔT2 = -17 ms) and normal ROIs (ΔT2 = -52 ms). PQ4 clearly differentiated normal ROIs from prostate cancer ROIs (p = 0.0004) and showed significant correlation with Gleason score (ρ = 0.508, p < 0.0001).

CONCLUSION

Hybrid MRI measures the response of ADC and T2 to changing TEs and b values, respectively. This approach shows promise for detecting prostate cancer and determining its aggressiveness noninvasively.

Benign causes of diffusion restriction foci in the peripheral zone of the prostate: diagnosis and differential diagnosis

Multiparametric-MRI is an important tool in the diagnosis of prostate cancer (PCa), particularly diffusion-weighted imaging for peripheral zone (PZ) cancer in the untreated prostate. However, there are many benign entities that demonstrate diffusion restriction in the PZ mimicking PCa resulting in diagnostic challenges. Fortunately, these benign entities usually have unique MR features that may help to distinguish them from PCa. The purpose of this pictorial review is to discuss benign entities with diffusion restriction in the PZ and to emphasize the key MR features of these entities that may help to differentiate them from PCa.

Practical aspects of prostate MRI: hardware and software considerations, protocols, and patient preparation

The use of multiparametric MRI scans for the evaluation of men with prostate cancer has increased dramatically and is likely to continue expanding as new developments come to practice. However, it has not yet gained the same level of acceptance of other imaging tests. Partly, this is because of the use of suboptimal protocols, lack of standardization, and inadequate patient preparation. In this manuscript, we describe several practical aspects of prostate MRI that may facilitate the implementation of new prostate imaging programs or the expansion of existing ones.

Restriction spectrum imaging improves MRI-based prostate cancer detection

PURPOSE

To compare the diagnostic performance of restriction spectrum imaging (RSI), with that of conventional multi-parametric (MP) magnetic resonance imaging (MRI) for prostate cancer (PCa) detection in a blinded reader-based format.

METHODS

Three readers independently evaluated 100 patients (67 with proven PCa) who underwent MP-MRI and RSI within 6 months of systematic biopsy (N = 67; 23 with targeting performed) or prostatectomy (N = 33). Imaging was performed at 3 Tesla using a phased-array coil. Readers used a five-point scale estimating the likelihood of PCa present in each prostate sextant. Evaluation was performed in two separate sessions, first using conventional MP-MRI alone then immediately with MP-MRI and RSI in the same session. Four weeks later, another scoring session used RSI and T2-weighted imaging (T2WI) without conventional diffusion-weighted or dynamic contrast-enhanced imaging. Reader interpretations were then compared to prostatectomy data or biopsy results. Receiver operating characteristic curves were performed, with area under the curve (AUC) used to compare across groups.

RESULTS

MP-MRI with RSI achieved higher AUCs compared to MP-MRI alone for identifying high-grade (Gleason score greater than or equal to 4 + 3=7) PCa (0.78 vs. 0.70 at the sextant level; P < 0.001 and 0.85 vs. 0.79 at the hemigland level; P = 0.04). RSI and T2WI alone achieved AUCs similar to MP-MRI for high-grade PCa (0.71 vs. 0.70 at the sextant level). With hemigland analysis, high-grade disease results were similar when comparing RSI + T2WI with MP-MRI, although with greater AUCs compared to the sextant analysis (0.80 vs. 0.79).

CONCLUSION

Including RSI with MP-MRI improves PCa detection compared to MP-MRI alone, and RSI with T2WI achieves similar PCa detection as MP-MRI.

The expanding landscape of diffusion-weighted MRI in prostate cancer

The added value of diffusion-weighted magnetic resonance imaging (DW-MRI) for the detection, localization, and staging of primary prostate cancer has been extensively reported in original studies and meta-analyses. More recently, DW-MRI and related techniques have been used to noninvasively assess prostate cancer aggressiveness and estimate its biological behavior. The present article aims to summarize the potential applications of DW-MRI for noninvasive optimization of pretherapeutic risk assessment, patient management decisions, and evaluation of treatment response.

Comparison of T2(*) mapping with diffusion-weighted imaging in the characterization of low-grade vs intermediate-grade and high-grade prostate cancer

OBJECTIVE

To evaluate the diagnostic value of T2(*) mapping compared with apparent diffusion coefficient (ADC) mapping in the characterization of low-grade (Gleason score, ≤6) vs intermediate-grade and high-grade (Gleason score ≥7) prostate cancer (PCa).

METHODS

62 patients who underwent MRI before prostatectomy were evaluated. Two readers independently scored the probabilities of tumours in 12 regions of the prostate on T2(*) and ADC images. The data were divided into two groups, i.e. low- vs intermediate- and high-grade PCa, and correlated with the histopathological results. The diagnostic performance parameters, areas under the receiver-operating characteristic curves and interreader agreements were calculated.

RESULTS

For Reader 2, ADC mapping exhibited a greater accuracy for intermediate-grade PCas than for high-grade PCas (0.77 vs 0.83, p < 0.05). For both readers, T2(*) mapping exhibited a greater accuracy for intermediate-grade PCas than for high-grade PCas (Reader 1, 0.86 vs 0.81; Reader 2, 0.83 vs 0.78; p < 0.05). The areas under the curve of T2(*) mappings were greater than those of the ADC mappings for the intermediate- and high-grade PCas (Reader 1, 0.83 vs 0.78; Reader 2, 0.80 vs 0.75; p < 0.05) but not for the low-grade PCas (Reader 1, 0.86 vs 0.84; Reader 2, 0.83 vs 0.82; p > 0.05). The weighted κ value of T2(*) mapping was 0.59.

CONCLUSION

T2(*) mapping improves the accuracy of the characterization of intermediate- and high-grade PCas but not low-grade PCas compared with ADC mapping.

ADVANCES IN KNOWLEDGE

T2(*) mapping exhibited greater diagnostic accuracy than ADC mapping in the characterization of intermediate- and high-grade PCas. T2(*) mapping exhibited limited value in the characterization of low-grade PCa.

Amide proton transfer (APT) magnetic resonance imaging of prostate cancer: comparison with Gleason scores

OBJECTIVE

To evaluate the utility of amide proton transfer (APT) imaging in estimating the Gleason score (GS) of prostate cancer (Pca).

MATERIALS AND METHODS

Sixty-six biopsy-proven cancers were categorized into four groups according to the GS: GS-6 (3 + 3); GS-7 (3 + 4/4 + 3); GS-8 (4 + 4) and GS-9 (4 + 5/5 + 4). APT signal intensities (APT SIs) and apparent diffusion coefficient (ADC) values of each GS group were compared by one-way analysis of variance with Tukey's HSD post hoc test.

RESULTS

The mean and standard deviation of the APT SIs (%) and ADC values (×10(-3) mm(2)/s) were as follows: GS-6, 2.48 ± 0.59 and 1.16 ± 0.26; GS-7, 5.17 ± 0.66 and 0.92 ± 0.18; GS-8, 2.56 ± 0.85 and 0.86 ± 0.17; GS-9, 1.96 ± 0.75 and 0.85 ± 0.18, respectively. The APT SI of the GS-7 group was highest, and there were significant differences between the GS-6 and GS-7 groups and the GS-7 and GS-9 groups (p < 0.05). The ADC value of the GS-6 group was significantly higher than each value of the GS-7, GS-8, and GS-9 groups (p < 0.05), but no significant differences were obtained among the GS-7, GS-8, and GS-9 groups.

CONCLUSION

The mean APT SI in Pca with a GS of 7 was higher than that for the other GS groups.

Stratification of the aggressiveness of prostate cancer using pre-biopsy multiparametric MRI (mpMRI)

Risk stratification, based on the Gleason score (GS) of a prostate biopsy, is an important decision-making tool in prostate cancer management. As low-grade disease may not need active intervention, the ability to identify aggressive cancers on imaging could limit the need for prostate biopsies. We assessed the ability of multiparametric MRI (mpMRI) in pre-biopsy risk stratification of men with prostate cancer. One hundred and twenty men suspected to have prostate cancer underwent mpMRI (diffusion MRI and MR spectroscopic imaging) prior to biopsy. Twenty-six had cancer and were stratified into three groups based on GS: low grade (GS ≤ 6), intermediate grade (GS = 7) and high grade (GS ≥ 8). A total of 910 regions of interest (ROIs) from the peripheral zone (PZ, range 25-45) were analyzed from these 26 patients. The metabolite ratio [citrate/(choline + creatine)] and apparent diffusion coefficient (ADC) of voxels were calculated for the PZ regions corresponding to the biopsy cores and compared with histology. The median metabolite ratios for low-grade, intermediate-grade and high-grade cancer were 0.29 (range: 0.16, 0.61), 0.17 (range: 0.13, 0.32) and 0.13 (range: 0.05, 0.23), respectively (p = 0.004). The corresponding mean ADCs (×10(-3) mm(2) /s) for low-grade, intermediate-grade and high-grade cancer were 0.99 ± 0.08, 0.86 ± 0.11 and 0.69 ± 0.12, respectively (p < 0.0001). The combined ADC and metabolite ratio model showed strong discriminatory ability to differentiate subjects with GS ≤ 6 from subjects with GS ≥ 7 with an area under the curve of 94%. These data indicate that pre-biopsy mpMRI may stratify PCa aggressiveness noninvasively. As the recent literature data suggest that men with GS ≤ 6 cancer may not need radical therapy, our data may help limit the need for biopsy and allow informed decision making for clinical intervention. Copyright © 2015 John Wiley & Sons, Ltd.

Diffusion-weighted imaging predicts upgrading of Gleason score in biopsy-proven low grade prostate cancers

OBJECTIVE

To analyse whether diffusion-weighted imaging (DWI) predicts Gleason score (GS) upgrading in biopsy-proven low grade prostate cancer (PCa).

PATIENTS AND METHODS

A total of 132 patients who had biopsy-proven low grade (GS < 7) PCa, 3T DWI results, and surgical confirmation were retrospectively included in the study. Clinical variables (prostate-specific antigen, greatest percentage of cancer in a biopsy core and percentage of positive cores) and DWI variables (minimum apparent diffusion coefficient [ADC_min ] and mean ADC [ADC_mean ]) were evaluated. ADC_min was measured, by two independent, blinded readers, using a region of interest (ROI) of 5-10 mm² at the area of lowest ADC value within a cancer, while ADC_mean was measured using an ROI covering more than half of a cancer. Logistic regression and receiver-operating characteristic curve analyses were performed.

RESULTS

The rate of GS upgrading was 46.1% (61/132). In both univariate and multivariate analyses, ADC_min and ADC_mean were persistently significant for predicting GS upgrading (P < 0.05), whereas clinical variables were not (P > 0.05). In both readers' results, the area under the curve (AUC) of ADC_min was significantly greater than that of ADC_mean (reader 1: AUC 0.760 vs 0.711; P < 0.001; reader 2: AUC 0.752 vs 0.714; P = 0.003).

CONCLUSION

Our results showed that DWI may predict GS upgrading of biopsy-proven low grade PCa. The variable ADC_min in PCa may perform better than ADC_mean .

The Efficacy of Multiparametric Magnetic Resonance Imaging and Magnetic Resonance Imaging Targeted Biopsy in Risk Classification for Patients with Prostate Cancer on Active Surveillance

PURPOSE

We determined whether multiparametric magnetic resonance imaging targeted biopsies may replace systematic biopsies to detect higher grade prostate cancer (Gleason score 7 or greater) and whether biopsy may be avoided based on multiparametric magnetic resonance imaging among men with Gleason 3+3 prostate cancer on active surveillance.

MATERIALS AND METHODS

We identified men with previously diagnosed Gleason score 3+3 prostate cancer on active surveillance who underwent multiparametric magnetic resonance imaging and a followup prostate biopsy. Suspicion for higher grade cancer was scored on a standardized 5-point scale. All patients underwent a systematic biopsy. Patients with multiparametric magnetic resonance imaging regions of interest also underwent magnetic resonance imaging targeted biopsy. The detection rate of higher grade cancer was estimated for different multiparametric magnetic resonance imaging scores with the 3 biopsy strategies of systematic, magnetic resonance imaging targeted and combined.

RESULTS

Of 206 consecutive men on active surveillance 135 (66%) had a multiparametric magnetic resonance imaging region of interest. Overall, higher grade cancer was detected in 72 (35%) men. A higher multiparametric magnetic resonance imaging score was associated with an increased probability of detecting higher grade cancer (Wilcoxon-type trend test p <0.0001). Magnetic resonance imaging targeted biopsy detected higher grade cancer in 23% of men. Magnetic resonance imaging targeted biopsy alone missed higher grade cancers in 17%, 12% and 10% of patients with multiparametric magnetic resonance imaging scores of 3, 4 and 5, respectively.

CONCLUSIONS

Magnetic resonance imaging targeted biopsies increased the detection of higher grade cancer among men on active surveillance compared to systematic biopsy alone. However, a clinically relevant proportion of higher grade cancer was detected using only systematic biopsy. Despite the improved detection of disease progression using magnetic resonance imaging targeted biopsy, systematic biopsy cannot be excluded as part of surveillance for men with low risk prostate cancer.

Assessment of Prostate Cancer Aggressiveness by Use of the Combination of Quantitative DWI and Dynamic Contrast-Enhanced MRI

OBJECTIVE

The objective of this study was to investigate whether the apparent diffusion coefficient (ADC) value from DWI and the forward volume transfer constant (K(trans)) value from dynamic contrast-enhanced MRI independently predict prostate cancer aggressiveness, and to determine whether the combination of both parameters performs better than either parameter alone in assessing tumor aggressiveness before treatment.

MATERIALS AND METHODS

This retrospective study included 158 men with histopathologically confirmed prostate cancer who underwent 3-T MRI before undergoing prostatectomy in 2011. Whole-mount step-section pathologic maps identified 195 prostate cancer foci that were 0.5 mL or larger; these foci were then volumetrically assessed to calculate the per-tumor ADC and K(trans) values. Associations between MRI and histopathologic parameters were assessed using Spearman correlation coefficients, univariate and multivariable logistic regression, and AUCs.

RESULTS

The median ADC and K(trans) values showed moderate correlation only for tumors for which the Gleason score (GS) was 4 + 4 or higher (ρ = 0.547; p = 0.042). The tumor ADC value was statistically significantly associated with all dichotomized GSs (p < 0.005), including a GS of 3 + 3 versus a GS of 3 + 4 or higher (AUC, 0.693; p = 0.001). The tumor K(trans) value differed statistically significantly only between tumors with a GS of 3 + 3 and those with a primary Gleason grade of 4 (p ≤ 0.015), and it made a statistically significant contribution only in differentiating tumors with a GS of 4 + 3 or higher (AUC, 0.711; p < 0.001) and those with a GS of 4 + 4 or higher (AUC, 0.788; p < 0.001) from lower-grade tumors. Combining ADC and K(trans) values improved diagnostic performance in characterizing tumors with a GS of 4 + 3 or higher and those with a GS of 4 + 4 or higher (AUC, 0.739 and 0.856, respectively; p < 0.01).

CONCLUSION

Although the ADC value helped to differentiate between all GSs, the K(trans) value was only a benefit in characterizing more aggressive tumors. Combining these parameters improves their performance in identifying patients with aggressive tumors who may require radical treatment.

Whole-Tumor Quantitative Apparent Diffusion Coefficient Histogram and Texture Analysis to Predict Gleason Score Upgrading in Intermediate-Risk 3 + 4 = 7 Prostate Cancer

OBJECTIVE

The objective of our study was to evaluate whole-lesion quantitative apparent diffusion coefficient (ADC) for the prediction of Gleason score (GS) upgrading in 3 + 4 = 7 prostate cancer.

MATERIALS AND METHODS

Fifty-four patients with GS 3 + 4 = 7 prostate cancer diagnosed at systematic transrectal ultrasound (TRUS)-guided biopsy underwent 3-T MRI and radical prostatectomy (RP) between 2012 and 2014. A blinded radiologist contoured dominant tumors on ADC maps using histopathologic correlation. The whole-lesion mean ADC, ADC ratio (normalized to peripheral zone), ADC histogram, and texture analysis were compared between tumors with GS upgrading and those without GS upgrading using multivariate ROC analyses and logistic regression modeling.

RESULTS

Tumors were upgraded to GS 4 + 3 = 7 after RP in 26% (n = 14) of the 54 patients, and tumors were downgraded after RP in none of the patients. The mean ADC, ADC ratio, 10th-centile ADC, 25th-centile ADC, and 50th-centile ADC were similar between patients with GS 3 + 4 = 7 tumors (0.99 ± 0.22, 0.58 ± 0.15, 0.77 ± 0.31, 0.94 ± 0.28, and 1.15 ± 0.24, respectively) and patients with upgraded GS 4 + 3 = 7 tumors (1.02 ± 0.18, 0.55 ± 0.11, 0.71 ± 0.26, 0.89 ± 0.20, and 1.11 ± 0.16) (p > 0.05). Regression models combining texture features improved the prediction of GS upgrading. The combination of kurtosis, entropy, and skewness yielded an AUC of 0.76 (SE = 0.07) (p < 0.001), a sensitivity of 71%, and a specificity of 73%. The combination of kurtosis, heterogeneity, entropy, and skewness yielded an AUC of 0.77 (SE = 0.07) (p < 0.001), a sensitivity of 71%, and a specificity of 78%.

CONCLUSION

In this study, whole-lesion mean ADC, ADC ratio, and ADC histogram analysis were not predictive of pathologic upgrading of GS 3 + 4 = 7 prostate cancer after RP. ADC texture analysis improved accuracy.

Endorectal multiparametric MRI of the prostate: incremental effect of perfusion imaging on biopsy target identification

PURPOSE

To evaluate the incremental effect of perfusion imaging on biopsy target identification at endorectal multiparametric prostate magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We retrospectively 52 patients who underwent endorectal multiparametric prostate MRI for suspected or untreated prostate cancer. Two readers independently identified biopsy targets without and with perfusion images.

RESULTS

Reader 1 identified 36 targets without and 39 targets with perfusion imaging (P>.05). The corresponding numbers for reader 2 were 38 and 38, respectively (P=.5).

CONCLUSION

Perfusion imaging does not significantly increase the number of biopsy targets identified at endorectal multiparametric prostate MRI.

T2* relaxation time in the detection and assessment of aggressiveness of peripheral zone cancer in comparison with diffusion-weighted imaging

AIM

To investigate the feasibility of T2* relaxation time for distinguishing benign from malignant regions, as well as tumour aggressiveness, within the peripheral zone (PZ) of the prostate in comparison with diffusion-weighted imaging (DWI).

MATERIALS AND METHODS

Fifty-eight patients with prostate cancer underwent 3 T magnetic resonance imaging using multi-echo T2* and DWI (maximum b-value, 2000 s/mm(2)). Parametric maps were obtained for apparent diffusion coefficient (ADC) and T2* values. Two radiologists reviewed these maps and measured ADC and T2* values in sextants positive for cancer at biopsy. Data were analysed using mixed-model analysis of variance and receiver operating characteristic curves.

RESULTS

Ninety-three sextants exhibited a Gleason score of 6; 59 exhibited a Gleason score of 7 or 8. The T2* value was significantly lower in cancerous sextants than in the benign PZ (48.69+0.60 versus 74.14+0.56, p<0.001), as well as in cancerous sextants with higher rather than lower Gleason scores (43.18+0.89 versus 52.18+0.55, p<0.001). The T2* value showed significantly greater specificity for differentiating cancerous sextants from benign PZ than ADC (93.1% versus 89.7%, p<0.001), with equal sensitivity (82.8% versus 81%, p>0.05). The T2* value exhibited significantly greater sensitivity and specificity for differentiating sextants with low- and high-grade cancer than ADC (79.6% versus 64.5% and 81.4% versus 72.9%, respectively; p<0.05). The T2* value had a significantly greater area under the receiver operating characteristic curve for differentiating sextants with low- and high-grade cancer than ADC (0.77 versus 0.71, p<0.01).

CONCLUSION

Preliminary findings suggest that the T2* relaxation time has increased diagnostic value compared with DWI in prostate PZ cancer assessment.

3T multiparametric MRI of the prostate: Does intravoxel incoherent motion diffusion imaging have a role in the detection and stratification of prostate cancer in the peripheral zone?

PURPOSE

To evaluate the potential added value of the intravoxel incoherent motion model to conventional multiparametric magnetic resonance protocol in order to differentiate between healthy and neoplastic prostate tissue in the peripheral zone.

MATERIAL AND METHODS

Mono-exponential and bi-exponential fits were used to calculate ADC and IVIM parameters in 53 patients with peripheral zone biopsy proved tumor. Inferential statistics analysis was performed on T2, ADC and IVIM parameters (D, D*, f) comparing healthy and neoplastic tissues. Linear discriminant analysis was performed for the conventional parameters (T2 and ADC), the IVIM parameters (molecular diffusion coefficient (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (f) and the combined T2-weighted imaging/DWI and IVIM parameters (T2, ADC, D, D* and f). A correlation with Gleason scores was achieved.

RESULTS

The values of T2, ADC and D were significantly lower in cancerous tissues (2749.82 ± 1324.67 ms, 0.76 ± 0.27 × 10(-3)mm(2)/s and 0.99 ± 0.38 × 10(-3)mm(2)/s respectively) compared to those found in the healthy tissues (3750.70 ± 1735.37 ms, 1.39 ± 0.48 × 10(-3)mm(2)/s and 1.77 ± 0.36 × 10(-3)mm(2)/s respectively); D* parameter was significantly increased in neoplastic compared to healthy tissue (15.56 ± 12.91 × 10(-3)mm(2)/s and 10.25 ± 10.52 × 10(-3)mm(2)/s respectively). The specificity, sensitivity and accuracy of the T2-weighted imaging/DWI and IVIM parameters were 100, 96 and 98%, respectively, compare to 88, 92 and 90% and 96, 92 and 94 for T2-weighted imaging/ADC and IVIM alone.

CONCLUSIONS

IVIM parameters increase the specificity and sensitivity in the evaluation of peripheral zone prostate cancer. A statistical difference between low grade tumors and high grade tumors has been demostrated in that ADC, D and D* dataset; in particular, D has been found to have the highest significativity.

Prostate cancer: correlation of intravoxel incoherent motion MR parameters with Gleason score

PURPOSE

To evaluate the potential of intravoxel incoherent motion (IVIM) imaging to predict histological prognostic parameters by investigating whether IVIM parameters correlate with Gleason score.

MATERIALS AND METHODS

The institutional review board approved this retrospective study, and informed consent was waived. A total of 41 patients with histologically proven prostate cancer who underwent prostate MRI using a 3T MRI machine were included. For eight diffusion-weighted imaging b-values (0, 10, 20, 50, 100, 200, 500, and 800s/mm(2)), a spin-echo echo-planar imaging sequence was performed. D, f, D(⁎), and ADCfit values were compared among three groups of patients with prostate cancer: Gleason score 6 (n=9), 7 (n=16), or 8 or higher (n=16). Receiver operating characteristic (ROC) curves were generated for D, f, D(⁎), and ADCfit to assess the ability of each parameter to distinguish cancers with low Gleason scores from cancers with intermediate or high Gleason scores.

RESULTS

Pearson's coefficient analysis revealed significant negative correlations between Gleason score and ADCfit (r=-0.490, P=.001) and Gleason score and D values (r=-0.514, P=.001). Gleason score was poorly correlated with f (r=0.168, P=.292) and D(⁎) values (r=-0.108, P=.500). The ADCfit and D values of prostate cancers with Gleason scores 7 or ≥8 were significantly lower than values for prostate cancers with Gleason score 6 (P<.05). ROC curves were constructed to assess the ability of IVIM parameters to discriminate prostate cancers with Gleason score 6 from cancers with Gleason scores 7 or ≥8. Areas under the curve were 0.671 to 0.974. ADCfit and D yielded the highest Az value (0.960-0.956), whereas f yielded the lowest Az value (0.633).

CONCLUSIONS

The pure molecular diffusion parameter, D, was the IVIM parameter that best discriminated prostate cancers with low Gleason scores from prostate cancers with intermediate or high Gleason scores.

Active Surveillance of Prostate Cancer: Use, Outcomes, Imaging, and Diagnostic Tools

Active surveillance (AS) has emerged as a standard management option for men with very low-risk and low-risk prostate cancer, and contemporary data indicate that use of AS is increasing in the United States and abroad. In the favorable-risk population, reports from multiple prospective cohorts indicate a less than 1% likelihood of metastatic disease and prostate cancer-specific mortality over intermediate-term follow-up (median 5-6 years). Higher-risk men participating in AS appear to be at increased risk of adverse outcomes, but these populations have not been adequately studied to this point. Although monitoring on AS largely relies on serial prostate biopsy, a procedure associated with considerable morbidity, there is a need for improved diagnostic tools for patient selection and monitoring. Revisions from the 2014 International Society of Urologic Pathology consensus conference have yielded a more intuitive reporting system and detailed reporting of low-intermediate grade tumors, which should facilitate the practice of AS. Meanwhile, emerging modalities such as multiparametric magnetic resonance imaging and tissue-based molecular testing have shown prognostic value in some populations. At this time, however, these instruments have not been sufficiently studied to consider their routine, standardized use in the AS setting. Future studies should seek to identify those platforms most informative in the AS population and propose a strategy by which promising diagnostic tools can be safely and efficiently incorporated into clinical practice.

The value of ADC, T2 signal intensity, and a combination of both parameters to assess Gleason score and primary Gleason grades in patients with known prostate cancer

BACKGROUND

The ability to non-invasively analyze tumor aggressiveness is an important predictor for individual treatment stratification and patient outcome in prostate cancer (PCA).

PURPOSE

To evaluate: (i) whether apparent diffusion coefficient (ADC), the T2 signal intensity (SI), and a combination of both parameters allow for an improved discrimination of Gleason Score (GS) ≥7 (intermediate and high risk) and GS <7 (low risk) in PCA; and (ii) whether ADC may distinguish between 3 + 4 and 4 + 3 PCA (primary Gleason grades [pGG]).

MATERIAL AND METHODS

Prostatectomy specimens of 66 patients (mean age, 63 ± 5.6 years; 104 PCA foci) with a preceding multiparametric 1.5 T endorectal coil magnetic resonance imaging (MRI) were included. ADC (b values = 0, 100, 400, 800 s/mm(2)), standardized T2 (T2s), and the ADC/T2s ratio were tested for correlation with GS applying multivariate analysis. ADC cutoff values were calculated for prediction of GS and pGG, and logarithm of the odds (LOGIT) was used to express the probability for GS and pGG. Diagnostic accuracy was assessed by ROC analysis.

RESULTS

We found an almost linear negative relationship of ADC for GS ≥7 (P = 0.002). The effect of ADC for GS ≥7 (adjusted odds ratio = 0.995) was almost identical for peripheral and transition zone PCA (P = 0.013 and P < 0.001, respectively). ADC showed an AUC of 78.9% for discrimination between GS <7 and GS ≥7. An ADC cutoff of <1.005 × 10(-3 )mm(2)/s indicated a GS ≥7 (90.5% sensitivity, 62.5% specificity). Within the group of GS = 7 PCA, an ADC > 0.762 × 10(-3 )mm(2)/s indicated a pGG of 3 (AUC = 69.6%).

CONCLUSION

T2s and the ADC/T2s ratio do not provide additional information regarding prediction of GS. ADC values have a good discriminatory power to distinguish tumors with GS ≥7 from GS <7 and to predict pGG in GS = 7 PCA.

Comparison of calculated and acquired high b value diffusion-weighted imaging in prostate cancer

PURPOSE

To determine whether the performance of calculated high b value diffusion-weighted images (DWI) derived from regular lower b value DWI using exponential diffusion decay models (intravoxel incoherent motion = IVIM and diffusional kurtosis = DK) is comparable to acquired high b value DWI in prostate cancer detection.

MATERIALS AND METHODS

One hundred six patients underwent diagnostic multiparametric prostate MRI at 3T using an endorectal coil. Five b value (b = 0, 188, 375, 563, 750 s/mm(2)) DWI and high b value (b = 0, 1000 and 2000 s/mm(2)) DWI were acquired. Calculated high b value (b = 1000 s/mm(2) and b = 2000 s/mm(2)) DWI were derived from the DWI dataset using DK and IVIM models. Calculated and acquired high b value DWI images were compared for lesion visibility and image quality by two experienced radiologists (1 and 6 years of experience). GEE with Wald test was used to compare the image quality among the four calculated high b value DWI by comparing the proportion of lesions in each model which were comparable to the acquired images. This comparison was done for all lesions and by lesion location (PZ or CG; low apical/anterior or apical/mid/base)

RESULTS

More lesions were visible on acquired b = 2000 s/mm(2) compared to b = 1000 s/mm(2) DWI. Calculated high b value DWI using the IVIM model had approximately the same number of lesions as acquired high b value DWI, whereas the DK model had fewer lesions than acquired images. The image quality of calculated high b value DWI was comparable to that of acquired images, and the highest quality images were obtained with b1000IVIM. The image quality of calculated b1000IVIM was the same as that of acquired DWI in apical/mid/base (98%) locations and comparable in low apical and anterior (95.4%) locations. The image quality of calculated b2000IVIM was inferior in both apical/mid/base (86.2%) locations and comparable in low apical and anterior (83.9%) locations.

CONCLUSION

Calculated high b value DWI obtained using IVIM model has same lesion visibility as that of acquired DWI. The image quality of calculated high b value DWI relative to corresponding acquired DWI decreases with increase in b value.

Exponential apparent diffusion coefficient in evaluating prostate cancer at 3 T: preliminary experience

OBJECTIVE

To investigate the feasibility of exponential apparent diffusion coefficient (eADC) derived from diffusion-weighted imaging (DWI) in evaluating prostate cancers at 3 T.

METHODS

74 consecutive patients with surgically confirmed single peripheral zone (PZ) prostate cancer ≥0.5 cm(3) who underwent pre-operative DWI at 3 T were retrospectively selected. Based on radiological-pathological correlation, eADC and apparent diffusion coefficient (ADC) (×10(-3) mm(2) s(-1)) for the cancers and benign PZ were measured by two independent readers. Tumour eADC or ADC was correlated with Gleason score. Receiver operating characteristic curve analysis was performed to differentiate between Gleason score 6 and 7 or higher, by eADC and ADC. Lesion-to-background contrast ratio was compared between eADC and ADC.

RESULTS

Mean tumour eADC (0.48-0.50) and ADC (0.72-0.75) were significantly different from those of benign PZ (eADC, 0.20-0.27; ADC, 1.34-1.66), respectively (p < 0.001). A moderate correlation between tumour eADC or ADC and Gleason score was seen. For differentiating between Gleason score 6 and 7 or higher, eADC (0.818-0.883) showed a similar area under the curve with ADC (0.840-0.889) (p > 0.05). Lesion-to-background contrast ratio of eADC (Reader 1, 2.43; Reader 2, 2.23) was significantly greater than that of ADC (Reader 1, 2.21; Reader 2, 2.12) (p < 0.001).

CONCLUSION

The eADC may offer similar diagnostic utility with ADC in the differentiation of the cancer from benign prostate tissue. Moreover, the eADC appears to allow improved tissue contrast.

ADVANCES IN KNOWLEDGE

The eADC may be a comparable alternative to ADC for evaluating prostate cancer, with removing T2 shine-through effects from DWI.

Development and evaluation of a multichannel endorectal RF coil for prostate MRI at 7T in combination with an external surface array

PURPOSE

To develop and evaluate a sterilizable multichannel endorectal coil (ERC) for use in combination with an external surface array (ESA) for high-resolution anatomical and functional studies of the prostate at 7T.

MATERIALS AND METHODS

A two-loop ERC (ERC-2L) and a microstrip-loop ERC (ERC-ML) were compared at 7T in terms of transmit and receive performance. The best-performing ERC was evaluated alone and in combination with the ESA through 1) simulations on both phantom and an anatomically correct numerical human model to assess B1+ transmit and specific absorption rate (SAR) efficiencies, and 2) phantom experiments to calculate B1+ transmit efficiency and signal-to-noise ratio (SNR). Phantom studies were also performed to look at heating when using the ERC as a transmitter and for comparing the new coil against a single-channel balloon-type ERC (ERC-b). High-resolution magnetic resonance imaging (MRI) acquisitions were performed on a single healthy subject using the two-channel ERC combined with the ESA.

RESULTS

Compared to the ERC-ML, the ERC-2L demonstrated 20% higher SAR efficiency and higher SNR 3 cm from the coil. The presence of a tuned and detuned ERC-2L did not alter the peak local SAR of the ESA alone; however, the detuned ERC-2L had 45% less peak local SAR around the rectum compared to the tuned ERC-2L. The receive-only version of the ERC-2L improved the SNR 4.7-fold and 1.3-fold compared to the ESA and ERC-b, respectively. In combination with the ESA, the ERC-2L supported in-plane voxel-size of 0.36 × 0.36 mm(2) in T2 -weighted anatomic imaging.

CONCLUSION

The reusable ERC-2L combined with an ESA offers a high SNR imaging platform for translational studies of the prostate at 7T. J. Magn. Reson. Imaging 2016;43:1279-1287.

Prediction of biochemical recurrence after radical prostatectomy with PI-RADS version 2 in prostate cancers: initial results

OBJECTIVES

To determine whether the Prostate Imaging Reporting and Data System version 2 (PI-RADSv2) helps predict biochemical recurrence (BCR) after radical prostatectomy for prostate cancer (PCa).

METHODS

We included 158 patients with PCa who underwent magnetic resonance imaging (MRI) and radical prostatectomy (RP). Clinical (prostate-specific antigen, greatest percentage of core, and percentage of positive core number), PI-RADSv2 score on MRI, and surgical parameters (Gleason score, extracapsular extension, seminal vesicle invasion, and tumour volume) were investigated. Univariate and multivariate analyses using Cox's proportional hazards model were performed to assess parameters predictive of BCR (two consecutive prostate specific antigens ≥0.2 ng/ml). Kaplan-Meier survival curves were analyzed.

RESULTS

The rate of BCR was 13.3 % (21/158) after surgery (median follow-up, 25 months; range, 12-36). No subject with a PI-RADS score <4 had BCR. In univariate analysis, all parameters were significant for BCR (p < 0.05), except seminal vesicle invasion (p = 0.254). Meanwhile, PI-RADS score was the only independent parameter for BCR in multivariate analysis (p < 0.05). Two-year, BCR-free survival post-RP was significantly lower for PI-RADS ≥4 (84.7-85.5 %) than for PI-RADS <4 (100 %; p < 0.05).

CONCLUSION

As a preoperative imaging tool, PI-RADSv2 may be useful to predict BCR after radical prostatectomy for PCa.

KEY POINTS

• No subject with PI-RADS <4 had BCR after RP • PI-RADSv2 was the only predictor of BCR in multivariate analysis • Two-year, BCR-free survival following RP was lower for PI-RADS≥4 than for PI-RADS<4 • Inter-rater agreement was good for PI-RADS ≥4 or not.

Automatic classification of prostate cancer Gleason scores from multiparametric magnetic resonance images

Noninvasive, radiological image-based detection and stratification of Gleason patterns can impact clinical outcomes, treatment selection, and the determination of disease status at diagnosis without subjecting patients to surgical biopsies. We present machine learning-based automatic classification of prostate cancer aggressiveness by combining apparent diffusion coefficient (ADC) and T2-weighted (T2-w) MRI-based texture features. Our approach achieved reasonably accurate classification of Gleason scores (GS) 6(3 + 3) vs. ≥7 and 7(3 + 4) vs. 7(4 + 3) despite the presence of highly unbalanced samples by using two different sample augmentation techniques followed by feature selection-based classification. Our method distinguished between GS 6(3 + 3) and ≥7 cancers with 93% accuracy for cancers occurring in both peripheral (PZ) and transition (TZ) zones and 92% for cancers occurring in the PZ alone. Our approach distinguished the GS 7(3 + 4) from GS 7(4 + 3) with 92% accuracy for cancers occurring in both the PZ and TZ and with 93% for cancers occurring in the PZ alone. In comparison, a classifier using only the ADC mean achieved a top accuracy of 58% for distinguishing GS 6(3 + 3) vs. GS ≥7 for cancers occurring in PZ and TZ and 63% for cancers occurring in PZ alone. The same classifier achieved an accuracy of 59% for distinguishing GS 7(3 + 4) from GS 7(4 + 3) occurring in the PZ and TZ and 60% for cancers occurring in PZ alone. Separate analysis of the cancers occurring in TZ alone was not performed owing to the limited number of samples. Our results suggest that texture features derived from ADC and T2-w MRI together with sample augmentation can help to obtain reasonably accurate classification of Gleason patterns.

Investigating the ability of multiparametric MRI to exclude significant prostate cancer prior to transperineal biopsy

INTRODUCTION

We characterized false negative prostate magnetic resonance imaging (MRI) reporting by using histology derived from MRI-transrectal ultrasound (TRUS)-guided transperineal (MTTP) fusion biopsies.

METHODS

In total, 148 consecutive patients were retrospectively reviewed. Men underwent multiparametric MRI (mpMRI), reported by a consultant/attending radiologist in line with European Society of Urogenital Radiology (ESUR) standards. MTTP biopsy of the lesions was performed according to the Ginsburg recommendations. Cases with an MRI-histology mismatch were identified and underwent a second read by an experienced radiologist. A third review was performed with direct histology comparison to determine a true miss from an MRI-occult cancer. Statistical analysis was performed with McNemar's test.

RESULTS

False negative lesions were identified in 29 MRI examinations (19.6%), with a total of 46 lesions. Most false negative lesions (21/46) were located in the anterior sectors of the prostate. The second read led to a significant decrease of false-negative lesions with 7/29 further studies identified as positive on a patient-by-patient basis (24.1% of studies, p = 0.016) and 11/46 lesions (23.9%; p = 0.001). Of these, 30 lesions following the first read and 23 lesions after the second read were considered significant cancer according to the University College London criteria. However, on direct comparison with histology, most lesions were MRI occult.

CONCLUSION

We demonstrate that MRI can fail to detect clinically relevant lesions. Improved results were achieved with a second read but despite this, a number of lesions remain MRI-occult. Further advances in imaging are required to reduce false negative results.

TE = 32 ms vs TE = 100 ms echo-time (1)H-magnetic resonance spectroscopy in prostate cancer: Tumor metabolite depiction and absolute concentrations in tumors and adjacent tissues

PURPOSE

To compare the depiction of metabolite signals in short and long echo time (TE) prostate cancer spectra at 3T, and to quantify their concentrations in tumors of different stage and grade, and tissues adjacent to tumor.

MATERIALS AND METHODS

First, single-voxel magnetic resonance imaging (MRI) spectra were acquired from voxels consisting entirely of tumor, as defined on T2-weighted and diffusion-weighted (DW)-MRI and from a biopsy-positive octant, at TEs of 32 msec and 100 msec in 26 prostate cancer patients. Then, in a separate cohort of 26 patients, single-voxel TE = 32 msec MR spectroscopy (MRS) was performed over a partial-tumor region and a matching, contralateral normal-appearing region, defined similarly. Metabolite depiction was compared between TEs using Cramér-Rao lower bounds (CRLB), and absolute metabolite concentrations were calculated from TE = 32 msec spectra referenced to unsuppressed water spectra.

RESULTS

Citrate and spermine resonances in tumor were better depicted (had significantly lower CRLB) at TE = 32 msec, while the choline resonance was better depicted at TE = 100 msec. Citrate and spermine concentrations were significantly lower in patients of more advanced stage, significantly lower in Gleason grade 3+4 than 3+3 tumors, and significantly lower than expected from the tumor fraction in partial-tumor voxels (by 14 mM and 4 mM, respectively, P < 0.05).

CONCLUSION

Citrate and spermine resonances are better depicted at short TE than long TE in tumors. Reduction in these concentrations is related to increasing tumor stage and grade in vivo, while reductions in the normal-appearing tissues immediately adjacent to tumor likely reflect tumor field effects.

Can multiparametric MRI rule in or rule out significant prostate cancer?

PURPOSE OF REVIEW

To show how multiparametric MRI can rule in the presence of significant prostate cancer (PCa), allowing for magnetic resonance-targeted biopsies to detect aggressive tumors eligible for immediate treatment and to evaluate if mp-MRI can rule out significant tumor foci to avoid overdiagnosis and overtreatment of PCa.

RECENT FINDINGS

Diffusion-weighted MRI plays a major role to detect tumor foci and to rule in significant PCa. A low apparent diffusion coefficient (ADC) value indicates that high Gleason grade tumors are present. Conversely, the absence of any suspicious focus or foci with a high apparent diffusion coefficient value indicates either benign tissue or low-grade tumor

SUMMARY

mp-MRI Multiparametric MRI is a highly accurate filter to detect aggressive tumors and to avoid detection of insignificant cancer. There is growing evidence that it may be indicated in any man with an elevated Prostatic Specific Antigen level before considering whether an immediate biopsy should be performed or whether a simple follow-up should be the option.

Role of MRI in the diagnosis and management of prostate cancer

Multiparametric MRI of the prostate consists of T1- and T2-weighted sequences, which provide anatomical information, and one or more 'functional' sequences, that is, diffusion-weighted imaging, dynamic contrast-enhanced sequences and magnetic resonance spectroscopy. Prostate MRI is the most accurate imaging method for local staging of prostate cancer and can also be used for the noninvasive evaluation of tumor aggressiveness. By magnetic resonance-guided prostate biopsy it is possible to target the most cancer-suspicious areas of the gland, especially in patients with a negative transrectal biopsy. In patients with biochemical recurrence after radical treatment, MRI is a valuable tool for the detection of local tumor recurrence and whole-body MRI can be used for the diagnosis of distant metastases.

Five-point Likert scaling on MRI predicts clinically significant prostate carcinoma

Background

To clarify the relationship between the probability of prostate cancer scaled using a 5-point Likert system and the biological characteristics of corresponding tumor foci.

Methods

The present study involved 44 patients undergoing 3.0-Tesla multiparametric MRI before laparoscopic radical prostatectomy. Tracing based on pathological and MRI findings was performed. The relationship between the probability of cancer scaled using the 5-point Likert system and the biological characteristics of corresponding tumor foci was evaluated.

Results

A total of 102 tumor foci were identified histologically from the 44 specimens. Of the 102 tumors, 55 were assigned a score based on MRI findings (score 1: n = 3; score 2: n = 3; score 3: n = 16; score 4: n = 11 score 5: n = 22), while 47 were not pointed out on MRI. The tracing study revealed that the proportion of >0.5 cm³ tumors increased according to the upgrade of Likert scores (score 1 or 2: 33 %; score 3: 68.8 %; score 4 or 5: 90.9 %, χ² test, p < 0.0001). The proportion with a Gleason score >7 also increased from scale 2 to scale 5 (scale 2: 0 %; scale 3: 56.3 %; scale 4: 72.7 %; 5: 90.9 %, χ² test, p = 0.0001). On using score 3 or higher as the threshold of cancer detection on MRI, the detection rate markedly improved if the tumor volume exceeded 0.5 cm³ (<0.2 cm³: 10.3 %; 0.2-0.5 cm³: 25 %; 0.5-1.0 cm³: 66.7 %; 1.0 < cm³: 92.1 %).

Conclusions

Each Likert scale favobably reflected the corresponding tumor’s volume and Gleason score. Our observations show that “score 3 or higher” could be a useful threshold to predict clinically significant carcinoma when considering treatment options.

Updates in advanced diffusion-weighted magnetic resonance imaging techniques in the evaluation of prostate cancer

Diffusion-weighted magnetic resonance imaging (DW-MRI) is considered part of the standard imaging protocol for the evaluation of patients with prostate cancer. It has been proven valuable as a functional tool for qualitative and quantitative analysis of prostate cancer beyond anatomical MRI sequences such as T2-weighted imaging. This review discusses ongoing controversies in DW-MRI acquisition, including the optimal number of b-values to be used for prostate DWI, and summarizes the current literature on the use of advanced DW-MRI techniques. These include intravoxel incoherent motion imaging, which better accounts for the non-mono-exponential behavior of the apparent diffusion coefficient as a function of b-value and the influence of perfusion at low b-values. Another technique is diffusion kurtosis imaging (DKI). Metrics from DKI reflect excess kurtosis of tissues, representing its deviation from Gaussian diffusion behavior. Preliminary results suggest that DKI findings may have more value than findings from conventional DW-MRI for the assessment of prostate cancer.