MR imaging of the prostate and adjacent anatomic structures before, during, and after ejaculation: qualitative and quantitative evaluation

Prostate Cancer Local Staging with Magnetic Resonance Imaging

Accurate determination of the local stage of prostate cancer is crucial for treatment planning and prognosis. The primary objective of local staging is to distinguish between organ-confined and locally advanced disease, with the latter carrying a worse clinical prognosis. The presence of locally advanced disease features of prostate cancer, such as extra-prostatic extension, seminal vesicle invasion, and positive surgical margin, can impact the choice of treatment. Over the past decade, multiparametric MRI (mpMRI) has become the preferred imaging modality for the local staging of prostate cancer and has been shown to provide accurate information on the location and extent of disease. It has demonstrated superior performance compared to staging based on traditional clinical nomograms. Despite being a relatively new technique, mpMRI has garnered considerable attention and ongoing investigations. Therefore, in this review, we will discuss the current use of mpMRI on prostate cancer local staging.

Quantitative longitudinal mapping of radiation-treated prostate cancer using MR fingerprinting with radial acquisition and subspace reconstruction

MR fingerprinting (MRF) enables fast multiparametric quantitative imaging with a single acquisition and has been shown to improve diagnosis of prostate cancer. However, most prostate MRF studies were performed with spiral acquisitions that are sensitive to B0 inhomogeneities and consequent blurring. In this work, a radial MRF acquisition with a novel subspace reconstruction technique was developed to enable fast T1/T2 mapping in the prostate in under 4 min. The subspace reconstruction exploits the extensive temporal correlations in the MRF dictionary to pre-compute a low dimensional space for the solution and thus reduce the number of radial spokes to accelerate the acquisition. Iterative reconstruction with the subspace model and additional regularization of the signal representation in the subspace is performed to minimize the number of spokes and maintain matching quality and SNR. Reconstruction accuracy was assessed using the ISMRM NIST phantom. In-vivo validation was performed on two healthy subjects and two prostate cancer patients undergoing radiation therapy. The longitudinal repeatability was quantified using the concordance correlation coefficient (CCC) in one of the healthy subjects by repeated scans over 1 year. One prostate cancer patient was scanned at three time points, before initiating therapy and following brachytherapy and external beam radiation. Changes in the T1/T2 maps obtained with the proposed method were quantified. The prostate, peripheral and transitional zones, and visible dominant lesion were delineated for each study, and the statistics and distribution of the quantitative mapping values were analyzed. Significant image quality improvements compared with standard reconstruction methods were obtained with the proposed subspace reconstruction method. A notable decrease in the spread of the T1/T2 values without biasing the estimated mean values was observed with the subspace reconstruction and agreed with reported literature values. The subspace reconstruction enabled visualization of small differences in T1/T2 values in the tumor region within the peripheral zone. Longitudinal imaging of a volunteer subject yielded CCC of 0.89 for MRF T1, and 0.81 for MRF T2 in the prostate gland. Longitudinal imaging of the prostate patient confirmed the feasibility of capturing radiation treatment related changes. This work is a proof-of-concept for a high resolution and fast quantitative mapping using golden-angle radial MRF combined with a subspace reconstruction technique for longitudinal treatment response assessment in subjects undergoing radiation treatment.

State-of-the-art Prostate Imaging

Prostate cancer is one of the most common cancers in men. In addition to methods such as prostate-specific antigen test, digital rectal examination, and transrectal ultrasonography, magnetic resonance imaging has an important role for accurate and reproducible diagnosis. However, guidance in targeted biopsies and recent use in determining localization for treatment increase its importance. Due to technical difficulties, patient tolerance, and differences in interpretation, the prostate imaging reporting and data system recommends preparations for the patient and magnetic resonance imaging techniques. However, techniques continue to be developed to improve the diagnosis rate and image quality. In our article, patient preparation before imaging and techniques were tried to be discussed in detail. In addition, current approaches in biparametric magnetic resonance imaging and radiomics and new techniques such as T1 and T2 mapping will be mentioned.

Staging accuracy of MRI of the prostate with special reference to the influence of the time of last ejaculation on the detection of seminal vesicle invasion

AIM

To evaluate the Prostate Imaging Reporting and Data System, version 2.1 (PIRADS V2.1) criteria for seminal vesicle invasion (SVI) and examine whether the timing of last ejaculation influences the detection of SVI.

MATERIALS AND METHODS

The study population consisted of 68 patients (34 with SVI, 34 without SVI, matching groups by age and prostate volume) who underwent PIRADS V2.1-compliant multiparametric magnetic resonance imaging (MRI; 34 at 1.5 T, 34 at 3 T). Before the examination, the time of last ejaculation (38/68 ≤ 5 days, 30/68 > 5 days) was collected via a questionnaire. The five PIRADS V2.1 criteria for SVI with subsequent overall assessment were evaluated retrospectively by two independent examiners (examiner 1 with >10 years of experience, examiner 2 with 6 months of experience) in a single-blinded fashion for all patients using a questionnaire and a six-point scale (0 = no, 1 = very likely not, 2 = probably not, 3 = possible, 4 = probable, 5 = certain).

RESULTS

E1 achieved high specificity (100%) and positive predictive value (PPV; 100%) in the overall assessment, independent of the time of last ejaculation (sensitivity = 76.5%, negative predictive value [NPV] = 81%). The area under the curve (AUC) value was 0.882; for E2, it was 0.765. At ≤5 days, the AUC values of E1 and E2 differed significantly (0.867 versus 0.681, p=0.016), as did the diffusion restriction criterion (0.833 versus 0.681, p=0.028). E1 showed high AUC values independent of time. E2 had better values for all criteria at >5 days than at ≤5 days. There were no significant differences between the examiners in all observations at >5 days.

CONCLUSION

The PIRADS V2.1 criteria are well suited for an experienced examiner to detect SVI independent of time point. An inexperienced examiner will benefit from patients being abstinent >5 days prior to MRI.

Prostate imaging features on magnetic resonance imaging of young patients

OBJECTIVE

To identify magnetic resonance imaging findings of the prostate in young adults, including symptomatic and asymptomatic patients. The aim of this study is to evaluate the main aspects of prostate imaging in young patients.

METHODS

A total of 102 patients under 40 years of age, who underwent prostate magnetic resonance imaging between January 2016 and January 2019, were included in this study. The patients were divided into two groups: symptomatic for prostatitis (Group 1) and asymptomatic (Group 2). Magnetic resonance imaging scans were anonymized and interpreted by a radiologist blinded for clinical information. The study evaluated peripheral zone signal in T2-weighted sequences, diffusion and apparent diffusion coefficient map; peripheral zone enhancement pattern; seminal vesicles and periprostatic fat.

RESULTS

All evaluated criteria did not present statistically significant differences between the two groups. The most common pattern was heterogeneous hyposignal on T2 (57.9% in Group 1 and 57.8% in Group 2; p=0.506), mild diffuse / wedge-shaped areas of hypointensity on apparent diffusion coefficient map (61.4% in Group 1 and 64.4% in Group 2; p=0.931) and early post-contrast enhancement (73.7% in Group 1 and 68.9% in Group 2, p=0719).

CONCLUSION

The magnetic resonance imaging aspect of young patients showed no differences between symptomatic and asymptomatic patients.

Repeatability and Reproducibility Assessment of the Apparent Diffusion Coefficient in the Prostate: A Trial of the ECOG-ACRIN Research Group (ACRIN 6701)

BACKGROUND

Uncertainty regarding the reproducibility of the apparent diffusion coefficient (ADC) hampers the use of quantitative diffusion-weighted imaging (DWI) in evaluation of the prostate with magnetic resonance imaging MRI. The quantitative imaging biomarkers alliance (QIBA) profile for quantitative DWI claims a within-subject coefficient of variation (wCV) for prostate lesion ADC of 0.17. Improved understanding of ADC reproducibility would aid the use of quantitative diffusion in prostate MRI evaluation.

PURPOSE

Evaluation of the repeatability (same-day) and reproducibility (multi-day) of whole-prostate and focal-lesion ADC assessment in a multi-site setting.

STUDY TYPE

Prospective multi-institutional.

SUBJECTS

Twenty-nine males, ages 53 to 80 (median 63) years, following diagnosis of prostate cancer, 10 with focal lesions.

FIELD STRENGTH/SEQUENCE

3T, single-shot spin-echo diffusion-weighted echo-planar sequence with four b-values.

ASSESSMENT

Sites qualified for the study using an ice-water phantom with known ADC. Readers performed DWI analyses at visit 1 ("V1") and visit 2 ("V2," 2-14 days after V1), where V2 comprised scans before ("V2pre") and after ("V2post") a "coffee-break" interval with subject removal and repositioning. A single reader segmented the whole prostate. Two readers separately placed region-of-interests for focal lesions.

STATISTICAL TESTS

Reproducibility and repeatability coefficients for whole prostate and focal lesions derived from median pixel ADC. We estimated the wCV and 95% confidence interval using a variance stabilizing transformation and assessed interreader reliability of focal lesion ADC using the intraclass correlation coefficient (ICC).

RESULTS

The ADC biases from b0 -b600 and b0 -b800 phantom scans averaged 1.32% and 1.44%, respectively; mean b-value dependence was 0.188%. Repeatability and reproducibility of whole prostate median pixel ADC both yielded wCVs of 0.033 (N = 29). In 10 subjects with an evaluable focal lesion, the individual reader wCVs were 0.148 and 0.074 (repeatability) and 0.137 and 0.078 (reproducibility). All time points demonstrated good to excellent interreader reliability for focal lesion ADC (ICCV1  = 0.89; ICCV2pre  = 0.76; ICCV2post  = 0.94).

DATA CONCLUSION

This study met the QIBA claim for prostate ADC. Test-retest repeatability and multi-day reproducibility were largely equivalent. Interreader reliability for focal lesion ADC was high across time points.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2 TOC CATEGORY: Pelvis.

Reproducibility of apparent diffusion coefficient measurement in normal prostate peripheral zone at 1.5T MRI

PURPOSE

The purpose of this study was to quantify the influence of factors of variability on apparent diffusion coefficient (ADC) estimation in the normal prostate peripheral zone (PZ).

MATERIALS AND METHODS

Fifty healthy volunteers underwent in 2017 (n = 17) or 2020 (n = 33) two-point (0, 800 s/mm²) prostate diffusion-weighted imaging in the morning on 1.5 T scanners A and B from different manufacturers. Additional five-point (50, 150, 300, 500, 800 s/mm²) acquisitions were performed on scanner B in the morning and evening. ADC was measured in PZ at midgland using ADC maps reconstructed with various b-value combinations. ADC distributions from 2017 and 2020 were compared using Wilcoxon rank sum test. ADC obtained in the same volunteers were compared using Bland Altman methodology. The 95% confidence interval upper limit of the repeatability/reproducibility coefficient defined the lowest detectable ADC difference.

RESULTS

Forty-nine participants with a mean age of 24.6 ± 3.8 [SD] years (range: 21-37 years) were finally included. ADC distributions from 2017 and 2020 were not significantly different and were combined. Despite high individual variability, there was no significant bias (10 × 10^-6 mm²/s, P = 0.58) between ADC measurements made on both scanners. On scanner B, differences in lowest b-values chosen within the 0-500 s/mm² range for two-point ADC computation induced significant biases (56-109 × 10^-6 mm²/s, P < 0.0001). ADC was significantly lower in the morning (bias: 33 × 10^-6 mm²/s, P = 0.006). The number of b-values had little influence on ADC values. The lowest detectable ADC difference varied from 85 × 10^-6 to 311 × 10^-6 mm²/s across scanners, b-value combinations and periods of the day.

CONCLUSIONS

The MRI scanner, the lowest b-value used and the period of the day induce substantial variability in ADC computation.

Relevance of dog as an animal model for urologic diseases

We utilize animal models in urologic research to improve understanding of urinary physiology, determine the etiology of many urologic diseases, and discover and test novel therapeutic interventions. Dogs have a similar urinary tract anatomy and physiology to human and they develop many urologic diseases spontaneously. This chapter offers detailed comparisons of urinary tract anatomy, physiology, and the most common urologic diseases between humans and dogs. Dogs offer a unique opportunity for urologic research because they can be studied in research colonies and in client owned cohorts. Dogs also are among a limited number of non-human species that require continence and socially appropriate urinary behaviors (ex. going to the bathroom outside, training to not have submissive urination, etc.). These features make dogs unique in the animal kingdom and make them an ideal animal model for urologic research.

Male Lower Urinary Tract Dysfunction: An Underrepresented Endpoint in Toxicology Research

Lower urinary tract dysfunction (LUTD) is nearly ubiquitous in men of advancing age and exerts substantial physical, mental, social, and financial costs to society. While a large body of research is focused on the molecular, genetic, and epigenetic underpinnings of the disease, little research has been dedicated to the influence of environmental chemicals on disease initiation, progression, or severity. Despite a few recent studies indicating a potential developmental origin of male LUTD linked to chemical exposures in the womb, it remains a grossly understudied endpoint in toxicology research. Therefore, we direct this review to toxicologists who are considering male LUTD as a new aspect of chemical toxicity studies. We focus on the LUTD disease process in men, as well as in the male mouse as a leading research model. To introduce the disease process, we describe the physiology of the male lower urinary tract and the cellular composition of lower urinary tract tissues. We discuss known and suspected mechanisms of male LUTD and examples of environmental chemicals acting through these mechanisms to contribute to LUTD. We also describe mouse models of LUTD and endpoints to diagnose, characterize, and quantify LUTD in men and mice.

mpMRI of the Prostate (MR-Prostatography): Updated Recommendations of the DRG and BDR on Patient Preparation and Scanning Protocol

The Working Group Uroradiology and Urogenital Diagnosis of the German Roentgen Society (DRG) revised and updated the recommendations for preparation and scanning protocol of the multiparametric MRI of the Prostate in a consensus process and harmonized it with the managing board of German Roentgen Society and Professional Association of the German Radiologist (BDR e. V.). These detailed recommendation define the referenced "validated quality standards" of the German S3-Guideline Prostate Cancer and describe in detail the topic 1. anamnestic datas, 2. termination of examinations and preparation of examinations, 3. examination protocol and 4. MRI-(in-bore)-biopsy. KEY POINTS:: · The recommendations for preparation and scanning protocol of the multiparametric MRI of the Prostate were revised and updated in a consensus process and harmonized with the managing board of German Roentgen Society (DRG) and Professional Asssociation of the German Radiologist (BDR).. · Detailed recommendations are given for topic 1. anamnestic datas, 2. termination and preparation of examinations, 3. examination protocoll and 4. MRI-(in-bore)-biopsy.. · These recommendations define the referenced "validated quality standards" of the German S3-Guideline Prostate Cancer.. CITATION FORMAT: · Franiel T, Asbach P, Beyersdorff D et al. mpMRI of the Prostate (MR-Prostatography): Updated Recommendations of the DRG and BDR on Patient Preparation and Examination Protocol. Fortschr Röntgenstr 2021; 193: 763 - 776.

Quality of Prostate MRI: Is the PI-RADS Standard Sufficient?

RATIONALE AND OBJECTIVE

The Prostate Imaging Reporting and Data System version 2 (PI-RADSv2) published a set of minimum technical standards (MTS) to improve image quality and reduce variability in multiparametric prostate MRI. The effect of PIRADSv2 MTS on image quality has not been validated. We aimed to determine whether adherence to PI-RADSv2 MTS improves study adequacy and perceived quality.

MATERIALS AND METHODS

Sixty-two prostate MRI examinations including T2 weighted (T2W) and diffusion weighted image (DWI) consecutively referred to our center from 62 different institutions within a 12-month period (September 2017 to September 2018) were included. Six readers assessed images as adequate or inadequate for use in PCa detection and a numerical image quality ranking was given using a 1-5 scale. The PI-RADSv2 MTS were synthesized into sets of seven and 10 rules for T2W and DWI, respectively. Image adherence was assessed using Digital Imaging and Communications in Medicine (DICOM) metadata. Statistical analysis of survey results and image adherence was performed based on reader quality scoring (Kendall Rank tau-b) and reader adequate scoring (Wilcoxon test for association) for T2 and DWI quality assessment.

RESULTS

Out of 62 images, 52 (83%) T2W and 38 (61%) DWIs were rated to be adequate by a majority of readers. Reader adequacy scores showed no significant association with adherence to PI-RADSv2. There was a weak (tau-b = 0.22) but significant (p value = 0.01) correlation between adherence to PIRADSv2 MTS and image quality for T2W. Studies following all PI-RADSv2 T2W rules achieved a higher median average quality score (3.58 for 7/7 vs. 3.0 for <7/7, p = 0.012). No statistical relationship with PI-RADSv2 MTS adherence and DWI quality was found.

CONCLUSION

Among 62 sites performing prostate MRI, few were considered of high quality, but the majority were considered adequate. DWI showed considerably lower rates of adequate studies in the sample. Adherence to PI-RADSv2 MTS did not increase the likelihood of having a qualitatively adequate T2W or DWI.

Spontaneous Ejaculation: A Focused Review for the Clinicians

INTRODUCTION

The process of ejaculation has important meanings not only for its association with orgasm but also for the timing to ejaculate in the context of sexual activity. Spontaneous (involuntary) ejaculation (SE) without any sexual stimulation is a distressing symptom. Our understanding of SE is limited. Unfortunately, many physicians are not aware of these cases.

OBJECTIVES

The objective of this study is to describe the etiopathogenesis, clinical features, diagnosis, and treatment options for SE.

METHODS

We searched the literature for publications on "SE," "spontaneous emission" or "involuntary ejaculation," and factors influencing SE in the PUBMED/MEDLINE, Scopus, Cochrane Library, EMBASE, PsycINFO, ProQuest, Academic Search Complete database, Google Scholar, and CINAHL databases from inception to August 2020.

RESULTS

The literature search yielded 36 relevant publications reporting on 43 patients with SE. Attempts to explain the cause of pathologic SE have included 4 etiological groups (spinal cord lesions, psychological causes, rabies, and drug-induced). The underlying mechanisms responsible for induction of SE may include increased adrenergic activity, overactivity in dopaminergic system, decreased serotonergic activity, damage of descending inhibitory pathway, or penile hyperexcitability. SE may occur in the absence of an identifiable trigger or may be triggered by non-sexual circumstances (micturition, defecation, glans touch, anxiety, panic attack, or school examinations). Treatment options include psychoanalytic treatment, paroxetine, citalopram, sertraline, silodosin, and anxiolytics. In drug-induced SE, dose reduction and drug withdrawal with or without switching to another drug may relief SE.

CONCLUSIONS

SE is one of the least reported ejaculatory dysfunction. The key feature shared in common by these men is SE without any sexual thoughts or fantasies, may be triggered by non-sexual contexts, rarely associated with orgasm or erection. Treatment by psychoanalytic treatment and pharmacotherapy may be helpful. Further research might explore the definite underlying mechanisms. Abdel-Hamid IA, Ali OI. Spontaneous Ejaculation: A Focused Review for the Clinicians. Sex Med Rev 2021;9:406-422.

Optimising prostate mpMRI: prepare for success

Multiparametric magnetic resonance imaging (MRI) now plays an essential role in prostate cancer diagnosis and management. The increasing use of MRI before biopsy makes obtaining images of the highest quality vital. The European Society of Urogenital Radiology (ESUR) 2012 guidelines and subsequent Prostate Imaging -Reporting Data System (PI-RADS) version 2 recommendations in 2015 address the technical considerations for optimising MRI acquisition; however, the quality of the multiparametric sequences employed depends not only on the hardware and software utilised and scanning parameters selected, but also on patient-related factors, for which current guidance is lacking. Patient preparation factors include bowel peristalsis, rectal distension, the presence of total hip replacement (THR), post-biopsy haemorrhage, and abstinence from ejaculation. New evidence has been accrued since the release of PI-RADS v2, and this review aims to explore the key issues of patient preparation and their potential to further optimise the image quality of mpMRI.

Assessing the Clinical Value of Positive Multiparametric Magnetic Resonance Imaging in Young Men with a Suspicion of Prostate Cancer

BACKGROUND

There is a lack of evidence on the ability of magnetic resonance imaging (MRI) of the prostate to detect clinically significant prostate cancer (csPCa) in young patients.

OBJECTIVE

We hypothesised that the diagnostic performance of MRI for csPCa varies according to patient's age. To address this, we assessed the variation in the csPCa detection rate of MRI targeted biopsy (MRI-TBx) versus systematic random biopsy (SBx) across different patient ages.

DESIGN, SETTING, AND PARTICIPANTS

We retrospectively identified 930 patients who underwent prostate MRI and subsequent biopsy at two referral centres between 2013 and 2018. The Prostate Imaging Reporting and Data System (PI-RADS) was used for MRI reporting.

INTERVENTION

A lesion with a PI-RADS score of ≥3 detected at MRI received an MRI-TBx in addition to an SBx during the same session.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The outcome of our study was the relationship between age and csPCa detection rate at MRI-TBx and SBx, respectively. Clinically significant prostate cancer (PCa) was defined as the presence of PCa with Gleason score ≥3+4. Multivariable logistic regression analyses (MVAs) predicting csPCa detection were assessed for both MRI-TBx and SBx. Covariates were age, prostate-specific antigen density, PI-RADS score, previous biopsy status, digital rectal examination, and the number of targeted and systematic cores. The hypothesis that MRI accuracy in detecting csPCa differed by age was finally tested with a nonparametric loess analysis.

RESULTS AND LIMITATIONS

The overall rate of csPCa was 54% (n=506). Overall, 325 (35%) and 461 (50%) patients had csPCa at SBx and MRI-TBx, respectively. The median numbers of SBx and MRI-TBx cores were 12 (interquartile range [IQR]: 10-13) and 5 (IQR: 4-7), respectively. At MVA, age at biopsy was an independent predictor of csPCa at MRI-TBx only (odds ratio: 1.05), after accounting for confounders. In men aged less than roughly 50yr, SBx had a higher probability of detecting csPCa relative to MRI-TBx (25% vs 16% at 40yr). Conversely, in patients aged >50yr, the probability of csPCa was higher in MRI-TBx than in SBx, reaching the highest difference for very elderly patients (48% vs 68% at 80yr). The main limitations were the retrospective design and the small number of young patients.

CONCLUSIONS

In this study, we reported the performance of MRI and MRI-TBx in detecting csPCa changes according to patients' age.

PATIENT SUMMARY

In young patients, the performance of a systematic random biopsy in detecting clinically significant prostate cancer (csPCa) is higher relative to magnetic resonance imaging targeted biopsy (MRI-TBx), reflecting the lower accuracy of MRI in younger men. Conversely, in older patients, MRI-TBx showed a clinical benefit with a higher csPCa detection rate compared with SBx, suggesting an increase of MRI accuracy with the increase of age.

Multiparametric MRI - local staging of prostate cancer and beyond

Background Accurate local staging is critical for treatment planning and prognosis in patients with prostate cancer (PCa). The primary aim is to differentiate between organ-confined and locally advanced disease with the latter carrying a worse clinical prognosis. Multiparametric MRI (mpMRI) is the imaging modality of choice for the local staging of PCa and has an incremental value in assessing pelvic nodal disease and bone involvement. It has shown superior performance compared to traditional staging based on clinical nomograms, and provides additional information on the site and extent of disease. MRI has a high specificity for diagnosing extracapsular extension (ECE), seminal vesicle invasion (SVI) and lymph node (LN) metastases, however, sensitivity remains poor. As a result, extended pelvic LN dissection remains the gold standard for assessing pelvic nodal involvement, and there has been recent progress in developing advanced imaging techniques for more distal staging. Conclusions T2W-weighted imaging is the cornerstone for local staging of PCa. Imaging at 3T and incorporating both diffusion weighted and dynamic contrast enhanced imaging can further increase accuracy. "Next generation" imaging including whole body MRI and PET-MRI imaging using prostate specific membrane antigen (68Ga-PSMA), has shown promising for assessment of LN and bone involvement as compared to the traditional work-up using bone scintigraphy and body CT.

Stimulated echo based mapping (STEM) of T1 , T2 , and apparent diffusion coefficient: validation and protocol optimization

PURPOSE

To present a stimulated-echo based mapping (STEM) approach for simultaneous T₁ , T₂ , and ADC mapping.

METHODS

Diffusion-weighted stimulated-echo images with various combinations of mixing time (TM), TE, and b-value were acquired to enable simultaneous mapping of T₁ , T₂ , and ADC. The proposed STEM method was performed by densely sampling the TM-TE-b space in a phantom and in brain and prostate of healthy volunteers. T₁ , T₂ , and ADC from STEM were compared to reference mapping methods. Additionally, protocol optimization was performed to enable rapid STEM acquisition within 2 min by sparsely sampling the TM-TE-b space. The T₁ , T₂ , and ADC measurements from rapid acquisitions were compared to the densely sampled STEM for evaluation. Finally, a patient with biopsy-proven high-risk prostate cancer was imaged to demonstrate the ability of STEM to differentiate cancer and healthy tissues.

RESULTS

Relative to the reference measurements, densely sampled STEM provided accurate quantitative T₁ , T₂ , and ADC mapping in phantoms (R²  = 0.999, slope between 0.97-1.03), as well as in brain and prostate. Further, the T₁ , T₂ , and ADC measurements from the optimized rapid STEM acquisitions agreed closely with densely sampled STEM. Finally, STEM showed decreased T₂ and ADC in prostate cancer compared to healthy prostate tissue.

CONCLUSION

STEM provides accurate simultaneous mapping of T₁ , T₂ , and ADC. This method may enable rapid and accurate multi-parametric tissue characterization for clinical and research applications.

Quantitative diffusion MRI using reduced field-of-view and multi-shot acquisition techniques: Validation in phantoms and prostate imaging

PURPOSE

To evaluate the reproducibility of quantitative diffusion measurements obtained with reduced Field of View (rFOV) and Multi-shot EPI (msEPI) acquisitions, using single-shot EPI (ssEPI) as a reference.

METHODS

Diffusion phantom experiments, and prostate diffusion-weighted imaging in healthy volunteers and patients with known or suspected prostate cancer were performed across the three different sequences. Quantitative diffusion measurements of apparent diffusion coefficient, and diffusion kurtosis parameters (healthy volunteers), were obtained and compared across diffusion sequences (rFOV, msEPI, and ssEPI). Other possible confounding factors like b-value combinations and acquisition parameters were also investigated.

RESULTS

Both msEPI and rFOV have shown reproducible quantitative diffusion measurements relative to ssEPI; no significant difference in ADC was observed across pulse sequences in the standard diffusion phantom (p = 0.156), healthy volunteers (p ≥ 0.12) or patients (p ≥ 0.26). The ADC values within the non-cancerous central gland and peripheral zone of patients were 1.29 ± 0.17 × 10^-3 mm²/s and 1.74 ± 0.23 × 10^-3 mm²/s respectively. However, differences in quantitative diffusion parameters were observed across different number of averages for rFOV, and across b-value groups and diffusion models for all the three sequences.

CONCLUSION

Both rFOV and msEPI have the potential to provide high image quality with reproducible quantitative diffusion measurements in prostate diffusion MRI.

Technique of Multiparametric MR Imaging of the Prostate

Multiparametric MR imaging provides detailed anatomic assessment of the prostate as well as information that allows the detection and characterization of prostate cancer. To obtain high-quality MR imaging of the prostate, radiologists must understand sequence optimization to overcome commonly encountered technical challenges. This review discusses the techniques that are used in state-of-the-art MR imaging of the prostate, including imaging protocols, hardware considerations, and important aspects of patient preparation, with an emphasis on the recommendations provided in the prostate imaging-reporting and data system version 2 guidelines.

The longitudinal effect of ejaculation on seminal vesicle fluid volume and whole-prostate ADC as measured on prostate MRI

OBJECTIVE

To prospectively investigate the longitudinal effect of ejaculatory abstinence on MRI-measured seminal vesicle (SV) volume and whole-prostate ADC over consecutive days.

METHODS

15 healthy male volunteers (mean 35.9 years, range 27-53) underwent 3-T MRI at baseline and 1, 2 and 3 days post-ejaculation. Prostate and SV volumes were derived by volume segmentation and whole-gland apparent diffusion coefficient (ADC) values calculated. A mixed-effects linear regression compared ADC values and prostate/seminal vesicle volumes in each volunteer between studies in a pairwise manner.

RESULTS

All subjects completed the four MRIs. Mean prostate volume was 22.45 cm3 (range 13.04-31.21 cm3), with no change between the four studies (p = 0.89-0.99). 13/15 subjects showed SV volume reduction from baseline to day 1, with group-mean decreasing from 6.45 to 4.80 cm3 (-25.6%, p < 0.001), and a significant reduction from baseline to day 2 (-18.1%, p = 0.002). There was a significant volume increase from both day 1 (+21.3%, p = 0.006) and day 2 (+10.2%, p = 0.022) to day 3 post-ejaculation. There was a significant reduction in ADC from 1.105 at baseline to 1.056 × 10-3 mm2/s at day 1 (mean -4.3%, p = 0.009).

CONCLUSION

The longitudinal effect of ejaculation on SV volume was demonstrated. Significant reductions in SV volume and whole-gland ADC were observed post-ejaculation, supporting a 3-day period of abstinence before prostate MRI.

KEY POINTS

• Seminal vesicle volume significantly reduced 24 h post-ejaculation remaining reduced at day 2 • Seminal vesicle fluid volume significantly increased from day 1 to day 3 post-ejaculation • There was a significant reduction in whole-gland prostate ADC values day 1 post-ejaculation • 3-day abstinence from ejaculation is required to ensure maximal seminal vesicle distension.

Performance of a fast and high-resolution multi-echo spin-echo sequence for prostate T2 mapping across multiple systems

PURPOSE

To evaluate the performance of a multi-echo spin-echo sequence with k-t undersampling scheme (k-t T₂ ) in prostate cancer.

METHODS

Phantom experiments were performed at five systems to estimate the bias, short-term repeatability, and reproducibility across all systems expressed with the within-subject coefficient of variation (wCV). Monthly measurements were performed on two systems for long-term repeatability estimation. To evaluate clinical repeatability, two T₂ maps (voxel size 0.8 × 0.8 × 3 mm³ ; 5 min) were acquired at separate visits on one system for 13 prostate cancer patients. Repeatability was assessed per patient in relation to spatial resolution. T₂ values were compared for tumor, peripheral zone, and transition zone.

RESULTS

Phantom measurements showed a small bias (median = -0.9 ms) and good short-term repeatability (median wCV = 0.5%). Long-term repeatability was 0.9 and 1.1% and reproducibility between systems was 1.7%. The median bias observed in patients was -1.1 ms. At voxel level, the median wCV was 15%, dropping to 4% for structures of 0.5 cm³ . The median tumor T₂ values (79 ms) were significantly lower (P < 0.001) than in the peripheral zone (149 ms), but overlapped with the transition zone (91 ms).

CONCLUSIONS

Reproducible T₂ mapping of the prostate is feasible with good spatial resolution in a clinically reasonable scan time, allowing reliable measurement of T₂ in structures as small as 0.5 cm³ . Magn Reson Med 79:1586-1594, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

MR/US Fusion Technology: What Makes It Tick?

MR/US fusion biopsy has emerged as a significant refinement of traditional prostate cancer diagnostic techniques. Utilizing not only quantitative imaging suspicion information from mpMRI but also the spatial accuracy and three-dimensional localization allows such strategies to specifically sample areas of concern with the gland. As such, diagnostic certainty is markedly improved. In this manuscript, we aim to highlight the multidisciplinary approach (amongst urologists, radiologists, pathologists, imaging technologists, nursing staff, and patients) which is required to launch and maintain a successful prostate imaging program.

Multiparametric MR Imaging for Detection and Locoregional Staging of Prostate Cancer

Detection and staging of prostate cancer (PCa) based on digital rectal examination, prostate-specific antigen levels, and systematic transrectal ultrasound-guided biopsies show notorious limitations in light of the current needs of PCa management. Multiparametric magnetic resonance imaging (mpMRI) has emerged as a useful noninvasive imaging technique for detection, staging, assessment of aggressiveness, and treatment monitoring of PCa, combining anatomic high-resolution T2-weighted images with functional techniques, such as diffusion-weighted imaging and dynamic contrast enhancement evaluation. In this article, the authors review the technical aspects and the current clinical role of mpMRI for detection and locoregional staging of PCa.

The association between seminal vesicle size and duration of abstinence from ejaculation

There are few data describing the relationship between seminal vesicle (SV) size and duration of abstinence between ejaculations. This study evaluates the association between SV size and duration of abstinence from ejaculation using pelvic magnetic resonance imaging (MRI). Sexually active men 18-68 years old who underwent pelvic MRI for various medical indications were included. The date of last ejaculation was recorded, and the cross-sectional areas of the right and left seminal vesicles were calculated separately using mediolateral and anteroposterior measurements on T2-weighted MRI images. The association between SV area and duration of abstinence between ejaculations was determined via linear regression analysis. The study cohort consisted of 104 men with a mean age of 46.45 ± 11.4 (range 18-68) years old. Mean right and left SV cross-sectional areas were 744.1 ± 351.1 (range: 149.9-1794.7) mm² and 727.6 ± 359.2 (range 171.4-2248.4) mm² respectively. The mean duration of abstinence between ejaculations in the cohort was 3.6 ± 2.6 (range 1-15) days. Although no correlation between age and SV area was observed (r = .007, p = .947), linear regression analysis demonstrated a positive correlation between SV area and the duration of abstinence from ejaculation (r = .372, p = .0001). SV cross-sectional area increases with duration of abstinence from ejaculation and can be assessed using MRI. The use of SV size estimation may be applicable in diagnosis, risk stratification and treatment of urological diseases.

Does Abstinence From Ejaculation Before Prostate MRI Improve Evaluation of the Seminal Vesicles?

OBJECTIVE

The purpose of the present study is to determine whether abstinence from ejaculation before undergoing multiparametric prostate MRI increases seminal vesicle (SV) volume and therefore improves diagnostic interpretation of the SVs.

MATERIALS AND METHODS

This retrospective study included 238 patients who underwent 3-T MRI of the prostate over a 4-month period. Patients were requested to complete a questionnaire that asked how long it had been since their last ejaculation (i.e., < 3 days vs ≥ 3 days). Forty-two patients (mean patient age, 62.0 years) indicated that it had been less than 3 days since their last ejaculation and were designated as group 1, whereas the remainder indicated an interval of 3 days or more since their last ejaculation. A group of 42 age-matched subjects (mean patient age, 62.1 years) were randomly selected from the remaining 196 patients and were designated as group 2. SV volumes were measured manually. Two radiologists who were blinded to group assignment and patient characteristics scored the right and left SVs separately to determine diagnostic interpretability, which was scored on a 3-point scale as follows: a score of 1 denoted that the SVs were not dilated and the score was nondiagnostic, a score of 2 indicated that the SVs were not dilated but the score was diagnostic, and a score of 3 denoted that the SVs were dilated and the score was diagnostic. Volume differences and interpretability scores were analyzed using a t test. Interobserver agreement was analyzed using the Cohen kappa statistic. A separate analysis was performed to evaluate differences in diagnostic interpretability for patients 60 years and younger versus patients older than 60 years, by use of the chi-square test and relative risk ratio analysis.

RESULTS

The right, left, and total SV volumes for group 1 were 3.1 mL, 2.9 mL, and 6.0 mL, respectively, whereas those for group 2 were 4.7 mL, 4.1 mL, and 8.8 mL, respectively (p = 0.011). The mean interpretability scores for group 1 and group 2 were 2.0 and 2.5, respectively. For group 1, reader 1 and reader 2 assigned a nondiagnostic score for 10 and 13 patients, respectively, whereas for group 2, they assigned a nondiagnostic score for two and five patients, respectively (p = 0.01, for reader 1; and p = 0.03, for reader 2). For men in group 1 who were older than 60 years, reader 1 and reader 2 gave a nondiagnostic score for nine and 11 patients, respectively; whereas for men in group 2 who were older than 60 years, the readers gave a nondiagnostic score for two and five patients, respectively (p = 0.01, for reader 1; and p = 0.05, for reader 2).

CONCLUSION

For men older than 60 years, abstinence from ejaculation for 3 or more days before undergoing MRI examination resulted in larger SV volumes and lower rates of nondiagnostic evaluation and therefore might improve evaluation of SV invasion on multi-parametric MRI. The difference is less striking in men 60 years and younger.

[MR imaging of the prostate]

CLINICAL ISSUE

Prostate cancer is the most common form of cancer in men in Germany; however, there is a distinct difference between incidence and mortality.

STANDARD TREATMENT

The detection of prostate cancer is based on clinical and laboratory testing using serum prostate-specific antigen (PSA) levels and transrectal ultrasound with randomized biopsy.

DIAGNOSTIC WORK-UP

Multiparametric MR imaging of the prostate can provide valuable diagnostic information for detection of prostate cancer, especially after negative results of a biopsy prior to repeat biopsy.

PERFORMANCE

In addition the use of MR ultrasound fusion-guided biopsy has gained in diagnostic importance and has increased the prostate cancer detection rate.

ACHIEVEMENTS AND PRACTICAL RECOMMENDATIONS

The prostate imaging reporting and data system (PI-RADS) classification has standardized the reporting of prostate MRI which has positively influenced the acceptance by urologists.

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.

PI-RADS Prostate Imaging - Reporting and Data System: 2015, Version 2

The Prostate Imaging - Reporting and Data System Version 2 (PI-RADS™ v2) is the product of an international collaboration of the American College of Radiology (ACR), European Society of Uroradiology (ESUR), and AdMetech Foundation. It is designed to promote global standardization and diminish variation in the acquisition, interpretation, and reporting of prostate multiparametric magnetic resonance imaging (mpMRI) examination, and it is based on the best available evidence and expert consensus opinion. It establishes minimum acceptable technical parameters for prostate mpMRI, simplifies and standardizes terminology and content of reports, and provides assessment categories that summarize levels of suspicion or risk of clinically significant prostate cancer that can be used to assist selection of patients for biopsies and management. It is intended to be used in routine clinical practice and also to facilitate data collection and outcome monitoring for research.