Dynamic contrast-enhanced MRI of the prostate: An intraindividual assessment of the effect of temporal resolution on qualitative detection and quantitative analysis of histopathologically proven prostate cancer

[Application of dynamic contrast enhanced status in multiparametric magnetic resonance imaging for prostatic cancer with PI-RADS 4 lesion]

OBJECTIVE

To evaluate the diagnostic value of dynamic contrast enhanced (DCE) of multiparametric magnetic resonance imaging (mpMRI) for prostate imaging reporting and data system (PI-RADS) 4 lesion in prostate peripheral zone.

METHODS

The clinical data of patients with PI-RADS 4 lesion in prostate peripheral zone who underwent prostate biopsy from January 2018 to September 2021 in Peking University First Hospital were retrospectively included. According to DCE status, the patients were divided into the conventional group (4 points for diffusion-weighted imaging) and the comprehensive group (3 points for diffusion-weighted imaging + 1 point for DCE positive). Pearson's chi-square test or Fisher's exact test for comparison was conducted between prostate cancer and non-cancer patients. Univariate and multivariate Logistic regression were performed to analyze the correlation of positive biopsy with age, total prostate specific antigen (PSA), free PSA/total PSA (f/tPSA), prostate volume (PV), PSA density (PSAD) and DCE status.

RESULTS

Among the 267 prostate biopsy patients, 217 cases were diagnosed as prostatic cancer (81.27%) and 50 cases were non-cancer (18.73%). Statistical analysis between the prostatic cancer group and the non-cancer group showed that there were significant differences in age, tPSA, PV and PSAD (all P < 0.05), but no significant differences in f/tPSA between the two groups. About different PI-RADS 4 lesion groups, the conventional group and the comprehensive group showed significant difference in biopsy results (P=0.001), and the conventional group had a higher positive rate. The PV of comprehensive group was larger than that of the conventional group. Among the prostate cancer patients diagnosed by biopsy, statistical analysis between the conventional group and comprehensive group showed that there were not significant differences in International Society of Urological Pathology (ISUP) grade and distinguishing clinically significant prostate cancer (all P > 0.05). Logistic univariate analysis showed that the diagnosis of prostate cancer was related to age, tPSA, f/tPSA, PV and DCE group status (all P < 0.05). Multivariate analysis showed that age, tPSA, PV and DCE group status (all P < 0.05) were independent risk factors for the diagnosis of prostatic cancer.

CONCLUSION

tPSA, f/tPSA, PV and PSAD are the indicators to improve the diagnosis of prostatic cancer with PI-RADS 4 lesion in peripheral zone lesions. DCE status is worth considering, so that we can select patients for biopsy more accurately, reduce the rate of missed diagnosis of prostate cancer as well as avoid unnecessary prostate puncture.

[Prostate Imaging Reporting and Data System (PI-RADS) v 2.1: Overview and Critical Points]

The technical parameters and imaging interpretation criteria of the Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) using multiparametric MRI (mpMRI) are updated in PI-RADS v2.1. These changes have been an expected improvement for prostate cancer evaluation, although some issues remain unsolved, and new issues have been raised. In this review, a brief overview of PI-RADS v2.1 is and several critical points are discussed as follows: the need for more detailed protocols of mpMRI, lack of validation of the revised transition zone interpretation criteria, the need for clarification for the revised diffusion-weighted imaging and dynamic contrast-enhanced imaging criteria, anterior fibromuscular stroma and central zone assessment, assessment of background signal and tumor aggressiveness, changes in the structured report, the need for the parameters for imaging quality and performance control, and indications for expansion of the system to include other indications.

Canadian Association of Radiologists Prostate MRI White Paper

Prostate cancer is the most common malignancy and the third most common cause of death in Canadian men. In light of evolving diagnostic pathways for prostate cancer and the increased use of MRI, which now includes its use in men prior to biopsy, the Canadian Association of Radiologists established a Prostate MRI Working Group to produce a white paper to provide recommendations on establishing and maintaining a Prostate MRI Programme in the context of the Canadian healthcare system. The recommendations, which are based on available scientific evidence and/or expert consensus, are intended to maintain quality in image acquisition, interpretation, reporting and targeted biopsy to ensure optimal patient care. The paper covers technique, reporting, quality assurance and targeted biopsy considerations and includes appendices detailing suggested reporting templates, quality assessment tools and sample image acquisition protocols relevant to the Canadian healthcare context.

PI-RADS: multiparametric MRI in prostate cancer

Multiparametric MRI of the prostate gland has become the initial evaluation of biopsy naïve men with a clinical suspicion for prostate cancer. PI-RADS 2.1 is a joint initiative and framework for prostate MRI acquisition and reporting, which aims to standardize technique and interpretation across centers. Building upon experience accrued following the introduction of PI-RADS 2.0, version 2.1 provides key updates and important clarifications, although it is intended to be an active document, which continues to be updated. Continued advances in our understanding of prostate cancer and progress in imaging technology will undoubtedly shape future iterations of the reporting system.

Artificial intelligence and imaging biomarkers for prostate radiation therapy during and after treatment

Magnetic resonance imaging (MRI) is increasingly used in the management of prostate cancer (PCa). Quantitative MRI (qMRI) parameters, derived from multi-parametric MRI, provide indirect measures of tumour characteristics such as cellularity, angiogenesis and hypoxia. Using Artificial Intelligence (AI), relevant information and patterns can be efficiently identified in these complex data to develop quantitative imaging biomarkers (QIBs) of tumour function and biology. Such QIBs have already demonstrated potential in the diagnosis and staging of PCa. In this review, we explore the role of these QIBs in monitoring treatment response during and after PCa radiotherapy (RT). Recurrence of PCa after RT is not uncommon, and early detection prior to development of metastases provides an opportunity for salvage treatments with curative intent. However, the current method of monitoring treatment response using prostate-specific antigen levels lacks specificity. QIBs, derived from qMRI and developed using AI techniques, can be used to monitor biological changes post-RT providing the potential for accurate and early diagnosis of recurrent disease.

Diagnostic Performance of PI-RADS v2, Proposed Adjusted PI-RADS v2 and Biparametric Magnetic Resonance Imaging for Prostate Cancer Detection: A Preliminary Study

Purpose: To evaluate the diagnostic performance of PI-RADS v2, proposed adjustments to PI-RADS v2 (PA PI-RADS v2) and biparametric magnetic resonance imaging (MRI) for prostate cancer detection. Methods: A retrospective cohort of 224 patients with suspected prostate cancer was included from January 2016 to November 2018. All the patients underwent a multi-parametric MR scan before biopsy. Two radiologists independently evaluated the MR examinations using PI-RADS v2, PA PI-RADS v2, and a biparametric MRI protocol, respectively. Receiver operating characteristic (ROC) curves for the three different protocols were drawn. Results: In total, 90 out of 224 cases (40.18%) were pathologically diagnosed as prostate cancer. The area under the ROC curves (AUC) for diagnosing prostate cancers by biparametric MRI, PI-RADS v2, and PA PI-RADS v2 were 0.938, 0.935, and 0.934, respectively. For cancers in the peripheral zone (PZ), the diagnostic sensitivity was 97.1% for PI-RADS v2/PA PI-RADS v2 and 96.2% for biparametric MRI. Moreover, the specificity was 84.0% for biparametric MRI and 58.0% for PI-RADS v2/PA PI-RADS v2. For cancers in the transition zone (TZ), the diagnostic sensitivity was 93.4% for PA PI-RADS v2 and 88.2% for biparametric MRI/PI-RADS v2. Furthermore, the specificity was 95.4% for biparametric MRI/PI-RADS v2 and 78.0% for PA PI-RADS v2. Conclusions: The overall diagnostic performance of the three protocols showed minimal differences. For lesions assessed as being category 3 using the biparametric MRI protocol, PI-RADS v2, or PA PI-RADS v2, it was thought prostate cancer detection could be improved. Attention should be paid to false positive results when PI-RADS v2 or PA PI-RADS v2 are used.

Signal intensity form of the Tofts model for quantitative analysis of prostate dynamic contrast enhanced MRI data

The aim of this study is to develop a signal intensity (S(t)) form of the standard Tofts pharmacokinetic model that avoids the need to calculate tissue contrast agent concentration (C(t)) as function of time (t). We refer to this as 'SI-Tofts' model. Physiological parameters (K ^trans and v _e) calculated using the SI-Tofts and standard Tofts models were compared by using simulations and human prostate dynamic contrast enhanced (DCE) MRI data. This approach was also applied to the Patlak model to compare K ^trans values calculated from C(t) and S(t). Simulations were performed on DCE-MRI data from the quantitative imaging biomarkers alliance to validate SI-Tofts model. In addition, ultrafast DCE-MRI data were acquired from 18 prostate cancer patients on a Philips Achieva 3T-TX scanner. Regions-of-interest (ROIs) for prostate cancer, normal tissue, gluteal muscle, and iliac artery were manually traced. The C(t) was calculated for each ROI using the standard model with measured pre-contrast tissue T ₁ values. Both the simulation and clinical results showed strong correlation (r = 0.87-0.99, p < 0.001) for K ^trans and v _e calculated from the SI-Tofts and standard Tofts models. The SI-Tofts model with a correction factor using the T ₁ ratio of blood to tissue significantly improved the K ^trans estimates. The correlation of K ^trans obtained from the Patlak model with C(t) vs S(t) was also strong (r = 0.95-0.99, p < 0.001). These preliminary results suggest that physiological parameters from DCE-MRI can be reliably estimated from the SI-Tofts model without contrast agent concentration calculation.

PI-RADS 2.1 - Image Interpretation: The Most Important Updates and Their Clinical Implications

BACKGROUND

 Multiparametric magnetic resonance imaging (MRI) of the prostate plays a central role in the diagnosis of patients with suspected prostate cancer. The increasing distribution and application of the guideline for the standardization of image acquisition, evaluation, and reporting (Prostate Imaging - Reporting and Data System, PI-RADS), which was updated in 2019 to version 2.1, contributes to the success of the technique.

MATERIALS AND METHODS

 The most important updates of PI-RADS version 2.1 presented in 2019 compared to the previous version PI-RADS 2.0 are highlighted and interpreted with regard to their clinical implications.

RESULTS

 PI-RADS version 2.1 aims to simplify the application of the scoring scheme without changing the basic concept of dominant sequences (DWI in the peripheral zone, T2 in the transition zone). Of particular importance are the increasing role of diffusion-weighted imaging in the transition zone, the now mandatory high b-value of at least 1400 s/mm², and new information on the assessment of the central zone and the anterior fibromuscular stroma.

CONCLUSION

 PI-RADS version 2.1 published in 2019 addresses a number of changes to the previous version, including both the examination technique and image interpretation. Prospective clinical studies have yet to prove the extent to which the goals of reducing interreader variability and increasing the detection rate in the transition zone will be achieved.

KEY POINTS

  · The new PI-RADS version 2.1. includes changes regarding image interpretation and examination technique. · The role of diffusion-weighted imaging is strengthened in the transition zone. · An ultra-high b-value of at least 1400 s/mm2 is mandatory according to PI-RADS 2.1. · Biparametric MRI is not recommended for general application.

CITATION FORMAT

· Beyer T, Schlemmer H, Weber M et al. PI-RADS 2.1 - Image Interpretation: The Most Important Updates and Their Clinical Implications. Fortschr Röntgenstr 2021; 193: 787 - 795.

PI-RADS Version 2.1: A Critical Review, From the AJR Special Series on Radiology Reporting and Data Systems

PI-RADS version 2.1 updates the technical parameters for multiparametric MRI (mpMRI) of the prostate and revises the imaging interpretation criteria while maintaining the framework introduced in version 2. These changes have been considered an improvement, although some issues remain unresolved, and new issues have emerged. Areas for improvement discussed in this review include the need for more detailed mpMRI protocols with optimization for 1.5-T and 3-T systems; lack of validation of revised transition zone interpretation criteria and need for clarifications of the revised DWI and dynamic contrast-enhanced imaging criteria and central zone (CZ) assessment; the need for systematic evaluation and reporting of background changes in signal intensity in the prostate that can negatively affect cancer detection; creation of a new category for lesions that do not fit into the PI-RADS assessment categories (i.e., PI-RADS M category); inclusion of quantitative parameters beyond size to evaluate lesion aggressiveness; adjustments to the structured report template, including standardized assessment of the risk of extraprostatic extension; development of parameters for image quality and performance control; and suggestions for expansion of the system to other indications (e.g., active surveillance and recurrence).

Assessment of the compliance with minimum acceptable technical parameters proposed by PI-RADS v2 guidelines in multiparametric prostate MRI acquisition in tertiary referral hospitals in the Republic of Turkey

PURPOSE

Although the clinical use of multiparametric prostate magnetic resonance imaging (mpMRI) is increasing, the adherence to parameters for mpMRI, which had been described in the Prostate Imaging-Reporting and Data System version 2 (PI-RADS v2) for an optimum image acquisition is unknown. In this paper, we aimed to determine the compliance with the minimum acceptable technical parameters for prostate mpMRI defined by PI-RADS v2 in tertiary care centers in Turkey.

METHODS

We sent a survey to all radiology departments of tertiary referral hospitals in Turkey (n=120) to evaluate their adherence to PI-RADS v2 technical specifications. Statistical analysis was performed using chi-square, Fisher exact, ANOVA, and the Student t tests. The cutoff values for image acquisition times were also determined with receiver operating characteristics (ROC) analysis. P values <0.05 were considered statistically significant.

RESULTS

One hundred and eleven clinics responded to our survey (response rate, 92.5%). Prostate MRI was reported to be performed in 61 centers, of which 26 (42.6%) used 3 T (Tesla) scanner while 35 (57.4%) used 1.5 T. The adherence to slice thickness, in-plane phase and frequency resolutions on T2-weighted imaging were 68.9%, 41%, and 9.8%, respectively. The adherence to the same parameters on diffusion-weighted imaging (DWI) were higher compared with T2-weighted imaging (85.2%, 62.3%, and 78.7%, respectively). In comparative analysis, the adherence to slice thickness, field of view (FOV) and in-plane phase resolution on T2-weighted imaging were higher for 3 T compared with 1.5 T scanners (P = 0.004, P = 0.041, and P = 0.001, respectively). T2-weighted imaging acquisition time was significantly longer for the centers that adhered to FOV (P = 0.034) and in-plane T2-weighted imaging phase resolution (P = 0.028). The DWI scan time was significantly longer when they adhered to DWI-FOV (P = 0.014) and b value ≥1400 s/mm2 (P = 0.008). The calculated cutoff of scan times were 220 s in T2-weighted imaging and 312 s in DWI to ensure the compliance with voxel sizes and b value criteria.

CONCLUSION

The tertiary referral centers in Turkey did not meet majority of the technical specifications of PI-RADS v2 during prostate MRI acquisition. Awareness to the minimum acceptable technical parameters of mpMRI should be increased to potentially improve the quality of prostate cancer imaging.

PI-RADS version 2.1: one small step for prostate MRI

Multiparametric (mp) prostate magnetic resonance imaging (MRI) is playing an increasingly prominent role in the diagnostic work-up of patients with suspected prostate cancer. Performing mpMRI before biopsy offers several advantages including biopsy avoidance under certain clinical circumstances and targeting biopsy of suspicious lesions to enable the correct diagnosis. The success of the technique is heavily dependent on high-quality image acquisition, interpretation, and report communication, all areas addressed by previous versions of the Prostate Imaging-Reporting and Data System (PI-RADS) recommendations. Numerous studies have validated the approach, but the widespread adoption of PI-RADS version 2 has also highlighted inconsistencies and limitations, particularly relating to interobserver variability for evaluation of the transition zone. These limitations are addressed in the recently released version 2.1. In this article, we highlight the key changes proposed in PI-RADS v2.1 and explore the background reasoning and evidence for the recommendations.

Compressed Sensing Radial Sampling MRI of Prostate Perfusion: Utility for Detection of Prostate Cancer

Purpose To investigate the diagnostic performance of a dual-parameter approach by combining either volumetric interpolated breath-hold examination (VIBE)- or golden-angle radial sparse parallel (GRASP)-derived dynamic contrast agent-enhanced (DCE) MRI with established diffusion-weighted imaging (DWI) compared with traditional single-parameter evaluations on the basis of DWI alone. Materials and Methods Ninety-four male participants (66 years ± 7 [standard deviation]) were prospectively evaluated at 3.0-T MRI for clinical suspicion of prostate cancer. Included were 101 peripheral zone prostate cancer lesions. Histopathologic confirmation at MRI transrectal US fusion biopsy was matched with normal contralateral prostate parenchyma. MRI was performed with diffusion weighting and DCE by using GRASP (temporal resolution, 2.5 seconds) or VIBE (temporal resolution, 10 seconds). Perfusion (influx forward volume transfer constant [K^trans] and rate constant [K_ep]) and apparent diffusion coefficient (ADC) parameters were determined by tumor volume analysis. Areas under the receiver operating characteristic curve were compared for both sequences. Results Evaluated were 101 prostate cancer lesions (GRASP, 61 lesions; VIBE, 40 lesions). In a combined analysis, diffusion and perfusion parameters ADC with K^trans or K_ep acquired with GRASP had higher diagnostic performance compared with diffusion characteristics alone (area under the curve, 0.97 ± 0.02 [standard error] vs 0.93 ± 0.03; P < .006 and .021, respectively), whereas ADC with perfusion parameters acquired with VIBE had no additional benefit (area under the curve, 0.94 ± 0.03 vs 0.93 ± 0.04; P = .18and .50, respectively, for combination of ADC with K^trans and K_ep). Conclusion If used in a dual-parameter model, incorporating diffusion and perfusion characteristics, the golden-angle radial sparse parallel acquisition technique improves the diagnostic performance of multiparametric MRI examinations of the prostate. This effect could not be observed combining diffusing with perfusion parameters acquired with volumetric interpolated breath-hold examination. © RSNA, 2018.

Imaging Facilities' Adherence to PI-RADS v2 Minimum Technical Standards for the Performance of Prostate MRI

PURPOSE

This study aimed to assess variability in imaging facilities' adherence to the minimum technical standards for prostate magnetic resonance imaging acquisition established by Prostate Imaging-Reporting and Data System (PI-RADS) version 2 (v2).

METHODS

A total of 107 prostate magnetic resonance imaging examinations performed at 107 unique imaging facilities after the release of PI-RADS v2 and that were referred to a tertiary care center for secondary interpretation were included. Image sets, DICOM headers, and outside reports were reviewed to assess adherence to 21 selected PI-RADS v2 minimum technical standards.

RESULTS

Hardware arrangements were 23.1%, 1.5T without endorectal coil; 7.7%, 1.5T with endorectal coil; 63.5%, 3T without endorectal coil; and 5.8%, 3T with endorectal coil. Adherence to minimum standards was lowest on T2 weighted imaging (T2WI) for frequency resolution ≤0.4 mm (16.8%) and phase resolution ≤0.7 mm (48.6%), lowest on diffusion-weighted imaging (DWI) for field of view (FOV) 120-220 mm (30.0%), and lowest on dynamic contrast-enhanced (DCE) imaging for slice thickness 3 mm (33.3%) and temporal resolution <10 s (31.5%). High b-value (≥1400 s/mm²) images were included in 58.0% (calculated in 25.9%). Adherence to T2WI phase resolution and DWI inter-slice gap were greater (P < .05) at 3T than at 1.5T. Adherence did not differ (P > .05) for any parameter between examinations performed with and without an endorectal coil. Adherence was greater for examinations performed at teaching facilities for T2WI slice thickness and DCE temporal resolution (P < .05). Adherence was not better for examinations performed in 2016 than in 2015 for any parameter (P > .05).

CONCLUSION

Facilities' adherence to PI-RADS v2 minimum technical standards was variable, being particularly poor for T2WI frequency resolution and DCE temporal resolution. The standards warrant greater community education. Certain technical standards may be too stringent, and revisions should be considered.

Proposed Adjustments to PI-RADS Version 2 Decision Rules: Impact on Prostate Cancer Detection

Purpose To test the impact of existing Prostate Imaging Reporting and Data System (PI-RADS) version 2 (V2) decision rules, as well as of proposed adjustments to these decision rules, on detection of Gleason score (GS) 7 or greater (GS ≥7) prostate cancer. Materials and Methods Two radiologists independently provided PI-RADS V2 scores for the dominant lesion on 343 prostate magnetic resonance (MR) examinations. Diagnostic performance for GS ≥7 tumor was assessed by using MR imaging-ultrasonography fusion-targeted biopsy as the reference. The impact of existing PI-RADS V2 decision rules, as well as a series of exploratory proposed adjustments, on the frequency of GS ≥7 tumor detection, was evaluated. Results A total of 210 lesions were benign, 43 were GS 6, and 90 were GS ≥7. Lesions were GS ≥7 in 0%-4.1% of PI-RADS categories 1 and 2, 11.4%-27.1% of PI-RADS category 3, 44.4%-49.3% of PI-RADS category 4, and 72.1%-73.7% of PI-RADS category 5 lesions. PI-RADS category 4 or greater had sensitivity of 78.9%-87.8% and specificity of 75.5%-79.1 for detecting GS ≥7 tumor. The frequency of GS ≥7 tumor for existing PI-RADS V2 decision rules was 30.0%-33.3% in peripheral zone (PZ) lesions upgraded from category 3 to 4 based on dynamic contrast enhancement (DCE) score of positive; 50.0%-66.7% in transition zone (TZ) lesions upgraded from category 3 to 4 based on diffusion-weighted imaging (DWI) score of 5; and 71.7%-72.7% of lesions in both zones upgraded from category 4 to 5 based on size of 15 mm or greater. The frequency of GS ≥7 tumor for proposed adjustments to the decision rules was 30.0%-60.0% for TZ lesions upgraded from category 3 to 4 based on DWI score of 4; 33.3%-57.1% for TZ lesions upgraded from category 3 to 4 based on DCE score of positive when incorporating new criteria (unencapsulated sheetlike enhancement) for DCE score of positive in TZ; and 56.4%-61.9% for lesions in both zones upgraded from category 4 to 5 based on size of 10-14 mm. Other proposed adjustments yielded GS ≥7 tumor in less than 15% of cases for one or more readers. Conclusion Existing PI-RADS V2 decision rules exhibited reasonable performance in detecting GS ≥7 tumor. Several proposed adjustments to the criteria (in TZ, upgrading category 3 to 4 based on DWI score of 4 or modified DCE score of positive; in PZ or TZ, upgrading category 4 to 5 based on size of 10-14 mm) may also have value for this purpose. ^© RSNA, 2016 Online supplemental material is available for this article.