Diffusion and perfusion MR imaging of the prostate

CCT-Unet: A U-Shaped Network Based on Convolution Coupled Transformer for Segmentation of Peripheral and Transition Zones in Prostate MRI

The accurate segmentation of prostate region in magnetic resonance imaging (MRI) can provide reliable basis for artificially intelligent diagnosis of prostate cancer. Transformer-based models have been increasingly used in image analysis due to their ability to acquire long-term global contextual features. Although Transformer can provide feature representations of the overall appearance and contour representations at long distance, it does not perform well on small-scale datasets of prostate MRI due to its insensitivity to local variation such as the heterogeneity of the grayscale intensities in the peripheral zone and transition zone across patients; meanwhile, the convolutional neural network (CNN) could retain these local features well. Therefore, a robust prostate segmentation model that can aggregate the characteristics of CNN and Transformer is desired. In this work, a U-shaped network based on the convolution coupled Transformer is proposed for segmentation of peripheral and transition zones in prostate MRI, named the convolution coupled Transformer U-Net (CCT-Unet). The convolutional embedding block is first designed for encoding high-resolution input to retain the edge detail of the image. Then the convolution coupled Transformer block is proposed to enhance the ability of local feature extraction and capture long-term correlation that encompass anatomical information. The feature conversion module is also proposed to alleviate the semantic gap in the process of jumping connection. Extensive experiments have been conducted to compare our CCT-Unet with several state-of-the-art methods on both the ProstateX open dataset and the self-bulit Huashan dataset, and the results have consistently shown the accuracy and robustness of our CCT-Unet in MRI prostate segmentation.

MR fingerprinting of the prostate

Multiparametric magnetic resonance imaging (mpMRI) has been adopted as the key tool for detection, localization, characterization, and risk stratification of patients suspected to have prostate cancer. Despite advantages over systematic biopsy, the interpretation of prostate mpMRI has limitations including a steep learning curve, leading to considerable interobserver variation. There is growing interest in clinical translation of quantitative imaging techniques for more objective lesion assessment. However, traditional mapping techniques are slow, precluding their use in the clinic. Magnetic resonance fingerprinting (MRF) is an efficient approach for quantitative maps of multiple tissue properties simultaneously. The T₁ and T₂ values obtained with MRF have been validated with phantom studies as well as in normal volunteers and patients. Studies have shown that MRF-derived T₁ and T₂ along with ADC values are all significant independent predictors in the differentiation between normal prostate tissue and prostate cancer, and hold promise in differentiating low and intermediate/high-grade cancers. This review seeks to introduce the basics of the prostate MRF technique, discuss the potential applications of prostate MRF for the characterization of prostate cancer, and describes ongoing areas of research.

Emerging role of multiparametric magnetic resonance imaging in identifying clinically relevant localized prostate cancer

PURPOSE OF REVIEW

To explore the recent advances and utility of multiparametric magnetic resonance imaging (mpMRI) in the diagnosis and risk-stratification of prostate cancer.

RECENT FINDINGS

Low-risk, clinically insignificant prostate cancer has a decreased risk of morbidity or mortality. Meanwhile, patients with intermediate and high-risk prostate cancer may significantly benefit from interventions like radiation or surgery. To appropriately risk stratify these patients, MRI has emerged as the imaging modality in the last decade to assist in defining prostate cancer significance, location, and biologic aggressiveness. Traditional 12-core transrectal ultrasound-guided biopsy is associated with over-detection, and ultimately over-treatment of clinically insignificant disease, and the under-detection of clinically significant disease. Biopsy accuracy is improved with MRI-guided targeted biopsy and with the use of standardized risk stratification imaging score systems. Cancer detection accuracy is further improved with combined biopsy techniques that include both systematic and MRI-targeted biopsy that aid in detection of MRI-invisible lesions.

SUMMARY

mpMRI is an area of expanding innovation that continues to refine the diagnostic accuracy of prostate biopsies. As mpMRI-targeted biopsy in prostate cancer becomes more commonplace, advances like artificial intelligence and less invasive dynamic metabolic imaging will continue to improve the utility of MRI.

MRI-targeted biopsy versus standard transrectal ultrasound-guided biopsy: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

For men with a suspicion of prostate cancer (PCa), the transrectal ultrasound-guided biopsy (TRUS-Bx) was recommended. Multi-parametric magnetic resonance imaging (mp-MRI) could be more useful to more accurately selected patients who are with a clinical suspicion of PCa and eligible for biopsy, and avoid a biopsy if the result was negative. In the present study, we compared the MRI-targeted biopsy (MRI-TBx) with TRUS-Bx.

METHODS

We searched the following online database: PubMed, Embase, and Cochrane Library, and the search was updated to March 2019.

RESULTS

Finally, a total of 8 randomized controlled trials (RCTs) comprising 2593 patients were enrolled in the final analysis. MRI-TBx and TRUS-Bx did not significantly differ in overall PCa (RR = 1.30; 95% CI 0.98-1.72; P = 0.067), clinically significant PCa (RR = 1.35; 95% CI 0.98-1.86; P = 0.065), and clinically insignificant PCa (RR = 0.76; 95% CI 0.40-1.46; P = 0.416). While in patients with initial biopsy, MRI-TBx had a significantly higher detection rate of overall PCa (RR = 1.40; 95% CI 1.01-1.94; P = 0.045).

CONCLUSION

In the present study, we found that MRI-TBx potentially benefits the detection of overall and clinically significant PCa compared with TRUS-Bx in patients with a suspicion of PCa. Furthermore, in patients with initial biopsy, MRI-TBx had a significantly higher detection rate of overall PCa and a potentially higher detection rate of clinically significant PCa. While for patients with prior negative biopsy, we did not detect significant differences in overall and clinically significant PCa between two groups. More large and multicenter RCTs are further required.

Multiparametric magnetic resonance imaging and multiparametric magnetic resonance imaging-guided biopsy in the diagnostic pathway of prostate cancer

Multiparametric magnetic resonance imaging (mpMRI) of the prostate and mpMRI-guided biopsy have proved to be a valuable part of the diagnostic pathway for prostate cancer. This review reports on the current results in terms of clinical performance of these diagnostic tools and their role in clinical decision-making.

Multiparametric MRI for prostate cancer diagnosis: current status and future directions

The current diagnostic pathway for prostate cancer has resulted in overdiagnosis and consequent overtreatment as well as underdiagnosis and missed diagnoses in many men. Multiparametric MRI (mpMRI) of the prostate has been identified as a test that could mitigate these diagnostic errors. The performance of mpMRI can vary depending on the population being studied, the execution of the MRI itself, the experience of the radiologist, whether additional biomarkers are considered and whether mpMRI-targeted biopsy is carried out alone or in addition to systematic biopsy. A number of challenges to implementation remain, such as ensuring high-quality execution and reporting of mpMRI and ensuring that this diagnostic pathway is cost-effective. Nevertheless, emerging clinical trial data support the adoption of this technology as part of the standard of care for the diagnosis of prostate cancer.

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

OBJECTIVE

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

ANIMALS

12 healthy sexually intact adult Beagles.

PROCEDURES

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

RESULTS

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

CONCLUSIONS AND CLINICAL RELEVANCE

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

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.

Diffusion-Weighted Genitourinary Imaging

This review article aims to provide an overview on of diffusion-weighted MR imaging (DW-MR imaging) in the urogenital tract. Compared with conventional cross-sectional imaging methods, the additional value of DW-MR imaging in the detection and further characterization of benign and malignant lesions of the kidneys, bladder, prostate, and pelvic lymph nodes is discussed as well as the role of DW-MR imaging in the evaluation of treatment response.

Comparing Three Different Techniques for Magnetic Resonance Imaging-targeted Prostate Biopsies: A Systematic Review of In-bore versus Magnetic Resonance Imaging-transrectal Ultrasound fusion versus Cognitive Registration. Is There a Preferred Technique?

CONTEXT

The introduction of magnetic resonance imaging-guided biopsies (MRI-GB) has changed the paradigm concerning prostate biopsies. Three techniques of MRI-GB are available: (1) in-bore MRI target biopsy (MRI-TB), (2) MRI-transrectal ultrasound fusion (FUS-TB), and (3) cognitive registration (COG-TB).

OBJECTIVE

To evaluate whether MRI-GB has increased detection rates of (clinically significant) prostate cancer (PCa) compared with transrectal ultrasound-guided biopsy (TRUS-GB) in patients at risk for PCa, and which technique of MRI-GB has the highest detection rate of (clinically significant) PCa.

EVIDENCE ACQUISITION

We performed a literature search in PubMed, Embase, and CENTRAL databases. Studies were evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 checklist and START recommendations. The initial search identified 2562 studies and 43 were included in the meta-analysis.

EVIDENCE SYNTHESIS

Among the included studies 11 used MRI-TB, 17 used FUS-TB, 11 used COG-TB, and four used a combination of techniques. In 34 studies concurrent TRUS-GB was performed. There was no significant difference between MRI-GB (all techniques combined) and TRUS-GB for overall PCa detection (relative risk [RR] 0.97 [0.90-1.07]). MRI-GB had higher detection rates of clinically significant PCa (csPCa) compared with TRUS-GB (RR 1.16 [1.02-1.32]), and a lower yield of insignificant PCa (RR 0.47 [0.35-0.63]). There was a significant advantage (p = 0.02) of MRI-TB compared with COG-TB for overall PCa detection. For overall PCa detection there was no significant advantage of MRI-TB compared with FUS-TB (p=0.13), and neither for FUS-TB compared with COG-TB (p=0.11). For csPCa detection there was no significant advantage of any one technique of MRI-GB. The impact of lesion characteristics such as size and localisation could not be assessed.

CONCLUSIONS

MRI-GB had similar overall PCa detection rates compared with TRUS-GB, increased rates of csPCa, and decreased rates of insignificant PCa. MRI-TB has a superior overall PCa detection compared with COG-TB. FUS-TB and MRI-TB appear to have similar detection rates. Head-to-head comparisons of MRI-GB techniques are limited and are needed to confirm our findings.

PATIENT SUMMARY

Our review shows that magnetic resonance imaging-guided biopsy detects more clinically significant prostate cancer (PCa) and less insignificant PCa compared with systematic biopsy in men at risk for PCa.

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.

An Ex Vivo Phantom Validation Study of an MRI-Transrectal Ultrasound Fusion Device for Targeted Prostate Biopsy

OBJECTIVES

To evaluate the ex vivo accuracy of an MRI-TRUS fusion device for guiding targeted prostate biopsies, to identify the origin of errors, and to evaluate the likelihood that lesions can be accurately targeted.

MATERIALS AND METHODS

Three prostate phantoms were used to perform 27 biopsies using transperineal MRI-TRUS fusion. All phantoms underwent 3-T MRI. The prostate contour and nine lesions were delineated onto the MRI. A 3D-US dataset was generated and fused with the MRI. Per lesion, one needle was virtually planned. The postbiopsy needle location was virtually registered. The needle trajectory was marked using an MRI-safe guidewire. Postinterventional MRI was performed. The coordinates of the lesion on preinterventional MRI, the virtually planned needle, the virtually registered needle, and the marked needle trajectory on postinterventional MRI were documented and used to calculate the planning error (PE), targeting error (TE), and overall error (OE). Using the OE in the transversal plane, an upper one-sided tolerance interval was calculated to assess the likelihood that a biopsy needle was on target.

RESULTS

In the transversal plane, the mean PE, TE, and OE were 1.18, 0.39, and 2.33 mm, respectively. Using a single biopsy core, the likelihood that lesions with a diameter of 2 mm can be accurately targeted is 26%; lesions of 3 mm 61%; lesions of 4 mm 86%; lesions of 5 mm 96%; and lesions of 6 mm 99%. The likelihood of accurate sampling increases if more biopsy cores are used.

CONCLUSION

MRI-TRUS fusion allows for accurate sampling of MRI-identified lesions with an OE of 2.33 mm. Lesions with a diameter of 3 mm or more can be accurately targeted. These results should be considered the lower limit of in vivo accuracy.

Role of multiparametric magnetic resonance imaging in early detection of prostate cancer

Abstract

Most prostate cancers (PC) are currently found on the basis of an elevated PSA, although this biomarker has only moderate accuracy. Histological confirmation is traditionally obtained by random transrectal ultrasound guided biopsy, but this approach may underestimate PC. It is generally accepted that a clinically significant PC requires treatment, but in case of an non-significant PC, deferment of treatment and inclusion in an active surveillance program is a valid option. The implementation of multiparametric magnetic resonance imaging (mpMRI) into a screening program may reduce the risk of overdetection of non-significant PC and improve the early detection of clinically significant PC. A mpMRI consists of T2-weighted images supplemented with diffusion-weighted imaging, dynamic contrast enhanced imaging, and/or magnetic resonance spectroscopic imaging and is preferably performed and reported according to the uniform quality standards of the Prostate Imaging Reporting and Data System (PIRADS). International guidelines currently recommend mpMRI in patients with persistently rising PSA and previous negative biopsies, but mpMRI may also be used before first biopsy to improve the biopsy yield by targeting suspicious lesions or to assist in the selection of low-risk patients in whom consideration could be given for surveillance.

Teaching Points

• MpMRI may be used to detect or exclude significant prostate cancer.

• MpMRI can guide targeted rebiopsy in patients with previous negative biopsies.

• In patients with negative mpMRI consideration could be given for surveillance.

• MpMRI may add valuable information for the optimal treatment selection.

Value of preoperative MRI for prostate cancer staging and continence outcomes prior to prostatectomy: A review of the literature

Pelvic imaging in newly diagnosed prostate cancer is primarily used for staging prior to definitive treatment. Over the past decade use of magnetic resonance imaging (MRI) for pre-surgical planning has increased, as well has he technology and methods for performing prostate MRI. To investigate and define the different MRI technologies available and further assess MRI technology ability to predict pathologic stage. Searching PubMed, we identified current published literature, where the cohort population underwent pre-operative MRI followed by prostatectomy. Keywords used in the PubMed literature search included: MRI, prostate cancer, prostate cancer staging, multiparamentric MRI and incontinence. Papers were included for review if they discussed use of MRI prior to prostatectomy and had corresponding pathologic data, staging, incontinence, and surgical outcomes. Primary information noted was MRI sensitivity, specificity and overall accuracy for detecting extracapsular extension (ECE) and seminal vesicle involvement (SVI). Secondary information derived included assessing the surgical influence of staging information, and identifying predictors of urinary incontinence recovery. Review of the literature showed that in regards to extracapsular extension the reported MRI accuracy ranged from 76%-98%, sensitivity from 20%-90% and specificity from 82%-99%. As for seminal vesicle involvement the reported MRI accuracy ranged from 76%-98%, sensitivity from 20%-90% and specificity from 82%-99%. There is a widely varying sensitivity and specificity for both ECE and SVI and the wide variability in the MRI technology used in the literature supports that use of MRI technology for prostate cancer remains investigational.

High-resolution diffusion-weighted imaging of the prostate

OBJECTIVE

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

SUBJECTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Multiparametric magnetic resonance imaging of the prostate: technical aspects and role in clinical management

The heterogeneity and largely indolent nature of prostate cancer require better tools to avoid overdetection of low-risk disease and improve diagnostic accuracy in high-risk patients. During the last 3 decades, magnetic resonance imaging (MRI) has evolved to become the most accurate imaging technique for prostate cancer detection and staging, with a promising role in risk stratification. Because each MRI technique has advantages and limitations, state of the art of the so-called multiparametric MRI of the prostate is achieved combining anatomical T2-weighted imaging integrated with other techniques in which image contrast is related to the pathophysiology of the disease, such as diffusion-weighted imaging, dynamic contrast-enhanced imaging, and MR spectroscopy. After reviewing this article, readers will understand the clinical challenges in the management of patients with confirmed or suspected prostate cancer, when and how multiparametric MRI of the prostate can provide meaningful information, and how to perform and interpret it.

Multiparametric MRI for recurrent prostate cancer post radical prostatectomy and postradiation therapy

The clinical suspicion of local recurrence of prostate cancer (PCa) after radical prostatectomy (RP) and after radiation therapy (RT) is based on the onset of biochemical failure. The aim of this paper was to review the current role of multiparametric-MRI (mp-MRI) in the detection of locoregional recurrence. A systematic literature search using the Medline and Cochrane Library databases was performed from January 1995 up to November 2013. Bibliographies of retrieved and review articles were also examined. Only those articles reporting complete data with clinical relevance for the present review were selected. This review article is divided into two major parts: the first one considers the role of mp-MRI in the detection of PCa local recurrence after RP; the second part provides an insight about the impact of mp-MRI in the depiction of locoregional recurrence after RT (interstitial or external beam). Published data indicate an emerging role for mp-MRI in the detection and localization of locally recurrent PCa both after RP and RT which represents an information of paramount importance to perform focal salvage treatments.

Contemporary role of salvage lymphadenectomy in patients with recurrence following radical prostatectomy

CONTEXT

Prostate cancer (PCa) patients with isolated clinical lymph node (LN) relapse, limited to the regional and/or retroperitoneal LNs, may represent a distinct group of patients who have a more favorable outcome than men with progression to the bone or to other visceral organs. Some data indirectly denote a beneficial impact of pelvic LN dissection on survival in these patients.

OBJECTIVE

To provide an overview of the currently available literature regarding salvage LN dissection (SLND) in PCa patients with clinical relapse limited to LNs after radical prostatectomy (RP).

EVIDENCE ACQUISITION

A systematic literature search was conducted using the Medline, Embase, and Web of Science databases to identify original articles, review articles, and editorials regarding SLND. Articles published between 2000 and 2012 were reviewed and selected with the consensus of all the authors.

EVIDENCE SYNTHESIS

Contemporary imaging techniques, such as 11C-choline positron emission tomography and diffusion-weighted magnetic resonance imaging, appear to enhance the accuracy in identifying LN relapse in patients with biochemical recurrence (BCR) and after RP. In these individuals, SLND can be considered as a treatment option. The currently available data suggest that SLND can delay clinical progression and postpone hormonal therapy in almost one-third of the patients, although the majority will have BCR. An accurate and attentive preoperative patient selection may help improve these outcomes. The most frequent complication after SLND was lymphorrhea (15.3%), followed by fever (14.5%) and ileus (11.2%). It is noteworthy that all examined cohorts originated from retrospective single-institution series, with limited sample size and short follow-up. Consequently, the current findings cannot be generalized and warrant further investigation in future prospective trials.

CONCLUSIONS

The current data suggest that SLND represents an option in patients with disease relapse limited to the LNs after RP; however, more robust data derived from well-designed clinical trials are needed to validate the role of SLND in this selected patient population.

PATIENT SUMMARY

Salvage lymph node dissection (SLND) represents a treatment option in for patients with prostate cancer relapse limited to the lymph nodes; however, more robust data derived from well-designed clinical trials are needed to validate the role of SLND in this selected patient population.

Prostate cancer and its mimics at multiparametric prostate MRI

One in six males will develop prostate cancer during their lifetime. Prostate cancer is the second leading cause of cancer death in American males, behind only lung cancer. Unfortunately, even though this disease is so common, clinical screening methods such as prostate-specific antigen test and transrectal ultrasound-guided prostate biopsy lack sensitivity and specificity in diagnosing prostate cancer. In recent years, multiparametric prostate MRI has emerged as a very important tool in the diagnosis of prostate carcinoma with a high accuracy. However, diagnostic difficulty is often encountered even with an experienced abdominal radiologist. That is mainly because many normal and abnormal entities can mimic prostate carcinoma at multiparametric MRI. Therefore, the purpose of this pictorial review is to discuss the usefulness of multiparametric prostate MRI in the diagnosis of prostate carcinoma, emphasizing the key MRI features that help to make a distinction of prostate carcinoma from its mimics.

Advanced imaging for the early diagnosis of local recurrence prostate cancer after radical prostatectomy

Currently the diagnosis of local recurrence of prostate cancer (PCa) after radical prostatectomy (RT) is based on the onset of biochemical failure which is defined by two consecutive values of prostate-specific antigen (PSA) higher than 0.2 ng/mL. The aim of this paper was to review the current roles of advanced imaging in the detection of locoregional recurrence. A nonsystematic literature search using the Medline and Cochrane Library databases was performed up to November 2013. Bibliographies of retrieved and review articles were also examined. Only those articles reporting complete data with clinical relevance for the present review were selected. This review article is divided into two major parts: the first one considers the role of PET/CT in the restaging of PCa after RP; the second part is intended to provide the impact of multiparametric-MRI (mp-MRI) in the depiction of locoregional recurrence. Published data indicate an emerging role for mp-MRI in the depiction of locoregional recurrence, while the performance of PET/CT still remains unclear. Moreover Mp-MRI, thanks to functional techniques, allows to distinguish between residual glandular healthy tissue, scar/fibrotic tissue, granulation tissue, and tumour recurrence and it may also be able to assess the aggressiveness of nodule recurrence.

Discrimination of prostate carcinoma from benign prostate tissue fragments in vitro by estimating the gross biochemical alterations through Raman spectroscopy

Raman spectroscopy has been proposed for detecting biochemical alterations in prostate cancer (PrCa) compared to benign prostate tissue in in vitro fragments from surgery for diagnostic purposes. Freezer-stored fragments of human prostate tissues were unfrozen and submitted to Raman spectroscopy with a dispersive spectrometer (830-nm and 200-mW laser parameters, 30-s exposure time). Fragments were fixed and submitted to histopathology to grade PrCa according to Gleason score. A total of 160 spectra were taken from 32 samples (16 benign tissues and 16 PrCa tissues). The relative concentrations of selected biochemicals were estimated using a least-squares fitting model applied to the spectra of pure compounds and the tissue spectrum. A discrimination model was developed employing the most statistically relevant compounds with capability of separating PrCa from benign tissues. The fitting model revealed that actin, hemoglobin, elastin, phosphatidylcholine, and water are the most important biochemicals to discriminate prostate depending on the Gleason score. A discrimination based on Euclidean distance using the relative concentrations of phosphatidylcholine and water showed the higher accuracy of 74 % to discriminate PrCa from benign tissue. Raman spectroscopy is an analytical technique with possibility for identifying biochemical constitution of prostate and could be used for diagnostic purposes.

Diffusion-weighted magnetic resonance diagnosis of local recurrences of prostate cancer after radical prostatectomy: preliminary evaluation on twenty-seven cases

OBJECTIVES

To assess the diagnostic performance of diffusion-weighted MR imaging (DWI) in patients affected by prostatic fossa (PF) relapse after radical prostatectomy (RP) for prostatic carcinoma (PC).

METHODS

Twenty-seven patients showing a nodular lesion in the PF at T2-weighted MR imaging after RP, with diagnosis of PC relapse established by biopsy or PSA determinations, were investigated by DWI. Two readers evaluated the DWI results in consensus and the apparent diffusion coefficient (ADC) of the nodules, separately; a mean value was obtained (ADCm).

RESULTS

Relapses did not significantly differ in size in respect of postsurgical benign nodules. The DWI qualitative evaluation showed sensitivity, specificity, accuracy, ppv, and npv values, respectively, of 83.3%, 88.9%, 85.2%, 93.7%, and 72.7% (100%, 87.5%, 95.6%, 93.7%, and 100%, for nodules >6 mm). The intraclass correlation coefficient (ICC) for ADC evaluation between the two readers was 0.852 (95% CI 0.661-0.935; P = 0.0001). The ADCm values for relapses and benign nodules were, respectively, 0.98 ± 0.21 × 10(-3) mm(2)/sec and 1.24 ± 0.32 × 10(-3) mm(2)/sec (P = 0.006). Sensitivity, specificity, accuracy, ppv and npv of ADCm were, respectively, 77.8%, 88.9%, 81.8%, 93.3%, and 66.7% (93.3%, 87.5%, 85.4%, 93.3%, and 87.5% for nodules >6 mm).

CONCLUSIONS

Diffusion-weighted MR imaging is a promising tool in the management of a hyperintense nodule detected by T2-weighted sequences. This might have a relevant importance in contouring radiotherapy treatment volumes.

MRI in prostate cancer

Imaging studies play an important role in detection and management of prostate cancer and MRI especially with the use of endorectal coil because of high contrast resolution is recognized as the best imaging modality in evaluation of prostate cancer. Multiparametric MR study including T1 and T2 weighted images, diffusion weighted images, dynamic contrast study and MR spectroscopy is useful for detection and local staging of prostate cancer as well as posts treatment evaluation of patients either after surgery or radiation therapy for detection of local recurrence.

Impact of field strength and RF excitation on abdominal diffusion-weighted magnetic resonance imaging

AIM: To retrospectively and prospectively compare diffusion-weighted (DW) images in the abdomen in a 1.5T system and 3.0T systems with and without two-channel functionality for B₁ shimming.

METHODS: DW images of the abdomen were obtained on 1.5T and 3.0T (with and without two-channel functionality for B₁ shimming) scanners on 150 patients (retrospective study population) and 10 volunteers (prospective study population). Eight regions were selected for clinical significance or artifact susceptibility (at higher field strengths). Objective grading quantified signal-to-noise ratio (SNR), and subjective evaluation qualified image quality, ghosting artifacts, and diagnostic value. Statistical significance was calculated using χ² tests (categorical variables) and independent two-sided t tests or Mann-Whitney U tests (continuous variables).

RESULTS: The 3.0T using dual-source parallel transmit (dpTX 3.0T) provided the significantly highest SNRs in nearly all regions. In regions susceptible to artifacts at higher field strengths (left lobe of liver, head of pancreas), the SNR was better or similar to the 1.5T system. Subjectively, both dpTX 3.0T and 1.5T systems provided higher image quality, diagnostic value, and less ghosting artifact (P < 0.01, most values) compared to the 3.0T system without dual-source parallel transmit (non-dpTX 3.0T).

CONCLUSION: The dpTX 3.0T scanner provided the highest SNR. Its image quality, lack of ghosting, and diagnostic value were equal to or outperformed most currently used systems.

Increased signal intensity of prostate lesions on high b-value diffusion-weighted images as a predictive sign of malignancy

OBJECTIVES

The evaluation of lesions detected in prostate magnetic resonance imaging (MRI) with increased signal intensity (SI) on high b-value diffusion-weighted images as a sign of malignancy.

METHODS

One hundred and three consecutive patients with prostate MRI examination and MRI-guided in-bore biopsy were retrospectively included in the study. MRI-guided in-bore biopsy histologically confirmed prostate cancer in 50 patients (n = 92 lesions). The other 53 patients (n = 122 lesions) had negative bioptical results.

RESULTS

In patients with histologically confirmed prostate cancer, 46 of the 92 lesions had visually increased SI on the high b-value images compared with the peripheral zone (SI = +27 ± 16%) or the central gland (SI = +37 ± 19%, P < 0.001 respectively). In patients with a negative biopsy, ten of the 122 lesions had visually increased SI (compared with the peripheral zone, SI = +29 ± 18%, and with the central gland, SI = +41 ± 15%, P < 0.001 respectively). Neither the apparent diffusion coefficient (ADC) values nor the Gleason Score of lesions with increased SI were significantly different from lesions without increased SI.

CONCLUSIONS

Visually increased SI on the high b-value images of diffusion-weighted imaging using standard b-values is a sign of malignancy but can occasionally also be a feature of benign lesions. However, it does not indicate more aggressive tumours.

KEY POINTS

• Diffusion weighted magnetic resonance imaging is increasingly used to diagnose prostatic cancer • Reduced signal intensity (SI) on apparent diffusion coefficient (ADC) mapping is characteristic • Prostatic tumours usually exhibit increased SI on high b-value images • But benign lesions can also yield increased SI on high b-value images.

Multiparametric magnetic resonance imaging of prostate cancer

In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up.

Magnetic resonance imaging for prostate cancer clinical application

As prostate cancer is a biologically heterogeneous disease for which a variety of treatment options are available, the major objective of prostate cancer imaging is to achieve more precise disease characterization. In clinical practice, magnetic resonance imaging (MRI) is one of the imaging tools for the evaluation of prostate cancer, the fusion of MRI or dynamic contrast-enhanced MRI (DCE-MRI) with magnetic resonance spectroscopic imaging (MRSI) is improving the evaluation of cancer location, size, and extent, while providing an indication of tumor aggressiveness. This review summarizes the role of MRI in the application of prostate cancer and describes molecular MRI techniques (including MRSI and DCE-MRI) for aiding prostate cancer management.

Prostate cancer imaging: what the urologist wants to know

No consensus exists at present regarding the use of imaging for the evaluation of prostate cancer. Ultrasonography is mainly used for biopsy guidance and magnetic resonance imaging is the mainstay in evaluating the extent of local tumor. Computed tomography and radionuclide bone scanning are mainly reserved for assessment of advanced disease. Positron emission tomography is gaining acceptance in the evaluation of treatment response and recurrence. The combination of anatomic, functional, and metabolic imaging modalities has promise to improve treatment. This article reviews current imaging techniques and touches on the evolving technologies being used for detection and follow-up of prostate cancer.

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

OBJECTIVE

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

CONCLUSION

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

Comparative analysis of multiparametric magnetic resonance and PET-CT in the management of local recurrence after radical prostatectomy for prostate cancer

PURPOSE

Our aim was to assess whether multiparametric magnetic resonance and PET-CT can have a role in detecting local recurrence in patients with biochemical recurrence after radical prostatectomy.

METHODS

We reviewed the recent international literature by carrying out a PUBMED search.

RESULTS

We critically reviewed 11 recent original studies about the use of PET-CT and 5 recent studies about the use of multiparametric magnetic resonance. PET-CT has not shown significant results in terms of detection rate for local recurrence in patients with low level of PSA. Multiparametric magnetic resonance showed encouraging results to detect local recurrence in patients with low PSA and with small diameter lesions.

CONCLUSIONS

Currently, most important urological societies do not consider multiparametric magnetic resonance and PET-CT in the follow-up of patients with suspected local recurrence after radical prostatectomy. We can assert that multiparametric magnetic resonance seems to have excellent results in detecting local recurrence in patients submitted to radical prostatectomy and PSA<1.5 ng/ml.

Comparison of prostate volume, shape, and contouring variability determined from preimplant magnetic resonance and transrectal ultrasound images

PURPOSE

To compare preimplant prostate contours and contouring variability between magnetic resonance (MR) and transrectal ultrasound images.

METHODS AND MATERIALS

Twenty-three patients were imaged using ultrasound (US) and MR before permanent brachytherapy treatment. Images were anonymized, randomized, and duplicated, and the prostate was independently delineated by five radiation oncologists. Contours were compared in terms of volume, dimensions, posterior rectal indentation, and observer variability. The Jaccard index quantified spatial overlap between contours from duplicated images.

RESULTS

The mean US/MR volume ratio was 0.99±0.08 (p=0.5). The width, height, and length ratios for the prostate were 0.98±0.06 (p=0.09), 0.99±0.08 (p=0.4), and 1.05±0.14 (p=0.1). Rectal indentation was larger on US by 0.18mL (p=0.01) and correlated with prostate volume (p<0.01). MR and US interobserver variability in volume were similar at 3.5±1.7 and 3.3±1.9mL (p=0.6). Intraobserver variability was smaller on US at 1.4±1.1mL compared with MR at 2.4±2.2mL (p=0.01). Local intraobserver variability was lower on US at the midgland slice (p<0.01) but lower on MR at the base (p<0.01) and apex (p<0.01) slices.

CONCLUSIONS

US is comparable to MR for preimplant prostate delineation, with no significant difference in volume and dimensions. Rectal indentation because of the transrectal ultrasound probe was measurable, although the effects were small. Intraobserver variability was lower on US for the prostate volume but was lower on MR locally at the base and apex. However, the difference was not observed for the interobserver variability, which was similar between MR and US.

Prostate cancer: multiparametric MR imaging for detection, localization, and staging

This review presents the current state of the art regarding multiparametric magnetic resonance (MR) imaging of prostate cancer. Technical requirements and clinical indications for the use of multiparametric MR imaging in detection, localization, characterization, staging, biopsy guidance, and active surveillance of prostate cancer are discussed. Although reported accuracies of the separate and combined multiparametric MR imaging techniques vary for diverse clinical prostate cancer indications, multiparametric MR imaging of the prostate has shown promising results and may be of additional value in prostate cancer localization and local staging. Consensus on which technical approaches (field strengths, sequences, use of an endorectal coil) and combination of multiparametric MR imaging techniques should be used for specific clinical indications remains a challenge. Because guidelines are currently lacking, suggestions for a general minimal protocol for multiparametric MR imaging of the prostate based on the literature and the authors' experience are presented. Computer programs that allow evaluation of the various components of a multiparametric MR imaging examination in one view should be developed. In this way, an integrated interpretation of anatomic and functional MR imaging techniques in a multiparametric MR imaging examination is possible. Education and experience of specialist radiologists are essential for correct interpretation of multiparametric prostate MR imaging findings. Supportive techniques, such as computer-aided diagnosis are needed to obtain a fast, cost-effective, easy, and more reproducible prostate cancer diagnosis out of more and more complex multiparametric MR imaging data.

Magnetic resonance imaging in staging of locoregional prostate cancer: comparison of results with analysis post-surgical histopathology

Conventional staging for locoregional prostate adenocarcinoma has been demonstrated as potentially underdiagnosing. Therefore, prostate MRI is emerging as an important tool for staging before surgery. Advanced techniques such as diffusion and dynamic contrast enhancement also contribute to increasing its accuracy. In this preliminary study, MRI was compared with prostate histopathology samples, reaching 78% sensitivity and 100% specificity for tumor localization; 33% sensitivity and 100% specificity for extracapsular extension; 100% sensitivity and 100% specificity for involvement of the seminal vesicles. It is possible to believe that these preliminary results are promising, and more cases will tend to confirm these data.

Predictors in the outcome of 125I brachytherapy as monotherapy for prostate cancer

A number of different prostate cancer treatment modalities exist. Nomograms are used to assist clinicians and patients in choosing the most appropriate treatment. However, the predicted outcome for (125)I brachytherapy is much worse than what would be expected considering the actual survival rates. This underestimation may result in suboptimal treatment decisions. Therefore, better predictors for outcome after (125)I brachytherapy are necessary. The following factors, which may either influence outcome or predict outcome after brachytherapy, are discussed: tumor characteristics and risk stratification, patient age at treatment, obesity, adjuvant androgen-deprivation therapy, prostate-specific antigen bounce, implantation technique and dosimetry. For the prediction of outcome after (125)I brachytherapy, as long as the quality of the implant is optimal, only high-risk prostate cancer was found to have a negative impact on outcome.

Diffusion-weighted magnetic resonance imaging for monitoring prostate cancer progression in patients managed by active surveillance

OBJECTIVES

We studied patients managed by active surveillance to determine whether there was a difference over time in apparent diffusion coefficients (ADCs) derived from diffusion-weighted MRI in those who progressed to radical treatment (progressors, n = 17) compared with those who did not (non-progressors, n = 33).

METHODS

50 consecutive patients (Stage T1/2a, Gleason grade ≤ 3+4, prostate-specific antigen (PSA) <15 ng ml⁻¹, <50% cores positive) were imaged endorectally (baseline and 1-3 years follow-up) with T₂ weighted (T₂W) and echo-planar diffusion-weighted MRI sequences. Regions of interest drawn on ADC maps with reference to the T₂W images yielded ADC(all) (b = 0-800), ADC(fast) (b = 0-300) and ADC(slow) (b = 300-800) for whole prostate (minus tumour) and tumour (low signal-intensity peripheral zone lesion in biopsy-positive octant).

RESULTS

Tumour and whole prostate ADC(all) and ADC(fast) were significantly reduced over time in progressors (p = 0.03 and 0.03 for tumours, respectively; p = 0.02 and 0.007 for the whole prostate, respectively). There were no significant changes in ADC over time in non-progressors. A 10% reduction in tumour ADC(all) indicated progression with a 93% sensitivity and 40% specificity (A(z) of receiver operating characteristic (ROC) curve = 0.68). Percentage reductions in whole prostate ADC(all), ADC(fast) and ADC(slow) were also significantly greater in progressors than in non-progressors (p = 0.01, 0.03 and 0.008, respectively).

CONCLUSION

This pilot study shows that DW-MRI has potential for monitoring patients with early prostate cancer who opt for active surveillance.

Magnetic resonance imaging in diagnosis, staging and radiotherapy planning for prostate cancer

T2-weighted magnetic resonance imaging (MRI), preferably using an endorectal coil, is able to clearly depict the normal prostatic anatomy and to identify prostate cancer with fair diagnostic accuracy. The latter can be further increased by using functional techniques such as spectroscopy (assessment of prostatic metabolism), dynamic contrast-enhanced MRI (assessment of angiogenesis) and diffusion-weighted imaging (assessment of cellular density). T2-weighted MRI is an important tool for local staging of prostate cancer in patients clinically staged as cT1 or cT2, because of its high specificity for macroscopic capsular extension or seminal vesicle invasion. Compared to CT-imaging, MRI depicts the internal prostatic anatomy, prostatic margins and the extent of prostatic tumours much more clearly. This benefit can be exploited to improve the accuracy of target delineations in radiotherapy planning.

Diffusion-weighted magnetic resonance imaging in patients with unilateral prostate cancer on extended prostate biopsy: predictive accuracy of laterality and implications for hemi-ablative therapy

PURPOSE

We evaluated the ability of extended prostate biopsy to detect unilateral prostate cancer and assessed the incremental diagnostic benefit of diffusion-weighted magnetic resonance imaging to predict unilateral prostate cancer.

MATERIALS AND METHODS

A total of 130 patients with prostate cancer detected by extended pattern prostate biopsy underwent magnetic resonance imaging before radical prostatectomy. Tumor laterality on extended prostate biopsy was compared with the corresponding lobe on the radical prostatectomy specimen. In patients with unilateral prostate cancer on biopsy we calculated the probability of a tumor in the contralateral lobe on magnetic resonance images and calculated area under the receiver operating characteristics curve. We compared the diagnostic accuracy of combined T2-weighted and diffusion-weighted magnetic resonance images to that of T2-weighted magnetic resonance images alone.

RESULTS

Of the 130 patients 88 (67.7%) had unilateral disease on extended prostate biopsy. Radical prostatectomy pathology showed that 19% of these patients had unilateral disease but 81% had bilateral disease. Area under the receiver operating characteristics curve of combined diffusion-weighted and T2-weighted magnetic resonance imaging was greater than that of T2-weighted magnetic resonance imaging alone (0.814, 95% CI 0.716-0.889 vs 0.510, 95% CI 0.401-0.618). T2-weighted plus diffusion-weighted magnetic resonance imaging had significantly higher sensitivity (84.1% vs 61.9%, p = 0.003) and specificity (72.0% vs 36.0%, p = 0.004) to predict cancer in the contralateral lobe than T2-weighted magnetic resonance alone.

CONCLUSIONS

Extended prostate biopsy cannot accurately determine prostate cancer unilaterality. Diffusion-weighted magnetic resonance combined with T2-weighted magnetic resonance imaging has an incremental diagnostic benefit to predict unilateral prostate cancer.

Diagnostic utility of DTI in prostate cancer

PURPOSE

The aim of this study was to compare the diffusion tensor parameters of prostate cancer, prostatitis and normal prostate tissue.

MATERIALS AND METHODS

A total of 25 patients with the suspicion of prostate cancer were included in the study. MRI was performed with 3 T system (Intera Achieva, Philips Medical Systems, The Netherlands). T2 TSE and DTI with ss-EPI were obtained in each subject. TRUS-guided prostate biopsy was performed after the MRI examination. Images were analyzed by two radiologists using a special software system. ROI's were drawn according to biopsy zones which are apex, midgland, base and central zone on each sides of the gland. FA and ADC values in areas of cancer, chronic prostatitis and normal prostate tissue were compared using Student's t-test.

RESULTS

Histopathological analysis revealed carcinoma in 68, chronic prostatitis in 67 and was reported as normal in 65 zones. The mean FA of cancerous tissue was significantly higher (p<0.01) than the FA of chronic prostatitis and normal gland. The mean ADC of cancerous tissue was found to be significantly lower (p<0.01), compared with non-cancerous tissue.

CONCLUSION

Decreased ADC and increased FA are compatible with the hypercellular nature of prostate tumors. These differences may increase the accuracy of MRI in the detection of carcinoma and to differentiate between cancer and prostatitis.

Multidisciplinary functional MR imaging for prostate cancer

Various functional magnetic resonance (MR) imaging techniques are used for evaluating prostate cancer including diffusion-weighted imaging, dynamic contrast-enhanced MR imaging, and MR spectroscopy. These techniques provide unique information that is helpful to differentiate prostate cancer from non-cancerous tissue and have been proven to improve the diagnostic performance of MRI not only for cancer detection, but also for staging, post-treatment monitoring, and guiding prostate biopsies. However, each functional MR imaging technique also has inherent challenges. Therefore, in order to make accurate diagnoses, it is important to comprehensively understand their advantages and limitations, histologic background related with image findings, and their clinical relevance for evaluating prostate cancer. This article will review the basic principles and clinical significance of functional MR imaging for evaluating prostate cancer.