Carcinoma of the prostate: MR images obtained with body coils do not accurately reflect tumor volume

Magnetic resonance imaging in the early detection of prostate cancer and review of the literature on magnetic resonance imaging-stratified clinical pathways

INTRODUCTION

With level 1 evidence now available on the diagnostic accuracy of multiparametric magnetic resonance imaging (MRI) we must now utilise this data in developing an MRI-stratified diagnostic pathway for the early detection of prostate cancer. Areas covered: A literature review was conducted and identified seven randomised control trials (RCT's) assessing the diagnostic accuracy of such a pathway against the previously accepted systematic/random trans-rectal ultrasound guided (TRUS) biopsy pathway. The studies were heterogeneous in their design. Five studies assessed the addition of MRI-targeted biopsies to a standard care systematic TRUS biopsy pathway. Three of these studies showed either an increase in their diagnostic accuracy or the potential to remove systematic biopsies. Two studies looked specifically at a targeted biopsy only pathway and although the results were again mixed, there was no decrease in the diagnostic rate and overall significantly fewer biopsy cores were taken in the MRI group. Expert commentary: Results from these RCT's together with multiple retrospective and prospective studies point towards either an improved diagnostic rate for clinically significant cancer and/or a reduction in the need for systematic biopsies with a MRI-stratified pathway. The challenge for the urological community will be to implement pre-biopsy MRI into a routine clinical pathway with likely independent monitoring of standards.

Multi-parametric MRI imaging of the prostate-implications for focal therapy

The primary goal of a focal therapy treatment paradigm is to achieve cancer control through targeted tissue destruction while simultaneously limiting deleterious effects on peri-prostatic structures. Focal therapy approaches are employed in several oncologic treatment protocols, and have been shown to provide equivalent cancer control for malignancies such as breast cancer and renal cell carcinoma. Efforts to develop a focal therapy approach for prostate cancer have been challenged by several concepts including the multifocal nature of the disease and limited capability of prostate ultrasound and systematic biopsy to reliably localize the site(s) and aggressiveness of disease. Multi-parametric MRI (mpMRI) of the prostate has significantly improved disease localization, spatial demarcation and risk stratification of cancer detected within the prostate. The accuracy of this imaging modality has further enabled the urologist to improve biopsy approaches using targeted biopsy via MRI-ultrasound fusion. From this foundation, an improved delineation of the location of disease has become possible, providing a critical foundation to the development of a focal therapy strategy. This chapter reviews the accuracy of mpMRI for detection of “aggressive“ disease, the accuracy of mpMRI in determining the tumor volume, and the ability of mpMRI to accurately identify the index lesion. While mpMRI provides a critical, first step in developing a strategy for focal therapy, considerable questions remain regarding the relationship between MR identified tumor volume and pathologic tumor volume, the accuracy and utility of mpMRI for treatment surveillance and the optimal role and timing of follow-up mpMRI.

Magnetic resonance imaging-targeted, 3D transrectal ultrasound-guided fusion biopsy for prostate cancer: Quantifying the impact of needle delivery error on diagnosis

PURPOSE

Magnetic resonance imaging (MRI)-targeted, 3D transrectal ultrasound (TRUS)-guided "fusion" prostate biopsy intends to reduce the ∼23% false negative rate of clinical two-dimensional TRUS-guided sextant biopsy. Although it has been reported to double the positive yield, MRI-targeted biopsies continue to yield false negatives. Therefore, the authors propose to investigate how biopsy system needle delivery error affects the probability of sampling each tumor, by accounting for uncertainties due to guidance system error, image registration error, and irregular tumor shapes.

METHODS

T2-weighted, dynamic contrast-enhanced T1-weighted, and diffusion-weighted prostate MRI and 3D TRUS images were obtained from 49 patients. A radiologist and radiology resident contoured 81 suspicious regions, yielding 3D tumor surfaces that were registered to the 3D TRUS images using an iterative closest point prostate surface-based method to yield 3D binary images of the suspicious regions in the TRUS context. The probabilityP of obtaining a sample of tumor tissue in one biopsy core was calculated by integrating a 3D Gaussian distribution over each suspicious region domain. Next, the authors performed an exhaustive search to determine the maximum root mean squared error (RMSE, in mm) of a biopsy system that gives P ≥ 95% for each tumor sample, and then repeated this procedure for equal-volume spheres corresponding to each tumor sample. Finally, the authors investigated the effect of probe-axis-direction error on measured tumor burden by studying the relationship between the error and estimated percentage of core involvement.

RESULTS

Given a 3.5 mm RMSE for contemporary fusion biopsy systems,P ≥ 95% for 21 out of 81 tumors. The authors determined that for a biopsy system with 3.5 mm RMSE, one cannot expect to sample tumors of approximately 1 cm(3) or smaller with 95% probability with only one biopsy core. The predicted maximum RMSE giving P ≥ 95% for each tumor was consistently greater when using spherical tumor shapes as opposed to no shape assumption. However, an assumption of spherical tumor shape for RMSE = 3.5 mm led to a mean overestimation of tumor sampling probabilities of 3%, implying that assuming spherical tumor shape may be reasonable for many prostate tumors. The authors also determined that a biopsy system would need to have a RMS needle delivery error of no more than 1.6 mm in order to sample 95% of tumors with one core. The authors' experiments also indicated that the effect of axial-direction error on the measured tumor burden was mitigated by the 18 mm core length at 3.5 mm RMSE.

CONCLUSIONS

For biopsy systems with RMSE ≥ 3.5 mm, more than one biopsy core must be taken from the majority of tumors to achieveP ≥ 95%. These observations support the authors' perspective that some tumors of clinically significant sizes may require more than one biopsy attempt in order to be sampled during the first biopsy session. This motivates the authors' ongoing development of an approach to optimize biopsy plans with the aim of achieving a desired probability of obtaining a sample from each tumor, while minimizing the number of biopsies. Optimized planning of within-tumor targets for MRI-3D TRUS fusion biopsy could support earlier diagnosis of prostate cancer while it remains localized to the gland and curable.

Computer-Aided Detection and diagnosis for prostate cancer based on mono and multi-parametric MRI: a review

Prostate cancer is the second most diagnosed cancer of men all over the world. In the last few decades, new imaging techniques based on Magnetic Resonance Imaging (MRI) have been developed to improve diagnosis. In practise, diagnosis can be affected by multiple factors such as observer variability and visibility and complexity of the lesions. In this regard, computer-aided detection and computer-aided diagnosis systems have been designed to help radiologists in their clinical practice. Research on computer-aided systems specifically focused for prostate cancer is a young technology and has been part of a dynamic field of research for the last 10 years. This survey aims to provide a comprehensive review of the state-of-the-art in this lapse of time, focusing on the different stages composing the work-flow of a computer-aided system. We also provide a comparison between studies and a discussion about the potential avenues for future research. In addition, this paper presents a new public online dataset which is made available to the research community with the aim of providing a common evaluation framework to overcome some of the current limitations identified in this survey.

Prostate cancer detection on dynamic contrast-enhanced MRI: computer-aided diagnosis versus single perfusion parameter maps

OBJECTIVE

The purpose of this article is to assess the value of computer-aided diagnosis (CAD) for prostate cancer detection on dynamic contrast-enhanced MRI (DCE-MRI).

MATERIALS AND METHODS

DCE-MRI examinations of 42 patients with prostate cancer were used to generate perfusion parameters, including baseline and peak signal intensities, initial slope, maximum slope within the initial 50 seconds after the contrast injection (slope(50)), wash-in rate, washout rate, time to peak, percentage of relative enhancement, percentage enhancement ratio, time of arrival, efflux rate constant from the extravascular extracellular space to the blood plasma (k(ep)), first-order rate constant for eliminating gadopentetate dimeglumine from the blood plasma (k(el)), and constant depending on the properties of the tissue and represented by the size of the extravascular extracellular space (A(H)). CAD for cancer detection was established by comprehensive evaluation of parameters using a support vector machine. The diagnostic accuracy of single perfusion parameters was estimated using receiver operating characteristic analysis, which determined threshold and parametric maps for cancer detection. The diagnostic performance of CAD for cancer detection was compared with those of T2-weighted imaging (T2WI) and single perfusion parameter maps, using histologic results as the reference standard.

RESULTS

The accuracy, sensitivity, and specificity of CAD were 83%, 77%, and 77%, respectively, in the entire prostate; 77%, 91%, and 64%, respectively, in the transitional zone; and 89%, 89%, and 89%, respectively, in the peripheral zone. Values for k(ep), k(el), initial slope, slope(50), wash-in rate, washout rate, and time to peak showed greater area under the curve values (0.803-0.888) than did the other parameters (0.545-0.665) (p < 0.01) and were compared with values for CAD. In the entire prostate, accuracy was greater for CAD than for all perfusion parameters or T2WI (63-77%); sensitivity was greater for CAD than for T2WI, initial slope, wash-in rate, slope(50), and washout rate (38-77%); and specificity was greater for CAD than for T2WI, k(ep), k(el), and time to peak (59-68%) (p < 0.05).

CONCLUSION

CAD can improve the diagnostic performance of DCE-MRI in prostate cancer detection, which may vary according to zonal anatomy.

High-field magnetic resonance imaging of the pelvis: uterus, ovary, and prostate gland

Today, magnetic resonance imaging (MRI) is a standard imaging modality for various pathologic disorders in the human pelvis. It has given proof of its usefulness in the diagnosis of several benign and malignant disorders, and it is routinely used for the local staging of different tumors even when confined to specific parts of a pelvic organ. Signal-to-noise ratio and motion artifacts of the examined organ and adjacent bowel structures are major factors for image quality. Setting at 3 T with surface coils avoids technical limitations and discomfort of additional endovaginal or endorectal coils. Definition of high field seems fuzzy because of the availability of MRI machines with 3, 7 T, or higher; therefore, the general aspects of MRI of pelvic structures with emphasis on uterus, ovary, and prostate gland and attention to promising newer techniques such as 3 T, dynamic contrast imaging, and diffusion-weighted imaging are reviewed in this article.

Dynamic contrast-enhanced magnetic resonance imaging in the evaluation of the prostate

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a novel MR technique that allows to interrogate pharmacokinetic processes in the tissues at a voxel level and to generate parametric maps that can be displayed for clinical interpretation. Dynamic contrast-enhanced MRI is an important imaging technique for the imaging of angiogenesis and vasculogenesis because it probes the microvascular networks at a microscopic level by being sensitive to the compartmentalization of tissue into the vascular and extravascular-extracellular space and to the diffusion of contrast molecules across the vascular endothelium and capillary boundaries. Dynamic contrast-enhanced MRI has already shown to improve detection and localization of prostate cancer, to improve prediction of extracapsular extension, determination of tumor volume, and after treatment follow-up. In this article, we outline the fundamental principles of DCE-MRI and describe the application of DCE methods in the imaging of the prostate.

Dynamic contrast-enhanced MRI of prostate cancer at 3 T: a study of pharmacokinetic parameters

OBJECTIVE

The objectives of our study were to determine whether dynamic contrast-enhanced MRI performed at 3 T and analyzed using a pharmacokinetic model improves the diagnostic performance of MRI for the detection of prostate cancer compared with conventional T2-weighted imaging, and to determine which pharmacokinetic parameters are useful in diagnosing prostate cancer.

SUBJECTS AND METHODS

This prospective study included 50 consecutive patients with biopsy-proven prostate cancer who underwent imaging of the prostate on a 3-T scanner with a combination of a sensitivity-encoding (SENSE) cardiac coil and an endorectal coil. Scans were obtained at least 5 weeks after biopsy. T2-weighted turbo spin-echo images were obtained in three planes, and dynamic contrast-enhanced images were acquired during a single-dose bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were estimated for T2-weighted and dynamic contrast-enhanced MRI. The following pharmacokinetic modeling parameters were determined and compared for cancer, inflammation, and healthy peripheral zone: K(trans) (forward volume transfer constant), k(ep) (reverse reflux rate constant between extracellular space and plasma), v(e) (the fractional volume of extracellular space per unit volume of tissue), and the area under the gadolinium concentration curve (AUGC) in the first 90 seconds after injection.

RESULTS

Pathologically confirmed cancers in the peripheral zone of the prostate were characterized by their low signal intensity on T2-weighted scans and by their early enhancement, early washout, or both on dynamic contrast-enhanced MR images. The overall sensitivity, specificity, PPV, and NPV of T2-weighted imaging were 94%, 37%, 50%, and 89%, respectively. The sensitivity, specificity, PPV, and NPV of dynamic contrast-enhanced MRI were 73%, 88%, 75%, and 75%, respectively. K(trans), k(ep), and AUGC were significantly higher (p < 0.001) in cancer than in normal peripheral zone. The ve parameter was not significantly associated with prostate cancer.

CONCLUSION

MRI of the prostate performed at 3 T using an endorectal coil produces high-quality T2-weighted images; however, specificity for prostate cancer is improved by also performing dynamic contrast-enhanced MRI and using pharmacokinetic parameters, particularly K(trans) and k(ep), for analysis. These results are comparable to published results at 1.5 T.

Clinically significant prostate cancer local recurrence after radiation therapy occurs at the site of primary tumor: magnetic resonance imaging and step-section pathology evidence

PURPOSE

To determine whether prostate cancer local recurrence after radiation therapy (RT) occurs at the site of primary tumor by retrospectively comparing the tumor location on pre-RT and post-RT magnetic resonance imaging (MRI) and using step-section pathology after salvage radical prostatectomy (SRP) as the reference standard.

METHODS AND MATERIALS

Nine patients with localized prostate cancer were treated with intensity modulated RT (69-86.4 Gy), and had pre-RT and post-RT prostate MRI, biopsy-proven local recurrence, and SRP. The location and volume of lesions on pre-RT and post-RT MRI were correlated with step-section pathology findings. Tumor foci >0.2 cm(3) and/or resulting in extraprostatic disease on pathology were considered clinically significant.

RESULTS

All nine significant tumor foci (one in each patient; volume range, 0.22-8.63 cm(3)) were detected both on pre-RT and post-RT MRI and displayed strikingly similar appearances on pre-RT and post-RT MRI and step-section pathology. Two clinically insignificant tumor foci (</=0.06 cm(3)) were not detected on imaging. The ratios between tumor volumes on pathology and on post-RT MRI ranged from 0.52 to 2.80.

CONCLUSIONS

Our study provides a direct visual confirmation that clinically significant post-RT local recurrence occurs at the site of primary tumor. Our results are in agreement with reported clinical and pathologic results and support the current practice of boosting the radiation dose within the primary tumor using imaging guidance. They also suggest that monitoring of primary tumor with pre-RT and post-RT MRI could lead to early detection of local recurrence amenable to salvage treatment.

MR imaging in local staging of prostate cancer

Clinical staging to differentiate between localized and advanced disease stage appear to be unreliable. Curative therapy can only be performed in patients with localized prostate cancer. Accurate staging is therefore especially important for proper disease management. Since 1984 magnetic resonance (MR) imaging has been applied for this purpose. However, the role of MR imaging of the prostate is debated extensively in the literature. Initially MR imaging was performed using a conventional body coil with subsequent limited anatomical detail due to insufficient spatial resolution. With the introduction of new MR sequences, new coils and other technical developments numerous studies have attempted to improve local staging. The diagnostic capability of MR imaging in preoperative staging of prostate cancer is currently being established. In this review the role of MR imaging in staging prostate cancer is discussed.

Prostate cancer: value of magnetic resonance spectroscopy 3D chemical shift imaging

The results of recent studies of magnetic resonance imaging (MRI) combined with three-dimensional magnetic resonance spectroscopic imaging (3D-MRSI) demonstrate that the MRI/3D-MRSI exam is a unique method by which to noninvasively study the cellular metabolism and anatomy of the prostate. 3D-MRSI is emerging as the most specificity tool for non-invasive evaluation of the prostate cancer. The results of current MRI/3D-MRSI studies also provide evidence that the magnitude of metabolic changes in regions of cancer before therapy, as well as the extent of the time course of metabolic changes after therapy, may improve our understanding of cancer aggressiveness. Assessment of cancer spread outside the prostate can be significantly improved by combining MRI findings with estimates of metabolic abnormalities provided by 3D-MRSI. Clinically, combined MRI/3D-MRSI has already demonstrated a potential for improved diagnosis, staging, and treatment planning for patients with prostate cancer. This article reviewed the value of 3D-MRS imaging for the diagnosis, localization, staging, aggressiveness, and treatment planning of prostate cancer.

Contribution of the MR spectroscopic imaging in the diagnosis of prostate cancer in the peripheral zone

PURPOSE

To establish the additional value of 3D magnetic resonance spectroscopy (3D-MRS) imaging to endorectal MR imaging in the diagnosis of prostrate cancer in the peripheral zone.

MATERIALS AND METHODS

MR imaging and MRS imaging were performed in 79 patients with suspicion of prostate cancer on the basis of digital rectal exploration, transrectal ultrasound and PSA level. All the examinations were performed with 1.5 T MR scan using an endorectal coil (transverse and coronal FSE T2-weighted sequences, axial SE T1-weighted and PRESS 3D CSI). MR examinations have been evaluated by two Radiologists blind of the clinical data in a "per patients" analysis. MR imaging and MRS imaging findings were compared with the result of histological data from radical prostatectomy in 53 patients and biopsy in 17 patients.

RESULTS

Nine patients (11.4%) were excluded because of serious artefacts in the MR spectrum. The reported values of sensitivity, specificity, PPV and NPV for MR imaging alone were respectively 84%, 50%, 76% and 63% (LR+ 1.7; LR- 0.3). Instead the reported values of sensitivity, specificity, PPV and NPV for the combination of MR imaging to MRS imaging were respectively 89%, 79%, 89% and 79% (LR+ 4.28; LR- 0.14). We found an incremental benefit of MRS imaging to MR imaging for tumour diagnosis although these results did not show statistically significant differences.

CONCLUSIONS

The MRS imaging improves the accuracy of the endorectal MR imaging in the diagnosis of prostate cancer.

Prostate cancer: comparison of local staging accuracy of pelvic phased-array coil alone versus integrated endorectal-pelvic phased-array coils. Local staging accuracy of prostate cancer using endorectal coil MR imaging

To compare the visibility of anatomical details and prostate cancer local staging performance of pelvic phased-array coil and integrated endorectal-pelvic phased-array coil MR imaging, with histologic analysis serving as the reference standard. MR imaging was performed in 81 consecutive patients with biopsy-proved prostate cancer, prior to radical prostatectomy, on a 1.5T scanner. T2-weighted fast spin echo images of the prostate were obtained using phased-array coil and endorectal-pelvic phased-array coils. Prospectively, one radiologist, retrospectively, two radiologists and two less experienced radiologists working in consensus, evaluated and scored all endorectal-pelvic phased-array imaging, with regard to visibility of anatomical details and local staging. Receiver operator characteristics (ROC) analysis was performed. Anatomical details of the overall prostate were significantly better evaluated using the endorectal-pelvic phased-array coil setup (P<0.05). The overall local staging accuracy, sensitivity and specificity for the pelvic phased-array coil was 59% (48/81), 56% (20/36) and 62% (28/45), and for the endorectal-pelvic phased-array coils 83% (67/81), 64% (23/36) and 98% (44/45) respectively, for the prospective reader. Accuracy and specificity were significantly better with endorectal-pelvic phased-array coils (P<0.05). The overall staging accuracy, sensitivity and specificity for the retrospective readers were 78-79% (P<0.05), 56-58% and 96%, for the endorectal-pelvic phased-array coils. Area under the ROC curve (Az) was significantly higher for endorectal-pelvic phased-array coils (Az=0.74) compared to pelvic phased-array coil (Az=0.57), for the prospective reader. The use of endorectal-pelvic phased array coils resulted in significant improvement of anatomic details, extracapsular extension accuracy and specificity. Overstaging is reduced significantly with equal sensitivity when an endorectal-pelvic phased-array coil is used.

How good is MRI at detecting and characterising cancer within the prostate?

OBJECTIVES

As well as detecting prostate cancer, it is becoming increasingly important to estimate its location, size and grade. We aim to summarise current data on the efficacy of magnetic resonance imaging (MRI) in this setting.

METHODS

Literature review of original research correlating MRI and histologic appearances.

RESULTS

Estimates of the sensitivity of MRI for the detection of cancer vary widely depending on method of analysis used and the definition of significant disease. Recent estimates using T2-weighted sequences and endorectal coils vary from 60% to 96%. Several groups have convincingly shown that dynamic contrast enhancement and spectroscopy each improve detection and that the sensitivity of MRI is comparable to and may exceed that of transrectal biopsy. Specificity is not yet good enough to consider the use of MRI in screening. High-grade and large tumours are detected significantly more often with both T2 sequences and spectroscopy. Estimation of size is improved by dynamic contrast and spectroscopy, but errors of >25% are common.

CONCLUSIONS

The sensitivity of MRI has improved to the point that it has potential in several new areas: targeting of biopsies, monitoring of disease burden both during active surveillance and after focal therapy, and exclusion of cancer in patients with a raised prostate-specific antigen level.

Endorectal MRI for prediction of tumor site, tumor size, and local extension of prostate cancer

OBJECTIVES

To assess the value of endorectal magnetic resonance imaging (MRI) for detecting the tumor site, tumor size, and disease extent in patients with localized prostate cancer.

METHODS

The MRI findings were compared with the histopathologic findings of radical prostatectomy specimens in 95 patients.

RESULTS

The histologic examination revealed 186 cancer foci. Endorectal MRI detected 109 cancer foci. The accuracy, sensitivity, and positive predictive value of endorectal MRI for detecting tumor foci greater than 1.0 cm in diameter was 79.8%, 85.3%, and 92.6%, respectively; the corresponding value for detecting tumor foci smaller than 1.0 cm was 24.2%, 26.2%, and 75.9%, respectively. The maximal tumor diameter on endorectal MRI correlated with that shown by histologic examination for tumors larger than 1.0 cm in diameter. However, it did not correlate significantly with the histologic diameter of tumors smaller than 1.0 cm. The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of endorectal MRI was 74.7%, 57.1%, 82.1%, 57.1%, and 82.1%, respectively, for the detection of extracapsular extension and was 75.8%, 62.1%, 81.8%, 60.0%, and 83.1%, respectively, for local staging.

CONCLUSIONS

The results of the present study suggest that endorectal MRI is useful for predicting local extension, as well as tumor site and tumor size, of cancer foci greater than 1.0 cm in diameter.

Discrimination of prostate cancer from normal peripheral zone and central gland tissue by using dynamic contrast-enhanced MR imaging

PURPOSE

To evaluate which parameters of dynamic magnetic resonance (MR) imaging and T2 relaxation rate would result in optimal discrimination of prostatic carcinoma from normal peripheral zone (PZ) and central gland (CG) tissues and to correlate these parameters with tumor stage, Gleason score, patient age, and tumor markers.

MATERIALS AND METHODS

Of 58 patients with prostatic carcinoma, 36 were included for analysis. Patients underwent MR imaging at 1.5 T with an endorectal-pelvic phased-array coil and subsequently underwent prostatectomy. A T2-weighted turbo spin-echo sequence, an intermediate-weighted sequence, and a fast T1-weighted gradient-echo sequence (seven sections in 2.03 seconds) during bolus injection of 0.1 mmol gadopentetate dimeglumine per kilogram of body weight were performed. Contrast agent concentration-time curves were obtained for prostatic carcinoma and normal PZ and CG tissue by using whole-mount sections to guide placement of regions of interest. Onset time, time to peak, peak enhancement, relative peak enhancement, washout, and T2 relaxation rates were calculated. Multivariate receiver operating characteristic analysis was performed with and without relative peak enhancement.

RESULTS

Results of multivariate receiver operating characteristic analysis showed that relative peak enhancement demonstrated the highest area under the receiver operating characteristic curve (AUC) in the PZ and the CG (AUC = 0.93, 0.82). Results of multivariate analysis without relative peak enhancement showed that relative peak enhancement in the PZ and washout in the CG demonstrated the highest AUC (AUC = 0.9, 0.81). Pearson correlation coefficients between the dynamic parameters or T2 relaxation rates in carcinoma and the tumor stage, Gleason score, patient age, and tumor markers ranged between 0.02 and 0.44.

CONCLUSION

The optimal parameter for discrimination of prostatic carcinoma in the PZ and CG was relative peak enhancement. If relative peak enhancement was not used, then peak enhancement was optimal in the PZ, and washout was optimal in the CG. Poor-to-moderate correlation was present between the dynamic parameters or T2 relaxation rate in carcinoma and the tumor stage, Gleason score, patient age, tumor volume, and prostate-specific antigen.

Visualization of prostate cancer using dynamic contrast-enhanced MRI: comparison with transrectal power Doppler ultrasound

This study was designed to assess the efficacy of dynamic contrast-enhanced MRI (DCE-MRI), in comparison with power Doppler ultrasound (PDUS), for visualizing prostate cancer. 111 men suspected of having prostate cancer underwent imaging before undergoing octant biopsy. Subsequently, 31 cancer-positive patients were enrolled in this study. DCE-MRI was obtained using a three-dimensional fast-field echo sequence, which assured wide coverage of the prostate gland. The transrectal PDUS were scored according to the degree of power Doppler flow signals. The time intensity curve types for the DCE-MRI and the PDUS scores were compared with the histopathologic results for each region. The time intensity curves were correlated significantly with PDUS scores (p<0.001). Using PDUS, the overall sensitivity, specificity and accuracy of cancer visualization in peripheral zones were 69%, 61% and 66%, respectively. Using DCE-MRI, the corresponding values were 87%, 74% and 82%. In the inner gland, using PDUS, the overall sensitivity, specificity and accuracy were 68%, 94% and 83%, respectively. Using DCE-MRI, the corresponding values were similar (68%, 86% and 78%). DCE-MRI was significantly more sensitive than transrectal PDUS in peripheral zones (p<0.05). In conclusion, both transrectal PDUS and DCE-MRI can be used to demonstrate hypervascularity in many prostate cancers. DCE-MRI was significantly more sensitive than PDUS for visualizing of prostate cancers without loss of specificity in the peripheral zone.

The value of endorectal MRI in the early diagnosis of prostate cancer

OBJECTIVE

Assess the value of endorectal MR imaging (EMRI) in the early diagnosis of prostate cancer (PCa) and compare this test to prostate specific antigen (PSA) and digital rectal examination (DRE) in the prediction of negative biopsies.

MATERIAL AND METHODS

92 patients with elevated PSA (>4 ng/ml) and/or abnormal DRE were studied. All patients underwent an EMRI previous to transrectal ultrasound guided needle sextant biopsies (3 cores in each peripheral zone), and were followed up. We performed a total of 184 biopsies: 92 patients underwent 1 biopsy; out of them, 61 patients underwent 2 biopsies, 27 patients 3 biopsies, 3 patients 4 biopsies and 1 patient 5 biopsies. 67 patients had a final negative biopsy and 25 had a final positive biopsy. Mean PSA was 10.44 ng/ml, and the mean % fPSA/tPSA was 0.20. Uni- and multivariate analysis and ROC curves were used to compare the accuracy of the different tests. The probability of positive biopsy with each technique was also assessed.

RESULTS

EMRI had a high negative predictive value (91.07%) and the highest accuracy (77%) of all tests, higher than PSA (62%). Mean PSA was not statistically different in patients with negative biopsies (9.44 ng/ml) and positive biopsies (11.8 ng/ml) (p=0.064). The association of EMRI-DRE-PSA had the highest accuracy (83%) significantly higher than DRE-PSA (70%). The probability of positive biopsy in patients with negative DRE and EMRI, and PSA values between 5 and 15 ng/ml was 5-10% at first and second biopsies, but decreased progressively on subsequent biopsies (<8% at third biopsy, <5% at fourth biopsy and <3% at fifth biopsy).

CONCLUSION

In patients with elevated PSA and/or abnormal DRE with two previous negative biopsies, an EMRI is a useful test to rule out PCa, when negative, and avoid subsequent biopsies, as they have a low chance of positive biopsy.

CT-MRI image fusion for delineation of volumes in three-dimensional conformal radiation therapy in the treatment of localized prostate cancer

The objective of this study was to assess the utility of CT-MRI image fusion software and compare both prostate volume and localization with CT and MRI studies. We evaluated the differences in clinical volumes in patients undergoing three-dimensional conformal radiation therapy for localized prostate cancer. After several tests performed to ensure the quality of image fusion software, eight patients suffering from prostate adenocarcinoma were submitted to CT and MRI studies in the treatment position within an immobilization device before the start of radiotherapy. The clinical target volume (CTV) (prostate plus seminal vesicles) was delineated on CT and MRI studies and image fusion was obtained from the superimposition of anatomical fiducial markers. A comparison of dose-volume histograms relative to CTV, rectum, bladder and femoral heads was performed for both studies. Image fusion showed a mean overestimation of CTV of 34% with CT compared with MRI. Along the anterior-posterior and superior-inferior direction, CTV was a mean 5 mm larger with CT study compared with MRI. The dose-volume histograms resulting from CT and MRI comparison showed that it is possible to spare a mean 10% of rectal volume and approximately 5% of bladder and femoral heads, respectively. This study confirmed an overestimation of CTV with CT images compared with MRI. Because this finding only allows a minimal sparing of organs at risk, considering the organ motion during each radiotherapy session and the excellent outcomes of prostate cancer treatment with CT based target identification, we are still reluctant to reduce the CTV to that identified by MRI.

Prostate cancer tumor volume: measurement with endorectal MR and MR spectroscopic imaging

PURPOSE

To determine accuracy of magnetic resonance (MR) and three-dimensional (3D) MR spectroscopic imaging in prostate cancer tumor volume measurement.

MATERIALS AND METHODS

Endorectal MR and 3D MR spectroscopic imaging were performed in 37 patients before radical prostatectomy. Two independent readers recorded peripheral zone tumor nodule location and volume. Results were analyzed with step-section histopathologic tumor localization and volume measurement as the standard. Accuracy of tumor volume measurement was assessed with the Pearson correlation coefficient. P values were calculated with a random effects model. Bland-Altman regression analysis was used to evaluate systematic bias between tumor volumes measured with MR imaging and true tumor volumes. Analyses were performed for all nodules and nodules greater than 0.50 cm(3).

RESULTS

Mean volume of peripheral zone tumor nodules (n = 51) was 0.79 cm(3) (range, 0.02-3.70 cm(3)). Two readers detected 20 (65%) and 23 (74%) of 31 peripheral zone tumor nodules greater than 0.50 cm(3). For these nodules, measurements of tumor volume with MR imaging, 3D MR spectroscopic imaging, and a combination of both were all positively correlated with histopathologic volume (Pearson correlation coefficients of 0.49, 0.59, and 0.55, respectively); only measurements with 3D MR spectroscopic imaging and a combination of MR and 3D MR spectroscopic imaging demonstrated statistical significance (P <.05). Tumor volume estimation with all three methods was more accurate for higher tumor volumes.

CONCLUSION

Addition of 3D MR spectroscopic imaging to MR imaging increases overall accuracy of prostate cancer tumor volume measurement, although measurement variability limits consistent quantitative tumor volume estimation, particularly for small tumors.

Magnetic resonance imaging of the prostate

Magnetic resonance imaging has been shown to be more accurate than other imaging modalities in the evaluation of both malignancies and various benign lesions of the prostate. Despite its superiority, because of its cost and low availability, magnetic resonance imaging should play a role as a problem-solver secondary to computed tomography or ultrasonography. The routine use of magnetic resonance imaging in the staging of prostate cancer before surgery cannot be justified on the basis of published data. Magnetic resonance imaging has been proved to be of value in the planning and delivery of different types of radiotherapy to patients with prostate cancer. Through the use of combined magnetic resonance imaging and the new modality, magnetic resonance spectroscopy, the accuracy and specificity of tumour detection and the delineation of tumour extent can be improved. Magnetic resonance technology is rapidly evolving, and in the near future, new possibilities such as biological imaging will have a great impact on magnetic resonance imaging of the prostate.

Dynamic contrast enhanced MRI of prostate cancer: correlation with morphology and tumour stage, histological grade and PSA

AIM

To quantify MRI enhancement characteristics of normal and abnormal prostatic tissues and to correlate these with tumour stage, histological grade and tumour markers.

MATERIALS AND METHODS

Quantitative gradient recalled echo MR images were obtained following bolus injection of gadopentetate dimeglumine in 48 patients with prostate cancer. Turbo spin-echo T2-weighted images at the same anatomical position were reviewed for the presence of tumours (45 regions), normal peripheral zone (33 regions), and normal appearing central gland (30 regions). Time-signal intensity parameters (onset time, mean gradient and maximal amplitude of enhancement and wash-out score) and modelling parameters (permeability surface area product, lesion leakage space and maximum gadolinium concentration) were correlated with tumour stage, histological grade (Gleason score) and serum prostatic specific antigen (PSA) levels.

RESULTS

Significant differences were noted between peripheral zone and tumour with respect to signal intensity and modelling parameters (P = 0.0001), except onset time. No differences between central gland and tumour enhancement values were seen. There was weak correlation between MRI tumour stage and tumour vascular permeability (r(2) = 12%; P = 0.02) and maximum tumour gadolinium concentration (r(2) = 14%; P = 0.015). However, no significant correlations were seen with Gleason score or PSA levels.

CONCLUSION

Quantification of MR contrast enhancement characteristics allows tissue discrimination in prostate cancer consistent with known variations in microvessel density estimates.

Prostate cancer: localization with three-dimensional proton MR spectroscopic imaging--clinicopathologic study

PURPOSE

To assess the efficacy of combined magnetic resonance (MR) imaging and three-dimensional (3D) proton MR spectroscopic imaging in the detection and localization of prostate cancer.

MATERIALS AND METHODS

MR imaging and 3D MR spectroscopic imaging examinations were performed in 53 patients with biopsy-proved prostate cancer and subsequent radical prostatectomy with step-section histopathologic examination. The prostate was divided into sextants. At MR imaging, the presence or absence of cancer in the peripheral zone of each sextant was assessed independently by two readers (readers 1 and 2) unaware of the findings at 3D MR spectroscopic imaging and histopathologic examination. At 3D MR spectroscopic imaging, cancer was diagnosed as possible if the ratio of choline plus creatine to citrate exceeded 2 SD above population norms or as definite if that ratio exceeded 3 SDs above the norm.

RESULTS

On the basis of sextants, sensitivity and specificity, respectively, for MR imaging were 77% and 61% (reader 1) and 81% and 46% (reader 2) with moderate interreader agreement (kappa = 0.43). The 3D MR spectroscopic imaging diagnosis of definite cancer had significantly higher specificity (75%, P < .05) but lower sensitivity (63%, P < .05). Receiver operating characteristic analysis showed significantly (P < .001) improved tumor localization for both readers when 3D MR spectroscopic imaging was added to MR imaging. High specificity (up to 91%) was obtained when combined MR imaging and 3D MR spectroscopic imaging indicated cancer, whereas high sensitivity (up to 95%) was obtained when either test alone indicated a positive result.

CONCLUSION

The addition of 3D MR spectroscopic imaging to MR imaging provides better detection and localization of prostate cancer in a sextant of the prostate than does use of MR imaging alone.

Prostate cancer: prediction of extracapsular extension with endorectal MR imaging and three-dimensional proton MR spectroscopic imaging

PURPOSE

To determine if the addition of three-dimensional (3D) proton magnetic resonance (MR) spectroscopic imaging to endorectal MR imaging helps diagnose extracapsular extension (ECE) of prostate cancer.

MATERIALS AND METHODS

Endorectal MR imaging and 3D MR spectroscopic imaging were performed in 53 patients with prostate cancer before radical prostatectomy. MR imaging studies were evaluated by two independent readers unaware of histopathologic findings. The presence of ECE was graded on a five-point scale. At 3D MR spectroscopic imaging, cancer was diagnosed if the ratio of choline plus creatine to citrate was 2 or more SDs above normal. The accuracy of MR imaging alone was compared with that of combined MR imaging and 3D MR spectroscopic imaging, with use of the step-section histopathologic results as the standard of reference.

RESULTS

For the less experienced reader, the addition of 3D MR spectroscopic imaging to MR imaging significantly improved accuracy (area under the receiver operating characteristic curve [Az] = 0.75 vs Az = 0.62, P < .05). For the more experienced reader, the addition improved accuracy but not significantly (Az = 0.86 vs Az = 0.78). The addition also reduced interobserver variability (Az = 0.86 vs Az = 0.75).

CONCLUSION

The addition of 3D MR spectroscopic imaging to MR imaging improves accuracy for less experienced readers and reduces interobserver variability in the diagnosis of ECE of prostate cancer.

The value of dynamic MR imaging for hypointensity lesions of the peripheral zone of the prostate

The aim was to evaluate the role of dynamic magnetic resonance (MR) imaging for prostatic carcinoma. Forty-two men with clinical suspicion of a prostatic carcinoma underwent MR imaging. Dynamic MR was performed, followed by postcontrast T1-weighted imaging with fat suppression. Histologic diagnosis was 21 prostatic carcinomas (in 19 patients), 21 benign tissues, and 2 chronic prostatitis. The diagnostic accuracy was 75% for T2-weighted images, and 79% for dynamic images. The accuracy of the combination of dynamic MR images with postcontrast T1-weighted images was 82%. It was concluded that dynamic MR imaging was useful in differentiation of low intensity lesions in the peripheral zone.

MR imaging of the prostate and bladder

Magnetic resonance imaging has become an important imaging modality for the male pelvis. Its unparalleled ability to depict soft tissue structures and highlight pathology have made it the best method for determining the extent of many disease processes. This article reviews the use of MR to evaluate diseases of the prostate gland and bladder. In both, the major indication for imaging is the local staging of cancer, and MR is currently the best imaging modality. This article will discuss the critical clinical issues concerning prostate cancer and neoplasms of the bladder, and the contribution of MR imaging.

Prediction of pathological tumor volume in clinically localized prostate cancer: value of endorectal coil magnetic resonance imaging

The purpose of this study was to determine whether endorectal coil magnetic resonance imaging (MRI) enables accurate assessment of pathologic tumor volume in patients with clinically localized prostate carcinoma. Twenty-four patients with biopsy-proved prostate carcinoma underwent MRI at 0.5 T before radical prostatectomy. Tumor volumes were determined independently on axial fast-spin-echo (SE) T2-weighted MR images and whole-mount pathology slides of the surgical specimens. At pathology, tumor volumes ranged from 0.17 to 9.42 cm3 (mean +/- SD, 3.11 +/- 2.99 cm3). A strong correlation (r = .944) was found between measurements of tumor volume based on MR images and pathological specimens. The error was less than 0.5 cm3 in 14 cases, in the range of 0.5-1 cm3 in 7 cases, and more than 1 cm3 in 3 cases. By using an MR tumor volume of 2 cm3 as cutoff value, extracapsular tumor spread could be predicted with a sensitivity of 81.2%, a specificity of 100%, and an accuracy of 87.5%. Tumor volume determinations based on MR images seem to be accurate enough to be helpful in clinical decision-making.

Gadolinium-enhanced MRI of the abnormal prostate

A prospective study of the use of a low osmolar gadolinium-based intravenous contrast material for MRI of the abnormal prostate was performed. Eight patients scheduled for prostatectomy, six with prostate cancer and two with benign prostatic hyperplasia (BPH), were imaged preoperatively on a 1.5 T system using a pelvic coil array and employing Gadodiamide (0.3 mmol/kg). T2-weighted fast-spin echo (FSE) imaging was also performed in the same axial planes employed for gadolinium-enhanced studies. Detailed pathologic correlation was performed for the six patients with carcinoma. While regions of BPH and cancer enhanced to a similar degree following intravenous contrast agent, BPH enhancement was more heterogeneous than cancer. No advantages in detecting prostate cancer, in differentiating cancer from BPH or normal prostatic tissue, or in assessing extra-prostatic spread of cancer were observed for the contrast-enhanced studies compared to T2-weighted FSE imaging.