Peripheral zone prostate cancer: accuracy of different interpretative approaches with MR and MR spectroscopic imaging

Prediction of prostate cancer recurrence after radiation therapy using multiparametric magnetic resonance imaging and spectroscopy: assessment of prognostic factors on pretreatment imaging

BACKGROUND

To assess whether data from pre-therapeutic multiparametric magnetic resonance imaging (mpMRI) combined with three-dimensional magnetic resonance spectroscopy (3D MRS) provide prognostic factors of biochemical relapse in patients with localized prostate cancer treated by external radiotherapy or brachytherapy.

METHODS

In our single institution observational retrospective study we included a cohort of 230 patients treated by external radiotherapy or brachytherapy who had an initial mpMRI with 3D MRS from January 2008 to December 2015 for newly diagnosed localized prostatic cancer, proven histologically. Three trained radiologists recorded tumor characteristics, MRI T-stage and metabolic abnormalities from 3D MRS data. Univariate and multivariate Cox analyzes explored the relationship between clinical and imaging variables to highlight prognostic factors for recurrence, using biochemical relapse as the primary endpoint.

RESULTS

mpMRI data analysis allowed to reclassify 21.7% of the patients in a MRI National Comprehensive Cancer Network (NCCN) group higher than their initial clinical T-stage, but also to detect a lesion in 78% of the patients considered as clinically T1c. After a median of follow-up of 8.7 years (IQR, 6.6-10.1) following cancer diagnosis, 36 (16%) patients developed a biochemical relapse. The multivariate Cox analysis demonstrated the existence of 3 independent factors for prediction of biochemical recurrence: extracapsular extension (ECE) (HR =3.33; 95% CI: 1.93-5.73; P<0.01), choline/citrate ratio in healthy tissue in the transition zone (TZ) (HR =2.96; 95% CI: 1.06-8.28; P=0.04) and the NCCN Magnetic Resonance Imaging classification (intermediate versus low-risk, HR =3.06; 95% CI: 1.13-8.30; P<0.01).

CONCLUSIONS

Combination of mpMRI and 3DMRS could aid in the prognostic stratification of localized prostate cancer treated by radiotherapy or brachytherapy, by combining accurate evaluation of tumor extension, and quantification of prostate metabolism.

Magnetic resonance biomarkers in radiation oncology: The report of AAPM Task Group 294

A magnetic resonance (MR) biologic marker (biomarker) is a measurable quantitative characteristic that is an indicator of normal biological and pathogenetic processes or a response to therapeutic intervention derived from the MR imaging process. There is significant potential for MR biomarkers to facilitate personalized approaches to cancer care through more precise disease targeting by quantifying normal versus pathologic tissue function as well as toxicity to both radiation and chemotherapy. Both of which have the potential to increase the therapeutic ratio and provide earlier, more accurate monitoring of treatment response. The ongoing integration of MR into routine clinical radiation therapy (RT) planning and the development of MR guided radiation therapy systems is providing new opportunities for MR biomarkers to personalize and improve clinical outcomes. Their appropriate use, however, must be based on knowledge of the physical origin of the biomarker signal, the relationship to the underlying biological processes, and their strengths and limitations. The purpose of this report is to provide an educational resource describing MR biomarkers, the techniques used to quantify them, their strengths and weakness within the context of their application to radiation oncology so as to ensure their appropriate use and application within this field.

Prostate magnetic resonance imaging technique

Multiparametric magnetic resonance (MR) imaging of the prostate is an excellent tool to detect clinically significant prostate cancer, and it has widely been incorporated into clinical practice due to its excellent tissue contrast and image resolution. The aims of this article are to describe the prostate MR imaging technique for detection of clinically significant prostate cancer according to PI-RADS v2.1, as well as alternative sequences and basic aspects of patient preparation and MR imaging artifact avoidance.

The emerging role of imaging in prostate cancer secondary screening: multiparametric magnetic resonance imaging and the incipient incorporation of molecular imaging

An increasingly robust body of evidence indicates that multiparametric MRI (mpMRI) prior to prostate biopsy can improve the detection of clinically significant prostate cancer while avoiding unnecessary biopsies. As a result, the use of mpMRI and biopsy platforms that allow for the real-time fusion of mpMRI and transrectal ultrasound images is now routinely used in clinical practice. On the horizon, molecular imaging offers the promise of improved sensitivity relative to mpMRI and early data would suggest that the combination of mpMRI and positron emission tomography using radiotracers targeting prostate-specific membrane antigen provide a more accurate assessment than either modality alone. In this review, we examine the current role of imaging to aid in the initial diagnosis of prostate cancer.

Trends in targeted prostate brachytherapy: from multiparametric MRI to nanomolecular radiosensitizers

The treatment of localized prostate cancer is expected to become a significant problem in the next decade as an increasingly aging population becomes prone to developing the disease. Recent research into the biological nature of prostate cancer has shown that large localized doses of radiation to the cancer offer excellent long-term disease control. Brachytherapy, a form of localized radiation therapy, has been shown to be one of the most effective methods for delivering high radiation doses to the cancer; however, recent evidence suggests that increasing the localized radiation dose without bound may cause unacceptable increases in long-term side effects. This review focuses on methods that have been proposed, or are already in clinical use, to safely escalate the dose of radiation within the prostate. The advent of multiparametric magnetic resonance imaging (mpMRI) to better identify and localize intraprostatic tumors, and nanomolecular radiosensitizers such as gold nanoparticles (GNPs), may be used synergistically to increase doses to cancerous tissue without the requisite hazard of increased side effects.

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.

Exploration of analysis methods for diagnostic imaging tests: problems with ROC AUC and confidence scores in CT colonography

BACKGROUND

Different methods of evaluating diagnostic performance when comparing diagnostic tests may lead to different results. We compared two such approaches, sensitivity and specificity with area under the Receiver Operating Characteristic Curve (ROC AUC) for the evaluation of CT colonography for the detection of polyps, either with or without computer assisted detection.

METHODS

In a multireader multicase study of 10 readers and 107 cases we compared sensitivity and specificity, using radiological reporting of the presence or absence of polyps, to ROC AUC calculated from confidence scores concerning the presence of polyps. Both methods were assessed against a reference standard. Here we focus on five readers, selected to illustrate issues in design and analysis. We compared diagnostic measures within readers, showing that differences in results are due to statistical methods.

RESULTS

Reader performance varied widely depending on whether sensitivity and specificity or ROC AUC was used. There were problems using confidence scores; in assigning scores to all cases; in use of zero scores when no polyps were identified; the bimodal non-normal distribution of scores; fitting ROC curves due to extrapolation beyond the study data; and the undue influence of a few false positive results. Variation due to use of different ROC methods exceeded differences between test results for ROC AUC.

CONCLUSIONS

The confidence scores recorded in our study violated many assumptions of ROC AUC methods, rendering these methods inappropriate. The problems we identified will apply to other detection studies using confidence scores. We found sensitivity and specificity were a more reliable and clinically appropriate method to compare diagnostic tests.

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.

Endorectal MRI and MR spectroscopic imaging of prostate cancer: developing selection criteria for MR-guided focal therapy

PURPOSE

To investigate criteria that can identify dominant treatable prostate cancer foci with high certainty at endorectal magnetic resonance imaging (MRI) and MR spectroscopic (MRS) imaging, and thus facilitate selection of patients who are radiological candidates for MR-guided focal therapy.

MATERIALS AND METHODS

We retrospectively identified 88 patients with biopsy-proven prostate cancer who underwent endorectal MRI and MRS imaging prior to radical prostatectomy with creation of histopathological tumor maps. Two independent readers noted the largest tumor foci at MRI, if visible, and the volume of concordant abnormal tissue at MRS imaging, if present. A logistic random intercept model was used to determine the association between clinical and MR findings and correct identification of treatable (over 0.5 cm3) dominant intraprostatic tumor foci.

RESULTS

Readers 1 and 2 identified dominant tumor foci in 50 (57%) and 58 (65%) of 88 patients; 42 (84%) and 48 (83%) of these were dominant treatable lesions at histopathology, respectively. Within the statistical model, the volume of concordant spectroscopic abnormality was the only factor that predicted correct identification of a dominant treatable lesion on T2-weighted images (odds ratio=1.75; 95% confidence interval=1.08 to 2.82; P value=0.02). In particular, all visible lesions on T2-weighted imaging associated with at least 0.54 cm3 of concordant spectroscopic abnormality were correctly identified dominant treatable tumor foci.

CONCLUSION

Patients with dominant intraprostatic tumor foci seen on T2-weighted MRI and associated with at least 0.54 cm3 of concordant MRS imaging abnormality may be radiological candidates for MR-guided focal therapy.

Prostate cancer magnetic resonance imaging (MRI): multidisciplinary standpoint

Prostate cancer is the most common cancer diagnosed in men and a leading cause of death. Accurate assessment is a prerequisite for optimal clinical management and therapy selection of prostate cancer. There are several parameters and nomograms to differentiate between patients with clinically insignificant disease and patients in need of treatment. Magnetic resonance imaging (MRI) is a technique which provides more detailed anatomical images due to high spatial resolution, superior contrast resolution, and multiplanar capability. State-of-the-art MRI techniques, such as diffusion weighted imaging (DWI), MR spectroscopic imaging (MRSI), dynamic contrast enhanced MRI (DCE-MRI), improve interpretation of prostate cancer imaging. In this article, we review the major role of MRI in the advanced management of prostate cancer to noninvasively improve tumor staging, biologic potential, treatment planning, therapy response, local recurrence, and to guide target biopsy for clinical suspected cancer with previous negative biopsy. Finally, future challenges and opportunities in prostate cancer management in the area of functional MRI are discussed as well.

Usefulness of a combined approach of t1-weighted, t2-weighted, dynamic contrast-enhanced, and diffusion-weighted imaging in prostate cancer

Purpose

We evaluated the value of a combined approach of T1-weighted (T1W) imaging, T2-weighted (T2W) imaging, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and diffusion-weighted imaging (DWI) for the detection of prostate cancer and extracapsular extension (ECE) in patients with prostate cancer by using pathologic data after radical prostatectomy.

Materials and Methods

From April 2009 to December 2011, 126 patients who underwent radical prostatectomy and prostate MRI for prostate cancer were analyzed retrospectively. The MRI findings were compared with the pathologic findings of the radical prostatectomy specimens in each patient. The sensitivity, specificity, and accuracy of the detection of prostate cancer and extracapsular extension were analyzed.

Results

The prostate cancer detection rate by use of T1W and T2W imaging, DCE-MRI, and their combination was 65.1%, 69.0%, and 80.2%, respectively (p=0.023). The detection rate using T1W and T2W imaging, DCE-MRI, DWI, and their combination was 57.7%, 65.4%, 67.3%, and 80.8%, respectively (p=0.086). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of combination MRI (T1W, T2W, and DCE-MRI) for ECE were 46.4%, 91.4%, 83.9%, and 68.1%, respectively. The sensitivity of combination MRI (T1W, T2W, and DCE-MRI) for ECE tended to increase as the prostate-specific antigen level rose (p=0.010). The sensitivity, specificity, PPV, and NPV of combination MRI (T1W, T2W, DCE-MRI, and DWI) for ECE were 65.0%, 87.5%, 76.5%, and 80.0%, respectively.

Conclusions

A combined approach of T1W, T2W, and DCE-MRI with DWI demonstrated an accurate detection rate of prostate cancer. Also, combination approaches showed a high specificity for predicting ECE, although sensitivity was relatively lower. Therefore, these methods are reliable for predicting prostate cancer. However, a new protocol is necessary to enhance the sensitivity for predicting ECE.

Multi-kernel graph embedding for detection, Gleason grading of prostate cancer via MRI/MRS

Even though 1 in 6 men in the US, in their lifetime are expected to be diagnosed with prostate cancer (CaP), only 1 in 37 is expected to die on account of it. Consequently, among many men diagnosed with CaP, there has been a recent trend to resort to active surveillance (wait and watch) if diagnosed with a lower Gleason score on biopsy, as opposed to seeking immediate treatment. Some researchers have recently identified imaging markers for low and high grade CaP on multi-parametric (MP) magnetic resonance (MR) imaging (such as T2 weighted MR imaging (T2w MRI) and MR spectroscopy (MRS)). In this paper, we present a novel computerized decision support system (DSS), called Semi Supervised Multi Kernel Graph Embedding (SeSMiK-GE), that quantitatively combines structural, and metabolic imaging data for distinguishing (a) benign versus cancerous, and (b) high- versus low-Gleason grade CaP regions from in vivo MP-MRI. A total of 29 1.5Tesla endorectal pre-operative in vivo MP MRI (T2w MRI, MRS) studies from patients undergoing radical prostatectomy were considered in this study. Ground truth for evaluation of the SeSMiK-GE classifier was obtained via annotation of disease extent on the pre-operative imaging by visually correlating the MRI to the ex vivo whole mount histologic specimens. The SeSMiK-GE framework comprises of three main modules: (1) multi-kernel learning, (2) semi-supervised learning, and (3) dimensionality reduction, which are leveraged for the construction of an integrated low dimensional representation of the different imaging and non-imaging MRI protocols. Hierarchical classifiers for diagnosis and Gleason grading of CaP are then constructed within this unified low dimensional representation. Step 1 of the hierarchical classifier employs a random forest classifier in conjunction with the SeSMiK-GE based data representation and a probabilistic pairwise Markov Random Field algorithm (which allows for imposition of local spatial constraints) to yield a voxel based classification of CaP presence. The CaP region of interest identified in Step 1 is then subsequently classified as either high or low Gleason grade CaP in Step 2. Comparing SeSMiK-GE with unimodal T2w MRI, MRS classifiers and a commonly used feature concatenation (COD) strategy, yielded areas (AUC) under the receiver operative curve (ROC) of (a) 0.89±0.09 (SeSMiK), 0.54±0.18 (T2w MRI), 0.61±0.20 (MRS), and 0.64±0.23 (COD) for distinguishing benign from CaP regions, and (b) 0.84±0.07 (SeSMiK),0.54±0.13 (MRI), 0.59±0.19 (MRS), and 0.62±0.18 (COD) for distinguishing high and low grade CaP using a leave one out cross-validation strategy, all evaluations being performed on a per voxel basis. Our results suggest that following further rigorous validation, SeSMiK-GE could be developed into a powerful diagnostic and prognostic tool for detection and grading of CaP in vivo and in helping to determine the appropriate treatment option. Identifying low grade disease in vivo might allow CaP patients to opt for active surveillance rather than immediately opt for aggressive therapy such as radical prostatectomy.

Diffusion-weighted imaging of local recurrent prostate cancer after radiation therapy: comparison with 22-core three-dimensional prostate mapping biopsy

Accurate localization of local recurrence within the prostate gland is important to perform focal salvage therapy effectively with minimal complications. The purpose of this study was to evaluate the usefulness of diffusion-weighted imaging (DWI) in the detection and localization of prostate cancer recurrence in patients with biochemical failure after definitive radiation therapy using 22-core three-dimensional prostate mapping biopsy (3D-PMB) as a standard reference. Ten patients who underwent magnetic resonance imaging and 22-core 3D-PMB were retrospectively analyzed. For visual assessment of DWI, the prostate was divided into 22 regions corresponding to 3D-PMB. Two diagnostic radiologists determined the presence of abnormal high signal intensity in each region on DWI, and the results of DWI were compared with those of 3D-PMB. Of the 220 regions, 16 regions in six patients were positive for cancer on 3D-PMB, and 30 regions in six patients were judged as positive on DWI. On a patient-by-patient basis, sensitivity and specificity were 100% (6/6) and 100% (4/4), respectively. On a region-by-region basis, sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 69% (11/16), 91% (185/204), 37% (11/30), 97% (185/190) and 89% (196/220), respectively. For discrepant localization between DWI and pathology, DWI-positive and pathology-positive regions tended to be adjacent to each other. In conclusion, DWI is a useful tool for the detection and localization of recurrent prostate cancer in patients with biochemical failure after radiation therapy and may be helpful in the planning of focal salvage therapy.

Automatic conformal prescription of very selective saturation bands for in vivo 1H-MRSI of the prostate

An important step in the implementation of three-dimensional in vivo proton magnetic resonance spectroscopic imaging ((1)H-MRSI) of the prostate is the placement of spatial saturation pulses around the region of interest (ROI) for the removal of unwanted contaminating signals from peripheral tissue. The present study demonstrates the use of a technique called conformal voxel magnetic resonance spectroscopy (CV-MRS). This method automates the placement, orientation, timing and flip angle of very selective saturation (VSS) pulses around an irregularly-shaped, user-defined ROI. The method employs a user adjustable number of automatically positioned VSS pulses (20 used in the present study) which null the signal from periprostatic lipids while closely conforming the shape of the excitation voxel to the shape of the prostate. A standard endorectal coil in combination with a torso-phased array coil was used for all in vivo prostate studies. Three-dimensional in vivo prostate (1)H-MRSI data were obtained using the proposed semi-automated CV-MRS technique, and compared with a standard point resolved spectroscopy (PRESS) technique at TE = 130 ms using manual placement of saturation pulses. The in vivo prostate (1)H-MRSI data collected from 12 healthy subjects using the CV-MRS method showed significantly reduced lipid contamination throughout the prostate, and reduced baseline distortions. On average there was a 50 ± 17% (range 12% - 68%) reduction in lipids throughout the prostate. A voxel-by-voxel benchmark test of over 850 voxels showed that there were 63% more peaks fitted using the LCModel when using a Cramer-Rao Lower Bound (CRLB) cut-off of 40% when using the optimized conformal voxel technique in comparison to the manual placement approach. The evaluation of this CV-MRS technique has demonstrated the potential for easy automation of the graphical prescription of saturation bands for use in (1)H-MRSI.

MR imaging of treated prostate cancer

Many management options are available to patients with newly diagnosed prostate cancer. Magnetic resonance (MR) imaging plays an important role in initial staging of prostate cancer, but it also aids in tumor detection when there is clinical or biochemical suspicion of residual or recurrent disease after treatment. The purpose of this review is to describe the normal appearances of the prostatic region after different kinds of treatment for prostate cancer and to discuss how these appearances differ from those of recurrent and residual disease. Several MR imaging techniques used in evaluating patients with prostate cancer are described, including conventional MR imaging sequences (mainly T1- and T2-weighted sequences), MR spectroscopic imaging, diffusion-weighted imaging, and dynamic contrast agent-enhanced MR imaging. Clinical considerations, together with the different approaches for interpreting serum prostate-specific antigen values in the posttreatment setting, are also presented. All forms of treatment alter the MR imaging features of the prostatic region to a greater or lesser extent, and it is important to be able to recognize expected posttreatment appearances and distinguish them from the features of recurrent or residual cancer to aid subsequent clinical management.

Does local recurrence of prostate cancer after radiation therapy occur at the site of primary tumor? Results of a longitudinal MRI and MRSI study

PURPOSE

To determine if local recurrence of prostate cancer after radiation therapy occurs at the same site as the primary tumor before treatment, using longitudinal magnetic resonance (MR) imaging and MR spectroscopic imaging to assess dominant tumor location.

METHODS AND MATERIALS

This retrospective study was HIPAA compliant and approved by our Committee on Human Research. We identified all patients in our institutional prostate cancer database (1996 onward) who underwent endorectal MR imaging and MR spectroscopic imaging before radiotherapy for biopsy-proven prostate cancer and again at least 2 years after radiotherapy (n = 124). Two radiologists recorded the presence, location, and size of unequivocal dominant tumor on pre- and postradiotherapy scans. Recurrent tumor was considered to be at the same location as the baseline tumor if at least 50% of the tumor location overlapped. Clinical and biopsy data were collected from all patients.

RESULTS

Nine patients had unequivocal dominant tumor on both pre- and postradiotherapy imaging, with mean pre- and postradiotherapy dominant tumor diameters of 1.8 cm (range, 1-2.2) and 1.9 cm (range, 1.4-2.6), respectively. The median follow-up interval was 7.3 years (range, 2.7-10.8). Dominant recurrent tumor was at the same location as dominant baseline tumor in 8 of 9 patients (89%).

CONCLUSIONS

Local recurrence of prostate cancer after radiation usually occurs at the same site as the dominant primary tumor at baseline, suggesting supplementary focal therapy aimed at enhancing local tumor control would be a rational addition to management.

Magnetic resonance spectroscopy: a promising tool for the diagnostics of human prostate cancer?

BACKGROUND

Prostate cancer (CaP) is one of the topmost diagnosed malignant diseases worldwide. In developed countries, early cancer detection methods have led to an increase of incidence rates over the last decades; however, with great variance of the prognosis. There is no diagnostic tool for an exact prediction of tumor aggressiveness, thus there is a lack of adequate and optimal treatment planning.

METHODS

Electronic databases (Medline, PubMed) were scanned for scientific literature. Basic concepts of magnetic resonance spectroscopy (MRS), important results and its clinical applications were extracted and reviewed in this article.

CONCLUSIONS

MRS provides crucial information about the metabolic status of human prostate samples while preserving the specimens for further investigations. Single metabolites and metabolomic profiles can be quantified to distinguish benign from malignant tissue and to predict aggressiveness, such as the recurrence rates of CaP. Studies are also anticipating that MRS might be beneficially applicable for in vivo investigations in the future.

Effect of Prostate Biopsy Hemorrhage on MRDW and MRS Imaging

Purpose

To retrospectively evaluate the effect of post-prostate-biopsy hemorrhage on the interpretation of magnetic resonance diffusion-weighted (MRDW) and magnetic resonance spectroscopic (MRS) imaging in the detection of prostate cancer. We also investigated the optimal timing for magnetic resonance examination after prostate biopsy.

Materials and Methods

We reviewed the records of 135 men. All patients underwent prostate magnetic resonance imaging (MRI). The prostate was divided into eight regions according to the biopsy site. Subsequently, we measured hemorrhage on apparent diffusion coefficient (ADC) values and (choline+creatinine)/citrate ([Cho+Cr]/Cit) ratios in the same regions on the MRI. We investigated the effect of hemorrhage at ADC values and (Cho+Cr)/Cit ratios on MRI and the relationship between prostate biopsy results and MRI findings.

Results

The mean patient age was 68.7 years and the mean time between biopsy and MRI was 23.5 days. The total hemorrhagic score demonstrated no significant associations with intervals from biopsy to MRI. Higher hemorrhagic scores were associated with higher ADC values, prostate cancer, and noncancer groups, respectively (p<0.001). ADC values were lower in tumors than in normal tissue (p<0.001), and ADC values were inversely correlated with tumor Gleason score in biopsy cores (p<0.001). However, (Cho+Cr)/Cit ratios did not exhibit any association with prostate biopsy results and hemorrhage.

Conclusions

Hemorrhage had no significant associations with the interval from biopsy to MRI. ADC values may help to detect prostate cancer and predict the aggressiveness of cancer; however, it is important to consider the bias effect of hemorrhage on the interpretation of MRDW imaging given that hemorrhage affects ADC values.

Integrating multiparametric prostate MRI into clinical practice

Multifunctional magnetic resonance imaging (MRI) techniques are increasingly being used to address bottlenecks in prostate cancer patient management. These techniques yield qualitative, semi-quantitative and fully quantitative biomarkers that reflect on the underlying biological status of a tumour. If these techniques are to have a role in patient management, then standard methods of data acquisition, analysis and reporting have to be developed. Effective communication by the use of scoring systems, structured reporting and a graphical interface that matches prostate anatomy are key elements. Practical guidelines for integrating multiparametric MRI into clinical practice are presented.

Reproducibility of 3D 1H MR spectroscopic imaging of the prostate at 1.5T

PURPOSE

To determine the reproducibility of 3D proton magnetic resonance spectroscopic imaging ((1)H-MRSI) of the human prostate in a multicenter setting at 1.5T.

MATERIALS AND METHODS

Fourteen subjects were measured twice with 3D point-resolved spectroscopy (PRESS) (1)H-MRSI using an endorectal coil. MRSI voxels were selected in the peripheral zone and combined central gland at the same location in the prostate in both measurements. Voxels with approved spectral quality were included to calculate Bland-Altman parameters for reproducibility from the choline plus creatine to citrate ratio (CC/C). The repeated spectroscopic data were also evaluated with a standardized clinical scoring system.

RESULTS

A total of 74 voxels were included for reproducibility analysis. The complete range of biologically interesting CC/C ratios was covered. The overall within-voxel standard deviation (SD) of the CC/C ratio of the repeated measurements was 0.13. This value is equal to the between-subject SD of noncancer prostate tissue. In >90% of the voxels the standardized clinical score did not differ relevantly between the measurements.

CONCLUSION

Repeated measurements of in vivo 3D (1)H-MRSI of the complete prostate at 1.5T produce equal and quantitative results. The reproducibility of the technique is high enough to provide it as a reliable tool in assessing tumor presence in the prostate.

Fast T2*-weighted MRI of the prostate at 3 Tesla

PURPOSE

To describe a rapid T2*-weighted (T2*W), three-dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1-weighted turbo-spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS).

MATERIALS AND METHODS

B(0) susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k-space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six-channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed.

RESULTS

Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W-positive areas. Post-biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS.

CONCLUSION

The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T.

A decade in prostate cancer: from NMR to metabolomics

Over the past 30 years, continuous progress in the application of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance spectroscopic imaging (MRSI) to the detection, diagnosis and characterization of human prostate cancer has turned what began as scientific curiosity into a useful clinical option. In vivo MRSI technology has been integrated into the daily care of prostate cancer patients, and innovations in ex vivo methods have helped to establish NMR-based prostate cancer metabolomics. Metabolomic and multimodality imaging could be the future of the prostate cancer clinic--particularly given the rationale that more accurate interrogation of a disease as complex as human prostate cancer is most likely to be achieved through paradigms involving multiple, instead of single and isolated, parameters. The research and clinical results achieved through in vivo MRSI and ex vivo NMR investigations during the first 11 years of the 21st century illustrate areas where these technologies can be best translated into clinical practice.

Imaging in prostate cancer

Prostate cancer is the most common malignancy in men, in general. Most patients diagnosed with prostate cancer have localized disease confined to the prostate. A small percentage of patients with aggressive tumors will progress to develop local, extracapsular tumor extension and distant metastases. The aim of prostate cancer management is to identify and treat those patients with aggressive disease before they develop locally advanced or metastatic disease, and to avoid overtreating indolent tumors, which are unlikely to be life threatening. Imaging has been shown to be valuable in local staging of prostate cancer and as an aid to the management of clinically significant disease. In this article, we discuss the different established imaging modalities and emerging techniques for prostate cancer imaging in patients with clinically localized disease who may be suitable for radical treatment.

Discriminating cancer from noncancer tissue in the prostate by 3-dimensional proton magnetic resonance spectroscopic imaging: a prospective multicenter validation study

OBJECTIVES

A prospective multicenter validation of the ability of 1H magnetic resonance spectroscopic imaging (MRSI) to distinguish cancer from noncancer tissues throughout the prostate with histopathology of the resected organ as the standard of reference.

MATERIALS AND METHODS

Institutional review board approval was obtained for all centers and all participating patients and volunteers provided written informed consent. Ninety-nine patients and 10 age-matched volunteers from 8 participating centers underwent magnetic resonance imaging and 3-dimensional MRSI with an endorectal coil at 1.5 T. Selected MRSI voxels were assigned to the peripheral zone (PZ), the central gland (CG), the periurethral area, and cancer tissue. Signal ratios of choline + creatine to citrate (CC/C) in spectra of these voxels were automatically calculated. Receiver operating characteristic curves were constructed to assess the accuracy by which this ratio can discriminate cancer from noncancer tissue.

RESULTS

A total of 70% of voxels in noncancer tissue and 90% of voxels in cancer tissue passed the quality check of the automatically fitted spectra. The median CC/C was significantly different between any noncancer and cancer tissue (P < 0.0001), but not between the different contributing centers. CC/C increased with cancer focus size (P =0.0008) and certainty of voxel mapping to histopathologic cancer site (P 0.0001). The area under the receiver operating characteristic curve for discriminating voxels of cancer tissue from noncancer tissue was 0.88 (confidence interval: 0.84-0.92) in the PZ and 0.76 (confidence interval: 0.71- 0.81) in the CG.

Detection of fully refocused polyamine spins in prostate cancer at 7 T

(1)H MRSI is often used at 1.5 or 3 T to study prostate cancer, where the ratio of choline + creatine to citrate is taken as a marker for tumour presence. Recently, the level of polyamines (mainly spermine) has been shown to improve specificity even further. However, the in vivo detection of these polyamines (at 3.1  ppm) is hampered by signal cancellation as a result of J-coupling effects and signal overlap with choline (3.2  ppm) and creatine (3.0  ppm) resonances. At higher magnetic field strengths, the chemical shift dispersion will increase, which allows the use of very selective radiofrequency pulses to refocus J-coupled spins. In this work, we added selective refocusing pulses to a semi-LASER (localisation based on adiabatic selective refocusing) sequence at 7 T, and optimised the inter-pulse timings of the sequence for fully refocused detection of spermine spins, whilst maintaining optimised detection of choline, creatine and the strongly coupled spin system of citrate.

Value of multiparametric prostate MRI of the peripheral zone

RATIONALE AND OBJECTIVES

MRI of the prostate offers the possibility to localize and stage prostate cancer and may improve detection of disease. Currently, T2-weighted images and spectroscopy are the most commonly used MRI techniques. To assess the value of prostate MRI and its different modalities in the process of diagnosis, the currently available MRI techniques were compared.

MATERIALS AND METHODS

16 patients were examined on a 1.5 T MR system. All patients underwent the same MR protocol using an endorectal coil: T2-weighted triplanar turbo-spin-echo (TSE), axial echo-planar diffusion-weighted imaging (DWI), 3D chemical-shift imaging MR spectroscopy (MRS) and axial dynamic-contrast-enhanced TurboFLASH (DCE). Parametric maps of the choline+creatine/citrate ratio (CC-CR), apparent diffusion coefficient (ADC) and plasma flow/mean transit time (PF/MTT) were calculated. Additionally, average time for reading and scanning were evaluated. As reference, biopsy results were used.

RESULTS

Sensitivity/specificity were 50.0-85.7%/44.4-72.2% for the T2 weighted images, 78.6-100.0%/38.9-55.6% for the ADC maps, 71.4-85.7%/44.4-55.6% for the PF/MTT maps and 64.3-78.6%/50.0-77.8% for the CC-CR. Average scan and reading time were 8:46/1:54 min for T2, 1:28/3:17 min for DWI, 8:41/2:12 min for DCE and 11:36/3:47 for spectroscopy.

CONCLUSION

We found no significant differences in accuracy between the modalities. We observed DWI to be advantageous in examination and reading compared to DCE and MRS, therefore it might be the preferred modality when a shortened protocol is needed.

Clinically low-risk prostate cancer: evaluation with transrectal doppler ultrasound and functional magnetic resonance imaging

OBJECTIVES

To evaluate transrectal ultrasound, amplitude Doppler ultrasound, conventional T2-weighted magnetic resonance imaging, spectroscopy and dynamic contrast-enhanced magnetic resonance imaging in localizing and locally staging low-risk prostate cancer.

INTRODUCTION

Prostate cancer has been diagnosed at earlier stages and the most accepted classification for low-risk prostate cancer is based on clinical stage T1c or T2a, Gleason score ≤6, and prostate-specific antigen (PSA) ≤10 ng/ml.

METHODS

From 2005 to 2006, magnetic resonance imaging was performed in 42 patients, and transrectal ultrasound in 26 of these patients. Seven patients were excluded from the study. Mean patient age was 64.94 years and mean serum PSA was 6.05 ng/ml. The examinations were analyzed for tumor identification and location in prostate sextants, detection of extracapsular extension, and seminal vesicle invasion, using surgical pathology findings as the gold standard.

RESULTS

Sixteen patients (45.7%) had pathologically proven organ-confined disease, 11 (31.4%) had positive surgical margin, 8 (28.9%) had extracapsular extension, and 3 (8.6%) presented with extracapsular extension and seminal vesicle invasion. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy values for localizing low-risk prostate cancer were 53.1%, 48.3%, 63.4%, 37.8% and 51.3% for transrectal ultrasound; 70.4%, 36.2%, 65.1%, 42.0% and 57.7% for amplitude Doppler ultrasound; 71.5%, 58.9%, 76.6%, 52.4% and 67.1% for magnetic resonance imaging; 70.4%, 58.7%, 78.4%, 48.2% and 66.7% for magnetic resonance spectroscopy; 67.2%, 65.7%, 79.3%, 50.6% and 66.7% for dynamic contrast-enhanced magnetic resonance imaging, respectively. Sensitivity, specificity, PPV, NPV and accuracy values for detecting extracapsular extension were 33.3%, 92%, 14.3%, 97.2% and 89.7% for transrectal ultrasound and 50.0%, 77.6%, 13.7%, 95.6% and 75.7% for magnetic resonance imaging, respectively. For detecting seminal vesicle invasion, these values were 66.7%, 85.7%, 22.2%, 97.7% and 84.6% for transrectal ultrasound and 40.0%, 83.1%, 15.4%, 94.7% and 80.0% for magnetic resonance imaging.

CONCLUSION

Although preliminary, our results suggest that imaging modalities have limited usefulness in localizing and locally staging clinically low-risk prostate cancer.

Is apparent diffusion coefficient associated with clinical risk scores for prostate cancers that are visible on 3-T MR images?

PURPOSE

To investigate whether apparent diffusion coefficients (ADCs) derived from diffusion-weighted (DW) magnetic resonance (MR) imaging at 3 T correlate with the clinical risk of prostate cancer in patients with tumors that are visible on MR images, with MR imaging/transrectal ultrasonography (US) fusion-guided biopsy as a reference.

MATERIALS AND METHODS

Forty-eight consecutive patients (median age, 60 years; median serum prostate-specific antigen value, 6.3 ng/mL) who underwent DW imaging during 3-T MR imaging with an endorectal coil were included in this retrospective institutional review board-approved study, and informed consent was obtained from each patient. Patients underwent targeted MR imaging/transrectal US fusion-guided prostate biopsy. Mean ADCs of cancerous target tumors were correlated with Gleason and D'Amico clinical risk scores. The true risk group rate and predictive value of the mean ADC for classifying a tumor by its D'Amico clinical risk score was determined by using linear discriminant and receiver operating characteristic analyses.

RESULTS

A significant negative correlation was found between mean ADCs of tumors in the peripheral zone and their Gleason scores (P = .003; Spearman ρ = -0.60) and D'Amico clinical risk scores (P < .0001; Spearman ρ = -0.69). ADC was found to distinguish tumors in the peripheral zone with intermediate to high clinical risk from those with low clinical risk with a correct classification rate of 0.73.

CONCLUSION

There is a significant negative correlation between ADCs and Gleason and D'Amico clinical risk scores. ADCs may therefore be useful in predicting the aggressiveness of prostate cancer.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100667/-/DC1.

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.

Prostate cancer: 1.5 T endo-coil dynamic contrast-enhanced MRI and MR spectroscopy--correlation with prostate biopsy and prostatectomy histopathological data

PURPOSE

To investigate diagnostic accuracy of detection of prostate cancer by magnetic resonance: to evaluate the performance of T2WI, DCEMRI and CSI and to correlate the results with biopsy and radical prostatectomy histopathological data.

MATERIALS AND METHODS

43 patients, scheduled for radical prostatectomy, underwent prostate MR examination. Prostate cancer was identified by transrectal ultrasonographically (TRUS) guided sextant biopsy. MR examination was performed at 1.5 T with an endorectal MR coil. Cancer localisation was performed on sextant-basis--for comparison between TRUS biopsy, MR techniques and histopathological findings on prostatectomy specimens.

RESULTS

Prostate cancer was identified in all 43 patients by combination of the three MR techniques. The detection of prostate cancer on sextant-basis showed sensitivity and specificity: 50% and 91% for TRUS, 72% and 55% for T2WI, 49% and 69% for DCEMRI, and 46% and 78% for CSI.

CONCLUSION

T2WI, DCEMRI and CSI in combination can identify prostate cancer. Further development of MR technologies for these MR methods is necessary to improve the detection of the prostate cancer.

[MR spectroscopy of the prostate with external surface coils: clinical feasibility]

PURPOSE

To determine the clinical feasibility of MR spectroscopy (MRS) of prostate cancer using external multi-channel surface coils at 1.5T. Materials and methods. Retrospective study of 31 patients with prostate cancer who underwent MRS as part of the staging work-up prior to radical prostatectomy. The ratio of the three main metabolites ([choline + creatine]/citrate) were measured along with spectral analysis of different regions of interest (ROI) placed in areas of normal tissue and cancer using the surgical specimen as the standard of reference.

RESULTS

One hundred and eighty-three voxels were analyzed. Qualitative visual analysis identified pathological spectra in 88.5% of cancer ROI, 11.7% of normal transitional zone ROI and 1.6% of normal peripheral zone ROI. The ratios of normal prostate tissue were significantly more elevated (p<0.0001) in the transition zone (0.41 +/- 0.24) than in the peripheral zone (0.22 +/- 0.36). Tumor containing voxels had significantly higher ratios (2.84 +/- 2.74) than normal tissue containing voxels of the transition zone (p<0.0001) and peripheral zone (p<0.0001).

CONCLUSION

Prostate MRS using external surface coils appears routinely feasible at 1.5T, even though it presents some limitations.

Prostate cancer: value of multiparametric MR imaging at 3 T for detection--histopathologic correlation

PURPOSE

To determine utility of multiparametric imaging performed at 3 T for detection of prostate cancer by using T2-weighted magnetic resonance (MR) imaging, MR spectroscopy, and dynamic contrast material-enhanced MR imaging, with whole-mount pathologic findings as reference standard.

MATERIALS AND METHODS

This prospectively designed, HIPAA-compliant, single-institution study was approved by the local institutional review board. Seventy consecutive patients (mean age, 60.4 years; mean prostate-specific antigen level, 5.47 ng/mL [5.47 microg/L]; range, 1-19.9 ng/mL [1-19.9 microg/L]) were included; informed consent was obtained from each patient. All patients had biopsy-proved prostate cancer, with a median Gleason score of 7 (range, 6-9). Images were obtained by using a combination of six-channel cardiac and endorectal coils. MR imaging and pathologic findings were evaluated independently and blinded and then correlated with histopathologic findings by using side-by-side comparison. Analyses were conducted with a raw stringent approach and an alternative neighboring method, which accounted for surgical deformation, shrinkage, and nonuniform slicing factors in pathologic specimens. Generalized estimating equations (GEEs) were used to estimate the predictive value of region-specific, pathologically determined cancer for all three modalities. This approach accounts for the correlation among multiple regions in the same individual.

RESULTS

For T2-weighted MR imaging, sensitivity and specificity values obtained with stringent approach were 0.42 (95% confidence interval [CI]: 0.36, 0.47) and 0.83 (95% CI: 0.81, 0.86), and for the alternative neighboring approach, sensitivity and specificity values were 0.73 (95% CI: 0.67, 0.78) and 0.89 (95% CI: 0.85, 0.93), respectively. The combined diagnostic accuracy of T2-weighted MR imaging, dynamic contrast-enhanced MR imaging, and MR spectroscopy for peripheral zone tumors was examined by calculating their predictive value with different combinations of techniques; T2-weighted MR imaging, dynamic contrast-enhanced MR imaging, and MR spectroscopy provided significant independent and additive predictive value when GEEs were used (P < .001, P = .02, P = .002, respectively).

CONCLUSION

Multiparametric MR imaging (T2-weighted MR imaging, MR spectroscopy, dynamic contrast-enhanced MR imaging) of the prostate at 3 T enables tumor detection, with reasonable sensitivity and specificity values.

The targeting behavior of folate-nanohydrogel evaluated by near infrared imaging system in tumor-bearing mouse model

PURPOSE

To synthesize P[(Folate-Allylamine)-co-(N-isopropylacrylamine)- co-Acrylamide] (P(FoAAn-co-NIPA-AAm), folate-NHG) with appropriate diameter and lower critical solution temperature (LCST) for targeting to folate receptor (FR) expressing tumors.

METHODS

Folate-NHG was synthesized by free-radical precipitation polymerization method reported in our previous work and other reports. LCST, diameter and morphology of folate-NHG were characterized by UV-vis spectrophotometer, laser particle size analyzer (LPSA) and transmission electron microscope (TEM), respectively. No.12 near infrared dye (NIRD-12) was entrapped into folate-NHG by hydrophobic association to trace the in vivo dynamic behavior of folate-NHG. This process was evaluated by a homemade near infrared (NIR) imaging system.

RESULTS

Spherical folate-NHG with diameter of about 50 nm and LCST of about 40 degrees C was successfully synthesized. The photo stability of NIRD-12 was strengthened after being entrapped into folate-NHG, which enabled NIRD-12 to better trace the in vivo dynamic process of folate-NHG. Folate-NHG showed good targeting capability for all three folate receptor expressing tumor models (SMMC-7721, Bel-7402 and HeLa) with different sizes, and this accumulation could last for more than 96 h. D-folate-NHG, synthesized with double amount of FoAAn, showed better targeting effect for SMMC-7721 tumor model than that of folate-NHG.

CONCLUSIONS

Folate-NHG could actively accumulate in three models of folate receptor positive tumors with different sizes and keep retention for more than 96 h, which enables it to be used as a diagnostic reagent or anti-tumor drug carrier for tumor therapy.

A feasibility study of novel ultrasonic tissue characterization for prostate-cancer diagnosis: 2D spectrum analysis of in vivo data with histology as gold standard

This study demonstrates the feasibility of using a novel 2D spectrum ultrasonic tissue characterization (UTC) technique for prostate-cancer diagnosis. Normalized 2D spectra are computed by performing Fourier transforms along the range (beam) and the cross-range directions of the digital radio-frequency echo data, then dividing by a reference spectrum. This 2D spectrum method provides axial and lateral information of tissue microstructures, an improvement over the current 1D spectrum analysis which only provides axial information. A pilot study was conducted on four prostate-cancer patients who underwent radical prostatectomies. Cancerous and noncancerous regions of interest, identified through histology, were compared using four 2D spectral parameters: peak value and 3 dB width of the radially integrated spectral power (RISP), slope and intercept of the angularly integrated spectral power (AISP). For noncancerous and cancerous prostatic tissues, respectively, our investigation yielded 23 +/- 1 and 26 +/- 1 dB for peak value of RISP, 7.8 +/- 0.5 degrees and 7.6 +/- 0.6 degrees for 3 dB of RISP, -2.1 +/- 0.2 and -2.7 +/- 0.4 dB/MHz for slope of AISP, and 92 +/- 5 and 112 +/- 6 dB for intercept of AISP. Preliminary results indicated that 2D spectral UTC has the potential for identifying tumor-bearing regions within the prostate gland.

Peripheral zone prostate cancer. Pre-treatment evaluation with MR and 3D ¹H MR spectroscopic imaging: correlation with pathologic findings

The purpose of this study was to retrospectively characterize benign and malignant prostate peripheral zone tissue by using endorectal MRI and 3D ¹H MRS. Fifty-two men with untreated biopsy-proven prostate cancer underwent combined endorectal MRI and MRSI. Whole-mount step-section histopathologic analysis constituted the reference standard. Biopsy correctly detected 74 locations; MRI correctly detected 72 locations; MRS correctly detected 72 locations; MRI + MRS correctly detected 78 locations. Cohen's test showed that biopsy had a lower degree of agreement with histology than MRI + MRS combined. The ratio of [(Cho + Cr)]/Cit correlates with the pathologic Gleason score. The addition of 3D¹H MRSI to MRI can improve diagnosis of prostate cancer contributing indirectly to improve local staging. In addition, the correlation between metabolic 3D¹H MRSI data with pathological Gleason grade may offer a non-invasive means to better predict prostate cancer aggressiveness.

Three-Dimensional Prostate Mapping Biopsy Has a Potentially Significant Impact on Prostate Cancer Management

Purpose

To compare a new staging, three-dimensional prostate mapping biopsy (3D-PMB) method with traditional transrectal ultrasound (TRUS) biopsy and assess its possible impact on patient management.

Patients and Methods

One hundred eighty patients with unilateral cancer on TRUS biopsy, who were considering conservative management, underwent restaging with 3D-PMB. The 3D-PMB was carried out transperineally using a brachytherapy grid under TRUS guidance. Biopsies were taken every 5 mm throughout the volume of the prostate, and labeling of the specimen coordinates allowed accurate reconstruction of the location and extent of a patient's cancer.

Results

3D-PMB obtained a median of 50 cores (standard deviation, ± 20.61). One hundred ten patients (61.1%) were positive bilaterally, and 41 patients (22.7%) had Gleason scores increased to 7 or higher. Thirty-six patients had negative results on 3D-PMB. Complications of 3D-PMB were self-limited and included 14 patients (7.7%) who required short-term indwelling catheter drainage and two patients with hematuria, one of whom required overnight bladder irrigation.

Conclusion

3D-PMB is a transperineal biopsy that can be safely used to accurately stage prostate cancer patients. At the present time, when patient management is increasingly based on the extent and characteristics of prostate cancer, 3D-PMB could have a profound effect on patient management.

Prostate cancer: sextant localization at MR imaging and MR spectroscopic imaging before prostatectomy--results of ACRIN prospective multi-institutional clinicopathologic study

PURPOSE

To determine the incremental benefit of combined endorectal magnetic resonance (MR) imaging and MR spectroscopic imaging, as compared with endorectal MR imaging alone, for sextant localization of peripheral zone (PZ) prostate cancer.

MATERIALS AND METHODS

This prospective multicenter study, conducted by the American College of Radiology Imaging Network (ACRIN) from February 2004 to June 2005, was institutional review board approved and HIPAA compliant. Research associates were required to follow consent guidelines approved by the Office for Human Research Protection and established by the institutional review boards. One hundred thirty-four patients with biopsy-proved prostate adenocarcinoma and scheduled to undergo radical prostatectomy were recruited at seven institutions. T1-weighted, T2-weighted, and spectroscopic MR sequences were performed at 1.5 T by using a pelvic phased-array coil in combination with an endorectal coil. Eight readers independently rated the likelihood of the presence of PZ cancer in each sextant by using a five-point scale-first on MR images alone and later on combined MR-MR spectroscopic images. Areas under the receiver operating characteristic curve (AUCs) were calculated with sextant as the unit of analysis. The presence or absence of cancer at centralized histopathologic evaluation of prostate specimens was the reference standard. Reader-specific receiver operating characteristic curves for values obtained with MR imaging alone and with combined MR imaging-MR spectroscopic imaging were developed. The AUCs were estimated by using Mann-Whitney statistics and appropriate 95% confidence intervals.

RESULTS

Complete data were available for 110 patients (mean age, 58 years; range, 45-72 years). MR imaging alone and combined MR imaging-MR spectroscopic imaging had similar accuracy in PZ cancer localization (AUC, 0.60 vs 0.58, respectively; P > .05). AUCs for individual readers were 0.57-0.63 for MR imaging alone and 0.54-0.61 for combined MR imaging-MR spectroscopic imaging.

CONCLUSION

In patients who undergo radical prostatectomy, the accuracy of combined 1.5-T endorectal MR imaging-MR spectroscopic imaging for sextant localization of PZ prostate cancer is equal to that of MR imaging alone.

Espectroscopia por ressonância magnética no diagnóstico do câncer de próstata: experiência inicial

OBJETIVO: Demonstrar a experiência na implantação de um protocolo de espectroscopia por ressonância magnética do 1H tridimensional (3D 1H MRSI), disponível comercialmente, aplicando-o em pacientes com suspeita de neoplasia prostática e com diagnóstico estabelecido de tumor prostático. MATERIAIS E MÉTODOS: Estudo realizado de forma prospectiva, em 41 pacientes com idades entre 51 e 80 anos (média de 67 anos). Dois grupos foram formados: pacientes com uma ou mais biópsias negativas para câncer e antígeno prostático específico elevado (grupo A) e pacientes com câncer confirmado por biópsia (grupo B). Procurou-se, a partir dos resultados da ressonância magnética e espectroscopia por ressonância magnética, determinar a área-alvo (grupo A) ou a extensão do câncer conhecido (grupo B). RESULTADOS: No diagnóstico de câncer de próstata a espectroscopia por ressonância magnética apresentou especificidade abaixo da descrita pela literatura, cerca de 47%. Já para o estadiamento do tumor diagnosticado, houve correspondência com a literatura. CONCLUSÃO: A implantação e padronização da espectroscopia por ressonância magnética permitiram a obtenção de informações importantes para o diagnóstico presuntivo da existência de câncer de próstata, combinando as imagens por ressonância magnética com os dados metabólicos da espectroscopia por ressonância magnética.

Re-Biopsies of the Prostate after Endo-Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) in Patients with ASAP: Preliminary Results

Introduction e Objectives

There are some evidences that the combination of EndoMRI and MRS might be able to limit the number of iterative biopsies in patients with negative biopsies of the prostate and a still rising PSA. The aim of this study is to evaluate the possible role of EndoMRI/MRS in patients with ASAP.

Methods

From November 2005 to September 2008 we enrolled 28 consecutive patients diagnosed with ASAP at a TRUS-guided needle prostate biopsy. All patients underwent prostatic EndoMRI and MRS. A prostatic zone was classified as: suspicious for prostate cancer if low intensity signal was present on T2-weighted images and/or if the choline + creatine / citrate ratio was >0.86; equivocal or negative otherwise. A subsequent 12-core needle prostate biopsy was performed and supplementary biopsies were added in the suspicious zones. The results of MRI/MRS were then compared with histological findings.

Results

The combination of EndoMRI and MRS was suspicious for cancer in 70% of patients, equivocal in 23% and negative in 7%. Histological findings at re-biopsy included: prostate cancer in 35%, ASAP in 23%, BPH or prostatitis in 42%. In 78% of patients diagnosed with prostate cancer the combination MRI/MRS was suspicious and in 22% equivocal. In all patients the cancer was found in suspicious zones at MRI/MRS where targeted biopsies were performed.

Conclusions

The combination of EndoMRI and MRS proved to have a good sensitivity but a poor specificity in identifying a concurrent prostate cancer among patients with ASAP. The location of positive cores for prostate cancer was consistent with the suspicious zones at MRI/MRS.