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

Functional magnetic resonance imaging in prostate cancer

CONTEXT

Magnetic resonance imaging (MRI) combined with magnetic resonance spectroscopy imaging (MRSI), dynamic contrast-enhanced MRI, and diffusion-weighted MRI emerged as promising tests in the diagnosis of prostate cancer, and they show encouraging results.

OBJECTIVE

This review emphasizes different functional MRI techniques in the diagnosis of prostate cancer and includes information about their clinical value and usefulness.

EVIDENCE ACQUISITION

The authors searched the Medline, Embase, and Cochrane Library databases. There were no language restrictions. The last search was performed in October 2008.

EVIDENCE SYNTHESIS

The combination of conventional MRI with functional MRI techniques is more reliable for differentiating benign and malignant prostate tissues than any other diagnostic procedure. At present, no guideline is available that outlines which technique is best in a specific clinical situation. It also remains uncertain whether improved spatial resolution and signal-to-noise ratio of 3-T MRI will improve diagnostic performance.

CONCLUSIONS

A limited number of small studies suggest that functional MRI may improve the diagnosis and staging of prostate cancer. This finding needs further confirmation in larger studies, and cost-effectiveness needs to be established.

Clinical applications of metabolomics in oncology: a review

Metabolomics, an omic science in systems biology, is the global quantitative assessment of endogenous metabolites within a biological system. Either individually or grouped as a metabolomic profile, detection of metabolites is carried out in cells, tissues, or biofluids by either nuclear magnetic resonance spectroscopy or mass spectrometry. There is potential for the metabolome to have a multitude of uses in oncology, including the early detection and diagnosis of cancer and as both a predictive and pharmacodynamic marker of drug effect. Despite this, there is lack of knowledge in the oncology community regarding metabolomics and confusion about its methodologic processes, technical challenges, and clinical applications. Metabolomics, when used as a translational research tool, can provide a link between the laboratory and clinic, particularly because metabolic and molecular imaging technologies, such as positron emission tomography and magnetic resonance spectroscopic imaging, enable the discrimination of metabolic markers noninvasively in vivo. Here, we review the current and potential applications of metabolomics, focusing on its use as a biomarker for cancer diagnosis, prognosis, and therapeutic evaluation.

Citrate transport and metabolism in mammalian cells: prostate epithelial cells and prostate cancer

Citrate, an organic trivalent anion, is a major substrate for generation of energy in most cells. It is produced in mitochondria and used either in the Krebs' cycle or released into cytoplasm through a specific mitochondrial carriers. Citrate can also be taken up from blood through different plasma membrane transporters. In the cytoplasm, citrate can be used ultimately for fatty acid synthesis, which is increased in cancer cells. Here, we review the ways in which citrate can be transported and discuss the changes in transport and metabolism that occur in cancer cells. The primary focus is on the prostate gland, which is known to produce and release large amounts of citrate during its normal secretory function. The significant changes that occur in citrate-related metabolism and transport in prostate cancer are the second focus. This review strives to relate these mechanisms to molecular biology on the one hand and to clinical applications on the other.

Intermixed normal tissue within prostate cancer: effect on MR imaging measurements of apparent diffusion coefficient and T2--sparse versus dense cancers

PURPOSE

To investigate differences in apparent diffusion coefficient (ADC) and T2 values between dense and sparse regions in prostate cancer.

MATERIALS AND METHODS

Eighteen patients (median age, 61 years; range, 44-72 years) gave informed consent for this retrospective Research Ethics Board-approved study. Prior to radical prostatectomy, ADC (b value, 600 sec/mm(2)) and T2 maps were obtained by using 1.5-T magnetic resonance (MR) imaging. Twenty-eight peripheral zone (PZ) tumors were reviewed by using whole-mount histologic findings, and regions assessed to contain primarily (>60%) normal PZ tissue were delineated. Tumors were categorized as "sparse" if more than 50% of their cross-sectional areas were these primarily normal PZ regions and were considered "dense" otherwise. Normal PZ tissue was outlined separately on the same section. Tumor and normal tissue outlines were transferred to corresponding ADC and T2 maps, and median values were calculated. Values were compared by using multiple regression analysis. Matched-pair tumor-to-normal tissue differences and log(2)-transformed ratios were assessed by using nonparametric tests.

RESULTS

Thirty-six percent (10 of 28) of tumors were sparse; 64% (18 of 28) were dense. For both overall and intrapatient comparisons, dense tumors had significantly lower ADC and T2 values than normal PZ tissue (P < .05), but no significant differences were observed between sparse tumors and normal tissue. Log(2)-transformed tumor-to-normal tissue ratios were significantly less than zero for dense tumors for both ADC and T2 (P < .01) measurements but not for sparse tumors. Both matched-pair differences and log(2)-transformed ratios were significantly different between sparse and dense tumors (P < .01). ADC and T2 values were moderately correlated (Pearson correlation coefficient range, r = 0.770-0.804).

CONCLUSION

Sparse prostate tumors have similar ADC and T2 values to those of normal PZ tissue. This may limit MR imaging detection and the assessment of tumor volume of some cancers.

A qualitative approach to combined magnetic resonance imaging and spectroscopy in the diagnosis of prostate cancer

PURPOSE

To investigate the feasibility and diagnostic value of a whole prostate qualitative approach to combined magnetic resonance imaging and spectroscopy (MRI+MRS) in the detection of prostate cancer in patients with elevated PSA.

MATERIALS AND METHODS

Three hundred and fifty six subjects (mean serum PSA 11.47ng/ml, range 0.40-133ng/ml) were examined with fast-T2-weighted images (MRI) and 3D-magnetic resonance spectroscopy (MRS). Both modalities were qualitatively analyzed on a whole prostate basis by a single radiologist using a 4-point diagnostic scale. Prostate cancer was histopathologically proven in 220 patients and non-evidence of cancer was determined after at least 12 months clinical follow-up in 136 subjects.

RESULTS

Receiver operating curve analysis revealed a significantly better diagnostic performance of MRI+MRS (A(z)=0.857) than MRI alone (A(z)=0.801) and MRS alone (A(z)=0.810). The sensitivity, specificity and accuracy of MRI+MRS for detection of prostate cancer were 72.3%, 92.6%, and 80.1%, respectively.

CONCLUSIONS

Spectral evaluation with a whole prostate qualitative approach is feasible in routine clinical practice. The combination of MRI and MRS yields superior diagnostic results than either modality alone.

Design and evaluation of a 3D transrectal ultrasound prostate biopsy system

Biopsy of the prostate using ultrasound guidance is the clinical gold standard for diagnosis of prostate adenocarcinoma. The current prostate biopsy procedure is limited to using 2D transrectal ultrasound (TRUS) images to target biopsy sites and record biopsy core locations for postbiopsy confirmation. Localization of the 2D image in its actual 3D position is ambiguous and limits procedural accuracy and reproducibility. We have developed a 3D TRUS prostate biopsy system that provides 3D intrabiopsy information for needle guidance and biopsy location recording. The system conforms to the workflow and imaging technology of the current biopsy procedure, making it easier for clinical integration. In this paper, we describe the system design and validate the system accuracy by performing mock biopsies on US/CT multimodal patient-specific prostate phantoms. Our biopsy system generated 3D patient-specific models of the prostate with volume errors less than 3.5% and mean boundary errors of less than 1 mm. Using the 3D biopsy system, needles were guided to within 2.3 +/- 1.0 mm of 3D targets and with a high probability of biopsying clinically significant tumors. The positions of the actual biopsy sites were accurately localized to within 1.5 +/- 0.8 mm.

Diffusion-weighted imaging with apparent diffusion coefficient mapping and spectroscopy in prostate cancer

Prostate cancer is a major health problem, and the exploration of noninvasive imaging methods that have the potential to improve specificity while maintaining high sensitivity is still critically needed. Tissue changes induced by tumor growth can be visualized by magnetic resonance imaging (MRI) methods. Current MRI methods include conventional T2-weighted imaging, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping and magnetic resonance spectroscopy (MRS). Techniques such as DWI/ADC provide functional information about the behavior of water molecules in tissue; MRS can provide biochemical information about the presence or absence of certain metabolites, such as choline, creatine, and citrate. Finally, vascular parameters can be investigated using dynamic contrast-enhanced MRI. Moreover, with whole-body MRI and DWI, metastatic disease can be evaluated in 1 session and may provide a way to monitor treatment. Therefore, when combining these various methods, a multiparametric data set can be built to assist in the detection, localization, assessment of prostate cancer aggressiveness, and tumor staging. Such a comprehensive approach offers more power to evaluate prostate disease than any single measure alone. In this article, we focus on the role of DWI/ADC and MRS in the detection and characterization using both in vivo and ex vivo imaging of prostate pathology.

Prognostic factors in patients with acute liver failure undergoing live donor liver transplantation

Mortality from acute liver failure (ALF) is high. Live donor liver transplantation (LDLT) is the treatment of choice for ALF in Asia, because cadaveric donors are rare. We sought to review our results in ALF patients with undergoing LDLT at our center. One hundred two LDLTs were performed at our center from April 2002 to November 2007, 15 (14%) because of ALF. Mean (SEM; median, range) follow-up was 1,065 (189; 1400; 3-2046) days. Nine patients (60%) had acute exacerbation of chronic hepatitis B; and 6 (40%) had drug-induced liver injury. Age was 47 (3; 50; 27-65) years. Ten patients (67%) were men. At transplantation, laboratory values were included bilirubin, 449 (35) micromol/L; creatinine concentration, 182 (32) mmol/L. The international normalized ratio was 2.4 (0.2). The Model for End-Stage Liver Disease (MELD) score was 34 (2). Both inpatient and long-term mortality was 20% 3 of 15 patients died. The 5-year survival was 80%. Compared with survivors, patients who died had a significantly higher creatinine concentration 289 vs 155 micromol/L, international normalized ratio (3.4 vs 2.1), MELD score (47 vs 32). We conclude that despite being sick with median and mean MELD scores of 32 and 34, 80% of patients with ALF can achieve good long-term survival after LDLT.

Advances in MR spectroscopy of the prostate

Commercial MR imaging/magnetic resonance spectroscopic imaging (MRSI) packages for staging prostate cancer on 1.5-T MR scanners are now available. The technology is becoming mature enough to begin assessing its clinical utility in selecting, planning, and following prostate cancer therapy. Before therapy, 1.5-T MR imaging/MRSI has the potential to improve the local evaluation of prostate cancer presence and volume and has a significant incremental benefit in the prediction of pathologic stage when added to clinical nomograms. After therapy, two metabolic biomarkers of effective and ineffective therapy have been identified and are being validated with 10-year outcomes. Accuracy can be improved by performing MR imaging/MRSI at higher magnetic field strengths, using more sensitive hyperpolarized (13)C MRSI techniques and through the addition of other functional MR techniques.

Value of endorectal MRI and MRS in patients with elevated prostate-specific antigen levels and previous negative biopsies to localize peripheral zone tumours

AIM

To evaluate prospectively the role of endorectal magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in detecting peripheral zone tumour in patients with total prostate-specific antigen (PSA) values>or=4 ng/ml and one or more negative transrectal ultrasound (TRUS) biopsy rounds.

MATERIAL AND METHODS

Fifty-four consecutive men (mean age 65.4+/-5.2 years, mean total PSA 10.8+/-7.5 ng/ml), underwent a combined MRI-MRS examination with endorectal coil. MRI included transverse, coronal, and sagittal T2-weighted and transverse T1-weighted fast spin-echo sequences. MRS data were acquired using a double spin-echo point resolved spectroscopy (PRESS) sequence. A 10-site scheme was adopted to evaluate the prostate peripheral zone. A peripheral prostatic site was classified as suspicious if low intensity signal was present on T2-weighted images and/or if the choline+creatine/citrate ratio was >0.86. Following MRI-MRS all patients were submitted to a standard 10-core biopsy scheme to which from one to three supplementary samples were added from suspicious MRI and/or MRS sites. In per-patient analysis findings were considered true-positive if biopsy positive patients were classified as suspicious, irrespectively of lesion site indication.

RESULTS

Prostate cancer (PC) was detected in 17 of 54 patients (31.5%); median Gleason score was 6 (range 4-8). On a per-patient basis sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were respectively 100, 64.9, 56.7, 100, and 75.9% for MRI; 82.2, 70.3, 57.7, 92.9, and 75.9% for MRS; and 100, 51.4, 48.6, 100, and 66.7% for combined MRI-MRS. In all the 17 PC patients, combined MRI-MRS correctly indicated the sites harbouring cancer, whereas both MRI and MRS gave erroneous indications in two patients.

CONCLUSION

The results of the present study show that MRI alone might be able to select negative patients in whom further biopsies are unnecessary. The combination of MRI and MRS might be able to drive biopsies in suspicious sites and increase the cancer detection rate. Further studies are required to confirm these data.

Hyperpolarized 13C lactate, pyruvate, and alanine: noninvasive biomarkers for prostate cancer detection and grading

An extraordinary new technique using hyperpolarized (13)C-labeled pyruvate and taking advantage of increased glycolysis in cancer has the potential to improve the way magnetic resonance imaging is used for detection and characterization of prostate cancer. The aim of this study was to quantify, for the first time, differences in hyperpolarized [1-(13)C] pyruvate and its metabolic products between the various histologic grades of prostate cancer using the transgenic adenocarcinoma of mouse prostate (TRAMP) model. Fast spectroscopic imaging techniques were used to image lactate, alanine, and total hyperpolarized carbon (THC = lactate + pyruvate + alanine) from the entire abdomen of normal mice and TRAMP mice with low- and high-grade prostate tumors in 14 s. Within 1 week, the mice were dissected and the tumors were histologically analyzed. Hyperpolarized lactate SNR levels significantly increased (P < 0.05) with cancer development and progression (41 +/- 11, 74 +/- 17, and 154 +/- 24 in normal prostates, low-grade primary tumors, and high-grade primary tumors, respectively) and had a correlation coefficient of 0.95 with the histologic grade. In addition, there was minimal overlap in the lactate levels between the three groups with only one of the seven normal prostates overlapping with the low-grade primary tumors. The amount of THC, a possible measure of substrate uptake, and hyperpolarized alanine also increased with tumor grade but showed more overlap between the groups. In summary, elevated hyperpolarized lactate and potentially THC and alanine are noninvasive biomarkers of prostate cancer presence and histologic grade that could be used in future three-dimensional (13)C spectroscopic imaging studies of prostate cancer patients.

MR imaging of the prostate in clinical practice

Magnetic resonance imaging (MRI) is the imaging tool of choice in the evaluation of prostate cancer. The main applications of MR imaging in the management of prostate cancer are: (1) to guide targeted biopsy when prostate cancer is clinically suspected and previous ultrasound-guided biopsy results are negative; (2) to localize and stage prostate cancer and provide a roadmap for treatment planning; and (3) to detect residual or locally recurrent cancer after treatment. Other MR techniques such as proton MR spectroscopic imaging (MRSI), diffusion-weighted imaging (DWI), and contrast-enhanced MRI (CE-MRI) complement conventional MR imaging by providing metabolic and functional information that can improve the accuracy of prostate cancer detection and characterization. In everyday clinical practice, and to account for patient comfort, MR imaging studies are limited to 1 h. To obtain consistently high-quality images, a well-designed protocol is necessary. Routine MR imaging can be supplemented by other MR techniques such as MRSI, DWI or CE-MRI depending on the expertise available and the clinical questions that need to be answered. This review summarizes the role of MR imaging in the management of prostate cancer and describes practical approaches to implementing anatomic, metabolic and functional MR imaging techniques in the clinic.

Evaluation of lactate and alanine as metabolic biomarkers of prostate cancer using 1H HR-MAS spectroscopy of biopsy tissues

The goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using (1)H high-resolution magic angle spinning (HR-MAS) spectroscopy of snap-frozen transrectal ultrasound (TRUS)-guided prostate biopsy tissues. A long-echo-time rotor-synchronized Carr-Purcell-Meiboom-Gill (CPMG) sequence including an electronic reference to access in vivo concentrations (ERETIC) standard was used to determine the concentrations of lactate and alanine in 82 benign and 16 malignant biopsies (mean 26.5% +/- 17.2% of core). Low concentrations of lactate (0.61 +/- 0.28 mmol/kg) and alanine (0.14 +/- 0.06 mmol/kg) were observed in benign prostate biopsies, and there was no significant difference between benign predominantly glandular (N = 54) and stromal (N = 28) biopsies between patients with (N = 38) and without (N = 44) a positive clinical biopsy. In biopsies containing prostate cancer there was a highly significant (P < 0.0001) increase in lactate (1.59 +/- 0.61 mmol/kg) and alanine (0.26 +/- 0.07 mmol/kg), and minimal overlap with lactate concentrations in benign biopsies. This study demonstrates for the first time very low concentrations of lactate and alanine in benign prostate biopsy tissues. The significant increase in the concentration of both lactate and alanine in biopsy tissue containing as little as 5% cancer could be exploited in hyperpolarized (13)C spectroscopic imaging (SI) studies of prostate cancer patients.

The role of endorectal coil MRI in preoperative staging and decision-making for the treatment of clinically localized prostate cancer

INTRODUCTION

The optimal management of newly diagnosed prostate cancer requires individualization of the treatment plan based upon the most accurate clinical characterization of tumor location and extent of disease. The role of imaging in prostate cancer staging continues to evolve. In this review, we address the utility of endorectal coil magnetic resonance imaging (eMRI) in both local staging and its ability to facilitate the decision in choosing one treatment strategy over another after the initial diagnosis of localized prostate cancer.

MATERIALS AND METHODS

Using the PubMed database and reference lists of key articles, we identified studies addressing the use of eMRI in tumor characterization and risk stratification in patients undergoing treatment for clinically localized prostate cancer.

RESULTS

The findings identified within 54 selected studies were incorporated into a summary discussing the current limitations in cancer staging and the role eMRI plays in both the preoperative assessment and clinical decision-making in an attempt to improve our ability to individualize management approaches and tailor treatment.

CONCLUSION

eMRI allows for more accurate local staging by complementing the existing clinical variables through improvements in spatial characterization of the prostatic zonal anatomy and molecular changes. These improvements in tumor staging enhance our ability to individualize treatment selection and tailor the approach to maximize cancer control while minimizing treatment related morbidity.

Tumor cell metabolism imaging

Molecular imaging of tumor metabolism has gained considerable interest, since preclinical studies have indicated a close relationship between the activation of various oncogenes and alterations of cellular metabolism. Furthermore, several clinical trials have shown that metabolic imaging can significantly impact patient management by improving tumor staging, restaging, radiation treatment planning, and monitoring of tumor response to therapy. In this review, we summarize recent data on the molecular mechanisms underlying the increased metabolic activity of cancer cells and discuss imaging techniques for studies of tumor glucose, lipid, and amino acid metabolism.

Quantitative J-resolved prostate spectroscopy using two-dimensional prior-knowledge fitting

Two-dimensional (2D) prior-knowledge fitting (ProFit) was adapted and applied for the quantification of J-resolved (JPRESS) spectra acquired at a field strength of 3T from the human prostate in vivo. In contrast to methods based on simple line fitting and peak integration, commonly applied for metabolite quantification in the prostate, ProFit yields metabolite concentration ratios that are independent of sequence and field strength, since it is based on the linear combination of 2D basis spectra. It is demonstrated that ProFit benefits from the increased information content and reduced baseline distortion in JPRESS prostate spectra, in particular for the quantification of coupled metabolites like citrate (Cit), spermine (Spm), and myo-inositol (mI). The method is validated with 10 repetitive prostate measurements on the same subject. Furthermore, a study carried out on 10 healthy subjects shows that the six prostate metabolites creatine (Cr), total choline (Cho), Cit, Spm, mI, and scyllo-inositol (sI) can be reliably detected in vivo, some of which--especially total Cho and Cit--have proven to be useful markers for the detection of prostate cancer.

Two-dimensional spectroscopic imaging for pretreatment evaluation of prostate cancer: comparison with the step-section histology after radical prostatectomy

PURPOSE

To minimize user and vendor dependence of the spectrum processing of prostate spectra, to measure the ratio of choline (Cho) plus creatine (Cr) to citrate (Cit) in the prostate tissue of normal volunteers and cancer patients, and to compare the results with pathologic findings after radical prostatectomy.

MATERIALS AND METHODS

Four healthy volunteers and 13 patients with prostate cancer were measured. Measurements were performed using two-dimensional magnetic resonance spectroscopic imaging (MRSI) and endorectal coil. A standard vendor's spectrum processing approach has been modified. An original feature of this methodology was the combination of vendor-optimized and user-independent spectrum preprocessing in the scanner and user-independent quantitation in the environment of an MRUI software package. (Cho+Cr)/Cit ratio was used for the classification of prostate tissue. Results were compared with histopathology after radical prostatectomy.

RESULTS

Eight of 13 cancer patients were classified as suspicious or very suspicious for cancer at spectroscopy, three were ambiguous for cancer and two patients were evaluated as false negative. A considerable overlap of metabolite ratios at various Gleason score was found.

CONCLUSION

The proposed spectrum processing has the potential to improve the accuracy and user independency of the (Cho+Cr)/Cit quantitation. This study confirmed the previous results that a considerable overlap of (Cho+Cr)/Cit ratios exists at various Gleason score levels.

Newer imaging modalities to assist with target localization in the radiation treatment of prostate cancer and possible lymph node metastases

Precise localization of prostate cancer and the drainage lymph nodes is mandatory to define an accurate clinical target volume for conformal radiotherapy. Better target definition and delineation on a daily basis is surely important in quality assurance for fractionated radiation therapy. This article reviews the evidence for major emerging techniques that show promise in better identifying the clinical target volume. Partial prostate boost by brachytherapy, intensity-modulated radiation therapy, or protons has become possible not only with standard imaging techniques but also with the availability of metabolic images obtained by magnetic resonance spectroscopy. Even though fluorine-18 fluorodeoxyglucose ((18)F-FDG) positron emission tomography has not been found to be useful, novel radiolabeled tracers may eventually prove of value in the diagnosis and treatment planning of prostate cancer. For the metastatic lymph nodes, lymphotropic nanoparticle-enhanced magnetic resonance imaging using ultra-small superparamagnetic iron oxide particles has greater accuracy as compared with conventional techniques and has been instrumental in delineating the lymphatic drainage of the prostate gland. These novel investigational techniques could further help in optimizing conformal radiotherapy for patients with prostate cancer. The concepts of biologic target volume, real target volume, and multidimensional conformal radiotherapy are being explored.

[Prostate MRI spectroscopy]

MRI spectroscopy is a non invasive method for detecting active metabolites used as markers. Chorine and citrate are used for analyzing prostate cancer. MRI spectroscopy combines morphologic imaging and metabolic cartography. This combination allows a new approach for the diagnosis of prostate cancer in patients with negative biopsy and high Levels of PSA. With MRI spectroscopy the Local staging of prostate cancer has a better accuracy than with MRI alone. It can also be used for the diagnosis of residual disease and recurrence in patients treated with conservative therapy.

Computerized analysis of prostate lesions in the peripheral zone using dynamic contrast enhanced MRI

A novel automated computerized scheme has been developed for determining a likelihood measure of malignancy for cancer suspicious regions in the prostate based on dynamic contrast-enhanced magnetic resonance imaging (MRI) (DCE-MRI) images. Our database consisted of 34 consecutive patients with histologically proven adenocarcinoma in the peripheral zone of the prostate. Both carcinoma and non-malignant tissue were annotated in consensus on MR images by a radiologist and a researcher using whole mount step-section histopathology as standard of reference. The annotations were used as regions of interest (ROIs). A feature set comprising pharmacokinetic parameters and a T1 estimate was extracted from the ROIs to train a support vector machine as classifier. The output of the classifier was used as a measure of likelihood of malignancy. Diagnostic performance of the scheme was evaluated using the area under the ROC curve. The diagnostic accuracy obtained for differentiating prostate cancer from non-malignant disorders in the peripheral zone was 0.83 (0.75-0.92). This suggests that it is feasible to develop a computer aided diagnosis system capable of characterizing prostate cancer in the peripheral zone based on DCE-MRI.

Update of prostate magnetic resonance imaging at 3 T

More recently, 3-T magnetic resonance (MR) scanner become more clinically available, and clinical application of 3-T MR imaging (MRI) of the abdomen and pelvis is now feasible and being performed at many institutions. However, few prostrate 3-T MRI studies have been published. The increase in signal-to-noise ratio at 3 versus 1.5 T clearly improves spatiotemporal and spectral resolutions of the prostate. Thus, we asked whether 3-T MRI improves the localization and staging of prostate cancer versus 1.5-T MRI. To answer this question, this article reviews the current limitations of prostate 1.5-T MRI and addresses its pros and cons. Moreover, we present preliminary results of prostate 3-T MRI and introduce our experience for prostate 3-T MRI using a phased-array coil, with an emphasis on imaging sequences, for example, T2-weighted, dynamic contrast-enhanced, diffusion-weighted, and MR spectroscopic imaging.

Endorectal magnetic resonance imaging and magnetic resonance spectroscopy to monitor the prostate for residual disease or local cancer recurrence after transrectal high-intensity focused ultrasound

OBJECTIVE

To assess the role of magnetic resonance imaging (MRI) for evaluating changes in the prostate after transrectal high-intensity focused ultrasound (HIFU) for treating prostate cancer, correlating the findings with histology to assess its possible role in predicting the outcome, evaluating residual cancer or local recurrence of disease.

PATIENTS AND METHODS

Ten patients with prostate cancer were assessed with MR and MR spectroscopy (MRS) before and at 1, 4 and 12 months after HIFU, assessing the glandular volume and MRI and MRS data after HIFU. These data were correlated with the prostate-specific antigen (PSA) levels at each examination (suspicious for residual cancer if >0.5 ng/mL) and with histological findings of prostate biopsy sampling at 6-8 months (random or targeted at suspicious MR areas).

RESULTS

Variations in volume during the follow-up were not associated with treatment outcome. MRI was suspicious for residual cancer in one patient at 1 month and in another two at 4 months; in all three patients (one with a PSA level of <0.5 ng/mL) targeted biopsies were positive for cancer. MRI was negative in seven patients; in six of these (one with a PSA level of >0.5 ng/mL) random biopsies were negative, and in one the random biopsies were positive for residual cancer. At 4 months there was a statistically significant difference (P = 0.015) between patients responsive to treatment and those with persistent disease, by combining negative MRI with a PSA level of <0.5 ng/mL; MRS data were suitable for analysis only in three patients with partial necrosis.

CONCLUSION

Our preliminary data support the role of MRI in association with PSA levels as a useful and accurate tool in the follow-up of patients treated with HIFU for prostate cancer. However, considering the economic issue, it should not be used routinely and should be limited to detecting residual cancer (in patients with a PSA level of >0.5 ng/mL) with the main purpose of improving the detection rate of transrectal ultrasonography (TRUS)-guided prostate biopsy. MRS data had no additional value over MRI. Further evaluation is needed to compare the use of contrast media and other techniques (e.g. colour Doppler TRUS) in detecting residual or local recurrent cancer.

Use of perfluorocarbon compound in the endorectal coil to improve MR spectroscopy of the prostate

OBJECTIVE

The purpose of this study was to evaluate the utility of perfluorocarbon (PFC) compound compared with air in the endorectal coil in improving the quality of conventional MR spectroscopy of the prostate.

SUBJECTS AND METHODS

A total of 62 consecutively registered patients were selected. MR spectroscopy of the prostate was performed with PFC in the endorectal coil for 34 of the patients and with air for 28. In the cases of 13 of the 28 patients, MR spectroscopy was repeated with a PFC-filled endorectal coil. The spectral line widths and the spectral separations from MR spectroscopy with an air-filled endorectal coil were compared with those obtained with a PFC-filled coil.

RESULTS

In all 62 patients, the mean line width values were reduced, from 13.3 +/- 3.0 Hz with air to 7.3 +/- 2.0 Hz with PFC (p = 0.0001, Student's t test). In 13 patients who underwent MR spectroscopy with air followed by MR spectroscopy with PFC, the mean line width values were reduced, from 14.8 +/- 3.4 Hz with air to 7.0 +/- 1.5 Hz with PFC (p = 0.0001, Student's t test). In 72 voxels analyzed for spectral separation, clear separations between the choline, polyamine, and creatine peaks were found in 57 voxels with PFC and four with air. Better splitting of the citrate peaks was found in 35 voxels with PFC and one with air.

CONCLUSION

The use of PFC compound in the endorectal coil is a safe and cost-effective way to consistently generate high-quality prostate MR spectroscopic results and to substantially improve quantitation of prostatic metabolites. These improvements should increase the diagnostic value of MR spectroscopy in the care of patients with prostate cancer.

Evaluation of the role of magnetization transfer imaging in prostate: a preliminary study

Results of the preliminary study on the evaluation of the role of magnetization transfer imaging (MTI) of prostate in men who had raised prostate-specific antigen (PSA) (>4 ng/ml) or abnormal digital rectal examination (DRE) are reported. MT ratio (MTR) was calculated for 20 patients from the hyper- (normal) and hypo-intense regions (area suspicious of malignancy as seen on T2-weighted MRI) of the peripheral zone (PZ) and the central gland (CG) at 1.5 T. In addition, MTR was calculated for three healthy controls. Mean MTR was also calculated for the whole of the PZ (including hyper- and hypo-intense area) in all patients. Out of 20 patients, biopsy revealed malignancy in 12 patients. Mean MTR value (8.29+/-3.49) for the whole of the PZ of patients who were positive for malignancy on biopsy was statically higher than that observed for patients who were negative for malignancy (6.18+/-3.15). The mean MTR for the whole of the PZ of controls was 6.18+/-1.63 and is similar to that of patients who were negative for malignancy. Furthermore, for patients who showed hyper- (normal portion) and hypo-intense (region suspicious of malignancy) regions of the PZ, the MTR was statistically significantly different. These preliminary results reveal the potential role of MT imaging in the evaluation of prostate cancer.

[Diagnostic radiology of the pelvis. Prostate cancer, bladder cancer, and incontinence]

Prostate cancer, bladder cancer, and pelvic floor weakness are among the most common diseases of the pelvis. Cardinal symptoms include painless macrohematuria in bladder cancer and urinary and fecal incontinence in pelvic floor weakness. Suspicion of prostate cancer currently is most frequently raised when the serum concentration of prostate-specific antigen is pathologically elevated. Besides extensive clinical and invasive diagnosis, clinical imaging is frequently applied for the localization, locoregional staging, and diagnosis of recurrence of prostate cancer and invasive bladder cancer, and in clinically difficult cases of cystocele, enterocele, rectocele, descensus or prolapse of vagina, uterus, and rectum, and rectal intussusception. Magnetic resonance imaging with T2-weighted TSE or FSE images in several planes combined with either axial, T1-weighted images and MR spectroscopy for the prostate, dynamic contrast-enhanced T1-weighted images for the urinary bladder, or dynamic T2-weighted functional images for pelvic floor incontinence are particularly well suited as clinical imaging methods.

Role of magnetic resonance imaging and magnetic resonance spectroscopic imaging before and after radiotherapy for prostate cancer

PURPOSE

To describe the practical technical aspects of magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) and to summarize the current and potential future status of MRI and MRSI in the localization, staging, treatment planning, and post-treatment follow-up of prostate cancer.

TECHNIQUE

Published contemporary series of patients with prostate cancer evaluated by MRI and MRSI before or after radiation therapy were reviewed, with particular respect to the role of MRI and MRSI in treatment planning, outcome prediction, and detecting local recurrence.

RESULTS

Volumetric localization is of limited accuracy for tumors less than 0.5 cm(3). Staging by MRI, which is improved by the addition of MRSI, is of incremental prognostic significance in patients with moderate and high-risk tumors. The finding of more than 5 mm of extracapsular extension prior to radiation seems to be of particular negative prognostic significance, and the latter group may be candidates for more aggressive supplemental therapy. The use of MRI to assist radiation treatment planning has been shown to improve outcome. MRSI may be helpful in the detection of local recurrence after radiation.

CONCLUSIONS

Only MRI and MRSI allow combined structural and metabolic evaluation of prostate cancer location, aggressiveness, and stage. Combined MRI and MRSI provide clinically and therapeutically relevant information that may assist in planning and post-treatment monitoring in patients undergoing radiation therapy.

Prostate cancer: identification with combined diffusion-weighted MR imaging and 3D 1H MR spectroscopic imaging--correlation with pathologic findings

PURPOSE

To retrospectively measure the mean apparent diffusion coefficient (ADC) with diffusion-weighted magnetic resonance (MR) imaging and the mean metabolic ratio (MET) with three-dimensional (3D) hydrogen 1 ((1)H) MR spectroscopic imaging in regions of interest (ROIs) drawn over benign and malignant peripheral zone (PZ) prostatic tissue and to assess ADC, MET, and combined ADC and MET for identifying malignant ROIs, with whole-mount histopathologic examination as the reference standard.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant retrospective study and issued a waiver of informed consent. From among 61 consecutive patients with prostate cancer, 38 men (median age, 61 years; range, 42-72 years) who underwent 1.5-T endorectal MR imaging before radical prostatectomy and who fulfilled all inclusion criteria of no prior hormonal or radiation treatment and at least one PZ lesion (volume, >0.1 cm(3)) at whole-mount pathologic examination were included. ADC maps were generated from diffusion-weighted MR imaging data, and MET maps of (choline plus polyamine plus creatine)/citrate were calculated from 3D (1)H MR spectroscopic imaging data. ROIs in the PZ identified by matching pathologic slides with T2-weighted images were overlaid on MET and ADC maps. Areas under the receiver operating characteristic curves (AUCs) were used to evaluate accuracy.

RESULTS

The mean ADC +/- standard deviation, (1.39 +/- 0.23) x 10(-3) mm(2)/sec, and mean MET (0.92 +/- 0.32) for malignant ROIs differed significantly from the mean ADC, (1.69 +/- 0.24) x 10(-3) mm(2)/sec, and mean MET (0.73 +/- 0.18) for benign ROIs (P < .001 for both). In distinguishing malignant ROIs, combined ADC and MET (AUC = 0.85) performed significantly better than MET alone (AUC = 0.74; P = .005) and was also better than ADC alone (AUC = 0.81), although the difference was not statistically significant (P = .09).

CONCLUSION

The combination of ADC and MET performs significantly better than MET for differentiating between benign and malignant ROIs in the PZ.

Prostate cancer: role of pretreatment MR in predicting outcome after external-beam radiation therapy--initial experience

PURPOSE

To retrospectively determine if pretreatment endorectal magnetic resonance (MR) imaging findings are predictive of outcome in patients who undergo external-beam radiation therapy for prostate cancer.

MATERIALS AND METHODS

Committee on Human Research approval, with waiver of the requirement for informed consent, was obtained for this HIPAA-compliant study. Eighty men with biopsy-proved prostate cancer (mean age, 59 years; range, 47-75 years) who underwent endorectal MR imaging of the prostate prior to external-beam radiation therapy were retrospectively identified; details of baseline tumor characteristics, treatment, and outcome were recorded. Two experienced readers independently reviewed all MR imaging studies and recorded tumor T stage and the radial diameter of extracapsular extension (if present). Univariate and multivariate stepwise Cox regression analyses were used to investigate the relationship between baseline imaging and clinical predictive variables and the end point of metastatic failure.

RESULTS

At MR imaging, readers 1 and 2, respectively, considered 50 and 60 patients to have T1 or T2 disease (ie, organ-confined disease) and 30 and 20 patients to have T3 disease. After a mean follow-up of 43 months, four patients developed metastases. Univariate Cox analysis revealed that baseline serum prostate-specific antigen level, presence of extracapsular extension at MR imaging (according to either reader), and degree of extracapsular extension (according to either reader) were all significantly (P < .05) related to the development of metastases. Multivariate Cox analysis revealed that the sole independent predictive variable was mean diameter of extracapsular extension (relative hazard ratio, 2.06; 95% confidence interval: 1.22, 3.48; P = .007). In particular, three of five patients with extracapsular extension of more than 5 mm at pretreatment MR imaging developed metastases 24, 43, and 63 months after therapy.

CONCLUSION

The presence and degree of extracapsular extension at MR imaging prior to external-beam radiation therapy are important predictors of posttreatment metastatic recurrence.

The value of 18F-choline PET/CT in patients with elevated PSA-level and negative prostate needle biopsy for localisation of prostate cancer

PURPOSE

Patients with persistent elevated PSA and repeated negative prostate biopsy, that means having the prostate biopsied at multiple times, were investigated with 18F-choline PET/CT to delineate prostate cancer and guide renewed prostate biopsy.

METHODS

Twenty patients with elevated PSA and negative prostate biopsies underwent 18F-choline PET/CT. We performed an early examination of the pelvic region 3-5 min after application. After 30 minutes a whole body PET/CT examination was performed. Image analysis was performed visually and by semi-quantitative analysis calculating the maximum standardised uptake value (SUVmax). 18F-choline uptake was defined as focal, multifocal or inhomogeneous. After the 18F-choline PET/CT, all patients underwent a repeated prostate biopsy, and in the cases where a focal or multifocal uptake was found, the biopsy was guided by the result of the examination.

RESULTS

Qualitative image analysis revealed focal 18F-choline uptake in 13 out of 20 patients. In five patients, prostate cancer was revealed by repeated aspiration biopsy. None of the patients with a multifocal or inhomogeneous 18F-choline uptake had a malignant neoplasm in the prostate. Semiquantitative analysis performed with SUVmax was not helpful in the discrimination of malignancy but showed high values also in benign prostate diseases, as well as in normal prostate tissue. The dual-phase protocol delivered no clear benefit in discriminating malignancy from benign alterations.

CONCLUSION

The use of 18F-choline cannot be generally recommended for localising prostate cancer; however, in highly selected patients, we found useful additional information. In 25% of patients, 18F-choline PET/CT allowed the identification of neoplastic prostatic zones.

MR imaging of the prostate: 1.5T versus 3T

Over the past several years, evidence supporting the use of MR imaging in the evaluation of prostate cancer has grown. Almost all this work has been performed at 1.5T. The gradual introduction of 3T scanners into clinical practice provides a potential opportunity to improve the quality and usefulness of prostate imaging. Increased signal to noise allows for imaging at higher resolution, higher temporal resolution, or higher bandwidth. Although this may improve the quality of conventional T2-weighted prostate imaging, which has been the standard sequence for detecting and localizing prostate cancer for years, the real potential for improvement at 3T involves more advanced techniques, such as spectroscopy, diffusion-weighted imaging, dynamic contrast imaging, and susceptibility imaging. This review presents the current data on 3T MR imaging of the prostate as well as the authors' impressions based on their experience at Yale-New Haven Hospital.

Multiparametric magnetic resonance imaging in prostate cancer: present and future

PURPOSE OF REVIEW

The purpose of this article is to review the current status of advanced MRI techniques based on anatomic, metabolic and physiologic properties of prostate cancer with a focus on their impact in managing prostate cancer patients.

RECENT FINDINGS

Prostate cancer can be identified based on reduced T2 signal intensity on MRI, increased choline and decreased citrate and polyamines on magnetic resonance spectroscopic imaging (MRSI), decreased diffusivity on diffusion tensor imaging (DTI), and increased uptake on dynamic contrast enhanced (DCE) imaging. All can be obtained within a 60-min 3T magnetic resonance exam. Each complementary method has inherent advantages and disadvantages: T2 MRI has high sensitivity but poor specificity; magnetic resonance spectroscopic imaging has high specificity but poor sensitivity; diffusion tensor imaging has high spatial resolution, is the fastest, but sensitivity/specificity needs to be established; dynamic contrast enhanced imaging has high spatial resolution, but requires a gadolinium based contrast agent injection, and sensitivity/specificity needs to be established.

SUMMARY

The best characterization of prostate cancer in individual patients will most likely result from a multiparametric (MRI/MRSI/DTI/DCE) exam using 3T magnetic resonance scanners but questions remain as to how to analyze and display this large amount of imaging data, and how to optimally combine the data for the most accurate assessment of prostate cancer. Histological correlations or clinical outcomes are required to determine sensitivity/specificity for each method and optimal combinations of these approaches.

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

PURPOSE

To retrospectively compare relative accuracy of different interpretative approaches to magnetic resonance (MR) and MR spectroscopic imaging of peripheral zone prostate cancer, by using histologic examination results as the reference standard.

MATERIALS AND METHODS

This HIPAA-compliant study had institutional Committee on Human Research approval, with waiver of written consent requirement. Spectroscopic voxels of unequivocally benign (n = 66) or malignant (n = 77) peripheral zone tissue were identified by using step-section histopathologic tumor maps created for 28 men (mean age, 60 years; range, 46-71 years) who underwent endorectal MR and MR spectroscopic imaging before radical prostatectomy. Two readers (9 and 8 years of experience) independently scored the selected voxels on a scale from 1 (likely benign) to 5 (likely malignant) at randomized review of the corresponding tissue outlined on a transverse T2-weighted MR image (T2 approach), the MR spectrum from the selected voxel only (single-voxel approach), the MR spectra from all voxels at the same axial level (multivoxel approach), and both the corresponding tissue outlined on a transverse T2-weighted image and the MR spectra from all voxels at the same axial level (integrated approach). Readers were aware that spectra were derived in patients with biopsy-proved diagnoses of prostate cancer and represented either benign or malignant tissue but were unaware of which voxels had been labeled benign or malignant and of all other clinical, histopathologic, and MR imaging findings. Receiver operating characteristic (ROC) curve analysis was performed. Generalized estimating equation method was used to estimate sensitivity and specificity for specific cutoff values.

RESULTS

Mean areas under the ROC curve (AUCs) for the T2, single-voxel, multivoxel, and integrated approaches were 0.69, 0.72, 0.72, and 0.76, respectively. AUC of the integrated approach was significantly higher than those of the other three approaches (P < .001). kappa Values for assessment of interobserver variability for the T2, single-voxel, multivoxel, and integrated approaches were 0.39, 0.39, 0.34, and 0.48, respectively.

CONCLUSION

Addition of MR spectroscopic imaging to MR imaging significantly improves characterization of peripheral zone prostate tissue as benign or malignant; improved performance is obtained when both data sets are interpreted in an integrated fashion.

Imaging in Oncology from The University of Texas M. D. Anderson Cancer Center: Diagnosis, Staging, and Surveillance of Prostate Cancer

OBJECTIVE

The purpose of this article is to discuss the epidemiology, risk factors, and presentation of prostate cancer. After reviewing the prostate anatomy, the article will show how imaging plays an important role in establishing the diagnosis, staging, and monitoring the therapeutic response in prostate cancer, with a focus on adenocarcinomas.

CONCLUSION

Imaging studies, in the appropriate laboratory and clinical context, contribute essential information that enhances the capacity to provide individualized risk stratification, a suitable treatment strategy, and monitoring for the patient with prostate cancer.

Detection of prostate cancer with MR spectroscopic imaging: an expanded paradigm incorporating polyamines

PURPOSE

To characterize benign and malignant prostate peripheral zone (PZ) tissue retrospectively by using a commercial magnetic resonance (MR) spectroscopic imaging package and incorporating the choline plus creatine-to-citrate ratio ([Cho + Cr]/Cit) and polyamine (PA) information into a statistically based voxel classification procedure.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant study and waived the requirement for informed consent. Fifty men (median age, 60 years; range, 44-69 years) with untreated biopsy-proved prostate cancer underwent combined endorectal MR imaging and MR spectroscopic imaging. Commercial software was used to acquire and process MR spectroscopic imaging data. The (Cho + Cr)/Cit and the PA level were tabulated for each voxel. The PA level was scored on a scale of 0 (PA undetectable) to 2 (PA peak as high as or higher than Cho peak). Whole-mount step-section histopathologic analysis constituted the reference standard. Classification and regression tree analysis in a training set generated a decision-making tree (rule) for classifying voxels as malignant or benign, which was validated in a test set. Receiver operating characteristic and generalized estimating equation regression analyses were used to assess accuracy and sensitivity, respectively.

RESULTS

The median (Cho + Cr)/Cit was 0.55 (mean +/- standard deviation, 0.59 +/- 0.03) in benign and 0.77 (mean, 1.08 +/- 0.20) in malignant PZ voxels (P = .027). A significantly higher percentage of benign (compared with malignant) voxels had higher PA than choline peaks (P < .001). In the 24-patient training set (584 voxels), the rule yielded 54% sensitivity and 91% specificity for cancer detection; in the 26-patient test set (667 voxels), it yielded 42% sensitivity and 85% specificity. The percentage of cancer in the voxel at histopathologic analysis correlated positively (P < .001) with the sensitivity of the classification and regression tree rule, which was 75% in voxels with more than 90% malignancy.

CONCLUSION

The statistically based classification rule developed indicated that PAs have an important role in the detection of PZ prostate cancer. With commercial software, this method can be applied in clinical settings.

Combined T2-weighted and diffusion-weighted MRI for localization of prostate cancer

OBJECTIVE

The objective of our study was to compare T2-weighted MRI alone and T2 combined with diffusion-weighted imaging (DWI) for the localization of prostate cancer.

SUBJECTS AND METHODS

T2-weighted imaging and DWI (b value = 600 s/mm2) were performed in 49 patients before radical prostatectomy using an endorectal coil at 1.5 T in this prospective trial. The peripheral zone of the prostate was divided into sextants and the transition zone into left and right halves. T2 images alone and then T2 images combined with apparent diffusion coefficient (ADC) maps (T2 + DWI) were scored for the likelihood of tumor and were compared with whole-mount histology results. Fixed window and level settings were used to display the ADC maps. Only tumors with an area of more than 0.13 cm2 (> 4 mm diameter) and a Gleason score of > or = 6 were considered significant. The area under the receiver operating characteristic curve (A(z)) was used to assess accuracy.

RESULTS

In the peripheral zone, the A(z) value was significantly higher (p = 0.004) for T2 plus DWI (A(z) = 0.89) than for T2 imaging alone (A(z) = 0.81). Performance was poorer in the transition zone for both T2 plus DWI (A(z) = 0.78) and T2 (A(z) = 0.79). For the whole prostate, sensitivity was significantly higher (p < 0.001) with T2 plus DWI (81% [120/149]) than with T2 imaging alone (54% [81/149]), with T2 plus DWI showing only a slight loss in specificity compared with T2 imaging alone (84% [204/243] vs 91% [222/243], respectively).

CONCLUSION

Combined T2 and DWI MRI is better than T2 imaging alone in the detection of significant cancer (Gleason score > or = 6 and diameter > 4 mm) within the peripheral zone of the prostate.

Prostate Postbrachytherapy Seed Distribution: Comparison of High-Resolution, Contrast-Enhanced, T1- and T2-Weighted Endorectal Magnetic Resonance Imaging Versus Computed Tomography: Initial Experience

PURPOSE

To compare contrast-enhanced, T1-weighted, three-dimensional magnetic resonance imaging (CEMR) and T2-weighted magnetic resonance imaging (T2MR) with computed tomography (CT) for prostate brachytherapy seed location for dosimetric calculations.

METHODS AND MATERIALS

Postbrachytherapy prostate MRI was performed on a 1.5 Tesla unit with combined surface and endorectal coils in 13 patients. Both CEMR and T2MR used a section thickness of 3 mm. Spiral CT used a section thickness of 5 mm with a pitch factor of 1.5. All images were obtained in the transverse plane. Two readers using CT and MR imaging assessed brachytherapy seed distribution independently. The dependency of data read by both readers for a specific subject was assessed with a linear mixed effects model.

RESULTS

The mean percentage (+/- standard deviation) values of the readers for seed detection and location are presented. Of 1205 implanted seeds, CEMR, T2MR, and CT detected 91.5% +/- 4.8%, 78.5% +/- 8.5%, and 96.1% +/- 2.3%, respectively, with 11.8% +/- 4.5%, 8.5% +/- 3.5%, 1.9% +/- 1.0% extracapsular, respectively. Assignment to periprostatic structures was not possible with CT. Periprostatic seed assignments for CEMR and T2MR, respectively, were as follows: neurovascular bundle, 3.5% +/- 1.6% and 2.1% +/- 0.9%; seminal vesicles, 0.9% +/- 1.8% and 0.3% +/- 0.7%; periurethral, 7.1% +/- 3.3% and 5.8% +/- 2.9%; penile bulb, 0.6% +/- 0.8% and 0.3% +/- 0.6%; Denonvillier's Fascia/rectal wall, 0.5% +/- 0.6% and 0%; and urinary bladder, 0.1% +/- 0.3% and 0%. Data dependency analysis showed statistical significance for the type of imaging but not for reader identification.

CONCLUSION

Both enumeration and localization of implanted seeds are readily accomplished with CEMR. Calculations with MRI dosimetry do not require CT data. Dose determinations to specific extracapsular sites can be obtained with MRI but not with CT.

Transrectal high-intensity focused ultrasound ablation of prostate cancer: Effective treatment requiring accurate imaging

Transrectal HIFU ablation has become a reasonable option for the treatment of localized prostate cancer in non-surgical patients, with 5-year disease-free survival similar to that of radiation therapy. It is also a promising salvage therapy of local recurrence after radiation therapy. These favourable results are partly due to recent improvements in prostate cancer imaging. However, further improvements are needed in patient selection, pre-operative localization of the tumor foci, assessment of the volume treated and early detection of recurrence. A better knowledge of the factors influencing the HIFU-induced tissue destruction and a better pre-operative assessment of them by imaging techniques should improve treatment outcome. Whereas prostate HIFU ablation is currently performed under transrectal ultrasound guidance, MR guidance with real-time operative monitoring of temperature will be available in the near future. If this technique will give better targeting and more uniform tissue destruction, its cost-effectiveness will have to be carefully evaluated. Finally, a recently reported synergistic effect between HIFU ablation and chemotherapy opens possibilities for treatment in high-risk or clinically advanced tumors.