The prostate: MR imaging and spectroscopy. Present and future

[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.

The role of imaging in the detection of prostate cancer local recurrence after radiation therapy and surgery

PURPOSE OF REVIEW

The aim of this article is to review novel MRI and nuclear medicine methods for detecting and planning salvage treatment for prostate cancer local recurrence after radical prostatectomy or radiation therapy.

RECENT FINDINGS

Traditional methods for detecting local recurrence (i.e., digital rectal exam or transrectal ultrasound and digital rectal exam or transrectal ultrasound-guided biopsy) have limited accuracy in determining the presence and extent of local recurrence and therefore have limited ability to guide salvage therapy. Recent studies indicate that conventional T1 and T2-weighted prostate MRI could improve the detection of recurrent prostate cancer after radical prostatectomy or radiation therapy and salvage treatment planning. Promising new sequences could further increase the accuracy of MRI. In addition, the use of technically improved PET/computed tomography scanners with new tracers like (11)C and (18)F choline and acetate might offer better assessment of recurrent prostate cancer than (18)F-2-fluoro-D-deoxyglucose-PET and monoclonal antibody imaging with the prostate specific membrane antigen antibody (111)In-capromab pendetide (ProstaScint).

SUMMARY

With systemic therapies for recurrent prostate cancer after radical prostatectomy or radiation therapy being noncurative, the application of MRI and nuclear medicine modalities can help to identify patients who have isolated local recurrence amenable to salvage treatment.

Permanent prostate seed brachytherapy: a current perspective on the evolution of the technique and its application

This Review highlights current areas of controversy and development in the field of transperineal permanent prostate seed implantation brachytherapy (PPI), in particular the technological evolution of PPI treatment planning that has led to intra-operative treatment planning and execution, the use of MRI spectroscopy and ultrasonography to target intraprostatic tumor foci, and the introduction of (131)Cs as a new PPI isotope. Here we present a comprehensive review of mature data for PPI monotherapy and PPI combined with supplemental external beam radiation therapy, and a critical discussion of issues pertinent to supplemental EBRT. We also present our current policies in the treatment of prostate cancer at the University of California, San Francisco.

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.

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.

Current role and future perspectives of magnetic resonance spectroscopy in radiation oncology for prostate cancer

Prostatic neoplasms are not uniformly distributed within the prostate volume. With recent developments in three-dimensional intensity-modulated and image-guided radiation therapy, it is possible to treat different volumes within the prostate to different thresholds of doses. This approach has the potential to adapt the dose to the biologic aggressiveness of various clusters of tumor cells within the gland. The definition of tumor burden volume in prostate cancer can be facilitated by the use of magnetic resonance spectroscopy (MRS). The increasing sensitivity and specificity of MRS to the prostate is causing new interest in its potential role in the definition of target subvolumes at higher risk of failure following radical radiotherapy. Prostate MRS might also play a role as a noninvasive predictive factor for tumor response and treatment outcome. We review the use of MRS in radiation therapy for prostate cancer by evaluating its accuracy in the classification of aggressive cancer regions and target definition; its current role in the radiotherapy planning process, with special interest in technical issues behind the successful inclusion of MRS in clinical use; and available early experiences as a prognostic tool.

Robot-assisted needle placement in open MRI: system architecture, integration and validation

In prostate cancer treatment, there is a move toward targeted interventions for biopsy and therapy, which has precipitated the need for precise image-guided methods for needle placement. This paper describes an integrated system for planning and performing percutaneous procedures with robotic assistance under MRI guidance. A graphical planning interface allows the physician to specify the set of desired needle trajectories, based on anatomical structures and lesions observed in the patient's registered pre-operative and pre-procedural MR images, immediately prior to the intervention in an open-bore MRI scanner. All image-space coordinates are automatically computed, and are used to position a needle guide by means of an MRI-compatible robotic manipulator, thus avoiding the limitations of the traditional fixed needle template. Automatic alignment of real-time intra-operative images aids visualization of the needle as it is manually inserted through the guide. Results from in-scanner phantom experiments are provided.

Repeatability of echo-planar-based diffusion measurements of the human prostate at 3 T

Echo-planar-based diffusion-weighted imaging (DWI) of the prostate is increasingly being suggested as a viable technique, complementing information derived from conventional magnetic resonance imaging methods for use in tissue discrimination. DWI has also been suggested as a potentially useful tool in the assessment of tumor response to treatment. In this study, the repeatability of apparent diffusion coefficient (ADC) values obtained from both DWI and diffusion tensor imaging (DTI) has been assessed as a precursor to determining the magnitude of treatment-induced changes required for reliable detection. The repeatability values of DWI and DTI were found to be similar, with ADC values repeatable to within 35% or less over a short time period of a few minutes and a longer time period of a month. Fractional anisotropy measurements were found to be less repeatable (between 26% and 71%), and any changes duly recorded in longitudinal studies must therefore be treated with a degree of caution.

Prostate cancer detection: magnetic resonance (MR) spectroscopic imaging

Magnetic resonance spectroscopic imaging (MRSI) represents a noninvasive technique to extend the diagnostic evaluation of prostatic cancer, beyond the morphologic information provided by MR imaging throughout the detection of cellular metabolites (choline and citrate). MRSI combined with the anatomical information provided by MRI can improve the assessment cancer location and extent within the prostate, extracapsular spread and cancer aggressiveness; both before and after treatment. We review the performance of MRI with MRSI and the role in the detection, localization, staging and management of the patient pre- and posttherapy for prostate cancer.

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

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

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

High-grade prostatic intraepithelial neoplasia in patients with prostate cancer: MR and MR spectroscopic imaging features--initial experience

PURPOSE

To retrospectively determine the magnetic resonance (MR) and MR spectroscopic imaging features of high-grade prostatic intraepithelial neoplasia (HGPIN) in patients with prostate cancer.

MATERIALS AND METHODS

Approval of the committee on human research was obtained, with a waiver of consent for this HIPAA-compliant study. Endorectal MR imaging and MR spectroscopic imaging were performed in 48 men (mean age, 59 years; range, 47-75 years) prior to radical prostatectomy for prostate cancer. T2-weighted signal intensity and metabolic ratios of peripheral zone HGPIN foci of 6 mm or greater in diameter were recorded by two readers with knowledge of step-section histopathologic findings using areas of confirmed normal and cancerous peripheral zone tissue for comparison. A random effects statistical model was used to compare metabolic ratios from normal, HGPIN, and cancer voxels.

RESULTS

A total of 123 peripheral zone HGPIN foci with a mean diameter of 3 mm (range, 1-28 mm) were identified in 37 (77%) patients, but only 20 foci in 14 patients had a diameter of 6 mm or greater. Six foci were excluded, yielding 14 large HGPIN lesions from 11 patients in the final statistical analysis. The larger HGPIN foci were not associated with any focal reduction in T2-weighted signal intensity but demonstrated metabolic findings intermediate between normal and cancerous tissue; the mean ratios of choline (Cho) to creatine (Cr) for normal, HGPIN, and cancer were 0.92, 1.75, and 1.99, respectively, (P < .01), and the corresponding ratios of Cho plus Cr to citrate were 0.34, 0.50, and 0.78 (P < .01).

CONCLUSION

HGPIN is metabolically intermediate between normal peripheral zone tissue and prostate cancer at MR spectroscopic imaging but does not manifest any MR imaging abnormality and is rarely of sufficient size to cause substantial error in evaluation of peripheral zone tumor extent in patients with prostate cancer.

Bilder in der Urologie: Faszination und Perspektiven

In contrast to other countries (e.g., USA) the German urologist routinely utilizes imaging in order to evaluate urological disorders. Ultrasound as a basic tool has acquired importance similar to the physical examination or the patient history. Because of its minimal invasiveness and low cost, it is increasingly utilized as a first-line exam.In correlation with the patient history and laboratory data more invasive imaging studies are performed and in unclear cases or in the preoperative work-up more extensive imaging procedures like computed tomography (CT) or magnetic resonance imaging (MRI) are utilized. Even in emergency situations the urologist is able to guide interventions under ultrasound or conventional X-ray guidance (e.g., percutaneous drainage of dilated kidney), which resulted in a much lower complication rate of the various procedures. In those cases in which ultrasound is technically infeasible or in unclear cases CT and MRI are used as problem-solving procedures and are able to give the correct diagnosis in a large percentage of cases.After a brief historical overview, newer modalities and innovative techniques are explored and presented. Assuming that these innovative approaches lead to more accurate diagnosis and staging of various neoplastic and nonneoplastic conditions, treatment can be performed in earlier stages of diseases and better stage-adapted treatment can be offered to the patients.

[18F]fluorocholine PET/CT imaging for the detection of recurrent prostate cancer at PSA relapse: experience in 100 consecutive patients

PURPOSE

We evaluated the potential of PET/CT and [(18)F]fluoromethylcholine (FCH) in the assessment of suspected recurrence of prostate cancer after treatment.

METHODS

One hundred consecutive prostate cancer patients with a persistent increase in serum PSA (>0.1 ng/ml) after radical prostatectomy (58 cases), radiotherapy (21 cases) or hormonal therapy alone (21 cases) were investigated. After injection of 3.7-4.07 MBq/kg of FCH, both early (at <15 min) and delayed (at >60 min) PET/CT scans were performed in 43 patients, delayed PET/CT scans in 53 patients and early PET/CT scans in four patients.

RESULTS

Of the 100 patients, 54 (PSA 0.22-511.79 ng/ml) showed positive FCH PET/CT scans. Thirty-seven patients had bone and/or abdominal lymph node uptake, while 17 showed pelvic activity. Malignant disease was confirmed in all but one. Delayed SUV(max) of bone metastases was significantly higher (p<0.0001 by paired t test) than that measured at <15 min, whereas no differences were observed between early and delayed SUVs of malignant lymph nodes or pelvic disease. Forty-six patients (PSA 0.12-14.3 ng/ml) showed negative FCH PET/CT scans. Of the negative PET/CT scans, 89% were obtained in patients with serum PSA <4 ng/ml and 87% in patients with a Gleason score <8. In none of these cases could recurrent tumour be proven clinically during a follow-up of 6 months.

CONCLUSION

FCH PET/CT is not likely to have a significant impact on the care of prostate cancer patients with biochemical recurrence until PSA increases to above 4 ng/ml. However, in selected patients, FCH PET/CT helps to exclude distant metastases when salvage local treatment is intended.

[MR spectroscopic imaging for evaluation of prostate cancer]

MR spectroscopic imaging (MRSI) provides a noninvasive method of evaluating metabolic markers of prostate cancer or healthy prostatic tissue (the metabolites choline and citrate), and is performed in conjunction with high-resolution MR anatomic imaging. Multiple studies have showed the incremental role of MRSI combined with the anatomical information provided by MRI for assessment of cancer location and extent within the prostate, staging, and cancer aggressiveness. In addition, MRSI has a potential role for pre- and post-treatment evaluation in non surgical patients. Ongoing technical developments show the potential role of MRSI for guidance of biopsies or focal treatment. Further developments - including new 3T technology - will likely provide improved spectral resolution for better prostate cancer detection and characterization.

Biexponential characterization of prostate tissue water diffusion decay curves over an extended b-factor range

Detailed measurements of water diffusion within the prostate over an extended b-factor range were performed to assess whether the standard assumption of monoexponential signal decay is appropriate in this organ. From nine men undergoing prostate MR staging examinations at 1.5 T, a single 10-mm-thick axial slice was scanned with a line scan diffusion imaging sequence in which 14 equally spaced b factors from 5 to 3,500 s/mm(2) were sampled along three orthogonal diffusion sensitization directions in 6 min. Due to the combination of long scan time and limited volume coverage associated with the multi-b-factor, multidirectional sampling, the slice was chosen online from the available T2-weighted axial images with the specific goal of enabling the sampling of presumed noncancerous regions of interest (ROIs) within the central gland (CG) and peripheral zone (PZ). Histology from prescan biopsy (n=9) and postsurgical resection (n=4) was subsequently employed to help confirm that the ROIs sampled were noncancerous. The CG ROIs were characterized from the T2-weighted images as primarily mixtures of glandular and stromal benign prostatic hyperplasia, which is prevalent in this population. The water signal decays with b factor from all ROIs were clearly non-monoexponential and better served with bi- vs. monoexponential fits, as tested using chi(2)-based F test analyses. Fits to biexponential decay functions yielded intersubject fast diffusion component fractions in the order of 0.73+/-0.08 for both CG and PZ ROIs, fast diffusion coefficients of 2.68+/-0.39 and 2.52+/-0.38 microm(2)/ms and slow diffusion coefficients of 0.44+/-0.16 and 0.23+/-0.16 um(2)/ms for CG and PZ ROIs, respectively. The difference between the slow diffusion coefficients within CG and PZ was statistically significant as assessed with a Mann-Whitney nonparametric test (P<.05). We conclude that a monoexponential model for water diffusion decay in prostate tissue is inadequate when a large range of b factors is sampled and that biexponential analyses are better suited for characterizing prostate diffusion decay curves.

Nuclear Medicine Studies of the Prostate, Testes, and Bladder

During the last decade, there has been a significant advancement in imaging of urologic diseases. Transrectal ultrasound (TRUS), computerized tomography (CT), magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and positron emission tomography (PET) are still experiencing new developments in urology. Despite these many technological advances, the initial diagnostic procedure for a patient with suspected prostate cancer (PC) is multiple site blind prostate biopsies. There is a need for a noninvasive metabolic imaging modality to direct the site of biopsy to decrease the sampling error. MRS seems promising but as it is a costly and more time-consuming test, further studies are needed to evaluate its clinical utility. Currently, PET does not play any role to direct biopsy. Acetate and choline appear to be better tracers than FDG for the detection of a prostate lesion, however, further well-organized studies are needed before any of these agents can be used clinically. Incidental detection of intense focal uptake in the prostate during whole body PET scanning should be evaluated with prostate-specific antigen (PSA) and TRUS-guided biopsy. Although FDG is inferior to other tracers for primary staging, it may be useful in selected patients with suspected high-grade cancer. The role of ProstaScint scan is still controversial for detection of recurrent PC. This study may be helpful for evaluating nodal metastases when PSA is elevated and bone scan is negative. Bone scan remains the study of choice when bone metastases are suspected (PSA>15-20 ng/mL+/-bone pain). Acetate and choline provide better accuracy than FDG in the detection of local soft tissue disease, nodal involvement, and distant metastases. High FDG uptake may be indicative of more aggressive and possibly androgen-independent disease. PET/CT with any of the above PET tracers will most likely be preferred to the PET scan alone due to better localization of a hot lesion in PET/CT. Nuclear medicine studies also have been used to evaluate acute scrotum and testicular neoplasms. Scrotal scintigraphy has lost its popularity to Doppler ultrasound in the evaluation of the acute scrotum. In testicular tumors, FDG-PET appears to be superior to conventional imaging modalities in initial staging, detection of residual/recurrence, and monitoring treatment response. Tumor markers after treatment occasionally are elevated and cannot locate the site of recurrence, FDG-PET can play a very important role in this regard. Nuclear medicine studies also have been used to evaluate diseases of the urinary bladder. Radionuclide cystography is more sensitive and has less than 1/20 the radiation exposure of the conventional contrast enhanced micturating cystourethrogram (MCU). However, the utility of FDG-PET in the evaluation of bladder cancer seems to be limited to the evaluation of distant metastases. 11C-Methionine and choline may be a better option for local and nodal disease due to their negligible excretion in the urine.

Magnetic resonance-guided prostate interventions

We review our experience using an open 0.5-T magnetic resonance (MR) interventional unit to guide procedures in the prostate. This system allows access to the patient and real-time MR imaging simultaneously and has made it possible to perform prostate biopsy and brachytherapy under MR guidance. We review MR imaging of the prostate and its use in targeted therapy, and describe our use of image processing methods such as image registration to further facilitate precise targeting. We describe current developments with a robot assist system being developed to aid radioactive seed placement.

Prostate MR imaging at high-field strength: evolution or revolution?

As 3 T MR scanners become more available, body imaging at high field strength is becoming the subject of intensive research. However, little has been published on prostate imaging at 3 T. Will high-field imaging dramatically increase our ability to depict and stage prostate cancer? This paper will address this question by reviewing the advantages and drawbacks of body imaging at 3 T and the current limitations of prostate imaging at 1.5 T, and by detailing the preliminary results of prostate 3 T MRI. Even if slight adjustments of imaging protocols are necessary for taking into account the changes in T1 and T2 relaxation times at 3 T, tissue contrast in T2-weighted (T2w) imaging seems similar at 1.5 T and 3 T. Therefore, significant improvement in cancer depiction in T2w imaging is not expected. However, increased spatial resolution due to increased signal-to-noise ratio (SNR) may improve the detection of minimal capsular invasion. Higher field strength should provide increased spectral and spatial resolution for spectroscopic imaging, but new pulse sequences will have to be designed for overcoming field inhomogeneities and citrate J-modulation issues. Finally, dynamic contrast-enhanced MRI is the method of imaging that is the most likely to benefit from the increased SNR, with a significantly better trade-off between temporal and spatial resolution.

Magnetic resonance imaging and magnetic resonance spectroscopic imaging of prostate cancer

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) are evolving techniques that offer noninvasive evaluation of anatomic and metabolic features of prostate cancer. The ability of MRI to determine the location and extent of the tumor and to identify metastatic spread is useful in the pretreatment setting, enabling treatment decision-making that is evidence-based. MRSI of the prostate gland expands the diagnostic assessment of prostate cancer through the detection of cellular metabolites, and can lead to noninvasive differentiation of cancer from healthy tissue. MRI/MRSI can also be used to evaluate both local and systemic recurrence, with endorectal MRI being capable of detecting local recurrence, even in patients with rising serum PSA level but no palpable tumor on digital rectal examination. Considering the benefits that MRI and MRSI have been shown to offer patients, the skills and technology required to perform these tests should be widely disseminated to make their routine use possible. Teamwork between members of radiology, pathology, urology and radiation oncology departments is essential in order to exploit these technologies fully.

Complications of radiotherapy: improving the therapeutic index

For every course of radiotherapy treatment, the potential benefit has to be weighed against the risk of normal tissue damage. Radiation-induced proctitis during and after radical radiotherapy for prostate cancer can be decreased by reducing both the size of the target volume and the margins required around this volume. In the future, target volumes could be reduced by both CT/MRI co-registration and dose painting using MR spectroscopy of choline and citrate in the prostate. Improved immobilisation and image-guided radiotherapy should allow reduced margins without compromising the effectiveness of treatment. Similarly, in breast radiotherapy treatment, lung and cardiac complications can be reduced by better patient positioning and ensuring that doses to the heart and lung are minimised during radiotherapy treatment planning. Cosmesis can be improved by using 3D breast planning techniques rather than the conventional 2D approach. These ongoing improvements and developments in radiotherapy treatment planning are leading to treatments which offer both better tumour volume coverage, and are minimising the risk of treatment-related complications. In time, these changes should allow the escalation in dose delivered to the tumour volume with the potential for increased cure rates.

Prostate cancer: correlation of MR imaging and MR spectroscopy with pathologic findings after radiation therapy-initial experience

PURPOSE

To prospectively evaluate magnetic resonance (MR) imaging and MR spectroscopy for depiction of local prostate cancer recurrence after external-beam radiation therapy, with step-section pathologic findings as the standard of reference.

MATERIALS AND METHODS

Study received institutional approval, and written informed consent was obtained. Study was compliant with Health Insurance Portability and Accountability Act. Sextant biopsy, digital rectal examination, MR imaging, MR spectroscopy, and salvage radical prostatectomy with step-section pathologic examination were performed in nine patients with increasing prostate-specific antigen levels after external-beam radiation therapy. MR imaging criterion for tumor was a focal nodular region of reduced signal intensity at T2-weighted imaging. MR spectroscopic criteria for tumor were voxels with choline (Cho) plus creatine (Cr) to citrate (Cit) ratio ([Cho + Cr]/Cit) of at least 0.5 or voxels with detectable Cho and no Cit in the peripheral zone. Sensitivity and specificity of sextant biopsy, digital rectal examination, MR imaging, and MR spectroscopy were determined by using a prostate sextant as the unit of analysis. For feature analysis, MR imaging and MR spectroscopic findings were correlated with step-section pathologic findings.

RESULTS

MR imaging and MR spectroscopy showed estimated sensitivities of 68% and 77%, respectively, while sensitivities of biopsy and digital rectal examination were 48% and 16%, respectively. MR spectroscopy appears to be less specific (78%) than the other three tests, each of which had a specificity higher than 90%. MR spectroscopic feature analysis showed that a metabolically altered benign gland could be falsely identified as tumor by using MR spectroscopic criteria; further analysis of MR spectroscopic features did not lead to improved MR spectroscopic criteria for recurrent tumor.

CONCLUSION

In summary, MR imaging and MR spectroscopy may be more sensitive than sextant biopsy and digital rectal examination for sextant localization of cancer recurrence after external-beam radiation therapy.

Magnetic resonance imaging in prostate cancer

With the recently published National Institute of Clinical Excellence guidelines, it is now generally accepted that magnetic resonance imaging (MRI) is the imaging method of choice for staging prostate cancer in patients for whom radical treatment is being considered. MRI offers the single most accurate assessment of local disease and regional metastatic spread. As well as detecting extraprostatic extension, this technique can locate the site of intraprostatic disease, which may prove useful in planning disease-targeting therapies currently being developed. However, numerous studies have reported widely varying accuracies indicating that MRI is not the perfect imaging modality; microscopic and early macroscopic invasion cannot be reliably shown using current technology. The role of MRI including advantages, limitations and future developments will be discussed.

In vivo and ex vivo proton MR spectroscopy of primary and secondary melanoma

In vivo magnetic resonance (MR) spectroscopy at 1.5T was performed on a large polypoid cutaneous melanoma, and two enlarged lymph nodes containing metastatic melanoma, from three patients. Spectra were acquired in vivo from voxels wholly within the primary tumour or secondary lymph node and were thus uncontaminated by signals from adjacent tissue. Tissue biopsies taken after resection of primary tumours and secondary lymph nodes were examined by 8.5T magnetic resonance spectroscopy (MRS) and the results compared with the in vivo spectra, and with spectra from normal skin and a benign skin lesion. There was good agreement between the dominant features of 1.5T spectra acquired in vivo and 8.5T spectra acquired from resected tissue. However, less intense resonances observed at 8.5T in malignant biopsy tissue were not consistently observed at 1.5T in vivo. In vivo spectra from primary and metastatic melanoma showed high levels of choline metabolites. An intense lactate resonance was also present in the in vivo spectrum of primary melanoma. All 8.5T spectra of biopsies from primary and secondary melanoma showed high levels of choline metabolites and lactate, and additional resonances consistent with elevated levels of taurine, alanine, lysine, and glutamate/glutamine relative to normal and benign tissue. Elevated levels of choline, lactate, taurine, and amino acids appear to be clinically useful markers for identifying the pathology of primary and metastatic melanoma.

Preliminary assessment of magnetic resonance spectroscopic imaging in predicting treatment outcome in patients with prostate cancer at high risk for relapse

The purpose of the study was to determine whether 3D proton magnetic resonance spectroscopic imaging (MRSI) can predict treatment outcome in high risk patients with prostate cancer. Endorectal magnetic resonance imaging (MRI) and 1H-MRSI were performed in 16 patients with prostate cancer who were considered high risk because of clinical stage T3-4, Gleason score>/=8, and/or prostate-specific antigen (PSA) level>20 ng/mL. Patients were treated with chemotherapy/hormone therapy, underwent radical prostatectomy (RP) or radiation therapy, and were followed for PSA relapse (follow-up, 19-43 months). The ratio of choline plus creatine to citrate was used to localize peripheral zone cancer. An MRSI risk score on a scale of 0-3 was derived from the volume and degree of metabolic abnormality. Magnetic resonance spectroscopic imaging risk score, MRI tumor/node (TN) stage, clinical stage, Gleason score, and PSA were used as predictors of pathologic stage in patients treated with RP (n=10) and PSA relapse in all patients. Magnetic resonance imaging TN stage (P<0.01) and MRSI risk score (P<0.05) correlated with pathologic stage, but clinical stage did not (P=0.35). Magnetic resonance imaging TN stage was the only significant predictor of PSA relapse in the univariate analysis (P<0.05). Although the MRSI risk score did not reach significance (P=0.13), 6 patients with a score<0.9 were relapse-free, whereas 7 of 10 patients with a score>0.9 relapsed. Magnetic resonance imaging and MRSI risk assessments agreed in 15 of 16 patients. These preliminary results suggest that tumor metabolic assessment may indicate treatment outcome in high-risk patients with prostate cancer. Although MRSI did not provide added prognostic value to MRI in this small number of patients, MRSI might increase the confidence of the clinician in assessing risk on MRI by contributing supporting metabolic data.

Prostate Depiction at Endorectal MR Spectroscopic Imaging: Investigation of a Standardized Evaluation System

PURPOSE

To investigate the accuracy and interobserver variability of a standardized evaluation system for endorectal three-dimensional (3D) magnetic resonance (MR) spectroscopic imaging of the prostate.

MATERIALS AND METHODS

The human research committee approved the study, and all patients provided written informed consent. Endorectal MR imaging and MR spectroscopic imaging were performed in 37 patients before they underwent radical prostatectomy. For the 22 patients with good or excellent MR spectroscopic imaging data, step-section histopathologic tumor maps were used to identify spectroscopic voxels of unequivocally benign (n = 306) or malignant (n = 81) peripheral zone tissue. Two independent spectroscopists, unaware of all other findings, scored the spectra of the selected voxels by using a scale of 1 (benign) to 5 (malignant) that was based on standardized metabolic criteria. Descriptive statistical, receiver operating characteristics (ROC), and kappa statistical analyses of the data obtained by both readers were performed by using two definitions of cancer: one based on a voxel score of 3-5 and the other based on a score of 4 or 5.

RESULTS

The scoring system had good accuracy (74.2%-85.0%) in the differentiation between benign and malignant tissue voxels, with areas under the ROC curve of 0.89 for reader 1 and 0.87 for reader 2. Specificities of 84.6% and 89.3% were achieved when a voxel score of 4 or 5 was used to identify cancer, and sensitivities of 90% and 93% were achieved when a score of 3-5 was used to identify cancer. Readers demonstrated excellent interobserver agreement (kappa values, 0.79 and 0.80).

CONCLUSION

The good accuracy and excellent interobserver agreement achieved by using the standardized five-point scale to interpret peripheral zone metabolism demonstrate the potential effectiveness of using metabolic information to identify prostate cancer, and the clinical usefulness of this system warrants testing in prospective clinical trials of MR imaging combined with MR spectroscopic imaging.

Tissue ablation technologies for localized prostate cancer

Traditional treatments for men with localized prostate cancer have included both surgical removal and radiation therapy, with their potential adverse effects on patient quality of life. Thus, there has been increasing interest in the development of minimally invasive procedures that use various technologies to deliver lethal doses of heat or cold to the prostate in an attempt to kill cancer cells. At the same time, it is vital that these newer techniques ablate prostate tissue and spare vital periprostatic organs essential for maintaining function and quality of life. In this article, we evaluate the current status of tissue ablation modalities in the treatment of clinically localized prostate cancer, focusing on the different methods, early results, and possible future directions. Although still in the beginning stages, these newer forms of treatment offer exciting potential for first-line and second-line treatment of this common urologic malignancy.

Organ-Confined Prostate Cancer: Effect of Prior Transrectal Biopsy on Endorectal MRI and MR Spectroscopic Imaging

OBJECTIVE

Our aim was to determine the effect of prior transrectal biopsy on endorectal MRI and MR spectroscopic imaging findings in patients with organ-confined prostate cancer.

MATERIALS AND METHODS

Endorectal MRI and MR spectroscopic imaging were performed in 43 patients with biopsy-proven prostate cancer before radical prostatectomy confirming organ-confined disease. For each sextant, two independent reviewers scored the degree of hemorrhage on a scale from 1 to 5 and recorded the presence or absence of capsular irregularity. A spectroscopist recorded the number of spectrally degraded voxels in the peripheral zone. The outcome variables of capsular irregularity and spectral degradation were correlated with the predictor variables of time from biopsy and degree of hemorrhage after biopsy.

RESULTS

Capsular irregularity was unrelated to time from biopsy or to degree of hemorrhage. Spectral degradation was inversely related to time from biopsy (p < 0.01); the mean percentage of degraded peripheral zone voxels was 18.5% within 8 weeks of biopsy compared with 7% after 8 weeks. Spectral degradation was unrelated to the degree of hemorrhage.

CONCLUSION

In organ-confined prostate cancer, capsular irregularity can be seen at any time after biopsy and is independent of the degree of hemorrhage, whereas spectral degradation is seen predominantly in the first 8 weeks after biopsy. MRI staging criteria and guidelines for scheduling studies after biopsy may require appropriate modification.

MR imaging of the prostate at 3 Tesla: comparison of an external phased-array coil to imaging with an endorectal coil at 1.5 Tesla

RATIONALE AND OBJECTIVES

To qualitatively compare the image quality of torso phased-array 3-Tesla (3T) imaging of the prostate with that of endorectal 1.5-Tesla imaging.

MATERIALS AND METHODS

Twenty cases of torso phased-array prostate imaging performed at 3-Tesla with FSE T2 weighted images were evaluated by two readers independently for visualization of the posterior border (PB), seminal vesicles (SV), neurovascular bundles (NVB), and image quality rating (IQR). Studies were performed at large fields of view(FOV) (25 cm) (14 cases) (3TL) and smaller FOV (14 cm) (19 cases) (3TS). A comparison was made to 20 consecutive cases of 1.5-T endorectal evaluation performed during the same time period.Results. 3TL produced a significantly better image quality compared with the small FOV for PB (P = .0001), SV (P =.0001), and IQR (P = .0001). There was a marginally significant difference within the NVB category (P = .0535). 3TL produced an image of similar quality to image quality at 1.5 T for PB (P = .3893), SV (P = .8680), NB (P = .2684), and IQR (P = .8599).

CONCLUSION

Prostate image quality at 3T with a torso phased-array coil can be comparable with that of endorectal 1.5-T imaging. These findings suggest that additional options are now available for magnetic resonance imaging of the prostate gland.

MR imaging and MR spectroscopic imaging of prostate cancer

The primary indication for prostate MR and MR spectroscopic imaging is evaluating men with newly diagnosed prostate cancer who are deciding whether to undergo surgery or radiotherapy. Other applications of MR and MR spectroscopic imaging in prostate cancer are not defined fully. Areas of research include volumetric localization of prostate cancer, in vivo MR spectroscopic imaging at high field strength, in vitro MR spectroscopic imaging at very high field strength, novel spectroscopic markers of malignancy,and interventional MR guidance of biopsy and therapy. MR spectroscopic imaging remains a relatively novel technique, and successful implementation is demanding. Nonetheless, only MR and MR spectroscopic imaging allow structural and metabolic evaluation of prostate cancer location, aggressiveness, and stage, and MR imaging provides clinically and therapeutically relevant information on prostatic and periprostatic anatomy.

Time to metabolic atrophy after permanent prostate seed implantation based on magnetic resonance spectroscopic imaging

PURPOSE

To characterize the time to metabolic atrophy (TMA) after permanent prostate implantation (PPI) using combined MRI and magnetic resonance spectroscopic imaging (MRSI) compared with the time to prostate-specific antigen (PSA) nadir.

METHODS AND MATERIALS

This study was based on a posttreatment analysis comparing the MRI/MRSI findings with the PSA levels of 65 patients treated with PPI alone or combined with external beam radiotherapy and/or HT. The fraction of interpretable voxels demonstrating metabolic atrophy was used to compare the TMA with the time to PSA nadir.

RESULTS

The fraction of patients with metabolic atrophy in >95% of usable voxels after PPI increased from approximately 46% to 100% at 6 and 48 months, respectively. The mean time for PSA nadir vs. TMA was 42.5 vs. 28.9 months (PPI), 32.8 vs. 25.6 months (external beam radiotherapy + PPI), and 25.3 vs. 28.0 months (external beam radiotherapy + hormonal therapy + PPI).

CONCLUSION

Magnetic resonance spectroscopic imaging may provide an early tool for evaluating the treatment response for patients treated with PPI. If supported by longer follow-up, TMA may be a useful adjunct to PSA measurement for assessing local control after PPI and could be useful in evaluating the complex relationships between the quality of the implant and the time to indication of successful therapy.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Chronic prostatitis: MR imaging and 1H MR spectroscopic imaging findings--initial observations

PURPOSE

To determine whether chronic prostatitis affects three-dimensional proton magnetic resonance (MR) spectroscopic imaging in evaluation of disease in the peripheral zone.

MATERIALS AND METHODS

Combined MR imaging and three-dimensional MR spectroscopic imaging data were examined retrospectively in 12 patients with radical prostatectomy specimens that contained regions of chronic prostatitis larger than 6 mm in the peripheral zone. The 6-mm restriction was based on MR spectroscopic imaging spatial resolution of 6.25 mm. Transverse T2-weighted MR images were reviewed for changes in signal intensity (SI): normal, suspicious for cancer (nodular focal low SI), or indeterminate (focal low SI that was not nodular or contour deforming or diffuse low SI). At MR spectroscopic imaging, proton spectra were considered suspicious for cancer if the ratio of choline plus creatine to citrate was more than 2 SDs above normal mean peripheral zone values.

RESULTS

In the 12 patients, mean pretreatment prostate-specific antigen level was 5.77 +/- 2.07 (SD), and median biopsy Gleason score for the gland was 6. At MR imaging in the area of histopathologically confirmed chronic prostatitis, seven of 12 patients had focal low SI that was not nodular (contour deforming) over a region in and around the pathologically defined focus of chronic prostatitis. MR imaging in one patient showed diffuse low SI that correlated with a diffuse area of chronic prostatitis at pathologic examination. MR imaging in another patient showed nodular focal low SI that was suspicious for cancer and corresponded to a focus of chronic prostatitis at pathologic examination. The remaining three patients had no MR imaging abnormality in the region of chronic prostatitis. In the pathologically identified regions of chronic prostatitis, MR spectroscopic imaging data in nine of 12 patients demonstrated elevated choline peak and reduced or no citrate, findings that mimic those of cancer. In two patients, the spectra were normal, and in the remaining patient, the spectra were nondiagnostic.

CONCLUSION

At MR spectroscopic imaging, pathologically confirmed chronic prostatitis may demonstrate metabolic abnormality that leads to false-positive diagnosis of cancer. The most common MR imaging finding in chronic prostatitis was focal low SI that was not specific for cancer. In one patient, the MR imaging diagnosis of cancer could not be excluded.

Endorectal magnetic resonance imaging and spectroscopy for the detection of tumor foci in men with prior negative transrectal ultrasound prostate biopsy

PURPOSE

We determined the ability of combined endorectal magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) to detect prostate cancer foci prospectively in men with prior negative transrectal ultrasound (TRUS) prostate biopsy.

MATERIALS AND METHODS

Endorectal MRI with spectroscopy was performed in 24 consecutive patients with 1 or more prior negative TRUS prostatic biopsies for persistently increased prostate specific antigen and/or abnormal digital rectal examination. All studies were interpreted by a dedicated radiologist who reported areas of interest in the peripheral zone as normal, equivocal or suspicious on MRI and MRSI separately. Equivocal and suspicious areas were then correlated with a 3-dimensional prostate model. All patients underwent a standard TRUS 10-core peripheral zone biopsy with up to 4 additional biopsies targeted at the equivocal or suspected sites.

RESULTS

Prostate cancer was detected in 7 of 24 subjects (29.2%). Considering the equivocal category as test negative the sensitivity, specificity, positive and negative predictive values, and the accuracy of MRI, MRSI and combined MRI/MRSI for the detection of prostate cancer were 57.1%, 57.1% and 100.0%, 88.2%, 82.4% and 70.6%, 66.7%, 57.1% and 58.3%, 83.3%, 82.1% and 100%, and 79.2%, 75.0% and 79.2%, respectively. The site of positive biopsy correlated correctly in 50% and 28.6% of MRI and MRSI labeled suspicious cores, respectively.

CONCLUSIONS

MRI and MRSI have the potential to identify cancer foci and direct TRUS in patients with a previous negative TRUS biopsy. Further, larger studies are required to quantify the amount of benefit.

Endorectal diffusion-weighted imaging in prostate cancer to differentiate malignant and benign peripheral zone tissue

PURPOSE

To determine if the apparent diffusion coefficient (ADC) can discriminate benign from malignant peripheral zone (PZ) tissue in patients with biopsy-proven prostate cancer that have undergone endorectal diffusion-weighted imaging (DWI) of the prostate.

MATERIALS AND METHODS

Ten patients with prostate cancer underwent endorectal magnetic resonance imaging (MRI) in addition to DWI. A two-dimensional grid was placed over the axial images, and each voxel was graded by a 4-point rating scale to discriminate nonmalignant from malignant PZ tissue based on MR images alone. ADC was then determined for each voxel and plotted for nonmalignant and malignant voxels for the entire patient set. Second, with the radiologist aware of biopsy locations, any previously assigned voxel grade that was inconsistent with biopsy data was regrouped and ADCs were replotted.

RESULTS

For the entire patient set, without and with knowledge of the biopsy data, the mean ADCs for nonmalignant and malignant tissue were 1.61 +/- 0.27 and 1.34 +/- 0.38 x 10(-3) mm2/second (P = 0.002) and 1.61 +/- 0.26 and 1.27 +/- 0.37 x 10(-3) mm2/second (P = 0.0005), respectively.

CONCLUSION

DWI of the prostate is possible with an endorectal coil. The mean ADC for malignant PZ tissue is less than nonmalignant tissue, although there is overlap in individual values.

Prostate Cancer Localization with Endorectal MR Imaging and MR Spectroscopic Imaging: Effect of Clinical Data on Reader Accuracy

PURPOSE

To determine the effect of digital rectal examination findings, sextant biopsy results, and prostate-specific antigen (PSA) levels on reader accuracy in the localization of prostate cancer with endorectal magnetic resonance (MR) imaging and MR spectroscopic imaging.

MATERIALS AND METHODS

This was a retrospective study of 37 patients (mean age, 57 years) with biopsy-proved prostate cancer. Transverse T1-weighted, transverse high-spatial-resolution, and coronal T2-weighted MR images and MR spectroscopic images were obtained. Two independent readers, unaware of clinical data, recorded the size and location of suspicious peripheral zone tumor nodules on a standardized diagram of the prostate. Readers also recorded their degree of diagnostic confidence for each nodule on a five-point scale. Both readers repeated this interpretation with knowledge of rectal examination findings, sextant biopsy results, and PSA level. Step-section histopathologic findings were the reference standard. Logistic regression analysis with generalized estimating equations was used to correlate tumor detection with clinical data, and alternative free-response receiver operating characteristic (AFROC) curve analysis was used to examine the overall effect of clinical data on all positive results.

RESULTS

Fifty-one peripheral zone tumor nodules were identified at histopathologic evaluation. Logistic regression analysis showed awareness of clinical data significantly improved tumor detection rate (P <.02) from 15 to 19 nodules for reader 1 and from 13 to 19 nodules for reader 2 (27%-37% overall) by using both size and location criteria. AFROC analysis showed no significant change in overall reader performance because there was an associated increase in the number of false-positive findings with awareness of clinical data, from 11 to 21 for reader 1 and from 16 to 25 for reader 2.

CONCLUSION

Awareness of clinical data significantly improves reader detection of prostate cancer nodules with endorectal MR imaging and MR spectroscopic imaging, but there is no overall change in reader accuracy, because of an associated increase in false-positive findings. A stricter definition of a true-positive result is associated with reduced sensitivity for prostate cancer nodule detection.

Can pre-operative contrast-enhanced dynamic MR imaging for prostate cancer predict microvessel density in prostatectomy specimens?

The aim of this study was to correlate quantitative dynamic contrast-enhanced MRI (DCE MRI) parameters with microvessel density (MVD) in prostate carcinoma. Twenty-eight patients with biopsy-proven prostate carcinoma were examined by endorectal MRI including multiplanar T2- and T1-weighted spin-echo and dynamic T1-weighted turbo-FLASH MRI during and after intravenous Gd-DTPA administration. Microvessels were stained on surgical specimens using a CD31 monoclonal antibody. The MVD was quantified in hot spots by counting (MVC) and determining the area fraction by morphometry (MVAF). The DCE MRI data were analyzed using an open pharmacokinetic two-compartment model. In corresponding anatomic locations the time shift (Deltat) between the beginning of signal enhancement of cancer and adjacent normal prostatic tissue, the degree of contrast enhancement and the contrast exchange rate constant (k21) were calculated. The MVC and MVAF were elevated in carcinoma (p<0.001 and p=0.002, respectively) and correlated to k21 (r=0.62, p<0.001 and r=0.80, p<0.001, respectively). k21-values of carcinoma were significantly higher compared with normal peripheral but not central zone tissue. Deltat was longer in high compared with low-grade tumors (p=0.025). The DCE MRI can provide important information about individual MVD in prostate cancer, which may be helpful for guiding biopsy and assessing individual prognosis.

Noninvasive detection of clinically occult lymph-node metastases in prostate cancer

BACKGROUND

Accurate detection of lymph-node metastases in prostate cancer is an essential component of the approach to treatment. We investigated whether highly lymphotropic superparamagnetic nanoparticles, which gain access to lymph nodes by means of interstitial-lymphatic fluid transport, could be used in conjunction with high-resolution magnetic resonance imaging (MRI) to reveal small nodal metastases.

METHODS

Eighty patients with presurgical clinical stage T1, T2, or T3 prostate cancer who underwent surgical lymph-node resection or biopsy were enrolled. All patients were examined by MRI before and 24 hours after the intravenous administration of lymphotropic superparamagnetic nanoparticles (2.6 mg of iron per kilogram of body weight). The imaging results were correlated with histopathological findings.

RESULTS

Of the 334 lymph nodes that underwent resection or biopsy, 63 (18.9 percent) from 33 patients (41 percent) had histopathologically detected metastases. Of these 63 nodes, 45 (71.4 percent) did not fulfill the usual imaging criteria for malignancy. MRI with lymphotropic superparamagnetic nanoparticles correctly identified all patients with nodal metastases, and a node-by-node analysis had a significantly higher sensitivity than conventional MRI (90.5 percent vs. 35.4 percent, P<0.001) or nomograms.

CONCLUSIONS

High-resolution MRI with magnetic nanoparticles allows the detection of small and otherwise undetectable lymph-node metastases in patients with prostate cancer.

Neoadjuvant docetaxel and estramustine chemotherapy in high-risk/locallyadvanced prostate cancer

OBJECTIVES

To evaluate the efficacy and safety of neoadjuvant docetaxel and estramustine in patients with high-risk, newly diagnosed, prostate cancer.

METHODS

Eligible patients had prostate cancer with one or more of the following criteria: clinical Stage T2b or greater, prostate-specific antigen (PSA) of 15 ng/mL or greater, and/or Gleason score of 8 to 10. Chemotherapy consisted of docetaxel (70 mg/m(2)) on day 1 and estramustine (280 mg three times daily) on days 1 to 3 every 21 days for three to six courses. This was followed by local therapy, as deemed appropriate.

RESULTS

Twenty-one patients with a median age of 60 years, median PSA level of 16.1 ng/mL (range 2.4 to 175), and median baseline testosterone of 3.4 ng/mL were enrolled. Seven patients met one of the inclusion criteria, 10 met two, and 4 met three. The Gleason score was 8 or greater in 14 patients. A median of five cycles of chemotherapy was delivered. The most frequent high-grade toxicities were grade 3 (8 patients) and 4 (1 patient) neutropenia and deep venous thrombosis (grade 3 in 2 patients) before institution of low-dose warfarin. All patients responded as determined by protocol-defined criteria. Ten patients underwent radical prostatectomy, with negative surgical margins in 7 patients, and 11 received radiotherapy with negative preradiotherapy biopsies in 2.

CONCLUSIONS

Induction docetaxel and estramustine is well tolerated and feasible in patients with newly diagnosed, high-risk prostate cancer. This combination is active; however, its efficacy relative to hormonal therapy will require a controlled randomized trial.

Proton two-dimensional chemical shift imaging for evaluation of prostate cancer: external surface coil vs. endorectal surface coil

PURPOSE

To compare the diagnostic ability of proton magnetic resonance spectroscopy (MRS) using an external surface coil with that using an endorectal surface coil in patients with prostate cancer.

MATERIALS AND METHODS

MR imaging (MRI) and two-dimensional chemical shift imaging (2D CSI) were performed in 5 healthy volunteers and in 35 patients with prostate cancer. The receiver coil was the anterior lower part of a phased-array coil or an endorectal surface coil.

RESULTS

Receiver-operating characteristic analysis for diagnosing prostate cancer showed no significant difference (P = 0.784) between the area under the curve of phased-array coil CSI and that of endorectal surface coil CSI.

CONCLUSION

The phased-array coil CSI could provide comparable detection accuracy to endorectal surface coil CSI. In patients with rectal diseases or patients who could not tolerate the discomfort with insertion of an endorectal surface coil, we recommend the phased-array coil CSI.

Towards integrating functional imaging in the treatment of prostate cancer with radiation: the registration of the MR spectroscopy imaging to ultrasound/CT images and its implementation in treatment planning

PURPOSE

Dose-escalation to intraprostatic tumor deposits detected by magnetic resonance spectroscopy (MRS) is an example of tumor-targeted radiation therapy. Because treatment planning for prostate brachytherapy is performed based on ultrasound (US)/computed tomography (CT) images, a sine qua non of this technique is the ability to map MRS-positive volumes (obtained in a gland deformed by the endorectal balloon coil) to the US/CT images. An empirical algorithm designed to perform this function, and its validation, are described.

METHODS AND MATERIALS

Mathematically, the problem of mapping points between the MR and US/CT domains comes to: (a) ascertaining that the position of any point in the interior of the prostate is uniquely determined by the shape of the gland, and (b) finding an algorithm that describes this relationship. The image registration algorithm described here is based on the assumption that points within the gland maintain the same relative position with respect to both the axial contours of the prostate and the center of the prostate along the superior-inferior direction. Relative positions of MRS-positive voxels are calculated with this method in both MR and US/CT space. For a particular voxel in the MR space, one obtains first the z coordinate in the US/CT space, that is, along the superior-inferior direction. This determines the axial slice in the US/CT frame of reference where the other two coordinates (x, y) will be calculated. The validity of this algorithm was examined with the aid of a pelvic phantom built to simulate realistically the prostate and its surrounding bony and tissue structures and with CT scans of implanted patients obtained, at several weeks' intervals, as part of an edema-resolution study. Seventy-five "dummy" seeds were placed in the phantom, within the simulated prostate gland, in a quasi-regular pattern. The coordinates of these seeds were determined and thus served as markers of prostate deformation when an inflated rectal probe was introduced in the phantom. CT images of this phantom were taken for different volumes of the MR rectal probe and in each case the prostate outlines were contoured and seed coordinates calculated. Using these data, the predictions of the mapping algorithm could be directly verified.

RESULTS

Absolute values of the 3D-positional errors in this algorithm were 2.2 mm +/- 1.2 mm (average +/- SD). Only 6 of 75 seeds had positional displacement of 4 mm or more. Similar results were obtained in the patient analysis.

CONCLUSIONS

In comparison to the MRS voxel size (6.25 x 6.25 x 3.0 mm3), the present algorithm achieves the desired clinical accuracy. As well, with this 3D algorithm seed positions are reconstructed with an uncertainty that, along the z direction, is less than half the thickness of the typical US slice (0.5 cm).

Combined magnetic resonance imaging and spectroscopic imaging approach to molecular imaging of prostate cancer

Magnetic resonance spectroscopic imaging (MRSI) provides a noninvasive method of detecting small molecular markers (historically the metabolites choline and citrate) within the cytosol and extracellular spaces of the prostate, and is performed in conjunction with high-resolution anatomic imaging. Recent studies in pre-prostatectomy patients have indicated that the metabolic information provided by MRSI combined with the anatomical information provided by MRI can significantly improve the assessment of cancer location and extent within the prostate, extracapsular spread, and cancer aggressiveness. Additionally, pre- and post-therapy studies have demonstrated the potential of MRI/MRSI to provide a direct measure of the presence and spatial extent of prostate cancer after therapy, a measure of the time course of response, and information concerning the mechanism of therapeutic response. In addition to detecting metabolic biomarkers of disease behavior and therapeutic response, MRI/MRSI guidance can improve tissue selection for ex vivo analysis. High-resolution magic angle spinning ((1)H HR-MAS) spectroscopy provides a full chemical analysis of MRI/MRSI-targeted tissues prior to pathologic and immunohistochemical analyses of the same tissue. Preliminary (1)H HR-MAS spectroscopy studies have already identified unique spectral patterns for healthy glandular and stromal tissues and prostate cancer, determined the composition of the composite in vivo choline peak, and identified the polyamine spermine as a new metabolic marker of prostate cancer. The addition of imaging sequences that provide other functional information within the same exam (dynamic contrast uptake imaging and diffusion-weighted imaging) have also demonstrated the potential to further increase the accuracy of prostate cancer detection and characterization.

Novel methodology for the archiving and interactive reading of clinical magnetic resonance spectroscopic imaging

Archiving clinical magnetic resonance spectroscopic imaging (MRSI) data and presenting the data to specialists (e.g., neuroradiologists, neurosurgeons, neurologists, neuro-oncologists, and MR scientists) who work in different physical locations is a practical problem of significance. This communication describes a novel solution. The study hypothesis was that it is possible to use widely available distributed computing techniques to create a clinical MRSI user interface addressable from any personal computer with a suitable network connection. A worldwide web MRSI archive and interface system was created that permits the user to interactively view individual MRSI voxel spectra with correlation to MR images and to parametric spectroscopic images. Web browser software (i.e., Netscape and Internet Explorer) permits users in various physical locations to access centrally archived MRSI data using a variety of operating systems and client workstations. The system was used for archiving and displaying more than 1000 clinical MRSI studies performed at the authors' institution. The system also permits MRSI data to be viewed via the Internet from distant locations worldwide. The study illustrates that widely available software operating within highly distributed electronic networks can be used for archiving and interactive reading of large amounts of clinical MRSI data.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Magnetic resonance spectroscopic imaging-guided brachytherapy for localized prostate cancer

PURPOSE

Prostate brachytherapy (PB) entails the placement of radioactive sources throughout the entire prostate gland to treat localized cancer. Typically, the target volume in PB encompasses the entire prostate gland because of the inability to localize the cancer and the multifocal nature of this malignancy. However, because of the unique biochemical nature of the prostate gland, recent advances in magnetic resonance spectroscopic imaging (MRSI) of the prostate have allowed precise delineation of the cancer location within the prostate gland. This report reveals our initial experience of MRSI-guided PB.

METHODS

A MRSI study was obtained in 15 localized prostate cancer patients before their scheduled PB. The results of this study were used to internally map 7 x 7 x 9-mm volumes of prostate tissue to assign cancerous areas a higher dose of radiation. Such tumor-bearing areas had a low citrate/(choline+creatine) ratio consistent with cancer. On the basis of the anatomic MRI and MRSI correlation, three-dimensional coordinates were assigned to the locations of MRSI-defined cancer. The entire target volume was treated to a standard prescription dose using I-125 or Pd-103. Abnormal citrate regions, termed the biologic tumor volume, were prescribed a dose of 130% of the target volume dose to dose escalate in the abnormal citrate regions while respecting the normal radiation tolerances of the surrounding areas. Three-dimensional treatment planning was used to perform the implant.

RESULTS

Of the 15 prostate cancer patients evaluated, all had successful three-dimensional MRSI acquisition before their scheduled PB procedure. In 14 of the 15 patients planned with MRSI, the data were successfully incorporated into their treatment planning and were used to increase the radiation dose prescription to 130% in the MRSI-defined volumes. In 1 patient, MRSI revealed significant background artifact that made a focal boost impractical. Postimplant dosimetry confirmed a median V100 of 95% (range 72%-100%) in the 15 evaluated patients for the prescription dose. Furthermore, the median BTV100 for the abnormal citrate region was 90% (range 80-100%) as determined by postimplant dosimetry. Urethral and rectal dose-volume histograms were within normal limits. Morbidity was comparable with that for conventionally treated patients.

CONCLUSION

MRSI offers a promising new approach for the delivery of ionizing radiation in PB. Although this series was small and with a short follow-up, MRSI-guided implants are feasible and warrant further investigation as a means of improving the therapeutic ratio in PB [corrected].

[Prostate cancer]

Radiation therapy of prostate carcinoma with a curative intent implies to treat the whole prostate at high dose (at least 66 Gy). According to clinical stage, PSA level, Gleason's score, the clinical target volume may include seminal vesicles and less often pelvic lymph nodes. Microscopic extracapsular extension is found in 15 to 60% of T1-T2 operated on, specially in apex tumors. On contrary, cancers developing from the transitional zone may stay limited to the prostate even with a big volume and with a high PSA level. Zonal anatomy of the prostate identifies internal prostate, including the transitional zone (5% of the prostate in young people). External prostate includes central and peripheral zones. The inferior limit of the prostate is not lower than the inferior border of the pubic symphysis. Clinical and radiological examination: ultrasonography, nuclear magnetic resonance (NMR), CT-scan identify prognostic factors as tumor volume, capsule effraction, seminal vesicles invasion and lymph node extension. The identification of the clinical target volume is now done mainly by CT-Scan which identifies prostate and seminal vesicles. NMR could be helpful to identify more precisely prostate apex. The definition of margins around the clinical target volume has to take in account daily reproducibility and organ motion and of course the maximum tolerable dose for organs at risk.