Endorectal MR imaging and MR spectroscopic imaging for locally recurrent prostate cancer after external beam radiation therapy: preliminary experience

PURPOSE: To evaluate endorectal magnetic resonance (MR) imaging and MR spectroscopic imaging for the depiction of locally recurrent prostate cancer after external beam radiation therapy. MATERIALS AND METHODS: Endorectal MR imaging and MR spectroscopic imaging were performed in 21 patients with biochemical failure after external beam radiation therapy for prostate cancer. Two readers independently and retrospectively reviewed MR images and rated the likelihood of recurrent tumor on a five-point scale. Spectroscopic voxels were considered suspicious for malignancy if the choline level was elevated and citrate was absent. Receiver operating characteristic curve analysis was used to assess cancer detection in each side of the prostate with endorectal MR imaging and spectroscopic imaging at different thresholds based on the scores assigned by the two readers and on the number of suspicious voxels in each hemiprostate, respectively. The presence or absence of cancer at subsequent transrectal biopsy was used as the standard of reference. RESULTS: Biopsy demonstrated locally recurrent prostate cancer in nine hemiprostates in six patients. The area under the receiver operating characteristic curve for the detection of locally recurrent cancer with MR imaging was 0.49 and 0.51 for readers 1 and 2, respectively. By using the number of suspicious voxels to define different diagnostic thresholds, the area under the receiver operating characteristic curve for MR spectroscopic imaging was significantly (P < .005) higher, at 0.81. In particular, the presence of three or more suspicious voxels in a hemiprostate showed a sensitivity and specificity of 89% and 82%, respectively, for the diagnosis of local recurrence. Seven hemiprostates demonstrated complete metabolic atrophy at spectroscopic imaging and only postirradiation atrophy at biopsy. CONCLUSION: Preliminary data suggest that MR spectroscopic imaging, but not endorectal MR imaging, may be of value for the depiction of locally recurrent prostate cancer after radiation therapy.     

Lymphotropic nanoparticle-enhanced magnetic resonance imaging (LNMRI) identifies occult lymph node metastases in prostate cancer patients prior to salvage radiation therapy

Twenty-six patients with prostate cancer status post-radical prostatectomy who were candidates for salvage radiation therapy (SRT) underwent lymphotropic nanoparticle enhanced MRI (LNMRI) using superparamagnetic nanoparticle ferumoxtran-10. LNMRI was well tolerated, with only two adverse events, both Grade 2. Six (23%) of the 26 patients, previously believed to be node negative, tested lymph node positive by LNMRI. A total of nine positive lymph nodes were identified in these six patients, none of which were enlarged based on size criteria.     

Sequence design for magnetic resonance spectroscopic imaging of prostate cancer at 3 T.

Magnetic resonance spectroscopic imaging (MRSI) has proven to be a powerful tool for the metabolic characterization of prostate cancer in patients before and following therapy. The metabolites that are of particular interest are citrate and choline because an increased choline-to-citrate ratio can be used as a marker for cancer. High-field systems offer the advantage of improved spectral resolution as well as increased magnetization. Initial attempts at extending MRSI methods to 3 T have been confounded by the J-modulation of the citrate resonances. A new pulse sequence is presented that controls the J-modulation of citrate at 3 T such that citrate is upright, with high amplitude, at a practical echo time. The design of short (14 ms) spectral-spatial refocusing pulses and trains of nonselective refocusing pulses are described. Phantom studies and simulations showed that upright citrate with negligible sidebands is observed at an echo time of 85 ms. Studies in a human subject verified that this behavior is reproduced in vivo and demonstrated that the water and lipid suppression of the new pulse sequence are sufficient for application in prostate cancer patients.     

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.     

In vivo prostate magnetic resonance spectroscopic imaging using two-dimensional J-resolved PRESS at 3 T.

In vivo magnetic resonance spectroscopic imaging of the prostate using single-voxel and multivoxel two-dimensional (2D) J-resolved sequences is investigated at a main magnetic field strength of 3 T. Citrate, an important metabolite often used to aid the detection of prostate cancer in magnetic resonance spectroscopic exams, can be reliably detected along with the other metabolites using this method. We show simulations and measurements of the citrate metabolite using 2D J-resolved spectroscopy to characterize the spectral pattern. Furthermore, using spiral readout gradients, the single-voxel 2D J-resolved method is extended to provide the spatial distribution information as well all within a reasonable scan time (17 min). Phantom and in vivo data are presented to illustrate the multivoxel 2D J-resolved spiral chemical shift imaging sequence.     

Multiparametric 3T endorectal mri after external beam radiation therapy for prostate cancer

Purpose:

To determine the best combination of magnetic resonance imaging (MRI) parameters for the detection of locally recurrent prostate cancer after external beam radiation therapy.

Materials and Methods:

Our Institutional Review Board approved this study with a waiver of informed consent. Twenty‐six patients with suspected recurrence due to biochemical failure were part of this research. The MR protocol included T2‐weighted, MR spectroscopy, and diffusion‐weighted MRI. Transrectal ultrasound‐guided biopsy was the standard of reference. We used logistic regression to model the probability of a positive outcome and generalized estimating equations to account for clustering. The diagnostic performance of imaging was described using receiver operating characteristic (ROC) curves.

Results:

The area under the ROC curve of MR spectroscopic imaging (MRSI) was 83.0% (95% confidence interval [CI] = 75.5–89.1). The combination of all MR techniques did not significantly improve the performance of imaging beyond the accuracy of MRSI alone, but a trend toward improved discrimination was noted (86.9%; 95% CI = 77.6–93.4; P = 0.09).

Conclusion:

Incorporation of MRSI to T2‐weighted and/or diffusion‐weighted MRI significantly improves the assessment of patients with suspected recurrence after radiotherapy and a combined approach with all three modalities may have the best diagnostic performance. J. Magn. Reson. Imaging 2012;36:430–437. ©2012 Wiley Periodicals, Inc.     

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.     

Standardized threshold approach using three-dimensional proton magnetic resonance spectroscopic imaging in prostate cancer localization of the entire prostate

OBJECTIVES: We sought to determine the localization accuracy using 3-dimensional (3D) proton magnetic resonance spectroscopic imaging (MRSI) of the entire prostate with a standardized thresholds approach in prostate cancer patients. MATERIALS AND METHODS: In a prospective study, 32 consecutive patients were examined. Mean age and prostate specific antigen level were 61 years and 7.8 ng/mL, respectively. Median biopsy Gleason score was 6. T2-weighted MRI and 3D MRSI of the entire prostate were performed. Three readers recorded the location of suspicious peripheral zone and central gland cancer nodules on a standardized division of the prostate (14 regions of interest [ROI]) using a standardized thresholds approach. The degree of diagnostic confidence for each ROI was recorded on a 5-point scale. Reconstructed whole-mount section histopathology was the standard of reference. The sensitivity, specificity, positive, and negative predictive value, overall accuracy and interobserver agreement were calculated. Areas under the ROI-based receiver operating characteristic curve (AUC) and diagnostic performance parameters were determined. RESULTS: The standardized thresholds approach had an accuracy of 81% and an AUC of 0.85-0.86 for differentiation between benign and malignant ROIs in the peripheral zone and an accuracy of 87% and an AUC of 0.86-0.91 for this differentiation in the central gland, respectively. Specificities of 81% to 88% were achieved with accompanying sensitivities of 75% to 92% for both peripheral zone and central gland, respectively. Moderate to near-perfect interobserver agreement was demonstrated (kappa=0.42-0.91). CONCLUSION: Our data indicate that a standardized zone-specific threshold approach in MRSI of the prostate is able to prospectively differentiate between benign and malignant tissues in the peripheral zone and the central gland with good accuracy and interobserver agreement.     

Chemical-shift artifact reduction in Hadamard-encoded MR spectroscopic imaging at high (3T and 7T) magnetic fields.

Proton MR spectroscopic imaging (MRSI) at higher magnetic fields (B(0)) suffers metabolite localization errors from different chemical-shift displacements (CSDs) if spatially-selective excitation is used. This phenomenon is exacerbated by the decreasing radiofrequency (RF) field strength, B(1), at higher B(0)s, precluding its suppression with stronger gradients. To address this, two new methods are proposed: 1) segmenting the volume-of-interest (VOI) into several slabs, allowing proportionally stronger slice-select gradients; and 2) sequentially cascading rather than superposing the components of the Hadamard selective pulses used for reasons of better point-spread function (PSF) to localize the few slices within each slab. This can reduce the peak B(1) to that of a single slice. Combining these approaches permits us to increase the selective gradient four- to eightfold per given B(1), to 12 or 18mT/m for 4- or 2-cm VOIs. This "brute force" approach reduces the CSD to under 0.05 cm/ppm at 7T, or less than half that at 3T.     

Detection of lymph node metastasis in cervical and uterine cancers by diffusion-weighted magnetic resonance imaging at 3T

PURPOSE: To evaluate diffusion-weighted imaging (DWI) for detection of pelvic lymph node metastasis in patients with cervical and uterine cancers. MATERIALS AND METHODS: Fifty patients scheduled for pelvic lymph node dissection were enrolled for 3T magnetic resonance imaging (MRI) using a single-shot echo-planar DWI technique, body-phased array coil, b = 0, 1000 s/mm(2). We measured short/long-axis diameters, mean apparent diffusion coefficient (ADC) values of all identifiable nodes, relative ADC values between tumors and nodes, and utilized their cutoff values to validate the diagnostic accuracy internally. Histopathologic results served as the reference standard. RESULTS: The relative ADC values between tumor and nodes were significantly lower in metastatic than in benign nodes (0.06 vs. 0.21 x 10(-3) mm(2)/s, P < 0.001; cutoff value 0.10 x 10(-3) mm(2)/s). Compared to conventional MRI, the method combining size and relative ADC values resulted in better sensitivity (25% vs. 83%) and similar specificity (98% vs. 99%). The smallest metastatic lymph node detected by this method measured 5 mm on its short axis. CONCLUSION: The combination of size and relative ADC values was useful in detecting pelvic lymph node metastasis in patients with cervical and uterine cancers.     

Prostate MR imaging at 3T with a longitudinal array endorectal surface coil and phased array body coil

PURPOSE: To demonstrate the feasibility of using a double loop phased array endorectal coil combined with a phased array body coil to image the prostate at 3T. MATERIALS AND METHODS: We designed and constructed a novel prostate coil employing two arrayed 4.0 x 5.0 cm loops, tuned the device for optimal performance at 3T, and characterized the signal-to-noise ratio (SNR) associated with it. RESULTS: The coil Q factor was calculated to be approximately 50 unloaded, and 30 when loaded on human tissue. SNR maps at multiple orientations were constructed and images were acquired on both a phantom and a human. As expected, SNR was highest along the midpoint of the array and demonstrated strong signal even at 4 cm from the coil. CONCLUSION: The double loop phased array endorectal coil combined with a phased array body coil at 3T is feasible in vivo and compelling enough to warrant future clinical trials to evaluate its efficacy. These trials are currently under way.     

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

Purpose:

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

Materials and Methods:

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

Results:

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

Conclusion:

Repeated measurements of in vivo 3D ¹H‐MRSI of the complete prostate at 1.5T produce equal and quantitative results. The reproducibility of the technique is high enough to provide it as a reliable tool in assessing tumor presence in the prostate. J. Magn. Reson. Imaging 2012;35:166‐173. © 2011 Wiley Periodicals, Inc.     

Time-dependent effects of hormone-deprivation therapy on prostate metabolism as detected by combined magnetic resonance imaging and 3D magnetic resonance spectroscopic imaging.

Combined MRI and 3D spectroscopic imaging (MRI/3D-MRSI) was used to study the metabolic effects of hormone-deprivation therapy in 65 prostate cancer patients, who underwent either short, intermediate, or long-term therapy, compared to 30 untreated control patients. There was a significant time-dependent loss of the prostatic metabolites choline, creatine, citrate, and polyamines during hormone-deprivation therapy, resulting in the complete loss of all observable metabolites (total metabolic atrophy) in 25% of patients on long-term therapy. The amount and time-course of metabolite loss during therapy significantly differed for healthy and malignant tissues. Citrate levels decreased faster than choline and creatine levels during therapy, resulting in an increase in the mean (choline + creatine)/citrate ratio with duration of therapy. Due to a loss of all MRSI detectable citrate, this ratio could not be used to identify cancer in 69% of patients on long-term therapy. In the absence of citrate, however, residual prostate cancer could still be detected by elevated choline levels (choline/creatine ratio > or =1.5), or the presence of only choline in the proton spectrum. The loss of citrate and the presence of total metabolic atrophy correlated roughly with decreasing serum prostatic specific antigen levels with increasing therapy. In summary, MRI/3D-MRSI provided both a measure of residual cancer and a time-course of metabolic response following hormone-deprivation therapy. Magn Reson Med 46:49-57, 2001.     

Combined quantitative dynamic contrast-enhanced MR imaging and (1)H MR spectroscopic imaging of human prostate cancer

PURPOSE: To differentiate prostate carcinoma from healthy peripheral zone and central gland using quantitative dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging and two-dimensional (1)H MR spectroscopic imaging (MRSI) combined into one clinical protocol. MATERIALS AND METHODS: Twenty-three prostate cancer patients were studied with a combined DCE-MRI and MRSI protocol. Cancer regions were localized by histopathology of whole mount sections after radical prostatectomy. Pharmacokinetic modeling parameters, K(trans) and k(ep), as well as the relative levels of the prostate metabolites citrate, choline, and creatine, were determined in cancer, healthy peripheral zone (PZ), and in central gland (CG). RESULTS: K(trans) and k(ep) were higher (P < 0.05) in cancer and in CG than in normal PZ. The (choline + creatine)/citrate ratio was elevated in cancer compared to the PZ and CG (P < 0.05). While a (choline + creatine)/citrate ratio above 0.68 was found to be a reliable indicator of cancer, elevated K(trans) was only a reliable cancer indicator in the diagnosis of individual patients. K(trans) and (choline + creatine)/citrate ratios in cancer were poorly correlated (Pearson r(2) = 0.07), and thus microvascular and metabolic abnormalities may have complementary value in cancer diagnosis. CONCLUSION: The combination of high-resolution spatio-vascular information from dynamic MRI and metabolic information from MRSI has excellent potential for improved localization and characterization of prostate cancer in a clinical setting. J. Magn. Reson. Imaging 2004;20:279-287. Copyright 2004 Wiley-Liss, Inc.     

3T MR三维质子波谱成像对乳腺良恶性病变的鉴别诊断

目的评估3TMR三维(3D)波谱成像依据胆碱信噪比(SNR)的阈值水平,在临床允许的时间范围内对乳腺良恶性病变定量诊断的准确性。材料与方法本研究经伦     

The use of MR imaging to detect residual versus recurrent nasopharyngeal carcinoma following treatment with radiation therapy

Objective

Residual tumor and fibrosis are commonly observed with magnetic resonance (MR) imaging following radiotherapy for nasopharyngeal carcinoma (NPC). Therefore, MR images of NPC following treatment with radiotherapy were retrospectively analyzed to evaluate whether post-radiation changes associated with residual tumors, recurrent tumors, and fibrosis could be distinguished 1 month and 3–6 months after treatment.

Methods

MR images were analyzed for 108 patients who completed radiotherapy for NPC and underwent 5-years of follow-up. The presence and incidence of residual tumor versus fibrosis was evaluated and compared with 5-year tumor recurrence rates.

Results

Residual tumors were detected in 54/108 (50.0%) patients 1 month after radiotherapy, and in 18/108 (16.7%) patients 3–6 months after radiotherapy. Fibrosis was only detected in 59/108 (54.6%) patients 3–6 months after radiotherapy. After 5 years, tumor recurrence occurred in 13/108 (12%) patients, with the average interval between tumor recurrence and the completion of radiotherapy being 29.15 months. In addition, the 1-, 2-, 3-, 4-, and 5-year relapse rates were 1.9%, 5.6%, 9.3%, 11.1%, and 12.0%, respectively. Based on the images analyzed, significant differences in tumor recurrence and residual tumor rate (P = 0.038), and between tumor recurrence and fibrosis (P = 0.021), were observed 1 month and 3–6 months after radiotherapy, respectively.

Conclusions

In this cohort, tumor recurrence was detected 2–3 year after irradiation and a strong correlation between 5-year recurrence rate and detection of residual tumor or fibrosis by MRI up to six months after radiotherapy was observed.