Technical Note: A custom-designed flexible MR coil array for spine radiotherapy treatment planning

PURPOSE

To assess the performance and optimize the MR image quality when using a custom-built flexible radiofrequency (RF) spine coil array fitted between the immobilization device and the patient for spine radiotherapy treatment planning.

METHODS

A 32 channel flexible custom-designed receive-only coil array has been developed for spine radiotherapy simulation for a 3 T Philips MR scanner. Coil signal-to-noise performance and interactions with standard vendor hardware were assessed. In four volunteers, immobilization molds were created with a dummy version of the array within the mold, and subjects were scanned using the custom array in the mold. Phantoms and normal volunteers were scanned with both the custom spine coil array and the vendor's FDA-approved in-table posterior coil array to compare performance.

RESULTS

The superior-inferior field of view for the custom spine array was ~30 cm encompassing at least 10 vertebrae. A noise correlation matrix showed at least 25 dB isolation between all coil elements. Signal-to-noise ratio (SNR) calculated on a phantom scan at the depth of the spinal cord was a factor of 3 higher with the form-fit spine array as compared to the vendor's posterior coil array. The body coil B₁ transmit map was equivalent with and without the spine array in place demonstrating that the elements are decoupled from the body coil. Volunteer imaging showed improved SNR as compared to the vendor's posterior coil array. The custom array permitted a high degree of acceleration making possible the acquisition of isotropic high-resolution 1.1 × 1.1 × 1.1 mm³ three-dimensional data set over a 30-cm section of the spine in less than 5 min.

CONCLUSION

The custom-designed form-fitting flexible spine coil array provided enhanced SNR and increased acceleration compared to the vendor's posterior array. Future studies will assess MR-based spinal cord imaging with the custom coil in comparison to CT myelogram.

Limited accuracy of DCE-MRI in identification of pathological complete responders after chemoradiotherapy treatment for rectal cancer

OBJECTIVES

To examine whether post-chemoradiotherapy (CRT) DCE-MRI can identify rectal cancer patients with pathologic complete response (pCR).

METHODS

From a rectal cancer surgery database 2007-2014, 61 consecutive patients that met the following inclusion criteria were selected for analysis: (1) stage II/III primary rectal adenocarcinoma; (2) received CRT; (3) underwent surgery (4); underwent rectal DCE-MRI on a 1.5-T MRI scanner. Two experienced radiologists, in consensus, drew regions of interest (ROI) on the sagittal DCE-MRI image in the tumour bed. These were exported from ImageJ to in-house Matlab code for modelling using the Tofts model. K ^trans, K _ep and v _e values were compared to pathological response.

RESULTS

Of the 61 initial patients, 37 had data considered adequate for fitting to obtain perfusion parameters. Among the 13 men and 24 women, median age 53 years, there were 8 pCR (22 %). K ^trans could not distinguish patients with pCR. For patients with 90 % or greater response, mean K ^trans and K _ep values were statistically significant (p = 0.032 and 0.027, respectively). Using a cutoff value of K ^trans = 0.25 min^-1, the AUC was 0.71.

CONCLUSION

K ^trans could be used to identify patients with 90 % or more response to chemoradiotherapy for rectal cancer with an AUC of 0.7.

KEY POINTS

• Chemoradiotherapy for rectal cancer causes decreased blood flow and permeability in the tumour bed. • Lower values of blood flow and permeability correlate with good tumour response. • K ^trans of 0.25min ^-1 best identifies patients with ≥90 % response with AUC 0.71.

Long-term outcome of magnetic resonance spectroscopic image-directed dose escalation for prostate brachytherapy

PURPOSE

To report the long-term control and toxicity outcomes of patients with clinically localized prostate cancer, who underwent low-dose-rate prostate brachytherapy with magnetic resonance spectroscopic image (MRSI)-directed dose escalation to intraprostatic regions.

METHODS AND MATERIALS

Forty-seven consecutive patients between May 2000 and December 2003 were analyzed retrospectively. Each patient underwent a preprocedural MRSI, and MRS-positive voxels suspicious for malignancy were identified. Intraoperative planning was used to determine the optimal seed distribution to deliver a standard prescription dose to the entire prostate, while escalating the dose to MRS-positive voxels to 150% of prescription. Each patient underwent transperineal implantation of radioactive seeds followed by same-day CT for postimplant dosimetry.

RESULTS

The median prostate D90 (minimum dose received by 90% of the prostate) was 125.7% (interquartile range [IQR], 110.3-136.5%) of prescription. The median value for the MRS-positive mean dose was 229.9% (IQR, 200.0-251.9%). Median urethra D30 and rectal D30 values were 142.2% (137.5-168.2%) and 56.1% (40.1-63.4%), respectively. Median followup was 86.4 months (IQR, 49.8-117.6). The 10-year actuarial prostate-specific antigen relapse-free survival was 98% (95% confidence interval, 93-100%). Five patients (11%) experienced late Grade 3 urinary toxicity (e.g., urethral stricture), which improved after operative intervention. Four of these patients had dose-escalated voxels less than 1.0 cm from the urethra.

CONCLUSIONS

Low-dose-rate brachytherapy with MRSI-directed dose escalation to suspicious intraprostatic regions exhibits excellent long-term biochemical control. Patients with dose-escalated voxels close to the urethra were at higher risk of late urinary stricture.

Prostate MRSI predicts outcome in radical prostatectomy patients

BACKGROUND

New non-invasive methods are needed for sub-stratifying high-risk prostate cancer patients. Magnetic resonance spectroscopic imaging (MRSI) maps metabolites in prostate cancer, providing information on tumor aggressiveness and volume.

PURPOSE

To investigate the correlation between MRSI and treatment failure (TF) after radical prostatectomy (RP).

METHODS

Two-hundred sixty-two patients who underwent endorectal MRI/MRSI followed by RP at our institution from 2003 to 2007 were studied. MRI stage, number of voxels in the MRSI index lesion (NILV), number of high-grade voxels (NHGV), and number of voxels containing undetectable polyamines (NUPV) were derived. Clinical outcome was followed until August, 2014. Treatment failure was defined as 1) biochemical recurrence (BCR), 2) persistently detectable PSA after RP, or 3) adjuvant therapy initiated in the absence of BCR. MRI/MRSI features and clinical parameters were compared to TF by univariate Cox Proportional Hazards Regression. After backward selection, each MRSI parameter was included in a separate regression model adjusted for NCCN-based clinical risk score (CRS), number of biopsy cores positive (NPC), and MRI stage.

RESULTS

In univariate analysis, all clinical variables were associated with TF in addition to MRI stage, NILV, NHGV, and NUPV. In multivariate analysis, NILV, NHGV, and NUPV were also significant risk factors for TF (p=0.016, p=0.002, p=0.006, respectively). The association between the number of tumor voxels with undetectable polyamines and the probability of treatment failure has not been previously reported. The number of MRSI cancer voxels correlated with extracapsular extension (ECE) (p<0.0001).

CONCLUSIONS

MRSI was associated with post-radical prostatectomy treatment failure in models adjusted for the number of positive biopsy cores and clinical risk score. This is the first report that in radical prostatectomy patients MRSI has an association with treatment failure independent of the number of positive biopsy cores. MRSI may help the clinician determine whether patients with high risk disease who undergo RP are candidates for specialized additional treatment.

Anatomic segmentation improves prostate cancer detection with artificial neural networks analysis of 1H magnetic resonance spectroscopic imaging

PURPOSE

To assess whether an artificial neural network (ANN) model is a useful tool for automatic detection of cancerous voxels in the prostate from (1)H-MRSI datasets and whether the addition of information about anatomical segmentation improves the detection of cancer.

MATERIALS AND METHODS

The Institutional Review Board approved this HIPAA-compliant study and waived informed consent. Eighteen men with prostate cancer (median age, 55 years; range, 36-71 years) who underwent endorectal MRI/MRSI before radical prostatectomy were included in this study. These patients had at least one cancer area on whole-mount histopathological map and at least one matching MRSI voxel suspicious for cancer detected. Two ANN models for automatic classification of MRSI voxels in the prostate were implemented and compared: model 1, which used only spectra as input, and model 2, which used the spectra plus information from anatomical segmentation. The models were trained, tested and validated using spectra from voxels that the spectroscopist had designated as cancer and that were verified on histopathological maps.

RESULTS

At ROC analysis, model 2 (AUC = 0.968) provided significantly better (P = 0.03) classification of cancerous voxels than did model 1 (AUC = 0.949).

CONCLUSION

Automatic analysis of prostate MRSI to detect cancer using ANN model is feasible. Application of anatomical segmentation from MRI as an additional input to ANN improves the accuracy of detecting cancerous voxels from MRSI.

Relationships between LDH-A, lactate, and metastases in 4T1 breast tumors

PURPOSE

To investigate the relationship between lactate dehydrogenase A (LDH-A) expression, lactate concentration, cell metabolism, and metastases in murine 4T1 breast tumors.

EXPERIMENTAL DESIGN

Inhibition of LDH-A expression and protein levels were achieved in a metastatic breast cancer cell line (4T1) using short hairpin RNA (shRNA) technology. The relationship between tumor LDH-A protein levels and lactate concentration (measured by magnetic resonance spectroscopic imaging, MRSI) and metastases was assessed.

RESULTS

LDH-A knockdown cells (KD9) showed a significant reduction in LDH-A protein and LDH activity, less acid production, decreased transwell migration and invasion, lower proliferation, reduced glucose consumption and glycolysis, and increase in oxygen consumption, reactive oxygen species (ROS), and cellular ATP levels, compared with control (NC) cells cultured in 25 mmol/L glucose. In vivo studies showed lower lactate levels in KD9, KD5, and KD317 tumors than in NC or 4T1 wild-type tumors (P < 0.01), and a linear relationship between tumor LDH-A protein expression and lactate concentration. Metastases were delayed and primary tumor growth rate decreased.

CONCLUSIONS

We show for the first time that LDH-A knockdown inhibited the formation of metastases, and was accompanied by in vivo changes in tumor cell metabolism. Lactate MRSI can be used as a surrogate to monitor targeted inhibition of LDH-A in a preclinical setting and provides a noninvasive imaging strategy to monitor LDH-A-targeted therapy. This imaging strategy can be translated to the clinic to identify and monitor patients who are at high risk of developing metastatic disease.

Serial measurement of hepatic lipids during chemotherapy in patients with colorectal cancer: a 1 H MRS study

Hepatic steatosis is a hallmark of chemotherapy-induced liver injury. We made serial (1) H MRS measurements of hepatic lipids in patients over the time course of a 24-week chemotherapeutic regimen to determine whether (1) H MRS could be used to monitor the progression of chemotherapy-induced steatosis. Thirty-four patients with stage III or IV colorectal cancer receiving 5-fluorouracil, folinic acid and oxaliplatin (n=21) or hepatic arterial infusion of floxuridine with systemic irinotecan (n=13) were studied prospectively. (1) H MRS studies were performed at baseline and after 6 and 24 weeks of treatment. A (1) H MR spectrum was acquired from the liver during a breath hold and the ratio of fat to fat+water (FFW) was calculated to give a measure of hepatic triglycerides (HTGCs). The methodology was histologically validated in 18 patients and the reproducibility was assessed in 16 normal volunteers. Twenty-seven patients completed baseline, 6-week and 24-week (1) H MRS examinations and one was censored. Thirteen of 26 patients (50%) showed an increase in FFW after completion of treatment. Six patients (23%) developed hepatic steatosis and two patients converted from steatosis to nonsteatotic liver. Patients whose 6-week hepatic lipid levels had increased significantly relative to baseline also had a high probability of lipid elevation relative to baseline at the completion of treatment. Serial (1) H MRS is effective for the monitoring of HTGC changes during chemotherapy and for the detection of chemotherapy-associated steatosis. Six of 26 patients developed steatosis during chemotherapy. Lipid changes were observable at 6 weeks.

Performance characteristics of MR imaging in the evaluation of clinically low-risk prostate cancer: a prospective study

PURPOSE

To prospectively evaluate diagnostic performance of T2-weighted magnetic resonance (MR) imaging and MR spectroscopic imaging in detecting lesions stratified by pathologic volume and Gleason score in men with clinically determined low-risk prostate cancer.

MATERIALS AND METHODS

The institutional review board approved this prospective, HIPAA-compliant study. Written informed consent was obtained from 183 men with clinically low-risk prostate cancer (cT1-cT2a, Gleason score≤6 at biopsy, prostate-specific antigen [PSA] level<10 ng/mL [10 μg/L]) undergoing MR imaging before prostatectomy. By using a scale of 1-5 (score 1, definitely no tumor; score 5, definitely tumor), two radiologists independently scored likelihood of tumor per sextant on T2-weighted images. Two spectroscopists jointly recorded locations of lesions with metabolic features consistent with tumor on MR spectroscopic images. Whole-mount step-section histopathologic analysis constituted the reference standard. Diagnostic performance at sextant level (T2-weighted imaging) and detection sensitivities (T2-weighted imaging and MR spectroscopic imaging) for lesions of 0.5 cm3 or larger were calculated.

RESULTS

For T2-weighted imaging, areas under the receiver operating characteristic curves for sextant-level detection were 0.77 (reader 1) and 0.82 (reader 2). For lesions of ≥0.5 cm3 and, 1

CONCLUSION

In men with clinically low-risk prostate cancer, detection of lesions of <1 cm3 with T2-weighted imaging is significantly dependent on lesion Gleason score; detection of lesions of ≥1 cm3 is significantly better than detection of smaller lesions and is not affected by lesion Gleason score. The role of MR spectroscopic imaging alone in this population is limited.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Humans
• Image Enhancement/methods
• Image Interpretation, Computer-Assisted/methods
• Male
• Middle Aged
• Preoperative Care/methods
• Prospective Studies
• Prostatic Neoplasms/pathology
• Reproducibility of Results
• Risk Factors
• Sensitivity and Specificity

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Grants

• R01 CA076423 NCI NIH HHS

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Affiliation(s)

Hebert Alberto Vargas Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, Room C-278, New York, NY 10065, USA
Oguz Akin
Amita Shukla-Dave
Jingbo Zhang
Kristen L Zakian
Junting Zheng
Kent Kanao
Debra A Goldman
Chaya S Moskowitz
Victor E Reuter
James A Eastham
Peter T Scardino
Hedvig Hricak

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Abstract 3223: Magnetic resonance spectroscopic imaging of lactate in LDH-A silenced metastatic breast tumors

Glucose and glutamine are the major carbon sources for rapidly proliferating tumors. They provide the precursors for proteins, lipids, and nucleic acids, and as well as metabolic-reducing capability (NADPH). Pyruvate is mainly derived from glucose and glutamine metabolism and can be converted to lactate by the lactate dehydrogenase (LDH) complex or enter the TCA cycle for conversion to CO2 and ATP. Recently, a link between tumor lactate levels (monitored by MRSI), LDH-A expression and tumor phenotype has been demonstrated (Serganova I. et al., 2011). We hypothesize that tumor lactate levels monitored by MRSI will reflect LDH-A enzymatic activity, tumor “aggressiveness” and the propensity for developing metastases. The current study employs 4T1 cells bearing the stable produced LDH-A shRNA to down regulate the level of LDH-A expression. LDH-A silenced and control 4T1 breast cancer cells were injected into the mammary fat pad of athymic nu/nu female mice (5 mice for each group). The in vivo growth rate of the LDH-A silenced tumors was significantly slower than that of control tumors; the average doubling time of the LDH-A silenced tumors was 1.5 fold higher than control tumors (p&lt;0.01). The lactate signal was acquired using a selective multiple-quantum coherence transfer (SelMQC) editing sequence in combination with chemical shift imaging (CSI) (He Q. et al., 1995). The tumors were scanned at small (∼100 mm3) and larger (∼300 mm3) volumes and in vivo lactate concentration was measured. The LDH-A silenced tumors produce less lactate, ∼ 6 mM at small volumes and ∼ 3 mM at larger volumes, whereas the control tumors produce ∼ 11 mM at small, and ∼7 mM at larger volumes. Preliminary results suggest that high tumor lactate concentrations are linked with a greater propensity to develop metastases. Studies evaluating metastatic burden are ongoing. We suggest that LDH-A expression and tumor lactate levels may be potential markers of elevated metastatic potential. In addition, MRSI might offer a noninvasive approach for assessing tumor progression and metastatic potential.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3223. doi:1538-7445.AM2012-3223

31P MR spectroscopic imaging detects regenerative changes in human liver stimulated by portal vein embolization

PURPOSE

First, to evaluate hepatocyte phospholipid metabolism and energetics during liver regeneration stimulated by portal vein embolization (PVE) using proton-decoupled (31)P MR spectroscopic imaging ((31)P-MRSI). Second, to compare the biophysiologic differences between hepatic regeneration stimulated by PVE and by partial hepatectomy (PH).

MATERIALS AND METHODS

Subjects included six patients with hepatic metastases from colorectal cancer who were scheduled to undergo right PVE before definitive resection of right-sided tumor. (31)P-MRSI was performed on the left liver lobe before PVE and 48 h following PVE. Normalized quantities of phosphorus-containing hepatic metabolites were analyzed from both visits. In addition, MRSI data at 48 h following partial hepatectomy were compared with the data from the PVE patients.

RESULTS

At 48 h after PVE, the ratio of phosphomonoesters to phosphodiesters in the nonembolized lobe was significantly elevated. No significant changes were found in nucleoside triphosphates (NTP) and Pi values. The phosphomonoester (PME) to phosphodiester (PDE) ratio in regenerating liver 48 h after partial hepatectomy was significantly greater than PME/PDE 48 h after PVE.

CONCLUSION

(31)P-MRSI is a valid technique to noninvasively evaluate cell membrane metabolism following PVE. The different degree of biochemical change between partial hepatectomy and PVE indicates that hepatic growth following these two procedures does not follow the same course.

Lactate MRSI and DCE MRI as surrogate markers of prostate tumor aggressiveness

Longitudinal studies of lactate MRSI and dynamic contrast-enhanced MRI were performed at 4.7 T in two prostate tumor models grown in rats, Dunning R3327-AT (AT) and Dunning R3327-H (H), to determine the potential of lactate and the perfusion/permeability parameter Ak(ep) as markers of tumor aggressiveness. Subcutaneous AT (n = 12) and H (n = 6) tumors were studied at different volumes between 100 and 2900 mm(3) (Groups 1-5). Lactate concentration was determined using selective multiple quantum coherence MRSI with the phantom substitution method. Tumor enhancement after the administration of gadolinium diethylenetriaminepenta-acetic acid was analyzed using the Brix-Hoffmann model and the Ak(ep) parameter was used as a measure of tumor perfusion/permeability. Lactate was not detected in the smallest AT tumors (Group 1; 100-270 mm(3) ). In larger AT tumors, the lactate concentration increased from 2.8 ± 1.0 mm (Group 2; 290-700 mm(3)) to 8.4 ± 2.9 mm (Group 3; 1000-1340 mm(3)) and 8.2 ± 2.2 mm (Group 4; 1380-1750 mm(3) ), and then decreased to 5.0 ± 1.7 mm (Group 5; 1900-2500 mm(3)), and was consistently higher in the tumor core than in the rim. Lactate was not detected in any of the H tumors. The mean tumor Ak(ep) values decreased with increasing volume in both tumor types, but were significantly higher in H tumors. In AT tumors, the Ak(ep) values were significantly higher in the rim than in the core. Histological hypoxic and necrotic fractions in AT tumors increased with volume from 0% in Group 1 to about 20% and 30%, respectively, in Group 5. Minimal amounts of hypoxia and necrosis were found in H tumors of all sizes. Thus, the presence of lactate and heterogeneous perfusion/permeability are signatures of aggressive, metabolically deprived tumors.

Preclinical study of treatment response in HCT-116 cells and xenografts with (1) H-decoupled (31) P MRS

The topoisomerase I inhibitor, irinotecan, and its active metabolite SN-38 have been shown to induce G(2) /M cell cycle arrest without significant cell death in human colon carcinoma cells (HCT-116). Subsequent treatment of these G(2) /M-arrested cells with the cyclin-dependent kinase inhibitor, flavopiridol, induced these cells to undergo apoptosis. The goal of this study was to develop a noninvasive metabolic biomarker for early tumor response and target inhibition of irinotecan followed by flavopiridol treatment in a longitudinal study. A total of eleven mice bearing HCT-116 xenografts were separated into two cohorts where one cohort was administered saline and the other treated with a sequential course of irinotecan followed by flavopiridol. Each mouse xenograft was longitudinally monitored with proton ((1) H)-decoupled phosphorus ((31) P) magnetic resonance spectroscopy (MRS) before and after treatment. A statistically significant decrease in phosphocholine (p = 0.0004) and inorganic phosphate (p = 0.0103) levels were observed in HCT-116 xenografts following treatment, which were evidenced within twenty-four hours of treatment completion. Also, a significant growth delay was found in treated xenografts. To discern the underlying mechanism for the treatment response of the xenografts, in vitro HCT-116 cell cultures were investigated with enzymatic assays, cell cycle analysis, and apoptotic assays. Flavopiridol had a direct effect on choline kinase as measured by a 67% reduction in the phosphorylation of choline to phosphocholine. Cells treated with SN-38 alone underwent 83 ± 5% G(2) /M cell cycle arrest compared to untreated cells. In cells, flavopiridol alone induced 5 ± 1% apoptosis while the sequential treatment (SN-38 then flavopiridol) resulted in 39 ± 10% apoptosis. In vivo (1) H-decoupled (31) P MRS indirectly measures choline kinase activity. The decrease in phosphocholine may be a potential indicator of early tumor response to the sequential treatment of irinotecan followed by flavopiridol in noninvasive and/or longitudinal studies.

Preoperative nomograms incorporating magnetic resonance imaging and spectroscopy for prediction of insignificant prostate cancer

Study Type--Prognosis (case series). Level of Evidence 4. What's known on the subject? And what does the study add? Nomograms are available that combine clinical and biopsy findings to predict the probability of pathologically insignificant prostate cancer in patients with clinically low-risk disease. Based on data from patients with Gleason score 6, clinical stage ≤ T2a and PSA <20 ng/ml, our group developed the first nomogram models for predicting insignificant prostate cancer that incorporated clinical data, detailed biopsy data and findings from MRI or MRI/MRSI (BJU Int. 2007;99(4):786-93). When tested retrospectively, these MR models performed significantly better than standard clinical models with and without detailed biopsy data. We prospectively validated the previously published MR-based nomogram models in a population of patients with Gleason score 6, clinical stage ≤ T2a and PSA <10 ng/ml. Based on data from this same population, we also developed two new models for predicting insignificant prostate cancer that combine MR findings and clinical data without detailed biopsy data. Upon initial testing, the new MR models performed significantly better than a clinical model lacking detailed biopsy data.

OBJECTIVES

• To validate previously published nomograms for predicting insignificant prostate cancer (PCa) that incorporate clinical data, percentage of biopsy cores positive (%BC+) and magnetic resonance imaging (MRI) or MRI/MR spectroscopic imaging (MRSI) results. • We also designed new nomogram models incorporating magnetic resonance results and clinical data without detailed biopsy data. Nomograms for predicting insignificant PCa can help physicians counsel patients with clinically low-risk disease who are choosing between active surveillance and definitive therapy.

PATIENTS AND METHODS

• In total, 181 low-risk PCa patients (clinical stage T1c-T2a, prostate-specific antigen level <10 ng/mL, biopsy Gleason score of 6) had MRI/MRSI before surgery. • For MRI and MRI/MRSI, the probability of insignificant PCa was recorded prospectively and independently by two radiologists on a scale from 0 (definitely insignificant) to 3 (definitely significant PCa). • Insignificant PCa was defined on surgical pathology. • There were four models incorporating MRI or MRI/MRSI and clinical data with and without %BC+ that were compared with a base clinical model without %BC and a more comprehensive clinical model with %BC+. Prediction accuracy was assessed using areas under receiver-operator characteristic curves.

RESULTS

• At pathology, 27% of patients had insignificant PCa, and the Gleason score was upgraded in 56.4% of patients. • For both readers, all magnetic resonance models performed significantly better than the base clinical model (P ≤ 0.05 for all) and similarly to the more comprehensive clinical model.

CONCLUSIONS

• Existing models incorporating magnetic resonance data, clinical data and %BC+ for predicting the probability of insignificant PCa were validated. • All MR-inclusive models performed significantly better than the base clinical model.

An exploratory study of endorectal magnetic resonance imaging and spectroscopy of the prostate as preoperative predictive biomarkers of biochemical relapse after radical prostatectomy

PURPOSE

Radical prostatectomy has significant side effects. Preoperative information predicting its long-term outcome would be valuable to patients and physicians. We determined whether pretreatment endorectal magnetic resonance imaging/magnetic resonance spectroscopic imaging predicts biochemical recurrence after radical prostatectomy.

MATERIALS AND METHODS

Of 202 patients who underwent endorectal magnetic resonance imaging/magnetic resonance spectroscopic imaging from January 2000 to December 2002 before radical prostatectomy 130 satisfied study inclusion criteria and were included in analysis. We compared imaging factors with potential predictive capability to biochemical recurrence data, including magnetic resonance imaging risk score based on local disease extent and magnetic resonance spectroscopic imaging index lesion characteristics, such as the number of voxels and degree of metabolic abnormality (magnetic resonance spectroscopic imaging grade). We evaluated associations of these imaging variables with time to biochemical recurrence by Cox proportional hazards regression adjusted for known predictors of biochemical recurrence, such as stage, grade and prostate specific antigen.

RESULTS

At a median 68-month followup there were 26 biochemical failures. Risk score, lesion volume and high grade voxels each correlated with time to biochemical recurrence. In a model combining clinical parameters risk score, lesion volume and at least 1 high grade voxel the magnetic resonance spectroscopic imaging variables remained significant but the magnetic resonance imaging score dropped out.

CONCLUSIONS

Index lesion volume on magnetic resonance spectroscopic imaging and high grade magnetic resonance spectroscopic imaging voxels correlate with time to biochemical recurrence after radical prostatectomy even when adjusted for clinical data. Results suggest the preoperative predictive usefulness of endorectal magnetic resonance imaging/magnetic resonance spectroscopic imaging in patients considering radical prostatectomy.

Prostate tumor volume measurement with combined T2-weighted imaging and diffusion-weighted MR: correlation with pathologic tumor volume

PURPOSE

To retrospectively determine the accuracy of diffusion-weighted (DW) magnetic resonance (MR) imaging for identifying cancer in the prostate peripheral zone (PZ) and to assess the accuracy of tumor volume measurements made with T2-weighted imaging and combined T2-weighted and DW MR imaging by using surgical pathologic examination as the reference standard.

MATERIALS AND METHODS

The institutional review board issued a waiver of informed consent for this HIPAA-compliant study. Forty-two patients underwent endorectal MR at 1.5 T before undergoing radical prostatectomy for prostate cancer and had at least one PZ tumor larger than 0.1 cm(3) at surgical pathologic examination. On T2-weighted images, an experienced radiologist outlined suspected PZ tumors. Two apparent diffusion coefficient (ADC) cutoff values were identified by using the Youden index and published literature. Image cluster analysis was performed on voxels within the suspected tumor regions. Associations between volume measurements from imaging and from pathologic examination were assessed by using concordance correlation coefficients (CCCs). The sensitivity and specificity of ADCs for identifying malignant PZ voxels were calculated.

RESULTS

In identifying malignant voxels, respective ADC cutoff values of 0.0014 and 0.0016 mm(2)/sec yielded sensitivity of 82% and 95% and specificity of 85% and 65%, respectively. Sixty PZ cancer lesions larger than 0.1 cm(3) were found at pathologic examination; 43 were detected by the radiologist. CCCs between imaging and pathologic tumor volume measurements were 0.36 for T2-weighted imaging, and 0.46 and 0.60 for combined T2-weighted and DW MR imaging with ADC cutoffs of 0.0014 and 0.0016 mm(2)/sec, respectively; the CCC of combined T2-weighted and DW MR imaging (ADC cutoff, 0.0016 mm(2)/sec) was significantly higher (P = .006) than that of T2-weighted imaging alone.

CONCLUSION

Adding DW MR to T2-weighted imaging can significantly improve the accuracy of prostate PZ tumor volume measurement.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/252/2/449/DC1.

Prediction of prostate cancer recurrence using magnetic resonance imaging and molecular profiles

PURPOSE

To evaluate whether pretreatment magnetic resonance imaging (MRI)/MR spectroscopic imaging (MRSI) findings and molecular markers in surgical specimens correlate with each other and with pretreatment clinical variables (biopsy Gleason score, clinical stage, and prostate-specific antigen level) and whether they contribute incremental value in predicting prostate cancer recurrence.

EXPERIMENTAL DESIGN

Eighty-eight prostate cancer patients underwent MRI/MRSI before radical prostatectomy; imaging findings were scored on a scale of 1 to 7 (no tumor seen-lymph node metastasis). Ki-67, phospho-Akt, and androgen receptor expression in surgical specimens were assessed by immunohistochemistry. To examine correlations between markers and imaging scores, Spearman's correlation was used. To test whether markers and imaging scores differed by clinical stage or Gleason score, Wilcoxon's rank sum test was used. To examine time to recurrence, the methods of Kaplan-Meier were used. Cox proportional hazards models were built and their concordance indices (C-indices) were calculated to evaluate prediction of recurrence.

RESULTS

All markers correlated moderately strongly with MRI/MRSI score (all correlation coefficients >0.5). Markers and MRI/MRSI score were strongly associated with clinical stage and biopsy Gleason score (P < 0.01 for all). At last follow-up, 27 patients had recurrence. C-indices for MRI/MRSI score and all markers were associated with time to recurrence and ranged from 0.78 to 0.89. A Cox model combining all clinical predictors had a C-index of 0.89; the C-index increased to 0.95 when MRI/MRSI score was added and to 0.97 when markers were also added.

CONCLUSIONS

MRI/MRSI findings and molecular markers correlated well with each other and contributed incremental value to clinical variables in predicting prostate cancer recurrence.

Correlation of MR imaging and MR spectroscopic imaging findings with Ki-67, phospho-Akt, and androgen receptor expression in prostate cancer

PURPOSE

To retrospectively assess whether magnetic resonance (MR) imaging and MR spectroscopic imaging and selected molecular markers correlate with each other and with clinically insignificant and significant prostate cancer (PCa), as defined at surgical pathologic analysis.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant study and waived informed consent. Eighty-nine men (mean age, 63 years; range, 46-79 years) with biopsy-proved PCa underwent combined endorectal MR imaging and MR spectroscopic imaging before radical prostatectomy. Suspicion of clinically insignificant PCa was retrospectively and separately recorded for MR imaging and combined MR imaging and MR spectroscopic imaging by using a scale of 0-3. Clinically insignificant PCa was pathologically defined as organ-confined cancer of 0.5 cm(3) or less without poorly differentiated elements. Prostatectomy specimens underwent immunohistochemical analysis for three molecular markers: Ki-67, phospho-Akt (pAkt), and androgen receptor (AR). To examine differences in marker levels for clinically insignificant and significant cancer, a Wilcoxon rank sum test was used. To examine correlations between marker levels and MR imaging or combined MR imaging and MR spectroscopic imaging scores, the Spearman correlation was used.

RESULTS

Twenty-one (24%) patients had clinically insignificant and 68 (76%) had clinically significant PCa at surgical pathologic review. All markers were significantly correlated with MR imaging and combined MR imaging and MR spectroscopic imaging findings (all correlation coefficients >0.5). In differentiating clinically insignificant from clinically significant PCa, areas under the receiver operating characteristic curves for Ki-67, AR, pAkt, MR imaging, and combined MR imaging and MR spectroscopic imaging were 0.75, 0.78, 0.80, 0.85, and 0.91, respectively.

CONCLUSION

The use of pretreatment MR imaging or combined MR imaging and MR spectroscopic imaging and molecular marker analyses of biopsy samples could facilitate better treatment selection.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/250/3/803/DC1.

J-difference lactate editing at 3.0 Tesla in the presence of strong lipids

PURPOSE

To implement in vivo detection of lactate in the presence of lipids by proton magnetic resonance spectroscopy at a 3 Tesla (T) field strength for potential applications in human tumors outside of the brain.

MATERIALS AND METHODS

The BASING J-difference sequence was implemented in the presence of high lipid concentrations in phantoms and in vivo at 3 Tesla.

RESULTS

The effectiveness of the lactate editing scheme is demonstrated in phantoms containing both lactate and lipids and in vivo in ischemic induced human muscle.

CONCLUSION

The ability of the BASING J-difference technique to detect lactate in the presence of strong lipid signals outside the brain at 3T is feasible. This robust technique should permit noninvasive lactate measurements in human tumors to investigate its potential as a prognostic indicator.

Imaging transgene activity in vivo

The successful translation of gene therapy for clinical application will require the assessment of transgene activity as a measure of the biological function of a therapeutic transgene. Although current imaging permits the noninvasive detection of transgene expression, the critical need for quantitative imaging of the action of the expressed transgene has not been met. In vivo magnetic resonance spectroscopic imaging (MRSI) was applied to quantitatively delineate both the concentration and activity of a cytosine deaminase-uracil phosphoribosyltransferase (CD-UPRT) fusion enzyme expressed from a transgene. MRSI enabled the generation of anatomically accurate maps of the intratumoral heterogeneity in fusion enzyme activity. We observed an excellent association between the CD-UPRT concentration and activity and the percentage of CD-UPRT(+) cells. Moreover, the regional levels of UPRT activity, as measured by imaging, correlated well with the biological affect of the enzyme. This study presents a translational imaging paradigm for precise, in vivo measurements of transgene activity with potential applications in both preclinical and clinical settings.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

The utility of magnetic resonance imaging and spectroscopy for predicting insignificant prostate cancer: an initial analysis

OBJECTIVE

To design new models that combine clinical variables and biopsy data with magnetic resonance imaging (MRI) and MR spectroscopic imaging (MRSI) data, and assess their value in predicting the probability of insignificant prostate cancer.

PATIENTS AND METHODS

In all, 220 patients (cT stage T1c or T2a, prostate-specific antigen level <20 ng/mL, biopsy Gleason score 6) had MRI/MRSI before surgery and met the inclusion criteria for the study. The probability of insignificant cancer was recorded retrospectively and separately for MRI and combined MRI/MRSI on a 0-3 scale (0, definitely insignificant; - 3, definitely significant). Insignificant cancer was defined from surgical pathology as organ-confined cancer of </= 0.5 cm(3) with no poorly differentiated elements. The accuracy of predicting insignificant prostate cancer was assessed using areas under receiver operating characteristic curves (AUCs), for previously reported clinical models and for newly generated MR models combining clinical variables, and biopsy data with MRI data (MRI model) and MRI/MRSI data (MRI/MRSI model).

RESULTS

At pathology, 41% of patients had insignificant cancer; both MRI (AUC 0.803) and MRI/MRSI (AUC 0.854) models incorporating clinical, biopsy and MR data performed significantly better than the basic (AUC 0.574) and more comprehensive medium (AUC 0.726) clinical models. The P values for the differences between the models were: base vs medium model, <0.001; base vs MRI model, <0.001; base vs MRI/MRSI model, <0.001; medium vs MRI model, <0.018; medium vs MRI/MRSI model, <0.001.

CONCLUSIONS

The new MRI and MRI/MRSI models performed better than the clinical models for predicting the probability of insignificant prostate cancer. After appropriate validation, the new MRI and MRI/MRSI models might help in counselling patients who are considering choosing deferred therapy.

In vivo 31P MR spectral patterns and reproducibility in cancer patients studied in a multi-institutional trial

The standardization and reproducibility of techniques required to acquire anatomically localized 31P MR spectra non-invasively while studying tumors in cancer patients in a multi-institutional group at 1.5 T are reported. This initial group of patients was studied from 1995 to 2000 to test the feasibility of acquiring in vivo localized 31P MRS in clinical MR spectrometers. The cancers tested were non-Hodgkin's lymphomas, sarcomas of soft tissue and bone, breast carcinomas and head and neck carcinomas. The best accrual and spectral quality were achieved with the non-Hodgkin's lymphomas. The initial analysis of the spectral values of the sum of phosphoethanolamine plus phosphocholine normalized by the content of nucleotide triphosphates in a homogeneous sample of 32 NHL patients studied by in vivo (31)P MRS showed good reproducibility among different institutions. No statistical differences were found between the institution with the largest number of cases accrued and the rest of the multi-institutional NHL data (2.28 +/- 0.64, mean +/- standard error; n = 17, vs 2.08 +/- 0.14, n = 15). The preliminary data reported demonstrate that the institutions involved in this trial are obtaining reproducible 31P MR spectroscopic data non-invasively from human tumors. This is a fundamental prerequisite for the international cooperative group to be able to demonstrate the clinical value of the normalized determination of phosphoethanolamine plus phosphocholine by 31P MRS as predictor for treatment response in cancer patients.

Liver regeneration in humans is characterized by significant changes in cellular phosphorus metabolism: assessment using proton-decoupled 31P-magnetic resonance spectroscopic imaging

In the present study we applied proton-decoupled 31P magnetic resonance spectroscopic imaging (MRSI) to noninvasively assess liver metabolism in patients who had undergone a partial hepatectomy (PH). Proton-decoupled 31P chemical shift imaging was performed in 47 patients 2-28 days following major hepatectomy, and the results were compared with those from eight control subjects. All studies were performed on a 1.5T MR imager (General Electric, Milwaukee, WI) equipped with a stand-alone proton decoupler. A 31P-1H resonator pair was used for data acquisition, and 31P data were obtained in 34 min. Liver regeneration was characterized by increases in phosphoethanolamine (PE), and decreases in nucleoside triphosphates (NTP), glycerophosphoethanolamine (GPE), and glycerophosphocholine (GPC). These alterations were most marked 48-72 hr after hepatectomy and returned to baseline within 3 weeks. The level of PE measured by MRSI was also found to depend on the percentage of liver that was removed, while changes in levels of cellular high energy phosphates were independent of the size of liver resection. Implementation of proton-decoupling was critical for assessing individual phosphomonoester and phosphodiester components. This study demonstrates that 31P MRSI can be used to assess metabolic changes in humans during liver regeneration, and may be useful for assessing derangement of the regenerative process or guiding adjuvant chemotherapies.

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.

Correlation of proton MR spectroscopic imaging with gleason score based on step-section pathologic analysis after radical prostatectomy

PURPOSE

To determine whether hydrogen 1 magnetic resonance (MR) spectroscopic imaging can be used to predict aggressiveness of prostate cancer.

MATERIALS AND METHODS

All patients gave informed consent according to an institutionally approved research protocol. A total of 123 patients (median age, 58 years; age range, 40-74 years) who underwent endorectal MR imaging and MR spectroscopic imaging between January 2000 and December 2002 were included. MR imaging and spectroscopy were performed by using combined pelvic phased-array and endorectal probe. Water and lipids were suppressed, and phase-encoded data were acquired with 6.2-mm resolution. Voxels in the peripheral zone were considered suspicious for cancer if (Cho + Cr)/Cit was at least two standard deviations above the normal level, where Cho represents choline-containing compounds, Cr represents creatine and phosphocreatine, and Cit represents citrate. Correlation between metabolite ratio and four Gleason score groups identified at step-section pathologic evaluation (3 + 3, 3 + 4, 4 + 3, and > or =4 + 4) was assessed with generalized estimating equations.

RESULTS

Data from 94 patients were included. Pathologic evaluation was used to identify 239 lesions. Overall sensitivity of MR spectroscopic imaging was 56% for tumor detection, increasing from 44% in lesions with Gleason score of 3 + 3 to 89% in lesions with Gleason score greater than or equal to 4 + 4. There was a trend toward increasing (Cho + Cr)/Cit with increasing Gleason score in lesions identified correctly with MR spectroscopic imaging. Tumor volume assessed with MR spectroscopic imaging increased with increasing Gleason score.

CONCLUSION

MR spectroscopic imaging measurement of prostate tumor (Cho + Cr)/Cit and tumor volume correlate with pathologic Gleason score. There is overlap between MR spectroscopic imaging parameters at various Gleason score levels, which may reflect methodologic and physiologic variations. MR spectroscopic imaging has potential in noninvasive assessment of prostate cancer aggressiveness.

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.

Proton magnetic resonance spectroscopy in immunocompetent patients with primary central nervous system lymphoma

BACKGROUND

Magnetic resonance spectroscopy imaging (MRSI) non-invasively evaluates the metabolic profile of normal and abnormal brain tissue. Primary central nervous system lymphoma (PCNSL) is a highly aggressive tumor responsive to high-dose methotrexate based regimens. Patients often have complete responses but relapses are common. We characterized the MR spectra of PCNSL patients, correlated MRSI with MRI and evaluated whether early recurrence could be detected by MRSI.

METHODS

Patients with PCNSL had multi-voxel MRSI before, during, and after treatment. The region of interest was defined using axial FLAIR images. Metabolites assessed were N-acetyl-aspartate (NAA), choline (Cho), creatine (Cr), lipid, and lactate. Ratios of Cho/Cr, NAA/Cho, and NAA/Cr were calculated and correlated with MRI. Overall survival (OS), progression free survival (PFS), and relative risks of each of the ratios were determined.

RESULTS

MRSI was performed on 11 men and seven women; median age of 59. Sixty-seven MRSI studies were performed, 17 baseline and 48 follow-up studies. Median ratios in 16 pretreated patients were Cho/Cr-1.90, NAA/Cho-0.39, and NAA/Cr-1.27. Two patients had lipid at baseline, five had lactate and two had both. MRSI correlated with tumor response or progression on MRI; in three patients MRSI suggested disease progression prior to changes on MRI. Univariate analysis of metabolite ratios, lipid, and lactate revealed that none significantly affected PFS or OS. Kaplan-Meier analysis of the presence or absence of lipid, lactate or both revealed a trend for increased PFS.

CONCLUSION

MRSI and MRI correlate with tumor response or progression and may allow early detection of disease recurrence. The presence or absence of lipid and/or lactate may have prognostic significance. Further research using MRSI needs to be done to validate our findings and determine the role of MRSI in PCNSL.

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.

In vivo 5-fluorouracil and fluoronucleotideT1 relaxation time measurements using the variable nutation angle method

19Fluorine NMRS has the potential to enable noninvasive predictions of tumor response to 5-fluorouracil (5FU) therapy based on tumor pharmacokinetics. Knowledge of the T1's of 5FU and its fluoronucleotide anabolites (FNuc) is required for quantitative spectral analysis and selection of optimal pulse parameters. We used the variable nutation angle (VNA) method to determine T1's of 5FU and FNuc in subcutaneous Walker 256 rat mammary carcinosarcoma tumors transfected with a cytosine deaminase/uracil phosphoribosyltransferase fusion gene. We calibrated in vivo NAs using methoxydifluoroacetate to ensure the accuracy of these measurements. The T1's were calculated based on signal intensities acquired with NAs of 20 degrees, 35 degrees, 45 degrees, 60 degrees, and 75 degrees. The acquisition order of these NAs was shuffled to reduce the effect of signal variations. The determined T1's for 5FU and FNuc (2.3 +/- 0.1 s and 1.3 +/- 0.1 s, respectively) represent the first reported in vivo measurements for these metabolites in tumor.

Identification of prognostic markers in bone sarcomas using proton-decoupled phosphorus magnetic resonance spectroscopy

It has been hypothesized that the (31)Phosphorus ((31)P) nuclear magnetic resonance spectrum from certain tumors may provide prognostic information. The goal of the present study was to identify prognostic metabolic markers by using proton-decoupled phosphorus magnetic resonance spectroscopic imaging ((31)P MRSI). Twenty patients with bone [osteogenic (OS) and Ewing's (ES) and/or primitive neuroectodermal tumor (PNET)] sarcoma, treated with chemotherapy and surgery or with chemotherapy alone, underwent (31)P MRSI studies pre- and post-therapy. The studies were performed on a 1.5 Tesla General Electric (GE) clinical scanner equipped with a stand-alone proton decoupler and a dual (1)H/(31)P surface coil pair. The limited sensitivity of the (31)P nucleus required that a large soft tissue component of the disease be located within 10 cm (maximum distance) of the body surface and the use of a highly sensitive coil placed near the skin surface. Proton decoupling and nuclear Overhauser enhancement were used to improve the spectral resolution and signal:noise ratio. Baseline (31)P spectral features and metabolic changes with treatment were compared with treatment outcome. The patients were categorized depending on survival as event-free survivors or those who died. The pretreatment nucleoside triphosphate:inorganic phosphate (NTP:P(i)) ratio, an index of tumor bioenergetic status, was significant (P = 0.003) in differentiating event-free survivors versus those who died. The pretreatment NTP:P(i) was higher in patients who were destined to undergo a durable event-free survival compared with those who died. The results are promising, although a prospective study is necessary for confirmation. (31)P MRSI appears to be a useful tool for the prediction of survival before therapy in bone sarcomas.

Transition zone prostate cancer: metabolic characteristics at 1H MR spectroscopic imaging--initial results

PURPOSE

To determine whether cancers of the prostate transition zone (TZ) possess a unique metabolic pattern by which they may be identified at proton magnetic resonance (MR) spectroscopic imaging.

MATERIALS AND METHODS

Findings in 40 patients who underwent combined endorectal MR imaging and hydrogen 1 MR spectroscopic imaging before radical prostatectomy and who had TZ tumor identified subsequently at step-section pathologic analysis were retrospectively reviewed. Within this population, a subset of 16 patients whose TZ tumor had a largest diameter of 1 cm or greater and was included in the MR spectroscopic imaging excitation volume was identified. In these 16 patients, the ratios of choline-containing compounds (Cho) and creatine/phosphocreatine (Cr) to citrate (Cit) (ie, [Cho + Cr]/Cit), Cho/Cr, and Cho/Cit were compared in tumor and control tissues. The presence of only Cho and the absence of all metabolites were also assessed.

RESULTS

The mean values of (Cho + Cr)/Cit, Cho/Cr, and Cho/Cit were different between TZ cancer and control tissues (P =.001, P =.003, and P =.001, respectively; Wilcoxon signed rank test). Nine (56%) of 16 patients had at least one tumor voxel in which Cho comprised the only detectable peak, while no control voxels showed only Cho (P =.008, McNemar test). The percentage of voxels in which no metabolites were detected did not differ between tumor and control tissues (P =.134, McNemar test).

CONCLUSION

TZ cancer has a metabolic profile that is different from that of benign TZ tissue; however, the broad range of metabolite ratios observed in TZ cancer precludes the use of a single ratio to differentiate TZ cancer from benign TZ tissue.

Metabolic response of the CWR22 prostate tumor xenograft after 20 Gy of radiation studied by 1H spectroscopic imaging

PURPOSE

The ability to determine the spatial and metabolic distribution of prostate cancer is essential in assessing initial stage, prognosis, and treatment efficacy. Current markers of tumor progression such as prostate-specific antigen (PSA) do not provide spatial information about tumor extent or regions of high metabolic activity.

EXPERIMENTAL DESIGN

This study used the androgen-dependent CWR22 human prostate tumor xenograft in mice to characterize metabolic, PSA, and tumor volume changes that occurred with untreated growth or radiation therapy (XRT). One cohort of mice was studied as the tumor grew to 400 mm(3), whereas a second cohort was treated with a single 20-Gy fraction of radiation and studied before and 1, 2, and 4 days after XRT. In both cohorts, tumor volume, PSA, and choline:water ratios measured by nuclear magnetic resonance were monitored.

RESULTS

The CWR22 tumor had an untreated tumor-doubling time of 2.6 +/- 0.6 days (n = 7). In untreated mice, PSA strongly correlated with tumor volume (P < 0.01, R(2) = 0.99). The untreated tumor cohort had a PSA-doubling time of 3.2 +/- 0.6 days. Administration of 20 Gy produced a regrowth delay of >15.8 +/- 4.8 days (n = 6). PSA values after XRT were not correlated with post-XRT tumor volume (P < 0.20, R(2) = 0.02). A constant level of the choline:water ratio (0.010 +/- 0.001; n = 22, R(2) = 0.007, P < 0.3) was observed during the course of untreated tumor growth. A statistically significant (P < 0.04, one-tailed t test) 42% decrease in the choline:water ratio at 24 h after administration of XRT preceded observable changes in PSA.

CONCLUSIONS

Nuclear magnetic resonance spectroscopy provided a method with which to monitor metabolic changes of tumor response to XRT that preceded and predicted PSA and tumor volume changes.

Prediction of treatment response of head and neck cancers with P-31 MR spectroscopy from pretreatment relative phosphomonoester levels

RATIONALE AND OBJECTIVES

Combinations of chemotherapy and fractionated radiation therapy are the currently preferred nonsurgical treatment methods for squamous cell carcinoma of the head and neck, but to the authors' knowledge there is no reliable marker for predicting therapeutic response. Early identification of nonresponders would allow prompt replacement of ineffective, toxic therapy by alternative, potentially more effective procedures. Frequent regional node involvement facilitates surface coil investigation with phosphorus-31 magnetic resonance spectroscopy.

MATERIALS AND METHODS

P-31 magnetic resonance spectra were acquired from 12 patients before radiation therapy or chemotherapy. In vivo three-dimensional localized P-31 nuclear magnetic resonance chemical shift imaging was performed with a 1.5-T clinical imager and a dual-tuned H-1/P-31 surface coil. Proton decoupling and nuclear Overhauser enhancement were used to improve sensitivity and resolve overlapping signals in the phosphomonoester region of the spectrum.

RESULTS

The average pretreatment ratio of phosphomonoester to beta-nucleoside triphosphate was significantly smaller in complete responders (n = 4) than in incomplete responders (partial responders plus nonresponders, n = 8) (0.0 +/- 0.0 vs 1.22 +/- 0.17 [P = .004]).

CONCLUSION

Results of this preliminary study suggest that H-1-decoupled P-31 magnetic resonance spectroscopy may prove to be a useful predictor of therapeutic response in head and neck cancers.

A photothrombotic model of small early ischemic infarcts in the rat brain with histologic and MRI correlation

Over the last two decades several studies have suggested the role of photothrombotic occlusion of cerebral microvessels using rose bengal, resulting in small strokes in rodents that resemble those in humans. This paper describes such a photothrombotic method of acute small stroke induction in rats with histopathologic and in vivo magnetic resonance imaging (MRI) observations from 3 to 6 h after irradiation, which is homologous to a human autopsy specimen. Utilizing 30 min of irradiation with minimal beam intensity (0.1 W/cm(2)) cold white light in conjunction with 20 mg of intravenous (iv) rose bengal as a rapid infusion, small infarcts were induced photochemically in the frontal lobes of six rats. The infarcts showed a consistent pattern on histologic and in vivo MR sections when examined within 7 h or less of irradiation. Both MRI and histologic sections were comprised of (a) a superior zone of infarcted neurons, (b) a middle curvilinear transition zone of edema on MRI and histologically vacuolated neuropil, and (c) an inferior zone of normal neurons. Shorter duration water-sensitive (T2)- and postgadolinium longer duration (T1)-weighted signal decay images both showed a curvilinear hyperintense transition zone of edema. The mean infarct and transition zone areas measured from the histologic sections were comparable to those measured on the MRI. The infarct model described above allows in vivo observations using MRI with the potential for use in testing putative neuroprotective agents. As demonstrated by a comparison with the histologic features of such infarcts in surgical and autopsy brain specimens, the model is relevant to acute human ischemic infarcts.

Developments in nuclear magnetic resonance imaging and spectroscopy: application to radiation oncology

Nuclear magnetic resonance techniques have advanced to the point where functional, physiologic, and biochemical information may be obtained from patients. Magnetic resonance imaging of tissue water can be used to measure perfusion and diffusion with submillimeter resolution. Magnetic resonance spectroscopy may be applied to the assessment of tissue metabolites that contain protons, phosphorus, fluorine, or other nuclei. The combination of imaging and spectroscopy technologies has lead to spectroscopic imaging techniques that are capable of mapping proton metabolites at resolutions as small as 0.25 cm(3) within the time constraints of a clinical imaging study. This article provides a brief review of magnetic resonance techniques for imaging of tissue physiological function and addresses possible applications in the realm of radiation oncology.

Use of phosphorous-31 nuclear magnetic resonance spectroscopy to determine safe timing of chemotherapy after hepatic resection

Liver resection induces accelerated growth of residual hepatic micrometastases. Adjuvant chemotherapy may improve outcome if administered early after resection but may prove lethal if initiated prior to completion of DNA synthesis in regenerating liver. This study investigates phosphorus-31 nuclear magnetic resonance ((31)P-NMR) as a noninvasive tool for measuring energy changes reflective of hepatic DNA synthesis and for predicting safe timing of chemotherapy after 70% hepatectomy. To evaluate metabolic changes in regenerating liver, quantitative three-dimensional (31)P-NMR was performed, using the technique of chemical shift imaging at various time points after 70% hepatectomy in adult male Fischer rats. Animals receiving a course of 2'-deoxy-5-fluorouridine (FUDR; 100 mg/kg, i.p. four times per day x 5), initiated at the time of operation, were also evaluated to observe the effects of chemotherapy on liver regeneration. Forty-eight hours after resection, hepatic nucleoside triphosphate (NTP), which reflects ATP content, fell 37% (P < 0.03) in animals undergoing hepatectomy alone. By contrast, animals receiving FUDR after hepatectomy demonstrated a mitigated NTP response, with a drop of only 17% (P = not significant), suggesting that interruption of DNA synthesis leads to a reduced consumption of ATP. Direct measures of DNA synthesis and nuclear proliferation were correlated with NMR findings. [(3)H]Thymidine incorporation and Ki67 immunohistochemistry were performed on liver samples from rats undergoing 70% hepatectomy with and without FUDR. Both [(3)H]thymidine incorporation and Ki67 expression were inhibited significantly at 48 h in animals receiving hepatectomy and FUDR, compared with those not treated with FUDR. To determine whether NMR changes could be used to identify safe timing of chemotherapy after hepatectomy, rats were treated with a 5-day course of FUDR initiated either prior to or after NMR changes normalized. Animals treated with FUDR at the point of NTP normalization (72 h) showed significantly improved survival over those that began treatment at operation (75 % versus 17 %; P = 0.0005, log rank test). FUDR inhibits hepatic DNA synthesis and influences mortality if administered too early after hepatectomy. Chemical shift imaging is a noninvasive tool that can identify metabolic changes coinciding with DNA synthesis and nuclear proliferation after hepatectomy. (31)P-NMR may be useful for determining safe timing of chemotherapy after liver resection.

Intraoperative conformal optimization for transperineal prostate implantation using magnetic resonance spectroscopic imaging

PURPOSE

Recent studies have demonstrated that magnetic resonance spectroscopic imaging (MRSI) of the prostate may effectively distinguish between regions of cancer and normal prostatic epithelium. This diagnostic imaging tool takes advantage of the increased choline and creatine versus citrate ratio found in malignant, compared with normal, prostate tissue. The purpose of this report is to present our initial experience integrating MRSI data into an intraoperative computer-based optimization planning system for prostate cancer patients who underwent permanent interstitial I 125 implantation. The goal of this approach was to achieve dose escalation to intraprostatic tumor deposits on the basis of MRSI findings without exceeding the tolerance of adjacent normal tissue structures.

MATERIALS AND METHODS

MRSI was obtained before surgery for four consecutive patients with clinically localized prostate cancer. The ratios of choline and citrate for the prostate were analyzed, and regions in which malignant cells were suspected to be present were identified. These ratios were calculated on a spatial grid overlying the axial MRSI of the prostate. MRSI coordinates containing these suspicious regions were registered to the intraoperative ultrasound images. A computer-based treatment planning system, which relied on a genetic algorithm, was used to determine the optimal seed distribution necessary to achieve maximal target volume coverage with the prescription dose and to maintain urethra and rectal doses within tolerance ranges. The treatment planning system was specifically designed to escalate the dose to MRS-positive voxels while at the same time achieving preferential sparing of surrounding normal tissues. Patients underwent transperineal interstitial implantation with I 125 by use of this intraoperatively generated plan. Postimplant computed tomographic scans were performed on the same day of the procedure in all cases, and dosimetric guidelines of the American Brachytherapy Society were used to assess implant quality.

RESULTS

Based on the postimplant computed tomographic evaluation, the intraoperative optimization treatment planning program was able to achieve a minimum dose of 139% to 192% of the 144-Gy prescription dose to the MRS-positive voxels. The percentage of the prostate volume receiving 100% of the prescription dose ranged from 92% to 97%, and the dose delivered to 90% of the target for the target volume ranged from 96% to 124%. Despite the dose escalation achieved for the positive voxels, the urethral and rectal doses were maintained within tolerance ranges. The average and maximal rectal doses ranged from 28% to 43% and 69% to 115% of the prescription dose, respectively. The average and maximal urethral doses ranged from 66% to 144% and 118% to 166% of the prescription dose, respectively.

CONCLUSIONS

Using this brachytherapy optimization system, we could demonstrate the feasibility of MRS-optimized dose distributions for I 125 permanent prostate implants. This approach may have an impact on the ability to select regions within the prostate to safely employ dose escalation for patients treated with permanent interstitial implantation and to improve outcome for patients with organ-confined prostatic cancers.

Treatment planning for prostate implants using magnetic-resonance spectroscopy imaging

PURPOSE

Recent studies have demonstrated that magnetic-resonance spectroscopic imaging (MRSI) of the prostate may effectively distinguish between regions of cancer and normal prostatic epithelium. This diagnostic imaging tool takes advantage of the increased choline plus creatine versus citrate ratio found in malignant compared to normal prostate tissue. The purpose of this study is to describe a novel brachytherapy treatment-planning optimization module using an integer programming technique that will utilize biologic-based optimization. A method is described that registers MRSI to intraoperative-obtained ultrasound images and incorporates this information into a treatment-planning system to achieve dose escalation to intraprostatic tumor deposits.

METHODS

MRSI was obtained for a patient with Gleason 7 clinically localized prostate cancer. The ratios of choline plus creatine to citrate for the prostate were analyzed, and regions of high risk for malignant cells were identified. The ratios representing peaks on the MR spectrum were calculated on a spatial grid covering the prostate tissue. A procedure for mapping points of interest from the MRSI to the ultrasound images is described. An integer-programming technique is described as an optimization module to determine optimal seed distribution for permanent interstitial implantation. MRSI data are incorporated into the treatment-planning system to test the feasibility of dose escalation to positive voxels with relative sparing of surrounding normal tissues. The resultant tumor control probability (TCP) is estimated and compared to TCP for standard brachytherapy-planned implantation.

RESULTS

The proposed brachytherapy treatment-planning system is able to achieve a minimum dose of 120% of the 144 Gy prescription to the MRS positive voxels using (125)I seeds. The preset dose bounds of 100-150% to the prostate and 100-120% to the urethra were maintained. When compared to a standard plan without MRS-guided optimization, the estimated TCP for the MRS-optimized plan is superior. The enhanced TCP was more pronounced for smaller volumes of intraprostatic tumor deposits compared to estimated TCP values for larger lesions.

CONCLUSIONS

Using this brachytherapy-optimization system, we could demonstrate the feasibility of MRS-optimized dose distributions for (125)I permanent prostate implants. Based on probability estimates of anticipated improved TCP, this approach may have an impact on the ability to safely escalate dose and potentially improve outcome for patients with organ-confined but aggressive prostatic cancers. The magnitude of the TCP enhancement, and therefore the risks of ignoring the MR data, appear to be more substantial when the tumor is well localized; however, the gain achievable in TCP may depend quite considerably on the MRS tumor-detection efficiency.

The in vivo effect of bryostatin-1 on paclitaxel-induced tumor growth, mitotic entry, and blood flow

Pretreatment of tumor cells with the protein kinase C (PKC) inhibitor bryostatin-1 enhances the cytotoxicity of most chemotherapeutic agents. However, in the case of paclitaxel, this effect has been shown in vitro to be best achieved when bryostatin-1 follows (rather than precedes) paclitaxel treatment. With combination trials of bryostatin-1 and paclitaxel planned for clinical trials and with only in vitro data available regarding drug sequence, we elected to undertake an in vivo study evaluating the effect of sequential bryostatin-1 and paclitaxel in a tumor-bearing mouse model and to correlate this effect to cell cycle events, tumor metabolism, and tumor blood flow. At the maximum tolerated i.p. dose, bryostatin-1 at 80 microg/kg resulted in a small but significant increase in tumor doubling time (4.2 +/- 0.3 days) compared with control tumors (3.0 +/- 0.3 days; P < 0.01). Mice treated with i.v. paclitaxel, administered at a dose of 12 mg/kg every 12 h for three doses, weekly for 3 weeks, had a tumor doubling time of 23.4 +/- 1.7 days. Mice pretreated with i.p. bryostatin-1 (80 microg/kg) followed 12 h later by i.v. paclitaxel (12 mg/kg every 12h for three doses) weekly for 3 weeks had a tumor doubling time of 9.7 +/- 1.1 days. This was significantly less (P < .001) than paclitaxel alone, which indicated an inhibitory effect by bryostatin-1 on paclitaxel therapy. In comparison, tumor-bearing mice that were treated with the same dose but with the sequence of paclitaxel followed by bryostatin-1 had a tumor doubling time of 29.6 +/- 0.6 days. This was significantly greater than the tumor doubling times for any condition tested (P < 0.01), demonstrating the sequence dependence of this combination. The efficacy of paclitaxel is dependent on mitotic entry, a step that requires activation of p34cdc2 kinase activity. Treatment with paclitaxel in vivo increased p34 cdc2 kinase activity in the mouse mammary tumors, whereas administration of bryostatin-1 before paclitaxel prevented the p34cdc2 kinase activation by paclitaxel. This was further evaluated in vitro by flow cytometry in MKN-74 human gastric cancer cells. As determined by MPM-2 labeling, which identifies cells in mitosis, pretreatment with bryostatin-1 prevented paclitaxel-treated cells from entering mitosis. Bryostatin-1 has been reported to induce changes in muscle metabolism and to decrease muscle blood flow. These events could impact on the interaction of bryostatin-1 with paclitaxel. Using proton-decoupled phosphorus nuclear magnetic resonance (31P-NMR) spectroscopy in vivo, bryostatin-1 at 80 micro1g/kg induced a decrease in both intratumoral pH and high-energy phosphates. In vivo perfusion studies, using dynamic enhanced NMR imaging with gadolinium diethylenetriamine pentaacetic acid, also demonstrated decreased tumor blood flow. These studies suggest that the inhibition of tumor response to paclitaxel by bryostatin-1 is multifactorial and includes such diverse factors as inhibition of cell entry into mitosis, a decrease in pH and energy metabolism, and a decrease in tumor blood flow. These results indicate that, as this combination enters Phase I clinical trials, the sequence of paclitaxel followed by bryostatin-1 will be critical in the clinical trial design.

A quantitative assessment of liver metabolites during jaundice using three dimensional phosphorus chemical shift imaging

Phosphorus metabolites in the jaundiced rat liver were studied by three-dimensional phosphorus chemical shift imaging (CSI). Animals were studied at 1, 2, and 3 weeks post-ligation of the common bile duct. Quantitation of metabolites was performed using an external standard. Metabolite T(1) values were assessed in CSI experiments on normal untreated animals. High-performance liquid chromatography (HPLC) was used to measure adenine nucleotides in a separate group of jaundiced rats. 3D-CSI did not detect significant changes in NTP in jaundiced animals relative to baseline controls. At two and three weeks post bile duct ligation, pH was significantly elevated. HPLC data comparing ATP levels to baseline controls also detected no change except for elevated ATP detected on Day 21. (31)P NMR chemical shift imaging may be used to assess liver metabolites under conditions of stress such as jaundice. However, absolute quantitation requires careful attention to many factors including point spread function, correct T(1) values, and adequate signal-to-noise ratio.

A dual-tuned resonator for proton-decoupled phosphorus-31 chemical shift imaging of the brain

A fully quadrature dome-shaped resonator is presented that has been dual-tuned for proton and phosphorus operation at 1.5 T. The resonator is 16.5 cm in length and 23 cm in diameter. Phantom studies were performed to demonstrate the utility of the resonator for proton imaging, shimming, and proton-decoupled phosphorus spectroscopy. In human subjects, proton-decoupled phosphorus chemical shift imaging spectra of the brain were acquired at 27 cm3 resolution in 34 min. Volunteer studies demonstrated improved resolution of phosphomonoesters, phosphodiesters, and nucleoside triphosphates due to proton decoupling. Sensitive coverage of the brain extended from the most superior cerebral cortex to the cerebellum. Acquisition of good quality 31P spectra over this volume is due to the dome structure as well as quadrature operation at both proton and phosphorus frequencies.