Proton MR spectroscopy of the prostate

Label-Free Chemically and Molecularly Selective Magnetic Resonance Imaging

Biomedical imaging, especially molecular imaging, has been a driving force in scientific discovery, technological innovation, and precision medicine in the past two decades. While substantial advances and discoveries in chemical biology have been made to develop molecular imaging probes and tracers, translating these exogenous agents to clinical application in precision medicine is a major challenge. Among the clinically accepted imaging modalities, magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) exemplify the most effective and robust biomedical imaging tools. Both MRI and MRS enable a broad range of chemical, biological and clinical applications from determining molecular structures in biochemical analysis to imaging diagnosis and characterization of many diseases and image-guided interventions. Using chemical, biological, and nuclear magnetic resonance properties of specific endogenous metabolites and native MRI contrast-enhancing biomolecules, label-free molecular and cellular imaging with MRI can be achieved in biomedical research and clinical management of patients with various diseases. This review article outlines the chemical and biological bases of several label-free chemically and molecularly selective MRI and MRS methods that have been applied in imaging biomarker discovery, preclinical investigation, and image-guided clinical management. Examples are provided to demonstrate strategies for using endogenous probes to report the molecular, metabolic, physiological, and functional events and processes in living systems, including patients. Future perspectives on label-free molecular MRI and its challenges as well as potential solutions, including the use of rational design and engineered approaches to develop chemical and biological imaging probes to facilitate or combine with label-free molecular MRI, are discussed.

mpMRI of the Prostate (MR-Prostatography): Updated Recommendations of the DRG and BDR on Patient Preparation and Scanning Protocol

The Working Group Uroradiology and Urogenital Diagnosis of the German Roentgen Society (DRG) revised and updated the recommendations for preparation and scanning protocol of the multiparametric MRI of the Prostate in a consensus process and harmonized it with the managing board of German Roentgen Society and Professional Association of the German Radiologist (BDR e. V.). These detailed recommendation define the referenced "validated quality standards" of the German S3-Guideline Prostate Cancer and describe in detail the topic 1. anamnestic datas, 2. termination of examinations and preparation of examinations, 3. examination protocol and 4. MRI-(in-bore)-biopsy. KEY POINTS:: · The recommendations for preparation and scanning protocol of the multiparametric MRI of the Prostate were revised and updated in a consensus process and harmonized with the managing board of German Roentgen Society (DRG) and Professional Asssociation of the German Radiologist (BDR).. · Detailed recommendations are given for topic 1. anamnestic datas, 2. termination and preparation of examinations, 3. examination protocoll and 4. MRI-(in-bore)-biopsy.. · These recommendations define the referenced "validated quality standards" of the German S3-Guideline Prostate Cancer.. CITATION FORMAT: · Franiel T, Asbach P, Beyersdorff D et al. mpMRI of the Prostate (MR-Prostatography): Updated Recommendations of the DRG and BDR on Patient Preparation and Examination Protocol. Fortschr Röntgenstr 2021; 193: 763 - 776.

Free radical imaging of endogenous redox molecules using dynamic nuclear polarisation magnetic resonance imaging

Redox reactions accompanied by the oxidation-reduction of endogenous molecules play important roles in maintaining homeostasis in living organisms. In humans, numerous endogenous molecules that contribute towards maintaining physiological conditions form free radicals via electron transfer. A typical example of this is the mitochondrial electron transport chain, which is involved in energy production. If free radicals derived from endogenous molecules could be visualised and exploited as biological and functional probes, redox reactions mediated by endogenous molecules could be detected non-invasively. We succeeded in visualising the free radicals derived from endogenous molecules using an in vivo dynamic nuclear polarisation (DNP) magnetic resonance imaging (MRI) system. In this review, we describe the visualisation of endogenous redox molecules, such as flavins and ubiquinones, which are mitochondrial electron carriers, as well as vitamin E and vitamin C (ascorbate). In addition, we describe the application of melanin free radicals for the in vivo visualisation of metabola without using probes via in vivo DNP-MRI.

Comparison of prostate-specific membrane antigen ligands in clinical translation research for diagnosis of prostate cancer

BACKGROUND

Prostate-specific membrane antigen (PSMA), overexpressed on prostate cancer (PCa), is a well-characterized cell surface protein to selectively diagnose PCa. PSMA's unique characteristics and its 1000-fold higher expression in PCa compared with other tissues renders it as a suitable biomarker for detection of PCa in its early stage. In this report, we critically analyze and recommend the requirements needed for the development of variety of PSMA-targeted molecular imaging agents based on antibodies, small molecule ligands, peptides, and aptamers. The targeting moieties are either conjugated to radionuclear isotopes or near-infrared agents for efficient diagnosis of PCa.

RECENT FINDINGS

From the analysis, it was found that several small molecule-derived PCa imaging agents are approved for clinical trials in Europe and the United States, and few are already in the clinical use for diagnosis of PCa. Even though ¹¹¹In-labeled capromab pendetide was approved by the Food and Drug Administration (FDA) and other engineered antibodies are available for detection of PCa, but high production cost, low shelf life (less than 1 month at 4°C), possibility of human immuno reactions, and low blood clearance rate necessitated a need for developing new imaging agents, which are serum stable, cost-effective, and possesses longer shelf life (6 months), have fast clearance rate from nontargeted tissues during the diagnosis process. It is found that small molecule ligand-derived imaging agents possesses most of the desired properties expected for an ideal diagnostic agent when compared with other targeting moieties.

CONCLUSION

This report discusses in detail the homing moieties used in the development of targeted diagnostic tools for detection of PCa. The merits and demerits of monoclonal antibodies, small molecule ligands, peptides, and aptamers for imaging of PCa and intraoperative guided surgery are extensively analyzed. Among all, urea-based ligands were found to be most successful in preclinical and clinical trials and show a major promise for future commercialization.

The Use of Quantitative Imaging in Radiation Oncology: A Quantitative Imaging Network (QIN) Perspective

Modern radiation therapy is delivered with great precision, in part by relying on high-resolution multidimensional anatomic imaging to define targets in space and time. The development of quantitative imaging (QI) modalities capable of monitoring biologic parameters could provide deeper insight into tumor biology and facilitate more personalized clinical decision-making. The Quantitative Imaging Network (QIN) was established by the National Cancer Institute to advance and validate these QI modalities in the context of oncology clinical trials. In particular, the QIN has significant interest in the application of QI to widen the therapeutic window of radiation therapy. QI modalities have great promise in radiation oncology and will help address significant clinical needs, including finer prognostication, more specific target delineation, reduction of normal tissue toxicity, identification of radioresistant disease, and clearer interpretation of treatment response. Patient-specific QI is being incorporated into radiation treatment design in ways such as dose escalation and adaptive replanning, with the intent of improving outcomes while lessening treatment morbidities. This review discusses the current vision of the QIN, current areas of investigation, and how the QIN hopes to enhance the integration of QI into the practice of radiation oncology.

Three-dimensional proton magnetic resonance spectroscopy and diffusion-weighted imaging in the differentiation of incidental prostate carcinoma from benign prostate hyperplasia

The present study evaluated three-dimensional proton magnetic resonance spectroscopy (MRS) and diffusion-weighted imaging (DWI) features in differentiating incidental prostate carcinoma (IPCa) and benign prostate hyperplasia (BPH) in the central gland of the prostate. The clinical and imaging data of 9 patients with IPCa, 118 patients with BPH [including those with glandular hyperplasia (GH), stromal hyperplasia (SH) and mixed hyperplasia (MH)], were retrospectively analyzed. The mean (choline + creatine)/citrate (CC/C) value of 3D MRS, the apparent diffusion coefficient (ADC) value and the minimal ADC value of DWI were compared between carcinoma and non-carcinoma tissues. The mean CC/C values were 1.04±0.28, and 1.09±0.58 in IPCa and BPH, respectively (t=-0.205, P=0.838). No significant difference in CC/C values (χ²=2.595, P=0.458) could be detected between IPCa, GH, SH and MH groups. The ADC values of the central gland only differed between IPCa (1.48±0.18) ×10^-3 and GH (1.60±0.16) ×10^-3 mm²/sec (P=0.037). The minimal ADC values were similar between IPCa (1.15±0.10) ×10^-3 and BPH (1.14±0.11) ×10^-3 mm²/sec, no significant differences could be detected between IPCa and GH (P=0.930), IPCa and SH (P=0.192), and IPCa and MH (P=0.544). Although the ADC values of the central gland of the prostate differed between IPCa and GH, the findings of the present study therefore indicate that combining 3D MRS with DWI cannot potentially improve the detection of IPCa.

Choline-based imaging of prostate cancer with combined [18F] fluorocholine PET and 1H MR spectroscopy by means of integrated PET/MRI

PURPOSE

To evaluate integrated PET/MRI/¹H MR spectroscopy in patients with prostate cancer.

SUBJECTS AND METHODS

Data analysis comprised calculations of correlations of standardized uptake values (SUVs) and ratios of (choline+creatine)/citrate as well as of single metabolite values and a logistic regression analysis of PET data and MR spectroscopy data in 22 patients.

RESULTS

SUVmean and integral values of choline correlated significantly in tumors. Logistic regression analysis demonstrated diagnostic superiority of PET over spectroscopy.

CONCLUSION

Simultaneous acquisition of PET and MR spectroscopy with integrated PET/MRI is feasible. Choline compounds and choline metabolism show a positive significant correlation.

Impact of an endorectal coil for 1H-magnetic resonance spectroscopy of the prostate at 3.0T in comparison to 1.5T: Do we need an endorectal coil?

OBJECTIVES

To evaluate the influence of endorectal coil (ERC) regarding spectral quality and diagnostic suitability and diagnostic performance in 3.0T 1H-magnetic resonance spectroscopy imaging (MRSI) compared to 1.5T MRSI.

MATERIALS AND METHODS

The study was approved by the Institutional Review Board. MRSI of the prostate was performed on 19 patients at 1.5T with ERC (protocol 1), at 3.0T with a disabled ERC (protocol 2) and at 3.0T with ERC (protocol 3). Age, weight, body size, body-mass-index, prostate volume, time between measurements, diagnostic suitability of spectra, histopathological results after biopsy of cancer suspect lesions (CSL), sensitivity and specificity were evaluated. Signal-to-noise ratio (SNR) was calculated and compared using semiparametrical multiple Conover-comparisons. Correlations between SNR and prostate volume and BMI were indicated using Pearson correlation coefficient. Distribution of SNR was evaluated for prostate quadrants.

RESULTS

Diagnostic suitable spectra were achieved in 76 % (protocol 1, 100% in CSL), 32 % (protocol 2, 59% in CSL) and 50 % (protocol 3, 80% in CSL) of the voxels. SNR was significantly higher in protocol 3 compared to protocol 2 and 1 (93,729 vs. 27,836 vs. 32,897, p<0.0001) with significant difference between protocol 2 and 1 (p<0.023). Highest SNR was achieved in the dorsal prostate (protocols 1 and 3; p<0.0001). Sensitivity at 3.0T was higher with use of ERC. Specificity was highest at 1.5T with ERC.

CONCLUSION

The ERC improves the diagnostic suitability and the SNR in MRSI at 3.0T. Less voxels at 3.0T with disabled ERC are suitable for diagnosis compared to 1.5T with ERC. MRSI at 3.0T with ERC shows the highest SNR. SNR in dorsal quadrants of the prostate was higher using ERC.

Three-dimensional proton magnetic resonance spectroscopic imaging with and without an endorectal coil: a prostate phantom study

BACKGROUND

Proton magnetic resonance spectroscopic imaging (MRSI) of the prostate has been used with only a combination of external surface coils. The quality of spectral fitting of the (choline + creatine)/citrate ([Cho + Cr]/Cit) ratio at different field strengths and different coils is important for quantitative/semi-quantitative diagnosis of prostate cancer.

PURPOSE

To evaluate the quality of spectral fitting of the (Cho + Cr)/Cit ratio of a prostate phantom using MRSI at different field strengths and various coils.

MATERIAL AND METHODS

Experiments were using 1.5-T and 3.0-T MR systems. Measurements were taken on a homemade prostate phantom with different coils: spinal array; abdominal array; and endorectal. The signal-to-noise ratio (SNR) of choline, creatine, and citrate peaks as well as the (Cho + Cr)/Cit ratio in each voxel were compared among groups using multi-way analysis of variance.

RESULTS

Magnetic field strength, coils, and plane position had a significant effect on the SNR or (Cho + Cr)/Cit ratio, and there were interactions among groups (all P = 0.000). The 1.5-T (0.228 ± 0.044) exhibited a higher (Cho + Cr)/Cit ratio than the 3.0-T (0.125 ± 0.041) magnetic field strength (F = 3238, P = 0.000). The (Cho + Cr)/Cit ratio of both surface coils (0.183 ± 0.065) and all coils (0.181 ± 0.057) was significantly lower than that of the endorectal coil (0.195 ± 0.077) (both P < 0.05), but significant differences in the mean (Cho + Cr)/Cit ratio were not observed if surface coils and all coils were used (P > 0.05). No significant differences were found among the (Cho + Cr)/Cit ratios of all voxels in the middle planes by the post-hoc analyses (all P > 0.05).

CONCLUSION

Three-dimensional proton MRSI of prostate metabolites in a phantom using surface coils is feasible and reliable, but (Cho + Cr)/Cit ratios acquired at different magnetic fields and coils were different. This difference should be taken into account when calculating this ratio in a field strength-independent way.

Feasibility of multiparametric prostate magnetic resonance imaging in the detection of cancer distribution: histopathological correlation with prostatectomy specimens

Purpose

To prevent overtreatment, it is very important to diagnose the precise distribution and characteristics of all cancer lesions, including small daughter tumors. The purpose of this study was to evaluate the efficacy of T2-weighted magnetic resonance imaging (T2W), diffusion-weighted magnetic resonance imaging (DWI), magnetic resonance spectroscopy (¹H-MRS), and prostate biopsy (PBx) in the detection of intraprostatic cancer distribution.

Methods

All patients underwent T2W, DWI, ¹H-MRS, and PBx followed by radical prostatectomy (RP). Individual prostates were divided into 12 segmental regions, each of which was examined for the presence or absence of malignancy on the basis of T2W, DWI, ¹H-MRS, and PBx, respectively. These results were compared with the histopathological findings for RP specimens.

Results

We included 54 consecutive patients with biopsy-proven prostate cancer (mean age, 62.7 years; median prostate-specific antigen level, 5.7 ng/mL) in this study. We could detect cancer in 247 of 540 evaluable lesions. The area under the receiver operator characteristic curve analysis yielded a higher value for DWI (0.68) than for T2W (0.65), ¹H-MRS (0.54), or PBx (0.56). In 180 cancerous regions of RP specimens with false-negative PBx results, T2W+DWI had the highest positive rate (53.3%) compared with that of each sequence alone, including T2W (45.6%), DWI (41.1%), and ¹H-MRS (30.0%).

Conclusions

Multiparametric magnetic resonance imaging (T2W, ¹H-MRS, DWI) enables the detection of prostate cancer distribution with reasonable sensitivity and specificity. T2W+DWI was particularly effective in detecting cancer distribution with false-negative PBx results.

High-resolution NMR spectroscopy of human body fluids and tissues in relation to prostate cancer

High-resolution NMR spectroscopic studies of prostate tissue extracts, prostatic fluid, seminal fluid, serum and urine can be used for the detection of prostate cancer, based on the differences in their metabolic profiles. Useful diagnostic information is obtained by the detection or quantification of as many metabolites as possible and comparison with normal samples. Only a few studies have shown the potential of high-resolution in vitro NMR of prostate tissues. A survey of the literature has revealed that studies on body fluids, such as urine and serum, in relation to prostate cancer are rare. In addition, the potential of NMR of nuclei other than (1)H, such as (13)C and (31)P, has not been exploited fully. The metabolomic analysis of metabolites, detected by high-resolution NMR, may help to identify metabolites which could serve as useful biomarkers for prostate cancer detection. Such NMR-derived biomarkers would not only help in prostate cancer detection and in understanding the in vivo MRS metabolic profile, but also to investigate the biochemical and metabolic changes associated with cancer. Here, we review the published research work on body fluids in relation to prostate and prostate tissue extracts, and highlight the potential of such studies for future work.

A radiologist's guide to treatment response criteria in oncologic imaging: functional, molecular, and disease-specific imaging biomarkers

OBJECTIVE

This article reviews the functional, molecular, and disease-specific imaging biomarkers of treatment response.

CONCLUSION

Substantial progress has been made in the evolution of drugs directed at specific targets of the tumor lifecycle. These novel agents are predominantly cytostatic, and their efficacy may be optimally evaluated by functional, molecular, and disease-specific imaging biomarkers.

Translational Molecular Imaging of Prostate Cancer

Prostate cancer is a heterogeneous disease, and its management is now evolving to become more personalized and to incorporate new targeted therapies. With these new changes comes a demand for molecular imaging techniques that can not only detect disease but also assess biology and treatment response. This review article summarizes current molecular imaging approaches in prostate cancer (e.g. 99mTc bone scintigraphy and 18F-fluorodeoxyglucose positron emission tomography) and highlights emerging clinical and preclinical imaging agents, with an emphasis on mechanism and clinical application. Emerging agents at various stages of clinical translation include radiolabeled analogs of lipid, amino acid, and nucleoside metabolism, as well as agents more specifically targeting prostate cancer biomarkers including androgen receptor, prostate-specific membrane antigen and others. We also highlight new techniques and targeted contrast agents for magnetic resonance imaging and spectroscopy. For all these imaging techniques, a growing and important unmet need is for well-designed prospective clinical trials to establish clear indications with clinical benefit in prostate cancer.

Prostate cancer magnetic resonance imaging (MRI): multidisciplinary standpoint

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

3.0 T proton magnetic resonance spectroscopy of the liver: Quantification of choline

AIM: To investigate the normal hepatic magnetic resonance spectroscopy findings choline/lipid2 (Cho/Lip2) associated with age and body mass index (BMI).

METHODS: A total of 58 single-voxel proton spectra of the liver were acquired at 3.0 T using the eight-channel phased array abdominal coil as the receiver coil. Consecutive stacks of breath-hold spectra were acquired using the point resolved spectroscopy technique at a short echo time of 30 ms and a repetition time of 1500 ms. The spectra were processed with the SAGE software package. Areas and heights for metabolite resonance were obtained. Student’s t test for unpaired data was used for comparisons of shimming, Cho/Lip2, and lipid content.

RESULTS: There were significant negative correlations between the Cho/Lip2 peak height ratios and BMI (r = -0.615) and age (r = -0.398) (all P < 0.01). Compared with the high-BMI group, the low-BMI group was younger (39.1 ± 13.0 years vs 47.6 ± 8.5 years, t = -2.954, P = 0.005); had better water suppression (93.4% ± 1.4% vs 85.6% ± 11.6%, t = 2.741, P = 0.014); had higher Cho/Lip2 peak heights ratio (0.2 ± 0.14 vs 0.05 ± 0.04, t = 6.033, P < 0.000); and had lower lipid content (0.03 ± 0.08 vs 0.29 ± 0.31, t = -3.309, P = 0.004). Compared with the older group, the younger group had better shimming effects (17.1 ± 3.6 Hz vs 22.0 ± 6.8 Hz, t = -2.919, P = 0.008); higher Cho/Lip2 peak heights ratios (0.03 ± 0.05 vs 0.09 ± 0.12, t = 2.4, P = 0.020); and lower lipid content (0.05 ± 0.11 vs 0.23 ± 0.32, t = -2.337, P = 0.031). Compared with the low-choline peak group, the high-choline peak group had lower lipid content (0.005 ± 0.002 vs 0.13 ± 0.23, t = -3.796, P < 0.000); lower BMI (19.6 ± 2.4 vs 23.9 ± 3.0, t = -4.410, P < 0.000); and younger age (34.7 ± 10.0 years vs 43.2 ± 12.5 years, t = -2.088, P = 0.041).

CONCLUSION: Lipid accumulation could result from the increased fat in the body depending on age and BMI. Lipid can mask the resonance signal of choline.

A phase and frequency alignment protocol for 1H MRSI data of the prostate

(1)H MRSI of the prostate reveals relative metabolite levels that vary according to the presence or absence of tumour, providing a sensitive method for the identification of patients with cancer. Current interpretations of prostate data rely on quantification algorithms that fit model metabolite resonances to individual voxel spectra and calculate relative levels of metabolites, such as choline, creatine, citrate and polyamines. Statistical pattern recognition techniques can potentially improve the detection of prostate cancer, but these analyses are hampered by artefacts and sources of noise in the data, such as variations in phase and frequency of resonances. Phase and frequency variations may arise as a result of spatial field gradients or local physiological conditions affecting the frequency of resonances, in particular those of citrate. Thus, there are unique challenges in developing a peak alignment algorithm for these data. We have developed a frequency and phase correction algorithm for automatic alignment of the resonances in prostate MRSI spectra. We demonstrate, with a simulated dataset, that alignment can be achieved to a phase standard deviation of 0.095  rad and a frequency standard deviation of 0.68  Hz for the citrate resonances. Three parameters were used to assess the improvement in peak alignment in the MRSI data of five patients: the percentage of variance in all MRSI spectra explained by their first principal component; the signal-to-noise ratio of a spectrum formed by taking the median value of the entire set at each spectral point; and the mean cross-correlation between all pairs of spectra. These parameters showed a greater similarity between spectra in all five datasets and the simulated data, demonstrating improved alignment for phase and frequency in these spectra. This peak alignment program is expected to improve pattern recognition significantly, enabling accurate detection and localisation of prostate cancer with MRSI.

Application of compressed sensing to multidimensional spectroscopic imaging in human prostate

The application of compressed sensing is demonstrated in a recently implemented four-dimensional echo-planar based J-resolved spectroscopic imaging sequence combining two spatial and two spectral dimensions. The echo-planar readout simultaneously acquires one spectral and one spatial dimension. Therefore, the compressed sensing undersampling is performed along the indirectly acquired spatial and spectral dimensions, and the reconstruction is performed using the split Bregman algorithm, an efficient TV-minimization solver. The four-dimensional echo-planar-based J-resolved spectroscopic imaging data acquired in a prostate phantom containing metabolites at physiological concentrations are accurately reconstructed with as little as 20% of the original data. Experimental data acquired in six healthy prostates using the external body matrix "receive" coil on a 3T magnetic resonance imaging scanner are reconstructed with acquisitions using only 25% of the Nyquist-Shannon required amount of data, indicating the potential for a 4-fold acceleration factor in vivo, bringing the required scan time for multidimensional magnetic resonance spectroscopic imaging within clinical feasibility.

Assessing prostate cancer growth with citrate measured by intact tissue proton magnetic resonance spectroscopy

BACKGROUND

Annual PSA tests have led to a significant increase in the number of prostate cancer (PCa) cases diagnosed. This increased incidence has led to overtreatment of many patients, as current pathology often cannot distinguish latent from aggressive PCa. Studies have shown that the depletion of zinc in prostate cells correlated with cell-line growth rates, and may therefore relate to the progression of PCa. Furthermore, as zinc is normally an inhibitor of citrate oxidation, the reduction of zinc in PCa may cause a decrease in citrate secretion levels in the glandular epithelia of PCa patients.

METHODS

Using high-resolution magic angle spinning proton magnetic resonance spectroscopy followed by quantitative histopathology, we investigate unit histo-benign prostate epithelial citrate concentrations in intact tissue samples obtained from 18 patients with pre-surgical PSA values less than 20 ng/ml. Using these data, we evaluate correlations between citrate concentrations and PSA velocities, densities and blood percent-free PSA.

RESULTS

We observe different linear patterns between citrate concentrations and histo-benign glandular epithelia from patients of different PSA velocities. More importantly, we obtain a significant correlation between PSA velocity, density and percent-free PSA, and citrate concentrations in unit volume of histo-benign epithelial glands of the peripheral zone.

CONCLUSIONS

Low levels of citrate in unit volume represent rapidly increasing PSA values, and, therefore, may be used as an indicator of fast-growing PCa. Thus, tissue samples obtained at the time of biopsy may be evaluated for their citrate concentrations for the prediction of PCa growth rates, allowing for the implementation of alternative treatment options and reducing overtreatment.

Molecular preservation by extraction and fixation, mPREF: a method for small molecule biomarker analysis and histology on exactly the same tissue

Background

Histopathology is the standard method for cancer diagnosis and grading to assess aggressiveness in clinical biopsies. Molecular biomarkers have also been described that are associated with cancer aggressiveness, however, the portion of tissue analyzed is often processed in a manner that is destructive to the tissue. We present here a new method for performing analysis of small molecule biomarkers and histology in exactly the same biopsy tissue.

Methods

Prostate needle biopsies were taken from surgical prostatectomy specimens and first fixed, each in a separate vial, in 2.5 ml of 80% methanol:water. The biopsies were fixed for 24 hrs at room temperature and then removed and post-processed using a non-formalin-based fixative (UMFIX), embedded, and analyzed by hematoxylin and eosin (H&E) and by immunohistochemical (IHC) staining. The retained alcohol pre-fixative was analyzed for small molecule biomarkers by mass spectrometry.

Results

H&E analysis was successful following the pre-fixation in 80% methanol. The presence or absence of tumor could be readily determined for all 96 biopsies analyzed. A subset of biopsy sections was analyzed by IHC, and cancerous and non-cancerous regions could be readily visualized by PIN4 staining. To demonstrate the suitability for analysis of small molecule biomarkers, 28 of the alcohol extracts were analyzed using a mass spectrometry-based metabolomics platform. All extracts tested yielded successful metabolite profiles. 260 named biochemical compounds were detected in the alcohol extracts. A comparison of the relative levels of compounds in cancer containing vs. non-cancer containing biopsies showed differences for 83 of the compounds. A comparison of the results with prior published reports showed good agreement between the current method and prior reported biomarker discovery methods that involve tissue destructive methods.

Conclusions

The Molecular Preservation by Extraction and Fixation (mPREF) method allows for the analysis of small molecule biomarkers from exactly the same tissue that is processed for histopathology.

Prostate cancer: multiparametric MR imaging for detection, localization, and staging

This review presents the current state of the art regarding multiparametric magnetic resonance (MR) imaging of prostate cancer. Technical requirements and clinical indications for the use of multiparametric MR imaging in detection, localization, characterization, staging, biopsy guidance, and active surveillance of prostate cancer are discussed. Although reported accuracies of the separate and combined multiparametric MR imaging techniques vary for diverse clinical prostate cancer indications, multiparametric MR imaging of the prostate has shown promising results and may be of additional value in prostate cancer localization and local staging. Consensus on which technical approaches (field strengths, sequences, use of an endorectal coil) and combination of multiparametric MR imaging techniques should be used for specific clinical indications remains a challenge. Because guidelines are currently lacking, suggestions for a general minimal protocol for multiparametric MR imaging of the prostate based on the literature and the authors' experience are presented. Computer programs that allow evaluation of the various components of a multiparametric MR imaging examination in one view should be developed. In this way, an integrated interpretation of anatomic and functional MR imaging techniques in a multiparametric MR imaging examination is possible. Education and experience of specialist radiologists are essential for correct interpretation of multiparametric prostate MR imaging findings. Supportive techniques, such as computer-aided diagnosis are needed to obtain a fast, cost-effective, easy, and more reproducible prostate cancer diagnosis out of more and more complex multiparametric MR imaging data.

Reliable non-invasive measurement of human neurochemistry using proton spectroscopy with an anatomically defined amygdala-specific voxel

Given the central role of the amygdala in fear perception and expression and its likely abnormality in affective disorders and autism, there is great demand for a technique to measure differences in neurochemistry of the human amygdala. Unfortunately, it is also a technically complex target for magnetic resonance spectroscopy (MRS) due to a small volume, high field inhomogeneity and a shared boundary with hippocampus, which can undergo opposite changes in response to stress. We attempted to achieve reliable PRESS-localized single-voxel MRS at 3T of the isolated human amygdala by using anatomy to guide voxel size and location. We present data from 106 amygdala-MRS sessions from 58 volunteers aged 10 to 52 years, including two tests of one-week stability and a feasibility study in an adolescent sample. Our main outcomes were indices of spectral quality, repeated measurement variability (within- and between-subject standard deviations), and sensitivity to stable individual differences measured by intra-class correlation (ICC). We present metrics of amygdala-MRS reliability for n-acetyl-aspartate, creatine, choline, myo-Inositol, and glutamate+glutamine (Glx). We found that scan quality suffers an age-related difference in field homogeneity and modified our protocol to compensate. We further identified an effect of anatomical inclusion near the endorhinal sulcus, a region of high synaptic density, that contributes up to 29% of within-subject variability across 4 sessions (n=14). Remaining variability in line width but not signal-to-noise also detracts from reliability. Statistical correction for partial inclusion of these strong neurochemical gradients decreases n-acetyl-aspartate reliability from an intraclass correlation of 0.84 to 0.56 for 7-minute acquisitions. This suggests that systematic differences in anatomical inclusion can contribute greatly to apparent neurochemical concentrations and could produce false group differences in experimental studies. Precise, anatomically-based prescriptions that avoid age-related sources of inhomogeneity and use longer scan times may permit study of individual differences in neurochemistry throughout development in this late-maturing structure.

Quantitative proton MR spectroscopy as a biomarker of tumor necrosis in the rabbit VX2 liver tumor

PURPOSE

To compare metabolic magnetic resonance (MR) imaging findings (ie, quantification of tumor choline concentration) with percentage of necrosis on pathologic examination in rabbits bearing VX2 liver tumors.

MATERIALS AND METHODS

VX2 tumors were implanted in the livers of 16 rabbits. MR imaging was performed with a 1.5-T MR scanner and extremity coil, and a hydrogen-1 ((1)H) proton MR spectroscopy ((1)H MRS) imaging protocol was used. Rabbits were euthanized immediately after imaging, and the tumor was harvested and sliced at 4-mm intervals in the axial plane. Choline concentration was calculated and was compared with the percentage of tumor necrosis on pathologic examination.

RESULTS

Mean tumor size at pathologic examination was 16 mm (range, 12-22 mm). Mean percentage of necrosis at pathologic examination was 22% (range, 4%-44%). Choline concentration showed a relatively high inverse correlation with percentage of necrosis on pathologic examination, with an r value of 0.78 (P < .002).

CONCLUSIONS

Choline concentration showed a relatively high inverse correlation with tumor necrosis on pathologic examination. Therefore, (1)H MRS may be useful to assess tumor necrosis.

Early response of hepatic malignancies to locoregional therapy-value of diffusion-weighted magnetic resonance imaging and proton magnetic resonance spectroscopy

PURPOSE

The objective of our study was to determine the usefulness of the diffusion-weighted magnetic resonance imaging and proton magnetic resonance spectroscopy (H-MRS) of hepatic malignancies for the assessment of response to locoregional treatment.

METHODS

Forty-four patients (29 men; mean age, 58 years) with hepatic malignancies were treated locally. Magnetic resonance imaging examinations obtained before and at 1 and 6 months after transarterial chemoembolization were analyzed retrospectively. Imaging criteria included change in tumor size, percentage of enhancement in the arterial and portal venous phases, diffusion-weighted magnetic resonance imaging apparent diffusion coefficients, and choline concentration by quantitative H-MRS. Response to treatment was grouped according to RECIST (Response Evaluation Criteria in Solid Tumors) and European Association for the Study of the Liver (EASL) criteria based on magnetic resonance imaging at 6 months after treatment. Statistical analysis used paired t test, Fisher exact test, and univariate and multivariate Cox proportional hazards models.

RESULTS

Before treatment, the median tumor diameter was 6 cm; at 6 months after treatment, median tumor diameter was 5.1 cm. According to RECIST and EASL, 66% of the patients achieved partial response, 31% had stable disease, and 3% of the patients showed progressive disease. One month after transarterial chemoembolization, apparent diffusion coefficient increased (P < 0.14), and mean choline concentration of the tumors decreased (P < 0.008).

CONCLUSIONS

Diffusion-weighted imaging and hepatic choline levels by H-MRS could predict response to locoregional therapy.

Metabolomics in urogenital cancer

Although in recent decades the development of many drugs against cancer has been witnessed, the morbidity and mortality for the most prevalent urogenital cancer have not been significantly reduced. A key task in cancer medicine is to detect the disease as early as possible. In order to achieve this, many new technologies have been developed for cancer biomarker discovery. Monitoring fluctuations of certain metabolite levels in body fluids, such as urine, has become an important way to detect early stages in carcinogenesis. Moreover metabolomic approaches are likely to be used to screen for potential diagnostic and prognostic biomarkers of urogenital cancer. In future work, these potential biomarkers should be further validated with a large enough patient cohort to achieve earlier diagnosis not only of urogenital cancer, but also other malignancies. Moreover, the improvement of patient prognosis will be another aim of such investigations. This novel metabolomic approach has the potential to provide more information about the pathophysiological status of an organism and distinguish precancerous and cancerous stages.

Determination of the time for maximal response to neoadjuvant hormone therapy for prostate cancer using magnetic resonance with spectroscopy (MRSI) and dynamic contrast enhancement (DCEMR)

PURPOSE

To determine the time-dependent metabolic and angiogenic changes that occur in prostate cancer (CaP) during neoadjuvant hormone therapy (HT), using a combination of MRSI and DCEMR analysis.

MATERIALS AND METHODS

This is a prospective study on a population of non-metastatic CaP submitted to neoadjuvant HT prior to radiation therapy. All cases homogeneously received a 6-month period of neoadjuvant HT using leuprorelin acetate 7.5 mg every 28 days. In all cases, a MRSI/DCEMR study was performed at baseline (pretreatment) and at regular intervals (4, 12, 24 weeks) during HT. Serum PSA was measured at baseline and at the same intervals (4, 12, 24 weeks). All MRI examinations were performed on a commercially available 3 T scanner.

RESULTS

There was a significant ( P < 0.01) time-dependent loss of all prostate metabolites during HT. In regions of CaP no significant variation in the absolute value of metabolites was reported at 1-month interval and a higher variation was observed at 24-week compared with 12-week interval. A complete metabolic atrophy was a common feature (30%) at a 24-week interval of HT, but not at short (4-week 0%), and lower at an intermediate interval (12-week 10%). At DCEMR, onset time and time to peak parameters significantly (P < 0.05) increased at 12- and 24-week intervals.

CONCLUSIONS

To individualize neoadjuvant HT courses prior to definitive treatment, the combination of MRSI and DCEMR may represent a valid noninvasive method, and the addition to PSA data could be used to better assess the time-dependent efficacy of HT in our patients.

Imaging and 'omic' methods for the molecular diagnosis of cancer

Molecular imaging methods can noninvasively detect specific biological processes that are aberrant in cancer, including upregulated glycolytic metabolism, increased cellular proliferation and altered receptor expression. PET using the glucose analogue 18F-fluoro-2-deoxyglucose, which detects the increased glucose uptake that is a characteristic of tumor cells, has been widely used in the clinic to detect tumors and their responses to treatment; however, there are many new PET tracers being developed for a wide range of biological targets. Magnetic resonance spectroscopy (MRS), which can be used to detect cellular metabolites, can also provide prognostic information, particularly in brain, breast and prostate cancers. An emerging technique, which by hyperpolarizing 13C-labeled cell substrates dramatically enhances their sensitivity to detection, could further extend the use of MRS in molecular imaging in the clinic. Molecular diagnostics applied to serum samples or tumor samples obtained by biopsy, can measure changes at the individual cell level and the underlying changes in gene or protein expression. DNA microarrays enable high-throughput gene-expression profiling, while mass spectrometry can detect thousands of proteins that may be used in the future as biomarkers of cancer. Probing molecular changes will aid not only cancer diagnosis, but also provide tumor grading, based on gene-expression analysis and imaging measurements of cell proliferation and changes in metabolism; staging, based on imaging of metastatic spread and elevation of protein biomarkers; and the detection of therapeutic response, using serial molecular imaging measurements or monitoring of serum markers. The present article provides a summary of the molecular diagnostic methods that are currently being trialed in the clinic.

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

PURPOSE

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

RESULTS

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

CONCLUSION

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

Role of MRI in follow-up after focal therapy for prostate carcinoma

OBJECTIVE

In patients with clinically suspected local recurrence of prostate cancer, a lobulated hyperintense mass in the radical prostatectomy fossa can be readily visualized with T2-weighted MRI, but this imaging technique is less successful after treatments such as radiation therapy, high-intensity focused ultrasound, and cryosurgery. We describe the additional value of functional techniques in the assessment of local recurrence.

CONCLUSION

The use of functional MRI techniques such as MR spectroscopy, diffusion-weighted imaging, and dynamic contrast-enhanced MRI has shown promise in increasing overall imaging performance in the detection of local recurrence.

MR-perfusion (MRP) and diffusion-weighted imaging (DWI) in prostate cancer: quantitative and model-based gadobenate dimeglumine MRP parameters in detection of prostate cancer

BACKGROUND

Various MR methods, including MR-spectroscopy (MRS), dynamic, contrast-enhanced MRI (DCE-MRI), and diffusion-weighted imaging (DWI) have been applied to improve test quality of standard MRI of the prostate.

PURPOSE

To determine if quantitative, model-based MR-perfusion (MRP) with gadobenate dimeglumine (Gd-BOPTA) discriminates between prostate cancer, benign tissue, and transitional zone (TZ) tissue.

MATERIAL AND METHODS

27 patients (age, 65±4 years; PSA 11.0±6.1 ng/ml) with clinical suspicion of prostate cancer underwent standard MRI, 3D MR-spectroscopy (MRS), and MRP with Gd-BOPTA. Based on results of combined MRI/MRS and subsequent guided prostate biopsy alone (17/27), biopsy and radical prostatectomy (9/27), or sufficient negative follow-up (7/27), maps of model-free, deconvolution-based mean transit time (dMTT) were generated for 29 benign regions (bROIs), 14 cancer regions (cROIs), and 18 regions of transitional zone (tzROIs). Applying a 2-compartment exchange model, quantitative perfusion analysis was performed including as parameters: plasma flow (PF), plasma volume (PV), plasma mean transit time (PMTT), extraction flow (EFL), extraction fraction (EFR), interstitial volume (IV) and interstitial mean transit time (IMTT). Two-sided T-tests (significance level p<0.05) discriminated bROIs vs. cROIs and cROIs vs. tzROIs, respectively.

RESULTS

PMTT discriminated best between bROIs (11.8±3.0 s) and cROIs (24.3±9.6 s) (p<0.0001), while PF, PV, PS, EFR, IV, IMTT also differed significantly (p 0.00002-0.0136). Discrimination between cROIs and tzROIs was insignificant for all parameters except PV (14.3±2.5 ml vs. 17.6±2.6 ml, p<0.05).

CONCLUSIONS

Besides MRI, MRS and DWI quantitative, 2-compartment MRP with Gd-BOPTA discriminates between prostate cancer and benign tissue with several parameters. However, distinction of prostate cancer and TZ does not appear to be reliable.

Molecular origin of plasma membrane citrate transporter in human prostate epithelial cells

The main function of the prostate gland is to produce and release large amounts of citrate into the prostatic fluid in order to sustain sperm motility and vitality. Mycielska and colleagues have now cloned the citrate transporter responsible for citrate release from prostatic cells. Interestingly, they find that it is an isoform of the transporter that is expressed in the mitochondrial membrane.

The prostate is a highly specialized mammalian organ that produces and releases large amounts of citrate. However, the citrate release mechanism is not known. Here, we present the results of molecular cloning of a citrate transporter from human normal prostate epithelial PNT2-C2 cells shown previously to express such a mechanism. By using rapid amplification of cDNA ends PCR, we determined that the prostatic carrier is an isoform of the mitochondrial transporter SLC25A1 with a different first exon. We confirmed the functionality of the clone by expressing it in human embryonic kidney cells and performing radiotracer experiments and whole-cell patch-clamp recordings. By using short interfering RNAs targeting different parts of the sequence, we confirmed that the cloned protein is the main prostatic transporter responsible for citrate release. We also produced a specific antibody and localized the cloned transporter protein to the plasma membrane of the cells. By using the same antibody, we have shown that the cloned transporter is expressed in non-malignant human tissues.

Technical feasibility of transperineal MR-guided prostate interventions in a low-field open MRI unit: canine study

Magnetic resonance imaging (MRI) provides superior visualization of the prostate, its substructure, surrounding tissues, and, most important, focal lesions or cancer. The purpose of our canine study was to demonstrate the feasibility of a low-field (0.35 T) transperineal system that enables precise MR image guidance of prostate interventions. The canines were placed in the right lateral decubitus position. Template reconstruction, trajectory planning, contouring were based on T2-weighted FSE images. For image guidance and target confirmation, fast gradient spoiled-echo (FSPGR) sequence was used. MR compatible coaxial needles were manually inserted through the perineum to the base of the prostate. After satisfactory position was confirmed, brachytherapy catheters were placed through the coaxial needles. The mean deviation of the needle displacements was 2.9 mm with a median value of 2.7 mm. 97% of the errors were less than 4.0 mm. The needle placement accuracy was modelled by the Rayleigh distribution with a sigma value of 2.3 mm. Visual confirmation of needle placements was demonstrated on pathology tissue slices. The time needed for each step was: anaesthesia - 15 min, setup and positioning - 15 min, initial imaging - 15 min, template registration, projection - 15 min, contouring, trajectory planning, insertion of 12 needles - 60 min Based on our canine experiences our method seems to be a promising approach for performing feasible, accurate, reliable and high-quality prostate MR guidance within a reasonable time span.

MR spectroscopy of the liver: principles and clinical applications

Magnetic resonance (MR) spectroscopy allows the demonstration of relative tissue metabolite concentrations along a two- or three-dimensional spectrum based on the chemical shift phenomenon. An MR spectrum is a plot of the signal intensity and frequency of a chemical or metabolite within a given voxel. At proton MR spectroscopy, the frequency at which a chemical or compound occurs depends on the configuration of the protons within the structure of that chemical. At in vivo proton MR spectroscopy, the frequency location of water is used as the standard of reference to identify a chemical. The frequency shift or location of chemicals relative to that of water allows generation of qualitative and quantitative information about the chemicals that occur within tissues, forming the basis of tissue characterization by MR spectroscopy. MR spectroscopy also may be used to quantify liver fat by measuring lipid peaks and to diagnose malignancy, usually by measuring the choline peak. Interpretation of MR spectroscopic data requires specialized postprocessing software and is subject to technical limitations including low signal-to-noise ratio, masking of metabolite peaks by dominant water and lipid peaks, partial-volume averaging from other tissue within the voxel, and phase and frequency shifts from motion. MR spectroscopy of the liver is an evolving technology with potential for improving the diagnostic accuracy of tissue characterization when spectra are interpreted in conjunction with MR images.

Proton MRS detects metabolic changes in hormone sensitive and resistant human prostate cancer models CWR22 and CWR22r

17-Allylamino, 17-demethoxygeldanamycin (17-AAG), an effective inhibitor of the heat shock protein hsp90, preferentially inhibiting tumor hsp90 compared to hsp90 from normal cells, has shown promising results against several cancers, including hormone-resistant prostate cancer. Levels of several oncogenic proteins critical to tumor growth and progression, such as androgen receptor and HER2/neu, were reduced 4 h post 17-allylamino, 17-demethoxygeldanamycin treatment. Posttreatment metabolic changes have also been observed in several tumor cell lines. In this study, total choline distributions in hormone sensitive CWR22 and hormone resistant CWR22r prostate cancer xenograft tumors in mice were measured before and at 4 h and 48 h after a single-bolus 17-allylamino, 17-demethoxygeldanamycin treatment at 100 mg/kg, using proton MR spectroscopy. Our results show that tumor total choline levels declined 4 h after the treatment for CWR22 (P = 0.001) and 48 h post treatment for CWR22r (P = 0.003). Metabolic changes, in particular of total choline intensity detected by proton magnetic resonance spectroscopic imaging (MRSI), are consistent with the observed immunohistochemistry changes, tumor growth inhibition for CWR22r (P = 0.01 at 14 days post treatment), and a constant prostate specific antigen level versus increasing prostate specific antigen for control CWR22 (P = 0.01). Metabolic changes in total choline by proton MRSI can be used as an early biomarker of response for advanced-stage prostate cancer in targeted therapy such as 17-allylamino, 17-demethoxygeldanamycin.

Classification of prostatic diseases by means of multivariate analysis on in vivo proton MRSI and DCE-MRI data

Multivariate analysis has been applied on proton magnetic resonance spectroscopic imaging ((1)H-MRSI) and dynamic contrast enhanced MRI (DCE-MRI) data of patients with different prostatic diseases such as chronic inflammation, fibrosis and adenocarcinoma. Multivariate analysis offers a global view of the entire range of information coming from both the imaging and spectroscopic side of NMR technology, leading to an integrated picture of the system relying upon the entire metabolic and dynamic profile of the studied samples. In this study, we show how this approach, applied to (1)H-MRSI/DCE-MRI results, allows us to differentiate among the various prostatic diseases in a non-invasive way with a 100% accuracy. These findings suggest that multivariate analysis of (1)H-MRSI/DCE-MRI can significantly improve the diagnostic accuracy for these pathological entities. From a more theoretical point of view, the complementation of a single biomarker approach with an integrated picture of the entire metabolic and dynamic profile allows for a more realistic appreciation of pathological entities.

New agents and techniques for imaging prostate cancer

The successful management of prostate cancer requires early detection, appropriate risk assessment, and optimum treatment. An unmet goal of prostate cancer imaging is to differentiate indolent from aggressive tumors, as treatment may vary for different grades of the disease. Different modalities have been tested to diagnose, stage, and monitor prostate cancer during therapy. This review briefly describes the key clinical issues in prostate cancer imaging and therapy and summarizes the various new imaging modalities and agents in use and on the horizon.

Tradeoffs of integrating real-time tracking into IGRT for prostate cancer treatment

This study investigated the integration of the Calypso real-time tracking system, based on implanted ferromagnetic transponders and a detector array, into the current process for image-guided radiation treatment (IGRT) of prostate cancer at our institution. The current IGRT process includes magnetic resonance imaging (MRI) for prostate delineation, CT simulation for treatment planning, daily on-board kV and CBCT imaging for target alignment, and MRI/MRS for post-treatment assessment. This study assesses (1) magnetic-field-induced displacement and radio-frequency (RF)-induced heating of transponders during MRI at 1.5 T and 3 T, and (2) image artifacts caused by transponders and the detector array in phantom and patient cases with the different imaging systems. A tissue-equivalent phantom mimicking prostate tissue stiffness was constructed and implanted with three operational transponders prior to phantom solidification. The measurements show that the Calypso system is safe with all the imaging systems. Transponder position displacements due to the MR field are minimal (<1.0 mm) for both 1.5 T and 3 T MRI scanners, and the temperature variation due to MRI RF heating is <0.2 degrees C. The visibility of transponders and bony anatomy was not affected on the OBI kV and CT images. Image quality degradation caused by the detector antenna array is observed in the CBCT image. Image artifacts are most significant with the gradient echo sequence in the MR images, producing null signals surrounding the transponders with radii approximately 1.5 cm and length approximately 4 cm. Thus, Calypso transponders can preclude the use of MRI/MRS in post-treatment assessment. Modifications of the clinical flow are required to accommodate and minimize the substantial MRI artifacts induced by the Calypso transponders.

Biomarkers and imaging: physics and chemistry for noninvasive analyses

The era of ‘modern medicine’ has changed its name to ‘molecular medicine’, and reflects a new age based on personalized medicine utilizing molecular biomarkers in the diagnosis, staging and monitoring of therapy. Alzheimer’s disease has a classical biomarker determined at autopsy with the histologic staining of amyloid accumulation in the brain. Today we can diagnose Alzheimer’s disease using the same classical pathologic biomarker, but now using a noninvasive imaging probe to image the amyloid deposition in a patient and potentially provide treatment strategies and measure their effectiveness. Molecular medicine is the exploitation of biomarkers to detect disease before overt expression of pathology. Physicians can now find, fight and follow disease using imaging, and the need for other disease biomarkers is in high demand. This review will discuss the innovative physical and molecular biomarker probes now being developed for imaging systems and we will introduce the concepts needed for validation and regulatory acceptance of surrogate biomarkers in the detection and treatment of disease.

Radiohalogenated prostate-specific membrane antigen (PSMA)-based ureas as imaging agents for prostate cancer

To extend our development of new imaging agents targeting the prostate-specific membrane antigen (PSMA), we have used the versatile intermediate 2-[3-(5-amino-1-carboxy-pentyl)-ureido]-pentanedioic acid (Lys-C(O)-Glu), which allows ready incorporation of radiohalogens for single photon emission computed tomography (SPECT) and positron emission tomography (PET). We prepared 2-[3-[1-carboxy-5-(4-[(125)I]iodo-benzoylamino)-pentyl]-ureido]-pentanedioic acid ([(125)I]3), 2-[3-[1-carboxy-5-(4-[(18)F]fluoro-benzoylamino)-pentyl]-ureido]-pentanedioic acid ([(18)F]6), and 2-(3-[1-carboxy-5-[(5-[(125)I]iodo-pyridine-3-carbonyl)-amino]-pentyl]-ureido)-pentanedioic acid ([(125)I]8) in 65-80% (nondecay-corrected), 30-35% (decay corrected), and 59-75% (nondecay-corrected) radiochemical yields. Compound [(125)I]3 demonstrated 8.8 +/- 4.7% injected dose per gram (%ID/g) within PSMA(+) PC-3 PIP tumor at 30 min postinjection, which persisted, with clear delineation of the tumor by SPECT. Similar tumor uptake values at early time points were demonstrated for [(18)F]6 (using PET) and [(125)I]8. Because of the many radiohalogenated moieties that can be attached via the epsilon amino group, the intermediate Lys-C(O)-Glu is an attractive template upon which to develop new imaging agents for prostate cancer.

[Magnetic resonance imaging and proton magnetic resonance spectroscopy in the diagnosis of prostate carcinoma ]

PURPOSE

To estimate the diagnostic possibilities of magnetic resonance imaging (MRI) techniques and three-dimensional multivoxel proton magnetic resonance spectroscopy (MRS) in patients with clinical suspicion of prostate carcinoma.

MATERIALS AND METHODS

36 patients suspected to have prostate carcinoma underwent MRI with dynamic contrast enhanced study and MRS at 1.5T MRI unit using a pelvic phased array coil. MRI and MRS results were correlated with pathohystological findings after radical prostatectomy and standard biopsy with 12 or 24 cores or guided biopsy.

RESULTS

Out of 44 detected prostate carcinomas, 38 (86.36%) demonstrated low T2W signal intensity while pathognomonic contrast enhancement has been detected in 40 (91%) carcinomas. MRS showed (Cho+Cr)/Ci ratio mean value of 3.52 in carcinoma, and 0.14 in normal prostatic tissue (p < 0.01).

CONCLUSION

MR techniques, both nonenhanced and contrast enhanced when combined with MRS can provide reliable diagnostic results in the evaluation of prostate carcinoma even by use of pelvic phased array coil at 1.5T unit.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Molecular imaging as a tool for translating breast cancer science

The ability to measure biochemical and molecular processes underlies progress in breast cancer biology and treatment. These assays have traditionally been performed by analysis of cell culture or tissue samples. More recently, functional and molecular imaging has allowed the in vivo assay of biochemistry and molecular biology, which is highly complementary to tissue-based assays. This review briefly describes different imaging modalities used in molecular imaging and then reviews applications of molecular imaging to breast cancer, with a focus on translational work. It includes sections describing work in functional and physiological tumor imaging, imaging gene product expression, imaging the tumor microenvironment, reporter gene imaging, and cell labeling. Work in both animal models and human is discussed with an eye towards studies that have relevance to breast cancer treatment in patients.

Imaging techniques to evaluate the response to treatment in oncology: current standards and perspectives

Response evaluation in solid tumours currently uses radiological imaging techniques to measure changes under treatment. Imaging requires a well-defined anatomical lesion to be viewed and relies on the measurement of a reduction in tumour size during treatment as the basis for presumed clinical benefit. However, with the development of anti-angiogenesis agents, anatomical imaging has became inappropriate as certain tumours would not reduce in size. Functional studies are therefore necessary and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), DCE-computed tomography (CT) and DCE-ultrasonography (US) are currently being evaluated for monitoring treatments. Diffusion-weighted MR imaging (DW-MRI) and magnetic resonance spectroscopy (MRS) are also capable of detecting changes in cell density and metabolite content within tumours. In this article, we review anatomical and functional criteria currently used for monitoring therapy. We review the published data on DCE-MRI, DCE-CT, DCE-US, DW-MRI and MRS. This literature review covers the following area: basic principles of the technique, clinical studies, reproducibility and repeatability, limits and perspectives in monitoring therapy. Anatomical criteria such as response evaluation criteria in solid tumours (RECIST) will require adaptation to employ not only new tools but also different complementary techniques such as functional imaging in order to monitor therapeutic effects of conventional and new anti-cancer agents.