Proton magnetic resonance spectroscopy of the central,transition and peripheral zones of the prostate: assignments and correlation with histopathology

Proton magnetic resonance spectroscopy (MRS) is used to compare the chemistry of the transition, central and peripheral zones of the prostate. The assignments are made using two-dimensional correlated spectroscopy and the results compared with histopathology. The chemistry associated with benign prostatic hyperplasia (BPH), prostate intraepithelial neoplasia (PIN) and malignant biopsy tissues are described. There are distinct MR spectral patterns for glandular and stromal BPH, PIN and adenocarcinoma. Importantly, there are also different spectral patterns from BPH in the transitional and central zones when compared to BPH in the peripheral zone. A pattern recognition method is used to analyze the MR spectra from the biopsy specimens. The resultant mathematical classifiers generated a high level of accuracy (sensitivity and specificity of 100 and 97%). It was found that for this accuracy to be achieved, the classifiers need to be developed by comparing the spectra with specialist serial sectioned histopathology. With serial sectioned pathology the pattern recognition method was capable of identifying less than 5% of adenocarcinoma in a given piece of tissue. Many of the chemicals identified in the biopsy specimens are available for inspection from the prostate, in vivo, at 3 T.     

Measurements of left ventricular dimensions using real-time acquisition in cardiac magnetic resonance imaging: comparison with conventional gradient echo imaging

This study investigates the use of real-time acquisition in cardiac magnetic resonance imaging (MRI) for measurements of left ventricular dimensions in comparison with conventional gradient echo acquisition. Thirty-one subjects with a variety of left ventricular morphologies to represent a typical clinical population were studied. Short-axis data sets of the left ventricle (LV) were acquired using a conventional turbo-gradient echo and an ultrafast hybrid gradient echo/echo planar sequence with acquisition in real-time. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF) and left ventricular mass (LV mass) were measured. The agreement between the two acquisitions and interobserver, intraobserver and interstudy variabilities were determined. The bias between the two methods was 5.86 ml for EDV, 0.23 ml for ESV and 0.94% for EF. LV mass measurements were significantly lower with the real-time method (mean bias 14.38 g). This is likely to be the result of lower spatial resolution and chemical shift artefacts with the real-time method. Interobserver, intraobserver and interstudy variabilities were low for all parameters. In conclusion, real time acquisition in MRI can provide accurate and reproducible measurements of LV dimensions in subjects with normal as well as abnormal LV morphologies, but LV mass measurements were lower than with conventional gradient echo imaging. Presented in abstract form at the International Society of Magnetic Resonance in Medicine meeting in Denver, Colorado in April 2000.     

Proton MR spectroscopy of prostatic tissue focused on the etection of spermine, a possible biomarker of malignant behavior in prostate cancer

To investigate whether polyamines may be valuable diagnostic and prognostic markers in prostate cancer, the presence of alyamines was studied in various human prostatic tissues using both proton magnetic resonance (MR) spectroscopy and righ-pressure liquid chromatography (HPLC). The HPLC results showed that normal and benign hyperplastic prostatic tissues re characterized by a high content of spermine. Spermine levels were reduced in tumor tissue, especially in prostatic carcinoma h metastases, and in xenografts of human prostatic carcinoma cells. These preliminary results indicate that spermine may be d as a biomarker for malignant behavior. The MR spectroscopy study showed that it is possible to detect spermine resonances prostatic biopsy material by one-dimensional and two-dimensional J-resolved MR spectroscopy at high field (600 MHz). ocalized one-dimensional in vitro MR spectra obtained at the clinical field strength of 1.5 T showed spermine signals in the region between 3.0 and 3.3 ppm. In in vivo MR spectra of the human prostate, however, these signals were obscured by esonances of choline (3.2 ppm) and creatine (3.0 ppm).     

Comparison of plain radiographs and magnetic resonance images in the evaluation of periosteal reaction and osteoid matrix in osteosarcomas

To determine the relationship and the degree of agreement between radiographs and MR images for the existence of osteoid matrix and periosteal reactions in the initial diagnosis of osteosarcomas. the plain radiographs and MR studies of 54 patients with proven osteosarcoma were retrospectively evaluated. In each tumor the visualization and type of osseous matrix, periosteal reaction and Codman angle were recorded independently for both techniques and by consensus between two radiologists. In 37 tumors agreement existed regarding osteoid matrix and in 31 cases regarding periosteal reactions. The Kappa statistic showed a significant relationship between both tests (0.49 and 0.44, respectively). Both techniques were also not statistically different in the proportion of findings with the McNemar test. Therefore, the ability of MR images seems important in reporting the MR features of bone tumors. Identification of osteoid mineralization and periosteal reaction can also be used with MR in the diagnosis of osteosarcoma.     

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

Introduction  The optimal management of newly diagnosed prostate cancer requires individualization of the treatment plan based upon the most accurate clinical characterization of tumor location and extent of disease. The role of imaging in prostate cancer staging continues to evolve. In this review, we address the utility of endorectal coil magnetic resonance imaging (eMRI) in both local staging and its ability to facilitate the decision in choosing one treatment strategy over another after the initial diagnosis of localized prostate cancer. Materials and methods  Using the PubMed database and reference lists of key articles, we identified studies addressing the use of eMRI in tumor characterization and risk stratification in patients undergoing treatment for clinically localized prostate cancer. Results  The findings identified within 54 selected studies were incorporated into a summary discussing the current limitations in cancer staging and the role eMRI plays in both the preoperative assessment and clinical decision-making in an attempt to improve our ability to individualize management approaches and tailor treatment. Conclusion  eMRI allows for more accurate local staging by complementing the existing clinical variables through improvements in spatial characterization of the prostatic zonal anatomy and molecular changes. These improvements in tumor staging enhance our ability to individualize treatment selection and tailor the approach to maximize cancer control while minimizing treatment related morbidity.     

Evolution of beta-amyloid induced neuropathology: magnetic resonance imaging and anatomical comparisons in the rodent hippocampus

Alzheimer’s disease (AD) is characterized by the anatomical appearance of β-amyloid (βA) plaques and neurofibrillary tangles. These changes are also associated with cyclical inflammation, oxidative damage and, as inferred from the autopsied brains of patients, progressive injury to neurons. Here, we report the short-term effects of an intrahippocampal injection of the toxic βA peptide fragment 25–35 in rats using quantitative magnetic resonance imaging (MRI) methods. Physiological changes within the cornu ammonis 1 (CA1) region of the hippocampus were monitored using a 1.5 T scanner at time points of 0.25, 1 and 24 h, and 7 and 14 days post injection. Spin echo T2-weighted (T2W) and diffusion weighted (DW) images were sequentially acquired. Apparent diffusion coefficients (ADC) were calculated and compared with histological alterations. A significant elevation in mean ADC values (17%) was observed in the ipsilateral CA1 at 14 days. The ADC changes were associated with disrupted pyramidal cells and nuclear lysis observed in histological sections. The contralateral CA1 exhibited a significant decrease in mean ADC of 15% at 14 days post treatment. Histological changes in the contralateral hippocampus suggested decreased neuronal density. T2W maps revealed no significant differences between the active βA 25–35 fragment and its non-active analog, βA 35–25. In conclusion, these results, based on changes in hippocampal ADC, demonstrate that the βA 25–35 treatment induced pathology consistent with edema and cellular necrosis. This is the first report describing the evolution of AD-like pathology in an animal model using DW imaging.     

Time-domain quantitation of <Superscript>1</Superscript>H short echo-time signals: background accommodation

Quantitation of ¹H short echo-time signals is often hampered by a background signal originating mainly from macromolecules and lipids. While the model function of the metabolite signal is known, that of the macromolecules is only partially known. We present time-domain semi-parametric estimation approaches based on the QUEST quantitation algorithm (QUantitation based on QUantum ESTimation) and encompassing Cramér–Rao bounds that handle the influence of nuisance parameters related to the background. Three novel methods for background accommodation are presented. They are based on the fast decay of the background signal in the time domain. After automatic estimation, the background signal can be automatically (1) subtracted from the raw data, (2) included in the basis set as multiple components, or (3) included in the basis set as a single entity. The performances of these methods combined with QUEST are evaluated through extensive Monte Carlo studies. They are compared in terms of bias–variance trade-off. Because error bars on the amplitudes are of paramount importance for diagnostic reliability, Cramér–Rao bounds accounting for the uncertainty caused by the background are proposed. Quantitation with QUEST of in vivo short echo-time ¹H human brain with estimation of the background is demonstrated.     

Low-field magnetic resonance imaging of the pelvis in patients with anal dynamic graciloplasty: initial experience

The aim of this study was to determine whether low-field magnetic resonance (MR) imaging can safely and accurately depict inflammatory changes in patients with anal dynamic graciloplasty, in whom high-field MR imaging is contraindicated and ultrasonography and computed tomography are inadequate. A 0.2-T field-strength MR examination was performed in six patients with anal dynamic graciloplasty malfunction in whom reoperation was contemplated. The following sequences were applied:T ₂-weighted turbo spinecho with fat saturation,T ₁-weighted conventional spin-echo, and contrastenhancedT ₁-weighted conventional spin-echo with fat saturation. Results indicated that none of the patients experienced relevant discomfort, pacemaker malfunction, or electrode dislocation with low-field MR imaging. Inflammatory pelvic changes were visualized in four patients and atrophy of the transposed gracilis muscle in another. Surgery was thus avoided in the four, who underwent conservative treatment for their pelvic inflammation. It was concluded that these prelininary results demonstrate the feasibility of MR imaging with a low field strength in patients with anal dynamic graciloplasty. In such patients, in whom diagnostic imaging had been problematic, the potential for safe and accurate visualization will be a boon to treatment planning.     

Water household of the common carp,Cyprinus carpio, when submitted to an osmotic challenge, as determined by diffusion-weighted magnetic resonance imaging at 7 T

In vivo diffusion-weighted magnetic resonance imaging (MRI) was used to determine the effects of an osmotic challenge (1% NaCl) to a freshwater fish, the common carp (Cyprinus carpio). The imaged region covered organs such as the swimbladder, the liver, the kidney, the intestine, the spinal cord, and muscle tissue. A striking difference between salt-treated and control fish was found in the liver. The apparent diffusion coefficient value of livers from control fish was (0.39±0.16) 10⁻⁹ m²/s and of salt-treated fish was (1.23±0.14) 10⁻⁹ m²/s, which points to an increase in extracellular water content. These results were partially confirmed by a decrease in dry/wet weight ratio of the liver tissue. We also found increased levels of stress proteins in liver tissue. TheQ factor of the applied radiofrequency coil dropped dramatically when we performed experiments with salt-exposed fish, indicating an increased conductivity resulting from the increased ion concentration and osmolarity of the fish. The data on plasma osmolarity of salt-exposed fish confirm a significant osmolarity increase upon salt exposure (from 334 to 430 mOsm/kg) and exceeded the osmolarity of the salt water (324 mOsm/kg), indicating that carp tend to cope with an increased salinity by increasing the internal osmolarity (hyperosmotic regulation). These data demonstrate that diffusion-weighted MRI might be a useful and noninvasive tool in the study of osmotic challenges of aquatic organisms.     

Glycogen resynthesis in liver and muscle after exercise: measurement of the rate of resynthesis by13C magnetic resonance spectroscopy

We have used natural abundance¹³C magnetic resonance spectroscopy (MRS) to measure glycogen content of muscle and liver before and after heavy exercise, and after consumption of different carbohydrate-based drinks. After an overnight fast, five healthy men (mean±SEM age 23±1 years) exercised to exhaustion at 75% of VO_2max on two occasions (mean work rate 165±8 W for 78±14 min) and then, in a single blind random order, consumed either of two drinks containing the same carbohydrate load (177 g). Spectra were recorded over Vastus Lateralis muscle and the liver before and after exercise, and hourly for 5 h after the carbohydrate load. In muscle, glycogen content after exercise was 37% and 31% of basal (preexercise) concentration before consuming the drinks. After carbohydrate loading, glycogen concentration had increased significantly (p<0.05) to 70% and 64% of basal concentration respectively after 5 h. Hepatic glycogen concentration did not change significantly throughout. The study demonstrates the feasibility of sequential MRS measurement of muscle and liver glycogen before and after exercise and after carbohydrate loading.     

Evaluation of adipose tissue distribution in obese fa/fa Zucker rats by in vivo MR imaging: effects of peroxisome proliferator-activated receptor agonists

High-resolution MRI of obese (fa/fa) Zucker rats was investigated to characterize and assess in vivo adipose tissue distribution. Thirty animals were gavaged with a placebo, a PPAR activator (pioglitazone), or a dual PPAR activator (LM 4156). At day 15, T₁-weighted images were acquired in vivo using a 2TMRI system with a high in-plane spatial resolution (254 m). Fat volumes of selected territories were measured by image segmentation, and the retroperitoneal fat was weighed post-mortem. Body-weight gain was significant with pioglitazone (101.8±5.9 g, p<0.01 vs. placebo). The good quality of MR images allowed the delimitation and quantification of different fat territories. In response to pioglitazone, the retroperitoneal fat was more important compared to placebo (+23%, p<0.01) while subcutaneous fat was not different. No significant effects were observed with LM 4156. In vivo measurements of fat volumes were strongly correlated with ex vivo tissue weights (r=0.91). High-resolution MRI provides an in vivo measurement of adipose tissue distribution in obese Zucker rats. Specific fat depots of regions that were particularly involved in drug response were determined in vivo. Fat remodeling was observed with pioglitazone but not with a dual PPAR activator (LM 4156).