Signal-to-noise per unit time optimization for in vivo single-voxel proton magnetic resonance spectroscopy of the brain: Theoretical formulation and experimental verification at two field strengths

Signal-to-noise ratio optimization, regarding repetition time selection, was explored mathematically and experimentally for single-voxel proton magnetic resonance spectroscopy. Theoretical findings were benchmarked against phantom measurements at 1.5 Tesla and localized in vivo proton brain spectra acquired at both 1.5 Tesla/3.0 Tesla. A detailed mathematical description of signal-to-noise ratio per unit time was derived, yielding an optimal repetition time of 1.256 times the metabolite longitudinal relaxation time. While long-repetition-time acquisitions minimize longitudinal relaxation time contributions, a repetition time of ~1.5s results in maximum signal-to-noise ratio per unit time, which can in turn be invested into smaller voxel sizes. The latter is of utmost importance in brain oncology, allowing accurate spectroscopic characterization of small lesions.Comment: 26 pages, 4 figures, submitted to Spectroscopy Letter

Cardiac magnetic resonance imaging R2* assessments and analysis of historical parameters in patients with transfusion-dependent thalassemia

Recent advances in magnetic resonance imaging (MRI) techniques allow the assessment of iron overload in tissues1 especially the heart,2 in transfusion- dependent thalassemia patients. The R2* value (1/T2*) recorded in the intraventricular septum of the heart indirectly measures the degree of cardiac iron load. Applying this new technology we looked at a number of historical and biochemical parameters in order to determine their relationship to cardiac iron overload and the effect of cardiac iron on functional and structural changes of the heart in transfusion-dependent thalassemics

Effect of deferiprone or deferoxamine on right ventricular function in thalassemia major patients with myocardial iron overload

<p>Abstract</p> <p>Background</p> <p>Thalassaemia major (TM) patients need regular blood transfusions that lead to accumulation of iron and death from heart failure. Deferiprone has been reported to be superior to deferoxamine for the removal of cardiac iron and improvement in left ventricular (LV) function but little is known of their relative effects on the right ventricle (RV), which is being increasingly recognised as an important prognostic factor in cardiomyopathy. Therefore data from a prospective randomised controlled trial (RCT) comparing these chelators was retrospectively analysed to assess the RV responses to these drugs.</p> <p>Methods</p> <p>In the RCT, 61 TM patients were randomised to receive either deferiprone or deferoxamine monotherapy, and CMR scans for T2* and cardiac function were obtained. Data were re-analysed for RV volumes and function at baseline, and after 6 and 12 months of treatment.</p> <p>Results</p> <p>From baseline to 12 months, deferiprone reduced RV end systolic volume (ESV) from 37.7 to 34.2 mL (p = 0.008), whilst RV ejection fraction (EF) increased from 69.6 to 72.2% (p = 0.001). This was associated with a 27% increase in T2* (p < 0.001) and 3.1% increase in LVEF (p < 0.001). By contrast, deferoxamine showed no change in RVESV (38.1 to 39.1 mL, p = 0.38), or RVEF (70.0 to 69.9%, p = 0.93) whereas the T2* increased by 13% (p < 0.001), but with no change in LVEF (0.32%; p = 0.66). Analysis of between drugs treatment effects, showed significant improvements favouring deferiprone with a mean effect on RVESV of -1.82 mL (p = 0.014) and 1.16% for RVEF (p = 0.009). Using regression analysis the improvement in RVEF at 12 months was shown to be greater in patients with lower baseline EF values (p < 0.001), with a significant difference in RVEF of 3.5% favouring deferiprone over deferoxamine (p = 0.012).</p> <p>Conclusion</p> <p>In this retrospective analysis of a prospective RCT, deferiprone monotherapy was superior to deferoxamine for improvement in RVEF and end-systolic volume. This improvement in the RV volumes and function may contribute to the improved cardiac outcomes seen with deferiprone.</p

OXYGEN-17 AND NITROGEN-14 NMR STUDIES OF COMPLEXES OF PARAMAGNETIC IONS WITH AMINO ACIDS AND PEPTIDES IN SOLUTION.

OXYGEN-17 AND NITROGEN-14 NMR STUDIES OF COMPLEXES OF PARAMAGNETIC IONS WITH AMINO ACIDS AND PEPTIDES IN SOLUTION

Noninvasive histologic grading of solid astrocytomas using proton magnetic resonance spectroscopy

Background: Proton magnetic resonance spectroscopy (1H MRS) constitutes a promising modality to assess intracranial pathology. We present our experience using this method in grading solid brain astrocytomas. Material and Methods: Using a 1.5-Tesla MRI unit, 71 patients with the radiographic diagnosis of astrocytoma were examined. Water-suppressed single-voxel 1H MRS was employed in all of our patients. The concentrations of choline (Cho), N-acetyl-aspartate (NAA), phosphocreatine-creatine (Pcr-Cr), myo-inositol (MI), lactate (Lac), lipids (Lip) as well as the metabolite ratios of Cho/Pcr-Cr, NAA/PCr-Cr and NAA/Cho were calculated. An appropriate surgical biopsy was performed. Standard pathology examination was employed in a double-blinded fashion. Results: An increased concentration of Cho and decreased concentrations of Pcr-Cr and NAA were detected. The concentrations of Lac, Lip and MI varied inconsistently, even among tumors of the same histologic grade. The Cho/Pcr-Cr ratio was calculated. This ratio was found to be 2.15 ± 0.26 in 27 patients with astrocytomas grade I and II, 2.78 ± 0.09 in 18 patients with grade III, and 5.40 ± 0.16 in 26 patients with grade IV. Discussion: The increased concentration of Cho is due to the increased cellularity and a relatively increased number of membranous structures in highly malignant tumors. In abnormal anaerobic metabolic tumor states there is relatively less phosphorylization of creatine. By using the Cho/Pcr-Cr ratio the concomitant effects of structural and metabolic alteration can thereby be emphasized for diagnostic advantage. Conclusion: The Cho/ Pcr-Cr is a very important and statistically significant marker (p = 0.043) determining the degree of intracranial astrocytoma malignancy. Copyright © 2004 S. Karger AG, Basel

Effect of deferiprone or deferoxamine on right ventricular function in thalassemia major patients with myocardial iron overload

Background: Thalassaemia major (TM) patients need regular blood transfusions that lead to accumulation of iron and death from heart failure. Deferiprone has been reported to be superior to deferoxamine for the removal of cardiac iron and improvement in left ventricular (LV) function but little is known of their relative effects on the right ventricle (RV), which is being increasingly recognised as an important prognostic factor in cardiomyopathy. Therefore data from a prospective randomised controlled trial (RCT) comparing these chelators was retrospectively analysed to assess the RV responses to these drugs. Methods: In the RCT, 61 TM patients were randomised to receive either deferiprone or deferoxamine monotherapy, and CMR scans for T2* and cardiac function were obtained. Data were re-analysed for RV volumes and function at baseline, and after 6 and 12 months of treatment. Results: From baseline to 12 months, deferiprone reduced RV end systolic volume (ESV) from 37.7 to 34.2 mL (p = 0.014), whilst RV ejection fraction (EF) increased from 69.6 to 72.2% (p = 0.001). This was associated with a 27% increase in T2* (p &lt; 0.001) and 3.1% increase in LVEF (p &lt; 0.001). By contrast, deferoxamine showed no change in RVESV (38.1 to 39.1 mL, p = 0.38), or RVEF (70.0 to 69.9%, p = 0.93) whereas the T2* increased by 13% (p &lt; 0.001), but with no change in LVEF (0.32%; p = 0.66). Analysis of between drugs treatment effects, showed significant improvements favouring deferiprone with a mean effect on RVESV of-1.82 mL (p = 0.013) and 1.16% for RVEF (p = 0.008). Using regression analysis the improvement in RVEF at 12 months was shown to be greater in patients with lower baseline EF values (p &lt; 0.001), with a significant difference in RVEF of 3.5% favouring deferiprone over deferoxamine (p = 0.012). Conclusion: In this retrospective analysis of a prospective RCT, deferiprone monotherapy was superior to deferoxamine for improvement in RVEF and end-systolic volume. This improvement in the RV volumes and function may contribute to the improved cardiac outcomes seen with deferiprone