Metabolic Magnetic Resonance Spectroscopy Research Articles

Science to Practice: Hyperpolarized Metabolic MR Imaging--The Light at the End of the Tunnel for Clinical (13)C MR Spectroscopy?

Hyperpolarized metabolic magnetic resonance (MR) imaging offers greatly enhanced sensitivity to multinuclear MR spectroscopy, opening up a new tool with which to noninvasively assess metabolic changes in the diseased heart. In this issue of Radiology, O h-Ici et al ( 1 ) have demonstrated this ability by exploring the metabolic changes that occur in the setting of ischemia-reperfusion. They have shown the acute metabolic alterations that occur immediately after reperfusion (increased anaerobic and decreased oxidative metabolism) that then normalize over the following 60 minutes. This demonstration paves the way for the use of hyperpolarized metabolic MR imaging in the assessment of coronary artery disease in humans and shows the potential for this new tool to aid in the assessment of the diseased heart.

Detection of radiation-induced lung injury using hyperpolarized13C magnetic resonance spectroscopy and imaging

Radiation-induced lung injury limits radiotherapy of thoracic cancers. Detection of radiation pneumonitis associated with early radiation-induced lung injury (2–4 weeks postirradiation) may provide an opportunity to adjust treatment, before the onset of acute pneumonitis and/or irreversible fibrosis. In this study, localized magnetic resonance (MR) spectroscopy and imaging of hyperpolarized 13C-pyruvate (pyruvate) and 13C-lactate (lactate) were performed in the thorax and kidney regions of rats 2 weeks following whole-thorax irradiation (14 Gy). Lactate-to-pyruvate signal ratio was observed to increase by 110% (P < 0.01), 57% (P < 0.02), and 107% (P < 0.01), respectively, in the thorax, lung, and heart tissues of the radiated rats compared with healthy age-matched rats. This was consistent with lung inflammation confirmed using cell micrographs of bronchioalveolar lavage specimens and decreases in arterial oxygen partial pressure (paO2), indicative of hypoxia. No statistically significant difference was observed in either lactate-to-pyruvate signal ratios in the kidney region (P = 0.50) between the healthy (0.215 ± 0.100) and radiated cohorts (0.215 ± 0.054) or in blood lactate levels (P = 0.69) in the healthy (1.255 ± 0.247 mmol/L) and the radiated cohorts (1.325 ± 0.214 mmol/L), confirming that the injury is localized to the thorax. This work demonstrates the feasibility of hyperpolarized 13C metabolic MR spectroscopy and imaging for detection of early radiation-induced lung injury. Magn Reson Med 70:601–609, 2013. © 2012 Wiley Periodicals, Inc.

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 ( 1H) proton MR spectroscopy ( 1H 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, 1H MRS may be useful to assess tumor necrosis.

Spectroscopic metabolomic abnormalities in the thalamus related to auditory hallucinations in patients with schizophrenia

ObjectivePrevious studies have found neurochemical abnormalities in thalamic nuclei in patients with schizophrenia. These abnormalities have been associated with information processing deficiencies and symptom formation. There are no metabolic spectroscopy studies in patients with schizophrenia attending to auditory hallucinations. The aim of the present study is to explore metabolic Magnetic Resonance Spectroscopy (MRS) ratio differences in the thalamus between schizophrenic patients with and without auditory hallucinations and control subjects. MethodsMRS studies (MRI 1.5 T unit) were performed in 49 patients with schizophrenia (30 with auditory hallucinations and 19 without auditory hallucinations) and 37 controls. 1H MRS imaging was used to acquire 2 transverse slices (TR/TE 2700/272 ms, region of interest 110×100×23 mm). In the quantitative analysis four elements of volume (9.2×9.2×23×4 mm), added into one spectrum representative of each thalamus, were chosen in the slice passing through the main body of the thalamus. The areas of metabolites were integrated with the jMRUI program. ResultsThe patients with schizophrenia had significantly lower bilateral NAA/Cho ratios when compared with healthy subjects. There was also a lower NAA/Cho ratio in the right thalamus in patients with auditory hallucinations compared to patients without auditory hallucinations and control subjects. Significant correlations were found between metabolic ratios and BPRS, PANSS and PSYRATS scores, age of onset of auditory hallucinations, and age of subjects. ConclusionsCholine and NAA ratio abnormalities determined by thalamic spectroscopy may be related to the pathogenesis of auditory hallucinations in patients with schizophrenia.