Unshielded asymmetric transmit-only and endorectal receive-only radiofrequency coil for (23) Na MRI of the prostate at 3 tesla.

BACKGROUND: To develop and optimize radiofrequency (RF) hardware for the detection of endogenous sodium ((23) Na) by 3.0 Tesla (T) MRI in the human prostate. METHODS: A transmit-only receive-only (TORO) RF system of resonators consisting of an unshielded, asymmetric, quadrature birdcage (transmit), and an endorectal (ER), linear, surface (receive) coil were developed and tested on a 3T MRI scanner. Two different ER receivers were constructed; a single-tuned ((23) Na) and a dual-tuned ((1) H/(23) Na). Both receivers were evaluated by the measurements of signal-to-noise ratio (SNR) and B1 homogeneity. For tissue sodium concentration (TSC) quantification, vials containing known sodium concentrations were incorporated into the ER. The system was used to measure the prostate TSC of three men (age 55 ± 5 years) with biopsy-proven prostate cancer. RESULTS: B1 field inhomogeneity of the asymmetric transmitter was estimated to be less than 5%. The mean SNR measured in a region of interest within the prostate using the single-tuned ER coil was 54.0 ± 4.6. The mean TSC in the central gland was 60.2 ± 5.7 mmol/L and in the peripheral gland was 70.5 ± 9.0 mmol/L. CONCLUSION: A TORO system was developed and optimized for (23) Na MRI of the human prostate which showed good sensitivity throughout the prostate for quantitative measurement of TSC.

Sodium 3D COncentration MApping (COMA 3D) using (23)Na and proton MRI.

Functional changes of sodium 3D MRI signals were converted into millimolar concentration changes using an open-source fully automated MATLAB toolbox. These concentration changes are visualized via 3D sodium concentration maps, and they are overlaid over conventional 3D proton images to provide high-resolution co-registration for easy correlation of functional changes to anatomical regions. Nearly 5000/h concentration maps were generated on a personal computer (ca. 2012) using 21.1T 3D sodium MRI brain images of live rats with spatial resolution of 0.8×0.8×0.8 mm(3) and imaging matrices of 60×60×60. The produced concentration maps allowed for non-invasive quantitative measurement of in vivo sodium concentration in the normal rat brain as a functional response to migraine-like conditions. The presented work can also be applied to sodium-associated changes in migraine, cancer, and other metabolic abnormalities that can be sensed by molecular imaging. The MATLAB toolbox allows for automated image analysis of the 3D images acquired on the Bruker platform and can be extended to other imaging platforms. The resulting images are presented in a form of series of 2D slices in all three dimensions in native MATLAB and PDF formats. The following is provided: (a) MATLAB source code for image processing, (b) the detailed processing procedures, (c) description of the code and all sub-routines, (d) example data sets of initial and processed data. The toolbox can be downloaded at: http://www.vuiis.vanderbilt.edu/~truongm/COMA3D/.

Imaging of tumor viability in lung cancer: initial results using 23Na-MRI.

PURPOSE: 23Na-MRI has been proposed as a potential imaging biomarker for the assessment of tumor viability and the evaluation of therapy response but has not yet been evaluated in patients with lung cancer. We aimed to assess the feasibility of 23Na-MRI in patients with lung cancer. MATERIALS AND METHODS: Three patients with stage IV adenocarcinoma of the lung were examined on a clinical 3 Tesla MRI system (Magnetom TimTrio, Siemens Healthcare, Erlangen, Germany). Feasibility of 23Na-MRI images was proven by comparison and fusion of 23Na-MRI with 1H-MR, CT and FDG-PET-CT images. 23Na signal intensities (SI) of tumor and cerebrospinal fluid (CSF) of the spinal canal were measured and the SI ratio in tumor and CSF was calculated. One chemonaive patient was examined before and after the initiation of combination therapy (Carboplatin, Gemcitabin, Cetuximab). RESULTS: All 23Na-MRI examinations were successfully completed and were of diagnostic quality. Fusion of 23Na-MRI images with 1H-MRI, CT and FDG-PET-CT was feasible in all patients and showed differences in solid and necrotic tumor areas. The mean tumor SI and the tumor/CSF SI ratio were 13.3 ± 1.8 × 103 and 0.83 ± 0.14, respectively. In necrotic tumors, as suggested by central non-FDG-avid areas, the mean tumor SI and the tumor/CSF ratio were 19.4 × 103 and 1.10, respectively. CONCLUSION: 23Na-MRI is feasible in patients with lung cancer and could provide valuable functional molecular information regarding tumor viability, and potentially treatment response.

Subcellular imaging of RNA distribution and DNA replication in single mammalian cells with SIMS: the localization of heat shock induced RNA in relation to the distribution of intranuclear bound calcium.

The subcellular localization of RNA for understanding transcriptional activity by using RNA precursors, like 5-bromouridine (BrU), generally requires chemical fixation and staining of cells with monoclonal antibody for imaging BrU-containing RNA in individual cells. Although effective for RNA localization, the native chemical composition of diffusible ions and molecules is destroyed in this approach and one cannot study their spatial relationship with RNA localization sites in this sample type. This work presents a novel secondary ion mass spectrometry approach in cryogenically prepared cells, which allows the same cell imaging of RNA (and/or replicating DNA) distribution in relation to intracellular chemical composition. The heat shock treatment of HeLa cells was used as a model system because the transcription of heat shock genes is activated during heat shock while other transcriptional activities of the cell are suppressed. The HeLa cells were heat-shocked for 1 h at 42 degrees C in presence of 100 muM BrU and/or 100 microM IdU (5-iododeoxyuridine). Following the heat shock treatments, the cells were cryogenically prepared with our sandwich freeze-fracture method and freeze-dried prior to secondary ion mass spectrometry analysis. A CAMECA IMS 3f secondary ion mass spectrometry ion microscope (CAMECA, Paris, France) capable of producing elemental (isotopic) distributions with a spatial resolution of 500 nm was used in the study. Secondary ion mass spectrometry analysis of fractured freeze-dried HeLa cells revealed well-preserved intracellular (39)K and (23)Na concentrations in heat-shocked cells. Both DNA replication and RNA distribution (total RNA) were imaged directly in the same cell by secondary ion mass spectrometry imaging of masses (127)I (from IdU) and (81)Br (from BrU), respectively. Surprisingly, the nucleus of heat-shocked cells contained spatially resolved regions with elevated levels of bound calcium (approximately 0.75 mM total calcium instead of 0.50 mM total calcium in the nucleoplasm). These regions spatially correlated with depleted levels of BrU-RNA in (81)Br secondary ion mass spectrometry images. The remainder of intranuclear regions displayed the presence of BrU-RNA with heterogeneous distribution. These observations indicate that calcium in its bound form may play a fundamental role in processes such as transcription and/or processing and storage of RNA. The shape of intranuclear regions with elevated levels of bound calcium resembled the heat shock induced nuclear bodies in HeLa cells. The analysis of cryogenically prepared frozen freeze-dried cells provides an ideal sample type for further understanding of the role of bound calcium in transcription of genes under physiological and pathological conditions.