Minutes Of Acquisition Time Research Articles

Comparison Between In-Beam and Offline Positron Emission Tomography Imaging of Proton and Carbon Ion Therapeutic Irradiation at Synchrotron- and Cyclotron-Based Facilities

The benefit of using dedicated in-beam positron emission tomography (PET) detectors in the treatment room instead of commercial tomographs nearby is an open question. This work quantitatively compares the measurable signal for in-beam and offline PET imaging, taking into account realistic acquisition strategies at different ion beam facilities. Both scenarios of pulsed and continuous irradiation from synchrotron and cyclotron accelerators are considered, because of their widespread use in most carbon ion and proton therapy centers. A mathematical framework is introduced to compare the time-dependent amount and spatial distribution of decays from irradiation-induced isotope production. The latter is calculated with Monte Carlo techniques for real proton treatments of head-and-neck and paraspinal tumors. Extrapolation to carbon ion irradiation is based on results of previous phantom experiments. Biologic clearance is modeled taking into account available data from previous animal and clinical studies. Ratios between the amount of physical decays available for in-beam and offline detection range from 40% to 60% for cyclotron-based facilities, to 65% to 110% (carbon ions) and 94% to 166% (protons) at synchrotron-based facilities, and increase when including biologic clearance. Spatial distributions of decays during irradiation exhibit better correlation with the dose delivery and reduced influence of biologic processes. In-beam imaging can be advantageous for synchrotron-based facilities, provided that efficient PET systems enabling detection of isotope decays during beam extraction are implemented. For very short (<2 min) irradiation times at cyclotron-based facilities, a few minutes of acquisition time after the end of irradiation are needed for counting statistics, thus affecting patient throughput.

A set of BEST triple-resonance experiments for time-optimized protein resonance assignment

A series of sequential, intra-residue, and bi-directional BEST H–N–CA, H–N–CO, and H–N–CB pulse sequences is presented that extends the BEST concept introduced recently for fast multidimensional protein NMR [Schanda et al., J. Am. Chem. Soc. 128 (2006) 9042] to the complete set of experiments required for sequential resonance assignment. We demonstrate for the protein ubiquitin that 3D BEST H–N–C correlation spectra can be recorded on a 600 MHz NMR spectrometer equipped with a cryogenic probe in only a few minutes of acquisition time with sufficient sensitivity to detect all expected cross peaks.

Speeding Up Three-Dimensional Protein NMR Experiments to a Few Minutes

We demonstrate for different protein samples that three-dimensional HNCO and HNCA correlation spectra may be recorded in a few minutes acquisition time using the band-selective excitation short-transient sequences presented here. This opens new perspectives for the NMR structural investigation of unstable protein samples and real-time site-resolved studies of protein kinetics.

Ultrahigh field magnetic resonance imaging and spectroscopy.

1. IntroductionIn our laboratory, the effort to pursue high magneticfields has been intricately tied to our interest in developingmethods for the acquisition of physiological and biochem-ical information noninvasively using the nuclear spins of thewater molecules and metabolites in the human body. In thiseffort, a relatively recent and unique accomplishment hasbeen the introduction of the ability to map human brainfunction noninvasively. The concurrent and independentwork performed at the University of Minnesota, Center forMagnetic Resonance Research [1] and at MGH [2], was, inour case, conducted at 4 Tesla. It was one of the firstexperiments performed at 4 Tesla in our laboratory. Today,functional images with subcentimeter resolution of the en-tire human brain can be generated in single subjects and indata acquisition times of several minutes using 1.5 TeslaMRI scanners that are often employed in hospitals for clin-ical diagnosis. However, there have been advantages inusing significantly higher magnetic fields such as 4 Tesla,and recently 7 Tesla in humans, and 9.4 Tesla in animalmodels. Similarly, over the last two-and-a-half decades,spectroscopy studies in intact cells have proven to be rich inbiochemical information. However, the most useful of thesestudies were performed in isolated cells or perfused tissues.Only recently, they were extended to small animal modelsusing high magnetic fields. In human applications, spectros-copy efforts pursued at the commonly available magneticfield of 1.5 Tesla were in general unable to produce datacomparable in information to the high field perfusedorgan or animal model data. This has changed with theavailability of ultrahigh magnetic fields for human appli-cations. While the use of very high magnetic fields suchas 7 Tesla in human studies is still in its infancy, the datagathered to date suggest that there are significant gainsfor spectroscopy studies in general and some of theseaccomplishments relevant to high magnetic fields arereviewed in article.2. Imaging using the hydrogen nucleus2.1. Signal-to-noise ratio (SNR)In all NMR experiments, especially in in vivo applica-tions, gains in SNR are the key to extending the applicationsof this phenomenon to new frontiers in research. SNR gainscan be achieved in going to higher fields. SNR, however,becomes rather complex when high magnetic fields (hencehigh frequencies) are considered with lossy biologic sam-ples such as the human body and the human head. Therelationship between SNR and resonance frequency, ,orequivalently field strength has been examined for biologicsamples in numerous studies [3–9], predicting increaseswith field strength. At high frequencies such as 170 MHz(

High resolution electron spin resonance microscopy

NMR microscopy is routinely employed in fields of science such as biology, botany, and materials science to observe magnetic parameters and transport phenomena in small scale structures. Despite extensive efforts, the resolution of this method is limited (>10 μm for short acquisition times), and thus cannot answer many key questions in these fields. We show, through theoretical prediction and initial experiments, that ESR microscopy, although much less developed, can improve upon the resolution limits of NMR, and successfully undertake the 1 μm resolution challenge. Our theoretical predictions demonstrate that existing ESR technology, along with advanced imaging probe design (resonator and gradient coils), using solutions of narrow linewidth radicals (the trityl family), should yield 64 × 64 pixels 2D images (with z slice selection) with a resolution of 1 × 1 × 10 μm at ∼60 GHz in less than 1 h of acquisition. Our initial imaging results, conducted by CW ESR at X-band, support these theoretical predictions and already improve upon the previously reported state-of-the-art for 2D ESR image resolution achieving ∼10 × 10 μm, in just several minutes of acquisition time. We analyze how future progress, which includes improved resonators, increased frequency of measurement, and advanced pulsed techniques, should achieve the goal of micron resolution.

Po-topic I-01: Detection of ischemic areas in the in vivo pig hearts by near-infrared spectroscopic imaging

We hypothesize that near-infrared (NIR) imaging can visualize ischemic areas in the beating heart, highlighting areas of increased deoxy-hemoglobin and -myoglobin (deoxy-(Hb+Mb)) concentrations and reduced flow. Open-chest pigs (n = 6) under general anesthesia were provided with lidocaine (20 μg/min/kg) and glucose (in saline) intravenous infusion over the experimental protocol. The protocol consisted of baseline, occlusion of the left anterior descending artery (LAD) between 2nd and 3rd branches for 90 minutes, and reflow for 120 minutes. ECG-gated NIR images of the heart were obtained using a CCD-array camera with a liquid crystal tunable filter, which acquired absorption spectra in the range of 650–1,050 nm for each of 256 × 256 pixels (< 1 mm2 resolution, 5 minutes acquisition time). Deoxy-, oxy- and total-(Hb+Mb) concentrations were mapped using a spectral fitting algorithm based on their absorption spectra between 650–890 nm. To visualize flow distribution of a bolus of intravascular tracer, indocyanine green (ICG, 12.5 mg/5 mL) was injected intravenously at each step of the protocol and images gated to cardiac cycle were acquired at 800 nm every second over a 3-minute period. Following LAD occlusion deoxy-(Hb+Mb) levels increased and oxy-(Hb+Mb) decreased in the area at risk, determined by the lack of Evans Blue staining (17.3±3.9% of the total ventricular mass). ICG images showed rapid distribution of the dye through the large vessels (LAD and its branches) and capillaries and no dye in the area at risk, indicating severe flow reduction. The areas that remained unstained with ICG coincided with those of increased deoxy-(Hb+Mb) levels. Time courses of ICG absorbance in the normally perfused areas showed rapid absorbance rise (2–5 seconds) with subsequent decrease and equilibration within 1 minute. Reflow restored oxygenation levels at the area at risk and made it accessible to ICG. We conclude that NIR imaging is well suited for visualizing cardiac ischemia in vivo.

PET examination of [ 11C]5-methyl-6-nitroquipazine, a radioligand for visualization of the serotonin transporter

Radiohalogenated 5-halo-6-nitroquipazine analogues have been shown to be potential radioligands for visualization of the serotonin transporter (5-HTT) with PET and SPECT. In the present study a methylated analogue, 5-methyl-6-nitroquipazine (MNQP), was radiolabeled with carbon-11 in a two step reaction via a palladium catalyzed cross coupling reaction between N- t-BOC-protected 5-tributylstannyl-6-nitroquipazine and [ 11C]methyl iodide as key step. [ 11C]MNQP was examined in the cynomolgus monkey brain with positron emission tomography (PET) and the appearance of labeled metabolites in monkey plasma was measured with gradient HPLC. Radioactivity increased continuously in all brain regions during the 90 minutes acquisition time. Highest accumulation of radioactivity was observed in the thalamus and brainstem, regions with a known high density of 5-HTT. The calculated ratios between the thalamus and brainstem to the 5-HTT poor cerebellum were 1.5 and 1.3–1.4, respectively, 80 minutes after radioligand injection. Pretreatment with citalopram prior to the PET measurement markedly reduced the binding in the thalamus and the brainstem. At 15 and 30 minutes after injection of [ 11C]MNQP approximately 90% and 60%, respectively, of radioactivity in plasma represented unchanged radioligand. The slow kinetics and moderate ratios recorded however, may limit its use as a PET radioligand for quantitative studies of the serotonin transporter with PET.

On the phosphorus characterization in thin SiO 2 (P,B) CVD layer deposited onto a silicon substrate by PIXE

In this work the capability of the PIXE technique to monitor a rapid and accurate quantification of P in thin SiO 2 (P,B) CVD layers (400 nm) deposited onto silicon substrate is discussed. In order to improve the sensitivity for P determination, a systematic study was undertaken using protons and helium ion beams at different energies using different thickness of Kapton X-ray absorbers. 600 keV proton or 1.5 MeV helium under normal incidence, using 146 μm Kapton as X-ray absorber, permits an accurate quantification of P with high sensitivity within few minutes of acquisition time. This sensitivity is highly improved when using grazing incidence angles (e.g. 80°), thus 1 MeV protons can be easily used. Finally, the PIXE results show that the phosphorus concentration in the CVD layer varies linearly with the percentage of the phosphine gas used in the CVD gas mixture.

Functional mapping in the human brain using high magnetic fields.

An avidly pursued new dimension in magnetic resonance imaging (MRI) research is the acquisition of physiological and biochemical information non-invasively using the nuclear spins of the water molecules in the human body. In this trial, a recent and unique accomplishment was the introduction of the ability to map human brain function non-invasively. Today, functional images with subcentimetre resolution of the entire human brain can be generated in single subjects and in data acquisition times of several minutes using 1.5 tesla (T) MRI scanners that are often used in hospitals for clinical purposes. However, there have been accomplishments beyond this type of imaging using significantly higher magnetic fields such as 4 T. Efforts for developing high magnetic field human brain imaging and functional mapping using MRI (fMRI) were undertaken at about the same time. It has been demonstrated that high magnetic fields result in improved contrast and, more importantly, in elevated sensitivity to capillary level changes coupled to neuronal activity in the blood oxygenation level dependent (BOLD) contrast mechanism used in fMRI. These advantages have been used to generate, for example, high resolution functional maps of ocular dominance columns, retinotopy within the small lateral geniculate nucleus, true single-trial fMRI and early negative signal changes in the temporal evolution of the BOLD signal. So far these have not been duplicated or have been observed as significantly weaker effects at much lower field strengths. Some of these high-field advantages and accomplishments are reviewed in this paper.

Rapid MRI and velocimetry of cylindrical couette flow

A narrow-gap, temperature-controlled Couette flow rheometer has been developed to study fluid velocities within the annular gap between two concentric cylinders by nuclear magnetic resonance (NMR) imaging and velocimetry. Alternative pulsed-field-gradient-based nuclear magnetic resonance imaging strategies which may be used for measurement of velocity within the Couette flow device have been evaluated. These include two-dimensional (2-D) imaging techniques with acquisition times of several minutes and a one-dimensional (1-D) projection method which exploits the symmetry of the device to reduce overall measurement time to less than 1 min. Velocity measurements made using each technique are presented for a Newtonian fluid undergoing Couette flow at shear rates of approximately 20 and 60 s –1.

Automation of matrix-assisted laser desorption/ionization mass spectrometry using fuzzy logic feedback control.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is a sensitive and versatile method for biomolecular analysis which has potential for high-throughput screening in many applications. To obtain mass spectra of optimal quality, however, laser fluence is continuously adjusted during data acquisition to be close to the threshold level of ion production, requiring a skilled operator and several minutes of acquisition time per sample. Using real-time fuzzy logic control of the laser fluence, we here demonstrate that the acquisition of MALDI spectra can be automated without reduction of data quality. The control algorithm evaluates signal intensity and mass resolution of the base peak. It then regulates the laser fluence to keep the ion signal intensity within the dynamic range of the data acquisition hardware while maintaining high mass resolution. This fuzzy logic control system allows unattended data acquisition using either static ion extraction or delayed ion extraction MALDI. Even for difficult samples such as femtomole-level peptide mixtures, no significant reduction in data quality is observed, as compared to manually obtained spectra. Automated analysis of 78 chromatographic fractions with high mass accuracy demonstrates the utility of the method. The control algorithm has been combined with other software modules to completely automate database identification of proteins by their peptide mass maps. The success of fuzzy logic in MALDI automation suggests wider uses of this technique in mass spectrometry.

NDE and fracture studies of hot-pressed Si3N4 37721 Roberts, R.A.; Singh, J.P.; Vaitekunas, J.J. Argonne National Laboratory, Illinois (United States), DE87-011481 21 pp. (Feb. 1987)

The benefit of using dedicated in-beam positron emission tomography (PET) detectors in the treatment room instead of commercial tomographs nearby is an open question. This work quantitatively compares the measurable signal for in-beam and offline PET imaging, taking into account realistic acquisition strategies at different ion beam facilities. Both scenarios of pulsed and continuous irradiation from synchrotron and cyclotron accelerators are considered, because of their widespread use in most carbon ion and proton therapy centers.A mathematical framework is introduced to compare the time-dependent amount and spatial distribution of decays from irradiation-induced isotope production. The latter is calculated with Monte Carlo techniques for real proton treatments of head-and-neck and paraspinal tumors. Extrapolation to carbon ion irradiation is based on results of previous phantom experiments. Biologic clearance is modeled taking into account available data from previous animal and clinical studies.Ratios between the amount of physical decays available for in-beam and offline detection range from 40% to 60% for cyclotron-based facilities, to 65% to 110% (carbon ions) and 94% to 166% (protons) at synchrotron-based facilities, and increase when including biologic clearance. Spatial distributions of decays during irradiation exhibit better correlation with the dose delivery and reduced influence of biologic processes.In-beam imaging can be advantageous for synchrotron-based facilities, provided that efficient PET systems enabling detection of isotope decays during beam extraction are implemented. For very short (<2 min) irradiation times at cyclotron-based facilities, a few minutes of acquisition time after the end of irradiation are needed for counting statistics, thus affecting patient throughput.

Processing of real-time images for quantitative neutron radiography : 37863 Polichar, R.; Shreve, D. Neutron Radiography, Proceedings of the Second World Conference, Paris (France), 16–20 Jun. 1986. pp. 587–594. D. Reidel Publishing Company

The benefit of using dedicated in-beam positron emission tomography (PET) detectors in the treatment room instead of commercial tomographs nearby is an open question. This work quantitatively compares the measurable signal for in-beam and offline PET imaging, taking into account realistic acquisition strategies at different ion beam facilities. Both scenarios of pulsed and continuous irradiation from synchrotron and cyclotron accelerators are considered, because of their widespread use in most carbon ion and proton therapy centers.A mathematical framework is introduced to compare the time-dependent amount and spatial distribution of decays from irradiation-induced isotope production. The latter is calculated with Monte Carlo techniques for real proton treatments of head-and-neck and paraspinal tumors. Extrapolation to carbon ion irradiation is based on results of previous phantom experiments. Biologic clearance is modeled taking into account available data from previous animal and clinical studies.Ratios between the amount of physical decays available for in-beam and offline detection range from 40% to 60% for cyclotron-based facilities, to 65% to 110% (carbon ions) and 94% to 166% (protons) at synchrotron-based facilities, and increase when including biologic clearance. Spatial distributions of decays during irradiation exhibit better correlation with the dose delivery and reduced influence of biologic processes.In-beam imaging can be advantageous for synchrotron-based facilities, provided that efficient PET systems enabling detection of isotope decays during beam extraction are implemented. For very short (<2 min) irradiation times at cyclotron-based facilities, a few minutes of acquisition time after the end of irradiation are needed for counting statistics, thus affecting patient throughput.

Improvement of reconstructed image quality in neutron CT : 37871 Matsumoto, G.; Sendo, T.; Honda, S.; Ohkubo, K.; Ikeda, Y. Neutron Radiography, Proceedings of the Second World Conference, Paris (France), 16–20 Jun. 1986. pp. 745–752. D. Reidel Publishing Company

The benefit of using dedicated in-beam positron emission tomography (PET) detectors in the treatment room instead of commercial tomographs nearby is an open question. This work quantitatively compares the measurable signal for in-beam and offline PET imaging, taking into account realistic acquisition strategies at different ion beam facilities. Both scenarios of pulsed and continuous irradiation from synchrotron and cyclotron accelerators are considered, because of their widespread use in most carbon ion and proton therapy centers.A mathematical framework is introduced to compare the time-dependent amount and spatial distribution of decays from irradiation-induced isotope production. The latter is calculated with Monte Carlo techniques for real proton treatments of head-and-neck and paraspinal tumors. Extrapolation to carbon ion irradiation is based on results of previous phantom experiments. Biologic clearance is modeled taking into account available data from previous animal and clinical studies.Ratios between the amount of physical decays available for in-beam and offline detection range from 40% to 60% for cyclotron-based facilities, to 65% to 110% (carbon ions) and 94% to 166% (protons) at synchrotron-based facilities, and increase when including biologic clearance. Spatial distributions of decays during irradiation exhibit better correlation with the dose delivery and reduced influence of biologic processes.In-beam imaging can be advantageous for synchrotron-based facilities, provided that efficient PET systems enabling detection of isotope decays during beam extraction are implemented. For very short (<2 min) irradiation times at cyclotron-based facilities, a few minutes of acquisition time after the end of irradiation are needed for counting statistics, thus affecting patient throughput.