Ayhan Bingölbali

Comparison of optimized long echo time STEAM and PRESS proton MR spectroscopy of lipid olefinic protons at 3 Tesla

To investigate the response of lipid olefinic protons (≈ 5.35 ppm) as a function of STEAM (Stimulated Echo Acquisition Mode) mixing time (TM), and echo time (TE), to find values that resolve the olefinic resonance from water in vivo while retaining sufficient olefinic signal.

Curved crystal x‐ray optics for monochromatic imaging with a clinical source

Monochromatic x-ray imaging has been shown to increase contrast and reduce dose relative to conventional broadband imaging. However, clinical sources with very narrow energy bandwidth tend to have limited intensity and field of view. In this study, focused fan beam monochromatic radiation was obtained using doubly curved monochromator crystals. While these optics have been in use for microanalysis at synchrotron facilities for some time, this work is the first investigation of the potential application of curved crystal optics to clinical sources for medical imaging. The optics could be used with a variety of clinical sources for monochromatic slot scan imaging. The intensity was assessed and the resolution of the focused beam was measured using a knife-edge technique. A simulation model was developed and comparisons to the measured resolution were performed to verify the accuracy of the simulation to predict resolution for different conventional sources. A simple geometrical calculation was also developed. The measured, simulated, and calculated resolutions agreed well. Adequate resolution and intensity for mammography were predicted for appropriate source/optic combinations.

Focused beam powder diffraction with polycapillary and curved crystal optics

Focusing x-ray optics can be used to increase the intensity onto small samples, greatly reducing the data collection time for powder diffraction. Typically, the beam convergence is restricted to avoid loss of resolution since the focused beams broaden the resulting powder diffraction rings. However, the resolution, as defined by the uncertainty in peak location, can be much less than the peak width. Two types of x-ray optics, polycapillary and doubly curved crystals, were used to focus x rays onto standard inorganic powder diffraction samples. Comparisons were made of system resolution and diffracted beam intensity using low power microfocus sources.

Development of polarized and monochromatic x-ray beams from tube sources

The development of sources and optics has allowed the migration of techniques originally developed for synchrotron beam lines to field, industrial and clinical applications. For example, monochromatic beams produced with synchrotron sources are known to give higher contrast for mammography than clinical broadband sources. However, clinical sources with very narrow energy bandwidth, produced for example with flat monochromator crystals, tend to have limited intensity and field of view. Doubly curved crystal x-ray optics can provide intense focused monochromatic fan beams from laboratory x-ray tube sources. These optics are routinely employed in crystallography and x-ray fluorescence, however, careful analysis is required to assess whether the focused beam creates unacceptable divergence and hence poor spatial resolution in imaging. The intensity and resolution of the focused beam were measured and compared to simulation results. The measurements and simulations were in good agreement, allowing for system design to provide the required resolution. High efficiency collimating optics coupled with diffracting crystals also can produce relatively high intensity and resolution. For both methods, monochromatization occurs before the patient, resulting in a potential dose reduction as well as significant measured contrast enhancement. If the diffraction angle is chosen at 90 degrees, a polarized monochromatic beam is produced. While synchrotron sources are naturally polarized, polarized beams have been less accessible for field and clinical applications. Development has begun of polarized beam sources using very low power x-ray tubes coupled to polycapillary optics. The choice of the polarizing and analyzing crystals is a tradeoff between intensity and sensitivity to depolarization effects. Intensity and rocking curve measurements have been performed with matched silicon crystals and graphite crystals.

Analysis of focused‐beam powder X‐ray diffraction resolution using doubly curved crystal optics

In this work, focusing doubly curved crystal X-ray optics were used in powder diffraction to produce an intense spot for use with small powder or polycrystalline samples. Measurements of several standard small inorganic samples were made using a low-power microfocus source. Diffracted peak width, resolution and intensity were analyzed. The measured resolution, defined as the uncertainty in the peak center, was much smaller than the peak width, which was broadened owing to the use of a focused beam. Resolution was limited by the pixel size of the area detector. Resolution and intensity measurements were in good agreement with those obtained from simple geometric analysis and from a Monte Carlo model used to simulate the diffraction ring shape and width.

Küçük hücreli dışı akciğer kanserli hastaların tedavisinde hibrid volümetrik ark radyoterapi, yoğunluk ayarlı radyoterapi ve volumetrik yoğunluk ayarlı ark radyoterapisinin avantajlarını birleştirerek, hızlı, konformal ve homojen bir tedaviyi düşük doz banyosundan sakınarak yapabilmektedir: Dozimetrik çalışma

Intensity Modulated Radiotherapy (IMRT, step and shoot) is emerging as the standard of care in non-small cell lung cancer (NSCLC) patient treatments. Volumetric Arc Therapy (VMAT) delivered with two arcs offers fast and homogeneous dose delivery with known limitations of increased volumes of low dose. The aim of this study is to define whether Hybrid volumetric arc IMRT (HA-IMRT: IMRT and VMAT combination) offers a superior dose distribution over IMRT without the limitations found in VMAT delivery alone. Ten (previously 4DCT planned) locally advanced NSCLC patients treated by IMRT to 70 Gy in 35 fractions were retrospectively re-planned using the HA-IMRT technique. Respiratory correlated imaging (3 mm slice thickness) were generated utilizing the Philips Large Bore 16 slice CT Scanner (Phillips, Inc.). Treatment planning was performed using The Philips Pinnacle Treatment Planning System v. 9.0 (Philips Medical, Cleveland, OH). The PTV was defined as the Integrated Tumor Volume (ITV= internal GTV contoured on all respiratory data sets plus 8 mm margin for all histologies) with a 4 mm margin added. Lung parenchyme was defined and contoured using the 50% phase. Conventional IMRT plans used 6:8 non coplanar or coplanar fields and VMAT plans were generated using two 1800 arcs. HAIMRT plans were generated using a combination of 60% conventional IMRT with 40% VMAT. The maximum dose (Gy) to the spinal cord, V5, V10, V20 for total lung, V20 and V30 for the ipsilateral lung, V30 for heart, V50and V70 for esophagus, and the V77 for the Clinical Treat Volume (CTV) were compared for all techniques utilizing the Dose Volume Histograms. In addition, total monitor units (MU), total treatment time (TT) and the conformality index (CI) were compared. . Conventional IMRT delivers less low dose to the lung compared to VMAT alone. (V5 VMAT (V5: 55.0% vs 63.0%, p= 0.005; V10: 41.4% vs 43.9%, p= 0.018). However, VMAT is superior in total lung V20 (V20:30.6% vs 29.3% p= 0.010), ipsilateral lung doses (V20:55.5% vs 52.8% p= 0.008; V30: 46.1% vs 42.9% p= 0.012), and in heart sparing. (V30: 21.09% vs 17.78% p= 0.015; MHD: 15.92% vs 14.81% p= 0.021). It is also superior in conformality (CI 1.51 vs 1.26 p= 0.005) and treatment delivery is faster ( 293 min vs 108 min p= 0.005) with lower MUs (24805 vs 19141 p= 0.005). HA-IMRT was found to be superior to VMAT in terms of total lung low dose volumes (V5:58.1% vs 63.0%, p= 0.005; V10:42.2% vs 44.9%, p= 0.027), superior to IMRT for ipsilateral lung doses (V20: 53.6% vs 55.5%, p= 0.007; V30: 43.4% vs 46.1%, p= 0.018), and superior in treatment time (199 min vs 293 min, p= 0.005) with lower MU’s (22155 vs 24805, p=.005). Overall, HA-IMRT provides a more homogenous dose distribution (CTV: V77: 0.55% vs 2.1% vs 1.7%, p= 0.000) compared to IMRT and VMAT alone. All three plans provided comparable esophagus and spinal cord Organ at Risk (OAR) doses. HA-IMRT seems to combine the benefits of both conventional IMRT and VMAT; such as to deliver a faster, more conformal, homogeneous treatment in comparison to ssIMRT, and to deliver lower dose to lung in comparison to VMAT.

Comparison of some magnetic multicomponent nanoparticles for biomedical applications

Magnetic nanoparticles (NPs) are increasingly important in many biomedical applications, such as drug delivery, hyperthermia, and magnetic resonance imaging (MRI) contrast enhancement. To build the most effective magnetic nanoparticle systems for various biomedical applications, characteristics of particle, including size, surface chemistry, magnetic properties, and toxicity have to be fully investigated. In this work, comparison of some magnetic multicomponent nanoparticles for bio-medical applications is discussed. In this investigation, multi-component ferrite nanoparticles were prepared by the hydrothermal synthesis, sol-gel, and solid state methods. In addition, x-ray powder diffractometry (XRD), scanning electron microscopy (SEM), and Quantum Design Physical Properties System (PPMS) were used to characterize the structural, morphological and magnetic properties of the nanoparticles. The size and crystal structure of the nanoparticles were characterized by using XRD results. The magnetic properties of the samples were performed for each sample at ± 1.5 T by PPMS.

Effects of number of magnet in halbach magnet system for producing homogeneous magnetic field

Effects of number of magnet in Halbach magnet system for producing homogeneous magnetic field It has been demonstrated that the field homogeneity of the Halbach magnet is high enough to be used in various versions of portable devices such as NMR relaxometer, and MRI. This study discussed effects of the number of magnets used in the Halbach magnet system, and compared their initial simulation outcomes. Two kinds of magnets settlements were modeled and investigated within a multidimensional framework. The simulation outcomes show that the settlements of permanent magnets play important role on the magnetic flux density and homogeneity at the center of the magnet design. The maximum magnetic flux density was obtained at the centre, as expected.

Preparation, structure, and magnetic properties of CuMnFe 2 O 4 nanoparticles for magnetic particle imaging

The crystal structure of the synthesized magnetic nanoparticles was analyzed with XRD and SEM. Effect of doping value on microstructure was analyzed by XRD. Results are shown in Figure 1. The average particles sizes of samples were obtained by nanosize measure of Zeta Sizer Nano-ZS instrument results at room temperature. Particle size determined within 42-57 nm given Table 1.