How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

It is well known that inter-crystal scattering and penetration(ICS-P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated crystal.In this study,the effect of ICS-P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation.A ^(99m)Tc pencil-beam toward central crystal element was utilized.Beam incident angle was assumed to vary from 0° to 45° in 5° steps.The effects of various crystal configurations such as pixel-size,pixel-gap,and crystal material were studied.The influence of photon energy on the crystal identification(CI) was also investigated.Position detection accuracy(PDA) was defined as a factor indicating performance of the crystal.Furthermore,a set of ^(99m)Tc point-source simulations was performed in order to calculate peak-to-valley(PVR) ratio for each configuration.The results show that the CsI(Na)manifests higher PDA than NaI(TI) and YAP(Ce).In addition,as the incident angle increases,the crystal becomes less accurate in positioning of the events.Beyond a crystal-dependent critical angle,the PDA monotonically reduces.The PDA reaches 0.44 for the CsI(Na) at 45° beam angle.The PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam irradiations.In addition,the PVRs derived from flood images linearly correlate their corresponding PDAs.In conclusion,quantitative assessment of ICS-P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.

Radiation-induced inflammation and autoimmune diseases

Currently,ionizing radiation(IR)plays a key role in the agricultural and medical industry,while accidental exposure resulting from leakage of radioactive sources or radiological terrorism is a serious concern.Exposure to IR has various detrimental effects on normal tissues.Although an increased risk of carcinogenesis is the best-known long-term consequence of IR,evidence has shown that other diseases,particularly diseases related to inflammation,are common disorders among irradiated people.Autoimmune disorders are among the various types of immune diseases that have been investigated among exposed people.Thyroid diseases and diabetes are two autoimmune diseases potentially induced by IR.However,the precise mechanisms of IR-induced thyroid diseases and diabetes remain to be elucidated,and several studies have shown that chronic increased levels of inflammatory cytokines after exposure play a pivotal role.Thus,cytokines,including interleukin-1(IL-1),tumor necrosis factor(TNF-α)and interferon gamma(IFN-α),play a key role in chronic oxidative damage following exposure to IR.Additionally,these cytokines change the secretion of insulin and thyroid-stimulating hormone(TSH).It is likely that the management of inflammation and oxidative damage is one of the best strategies for the amelioration of these diseases after a radiological or nuclear disaster.In the present study,we reviewed the evidence of radiation-induced diabetes and thyroid diseases,as well as the potential roles of inflammatory responses.In addition,we proposed that the mitigation of inflammatory and oxidative damage markers after exposure to IR may reduce the incidence of these diseases among individuals exposed to radiation.

Quantification of the impact of TOF and PSF on PET images using the noise-matching concept: clinical and phantom study

This study was to assess quantitatively the accuracy of ^(18)F-FDG PET/CT images reconstructed by TOF+PSF and TOF only, considering the noise-matching concept to minimize probable bias in evaluating algorithm performance caused by noise. PET images of similar noise level were considered. Measurements were made on an inhouse phantom with hot inserts of Φ10–37 mm, and oncological images of 14 patients were analyzed. The PET images were reconstructed using the OSEM, OSEM+TOF and OSEM+TOF+PSF algorithms. Optimal reconstruction parameters including iteration, subset, and FWHM of post-smoothing filter were chosen for both the phantom and patient data. In terms of quantitative accuracy, the recovery coefficient(RC) was calculated for the phantom PET images. The signal-to-noise ratio(SNR),lesion-to-background ratio(LBR), and SUV_(max)were evaluated from the phantom and clinical data. The smallest hot insert(Ф10 mm) with 2:1 activity concentration ratio could be detected in the PET image reconstructed using the TOF and TOF+PSF algorithms, but not the OSEM algorithm. The relative difference for SNR between the TOF+PSF and OSEM showed significantly higher values for smaller sizes, while SNR change was smaller for Ф22–37 mm inserts both 2:1 and 4:1 activity concentration ratio. In the clinical study, SNR gains were 1.6 ± 0.53 and 2.7 ± 0.74 for the TOF and TOF+PSF, while the relative difference of contrast was 17 ± 1.05 and 41.5 ± 1.85% for the TOF only and TOF+PSF, respectively. The impact of TOF+PSF is more significant than that of TOF reconstruction, in smaller inserts with low activity concentration ratio. In the clinical PET/CT images, the use of the TOF+PSF algorithm resulted in better SNR and contrast for lesions, and the highest SUV_(max)was also seen for images reconstructed with the TOF+PSF algorithm.

Characterization of Cysteine Coated Magnetite Nanoparticles as MRI Contrast Agent

In this work,a kind of stabilized ferrofluid based on magnetite nanoparticles(mean core and its coating size about 21.9 and 1.6 nm,respectively)was synthesized via coprecipitation method.Cysteine was used as surfactant due to its proper conjunction to the surface of magnetite nanoparticles.Coating density and synthesized ferrofluids were characterized by using transmission electron microscope,thermogravimetry analysis,dynamic light scattering and fourier transform infrared spectroscopy techniques.Magnetic resonance imaging studies show that the synthesized ferrofluid can be used as a potential contrast enhancement agent especially for imaging lymphatic system.

The Role of Baseline Functional MRI as a Predictor of Post-Stroke Rehabilitation Efficacy in Patients with Moderate to Severe Upper Extremity Dysfunction

Introduction: Upper extremity impairment is one of the common complications following a stroke. There are numerous rehabilitation strategies to address this problem. However, patients with moderate to severe upper limb disabilities respond differently to the same rehabilitation protocol. Apart from each patient’s unique characteristics, there are specific brain reorganizing patterns that affect the post-rehabilitation response rate. Functional magnetic resonance imaging (fMRI) determines brain activation area and connectivity patterns and has been utilized in the neurorehabilitation field. Material and Methods: Six stroke patients who suffered from moderate to severe upper extremity dysfunction were enrolled in this pilot study. Upper extremity function tests including the Fugl-Meyer assessment test for upper extremity (FMA-UE), and Wolf Motor Function Test (WMFT) were utilized before and after completing an intensive rehabilitation. The intensive rehabilitation program was conducted one hour a day for five days per week for four weeks. Moreover, fMRI was applied before initiating rehabilitation. The regions of interest were those associated with movement, including Brodmann areas (BA) BA1-BA6. Results: Six stroke patients in the sub-acute to chronic phase and ages ranging between 33 - 75 years were enrolled. All patients showed an improvement in upper limb function after four weeks of rehabilitation. Patient number one (Pt1) had the most improvement in FMA-UE, while patient number four (Pt4) recovered the most measured by WMFT. Pt1 demonstrated increased activity in all contralesional regions, whereas Pt4 had only increased activity in ipsilesional areas. Furthermore, patients with greater activation in the ipsilesional BA6 (Pt1, Pt4, Pt5, and Pt6) had better responses to the rehabilitation therapy. Conclusion: Patients with greater activation in the baseline fMRI, particularly ipsilesional BA6, had a better response to the intensive rehabilitation therapy. However, the patients with the most severe hand dysfunction showed lesser improvement despite the same brain activity as others in the initial fMRI.

A new three-dimensional elastography using phase based shifted Fourier transform

Elastography is an imaging technique with the ability to determine low quantities of some of the mechanical properties of tissues.The aim of our research is to design a new 3D algorithm using the Shifted Fourier Transform(SFT)to perform a quasi-static elastography.Our innovative idea is implementation of a 3D convolution instead of using three 2D convulsions.At first,we collected the raw data from Abaqus engineering software in the form of breast tissue with a coefficient of elasticity of healthy tissue and tumor tissue with a coefficient of elasticity of tumor tissue.The primary raw data consists of a number of points with x,y and z specified for tumor and healthy breast tissue.At this step,we simulated the displacements in directions of x,y and z at each point of the prescribed tissues for 15 mm displacement of probe in–Y direction then we collected 1831 points for tumor and 4186 points for breast before and after pressure.After applying a novel reconstruction algorithm,we convolved all images with the 3D Gabor filters to obtain phases,represented displacements of the breast and tumor images for before and after pressure.To reach this goal,we designed a Gabor filter bank based on the dimensions of the input images in different scales,directions,and deviations.Using the 3D SFT,we calculated the displacements of the breast and tumor tissues followed by 3D elastogram representation of the images.Finally,we implemented a 2D analysis of SFT in order to investigate validation of the 3D SFT.In 2D algorithm,we used three two-dimensional convulsions in XY,YZ and XZ planes.The results obtained from the small displacements marked by circles,confirmed the accuracy of the 3D SFT algorithm.These areas of interest are the tumor areas in the 2D analysis.

Lipoid Proteinosis Due to Homozygous Deletion Mutation(c.735delTG)in the ECM1 Gene Presents with Seizures and Hoarseness but No Skin Involvement

Histopathology The histopathological features of bowenoid papulosis(BP)are hyperkeratosis,focal keratosis,acanthosis,and cellular atypia of the epidermis characterized by hyperchromatic nuclei,prominent nucleoli,mitotic figures,epidermal multinucleated giant cells,and dyskeratotic cells.1 Slight or moderate perinuclear vacuole formation is occasionally observed.Histopathologically,BP shows similar but generally milder changes compared with Bowen's disease.Dilated capillaries and perivascular diffuse infiltration of lymphocytes can be observed in the upper dermis.The most characteristic finding of BP is an occasional transformation of bowenoid atypia to benign proliferation as time progresses,especially during the course of spontaneous regression.1 Parakeratosis,acanthosis,scattered cellular atypia of the epidermis,dyskeratotic cells,dilated capillaries,and perivascular diffuse infiltration of lymphocytes,all of which are typical histopathological features of BP,were observed in our patient(Fig.1).