Value of Emergent Neurovascular Imaging for "Seat Belt Injury": A Multi-institutional Study.

BACKGROUND AND PURPOSE: Screening for blunt cerebrovascular injury in patients after motor vehicle collision (MVC) solely based on the presence of cervical seat belt sign has been debated in the literature without consensus. Our aim was to assess the value of emergent neurovascular imaging in patients after an MVC who present with a seat belt sign through a large-scale multi-institutional study. MATERIALS AND METHODS: The electronic medical records of patients admitted to the emergency department with CTA/MRAs performed with an indication of seat belt injury of the neck were retrospectively reviewed at 5 participating institutions. Logistic regression analysis was used to determine the association among age, sex, and additional trauma-related findings with blunt cerebrovascular injury. RESULTS: Five hundred thirty-five adult and 32 pediatric patients from June 2003 until March 2020 were identified. CTA findings were positive in 12/567 (2.1%) patients for the presence of blunt cerebrovascular injury of the vertebral (n = 8) or internal carotid artery (n = 4) in the setting of acute trauma with the seat belt sign. Nine of 12 patients had symptoms, signs, or risk factors for cervical blunt cerebrovascular injury other than the seat belt sign. The remaining 3 patients (3/567, 0.5%) had Biffl grades I-II vascular injury with no neurologic sequelae. The presence of at least 1 additional traumatic finding or the development of a new neurologic deficit was significantly associated with the presence of blunt cerebrovascular injury among adult patients, with a risk ratio of 11.7 (P = .001). No children had blunt cerebrovascular injury. CONCLUSIONS: The risk of vascular injury in the presence of the cervical seat belt sign is small, and most patients diagnosed with blunt cerebrovascular injury have other associated findings. Therefore, CTA based solely on this sign has limited value (3/567 = a 0.5% positivity rate). We suggest that in the absence of other clinical findings, the seat belt sign does not independently justify neck CTA in patients after trauma.

Radiofrequency ablation of the spleen in patients with thalassemia intermedia: a pilot study.

OBJECTIVE: We investigated the efficacy and safety of radiofrequency ablation on the hematologic parameters in patients with thalassemia intermedia (TI). MATERIALS AND METHODS: Radiofrequency ablation of the spleen was performed in 15 children with TI under general anesthesia using a cool-tip radiofrequency probe. These patients were regarded as the radiofrequency ablation group. Nine patients with TI who underwent partial splenectomy during the past 3 years and another 14 patients with TI who underwent total splenectomy were also enrolled in this study as the first and second control groups (CG1 and CG2). RESULTS: In the radiofrequency ablation group, two (13%) patients showed a significant increase in the mean hemoglobin level compared with the year before (1.5 and 1.8 g/dL). In addition, three (20%) other patients became transfusion-free in the year after radiofrequency ablation. In CG1, one (11%) patient showed a significant increase in hemoglobin the year after partial splenectomy, and another two (22%) patients became transfusion-free. In CG2, six (43%) patients revealed a significant increase in hemoglobin in the year after total splenectomy, and another four (29%) revealed a significant decrease in the need for transfusions. The mean increase in hemoglobin and platelet count was more significant in CG2 than in the radiofrequency ablation group and CG1. The mean hospital stay was significantly shorter in the radiofrequency ablation group (1.7 days vs 7.5 and 8.2 days in CG1 and CG2, respectively). CONCLUSION: We believe that radiofrequency ablation of the spleen can be a safe procedure in patients with TI and is at least as effective as partial splenectomy, having only minor self-limiting complications.

Clinical trials in dermatology.

Clinical trials are the backbone of modern day medicine. Randomized, double-blinded, placebo-controlled studies are critical for advancement in medicine and dermatology. Skin conditions such as psoriasis and atopic dermatitis are among the most common health problems in the United States. Clinical trials can provide treatments that not only offer objective improvements in clinical disease status but also subjective improvements in the quality of life of patients who are afflicted with the disease. In this article, we discuss the processes and resources of a clinical trials unit and the challenges that can be encountered during the study process. It is critical to engage in clinical trials to treat patients most effectively with new and innovative therapies that are rooted in trial-validated, evidence-based medicine.

Estimation of contrast agent concentration in intra- and extra-vascular spaces of brain tissue.

This article presents a new method for estimating the leakage of a contrast agent out of a vessel. The proposed method is developed based on tissue homogeneity (TH) model, modified Patlak model, and Monte Carlo simulation. The analytical methods published in the literature estimate the contrast agent leakage by solving the coupled differential equations associated with the TH model under adiabatic conditions. These methods employ unrealistic simplifying assumptions and become intractable in their applications to the vessels that have a non-uniform permeability. Without making any unrealistic assumptions, our approach simply tracks the passage of the contrast agent through the capillary and its crossing of the vessel walls based on the blood flow in the vessel, the vessel's permeability, and the condition of the blood-brain barrier (BBB). These are treated as statistical processes that can be modeled reasonably well using the Monte Carlo method. In the proposed approach, the intra- and extra-vascular spaces are divided into multiple compartments, similar to the Patlak model. A real, measured arterial input function (AIF) is used as the capillary input and the concentration of the contrast agent is found as a function of time and distance, inside and outside of the capillary. This is done for normal and abnormal capillaries with uniform and non-uniform permeability. The proposed method generates concentration curves similar to those of the analytical method for simple AIF models. It also generates reasonable concentration curves for a real AIF. The proposed method does not fit a mathematical function to the measured AIF and does not make unrealistic simplifying assumptions. It is not therefore prone to the fitting errors and generates more realistic and more accurate results than the analytical methods.

Assessment of different computational models for generation of x-ray spectra in diagnostic radiology and mammography.

Different computational methods based on empirical or semi-empirical models and sophisticated Monte Carlo calculations have been proposed for prediction of x-ray spectra both in diagnostic radiology and mammography. In this work, the x-ray spectra predicted by various computational models used in the diagnostic radiology and mammography energy range have been assessed by comparison with measured spectra and their effect on the calculation of absorbed dose and effective dose (ED) imparted to the adult ORNL hermaphroditic phantom quantified. This includes empirical models (TASMIP and MASMIP), semi-empirical models (X-rayb&m, X-raytbc, XCOMP, IPEM, Tucker et al., and Blough et al.), and Monte Carlo modeling (EGS4, ITS3.0, and MCNP4C). As part of the comparative assessment, the K x-ray yield, transmission curves, and half value layers (HVLs) have been calculated for the spectra generated with all computational models at different tube voltages. The measured x-ray spectra agreed well with the generated spectra when using X-raytbc and IPEM in diagnostic radiology and mammography energy ranges, respectively. Despite the systematic differences between the simulated and reference spectra for some models, the student's t-test statistical analysis showed there is no statistically significant difference between measured and generated spectra for all computational models investigated in this study. The MCNP4C-based Monte Carlo calculations showed there is no discernable discrepancy in the calculation of absorbed dose and ED in the adult ORNL hermaphroditic phantom when using different computational models for generating the x-ray spectra. Nevertheless, given the limited flexibility of the empirical and semi-empirical models, the spectra obtained through Monte Carlo modeling offer several advantages by providing detailed information about the interactions in the target and filters, which is relevant for the design of new target and filter combinations and optimization of radiological imaging protocols.

Slit slat collimator optimization with respect to MTF.

Conventional single photon emission computed tomography (SPECT) collimators are not suitable for 511 keV imaging. In order to use a SPECT system for single positron emission tomography (SPET), we need to design high-efficiency collimators capable of absorbing 511 keV photons. Slit slat (SS) collimators have been proposed for this purpose even though the optimization of such collimators has not yet been performed. In order to investigate the reliability of the system with SS collimator, it was decided to evaluate such a system. A gamma camera system with both parallel hole (PH) and SS collimators was simulated by Monte Carlo method. In these simulation parameters of the simulated system having 3/8 in NaI(Tl) crystal for 140 keV gamma-rays with PH collimator was compared with practical results and a good correlation was found between the simulated and practical results. In this way, the validity of our simulation code was confirmed. The crystal thickness for simulated gamma-camera system with SS collimator for detection of 511 keV photons was set to be 5/8 in which resulted in an intrinsic spatial resolution of 4mm. The simulated SS collimators consisted of 50 lead plates of various height, thickness and spacing. The imaging was performed by rotating the SS collimator from 0 degrees to 180 degrees in 73 steps of 2.5 degrees each. The physical parameters such as spatial resolution, efficiency and modulation transfer function (MTF) of this system for different SS collimator designs, (i.e. SS(64,3,3), SS(80,3,3), SS(64,4,5), SS(80,4,5), SS(85,4,5), where in SS(h,s,t) is used to indicate the septal height (h), septal separation (s), and septal thickness (t) in millimeters were evaluated. The value of these parameters were compared with the values obtained employing a 511 keV PH(85,4,2.5) collimator. Based on MTF values, our result showed that the SS(85,4,5) collimator has an optimum performance to the other SS collimators. The relative efficiency of the system with SS(85,4,5) collimator was about 20 times higher than the efficiency of the system with the PH(85,4,2.5) collimator whereas in this case the spatial resolution had deteriorated by almost 8% (i.e. from 14.1 to 15.0 mm). The result of this study shows that the SS collimators have great advantages over the conventional PH collimators for 511 keV imaging, providing much higher efficiency while maintaining a comparable spatial resolution. Employing this collimator makes it possible to use a SPECT system for metabolic imaging by SPET system.

Monte carlo simulation of x-ray spectra in diagnostic radiology and mammography using MCNP4C.

The general purpose Monte Carlo N-particle radiation transport computer code (MCNP4C) was used for the simulation of x-ray spectra in diagnostic radiology and mammography. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and characteristic x-ray production were considered in this work. We focus on the simulation of various target/filter combinations to investigate the effect of tube voltage, target material and filter thickness on x-ray spectra in the diagnostic radiology and mammography energy ranges. The simulated x-ray spectra were compared with experimental measurements and spectra calculated by IPEM report number 78. In addition, the anode heel effect and off-axis x-ray spectra were assessed for different anode angles and target materials and the results were compared with EGS4-based Monte Carlo simulations and measured data. Quantitative evaluation of the differences between our Monte Carlo simulated and comparison spectra was performed using student's t-test statistical analysis. Generally, there is a good agreement between the simulated x-ray and comparison spectra, although there are systematic differences between the simulated and reference spectra especially in the K-characteristic x-rays intensity. Nevertheless, no statistically significant differences have been observed between IPEM spectra and the simulated spectra. It has been shown that the difference between MCNP simulated spectra and IPEM spectra in the low energy range is the result of the overestimation of characteristic photons following the normalization procedure. The transmission curves produced by MCNP4C have good agreement with the IPEM report especially for tube voltages of 50 kV and 80 kV. The systematic discrepancy for higher tube voltages is the result of systematic differences between the corresponding spectra.

Borehole parametric study for neutron induced capture gamma-ray spectrometry using the MCNP code.

The MCNP Monte Carlo code has been used to simulate neutron transport from an Am-Be source into a granite formation surrounding a borehole. The effects of the moisture and the neutron poison on the thermal neutron flux distribution and the capture by the absorbing elements has been calculated. Thermal and nonthermal captures for certain absorbers having resonance structures in the epithermal and fast energy regions such as W and Si were performed. It is shown that for those absorbers having large resonances in the epithermal regions when they are present in dry formation or when accompanied by neutron poisons the resonance captures may be significant compared to the thermal captures.

Gamma irradiator dose mapping simulation using the MCNP code and benchmarking with dosimetry.

The Monte Carlo transport code, MCNP, has been applied in simulating dose rate distribution in the IR-136 gamma irradiator system. Isodose curves, cumulative dose values, and system design data such as throughputs, over-dose-ratios, and efficiencies have been simulated as functions of product density. Simulated isodose curves, and cumulative dose values were compared with dosimetry values obtained using polymethyle-methacrylate, Fricke, ethanol-chlorobenzene, and potassium dichromate dosimeters. The produced system design data were also found to agree quite favorably with those of the system manufacturer's data. MCNP has thus been found to be an effective transport code for handling of various dose mapping excercises for gamma irradiators.

Prevalence of endocrine complications in beta-thalassaemia major in the Islamic Republic of Iran.

To identify the prevalence of endocrine dysfunction in Iranians with beta-thalassaemia, we assessed thyroid, parathyroid, pancreatic and adrenal function in 150 beta-thalassaemic patients aged 10-22 years at the Paediatrics Unit, Shiraz University of Medical Sciences. Primary hypothyroidism was found in 6.0% of patients (mean age: 14.6 +/- 1.9 years), hypoparathyroidism in 7.3% (14.5 +/- 3.2 years), type 1 diabetes mellitus in 7.3% (13.9 +/- 2.8 years) and adrenal insufficiency in 1 patient. The relatively high frequency of endocrine dysfunction found in our study may be a result of poor disease control and management in early life when irreversible tissue damage occurs due to iron overload. These findings reinforce the importance of regular follow-up of patients with beta-thalassaemia major for early detection and management of associated complications.

Monte Carlo simulation of X-ray spectra and evaluation of filter effect using MCNP4C and FLUKA code.

The general-purpose MCNP4C and FLUKA codes were used for simulating X-ray spectra. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and characteristic X-ray production were considered in this work. Tungsten/aluminum combination was used as target/filter in the simulation. The results of two codes were generated in 80, 100, 120 and 140 kV and compared with each other. In order to survey filter effect on X-ray spectra, the attenuation coefficient of filter was calculated in 120 kV. More details of filter effect have been investigated. The results of MCNP4C and FLUKA are comparable in the range of bremsstrahlung spectra, but there are some differences between them especially in specific X-ray peaks. Since the specific peaks have not significant role on image quality, both FLUKA and MCNP4C codes are fairly appropriate for production of X-ray spectra and evaluating image quality, absorbed dose and improvement in filter design.

Unfolding the neutron spectrum of a NE213 scintillator using artificial neural networks.

Artificial neural networks technology has been applied to unfold the neutron spectra from the pulse height distribution measured with NE213 liquid scintillator. Here, both the single and multi-layer perceptron neural network models have been implemented to unfold the neutron spectrum from an Am-Be neutron source. The activation function and the connectivity of the neurons have been investigated and the results have been analyzed in terms of the network's performance. The simulation results show that the neural network that utilizes the Satlins transfer function has the best performance. In addition, omitting the bias connection of the neurons improve the performance of the network. Also, the SCINFUL code is used for generating the response functions in the training phase of the process. Finally, the results of the neural network simulation have been compared with those of the FORIST unfolding code for both (241)Am-Be and (252)Cf neutron sources. The results of neural network are in good agreement with FORIST code.

Active silica-gel films for hydrogen sulfide optical sensor application.

We have developed a novel H(2)S-sensitive film by immobilizing thionine in a silica matrix by means of the solgel process. The film is stable, reversible, and sensitive to dissolved H(2)S to as low as parts-per-billion levels. The photochemical instability of thionine in basic solution has been improved dramatically by use of this immobilization technique and silica substrate. Based on the developed new films, sensors for monitoring H(2)S may be prepared either by a fiber-optic approach or by integrated optical circuit techniques.

Porous optical fibers for high-sensitivity ammonia-vapor sensors.

A new porous glass optical fiber has been developed for use as a sensor for the detection of ammonia vapors at low concentrations. The porous structure that remains after selective heat treatment, phase separation, and chemical leaching of a borosilicate glass imparts a high surface area to the fiber core. Ammonia vapors permeating into the porous zone, which is pretreated with a reversible pH dye indicator, produce a spectral change in transmission. The resulting pH change is measured by in-line optical absorbance and is proportional to the ambient-ammonia concentration. Ammonia-vapor concentrations as low as 0.7 part in 10(6) have been detected.

Development of a porous polymer pH optrode.

A novel fiber-optic pH sensor has been developed with long-term stability and high sensitivity. The sensor is based on a porous cellulose triacetate fiber immobilized with Congo Red (pH indicator). This intrinsic fiberoptic pH sensor has shown excellent sensitivity, reversibility, and stability. It has also been demonstrated that the pH optrode is immune to metal-ion interferences.

Remote infrared chemical sensing using highly durable AlF(3)-based glass fibers.

Unclad, low-loss AlF(3)-based glass fibers with enhanced chemical durability have been successfully used for the first time to our knowledge as intrinsic evanescent infrared sensors for monitoring liquid chemicals. Different liquids with absorption bands between 1 and 4.5 microm, such as alcohol, acetonitrile, and mixtures of alcohol/acetonitrile and water/acetonitrile, have been tested. These fibers have also been used successfully as distributed sensors for simultaneous monitoring of different chemical species.

Multidrug-resistant strains of Mycobacterium tuberculosis isolated from patients in Tehran belong to a genetically distinct cluster.

Restriction fragment length polymorphism (RFLP) analysis was used to study the molecular epidemiology of tuberculosis (TB) in certain areas of Tehran. 120 isolates of Mycobacterium tuberculosis, including drug-resistant strains (n = 23), were analysed using polymorphic GC-rich sequence (PGRS) and IS6110 probes. There was considerable diversity among the strains cultured from patients from certain areas. The results of RFLP showed that multidrug resistant (MDR) isolates of M. tuberculosis in Tehran belong to a group of strains with low copies of IS6110 and PGRS. The degree of clustering was higher for the drug-resistant strains than for the susceptible ones (65% vs 20%). Based on the demographic data and results of RFLP, it appears that recent transmissions of TB from old patients have occurred in Tehran. However, drug-resistant TB in the city is mainly caused by strains that look different from those cultured from such patients. The majority of MDR isolates (85%) in this study contained a low copy number of IS6110 and PGRS in RFLP, and were mostly recovered from immigrants and refugees.

Optical properties of AlF(3)-based glasses doped with Pr(3+), Yb(3+) and Lu(3+).

Rare-earth ions can easily be incorporated into fluoride glasses in moderate to large concentrations. Because these glasses possess low fundamental frequencies, they appear to have many advantages over oxide glasses as hosts for rare-earth ions used in optical amplifiers and lasers. We have investigated the optical properties (fluorescence, absorption, and excited-state lifetimes) of AlF(3)-based glass doped with Pr(3+), Yb(3+) and Lu(3+). The effects of different dopant levels on the optical properties of this glass system have also been investigated. These results are compared to those obtained for the same ions in other glass hosts.

Prevalence of endocrine complications in beta-thalassaemia major in the Islamic Republic of Iran

To identify the prevalence of endocrine dysfunction in Iranians with beta-thalassaemia, we assessed thyroid, parathyroid, pancreatic and adrenal function in 150 beta-thalassaemic patients aged 10-22 years at the Paediatrics Unit, Shiraz University of Medical Sciences. Primary hypothyroidism was found in 6.0% of patients [mean age: 14.6 +/- 1.9 years], hypoparathyroidism in 7.3% [14.5 +/- 3.2 years], type 1 diabetes mellitus in 7.3% [13.9 +/- 2.8 years] and adrenal insufficiency in 1 patient. The relatively high frequency of endocrine dysfunction found in our study may be a result of poor disease control and management in early life when irreversible tissue damage occurs due to iron overload. These findings reinforce the importance of regular follow-up of patients with beta-thalassaemia major for early detection and management of associated complications