An acoustic inverse scattering problem for spheres with radially inhomogeneous compressibility.

An inverse acoustic scattering problem the main aim of which is to reconstruct the one-dimensional variation of the acoustical parameters of a spherical object is investigated. The problem is first formulated conventionally through a coupled system of integral equations, and then this system is reduced to one-dimensional form by using the orthogonality properties of spherical harmonics. The inverse problem is solved in an iterative fashion via classical Newton algorithm. Some numerical simulations are carried out to test the feasibility of the method as well as to see the effects of some parameters on the solution. It is shown that the method is very effective for the profiles having smooth variations provided that an appropriate initial guess is chosen. However, some of the classical disadvantages of the Newton type algorithms are also observed in numerical experiments which may limit the applicability of the method to a certain extent.

Monitoring of intracerebral hemorrhage with a linear microwave imaging algorithm.

Intracerebral hemorrhage is a life-threatening condition where conventional imaging modalities such as CT and MRI are indispensable in diagnosing. Nevertheless, monitoring the evolution of intracerebral hemorrhage still poses a technological challenge. We consider continuous monitoring of intracerebral hemorrhage in this context and present a differential microwave imaging scheme based on a linearized inverse scattering. Our aim is to reconstruct non-anatomical maps that reveal the volumetric evolution of hemorrhage by using the differences between consecutive electric field measurements. This approach can potentially allow the monitoring of intracerebral hemorrhage in a real-time and cost-effective manner. Here, we devise an indicator function, which reveals the position, volumetric growth, and shrinkage of hemorrhage. Later, the method is numerically tested via a 3D anthropomorphic dielectric head model. Through several simulations performed for different locations of intracerebral hemorrhage, the indicator function-based technique is demonstrated to be capable of detecting the changes accurately. Finally, the robustness under noisy conditions is analyzed to assess the feasibility of the method. This analysis suggests that the method can be used to monitor the evolution of intracerebral hemorrhage in real-world scenarios.

Single-slice microwave imaging of breast cancer by reverse time migration.

PURPOSE: Microwave imaging of breast cancer is considered and a new microwave imaging prototype including the imaging algorithm, the antenna array, and the measurement configuration is presented. The prototype aims to project the geometrical features of the anomalies inside the breast to a single-slice image at the coronal plane depending on the complex dielectric permittivity variation among the tissues to aid the diagnosis. METHODS: The imaging prototype uses a solid cylindrical dielectric platform, where a total of 24 optimized Vivaldi antennas are embedded inside to form a uniform circular antenna array. The center of the platform is carved to create a hollow part for placement of the breast and the multistatic, microwave scattering parameters are collected with the antenna array around the hollow center. The dielectric platform further enhances the microwave impedance matching against the breast fat tissue and preserves the vertical polarization during the measurements. In the imaging phase, a computationally efficient inverse electromagnetic scattering method-reverse time migration (RTM)-is considered and adapted in terms of scattering parameters to comply with the actual measurements. RESULTS: The prototype system is experimentally tested against tissue-mimicking breast phantoms with realistic dielectric permittivity profiles. The reconstructed single-slice images accurately determined the locations and the geometrical extents of the tumor phantoms. These experiments not only verified the microwave imaging prototype but also provided the first experimental results of the imaging algorithm. CONCLUSIONS: The presented prototype system implementing the RTM method is capable of reconstructing single-slice, nonanatomical images, where the hotspots correspond to the geometrical projections of the anomalies inside the breast.

Microwave imaging of breast cancer with factorization method: SPIONs as contrast agent.

Female breast at macroscopic scale is a nonmagnetic medium, which eliminates the possibility of realizing microwave imaging of the breast cancer based on magnetic permeability variations. However, by administering functionalized, superparamagnetic iron oxide nanoparticles (SPIONs) as a contrast material to modulate magnetic permeability of cancer cells, a small variation on the scattered electric field from the breast is achievable under an external, polarizing magnetic field. PURPOSE: We demonstrate an imaging technique that can locate cancerous tumors inside the breast due to electric field variations caused by SPION tracers under different magnetic field intensities. Furthermore, we assess the feasibility of SPION-enhanced microwave imaging for breast cancer with simulations performed on a multi-static imaging configuration. METHODS: The imaging procedure is realized as the factorization method of qualitative inverse scattering theory, which is essentially a shape retrieval algorithm for inaccessible objects. The formulation is heuristically modified to accommodate the scattering parameters instead of the electric field to comply with the requirements of experimental microwave imaging systems. RESULTS: With full-wave electromagnetic simulations performed on an anthropomorphically realistic breast phantom, which is excited with a cylindrical imaging prototype of 18 dipole antenna arranged as a single row, the technique is able to locate cancerous tumors for a experimentally achievable doses. CONCLUSIONS: The technique generates nonanatomic microwave images, which map the cancerous tumors depending on the concentration of SPION tracers, to aid the diagnosis of the breast cancer.

The effect of preventive use of alanyl-glutamine on diaphragm muscle function in cecal ligation and puncture-induced sepsis model.

BACKGROUND: Low muscle glutamine levels during sepsis are associated with reduced protein synthesis and elevated protein breakdown, in particular myofibrillar protein breakdown. Thus, in a cecal ligation and puncture (CLP)-induced sepsis model in the rat, we hypothesized that glutamine pretreatment would protect the diaphragm muscle function. METHODS: Eighty-four male Wistar rats weighing between 180 g and 200 g received standard amino acid solution 1.2 g kg(-1) per day intraperitoneally (IP) or standard amino acid solution 1.2 g kg(-1) per day plus alanyl-glutamine (GLN) 0.25 g kg(-1) per day (IP) during the first 6 days of the experiment. On the seventh day, CLP or sham procedures were applied. The sham and CLP groups were equally divided into 3 subgroups according to the termination of the experiment, which took place at either the 24th hour, 48th hour, or 72nd hour. After the compound muscle action potentials (CMAP) were recorded from the diaphragms of the rats at these selected times, they were decapitated under ketamine/xylazine anesthesia, and diaphragms were harvested for biochemical and histopathological examination. RESULTS: The mean area and amplitude of CMAP were significantly larger in sham+GLN groups when compared with CLP and CLP+GLN groups at all times (p < .05). Diaphragm Ca+2 -ATPase levels were found to be significantly decreased in CLP group at all times compared to sham groups (p < .05). Diaphragm reduced glutathione levels were significantly higher in sham+GLN groups when compared with CLP and CLP+GLN groups at all times (p < .05). In histopathologic assessment, moderate neutrophil infiltration, which was observed in CLP48, was significantly reduced with alanyl-glutamine supplementation in CLP+GLN48 group (p < .05). CONCLUSIONS: This study showed that glutamine pretreatment did not improve diaphragm muscle function, but prevented the biochemical and histopathological changes in diaphragmatic muscle in CLP-induced sepsis. However, further studies are needed to clarify whether a higher dose of glutamine supplementation might protect the diaphragmatic muscle functions.

General anesthesia does not affect the serum complexed and free prostate specific antigen levels.

PRINCIPLES: Serum prostate-specific antigen (PSA) level is a widely used serum marker for diagnosis and management of prostate cancer. Although not well-defined, liver appears to be the most likely site of PSA metabolism. However, general anaesthesia usually changes hepatic blood flow, therefore it may affect the metabolism of PSA. In this study we investigated the affect of general anaesthesia on the serum total PSA, free PSA and free to total PSA levels. METHODS: 30 male patients who were hospitalised in the internal medicine clinic (non-surgery group) and 30 male patients who would undergo operation under general anaesthesia (15 for cholecystectomy and 15 for inguinal hernia repair) enrolled into the study. PSA measurement was done on the day of the hospitalisation (which was also the day of operation for surgery group), on the 24th hour following the first measurement and on the 21st day. Anaesthesia was standardized for all patients. RESULTS: There was no statistically significant difference in serum total PSA (p >0.05), free PSA levels (p >0.05) and free to total PSA ratio (p >0.05) between the surgery and non-surgery groups. There were statistically significant decreases in the 24th hour total PSA levels (13.8% in surgery group, p <0.05, and 13.1% in non-surgery group, p <0.05) and in the free PSA levels (4.0% in surgery group, p <0.05, and 8.2% in non-surgery group, p <0.05). There was no statistically significant difference in the free to total PSA ratios (p >0.05 and p >0.05, respectively). CONCLUSIONS: Anaesthesia does not affect PSA levels alone. However, hospitalisation decreases total and free PSA levels, although it does not have an affect on free to total PSA ratio.

Postoperative effects of low-dose intrathecal morphine in coronary artery bypass surgery.

BACKGROUND: Intrathecal morphine has been used in hopes of providing long-lasting postoperative analgesia in patients after cardiac surgery. The aim of this study was to evaluate the effects of 7 micro/kg intrathecal morphine administration in coronary bypass surgery in the postoperative period. METHODS: We conducted a prospective, randomized, blinded, and controlled study. Twenty-three patients, who underwent primary elective coronary bypass surgery, were randomly allocated to receive morphine 7 micro/kg intrathecally, before the induction of general anesthesia (Group M, n = 12) or no intrathecal injection (Group C, n = 11). Pain scores, determined by visual analogue scale (VAS), were recorded immediately after extubation upon admission to the intensive care unit (ICU), at the 2nd, 4th, 6th, and 18th hour after extubation. Pethidine was administered if the patient's VAS > or = 4 and consumption was recorded. Extubation time and ICU length of stay were also recorded. RESULTS: VAS scores were lower in the Group M at each measured time than the control group (p = 0.016, 0.023, 0.004, 0.0001, and 0.001, respectively). According to the VAS scores, pethidine requirement was lower in the Group M than the control (p = 0.001). Extubation time (3.58 +/- 1.57 vs. 4.86 +/- 1.38 hours, p = 0.045) and ICU length of stay (16.25 +/- 2.70 vs. 19.30 +/- 2.45 hours, p = 0.014) were also significantly shorter in the Group M than the control group. No significant complications were seen in this group of patients. CONCLUSIONS: Intrathecal morphine provided effective analgesia, earlier tracheal extubation and less ICU length stay after on-pump coronary bypass surgery. The influence on ICU length of stay requires further evaluations.

Anti-apoptotic effect of succinyl gelatine in a liver ischaemia-reperfusion injury model (Bcl-2, Bax, Caspase 3)?

Apoptosis of tissues may contribute to ischaemia-reperfusion injury. The aim of the present study was to determine whether administration of a colloid solution would prevent apoptosis after liver ischaemia-reperfusion. New Zealand rabbits, weighing 1.5-2 kg, were randomized to receive either 4% SG (20 ml kg (-1)h(-1) ) by 30 min of intravenous (i.v.) infusion (Group I, n= 7) or equivalent volumes of 0.9% sodium chloride (Group II, n= 6) i.v. before a 45 min interruption of the portal vein blood flow and then 45 min of reperfusion. The animals were killed following the reperfusion period. Their livers were processed for histopathological examination and paraffin sections of these tissues were examined. The expression of Bcl-2, Bax and caspase 3 were analysed by immunohistochemistry. ANOVA and the Wilcoxon W -test were used for statistical analysis, and mean values were expressed +/-sd. Histologically, the foci of ischaemic necrosis were observed in liver specimens of the periportal area in one of the animals in Group I and in two in Group II. Immunhistochemical analysis demonstrated an increase in Bcl-2 protein levels in Group I compared to Group II ( P< 0.05). Bax expression was lower in Group I than in Group II. Immunoreactivity for caspase 3 did not differ significantly between the two groups (47.0 +/- 35.93 in Group I, 32.83 +/- 23.63 in Group II). Our results indicate that gelofusine did not protect the liver tissue against ischaemia-reperfusion-induced apoptosis.