Frontiers in Biomedical Technologies
Volume:2 Issue: 1, Winter 2015

The risk effect of long-term occupational exposure to extremely low-frequencyelectromagnetic fields (ELF-EMFs) has been studied extensively. However,due to several experimental issues such as exposure measurement error and thelack of standard ELF-EMFs exposing devices, the obtained results are controversial.The inconsistent reported results preclude clear conclusions on the evidenceof an association between EMF exposure and the disorders reported. To assist withresolving these issues, a digital–low cost ELF-EMFs generator to produce EMFswith desired magnitude and frequency is proposed. A sinusoidal waveform with adjustable amplitude and frequency controlledby a microprocessor is generated and then is applied to a coil with a U-shapecore. To increase the accuracy of the instrument, three coils with 250 turns; 500turns; and 1200 turns were designed and used in the instrument. The amplitude andfrequency of the voltage delivered to each of these coil are controlled by turningoff and on TRIAC transistors controlled by a microprocessor–based system. The designed instrument provided EMF with magnitude of 0.55 mTeslato 1.56 mTesla with error rate < 5.9% and frequency of 10 Hz to 50 Hz with errorrate <1%. The provided EMF was sufficiently homogeneous over a given volumeand was stable over time. The quantitative and qualitative experimental results showed that the designedinstrument is reliable and accurate to be used in research laboratories for furtherinvestigation of the health effect of long-term occupational exposure to ELF-EMFs.

Proton magnetic resonance spectroscopy (1H-MRS) is a non-invasivemethod with the capability to correctly lateralize the seizure foci in patients withTemporal Lobe Epilepsy (TLE), with the first evidence published in 1993. Onemajor drawback of this modality is that the MRS data is naturally high dimensional.This, along with the time-consuming post-processing and quantificationprocedures such as spectral fitting, have made MRS impractical for clinical use.Dimension reduction techniques eliminate undesired properties of high-dimensionalspaces, suggesting simple and feasible analysis techniques in comparisonwith quantification procedures. In this study, we use two dimension reduction techniques so-called Isomapand Diffusion maps to quantify MRS data obtained from TLE patients for localizationseizure foci. Then, we evaluate the results by comparison with obtainedratio of NAA/ (Cr+Cho) from the quantification method. Our results show that the proposed methodology has the ability to localizeand/or to lateralize the seizure foci in such patients, while itmaintains minimal requiredamount of computations and time (Sensitivity=60%, Specificity=82.81%). We are hoping that this method broadens new horizons to explore theinformative yetcomplicated MRS modality into Epileptic diagnosis.

The physical and mechanical properties of resin composites are highly affected bythe extent of conversion obtained by polymerization. The hardness testcan be used as an indirectmethod to evaluate degree of conversion.The purpose of this study was to evaluate theeffect of three preheating temperatures on microhardness of three different nanohybrid resinbased composites. The 30 specimens for each commercial resin composite[Grandio (Voco), Simile(Pentron) and Tetric N-Ceram (IvoclarVivadent)] were randomly subdivided in 3 subgroupswhich 10 specimens were used for each one {subgroup 1=preheating at room temperature (21˚C), subgroup 2= preheating temperature 37˚ C and subgroup 3= preheating temperature 54˚C}.The specimenswerephotopolymerized with QTH light-curing unit for 20 s following thepreheating process. Vickers microhardness test was performed for the top and bottom surfacesof each specimen. Three random indentations were taken for each surface and a mean valuewas calculated. The microhardness values in Grandio group were significantly different between allthree subgroups(p value ≤ 0.001). In Simile group the only significant difference was between21˚ C and 54˚ C (p value ≤ 0.005) and in Tetric N-Ceram group the difference between 21˚ Cand 54˚ C (p value ≤ 0.001) and also between 21˚ C and 37˚ C (p value ≤ 0.01) were consideredas statistically significant. Regardlessof theresin composite material used, surface hardness was considerablyimproved by increasing temperature. The microhardness values were influenced significantlyby resin-based composite brand.

The complex geometry of breast tissue, variable shape, size of breasts,their lack of homogeneity and other organs at risk like the heart and lungs makedose distribution difficult, especially for cases involving large breasts. Assessmentof breast dosimetry includes homogeneity dose distribution with complete targetcoverage and the avoidance of organs at risk as much as possible. The aim of thisstudy is to assess dose distribution and coverage of the target by TLD dosimeterin slab breast phantoms. This study used a slab anatomical phantom with lung inhomogenity fortwo different breast sizes, large and small. Exposure was done with 6 MV, utilizedPTW reader, oven LTM to annulling Conventional methods were carried out witha hand generated contour, 3D treatment planning used RT Dose Plan software. There were areas with lower than 95 percent reference dose in 3D methodsdecreased in compare of conventional methods. This result for large breastswas remarkable. Received area of target for both size more than 105 percent referencedose reduce to some extent, therefore getting more homogeneity also bettercoverage for target volume for large breast. This study has shown that conventional methods are not suitable toassessment of dose distribution and coverage in target volume, especially for largebreast. Also there was not sufficient dose distribution for small breast a as result ofthe 3D method, and so can it be useful for crowded hospitals with restricted facilitycenters because they

The most general form to report dose in Multislice CT is the CTDI andDLP which are computed for several slices. The goal of the current study was toestimate actual doses and dose distribution during CT examinations in a head andneck anthropomorphic phantom. After construction of the head and neck phantom using natural bone andparaffin wax with NaCl as impurity, several places were considered in differentsites to fill with badges of Gafchromic film. These places include brain, Parotid,Thyroid and Lens of eye. Phantom was scanned at CT Angio and Spiral protocolswith 10 and 256 slice scanners. Our findings showed that in 10 slice scanner, selected organ doses werein the range of 0.09-23.1 mSv while in the 256 slice scanner, it was in the range of0.14-18.01 mSv. The CT Angio protocol has a higher organ dose at all. In CT Angio protocol, organ dose (except for the lens of eye) is lowerin 10 slice compared to 256 slice CT; the brain dose in both protocols has no differencestatistically. In the spiral protocol, the dose in 256 slice scanner is lowerthan the 10 slice scanner which might be due to higher number of detector arraysin 256 slice scanner.Thyroid dose is mainly due to scattered radiation and becauseof strict beam collimation;it has a small value in all protocols.

In cataract surgery, the defected lens is replaced with an artificial intraocularlens (IOL). The refraction power of this lens is specified by ophthalmologistsbefore the surgery. There are different formulas that propose the IOL powerbased on corneal power and axial length. Six common formulas is used in thisstudy and the one which minimizes the postoperative error for a specific patienthave to be selected. Refraction is measured three times at most, during six month after surgeryand the best result is considered as postoperative refraction for each patient. Asupport vector machine (SVM) is used to classify the data to two groups based onaxial length and corneal power. Each class needs a formula with a specific tendencytoward stronger or weaker IOL lenses according to the feature vector. Experimental tests lead to a nearly diagonal confusion matrix whichsupports the performance of the proposed method strongly. Mean Absolute Error(MAE) is 0.47 which shows 6% decrease in postoperative refraction error comparedto the best reported result. In calculating IOL power, we expect stronger IOL powers for eyeshaving shorter axial length or weaker corneal power. In the contrary, a weaker IOLpower is expected for longer axial length and stronger corneal power. But experimentalresults show that for the first group, formulas proposing weaker powers winthe race for decreased postoperative refraction error while for the second group,formulas leading to stronger powers perform better. This shows that these formulasoverestimate and underestimate for marginal cases.

Patient setup optimization has been required to fill the gap between individualtreatment and uncertainty in the external beam radiotherapy at each of thetreatment sessions. This uncertainty error consists of patient body misalignmentsand patient body displacement between different fractions. In this study, the patient geometrical set-up has been simulated comprehensivelyby 4D XCAT anthropomorphic phantom where the XCAT phantomwas used to access 4D modeling of dynamic organs motion. All of the possibleroto-translation displacement parameters that were effective on instigate patientposition before re-alignment were considered. While the data set was assembledfrom XCAT phantom including 2D translation and 2D rotation, the parallelismsof the dada set between position of the external markers and reference point (patientcouch) were considered. Moreover, the experimental validation models forfurther investigation were considered. For this aim, the captured data from XCATphantom was extended to four real patients. In some clinically available strategies,the corrective models have been implemented to estimate patient displacementof patient setup. In this study, four intelligent models were proposed for set-up,realignment, and continuous tracking of the patient positioning. Final results illustrate that Adaptive Neuro Fuzzy Interference Systemwith all markers can estimate the true patient position with less error. In this study, the four intelligent models were demonstrated to investigatethe robustness of various intelligent models in re-alignment and patientset-up at external beam radiotherapy. Finally, our correlation model “ANFIS” canestimate the true patient position with less error.

Virtual reality based minimally invasive surgical trainers have beenproved to be highly effective for training of surgical residents before clinical practice.In this article we introduce the SinaSim, a low-cost laparoscopic surgery simulatorbased on virtual reality environment. The most important part in developing a virtual reality system is tomaking the virtual reality software of a surgical practice and modeling the physicalproperties and reaction of soft tissues in real time. At SinaSim we used a newlydeveloped graphical engine to minimize the cost and maximize the widespreadusage of this system. Screenshots of the final graphical view of each training task as well asgraphical user interface which provides the trainees with necessary informationabout their learning progress, are included in this report. The preliminary results of this study shows that the performance ofboth hardware and software of the SinaSim laparoscopic surgery simulator arecomparable with a commercial virtual reality based trainer in spite of its lowerfinal price.