- Volume:6 Issue: 1, 2019
- تاریخ انتشار: 1398/03/05
- تعداد عناوین: 5
Pages 1-21Magnetic Resonance Spectroscopy (MRS) has at least two major roles in the evaluation of epileptic patients. First, MRS can help to understand the interaction between seizures and metabolic function. Thus, MRS is particularly interesting for basic science studies of seizures and epilepsy. Second, MRS can explain the nature of seizure control and/or provide localization information by measuring metabolic changes. So MRS can be used as a powerful complementary technique to structural MRI for diagnosis and assessment of response to therapy, and measurement of disease progression. The aim of this paper is to review the methodological aspects of 1H-MRS publications between 1994 to 2016, which utilized 1H-MRS in lateralizing the epileptogenic zone in lesional and non-lesional Temporal Lobe Epilepsy (TLE), Extra-Temporal Lobe Epilepsy (ETLE), and generalized epileptic patients to help the spectroscopist, magnetic resonance imaging technologists, and radiologists to improve the overall diagnostic sensitivity in epileptic patients.Keywords: Proton Magnetic Resonance Spectroscopy, Epilepsy, Temporal Lobe Epilepsy, Juvenile Myoclonic Epilepsy, Generalized Epilepsy
Pages 22-26PurposeIn some gamma spectroscopy experiments, neutrons may also be present, so depending on experimental conditions, Gamma spectroscopy can be influenced by the presence of neutrons.
Materials and MethodsIn this study, a NaI(Tl)(63 mm×63 mm) detector is used to investigate the effects of fast neutrons on the spectrum of gamma photons. The radiation source used in these experiments is made up of two point sources: an AmBe (50 mCi) neutron source and a 137Cs(10 mCi) gamma source.
ResultsResults were determined through both measurements and Monte Carlo simulation (MCNPX) under two different experimental conditions and were compared. When the detector is placed under an angle to the source, gamma photon energy peaks resulting from inelastic interactions of the fast neutrons with the detector materials and surrounding materials in the energy range of 0.1-0.9(MeV) are pretty visible in the gamma main spectrum. These results can be used to optimize industrial tomography experiments carried out with NaI(Tl) scintillators.
ConclusionAlso, the results show that the detection of fast neutrons with a NaI(Tl) scintillator is possible with low efficiency.Keywords: Gamma Spectroscopy, Neutron Source, Monte Carlo Simulation, Monte Carlo N-Particle Transport Code
Physical Parameters Measurement of Breast Equivalent Phantom for Clinical Studies in Radiofrequency HyperthermiaPages 28-34PurposeBreast cancer is one of the fatal diseases which causes death in women. Microwave hyperthermia is one way to treat cancer cells by irradiating RF waves to the cells and increasing their temperature. In our study, we fabricated breast phantom. Then we placed it in an RF field with a frequency of 13.56 MHz. We measured the temperature difference in several parts of the phantom, eventually.
Materials and MethodsWe designed a 5cm radius hemisphere geometry which is similar to real breast considering as fat tissue, glandular tissue as a semi-oval embedded in the hemisphere and a 1cm radius sphere as a tumor region in it. Then, it is utilized in a three-dimensional printer. After that, each layer of the phantom was filled with a suitable mixture of oil-gelatin which had similar properties of a real breast. Finally, we placed it in a microwave device with a frequency of 13.56 MHz.
ResultsDuring exposing RF to the phantom, the temperature differences were measured in four different points of the phantom. Our power and time in this treatment were 40 watt and 5 minutes, respectively. Temperature and Specific Absorption Rate (SAR) plots were obtained in several graphs for 5 minutes.
ConclusionThe results showed that the heat generation with this frequency is much enough to cause damage in tumor tissues while healthy tissues tolerate a lower amount of heat. The results have shown that this band of frequency can cause ablation in tumor tissues and can be used for breast cancer treatments.Keywords: Breast Phantom, Oil-Gelatin Phantom, Microwave Hyperthermia, Breast Cancer, Radio Frequency Ablation
Pages 35-40PurposeDental caries is known as one of the most common oral diseases in the world. Tooth decay progresses slowly, and the symptoms are not regularly visible until it reaches an irreversible phase and needs to be removed with extensive restoration treatment. If the lesions could be diagnosed at an initial stage, the progress of dental diseases would be stopped through preventive treatments. Conventional methods for caries detection are visual examinations and X-Ray imaging methods that have significant limitations such as poor sensitivity and specificity at the earliest stages of the disease due to the small size of the lesions.
Materials and MethodsPhotoacoustic imaging as a non-invasive hybrid imaging modality combines the high spatial resolution of ultrasound with the rich optical contrasts of optical imaging, and it is much safer than the ionizing radiation like X-ray imaging. In this study, the simulation of the light propagation and energy deposition in the tooth was done using Monte Carlo to form the initial pressure for acoustic simulations which is done by the K-Wave toolbox. The simulations were implemented by a tooth model which is including enamel, dentin, pulp, and gum layers.
ResultsSimulation results revealed that early tooth lesions could be detected by a broad beam light source better than the pencil beam light source in photoacoustic imaging. Also, as our simulation results proved, the amount of energy deposition for the bigger lesions is significantly higher than the smaller lesions using the broad beam light source.
ConclusionPhotoacoustic imaging as a promising imaging modality which is non-contact, non- invasive and non-ionizing imaging modality could detect early-stage tooth caries and provide quantitative information for white spot lesion evaluationKeywords: Photoacoustic Imaging, Early Detection, Dental Caries, Simulation Study
Event-Related Potential Correlates of Biased Cognitive Processing and Control in Substance Abusers: a ReviewPages 41-63
Event-related potentials (ERPs) have been used in addiction studies to evaluate cognitive performance and craving in individuals with substance use dependence (SUD). This paper reviews studies that used ERPs to investigate cue reactivity, inhibitory control and error processing in SUDs. Five abused substances are included in the investigation, i.e. alcohol, nicotine, cannabis, cocaine, and methamphetamine. For each substance, the main recent findings related to the ERPs are specifically discussed, according to the latency of ERPs.
The results show that individuals with SUDs allocate more attention resources to the cognitive processing of substance-related cues, indexed by increased amplitude of middle and late latency ERPs. Laboratory observations also show amplitude enlargement for early latency ERPs. SUDs reveal a deficiency in the inhibitory control and conscious error processing, indexed by attenuated N2 and Pe amplitude. The cognitive and motor inhibitory component (P3) changes show a controversial result.
This study expands the findings of previous related reviews implying that substance abusers allocate more attentional resources to drug cues indexed by enlarged P3 and LPP amplitude. Regarding P3 elicited in inhibitory control tasks, there is not still convergent results, while N2 and Pe become attenuated as reported in previous reviews. The outcomes also show that the chance of relapse to substance abuse could be predicted by recording ERPs reflecting inhibitory control and error processing.Keywords: Event-Related Potentials, Substance Abusers, Cue-Reactivity, Cognitive Inhibitory Control, Cognitive Error Processing