Quantitative Myocardial Magnetic Resonance Imaging

Quantitative magnetic resonance imaging (MRI) is a robust and reproducible analysis method that has become the gold standard for cardiac analysis in clinical care. This thesis aims to optimize quantitative MRI characterization of myocardial tissue. A new method was introduced to obtain a synthetic image for drawing the left ventricle myocardial contours used for quantifying T2* for iron deposition detection, called the contrast-optimized composite image method, followed by a semi-automatic myocardial segmentation to ease segmentation difficulties in the bright blood multi-gradient echo image series. Two monoexponential T2* truncation methods were compared in quantifying iron loading at different iron content classifications. In T1 mapping, mean and median pixel value quantification were compared for their ability to detect heart function abnormality. Meanwhile, different perfusion models for quantifying myocardial blood flow (MBF) were equally sensitive to heart function. Higher reproducibility of T2* quantification was obtained by improving the TE image quality for myocardial segmentation and performing a semi-automatic myocardial segmentation. The two truncation methods showed similar T2* values at severe myocardial iron loading and diverged in lower myocardial iron content regions. Median quantification of pixel-wise measurement can replace the mean regardless of statistical data distribution, as shown in the early abnormality of heart function detected by native T1. Different MBF estimations are found between different perfusion models with the extended Toft and Fermi models allowing for better differentiation of the presence of significant stenosis. To conclude, this thesis has provided improved methods for characterizing myocardial tissue quantitatively

A comparison of image quality of cerium oxide nanoparticles and iodine contrast agents in computed tomography scan

Computed tomography (CT) scan, with iodine-based contrast, produces good image quality by improving the visualisation of relatively low-contrast internal body structures. However, the impact of using iodinated difference should be considered in patients susceptible to contrast allergy and renal impairment. Therefore, alternative contrast materials, such as cerium oxide nanoparticles (CeO2 NPs), must be used, with biocompatible properties and strong X-ray attenuation capabilities. This study compared the CT scan image quality of CeO2 NPs and iodinated contrast agents. This experimental study started by preparing a suspension of CeO2 NPs and iodine in aquabidest at a concentration of 500 ppm. The suspension was scanned using a CT scan with a helical scanning method. The exposure coefficient parameters were set for the tube voltage of 80 kV, Field of View of 28 cm, slice thickness of 5 mm, and tube current time of 150 mAs, 200 mAs, and 250 mAs. Then, CT images in DICOM data format were processed using MicroDICOM Viewer software. The quality of the CT scan images was analysed based on the CT number value, noise level, and contrast resolution. The images of CeO2 nanoparticles have higher CT values, lower noise levels, and better contrast resolution than those of iodine contrast agents. The results show that the CT image results of CeO2 NPs have better quality than those of iodine-containing contrast agents

Cardiac T-2* mapping:Techniques and clinical applications

Cardiac T-2* mapping is a noninvasive MRI method that is used to identify myocardial iron accumulation in several iron storage diseases such as hereditary hemochromatosis, sickle cell disease, and beta-thalassemia major. The method has improved over the years in terms of MR acquisition, focus on relative artifact-free myocardium regions, and T-2* quantification. Several improvement factors involved include blood pool signal suppression, the reproducibility of T-2* measurement as affected by scanner hardware, and acquisition software. Regarding the T-2* quantification, improvement factors include the applied curve-fitting method with or without truncation of the signals acquired at longer echo times and whether or not T-2* measurement focuses on multiple segmental regions or the midventricular septum only. Although already widely applied in clinical practice, data processing still differs between centers, contributing to measurement outcome variations. State of the art T-2* measurement involves pixelwise quantification providing better spatial iron loading information than region of interest-based quantification. Improvements have been proposed, such as on MR acquisition for free-breathing mapping, the generation of fast mapping, noise reduction, automatic myocardial contour delineation, and different T-2* quantification methods. This review deals with the pro and cons of different methods used to quantify T-2* and generate T-2* maps. The purpose is to recommend a combination of MR acquisition and T-2* mapping quantification techniques for reliable outcomes in measuring and follow-up of myocardial iron overload. The clinical application of cardiac T-2* mapping for iron overload's early detection, monitoring, and treatment is addressed. The prospects of T-2* mapping combined with different MR acquisition methods, such as cardiac T-1 mapping, are also described. Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019

Improving water absorption time and the natural silk strength (Bombyx Mori) using atmospheric dielectric barrier discharge plasma

This researchaimed to obtain Dielectric Barrier Discharge plasma discharge characteristics with and without the placement of natural silkBombyx Mori on one of the electrodes. Furthermore, the strength and the water absorption time of the irradiated silk samples will be analyzed.  Plasma discharge is generated by connecting electrodes of point-to-plane configuration with a sheet of glass inserted on the plane electrode at atmospheric conditions. The characterization of plasma discharge, either with or without the natural silk samples' placement on the plane electrode, was performed by increasing A.C.'s high voltage power source to reach arch discharge. Theelectrode spacing varied from 0.7 cm to 2.5 cm with a 0.3 cm increment. Sample irradiation was performed using cold plasma for 5, 15, and 30 minutes respectively. Placing or not placing the natural silk samples on the plane electrode will increase the plasma's discharge current and increase the high voltage. Moreover, increasing the distance between the electrodes and placing the sample on the plane electrode decreases the discharge current. Using Scanning Electron Microscopy, it was found that increasing plasma irradiation time on samples decreases the silk thread'sdiameterand shortening its water absorption time. The strength of irradiated fabric was reduceduntil 15 minutes of irradiation. However, at 30 minutes of irradiation, there was an increase in sample thickness compared to control samples

KARAKTERISASI PLASMA LUCUTAN PIJAR KORONA POSITIF PADA KONDISI ATMOSFER DENGAN KONFIGURASI ELEKTRODA TITIK BIDANG DAN PENGARUHNYA TERHADAP KAIN SUTRA ALAM (BOMBYX MORI)

Eksperimen pembangkitan plasma lucutan pijar korona telah dilakukan dengan menggunakan konfigurasi elektroda titik dan bidang. Kondisi plasma lucutan pijar korona terbentuk secara optimal pada jarak antar elektroda (d) setinggi 2,1 cm dan 2,4 cm dan arus saturasi (Is) terukur sebesar 0,75 mA dan 1,0 mA. Kondisi tersebut digunakan sebagai dua karakteristik lucutan yang digunakan dalam tahap perlakuan sampel kain sutra alam (Bombyx mori). Pengujian sifat mekanis pada sampel kain sutra alam dengan perlakuan plasma menunjukkan nilai ketahanan jebol yang menurun dibandingkan nilai ketahanan jebol pada sampel kain sutra alam tanpa perlakuan. Pengujian kekuatan serap zat cair (akuades) pada sampel kain sutra alam dengan perlakuan plasma menunjukkan nilai rerata waktu serap (τ) yang lebih singkat dibandingkan nilai τ pada sampel kain sutra tanpa perlakuan. Pada kedua tahap tersebut, pengoptimalan maksimum dari nilai ketahanan jebol dan daya serap zat cair (akuades) dicapai pada jarak antar elektroda (d) setinggi 2,1 cm, arus saturasi (Is) sebesar 0,75 mA dan waktu perlakuan selama 30 menit. Pengujian sifat mikroskopik membuktikan bahwa dengan adanya perubahan struktur permukaan pada sampel cukup berpengaruh terhadap nilai ketahanan jebol dan rerata waktu penyerapan zat cair (akuades) yang dimiliki.  Hasil pengujian pada tahap ini juga menyatakan bahwa tidak ada penambahan jenis baru dari gugus fungsi terkandung pada sampel kain sutra alam yang diberi perlakuan plasma

T2* assessment of the three coronary artery territories of the left ventricular wall by different monoexponential truncation methods

OBJECTIVES: This study aimed at evaluating left ventricular myocardial pixel-wise T2* using two truncation methods for different iron deposition T2* ranges and comparison of segmental T2* in different coronary artery territories. MATERIAL AND METHODS: Bright blood multi-gradient echo data of 30 patients were quantified by pixel-wise monoexponential T2* fitting with its R2 and SNR truncation. T2* was analyzed at different iron classifications. At low iron classification, T2* values were also analyzed by coronary artery territories. RESULTS: The right coronary artery has a significantly higher T2* value than the other coronary artery territories. No significant difference was found in classifying severe iron by the two truncation methods in any myocardial region, whereas in moderate iron, it is only apparent at septal segments. The R2 truncation produces a significantly higher T2* value than the SNR method when low iron is indicated. CONCLUSION: Clear T2* differentiation between the three coronary territories by the two truncation methods is demonstrated. The two truncation methods can be used interchangeably in classifying severe and moderate iron deposition at the recommended septal region. However, in patients with low iron indication, different results by the two truncation methods can mislead the investigation of early iron level progression

A comparison of image quality of cerium oxide nanoparticles and iodine contrast agents in computed tomography scan

Computed tomography (CT) scan, with iodine-based contrast, produces good image quality by improving the visualisation of relatively low-contrast internal body structures. However, the impact of using iodinated difference should be considered in patients susceptible to contrast allergy and renal impairment. Therefore, alternative contrast materials, such as cerium oxide nanoparticles (CeO2 NPs), must be used, with biocompatible properties and strong X-ray attenuation capabilities. This study compared the CT scan image quality of CeO2 NPs and iodinated contrast agents. This experimental study started by preparing a suspension of CeO2 NPs and iodine in aquabidest at a concentration of 500 ppm. The suspension was scanned using a CT scan with a helical scanning method. The exposure coefficient parameters were set for the tube voltage of 80 kV, Field of View of 28 cm, slice thickness of 5 mm, and tube current time of 150 mAs, 200 mAs, and 250 mAs. Then, CT images in DICOM data format were processed using MicroDICOM Viewer software. The quality of the CT scan images was analysed based on the CT number value, noise level, and contrast resolution. The images of CeO2 nanoparticles have higher CT values, lower noise levels, and better contrast resolution than those of iodine contrast agents. The results show that the CT image results of CeO2 NPs have better quality than those of iodine-containing contrast agents

PENGARUH DEPOSISI PARTIKEL-PARTIKEL ION NEGATIF PADA KONDISI ATMOSFER TERHADAP KAIN POLYESTER GREY

Penelitian ini bertujuan untuk menganalisa daerah kerja plasma korona pada kondisi atmosfer dalam pembangkitan partikel - partikel ion negatif guna memperoleh  nilai mobilitas ion rerata pembawa muatannya. Karakteristik ini dilakukan dengan menggunakan sampel kain polyester grey dan tanpa kain sebagai pembanding.  Lebih lanjut, penelitian ini juga menganalisa karakteristik kain polyester grey setelah diiradiasi dengan plasma korona negatif. Penelitian ini menggunakan reaktor plasma berarus negatif yang tersusun atas elektroda multi titik dan elektroda bidang. Elektroda titik berdiameter 0,5 mm sebanyak 100 titik dengan jarak tiap titik 1,3 cm dan elektroda bidang berukuran 25 x 25 cm2. Sampel kain tenun berbahan Polyester Grey berukuran 10 x 10 cm2 diiradasi pada elektroda bidang. Daerah kerja plasma korona negatif pada kondisi atmosfer dianalisa melalui karakteristik arus-tegangan pada variasi jarak antara elektroda mulai 0,9 cm hingga 3,6 cm dengan beda potensial pembangkitan plasma antara 0 – 4 kV.  Hasil penelitian menunjukkan bahwa kuat arus listik meningkat bersamaan dengan penambahan beda potensial serta penempatan kain polyester grey pada elektroda bidang cenderung menurunkan arus listrik dari plasma korona negatif. Nilai mobilitas ion yang dihasilkan menunjukan semakin kecilnya mobilitas ion yang dihasilkan saat jarak antar elektroda (d) semakin jauh. Hasil pengujian tetes cairan pada kain polyester grey setelah iradiasi menunjukkan adanya perubahan sifat fisis kain. Pada jarak antar elektroda multi titik dan bidang  sebesar 2,1 cm dengan lama peradiasian 35 menit, hasil dominan kecepatan waktu serap rerata kain diperoleh sebesar 1,06 detik dimana sebelum iradiasi melebihi 17 detik

Comparison of I-V Curves Between the Experiment of Corona Discharge on Gradient Line-To-Plane (GL-P) Configuration and The Mathematical Approach

Research has been conducted on the comparison of the I-V characteristic curve between mathematical study and experiment of the generation of negative DC corona discharge in the Gradient Line-to-Plane (GL-P) electrode configuration. The reason for this research is to calculate the suitability of the corona discharge electrical current between the mathematical and experimental study. The active electrode used has length 2 cm and height 4 cm. This research is conducted with variations in the sharpness angle of the active electrode (θ) 300, 450, and 600 and variations in the distance between the electrodes () 2 cm, 3 cm, and 4 cm. The mathematical formulation of the value of the corona discharge electrical current in the configuration of the GL-P electrode is obtained by using the geometric concept approach, which is the formulation of the capacitance value of the ordinary electrical circuit, with the addition of the multiplication factor value k in the sharp area of the active electrode, because in that area the greatest plasma flow distance is obtained. The value of the multiplication factor  is obtained by fitting the curve between mathematical study and experiments. The I-V curve between the mathematical study and the corona discharge generation experiment has a high degree of similarity with the smallest percentage contacting point of 37.50%.The value of the multiplication factor  is influenced by the sharpness angle of the active electrode shape and the distance between the electrodes

KARAKTERISASI REAKTOR PLASMA BERARUS POSITIF KONFIGURASI ELEKTRODA MULTITITIK-BIDANG DAN PENERAPANNYA PADA KAIN POLYESTER GREY

Penelitian tentang teknologi plasma pada kondisi atmosfer telah dilakukan untuk mengembangkan industri tekstil. Penelitian ini bertujuan untuk membandingkan karakteristik plasma dengan maupun tanpa penempatan kain polyester grey diantara dua elektroda serta mendapatkan karakteristik serapan tetes air pada kain polyester grey setelah diiradiasi menggunakan plasma. Plasma dibangkitkan dengan mengggunakan reaktor berkonfigurasi elektroda multititik-bidang menggunakan elektroda titik sebanyak 100. Elektroda titik tersebut dihubungkan dengan sumber tegangan tinggi DC dan berperilaku sebagai anoda dengan elektroda bidang sebagai katoda. Jarak antar elektroda titik ditetapkan sebesar 1,3 cm yang dikonfigurasi pada 10 baris dan 10 kolom. Kain polyester grey yang diiradiasi berukuran (10x10) cm2 dan diletakkan pada elektroda bidang. Dalam proses iradiasi, jarak antar elektroda diatur pada jarak 0,9 cm hingga 3,6 cm dengan tiap kenaikan jarak sebesar 0,3 cm. Mobilitas ion dalam proses iradiasi ditentukan dengan menggunakan karakteristik arus – tegangan dari pembangkitan plasma. Proses iradiasi plasma pada kain polyester grey ditetapkan selama 5 menit hingga 35 menit dengan tiap kenaikan durasi selama 5 menit. Hasil pengukuran menunjukkan bahwa semakin besar jarak antara elektroda mengakibatkan besar arus pembangkitan plasma semakin kecil. Akar arus sebagai fungsi terhadap tegangan merupakan persamaan garis lurus sehingga nilai mobilitas ion dapat ditentukan dengan pendekatan persamaan Robinson. Perhitungan mobilitas ion tanpa kain diantara elektroda menunjukkan nilai 30,07 cm2/Vs pada jarak antar elektroda 0,9 cm dengan trend menurun hingga 4,32 cm2/Vs seiring pertambahan jarak antar elektroda. Sedangkan perhitungan mobilitas ion dengan menempatkan kain polyester grey pada elektroda menunjukkan nilai 10,25 cm2/Vs pada jarak antar elektroda 2,1 cm dengan trend yang juga menurun hingga 3,39 cm2/Vs seiring pertambahan jarak antar elektroda. Karakteristik kain polyester grey mengalami perubahan berupa penyerapan tetes air yang semakin cepat hingga 1,2 detik dimana sebelum diiradiasi terukur selama sebesar 15 detik