Rena Widita

Rena Widita
Bandung Institute of Technology | ITB · Physics

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30
Publications
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153
Citations

Publications

Publications (30)
Technical Report
Full-text available
IndoseCT is software to calculate and manage the radiation dose of a patient undergoing computed tomography (CT) examination. It does not only calculate the radiation output dose of CT machines (in terms of volume CT dose index, CTDIvol), but also the individual dose received by each patient (in terms of size-specific dose estimate, SSDE) either ba...
Technical Report
Full-text available
IndoseCT merupakan software untuk menghitung dan mendokumentasikan dosis radiasi dari setiap pasien yang menjalani pemeriksaan computed tomography (CT). Software ini tidak hanya menghitung dosis keluaran radiasi pesawat CT (dalam besaran volume CT dose index, CTDIvol), tetapi juga dosis individual yang diterima oleh setiap pasien (dalam besaran siz...
Article
Full-text available
Background: It is necessary to have an automated noise measurement system working accurately to optimize dose in computerized tomography (CT) examinations. Objective: This study aims to develop an algorithm to automate noise measurement that can be implemented in CT images of all body regions. Materials and methods: In this retrospective study...
Article
Full-text available
We study the structural, electronic, and magnetic properties of the antiferromagnetic-layered oxyarsenide (LaO)MnAs system from the first-principle calculation. The increasing Hubbard energy (U) in the Mn 3d orbital induces the increasing local-symmetry distortions (LSDs) in MnAs4 and OLa4 tetrahedra. The LSD in MnAs4 tetrahedra is possibly promote...
Article
Undoped ZnO nanostructures were deposited on Si (100) substrate using direct-current-unbalanced magnetron sputtering. The nanostructure modification of conelike into rod-shaped nanocolumnars is found after thermal annealing with O2. This modification transforms paramagnetism into room-temperature ferromagnetism, induced by Zn vacancy enhancement at...
Article
ZnO nanorods are one of the most studied materials for optoelectronics applications, thanks to their superior properties, such as high-surface-to-volume ratio, unique chemical, and physical properties. Sputtering method is believed as a promising technique to fabricate ZnO nanorods in a large-scale area. However, this method requires high substrate...
Article
Full-text available
We study the structural, electronic, and thermoelectric properties of p-type layered oxychalcogenides (La0.5Bi0.5O)CuCh (Ch = S, Se, Te) from first principles. Ch substitution from S to Te enhances the local-symmetry distortions (LSDs) in CuCh4 and OLa2Bi2 tetrahedra, where the LSD in OLa2Bi2 is more pronounced. The LSD in CuCh4 tetrahedra comes fr...
Article
We study the optical and conductivity properties of Fe-doped ZnO (ZnO:Fe) film. ZnO and ZnO:Fe films (0.6 at. % and 1.2 at. % Fe concentration) were deposited using direct-current-unbalanced magnetron sputtering at room temperature. The presence of Fe dopant enhances the photon absorption of ZnO. The I–V and spectroscopic ellipsometry (SE) characte...
Article
We study the structural, electronic, and magnetic properties of monolayer α-PbO0.875A0.125 (A = N, F), which are calculated using first principles. As a result, N doping induces local ferromagnetism centered at the N2− site, originating from the spin-down N 2p valence states. On the other hand, F doping induces nonmagnetism and induces ab-plane def...
Article
We study the structural and electronic properties of p‐type layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb), calculated by first principles. Pn substitution from P to Sb increases D2d‐type local symmetry distortions at ZnPn4 and OLa4 tetrahedra. (LaO)ZnP and (LaO)ZnAs exhibit direct band gaps (Γ → Γ) of 0.621 eV and 0.528 eV, respectively, while (L...
Article
Full-text available
The structural, optical, and electrical properties of undoped and Al-doped ZnO films deposited on p-Si (001) substrate were studied using DC-unbalanced magnetron sputtering. This study is motivated by the absence of detail reports concerning the orbital states inducing the optical bandgap (E g) blueshift. Besides, the influences of Al on the possib...
Article
We proposed and evaluated a water-equivalent diameter calculation without using a region of interest (ROI), (D w,t), and compared it with the results of using a ROI fitted to the patient border (D w,f). Evaluations were carried out on thoracic and head CT images. We found that the difference between D w,t and D w,f was within 5% for all images in t...
Article
Full-text available
The aims of this study were to investigate the noise reduction in a CT image using a modified Wiener filtering-edge detection method. We modified the noise reduction algorithm of a combination of the Wiener filter and edge detection by addition of a dilation stage after edge detection. We then evaluated kernel size of the Wiener filter, threshold v...
Article
Full-text available
This study aims to develop a simple method for estimating the size-specific effective dose using the ImPACT software. The size-specific effective dose was calculated from the images of patients who underwent CT examinations of the thorax and abdomen regions. Volume computed tomography dose index (CTDI vol) and mAs data were obtained from the dose r...
Article
Full-text available
The aim of this study was to evaluate the eye lens dose due to miscentering, either above or under the isocenter, and to assess the possibility of eye lens dose reduction by using miscentering phenomenon. We used two types of phantoms (head CTDI and adult anthropomorphic phantoms) and two types of detectors (pencil ionization chamber and radiophoto...
Article
We study the effects of post-annealing treatments on excitonic states and defects of nanostructured Ti-doped ZnO thin films grown by room-temperature magnetron sputtering technique. Here, the as-grown samples were annealed by varying the annealing environment, time, and temperature. We found that the higher excitonic emission was at 600 °C under N...
Article
We study the optical properties of ZnO films grown using plasma-assisted molecular beam epitaxy. We employ three different growth temperatures (Tgrowth) of 298, 373, and 423 K. The XRD patterns and field-emission SEM images indicate that Tgrowth increment linearly increases the c-axis strain and average growth rate. The photoluminescence spectra sh...
Article
Electronic and optical properties of ZnO nanorods grown by room temperature dc‐unbalanced magnetron sputtering are studied. As a comparison, ZnO thin film is deposited as well. Surface morphology images and X‐ray diffraction patterns show that ZnO nanorods are successfully grown with hexagonal wurtzite structure and the diameter varies from 50 to 9...
Article
We study electronic and optical properties of the two-dimensional (2D) systems of monolayer and bilayer alpha lead oxide (α-PbO) systems. The plane-wave method within the generalized gradient approximation is employed. We revisit the properties of bulk α-PbO system as the references. The indirect minimum bandgaps (Eg) of the bulk (1.645 eV, 0.2Δ →...
Article
The aim of this study was to compare the values of the computed tomography dose index 100 (CTDI100) obtained using two small detectors (i.e. a small ionization chamber and a small solid state detector) with those obtained from a 100-mm pencil ionization chamber for various input CT parameters: beam width, kVp, mAs, pitch, and head-body phantom vari...
Article
Full-text available
This study compared the spatial resolution and the amount of noise in CT images reconstructed using the iterative reconstruction (IR) and filtered back-projection (FBP) techniques. We used a circular homogeneous phantom (pixel value of 0.5) containing a small circle at its center, with a diameter of 0.53-cm and a pixel value of 1.0. In order to rec...
Article
Full-text available
Background: In the tube current modulation (TCM) technique, tube current is changed dynamically during the scanning process. To quantify the effect of a dynamic tube current, a distinct calculator is needed to estimate the CT output radiation dose in terms of volume CT dose index (CTDIvol) and individual patient dose in terms of size-specific dose...
Article
We have been successfully developed a new software for image segmentation This software is addressed to do segmentation of elastic organs. The segmentation components used in this software is region growing algorithms which have proven to be an effective approach for image segmentation. The implementations of region growing developed here are conne...
Article
Boron Neutron Capture Therapy (BNCT) is a cancer therapy by utilizing thermal neutron to produce alpha particles and lithium nuclei. The superiority of BNCT is that the radiation effects could be limited only for the tumor cells. BNCT radiation dose depends on the distribution of boron in the tumor. Absorbed dose to the cells from the reaction 10...
Article
We have been successfully improved our software, Automated Image Registration and Segmentation (AIRS), to fuse the CT and SPECT images of elastic organs. Segmentation and registration of elastic organs presents many challenges. Many artifacts can arise in SPECT/CT scans. Also, different organs and tissues have very similar gray levels, which consi...
Article
SIMULTANEOUS SELECTION OF BEAM DIRECTIONS FOR TREATMENT PLANNING AND FOR IMAGE RECONSTRUCTION. Dose verification in radiotherapy needs daily imaging of the patient so the anatomic or position changes can be seen which may suggest replanning before the next treatment. Using standard equipment, it is not possible to obtain the daily image while the p...
Article
In radiotherapy planning, margins are used to account for the uncertainties due to internal organ and patient motion as well as set-up error. Improvement in radiotherapy treatments may be achieved by reducing the set-up uncertainty and thus treatment margins allowing a higher dose to be delivered to the target volume. It is important to be able to...
Article
This paper presents a numerical simulation to calculating the absorbed dose delivered from reaction of 10 B(n,α) 7 Li near the interface between a region containing boron and boron free region. The method considers the contribution of the recoiled lithium particle to the absorbed dose and the variation of LET with charged particle energy. The geome...

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