A Prospective Study Measuring Resident and Faculty Contour Concordance: A Potential Tool for Quantitative Assessment of Residents' Performance in Contouring and Target Delineation in Radiation Oncology Residency.

Purpose/objective(s): Accurate target delineation (ie, contouring) is essential for radiation treatment planning and radiotherapy efficacy. As a result, improving the quality of target delineation is an important goal in the education of radiation oncology residents. The purpose of this study was to track the concordance of radiation oncology residents' contours with those of faculty physicians over the course of 1 year to assess for patterns.

Cleaning the dose falloff with low modulation in SBRT lung plans.

This dosimetric study is intended to lower the modulation factor in lung SBRT plans generated in the Eclipse TPS that could replace highly modulated plans that are prone to the interplay effect.Twenty clinical lung SBRT plans with high modulation factors (≥4) were replanned in Varian Eclipse TPS version 15.5 utilizing 2 mm craniocaudal and 1 mm axial block margins followed by light optimization in order to reduce modulation.

Design and performance evaluation of a slit-slat camera for 2D prompt gamma imaging in proton therapy monitoring: A Monte Carlo simulation study.

Purpose: We investigated the design of a prompt gamma camera for real-time dose delivery verification and the partial mitigation of range uncertainties.

Methods: A slit slat (SS) camera was optimized using the trade-off between the signal-to-noise ratio and spatial resolution. Then, using the GATE Monte Carlo package, the camera performances were estimated by means of target shifts, beam position quantification, changing the camera distance from the beam, and air cavity inserting.

BEAM MATCHING EVALUATION OF TWO SIMILAR LINEAR ACCELERATORS.

To evaluate the beam-matching of two Siemens Primus medical linear accelerators (Linacs), the output factor (Sc,p), wedge factor, quality index (TPR20/10), percentage depth dose (PDD) and beam profiles were compared for 6 and 15 MV photon beams. The output factor, the PDD and the beam profile for electron beam compared for 5, 7, 8, 10 and 12 MeV electron beams. The gamma (γ) analysis of 2 mm/2% and 3 mm/3% was performed.

A phantom-based study and clinical implementation of brainlab's treatment planning system for radiosurgical treatments of arteriovenous malformations.

Purpose: Development of a simple, phantom-based methodology allowing for pilot applications for the Elements TPS cranio-vascular module and clinical implementation prior to AVM treatments.

Methods: A customized phantom was developed to be visible in MRI and CT images. High resolution digital subtraction angiograms (DSAs) and CT images of the phantom were acquired and imported into the Brainlab Elements treatment planning system.

A dosimetric comparative analysis of Brainlab elements and Eclipse RapidArc for spine SBRT treatment planning.

. This is a dosimetric study comparing stereotactic body radiotherapy (SBRT) plans of spine tumors using Brainlab Elements Spine planning module against Eclipse RapidArc plans. Dose conformity, dose gradient, dose fall-off, and patient-specific quality assurance (QA) metrics were evaluated.

Monte Carlo simulation and analytical calculation methods to investigate the potential of nanoparticles for INTRABEAM® IORT machine.

In the present study, Monte Carlo (MC) simulation and analytical calculation methods were used to investigate the potential of cancer treatment for the combination of IORT with nanoparticles (NPs). The Geant4 MC toolkit was used to simulate ZEISS INTRABEAM® IORT machine and its smallest applicator with 1.5 cm diameter.

Simultaneous respiratory motion correction and image reconstruction in 4D-multi pinhole small animal SPECT.

Purpose: Respiratory motion in the chest region during single photon emission computed tomography (SPECT) is a major degrading factor that reduces the accuracy of image quantification. This effect is more notable when the tumor is very small, or the spatial resolution of the imaging system is less than the respiratory motion amplitude. Small animals imaging systems with sub-millimeter spatial resolution need more attention to the respiratory motion for quantitative studies.

Quantitative 4D-PET reconstruction for small animal using SMEIR-reconstructed 4D-CBCT.

Respiratory motions in small animals PET cause image degradation during reconstruction. This work aims to develop a motion compensated 4D-PET reconstruction method using accurate motion corrections and attenuation corrections from 4D-CBCT images reconstructed using a simultaneous motion estimation and image reconstruction (SMEIR) method. Projections of 4D-CBCT were calculated using a ray-tracing method on a digital 4D rat phantom, and list-mode data of 4D-PET with matched respiratory phases were simulated using the GATE Monte Carlo package.

Evaluation of normal lung tissue complication probability in gated and conventional radiotherapy using the 4D XCAT digital phantom.

Purpose: The present study was conducted to investigate normal lung tissue complication probability in gated and conventional radiotherapy (RT) as a function of diaphragm motion, lesion size, and its location using 4D-XCAT digital phantom in a simulation study.

Materials And Methods: Different time series of 3D-CT images were generated using the 4D-XCAT digital phantom. The binary data obtained from this phantom were then converted to the digital imaging and communication in medicine (DICOM) format using an in-house MATLAB-based program to be compatible with our treatment planning system (TPS).

Iterative reconstruction with boundary detection for carbon ion computed tomography.

In heavy ion radiation therapy, improving the accuracy in range prediction of the ions inside the patient's body has become essential. Accurate localization of the Bragg peak provides greater conformity of the tumor while sparing healthy tissues. We investigated the use of carbon ions directly for computed tomography (carbon CT) to create the relative stopping power map of a patient's body.

Internal dosimetry for radioembolization therapy with Yttrium-90 microspheres.

The absorbed doses in the liver and adjacent viscera in Yttrium-90 radioembolization therapy for metastatic liver lesions are not well-documented. We sought for a clinically practical way to determine the dosimetry of this advent treatment. Six different female XCAT BMIs and seven different male XCAT BMIs were generated.

The importance of BMI in dosimetry of Sm-EDTMP bone pain palliation therapy: A Monte Carlo study.

Using digital phantoms as an atlas compared to acquiring CT data for internal radionuclide dosimetry decreases patient overall radiation dose and reduces the required analysis effort and time for organ segmentation. The drawback is that the phantom may not match exactly with the patient. We assessed the effect of varying BMIs on dosimetry results for a bone pain palliation agent, Sm-EDTMP.

Attenuation correction in 4D-PET using a single-phase attenuation map and rigidity-adaptive deformable registration.

Purpose: Four-dimensional positron emission tomography (4D-PET) imaging is a potential solution to the respiratory motion effect in the thoracic region. Computed tomography (CT)-based attenuation correction (AC) is an essential step toward quantitative imaging for PET. However, due to the temporal difference between 4D-PET and a single attenuation map from CT, typically available in routine clinical scanning, motion artifacts are observed in the attenuation-corrected PET images, leading to errors in tumor shape and uptake.

Task Equivalence for Model and Human-Observer Comparisons in SPECT Localization Studies.

While mathematical model observers are intended for efficient assessment of medical imaging systems, their findings should be relevant for human observers as the primary clinical end users. We have investigated whether pursuing equivalence between the model and human-observer tasks can help ensure this goal. A localization ROC (LROC) study tested prostate lesion detection in simulated In-111 SPECT imaging with anthropomorphic phantoms.

Respiratory motion correction in 4D-PET by simultaneous motion estimation and image reconstruction (SMEIR).

In conventional 4D positron emission tomography (4D-PET), images from different frames are reconstructed individually and aligned by registration methods. Two issues that arise with this approach are as follows: (1) the reconstruction algorithms do not make full use of projection statistics; and (2) the registration between noisy images can result in poor alignment. In this study, we investigated the use of simultaneous motion estimation and image reconstruction (SMEIR) methods for motion estimation/correction in 4D-PET.

Practical Nuclear Medicine and Utility of Phantoms for Internal Dosimetry: XCAT Compared with Zubal.

Purpose: The absorbed doses for two radioisotopes, 99mTc and 131I, between previously validated Zubal phantom and the recently developed XCAT phantom were compared.

Materials And Methods: GATE Monte Carlo code was used to simulate the statistical process of radiation. A XCAT phantom with voxel and matrix sizes similar to a standard Zubal phantom was generated.

A New Approach for Scatter Removal and Attenuation Compensation from SPECT/CT Images.

Objective(s): In SPECT, the sinogram contains scatter and lack of attenuated counts that degrade the reconstructed image quality and quantity. Many techniques for attenuation and scatter correction have been proposed. An acceptable method of correction is to incorporate effects into an iterative statistical reconstruction.

The influence of resolution recovery by using collimator detector response during 3D OSEM image reconstruction on (99m)Tc-ECD brain SPET images.

Partial volume effect, due to the poor spatial resolution of single photon emission tomography (SPET), significantly restricts the absolute quantification of the regional brain uptake and limits the accuracy of the absolute measurement of blood flow. In this study the importance of compensation for the collimator-detector response (CDR) in the technetium-99m ethyl cysteinate dimer ((99m)Tc-ECD) brain SPET was assessed, by incorporating system response in the ordered-subsets expectation maximization (OSEM) reconstruction algorithm. By placing a point source of (99m)Tc at different distances from the face of the collimator, CDR were found and modeled using Gaussian functions.

Quantification and reduction of the collimator-detector response effect in SPECT by applying a system model during iterative image reconstruction: a simulation study.

Background: Detector blurring and non-ideal collimation decrease the spatial resolution of the single-photon emission computed tomography (SPECT) images. Iterative reconstruction algorithms such as ordered subsets expectation maximization (OSEM) can incorporate degrading factors during reconstruction. We investigated the quantitative errors associated with poor SPECT resolution and evaluated the importance of two-dimensional (2D) and three-dimensional (3D) resolution recovery by modelling system response during iterative image reconstruction.

Quantification and reduction of attenuation related artifacts in SPET by applying attenuation model during iterative image reconstruction: a Monte Carlo study.

Photon attenuation is one of the main causes of the quantitative errors and artifacts in SPET. A transmission or CT based attenuation map is necessary to correct for the effects of attenuation accurately. In this research, some important attenuation related artifacts are described.

Optimized energy window configuration for 201Tl imaging.

Unlabelled: A poor signal-to-noise ratio attributable to a low injected dose of thallium and the presence of scattered photons are the major impediments in the use of thallium as an imaging agent. Thallium decays in a complicated way and emits photons in a wide range of energies (68-82 keV). To increase the ratios of primary photons to scatter photons (primary-to-scatter ratios) and possibly increase system sensitivity, a new energy window for thallium was investigated.