Impact of CT reconstruction algorithm on auto-segmentation performance.

Model-based iterative reconstruction (MBIR) reduces CT imaging dose while maintaining image quality. However, MBIR reduces noise while preserving edges which may impact intensity-based tasks such as auto-segmentation. This work evaluates the sensitivity of an auto-contouring prostate atlas across multiple MBIR reconstruction protocols and benchmarks the results against filtered back projection (FBP).

Improving Bone Mineral Density Assessment Using Spectral Detector CT.

Introduction: Bone mineral density (BMD) analysis by Dual-Energy x-ray Absorptiometry (DXA) can have some false negatives due to overlapping structures in the projections. Spectral Detector CT (SDCT) can overcome these limitations by providing volumetric information. We investigated its performance for BMD assessment and compared it to DXA and phantomless volumetric bone mineral density (PLvBMD), the latter known to systematically underestimate BMD.

Impact of a novel exponential weighted 4DCT reconstruction algorithm.

Purpose: This work characterizes a novel exponential 4DCT reconstruction algorithm (EXPO), in phantom and patient, to determine its impact on image quality as compared to the standard cosine-squared weighted 4DCT reconstruction.

Methods: A motion platform translated objects in the superior-inferior (S-I) direction at varied breathing rates (8-20 bpm) and couch pitches (0.06-0.

Machine learning-based dual-energy CT parametric mapping.

The aim is to develop and evaluate machine learning methods for generating quantitative parametric maps of effective atomic number (Z), relative electron density (ρ ), mean excitation energy (I ), and relative stopping power (RSP) from clinical dual-energy CT data. The maps could be used for material identification and radiation dose calculation. Machine learning methods of historical centroid (HC), random forest (RF), and artificial neural networks (ANN) were used to learn the relationship between dual-energy CT input data and ideal output parametric maps calculated for phantoms from the known compositions of 13 tissue substitutes.

Accuracy of electron density, effective atomic number, and iodine concentration determination with a dual-layer dual-energy computed tomography system.

Purpose: This study aimed to quantitate the accuracy of the determination of electron density (ED), effective atomic number (Z ), and iodine concentration, directed for more accurate radiation therapy planning, with a new dual-layer dual-energy computed tomography (DL-DECT) system. The dependence of the accuracy of these values on the scan and reconstruction parameters, as well as on the phantom size, was also examined.

Methods: Measurements were performed on a commercial DECT system with a DL detector (IQon Spectral CT, Philips Healthcare), using phantoms with various tissue-equivalent inserts as well as iodine and calcium inserts of different concentrations.

A comparison study of size-specific dose estimate calculation methods.

Background: The size-specific dose estimate (SSDE) has emerged as an improved metric for use by medical physicists and radiologists for estimating individual patient dose. Several methods of calculating SSDE have been described, ranging from patient thickness or attenuation-based (automated and manual) measurements to weight-based techniques.

Objective: To compare the accuracy of thickness vs.

Individually optimized contrast-enhanced 4D-CT for radiotherapy simulation in pancreatic ductal adenocarcinoma.

Purpose: To develop an individually optimized contrast-enhanced (CE) 4D-computed tomography (CT) for radiotherapy simulation in pancreatic ductal adenocarcinomas (PDA).

Methods: Ten PDA patients were enrolled. Each underwent three CT scans: a 4D-CT immediately following a CE 3D-CT and an individually optimized CE 4D-CT using test injection.

How accurate is size-specific dose estimate in pediatric body CT examinations?

Background: Size-specific dose estimate is gaining increased acceptance as the preferred index of CT dose in children. However it was developed based on non-clinical data.

Objective: To compare the accuracy of size-specific dose estimate (SSDE) based on geometric and body weight measures in pediatric chest and abdomen CT scans, versus the more accurate [Formula: see text] (mean SSDE based on water-equivalent diameter).

Dosimetric impact of orthopedic metal artifact reduction (O-MAR) on Spine SBRT patients.

The dosimetric impact of orthopedic metal artifact reduction (O-MAR) on spine SBRT patients has not been comprehensively studied, particularly with spinal prostheses in high-dose gradient regions. Using both phantom and patient datasets, we investigated dosimetric effects of O-MAR in combination of various metal locations and dose calculation algorithms. A physical phantom, with and without a titanium insert, was scanned.

Effect of body size on dose reduction with longitudinal tube current modulation in pediatric patients.

Objective: The purpose of the study was to evaluate whether dose reduction by tube current modulation in pediatric abdominal CT depends on patient body size.

Materials And Methods: A 12-month (February 2012 through January 2013) retrospective evaluation of consecutive abdominal 128-MDCT examinations was performed. All studies were performed with longitudinal (z-axis) tube current modulation.

Evaluation of slice sensitivity profiles for helical and axial 4D-CT acquisitions on the Philips Brilliance CT Big Bore.

Purpose: 4D-CT can be performed using two acquisition modes. One employs a cine axial scan and the other acquires the data using a very low pitch helical acquisition. This study evaluates the longitudinal resolutions of each of these methods by creating slice sensitivity profiles (SSP).

Prospects for in vivo estimation of photon linear attenuation coefficients using postprocessing dual-energy CT imaging on a commercial scanner: comparison of analytic and polyenergetic statistical reconstruction algorithms.

Purpose: Accurate patient-specific photon cross-section information is needed to support more accurate model-based dose calculation for low energy photon-emitting modalities in medicine such as brachytherapy and kilovoltage x-ray imaging procedures. A postprocessing dual-energy CT (pDECT) technique for noninvasive in vivo estimation of photon linear attenuation coefficients has been experimentally implemented on a commercial CT scanner and its accuracy assessed in idealized phantom geometries.

Methods: Eight test materials of known composition and density were used to compare pDECT-estimated linear attenuation coefficients to NIST reference values over an energy range from 10 keV to 1 MeV.

Individually optimized uniform contrast enhancement in CT angiography for the diagnosis of pulmonary thromboembolic disease--a simulation study.

Purpose: To improve the diagnostic quality of CT pulmonary angiography (CTPA) by individually optimizing a biphasic contrast injection function to achieve targeted uniform contrast enhancement. To compare the results against a previously reported discrete Fourier transform (DFT) approach.

Methods: This simulation study used the CTPA datasets of 27 consecutive patients with pulmonary thromboembolic disease (PE).

Effect of tube voltage on CT noise levels in different phantom sizes.

Objective: The purpose of this study was to determine the effect of lowering tube voltage on dose and noise in cylindric water phantoms to optimize quality and decrease the radiation dose for body CT.

Materials And Methods: We performed CT on cylindric water phantoms with diameters of 10, 20, 25, and 30 cm, simulating the abdomen of an infant, child, adolescent, and adult. We used tube voltages of 120, 100, and 80 kVp.

Experimental implementation of a polyenergetic statistical reconstruction algorithm for a commercial fan-beam CT scanner.

Purpose: To present a framework for characterizing the data needed to implement a polyenergetic model-based statistical reconstruction algorithm, Alternating Minimization (AM), on a commercial fan-beam CT scanner and a novel method for assessing the accuracy of the commissioned data model.

Methods: The X-ray spectra for three tube potentials on the Philips Brilliance CT scanner were estimated by fitting a semi-empirical X-ray spectrum model to transmission measurements. Spectral variations due to the bowtie filter were computationally modeled.

Clinical evaluation of a commercial orthopedic metal artifact reduction tool for CT simulations in radiation therapy.

Purpose: Severe artifacts in kilovoltage-CT simulation images caused by large metallic implants can significantly degrade the conspicuity and apparent CT Hounsfield number of targets and anatomic structures, jeopardize the confidence of anatomical segmentation, and introduce inaccuracies into the radiation therapy treatment planning process. This study evaluated the performance of the first commercial orthopedic metal artifact reduction function (O-MAR) for radiation therapy, and investigated its clinical applications in treatment planning.

Methods: Both phantom and clinical data were used for the evaluation.

Effect of novel amplitude/phase binning algorithm on commercial four-dimensional computed tomography quality.

Purpose: Respiratory motion is a significant source of anatomic uncertainty in radiotherapy planning and can result in errors of portal size and the subsequent radiation dose. Although four-dimensional computed tomography allows for more accurate analysis of the respiratory cycle, breathing irregularities during data acquisition can cause considerable image distortions. The aim of this study was to examine the effect of respiratory irregularities on four-dimensional computed tomography, and to evaluate a novel image reconstruction algorithm using percentile-based tagging of the respiratory cycle.

Displacement-based binning of time-dependent computed tomography image data sets.

Respiration can cause tumors in the thorax or abdomen to move by as much as 3 cm; this movement can adversely affect the planning and delivery of radiation treatment. Several techniques have been used to compensate for respiratory motion, but all have shortcomings. Manufacturers of computed tomography (CT) equipment have recently used a technique developed for cardiac CT imaging to track respiratory-induced anatomical motion and to sort images according to the phase of the respiratory cycle they represent.

Gated CT imaging using a free-breathing respiration signal from flow-volume spirometry.

Respiration-induced tumor motion is known to cause artifacts on free-breathing spiral CT images used in treatment planning. This leads to inaccurate delineation of target volumes on planning CT images. Flow-volume spirometry has been used previously for breath-holds during CT scans and radiation treatments using the active breathing control (ABC) system.