McCollough effect

BACKGROUND: Mega-voltage fan-beam Computed Tomography (MV-FBCT) holds potential in accurate determination of relative electron density (RED) and proton stopping power ratio (SPR) but is not widely available. OBJECTIVE: To demonstrate the feasibility of MV-FBCT using a medical linear accelerator (LINAC) with a 2.5 MV imaging beam, an electronic portal imaging device (EPID) and multileaf collimators (MLCs). METHODS: MLCs were used to collimate MV beam along z direction to enable a 1 cm width fan-beam...

The McCollough Effect is a color aftereffect produced by exposure to colored, oriented patterns. For example, following adaptation to vertical red and horizontal green stripes in alternation, vertical black and white patterns appear greenish, while horizontal black and white patterns appear reddish. The striking aspect of the McCollough Effect is that just a few minutes of adaptation can produce an aftereffect lasting days or weeks. Though this effect is easily induced, previous work has shown that stronger effects can be achieved with longer periods of adaptation...

BACKGROUND: To investigate the effectiveness of the three-step supporting technique for prevention of eyelid malposition in the transcutaneous lower blepharoplasty. METHODS: It was a chart review of more than 10-year experiences of our method. From 2006 to 2017, a total of 697 patients underwent the three-step supporting technique in the transcutaneous lower blepharoplasty. The three steps included septum tightening, orbicularis canthopexy, and muscle plication...

PURPOSE: Talbot-Lau grating interferometry enables the use of polychromatic x-ray sources, extending the range of potential applications amenable to phase contrast imaging. However, these sources introduce beam hardening effects not only from the samples but also the gratings. As a result, grating inhomogeneities due to manufacturing imperfections can cause spectral nonuniformity artifacts when used with polychromatic sources. Consequently, the different energy dependencies of absorption, phase, and visibility contrasts impose challenges that so far have limited the achievable image quality...

The clinical demand for low image noise often limits the slice thickness used in many CT applications. However, a thick-slice image is more susceptible to longitudinal partial volume effects, which can blur key anatomic structures and pathologies of interest. In this work, we develop a prior knowledge aware iterative denoising (PKAID) framework that utilizes spatial data redundancy in the slice increment direction to generate low-noise, thin-slice images, and demonstrate its application in non-contrast head CT exams...

Purpose: Conventional stenosis quantification from single-energy computed tomography (SECT) images relies on segmentation of lumen boundaries, which suffers from partial volume averaging and calcium blooming effects. We present and evaluate a method for quantifying percent area stenosis using multienergy CT (MECT) images. Approach: We utilize material decomposition of MECT images to measure stenosis based on the ratio of iodine mass between vessel locations with and without a stenosis, thereby eliminating the requirement for segmentation of iodinated lumen...

PURPOSE: To develop a convolutional neural network (CNN) that can directly estimate material density distribution from multi-energy CT images without performing conventional material decomposition. METHODS: The proposed CNN (denoted as Incept-net) followed the general framework of encoder-decoder network, with an assumption that local image information was sufficient for modeling the non-linear physical process of multi-energy CT. Incept-net was implemented with a customized loss function, including an in-house-designed image-gradient-correlation (IGC) regularizer to improve edge preservation...

Purpose: Task-based image quality assessment using model observers (MOs) is an effective approach to radiation dose and scanning protocol optimization in computed tomography (CT) imaging, once the correlation between MOs and radiologists can be established in well-defined clinically relevant tasks. Conventional MO studies were typically simplified to detection, classification, or localization tasks using tissue-mimicking phantoms, as traditional MOs cannot be readily used in complex anatomical background. However, anatomical variability can affect human diagnostic performance...

PURPOSE: We report our single-institution stereotactic body radiation therapy (SBRT) experience on stage I renal cancer with prospectively collected toxicity and efficacy data. METHODS AND MATERIALS: A total of 21 patients with solitary renal tumors, including 14 surgical candidates who refused surgery (66%), were treated with SBRT. Histologic confirmation was obtained on all patients before treatment; 2 had transitional cell carcinoma and 19 had renal cell carcinoma...

In x-ray computed tomography (CT), materials with different elemental compositions can have identical CT number values, depending on the mass density of each material and the energy of the detected x-ray beam. Differentiating and classifying different tissue types and contrast agents can thus be extremely challenging. In multienergy CT, one or more additional attenuation measurements are obtained at a second, third or more energy. This allows the differentiation of at least two materials. Commercial dual-energy CT systems (only two energy measurements) are now available either using sequential acquisitions of low- and high-tube potential scans, fast tube-potential switching, beam filtration combined with spiral scanning, dual-source, or dual-layer detector approaches...

No abstract text is available yet for this article.

BACKGROUND: Most individuals with spinal cord injury who use manual wheelchairs experience shoulder pain related to wheelchair use, potentially in part from mechanical impingement of soft tissue structures within the subacromial space. There is evidence suggesting that scapula and humerus motion during certain wheelchair tasks occurs in directions that may reduce the subacromial space, but it hasn't been thoroughly characterized in this context. METHODS: Shoulder motion was imaged and quantified during scapular plane elevation with/without handheld load, propulsion with/without added resistance, sideways lean, and weight-relief raise in ten manual wheelchair users with spinal cord injury using biplane fluoroscopy and computed tomography...

OBJECTIVE: The aim of this study was to grade cartilage damage in a swine model of osteoarthritis using a whole-body photon-counting detector (PCD) CT. MATERIALS AND METHODS: A multienergy phantom containing gadolinium (Gd) (2, 4, 8, and 16 mg/mL) and hydroxyapatite (200 and 400 mg/cc) was scanned using a PCD-CT system (48 × 0.25 mm collimation, 80 kV, 800 mAs, D50 reconstruction kernel) to serve as calibration for material decomposition and to assess quantification accuracy...

PURPOSE: To determine how small bowel neuroendocrine neoplasms (SBNEN's) are diagnosed and examine the effect of CT enterography (CTE) on diagnosis and rates of disease-free survival. METHODS: Histopathologically-confirmed SBNEN's diagnosed at our institution between 1996 and 2016 were identified. Clinical presentation, radiology, endoscopy, surgery, and pathology reports were reviewed and compared between consecutive 5-year periods. RESULTS: Of the 178 SBNEN initially diagnosed at our institution, the incidence increased 12-fold from 9 (during 1996-2000) to 114 (during 2011-2016)...

BACKGROUND AND PURPOSE: Despite the frequent use of unenhanced head CT for the detection of acute neurologic deficit, the radiation dose for this exam varies widely. Our aim was to evaluate the performance of lower-dose head CT for detection of intracranial findings resulting in acute neurologic deficit. MATERIALS AND METHODS: Projection data from 83 patients undergoing unenhanced spiral head CT for suspected neurologic deficits were collected. Cases positive for infarction, intra-axial hemorrhage, mass, or extra-axial hemorrhage required confirmation by histopathology, surgery, progression of findings, or corresponding neurologic deficit; cases negative for these target diagnoses required negative assessments by two neuroradiologists and a clinical neurologist...

PURPOSE: The aim of this study was to demonstrate that a low helical pitch causes increased photon starvation artifacts at ultra-low-dose CT. METHODS: A cylindrical water phantom with a diameter of 30 cm was scanned on two different generation CT scanners: a 64-slice scanner (Sensation 64, Siemens Healthcare) and a 192-slice scanner (Somatom Force, Siemens Healthcare) at multiple effective mAs levels (mAs/pitch=200, 100, 50, 25, and 12). The corresponding CTDIvol values were 4...

Determination of the effect of protocol modifications on diagnostic performance in CT with human observers is extremely time-consuming, limiting the applicability of such methods in routine clinical practice. In this work, we sought to determine whether a channelized Hotelling observer (CHO) could predict human observer performance for the task of liver lesion localization as background, reconstruction algorithm, dose, and lesion size were varied. 
 Materials and Methods: Liver lesions (5mm, 7mm, and 9mm) were digitally inserted into the CT projection data of patients with normal livers and water phantoms...

We demonstrate a fast, flexible, and accurate paraxial wave propagation model to serve as a forward model for propagation-based X-ray phase contrast imaging (XPCI) in parallel-beam or cone-beam geometry. This model incorporates geometric cone-beam effects into the multi-slice beam propagation method. It enables rapid prototyping and is well suited to serve as a forward model for propagation-based X-ray phase contrast tomographic reconstructions. Furthermore, it is capable of modeling arbitrary objects, including those that are strongly or multi-scattering...

In the last decade or so, a number of disruptive technological advances have taken place in x-ray computed tomography, making possible new clinical applications. Changes in scanner design have included the use of two x-ray sources and two detectors or the use of large detector arrays that provide 16 cm of longitudinal coverage in one gantry rotation. These advances have allowed images of the entire heart to be acquired in just one heartbeat, lowering the effective dose from cardiac computed tomography from ~15 mSv to <1 mSv...

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the impact of effective detector-pixel-size and image voxel size on the accurate estimation of microvessel density (ratio of microvascular lumen volume/tissue volume) in an excised porcine myocardium specimen using microcomputed tomography (CT), and the ability of whole-body energy-integrating-detector (EID) CT and photon-counting-detector (PCD) CT to measure microvessel density in the same ex vivo specimen. MATERIALS AND METHODS: Porcine myocardial tissue in which the microvessels contained radio-opaque material was scanned using a micro-CT scanner and data were generated with a range of detector pixel sizes and image voxel sizes from 20 to 260 microns, to determine the impact of these parameters on the accuracy of microvessel density estimates...