Computed Tomography Angiography of the Aorta-Optimization of Automatic Tube Voltage Selection Settings to Reduce Radiation Dose or Contrast Medium in a Prospective Randomized Trial.

Objectives: The aim of this study was to compare the image quality of low-kV protocols with optimized automatic tube voltage selection (ATVS) settings to reduce either radiation dose or contrast medium (CM) with that of a reference protocol for computed tomography angiography (CTA) of the thoracoabdominal aorta.

Materials And Methods: In this institutional review board-approved, single-center, prospective randomized controlled trial, 126 patients receiving CTA of the aorta were allocated to one of three computed tomography protocols: (A) reference protocol at 120 kVp and standard weight-adapted CM dose; (B) protocol at 90 kVp, reduced radiation and standard CM dose; and (C) protocol at 90 kVp, standard radiation and reduced CM dose. All three protocols were performed on a third-generation dual-source computed tomography scanner using the semimode of the ATVS system.

Technical Note: Radiation dose reduction from computed tomography localizer radiographs using a tin spectral shaping filter.

Purpose: To evaluate the possibility of lowering radiation dose from a localizer radiograph (LR) using a tin spectral shaping filter and to investigate the effect of this adaptation on the radiation dose and image quality of subsequent computed tomography (CT) examination.

Methods: The study utilized a set of semianthropomorphic abdomen phantoms, representing small, medium, and large patients. The LR scans were performed with and without a tin spectral shaping filter using various kVp/mA settings.

Metal Artifact Reduction on Chest Computed Tomography Examinations: Comparison of the Iterative Metallic Artefact Reduction Algorithm and the Monoenergetic Approach.

Objective: The aim of the study was to compare iterative metallic artefact reduction (iMAR) and monochromatic imaging on metal artifact reduction.

Materials And Methods: Follow-up of 29 occluded pulmonary arteriovenous malformations was obtained with dual-energy computed tomography with reconstruction of averaged images using filtered back projection (group 1), iMAR (group 2), and creation of high-energy monoenergetic images (group 3). Two types of coils had been used: (a) nickel only (group A, n = 18) and (b) nickel and platinum (group B, n = 11).

Effect of Localizer Radiography Projection on Organ Dose at Chest CT with Automatic Tube Current Modulation.

Purpose To calculate the effect of localizer radiography projections to the total radiation dose, including both the dose from localizer radiography and that from subsequent chest computed tomography (CT) with tube current modulation (TCM). Materials and Methods An anthropomorphic phantom was scanned with 192-section CT without and with differently sized breast attachments. Chest CT with TCM was performed after one localizer radiographic examination with anteroposterior (AP) or posteroanterior (PA) projections.

Iterative metal artifact reduction improves dose calculation accuracy : Phantom study with dental implants.

Purpose: Metallic dental implants cause severe streaking artifacts in computed tomography (CT) data, which affect the accuracy of dose calculations in radiation therapy. The aim of this study was to investigate the benefit of the metal artifact reduction algorithm iterative metal artifact reduction (iMAR) in terms of correct representation of Hounsfield units (HU) and dose calculation accuracy.

Materials And Methods: Heterogeneous phantoms consisting of different types of tissue equivalent material surrounding metallic dental implants were designed.

Clinical evaluation of the iterative metal artifact reduction algorithm for CT simulation in radiotherapy.

Purpose: To clinically evaluate an iterative metal artifact reduction (IMAR) algorithm prototype in the radiation oncology clinic setting by testing for accuracy in CT number retrieval, relative dosimetric changes in regions affected by artifacts, and improvements in anatomical and shape conspicuity of corrected images.

Methods: A phantom with known material inserts was scanned in the presence/absence of metal with different configurations of placement and sizes. The relative change in CT numbers from the reference data (CT with no metal) was analyzed.

Iterative metal artifact reduction: evaluation and optimization of technique.

Objective: Iterative metal artifact reduction (IMAR) is a sinogram inpainting technique that incorporates high-frequency data from standard weighted filtered back projection (WFBP) reconstructions to reduce metal artifact on computed tomography (CT). This study was designed to compare the image quality of IMAR and WFBP in total shoulder arthroplasties (TSA); determine the optimal amount of WFBP high-frequency data needed for IMAR; and compare image quality of the standard 3D technique with that of a faster 2D technique.

Materials And Methods: Eight patients with nine TSA underwent CT with standardized parameters: 140 kVp, 300 mAs, 0.

Metal artefact reduction from dental hardware in carotid CT angiography using iterative reconstructions.

Purpose: To determine the value of a metal artefact reduction (MAR) algorithm with iterative reconstructions for dental hardware in carotid CT angiography.

Methods: Twenty-four patients (six of which were women; mean age 70 ± 12 years) with dental hardware undergoing carotid CT angiography were included. Datasets were reconstructed with filtered back projection (FBP) and using a MAR algorithm employing normalisation and an iterative frequency-split (IFS) approach.

Reduction of metal artifacts from hip prostheses on CT images of the pelvis: value of iterative reconstructions.

Purpose: To assess the value of iterative frequency split-normalized (IFS) metal artifact reduction (MAR) for computed tomography (CT) of hip prostheses.

Materials And Methods: This study had institutional review board and local ethics committee approval. First, a hip phantom with steel and titanium prostheses that had inlays of water, fat, and contrast media in the pelvis was used to optimize the IFS algorithm.

Comparison of a multileaf collimator tracking system and a robotic treatment couch tracking system for organ motion compensation during radiotherapy.

Purpose: One limitation of accurate dose delivery in radiotherapy is intrafractional movement of the tumor or the entire patient which may lead to an underdosage of the target tissue or an overdosage of adjacent organs at risk. In order to compensate for this movement, different techniques have been developed. In this study the tracking performances of a multileaf collimator (MLC) tracking system and a robotic treatment couch tracking system were compared under equal conditions.

Multileaf collimator tracking integrated with a novel x-ray imaging system and external surrogate monitoring.

We have previously developed a tumour tracking system, which adapts the aperture of a Siemens 160 MLC to electromagnetically monitored target motion. In this study, we exploit the use of a novel linac-mounted kilovoltage x-ray imaging system for MLC tracking. The unique in-line geometry of the imaging system allows the detection of target motion perpendicular to the treatment beam (i.

Position detection accuracy of a novel linac-mounted intrafractional x-ray imaging system.

Purpose: The authors have developed a system that monitors intrafractional target motion perpendicular to the treatment beam with the aid of radioopaque markers by means of separating kV image and megavoltage (MV) treatment field on a single flat-panel detector.

Methods: They equipped a research Siemens Artiste linear accelerator (linac) with a 41 × 41 cm(2) a-Si flat-panel detector underneath the treatment head. The in-line geometry allows kV (imaging) and MV (treatment) beams to share closely aligned beam axes.

Electromagnetic real-time tumor position monitoring and dynamic multileaf collimator tracking using a Siemens 160 MLC: geometric and dosimetric accuracy of an integrated system.

Purpose: Dynamic multileaf collimator tracking represents a promising method for high-precision radiotherapy to moving tumors. In the present study, we report on the integration of electromagnetic real-time tumor position monitoring into a multileaf collimator-based tracking system.

Methods And Materials: The integrated system was characterized in terms of its geometric and radiologic accuracy.

Real-time tumor tracking: automatic compensation of target motion using the Siemens 160 MLC.

Purpose: Advanced high quality radiation therapy techniques such as IMRT require an accurate delivery of precisely modulated radiation fields to the target volume. Interfractional and intrafractional motion of the patient's anatomy, however, may considerably deteriorate the accuracy of the delivered dose to the planned dose distributions. In order to compensate for these potential errors, a dynamic real-time capable MLC control system was designed.

Organization of rat vibrissa motor cortex and adjacent areas according to cytoarchitectonics, microstimulation, and intracellular stimulation of identified cells.

The relationship between motor maps and cytoarchitectonic subdivisions in rat frontal cortex is not well understood. We use cytoarchitectonic analysis of microstimulation sites and intracellular stimulation of identified cells to develop a cell-based partitioning scheme of rat vibrissa motor cortex and adjacent areas. The results suggest that rat primary motor cortex (M1) is composed of three cytoarchitectonic areas, the agranular medial field (AGm), the agranular lateral field (AG1), and the cingulate area 1 (Cg1), each of which represents movements of different body parts.