Agreement of the modified Medical Research Council and New York Heart Association scales for assessing the impact of self-rated breathlessness in cardiopulmonary disease.

Background: The functional impact of breathlessness is assessed using the modified Medical Research Council (mMRC) scale for chronic respiratory disease and with the New York Heart Association Functional Classification (NYHA) scale for heart failure. We evaluated agreement between the scales and their concurrent validity with other clinically relevant patient-reported outcomes in cardiorespiratory disease.

Methods: Outpatients with stable chronic respiratory disease or heart failure were recruited.

Feasibility of unconstrained three-material decomposition: imaging an excised human heart using a prototype silicon photon-counting CT detector.

Rationale And Objectives: The purpose of this study was to evaluate the feasibility of unconstrained three-material decomposition in a human tissue specimen containing iodinated contrast agent, using an experimental multi-bin photon-counting silicon detector. It was further to evaluate potential added clinical value compared to a 1st-generation state-of-the-art dual-energy computed tomography system.

Materials And Methods: A prototype photon-counting silicon detector in a bench-top setup for x-ray tomographic imaging was calibrated using a multi-material calibration phantom.

Minimal Clinically Important Differences and Feasibility of Dyspnea-12 and the Multidimensional Dyspnea Profile in Cardiorespiratory Disease.

Context: Breathlessness is a cardinal symptom in cardiorespiratory disease and consists of multiple dimensions that can be measured using the instruments Dyspnea-12 (D12) and the Multidimensional Dyspnea Profile (MDP).

Objectives: The objective of the study is to determine the minimal clinically important differences (MCIDs) of all D12 and MDP summary and subdomain scores as well as the instruments' feasibility in patients with cardiorespiratory disease.

Methods: Prospective multicenter cohort study of outpatients with diagnosed cardiorespiratory disease and breathlessness in daily life.

Erratum for "A Framework for Evaluating Threshold Variation Compensation Methods in Photon Counting Spectral CT".

On page 1862 of [1] (the second page of the article), in the second column, between (5) and (6), the current text "variations in the measured number of counts between different dels" should be replaced with "variations in the log normalized measured number of counts between different dels."

Validation of the Swedish Multidimensional Dyspnea Profile (MDP) in outpatients with cardiorespiratory disease.

Introduction: Breathlessness is a cardinal symptom in cardiorespiratory disease. An instrument for measuring different aspects of breathlessness was recently developed, the Multidimensional Dyspnea Profile (MDP). This study aimed to validate the MDP in terms of the underlying factor structure, internal consistency, test-retest reliability and concurrent validity in Swedish outpatients with cardiorespiratory disease.

Clinical validation of the Swedish version of Dyspnoea-12 instrument in outpatients with cardiorespiratory disease.

Introduction: Breathlessness is the cardinal symptom in both cardiac and respiratory diseases, and includes multiple dimensions. The multidimensional instrument Dyspnoea-12 has been developed to assess both physical and affective components of breathlessness. This study aimed to perform a clinical validation of the Swedish version of Dyspnoea-12 in outpatients with cardiorespiratory disease.

Subpixel x-ray imaging with an energy-resolving detector.

The detector pixel size can be a severe limitation in x-ray imaging of fine details in the human body. We demonstrate a method of using spectral x-ray measurements to image the spatial distribution of the linear attenuation coefficient on a length scale smaller than one pixel, based on the fact that interfaces parallel to the x-ray beam have a unique spectral response, which distinguishes them from homogeneous materials. We evaluate the method in a simulation study by simulating projection imaging of the border of an iodine insert with [Formula: see text] in a soft tissue phantom.

Errata: Spectral response model for a multibin photon-counting spectral computed tomography detector and its applications.

[This corrects the article DOI: 10.1117/1.JMI.

Upper limits of the photon fluence rate on CT detectors: Case study on a commercial scanner.

Purpose: The highest photon fluence rate that a computed tomography (CT) detector must be able to measure is an important parameter. The authors calculate the maximum transmitted fluence rate in a commercial CT scanner as a function of patient size for standard head, chest, and abdomen protocols.

Methods: The authors scanned an anthropomorphic phantom (Kyoto Kagaku PBU-60) with the reference CT protocols provided by AAPM on a GE LightSpeed VCT scanner and noted the tube current applied with the tube current modulation (TCM) system.

Spectral response model for a multibin photon-counting spectral computed tomography detector and its applications.

Variations among detector channels in computed tomography can lead to ring artifacts in the reconstructed images and biased estimates in projection-based material decomposition. Typically, the ring artifacts are corrected by compensation methods based on flat fielding, where transmission measurements are required for a number of material-thickness combinations. Phantoms used in these methods can be rather complex and require an extensive number of transmission measurements.

Theoretical comparison of a dual energy system and photon counting silicon detector used for material quantification in spectral CT.

Any method using dual energy computed tomography (CT) has to make prior assumptions in order to quantify k-edge contrast agents. This work estimates the mean square error (MSE) in contrast agent quantification employing a method based on assigning each reconstructed voxel a ratio of soft tissue and fat using dual energy CT. The results are compared to the MSE using a photon counting silicon detector with multiple bins.

Energy-resolved CT imaging with a photon-counting silicon-strip detector.

Photon-counting detectors are promising candidates for use in the next generation of x-ray computed tomography (CT) scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility.

Allowable forward model misspecification for accurate basis decomposition in a silicon detector based spectral CT.

Material basis decomposition in the sinogram domain requires accurate knowledge of the forward model in spectral computed tomography (CT). Misspecifications over a certain limit will result in biased estimates and make quantum limited (where statistical noise dominates) quantitative CT difficult. We present a method whereby users can determine the degree of allowed misspecification error in a spectral CT forward model and still have quantification errors that are limited by the inherent statistical uncertainty.

Optimal frequency-based weighting for spectral x-ray projection imaging.

The purpose of this work is to derive a weighting scheme that maximizes the frequency-dependent ideal observer signal-difference-to-noise ratio, commonly referred to as detectability index or Hotelling-SDNR, for spectral X-ray projection imaging. Starting from basic statistical decision theory, optimal frequency-dependent weights are derived for a multiple-bin system and the Hotelling-SDNR calculated. A 28% increase in detectability index is found for high frequency objects when applying optimal frequency-dependent weights instead of pixel-based weights to a simplified model of a silicon detector, decreasing towards 0% for low frequency objects.

Theoretical comparison of the iodine quantification accuracy of two spectral CT technologies.

We compare the theoretical limits of iodine quantification for the photon counting multibin and dual energy technologies. Dual energy systems by necessity have to make prior assumptions in order to quantify iodine. We explicitly allow the multibin system to make the same assumptions and also allow them to be wrong.

Eliminated risk of iodine contrast cancellation with multibin spectral CT.

This note compares the extent of contrast cancellation induced by iodinated contrast agents in energy integrating and photon counting multibin CT images. The contrast between a hypodense target and soft tissue is modeled for the two systems for a range of iodine concentrations and tube voltages. In energy integrating systems, we show that the contrast vanishes for low concentrations of iodine whereas the same effect is not seen in multibin systems.

A framework for evaluating threshold variation compensation methods in photon counting spectral CT.

One of the challenges in the development of photon counting spectral computed tomography (CT) detectors is that the location of the energy thresholds tends to vary among detector elements. If not compensated for, this threshold variation leads to ring artifacts in the reconstructed images. In this paper, a framework is presented for the systematic comparison of different methods of compensating for inhomogeneities among detector elements in photon counting CT with multiple energy bins.

Performance evaluation of a sub-millimetre spectrally resolved CT system on high- and low-frequency imaging tasks: a simulation.

We are developing a photon-counting silicon strip detector with 0.4 × 0.5 mm² detector elements for clinical CT applications.

Synthetic Hounsfield units from spectral CT data.

Beam-hardening-free synthetic images with absolute CT numbers that radiologists are used to can be constructed from spectral CT data by forming 'dichromatic" images after basis decomposition. The CT numbers are accurate for all tissues and the method does not require additional reconstruction. This method prevents radiologists from having to relearn new rules-of-thumb regarding absolute CT numbers for various organs and conditions as conventional CT is replaced by spectral CT.

XCOM intrinsic dimensionality for low-Z elements at diagnostic energies.

Purpose: To determine the intrinsic dimensionality of linear attenuation coefficients (LACs) from XCOM for elements with low atomic number (Z = 1-20) at diagnostic x-ray energies (25-120 keV). H(0) (q), the hypothesis that the space of LACs is spanned by q bases, is tested for various q-values.

Methods: Principal component analysis is first applied and the LACs are projected onto the first q principal component bases.

Task-based weights for photon counting spectral x-ray imaging.

Purpose: To develop a framework for taking the spatial frequency composition of an imaging task into account when determining optimal bin weight factors for photon counting energy sensitive x-ray systems. A second purpose of the investigation is to evaluate the possible improvement compared to using pixel based weights.

Methods: The Fourier based approach of imaging performance and detectability index d' is applied to pulse height discriminating photon counting systems.

Photon-counting spectral computed tomography using silicon strip detectors: a feasibility study.

We show how the spectral imaging framework should be modified to account for a high fraction of Compton interactions in low Z detector materials such as silicon. Using this framework, where deposited energies differ from actual photon energies, we compare the performance of a silicon strip detector, including the influence of scatter inside the detector and charge sharing but disregarding signal pileup, with an ideal energy integrating detector. We show that although the detection efficiency for silicon rapidly drops for the acceleration voltages encountered in clinical computed tomography practice, silicon detectors could perform on a par with ideal energy integrating detectors for routine imaging tasks.

Single-shot dual-energy subtraction mammography with electronic spectrum splitting: feasibility.

We present a single-shot dual-energy subtraction mammography technique using an energy sensitive photon counting detector. An electronic threshold near the middle of the X-ray spectrum discriminates between high- and low-energy photons, and allows the simultaneous acquisition of high- and low-energy images which can be combined to suppress anatomical clutter. By setting the electronic threshold close to 33.

Implications of unchanged detection criteria with CAD as second reader of mammograms.

In this paper we address the use of computer-aided detection (CAD) systems as second readers in mammography. The approach is based on Bayesian decision theory and its implication for the choice of optimal operating points. The choice of a certain operating point along an ROC curve corresponds to a particular tradeoff between false positives and missed cancers.