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Accuracy and efficiency of determining urinary calculi composition using dual-energy computed tomography compared with Hounsfield unit measurements for practicing physicians.

ABSTRACT: To compare speed and accuracy for determining urinary calculi composition between dual-energy computed tomography (DECT) and Hounsfield unit (HU) measurements of calculi by a set of reviewers at varying levels of training and practice.Sixteen patients with known stone composition were randomly selected. Fourteen reviewers of varying levels of practice interpreted DECT and HU images from the selected patients to predict stone composition in 2 sessions (day 1: tutorial or flow sheet available for image interpretation and day 2: tutorial or flow sheet not available). Reviewers recorded HU values, stone color, and predicted stone composition as they were timed. Accuracy of image interpretation, determination of calculi composition, and interpretation time were compared.DECT accuracy: image interpretation 100% (day 1) and 94% (day 2); predicted stone composition: 100% (day 1) and 73% (day 2). Mean interpretation time was the same for both days, 21 seconds per study (range, 11-40 seconds). HU accuracy: image interpretation 97% (day 1) and 91% (day 2); predicted stone composition was 45% accurate on both days. Mean interpretation time was 53 seconds per study (range, 28-79 seconds) and 41 seconds per study (range, 19-71 seconds) on days 1 and 2, respectively. Overall accuracy of determination of stone composition and interpretation time for DECT were essentially double those of the HU images (87% vs 45% and 21 vs 47 seconds, respectively). Reviewer's experience level did not affect accuracy or speed.DECT is easier to learn, faster to interpret, and more accurate than HU in determining urinary calculi composition for physicians at various levels of training and practice.

SUBMITTER: Jepperson MA

PROVIDER: S-EPMC4149808 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Accuracy and efficiency of determining urinary calculi composition using dual-energy computed tomography compared with Hounsfield unit measurements for practicing physicians.

Jepperson Maria A MA Ibrahim El-Sayed H el-SH Taylor Abby A Cernigliaro Joseph G JG Haley William E WE Thiel David D DD

Urology 20140715 3

<h4>Objective</h4>To compare speed and accuracy for determining urinary calculi composition between dual-energy computed tomography (DECT) and Hounsfield unit (HU) measurements of calculi by a set of reviewers at varying levels of training and practice.<h4>Materials and methods</h4>Sixteen patients with known stone composition were randomly selected. Fourteen reviewers of varying levels of practice interpreted DECT and HU images from the selected patients to predict stone composition in 2 sessio ...[more]

PMID: 25037635

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Project description:PURPOSE:This paper lays the groundwork for linking Hounsfield unit measurements to the International System of Units (SI), ultimately enabling traceable measurements across X-ray CT (XCT) machines. We do this by characterizing a material basis that may be used in XCT reconstruction giving linear combinations of concentrations of chemical elements (in the SI units of mol/m3) which may be observed at each voxel. By implication, linear combinations not in the set are not observable. METHODS AND MATERIALS:We formulated a model for our material basis with a set of measurements of elemental powders at four tube voltages, 80 kV, 100 kV, 120 kV, and 140 kV, on a medical XCT. The samples included 30 small plastic bottles of powders containing various compounds spanning the atomic numbers up to 20, and a bottle of water and one of air. Using the chemical formulas and measured masses, we formed a matrix giving the number of Hounsfield units per (mole per cubic meter) at each tube voltage for each of 13 chemical elements. We defined a corresponding matrix in units we call molar Hounsfield unit (HU) potency, the difference in HU values that an added mole per cubic meter in a given voxel would add to the measured HU value. We built a matrix of molar potencies for each chemical element and tube voltage and performed a singular value decomposition (SVD) on these to formulate our material basis. We determined that the dimension of this basis is two. We then compared measurements in this material space with theoretical measurements, combining XCOM cross section data with the tungsten anode spectral model using interpolating cubic splines (TASMICS), a one-parameter filter, and a simple detector model, creating a matrix similar to our experimental matrix for the first 20 chemical elements. Finally, we compared the model predictions to Hounsfield unit measurements on three XCT calibration phantoms taken from the literature. RESULTS:We predict the experimental HU potency values derived from our scans of chemical elements with our theoretical model built from XCOM data. The singular values and singular vectors of the model and powder measurements are in substantial agreement. Application of the Bayesian Information Criterion (BIC) shows that exactly two singular values and singular vectors describe the results over four tube voltages. We give a good account of the HU values from the literature, measured for the calibration phantoms at several tube voltages for several commercial instruments, compared with our theoretical model without introducing additional parameters. CONCLUSIONS:We have developed a two-dimensional material basis that specifies the degree to which individual elements in compounds effect the HU values in XCT images of samples with elements up to atomic number Z = 20. We show that two dimensions is sufficient given the contrast and noise in our experiment. The linear combination of concentrations of elements that can be observed using a medical XCT have been characterized, providing a material basis for use in dual-energy reconstruction. This approach provides groundwork for improved reconstruction and for the link of Hounsfield units to the SI.

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Project description:BackgroundPrevious surveys on the relationship between physicians and pharmaceutical representatives (PRs) have been of limited quality. The purpose of our survey of practicing physicians in Japan was to assess the extent of their involvement in pharmaceutical promotional activities, physician characteristics that predict such involvement, attitudes toward relationships with PRs, correlations between the extent of involvement and attitudes, and differences in the extent of involvement according to self-reported prescribing behaviors.Methods and findingsFrom January to March 2008, we conducted a national survey of 2621 practicing physicians in seven specialties: internal medicine, general surgery, orthopedic surgery, pediatrics, obstetrics-gynecology, psychiatry, and ophthalmology. The response rate was 54%. Most physicians met with PRs (98%), received drug samples (85%) and stationery (96%), and participated in industry-sponsored continuing medical education (CME) events at the workplace (80%) and outside the workplace (93%). Half accepted meals outside the workplace (49%) and financial subsidies to attend CME events (49%). Rules at the workplace banning both meetings with PRs and gifts predicted less involvement of physicians in promotional activities. Physicians valued information from PRs. They believed that they were unlikely to be influenced by promotional activities, but that their colleagues were more susceptible to such influence than themselves. They were divided about the appropriateness of low-value gifts. The extent of physician involvement in promotional activities was positively correlated with the attitudes that PRs are a valuable source of information and that gifts are appropriate. The extent of such involvement was higher among physicians who prefer to ask PRs for information when a new medication becomes available, physicians who are not satisfied with patient encounters ending only with advice, and physicians who prefer to prescribe brand-name medications.ConclusionsInvolvement in pharmaceutical promotional activities is widespread among practicing physicians in Japan. The extent of such involvement varies according to certain physician characteristics. As a group, they are at risk for influence by promotional activities.

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Dataset Information

Accuracy and efficiency of determining urinary calculi composition using dual-energy computed tomography compared with Hounsfield unit measurements for practicing physicians.

Publications

Accuracy and efficiency of determining urinary calculi composition using dual-energy computed tomography compared with Hounsfield unit measurements for practicing physicians.

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