Evaluation of low contrast detectability performance using two-alternative forced choice method on computed tomography dose reduction algorithms

2012 ◽  
Author(s):  
Jiahua Fan ◽  
Priti Madhav ◽  
Paavana Sainath ◽  
Ximiao Cao ◽  
Haifeng Wu ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Dose Reduction ◽  
Forced Choice ◽  
Low Contrast ◽  
Choice Method

Forced-Choice vs Free-Response in Personality Assessment

1963 ◽  
Vol 13 (1) ◽  
pp. 159-169 ◽  
Author(s):  
Peter F. Merenda ◽  
Walter V. Clarke
Keyword(s):  
Personality Assessment ◽  
Forced Choice ◽  
Self Concept ◽  
Personality Profiles ◽  
Psychological Measurement ◽  
Free Response ◽  
Relative Validity ◽  
General Consensus ◽  
Choice Method ◽  
Statistical Results

Two self-rating adjective check lists (ACL) were administered to 44 students in a course on psychological measurement. The first ACL administered was the regular free response list, followed immediately with a forced-choice version in which the adjectives were arranged into tetrad sets. Ipsative scoring was used and profiles compared. The correlations between the profiles ranged from −1.00 to 1.00, more than 40% falling in the negative range. Ss gave their impressions and reactions to both inventories, and evaluated the relative validity of the results. A majority favored the free-response technique and felt that it would yield a more accurate description of their self-concepts and personality structures. General consensus was that the forced-choice instructions led to frustration, increased irritability, and decreased motivation. Ss felt that the free-response instrument presented a more relaxing situation and was even enjoyable to take. Ss' verbal reactions were consistent with the statistical results. The findings suggest that the forced-choice method is likely to be inappropriate for use with adjective check lists in self-concept assessment and analysis, and may lead not only to distortion in the personality profiles, but also to reversals.

scholarly journals Dual-rotation C-arm cone-beam computed tomography to increase low-contrast detection

2017 ◽  
Vol 44 (9) ◽  
pp. e164-e173
Author(s):  
Aymeric Reshef ◽  
Cyril Riddell ◽  
Yves Trousset ◽  
Saïd Ladjal ◽  
Isabelle Bloch
Keyword(s):  
Computed Tomography ◽  
Cone Beam Computed Tomography ◽  
Cone Beam ◽  
Low Contrast ◽  
Contrast Detection ◽  
Dual Rotation

scholarly journals Design of a Monte Carlo model based on dual-source computed tomography (DSCT) scanners for dose and image quality assessment using the Monte Carlo N-Particle (MCNP5) code

2020 ◽  
Vol 26 (1) ◽  
pp. 11-20
Author(s):  
Stefania Chantzi ◽  
Emmanouil Papanastasiou ◽  
Christina Athanasopoulou ◽  
Elisavet Molyvda-Athanasopoulou ◽  
Panagiotis Bamidis ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Monte Carlo ◽  
Monte Carlo Model ◽  
Dose Assessment ◽  
Projection Algorithm ◽  
Projection Data ◽  
Ct Number ◽  
Low Contrast ◽  
Dual Source ◽  
Dual Source Computed Tomography

AbstractThe purpose of this work was to develop and validate a Monte Carlo model for a Dual Source Computed Tomography (DSCT) scanner based on the Monte Carlo N-particle radiation transport computer code (MCNP5). The geometry of the Siemens Somatom Definition CT scanner was modeled, taking into consideration the x-ray spectrum, bowtie filter, collimator, and detector system. The accuracy of the simulation from the dosimetry point of view was tested by calculating the Computed Tomography Dose Index (CTDI) values. Furthermore, typical quality assurance phantoms were modeled in order to assess the imaging aspects of the simulation. Simulated projection data were processed, using the MATLAB software, in order to reconstruct slices, using a Filtered Back Projection algorithm. CTDI, image noise, CT-number linearity, spatial and low contrast resolution were calculated using the simulated test phantoms. The results were compared using several published values including IMPACT, NIST and actual measurements. Bowtie filter shapes are in agreement with those theoretically expected. Results show that low contrast and spatial resolution are comparable with expected ones, taking into consideration the relatively limited number of events used for the simulation. The differences between simulated and nominal CT-number values were small. The present attempt to simulate a DSCT scanner could provide a powerful tool for dose assessment and support the training of clinical scientists in the imaging performance characteristics of Computed Tomography scanners.

scholarly journals Comparison of low-contrast detectability between uniform and anatomically realistic phantoms—influences on CT image quality assessment

2021 ◽  
Author(s):  
Juliane Conzelmann ◽  
Ulrich Genske ◽  
Arthur Emig ◽  
Michael Scheel ◽  
Bernd Hamm ◽  
...  
Keyword(s):  
Image Quality ◽  
Quality Assessment ◽  
Dose Reduction ◽  
Iterative Reconstruction ◽  
Image Quality Assessment ◽  
Lesion Detection ◽  
Detection Accuracy ◽  
Test Environment ◽  
Low Contrast ◽  
Dose Effects

Abstract Objectives To evaluate the effects of anatomical phantom structure on task-based image quality assessment compared with a uniform phantom background. Methods Two neck phantom types of identical shape were investigated: a uniform type containing 10-mm lesions with 4, 9, 18, 30, and 38 HU contrast to the surrounding area and an anatomically realistic type containing lesions of the same size and location with 10, 18, 30, and 38 HU contrast. Phantom images were acquired at two dose levels (CTDIvol of 1.4 and 5.6 mGy) and reconstructed using filtered back projection (FBP) and adaptive iterative dose reduction 3D (AIDR 3D). Detection accuracy was evaluated by seven radiologists in a 4-alternative forced choice experiment. Results Anatomical phantom structure impaired lesion detection at all lesion contrasts (p < 0.01). Detectability in the anatomical phantom at 30 HU contrast was similar to 9 HU contrast in uniform images (91.1% vs. 89.5%). Detection accuracy decreased from 83.6% at 5.6 mGy to 55.4% at 1.4 mGy in uniform FBP images (p < 0.001), whereas AIDR 3D preserved detectability at 1.4 mGy (80.7% vs. 85% at 5.6 mGy, p = 0.375) and was superior to FBP (p < 0.001). In the assessment of anatomical images, superiority of AIDR 3D was not confirmed and dose reduction moderately affected detectability (74.6% vs. 68.2%, p = 0.027 for FBP and 81.1% vs. 73%, p = 0.018 for AIDR 3D). Conclusions A lesion contrast increase from 9 to 30 HU is necessary for similar detectability in anatomical and uniform neck phantom images. Anatomical phantom structure influences task-based assessment of iterative reconstruction and dose effects. Key Points • A lesion contrast increase from 9 to 30 HU is necessary for similar low-contrast detectability in anatomical and uniform neck phantom images. • Phantom background structure influences task-based assessment of iterative reconstruction and dose effects. • Transferability of CT assessment to clinical imaging can be expected to improve as the realism of the test environment increases.

scholarly journals Feasible Dose Reduction in Routine Chest Computed Tomography Maintaining Constant Image Quality Using the Last Three Scanner Generations: From Filtered Back Projection to Sinogram-affirmed Iterative Reconstruction and Impact of the Novel Fully Integrated Detector Design Minimizing Electronic Noise

2014 ◽  
Vol 4 ◽  
pp. 38 ◽  
Author(s):  
Lukas Ebner ◽  
Felix Knobloch ◽  
Adrian Huber ◽  
Julia Landau ◽  
Daniel Ott ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Soft Tissue ◽  
Radiation Dose ◽  
Dose Reduction ◽  
Integrated Circuit ◽  
Chest Ct ◽  
Back Projection ◽  
Dose Length Product ◽  
Chest Computed Tomography ◽  
Tube Current

Objective: The aim of the present study was to evaluate a dose reduction in contrast-enhanced chest computed tomography (CT) by comparing the three latest generations of Siemens CT scanners used in clinical practice. We analyzed the amount of radiation used with filtered back projection (FBP) and an iterative reconstruction (IR) algorithm to yield the same image quality. Furthermore, the influence on the radiation dose of the most recent integrated circuit detector (ICD; Stellar detector, Siemens Healthcare, Erlangen, Germany) was investigated. Materials and Methods: 136 Patients were included. Scan parameters were set to a thorax routine: SOMATOM Sensation 64 (FBP), SOMATOM Definition Flash (IR), and SOMATOM Definition Edge (ICD and IR). Tube current was set constantly to the reference level of 100 mA automated tube current modulation using reference milliamperes. Care kV was used on the Flash and Edge scanner, while tube potential was individually selected between 100 and 140 kVp by the medical technologists at the SOMATOM Sensation. Quality assessment was performed on soft-tissue kernel reconstruction. Dose was represented by the dose length product. Results: Dose-length product (DLP) with FBP for the average chest CT was 308 mGy*cm ± 99.6. In contrast, the DLP for the chest CT with IR algorithm was 196.8 mGy*cm ± 68.8 (P = 0.0001). Further decline in dose can be noted with IR and the ICD: DLP: 166.4 mGy*cm ± 54.5 (P = 0.033). The dose reduction compared to FBP was 36.1% with IR and 45.6% with IR/ICD. Signal-to-noise ratio (SNR) was favorable in the aorta, bone, and soft tissue for IR/ICD in combination compared to FBP (the P values ranged from 0.003 to 0.048). Overall contrast-to-noise ratio (CNR) improved with declining DLP. Conclusion: The most recent technical developments, namely IR in combination with integrated circuit detectors, can significantly lower radiation dose in chest CT examinations.

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