EVALUATION OF VGC ANALYZER BY COMPARISON WITH GOLD STANDARD ROC SOFTWARE AND ANALYSIS OF SIMULATED VISUAL GRADING DATA

A prospective study comparing the quality of coronary computed tomography angiography images from photon counting and energy integrating detector systems

BACKGROUND

As guidelines endorse the use of computed tomography (CT) for examining coronary artery disease (CAD), it is important to compare the advantages and disadvantages of the novel photon counting detector CT (PCD-CT) technology with the established energy integrating detector CT (EID-CT).

PURPOSE

To compare the image quality of coronary computed tomography angiography (CCTA) and the Agatston scores (AS) derived from EID-CT and PCD-CT.

MATERIAL AND METHODS

In this prospective observational study, 28 patients underwent clinical calcium score and CCTA scans on an EID-CT and a PCD-CT scanner. CCTA images were qualitatively analyzed by five observers using visual grading characteristics. The correlation and agreement of the AS were assessed using Spearman's rank correlation and Bland-Altman plots.

RESULTS

This qualitative analyses demonstrated a high fraction of "good" or "excellent" ratings for the image criteria in both CT systems. The sharpness of the distal lumen and image quality regarding motion artifacts were rated significantly higher for EID-CT (P < 0.05). However, the sharpness of coronary calcification was rated significantly higher for PCD-CT (P < 0.05). Spearman's rank correlation and Bland-Altman plots showed good correlation (P = 0.95) and agreement regarding the AS between EID-CT and PCD-CT.

CONCLUSION

Both CT systems exhibited high CCTA image quality. The sharpness of calcifications was rated significantly higher for PCD-CT. A good correlation was observed between the AS derived from the two systems.

Investigation of the Impact of Defective Ultrasound Transducers on Clinical Image Quality in Grayscale 2-D Still Images

OBJECTIVE

There are several studies that show high defect rates of transducers in clinical use. The purpose of the present study was to investigate whether image quality and the risk for misdiagnosis is affected by using defective transducers.

METHODS

Four defective transducers with varying degrees of defect severity, still in clinical use, were selected. Forty artifact-affected clinical images from each transducer were compared with images acquired from fully functional transducers, of the same model, in an observer study where four experienced radiologists rated each of the 320 images. The rating tasks included if the artifacts were detectable, if the possible artifacts might affect the diagnosis, how well structural details were reproduced and, finally, an assessment of overall image quality.

RESULTS

The artifacts in the images were detectable for three of the four transducers (p < 0.05), and in 121 of 640 assessments of the images from the defective transducers the observers were confident that the artifacts could affect the diagnosis. All four faulty transducers were assessed to have decreased ability to resolve structural details (p < 0.05), and three of the four transducers were assessed to have worse overall image quality (p < 0.05).

CONCLUSION

The present study shows that image quality and the risk of misdiagnosis can be affected by using defective transducers. This highlights the importance of frequent quality control of the transducers to avoid decreased image quality and even misdiagnosis.

Image quality of spectral brain computed tomography angiography using halved dose of iodine contrast medium

PURPOSE

Reduction in iodinated contrast medium (CM) dose is highly motivated. Our aim was to evaluate if a 50% reduction of CM, while preserving image quality, is possible in brain CT angiography (CTA) using virtual monoenergetic images (VMI) on spectral CT. As a secondary aim, we evaluated if VMI can salvage examinations with suboptimal CM timing.

METHODS

Consecutive patients older than 18 years without intracranial stenosis/occlusion were included. Three imaging protocols were used: group 1, full CM dose; group 2, 50% CM dose suboptimal timing; and group 3, 50% CM dose optimized timing. Attenuation, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured in the internal carotid artery, M2 segment of the middle cerebral artery, and white matter for conventional images (CI) and VMI (40-200 keV). Qualitative image quality for CI and VMI (50 and 60 keV) was rated by 4 experienced reviewers.

RESULTS

Qualitatively and quantitatively, VMI (40-60 keV) improved image quality within each group. Significantly higher attenuation and CNR was found for group 3 VMI 40-50 keV, with unchanged SNR, compared to group 1 CI. Group 3 VMI 50 keV also received significantly higher rating scores than group 1 CI. Group 2 VMI (40-50 keV) had significantly higher CNR compared to group 3 CI, but the subjective image quality was similar.

CONCLUSION

VMI of 50 keV with 50% CM dose increases qualitative and quantitative image quality over CI with full CM dose. Using VMI reduces non-diagnostic examinations and may salvage CTA examinations deemed non-diagnostic due to suboptimal timing.

Optimisation of exposure parameters using a phantom for thoracic spine radiographs in antero-posterior and lateral views

INTRODUCTION

To investigate the exposure parameters for thoracic spine/(TS) radiography that allows the image acquisition at the lowest dose possible, while maintaining an adequate image quality/(IQ) to identify all relevant anatomical criteria.

METHODS

An experimental phantom study was conducted, and 48 different radiographs of TS (24 AP/24 lateral) were acquired. The Automatic Exposure Control/(AEC) with the central sensor was used to select the beam intensity, while Source-to-Detector-Distance/(SDD) (AP:115/125 cm; Lateral:115/150 cm), tube potential (AP:70/81/90 kVp; Lateral: 81/90/102 kVp), use of grid/no grid and focal spot (fine/broad) were manipulated. IQ was assessed by observers with ViewDEX. Effective Dose (ED) was estimated using PCXMC2.0 software. Descriptive statistics paired with intraclass correlation coefficient (ICC) were applied to analyse data.

RESULTS

The ED increased with a greater SDD for lateral-view, presenting a significant difference (p = 0.038), however IQ was not affected. For both AP and lateral, the use of grid had a significant effect on ED (p < 0.001). Despite the images acquired without grid had lower IQ scores, the observers considered the IQ adequate for clinical use. A 20% reduction in ED (0.042mSv-0.033 mSv) was observed when increasing the beam energy from 70 to 90 kVp for AP grid in. The observers ICC ranged from moderate to good (0.5-0.75) in lateral and good to excellent (0.75-0.9) for AP views.

CONCLUSIONS

The optimised parameters in this context were 115 cm SDD, 90 kVp with grid for the best IQ and lowest ED. Further studies in clinical setting are necessary to enlarge the context and cover different body habitus and equipment.

IMPLICATIONS FOR PRACTICE

The SDD impacts on dose for TS; Higher kVp and grid are necessary to better image quality.

Evaluation of deep-learning image reconstruction for chest CT examinations at two different dose levels

AIMS

The aims of the present study were to, for both a full-dose protocol and an ultra-low dose (ULD) protocol, compare the image quality of chest CT examinations reconstructed using TrueFidelity (Standard kernel) with corresponding examinations reconstructed using ASIR-V (Lung kernel) and to evaluate if post-processing using an edge-enhancement filter affects the noise level, spatial resolution and subjective image quality of clinical images reconstructed using TrueFidelity.

METHODS

A total of 25 patients were examined with both a full-dose protocol and an ULD protocol using a GE Revolution APEX CT system (GE Healthcare, Milwaukee, USA). Three different reconstructions were included in the study: ASIR-V 40%, DLIR-H, and DLIR-H with additional post-processing using an edge-enhancement filter (DLIR-H + E2). Five observers assessed image quality in two separate visual grading characteristics (VGC) studies. The results from the studies were statistically analyzed using VGC Analyzer. Quantitative evaluations were based on determination of two-dimensional power spectrum (PS), contrast-to-noise ratio (CNR), and spatial resolution in the reconstructed patient images.

RESULTS

For both protocols, examinations reconstructed using TrueFidelity were statistically rated equal to or significantly higher than examinations reconstructed using ASIR-V 40%, but the ULD protocol benefitted more from TrueFidelity. In general, no differences in observer ratings were found between DLIR-H and DLIR-H + E2. For the three investigated image reconstruction methods, ASIR-V 40% showed highest noise and spatial resolution and DLIR-H the lowest, while the CNR was highest in DLIR-H and lowest in ASIR-V 40%.

CONCLUSION

The use of TrueFidelity for image reconstruction resulted in higher ratings on subjective image quality than ASIR-V 40%. The benefit of using TrueFidelity was larger for the ULD protocol than for the full-dose protocol. Post-processing of the TrueFidelity images using an edge-enhancement filter resulted in higher image noise and spatial resolution but did not affect the subjective image quality.

Comparison of image quality assessments between interventional radiographers and interventional radiologists using digital subtraction angiography

Purpose

The aim of our study was to compare the image quality assessments of vascular anatomy between interventional radiographers and interventional radiologists using digital subtraction angiography (DSA) runs acquired during an interventional radiology procedure.

Approach

Visual grading characteristics (VGC) analysis was used to assess image quality by comparing two groups of images, where one group consisted of procedures in which radiation dose was optimized (group A, n = 10 ) and one group where dose optimization was not performed (group B, n = 10 ). The radiation dose parameters were optimized based on theoretical and empirical evidence to achieve radiation dose reductions during uterine artery embolization procedures. The two observer groups comprised of interventional radiologists ( n = 4 ) and interventional radiographers ( n = 4 ). Each observer rated the image quality of 20 DSA runs using a five-point rating scale.

Results

The VGC analysis produced an area under the VGC curve (AUC VGC ) of 0.55 for interventional radiographers ( P = 0.61 ) and AUCVGC of 0.52 for interventional radiologists ( P = 0.83 ). The optimization of radiation dose parameters demonstrated a reduction in kerma-area product by 35% ( P = 0.026 , d = 0.5 ) and reference air kerma (Ka, r ) by 43% ( P = 0.042 , d = 0.5 ) between group A and group B.

Conclusions

VGC analysis indicated that the image quality assessments of interventional radiographers were comparable with interventional radiologists, where a reduction in radiation dose revealed no effect on both observer groups regarding their image quality assessment of vascular anatomy.

UTERINE ARTERY EMBOLISATION: CONTINUOUS QUALITY IMPROVEMENT REDUCES RADIATION DOSE WHILE MAINTAINING IMAGE QUALITY

The purpose of this study was to introduce a continuous quality improvement (CQI) program for radiation dose optimisation during uterine artery embolisation (UAE) and assess its impact on dose reduction and image quality. The CQI program investigated the effects of optimising radiation dose parameters on the kerma-area product (KAP) and image quality when comparing a 'CQI intervention' group (n = 50) and 'Control' group (n = 50). Visual grading characteristics (VGC) analysis was used to assess image quality, using the 'Control' group as a reference. A significant reduction in KAP by 17% (P = 0.041, d = 0.2) and reference air kerma (Ka, r) by 20% (P = 0.027, d = 0.2) was shown between the two groups. The VGC analysis resulted in an area under the VGC curve (AUCVGC) of 0.54, indicating no significant difference in image quality between the two groups (P = 0.670). The implementation of the CQI program and optimisation of radiation dose parameters improved the UAE radiation dose practices at our centre. The dose reduction demonstrated no detrimental effects on image quality.