Aspects Of Image Quality Research Articles

An objective measure for assessing the quality of contrast enhancement on magnetic resonance images

Post-processing algorithms like histogram equalization and its variants have been widely employed to enhance the contrast of Magnetic Resonance (MR) images. Objective metrics that can collectively reflect the improvement in contrast and inadvertent distortions are necessary to rate the quality of enhanced images. The objective of this paper is to formulate an objective statistic for rating the quality of contrast enhancement on MR images and to test the agreement of the proposed metric with the subjective fidelity ratings. An objective metric named Cumulative Quality of Contrast-Enhanced Images (CQCEI), for assessing the quality of contrast enhancement, especially the performance of the histogram equalization and its variants, on MR images is proposed. The CQCEI is formulated such that it collectively accounts for various aspects of image quality pertaining to the contrast enhancement, namely improvement in contrast, shift in mean brightness, saturation and noise-amplification. The CQCEI has shown good agreement with subjective fidelity ratings on contrast-enhanced MR images.

IE-IQA: Intelligibility Enriched Generalizable No-Reference Image Quality Assessment.

Image quality assessment (IQA) for authentic distortions in the wild is challenging. Though current IQA metrics have achieved decent performance for synthetic distortions, they still cannot be satisfactorily applied to realistic distortions because of the generalization problem. Improving generalization ability is an urgent task to make IQA algorithms serviceable in real-world applications, while relevant research is still rare. Fundamentally, image quality is determined by both distortion degree and intelligibility. However, current IQA metrics mostly focus on the distortion aspect and do not fully investigate the intelligibility, which is crucial for achieving robust quality estimation. Motivated by this, this paper presents a new framework for building highly generalizable image quality model by integrating the intelligibility. We first analyze the relation between intelligibility and image quality. Then we propose a bilateral network to integrate the above two aspects of image quality. During the fusion process, feature selection strategy is further devised to avoid negative transfer. The framework not only catches the conventional distortion features but also integrates intelligibility features properly, based on which a highly generalizable no-reference image quality model is achieved. Extensive experiments are conducted based on five intelligibility tasks, and the results demonstrate that the proposed approach outperforms the state-of-the-art metrics, and the intelligibility task consistently improves metric performance and generalization ability.

Image quality is resilient against tube voltage variations in post-mortem skeletal radiography with a digital flat-panel detector

In recent phantom studies low-contrast detectability was shown to be independent from variations in tube voltage in digital radiography (DR) systems. To investigate the transferability to a clinical setting, the lower extremities of human cadavers were exposed at constant detector doses with different tube voltages in a certain range, as proposed in the phantom studies. Three radiologists independently graded different aspects of image quality (IQ) in a comparative analysis. The grades show no correlation between IQ and kV, which means that the readers were not able to recognize a significant IQ difference at different kV. Signal-to-noise and contrast-to-noise ratios showed no significant differences in IQ despite the kV-setting variations. These findings were observed from a limited kV range setting. Higher kV-settings resulted in lowest patient exposure at constant IQ. These results confirm the potential of DR-systems to contribute to standardization of examination protocols comparable to computed tomography. This may prevent the trend to overexpose. Further investigations in other body regions and other DR-systems are encouraged to determine transferability.

How to improve image quality of DWI of the prostate\u2014enema or catheter preparation?

ObjectivesTo compare the impact of laxative enema preparation versus air/gas suction through a small catheter on image quality of prostate DWI.MethodsIn this single-center study, 200 consecutive patients (100 in each arm) with either enema or catheter preparation were retrospectively included. Two blinded readers independently assessed aspects of image quality on 5-point Likert scales. Scores were compared between groups and the influence of confounding factors evaluated using multivariable logistic regression. Prostate diameters were compared on DWI and T2-weighted imaging using intraclass correlation coefficients.ResultsImage quality was significantly higher in the enema group regarding the severity of susceptibility-related artifacts (reader 1: 0.34 ± 0.77 vs. 1.73 ± 1.34, reader 2: 0.38 ± 0.86 vs. 1.76 ± 1.39), the differentiability of the anatomy (reader 1: 3.36 ± 1.05 vs. 2.08 ± 1.31, reader 2: 3.37 ± 1.05 vs. 2.09 ± 1.35), and the overall image quality (reader 1: 3.66 ± 0.77 vs. 2.26 ± 1.33, Reader 2: 3.59 ± 0.87 vs. 2.23 ± 1.38) with almost perfect inter-observer agreement (κ = 0.92–0.95). In the enema group, rectal distention was significantly lower and strongly correlated with the severity of artifacts (reader 1: ρ = 0.79, reader 2: ρ = 0.73). Furthermore, there were significantly fewer substantial image distortions, with odds ratios of 0.051 and 0.084 for the two readers which coincided with a higher agreement of the prostate diameters in the phase-encoding direction (0.96 vs. 0.89).ConclusionsEnema preparation is superior to catheter preparation and yields substantial improvements in image quality.Key Points• Enema preparation is superior to decompression of the rectum using air/gas suction through a small catheter.• Enema preparation markedly improves the image quality of prostate DWI regarding the severity of susceptibility-related artifacts, the differentiability of the anatomy, and the overall image quality and considerably reduces substantial artifacts that may impair a reliable diagnosis.

A comparative analysis framework of 3T and 7T TOF-MRA based on automated cerebrovascular segmentation.

High field strength 3T and 7T Time-Of-Flight Magnetic Resonance Angiography (TOF- MRA) achieves better visualization of intracranial vessels, so it attracts much attention. However, quantitative comparison between 3T and 7T MRA is lacking in the aspects of image quality and the practical application of cerebrovascular diseases. In this paper, a quantitative framework of 3T and 7T TOF-MRA comparison is proposed, which contains two steps including the automated cerebrovascular segmentation and statistical analysis. Firstly, the whole vascular structures on both 3T and 7T TOF-MRA images are segmented automatically, especially those small blood vessels in 7T MRA. The skeleton extraction-based automatic seed point detection is implemented to ensure the segmented vascular structure complete and precise. Secondly, the statistical analysis of the differences between 3T and 7T MRA is carried out in the aspects of image quality and the characteristics of some important vessels. The objects of statistical analysis are achieved and analyzed automatically without needing the time- consuming human beings' participation, therefore, it is efficient and objective. The comparison experiments on seven pairs of 3T and 7T TOF MRA images validated that about image quality, the contrast-to-noise ratio of 7T MRA was about 4.53 ± 0.95 times as much as that of 3T MRA. About the cerebrovascular information, small vessels were more abundant in 7T MRA compared with 3T MRA (branches number: 462.0 ± 58.5 vs 393.1 ± 63.3). The proposed framework can segment the whole cerebrovascular structure automatically and compare TOF-MRA with different field strengths objectively and quantitatively. It is helpful for clinical cerebrovascular disease, especially cerebral small vessel diseases.

Clinical Implementation of In-House Developed MR-Based Patient-Specific 3D Models of Liver Anatomy

Knowledge of patient-specific liver anatomy is key to patient safety during major hepatobiliary surgery. Three-dimensional (3D) models of patient-specific liver anatomy based on diagnostic MRI images can provide essential vascular and biliary anatomical insight during surgery. However, a method for generating these is not yet publicly available. This paper describes how these 3D models of the liver can be generated using open source software, and then subsequently integrated into a sterile surgical environment. The most common image quality aspects that degrade the quality of the 3D models as well possible ways of eliminating these are also discussed. Per patient, a single diagnostic multiphase MRI scan with hepatospecific contrast agent was used for automated segmentation of liver contour, arterial, portal, and venous anatomy, and the biliary tree. Subsequently, lesions were delineated manually. The resulting interactive 3D model could be accessed during surgery on a sterile covered tablet. Up to now, such models have been used in 335 surgical procedures. Their use simplified the surgical treatment of patients with a high number of liver metastases and contributed to the localization of vanished lesions in cases of a radiological complete response to neoadjuvant treatment. They facilitated perioperative verification of the relationship of tumors and the surrounding vascular and biliary anatomy, and eased decision-making before and during surgery.

Inclusion of quasi-vertex views in a brain-dedicated multi-pinhole SPECT system for improved imaging performance

With brain-dedicated multi-detector systems employing pinhole apertures the usage of detectors facing the top of the patient’s head (i.e. quasi-vertex (QV) views) can provide the advantage of additional viewing from close to the brain for improved detector coverage. In this paper, we report the results of simulation and reconstruction studies to investigate the impact of the QV views on the imaging performance of AdaptiSPECT-C, a brain-dedicated stationary SPECT system under development. In this design, both primary and scatter photons from regions located inferior to the brain can contribute to SPECT projections acquired by the QV views, and thus degrade AdaptiSPECT-C imaging performance. In this work, we determined the proportion, origin, and nature (i.e. primary, scatter, and multiple-scatter) of counts emitted from structures within the head and throughout the body contributing to projections from the different AdaptiSPECT-C detector rings, as well as from a true vertex view detector. We simulated phantoms used to assess different aspects of image quality (i.e. uniform activity concentration sphere, and Derenzo), as well as anthropomorphic phantoms with different count levels emulating clinical 123I activity distributions (i.e. DaTscan and perfusion). We determined that attenuation and scatter in the patient’s body greatly diminish the probability of the photons emitted outside the volume of interest reaching to detectors and being recorded within the 15% photopeak energy window. In addition, we demonstrated that the inclusion of the residual of such counts in the system acquisition does not degrade visual interpretation or quantitative analysis. The addition of the QV detectors improves volumetric sensitivity, angular sampling, and spatial resolution leading to significant enhancement in image quality, especially in the striato-thalamic and superior regions of the brain. Besides, the use of QV detectors improves the recovery of clinically relevant metrics such as the striatal binding ratio and mean activity in selected cerebral structures. Our findings proving the usefulness of the QV ring for brain imaging with 123I agents can be generalized to other commonly used SPECT imaging agents labelled with isotopes, such as 99mTc and likely 111In.

Multiscale Fusion Based Illumination Estimation for Image Enhancement

Image enhancement refers to improvement in the quality of images for their more accurate interpretation by vision-based systems. Many image enhancement algorithms have been previously proposed to tackle the problem of image enhancement. However, most of the techniques proposed for enhancement of images lose out on some or the other aspects of image quality or are computationally inefficient. This paper presents a novel image enhancement technique which works for a variety of different lighting conditions and is computationally efficient. The technique is based on the Retinex theory of images where an image can be considered as a product of illumination and reflectance. The proposed approach estimates illumination using fusion with the help of various components for estimation. The proposed method produces satisfactory results in various cases of Underexposed images. The resultant images show improvement in brightness and contrast of the underexposed images. The experimental analysis validates the superior performance of the proposed method.

A Framework for Objective Evaluation of Single Image De-Hazing Techniques

Real-world environment, where images are acquired with digital camera, may be subject to sever climatic conditions such as haze that may drastically reduce the quality performance of sophisticated computer vision algorithms used for various tasks, e.g., tracking, detection, classification etc. Even though several single image de-hazing techniques have been recently proposed with many deep-learning approaches among them, a general statistical framework that would permit an objective performance evaluation has not been independently introduced yet. In this manuscript, certain performance metrics that emphasize different aspects of image quality, output ranges and polarity, are identified and combined into a single performance indicator derived in an unbiased manner. A general methodology is thus introduced, as a framework for objective performance evaluation of current and future dehazing tasks, through an extensive comparison of 15 single image de-hazing techniques over a vast range of image data sets. The proposed unified framework shows several advantages in evaluating diverse and perceptually meaningful image features but also in elucidating future directions for improvement in image dehazing tasks.

Dose reduction potential of using gold fiducial markers for kilovoltage image-guided radiotherapy.

This study aimed to evaluate the possibility of reducing the imaging dose for image‐guided radiotherapy by using planar kilovoltage orthogonal imaging and fiducial markers (kV‐FM). We tested kilovoltage planar images under clinical imaging conditions for the pelvis (75 kVp, 200 mA, 50 ms) at a decreasing tube current (from 200 to 10 mA). Imaging doses were measured with a semiconductor detector. The visibility of the kV‐FM, aspects of image quality (spatial resolution, low contrast resolution), and the resultant image registration reproducibility were evaluated using various shapes (folded, linear, tadpole‐like) of fiducial markers containing 0.5% iron [Gold Anchor™ (GA); Naslund Medical AB, Huddinge, Sweden]. The GA phantom was created by placing these variously shaped GAs in an agar phantom. The imaging doses with 200 and 10 mA were approximately 0.74 and 0.04 mGy and they were correlated to the tube current (R2 = 0.999). Regardless of the marker’s shape, the GA phantom ensured visibility even when the tube current was reduced to the minimum value (10 mA). The low contrast resolution was gradually decreased at less than 50 mA, but the spatial resolution did not change. Although the auto‐registration function could not be used, manual‐registration could be achieved with an accuracy of within 1 mm, even when the imaging dose was reduced to 1/20 of the clinical imaging condition for the pelvis. When using the GA as the fiducial marker, the imaging dose could be reduced to 1/20 of that used clinically while maintaining the accuracy of manual‐registration using the kV‐FM for image‐guided radiotherapy of the pelvis.

Use of artificial intelligence in computed tomography dose optimisation.

The field of artificial intelligence (AI) is transforming almost every aspect of modern society, including medical imaging. In computed tomography (CT), AI holds the promise of enabling further reductions in patient radiation dose through automation and optimisation of data acquisition processes, including patient positioning and acquisition parameter settings. Subsequent to data collection, optimisation of image reconstruction parameters, advanced reconstruction algorithms, and image denoising methods improve several aspects of image quality, especially in reducing image noise and enabling the use of lower radiation doses for data acquisition. Finally, AI-based methods to automatically segment organs or detect and characterise pathology have been translated out of the research environment and into clinical practice to bring automation, increased sensitivity, and new clinical applications to patient care, ultimately increasing the benefit to the patient from medically justified CT examinations. In summary, since the introduction of CT, a large number of technical advances have enabled increased clinical benefit and decreased patient risk, not only by reducing radiation dose, but also by reducing the likelihood of errors in the performance and interpretation of medically justified CT examinations.

Effect of target/filter combination on the mean glandular dose and contrast-detail threshold: A phantom study

IntroductionIn mammography it is essential to combine aspects of image quality with compliance with glandular dose levels. The objective of this study was to combine the assessment of the contrast-detail threshold and the mean glandular dose for different target/filter combinations in digital mammography and to indicate the optimal combination through a figure of merit (FOM). MethodsIn a direct digital mammograph, performance and image quality standards were evaluated using a solid-state multidetector capable of measuring various parameters including kerma and standardized phantoms for image quality. After verifying the proper functioning of the mammograph, the contrast-detail detection threshold and the mean glandular dose values for thicknesses ranging from 20 mm to 70 mm in polymethylmethacrylate (PMMA) were evaluated. Combining these values, an FOM was defined to determine the optimal combination. ResultsThe results indicated that the Mo/Rh and W/Rh combinations present mean glandular doses below the limit for all thicknesses. In contrast, using the Mo/Mo combination, the mean glandular doses were below the limit only up to 45 mm. However, when considering the FOM that combines dosimetric aspects and the contrast-detail threshold, the use of W/Rh is the most optimal option. ConclusionThe results obtained in this study demonstrate that the W/Rh combination in direct digital mammography is the option that presents the best trade-off between the mean glandular dose and the contrast-detail detection threshold. Implications for practiceThe results demonstrate that the application of the W/Rh combination in direct digital mammography offers an optimized and applicable option, regardless of the thickness of the breast that will be radiographed.

Attachment, body appreciation, and body image quality of life in adolescents with eating disorders

ABSTRACT The aim of the current study was to determine the link between parental attachment style and body appreciation in adolescents with and without eating disorders, and to explore the association between attachment, positive aspects of body image and body image quality of life. The sample comprised 260 adolescents (M age = 15.35, SD age = 1.461): 129 non-clinical participants and 131 adolescents with eating disorders who received treatment in five Eating Disorders Units located in different regions in Spain. They were assessed via the Inventory of Parent and Peer Attachment (IPPA), Body Appreciation Scale (BAS), and Body Image Quality of Life Inventory (BIQLI). There was a significant relation between secure attachment and body appreciation in both groups, and body appreciation was positively related to body image quality of life. Patients with eating disorders had higher body image quality of life when they perceived better communication and trust with their father, which was mediated by the body appreciation they showed. Adolescents without eating disorders showed this same relationship form with their mother. This study aims to highlight the influence of parental attachment on a positive body image in adolescence.

Fast overlapped subaperture algorithm for high-squint spotlight SAR imaging

ABSTRACT The overlapped subaperture algorithm (OSA) is popular for high-squint spotlight synthetic aperture radar (SAR) imaging due to its ability of dealing with a much larger swath than the primary polar format algorithm. However, the traditional OSA suffers from the problem of low efficiency because of the high subaperture overlapping ratio (SOR) required to get rid of spurious targets. The contribution of this study is to loosen the original SOR limit by embedding an additional spatially variant apodization (SVA) into the architecture, resulting in a new fast OSA with lighter computational load and hence higher processing efficiency. Specifically, the algorithm is modified mainly from two aspects: First, a new spatial variant quadratic phase error (QPE) filter is induced to enable effective SVA implementation; Second, a new squint subaperture stitch method is induced to accommodate the subaperture extraction with the new data format led by the new QPE filter. The proposed approach is evaluated by both the point target simulations and the real airborne SAR data in aspects of spurious target suppression, image quality and processing efficiency.

Locally advanced rectal cancer: 3D diffusion-prepared stimulated-echo turbo spin-echo versus 2D diffusion-weighted echo-planar imaging

BackgroundDiffusion-weighted imaging (DWI) has shown great value in rectal cancer imaging. However, traditional DWI with echo-planar imaging (DW-EPI) often suffers from geometrical distortions. We applied a three-dimensional diffusion-prepared stimulated-echo turbo spin-echo sequence (DPsti-TSE), allowing geometrically undistorted rectal DWI. We compared DPsti-TSE with DW-EPI for locally advanced rectal cancer DWI.MethodsFor 33 prior-to-treatment patients, DWI images of the rectum were acquired with DPsti-TSE and DW-EPI at 3 T using b-values of 200 and 1000 s/mm2. Two radiologists conducted a blinded scoring of the images considering nine aspects of image quality and anatomical quality. Tumour apparent diffusion coefficient (ADC) and distortions were compared quantitatively.ResultsDPsti-TSE scored significantly better than DW-EPI in rectum distortion (p = 0.005) and signal pileup (p = 0.001). DPsti-TSE had better tumour Dice similarity coefficient compared to DW-EPI (0.84 versus 0.80, p = 0.010). Tumour ADC values were higher for DPsti-TSE compared to DW-EPI (1.47 versus 0.86 × 10-3 mm2/s, p < 0.001). Radiologists scored DPsti-TSE significantly lower than DW-EPI on aspects of overall image quality (p = 0.001), sharpness (p < 0.001), quality of fat suppression (p < 0.001), tumour visibility (p = 0.009), tumour conspicuity (p = 0.010) and rectum wall visibility (p = 0.005).ConclusionsDPsti-TSE provided geometrically less distorted rectal cancer diffusion-weighted images. However, the image quality of DW-EPI over DPsti-TSE was referred on the basis of several image quality criteria. A significant bias in tumour ADC values from DPsti-TSE was present. Further improvements of DPsti-TSE are needed until it can replace DW-EPI.

PENGARUH VARIASI TIME REPETITION (TR) TERHADAP KUALITAS CITRADAN INFORMASI CITRA PADA PEMERIKSAAN MRI LUMBALSEKUENS T2 FSE POTONGAN SAGITAL

Background : TR (Time Repetition) is an MRI parameter. TR controls the amount of longitudinal magnetization recovery before the next RF pulse. TR parameter is one of parameters that can affect image quality and image information. Long TR arrangements can increase SNR (Signal To Noise Ratio), CNR (Contrast To Noise Ratio) and provide better contrast, but increase the examination time. The purpose of this research is to know the effect of TR to image quality, difference of image information and TR optimal on MRI Lumbal sequence T2 FSE sagittal. Methods : The type of this research is quantitative research with experimental approach. The sample of research used is 6 probandus. TR variations used are TR 2000, 2500, 3000, 3500, 4000 with other parameters controlled. Aspects of image quality and image information values assessed in this study include Corpus Vertebrae, Discus Vertebrae, Cerebro Spinal Fluid (CSF), Medulla Spinalis, and Soft Tissue. Processing and analysis of image quality data is done by data normality test using shapiro-wilk, then test influence correlation pearson, linear regression and repeated anova. and for image information is done normality data test using shapiro-wilk, and friedman test. Result : The results of the test analysis showed that there was a TR effect on SNR image quality (p = 0.001) and CNR (p = 0.007) with (p <0.05) on all assessed organs. There is a difference in image information of MRI Lumbal T2 FSE sequence of sagittal pieces on Time Repetition variation with significance value (p <0.05). The optimal TR value on image quality is found on TR 4000 variation with mean of highest mean rank that is 42.82. While the optimal TR value on the image information is on the variation of TR 3000 with the highest mean mean rank is 3.25. TR 3000 is considered to produce better image information and is considered optimal on MRI Lumbal sequences of T2 FSE sagittal fragments compared to other TR variations with a duration of examination time of 2 minutes 30 seconds. Conclusion: Based on the results that good variation TR used on MRI Lumbal examination sequence T2 FSE sagital view is TR 3000 with best image qualit, informative image information and short scanning time.

The image-guided operating room-Utility and impact on surgeon's performance in the head and neck surgery.

The image-guided operating room (OR) is an emerging standard for dealing with complex cases in many surgical disciplines including neurosurgery, thoracic surgery, maxillofacial trauma, and orthopedic surgery. Its use in head and neck oncological surgery is not well established. The primary aim of this study was to assess the image quality of cone-beam CT (CBCT) under real clinical conditions. The secondary aim was to assess the effect on surgical performance and decision making. Intraoperative 3D imaging was performed using a CBCT capable C-Arm mounted on a multi-axis robot (Siemens Zeego) in the image-guided OR. All patients had immediate preoperative imaging taken with further intraoperative imaging performed as required. Ten initial patients, comprising 28 intraoperative scans, were used for questionnaire-based image reviews conducted with experienced head and neck clinicians. Scans were assessed for aspects of both image quality and clinical utility, on separate 5-point Likert scales (1-5). The median rating for bony detail was 4 out of 5. Vascular detail was increased (P < 10-8 ) from 1 to 3 with the use of IV contrast (region of interest CT# was 284 HU [SD, 47 HU]). Images were rated as 4 for freedom from artifact. Soft tissue definition was 2, with no significant improvement (P = .2) with the addition of IV iodinated contrast. Surgeons rated the greatest clinical utility (4) for the CBCT when assessing postreconstruction imaging of a complex case. The image quality of CBCT in the image-guided OR is good for bony detail and complex oncological reconstructions in the head and neck setting but probably has limited benefit for intraoperative soft tissue delineation. Future studies must also focus on clinical outcomes to help demonstrate the value of the image-guided OR.

Evaluation of the performance of radiological monitors in use, cities Salvador (BA) and Florianópolis (SC)

Evaluate the performance of the monitors used for diagnosis based on the parameters defined by AAMP. Materials and Methods: Using calibrated instrumentation traceable to NIST and RBC, were evaluated in 15 monitors, according to the procedures described in AAMP's report 03 and the Spanish protocol in the following parameters: the general aspects of image quality, geometric distortion, screen reflection and room illumination, luminance response, luminance dependence, spatial and low contrast resolution, noise, internal reflection blanking and screen chromaticity. Results: 100% compliance for geometric distortion tests and 0% compliance for the luminance dependence test. Conclusions: There are nonspecific monitors for diagnosis being used for these purposes, without routinely checking tests, in rooms with high illumination and dirt on the screens and the non-implementation or inadequacy of acceptance and quality control tests. The monitors declared by the manufacturers as diagnostic specific on average showed a higher compliance rate

Registration accuracy with the low dose kilovoltage cone-beam CT: A phantom study.

Objective:The aim of this study was to investigate low-dose kilovoltage cone-beam CT (kV-CBCT) for image-guided radiotherapy, with a particular focus on the accuracy of image registration with low-dose protocols.Methods:Imaging doses were measured with a NOMEX semiconductor detector positioned at the front of head, thorax, and pelvis human body phantoms while kV-CBCT scans were acquired at different tube currents. Aspects of image quality (spatial resolution, noise, uniformity, contrast, geometric distortion, and Hounsfield unit sensitivity) and image registration accuracy using bone and soft tissue were evaluated.Results:With preset and the lowest tube currents, the imaging doses were 0.16 and 0.08 mGy, 5.29 and 2.80 mGy, and 18.23 and 2.69 mGy for head, thorax, and pelvis, respectively. Noise was the only quality aspect directly dependent on tube current, being increased by 1.5 times with a tube current half that of the preset in head and thorax, and by 2.2 times with a tube current 1/8 of the preset in the pelvis. Accurate auto-bone matching was performed within 1 mm at the lowest tube current. The auto-soft tissue matching could not be performed with the lowest tube current; however, manual-soft tissue matching could still be performed within 2 mm or less.Conclusion:Noise was the only image quality aspect dependent on the imaging dose. Auto-bone and manual-soft tissue matching could still be performed at the lowest imaging dose.Advances in knowledge:When optimizing kV-CBCT imaging dose, the impact on bone and soft tissue image registration accuracy should be evaluated.

Assessment of Image Quality and Dosimetric Performance of CT Simulators

BackgroundCT simulator for radiation therapy aims to produce high-quality images for dose calculation and delineation of target and organs at risk in the process of treatment planning. Selection of CT imaging protocols that achieve a desired image quality while minimizing patient dose depends on technical CT parameters and their relationship with image quality and radiation dose. For similar imaging protocols using comparable technical CT parameters, there are also variations in image quality metrics between different CT simulator models. Understanding the relationship and variation is important for selecting appropriate imaging protocol and standardizing QC process. Here, we proposed an automated method to determine the relationship between image quality and radiation dose for various CT technical parameters. Material and MethodThe impact of scan parameters on various aspects of image quality and volumetric CT dose index for a Philips Brilliance Big Bore and a Toshiba Aquilion One CT scanners were determined by using commercial phantom and automated image quality analysis software and cylindrical radiation dose phantom. Results and DiscussionBoth scanners had very similar and satisfactory performance based on the diagnostic acceptance criteria recommended by ACR, International Atomic Energy Agency, and American Association of Physicists in Medicine. However, our results showed a compromise between different image quality components such as low-contrast and spatial resolution with the change of scanning parameters and revealed variations between the two scanners on their image quality performance. Measurement using a generic phantom and analysis by automated software was unbiased and efficient. ConclusionThis method provides information that can be used as a baseline for CT scanner image quality and dosimetric QC for different CT scanner models in a given institution or across sites.