Factors Influencing Image Quality Research Articles

SiPM-based fast-neutron resonance radiography camera part I- evaluation of intrinsic factors influencing image quality in a thick neutron converter

We present a new design of a fast-neutron camera based on SiPM array readout. This design has advantages over previous optical-readout designs, such as compactness and modularity. In this Part I contribution we evaluate by Geant4 Monte-Carlo simulations the hierarchy and neutron-energy-dependence of the contribution of various fast-neutron interactions and secondary processes to the creation of light and their influence on the intrinsic spatial resolution and radiographic contrast in a 200 × 200 × 50 mm3 organic scintillator screen. Specifically, the contribution of proton recoils, delta electrons, carbon recoils, high-energy electrons, positrons, alpha particles and Cherenkov radiation to the total light and their influence on the intrinsic spatial resolution was evaluated in the 2.5–14-MeV neutron energy range. In a 50-mm-thick scintillator camera the limiting intrinsic spatial resolution was about 450 μm for 14-MeV neutrons and appreciably better for lower neutron energies.

Physical Image Quality Metrics for the Characterization of X-ray Systems Used in Fluoroscopy-Guided Pediatric Cardiac Interventional Procedures: A Systematic Review.

Pediatric interventional cardiology procedures are essential in diagnosing and treating congenital heart disease in children; however, they raise concerns about potential radiation exposure. Managing radiation doses and assessing image quality in angiographs becomes imperative for safe and effective interventions. This systematic review aims to comprehensively analyze the current understanding of physical image quality metrics relevant for characterizing X-ray systems used in fluoroscopy-guided pediatric cardiac interventional procedures, considering the main factors reported in the literature that influence this outcome. A search in Scopus and Web of Science, using relevant keywords and inclusion/exclusion criteria, yielded 14 relevant articles published between 2000 and 2022. The physical image quality metrics reported were noise, signal-to-noise ratio, contrast, contrast-to-noise ratio, and high-contrast spatial resolution. Various factors influencing image quality were investigated, such as polymethyl methacrylate thickness (often used to simulate water equivalent tissue thickness), operation mode, anti-scatter grid presence, and tube voltage. Objective evaluations using these metrics ensured impartial assessments for main factors affecting image quality, improving the characterization of fluoroscopic X-ray systems, and aiding informed decision making to safeguard pediatric patients during procedures.

Fast Isocenter Determination Using 3D Polymer Gel Dosimetry with Kilovoltage Cone-Beam CT Reading and the PolyGeVero-CT Software Package for Linac Quality Assurance in Radiotherapy.

This work presents an approach to the fast determination of a medical accelerator irradiation isocenter as a quality assurance (QA) procedure in radiotherapy. The isocenter determination tool is the tissue equivalent high-resolution 3D polymer gel dosimeter (PABIGnx) in a dedicated container combined with kilovoltage imaging systems and the polyGeVero-CT software package (v. 1.2, GeVero Co., Poland). Two accelerators were employed: Halcyon and TrueBeam (Varian, USA), both equipped with cone beam computed tomography (CBCT) and iterative reconstruction CBCT (iCBCT) algorithms. The scope of this work includes: (i) the examination of factors influencing image quality (reconstruction algorithms and modes), radiation field parameters (dose and multi-leaf collimator (MLC) gaps), fiducial markers, signal averaging for reconstruction algorithms and the scanning time interval between consecutive scans, (ii) the examination of factors influencing the isocenter determination, image processing (signal averaging, background subtraction, image filtering) and (iii) an isocenter determination report using a 2D and 3D approach. An optimized protocol and isocenter determination conditions were found. The time and effort required to determine the isocenter are discussed.

Image quality and radiation doses of volumetric 320-row computed tomography angiography with prospective electrocardiogram-gating in the assessment of coronary arteries in neonates and infants.

Diagnostic imaging of coronary arteries is required in neonates and infants suspected of congenital or acquired coronary artery anomalies and in pre- and postoperative assessment of complex congenital heart diseases (CHD). Our study aimed to evaluate the image quality of volumetric 320-row computed tomography angiography (CTA) with prospective electrocardiogram (ECG)-gating for coronary arteries in neonates and infants with heart diseases, analyze factors influencing image quality and assess a radiation dose related to the procedure. The study included 110 CTA performed in neonates and infants with CHD. CTA was performed in 37 girls and 73 boys at a median (interquartile range [IQR]) age of 3.0 (0.5-5.0) months, median (IQR) body weight of 5 (3.66-6.5) kg, and median heart rate (HR) of 133 (92-150) beats per minute. The orifices of the left coronary artery were visible in 100% of CTA, the orifices of the right coronary arteries were visible in 96%, whereas all coronary segments were assessable in 45% of CTA. Patients with non-diagnostic segments were significantly younger, median (IQR) age of 2.0 (0.21-5.00) months, had lower body weight of 4.6 (3.45-6.07) kg and faster HR of 136.5 (120-150) beats per minute (P <0.05) than patients with diagnostic image quality in all segments (4.0, 2-6 months, 6.0, 4.2-7 kg, and 130; 110-150 beats per minute, respectively; P <0.05). CTA performed with volumetric 320-row prospective ECG-gating allows for good visibility of the coronary arteries with an acceptable radiation dose. Children aged >15 days, with body weight >4.85 kg and HR <130 beats per minute are good candidates for excellent quality non-invasive CTA of all segments of coronary arteries.

Evaluation of focus and deep learning methods for automated image grading and factors influencing image quality in adaptive optics ophthalmoscopy

Adaptive optics flood illumination ophthalmoscopy (AO-FIO) is an established imaging tool in the investigation of retinal diseases. However, the clinical interpretation of AO-FIO images can be challenging due to varied image quality. Therefore, image quality assessment is essential before interpretation. An image assessment tool will also assist further work on improving the image quality, either during acquisition or post processing. In this paper, we describe, validate and compare two automated image quality assessment methods; the energy of Laplacian focus operator (LAPE; not commonly used but easily implemented) and convolutional neural network (CNN; effective but more complex approach). We also evaluate the effects of subject age, axial length, refractive error, fixation stability, disease status and retinal location on AO-FIO image quality. Based on analysis of 10,250 images of 50 × 50 μm size, at 41 retinal locations, from 50 subjects we demonstrate that CNN slightly outperforms LAPE in image quality assessment. CNN achieves accuracy of 89%, whereas LAPE metric achieves 73% and 80% (for a linear regression and random forest multiclass classifier methods, respectively) compared to ground truth. Furthermore, the retinal location, age and disease are factors that can influence the likelihood of poor image quality.

Management of Respiratory Motion Artefacts in 18F-fluorodeoxyglucose Positron Emission Tomography using an Amplitude-Based Optimal Respiratory Gating Algorithm.

Positron emission tomography (PET) combined with X-ray computed tomography (CT) is an important molecular imaging platform that is required for accurate diagnosis and clinical staging of a variety of diseases. The advantage of PET imaging is the ability to visualize and quantify a myriad of biological processes in vivo with high sensitivity and accuracy. However, there are multiple factors that determine image quality and quantitative accuracy of PET images. One of the foremost factors influencing image quality in PET imaging of the thorax and upper abdomen is respiratory motion, resulting in respiration-induced motion blurring of anatomical structures. Correction of these artefacts is required for providing optimal image quality and quantitative accuracy of PET images. Several respiratory gating techniques have been developed, typically relying on acquisition of a respiratory signal simultaneously with PET data. Based on the respiratory signal acquired, PET data is selected for reconstruction of a motion-free image. Although these methods have been shown to effectively remove respiratory motion artefacts from PET images, the performance is dependent on the quality of the respiratory signal being acquired. In this study, the use of an amplitude-based optimal respiratory gating (ORG) algorithm is discussed. In contrast to many other respiratory gating algorithms, ORG permits the user to have control over image quality versus the amount of rejected motion in the reconstructed PET images. This is achieved by calculating an optimal amplitude range based on the acquired surrogate signal and a user-specified duty cycle (the percentage of PET data used for image reconstruction). The optimal amplitude range is defined as the smallest amplitude range still containing the amount of PET data required for image reconstruction. It was shown that ORG results in effective removal of respiration-induced image blurring in PET imaging of the thorax and upper abdomen, resulting in improved image quality and quantitative accuracy.

Influence of the menstrual cycle on compression-induced pain during mammography: correlation with the thickness and volume of the mammary gland.

In mammography, breast compression is necessary and an important factor influencing image quality. The purpose of this study was to determine the influence of the menstrual cycle on compression-induced pain during mammography and to evaluate the association between the thickness and volume of the mammary gland and pain. We examined basal body temperature and categorized the menstrual cycle into five phases. We executed breast compression in the craniocaudal view using a customized compression plate, to which we introduced an opening. We measured the thickness of the mammary gland under compression using echography. Immediately after releasing the compression, we evaluated pain using the visual analogue scale. We performed magnetic resonance imaging (MRI) on the same day and measured the volume of the mammary gland. The thickness of the mammary gland, pain, and the volume of the mammary gland were minimal in the late follicular phase and maximal in the late luteal and early follicular phases. It was shown that the changes in the thickness and volume of the mammary gland during the menstrual cycle accounted for the changes in compression-induced pain. On MRI examination of each breast quadrant, the same changes were observed in areas A and C. In area A, it was shown that both the anatomical characteristics and the increase in volume of the mammary gland were associated with pain. We concluded that the late follicular phase constitutes the optimal timing for mammography.

Preliminary numerical simulation of mirror seeing for the Chinese Future Giant Telescope

Mirror seeing will be one of the key factors influencing image quality of an extremely large ground-based optical telescope (ELT). Computational fluid dynamics (CFD) can be used to estimate the mirror seeing and the effects of ventilation. In this paper, we present a simplified approach to simulation of mirror seeing for the Chinese Future Giant Telescope (CFGT, 30 m in diameter) with the CFD software ANSYS Icepak. We get the FWHM of the image and the distribution of refractive index structure function (C2N) above the mirror. We demonstrate that thermal control and ventilation are effective ways to improve the image quality. Our simulation results agree with those of other authors for the ELT. To reduce the mirror seeing to a level of 0.5″, the suggested temperature excess of the primary mirror above the ambient air for thermal control of the CFGT is 0 – 2 K according to the present results of weakly forced convection. The limitations of the method are also discussed.

Evidence-based recommendations for musculoskeletal kinematic 4D-CT studies using wide area-detector scanners: a phantom study with cadaveric correlation.

To establish evidence-based recommendations for musculoskeletal kinematic 4D-CT on wide area-detector CT. In order to assess factors influencing image quality in kinematic CT studies, a phantom consisting of a polymethylmethacrylate rotating disk with round wells of different sizes was imaged with various acquisition protocols. Cadaveric acquisitions were performed on the ankle joint during motion in two different axes and at different speeds to allow validation of phantom data. Images were acquired with a 320 detector-row CT scanner and were evaluated by two readers. Motion artefacts were significantly correlated with various parameters (movement axis, distance to centre, rotation speed and volume acquisition speed) (p < 0.0001). The relation between motion artefacts and distance to motion fulcrum was exponential (R2 0.99). Half reconstruction led to a 23% increase in image noise and a 40% decrease in motion artefacts. Cadaveric acquisitions confirmed phantom data. Based on these findings, high tube rotation speed and half reconstruction are recommended for kinematic CT. The axis of motion significantly influences image artefacts and should be considered in patient training and evaluation of acquisition protocol suitability. This study provides evidence-based recommendations for musculoskeletal kinematic 4D-CT. • Motion artefacts can hamper the quality and interpretation of dynamic joint studies • The recommendations presented here help increase image quality • Patient training and preparation can be improved • The artefact-free distance concept helps protocol adaptation and comparison.

CT chest and gantry rotation time: does the rotation time influence image quality?

Computed tomography (CT) gantry rotation time is one factor influencing image quality. Until now, there has been no report investigating the influence of gantry rotation time on chest CT image quality. To investigate the influence of faster gantry rotation time on image quality and subjective and objective image parameters in chest CT imaging. Chest CT scans from 160 patients were examined in this study. All scans were performed using a single-source mode (collimation, 128 × 0.6 mm; pitch, 1.2) on a dual-source CT scanner. Only gantry rotation time was modified, while other CT parameters were kept stable for each scan (120 kV/110 reference mAs). Patients were divided into four groups based on rotation time: group 1, 1 s/ rotation (rot); group 2, 0.5 s/rot; group 3, 0.33 s/rot; group 4, 0.28 s/rot. Two blinded radiologists subjectively compared CT image quality, noise, and artifacts, as well as radiation exposure, from all groups. For objective comparison, all image datasets were analyzed by a radiologist with 5 years of experience concerning objective measurements as well as signal-to-noise ratio (SNR). We found that faster gantry rotation times (0.28 s/rot and 0.33 s/rot) resulted in more streak artifacts, image noise, and decreased image quality. However, there was no significant difference in radiation exposure between faster and slower rotation times (P > 0.7). Faster CT gantry rotation reduces scan time and motion artifacts. However, accelerating rotation time increases image noise and streak artifacts. Therefore, a slower CT gantry rotation speed is still recommended for higher image quality in some cases.

P‐165: The Most Important Factor Influencing Image Quality in 3D Short‐Throw Rear‐Projection System

AbstractTo improve the quality of 3D image observed with head‐rotation, the number and arrangement of the retarder‐films are optimized based on two main factors: crosstalk and color shift. However, these two factors cannot be reduced simultaneously. This paper gives a summary and shows which factor dominates in optimization.

320-detector row CT coronary angiography: effects of heart rate and heart rate variability on image quality, diagnostic accuracy and radiation exposure

To evaluate the effects of heart rate and heart rate variability on image quality, patient dose and diagnostic accuracy of 320-detector row CT. 94 patients were prospectively enrolled. Heart rate was defined as the mean value of different intervals elapsing between two consecutive R waves in an electrocardiogram (R-R intervals) and the heart rate variability was calculated as the standard deviation from the average heart rate. The image quality was evaluated by four grades, according to motion artefacts ("step artefacts" and "blurring artefacts"). The diagnostic accuracy was analysed in 43 patients who were scheduled for invasive coronary angiography (ICA). The coeffects of heart rate and heart rate variability on image quality, radiation dose and diagnostic accuracy were evaluated by multivariate regression. The mean image quality score was 1.2 ± 0.5 and the mean effective dose was 14.8 ± 9.8 mSv. The results showed that heart rate (74.0 ± 11.2 beats per minute) was the single factor influencing image quality (p<0.001) and radiation dose (p<0.001), while heart rate variability (3.7 ± 4.6) had no significant effect on them (p=0.16 and p=0.47, respectively). For 43 patients who underwent ICA, heart rate and heart rate variability showed no influence on the accuracy (p=0.17 and p=0.12, respectively). Overall sensitivity was 97.4% (37/38), specificity was 99.4% (351/353), positive predictive value was 94.9% (37/39) and negative predictive value was 99.7% (351/352). 320-detector row CT, with improved longitudinal coverage of detector, resolves step artefact and high patient dose caused by irregular heart rate. However, it is still recommended to control heart rate to a lower level to eliminate blurring artefact and radiation dose.

Influence of Image Acquisition Settings on Radiation Dose and Image Quality in Coronary Angiography by 320-Detector Volume Computed Tomography: The CORE320 Pilot Experience

The objective of this study was to investigate the impact of image acquisition settings and patients' characteristics on image quality and radiation dose for coronary angiography by 320-row computed tomography (CT). CORE320 is a prospective study to investigate the diagnostic performance of 320-detector CT for detecting coronary artery disease and associated myocardial ischemia. A run-in phase in 65 subjects was conducted to test the adequacy of the computed tomography angiography (CTA) acquisition protocol. Tube current, exposure window, and number of cardiac beats per acquisition were adjusted according to subjects' gender, heart rate, and body mass index (BMI). Main outcome measures were image quality, assessed by contrast/noise measurements and qualitatively on a 4-point scale, and radiation dose, estimated by the dose-length-product. Average heart rate at image acquisition was 55.0±7.3 bpm. Median Agatston calcium score was 27.0 (interquartile range 1–330). All scans were prospectively triggered. Single heart beat image acquisition was obtained in 61 of 65 studies (94%). Sixty-one studies (94%) and 437 of 455 arterial segments (96%) were of diagnostic image quality. Estimated radiation dose was significantly greater in obese (5.3±0.4 mSv) than normal weight (4.6±0.3 mSv) or overweight (4.7±0.3 mSv) subjects (P<0.001). BMI was the strongest factor influencing image quality (odds ratio=1.457, P=0.005). The CORE320 CTA image acquisition protocol achieved a good balance between image quality and radiation dose for a 320-detector CT system. However, image quality in obese subjects was reduced compared to normal weight subjects, possibly due to tube voltage/current restrictions mandated by the study protocol.

Effect of Image Motion and Vibration on Image Quality of TDICCD Camera

Image motion and vibration are significant factors influencing image quality of satellite-based TDI camera. In order to learn their effect on TDICCD, motion degradation models at two directions were established. Based on the models, Line spread functions (LSF) for image motion of different types and strict expressions of MTF for abnormal linear image motion were deduced. Modulation transfer function (MTF) for sinusoidal image vibration was calculated through numerical integration. Geometric distortion was evaluated by linear part of phase transfer function (PTF). The results indicate that abnormal linear motion and high frequency vibration cause space-invariant image blur while low frequency vibration brings space-variant image blur and geometric distortion.

Breast Mass Evaluation: Factors Influencing the Quality of US Elastography

To investigate factors influencing the quality of ultrasonographic (US) elastography in the evaluation of suspicious breast masses. This prospective study was conducted with institutional review board approval; written informed consent was obtained. Between January 2009 and February 2009, real-time US elastography of 312 breast masses (245 benign, 67 malignant) was performed in 268 consecutive patients (mean age, 45.7 years ± 10.2 [standard deviation]) prior to US-guided core biopsy. Five breast radiologists who had performed the examinations assessed the quality of elasticity images as inadequate, low, or high without histologic information. Age, body mass index (BMI), mammographic density, lesion size, lesion depth, and breast thickness at US were analyzed for their association with image quality by using the χ(2) test, Student t test, and multivariate analysis. Sensitivities and specificities for the differentiation of benign from malignant masses on the basis of elastography were calculated and compared between groups of quality scores by using the logistic regression method. The quality of elasticity images was assessed as inadequate in 21 (6.7%) cases, low in 134 (42.9%), and high in 157 (50.3%). According to univariate analysis, smaller lesion size (P = .001), shallower lesion depth (P = .005), less breast thickness where the lesion was located (P < .0001), and benign pathologic finding (P = .004) were significantly associated with higher image quality. There was no correlation of image quality with age (P = .213), BMI (P = .191), mammographic density (P = .091), or distance from the nipple (P = .100). Multivariable analysis showed that breast thickness at the location of target lesions was the most important factor influencing elasticity image quality (P = .001). There were significant differences in sensitivity between higher-quality and lower-quality images (87.0% vs 56.8%, respectively; P = .015) in the differentiation of benign from malignant masses. Breast thickness at the location of the lesion was the most important factor influencing image quality at US elastography. Sensitivity for classification of benign and malignant masses improved with higher quality scores.

Photorealistic ink‐jet digital printing – factors influencing image quality, image stability and print durability

Digital cameras have now replaced film‐based cameras as the most popular method of still image capture. As a consequence, there has been a rise in growth of the photo‐realistic digital‐printer market as many amateur and professional photographers choose to produce their own hard copy images. The most popular digital printing technology for producing photo‐realistic images is currently drop‐on‐demand ink jet. There has been much research into key factors influencing the quality, stability and durability of images produced using this, and other, digital printing technologies. A key area of study in achieving photo‐realistic images from digital printing systems has been ink‐receivable layers and dye/pigment colorants, and most importantly compatibility between the two. As with any new technology it is important to achieve an acceptable standard of performance and, to this end, research work has been instigated by the International Standards Institute since the mid‐1990s, to achieve a set of standards appertaining to areas such as light fastness, water fastness, thermal stability, humidity fastness and pollution susceptibility. This paper reviews the current state regarding the aforementioned areas with respect to their influence on print quality, stability and durability.

Detection of Myocardial Bridging by 64-Row Computed Tomography Angiography of the Coronaries

Myocardial bridging is a congenital condition in which a section of coronary artery is surrounded by myocardium. Historically, myocardial bridging has been diagnosed by catheter angiography. This study investigates the effectiveness of electrocardiogram-gated 64-slice multidetector computed tomography in detecting myocardial bridging. We retrospectively reviewed 167 consecutive patients referred for coronary computed tomography angiography between January 4, 2005, and May 24, 2006. We recorded the number of coronary segments exhibiting myocardial bridging and described the location of each according to the American Heart Association classification system. Association of bridging with factors influencing image quality (body mass index and heart rate) was analyzed. Of 152 eligible participants, 49 (32%) showed myocardial bridging. The mid-left anterior descending coronary artery (segment 7) was the most common location accounting for 69% of positive cases. Body mass index and heart rate did not affect detection rates. Electrocardiogram-gated 64-slice multidetector computed tomography is a feasible, noninvasive method of detecting myocardial bridging which may offer higher sensitivity than catheter angiography for this diagnosis.

Modelling of a novel x-ray phase contrast imaging technique based on coded apertures

X-ray phase contrast imaging is probably the most relevant among emerging x-ray imaging techniques, and it has the proven potential of revolutionizing the field of diagnostic radiology. Impressive images of a wide range of samples have been obtained, mostly at synchrotron radiation facilities. The necessity of relying on synchrotron radiation has prevented to a large extent a widespread diffusion of phase contrast imaging, thus precluding its transfer to clinical practice. A new technique, based on the use of coded apertures, was recently developed at UCL. This technique was demonstrated to provide intense phase contrast signals with conventional x-ray sources and detectors. Unlike other attempts at making phase contrast imaging feasible with conventional sources, the coded-aperture approach does not impose substantial limitations and/or filtering of the radiation beam, and it therefore allows, for the first time, exposures compatible with clinical practice. The technique has been thoroughly modelled, and this paper describes the technique in detail by going through the different steps of the modelling. All the main factors influencing image quality are discussed, alongside the viability of realizing a prototype suitable for clinical use. The model has been experimentally validated and a section of the paper shows the comparison between simulated and experimental results.For more information on this article, see medicalphysicsweb.org

SU-FF-I-17: An Evaluation On the Influence of MU Number and Field Length On MV-CBCT Image Quality On a Siemens Oncor Linac Machine

Purpose: We present an empirical evaluation of several factors influencing image quality in megavoltage cone beam CT (MV‐CBCT) to provide guidance for optimization of these parameters in a clinical setting. Method and Materials: A commercial system capable of MV‐CBCT imaging was recently installed in our clinic (MVision, Siemens Oncology Care Solutions). The system uses a 41 cm × 41 cm electronic portal imaging device specially optimized for 6 MV cone beam acquisition. Images are reconstructed from a 200 degree rotation of the gantry, resulting in a field of view of approximately 27×27×27 cm3. In preparation for routine use in image guided radiotherapy, we investigated the effect of varying the MU number and scan length on soft tissue contrast and system resolution. MV‐CBCT images were acquired of several phantoms using the Y‐jaws to vary the scan length, from 1.0 to 27.4 cm while keeping the X‐aperture fixed at 27.4 cm. Imaging was repeated for three MU setting of 5, 10, and 20. The signal to noise ratio (SNR) and the contrast to noise ratio (CNR) were determined in a low‐contrast CT phantom. A second phantom containing a series of line pair objects was used to assess spatial resolution. The image quality in terms of SNR,CNR, and spatial resolution were scored with respect to the MU and field length. Results: The SNR distribution exhibited a clear dependence on field length and MU number used in the acquisition. SNR improved significantly with increasing MU and with decreasing field length. CNR showed a similar dependence on both parameters, and was optimal at field lengths between 2 and 5 cm. Spatial resolution was independent of both parameters providing MU>5. Conclusion: With 20 MU and 2∼3 cm field length, MV‐CBCT can produce very good soft tissue contrast providing the possibility of MV‐CBCT based target delineation.

Ｔｈｒｅｅ‐ｄｉｍｅｎｓｉｏｎａｌ　Ｒｏｔａｔｉｏｎａｌ　Ａｎｇｉｏｇｒａｐｈｙ（３Ｄ‐ＲＡ）の画質に影響する撮影条件の検討

Because the imaging qualities of three-dimensional rotational angiography(3D-RA)are influenced by various imaging parameters, it is difficult to obtain high-quality images from 3D-RA. In this study, we compared two methods of 3D-RA, the propeller rotation technique(PRT)and the roll rotation technique(RRT)by changing image intensifier(I.I.)sizes(5, 7 and 9 inches)using a test chart and handmade phantom. The results of this study demonstrated that one of the factors determining the image quality of 3D-RA was spatial resolution. Therefore, it was important to choose an optimum I.I. size that was similar in size to collimating the region of interest(ROI)in clinical use. Another factor influencing image quality was radiographic condition, especially the setting of tube voltage. This factor was indispensable in obtaining good image contrast, but the use of high-voltage exposure was one of the reasons for lower image contrast. Therefore, if image contrast was insufficient, the image qualities of 3D-RA became worse with increasing tube voltage because the tube voltage in this study was automatically changed according to scanning method and I.I. size. In addition, because the spatial resolution of PRT was similar to that of RRT, we thought it better to use PRT because the data acquisition time(scan time)of this technique was 4 seconds shorter than that of RRT, whereas, if PRT was used, it was necessary to set a suitable rate of injection of contrast medium because the setting of the tube voltage of PRT was 10 kV higher than that of RRT. In conclusion, to improve the image qualities of 3D-RA, we considered it necessary to obtain sufficient image contrast not influenced by high tube voltage and to choose an optimum I.I. size suitable for the spatial resolution of ROI.