Multidetector Row Research Articles

Carotid artery calcification score and its association with cognitive impairment.

PurposeTo retrospectively investigate the possible association between carotid artery calcification score (CS) and cognitive impairment in carotid artery stenosis (CAS) patients.Patients and methodsCarotid artery was measured in 102 patients with cervical carotid arteries using Color Doppler ultrasound, multi-detector row spiral CT angiography and MRI scanning. Correlation analysis between CSs obtained by MD CT and cognitive scores was performed, and the correlation between CSs and vascular stenosis degree and MRI-measured plaque histological (lipid-rich necrotic nucleus [LRNC], intraplaque hemorrhage and fibrous cap surface rupture) and morphological parameters (lumen area [LA], wall area [WA], total area of blood vessels [TVA], plaque burden [PB]) was analyzed. Follow-up review analysis was conducted on 38 postoperative patients.ResultsSignificant negative correlation was discovered between CS value and cognitive scores in CAS patients (R=−0.359, P<0.001), which did not exist in postoperative patients (P=0.348); CS value also showed significant correlation with WA (R=0.521, P=0.042), TVA (R=0.215, P=0.017) and PB (R=0.237, P=0.003) and had a certain predictive value for the occurrence probability of carotid plaque LRNC (P=0.029, AUC =0.780) in preoperative patients.ConclusionCarotid artery CSs have significant correlation with cognitive scores, which could be used as risk factor for early screening of cognitive impairment in CAS patients. The possible mechanism may be related to the calcification impact on the plaque burden.

Estimating a size-specific dose for helical head CT examinations using Monte Carlo simulation methods.

Size-specific dose estimates (SSDE) conversion factors have been determined by AAPM Report 204 to adjust CTDIvol to account for patient size but were limited to body CT examinations. The purpose of this work was to determine conversion factors that could be used for an SSDE for helical, head CT examinations for patients of different sizes. Validated Monte Carlo (MC) simulation methods were used to estimate dose to the center of the scan volume from a routine, helical head examination for a group of patient models representing a range of ages and sizes. Ten GSF/ICRP voxelized phantom models and five pediatric voxelized patient models created from CT image data were used in this study. CT scans were simulated using a Siemens multidetector row CT equivalent source model. Scan parameters were taken from the AAPM Routine Head protocols for a fixed tube current (FTC), helical protocol, and scan lengths were adapted to the anatomy of each patient model. MC simulations were performed using mesh tallies to produce voxelized dose distributions for the entire scan volume of each model. Three tally regions were investigated: (1) a small 0.6cc volume at the center of the scan volume, (2) 0.8-1.0cm axial slab at the center of the scan volume, and (3) the entire scan volume. Mean dose to brain parenchyma for all three regions was calculated. Mean bone dose and a mass-weighted average dose, consisting of brain parenchyma and bone, were also calculated for the slab in the central plane and the entire scan volume. All dose measures were then normalized by CTDIvol for the 16cm phantom (CTDIvol,16 ). Conversion factors were determined by calculating the relationship between normalized doses and water equivalent diameter (Dw ). CTDIvol,16 -normalized mean brain parenchyma dose values within the 0.6cc volume, 0.8-1.0cm central axial slab, and the entire scan volume, when parameterized by Dw , had an exponential relationship with a coefficient of determination (R2 ) of 0.86, 0.84, and 0.88, respectively. There was no statistically significant difference between the conversion factors resulting from these three different tally regions. Exponential relationships between CTDIvol,16 -normalized mean bone doses had R2 values of 0.83 and 0.87 for the central slab and for the entire scan volume, respectively. CTDIvol,16 -normalized mass-weighted average doses had R2 values of 0.39 and 0.51 for the central slab and for the entire scan volume, respectively. Conversion factors that describe the exponential relationship between CTDIvol,16 -normalized mean brain dose and a size metric (Dw ) for helical head CT examinations have been reported for two different interpretations of the center of the scan volume. These dose descriptors have been extended to describe the dose to bone in the center of the scan volume as well as a mass-weighted average dose to brain and bone. These may be used, when combined with other efforts, to develop an SSDE dose coefficients for routine, helical head CT examinations.

Usefulness of noncontrast MRI in differentiation between gallbladder carcinoma and benign conditions manifesting as focal mild wall thickening

BackgroundMagnetic resonance imaging (MRI) is a reliable imaging tool for evaluating gallbladder carcinoma, but it is costly and time-consuming. PurposeTo compare noncontrast MRI with multidetector row CT (MDCT) and gadoxetic acid-enhanced whole MRI in distinguishing gallbladder carcinoma from benign disease. Materials and methods101 patients (36 with gallbladder carcinoma and 65 with benign disease) with mild focal gallbladder wall thickening were included. Two radiologists reviewed the MDCT and MRI to determine the differential features between malignancy and benignity. Then, the diagnostic performance of MDCT and MRI (T1-, T2- and diffusion-weighted images) with and without gadoxetic acid enhancement in the diagnosis of gallbladder carcinoma was evaluated. ResultsThe benign group more often showed T2 necklace sign or T2 hyperintensity within the thickened wall (P < 0.0001) and T1 hyperintensity within the wall or gallbladder lumen (P = 0.0002). Meanwhile, malignancy more frequently showed T2 moderate hyperintensity of the thickened wall, papillary appearance, and diffusion restriction (all P < 0.0001). There were significant differences in sensitivity (79.2% vs 98.6% for observer 1; 84.7% vs 100% for observer 2) and specificity (80.7% vs 96.9%; 79.2% vs 95.4%) between the MDCT and noncontrast MRI (P < 0.05). We found similar diagnostic values between the noncontrast MRI and whole MRI (P = 0.479–1.000) for both observers. ConclusionNoncontrast MRI could be a useful alternative to gadoxetic acid–enhanced MRI in the diagnosis of gallbladder carcinoma that presents as mild gallbladder wall thickening on MDCT.

Comparative Study of Transabdominal Ultrasonography and Multidetector Row Computed Tomography in Preoperative Staging of Gastric Carcinoma

Comparative Study of Transabdominal Ultrasonography and Multidetector Row Computed Tomography in Preoperative Staging of Gastric Carcinoma

Diagnosis by 64-Row Multidetector Computed Tomography for Longitudinal Superficial Extension of Distal Cholangiocarcinoma

BackgroundThis study aimed to demonstrate the diagnostic ability of 64-row multidetector computed tomography (64-row MDCT) for longitudinal superficial extension of distal cholangiocarcinoma (LSEDC). MethodsTwenty-seven patients with distal cholangiocarcinoma (DC) underwent preoperative 64-row MDCT without drainage tubes. LSEDC was diagnosed using curved planar reconstruction images reconstructed from 64-row MDCT, which were compared with pathologic findings. ResultsLSEDC was observed in 13 patients (48%). Ten patients (37%) had enhancing nonthickened bile ducts extending continuously from the main tumor (type 1). These coincided with pathologic findings of high-grade dysplasia (HGD) in 90.0% of cases; that is, a positive predictive value (9/10). Fourteen patients (52%) had only wall thickening of the main tumor with or without enhancement (type 2). Four patients with HGD in this group were difficult to diagnose. Three patients (11%) had enhancing nonthickened bile ducts not in continuity with the main tumor (type 3). This finding revealed an inflammatory change instead of a carcinoma in the pathologic findings. The sensitivity and specificity of detecting HGD were 75% and 93% on the liver side, 33% and 100% on the duodenal side, respectively. Four patients (67%) with HGD on the liver side were overdiagnosed, and one patient (17%) was underdiagnosed. Most of the patients overdiagnosed on the liver side (3/4 or 75%) had drainage tubes inserted before the MDCT. ConclusionsFor DC patients without drainage tubes, the 64-row MDCT technique may be useful for diagnosing HGD depicted as LSEDC on the liver side but not as useful on the duodenal side.

Gunshot Wounds: Ballistics and Imaging Findings

Ballistic traumas are defined by a projectile entering the body. Such projectiles include bullets, birdshot, and metal fragments from the covering or the contents of an explosive device. They frequently cause severe wounds characterized by a range of clinical pictures and a large spectrum of concomitant wounds. The major aims of imaging are to define the path of the projectile or projectiles, to evaluate which tissues have been injured, to estimate the severity of injury, and to determine what additional studies are needed. A routine radiograph is performed in patients with gunshot wounds. The diagnostic approach has been changed by the use of multidetector row computed tomography (MDCT) due to its technical developments particularly faster data acquisition and advanced image reconstructions. In the evaluation of patients with gunshot injuries, MDCT is considered the method of choice to identify hemorrhage, bullet, bone fragments, air, hemothorax, nerve lesions, musculoskeletal lesions, and vessel injuries. Moreover, MDCT technology and multiplanar reformation postprocessing allow meticulous trajectory analysis that potentially benefits the clinical outcomes of patients aiding time-saving triage and correct image-based diagnosis of organ and vessel damage. Familiarity of ballistics and forensic sciences will therefore help the radiologist in assessment and localization of the damage caused by projectiles.

Clinical Utility of Imaging Left Ventricular Assist Devices with 320 Row Multidetector Computed Tomography.

Evaluation of left ventricular devices is becoming increasingly important as the implantation of these devices increases. Cardiac computed tomography angiography (CCTA) has many potential advantages compared with plain radiographs and echocardiography to troubleshoot these devices and potentially help guide therapy. Heart failure (HF) remains a deadly, progressive disease with substantive and increasing morbidity, mortality, cost, and prevalence. Use of left ventricular assist devices (LVAD) as treatment for refractory HF has been steadily rising during the last decade. Seventy-four LVAD recipients who met an indication for CCTA were referred for scanning at our center for a total of 94 studies. All recipients had received a Heart Mate II (Thoratec, Pleasanton, CA) LVAD at a previous time. All patients underwent gated CCTA on a 320 row multidetector scanner (Aquilion ONE, Toshiba Medical Systems, Irvine, California, USA). Images were then reconstructed and analysis was performed using multiple oblique views. All 94 studies had technically good images. In survival analysis, 43 of the 74 LVAD patients had normal CCTA findings while 31 had abnormal CCTA results. The 6, 12, and 18 months survival was 93%, 79%, and 77% in those with normal results and 71%, 61%, and 61%, respectively, in the abnormal CCTA findings. Overall survival was statistically significant in when comparing the two groups (p = 0.003). Cardiac computed tomography angiography may be used as an aid for risk stratification and a potential indicator of short- and long-term prognosis in LVAD patients.

Estimation of effective doses from MDCT and CBCT imaging of extremities

Little research has been published on the radiation burden of cone beam computed tomography (CBCT) in comparison with multi-row detector computed tomography (MDCT) for extremity imaging. This manuscript reports effective doses produced by standard and reduced dose imaging protocols for a 128-slice MDCT unit and a dedicated extremity imaging device using CBCT technology. Anthropomorphic phantoms with x-ray attenuation characteristics simulating adult hand-wrist, foot-ankle, and knee areas were modified to receive optically stimulated luminescent dosimeters (OSL). Standard and lower kVp reduced dose (Lite) exposures were compared. Effective doses for four age groups (five years old to adult) were calculated following 2007 recommendations of the ICRP. Standard CBCT imaging protocols produced effective doses (1.3–21.1 μSv) that were on the order of daily US ubiquitous background radiation doses. CBCT doses were on average 90% less than comparable MDCT views of the same anatomy (9.1–204 μSv). Child doses were significantly greater than adult doses (p = 0.0001). CBCT doses could be further reduced by 36%–51% with Lite exposure protocols. These protocols can be recommended for children and in cases where increased image noise will not interfere with the diagnostic task.

CT Myocardial Perfusion Imaging: A New Frontier in Cardiac Imaging.

The past two decades have witnessed rapid and remarkable technical improvement of multidetector computed tomography (CT) in both image quality and diagnostic accuracy. These improvements include higher temporal resolution, high-definition and wider detectors, the introduction of dual-source and dual-energy scanners, and advanced postprocessing. Current new generation multidetector row (≥64 slices) CT systems allow an accurate and reliable assessment of both coronary epicardial stenosis and myocardial CT perfusion (CTP) imaging at rest and during pharmacologic stress in the same examination. This novel application makes CT the unique noninvasive “one-stop-shop” method for a comprehensive assessment of both anatomical coronary atherosclerosis and its physiological consequences. Myocardial CTP imaging can be performed with different approaches such as static arterial first-pass imaging, and dynamic CTP imaging, with their own advantages and disadvantages. Static CTP can be performed using single-energy or dual-energy CT, employing qualitative or semiquantitative analysis. In addition, dynamic CTP can obtain quantitative data of myocardial blood flow and coronary flow reserve. The purpose of this review was to summarize all available evidence about the emerging role of myocardial CTP to identify ischemia-associated lesions, focusing on technical considerations, clinical applications, strengths, limitations, and the more promising future fields of interest in the broad spectra of ischemic heart disease.

Comparability of dental implant site ridge measurements using ultra-low-dose multidetector row computed tomography combined with filtered back-projection, adaptive statistical iterative reconstruction, and model-based iterative reconstruction

ObjectiveTo assess the linear measurements of edentulous ridges recorded from multidetector row computed tomography (MDCT) images obtained by a previously untested ultra-low dose in combination with filtered back-projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR).MethodsThree cadavers were imaged using a reference protocol with a standard dose and FBP (volume CT dose index (CTDIvol): 29.4 mGy) and two ultra-low-dose protocols, LD1 and LD2 (CTDIvol: 0.53 and 0.29 mGy). All test examinations were reconstructed with FBP, ASIR 50, ASIR 100, and MBIR. Linear measurements from the images of the edentulous ridges recorded from the test protocols were compared with those from the reference using a one-sample t test, Bland–Altman plots, and linear regression. Statistical significance was set at a p value of 0.05.ResultsThe one-sample t test demonstrated a statistically significant difference between the measurements from the reference protocol and all test protocols. The difference was not clinically significant for the following three test protocols: LD1/FBP, LD1/ASIR 50, and LD2/FBP. Bland–Altman plots with linear regression showed no systematic variation between the measurements obtained with the reference protocol and these three test protocols.ConclusionsThe lowest-dose protocol to demonstrate comparable measurements with a standard MDCT dose was CTDIvol 0.29 mGy with FBP. These results must be considered with caution for areas of the jaws with thin cortication. The results in areas of thin cortication should be verified by studies with larger sample sizes at such areas and comparison with true gold standard measurements.

Computed tomographic bronchial collapsibility values over 50% may be detected in healthy dogs.

Bronchomalacia and bronchial collapse are important causes of chronic coughing in dogs. The current reference standard diagnostic tests for these problems are flexible bronchoscopy and biopsy. Previous human studies have also supported inspiration/expiration computed tomography (CT) as a diagnostic test. The current prospective, pilot study aimed to determine whether inspiration/expiration CT is also a feasible test for quantifying bronchial collapsibility in dogs. Thoracic CT images were acquired using a 64-row multidetector CT for 10 healthy Beagle dogs during maximal inspiration and expiration. For each scan, one observer measured transverse sectional areas of the mainstem and lobar bronchi, and the dorsal and ventral segmental bronchi of the left cranial lobar bronchus. Diameters for each bronchus were also measured in transverse, sagittal, and dorsal planes. Bronchial collapsibility (%) was calculated as the difference between inspiration/expiration transverse sectional areas divided by the inspiration transverse sectional areas. Mean bronchial collapsibility of all bronchi was 38.20±15.17%. A collapsibility of over 50% was found in the dorsal (n=7) and ventral (n=4) segmental bronchi of the left cranial lobar bronchus, and the left caudal (n=5) and right middle (n=2) lobar bronchus. Bronchial collapsibility measurements were greater in the dorsal and ventral segmental bronchi of the left cranial lobar bronchus and the left caudal lobar bronchus (P<0.001). Findings supported inspiration/expiration CT as a modality to noninvasively assess bronchial collapse in dogs and a bronchial collapsibility value greater than 50% for detecting pathologic bronchial collapse in clinically affected dogs.

Content-oriented sparse representation (COSR) for CT denoising with preservation of texture and edge.

Denoising has been a challenging research subject in medical imaging, since the suppression of noise conflicts with the preservation of texture and edges. To address this challenge, we develop a content-oriented sparse representation (COSR) method for denoising in computed tomography (CT). An image is segmented into a number of content areas and each of them consists of similar material. Having been ex-painted, each content area is sparsely coded using the dictionary learnt from patches extracted from the corresponding content area. By constraining sparsity, noise is suppressed and the final image is formed by aggregating all denoised content areas. The performance of COSR method is examined with images simulated by computer and generated by multidetector row CT (MDCT), cone beam CT (CBCT), and micro-CT, in which water phantom, anthropomorphic phantom, a human subject, and a small animal are engaged, using the figures of merit, such as standard division (SD), contrast to noise ratio (CNR), and thresholded edge keeping index (EKIth ) and structural similarity index (SSIM). In addition, the optimization of performance by parameter tuning is also investigated. Quantitatively gauged by metrics of noise, EKIth and SSIM, the performance evaluation shows that the proposed COSR method is effective in denoising (>50% reduction in noise) while it outperforms the conventional sparse representation method in preservation of texture and edge by ~20% (gauged by SSIM). It has also been shown that the COSR method is tolerable to inaccuracy in content area segmentation and variation in dictionary learning. Moreover, the computational efficiency of COSR can be substantially improved using prelearnt dictionaries. The COSR method would find its utility in clinical and preclinical applications, such as low-dose CT, image segmentation, registration, and computer-aided diagnosis. The proposal of COSR denoising is of innovation and significance in the theory and practice of denoising in medical imaging. A demonstration code package is available at https://github.com/xiehq/COSR.

Radiation Dose Reduction With a Low-Tube Voltage Technique for Pediatric Chest Computed Tomographic Angiography Based on the Contrast-to-Noise Ratio Index

IntroductionThe aim of this study was to evaluate the radiation dose and image quality at low tube-voltage pediatric chest computed tomographic angiography (CTA) that applies the same contrast-to-noise ratio (CNR) index as the standard tube voltage technique. Materials and MethodsContrast-enhanced chest CTA scans of 100 infants were acquired on a 64-row multidetector computed tomography (MDCT) scanner. In the retrospective study, we evaluated 50 images acquired at 120 kVp; the image noise level was set at 25 Hounsfield units. In the prospective study, we used an 80-kVp protocol; the image noise level was 40 Hounsfield units because the iodine contrast was 1.6 times higher than on 120-kVp scans; the CNR was as in the 120-kVp protocol. We compared the CT number, image noise, CT dose index volume (CTDIvol), and the dose-length product on scans acquired with the 2 protocols. A diagnostic radiologist and a pediatric cardiologist visually evaluated all CTA images. ResultsThe mean CTDIvol and the mean dose-length product were 0.5 mGy and 7.8 mGy-cm for 80- and 1.2 mGy and 20.8 mGy-cm for 120-kVp scans, respectively (P < .001). The mean CTDIvol was 42% lower at 80 kVp than at 120 kVp, and there was no significant difference in the visual scores assigned to the CTA images (P = .28). ConclusionsWith the CNR index being the same at 80-kVp and 120-kVp imaging, the radiation dose delivered to infants subjected to chest CTA can be reduced without degradation of the image quality.

Diagnostic accuracy of indocyanine green fluorescence imaging and multidetector row computed tomography for identifying hepatocellular carcinoma with liver explant correlation

Diagnostic accuracy of indocyanine green fluorescence imaging and multidetector row computed tomography for identifying hepatocellular carcinoma with liver explant correlation

3D-TEE for Measurement of the Aortic Annulus: a Review of the Literature and Step-By-Step Approach to an Essential Skill

The purpose of this paper is to review the measurement of the virtual aortic annulus using 3-dimensional (3D) transesophageal echocardiography (TEE). New software developments have allowed increased utility of 3D-TEE for aortic annulus analysis. 3D-TEE remains an alternative to multidetector row computed tomography (MDCT) for measurement of the aortic annulus prior to transcatheter aortic valve replacement (TAVR), but has been hampered by lack of semi-automated or automated technology. Automated software programs for 3D-TEE analysis of the aortic annulus are increasingly being developed to increase the ability for a wide array of users to perform pre-TAVR annulus analysis.

Ultrahigh-resolution CT scan of the temporal bone.

Ultrahigh-resolution CT (U-HRCT) provides better spatial resolution than conventional multi-detector row CT (ConvCT) and could be expected to identify microstructures with its 0.25-mm collimation, 1792 channels and 160 detector rows, 0.4 × 0.5mm focus size, and a 1024 matrix. The aim of the study was to evaluate key anatomic structures in temporal bone using U-HRCT comparing it to ConvCT. A total of 30 patients (14 males and 16 females; age range, 8-82 years; median 49years) underwent both U-HRCT and ConvCT. All CT images were obtained with 0.5mm section thickness and a 512 × 512 matrix, and field of view of 80mm. Transverse scans were acquired in a plane parallel to the orbitomeatal plane in the helical mode with 120kV. Images of the 30 temporal bones of unaffected side were reviewed by two independent neuroradiologists who rated the visibility of key anatomic structures for both U-HRCT and ConvCT. The ratings between U-HRCT and ConvCT were compared using Wilcoxon matched-pairs signed rank test. The interobserver agreement on the rating of stapedius tendon was evaluated using weighted κ statistics. Excellent interobserver agreement was shown for U-HRCT (κ = 0.920), whereas good agreement was obtained for ConvCT (κ = 0.733). According to both observers, stapedius tendon was more clearly visualized using U-HRCT than ConvCT (p < 0.0001). All other anatomic structures were well visualized using both CT scanners. The anatomy of temporal bone is more conspicuous on U-HRCT than on ConvCT because of its ultra-high-resolution detector. U-HRCT may provide beneficial information for determining surgical indication or procedures.

Usefulness of Epicardial Adipose Tissue Volume to Predict Recurrent Atrial Fibrillation After Radiofrequency Catheter Ablation

Although increasing evidence suggests that epicardial adipose tissue volume (EATV) is associated with post-ablation atrial fibrillation (AF), ranges of EATV predictive of post-ablation recurrence of AF remain unclear. In this study, we evaluated: (1) relationships between EATV and characteristics of AF, (2) impact of EATV on recurrent AF after radiofrequency ablation; , and (3) cut-off point for recurrent AF using a receiver operating characteristic curve. In 218 consecutive symptomatic patients undergoing who underwent ablation for AF (143 paroxysmal AF; 78 persistent AF), the EATV index (EATVI: EATV/body surface area, mL/m2) was measured using 320-row multidetector computed tomography. The high EATV group showed specific cardiometabolic derangements as well as left atrial dilatation and left ventricular dysfunction. Multivariate regression analysis showed that the EATVI was an independent predictor of recurrent AF after catheter ablation. High EATV (EATVI ≥ 85 mL/m2) or EATVI cutoff ≥116 mL/m2 can predict recurrent AF after catheter ablation, independent of other risk factors. In conclusion, EATVI was an independent predictor of recurrent AF after catheter ablation; a high EATV tertile or EATVI cutoff may be useful for prediction of recurrent AF after catheter ablation. Future studies should determine the utility of the EATVI in the clinical setting of AF ablation.

Differences in airway structural changes assessed by 3-dimensional computed tomography in asthma and asthma–chronic obstructive pulmonary disease overlap

BackgroundAsthma–chronic obstructive pulmonary disease (COPD) overlap (ACO) is a clinical phenotype sharing features of asthma and COPD. Multidetector row computed tomography (MDCT) can be used to evaluate the airway structure; however, differences between asthma and ACO seen on MDCT are poorly understood. ObjectiveTo investigate the difference in airway structural between asthma and ACO, using MDCT in patients with clinical asthma. MethodsSixty-four patients with asthma were allocated to an asthma group (never smokers and ex-smokers with a smoking history of < 10 pack-years) or an ACO group (patients with a ≥10-pack-year smoking history and forced expiratory volume in 1 second [FEV1]/forced vital capacity [FVC] < 0.7). The asthma group was further divided into patients with airflow limitation (AL; FEV1/FVC < 0.7) and those without AL. Wall thickness (WT) and airway inner luminal area in the third-generation to fifth-generation bronchi were evaluated using MDCT in both study groups and in 29 healthy controls. ResultsForty-three patients were included in the asthma group (20 with AL, 23 without AL) and 16 in the ACO group. Patients with asthma and ACO had significantly greater WT than the healthy controls. WT in the third-generation bronchi was significantly greater in the ACO group than in the asthma group. The ACO group and the asthma with AL group were matched for age, disease duration, and FEV1/FVC. The WT in the third-generation bronchi was still greater in the ACO group than in the asthma with AL group. ConclusionPatients with ACO have a thicker airway wall than those with asthma, suggesting that airway remodeling is more prominent in ACO than in asthma.UMIN Clinical Trials Registry (UMIN-CTR) system (http://www.umin.ac.jp/ctr/UMIN000028913).

Optimal tube potential and tube current for radiation dose reduction in routine adult head computed tomography scanning

ABSTRACTWe proposed a new, optimised scanning parameter that can reduce the patient’s radiation dose while maintaining image quality in a head computed tomography (CT) scan. We evaluated the clinical CT scan parameters (tube voltage, tube current, slice thickness pitch, scan range, rotation time, and CT dose index) for brain CT examination in a total of 52 multi-detector row spiral CTs (SOMATOM Definition AS+, Siemens Healthcare, Germany). The data were analysed, and the range of valid scan parameters was determined clinically using quartile distribution within the 95% confidence interval. The American Association of Physicists in Medicine performance evaluation phantom was used to acquire images using these scan parameters, and new, optimised CT scan parameters were proposed by analysing CT number accuracy, noise, uniformity, spatial resolution, and contrast resolution. The new CT scan parameters proposed were determined as tube voltage 100 kVp and tube current 300 mAs. Compared with conventional clinical scan parameters, tube voltage was reduced by 16.7% and tube current was decreased by 33.3%. Loss in imaging accuracy and uniformity of CT number was less than 20%, loss in noise was less than 40%, and no change in resolution was observed. Conversely, the CT dose index and effective dose was 20%–50%. A new systematic method for clinically assessing the optimised CT scan parameters were proposed, and the effective dose was decreased, with changing exposure conditions.

On the data acquisition, image reconstruction, cone beam artifacts, and their suppression in axial MDCT and CBCT - A review.

In the clinic, computed tomography (CT) has evolved into an essential modality for diagnostic imaging by multidetector row CT (MDCT) and image guided intervention by cone beam CT (CBCT). Recognizing the increasing importance of axial MDCT/CBCT in clinical and preclinical applications, and the existence of CB artifacts in MDCT/CBCT images, we provide a review of CB artifacts' root causes, rendering mechanisms and morphology, and possible solutions for elimination and/or reduction of the artifacts. By examining the null space in Radon and Fourier domain, the root cause of CB artifacts (i.e., data insufficiency) in axial MDCT/CBCT is analytically investigated, followed by a review of the data sufficiency conditions and the "circle +" source trajectories. The rendering mechanisms and morphology of CB artifacts in axial MDCT/CBCT and their special cases (e.g., half/short scan and full scan with latitudinally displaced detector) are then analyzed, followed by a survey of the potential solutions to suppress the artifacts. The phenomenon of imaged zone indention and its variation over FBP, BPF/DBPF, two-pass and iterative CB reconstruction algorithms and/or schemes are discussed in detail. An interdomain examination of the null space provides an insightful understanding of the root cause of CB artifacts in axial MDCT/CBCT. The decomposition of CB artifacts rendering mechanisms facilitates understanding of the artifacts' behavior under different conditions and the potential solutions to suppress them. An inspection of the imaged zone intention phenomenon provides guidance on the design and implementation of CB image reconstruction algorithms and schemes for CB artifacts suppression in axial MDCT/CBCT. With increasing importance of axial MDCT/CBCT in clinical and preclinical applications, this review article can update the community with in-depth information and clarification on the latest progress in dealing with CB artifacts and thus increase clinical/preclinical confidence.