Half-scan Reconstruction Research Articles

Myocardial CT perfusion imaging for the detection of obstructive coronary artery disease: multisegment reconstruction does not improve diagnostic performance

BackgroundMultisegment reconstruction (MSR) was introduced to shorten the temporal reconstruction window of computed tomography (CT) and thereby reduce motion artefacts. We investigated whether MSR of myocardial CT perfusion (CTP) can improve diagnostic performance in detecting obstructive coronary artery disease (CAD) compared with halfscan reconstruction (HSR).MethodsA total of 134 patients (median age 65.7 years) with clinical indication for invasive coronary angiography and without cardiac surgery prospectively underwent static CTP. In 93 patients with multisegment acquisition, we retrospectively performed both MSR and HSR and searched both reconstructions for perfusion defects. Subgroups with known (n = 68) or suspected CAD (n = 25) and high heart rate (n = 30) were analysed. The area under the curve (AUC) was compared applying DeLong approach using ≥ 50% stenosis on invasive coronary angiography as reference standard.ResultsPer-patient analysis revealed the overall AUC of MSR (0.65 [95% confidence interval 0.53, 0.78]) to be inferior to that of HSR (0.79 [0.69, 0.88]; p = 0.011). AUCs of MSR and HSR were similar in all subgroups analysed (known CAD 0.62 [0.45, 0.79] versus 0.72 [0.57, 0.86]; p = 0.157; suspected CAD 0.80 [0.63, 0.97] versus 0.89 [0.77, 1.00]; p = 0.243; high heart rate 0.46 [0.19, 0.73] versus 0.55 [0.33, 0.77]; p = 0.389). Median stress radiation dose was higher for MSR than for HSR (6.67 mSv versus 3.64 mSv, p < 0.001).ConclusionsMSR did not improve diagnostic performance of myocardial CTP imaging while increasing radiation dose compared with HSR.Trial registrationCORE320: clinicaltrials.gov NCT00934037, CARS-320: NCT00967876.

Reduction of misregistration on cerebral four-dimensional computed tomography angiography images using advanced patient motion correction reconstruction.

The aim of this study was to evaluate whether advanced patient motion correction (APMC) can reduce the misregistration of pixels between the different X-ray tube positions in four-dimensional CT angiography (4D-CTA). Eight patients with intracranial aneurysms were included in this retrospective study. We compared the CTA images with APMC reconstruction and half-scan reconstruction with regard to the following 3 items: (1) bone misalignment area; (2) image noise; and (3) aneurysm volume change. The bone misalignment area and image noise were significantly reduced in the APMC images, as compared to that in the half-scan reconstruction images (bone misalignment area: 33.0±18.1cm(3) vs 152.0±72.2cm(3), respectively; p<0.001) (image noise at pons: 9.70±2.58 vs 15.16±5.02, respectively, p<0.001). The aneurysm volume and volume variance were significantly smaller in the APMC reconstruction than those in the half-scan reconstruction (volume: 1107.2±1813.8mm(3) vs 1135.1±1853.8mm(3); p<0.05; coefficient of variation: 0.0291±0.014 vs 0.0463±0.026, p<0.05, respectively). Our results show that APMC reduces the reconstruction related misregistration between the cardiac phases compared to half-scan reconstruction.

Simultaneous achievement of accurate CT number and image quality improvement for myocardial perfusion CT at 320-MDCT volume scanning

PurposeTo investigate differences in image-to-image variations between full- and half-scan reconstruction on myocardial CT perfusion (CTP) study. MethodsUsing a cardiac phantom we performed ECG-gated myocardial CTP on a second-generation 320-multidetector CT volume scanner. The heart rate was set at 60 bpm; once per second for a total of 24 s were performed. CT images were acquired at 80- and 120 kVp and subjected to full- and half-scan reconstruction. On images acquired at the same slice level we then measured image-to-image variations, coefficients of variance (CV), and image noise. ResultsThe image-to-image variations with full- and half-scan reconstruction were 1.3 HU vs. 27.2 HU at 80 kVp (p < 0.001) and 0.70 HU vs. 9.3 HU at 120 kVp (p < 0.001) even though the mean HU value was almost the same for both reconstruction methods. The CV of 80- and 120-kVp images of the left ventricular cavity decreased by 0.16% and 0.17%, respectively, with full-scan reconstruction; with half-scan reconstruction it decreased by 3.34% and 2.30%, respectively. Compared with half-scan reconstruction, the image noise was reduced by 27.2% at 80 kVp and by 28.0% at 120 kVp with full-scan reconstruction. ConclusionMyocardial CTP with full-scan reconstruction substantially decreased image-to-image variations and provided accurate CT attenuation.

Myocardial delayed enhancement with dual-source CT: Advantages of targeted spatial frequency filtration and image averaging over half-scan reconstruction

BackgroundClinical utility of myocardial delayed-enhancement CT is currently limited because of relatively poor contrast-to-noise ratio (CNR) and artifacts. Targeted spatial-frequency filtration (TSFF) is a hybrid algorithm of half- and full-scan reconstruction that can achieve both high temporal resolution and improved stability of myocardial signal. ObjectiveThe purpose of this study was to evaluate image quality of delayed-enhancement CT using TSFF with image averaging and its reproducibility in infarct assessment in comparison with conventional half-scan reconstruction (HALF). MethodsForty patients with suspected coronary artery disease underwent delayed-enhancement CT with HALF and TSFF using dual-source CT. Two blinded readers independently determined the presence and size of delayed enhancement. Image quality, signal-to-noise ratio and CNR were assessed. The presence of delayed enhancement on CT was compared with magnetic resonance imaging in 12 patients. ResultsTSFF with averaging of 4 image stacks acquired during 1 breathhold demonstrated significantly better image quality compared with HALF. Good left ventricular lumen-myocardium contrast was consistently achieved with TSFF in patients who received iodine dose of >600mgI/kg. The signal-to-noise ratio and CNR were 11.3 ± 4.2 and 4.5 ± 1.6 by TSFF, being significantly higher than those by HALF (7.9 ± 2.9 and 3.3 ± 1.8; P < .01 for both). Interobserver reproducibility of infarct sizing was markedly improved by using TSFF instead of HALF (intraclass correlation coefficient: 0.86 vs 0.50). Agreement with magnetic resonance imaging by kappa statistics was 0.85 with TSFF and 0.74 with HALF. ConclusionsTSFF with image averaging can significantly improve image quality of delayed-enhancement CT and considerably enhances interobserver reproducibility of infarct sizing.

Automatic exposure control at single- and dual-heartbeat CTCA on a 320-MDCT volume scanner: Effect of heart rate, exposure phase window setting, and reconstruction algorithm

PurposeTo investigate whether electrocardiogram (ECG)-gated single- and dual-heartbeat computed tomography coronary angiography (CTCA) with automatic exposure control (AEC) yields images with uniform image noise at reduced radiation doses. Materials and methodsUsing an anthropomorphic chest CT phantom we performed prospectively ECG-gated single- and dual-heartbeat CTCA on a second-generation 320-multidetector CT volume scanner. The exposure phase window was set at 75%, 70–80%, 40–80%, and 0–100% and the heart rate at 60 or 80 or corr80 bpm; images were reconstructed with filtered back projection (FBP) or iterative reconstruction (IR, adaptive iterative dose reduction 3D). We applied AEC and set the image noise level to 20 or 25 HU. For each technique we determined the image noise and the radiation dose to the phantom center. ResultsWith half-scan reconstruction at 60 bpm, a 70–80% phase window- and a 20-HU standard deviation (SD) setting, the imagenoise level and -variation along the z axis manifested similar curves with FBP and IR. With half-scan reconstruction, the radiation dose to the phantom center with 70–80% phase window was 18.89 and 12.34 mGy for FBP and 4.61 and 3.10 mGy for IR at an SD setting SD of 20 and 25 HU, respectively. At 80 bpm with two-segment reconstruction the dose was approximately twice that of 60 bpm at both SD settings. However, increasing radiation dose at corr80 bpm was suppressed to 1.39 times compared to 60 bpm. ConclusionAEC at ECG-gated single- and dual-heartbeat CTCA controls the image noise at different radiation dose.

Radiation dose exposure of patients undergoing 320-row cardiac CT for assessing coronary angiography and global left ventricular function

A 320-row multidetector CT provides the capability for prospective electrocardiogram (ECG)-gated coronary CT angiography (CTA) and tube current modulated cardiac function assessment (CFA). We assessed and compared the effective radiation dose of these two modes. On a prospective basis, we performed ECG-gated cardiac CT on 119 patients (87 were males). For heart rates (HRs) </=65 beats/min (bpm), we used one-heartbeat acquisition and half-scan reconstruction. HRs from 66 to 79 bpm and >/=80 bpm were scanned with either two or three heartbeats acquisitions, respectively. We used two types of scans. One type was based on a prospective ECG-gated CTA mode and the other using a tube current modulated CFA mode covering an entire R-R interval. The mean BMI of patients was 25.4 (range 18.8-49.3). Fifty-one patients (42.9 %) underwent CFA scanning, while the remaining 68 (57.1 %) had CTA. The majority of patients completed the scan in a single heartbeat (59.7 %). The mean dose of CTA mode at 65-85 % phase window for one and two heartbeats was 3.68 mSv (2.40-7.23) and 8.61 mSv (6.76-10.60), respectively. The mean dose of CFA mode for a single heartbeat measurement with dose modulation (25 % dose for CFA, and 100 % dose during 65-85 % phase window for CTA) was 6.32 mSv (4.69-8.89). CTA with prospective ECG-gating allows for acceptable image quality and radiation dose. HR reduction is mandatory to minimize radiation exposure. Global left ventricle function can be assessed with a single heartbeat within an acceptable radiation dose.

320-row CT: does beat-to-beat motion of the coronary arteries affect image quality?

320-row CT: does beat-to-beat motion of the coronary arteries affect image quality?

Relationship between beat to beat coronary artery motion and image quality in prospectively ECG-gated two heart beat 320-detector row coronary CT angiography

The objective was to investigate the influence of the beat-to-beat movement of the coronary arteries on image quality of multi-segment reconstruction (MSR) images. Although MSR improves temporal resolution, image quality would be degraded by beat-to-beat movement of the coronary arteries. In a retrospectively review, 18 patients (mean age, 67.0 years) who underwent coronary CT angiography using a 320-detector row CT were included. The displacement and diameter of coronary artery segments for each of the identified nine landmarks was recorded. The motion ratio was calculated as the division of displacement by diameter. Image quality (IQ) was graded by a four-point scale. The correlation between MSR IQ score and the motion ratio showed stronger negative correlation than that between MSR IQ score and the displacement (r = -0.54 vs. r = -0.36). The average motion ratio for segments in which half-scan reconstruction (HSR) IQ was better than MSR IQ (29.1%, group A) was higher than that for segments in which MSR IQ was better than HSR IQ (16.0%, group C). The motion ratio in group C was lower than 25%. Difference in IQ scores of the HSR images was more frequent in group A than in the remaining segments in which the motion ratio was lower than 25% (16.7% vs. 66.0%; P < 0.0002). The motion ratio could be a better index than the displacement to evaluate the influence of the motion of coronary arteries on image quality. MSR images would be impaired by a motion ratio larger than 25%. Image impairment of one of the HSR images might also impair MSR images.

Stress echocardiography in the age of multi-detector computed tomography

The introduction of 64-slice multi-detector computed tomography (CT) in 2005 made the non-invasive imaging of coronary arteries relatively easy to perform. Computed tomography coronary angiography (CTCA) has been shown to be highly accurate at detecting coronary artery disease (CAD), when compared with invasive X-ray coronary angiography and, in particular, has an excellent negative predictive value (NPV).1,2 There are also prognostic data confirming very low risk for patients with normal CTCA.3 One of the limitations of multidetector CT and despite very good temporal resolution of 150 ms, with half scan reconstruction, is the need for beta-Blockers to slow the heart rate to 65 bpm, for retrospective, and 60 bpm, for the low radiation dose, prospective gated acquisitions. This is to minimize coronary motion particularly of the right coronary artery. Dual-source CT, with twice the temporal resolution, can cope with faster heart rates, whereas the 320-slice CT can image the heart in one heart beat. The UK national institute of clinical excellence (NICE) have recently produced guidelines on the management of patients with chest pain of recent onset, endorsing the use of CTCA in their investigational algorithm. We discuss the radiation dose associated with …

Multibeam field emission x‐ray system with half‐scan reconstruction algorithm

In this article, the authors propose a multibeam field emission x-ray (MBFEX) system along with a half-scan fan-beam reconstruction algorithm. The proposed system consists of a linear CNT-based MBFEX source array, a single large area detector that is divided into same number of segments as the number of x-ray beams, a multihole collimator that aligns each beam with a corresponding detector segment, and a sample rotation stage. The collimator is placed between the source and the object to restrict the x-ray radiations through the target object only. In this design, all the x-ray beams are activated simultaneously to provide multiple projection views of the object. The detector is virtually segmented and synchronized with the x-ray exposure and the physiological signals when gating is involved. The transmitted x-ray intensity from each beam is collected by the corresponding segment on the detector. After each exposure, the object is rotated by a step angle until sufficient data set is collected. The half-scan reconstruction formula for MBFEX system is derived from the conventional filtered backprojection algorithm. To demonstrate the advantages of the system and method in reducing motion artifacts, the authors performed simulations with both standard and dynamic Shepp-Logan phantoms. The numerical results indicate that the proposed multibeam system and the associated half-scan algorithm can effectively reduce the scanning time and improve the image quality for a time-varying object. The MBFEX technique offers an opportunity for the innovation of multisource imaging system.

Multibeam field emission x-ray system with half-scan reconstruction algorithm: MBFEX system with half-scan reconstruction algorithm

Multibeam field emission x-ray system with half-scan reconstruction algorithm: MBFEX system with half-scan reconstruction algorithm

Detectability of motions in AAA with ECG‐gated CTA: A quantitative study

ECG-gated CT enables the visualization of motions caused by the beating of the heart. Although ECG gating is frequently used in cardiac CT imaging, this technique is also very promising for evaluating vessel wall motion of the aortic artery and the motions of (stent grafts inside) abdominal aortic aneurysms (AAA). Late stent graft failure is a serious complication in endovascular repair of aortic aneurysms. Better understanding of the motion characteristics of stent grafts will be beneficial for designing future devices. In addition, these data can be valuable in predicting stent graft failure in patients. To be able to reliably quantify the motion, however, it is of importance to know the performance and limitations of ECG gating, especially when the motions are small, as is the case in AAA. Since the details of the reconstruction algorithms are proprietary information on the CT manufacturers and not in the public domain, empirical experiments are required. The goal of this study is to investigate as to what extent the motions in AAA can be measured using ECG-gated CT. The authors quantitatively investigate four aspects of motion in ECG-gated CT: The detectability of the motion of objects at different amplitudes and different periodic motions, the temporal resolution, and the volume gaps that occur as a function of heart rate. They designed an experiment on a standard static phantom to empirically determine temporal resolution. To investigate motion amplitude and frequency, as well as patient heart rate, they designed dynamic experiments in which a home-made phantom driven by a motion unit moves in a predetermined pattern. The duration of each ECG-gated phase was found to be 185 ms, which corresponds to half of the rotation time and is thus in accordance with half scan reconstruction applied by the scanner. By using subpixel localization, motions become detectable from amplitudes of as small as 0.4 mm in the x direction and 0.7 mm in the z direction. With the rotation time used in this study, motions up to 2.7 Hz can be reliably detected. The reconstruction algorithm fills volume gaps with noisy data using interpolation, but objects within these gaps remain hidden. This study gives insight into the possibilities and limitations for measuring small motions using ECG-gated CT. Application of the experimental method is not restricted to the CT scanner of a single manufacturer. From the results, they conclude that ECG-gated CTA is a suitable technique for studying the expected motions of the stent graft and vessel wall in AAA.

Comparison between the image quality of multisegment and halfscan reconstructions of non-invasive CT coronary angiography

The purpose of this study was to compare the image quality of multisegment and halfscan reconstructions of multislice computed tomography (MSCT) coronary angiography. 126 patients with suspected coronary artery disease and uninfluenced heart rates were examined by 16-slice CT before they underwent invasive coronary angiography. Multisegment and halfscan reconstructions were performed in all patients, and subjective image quality, overall vessel length, vessel length free of motion artefacts and contrast-to-noise ratios (CNRs) were compared for both techniques. The diagnostic accuracy of both approaches was compared with the results of invasive coronary angiography. Overall image quality scores of multisegment reconstruction were superior to those of halfscan reconstruction (13.3+/-2.1 vs 11.9+/-2.9; p<0.001). Multisegment reconstruction depicted significantly longer overall coronary vessel lengths (p<0.001) and larger vessel proportions free of motion artefacts in three of the four main coronary arteries. CNRs in the left main, left anterior descending and left circumflex coronary arteries were significantly higher when multisegment reconstruction was used (p<0.001). Overall accuracy was higher for multisegment reconstruction compared with halfscan reconstruction (87% vs 62%). In conclusion, multisegment reconstruction significantly improves image quality and diagnostic accuracy of MSCT coronary angiography compared with standard halfscan reconstruction, resulting in vessel lengths depicted free of motion comparable to those of CT performed in patients given beta-blockers to lower heart rates.

First experience with 320-row multidetector CT coronary angiography scanning with prospective electrocardiogram gating to reduce radiation dose

The 320-row multidetector CT (MDCT) provides the capability for prospective electrocardiogram-gated cardiac CT angiography. We assessed the effective radiation doses of MDCT with a 320-row detector volume scanner. Two hundred patients underwent clinically directed cardiac scanning (100 kVp, n=9 or 120 kVp, n=191; range, 300-580 mA). Effective radiation dose (in mSv) was estimated from extended dose-length product. For heart rates (HRs) <65 beats/min, exposure phase was 65% up to the end of R wave of the cardiac cycle, using a one-heart beat acquisition and half-scan reconstruction. HRs from 66 to 79 beats/min and > or =80 beats/min were scanned with either 2- or 3-heart beat acquisitions, respectively. Patients with arrhythmias were not excluded. The mean effective dose was 5.7+/-1.7 mSv (range, 1.6-11.1 mSv) for 151 patients (75%) scanned with a one-heart beat acquisition. Qualitative image quality was assessed to be in good to excellent range, and mottle image quality was in low-to-medium mottle range. For patients scanned with 2- or 3-heart beat acquisition, radiation dose was higher with mean exposures of 13.0+/-3.3 mSv and 19.5+/-5.3 mSv, respectively. Low effective radiation dose with acceptable image quality on 320-row MDCT can be achieved with one-heart beat scan acquisition when HR is <65 beats/min. Further reduction in dose can likely also be achieved by modification of the prospective-gated imaging parameters.

SU‐FF‐I‐23: Full‐Scan Versus Half‐Scan in Cone Beam Breast CT ‐ a Quantitative Comparison

Purpose: To evaluate and compare half‐scan and full scan techniques for cone beam breast CT in terms of CT number, radiation dose distribution and CNR. Method and Materials: CT number comparison: A 11 cm diameter breast phantom, made of a stack of glandular and fat tissue, was analytically modeled to evaluate the difference of CT numbers reconstructed from Feldkamp algorithm based half and full scan reconstruction. Radiation dose distribution: An 11 cm diameter cylindrical breast model was constructed to evaluate the dose distribution with Geant4 based Monte Carlo simulation. CNR evaluation: An 11 cm diameter polycarbonate cylinder was imaged to simulate breast imaging. Five holes of the same size (5 mm in diameter) were drilled at different radial distance from the phantom center. The phantom, filled with iodine solution, was imaged with an aSi/CsI flat panel detector based cone beam CT scanner. Iodine CNRs were measured for different half‐scan coverage selection. Results: It has been found that the CT numbers reconstructed from half‐scan were close to those from full‐scan. The radiation doses in the half‐scan coverage can be twice than those out the coverage as the radial distance increasing. The CNRs for different half‐scan coverage were approximately identical. Conclusion: Our results show that the reconstructed data from half‐scan are comparable to that from full‐scan. The radiation doses are low for the positions out the half‐scan coverage. The CNRs vary little with half‐scan coverage. Acknowledgement: This work was supported in part by grants CA104759 and CA124585 from NIH‐NCI, a grant EB00117 from NIH‐NIBIB, and a subcontract from NIST‐ATP.

ECG-Edited Middiastolic Phase Reconstruction Improves Image Quality at 64-MDCT Coronary Angiography of Patients with Atrial Fibrillation

The aims of this study were to evaluate image quality at the absolute middiastolic and absolute end-systolic phases of 64-MDCT coronary angiography of patients with atrial fibrillation and to compare the findings with those among patients in sinus rhythm. Nineteen consecutively registered patients with atrial fibrillation and 19 patients in sinus rhythm taking heart-rate-lowering agents as needed underwent MDCT. Images were reconstructed with a half-scan reconstruction algorithm after ECG editing (deletion of short R-R intervals, insertion of additional temporal windows into the middiastolic phase of long R-R intervals, and shift of R points). We used a 5-point scale (4, no motion artifacts; 0, unevaluable) to evaluate motion artifacts and coronary artery image discontinuities greater than 1 mm on the curved multiplanar reconstruction images. Each coronary artery image with a motion score of 2 or greater for all segments and with 2 or fewer discontinuities was considered acceptable for diagnosis. Middiastolic images of patients with atrial fibrillation showed fewer motion artifacts and image discontinuities than did end-systolic images of patients with atrial fibrillation. Despite greater heart rate variability under the condition of similar mean heart rates in patients with atrial fibrillation, motion artifacts and image discontinuities on middiastolic images were not significantly different from those on sinus rhythm images. Acceptable quality was achieved on 91% of middiastolic atrial fibrillation images and 93% of sinus rhythm images. ECG-edited middiastolic atrial fibrillation images with aggressive heart rate control were of better quality than end-systolic images in patients with atrial fibrillation. The diagnostic image quality of the middiastolic images was comparable with that of sinus rhythm images.

40: Improved Noninvasive Coronary Angiography in Morbidly Obese Patients Using Dual Source Computed Tomography and Half-Scan Reconstruction

40: Improved Noninvasive Coronary Angiography in Morbidly Obese Patients Using Dual Source Computed Tomography and Half-Scan Reconstruction

Influence of heart rate on diagnostic accuracy and image quality of 16-slice CT coronary angiography: comparison of multisegment and halfscan reconstruction approaches

The lower the heart rate the better image quality in multislice computed tomography (MSCT) coronary angiography. We prospectively assessed the influence of heart rate on per-patient diagnostic accuracy and image quality of MSCT coronary angiography and compared adaptive multisegment and standard halfscan reconstruction. A consecutive cohort of 126 patients scheduled to undergo conventional coronary angiography was examined with 16-slice CT. For all heart rate groups, per-patient diagnostic accuracy was significantly higher for multisegment than halfscan reconstruction with values of 95 vs. 79% (p < 0.05, <65 bpm, 38 patients), 85 vs. 66% (p < 0.05, 65-74 bpm, 47 patients), and 78% vs. 41% (p < 0.001, >74 bpm, 41 patients). Differences in diagnostic accuracy between adjacent heart rate groups were only significant for halfscan reconstruction for the comparison between the 65-74 and >74 bpm group (p < 0.05). The vessel lengths free of motion artifacts were significantly longer with multisegment reconstruction in all heart rate groups and for all coronary arteries (p < 0.005). For noninvasive MSCT coronary angiography, both per-patient diagnostic accuracy and image quality decline with increasing heart rate, and multisegment reconstruction at high heart rates yields similar results as standard halfscan reconstruction at low heart rates.

Evaluation of a Reduced Dose Protocol for Respiratory Gated Lung Computed Tomography in an Animal Model

We sought to evaluate and validate a low-dose protocol for respiratory-gated multislice computed tomography (CT) for volume calculations in small ventilated neonatal animals as a model for the ventilated human neonatal lung. Five mechanically ventilated newborn piglets were imaged in a multislice CT scanner (0.5-mm slice thickness, 4:16 pitch, 0.5 seconds rotation time, 120 kV) using a normal (100 mAs) and a reduced (10 mAs) dose protocol. All animals were scanned twice (at 100 and 10 mAs) at each of 3 different ventilator settings. Complete volume datasets were reconstructed throughout the respiratory cycle in increments of 10% using retrospective half-scan reconstruction. End-inspiratory volumes and volumes during maximal expiration (functional residual capacity) were calculated by a customized software and values for normal and reduced dose protocols were compared using Kolmogorov-Smirnov test and Bland-Altman plots. Two volume datasets (one normal and one reduced dose protocol) showed artifacts on the axial images, which could not be analyzed by the software. Those values were determined after manual segmentation and excluded from final analysis. The mean (+/-SD) end-inspiratory volumes and functional residual capacity were 34.3 +/- 10.1 mL and 25.3 +/- 8.0 mL for the normal-dose protocol versus 33.1 +/- 10.0 mL and 24.7 +/- 8.1 mL for the reduced-dose protocol, respectively. There was no statistically significant difference between normal and reduced dose protocol (KS-Test: D = 0.14 < Dmax). Lung volume calculation in ventilated newborn piglets (end-inspiratory volumes and functional residual capacity) can be performed using respiratory-gated multislice CT even at a substantially reduced dose (eg, to 10 mAs). This makes the technique a candidate for future pediatric use.

Cardiac imaging using 256-detector row four-dimensional CT: preliminary clinical report

Along with the increase of detector rows on the z-axis and a faster gantry rotation speed, the spatial and temporal resolutions of the multislice computed tomography (CT) have been improved for noninvasive coronary artery imaging. We investigated the feasibility of the second specification prototype 256-detector row four-dimensional CT for assessing coronary artery and cardiac function. The subjects were five patients with coronary artery disease. Contrast medium (40-60 ml) was intravenously administered at the rate of 3-4 ml/s. The patient's whole heart was scanned for 1.5 s to cover at least one cardiac cycle during breathholding without electrocardiographic gating. Parameters used were 0.5 mm slice thickness, 0.5 s/rotation, 120 Kv, and 350 mA, with a half-scan reconstruction algorithm (temporal resolution 250 ms). Twenty-six transaxial datasets were reconstructed at intervals of 50 ms. The assessability of the coronary arteries in AHA segments 1, 2, 3, 5, 6, 7, 9, and 11 was visually evaluated, resulting in 29 of 32 (90.9%) segments being assessable. Functional assessment was also performed using animated movies without banding artifacts in all cases. The 256-detector row four-dimensional CT can assess the coronary artery and cardiac function using data during 1.5 s without banding artifacts.