The Impact of Iterative Reconstruction on Computed Tomography Radiation Dosimetry: Evaluation in a Routine Clinical Setting

Purpose

To evaluate the effect of introduction of iterative reconstruction as a mandated software upgrade on radiation dosimetry in routine clinical practice over a range of computed tomography examinations.

Methods

Random samples of scanning data were extracted from a centralised Picture Archiving Communication System pertaining to 10 commonly performed computed tomography examination types undertaken at two hospitals in Western Australia, before and after the introduction of iterative reconstruction. Changes in the mean dose length product and effective dose were evaluated along with estimations of associated changes to annual cancer incidence.

Results

We observed statistically significant reductions in the effective radiation dose for head computed tomography (22–27%) consistent with those reported in the literature. In contrast the reductions observed for non-contrast chest (37–47%); chest pulmonary embolism study (28%), chest/abdominal/pelvic study (16%) and thoracic spine (39%) computed tomography. Statistically significant reductions in radiation dose were not identified in angiographic computed tomography. Dose reductions translated to substantial lowering of the lifetime attributable risk, especially for younger females, and estimated numbers of incident cancers.

Conclusion

Reduction of CT dose is a priority Iterative reconstruction algorithms have the potential to significantly assist with dose reduction across a range of protocols. However, this reduction in dose is achieved via reductions in image noise. Fully realising the potential dose reduction of iterative reconstruction requires the adjustment of image factors and forgoing the noise reduction potential of the iterative algorithm. Our study has demonstrated a reduction in radiation dose for some scanning protocols, but not to the extent experimental studies had previously shown or in all protocols expected, raising questions about the extent to which iterative reconstruction achieves dose reduction in real world clinical practice.     

Optimization of SPECT-CT Hybrid Imaging Using Iterative Image Reconstruction for Low-Dose CT: A Phantom Study

Background

Hybrid imaging combines nuclear medicine imaging such as single photon emission computed tomography (SPECT) or positron emission tomography (PET) with computed tomography (CT). Through this hybrid design, scanned patients accumulate radiation exposure from both applications. Imaging modalities have been the subject of long-term optimization efforts, focusing on diagnostic applications. It was the aim of this study to investigate the influence of an iterative CT image reconstruction algorithm (ASIR) on the image quality of the low-dose CT images.

Methodology/Principal Findings

Examinations were performed with a SPECT-CT scanner with standardized CT and SPECT-phantom geometries and CT protocols with systematically reduced X-ray tube currents. Analyses included image quality with respect to photon flux. Results were compared to the standard FBP reconstructed images. The general impact of the CT-based attenuation maps used during SPECT reconstruction was examined for two SPECT phantoms. Using ASIR for image reconstructions, image noise was reduced compared to FBP reconstructions for the same X-ray tube current. The Hounsfield unit (HU) values reconstructed by ASIR were correlated to the FBP HU values(R² ≥ 0.88) and the contrast-to-noise ratio (CNR) was improved by ASIR. However, for a phantom with increased attenuation, the HU values shifted for low X-ray tube currents I ≤ 60 mA (p ≤ 0.04). In addition, the shift of the HU values was observed within the attenuation corrected SPECT images for very low X-ray tube currents (I ≤ 20 mA, p ≤ 0.001).

Conclusion/Significance

In general, the decrease in X-ray tube current up to 30 mA in combination with ASIR led to a reduction of CT-related radiation exposure without a significant decrease in image quality.     

High-Pitch,Low-Voltage and Low-Iodine-Concentration CT Angiography of Aorta: Assessment of Image Quality and Radiation Dose with Iterative Reconstruction

ObjectiveTo assess the image quality of aorta obtained by dual-source computed tomography angiography (DSCTA), performed with high pitch, low tube voltage, and low iodine concentration contrast medium (CM) with images reconstructed using iterative reconstruction (IR).MethodsOne hundred patients randomly allocated to receive one of two types of CM underwent DSCTA with the electrocardiogram-triggered Flash protocol. In the low-iodine group, 50 patients received CM containing 270 mg I/mL and were scanned at low tube voltage (100 kVp). In the high-iodine CM group, 50 patients received CM containing 370 mg I/mL and were scanned at the tube voltage (120 kVp). The filtered back projection (FBP) algorithm was used for reconstruction in both groups. In addition, the IR algorithm was used in the low-iodine group. Image quality of the aorta was analyzed subjectively by a 3-point grading scale and objectively by measuring the CT attenuation in terms of the signal- and contrast-to-noise ratios (SNR and CNR, respectively). Radiation and CM doses were compared.ResultsThe CT attenuation, subjective image quality assessment, SNR, and CNR of various aortic regions of interest did not differ significantly between two groups. In the low-iodine group, images reconstructed by FBP and IR demonstrated significant differences in image noise, SNR, and CNR (p<0.05). The low-iodine group resulted in 34.3% less radiation (4.4 ± 0.5 mSv) than the high-iodine group (6.7 ± 0.6 mSv), and 27.3% less iodine weight (20.36 ± 2.65 g) than the high-iodine group (28 ± 1.98 g). Observers exhibited excellent agreement on the aortic image quality scores (κ = 0.904).ConclusionsCT images of aorta could be obtained within 2 s by using a DSCT Flash protocol with low tube voltage, IR, and low-iodine-concentration CM. Appropriate contrast enhancement was achieved while maintaining good image quality and decreasing the radiation and iodine doses.     

Infant Cardiac CT Angiography with 64-Slice and 256-Slice CT: Comparison of Radiation Dose and Image Quality Using a Pediatric Phantom

Background

The aims of this study were to investigate the image quality and radiation exposure of pediatric protocols for cardiac CT angiography (CTA) in infants under one year of age.

Methodology/Principal Findings

Cardiac CTA examinations were performed using an anthropomorphic phantom representing a 1-year-old child scanned with non-electrocardiogram-gated (NG), retrospectively electrocardiogram-gated helical (RGH) and prospectively electrocardiogram-gated axial (PGA) techniques in 64-slice and 256-slice CT scanners. The thermoluminescent dosimeters (TLD) were used for direct organ dose measurement, while dose-length product and effective mAs were also used to estimate the patient dose. For image quality, noise and signal-to-noise-ratio (SNR) were assessed based on regions-of-interest drawn on the reconstructed CT images, and were compared with the proposed cardiac image quantum index (CIQI). Estimated dose results were in accordant to the measured doses. The NG scan showed the best image quality in terms of noise and SNR. The PGA scan had better image quality than the RGH scan with 83.70% dose reduction. Noise and SNR were also corresponded to the proposed CIQI.

Conclusions/Significance

The PGA scan protocol was a good choice in balancing radiation exposure and image quality for infant cardiac CTA. We also suggested that the effective mAs and the CIQI were suitable in assessing the tradeoffs between radiation dose and image quality for cardiac CTA in infants. These results are useful for future implementation of dose reduction strategies in pediatric cardiac CTA protocols.     

The Impact of Different Levels of Adaptive Iterative Dose Reduction 3D on Image Quality of 320-Row Coronary CT Angiography: A Clinical Trial

Purpose

The aim of this study was the systematic image quality evaluation of coronary CT angiography (CTA), reconstructed with the 3 different levels of adaptive iterative dose reduction (AIDR 3D) and compared to filtered back projection (FBP) with quantum denoising software (QDS).

Methods

Standard-dose CTA raw data of 30 patients with mean radiation dose of 3.2 ± 2.6 mSv were reconstructed using AIDR 3D mild, standard, strong and compared to FBP/QDS. Objective image quality comparison (signal, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contour sharpness) was performed using 21 measurement points per patient, including measurements in each coronary artery from proximal to distal.

Results

Objective image quality parameters improved with increasing levels of AIDR 3D. Noise was lowest in AIDR 3D strong (p≤0.001 at 20/21 measurement points; compared with FBP/QDS). Signal and contour sharpness analysis showed no significant difference between the reconstruction algorithms for most measurement points. Best coronary SNR and CNR were achieved with AIDR 3D strong. No loss of SNR or CNR in distal segments was seen with AIDR 3D as compared to FBP.

Conclusions

On standard-dose coronary CTA images, AIDR 3D strong showed higher objective image quality than FBP/QDS without reducing contour sharpness.

Trial Registration

Clinicaltrials.gov NCT00967876     

Image Quality and Radiation Dose of CT Coronary Angiography with Automatic Tube Current Modulation and Strong Adaptive Iterative Dose Reduction Three-Dimensional (AIDR3D)

Purpose

To investigate image quality and radiation dose of CT coronary angiography (CTCA) scanned using automatic tube current modulation (ATCM) and reconstructed by strong adaptive iterative dose reduction three-dimensional (AIDR3D).

Methods

Eighty-four consecutive CTCA patients were collected for the study. All patients were scanned using ATCM and reconstructed with strong AIDR3D, standard AIDR3D and filtered back-projection (FBP) respectively. Two radiologists who were blinded to the patients'' clinical data and reconstruction methods evaluated image quality. Quantitative image quality evaluation included image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). To evaluate image quality qualitatively, coronary artery is classified into 15 segments based on the modified guidelines of the American Heart Association. Qualitative image quality was evaluated using a 4-point scale. Radiation dose was calculated based on dose-length product.

Results

Compared with standard AIDR3D, strong AIDR3D had lower image noise, higher SNR and CNR, their differences were all statistically significant (P<0.05); compared with FBP, strong AIDR3D decreased image noise by 46.1%, increased SNR by 84.7%, and improved CNR by 82.2%, their differences were all statistically significant (P<0.05 or 0.001). Segments with diagnostic image quality for strong AIDR3D were 336 (100.0%), 486 (96.4%), and 394 (93.8%) in proximal, middle, and distal part respectively; whereas those for standard AIDR3D were 332 (98.8%), 472 (93.7%), 378 (90.0%), respectively; those for FBP were 217 (64.6%), 173 (34.3%), 114 (27.1%), respectively; total segments with diagnostic image quality in strong AIDR3D (1216, 96.5%) were higher than those of standard AIDR3D (1182, 93.8%) and FBP (504, 40.0%); the differences between strong AIDR3D and standard AIDR3D, strong AIDR3D and FBP were all statistically significant (P<0.05 or 0.001). The mean effective radiation dose was (2.55±1.21) mSv.

Conclusion

Compared with standard AIDR3D and FBP, CTCA with ATCM and strong AIDR3D could significantly improve both quantitative and qualitative image quality.     

320排CT冠脉造影检查对冠状动脉斑块成分分析可行性初探

目的:研究320排CT冠脉造影对分析冠状动脉轻度及重度狭窄患者斑块成分的价值。方法:2011年4月-2012年5月间我院1132例(62±12岁,42%女性)冠心病患者行320排CT冠状动脉造影检查,依据美国心脏协会16分段标准,分析每一例患者每一节段血管狭窄程度及斑块性质,CT斑块分型如下:Ⅰ型为钙化斑块,Ⅱ型为钙化为主的混合斑块,Ⅲ型为非钙化为主的混合斑块,Ⅳ型为非钙化斑块。比较不同狭窄程度组斑块类型差别。结果:共363例为冠脉血管正常人群,冠状动脉狭窄患者共769例,其中管腔狭窄程度<50%的轻度人群为367例,重度狭窄组(≥50%)为402例。重度狭窄患者组冠脉血管混合斑块数量较多,而非钙化斑块相对较少(Ⅰ～Ⅳ型斑块所占比例分别为22%,,39%,21%,18%),轻度狭窄患者组各斑块所占比例分别为29%,29%,26%,16%(p=0.006)。结论:随着冠状动脉狭窄程度的不同,冠状动脉粥样硬化斑块的类型也不尽相同,重度狭窄人群组中混合斑块较多而非钙化斑块较少。320排CT冠脉造影可对冠状动脉斑块成分进行分析。     

A Dictionary Learning Approach with Overlap for the Low Dose Computed Tomography Reconstruction and Its Vectorial Application to Differential Phase Tomography

X-ray based Phase-Contrast Imaging (PCI) techniques have been demonstrated to enhance the visualization of soft tissues in comparison to conventional imaging methods. Nevertheless the delivered dose as reported in the literature of biomedical PCI applications often equals or exceeds the limits prescribed in clinical diagnostics. The optimization of new computed tomography strategies which include the development and implementation of advanced image reconstruction procedures is thus a key aspect. In this scenario, we implemented a dictionary learning method with a new form of convex functional. This functional contains in addition to the usual sparsity inducing and fidelity terms, a new term which forces similarity between overlapping patches in the superimposed regions. The functional depends on two free regularization parameters: a coefficient multiplying the sparsity-inducing norm of the patch basis functions coefficients, and a coefficient multiplying the norm of the differences between patches in the overlapping regions. The solution is found by applying the iterative proximal gradient descent method with FISTA acceleration. The gradient is computed by calculating projection of the solution and its error backprojection at each iterative step. We study the quality of the solution, as a function of the regularization parameters and noise, on synthetic data for which the solution is a-priori known. We apply the method on experimental data in the case of Differential Phase Tomography. For this case we use an original approach which consists in using vectorial patches, each patch having two components: one per each gradient component. The resulting algorithm, implemented in the European Synchrotron Radiation Facility tomography reconstruction code PyHST, has proven to be efficient and well-adapted to strongly reduce the required dose and the number of projections in medical tomography.     

CT Angiography of the Head-and-Neck Vessels Acquired with Low Tube Voltage,Low Iodine,and Iterative Image Reconstruction: Clinical Evaluation of Radiation Dose and Image Quality

Objectives

We aimed to assess the effectiveness and feasibility of head-and-neck Computed Tomography Angiography (CTA) with low tube voltage and low concentration contrast media combined with iterative reconstruction algorithm.

Methods

92 patients were randomly divided into group A and B: patients in group A received a conventional scan with 120 kVp and contrast media of 320 mgI/ml. Patients in group B, 80 kVp and contrast media of 270 mgI/ml were used along with iterative reconstruction algorithm techniques. Image quality, radiation dose and the effectively consumed iodine amount between two groups were analyzed and compared.

Results

Image quality of CTA of head-and-neck vessels obtained from patients in group B was significantly improved quantitatively and qualitatively. In addition, CT attenuation values in group B were also significantly higher than that in group A (p<0.001). Furthermore, compared with the protocol whereby 120 kVp and 320 mgI/dl were administrated, the mean radiation dose and consumed iodine amount in protocol B were also reduced by 50% and 15.6%, respectively (p<0.001).

Conclusions

With the help of iterative reconstruction algorithm techniques, the head-and-neck CTA with diagnostic quality can be adequately acquired with low tube voltage and low concentration contrast media. This method could be potentially extended to include any part of the body to reduce the risks related to ionizing radiation.     

Measurement of Mandibular Growth Using Cone-Beam Computed Tomography: A Miniature Pig Model Study

The purpose of this study was to measure the long-term growth of the mandible in miniature pigs using 3D Cone-Beam Computerized Tomography (CBCT). The mandibles of the pigs were scanned monthly over 12 months using CBCT and the 3D mandibular models were reconstructed from the data. Seventeen anatomical landmarks were identified and classified into four groups of line segments, namely anteroposterior, superoinferior, mediolateral and anteroinferior. The inter-marker distances, inter-segmental angles, volume, monthly distance changes and percentage of changes were calculated to describe mandibular growth. The total changes of inter-marker distances were normalized to the initial values. All inter-marker distances increased over time, with the greatest mean normalized total changes in the superoinferior and anteroposterior groups (p<0.05). Monthly distance changes were greatest during the first four months and then reduced over time. Percentages of inter-marker distance changes were similar among the groups, reaching half of the overall growth around the 4^th month. The mandibular volume growth increased non-linearly with time, accelerating during the first five months and slowing during the remaining months. The growth of the mandible was found to be anisotropic and non-homogeneous within the bone and non-linear over time, with faster growth in the ramus than in the body. These growth patterns appeared to be related to the development of the dentition, providing necessary space for the teeth to grow upward for occlusion and for the posterior teeth to erupt.     

Aortic Unfolding Determined Using Non-Contrast Cardiac Computed Tomography: Correlations with Age and Coronary Artery Calcium Score

Objective

Aortic unfolding occurs with aging and reflects proximal aortic dilation, aortic arch widening, and decreased curvature. This study 1) evaluated the relationship between aortic unfolding measured using non-contrast cardiac-gated computed tomography (CT) and age, 2) assessed factors influencing aortic unfolding, and 3) determined the association of this measurement with coronary artery calcium (CAC) score.

Methods

We reviewed the charts of 219 subjects (142 men, 77 women; mean age 54.2±9.3 years) who underwent coronary artery calcium scanning during routine health screening from December 2010 to May 2011. Multivariate regression analysis according to cardiovascular risk factors was performed. We also analyzed the relationship between aortic unfolding measurements and CAC score using stepwise multiple linear regression.

Results

Mean aortic unfolding was 103.7±13.9 mm (men, 106.5±13.5 mm; women, 98.4±12.9 mm). Age, body surface area, and hypertension were exclusively associated with aortic unfolding. The association between aortic unfolding and CAC score was significant after adjustment for age and gender (β = 1.89, p = 0.017) and for Framingham risk score (β = 2.83, p<0.001).

Conclusions

Aortic unfolding defined by measuring aortic width was a reproducible and practical method with non-contrast cardiac CT and associated with age, body surface area, and hypertension. CAC score, a well-established surrogate marker of cardiovascular disease, is positively associated with aortic unfolding. Further study to evaluate aortic unfolding as a potential predictor of cardiovascular risk is warranted.     

头颅电子计算机断层扫描血管造影和头颅磁共振血管成像在颅内动脉瘤中诊断价值比较的回顾性研究

摘要 目的：研究对比头颅电子计算机断层扫描血管造影（CTA）和头颅磁共振血管成像（MRA）在颅内动脉瘤中诊断价值。方法：回顾性分析医院2019年1月2日～2020年12月15日收治的60例疑似颅内动脉瘤患者资料,所有受试者均开展头颅CTA检查、MRA检查以及数字减影血管造影（DSA）检查。以DSA检查结果为金标准,比较头颅CTA和头颅MRA诊断颅内动脉瘤的效能。此外,对比头颅CTA和头颅MRA诊断不同分级、不同部位颅内动脉瘤的符合率。结果：DAS检查结果显示确诊动脉瘤患者48例,共检出动脉瘤74个,CTA检出动脉瘤65个,MRA检出动脉瘤51个,CTA动脉瘤检出率高于MRA检出率（均P＜0.05）。以DSA结果为金标准,CTA诊断颅内动脉瘤的灵敏度、特异度以及准确度分别为94.20%（65/69）、60.00%（3/5）、91.89%（68/74）,均高于MRA的82.26%（51/62）、41.67%（5/12）、75.68%（56/74）（均P＜0.05）。CTA诊断1级颅内动脉瘤的符合率为13.85%（9/65）,高于MRA的7.84%（4/51）（P＜0.05）。各种检查方式诊断不同部位颅内动脉瘤的符合率对比均无明显差异（均P＞0.05）。结论：CTA诊断颅内动脉瘤的灵敏度、特异度以及准确度均高于MRA,可提高对小直径肿瘤的检出率。然而,MRA具有无辐射、检测费用少、安全性高等优势,临床实际工作中可综合选择合理的检查方式。     

Image Quality of 3rd Generation Spiral Cranial Dual-Source CT in Combination with an Advanced Model Iterative Reconstruction Technique: A Prospective Intra-Individual Comparison Study to Standard Sequential Cranial CT Using Identical Radiation Dose

Objectives

To prospectively intra-individually compare image quality of a 3^rd generation Dual-Source-CT (DSCT) spiral cranial CT (cCT) to a sequential 4-slice Multi-Slice-CT (MSCT) while maintaining identical intra-individual radiation dose levels.

Methods

35 patients, who had a non-contrast enhanced sequential cCT examination on a 4-slice MDCT within the past 12 months, underwent a spiral cCT scan on a 3^rd generation DSCT. CTDI_vol identical to initial 4-slice MDCT was applied. Data was reconstructed using filtered backward projection (FBP) and 3^rd-generation iterative reconstruction (IR) algorithm at 5 different IR strength levels. Two neuroradiologists independently evaluated subjective image quality using a 4-point Likert-scale and objective image quality was assessed in white matter and nucleus caudatus with signal-to-noise ratios (SNR) being subsequently calculated.

Results

Subjective image quality of all spiral cCT datasets was rated significantly higher compared to the 4-slice MDCT sequential acquisitions (p<0.05). Mean SNR was significantly higher in all spiral compared to sequential cCT datasets with mean SNR improvement of 61.65% (p*_{Bonferroni0.05}<0.0024). Subjective image quality improved with increasing IR levels.

Conclusion

Combination of 3^rd-generation DSCT spiral cCT with an advanced model IR technique significantly improves subjective and objective image quality compared to a standard sequential cCT acquisition acquired at identical dose levels.     

Feasibility Study of Using Gemstone Spectral Imaging (GSI) and Adaptive Statistical Iterative Reconstruction (ASIR) for Reducing Radiation and Iodine Contrast Dose in Abdominal CT Patients with High BMI Values

Purpose

To prospectively investigate the effect of using Gemstone Spectral Imaging (GSI) and adaptive statistical iterative reconstruction (ASIR) for reducing radiation and iodine contrast dose in abdominal CT patients with high BMI values.

Materials and Methods

26 patients (weight > 65kg and BMI ≥ 22) underwent abdominal CT using GSI mode with 300mgI/kg contrast material as study group (group A). Another 21 patients (weight ≤ 65kg and BMI ≥ 22) were scanned with a conventional 120 kVp tube voltage for noise index (NI) of 11 with 450mgI/kg contrast material as control group (group B). GSI images were reconstructed at 60keV with 50%ASIR and the conventional 120kVp images were reconstructed with FBP reconstruction. The CT values, standard deviation (SD), signal-noise-ratio (SNR), contrast-noise-ratio (CNR) of 26 landmarks were quantitatively measured and image quality qualitatively assessed using statistical analysis.

Results

As for the quantitative analysis, the difference of CNR between groups A and B was all significant except for the mesenteric vein. The SNR in group A was higher than B except the mesenteric artery and splenic artery. As for the qualitative analysis, all images had diagnostic quality and the agreement for image quality assessment between the reviewers was substantial (kappa = 0.684). CT dose index (CTDI) values for non-enhanced, arterial phase and portal phase in group A were decreased by 49.04%, 40.51% and 40.54% compared with group B (P = 0.000), respectively. The total dose and the injection rate for the contrast material were reduced by 14.40% and 14.95% in A compared with B.

Conclusion

The use of GSI and ASIR provides similar enhancement in vessels and image quality with reduced radiation dose and contrast dose, compared with the use of conventional scan protocol.     

Whole-Organ CT Perfusion of the Pancreas: Impact of Iterative Reconstruction on Image Quality,Perfusion Parameters and Radiation Dose in 256-Slice CT-Preliminary Findings

Background

This study was performed to assess whether iterative reconstruction can reduce radiation dose while maintaining acceptable image quality, and to investigate whether perfusion parameters vary from conventional filtered back projection (FBP) at the low-tube-voltage (80-kVp) during whole-pancreas perfusion examination using a 256-slice CT.

Methods

76 patients with known or suspected pancreatic mass underwent whole-pancreas perfusion by a 256-slice CT. High- and low-tube-voltage CT images were acquired. 120-kVp image data (protocol A) and 80-kVp image data (protocol B) were reconstructed with conventional FBP, and 80-kVp image data were reconstructed with iDose⁴ (protocol C) iterative reconstruction. The image noise; contrast-to-noise ratio (CNR) relative to muscle for the pancreas, liver, and aorta; and radiation dose of each protocol were assessed quantitatively. Overall image quality was assessed qualitatively. Among 76 patients, 23 were eventually proven to have a normal pancreas. Perfusion parameters of normal pancreas in each protocol including blood volume, blood flow, and permeability-surface area product were measured.

Results

In the quantitative study, protocol C reduced image noise by 36.8% compared to protocol B (P<0.001). Protocol C yielded significantly higher CNR relative to muscle for the aorta, pancreas and liver compared to protocol B (P<0.001), and offered no significant difference compared to protocol A. In the qualitative study, protocols C and A gained similar scores and protocol B gained the lowest score for overall image quality (P<0.001). Mean effective doses were 23.37 mSv for protocol A and 10.81 mSv for protocols B and C. There were no significant differences in the normal pancreas perfusion values among three different protocols.

Conclusion

Low-tube-voltage and iDose⁴ iterative reconstruction can dramatically decrease the radiation dose with acceptable image quality during whole-pancreas CT perfusion and have no significant impact on the perfusion parameters of normal pancreas compared to the conventional FBP reconstruction using a 256-slice CT scanner.     

Using Multidetector Computed Tomography in a Swine Model to Assess the Effects of Sublingual Nitroglycerin and Intravenous Adenosine on Epicardial Coronary Arteries

This study examines the effects of intravenous infusion of adenosine and sublingual nitroglycerin on coronary angiograms obtained by current-generation multidetector computed tomography. We assessed coronary vasodilation at baseline and after intravenous adenosine (140 µg/kg/min) or sublingual nitroglycerin spray (800 µg) in 7 female swine (weight, 40.9 ± 1.4 kg) by using electrocardiogram-gated coronary angiography with a 64-detector scanner (rotation time, 400 ms; 120kV; 400 mA) and intravenous contrast (300 mg/mL iohexol, 4.5 mL/s, 2 mL/kg). Cross-sectional areas of segments in the left anterior descending, circumflex, and right coronary arteries were evaluated in oblique orthogonal views. Images were acquired at an average heart rate of 73 ± 11 beats per minute. Changes in aortic pressure were not significant with nitroglycerin but decreased (approximately 10%) with adenosine. Of the 76 segments analyzed (baseline range, 2 to 39 mm²), 1 distal segment could not be assessed after adenosine. Segment cross-sectional area increased by 11.3% with nitroglycerin but decreased by 9.6% during adenosine infusion. The results of the present study are consistent with the practice of using sublingual nitroglycerin to enhance visualization of epicardial vessels and suggest that intravenous adenosine may hinder coronary artery visualization. This study is the first repeated-measures electrocardiogram-gated CT evaluation to use the same imaging technology to assess changes in coronary cross-sectional area before and after treatment with a vasodilator. The nitroglycerin-associated changes in our swine model were modest in comparison with previously reported human studies.Abbreviations: LAD, left anterior descending artery; MDCT, multidetector computed tomographyRecent advances in multidetector computed tomography (MDCT) for coronary angiography, their increased availability, and the pending release of a new generation of CT scanners contribute to this methodology''s potential for revolutionizing the early diagnosis and functional assessment of coronary artery disease.^15,16,25 However, the benefits of methodologic advances do not diminish the need to validate and assess the safety, efficacy, and costs of technology.¹⁵ In this regard, the present study uses an animal model with coronary anatomy analogous to that of humans^11,43 to assess the effects of sublingual nitroglycerin and intravenous adenosine on coronary epicardial vessel visualization by using baseline imaging as a control. The radiation exposure associated with CT procedures precludes human studies that involve repeated measures on the same subjects.Sublingual nitroglycerin is hypothesized to enhance the visualization of epicardial coronary vessels due to its vasodilatory properties.^8-10 Nitroglycerin acts as a nitric oxide generator to induce relaxation of vascular smooth muscle independent of endothelial function.^1,18,20 Current evidence supporting improved coronary visualization with sublingual nitroglycerin is derived from clinical cross-sectional studies that compare results in different groups of patients with heterogeneous coronary lesions.^5,6,16,27,44 A recent survey reported that more than 80% of facilities in the United States routinely use nitroglycerin in cardiac MDCT angiography.²³In contrast to the action of nitroglycerin on epicardial vascular smooth muscle, intravenous adenosine frequently is used as a pharmacologic stress to affect vasodilatation within the coronary microcirculation.²⁰ Although current-generation CT scanners have limited capability to assess myocardial tissue perfusion, research efforts from advanced imaging centers suggest that future-generation CT scanners soon will permit myocardial perfusion imaging.^13,14,29 No studies to date have assessed epicardial vessel changes by MDCT with intravenous doses of adenosine appropriate for myocardial perfusion imaging.The objective of this study was to provide an animal model for MDCT studies that permits repeated measures of epicardial vessels without the limitations of cross-sectional designs or the complications of heterogeneity of vascular lesions within clinical populations. This study used routes of administration of nitroglycerin and adenosine that are consistent with clinical practice.     

Emphysema Is Common in Lungs of Cystic Fibrosis Lung Transplantation Patients: A Histopathological and Computed Tomography Study

Background

Lung disease in cystic fibrosis (CF) involves excessive inflammation, repetitive infections and development of bronchiectasis. Recently, literature on emphysema in CF has emerged, which might become an increasingly important disease component due to the increased life expectancy. The purpose of this study was to assess the presence and extent of emphysema in endstage CF lungs.

Methods

In explanted lungs of 20 CF patients emphysema was semi-quantitatively assessed on histology specimens. Also, emphysema was automatically quantified on pre-transplantation computed tomography (CT) using the percentage of voxels below -950 Houndfield Units and was visually scored on CT. The relation between emphysema extent, pre-transplantation lung function and age was determined.

Results

All CF patients showed emphysema on histological examination: 3/20 (15%) showed mild, 15/20 (75%) moderate and 2/20 (10%) severe emphysema, defined as 0–20% emphysema, 20–50% emphysema and >50% emphysema in residual lung tissue, respectively. Visually upper lobe bullous emphysema was identified in 13/20 and more diffuse non-bullous emphysema in 18/20. Histology showed a significant correlation to quantified CT emphysema (p = 0.03) and visual emphysema score (p = 0.001). CT and visual emphysema extent were positively correlated with age (p = 0.045 and p = 0.04, respectively).

Conclusions

In conclusion, this study both pathologically and radiologically confirms that emphysema is common in end-stage CF lungs, and is age related. Emphysema might become an increasingly important disease component in the aging CF population.