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

The Additional Diagnostic Value of the Three-dimensional Volume Rendering Imaging in Routine Radiology Practice

Three-dimensional volume rendering (3DVR) is useful in a wide variety of medical-imaging applications. The increasingly advanced capabilities of CT and MRI to acquire volumetric data sets with isotropic voxels have resulted in the increased use of the 3DVR techniques for clinical applications. The two most commonly used techniques are the maximum intensity projection (MIP) and, more recently, 3DVR. Several kinds of medical imaging data could be reconstructed for 3D display, including CT, MRI, and ultrasonography (US). In particular, the 3D CT imaging has been developed, improved, and widely used of late. Understanding the mechanisms of 3DVR is essential for the accurate evaluation of the resulting images. Although further research is required to detect the efficiency of 3DVR in radiological applications, with wider availability and improved diagnostic performance, 3DVR is likely to enjoy widespread acceptance in the radiology practice going forward.

Three-Dimensional Printing: Basic Principles and Applications in Medicine and Radiology

The advent of three-dimensional printing (3DP) technology has enabled the creation of a tangible and complex 3D object that goes beyond a simple 3D-shaded visualization on a flat monitor. Since the early 2000s, 3DP machines have been used only in hard tissue applications. Recently developed multi-materials for 3DP have been used extensively for a variety of medical applications, such as personalized surgical planning and guidance, customized implants, biomedical research, and preclinical education. In this review article, we discuss the 3D reconstruction process, touching on medical imaging, and various 3DP systems applicable to medicine. In addition, the 3DP medical applications using multi-materials are introduced, as well as our recent results.

A combined prognostic serum interleukin-8 and interleukin-6 classifier for stage 1 lung cancer in the prostate, lung, colorectal, and ovarian cancer screening trial

BACKGROUND

The advent of low-dose helical computed tomography for lung cancer screening will likely lead to an increase in the detection of stage I lung cancer. Presently, these patients are primarily treated with surgery alone and approximately 30% will develop recurrence and die. Biomarkers that can identify patients for whom adjuvant chemotherapy would be a benefit could significantly reduce both patient morbidity and mortality. Herein, we sought to build a prognostic inflammatory-based classifier for stage I lung cancer.

METHODS

We performed a retrospective analysis of 548 European American lung cancer cases prospectively enrolled in the Prostate, Lung, Colorectal and Ovarian study. C-reactive protein, interleukin (IL)-6, IL-8, tumor necrosis factor-α, and IL-1β were measured using an ultrasensitive electrochemiluminescence immunoassay in serum samples collected at the time of study entry.

RESULTS

IL-6 and IL-8 were each associated with significantly shorter survival (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.08-1.64; p = 0.007; and HR, 1.3; 95% CI, 1.09-1.67; p = 0.005, respectively). Moreover, a combined classifier of IL-6 and IL-8 were significantly associated with poor outcome in stage I lung cancer patients (HR, 3.39; 95% CI, 1.54-7.48, p = 0.002) and in stage 1 patients with more than or equal to 30 pack-years of smoking (HR, 3.15; 95% CI, 1.54-6.46, p = 0.002).

CONCLUSIONS

These results further support the association between inflammatory markers and lung cancer outcome and suggest that a combined serum IL-6/IL-8 classifier could be a useful tool for guiding therapeutic decisions in patients with stage I lung cancer.

Coronary CT angiography: Diagnostic value and clinical challenges

Coronary computed tomography (CT) angiography has been increasingly used in the diagnosis of coronary artery disease due to improved spatial and temporal resolution with high diagnostic value being reported when compared to invasive coronary angiography. Diagnostic performance of coronary CT angiography has been significantly improved with the technological developments in multislice CT scanners from the early generation of 4-slice CT to the latest 320- slice CT scanners. Despite the promising diagnostic value, coronary CT angiography is still limited in some areas, such as inferior temporal resolution, motion-related artifacts and high false positive results due to severe calcification. The aim of this review is to present an overview of the technical developments of multislice CT and diagnostic value of coronary CT angiography in coronary artery disease based on different generations of multislice CT scanners. Prognostic value of coronary CT angiography in coronary artery disease is also discussed, while limitations and challenges of coronary CT angiography are highlighted.

The vulnerable coronary plaque: update on imaging technologies

Several studies have been carried out on vulnerable plaque as the main culprit for ischaemic cardiac events. Historically, the most important diagnostic technique for studying coronary atherosclerotic disease was to determine the residual luminal diameter by angiographic measurement of the stenosis. However, it has become clear that vulnerable plaque rupture as well as thrombosis, rather than stenosis, triggers most acute ischaemic events and that the quantification of risk based merely on severity of the arterial stenosis is not sufficient. In the last decades, substantial progresses have been made on optimisation of techniques detecting the arterial wall morphology, plaque composition and inflammation. To date, the use of a single technique is not recommended to precisely identify the progression of the atherosclerotic process in human beings. In contrast, the integration of data that can be derived from multiple methods might improve our knowledge about plaque destabilisation. The aim of this narrative review is to update evidence on the accuracy of the currently available non-invasive and invasive imaging techniques in identifying components and morphologic characteristics associated with coronary plaque vulnerability.

Anatomical annotation on vascular structure in volume rendered images

The precise annotation of vascular structure is desired in computer-assisted systems to help surgeons identify each vessel branch. This paper proposes a method that annotates vessels on volume rendered images by rendering their names on them using a two-pass rendering process. In the first rendering pass, vessel surface models are generated using such properties as centerlines, radii, and running directions. Then the vessel names are drawn on the vessel surfaces. Finally, the vessel name images and the corresponding depth buffer are generated by a virtual camera at the viewpoint. In the second rendering pass, volume rendered images are generated by a ray casting volume rendering algorithm that considers the depth buffer generated in the first rendering pass. After the two-pass rendering is finished, an annotated image is generated by blending the volume rendered image with the surface rendered image. To confirm the effectiveness of our proposed method, we performed a computer-assisted system for the automated annotation of abdominal arteries. The experimental results show that vessel names can be drawn on the corresponding vessel surface in the volume rendered images at a computing cost that is nearly the same as that by volume rendering only. The proposed method has enormous potential to be adopted to annotate the vessels in the 3D medical images in clinical applications, such as image-guided surgery.

Three-dimensional anatomical accuracy of cranial models created by rapid prototyping techniques validated using a neuronavigation station

In neurosurgery and ear, nose and throat surgery the application of computerised navigation systems for guiding operations has been expanding rapidly. However, suitable models to train surgeons in using navigation systems are not yet available. We have developed a technique using an industrial, rapid prototyping process from which accurate spatial models of the cranium, its contents and pathology can be reproduced for teaching. We were able to register, validate and navigate using these models with common available navigation systems such as the Medtronic StealthStation S7®.

[Radiologists in the emergency department: when and how to use multislice CT]

Chest pain is a challenging clinical problem in the emergency department. Despite advances in clinical diagnosis, many patients with atypical chest pain are needlessly hospitalized and others are mistakenly discharged. Faced with the specific clinical situation in which a patient has chest pain, an initially normal or inconclusive electrocardiogram, and normal cardiac biomarkers, multislice CT has proven useful for ruling out the conditions that involve the greatest morbidity and mortality and for establishing the cause of pain. This article reviews the current usefulness of multislice CT in the diagnostic workup of patients presenting at the emergency department with chest pain. We review the technique, define the most appropriate population, describe the acquisition protocols, and discuss the advantages and disadvantages of each study protocol.

Coronary Angiography Using Noninvasive Imaging Techniques of Cardiac CT and MRI

Noninvasive coronary angiography has become an important imaging tool in the evaluation of patients with and at risk for coronary artery disease (CAD). Multidetector computed tomographic (MDCT) angiography offers excellent negative predictive value (≥95%) for the absence of coronary artery disease and has shown promising results in evaluating allograft vasculopathy, bypass grafts, and degenerative aortic valve disease. A single MDCT scan in the emergency department is valuable in ruling out both cardiac and noncardiac causes of acute chest pain. Cardiac magnetic resonance (MR) currently lacks the spatial resolution of MDCT limiting its assessment of the coronary vasculature, but the proximal coronary arteries can be evaluated along with myocardial function and viability without exposure to contrast dye or ionizing radiation. In addition, MR imaging also has great potential for characterizing coronary plaques, as well as following their progression and regression.

CT coronary angiography: 256-slice and 320-detector row scanners

Multidetector computed tomography (MDCT) has rapidly evolved from 4-detector row systems in 1998 to 256-slice and 320-detector row CT systems. With smaller detector element size and faster gantry rotation speed, spatial and temporal resolution of the 64-detector MDCT scanners have made coronary artery imaging a reliable clinical test. Wide-area coverage MDCT, such as the 256-slice and 320-detector row MDCT scanners, has enabled volumetric imaging of the entire heart free of stair-step artifacts at a single time point within one cardiac cycle. It is hoped that these improvements will be realized with greater diagnostic accuracy of CT coronary angiography. Such scanners hold promise in performing a rapid high quality "triple rule-out" test without high contrast load, improved myocardial perfusion imaging, and even four-dimensional CT subtraction angiography. These emerging technical advances and novel applications will continue to change the way we study coronary artery disease beyond detecting luminal stenosis.

Radiation dose reduction with increasing utilization of prospective gating in 64-multidetector cardiac computed tomography angiography

BACKGROUND

Medical radiation exposure is a major concern, and several methods have been proposed to reduce radiation doses in multidetector cardiac computed tomography (CT).

OBJECTIVE

The purpose of this study was to review radiation doses of clinical cardiac CT performed at our center and to evaluate the effect of radiation dose reduction strategies on the median dose delivered to patients over time.

METHODS

This study included 623 consecutive clinical patients (male, 58%) who were referred for imaging. The effective dose (mSv) was derived from the product of the dose-length-product (DLP) and a conversion coefficient for the chest (0.014).

RESULTS

The median radiation dose of all patients was 3.0 mSv (interquartile range [IQR], 1.9-8.1 mSv). A significant difference was observed in radiation dose between the prospective (n = 384) and retrospective (n = 239) gating groups (2.0 vs 9.6 mSv; P < 0.0001). Compared with patients with coronary artery bypass grafting (CABG; n = 52), patients without CABG had significantly lower median radiation dose (prospective gating: 2.0 vs 3.4 mSv, P < 0.0001; retrospective gating: 9.3 vs 10.3 mSv, P < 0.0001). In patients with CABG, a significant difference was observed in radiation dose between prospective and retrospective gating (3.4 vs 10.3; P < 0.0001). The median radiation doses per month at our center decreased from 6.2 to 2.1 mSv over time with increasing use of prospective gating (≤91%).

CONCLUSION

Radiation reduction techniques have led to progressive decreases in radiation exposure over time, primarily because of prospective gating.

Diagnostic value of SPECT, PET and PET/CT in the diagnosis of coronary artery disease: A systematic review

PURPOSE

The purpose of the study was to investigate the diagnostic value of SPECT, PET and PET/CT in the diagnosis of coronary artery disease, based on a systematic review.

MATERIAL AND METHODS

A search of PubMed/Medline and Sciencedirect databases in the English-language literature published over the last 24 years was performed. Only studies with at least 10 patients comparing SPECT, PET or combined PET/CT with invasive coronary angiography in the diagnosis of coronary artery disease (50% stenosis) were included for analysis. Sensitivities and specificities estimates pooled across studies were analysed using a Chi-square test.

RESULTS

Twenty-five studies met the selection criteria and were included for the analysis. Ten studies were performed with SPECT alone; while another six studies were performed with PET alone. Five studies were carried out with both PET and SPECT modalities, and the remaining four studies were investigated with integrated PET-CT. The mean value of sensitivity, specificity and accuracy of these imaging modalities for the diagnosis of coronary artery disease was 82% (95%CI: 76 to 88), 76% (95%CI: 70 to 82) and 83% (95%CI: 77 to 89) for SPECT; 91% (95%CI: 85 to 97), 89% (95%CI: 83 to 95) and 89% (95%CI: 83 to 95) for PET; and 85% (95%CI: 79 to 90), 83% (95%CI: 77 to 89) and 88% (95%CI: 82 to 94) for PET/CT, respectively. The diagnostic accuracy of these imaging modalities was dependent on the radiotracers used in these studies, with ammonia resulting in the highest diagnostic value.

CONCLUSION

Our review shows that PET has high diagnostic value for diagnosing coronary artery disease, and this indicates that it is a valuable technique for both detection and prediction of coronary artery disease.

Multislice CT angiography in cardiac imaging: prospective ECG-gating or retrospective ECG-gating?

With the advent of multislice CT more than a decade ago, multislice CT angiography has demonstrated a huge potential in the less invasive imaging of cardiovascular disease, especially in the diagnosis of coronary artery disease. The diagnostic accuracy of multislice CT angiography has been significantly augmented with the rapid technical developments ranging from the initial 4-slice, to the current 64-slice and 256 and 320-slice CT scanners. This is mainly demonstrated by the improved spatial and temporal resolution when compared to the earlier type of CT scanners. Traditionally, multislice CT angiography is acquired with retrospective ECG-gating with acquisition of volume data at the expense of increased radiation dose, since data is acquired at the entire cardiac cycle, although not all of them are used for postprocessing or reconstructions. Recently, there is an increasing trend of utilising prospective ECG-gating in cardiac imaging with latest multislice CT scanners (64 or more slices) with significant reduction of radiation dose when compared to retrospective ECG-gating method. However, there is some debate as to the diagnostic value of prospective ECG-gating in the diagnosis of coronary artery disease, despite its attractive ability to reduce radiation dose. This article will review the performance of retrospective ECG-gating in the diagnostic value of coronary artery disease, highlight the potential applications of prospective ECG-gating, and explore the future directions of multislice CT angiography in cardiac imaging.

CT of coronary artery disease

Technical innovation is rapidly improving the clinical utility of cardiac computed tomography (CT) and will increasingly address current technical limitations, especially the association of this test with relatively high levels of radiation. Guidelines for appropriate indications are in place and are evolving, with an increasing evidence base to ensure the appropriate use of this modality. New technologies and new applications, such as myocardial perfusion imaging and dual-energy CT, are being explored and are widening the scope of coronary CT angiography from mere coronary artery assessment to the integrative analysis of cardiac morphology, function, perfusion, and viability. The scientific evaluation of coronary CT angiography has left the stage of feasibility testing and increasingly, evidence-based data are accumulating on outcomes, prognosis, and cost-effectiveness. In this review, these developments will be discussed in the context of current pivotal transitions in cardiovascular disease management and their potential influence on the current role and future fate of coronary CT angiography will be examined.

Intrinsic gating for small-animal computed tomography: a robust ECG-less paradigm for deriving cardiac phase information and functional imaging

BACKGROUND

A projection-based method of intrinsic cardiac gating in small-animal computed tomography imaging is presented.

METHODS AND RESULTS

In this method, which operates without external ECG monitoring, the gating reference signal is derived from the raw data of the computed tomography projections. After filtering, the derived gating reference signal is used to rearrange the projection images retrospectively into data sets representing different time points in the cardiac cycle during expiration. These time-stamped projection images are then used for tomographic reconstruction of different phases of the cardiac cycle. Intrinsic gating was evaluated in mice and rats and compared with extrinsic retrospective gating. An excellent agreement was achieved between ECG-derived gating signal and self-gating signal (coverage probability for a difference between the 2 measurements to be less than 5 ms was 89.2% in mice and 85.9% in rats). Functional parameters (ventricular volumes and ejection fraction) obtained from the intrinsic and the extrinsic data sets were not significantly different. The ease of use and reliability of intrinsic gating were demonstrated via a chemical stress test on 2 mice, in which the system performed flawlessly despite an increased heart rate. Because of intrinsic gating, the image quality was improved to the extent that even the coronary arteries of mice could be visualized in vivo despite a heart rate approaching 430 bpm. Feasibility of intrinsic gating for functional imaging and assessment of cardiac wall motion abnormalities was successfully tested in a mouse model of myocardial infarction.

CONCLUSIONS

Our results demonstrate that self-gating using advanced software postprocessing of projection data promises to be a valuable tool for rodent computed tomography imaging and renders ECG gating with external electrodes superfluous.

[Clinical applications of computed tomography coronary angiography]

The clinical applications of computed tomography coronary angiography (CTCA) are constantly evolving. Initially employed to quantify coronary artery calcification, multidetector CT also makes it possible to evaluate the anatomy and anatomical variations of coronary circulation, rule out coronary disease, and follow up surgical and percutaneous revascularization procedures. Moreover, CTCA may potentially be useful to quantify ventricular function, characterize non-calcified atherosclerotic plaques, and analyze myocardial perfusion and viability, providing anatomical, morphological, and functional information in patients with suspected ischemic heart disease.

History of cardiac computed tomography: single to 320-detector row multislice computed tomography

Since the introduction of computed tomography (CT) over 30 years ago, the challenge of imaging the beating heart has been a driving force in the innovation of cardiac CT. Imaging the anatomy and physiology of the heart demands temporal, spatial and contrast resolution is arguably greater than for any other organ system in the body. Great progress has been achieved in using CT to evaluate coronary artery stenosis and plaque composition. In addition, techniques to evaluate cardiac function, including myocardial perfusion, regional ventricular wall motion, systolic thickening, ejection fraction, valve function, and congenital cardiac abnormalities are also gaining a foothold in clinical practice as adjuncts to or replacements for invasive coronary angiography, cardiac single photon emission CT (SPECT) imaging, ultrasound and magnetic resonance imaging (MRI). This review summarizes the major accomplishments and future directions in this field, with emphasis on developments over the past 10 years.

Quantification of regional myocardial blood flow using first-pass multidetector-row computed tomography and adenosine triphosphate in coronary artery disease

BACKGROUND

The feasibility of using cardiac multidetector-row computed tomography (MDCT) technology in the quantitative assessment of myocardial blood flow (MBF) using the adenosine triphosphate (ATP) load technique was investigated in the present study.

METHODS AND RESULTS

The study group comprised 14 patients (11 men, 3 women, age range 52-79 years, mean age 69.2 years) who underwent cardiac cine MDCT using the ATP-load technique. MBF was estimated from the slope of the linear regression equation with Patlak plots analysis. The overall average MBF was 1.83+/-0.62 ml . g(-1) . min(-1). Mean MBF in territories with stenosis on coronary angiography was 1.19+/-0.36 ml . g(-1) . min(-1) and 2.06+/-0.54 ml . g(-1) . min(-1) (p<0.01) in territories without stenosis. The average MBF in territories with moderate to severe ischemia on myocardial perfusion scintigraphy was 1.32+/-0.14 ml .g(-1 ). min(-1 )and 1.95+/-0.64 ml . g(-1) . min(-1) (p<0.01) in territories without ischemia.

CONCLUSION

MDCT can be used to quantify MBF using first-pass dynamic data.

Temporally targeted imaging method applied to ECG-gated computed tomography: preliminary phantom and in vivo experience

RATIONALE AND OBJECTIVES

Existing cardiac imaging methods do not allow for improved temporal resolution when considering a targeted region of interest (ROI). The imaging method presented here enables improved temporal resolution for ROI imaging (namely, a reconstruction volume smaller than the complete field of view). Clinically, temporally targeted reconstruction would not change the primary means of reconstructing and evaluating images, but rather would enable the adjunct technique of ROI imaging, with improved temporal resolution compared with standard reconstruction ( approximately 20% smaller temporal scan window). In gated cardiac computed tomography (CT) scans improved temporal resolution directly translates into a reduction in motion artifacts for rapidly moving objects such as the coronary arteries.

MATERIALS AND METHODS

Retrospectively electrocardiogram gated coronary angiography data from a 64-slice CT system were used. A motion phantom simulating the motion profile of a coronary artery was constructed and scanned. Additionally, an in vivo study was performed using a porcine model. Comparisons between the new reconstruction technique and the standard reconstruction are given for an ROI centered on the right coronary artery, and a pulmonary ROI.

RESULTS

In both a well-controlled motion model and a porcine model results show a decrease in motion induced artifacts including motion blur and streak artifacts from contrast enhanced vessels within the targeted ROIs, as assessed through both qualitative and quantitative observations.

CONCLUSION

Temporally targeted reconstruction techniques demonstrate the potential to reduce motion artifacts in coronary CT. Further study is warranted to demonstrate the conditions under which this technique will offer direct clinical utility. Improvement in temporal resolution for gated cardiac scans has implications for improving: contrast enhanced CT angiography, calcium scoring, and assessment of the pulmonary anatomy.

Effects of Intrafractional Motion on Water Equivalent Pathlength in Respiratory-Gated Heavy Charged Particle Beam Radiotherapy

PURPOSE

To analyze the water equivalent pathlength (WEL) fluctuations resulting from cardiac motion and display these variations on a beam's-eye-view image; the analysis provides insight into the accuracy of lung tumor irradiation with heavy charged particle beams.

MATERIALS AND METHODS

Volumetric cine computed tomography (CT) images were obtained on 7 lung cancer patients under free-breathing conditions with a 256-multislice CT scanner. Cardiac phase was determined by selecting systole and diastole. A WEL difference image (DeltaWEL) was calculated by subtracting the WEL image at end-systole from that at end-diastole at respiratory exhalation phase. Two calculation regions were defined: Region 1 was limited to the volume defined by planes bounding the heart; Region 2 included the entire body thickness for a given beam's-eye-view angle.

RESULTS

The DeltaWEL values observed in Region 1 showed fluctuations at the periphery of the heart that varied from 20.4 (SD, 5.2) mm WEL to -15.6 (3.2) mm WEL. The areas over which these range perturbation values were observed were 36.8 (32.4) mm(2) and 6.0 (2.8) mm(2) for positive and negative WEL, respectively. The WEL fluctuations in Region 2 increased by approximately 3-4 mm WEL, whereas negative WEL fluctuations changed by approximately -4 to -5 mm WEL, compared with WEL for Region 1; areas over 20 mm WEL changes in Region 2 increased by 9 mm(2) for positive DeltaWEL and 2 mm(2) for negative DeltaWEL.

CONCLUSIONS

Cine CT with a 256-multislice CT scanner captures both volumetric cardiac and respiratory motion with a temporal resolution sufficient to estimate range fluctuations by these motions. This information can be used to assess the range perturbations that charged particle beams may experience in irradiation of lung or esophageal tumors adjacent to the heart.