ECG-gated emission computed tomography of the cardiac blood pool

ECG-gated cross-sectional images of the cardiac blood pool were produced using a specially constructed emission computed tomographic scanner. A pair of large-field-of-view cameras were mounted in opposition in a gantry that rotates 360 degrees about the patient. The coordinates of each detected event, the output of a physiological synchronizer, and the position of the camera heads were input to a dedicated minicomputer which was used to produce the images. Display as a movie permitted evaluation of regional and global wall motion in cross section without the disadvantages of superimposed blood pools as obtained in nontomographic views.     

Cardiomyopathy: appearances on ECG-gated 64-detector row computed tomography

Multi-detector row cardiac computed tomography (MDCT) with its high spatial and temporal resolution now has an established clinical role in cardiac imaging. The present review illustrates the MDCT appearances of cardiomyopathy, with reference to the normal myocardium, using multi-planar, near-isotropic imaging, three-dimensional volume rendering, and ECG-gated multi-phasic functional imaging software capabilities of 64-MDCT. MRI and echocardiographic correlations are also provided where appropriate.     

Efficacy and safety of balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension guided by cone-beam computed tomography and electrocardiogram-gated area detector computed tomography

BackgroundChronic thromboembolic pulmonary hypertension (CTEPH) is a disease characterized by chronic obstructive thrombus and pulmonary hypertension. Balloon pulmonary angioplasty (BPA), an emerging alternative catheter-based treatment for inoperable patients with CTEPH, has not yet been standardised, especially for lesion assessment in distal pulmonary arteries. Recent advancement in computed tomography enables distal CTEPH lesions to be visualized.MethodsWe retrospectively studied 80 consecutive patients with inoperable CTEPH who received BPA guided by cone-beam computed tomography (CT) (CBCT) or electrocardiogram (ECG)-gated area detector CT (ADCT) for target lesion assessment. We collected clinical and hemodynamic data, including procedural complications, before BPA and at 3 months and 1 year after BPA.ResultsThree hundred eight-five BPA sessions (4.8 sessions/patient) were performed for the lesions of subsegmental arteries (1155 lesions), segmental arteries (738 lesions), and lobar arteries (4 lesions) identified by CBCT or ECG-gated ADCT. Significant improvements in the symptoms, 6-min walk distance, brain natriuretic peptide level, exercise capacity, and haemodynamics were observed 3 months and 1 year after BPA. No cases of death or cardiogenic shock with a low rate of severe wire perforation (0.3%) and severe reperfusion oedema (0.3%) were observed.ConclusionsBPA guided by CBCT or ECG-gated ADCT is effective and remarkably safe in patients with CTEPH . These new advanced CT techniques may be useful in pre-BPA target lesion assessment.     

Dual-energy computed tomography in pulmonary embolism

The introduction of modern dual-energy CT (DECT) scanners has enabled contrast material to be distinguished at imaging without the need for a separate unenhanced scan. Images of pulmonary parenchymal contrast enhancement obtained using DECT improve the detection of defects, augmenting our ability to detect pulmonary emboli; however, with these advances new pitfalls are also introduced. In this pictorial review, we present the technique, clinical applications and causes and remedies of false results of dual-energy pulmonary parenchymal enhancement defects in pulmonary embolism.More than 650, 000 cases of pulmonary embolism (PE) are reported each year, resulting in an estimated 300, 000 annual fatalities. This level of occurrence ranks PE as the third leading cause of death in the USA [1, 2]. Multidetector CT (MDCT) pulmonary angiography has now largely replaced ventilation/perfusion scintigraphy and conventional pulmonary angiography for the evaluation of possible PE [3]; in 2007, MDCT angiography was accepted as the reference standard for diagnosis of acute PE [4]. Unfortunately, conventional MDCT angiography only provides morphological information and its ability to assess subsegmental pulmonary arteries is variable: sensitivities range from 37–96% [5]. The ability to assess subsegmental pulmonary arteries has increased with advances in MDCT technology. Dual-source CT (DSCT), which uses two orthogonally mounted X-ray tubes and detectors to double the speed of image acquisition, was primarily intended to achieve high temporal resolution for cardiac imaging [6–8]. As each tube can be set at a different tube potential (e.g. 80 kVp for one tube and 140 kVp for the other), DSCT also allows for simultaneous dual-energy CT (DECT) image acquisition and largely excludes the need for interscan changes in contrast enhancement or patient movement between CT acquisitions [9–11]. DECT data can be readily post-processed to determine the amount of iodinated contrast material in any voxel. This is because iodine, as compared with soft tissue, attenuates X-ray spectra very differently at 80 kVp and 140 kVp settings. The image data from both energy levels are combined to form a hybrid image that is equivalent to a scan acquired at 120 kVp, which can be used for diagnostic evaluation of morphology and anatomy. In combination with the iodine map, which is related to the microvascular circulation in the lung, this scan can provide morphological and functional information, thus improving the CT assessment of subsegmental pulmonary arteries.The term “perfusion” is ambiguous in DECT; although it is frequently strictly defined as “the volume of blood flowing through a cubic centimetre of tissue per second” [12], it has been used more loosely in many publications on pulmonary emboli to refer to visible pulmonary enhancement with injected contrast material. In this looser application, the term lung “perfusion” at DECT does not correspond to blood flow analysis per se. Instead, this term refers to the iodine enhancement at one point in time, which approximates to the pulmonary blood flow or microcirculation [13]. Thus, we will not use the term “perfusion” to describe the DECT pulmonary iodine maps, but instead opt for “contrast enhancement”. In our review, we present the techniques, clinical applications, drawbacks and remedies of DECT in the diagnosis, prognosis and follow-up of PE.     

Imaging of coronary artery anomalies using ECG-gated 64-row computed tomography angiography

Objective

To shed light on coronary artery anomalies among cardiac patients using ECG-gated 64-row MDCTA during assessment of coronary arteries.

Patients and methods

Study included 840 patients out of whom twenty-one patients have congenital coronary artery anomalies. Patients were examined using ECG gated 64-row MDCT; 80–100 ml contrast agent, followed by a 50 ml saline chaser injected at 5 ml/s, 350 ms gantry rotation time, 0.65 mm detector collimation, ECG tube current modulation and 100–120 kV. Post-processing was done on second workstation including 3D VR, MPR and CMPR images.

Results

Anomalies of the coronary arteries were diagnosed in twenty-one patients. The prevalence of congenital anomalies in this study was 2.5% and included: anomalous origin of right coronary artery in 4 cases (0.48%), anomalous origin of left circumflex artery in 3 cases (0.36%), myocardial bridging of LAD in 12 cases (1.4%) and coronary artery fistula in 2 cases (0.24%).

Conclusion

Coronary artery anomalies are not uncommon among cardiac patients. Myocardial bridging is the most common followed by anomalous origin and proximal course and lastly coronary artery fistula. 64-Row MDCTA is an excellent promising modality and should be the first non-invasive diagnostic tool to rule out such anomalies.     

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.     

Quantification of aortic distensibility in abdominal aortic aneurysm using ECG-gated multi-detector computed tomography

Rationale and objectives

To detect distensibility changes that might be an indicator for an increased risk of rupture, cross-sectional area changes of abdominal aortic aneurysms (AAA) have been determined using ECG-gated CT.

Materials and methods

Distensibility measurements of the aorta were performed in 67 patients with AAA. Time-resolved images were acquired with a four detector-row CT system using a modified CT-angiography protocol. Pulsatility-related cross-sectional area changes were calculated above and at AAA level by semiautomatic segmentation; distensibility values were obtained using additional systemic blood pressure measurements. Values were compared for small Ø< 5 cm (n=44) and large Ø> 5 cm (n?=?23) aneurysms.

Results

The aorta could be segmented successfully in all patients. Upstream AAA distensibility D was significantly higher than at AAA level for both groups: means above AAA (at AAA) D _above = (1.3±0.8)·10^?5 Pa^?1 (D _AAA = (0.6±0.5)·10^?5 Pa^?1) t-test p_D<0.0001. Differences of the distensibility between smaller and larger aneurysms were not found to be significant.

Conclusion

Distensibility can be measured non-invasively with ECG-gated CT. The reduction of distensibility within aneurysms compared to normal proximal aorta is subtle; the lack of difference between both small and large aneurysms suggests that this reduction occurs early in the aneurysm's development. Hence, reduced distensibility might be a predictive parameter in patients with high risk of aortic disease.

     

Use of ECG-gated single-photon emission tomography to assess the evolution of perfusion after acute myocardial infarction

Serial improvement in myocardial perfusion images from the acute or subacute to the chronic stage of acute myocardial infarction (AMI) has been attributed to improved coronary microcirculation or cell function after acute ischaemia and reperfusion. However, conventionally used non-gated imaging cannot eliminate the effect of improved regional contraction. We studied the possibility that such scintigraphic improvement reflects the functional recovery by using ECG-gated myocardial perfusion imaging with technetium-99m sestamibi. Nineteen AMI patients who received acute reperfusion therapy underwent ECG-gated myocardial single-photon emission tomography (SPET) in the subacute and chronic stages. Serial changes in regional image count distributions were analysed on the non-gated, end-diastolic (ED) and end-systolic (ES) images by using segmental mean percent peak activity (MPA) and ΔMPA (MPA in chronic stage – MPA in subacute stage) on bull’s-eye polar maps. These changes were compared with those in regional wall motion on biplane left ventriculography (LVG) from the acute (just after reperfusion) to the chronic stage. During the follow-up, regional wall motion remained the same in 42 (group A) but improved in 17 (group B) of the 59 ischaemically compromised segments. MPA showed no improvement in group A but significant improvement in group B on the non-gated and ES images (P<0.0001 and P<0.001, respectively). However, MPA on the ED images showed no improvement in either group. In the follow-up study of AMI, the scintigraphic improvement documented on the non-gated myocardial images appears to be mainly related to the recovery of wall thickening and not to a real improvement in myocardial perfusion. Therefore, ECG-gated myocardial imaging, which enables simultaneous assessment of changes in perfusion and contraction, is preferable to conventional non-gated imaging for follow-up of AMI. Received 26 October 1999 and in revised form 20 January 2000     

ECG-gated multidetector computed tomography for the assessment of the postoperative ascending aorta

Purpose

This study was undertaken to define the role of electrocardiographically (ECG)-gated multidetector computed tomography (MDCT) in the assessment of the postoperative ascending aorta.

Materials and methods

From November 2006 to June 2007, 21 patients, [11 men, ten women; age ± standard deviation (SD): 62.7±10.8 years] with a history of ascending aorta replacement underwent ECG-gated MDCT and were prospectively included in our study. Ascending aorta replacement had been performed with different surgical techniques: Bentall-De Bono (four patients, 19%), Tirone-David (five patients, 23%), and modified Tirone-David with creation of aortic neosinuses (12 patients, 57%). Two patients were excluded from MDCT evaluation because they failed to fulfil the inclusion criteria. Transthoracic echocardiography was used as the reference standard. All patients provided informed consent.

Results

In all patients, ECG-gated MDCT provided a clear depiction of the aortic annulus, aortic root and ascending aorta, enabling accurate measurements in all cases. The aortic valve area (3.4±0.2 cm²), the diameter of the sinotubular junction (31.6±1.8 mm), the diameter of the neosinuses in the case of modified Tirone-David procedures (37.3±2.1 mm) and the distance between the cusps and the graft wall during systole (3.1±0.7 mm) fell within standard ranges and showed a good correlation (r=0.89) with the values obtained with transthoracic echocardiography.

Conclusions

MDCT is currently considered a compulsory diagnostic step in patients with suspected or known aortic pathology. MDCT is a reliable technique for anatomical and functional assessment of the postoperative aortic root and provides cardiac surgeons with new and detailed information, enabling them to formulate a prognostic opinion regarding the outcome of the surgical procedure.     

Detection of central pulmonary embolism on computed tomography densitometry images before computed tomography pulmonary angiography

OBJECTIVE: The purpose of this article is to describe the imaging findings of acute central pulmonary embolism on computed tomography (CT) densitometry images performed before contrast-enhanced CT pulmonary angiography. METHODS: A retrospective review was conducted of reports from all CT pulmonary angiograms performed at our institution, and cases of acute central pulmonary embolism, defined as those with clot in the main, left, or right pulmonary arteries, were identified. Images of positive studies were reviewed on a picture archiving and communications system (PACS) workstation. RESULTS: A total of 1282 CT pulmonary angiograms were obtained for evaluation of possible acute pulmonary embolism, and 1 combined CT aortogram and pulmonary angiogram was performed for aortic dissection and acute pulmonary embolism. Two hundred fourteen (16.7%) examinations positive for acute pulmonary embolism were identified, 26 (12.1%, 2.0% of total examinations) of which had central clots. Of the 26 patients with central acute pulmonary embolism, 12 (46.1%, 5.6% of all positive studies and 0.9% of all CT pulmonary angiograms) had clots that were visible on the densitometry images. CONCLUSION: Although an uncommon finding, acute central pulmonary embolism can be detected on CT densitometry performed to optimize opacification of the pulmonary arteries for CT pulmonary angiography and may prove useful in selected clinical situations.     

Relationship between pulmonary artery volumes at computed tomography and pulmonary artery pressures in patients with- and without pulmonary hypertension

OBJECTIVES: This study was designed to determine the relationship between pulmonary artery (PA) volumes at computed tomography (CT) and PA pressures at right-sided heart catheterization in patients with and without pulmonary hypertension (PAH) to develop a noninvasive CT method of PA pressure quantification. MATERIALS AND METHODS: Sixteen patients with chronic sleep apnea syndrome underwent contrast enhanced helical CT (slice thickness 3mm; pitch 2; increment 2mm) at inspiration. Eight patients had PAH while cardiopulmonary disease has been excluded in eight other patients. Vascular volumes were determined using a 3D technique (threshold seeded vascular tracing algorithm; thresholds -600H [lower] and 3000H [upper]). Right-sided heart catheterization measurements were available for linear regression analysis of PA volumes and pressures. RESULTS: Correlation between PA pressures and volumes (normalized for BMI), was high in both groups (without PAH: r=.85; with PAH .90, Pearson). Compared to elevated PA pressures in patients with pulmonary hypertension (p<.005), PA volumes also were significantly increased (p<.05) among the groups. CONCLUSIONS: High correlation was found between PA volumes and mean PA pressures in patients with- and without PAH. Significant differences in PA volumes at CT-volumetry may admit non-invasive determination of pulmonary hypertension.     

Dynamic computed tomography in solitary pulmonary nodules

OBJECTIVE: To evaluate the utility of dynamic computed tomography (CT) imaging in the management of solitary pulmonary nodules. METHODS: We examined solitary pulmonary nodules in 45 patients. The nodules included in the study were solid, homogenous, and spherical or oval-shaped in precontrast images. Nodules that had calcification or fat density were excluded from the study. We were not able to obtain clinical or pathological diagnosis of the nodules in 23 patients, and we excluded these patients from statistical analysis. Patients were examined with 2-mm collimation and 1-mm reconstruction interval. Computed tomography examinations were done before and after injection of contrast material. Computed tomography scans of the nodule were obtained in the first, second, third, fourth, and fifth minutes after contrast injection. RESULTS: The malignancy prevalence was 40%. The mean enhancement of malignant nodules were significantly higher than the benign ones. Also, the peak attenuation value obtained after the administration of contrast material was 82.44 +/- 19.56 HU in malignant lesions and 54 +/- 23.10 HU in benign ones, with statistical significance (P = 0.006). Using enhancement values greater than 15 HU as a threshold for malignancy, the calculated sensitivity, specificity, positive and negative predictive values, and accuracy of the dynamic CT examination were 100%, 69.2%, 69.2%, 100%, and 81%, respectively. CONCLUSION: Dynamic CT imaging demonstrates significantly greater enhancement in malignant nodules than in benign ones. Lung nodule enhancement of 15 HU or less strongly indicates benignity.     

组织多普勒测定肺毛细血管楔压评价左室收缩功能的应用研究

目的 探讨应用超声组织多普勒及频谱多普勒综合指标测量肺毛细血管楔压以判定左心功能的可行性.方法 依据二尖瓣瓣环部组织多普勒超声测定各瓣环位点的舒张早期运动速度Ea值,再依据超声血流频谱多普勒测定二尖瓣舒张早期血流速度E峰值,估算出肺毛细血管楔压,据其测量数据将左心功能衰竭的严重程度分为轻、中、重三度,并与患者临床心功能分级进行比较.结果 Ⅰ组患者仅有1例心功能为3级,其余均为2级,占90％,Ⅱ组患者有1例心功能2级,8例心功能为三级占80％,1例心功能为4级,Ⅲ组患者有2例心功能为Ⅲ级,8例心功能为4级,占80％.Ⅰ组和Ⅱ组比较心功能2级和3级差异有显著性意义（P＜0.01）,Ⅱ组和Ⅲ组比较心功能3级和4级差异有非常显著性意义（P＜0.01）.结论 组织多普勒测定肺动脉楔压或肺毛细血管楔压,与临床心功能评价有良好的相关性,是反映左心功能及其前负荷的可靠指标.     

High-resolution computed tomography in pulmonary cystic fibrosis

Twenty-one patients with established cystic fibrosis were examined using high-resolution, narrow-section computed tomography. The bronchiectasis of cystic fibrosis is described and is shown to be characteristic in many respects. Computed tomography was found to be more accurate than standard radiography in locating the disease process and demonstrated pleural involvement which was not apparent on chest radiographs.     

Imaging the pericardium: appearances on ECG-gated 64-detector row cardiac computed tomography

Multidetector row computed tomography (MDCT) with its high spatial and temporal resolution has now become an established and complementary method for cardiac imaging. It can now be used reliably to exclude significant coronary artery disease and delineate complex coronary artery anomalies, and has become a valuable problem-solving tool. Our experience with MDCT imaging suggests that it is clinically useful for imaging the pericardium. It is important to be aware of the normal anatomy of the pericardium and not mistake normal variations for pathology. The pericardial recesses are visible in up to 44% of non-electrocardiogram (ECG)-gated MDCT images. Abnormalities of the pericardium can now be identified with increasing certainty on 64-detector row CT; they may be the key to diagnosis and therefore must not be overlooked. This educational review of the pericardium will cover different imaging techniques, with a significant emphasis on MDCT. We have a large research and clinical experience of ECG-gated cardiac CT and will demonstrate examples of pericardial recesses, their variations and a wide variety of pericardial abnormalities and systemic conditions affecting the pericardium. We give a brief relevant background of the conditions and reinforce the key imaging features. We aim to provide a pictorial demonstration of the wide variety of abnormalities of the pericardium and the pitfalls in the diagnosis of pericardial disease.The rapid technological development of multidetector row computed tomography (MDCT) with its greatly improved spatial and temporal resolution and sophisticated ECG-gated image acquisition software has led to the more widespread use of dedicated cardiac imaging. Not only does this technology enable assessment of the coronary arteries [1, 2], but the same acquired data set also provides imaging detail of the overall cardiac morphology including the normal and diseased pericardium, features of which may also be readily appreciated on the non-ECG-gated thoracic CT [3]. It is important for the general radiologist to be familiar with both normal and variant pericardial anatomy and with that of the pericardial recesses, which can mimic some pathological processes. Several disease processes, either primary or secondary, can affect the pericardium. This review aims to illustrate normal pericardial anatomy, diagnostic pitfalls, commonly encountered abnormalities (some of which may be quite subtle) and some more unusual entities.     

Evaluation of organized thrombus in distal pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension using cone-beam computed tomography

Purpose

Balloon pulmonary angioplasty (BPA) is an emerging treatment for inoperable chronic thromboembolic pulmonary hypertension (CTEPH) patients. However, the approach to use to identify distal thrombi suitable for BPA has not yet been established. The purpose of this work was therefore to evaluate distal chronic thromboembolic lesions for BPA using cone-beam computed tomography (CBCT).

Materials and methods

Thirty-two patients (men/women: 9/23) with CTEPH who underwent CBCT before BPA were enrolled. We assessed representative forms of chronic thromboembolic lesions in 94 segmental and/or 208 subsegmental branches according to CBCT and compared the results to the findings of selective angiography during BPA.

Results

We classified CTEPH lesions into five subtypes as follows: type 1a (11.1 %), webs; type 1b (14.4 %), web with severe narrowing of the subsegmental artery; type 2, (58.2 %) web and slits; type 3 (2.4 %), slits; and type 4 (13.9 %), pouch defect with incomplete obstruction of subsegmental branches or complete occlusion. In our study, 92.6 % of the CTEPH lesions diagnosed by CBCT were highly consistent with the findings of selective angiography during BPA.

Conclusion

CBCT clearly revealed and classified distal lesions in CTEPH patients. The CBCT findings for distal lesions were highly consistent with those of selective angiography during BPA. CBCT could be a useful modality to detect target lesions before BPA.

     

Organized thrombus in pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension; imaging with cone beam computed tomography

Purpose

To assess the usefulness of cone-beam CT (CBCT) during pulmonary angiography for the evaluation of organized thrombus at segmental or subsegmental arteries in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

Materials and methods

The segmental and/or subsegmental pulmonary arteries of 13 patients with CTEPH were evaluated by CBCT. We classified representative forms of organized thrombus into 4 types (type 1: webs, type 2: web and slits, type 3: slits, and type 4: narrowing or complete occlusion), and the distribution and frequency of the organized thrombus were evaluated. The relative detectability of these lesions using CBCT was compared with that in contrast-enhanced CT pulmonary angiography (CTPA).

Results

Type 1 lesions were most frequently observed in both segmental (30/65 = 46 %) and subsegmental branches (72/156 = 46 %). Type 2 lesions were relatively less frequent than type 1, but subsegmental branches were frequently involved (29/156 = 19 %). Type 3 lesions observed as a thin flap in 9/156 subsegmental branches (6 %). Comparing with CTPA, all 40 lesions in segmental branches were detectable in CTPA, whereas only 62 lesions among 90 lesions (69 %) in subsegmental branches could be observed by CTPA.

Conclusion

CBCT is found to be useful for the treatment planning of balloon pulmonary angioplasty distal to segmental arteries.