Assessment of left ventricular function with 16- and 64-slice multi-detector computed tomography

BACKGROUND: Important to the risk stratification and management of cardiac patients is the assessment of left ventricular function (LVEF), thus imaging modalities which can provide both anatomical and functional data is desirable. Electrocardiographic (ECG) gated multi-detector computed tomographic (MDCT) images may provide accurate assessment of LV ejection fraction, volume and dimensions but have shown systemic errors in the past due to slow gantry rotation speed. METHODS: Between May 2004 and January 2005, 306 patients underwent ECG-gated cardiac CT studies at the Massachusetts General Hospital. Patients with available CT data sets and a recent (within 3 months) ECHO and/or SPECT perfusion imaging were included in the study. ECG-gated data sets were acquired either with a 16-slice or with a 64-slice MDCT. Functional MDCT data sets were reconstructed in 10 cardiac phases (5-95%) with 1.5mm slices. Images were processed and interpreted by two observers blinded to ECHO and SPECT results. RESULTS: A total of 69 patients had MDCT and ECHO or SPECT within 3 months (33 had 16-slice and 36 had 64-slice MDCT). There was fair correlation between LVEF measured by 16-slice MDCT and 'ECHO or SPECT' (62+/-10% vs. 62+/-10%; r=0.56). There was poor correlation between LVEF measured by 16-slice MDCT and ECHO (64+/-10% vs. 59+/-11%; r=0.26) and there was good correlation between LVEF measured by 16-slice MDCT and SPECT (62+/-11% and 64+/-9%, respectively; r=0.76). There was very good correlation between LVEF measured by 64-slice MDCT and 'ECHO or SPECT' (57+/-15% vs. 58+/-13%; r=0.86). There was very good correlation between LVEF measured by MDCT and ECHO (56+/-14% vs. 54+/-15%; r=0.89) and between LVEF measured by 64-slice MDCT and SPECT (60+/-13% and 60+/-14%, respectively; r=0.90). CONCLUSION: The assessment of LVEF and LV dimensions with 64-slice MDCT provide values which are similar to those obtained by echocardiography and Tc-99m gated SPECT. The accuracy of the 64-slice MDCT with a gantry rotation speed of 330ms (when compared to ECHO and SPECT) may be superior to that of the 16-slice MDCT at 420ms gantry rotation.     

Gadolinium-enhanced computed tomography angiography in multi-detector row computed tomography: initial observations

Rationale and Objectives. The feasibility of using gadolinium contrast medium for computed tomography angiography (CTA) in multi-detector row computed tomography and the effect of contrast medium dilution was investigated.Materials and Methods. Three pigs were each scanned in multiple sessions with injections of non-dilute and dilute contrast medium at a dose of 0.3 mmol/kg body weight. Non-spiral dynamic scanning at a fixed mid-abdominal aortic level and thoracoabdominal CTA were performed.Results. The magnitude of peak aortic enhancement was not significantly different between dilute and non-dilute contrast medium injections (P = .88), but the former showed earlier enhancement (mean of 2.3 seconds sooner, P < .01) than the latter. CT angiography with gadolinium contrast medium showed much lower enhancement than iodine contrast medium, but small vessels were readily identifiable.Conclusion. Gadolinium contrast medium combined with multi-detector row computed tomography may provide clinically useful CTA. Dilution of contrast medium shortens the enhancement time but has little effect on the magnitude.     

Left ventricular myocardium segmentation on arterial phase of multi-detector row computed tomography

Rationale and objectives

Variation of left ventricular myocardial volumes correlates closely with ischemic heart diseases. In clinical practice, because physicians and radiologists rely much on myocardial contour to diagnose many different cardiac diseases, automatic segmentation of left ventricular myocardium and quantifying myocardium characteristics is clinically beneficial. This paper presents a hybrid segmentation method for left ventricular myocardium on arterial phase of multi-detector row computed tomography (MDCT) imaging.

Materials and methods

The proposed method utilizes an intensity transformation equation as a preprocessing procedure to enhance contrast and reduce noise in MDCT imaging. By setting the centroid of left ventricle (LV) as an initial seed, the conventional region growing method is employed to identify the endocardial contour of LV cavity for each slice. Then the level-set method (LSM) utilizes the extracted endocardial contour as initial contour to delineate the epicardium of LV. The two extracted contours are integrated to form the region of interest (ROI) of the LV. Finally, the ROIs from all slices are combined to obtain the volume of the whole LV myocardium.

Results

Twenty-two healthy patients who had no symptoms of ischemic heart disease are applied to evaluate the performance of the proposed method. Compared with manual contours delineated by two experienced experts, the contouring results from computer simulation reveal that the proposed method always identifies similar contours as that obtained by the manual sketching.

Conclusion

The proposed method provides a robust and fast automatic contouring for LV myocardium on arterial phase of MDCT. The potential role of this technique may save much of the time required to manually sketch a precise contour with high stability.     

Adult midgut malrotation: multi-detector computed tomography (MDCT) findings of 14 cases

Purpose

To describe MDCT findings in adult patients of midgut malrotation and to correlate the types of adult midgut malrotation with its complications.

Materials and methods

CT scans were performed on 14 adult patients with midgut malrotation. The images were reviewed retrospectively by one radiologist. Abnormal intestinal location, mesenteric vascular arrangement, extraintestinal anomalies and complications were evaluated and correlated with patterns of adult midgut malrotation.

Results

The 14 cases of adult midgut malrotation revealed the following CT findings: intestinal malposition (n = 14), abnormally oriented mesenteric vessels (n = 8), extraintestinal anomalies (n = 14). These cases were classified into six types: complete nonrotation (n = 3), nonrotated duodenum and partially rotated colon (n = 6), isolated nonrotation of the duodenum (n = 2), partial rotation of the duodenum and colon (n = 1), partially rotated duodenum (n = 1) and isolated colonic partial rotation (n = 1). Four of these patients had accompanying complications, including volvulus (n = 2), right paraduodenal hernia (n = 1) and gastroduodenal intussusception (n = 1), respectively.

Conclusion

Imaging features of adult midgut malrotation are characteristic. Adult midgut malrotation has various manifestations, and types of midgut malrotation may be closely related to their complications.     

Measurement of cardiac ventricular volumes using multidetector row computed tomography: comparison of two- and three-dimensional methods

This study compared a three-dimensional volumetric threshold-based method to a two-dimensional Simpson’s rule based short-axis multiplanar method for measuring right (RV) and left ventricular (LV) volumes, stroke volumes, and ejection fraction using electrocardiography-gated multidetector computed tomography (MDCT) data sets. End-diastolic volume (EDV) and end-systolic volume (ESV) of RV and LV were measured independently and blindly by two observers from contrast-enhanced MDCT images using commercial software in 18 patients. For RV and LV the three-dimensionally calculated EDV and ESV values were smaller than those provided by two-dimensional short axis (10%, 5%, 15% and 26% differences respectively). Agreement between the two methods was found for LV (EDV/ESV: r=0.974/0.910, ICC=0.905/0.890) but not for RV (r=0.882/0.930, ICC=0.663/0.544). Measurement errors were significant only for EDV of LV using the two-dimensional method. Similar reproducibility was found for LV measurements, but the three-dimensional method provided greater reproducibility for RV measurements than the two-dimensional. The threshold value supported three-dimensional method provides reproducible cardiac ventricular volume measurements, comparable to those obtained using the short-axis Simpson based method.     

Assessment of cardiac function using multidetector row computed tomography

In patients with suspected or documented heart disease, a precise quantitative and qualitative assessment of cardiac function is critical for clinical diagnosis, risk stratification, management and prognosis. Cardiac CT is increasingly being used in diagnosis of coronary artery disease. Initially multi-detector row computed tomography (MDCT) was used chiefly for detecting coronary artery stenosis and assessment of cardiac morphology. Electron beam computed tomography has been shown to provide a highly accurate ejection fraction (+/-1%), with 50 ms image acquisition per image. Retrospective electrocardiographic gating allows for image reconstruction in any phase of the cardiac cycle. Thus, end systolic and end diastolic images can be produced to assess ventricular volumes and function. Despite lower temporal resolution than electron beam computed tomography, the ability of MDCT to assess ejection fraction is preserved. In the assessment of cardiac function, MDCT has been shown to be in good agreement with echocardiography, cineventriculography, single photon emission computed tomography and magnetic resonance imaging. The fast technical development of scanner hardware along with multisegmental image reconstruction has led to rapid improvement of spatial and temporal resolution and significantly faster cardiac scans. The same data that is acquired for MDCT angiography can also be used for evaluation of cardiac function. Considering contrast media application, radiation exposure, and limited temporal resolution, MDCT solely for analysis of cardiac function parameters seems not reasonable at the present time. However, because the data is already obtained during coronary evaluation, the combination of noninvasive coronary artery imaging and assessment of cardiac function with MDCT is a suitable approach to a conclusive cardiac workup in patients with suspected coronary artery disease. MDCT seems suitable for assessment of cardiac function by MDCT when results are held in comparison to magnetic resonance imaging as the reference standard. Given the radiation dose and contrast requirement, referring a patient to MDCT only for evaluation of function is not warranted, but rather adds important clinical information to the already acquired data during retrospective triggering for MDCT angiography.     

Assessment of left ventricular ejection fraction using low radiation dose computed tomography

Background

Cardiac CT is a non-invasive modality with the ability to estimate LVEF. However, given its limited temporal resolution and radiation, there has been initial resistance to use CT to measure LVEF. Developing an accurate, fast, low radiation dose protocol is desirable.

Objective

The objective of this study is to demonstrate that a ‘low radiation dose’ 64 slice cardiac computed tomography (CT) protocol is feasible and can accurately measure left ventricular ejection fraction (LVEF) while delivering a radiation dose lower than radionuclide angiography (RNA).

Methods

Patients undergoing RNA were prospectively screened and enrolled to undergo a ‘low-dose’ 64 slice CT LVEF protocol. LVEF measures, duration of each study and radiation dose between CT and RNA were compared.

Results

A total of 77 patients (mean age = 61.8 ± 12.2 years and 58 men) were analyzed. The mean LVEF measured by CT and RNA were 41.9 ± 15.2% and 39.4 ± 13.9%, respectively, (P = 0.154) with a good correlation (r = 0.863). Bland-Altman plot revealed a good agreement between the CT and RNA LVEF (mean difference of ?2.4). There was good agreement between CT LVEF and RNA for identifying patients with LVEF ≤30% (kappa = 0.693) and LVEF ≥50% (kappa = 0.749). The mean dose estimated effective dose for CT and RNA were 4.7 ± 1.6 and 9.5 ± 1.0 mSv, respectively. The mean CT LVEF imaging duration (4:32 ± 3:05 minutes) was significantly shorter than the RNA image acquisition time (9:05 ± 2:36 minutes; p < 0.001).

Conclusion

The results of our study suggest that low-dose CT LVEF protocol is feasible, accurate, and fast while delivering a lower radiation dose than traditional RNA.

     

Sixty-four multi-detector row computed tomography in multitrauma patient imaging: early experience

Sixty-four multi-detector row computed tomography (64-MDCT) offers the possibility of increasing the application of CT in multitrauma imaging. 64-MDCT affords significant increases in imaging speed while allowing for subisotropic voxel slice thicknesses. We have recently installed two 64-MDCT scanners in our Level I trauma center. Our routine protocols using these new scanners are detailed. Additionally, this new technology has made possible several novel protocols. These include an increased use of CT angiography in trauma imaging. The acquisition speed and table lengths available with 64-MDCT allow for whole-body scout images. These scout images may be used to plan complex, multistep CT studies incorporating pelvic and extremity angiography, when indicated, into a single study. Imaging speeds afforded by 64-MDCT allow for imaging in any number of phases, over any area to be imaged, all with a single initial bolus of contrast. Image quality afforded by 64-MDCT allows for increasing roles of MPR and 3D reformations. These alternatives to axial images are currently used both for primary interpretation by our trauma radiologists as well as for communication and use by our clinical colleagues. Technical challenges presented by 64-MDCT include further increases in the number of images generated. Currently, datasets may exceed 4,000 images when angiography is included in routine trauma protocols. Radiation doses are also an ever present concern. With the opportunity to image from head to toe in seconds with submillimeter slice thicknesses, radiologists must be constantly vigilant in their efforts to limit radiation. Novel techniques such as automated dose modulation currently offer means of reducing radiation doses. Though several technical challenges are faced, 64-MDCT represents an evolution in multitrauma imaging.     

Assessment of left ventricular wall motion using 16-channel multislice computed tomography: comparison with left ventriculography

Purpose Using the raw data from coronary computed tomography (CT) angiography, multislice CT (MSCT) can be used to evaluate cardiac function. However, the accuracy of left ventricular (LV) wall motion assessment by MSCT has not been thoroughly investigated. We investigated whether 16-channel MSCT could accurately assess LV wall motion by comparing its results with those of conventional biplane left ventriculography (LVG). Materials and methods The study included 20 patients with various kinds of heart disease. All patients underwent both contrast-enhanced MSCT and biplane LVG. Using a retrospective electrocardiography-gating technique, 10 phases over one cardiac cycle were extracted. The left ventricle was divided into seven segments according to the American Heart Association classification. Wall motion was scored as follows: 1, normal; 2, mild to moderate hypokinesis; 3, severe hypokinesis; 4, akinesis; 5, dyskinesis; and 6, aneurysm. The scores obtained by MSCT were compared with those obtained by LVG. The wall motion scores were analyzed using the chi-squared independence test (6 × 6 contingency table). Results Wall motion could be assessed in all segments of the 20 patients using interactive multiplanar animation. Among a total of 140 segments in 20 patients, scores in 118 were concordant between MSCT and LVG (118/140, 84.3%). Conclusion The 16-MSCT can accurately assess LV wall motion.     

Visualization of congenital thoracic vascular anomalies using multi-detector row computed tomography and two- and three-dimensional post-processing

Anomalies of the vascular system are caused by false embryogenesis and are therefore present from birth. Single-detector row spiral computed tomography angiography (CTA) and multi-detector row computed tomography angiography (MDCTA) have gained increasing importance in the non-invasive assessment of vascular pathologies and replace conventional angiography in many cases. High-resolution volumetric datasets that are acquired during a single breath-hold give the possibility of two- (2D) and three-dimensional (3D)-post-processing. Due to post-processing, even complex vascular malformations are visualized in an understandable way. Furthermore, CTA, in contrast to conventional angiography, depicts not only the vascular structures but also allows assessment of the surrounding anatomical structures. We present cases of rare congenital anomalies of the thoracic vessels using MDCT with special respect to 2D- and 3D-post-processing.     

Cardiac multidetector computed tomography (MDCT) of spontaneously closed ventricular septal defect

Purpose  

The authors present the findings of contrastenhanced electrocardiogram (ECG)-gated cardiac computed tomography (CT) in 18 patients with probably spontaneous closure of muscular ventricular septal defect (VSD).     

Assessment of global left ventricular function and volumes with 320-row multidetector computed tomography: A comparison with 2D-echocardiography

Background  

Multidetector computed tomography (MDCT) has been demonstrated as a feasible imaging modality for noninvasive assessment of coronary artery disease and left ventricular (LV) function. Recently, 320-row systems have become available with 16 cm anatomical coverage allowing image acquisition of the entire heart within a single heartbeat. The purpose of this study was to evaluate the accuracy of 320-row MDCT in the assessment of global LV function compared to two-dimensional (2D) echocardiography as the standard of reference.     

多层螺旋CT血管成像对脊髓Adamkiewicz动脉的显示

Adamkiewicz动脉是脊髓胸腰段重要的供血血管,术前对其解剖结构的了解,有助于术前设计周密的手术方案,能有效降低脊髓缺血性损伤及术后截瘫或下肢瘫的发生。以往利用选择性动脉造影来了解脊髓的血液供应,但属于有创检查,且技术要求高。随着现代医学影像的发展,多层螺旋CT血管成像技术凭借其较高的空间分辨率和时间分辨率,可以在注入对比剂后一次扫描即可完成全部数据的采集,再通过强大的后处理功能可以获得Adamldewicz动脉及起源的节段性动脉的清晰影像。它在显示脊髓Adamkiewicz动脉方面的优势日益突出。本文综述多层螺旋CT血管成像对脊髓Adamkiewicz动脉显示的临床应用价值。     

单层与多层螺旋CT所致儿童受检者辐射剂量研究

目的 研究和评价儿童受检者在单层与多层螺旋CT扫描中所受到的辐射剂量。方法 测试21台CT机的头部和体部剂量指数,并结合0～1岁组、5岁组、10岁组儿童和成年人的头部和胸部常规扫描条件,计算CTDI_w、CTDI_vol、DLP值,再由DLP与有效剂量转换系数计算头部和胸部常规扫描所致各年龄组儿童和成年人的有效剂量。 结果 单位mAs的头部CTDI大于体部CTDI;在头部常规扫描中,0～1岁组、5岁组、10岁组儿童受到的有效剂量分别为2.2、1.3、1.1 mSv;在胸部常规扫描中,0～1岁组、5岁组、10岁组儿童受到的有效剂量分别为5.3、3.1、3.4 mSv;每单位mAs所致儿童有效剂量平均比成人高1.8倍;多层CT的儿童头部CTDI_vol、DLP、有效剂量值均大于单层与双层CT,多层与双层CT的儿童胸部CTDI_vol、DLP、有效剂量值均小于单层CT。 结论 与成年人相比,儿童在CT检查中可能受到更大辐射危害,应严格遵循儿童CT检查适应证,并合理选择CT扫描参数,尽可能降低儿童受到的辐射剂量。     

Assessment of left ventricular ejection fraction with late-systolic and mid-diastolic cardiac phases using multi-slice computed tomography

IntroductionMulti-slice computed tomography (MSCT) is an accurate tool for the assessment of left ventricular ejection fraction (LVEF). However, in order to reduce radiation dose, prospective acquisition protocols are currently used, in which the end-systole and end-diastole are not scanned. Our aim was to study the accuracy of the assessment of LVEF using fixed late-systolic and mid-diastolic cardiac phases compared with echocardiography.MethodsMSCT-derived LVEF was measured with off-line commercially available software packages, and compared with echocardiography-derived LVEF using the Simpson's method. LVEF was categorized as normal vs. abnormal (50% cut-off) and was also analyzed as a quantitative parameter. Bland-Altman plots and Pearson correlations were used for inter-technique comparisons.Results58 patients were included. The sensitivity and specificity of fixed-phase MSCT when compared with echocardiography for detection of LVEF ≤50% was 79% (95% CI = 65–89%) and 43% (10–82%). Misclassification was associated with older age (68 ± 12 vs. 54 ± 13 years, p < 0.01), faster heart rate (79 ± 14 vs. 68 ± 10 bpm, p = 0.01), and LV hypertrophy (86% vs. 52%, p = 0.03). The quantitative comparison revealed no correlation (r = 0.095, p = 0.478) and a significantly different LVEF (median[IQR], 57.0[50.5–63.1]% vs. 61.0[57.3–64.3]%, p = 0.03). The observed bias between the two methods was −3.7% with broad limits of agreement (±25.5%).ConclusionsFixed-phase MSCT assessment using late-systole and mid-diastole agreed in defining normal and abnormal LVEF in 76% of patients when compared with echocardiography. Quantitation of LVEF by this method yielded significantly lower values of LVEF and showed no correlation. Thus, accurate quantitation of LVEF by MSCT requires the acquisition of end-systolic and end-diastolic phases.     

Quantitative analysis of left ventricular strain using cardiac computed tomography

Objectives

To investigate whether cardiac computed tomography (CCT) can determine left ventricular (LV) radial, circumferential and longitudinal myocardial deformation in comparison to two-dimensional echocardiography in patients with congestive heart failure.

Background

Echocardiography allows for accurate assessment of strain with high temporal resolution. A reduced strain is associated with a poor prognosis in cardiomyopathies. However, strain imaging is limited in patients with poor echogenic windows, so that, in selected cases, tomographic imaging techniques may be preferable for the evaluation of myocardial deformation.

Methods

Consecutive patients (n = 27) with congestive heart failure who underwent a clinically indicated ECG-gated contrast-enhanced 64-slice dual-source CCT for the evaluation of the cardiac veins prior to cardiac resynchronization therapy (CRT) were included. All patients underwent additional echocardiography. LV radial, circumferential and longitudinal strain and strain rates were analyzed in identical midventricular short axis, 4-, 2- and 3-chamber views for both modalities using the same prototype software algorithm (feature tracking). Time for analysis was assessed for both modalities.

Results

Close correlations were observed for both techniques regarding global strain (r = 0.93, r = 0.87 and r = 0.84 for radial, circumferential and longitudinal strain, respectively, p < 0.001 for all). Similar trends were observed for regional radial, longitudinal and circumferential strain (r = 0.88, r = 0.84 and r = 0.94, respectively, p < 0.001 for all). The number of non-diagnostic myocardial segments was significantly higher with echocardiography than with CCT (9.6% versus 1.9%, p < 0.001). In addition, the required time for complete quantitative strain analysis was significantly shorter for CCT compared to echocardiography (877 ± 119 s per patient versus 1105 ± 258 s per patient, p < 0.001).

Conclusion

Quantitative assessment of LV strain is feasible using CCT. This technique may represent a valuable alternative for the assessment of myocardial deformation in selected patients with poor echogenic windows and general contraindications for magnetic resonance imaging.     

Normal mediastinal and hilar lymph nodes in children on multi-detector row chest computed tomography

Objective  

To study normal mediastinal and hilar lymph nodes on multi-detector chest computed tomography (CT).