Relationship between cone-beam CT technique and diagnostic usefulness in patients undergoing embolotherapy for hepatocellular carcinoma.

AIM: To determine the effect of different numbers of projection images in C-arm cone-beam computed tomography (CBCT) on diagnostic content and image quality in patients undergoing angiographic embolotherapy for hepatocellular carcinoma (HCC). MATERIALS AND METHODS: A total of 29 patients who underwent contrast-enhanced conventional multidetector CT (MDCT) within 6 weeks prior to CBCT acquired during embolotherapy for HCC between 2010 and 2013 were included in the study. CBCT was acquired in each patient using a 5-s (248 projection images) or 8-s (396 projection images) protocol. Anonymised images were reviewed independently by an interventional radiologist blinded to CBCT group. MDCT was used as a reference to the patient's anatomy, and performance of CBCT was compared to that of MDCT in each group. The level of concordance between CBCT and MDCT within each group was assessed for the following variables: number of foci >1 cm, largest tumour diameter, highest order branching vessel identified, image quality, diagnostic quality, signal-to-noise ratio, and contrast-to-noise ratio (CNR). CBCT radiation dose was recorded. RESULTS: There was no significant difference between MDCT and CBCT within each group in the number of tumour foci >1 cm identified or size of the largest focus measured. MDCT had superior image quality compared to both CBCT groups (p<0.01), but CBCT demonstrated subsegmental branches more often in each group than MDCT. Both CBCT groups demonstrated higher CNR than MDCT (p<0.01). The dose-area product (3675±1295 versus 6598±1252 µGy·m2; p<0.001) and skin dose (119±41 versus 212±38 mGy; p<0.001) were significantly lower with 5-s CBCT than with 8-s CBCT. CONCLUSION: The relationship between MDCT and CBCT in both groups was consistent. The information obtained with 5-s CBCT was equivalent to that obtained with 8-s CBCT but with a lower radiation dose.

Steep left ventricle to aortic root angle and hypertrophic obstructive cardiomyopathy: study of a novel association using three-dimensional multimodality imaging.

BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) exhibit a difference in left ventricular outflow tract (LVOT) obstruction, independently of basal septal thickness (BST). Some patients with HCM have a steeper left ventricle to aortic root angle than controls. OBJECTIVE: To test the predictors of the LV-aortic root angle and the association between LV-aortic root angle and LVOT obstruction using three-dimensional imaging. PATIENTS: 153 consecutive patients with HCM (mean (SD) age 46 (14) years, 68% men) and 62 patients with hypertensive heart disease of the elderly (all >65 years of age, 73 (6) years, 34% men) who underwent whole-heart three-dimensional cardiac magnetic resonance (CMR) angiography (1.5 T) and Doppler echocardiography. Forty-two controls (age 43 (11) years, 38% men) who underwent contrast-enhanced multidetector computed tomography and were free of cardiovascular pathology were also studied. MAIN OUTCOMES: LV-aortic root angle, BST and maximal non-exercise LVOT gradient were measured in patients with HCM and in hypertensive-elderly patients. Additionally, LV-aortic root angle and BST were measured in controls. RESULTS: The mean (SD) LV-aortic root angle was significantly different (p<0.001) in the three groups: HCM (134 (10) degrees ), hypertensive-elderly (128 (10) degrees ), control (140 (7) degrees ). There was an inverse correlation between age and LV-aortic root angle in the three groups (all p<0.001): HCM (r = -0.56), hypertensive-elderly (r = -0.35), control (r = -0.48). On univariate analysis, in the HCM group, LV-aortic root angle (beta = -0.34, p<0.001), age (beta = 0.23, p = 0.01) and end-systolic volume index (beta = -0.20, p = 0.02), but not BST (beta = 0.02, p = 0.8), were associated with LVOT gradient. On multivariate analysis, only LV-aortic root angle was associated with LVOT gradient. CONCLUSIONS: Patients with HCM have a steeper LV-aortic root angle than controls. In patients with HCM, a steeper LV-aortic root angle predicts dynamic LVOT obstruction, independently of BST.

Abnormal papillary muscle morphology is independently associated with increased left ventricular outflow tract obstruction in hypertrophic cardiomyopathy.

BACKGROUND: Abnormal papillary muscles (PM) are often found in hypertrophic cardiomyopathy (HCM). OBJECTIVE: To assess the relationship between morphological alterations of PM in patients with HCM and left ventricular outflow tract (LVOT) obstruction, using magnetic resonance imaging (MRI) and echocardiography. METHODS: Fifty-six patients with HCM (mean age 42 years (interquartile range 27, 51), 70% male) and 30 controls (mean age (42 (30, 53) years, 80% male) underwent MRI on a 1.5 T scanner (Siemens, Erlangen, Germany). Standard cine images were obtained in short-axis (base to apex), along with two-, three- and four-chamber views. The presence of bifid PM (none, one or both) and anteroapical displacement of anterolateral PM was recorded by MRI and correlated with resting LVOT gradients obtained by echocardiography. RESULTS: Double bifid PM (70% vs 17%) and anteroapical displacement of anterolateral PM (77% vs 17%) were more prevalent in patients with HCM than in controls (p<0.001). Subjects with anteroapically displaced PM and double bifid PM had higher resting LVOT gradients than controls (45 (6, 81) vs 12 (0, 12) mm Hg (p<0.01) and 42 (6, 64) vs 11 (0, 17) mm Hg (p = 0.02), respectively. In patients with HCM, the odds ratio of having significant (>or=30 mm Hg) peak resting gradient was 7.1 (95% CI 1.4 to 36.7) for anteroapically displaced anterolateral PM and 10.4 (95% CI 1.2 to 91.2) for double bifid PM (both p = 0.005), independent of septal thickness, use of beta-blockers and/or calcium blockers and resting heart rate. CONCLUSIONS: Patients with HCM with abnormal PM have a higher degree of resting LVOT gradient, which is independent of septal thickness.

Assessment of ventricular contractility during cardiac magnetic resonance imaging examinations using normalized maximal ventricular power.

Normalized maximal ventricular power (nPWRmax) is an index of cardiac function which measures the innate blood pumping ability, or contractility, of the left ventricle (LV), and its noninvasive assessment could prove useful in a variety of patients. nPWRmax is defined as the maximum instantaneous product of LV pressure and the rate of change of LV volume, divided by the end diastolic volume squared. We have quantified nPWRmax noninvasively in humans by pairing magnetic resonance imaging (MRI) LV volume measurements with aortic pressure estimated using radial artery tonometry and a frequency domain transfer function. In healthy volunteers undergoing cardiac MRI we have tested the sensitivity of nPWRmax to LV contractility with dobutamine and to cardiac loading with methoxamine, a vasoconstrictor. We have found that aortic pressures can be reliably estimated using a transfer function, which we generated and validated in a group of patients undergoing cardiac catheterization. Furthermore, we found that nPWRmax was unchanged by methoxamine, yet sensitive to contractility, with a 325% increase at dobutamine levels half that given during routine clinical cardiac stress tests for ischemia. In conclusion, we have shown that ventricular contractility can be assessed independent of cardiac loading in patients during routine noninvasive cardiac imaging examinations.

Quantification of left ventricular function with magnetic resonance images acquired in real time.

The application of real-time magnetic resonance imaging (MRI) techniques to cardiac imaging is particularly attractive because current MR examinations of left ventricular (LV) function can be prohibitively long and are dependent on electrocardiographic triggering. We conducted a study of the minimum spatial and temporal resolution requirements necessary for real-time ventricular function MR imaging to quantify LV volumes accurately, both at resting conditions and during cardiac stress tests. In addition, we implemented a real-time segmented echoplanar imaging pulse sequence and used it to quantify LV volume in 10 healthy volunteers. We compared these results with those obtained using conventional gradient-echo cine imaging and found good agreement throughout the cardiac cycle (mean difference -0.8 +/- 10.6 ml). In conclusion, real-time cardiac MR imaging can be used to quantify LV volumes accurately throughout the cardiac cycle, over the physiologic range of heart rates, thereby decreasing the time required for a complete functional cardiac examination. J. Magn. Reson. Imaging 2000;12:430-438.

Left ventricular contractility is impaired following myocardial infarction in the pig and rat: assessment by the end systolic pressure-volume relation using a single-beat estimation technique and cine magnetic resonance imaging.

The end systolic pressure-volume relation (ESPVR) has been shown to be a relatively load independent measure of left ventricular (LV) contractility. Recently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need to alter vascular loading conditions on the heart. Using a single-beat ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effects of myocardial infarction on LV contractility in two species, the rat and the pig. In our studies, LV pressure was acquired invasively and LV volume determined noninvasively with magnetic resonance imaging, at one week postinfarction in pigs and at 12 weeks postinfarction in rats. Normalized systolic elastance curves in both animal species were not statistically different from that of humans. Also, the slope of the ESPVR (Ees) decreased significantly following infarction in both species, while the volume-axis intercept (V0) was unaffected. These results indicate that a single-beat ESPVR method can be used to measure the inotropic response of the heart to myocardial infarction, and that the basis for this method (i.e., constant normalized elastance) is applicable to a variety of mammalian species.

Left ventricular chamber stiffness from model-based image processing of transmitral Doppler E-waves.

BACKGROUND: Model-based image processing (MBIP) of Doppler E-waves eliminates the need for digitizing waveforms by hand or determining the contour 'by eye'. Little et al. (Circulation 1995, 92:1933-1939) used pressure-volume measurements for dogs to verify the physiologic-model-derived prediction that the left ventricular chamber stiffness, KLV1 can be determined from the deceleration time tdec, when that portion of the E-wave contour is fit by a cosine function. MBIP of clinical Doppler E-wave images to determine chamber stiffness KLV has not been performed. OBJECTIVE: We sought to determine KLV by MBIP of clinical Doppler E-wave images and elucidate the physiologic meaning of the harmonic oscillator filling model's parameter k. METHODS AND RESULTS: The unique mathematical relationship between the kinematic, harmonic oscillator model of filling and KLV predicts that the oscillator's spring constant k be linearly proportional to the chamber stiffness KLV. To verify this, digitally acquired, clinical Doppler transmitral flow velocity images from 21 subjects were analyzed. The parameter k and the stiffness KLV were computed independently for each subject and compared. In accordance with prediction, a linear relationship between k and the stiffness KLV, namely k = 1.16 [A/(rho L)]KLV+41, r = 0.96, was observed. CONCLUSIONS: The oscillator parameter k is linearly proportional to the left ventricular chamber stiffness KLV. The MBIP approach allows automated computation of k and KLV, provides a robust, automated, observer independent method of Doppler transmitral flow velocity analysis, and eliminates the need for visual determination of the contour or measurement of its attributes by eye. It provides a stimulus for further validation of the relationships among K, KLV, and catheterization-based diastolic chamber properties in humans and their correlations with selected diastolic function-altering syndromes.