Cardiovascular magnetic resonance in patients with pectus excavatum compared with normal controls.

PURPOSE: To assess cardiothoracic structure and function in patients with pectus excavatum compared with control subjects using cardiovascular magnetic resonance imaging (CMR). METHOD: Thirty patients with pectus excavatum deformity (23 men, 7 women, age range: 14-67 years) underwent CMR using 1.5-Tesla scanner (Siemens) and were compared to 25 healthy controls (18 men, 7 women, age range 18-50 years). The CMR protocol included cardiac cine images, pulmonary artery flow quantification, time resolved 3D contrast enhanced MR angiography (CEMRA) and high spatial resolution CEMRA. Chest wall indices including maximum transverse diameter, pectus index (PI), and chest-flatness were measured in all subjects. Left and right ventricular ejection fractions (LVEF, RVEF), ventricular long and short dimensions (LD, SD), mid-ventricle myocardial shortening, pulmonary-systemic circulation time, and pulmonary artery flow were quantified. RESULTS: In patients with pectus excavatum, the pectus index was 9.3 ± 5.0 versus 2.8 ± 0.4 in controls (P < 0.001). No significant differences between pectus excavatum patients and controls were found in LV ejection fraction, LV myocardial shortening, pulmonary-systemic circulation time or pulmonary flow indices. In pectus excavatum, resting RV ejection fraction was reduced (53.9 ± 9.6 versus 60.5 ± 9.5; P = 0.013), RVSD was reduced (P < 0.05) both at end diastole and systole, RVLD was increased at end diastole (P < 0.05) reflecting geometric distortion of the RV due to sternal compression. CONCLUSION: Depression of the sternum in pectus excavatum patients distorts RV geometry. Resting RVEF was reduced by 6% of the control value, suggesting that these geometrical changes may influence myocardial performance. Resting LV function, pulmonary circulation times and pulmonary vascular anatomy and perfusion indices were no different to controls.

High-spatial-resolution lower extremity MR angiography at 3.0 T: contrast agent dose comparison study.

PURPOSE: To determine whether contrast material dose reduction at 3.0 T allows preserved image quality for high-spatial-resolution magnetic resonance (MR) angiography of the lower extremities. MATERIALS AND METHODS: Forty-five consecutive patients (27 men, 18 women; mean age, 64 years) underwent contrast material-enhanced MR angiography of the lower extremities at 3.0 T. A waiver of informed consent was granted by the institutional review board. Sixteen patients received high-dose (approximately 0.3 mmol/kg), 15 received intermediate-dose (approximately 0.2 mmol/kg), and 14 received low-dose (approximately 0.1 mmol/kg) gadopentetate dimeglumine during a three-station, dual-injection examination. For scoring purposes, the arterial system from the celiac trunk to the plantar arteries was divided into 34 segments. The images were retrospectively and independently evaluated by two specialized radiologists who were blinded to the patient dose groups. All studies were assessed for overall image quality and the degree of contaminating venous enhancement. Each arterial segment was scored for the quality of vessel definition, the severity of stenoses, and the presence of collateral vessels. RESULTS: More than 99% of arterial segments were found to be of diagnostic image quality by both readers in all dose groups. Generalized estimating equation analysis showed a significant difference among the three groups with regard to vessel definition (P = .019). No significant difference was found between the high- and intermediate-dose groups; however, the low-dose group had significantly better vessel definition compared with the high-dose (P = .034) and intermediate-dose (P = .015) groups. There was no significant difference among the groups in visualization of collateral vessels. Venous contamination was seen less frequently in the low-dose group, but the difference did not achieve significance. CONCLUSION: The study showed that, compared with widely used dose strategies at 1.5 T, the contrast agent dose for 3.0-T lower extremity MR angiography can be reduced multifold without compromising image quality.

Ultra-low-dose, time-resolved contrast-enhanced magnetic resonance angiography of the carotid arteries at 3.0 tesla.

PURPOSE: To determine whether time-resolved magnetic resonance angiography (TR-MRA) with ultra-low-dose gadolinium chelate (1.5-3.0 mL) can reliably detect or rule out hemodynamically significant disease in the carotid-vertebral artery territory. MATERIALS AND METHODS: Hundred consecutive patients (62 women, 38 men, mean age = 56.6 years) underwent both TR-MRA and standard high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA), having been randomized to 1 of 2 groups; group A receiving a contrast dose of 1.5 mL for TR-MRA and group B receiving 3.0 mL. For scoring purposes the arterial system was divided into 21 segments. All TR-MRA and CE-MRA studies were blindly assessed by 2 radiologists for overall image quality, segmental arterial visualization, grading of arterial stenosis/occlusion, and incidence and severity of artifact. TR-MRA findings were directly compared with those of the corresponding CE-MRA examinations. RESULTS: Group A TR-MRA studies were of significantly inferior overall image quality compared with those of the corresponding CE-MRA examinations (P = 0.01 for both observers). In group B, overall image quality was similar for TR-MRA and single-phase CE-MRA examinations. On a segmental basis, a higher number of "insufficient quality" segments were identified in group A TR-MRA studies than in group B. A similar reduction in the incidence of artifacts was observed for group B relative to group A TR-MRA studies. Both groups A and B TR-MRA studies were of high specificity, negative predictive values, and accuracy (>97%). CONCLUSION: Ultra-low dose TR-MRA may be performed with 3 mL of gadolinium chelate with preservation of overall image quality and arterial segmental visualization relative to single phase CE-MRA, whereas a 1.5 mL contrast dose is associated with more suboptimal studies. Nonetheless, even at doses as low as 1.5 mL, TR-MRA can exclude arterial stenosis or occlusion.

Assessment of cerebral arteriovenous malformations with high temporal and spatial resolution contrast-enhanced magnetic resonance angiography: a review from protocol to clinical application.

The combination of high spatial and high temporal resolution contrast-enhanced magnetic resonance angiography (MRA) at 3.0 T has enabled the detailed evaluation of functional vascular anatomy and hemodynamics of cerebral arteriovenous malformations (AVMs). Key contributory technical factors for the successful implementation of MRA in patients with different vascular pathologies are multicoil and multichannel receiver arrays, which enable higher parallel acquisition at 3.0 T over a uniform and a large field of view for highly temporally and spatially resolved MRA. Magnetic resonance angiography enables both screening of patients with suspected AVMs and follow-up of patients after therapy. It allows the characterization of AVMs with respect to nidus configuration, size, venous drainage, and so on, according to the Spetzler-Martin classification.

Contrast-enhanced MR angiography of the chest and abdomen with use of controlled apnea in children.

PURPOSE: To retrospectively determine if controlled apnea improves the image quality of contrast material--enhanced magnetic resonance (MR) angiography of the chest and abdomen in children. MATERIALS AND METHODS: Institutional review board approval and waiver of informed consent were obtained for this HIPAA-compliant study. The authors evaluated contrast-enhanced MR angiographic procedures performed in the chest, abdomen, or both, in 23 children (14 boys, nine girls; age range, 1 month to 8 years) who were under general anesthesia. All patients underwent mechanical ventilation with preoxygenation (100% oxygen) prior to controlled apnea during image acquisition. In control subjects, the authors assessed contrast-enhanced MR angiographic procedures performed in the chest, abdomen, or both, in 23 children (matched for age and type of study with children in the controlled apnea group; 11 boys, 12 girls; age range, 1 month to 8 years) who were under general anesthesia (n=15) or deep sedation (n=8) and were breathing spontaneously during image acquisition. MR angiograms of the chest, abdomen, or both, were assessed for image quality, motion artifacts, and vessel definition by two radiologists working in consensus with a subjective grading scale. Wilcoxon signed rank test was used to assess differences in measurements. RESULTS: Image quality was rated excellent in 97% (30 of 31) of studies with controlled apnea and in 30% (nine of 31) of control studies (P<.001). Motion artifacts were absent in 97% (30 of 31) of studies with controlled apnea and 13% (four of 31) of control studies (P<.001). Vessel sharpness was rated as being significantly better on images obtained with controlled apnea (P<.05). There were no complications caused by anesthesia or sedation in either group. CONCLUSION: Controlled apnea is highly effective in children for eliminating respiratory motion artifacts with contrast-enhanced MR angiographic studies, resulting in greatly improved image quality and spatial resolution.