[Computer multidetector tomography of coronary arteries. State-of-the-art. Part 1. Technical aspects]. / Tomografía computada multidetector de arterias coronarias: estado del arte. Parte I: aspectos técnicos.

The study of atherosclerotic disease in coronary arteries is fundamental since it is the first cause of death in the Western hemisphere. The gold standard for its diagnosis is invasive angiography, but it contributes to an increase in costs for this group of patients. Nowadays fourth generation computed tomography (CT) equipments can construct acquisition data of up to 256 images in only 400 milliseconds (ms), which is 900 to 1000 times faster than first generation apparatus. CT multidetector (CTMD) is the noninvasive choice diagnosis method for a vascular evaluation of the thorax. Its role in the study of the heart was limited, but today it is possible to obtain three-dimensional heart and whole body images in only seconds. CTMD is a fast, low-cost, noninvasive method that generates cardiac and extra cardiac images without adjacent structure interference. The higher temporal resolution due to an increase of the gantry's rotation and new reconstruction algorithms, as well as its higher spatial resolution and elevated time acquisition due to the presence of more detectors, have permitted CTMD to give significantly better and precise diagnosis of coronary arteries.

The effect of heart rhythm on patient radiation dose with dual-source cardiac computed tomography.

BACKGROUND: To lower the radiation exposure associated with cardiac CT, it is essential to identify all factors that influence radiation dose. OBJECTIVES: We explored the effect of heart rhythm during scan acquisition on radiation dose with a 64-slice dual-source cardiac CT. METHODS: Patient and scan data were collected prospectively in 302 consecutive patients referred for a clinical dual-source cardiac CT. Electrocardiograms recorded during acquisition were interpreted by a cardiologist and categorized as (1) normal sinus rhythm (NSR), (2) premature atrial contraction (PAC) or premature ventricular contraction (PVC), or (3) atrial fibrillation or flutter. RESULTS: Of the 302 patients, 227 (75.2%) were in NSR and had no ectopy, 55 (18.2%) had PAC/PVC, and 20 (6.6%) had atrial fibrillation or flutter during the scan. Patients with irregular rhythm (PAC/PVC and atrial fibrillation or flutter) were older than patients with regular rhythm (61.0 vs 54.8 years; P = 0.006). Patients with NSR had the lowest estimated radiation dose, followed by PAC/PVC and atrial fibrillation/flutter (9.4, 14.5, 20.9 mSv; P < 0.001). The difference remained significant after adjustments for differences in examination type, tube current and voltage, scan length, pitch, and use of tube current modulation (9.8, 14.1, 17.9 mSv; P < 0.001). No significant association was observed between heart rhythm and subjective image quality although scans with regular rhythm and no ectopy had higher signal-to-noise and contrast-to-noise ratios (P < 0.01). CONCLUSION: Compared to patients with NSR, patients with atrial fibrillation/flutter had the highest radiation exposure, followed by those with PAC/PVC. Even after adjustment for factors associated with radiation exposure, a significant difference in radiation dose persisted. These findings can be used to identify patients who are more likely to receive higher radiation dose when undergoing cardiac CT and to develop future more-efficient scanner algorithms for use in patients with arrhythmias.

Use of 100 kV versus 120 kV in cardiac dual source computed tomography: effect on radiation dose and image quality.

To evaluate the effective radiation dose and image quality resulting from use of 100 vs. 120 kV among patients referred for cardiac dual source CT exam (DSCT). Prospective data was collected on 294 consecutive patients referred for DSCT. For each scan, a physician specializing in cardiac CT chose all parameters including tube current and voltage, axial versus helical acquisition, and use of tube current modulation. Lower tube voltage was selected for thinner patients or when lower radiation was desired for younger patients, particularly females. For each study, image quality (IQ) was rated on a subjective IQ score and contrast (CNR) and signal-to-noise (SNR) ratios were calculated. Tube voltage of 100 kV was used for 77 (26%) exams while 120 kV was used for 217 (74%) exams. Use of 100 kV was more common in thinner patients (weight 166 lbs vs. 199 lbs, P < .001). The effective radiation dose for the 100 and 120 kV scans was 8.5 and 15.4 mSv respectively. Among scans utilizing 100 and 120 kV, there was no difference in exam indication, use of beta blockers, heart rate, scan length and use of radiation saving techniques such as prospective ECG triggering and tube current modulation. The IQ score was significantly higher for 100 kV scans. While 100 kV scans were found to have higher image noise then those utilizing 120 kV, the contrast-to-noise and signal-to-noise were significantly higher (SNR: 9.4 vs. 8.3, P = .02; CNR: 6.9 vs. 6.0, P = .02). In selected non-obese patients, use of low kV results in a substantial reduction of radiation dose and may result in improved image quality. These results suggest that low kV should be used more frequently in non-obese patients.

Radiation dose and image quality of prospective triggering with dual-source cardiac computed tomography.

Prospectively triggered (PT) cardiac computed tomography (CT), whereby radiation is administered only at a predefined phase of the cardiac cycle, has been shown to substantially decrease radiation dose. The aim of our study was to assess the use of this technique in a clinical population using dual-source cardiac CT. Of 312 consecutive patients referred for a dual-source cardiac computed tomographic examination, PT was used in 42 patients for whom, based on physician judgment, it was decided to minimize radiation, whereas retrospective gating was used for 188 patients (coronary artery bypass grafting and pulmonary vein studies were excluded). Kilovolt and milliampere per second were chosen for each patient based on assessment of body habitus and effective radiation dose was calculated. Analysis of nonevaluable vessels was based on clinical readings. For each study, image quality (IQ) was rated on a subjective IQ score and contrast-to-noise and signal-to-noise ratios were calculated. Of the 42 PT examinations (mean age 44.3 years, body mass index 27.8 kg/m(2), 62% men), 28 were referred for coronary evaluation, 11 for aortic disease with/without coronaries, and 3 for other reasons (i.e., suspected mass and congenital disease). Average heart rate was 64.5 beats/min. Average radiation dose of all 42 PT scans was 3.2 +/- 1.6 vs 13.4 +/- 7.8 mSv for the 188 non-PT scans. There was no significant difference in IQ score and contrast-to-noise and signal-to-noise ratios between the 2 groups. Furthermore, the incidence of limited right coronary artery evaluation and of limitations related to right coronary artery motion did not differ between PT and non-PT scans. In conclusion, in selected patients, prospective triggering with dual-source cardiac CT is feasible and results in a dramatic decrease of radiation dose without compromising IQ. Future advances in cardiac CT may further improve this technique, thus allowing for wider use.

Tomografía computada multidetector de arterias coronarias: estado del arte. Parte I: aspectos técnicos / Computer multidetector tomography of coronary arteries: state-of-the-art. Part 1: technical aspects

The study of atherosclerotic disease in coronary arteries is fundamental since it is the first cause of death in the Western hemisphere. The gold standard for its diagnosis is invasive angiography, but it contributes to an increase in costs for this group of patients. Nowadays fourth generation computed tomography (CT) equipments can construct acquisition data of up to 256 images in only 400 milliseconds (ms), which is 900 to 1000 times faster than first generation apparatus. CT multidetector (CTMD) is the noninvasive choice diagnosis method for a vascular evaluation of the thorax. Its role in the study of the heart was limited, but today it is possible to obtain three-dimensional heart and whole body images in only seconds. CTMD is a fast, low-cost, noninvasive method that generates cardiac and extra cardiac images without adjacent structure interference. The higher temporal resolution due to an increase of the gantry's rotation and new reconstruction algorithms, as well as its higher spatial resolution and elevated time acquisition due to the presence of more detectors, have permitted CTMD to give significantly better and precise diagnosis of coronary arteries.