Radiation Dose Estimates From Cardiac Multislice Computed Tomography in Daily Practice

Abstract

Background-Multislice computed tomography angiography (CTA) is a promising technology for imaging patients with suspected coronary artery disease. Compared with 16-slice CTA, the improved spatial and temporal resolution of 64-slice CTA (0.6-versus 1.0-mm slice thickness and 330-versus 420-ms gantry rotation time) is associated with an increase in radiation dose. The objective of this retrospective investigation was to compare the estimated dose received during 16-and 64-slice CTA in daily practice and to investigate the impact of different scan protocols on dose and image quality. Methods and Results-Radiation dose was estimated for 1035 patients undergoing coronary CTA. Scanning algorithms with and without an ECG-dependent dose modulation and with a reduced tube voltage were investigated on dose estimates and image quality. In the entire patient cohort, radiation dose estimates were 6.4Ϯ1.9 and 11.0Ϯ4.1 mSv for 16-and 64-slice CTA, respectively (PϽ0.01). The reduction in radiation dose estimates ranged between 37% and 40% and between 53% and 64% with the use of ECG-dependent dose modulation and with the combined use of the dose modulation and a reduced tube voltage, respectively. The reduction in dose estimates was not associated with a reduction in diagnostic image quality as assessed by the signal-to-noise ratio and by the frequency of coronary segments with diagnostic image quality. Conclusions-The increase in spatial and temporal resolution with 64-slice CTA is associated with an increased radiation dose for coronary CTA. Dose-saving algorithms are very effective in reducing radiation exposure and should be used whenever possible.

Transitioning from 16-slice to 64-slice multidetector computed tomography for the assessment of coronary artery disease: Are we really making progress?

“…Thus far, most studies have yielded effective radiation dose values of 6 mSv to 16 mSv for 16-slice scanners and 11 mSv to 21 mSv for 64-slice scanners, compared with approximately 6 mSv for CCA (75)(76)(77). In practical terms, the National Council on Radiation Protection and Measurements identifies a risk factor for lifetime cancer mortality of 5×10 -2 per 1 Sv exposure, which, given the above data, translates into a risk of inducing a fatal cancer of 0.05% to 0.11% for each 64-slice MDCT and 0.03% for each CCA (1).…”

“…If screening was performed approximately every five years, patients aged 55 to 64 years would likely require at least two scans in their lifetime, resulting in a doubling (35,000 to 70,000) of expected cancers. More recently, newer measures, including lower scan voltage and algorithms involving electrocardiogram-gated image acquisition, have been initiated to reduce the effective radiation dose associated with MDCT (76).…”

Evaluation of coronary atheroma by 64-slice multidetector computed tomography: Comparison with intravascular ultrasound and angiography

“…Because MDCT and invasive angiography were performed within a relatively short period of time (four days) and both required injections of contrast material, serum creatinine greater than 120 µmol/L at screening was a prespecified exclusion criterion. Nevertheless, MDCT is associated with exposure to radiation (16), which, in the case of the 64-slice scanner and protocol (without ECG dose modulation) used in the present study, is estimated to be 20 mSv. Interestingly, 16% of our patients were found to have significant extracardiac findings, emphasizing the value of carefully reviewing all the information provided by the MDCT examination.…”

Coronary computerized tomography angiography for rapid discharge of low-risk patients with cocaine-associated chest pain

“…With implementation of dose-reduction protocols [57] that selectively utilize maximal x-ray exposure only during important phases of the cardiac cycle, radiation exposure becomes similar to nuclear cardiology examination [58]. Lower contrast volumes used in CTA reduce the likelihood of nephrotoxicity, which is especially important if findings warrant further evaluation by coronary angiography [56].…”