OBJECTIVE The purpose of this article is to familiarize the radiologist with radiation dose in cardiac CT imaging and explain the current methods for dose reductionCONCLUSION Advances in CT technology have resulted in a significant increase in cardiac CT applications It is imperative that the radiologist understand the resulting dose implication to the patient and actively engage in optimal protocol design to achieve adequate image quality with patient dose reduction in mind

Radiation Dose in Cardiac CT

CT Technology Overview: 64-Slice and Beyond

The increasing exposure to low-dose radiation from diagnostic testing has prompted renewed interest in evaluating its carcinogenic risk, but quantifying health risk from low-dose radiation exposure remains controversial. The current approach is to adopt the linear non-threshold model, which is commonly applied to high-dose exposure, and apply it to assess risk from low-dose exposure. However, existing data are conflicting and limited to epidemiological studies and/or in vitro analyses. In this article, we will discuss the potential cancer risk from low- and high-dose radiation, their effects on DNA repair response pathways, and the best course of action for patients and providers to minimize risk.

Radiation exposure from imaging tests: is there an increased cancer risk?

Iterative reconstruction and individualized automatic tube current selection reduce radiation dose while maintaining image quality in 320-multidetector computed tomography coronary angiography

OBJECTIVE. Tube voltage reduction has been shown to be an effective method to reduce radiation dose in nonobese patients undergoing coronary CT angiography. To date, the impact of reduced tube voltage on objective measures of diagnostic accuracy, as defined by quantitative coronary angiography (QCA), has not been established. The purpose of this article was to investigate the impact of tube voltage reduction on the diagnostic performance of coronary CTA compared with QCA.SUBJECTS AND METHODS. We performed a prospective randomized trial evaluating 50 consecutive patients referred for catheter angiography with a body mass index (BMI) ≤ 35 kg/m2. Patients were randomly assigned to reduced (n = 24) or standard tube voltage (n = 26). Reduced tube voltage was defined as 80 or 100 kVp for individuals with BMI < 25 kg/m2 or 25–35 kg/m2, respectively; whereas standard tube voltage was defined as 100 or 120 kVp for individuals with BMI < 25 kg/m2 or 25–35 kg/m2, respectively. Tube current was fixed by study protoco...

https://www.ajronline.org/doi/pdf/10.2214/AJR.10.5786

A Prospective Randomized Controlled Trial to Assess the Diagnostic Performance of Reduced Tube Voltage for Coronary CT Angiography

To compare tube current adaptation based on 3 body mass index (BMI) categories versus anterior-posterior chest diameter (APD) for radiation dose optimisation in patients undergoing dynamic volume cardiac CT. Two cardiac imaging centres participated in the study. 20 patients underwent a prospectively triggered 320-slice single beat cardiac CT using the X-ray tube current [mA] manually adjusted to the patient’s BMI (group I). In 20 subsequent patients, the tube current was adapted according to the patient’s APD (group II). All other parameters were kept constant. Image noise was defined as the standard deviation of attenuation values and measured using a ROI in the descending aorta. Variation in image noise was statistically compared between both patient groups. Average and standard deviation of pixel noise were 29.1 HU and 14.8 HU in group I and 28.0 HU and 4.2 HU in group II. Inter-individual variation of pixel noise was significantly lower in group II compared to group I (p < 0.0001). Tube current adaptation based on APD is superior to stepwise adaptation based on BMI for optimising radiation dose in dynamic volume cardiac CT and therefore limits unnecessary radiation dose while ensuring diagnostic image quality in patients with diverse body habitus.

Radiation dose optimisation in dynamic volume CT of the heart: tube current adaptation based on anterior–posterior chest diameter

Objective Previous investigations have shown the usefulness of electron-beam computed tomography (EBCT) to describe ventricular diastolic function and to detect constrictive filling pattern. We used EBCT to analyze diastolic function in patients who underwent passive epicardial constraint because data describing ventricular filling in these patients are still incomplete. Methods Ten patients with dilated cardiomyopathy (group 1) underwent EBCT examination before and again 6 months after surgery. Ten patients with normal diastolic function (group 2) and 5 male patients with constrictive pericarditis (group 3) served for comparison. Volume-time curves throughout the entire diastole were generated, and the rapidity of diastolic filling was assessed by calculating the percent filling fraction at consecutive EBCT frames throughout the diastole. Pericardial thickness was measured in a standardized fashion at different locations around both ventricles. Results Early left ventricular filling pattern in group 1 did not change postoperatively (filling fraction at third diastolic frame was 50.0 +/- 15.4% and 53.8 +/- 14.4% before and after surgery, respectively) and was not significantly different from group 2 (48.7 +/- 8.5%). In contrast, in group 3, early left ventricular filling was significantly accelerated (71.4 +/- 9.3%) when compared with groups 1 and 2. A similar pattern was observed for the right ventricle. Pericardial thickness between groups 1 (1.22 +/- 4.22 and 1.43 +/- 0.39 mm before and after surgery, respectively) and 2 (1.38 +/- 0.43 mm) did not differ significantly. In contrast, pericardium in group 3 was significantly thickened (4.93 +/- 1.11 mm) when compared with both groups 1 and 2. Conclusions The EBCT identified an abnormal accelerated diastolic filling and thickened pericardium in patients with constrictive pericarditis. Conversely, a normal diastolic filling pattern and pericardial thickness seem to be preserved in patients after passive epicardial constraint, when compared with baseline values and with normal subjects.

Evaluation of left and right ventricular diastolic function by electron-beam computed tomography in patients with passive epicardial constraint.

The results of this study showed that bolus injection duration of 11.5 seconds can be used for CT perfusion analysis but will allow underestimation of true perfusion by 8%.

How Influential Is the Duration of Contrast Material Bolus Injection in Perfusion CT? Evaluation in a Swine Model

A system and method for computing a projection image from a volume data set, in particular a medical imaging volume data set, involving determining 502 a plurality of rays intersecting the volume. Each ray 504 is associated with a respective pixel in a projection plane. For each ray 504, a plurality of intensity values is collected 504 associated with voxels in a neighborhood of the ray. Each weight of a plurality of predefined weights is associated 508 with a respective intensity value of the plurality of intensity values in dependence on an ordering of the plurality of intensity values with respect to intensity. At least two weights of the plurality of weights are nonzero and at least two weights of the plurality of weights have a mutually different value. A weighted sum 510 of the intensity values is computed using the associated weights. The outcome of the weighted sum is associated 512 with the respective pixel.

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Radiation dose optimisation in dynamic volume CT of the heart: tube current adaptation based on anterior–posterior chest diameter

Evaluation of left and right ventricular diastolic function by electron-beam computed tomography in patients with passive epicardial constraint.

How Influential Is the Duration of Contrast Material Bolus Injection in Perfusion CT? Evaluation in a Swine Model

Volumetric data projection