Dose reduction with adaptive bolus chasing computed tomography angiography.

Computed Tomography (CT) has become an effective diagnosis and evaluating tool in clinical; however, its radiation exposure has drawn great attention as more and more CT scans are performed every year. How to reduce the radiation dose and meanwhile keep the resultant CT images diagnosable becomes an important research topic. In this paper, we propose a dose reduction approach along with the adaptive bolus chasing CT Angiography (CTA) techniques, which are capable of tracking the contrast bolus peak over all the blood vessel segments during the CTA scan. By modulating the tube current (and collimator width) online, we can reduce the total radiation dose and maintain the contrast to noise ratio (CNR) of the blood vessel. Numerical experiments on reference DSA data sets show that by using the proposed dose reduction method, the effective radiation dose can be saved about 39%.

Strategies for reduction of radiation dose in cardiac multislice CT.

Because cardiac computed tomography (CT) (mainly coronary CT angiography) is a very promising technique, used more and more for coronary artery evaluation, the benefits and risks of this new low-invasive technique must be balanced. Radiation dose is a major concern for coronary CT angiography, especially in case of repeated examinations or in particular subgroups of patients (for example young female patients). Radiation dose to patient tends to increase from 16- to 64-slice CT. Radiation exposure in ECG-gated acquisitions may reach up to 40 mSv; considerable differences are attributable to the performance of CT machines, to technical dose-sparing tools, but also to radiological habits. Setting radiation dose at the lowest level possible should be a constant goal for the radiologist. Current technological tools are detailed in regard to their efficiency. Optimisation is necessary, by a judicious use of technological tools and also by individual adaptation of kV or mAs. This paper reviews the different current strategies for radiation dose reduction, keeping image quality constant. Data from the literature are discussed, and future technological developments are considered in regards to radiation dose reduction. The particular case of paediatric patients with congenital heart disease is also addressed.

Gelatine sponge particles: handling characteristics for endovascular use.

Gelatin sponge particles have been used since the mid 1960's in interventional radiology. It had played an important role as a temporary occlusive agent in the past. Embolization has gained a widespread acceptance in interventional radiology leading to different innovative new agents. This review is aimed to underline the persistent role of Gelfoam along with a better understanding of handling techniques in light of what we have learned from other particles as PVA and Embospheres. The clinical impact of embolization with gelfoam will be also stressed and discussed.

MDCT of the coronary arteries: feasibility of low-dose CT with ECG-pulsed tube current modulation to reduce radiation dose.

OBJECTIVE: The objective of our study was to show the feasibility of coronary CT using low kilovoltage (80 kV) combined with ECG-pulsed tube current modulation in selected patients. CONCLUSION: This study showed the combined effect of lowering the kilovoltage setting (80 kV) and using an automatic modulation technique (ECG-pulsed tube current modulation) for coronary CT. Radiation dose exposure can be reduced by up to 88% for slim patients without impairing image quality.

Low-kilovoltage multi-detector row chest CT in adults: feasibility and effect on image quality and iodine dose.

PURPOSE: To assess the feasibility of low-kilovoltage (ie, 80-kV) chest computed tomography (CT) protocols for adults and the effect of such protocols on image quality and iodine dose. MATERIALS AND METHODS: Preliminarily, 90 patients (30 women, 60 men; mean age, 59 years) requiring contrast material-enhanced chest CT were randomly assigned to one of three protocol groups: protocol A, with use of 80 kV and 135 mAs; protocol B, with use of 80 kV and 180 mAs; or the standard protocol, with use of 120 kV and 90 mAs. Contrast material injection protocols were standardized in all groups. Image noise was calculated and plotted against patient weight. Subsequently, another 52 consecutive patients (11 women, 41 men; mean age, 57 years) were assigned to one of the protocols according to their weight: Patients weighing less than 60 kg were assigned to protocol A; patients weighing 60-75 kg, to protocol B; and patients weighing more than 75 kg, to the standard protocol. Two readers evaluated the CT images qualitatively by using a five-point scale. Statistical analyses were performed by using analysis of variance, kappa, and Fisher exact tests. RESULTS: In the preliminary study, the mean image noise values with protocols A (24 HU) and B (20 HU) were significantly higher (P <.001) than that with the standard protocol (12 HU). With protocols A and B, in the patients weighing more than 60 kg and more than 75 kg, respectively, the noise increased exponentially with patient weight. In the subsequent study, qualitative analysis revealed no significant difference between the low-kilovoltage examinations and the standard examination. Compared with use of the standard protocol, use of protocols A and B resulted in the iodine-based contrast material dose being reduced by 54% and 39%, respectively. CONCLUSION: Weight-adapted low-kilovoltage contrast-enhanced chest CT examinations can be routinely performed with 80 kV. Use of these protocols results in good diagnostic image quality and makes it possible to reduce contrast material use by more than 50%.

Aneurysmal sizing after endovascular repair in patients with abdominal aortic aneurysm: interobserver variability of various measurement protocols and its clinical relevance.

The aim of this study was to determine the variability of various measurement protocols for measurement of abdominal aortic aneurysm (AAA) and the clinical relevance of variability. Three radiologists performed computed tomographic angiography measurements of both the aorta and the largest portion of the aneurysm on selected axial slices. Then measurements of the largest portion of the aneurysm were performed on unselected axial slices, sagittal and coronal reformatted. Finally, aortic volume was calculated. Measurements and volume calculation were performed before and after endovascular repair and assessed: Part 1: interobserver variability for maximum anteroposterior (MAP) and maximum transverse (MTR) diameters on selected slices; part 2: interobserver variability for unselected slices considering MAP and MTR; part 3: interobserver variability considering maximum diameter in any direction (MAD); part 4: interobserver variability for sagittal (SAG) and coronal (COR) free curved multiplanar reformation (MPR); and part 5: volume calculations. We then determined which technique of measurement was the most clinically relevant for detecting changes in aneurysm size or aortic volume. Parts 1 and 2: interobserver variability was 4.1 mm for both MAP and MTR; part 3: interobserver variability was 7 mm for MAD; part 4: interobserver variability was 5.5 mm (COR) and 4.9 mm (SAG); part 5: interobserver variability for volume was 5.5 ml. A combination of MAP and MTR was the most useful for detecting aortic modification. Volume calculation was needed in only a few cases. We recommend avoiding MAD and MPR measurements and suggest instead measuring both maximum anteroposterior and maximum transverse diameters. If aneurysm size remains stable after endovascular repair, aneurysm volume should be measured.

Embolization of large aneurysms with long wire coils.

The authors report the experience of using long coils of 2 m length in the management of large aneurysms. Knowledge of the characteristics of these coils is of value for correct placement. These coils are safe and cost-effective for excluding large aneurysms.