Introduction Of Multislice CT Research Articles

Analysis of Current Practice of CT examinations

Background. The number of CT examinations performed in Denmark increased from 14 500 examinations in 1979 to 301 617 in 2005. This implies increased radiation dose to the population. On this background, an analysis of the practice for CT examinations including potential limitations of radiation exposure and the associated risk is needed. Purposes. To analyse 1) the current use of CT in a university department compared to 1996, 2) the radiation dose and risk associated with the examinations and 3) the use of CT in Denmark since 1979. Material and methods. The administrative data of CT examinations performed in the Department of Radiology, Aarhus Sygehus, during 2005 and 1996, respectively, were obtained. Additionally national CT data were obtained from the database at the National Board of Health. Results. In 1996 1 840 patients obtained 5 538 CT examinations at Aarhus Sygehus. Their mean age was 46.7 years (0–88). The most frequent referring speciality was oncology followed by abdominal surgery and orthopaedic surgery. In 2005 3 769 patients obtained 11 216 CT examinations. They were generally older with a mean age of 56.9 years (0–97). The most frequent referring speciality was oncology followed by chest medicine and abdominal surgery. In 2005 the total effective dose was 71 043 mSv (mean 18.9 mSv/per patient). According to the BEIR VII model this radiation level corresponded to a risk for inducing a cancer in 7 patients, being fatal in half of them. The national data showed a gradual increase of the number of CT examinations from 1979 to 2005, most pronounced after year 2000 coinciding with the introduction of multi-slice CT (MSCT). Conclusion. The number of CT examinations at Aarhus Sygehus doubled during a 9 year period. The increase occured especially in middle and high age groups.

Patient dose reduction in CT

CT is undoubtedly a powerful diagnostic tool, but data from surveys of CT practice show that, over the 30 years of clinical use, CT has contributed an ever-increasing percentage to the population dose from medical X-ray examinations [1, 2]. Although some regard the radiation dose levels from CT as beneficial [3], the generally held view is one of alarm at the increasing dose contribution, and the consensus amongst the radiology professions is that steps should be taken to reverse, or at least arrest, this trend. However, the reasons for this increasing dose contribution should be examined. Is it only as a result of increased numbers of examinations, or also as a result of an increase in dose per examination? Increased numbers of examinations, if correctly justified, must be viewed as resulting in a net benefit to patient management. However, if the doses to individual patients are increasing, the reasons must be carefully examined. Monitoring of trends in CT patient doses is currently particularly important as the technology is evolving rapidly. Multislice CT scanners, capable of simultaneously acquiring four slices in a single rotation, were introduced into clinical practice in 1999 and, as a result of targeted government funding to replace older scanner models, their adoption in the UK has been rapid. After only 6 years since their launch, multislice systems constitute around 70% of the CT scanners operating in England [4]. Multislice scanning has led to a major revolution in CT practice. Four slice scanners have been followed by 8-slice, 16-slice and up to 64-slice scanners. The greatly reduced examination times on these systems and their capacity to scan long lengths with narrow slices have further increased the scope of CT as a diagnostic tool. The use of submillimetre slice widths increases the spatial resolution in the scan axis direction, allowing a high spatial resolution in all planes. This isotropic resolution capability results in high quality three-dimensional (3D) and multiplanar reconstructions which are of particular benefit in angiography and endoscopy studies. The 16and 64-slice scanners are also making an impact in the field of cardiology, and CT cardiac angiography in particular is now rivalling conventional diagnostic techniques, and has the advantage of being non-invasive. The trend in technology is generally towards more dose efficient equipment, with solid-state detectors, an emphasis on high geometric dose efficiency and the introduction of dose-saving and dose-awareness features. However, the ever increasing capabilities of modern CT scanners, in terms of fast examination time and more powerful X-ray tubes, allow for the scanning of longer patient lengths and the use of higher tube currents. Unfortunately, there is still little published data available on trends in doses following the introduction of multislice CT. Two recent studies suggest average increases in effective dose per patient of 10% and 34% for multislice compared with single slice scanning [5, 6]. The recently published results of the 2003 UK CT dose survey [7] show that there has been a reduction in average patient doses from CT examinations since the last national UK CT dose survey published in 1991 [8]. However, they also show that doses from multislice are generally slightly higher than current dose levels from single slice CT scanners.

Automatic matching of the pulmonary nodules in current and former CT studies: a clinical evaluation

It is important to determine that the nodules detected by radiologists on a CT scan are benign or malignant. One method of distinguishing a benign nodule from a malignant one is to evaluate the growth of the nodule over a period of time. After the follow-up scan, the radiologist has to manually identify and locate the same nodule in the two scans and evaluate the growth. With the introduction of multi-slice CT (MSCT) the number of slices in chest CT exams has increased significantly, making it very difficult and time consuming for the radiologists to scroll through the entire set of images. An automatic tool, which registers the two studies and help the radiologist scroll through the two studies simultaneously and locate the nodule or find the nodule in other study by clicking on it in the other study, would be very beneficial to them. This paper evaluates one such automatic tool on the cases under several different clinical conditions.

An introduction of multislice CT (MSCT) and one year of experience in Birendra Hospital

An introduction of multislice CT (MSCT) and one year of experience in Birendra Hospital

Multislice CT angiography.

The introduction of multislice CT into clinical radiology constitutes a quantum leap that significantly widens the scope of vascular CT imaging. The advances over conventional spiral CT have been quantitative, mainly in terms of increased image acquisition speed which provides unprecedented volume coverage and spatial resolution. Moreover, significant technical innovations, such as cardiac scanning capabilities, have brought about a qualitative shift towards applications that were thought to be beyond the scope of CT imaging. This way multislice CT offers a wealth of new opportunities for quickly and accurately diagnosing suspected vascular disease in all organ systems; however, as we move towards faster and faster image acquisition techniques, we are also facing new challenges that require development of novel strategies in order to take full advantage of the increased capabilities of multislice CT in its current form and future generations of CT scanners.

Multislice CT in imaging the liver.

The objective of this paper is to address the dramatic impact of multislice CT (MSCT) in imaging the liver. Standard helical (spiral) CT has finally allowed for scanning the majority of the liver during the critical portal venous phase (PVP). This is often referred to as the ‘optimal temporal window’. In general, it occurs following a 70 s scan delay and is coincidental with the maximal delivery of contrast via the portal vein that provides 80% of the hepatic blood supply. This yields maximal conspicuity between low-attenuation lesions and the dramatically enhanced normal liver parenchyma at routine injection rates of 2–3 ml/s. Most importantly, these scanners, when compared to single-slice scanners, avoid impinging on the ‘equilibrium’ phase where tumors can become isodense/invisible. The introduction of MSCT with four, eight and 16-detector systems has significantly increased imaging speed. Volumetric CT will continue to increase speed in the future. This provides a number of important gains that will be described.

New technical developments in multislice CT--Part 1: Approaching isotropic resolution with sub-millimeter 16-slice scanning.

The introduction of multislice CT was a breakthrough with regard to increased scan speed, improved axial resolution and better utilization of the tube output. The new generation of multislice CT scanners offering simultaneous acquisition of up to 16 sub-millimeter slices represents an important leap on the way towards true isotropic scanning. We present an evaluation of a state-of-the-art 16-slice CT system (SOMATOM Sensation 16, Siemens AG, Forchheim, Germany). After an introduction to the detector design we discuss dose utilization and finally elaborate on multislice spiral scanning with 16 slices. Due to the increased number of slices dose utilization is improved compared to current 4-slice CT scanners, and sub-millimeter collimation needs no longer be restricted to special applications. For CT systems with 8 or more slices, the cone-beam geometry causes severe artifacts if not corrected for by a so-called cone-correction, which thus becomes mandatory in this case. With the Adaptive Multiple Plane Reconstruction AMPR, cone beam artifacts are effectively suppressed, while the benefits of Adaptive Axial Interpolation are maintained: free selection of the spiral pitch according to the clinical needs of an examination, slice width independent of the pitch, full dose utilization at all pitch values. Clinical practice will have to demonstrate the application spectrum that is opened with the new generation of multislice CT systems.

Multislice CT in tumor detection

Multislice CT in tumor detection

Detection and quantification of coronary calcification: an update

The demonstration of calcification of the coronary arterial wall indicates the presence of coronary heart disease (CHD). The prevalence of coronary calcifications increases with age. The extent of the calcifications correlates with the total coronary plaque burden and with the probability of a future myocardial infarction in symptomatic patients. In asymptomatic subjects with risk factors for a myocardial event demonstration of coronary calcifications is diagnostic for coronary atherosclerotic disease before clinical manifestation of the disease. Exact quantification of coronary arterial calcifications (calcium scoring) has become possible with electron beam computed tomography (EBCT) or ECG triggered subsecond CT scanners. Further improvements in the detection of coronary calcifications can be expected with the introduction of multi-slice CT. The prognostic relevance of coronary calcium scoring in asymptomatic high-risk patients is not yet clearly defined. It remains to be clarified whether newer, volume based methods of calcium quantification will be superior to the classic calcium score (Agatston-Score) for risk assessment and follow-up in this patient group.