[Virtual colonoscopy--chances for a screening procedure?]. / Virtuelle Koloskopie--Chancen für ein Screeningverfahren?

In principle, virtual colonoscopy is capable to be used as method for early detection of colorectal cancer (CRC), even if the accuracy of the method and radiation exposure are matters discussion in the radiological community. Virtual colonoscopy is able to detect any pathology which is relevant for early detection of CRC especially when using multislice CT, but also with single slice CT. The diagnosis of small lesions, less than 7 mm in diameter (polyps and flat lesions) is still problematic as it is in conventional colonoscopy. The exposure to x-rays in asymptomatic patients, without any increased risk of developing cancer is highly problematic and should be reduced to a minimum. Using special post processing filters on the volume dataset it can be shown that a tube current of 20 mAs is sufficient without any loss in accuracy. Measurements on the Alderson-phantom showed, that an effective dose exposure of 1.2 mSv is obtained using these reduced mAs values. It has to be differentiated between virtual colonoscopy for early detection of polyps and CRC in individual patients or as a screening examination of a large population. Virtual colonoscopy as a screening examination necessitates reduction of radiation dose, a high degree of automatization in 3D reconstructions as well as the assessment of the entire mucosa. High risk patients, whom refuse fibreoptic colonoscopy should undergo virtual colonoscopy. Virtual colonoscopy has a good chance to become an accepted tool for general screening, if efficient dose reduction, complete visualization of the colon mucosa and automatization of the post processing procedures can be achieved.

Multi-slice computed tomography as a screening tool for colon cancer, lung cancer and coronary artery disease.

Recent promising trials that use low-dose CT for the early detection of lung cancer have reinvigorated the interest in screening approaches. At the same time the development of fast image acquisition techniques, such as multislice CT, have sparked renewed interest in cardiac imaging within the radiological community. In addition to special cardiac capabilities, multislice CT has several other features such as high acquisition speed and low-dose requirements that may make this modality a universal radiological screening tool. Non-invasive disease detection is the radiologist's domain. In this paper we identify criteria for effective screening and apply these criteria to screening approaches with multislice CT when used for detection of three disease entities: colon cancer; lung cancer; and cardiovascular disease.

[Virtual large intestine imaging with multi-level CT. Pain free coloscopy--that works!]. / Virtuelle Dickdarmspiegelung mit der Mehrschicht-CT. Schmerzfrei koloskopieren--das geht!

Provided that the bowel is carefully cleansed, virtual colonoscopy permits a safe, reliable and painfree diagnosis of the large bowel. It requires distension of the bowel with ambient air. Contraindications include pregnancy, acute inflammation of the bowel and recent surgery. Tumors and large polyps (10 mm and more) can be diagnosed with certainty, while polyps measuring 5 mm and more are detected with a high degree of sensitivity. It goes without saying that virtual colonoscopy does not allow for the taking of biopsy material or the performance of therapeutic measures, so that positive or suspicious findings must be clarified by conventional colonoscopy. In principle, virtual colonoscopy is also suitable for use as a screening procedure. Whether the radiation exposure associated with the conventional examination protocol can be considered acceptable for screening purposes is questionable. However, using mathematical means, the radiation dose can be reduced to one-tenth of the usual dose.

[Virtual coloscopy with multi-slice computerized tomography. Preliminary results]. / Virtuelle Koloskopie mit der Mehrschichtcomputertomographie. Vorläufige Ergebnisse.

SUBJECT: Using multi-slice computed tomography (MSCT) large body areas can scanned with high spatial resolution. In this study, MSCT was employed for virtual colonoscopy in various pathologies of the colon. MATERIALS AND METHODS: For MSCT a Somatom Plus 4, Volume Zoom scanner, (Siemens, Forchheim) was employed, equipped with four parallel detector rows. Twenty-five patients were included in this trial, prior to colonoscopy or partial colon resection. After cleaning the colon, distension was achieved by insufflation of room air using a rectal tube. The parameters of acquisition and reconstruction were as follows: collimation 4 x 1 mm and 4 x 2.5 mm respectively; tube charge per slice: 140-160 mAs; pitch 5-6; i.v. contrast medium: 120 ml Ultravist 300 (Schering) with a flow rate of 3 ml/s; delay: 35 s. For 3D reconstruction we used edge-enhanced volume rendering, virtual colonoscopy and extraluminal views of volume-rendered images. RESULTS: Nine polyps and four of five colon carcinomas were detected using MSCT virtual colonoscopy. In three patients with ulcerative colitis virtual coloscopy revealed morphological alterations compatible with this disease. In two of four patients with multiple diverticula of the colon the true extent of the disorder could be assessed in virtual colonoscopy. CONCLUSION: Utilizing virtual MSCT colonoscopy polyps and cancer of the colon can be reliably detected, if proper cleaning and distension is provided. On axial images alone smaller polyps may be assessed. The high z-axis resolution of MSCT offers superior conditions for CT-based virtual colonoscopy.

[Multislice computed tomography of the small intestine. Preliminary results]. / Mehrschicht-Computertomographie des Dünndarms. Vorläufige Ergebnisse.

SUBJECT: Spiral computer tomography (SCT) became an important supplement to the Sellink examination. Multi slice computer tomography (MSCT) achieves a z-axis resolution of 1-2 mm without considerable increase in the acquisition time. In this paper, examination technique in first clinical results of CT-Sellink examination with MSCT, including the 3D-reconstruction are presented. MATERIALS AND METHODS: The investigations were carried out with the Somatom Plus 4 Volume Zoom (Siemens, Forchheim) scanner. The following parameters were employed: 4 parallel detector ledges, collimation 4 x 1 mm, tube power 140 mA, tube voltage 120 kV, pitch 5 up to 6 mm, slice thickness 1 mm and 2 mm, reconstruction with 50% overlap. Via a duodenal tube, the small intestine was distended by means of 1.5 up to 2.5 l methyl-cellulose suspension. The data were acquired 35 s after injection of 120 ml contrast media (Ultravist). Various methods of postprocessing were applied on a workstation. RESULTS: As of yet, 16 patients were examined with MSCT-Sellink. In 4 cases pathological findings were detected with MSCT-Sellink, which were not recognized with X-ray Sellink. CONCLUSION: Due to high z-axis resolution and short acquisition time, the morphological details of the small intestine can be visualized utilizing MSCT-Sellink. The data set is well suited for 3D postprocessing. Improvement of diagnostic accuracy can be anticipated.

[Computed tomography of the abdomen with multidetector-array CT]. / Computertomographie des Abdomens mit der Mehrzeilen-Detektor Spiral-CT.

BACKGROUND: The advent of multidetector CT (MDCT) constitutes a quantum leap creating a wealth of new opportunities in medical imaging. However, while the basic principles of spiral CT still apply, we are now challenged to rethink our strategies in planning a CT study to take full advantage of the increased capabilities of MDCT. MATERIALS AND METHODS: We report here our preliminary experiences with MDCT for abdominal CT imaging within a 5-month period. During this time, suitable protocols for investigation of the abdomen using MDCT were developed. The capabilities of MDCT allow for tailoring dedicated CT protocols for routine applications as well as for biphasic liver studies and CT angiography of the aorta and abdominal vessels. RESULTS: The speed of MDCT can either be used to reduce the time needed to cover a given volume, or to use narrower beam collimations to increase the resolution of detail along the z-axis and reduce volume averaging. Higher scan speed allows reduction of the amount of contrast material in vascular applications and suppression of motion artifacts. Higher spatial resolution with thinner collimations reduces volume averaging and improves the detection of small hepatic and pancreatic lesions. Detailed analysis of vascular structures and high-quality three-dimensional reformations become feasible. New problems arise from the large amount of data generated by MDCT. CONCLUSIONS: MDCT offers a wealth of new opportunities that help us to come to a fast and accurate diagnosis in suspected abdominal disease. Traditional indications for performing CT are reemphasized and new clinical applications can be exploited.