High-pitch dual-source CT angiography of supra-aortic arteries: assessment of image quality and radiation dose.

INTRODUCTION: High-pitch CT angiography (CTA) is a recent innovation that allows significant shortening of scan time with volume coverage of 43 mm per second. The aim of our study was to assess this technique in CTA of the head and neck. METHODS: CTA of supra-aortic arteries was performed in 50 patients using two acquisition protocols: conventional single-source 64-slice (pitch 1.2) and high-pitch dual-source 128-slice CT (pitch 3.2). Subjective and objective image quality of supra-aortic vessel ostia as well as intra- and extra-cranial segments was retrospectively assessed by blinded readers and radiation dose compared between the two protocols. RESULTS: Conventional and high-pitch CTA achieved comparable signal-to-noise ratios in arterial (54.3 ± 16.5 versus 57.3 ± 14.8; p = 0.50) and venous segments (15.8 ± 6.7 versus 18.9 ± 8.9; p = 0.21). High-pitch scanning was, however, associated with sharper delineation of vessel contours and image quality significantly improved at the level of supra-aortic vessel ostia (p < 0.0001) as well as along the brachiocephalic trunk (p < 0.0001), the subclavian arteries (p < 0.0001), proximal common carotid arteries (p = 0.01), and vertebral V1 segments (p < 0.0001). Using the high-pitch mode, the dose-length product was reduced by about 35% (218.2 ± 30 versus 141.8 ± 20 mGy × cm). CONCLUSIONS: Due to elimination of transmitted cardiac motion, high-pitch CTA of the neck improves image quality in the proximity of the aortic arch while significantly lowering radiation dose. The technique thus qualifies as a promising alternative to conventional spiral CTA and may be particularly useful for identification of ostial stenosis.

Drug eluting stents versus PTA with GP IIb/IIIa blockade below the knee in patients with current ulcers--The BELOW Study.

The study was designed as a feasibility trial to evaluate the use of GP IIb/IIIa blockade in connection with drug eluting stents, bare stents and PTA only. Sixty patients with current ulcers were randomly assigned to receive abciximab plus a sirolimus coated stent (N.=14), abciximab plus a bare stent (N.=16), abciximab plus PTA (N.=14) and PTA alone (N.=19). Angiographic control was performed at two and six months. Recanalization was successful in all cases. Two month restenosis rate was 9%, 45.5%, 67% and 46%. At six month follow-up restenosis rate was 9%, 67%, 75% and 58%, respectively; 14% of all patients had major amputations within six months. Adjunctive administration of abciximab during peripheral arterial intervention below the knee was found to be safe. Sirolimus coated stent administration was followed by a higher patency rate.

Dual-energy CT for the characterization of urinary calculi: In vitro and in vivo evaluation of a low-dose scanning protocol.

The efficiency and radiation dose of a low-dose dual-energy (DE) CT protocol for the evaluation of urinary calculus disease were evaluated. A low-dose dual-source DE-CT renal calculi protocol (140 kV, 46 mAs; 80 kV, 210 mAs) was derived from the single-energy (SE) CT protocol used in our institution for the detection of renal calculi (120 kV, 75 mAs). An Alderson-Rando phantom was equipped with thermoluminescence dosimeters and examined by CT with both protocols. The effective doses were calculated. Fifty-one patients with suspected or known urinary calculus disease underwent DE-CT. DE analysis was performed if calculi were detected using a dedicated software tool. Results were compared to chemical analysis after invasive calculus extraction. An effective dose of 3.43 mSv (male) and 5.30 mSv (female) was measured in the phantom for the DE protocol (vs. 3.17/4.57 mSv for the SE protocol). Urinary calculi were found in 34 patients; in 28 patients, calculi were removed and analyzed (23 patients with calcified calculi, three with uric acid calculi, one with 2,8-dihyxdroxyadenine-calculi, one patient with a mixed struvite calculus). DE analysis was able to distinguish between calcified and non-calcified calculi in all cases. In conclusion, dual-energy urinary calculus analysis is effective also with a low-dose protocol. The protocol tested in this study reliably identified calcified urinary calculi in vivo.

Characterization of coronary atherosclerosis by dual-source computed tomography and HU-based color mapping: a pilot study.

To assess HU-based color mapping for characterization of coronary plaque, using intravascular ultrasound virtual histology (IVUS-VH) as a standard of reference. Dual-source computed tomography and IVUS-VH were prospectively performed in 13 patients. In five lesions, HU thresholds of the color-coding software were calibrated to IVUS-VH. In a 15-lesion verification cohort, volumes of vessel, lumen and plaque or percentages of lipid, fibrous and calcified components were obtained through use of pre-set HU cut-offs as well as through purely visual adjustment of color maps. Calibrated HU ranges for fatty or fibrous plaque, lumen and calcification were -10-69, 70-158, 159-436 and 437+. Using these cut-offs, HU-based analysis achieved good agreement of plaque volume with IVUS (47.0 vs. 51.0 mm(3)). Visual segmentation led to significant overestimation of atheroma (61.6 vs. 51.0 mm(3); P = 0.04) Correlation coefficients for volumes of vessel, lumen and plaque were 0.92, 0.87 and 0.83 with HU-based analysis or 0.92, 0.85 and 0.71 with visual evaluation. With both methods, correlation of percentage plaque composition was poor or insignificant. HU-based plaque analysis showed good reproducibility with intra-class correlation coefficients being 0.90 for plaque volume and 0.81, 0.94 or 0.98 for percentages of fatty, fibrous or calcified components. With use of optimized HU thresholds, color mapping allows for accurate and reproducible quantification of coronary plaque.

Noninvasive coronary angiography using 64-slice spiral computed tomography in an unselected patient collective: effect of heart rate, heart rate variability and coronary calcifications on image quality and diagnostic accuracy.

OBJECTIVE: The aim of this study was to assess the impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy in an unselected patient collective. SUBJECTS AND METHODS: One hundred and two consecutive patients with known or suspected coronary artery disease underwent both 64-MSCT and invasive coronary angiography. Image quality (IQ) was assessed by independent observers using a 4-point scale from excellent (1) to non-diagnostic (4). Accuracy of MSCT regarding detection or exclusion of significant stenosis (>50%) was evaluated on a per segment basis in a modified AHA 13-segment model. Effects of heart rate, heart rate variability, calcification and body mass index (BMI) on IQ and accuracy were evaluated by multivariate regression. IQ and accuracy were further analysed in subgroups of significant predictor variables and simple regression performed to calculate thresholds for adequate IQ. RESULTS: Mean heart rate was 68.2+/-13.3 bpm, mean heart rate variability 11.5+/-16.0 beats per CT-examination (bpct) and median Agatston score 226.5. Average IQ score was 2+/-0.6 whilst diagnostic quality was obtained in 89% of segments. Overall sensitivity, specificity, PPV or NPV was 91.2%, 99.2%, 95.3% or 98.3%. According to multivariate regression, overall IQ was significantly related to heart rate and calcification (P=0.0038; P<0.0001). The effect of heart rate variability was limited to IQ of RCA segments (P=0.018); BMI was not related to IQ (P=0.52). Calcification was the only predictor variable with significant effect on the number of non-diagnostic segments (P<0.0001). In a multivariate regression, calcification was also the single factor with impact on diagnostic accuracy (P=0.0049). CONCLUSION: Whilst heart rate, heart rate variability and calcification all show an inverse correlation to IQ, severe calcium burden remains the single factor with translation of such effect into decrease of diagnostic accuracy.

Sixty-four-MSCT in the characterization of porcine acute and subacute myocardial infarction: determination of transmurality in comparison to magnetic resonance imaging and histopathology.

OBJECTIVE: The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. MATERIALS AND METHODS: Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland-Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. RESULTS: Close spatial agreement was observed for MRI-MO and MSCT-MO (bias=0.55; CI=-1.49 to 2.60 at 5 min MSCT), TTC and MSCT-LE (bias=-1.28; CI=-3.76 to 1.19) or MRI-LE and MSCT-LE (bias=-0.79; CI=-4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa=0.93) and high agreement for transmural extent of TTC, MRI-LE and MSCT-LE (weighted kappa=0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa=0.33; 0.44). CONCLUSIONS: MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

[Left ventricular functional parameters: comparison of 16-slice spiral CT with MRI]. / Bestimmung linksventrikulärer Funktionsparameter: Vergleich von 16-Zeilen-Mehrschicht-CT mit der MR-Tomographie.

PURPOSE: The quantitative measurement of left ventricular functional parameters using multislice computed tomography (MSCT) with retrospective ECG-gating and comparison of the results with magnetic resonance imaging (MRI). MATERIALS AND METHODS: Thirty-one patients with suspected or known coronary artery disease underwent MSCT angiography with retrospective ECG-gating (Sensation 16, Siemens). Based on the CT data set, short axis reformations of the left ventricle were performed for functional analysis. On a commercially available workstation, end-diastolic- (EDV), end-systolic- (ESV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were calculated from MSCT (temporal resolution 105 - 210 ms) data according to the modified Simpson's rule and compared to MRI (1.5 T scanner, temporal resolution 48 ms) using a 2D TrueFISP cine sequence with respiration hold. RESULTS: In all cases, the quality was adequate for both MSCT and MRI. MSCT and MRI had an excellent correlation for EDV (r = 0.86), ESV (r = 0.91), EF (r = 0.87) and MM (r = 0.88), and a good correlation for SV (r = 0.70). The mean difference was 13.2 +/- 21.9 ml for EDV, 8.7 +/- 15.9 ml for ESV, 4.6 +/- 12.3 ml for SV, 1.4 +/- 5.2 % for EF, and 11.9 +/- 13.8 g for MM. However, EDV (p = 0.002), ESV (p = 0.005), SV (p = 0.048), and MM (p < 0.0001) were significantly overestimated with MSCT compared to MRI. For EF, no significant difference between MSCT and MRI was found (p = 0.15). CONCLUSION: For left ventricular functional parameters, MSCT of the heart with retrospective ECG-gating showed a high correlation with MRI, which has an important implication when using MSCT for non-invasive cardiac imaging. Despite the high correlation, overestimation of EDV, EVS, SV, and MM with MSCT has to be taken into account when applying this technology in clinical practice. EF was not significantly different between both modalities.

Image fusion of CT and MRI for the visualization of the auditory and vestibular system.

The aim of this study was to perform a realistic visualization of the auditory and vestibular system using volume data sets from high-resolution computed tomography (HR-CT) and high-resolution magnetic resonance imaging (HR-MRI). - In 10 patients with conductive and/or sensorineural hearing loss, vertigo and tinnitus, HR-CT and HR-MRI of the petrous bone were performed consecutively. CT was performed with a 16-slice computed tomography scanner using a high spatial resolution. MRI was performed with a 3.0 Tesla scanner using a three-dimensional-constructive interference in steady state (3D-CISS) gradient-echo, and T2-weighted, unenhanced and gadolinium (GD)-enhanced T1-weighted turbo spin-echo sequences. The middle ear structures were interactively segmented and visualized with a color-coded shaded-surface rendering method using the HR-CT volume data sets. The inner ear structures were interactively segmented and visualized with a color-coded shaded-surface rendering method using the high-resolution 3D-CISS MRI volume data sets. Finally, both shaded-surface rendered models were superimposed semi-automatically using a commercial available software program to visualize the auditory and vestibular system. - The representation of the middle and inner ear structures with image fusion of HR-CT and HR-MRI takes advantage of both the high bony contrast of HR-CT and the high soft tissue contrast discrimination and sensitivity to fluids of HR-MRI, as well as the high spatial resolution of both modalities. In comparison to the fused axial CT/MRI, the images of 3D CT/MRI fusion facilitates a clear representation and better spatial orientation. - The middle and inner ear consists of bony structures, soft tissue structures and fluid-filled spaces. For this reason, the image fusion of volume data sets from HR-CT and HR-MRI allowed an optimized and realistic visualization of the auditory and vestibular system.

Multislice CT in cardiac and coronary angiography.

In the last 2 years, mechanical multidetector-row CT (MDCT) systems with simultaneous acquisition of four slices and a half second scanner rotation time have become widely available. Data acquisition with these scanners allows for considerably faster coverage of the heart volume compared with single slice scanning. This increased scan speed can be used for retrospective gating together with 1 mm collimated slice widths and allows coverage of the entire cardiac volume in one breath-hold. First results from studies in correlation with intracoronary ultrasound suggest that MDCT technology not only offers the possibility to visualize intracoronary stenoses non-invasively, but also to differentiate plaque morphology. This is especially the case with the next generation of 16-row MDCT systems. An increased number of simultaneously acquired slices and submillimetre collimation for cardiac applications allows true isotropic scanning with high temporal resolution. Contrast-enhanced MDCT is a promising non-invasive technique for the detection, visualization and characterization of stenotic artery disease. It could act as a gatekeeper prior to cardiac catherization and finally replace conventional diagnostic modalities.

[Characterization of motion artifacts in multi-slice spiral CT]. / Charakterisierung von Bewegungsartefakten in der Mehrschicht-Spiral-CT.

PURPOSE: Motion artifacts in multi-slice spiral CT (MSCT) resulting from object motion in and against the table feed direction (z-direction) are examined using a spherical phantom. For image interpretation of complex anatomic structures, qualitative reference points are, also applicable to selected, which are ECG-gated cardiac imaging. In this case the motion of the coronary vessels in phase with the cardiac contraction must be considered. METHODS: Measurements are obtained with a multi-slice spiral CT with a rotation time of 500 ms for 4 x 1.0 mm and 2 x 0.5 mm collimation. The phantom consists of an acrylic glass body with imbedded glass beads of 1, 2, and 3 mm diameter. The object motion is sinusoidal with an amplitude of 5 mm and frequencies of 60/min and 90/min. Compensation of the table feed by object motion is examined as a special case. RESULTS: Small parameter changes can induce a strikingly different image quality, and the moving objects emerge in different slices. Depending on the phase of the movement with respect to the CT scan, objects up to a size of 3 mm can vanish completely or appear hyperintense in the image. The model investigated is also applicable to ECG-gated cardiac imaging for the detection of stenosis. It can explain variations in the reproducibility and absolute score values of the calcium scoring. CONCLUSION: The presented considerations and results must be taken into account in image interpretation with possible object motion in the z-direction. Variations in the determination of the degree of stenosis or in calcium score measurements can be explained by different vessel motion during the diastolic heart phase.

[Evaluation of different 16-row CT colonography protocols using a porcine model]. / Evaluation unterschiedlicher 16-Zeilen-CT-Colonographie-Protokolle am Schweinedarmmodell.

PURPOSE: To develop and to test an easily produced biological colon model with simulated polypoid lesions. Application of this phantom for the selection of an optimized scan protocol of 16-row CT colonography (CTC) for clinical use. METHODS AND MATERIAL: Six polypoid lesions (1 - 6 mm) were simulated with sutures on the inner face of a porcine colon segment (20 cm). After distending the colon segment with air, the phantom was placed in a water quench and CT scans were performed on a MDCT-scanner (Somatom Sensation 16, Siemens, Forchheim). At constant values for collimation (16x0.75 mm) and voltage (120 kV), 54 different combinations of mAs values (50, 75 and 100 mAs), pitch factors (1, 1.25 and 1.5) and slice thicknesses (0.75, 1.0, 1.5, 2.0, 3.0 and 5.0 mm) were tested systematically. The phantom was scanned in the longitudinal and transverse axis to simulate the different orientation of the colon in the abdomen. Axial slice images and virtual endoscopic views of all data sets were presented separately to 2 radiologists who independently determined number and size of detectable polyps. Dose exposure was measured with an Alderson phantom. RESULTS: The colon model offered a realistic imitation of a polyp-covered, human colon. The experimental set-up allowed a systematic evaluation of polyp detection related to lesion size, orientation of the colon and CTC parameters, with other influencing factors mostly excluded. Polyps were significantly better detected in the longitudinal than in the transverse orientation of the colon. For the detection of lesions of at least 3 mm, a low dose (50 mAs) 16-row CTC should be combined with a pitch of 1.5 and a maximum slice thickness of 3 mm. For the depiction of polyps smaller than 3 mm, slice thickness and pitch should amount to 1 mm and 1.0, respectively. Effective dose of this low dose protocol is 4.08 mSv. CONCLUSION: The porcine colon phantom represents a realistic and easily produced alternative to other colonography models. It allows a preselection of a CTC-protocol for subsequent clinical testings. If the high in vitro performance of the low-dose 16-row CTC-protocol is confirmed on a human collective, the use of 16-row technique would represent a big step for CTC toward a screening method.

[Multislice spiral CT of the paranasal sinuses: first experiences using various parameters of radiation dosage]. / Mehrschicht-Spiral-CT der Nasennebenhöhlen: Erste Erfahrungen unter besonderer Berücksichtigung der Strahlenexposition.

PURPOSE: To evaluate the potential of multislice CT in the diagnosis of the paranasal sinuses. METHODS: Dose measurements were performed exposing an Alderson Rando phantom in a four-slice spiral CT (MS-CT) while applying a variety of scan parameters. Additionally, 30 consecutive patients underwent a transversal examination by the MS-CT using 1/1/3.5/0.5 mm spiral parameters and an additional transversal or coronal scan on a conventional single slice spiral CT (SS-CT) with 2/3/1 mm. Coronal reformations of the MS-CT were compared with the primary coronal SS-CT, or coronal reformations of the transversal SS-CT, respectively, with regard to image quality and depiction of relevant anatomical details of the region. RESULTS: Superficial exposure values at the level of the eye lenses as well as for the thyroid gland were superior for MS-CT (3.62 mGy, and 0.12 mGy, resp.) as compared to SS-CT (2.96 mGy, and 0.07 mGy). Image quality was equal or superior for MS-CT as compared to SS-CT in all but one case. Drawbacks of SS-CT, such as dental amalgam artifacts, stair step artifacts or partial volume artifacts did not notably affect the coronal reformations of MS-CT. CONCLUSION: MS-CT seems to have the potential to replace primary coronal CT of the paranasal sinuses without any loss of image quality, but may even improve the overall diagnostic value. Radiation doses may still have to be reduced.

Estimation of radiation exposure in 16-detector row computed tomography of the heart with retrospective ECG-gating.

PURPOSE: We sought to evaluate the radiation exposure of cardiac CT scans with 16-row multidetector computed tomography (MDCT). Additionally the possibility of dose reduction by using a ECG-controlled tube current modulation technique was evaluated. METHODS AND MATERIAL: An Alderson Rando phantom equipped with thermoluminescent dosimeters was used for dose measurements. Effective dose was calculated according to ICRP 60. Exposure was performed on a 16-row MDCT scanner with standard protocols for CT coronary calcium scoring (120 kV, 133 mAs, 12 x 1.5 mm) and CT coronary angiography (120 kV, 400 mAs, 12 x 0.75 mm). Exposure was repeated at a simulated heart rate of 60 bpm with ECG-pulsed tube current modulation. RESULTS: Effective dose was 2.9 mSv (male) and 3.6 mSv (female) for the calcium scoring protocol. CT coronary angiography resulted in an effective dose of 8.1 mSv (male) and 10.9 mSv (female). Using ECG-pulsed tube current modulation radiation exposure can significant reduced: by 46 % (1.6 mSv) in calcium scoring and by 47 % (4.3 mSv) in CT coronary angiography. CONCLUSION: MDCT of the heart shows a significant radiation exposure, which can significantly be reduced by ECG-pulsed tube current modulation. Radiation exposure of cardiac MDCT is comparable to CT-examinations of chest or abdomen, but seem to be slightly higher compared to conventional coronary angiography.

[Analysis of artefacts by virtual endoscopy visualization of spiral CT data]. / Analyse von Artefakten bei der virtuellen endoskopischen Darstellung auf Basis von Spiral-CT-Daten.

PURPOSE: Analysis of patterns and causes of artifacts found in endographic visualization of spiral CT data. MATERIALS AND METHODS: A straight perspex tube with a diameter of 20 mm was scanned in three different positions with ten scan protocols of varying table feed, increment, kernel, and signal to noise ratio (Tomoscan AVE, Philips). The resulting 30 CT datasets were visualized as a virtual endoscopy (VE) with ten different visualization protocols (Easy Vision 4.2, Philips) of varying threshold, resolution, and perspective angle. 300 VE datasets were analyzed by two radiologists and compared with the visualization of a software-generated tube in order to differentiate scanning and software artifacts. RESULTS: Five different classes of artifacts have been identified. Two of them result from the scanning process and two from the specific visualization method. Spiral patterns and the unevenness of the tube wall vary with the scanning parameter. Moiré-like patterns are caused by the VE software and depend on the visualization matrix. A high perspective angle distorts the size and form of the tube and makes it difficult for the observer to locate his position within the tube. The appearance of pseudoforamina depends on both the scanning and the visualization parameters. CONCLUSION: The knowledge of the patterns and potential causes of artifacts in endographic visualization of spiral CT scans are the basis for interpretation and optimization of this visualization method.

[Quantification of cardiac function with multislice spiral CT using retrospective EKG-gating: comparison with MRI]. / Quantifizierung der Herzfunktion in der Mehrschicht Spiral CT mit retrospektivem EKG-Gating: Vergleich zur Kernspintomographie.

PURPOSE: To quantify left ventricular function derived from retrospectively ECG-gated multislice spiral CT (MSCT) data sets in comparison to MRI. MATERIALS AND METHODS: In 16 patients (14 males, 2 females, mean age 56.8 +/- 11.5 years), retrospectively ECG-gated MSCT angiography of the coronary arteries and breath-hold steady state free precession cine MRI were performed. From MSCT data-sets, 20 axial image series were reconstructed every 5 % of the RR interval. Multiplanar images were reformatted in the short axis orientation from axial images. End-systolic and end-diastolic images were selected. From these images end-systolic volume (ESV), end-diastolic volume (EDV) and stroke volume (SV) as well as the ejection fraction (EF) and myocardial mass (MM) were determined using the Simpson's method and compared with MRI. Furthermore, image quality was assessed for both imaging modalities using a four point grading scale. RESULTS: All parameters were found to have an excellent correlation between MSCT and MRI data (Pearson's correlation coefficient 0.95 - 0.99), without clinically relevant differences between both modalities. On average, the difference between both methods was 0.5 ml for ESV, 0.8 ml for EDV, 1.3 ml for SV, 0.9 % for EF and 2.3 g for MM. Image quality was slightly better for MRI (1.5 +/- 0.65) than for MSCT (1.64 +/- 0.74). CONCLUSION: Retrospectively ECG-gated MSCT angiography can not only visualize the coronary arteries but also enables precise quantification of the left ventricular function from the same MSCT data set.

[Visualization of pulmonary vein stenosis after radio frequency ablation for treatment of atrial fibrillation using multidetector computed tomography with retrospective gating]. / Darstellung von Pulmonalvenenstenosen nach Radiofrequenzablation zur Behandlung von Vorhofflimmern unter Verwendung der Multidetektor Computertomographie mit retrospektivem Gating.

PURPOSE: With the number of radio frequency ablations (RFA) for treatment of chronic atrial fibrillation increasing, the diagnostic evaluation for RFA associated pulmonary vein stenosis is getting more important. This study investigates the feasibility of the visualization of pulmonary vein stenosis using non-invasive multidetector computed tomography. MATERIALS AND METHODS: Twenty-eight patients were examined following RFA-treatment. A 4-slice (20 patients) and a 16-slice (8 patients) multidetector CT scanner (SOMATOM Volume Zoom and Sensation 16, Siemens, Forchheim, Germany) with retrospective gating was used to assess the pulmonary veins. Lesion severity was determined on a semi-quantitative scale (< 30 %, 30 - 50 %, > 50 %). RESULTS: CT was performed without any complications in all patients. Diagnostic image quality could be obtained in all examinations. The pulmonary veins showed lesions < 30 % in four patients, lesions of 30 -, 50 % in five patients and a stenosis > 50 % in one patient. Eighteen patients showed no lesions. CONCLUSION: Multidetector CT of the pulmonary veins seems to be able to visualize high-grade and low-grade lesions, but larger catheter-controlled studies are needed for further assessment of the diagnostic accuracy and clinical reliability of this noninvasive method.

[Left ventricular functional parameters using ECG-gated multidetector spiral CT in comparison with invasive ventriculography]. / Bestimmung linksventrikulärer Funktionsparameter mittels EKG-gesteuerter Mehrschicht-Computertomographie im Vergleich mit der invasiven Ventrikulographie.

PURPOSE: To evaluate the accuracy of left ventricular function using a multidetector CT (MDCT) with retrospective ECG-gating and to compare the results with conventional ventriculography. MATERIALS AND METHODS: In 26 patients, retrospectively ECG-gated MDCT of the heart (Volume Zoom, Siemens, Germany) as well as conventional coronary angiography including ventriculography was performed to exclude or follow coronary artery disease. CT examination (120 KV, 400 mAs) was carried out with 4 x 1 mm collimation (500 ms gantry rotation time). For CT angiography, 150 ml of contrast media was injected intravenously at a flow rate of 4 ml/s. All data sets of the functional cardiac parameters were reconstructed in end-systolic and end-diastolic phase. End-systolic volume (ESV), end-diastolic volume (EDV) and ejection fraction (EF) were determined from multiplanar reformations orthogonally through the cardiac short axis and analyzed using special evaluation software (ARGUS, Siemens). The results were compared with ESV, EDV and EF obtained from invasive ventriculography. RESULTS: In all cases, a sufficient quality of the MDCT images was achieved. EDV (150.1 +/- 16.2 ml MDCT vs. 138.7 +/- 16.9 ml ventriculography; mean difference 11.4 +/- 12.7 ml; r = 0.51) had an acceptable correlation to conventional ventriculography, and ESV (58.1 +/- 14.6 ml vs. 50.2 +/- 13.4 ml; mean difference 7.9 +/- 8.8 ml; r = 0.81) and EF (60.9 +/- 13.6 % vs. 64.9 +/- 12.7 %; mean difference 4.0 +/- 6.2 %; r = 0.79) showed a good correlation. In comparison with invasive ventriculography, MDCT tended to overestimate significantly EDV (p = 0.008) and ESV (p = 0.003) and to underestimate EF (p = 0.001). CONCLUSION: MDCT of the heart with retrospective ECG-gating enables efficient estimation of left ventricular function, providing important additional information of non-invasive cardiac imaging using MDCT. However, EDV and EVS were significantly overestimated and EF was underestimated in MDCT compared to ventriculography.

[Multidetector CT Angiography - is it a valuable screening tool to detect significant renal artery stenosis?]. / MDCTA der Nierenarterien - ein vollwertiges Screeningverfahren bei Nierenarterienstenose?

PURPOSE: To evaluate the diagnostic value of multidetector CT angiography (MDCTA) of the renal arteries. METHODS: 27 patients underwent MDCTA of the renal arteries. Scan parameters were: collimation 4 x 1 mm, pitch 1.5, effective slice thickness 1.25 mm, reconstruction increment 0.8 mm, circulation time measurement, power injection of 80 ml iomeprol 400, flow 4 ml/sec. Independent reading on laser film was done by two radiologists using edited maximum intensity projections, multiplanar reconstructions and source images. Standard of reference was a 3D-FLASH MR angiography (1.5 T, 3.9/1.2, 10 degrees 0.2 mmol GdDTPA/kg bw) in 10 and intraarterial angiography in 17 patients. RESULTS: Analysing 63 arteries, sensitivity, specificity, positive predictive value and negative predictive value in terms of detection of moderate and high grade renal artery stenosis (n = 10) were 90, 98, 90 and 98 % for reader A, and 90 % each for reader B, respectively (kappa = 0.91 interobserver agreement). 1/11 accessory renal arteries was missed by both angiography and MDCTA. Image quality was graded as excellent or good in 26/27 of cases by both readers. CONCLUSION: MDCTA proved to be a highly accurate tool in the detection of therapeutically relevant renal artery stenosis.

[Use of VR (virtual reality) software for preoperative implantation fitting with an implantable hearing aid as an example]. / Einsatz einer VR (Virtuelle Realität)-Software zur präoperativen Implantationsprüfung am Beispiel eines implantierbaren Hörgerätes.

PURPOSE: To prove the feasibility of a preoperative fitting test for an implantable hearing aid using a VR environment. METHODS: A high-resolution spiral CT was performed after mastoidectomy in 10 temporal bone specimens. The bony structures were segmented and merged with the Computer-Aided Design (CAD) data of the hearing aid in a VR environment. For each specimen a three-dimensional fitting test was carried out by three examiners determining the implantability of the hearing aid. The implantation simulation was compared with the real implantation procedure performed by an experienced ENT surgeon. RESULTS: The used VR system enabled real-time 3D-visualisation and manipulation of CT- and CAD-data. All objects could be independently moved in all three dimensions. The VR fitting test corresponded closely with the real implantation. The implantability of the hearing aid was properly predicted by all three examiners. CONCLUSION: Merging CT and CAD data in a virtual reality environment bears high potential for the pre-surgical determination of the fit and mountability of medical implants in complex anatomical regions.

[CT-angiography of the carotid artery: First results with a novel 16-slice-spiral-CT scanner]. / CT-Angiographie der A. carotis: Erste Erfahrungen mit einem 16-Schicht-Spiral-CT.

PURPOSE: To evaluate a novel multislice CT system (16-slice-spiral-CT scanner) for the diagnosis of carotid artery stenosis. MATERIAL AND METHODS: Five patients with symptomatic atherosclerotic disease of the carotid arteries were examined with a 16- slice-spiral-CT scanner. Collimation was 16 x 0.75 mm, table speed 36 mm/s (pitch of 1.5), rotation time 0.5 s, tube current was 160 eff.mAs at 120 kV. 60 ml of contrast material were injected with a power injector followed by a saline flush. The start delay was measured with test bolus method (20 ml CM). Interactive multiplanar reformation (iMPR) and thin slab MIP as well as volume rendering were used for image evaluation and presentation. RESULTS: Scan time was 9 s for a range of 300 mm. This allowed imaging the whole length of the carotid artery (aortic arch to circle of Willis) in a true arterial phase. Pulsation artefacts did not impair the evaluation of the vessels at the level of the aortic arch. Overall image quality of both "source images" and 3D-reconstructions was excellent, due to a reduced voxel size of 0.03 mm (3). Image evaluation and postprocessing (iMPR, MIP) was done within 15 min. iMPR was highly accurate for demonstrating plaque morphology and determining the percentage of the stenosis. CONCLUSION: For the first time, true arterial phase images of the entire carotid artery with high spatial resolution could be acquired using a 16-slice-spiral-CT scanner. This method offers the potential to replace catheter angiography in the evaluation of carotid artery stenosis.