Contrast-enhanced ultrasound-guided percutaneous cholangiography and cholangiodrainage (CEUS-PTCD).

We present our experience with contrast-enhanced ultrasound-guided percutaneous transhepatic cholangiodrainage in eight patients with obstructive jaundice and failure of conventional endoscopic retrograde cholangiography. The intraductal application of the ultrasound contrast agent led to sufficient cholangiography in all patients. In one patient, after accidental dislocation of the bile duct drain, the leakage could be detected by demonstration of the passage of contrast agent into the perihepatic peritoneal space. Further studies are necessary to evaluate this new technique in a larger numbers of patients.

[Computer-assisted navigation system for interventional CT-guided procedures: results of phantom and clinical studies]. / Computergestütztes Navigationssystem für CT-gesteuerte Interventionen: Ergebnisse am Phantom und im klinischen Einsatz.

PURPOSE: To evaluate the technical applicability and accuracy of a navigation system for CT-guided interventional procedures in a phantom and a patient study. MATERIALS AND METHODS: A novel navigation tool (CAPPA IRAD, CAS innovations AG, Erlangen, Germany) was employed for CT-guided biopsies in a phantom and in patients. The entire system consists of a PC, navigation software, an optical tracking system and a patient frame. For the phantom study, a spine phantom in wax was used. The phantom as well as the patients were placed on the CT table in a stable position and fixed within a double vacuum device. The patient frame equipped with optical and CT markers was placed above the target region, followed by acquisition of a planning scan. All data were transferred to the navigation system inside the scanning room, and with the aid of the above mentioned navigation software, the biopsy pathway was planned. Hereafter, the needle holder was aligned accordingly, and a coaxial biopsy needle was pushed forward to the planned target. An additional control scan confirmed needle position, and the navigation software was used to evaluate the distance between the target and needle tip. RESULTS: In the phantom study (n = 60) the average deviation between the planned and documented needle tip position was 1.1 mm. In the clinical study (n = 15), we performed biopsies of the lung, the mediastinal area, the pancreas and liver and some bone biopsies as well as a therapeutic nerve root infiltration. 12 of 15 cases required oblique needle access. In 9 / 15 cases merely a single planning and control scan were required, whereas in 5 / 15 cases additional safety or correction scans were performed. In the case of pancreas biopsy, the lesion (diameter 1 centimeter) visible during the arterial phase only could not be punctured even following repeated corrections due to severe breathing artifacts and pronounced peristaltic movement of the adjacent bowel. The time between planning CT and correct needle position was about 30 minutes. CONCLUSION: The navigation system allows for safe interventions in case of angulated needle access with high accuracy and little tissue trauma. However, insufficient corrections for respiration movement constitute a substantial limitation of the tool.

Evaluation of carotid artery stenosis with multisection CT and MR imaging: influence of imaging modality and postprocessing.

BACKGROUND AND PURPOSE: We prospectively evaluated the influence of different imaging techniques (time-of-flight MR angiography [TOF-MRA], contrast-enhanced MR angiography [CE-MRA], multisection CT angiography [CTA]) and postprocessing methods (maximum intensity projection [MIP], multiplanar reformation [MPR]) on carotid artery stenosis grading. MATERIALS AND METHODS: Fifty patients (34 men, 16 women) with symptomatic stenosis of the internal carotid artery were examined with a 16-section spiral CT and a 1.5T MR unit. Two MRA techniques were applied: 3D-TOF and CE-MRA. MPR was used for postprocessing with all modalities; MIP was used only with MRA. Four readers measured and calculated the percentage diameter stenosis independently according to NASCET criteria. The Wilcoxon test was used to measure interobserver variability, and the Friedman test was used to test the null-hypothesis of equality of the modalities. RESULTS: The hypothesis for global equality was rejected (P < .001). TOF-MRA and CTA assessed with MPR showed the highest concordance (difference, 0.6%; confidence interval [CI], -3.0, 4.3%), and CE-MRA with MIP and CTA showed the lowest concordance in stenosis grading (difference, 7.0%; CI, 3.4, 10.6%). MPR resulted in lower degrees of stenosis than MIP for both MRA sequences, although not statistically significant (CE, -3.0%; CI, -6.6, 0.6%; TOF, -2.2%; CI, -5.8, 1.4%). When only studies with good or excellent image quality were considered, the differences decreased, but the trends remained. CONCLUSION: Stenosis grading is dependent on the examination method and postprocessing technique. CTA and TOF-MRA evaluated with MPR revealed highest concordance.

Detection of coronary artery stenoses by contrast-enhanced, retrospectively electrocardiographically-gated, multislice spiral computed tomography.

BACKGROUND: Multislice spiral computed tomography (MSCT) with retrospectively ECG-gated image reconstruction permits coronary artery visualization. We investigated the method's ability to identify high-grade coronary artery stenoses and occlusions. METHODS AND RESULTS: A total of 64 consecutive patients were studied by MSCT (4x1 mm cross-sections, 500-ms rotation, table feed 1.5 mm/rotation, intravenous contrast agent, retrospectively ECG-gated image reconstruction). All coronary arteries and side branches with a luminal diameter >/=2.0 mm were assessed concerning evaluability and the presence of high-grade stenoses (>70% diameter stenosis) or occlusions. Results were compared with quantitative coronary angiography. Of 256 coronary arteries (left main, left anterior descending, left circumflex and right coronary artery, including their respective side branches), 174 could be evaluated (68%). In 19 patients (30%), all arteries were evaluable. Artifacts caused by coronary motion were the most frequent reason for unevaluable arteries. Overall, 32 of 58 high-grade stenoses and occlusions were detected by MSCT (58%). In evaluable arteries, 32 of 35 lesions were detected, and the absence of stenosis was correctly identified in 117 of 139 arteries (sensitivity, 91%; specificity, 84%). If analysis was extended to all stenoses with >50% diameter reduction, sensitivity was 85% (40 of 47) and specificity was 76% (96 of 127). CONCLUSIONS: MSCT with retrospective ECG gating permits the detection of coronary artery stenoses with high accuracy if image quality is sufficient, but its clinical use may presently be limited due to degraded image quality in a substantial number of cases, mainly due to rapid coronary motion.

Noninvasive coronary angiography by retrospectively ECG-gated multislice spiral CT.

BACKGROUND: We investigated the applicability and image quality of contrast-enhanced coronary artery visualization by multislice spiral CT using retrospective ECG gating. METHODS AND RESULTS: Twenty-five patients in sinus rhythm (significant coronary artery stenoses ruled out by invasive angiography) were studied with a multislice spiral CT (Siemens SOMATOM Volume Zoom). In inspiration (mean breath-hold, 37 seconds), a volume data set of the heart was acquired (intravenous contrast agent; 4 x 1-mm slice thickness; 500-ms rotation; table feed, 1.5 mm/360 degrees ). Simultaneous recording of the ECG permitted retrospective reconstruction of contiguous cross sections in intervals of 1 mm at any desired interval of the cardiac cycle. The mean duration of the image reconstruction window was 185 ms. Next to 3-dimensional reconstructions of the heart and coronary arteries, multiplanar reconstructions were rendered to determine the visualized length of the coronary arteries, the contrast-to-noise ratio, and the correlation of coronary artery diameters to quantitative coronary angiography. CONCLUSIONS: The coronary arteries could be visualized over long segments (left main, 9+/-4 mm; left anterior descending, 112+/-34 mm; left circumflex, 80+/-29 mm; right coronary artery, 116+/-33 mm). On average, 78+/-16% of these distances were visualized free of motion artifacts. The mean contrast-to-noise ratio was 9.3+/-3.3. Coronary artery diameters in multislice spiral CT showed close correlation to quantitative coronary angiography (CT, 3.3+/-1.0 mm; angiography, 3. 2+/-0.9 mm; mean difference, 0.38 mm; r=0.86). Contrast-enhanced multislice spiral CT permits visualization of the coronary artery lumen. Further studies are necessary to determine whether image quality is sufficient to reliably detect coronary artery stenoses.

Focal masses in a non-cirrhotic liver: The additional benefit of CEUS over baseline imaging.

Incidentally detected focal liver lesions are commonly encountered in clinical practice presenting a challenge in the daily department work flow. Guidelines for the management of incidental focal liver lesions have been published but comments, illustrations and recommendations regarding practical issues are crucial. The unique features of contrast-enhanced ultrasound in non-invasive assessment of focal liver lesion enhancement throughout the vascular phases in real-time has allowed an impressive improvement in the diagnostic accuracy of ultrasound. We highlight the additional benefit of contrast-enhanced ultrasound over conventional B-mode ultrasound imaging in detection, characterization, differential and final diagnosis of focal liver lesions, as well as for liver metastases screening. The current roles of cross-sectional imaging are explained in detail, with indications and limitations for each procedure. The advantages of CEUS, such as non-ionizing radiation exposure, cost benefits, non-iodinate contrast agents, and repeatability are also described ultimately improving patient management.

Morphological predictors of survival in colorectal carcinoma: univariate and multivariate analysis.

In 150 curative resected adenocarcinomas of the large bowel we analyzed the morphological parameters of the primary tumor and lymph node involvement which most efficiently expressed the relationship to survival time. Using univariate survival analysis (product limit estimator according Kaplan-Meier), several macroscopical and microscopical parameters of the primary tumor and lymph node involvement significantly correlated with survival time. A multivariate survival analysis of covariates according to the Cox regression model revealed that the significant correlations of all these parameters were expressed by a set of five variables: pT stage, number of inflammatory cells, sex, age, and pN stage. As shown by the Kaplan-Meier test, this set of variables allowed a more precise prediction of survival time than mere staging according to the TNM system. Parametric multiple stepwise survival analysis was inefficient. No distinct relationship was found between the morphology of the primary tumor and the involvement of lymph nodes.

Imaging of head and neck tumors--methods: CT, spiral-CT, multislice-spiral-CT.

Spiral-CT is standard for imaging neck tumors. In correspondence with other groups we routinely use spiral-CT with thin slices (3 mm), a pitch of 1.3-1.5 and an overlapping reconstruction increment (2-3 mm). In patients with dental fillings a short additional spiral parallel to the corpus of the mandible reduces artifacts behind the dental arches and improves the diagnostic value of CT. For the assessment of the base of the skull, the orbital floor, the palate and paranasal sinuses an additional examination in the coronal plane is helpful. Secondary coronal reconstructions of axial scans are helpful in the evaluation of the crossing of the midline by small tumors of the tongue base or palate. For an optimal vascular or tissue contrast a sufficient volume of contrast medium and a start delay greater than 70-80 s are necessary. In our opinion the best results can be achieved with a volume of 150 ml, a flow of 2.5 ml/s and a start delay of 80 s. Dynamic enhanced CT is only necessary in some special cases. There is clear indication for dynamic enhanced CT where a glomus tumor is suspected. Additional functional CT imaging during i-phonation and/or Valsalva's maneuver are of great importance to prove vocal cords mobility. Therefore, imaging during i-phonation is an elemental part of every thorough examination of the hypopharynx and larynx region. Multislice-spiral-CT allows almost isotropic imaging of the head and neck region and improves the assessment of tumor spread and lymph node metastases in arbitrary oblique planes. Thin structures (the base of the skull, the orbital floor, the hard palate) as well as the floor of the mouth can be evaluated sufficiently with multiplanar reformations. Usually, additional coronal scanning is not necessary with multislice-spiral-CT. Multislice-spiral-CT is especially advantageous in defining the critical relationships of tumor and lymph node metastases and for functional imaging of the hypopharynx and larynx not only in the transverse plane but also in the coronal plane.

Paranasal sinuses and nasopharynx CT and MRI.

Neoplastic disease of the nose, paranasal sinuses, the nasopharynx and the parapharyngeal space requires thorough assessment of location and extent in order to plan appropriate treatment. CT allows the deep soft tissue planes to be evaluated and provides a complement to the physical examination. It is especially helpful in regions involving thin bony structures (paranasal sinuses, orbita); here CT performs better than MRI. MRI possesses many advantages over other imaging modalities caused by its excellent tissue contrast. In evaluating regions involving predominantly soft tissue structures (ec nasopharynx and parapharyngeal space) MRI is superior to CT. The possibility to obtain strictly consecutive volume data sets with spiral CT or 3D MRI offer excellent perspectives to visualize the data via 2D or 3D postprocessing. Because head and neck tumors reside in a complex area, having a 3D model of the anatomical features may assist in the delineation of pathology. Data sets may be transferred directly into computer systems and thus be used in computer assisted surgery.

Oropharynx, oral cavity, floor of the mouth: CT and MRI.

Pretherapeutic staging of tumors of the oropharynx, the oral cavity and the floor of the mouth is important and should be thorough and exact to ensure appropriate therapy. Particularly important is the assessment of infiltration of deeper compartments and the topographic relationship of tumor to vascular structures (lingual artery and vein, hypoglossal nerve), or the presence of spread of the tumor across the midline. As spread of tumor may occur to a large degree underneath normal appearing mucosa, clinical assessment of the true tumor extent is difficult. In the last 20 years computed tomography (CT) has proved its value as a supplementary non-invasive method and established its role in modern diagnostic evaluation. Magnetic resonance imaging (MRI) is an non-invasive scanning method that offers excellent tissue contrast. Ultrasonography (US) is of secondary importance, but provides useful guidance due to its wide availability and its easy use. This paper aims to depict the possibilities of modern CT and MRI to provide 'one-stop-shopping' information to the clinician as a basis for the right therapeutic approach and correct estimation of the individual patient's prognosis. A clear problem oriented imaging strategy with standardized diagnostic criteria will lead to a cost effective evaluation.

Subsecond multi-slice computed tomography: basics and applications.

The recent advent of multislice-scanning is the first real quantum leap in computed tomography since the introduction of spiral CT in the early 90s. We discuss basic theoretical considerations important for the design of multislice scanners. Then, specific issues, like the design of the detector and spiral interpolation schemes are addressed briefly for the SOMATOM PLUS 4 Volume Zoom. The theoretical concepts are validated with phantom measurements. We finally show the large potential of the new technology for clinical applications. The concurrent acquisition of multiple slices results in a dramatic reduction of scan time for a given scan technique. This allows scanning volumes previously inaccessible. Similarly, given volumes can be scanned at narrower collimation, i.e. higher axial resolution in a given time. From data acquired at narrow collimation, both high-resolution studies and standard images can be reconstructed in the so-called Combi-Mode. This on the one hand reduces dose exposure to the patient because repeated scanning of a patient is no longer required. On the other hand, standard reconstructions benefit from narrow collimation as Partial Volume Artifacts are drastically suppressed. The rotational speed of 0.5 s of the SOMATOM PLUS 4 Volume Zoom furthermore opens up a whole range of new applications in cardiac CT. For the first time, virtually motion-free images can be acquired even for large volumes in a single breathhold by the combination of fast rotation and ECG triggering, respectively gating. We explain the underlying concepts and present initial results. The paper concludes with a brief discussion of the impact of the new technique on image display and postprocessing.

Head and neck tumors: imaging recurrent tumor and post-therapeutic changes with CT and MRI.

OBJECTIVE: To evaluate criteria for detection of tumor recurrence and post-treatment changes in patients with head and neck malignancies in computed tomography (CT) and magnetic resonance imaging (MRI). METHODS AND MATERIALS: Thirty-nine patients with head and neck carcinoma receiving radiochemotherapy were examined before, during and after therapy with MRI. Changes in signal intensity were correlated to histology or clinical course. Three hundred and thirty-one patients with head and neck malignancies were examined with CT after therapy. CT diagnoses were correlated with histology or clinical course. RESULTS: Main criteria for recurrent/residual tumor in MRI was infiltrative mass with high signal intensity in T2-weighted images and enhancement after Gd-DTPA in T1-weighted images. Radiation-induced changes led to false positive diagnosis in 46% in the interval up to 3 months after therapy and in 58% in the interval 3-6 months after therapy. The combination of a circumscribed, infiltrative mass with contrast enhancement in CT had a sensitivity of 86% and a specificity of 80%. CONCLUSION: CT could accurately demonstrate postoperative changes and tumor recurrence. MRI had advantages in differentiation of tumor and scar, but edema after radiation therapy can spoil diagnosis.

Adenocarcinoma of the gastro-esophageal junction: CT for monitoring during neoadjuvant chemotherapy.

OBJECTIVE: A clinical study was performed to assess the diagnostic value of spiral CT for evaluation of response during neoadjuvant chemotherapy (CTx) in patients with adenocarcinoma of the gastro-esophageal-junction (GEJ). Results were compared to those of endoscopy. METHODS AND MATERIAL: Twenty-five patients with histologically proven adenocarcinoma of the GEJ scheduled to undergo neoadjuvant CTx were studied. Before CT examination, 1200 ml of a vanilla flavoured paraffin emulsion were applied orally to the fasting patients and 40 mg BuscopanR or 2 mg glucagon were injected i.v. for hypotonia. Iodine (100 ml) was injected automatically (3 ml/s) and the CT scan was started 10 s after complete administration of CM. For response evaluation to CTx, four standardized parameters were measured by two experienced, blinded radiologists. The results were categorized according to the WHO classification of 1981 and compared to those of endoscopy. RESULTS: In 24 of 25 patients endoscopic and computed tomographic response evaluation showed a close correlation (r = 0.96). CONCLUSION: Spiral CT with negative oral contrast agent is a suitable technique for monitoring of GEJ masses. In combination with standardized metric parameters it offers a quantitative response evaluation in patients with GEJ masses during neoadjuvant CTx.

Preoperative Chemoradiation in Locally Advanced Pancreatic Carcinoma: A Phase II Study.

BACKGROUND: Effectiveness and feasibility of preoperative chemoradiation (CRT) in locally advanced adenocarcinoma of the pancreas are evaluated. MATERIAL AND METHODS: 29 eligible of 37 registered patients were treated. 3d-Conformal external radiotherapy was delivered with a 1.8-Gy single dose and a total dose of 50.4 Gy plus 5.4 Gy boost. Simultaneous chemotherapy consisted of 5-fluorouracil and mitomycin C. RESULTS: Among 27 completely treated patients, 16 (59%) underwent surgery, 6 of them being irresectable intraoperatively. Ten patients (37%) had clear resection margins at Whipple's procedure. Eleven patients were not considered for surgery (7 still irresectable at restaging, 3 distant metastases, 1 refusal of surgery). Toxicity was predominantly hematological (grade 3: 30%, grade 4: 7%); furthermore, there was nausea/vomiting (grade 3: 20%, grade 4: 0%). No patient died perioperatively. The tumor-related overall survival rate was better for resected patients than for nonresected patients (50% vs. 6%, 2-year survival, p = 0.07), median overall survival was 9 months (median follow-up, 28 months). CONCLUSIONS: Neoadjuvant CRT without significant acute toxicity produced a resectability rate of 37% (all R0), which should be confirmed by randomized phase III studies. Copyright 2000 S. Karger GmbH, Freiburg

[Dosage reduction in computed tomography by anatomy-oriented attenuation-based tube-current modulation: the first clinical results]. / Dosisreduktion in der Computertomographie durch anatomie-orientierte schwächungsbasierte Röhrenstromregelung: erste klinische Ergebnisse.

PURPOSE: To examine the feasibility of reducing exposition in CT examinations by applying a prototype device for tube current modulation with the image quality remaining unchanged. PATIENTS AND METHODS: The prototype device for tube current modulation was integrated into a Somatom Plus 4 CT scanner (Siemens). The method is based on anatomy-oriented modulation of the tube current. The attenuation of the X-ray beam by the patient's body was determined online, the tube current was adapted to changing anatomy after a delay of 180 degrees. In ten patients undergoing radiotherapy, four identical scans of the shoulder region were carried out with and without tube current modulation. For determining dose reduction, mAs product of both scans were compared. The evaluation of noise artifacts, low contrast detectability and overall image quality was performed by four radiologists in a blinded fashion. RESULTS: Patient doses could be reduced by 38% on an average. Scans with tube current modulation were superior to scans without it as to noise (75%), low contrast detectability (51%), artifacts (69%), and overall image quality (71%). CONCLUSIONS: A significant reduction in exposition during CT can be achieved by anatomy-oriented tube current modulation without image degradation.

[Automatic exposure control to reduce the dose in subsecond multislice spiral CT: phantom measurements and clinical results]. / Dosisautomatik bei der Mehrzeilenspiral-CT: Phantommessungen und klinische Ergebnisse.

PURPOSE: To investigate the potential of dose reduction in multislice spiral CT (MSCT) with automatic exposure control. MATERIALS AND METHODS: The study was performed on a Sensation 4 multislice scanner. This prototype implementation analyzed the distribution of the attenuation along the z-axis in the lateral and sagittal directions of the digital radiogram. Depending on this distribution of the attenuation, the tube current (mA) is defined for every tube rotation. In addition, the tube current was modulated during each tube rotation. First, a three step oval water phantom was measured to evaluate the potential of this method with respect to dose reduction and image quality. In a patient study (n = 26), four different scan regions (shoulder, thorax, abdomen, pelvis) were examined and dose (mAs) and image quality evaluated in comparison to examinations with a standard protocol for these regions in adults and a weight-adjusted standard protocol in children. The image quality was classified in consensus as good, sufficient and poor image quality. RESULTS: By adapting and modulating the tube current, we substantially reduced the variation of noise in one spiral scan and in one scan region of our patient collective. The dose (average mAs) was reduced by 31 % to 66 % in children (mean 44 %) and between 35 % and 64 % in adults (mean 53 %), depending on the scan region. The image quality was substantially improved in regions with high attenuation and did not suffer in low attenuation regions. CONCLUSION: The dose can be reduced substantially by an automatic exposure control including angular tube current modulation with the same or improved image quality.

[MR imaging of pancreatic lesions with Mn-DPDP. A histopathologic correlation]. / MRT von Läsionen des Pankreas mittels Mn-DPDP - Eine histopathologische Korrelation.

PURPOSE: To examine the diagnostic accuracy of pancreatic lesions using mangafodipir-trisodium (Mn-DPDP) enhanced MR imaging. The imaging results were correlated with the histopathological results. MATERIAL AND METHODS: 40 patients with suspicion of pancreatic carcinoma were examined with MRI before and after i. v. administration of Mn-DPDP (Philips Gyroscan ACS NT 1.5 T, phased array body-coil: TSE T 2 with and without SPIR, TR 2000 ms, TE 120ms; FFE T 1 breathhold, TR 115 ms, TE 4.6 ms; MRCP, TR 6000 ms, TE 1200 ms; Teslascan i. v. 5 micromol Mn/kg; FFE T 1 breathhold SPIR, TR 140 ms, TE 4,6 ms). Two observers evaluated in consensus the number and characteristics of focal pancreatic lesions. The MR findings were correlated with histopathological findings retrospectively. RESULTS: The following lesions were found: adenocarcinoma (19), pancreatitis (8), adenocarcinoma within pancreatitis (3), insulinoma (2), hematoma (1), papillitis stenosans (1), signet ring cell carcinoma (1), metastasis of rectal carcinoma (1), papillary mesothelioma (1). In three patients there was no pathological finding. Mn-DPDP enhanced MRI showed a sensitivity of 100 % and a specificity of 56 %. CONCLUSION: Mn-DPDP enhanced MRI in conjunction with MRCP showed a high sensitivity for the detection of pancreatic lesions. However, the specificity is low, thus recommending Mn-DPDP enhanced MRI only as a complementary imaging method.

[Improvement of the image quality of MSCT of the pelvis with a raw data-based, multidimensional filter]. / Verbesserung der Bildqualität in der MSCT des Beckens durch ein rohdaten-basiertes mehrdimensionales Filter.

PURPOSE: To evaluate the potential of raw data-based multidimensional adaptive filtering (MAF) by determining its effects on image noise and image quality in multi-slice spiral CT (MSCT) of the pelvis. MATERIALS AND METHODS: Fifty patients with rectal and bladder cancer were examined with MSCT using a high-resolution protocol. Reconstructions were performed with dedicated reconstruction software and a standard algorithm, both without and with MAF, with four different modification fractions selected from 5 % to 20 %. The noise was measured at six anatomic sites of the pelvis. Image quality and image noise were rated on a 5-point-scale. RESULTS: Modification fractions of 15 % (15 % MAF) and 20 % (20 % MAF) significantly reduced the noise level at all measurement points in comparison with lower modification fractions (p < 0.05). Overall quality of the reconstructed images was rated better with 15 % MAF and 20 % MAF than with other modification fractions (p < 0.05). No further improvement of the image quality was observed by changing from 15 % MAF to 20 % MAF (p > 0.05). 15 % MAF achieved a mean noise reduction of 33 %. All examinations showed an improved visualization of the rectal wall and perirectal lymph nodes. CONCLUSIONS: MAF improves the image quality by reducing the noise level and by removing noise structures. This technique offers new perspectives to radiation dose reduction in CT.

[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.

[Dose reduction in spiral-CT: detection of pulmonary coin lesions with and without anatomically adjusted modulation of tube current]. / Dosisreduktion bei der Spiral-CT: Detektion von Lungenrundherden mit und ohne anatomisch angepasster Röhrenstrommodulation.

PURPOSE: To investigate the potential of projection angle-dependent anatomical adaptation of tube current to reduce dose in spiral CT examinations of the thorax without loss in detectability of pulmonary nodules and image quality. PATIENTS AND METHODS: Dose can be reduced for non-circular patient cross-sections without an increase in noise if the tube current is reduced at those angular positions where the patient diameter and, consequently, attenuation are small. The examinations were dose with SOMATOM Plus 4 (Siemens AG). CT projection data were analysed to determine the optimum tube current for each projection angle in real time. We compared image quality, done, and detection rates of pulmonary nodules for thoracic spiral CT examinations with and without online anatomically adapted tube current control in a group of 38 patients. Three radiologists counted all intrapulmonary nodules in consensus separated in three different groups (< 5 mm, 5-10 mm, > 10 mm). Image quality was evaluated in a scale from 1-3 (1 = very good, 2 = good, 3 = worse). RESULTS: On average, the dose was reduced by 21% (15-34%). With a constant tube current, 704 pulmonary nodules were detected, with tube current modulation 707 pulmonary nodules. For three patients we saw more pulmonary nodules (five) with tube current modulation, for two patients we saw less pulmonary nodules (two). In a direct comparison, the missed intrapulmonary nodules were also detected in the respective method. Thus, the detection rate of intrapulmonary nodules was uninfluenced. In general, no deterioration of image quality was observed. CONCLUSION: On average, 21% dose reduction was achieved by an anatomically adapted tube current modulation in spiral CT examinations of the thorax without a loss in detectability of pulmonary nodules and image quality. This method is an important contribution to dose reduction in spiral CT.