Automated breast ultrasound: lesion detection and BI-RADS classification--a pilot study.

PURPOSE: Evaluation of an automated breast ultrasound system (ABUS) regarding the detection and classification of breast lesions according to BI-RADS. MATERIALS AND METHODS: Women were selected for the study who had unclear findings in breast diagnosis performed elsewhere (palpation, sonography or mammography) and who were referred for further work-up. All patients received a hand-held ultrasonography (HHUS) with a 13 MHz transducer, clinical examination and mammography of both breasts. Additionally, the affected breast received the ABUS (SomoVuTM, U-Systems, Inc., San Jose, CA, USA; EC Representative: Siemens, Erlangen, Germany) which was performed with an 8 MHz transducer. Five radiologists independently evaluated the ABUS images regarding lesion detectability. All detected lesions were classified according to BI-RADS assessment. The examiners had no knowledge of the patients' clinical examination or of the result of the mammography or the HHUS. Results of the ABUS were compared to HHUS. RESULTS: 35 women were included in the study. 25 BI-RADS 4 or 5 lesions had further histological (n = 23) or cytological (n = 2) work-up which revealed 13 malignant and 12 benign findings. The size of all lesions ranged from 6 to 32 mm (median 14 mm). With the ABUS all examiners detected 29 to 30 lesions while HHUS revealed 30 lesions. One suspicious area in HHUS was not reported by any of the five examiners with the ABUS. Histology of this area revealed mastopathic disease. No benign lesion was classified as BI-RADS 5 with the ABUS or HHUS. All breast cancers were found with the ABUS by all examiners and correctly classified as BI-RADS 4 or 5. There was good agreement regarding BI-RADS classification of HHUS and ABUS for the five different examiners with Kappa values between 0.83 and 0.87. CONCLUSION: These preliminary results show that the ABUS allows detection of solid and cystic lesions and their BI-RADS classification with a high reliability in a selected patient group.

MR imaging: influence of imaging technique and postprocessing on measurement of internal carotid artery stenosis.

BACKGROUND AND PURPOSE: MR angiography (MRA) is increasingly used as an alternative to digital subtraction angiography (DSA) to evaluate internal carotid artery (ICA) stenosis. Because MRA is not standardized in data acquisition and postprocessing, we sought to evaluate the effects of different acquisition techniques (time-of-flight MRA [TOF-MRA]) and contrast-enhanced MRA [CE-MRA]) and postprocessing methods (maximum intensity projection [MIP], multiplanar reformation [MPR], and volume-rendering on stenosis grading. MATERIALS AND METHODS: Fifty patients (33 men, 17 women) with symptomatic ICA stenosis were examined at 1.5T. Two imaging techniques and 3 postprocessing methods resulted in 6 image datasets per patient. Two readers independently evaluated ICA stenosis according to the North American Symptomatic Carotid Endarterectomy Trial criteria. Interobserver variability was calculated with the Pearson correlation coefficient and simultaneous confidence intervals (CI). The relationship of the values of ICA stenosis between the techniques was assessed by means of simultaneous 95% Tukey CI. RESULTS: Interobserver agreement was high. Higher concordance was found for postprocessing techniques with TOF- than with CE-MRA; the mean difference between TOF-MPR and TOF-MIP was 0.4% (95% CI, -2.9%-3.8%). Stenosis values for CE-MPR differed significantly from those of CE volume-rendering (7.2%; 95% CI, 3.9%-10.6%). CONCLUSION: Stenosis grading was found to be independent of the postprocessing technique except for comparison of CE-MPR with CE volume-rendering, with the volume-rendering technique resulting in higher stenosis values. MPR seems to be best-suited for measurement of ICA stenosis. Parameter setting is critical with volume-rendering, in which stenosis values were consistently higher compared with the other methods.

[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.

[Tolerance of magnetic resonance imaging in children and adolescents performed in a 1.5 Tesla MR scanner with an open design]. / Untersuchungstoleranz von Kindern und Adoleszenten in einem 1,5 Tesla MR-Tomografen mit offenem Magnetdesign.

PURPOSE: To investigate the tolerance of MR examinations in children and adolescents performed in a 1.5 Tesla MR scanner with an expanded bore diameter. METHOD AND MATERIALS: 163 patients, ages 4 to 25, underwent MR examinations in a 1.5 Tesla MR scanner with an open design (MAGNETOM Espree, Siemens, Erlangen, Germany), characterized by a compact length of 125 cm and an expanded 70 cm bore diameter. MR imaging of the brain was carried out in most cases (78.5 %), followed by examinations of the spinal canal (9.8 %), the extremities (9.2 %) and the neck (2.5 %). The patients were divided into four age groups and the success rate, motion artifacts and diagnostic quality of the MR examinations were assessed using a 3-grade scale. RESULTS: In 119 of 163 patients (73.0 %), MR examination was possible without any motion artifacts. With respect to the different age groups, 41.7 % of the 4 - 7-year-old children, 67.6 % of the 8 - 10-year-old children, 84.1 % of the 11 - 16-year-old children and 95.8 % of the patients older than 17 showed tolerance grade I without motion artifacts and excellent diagnostic image quality. In 39 of 163 children (23.9 %), the MR images showed moderate motion artifacts but had sufficient diagnostic quality. With regard to the different age groups, 52.8 % of the 4 - 7-year-old children, 26.5 % of the 8 - 10-year-old children, 15.9 % of the 11 - 16-year-old children and none of the patients older than 17 showed tolerance grade II with moderate motion artifacts and sufficient diagnostic image quality. In only 4 of 124 children < 10 years old and 1 child > 10 years old, the MR examination was not feasible and had to be repeated under sedation. CONCLUSION: Pediatric MR imaging using a 1.5 Tesla MR scanner with an open design can be conducted in children and adolescents with excellent acceptance. The failure rate of 3.0 % of cases for pediatric MR imaging is comparable to that of a conventional low-field open MR scanner.

[Experimental investigations for dose reduction by optimizing the radiation quality for digital mammography with an a-Se detector]. / Experimentelle Untersuchungen zur Dosisreduktion durch Optimierung der Strahlungsqualität bei digitaler Vollfeldmammografie mit einem Detektor auf Selenbasis.

PURPOSE: Reduction of radiation exposure at an adequate image quality by optimizing the radiation quality for a new system of full-field digital mammography using a digital detector (a-Se). MATERIALS AND METHODS: The investigations were performed using a digital mammography system Novation (Siemens, Erlangen). The system was constructed with a bimetal anode (molybdenum and tungsten) and the possibility of changing the filter (molybdenum/rhodium). The test object was the Wisconsin Mammography Random Phantom Model 152 A (Radiation Measurements Inc.) of which images were acquired using the digital technique with the tungsten anode and rhodium filter at different tube voltages (26-35 kV) and tube loads (40-100 mAs) and compared to images in the molybdan/molybdan molybdenum/molybdenum technique. To quantify the image quality, we used the detection rate of the simulated lesions in the phantom. RESULTS: Increasing the tube voltage significantly decreases the average glandular dose when using AEC (Automatic Exposure Control), i. e., constant detector dose. At the same time, the image quality decreases significantly with respect to the detection rate (26 kV, 1 mGy, 95.1 %; 35 kV, 0.7 mGy, 82.7 %). As a good compromise between the necessary diagnostic image quality and the lowest dose exposition, 28 kV and 60 mAs were selected for imaging with the tungsten/rhodium anode/filter combination. A further change to the tube load did not make sense because a decrease of 10 % resulted in a significant decrease in the detection rate while only a 2 % increase in detection rate was achieved for a 65 % increase in radiation exposure. CONCLUSION: The results of this phantom study demonstrate that the routine use of the tungsten anode in combination with a rhodium filter for full-field digital mammography with an a-Se detector in contrast to a molybdan/molybdan molybdenum/molybdenum anode/filter combination results in a reduction of the average glandular dose of up to 30 % without loss of diagnostic image quality.

[Comparing the clinical value of spot view mammography with reduced pixel size to monitor zooming by reporting microcalcifications in digital mammography]. / Vergleich der klinischen Wertigkeit von Zielaufnahmen mit reduzierter Pixelgrösse des Detektors und digitalem Monitorzooming bei der Beurteilung von Mikrokalzifikationen in der digitalen Mammografie.

PURPOSE: Evaluation of the diagnostic value of breast specimen imaging with a digital mammographic system using a detector system with changeable pixel size compared to standard mode imaging in different monitor display modes. MATERIALS AND METHODS: Using the digital mammographic system SenoScan (Fischer Imaging, Denver, USA), 50 diagnostic breast specimens with microcalcifications were visualized in both standard mode (pixel size 54 microm) and high resolution mode (pixel size 27 microm). The resulting radiographs were displayed 1:1 on a monitor. Standard mode images (pixel size 54 microm) were additionally displayed in a 2:1 mode. A total of 5 readers with different mammographic experience analyzed the type of the microcalcifications on the basis of the different display modes. The images were presented randomly. The findings were subsequently compared to the histology. RESULTS: The high resolution mode yielded slightly but not significantly better results than the standard mode on average for all 5 readers. Compared to a sensitivity of 80 % and a specificity of 72 % (PPV = 74 %, NPV = 78 %) in the standard mode, the high resolution mode provided a sensitivity of 86 % and a specificity of 74 % (PPV = 77 %, NPV = 83 %). The standard mode images on a 2:1 monitor display yielded 84 % and 74 % (PPV = 76 %, NPV = 82 %). CONCLUSION: The high resolution mode did not significantly increase the sensitivity and specificity of the microcalcification reading. A similar improvement was achieved by the 2:1 display mode, i. e. digital monitor zooming. For the clinical situation this means that there is no diagnostic advantage from using a high resolution target view with this mammographic system.

[How to cope with the demands of the new "Approbation Regulation" (AR) by radiology-related interdisciplinary courses. The Erlangen model]. / Wie wir die Herausforderungen der neuen Approbationsordnung (AO) durch neue computergestützte radiologisch-interdisziplinäre Programme bewältigen können. Das Erlanger Modell.

BACKGROUND: To create radiology-related interdisciplinary programs for the undergraduate education in terms of the new "Approbation Regulation". MATERIAL AND METHODS: Medical students developed in collaboration with radiologists and clinical partners virtual, radiology-related interdisciplinary training courses for different fields. Students and teachers evaluated the acceptance of the programs' structure and content as well as the possibility to replace the radiologist partly during interdisciplinary lessons. RESULTS: Six target group oriented virtual, radiology-related interdisciplinary training courses were developed which will relieve the implementation of the new AR's demands for more interdisciplinary education in small groups and the dreaded shortage of personnel. CONCLUSION: By the use of web- and CDRom-based interdisciplinary course models different fields of medicine and diagnostic radiology can be bridged in the sense of the new AR's demands as well as manpower in radiology can be saved.

Experimental phantom lesion detectability study using a digital breast tomosynthesis prototype system.

PURPOSE: To compare the sensitivity of conventional two-dimensional (2D) projection imaging with tomosynthesis with respect to the detectability of mammographic phantom lesions. MATERIALS AND METHODS: Using a breast tomosynthesis prototype based on a commercial FFDM system (Siemens MAMMOMAT Novation), but modified for a wide angle tube motion and equipped with a fast read-out amorphous selenium detector, we acquired standard 2D images and tomosynthesis series of projection views. We used the Wisconsin mammographic random phantom, model RMI 152A. The anode filter combinations Mo/Mo and W/Rh at two different doses were used as typical radiographic techniques. Slice images through the phantom parallel to the detector were reconstructed with a distance of 1 mm employing a filtered back-projection algorithm. The image data sets were read by five radiologists and evaluated with respect to the detectability of the phantom details. RESULTS: For all studied radiographic techniques, the detection rate in the tomosynthesis mode was 100 %, i. e. 75 true positive findings out of 75 possible hits. In contrast, the conventional projection mode yielded a detection rate between 80 and 93 % (corresponding to 60 and 70 detected details) depending on the dose and X-ray spectrum. CONCLUSION: Tomosynthesis has the potential to increase the sensitivity of digital mammography. Overlapping structures from out-of-plane tissue can be removed in the tomosynthesis reconstruction process, thereby enhancing the diagnostic accuracy.

[Quality improvement of resources in radiology on the internet]. / Qualitätsverbesserung radiologischer Lehrressourcen im Internet.

PURPOSE: Categorization and evaluation of online teaching files in radiology by representative members of the target group to make the specific search for adequate programs more effective. MATERIALS AND METHODS: A representative team of board qualified radiologists, residents and medical students performed a basic search for radiology teaching files on the Internet using search machines, international mailing lists and link lists to collections of national and international radiological societies and departments. The programs were categorized by language, modality, target group and special features, such as qualification for CME-accreditation. For final evaluation and ranking of the detected files, a questionnaire was developed to assess completeness, image quality, page loading time, layout, orientation, interactivity, annotation and maintenance. The results were stored in an Access database on a web server. A query form in HTML format, including the parameters described above, was made accessible to the online user. RESULTS: A search machine for radiological teaching files (RadList/Entity-link List) was made available online ( www.tnt-radiology.de/radlist and www.tnt-radiology.de/entitylinklist ). A submitted request calls a cgi script that searches the database for the appropriate sites according to the individual search parameters selected by the user. The list of matching URLs is returned to the user as HTML page. Evaluating the single sites by applying the criteria listed above contributed to the quality assurance of the radiological teaching resources on the Internet. CONCLUSION: Adapting a new Internet interface to the particular needs of the user allows a more effective access to specific radiological teaching files online. RadList/Entity-link List ( www.tnt-radiology.de/radlist and www.tnt-radiology.de/entitylinklist ) is conducive to quality improvement and benefits users as well as authors of radiological teaching files on the Internet.

[HNORAD]. / HNORAD. Eine interdisziplinäre interaktive Fallsammlung zu bildgebenden Verfahren in der Hals-Nasen-Ohren-Heilkunde im Internet.

BACKGROUND: New media are gaining importance in undergraduate as well as postgraduate and continued medical education. We aimed to create an interactive educational program for imaging diseases of the ear, nose and throat (ENT). MATERIALS AND METHODS: Cases and images representing clinical routine were collected, arranged by content and graphically presented according to instructional criteria. Undergraduate students participating in the project used an authoring system to generate case studies, which were then published at http://www.HNORAD.de. RESULTS: HNORAD is an interdisciplinary teaching program offering more than 100 classical disease presentations. Three systematic indices offer a choice of instructional approach. Apart from typical images, the information presented includes patient history, clinical findings, imaging findings as described by a board-qualified radiologist, diagnosis, differential diagnosis and internet links. Elements of the radiologist's report are linked with the images in such a way that the structure or finding described can be interactively highlighted. An evaluation index allows proficiency testing in self study and as a part of taught courses. CONCLUSION: HNORAD is a valuable resource for students, ENT surgeons and radiologists at the undergraduate, postgraduate and CME level for self study as well as for course work.

Bilateral orbital tumour as the presentation of mammographically occult breast cancer.

We report a rare case of bilateral orbital metastases as the presentation in a 63-year-old woman. Biopsy of a diffusely infiltrated medial rectus muscle suggested metastatic adenocarcinoma. Investigation revealed a palpable mass of the right breast not shown on mammography or sonography. Invasive lobular carcinoma was found at core-needle biopsy with histological features identical to those of the orbital lesion. Metastases to the extraocular muscles are uncommon, particularly as the initial abnormality in the absence of disseminated disease.

[Web-based training in radiology - student course in the Virtual University of Bavaria]. / Web-basiertes Training in der Radiologie - Studentenkurs in der Virtuellen Hochschule Bayern (VHB).

PURPOSE: The ninth version of the licensing regulation for medical doctors (Approbation Regulation (AR)) sets a benchmark in terms of practical experience, interdigitation of preclinical and clinical studies, interdisciplinary approach, economic efficiency, independence of students, added new teaching and learning modalities, and ongoing evaluation of the progress of the medical students. It is the aim to implement these major points of the AR in a model course for diagnostic radiology and radiation protection within the scope of the Virtual University of Bavaria and test them in practice. MATERIALS AND METHODS: In cooperation with residents and board certified radiologists, students developed the virtual course "Web-Based Training (WBT) Radiology" in diagnostic radiology and radiation protection for students in the first clinical semester. A representative target group taken from the student body was asked about the options to get access to the World Wide Web (Internet), and the satisfaction concerning configuration and content of the newly developed program. A comparison was made between the results of the final examination taken by students who made use of the virtual course in addition to conventional lessons and taken by students who did not subscribe to the virtual course and exclusively relied on conventional lessons. In addition, a pilot study was conducted in the winter semester 2002/03, which compared students taking either the traditional lessons or the new virtual course on the Internet. RESULTS: The virtual course-model had test results with a positive trend. All targeted students had Internet access. Constructive criticism was immediately implemented and contributed to rapid optimization. The learning success of the additive or alternative virtual course was in no way less than the learning success achieved with the conventional course. CONCLUSION: The learning success as measure of quality in teaching and the acceptance by students and teachers justify the continuation of this course model and its expansion. Besides enabling the learning in small study groups; the course "WBT Radiology" might not only help implementing the major points of the new AR but might also complement any deficiencies in the current education. Economic aspects may encourage their implementations.

[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.

A low-field MR system in acute traumatological imaging in radiology. Technical note.

PURPOSE: In this paper initial clinical observations with the application of a new low-field MR system in acute musculoskeletal imaging in radiology are presented. MATERIALS AND METHODS: This system is designed as a three-sided open permanent magnet with a revolving table. Main magnetic field strength is 0.2 T, maximal gradient field strength 20 mT/m, and minimal gradient rise time is 800 microseconds. First clinical experiences in 25 patients with acute trauma of peripheral joints were obtained. The following sequences were applied: gradient-echo (GRE) STIR, T1-weighted spin-echo, and PD- and T2-weighted turbo spin-echo. Correlation with the findings of high-field MR (1.5 T), plain radiograms (including stress views), CT or ultrasound was available in each patient confirming the low-field diagnoses. Furthermore, phantom measurements were performed to verify the spatial resolution of the system for some sequences with typical measurement parameters. DISCUSSION: This low-field system has several advantages: fast and economic installation, limited required space, easy operation, and high patient comfort. The medical benefit of such a system integrated in the traumatological suite of a radiological department seems to be evident due to the impact on the early initiation of the correct therapy which avoids additional diagnostic procedures and therefore may reduce costs. Implementation of such a system may be useful, if installation of an additional high-field scanner is not possible due to economic considerations.

Direct MR arthrography of the shoulder: 2D vs. 3D gradient-echo imaging.

The aim of this study was to determine the value of a fat suppressed 3D gradient-echo sequence (GRE) data set in comparison to a 2D GRE sequence in direct MR arthrography of the shoulder. For this purpose we examined 50 consecutive patients with subacute or chronic disorders of the shoulder using a 1.5 T scanner: Transverse T1-weighted 2D (slice thickness 4 mm) and 3D GRE (slice thickness 1.5 mm reconstructed from 3 mm), oblique coronal T2- and T1-weighted turbo spin-echo (TSE) and sagittal T1-weighted TSE with fat saturation were applied. Visual image analysis of anatomical and pathological structures was performed by two independent observers. A correlation to surgical results was available in 21 patients. Transverse GRE sequences were well suited for analysis of the anterior/posterior labrum, the middle glenohumeral ligament, and cartilage. 3D GRE with fat suppression was slightly superior to 2D GRE without fat suppression in the evaluation of the anterior/posterior labrum, and the middle glenohumeral ligament, whereas for cartilage no significant differences were found between both sequences. Concerning pathological findings, in most of the cases 2D delivered the same results as 3D. In conclusion, a T1-weighted 3D GRE data set with fat saturation in transverse orientation may be useful for evaluation of the anterior/posterior labrum, and the middle glenohumeral ligament. However, similar measured slice thickness of 3 mm-even if interpolated to 1.5 mm-compared to a 2D sequence with 4 mm does not provide significant diagnostic advantages.

[A hybrid technique for the automatic floating table MRA of peripheral arteries using a dedicated phased-array coil combination]. / Eine Hybridtechnik für die Schrittverschiebungs-MRA der Becken-Bein-Arterien mit einer dedizierten phased-array-Spulen-Kombination.

PURPOSE: We introduce a hybrid technique which allows a high resolution MRA of the peripheral arteries with a dedicated phased-array coil using the floating table technique. MATERIALS AND METHODS: Five patients with peripheral arterial occlusive disease were examined within one week with i.a. DSA and MRA using the hybrid technique. MRA examinations were done on a 1.5 T system. At first, pelvic arteries were examined in a single step mode applying the CareBolus technique. Subsequently, thighs and lower legs were examined using the floating table mode. 125 vascular segments were evaluated. RESULTS: The hybrid technique proved to be robust and could be performed in each case. Mean examination time was about 30 min. For 117 vascular segments no difference was found between i.a. DSA and MRA. Three segments revealed a higher grade of stenosis in DSA than in MRA, five segments were graded higher in MRA than in DSA. Occlusions were visualized identically in both methods. Venous overlap had no relevant effects on image evaluation. CONCLUSIONS: This hybrid technique in combination with phased-array coils allows a high resolution MRA of the peripheral arteries with very good image quality. If future studies confirm reduced venous overlap, this method may be an alternative also for users of the floating table MRA with the body resonator.

2D and 3D visualisation of head and neck tumours from spiral-CT data.

PURPOSE: This paper intends to demonstrate the possibilities of two- and three-dimensional visualisation methods from spiral-CT data sets in the head and neck region and demonstrates their value based on various studies. MATERIAL AND METHODS: The scanner was a Somatom PLUS 4 (Siemens, Forchheim/Germany). The patients were scanned using a slice thickness of 3 mm and a table feed of 5 mm (pitch 1,6). The images were reconstructed with an increment of 1 mm. Contrast agent (150 ml) was applied intravenously with a flow of 2.5 ml/s and a start delay of 80 s. In one study the start delay was 20 s in order to visualise the carotid arteries (extracranial aneurysm). Volumetric data sets were postprocessed with 'Vitrea' and 'VoxelView' (Vital Images) volume rendering software on a Silicon Graphics O2 workstation (virtual laryngoscopy). Multiplanar reformation and colour-coded 3D-reconstruction were done on a Prominence workstation (Siemens/Forchheim/Germany). RESULTS: In every region of the head and neck MPRs are useful as additional planes (with the exception of the hypopharynx and the larynx), SSDs are always useful if there is extensive bony destruction (skull, spine, skeleton larynx). Colour-coded three-dimensional reformations may be done for extensive tumours and before multi-specialty surgery. Perspective volume rendering is already in use for virtual endoscopy of the paranasal sinuses and the virtual laryngoscopy. In temporal bone evaluation, perspective volume rendering is a new and promising method of the future to assess the inner ear. SUMMARY: Two- and three-dimensional displays are used to visualise pathological findings in their topographic relation to anatomical leading structures. Thus, the radiologist can point out to the clinician the pathological findings by some essential images without having to demonstrate all axial slices.

Dose reduction in computed tomography by attenuation-based on-line modulation of tube current: evaluation of six anatomical regions.

This study investigated the potential of attenuation-based on-line modulation of tube current to reduce the dose of computed tomography (in milliamperes) without loss in image quality. The dose can be reduced for non-circular patient cross-sections by reducing the tube current at the angular positions at which the diameter through the patient diameter is smallest. We investigated a new technical approach with attenuation-based on-line modulation of tube current. Computed tomographic projection data were analyzed to determine the optimal milliampere values for each projection angle in real time, instead of performing prior measurements with localizer radiographs. We compared image quality, noise pattern, and dose for standard scans and for scans with attenuation-based on-line modulation of tube current in a group of 30 radiation therapy patients. Six different anatomical regions were examined: head, shoulder, thorax, abdomen, pelvis, and extremities (knee). Image quality was evaluated by four radiologists in a blinded fashion. We found the dose to be reduced typically by 15-50 %. In general, no deterioration in image quality was observed. Thus the dose in computed tomography be reduced substantially by technical measures without sacrificing image quality. Attenuation-based on-line modulation of tube current is an efficient and practical means for this.